Source: http://www.google.es/patents/US8761954
Timestamp: 2017-12-12 18:13:09
Document Index: 228524482

Matched Legal Cases: ['art 600', 'art 600', 'art 600', 'art 130', 'art 130', 'art 130', 'art 190', 'art 190', 'art 130', 'art 190', 'art 240', 'art 290', 'art 290', 'art 240', 'art 290', 'art 350', 'art 390', 'art 390', 'art 390', 'art 390', 'art 390', 'art 430', 'art 430', 'art 470', 'art 470', 'art 570', 'art 570']

Patente US8761954 - Devices and methods for decentralized coordinated volt/VAR control - Google Patentes
Devices and methods for decentralized coordinated Volt/VAR control are provided. Such a device may allow, for example, an operational parameter such as voltage, power losses, a combination of these, and/or power factor to be optimized on a segment of an electrical distribution system under certain conditions....http://www.google.es/patents/US8761954?utm_source=gb-gplus-sharePatente US8761954 - Devices and methods for decentralized coordinated volt/VAR control
Número de publicación US8761954 B2
Número de solicitud US 13/191,422
También publicado como CA2784999A1, US20130030599
Número de publicación 13191422, 191422, US 8761954 B2, US 8761954B2, US-B2-8761954, US8761954 B2, US8761954B2
Inventores Borka Milosevic, Willem Hendrik Du Toit, Aleksandar Vukojevic
Citas de patentes (74), Otras citas (7), Citada por (1), Clasificaciones (15), Eventos legales (1)
US 8761954 B2
a network interface configured to receive first measurements associated with a segment of an electrical distribution system and transmit a control signal configured to control equipment of the segment of the electrical distribution system; and
data processing circuitry configured:
to determine a total load on the segment of the electrical distribution system;
to run a first simulation of the segment of the electrical distribution system simulating various equipment configurations based at least in part on the first measurements;
to select from among the various equipment configurations, depending at least in part on the total load:
a first equipment configuration that is expected to cause a voltage deviation of the segment of the electrical distribution system to most closely approach a first desired value without causing voltage violations or power factor to fall beneath a power factor threshold;
a second equipment configuration that is expected to cause the voltage deviation of the segment of the electrical distribution system to more closely approach the first desired value than otherwise and active power losses of the segment of the electrical distribution system to more closely approach a second desired value than otherwise without causing voltage violations or power factor to fall beneath the power factor threshold; or
a third equipment configuration that is expected to cause the active power losses of the segment of the electrical distribution system to most closely approach the second desired value without causing voltage violations or power factor to fall beneath the power factor threshold; and
to generate the control signal, wherein the control signal is configured to cause the equipment of the segment of the electrical distribution system to conform to the equipment configuration.
2. The controller of claim 1, wherein the data processing circuitry is configured to select the first equipment configuration when the total load is within a first range, the second equipment configuration when the total load is within a second range, and the third equipment configuration when the total load is within a third range, wherein the first range is higher than the second range and the third range and wherein the second range is higher than the third range.
3. The controller of claim 1, wherein the data processing circuitry is configured to determine a power factor on the segment of the electrical system and select a fourth equipment configuration that is expected to cause the power factor to most closely approach a desired power factor value when the power factor is less than a power factor threshold.
4. The controller of claim 1, wherein the control signal is configured to control the equipment of the segment of the electrical distribution system, wherein the equipment comprises at least one capacitor, and wherein the data processing circuitry is configured to run the simulation of the segment of the electrical distribution system simulating various equipment configurations, wherein the various equipment configurations comprise various capacitor switching configurations.
5. The controller of claim 4, wherein the capacitor switching configuration indicates that a single one of a plurality of capacitors of the segment of the electrical distribution system is to be switched on or off.
6. The controller of claim 4, wherein the capacitor switching configuration indicates that a combination of a plurality of capacitors of the segment of the electrical distribution system are to be switched on or off.
7. The controller of claim 6, wherein the data processing circuitry is configured to determine a switching order of the combination of the plurality of capacitors.
8. The controller of claim 1, wherein the network interface is configured to obtain the first measurements from a plurality of remote terminal units, wherein the first measurements comprise:
a voltage magnitude at a low side bus of a substation of the segment of the electrical distribution system;
a voltage magnitude at capacitors of the segment of the electrical distribution system;
a voltage magnitude at low sides of voltage regulators of the segment of the electrical distribution system;
real and reactive power flows at capacitors and at all junction points between the capacitors and the voltage regulators and the substation;
real and reactive power flows at a high side bus of the substation or real and reactive power flows from each feeder of the segment of the electrical distribution system, or both;
end of line voltages of the segment of the electrical distribution system or a voltage drop between a last measurement point and an end of a feeder.
9. The controller of claim 1, wherein the data processing circuitry is configured to run a second simulation of the segment of the electrical distribution system based at least in part on the selected equipment configuration before generating the control signal to determine whether the selected equipment configuration is expected to cause a voltage violation on the segment of the electrical distribution system and, when the selected equipment configuration is expected to cause the voltage violation, to determine a tap position for a voltage regulator of the segment of the electrical distribution system that is expected to prevent the voltage violation from occurring.
10. The controller of claim 1, wherein the network interface is configured to receive second measurements associated with the segment of the electrical distribution system a period of time after transmitting the control signal, wherein the second measurements reflect an actual effect of the equipment configuration on the segment of the electrical distribution system, and wherein the data processing circuitry is configured to determine whether the second measurements indicate a voltage violation and, when the second measurements indicate the voltage violation, to vary the equipment configuration to prevent the voltage violation.
11. The controller of claim 10, wherein the data processing circuitry is configured, when the second measurements indicate the voltage violation, to identify a voltage regulator of the segment of the electrical distribution system that is situated closest to a substation of the electrical distribution system, to calculate a lower or higher tap position associated with the voltage regulator that is expected to prevent the voltage violation and, when the tap position is not higher than a maximum tap position or lower than a minimum tap position, to cause the to cause the voltage regulator to assume the tap position and, when the tap position is higher than the maximum tap position or lower than the minimum tap position, to cause a switchable capacitor of the segment of the electrical distribution system that is located furthest from the substation of the electrical distribution system or that is the largest capacitor of the segment of the electrical distribution system to be switched on or off.
12. The controller of claim 1, wherein the data processing circuitry is configured, after transmitting the control signal, to cause one or more voltage regulators of the segment of the electrical distribution system to cause a high side voltage of the one or more voltage regulators to be approximately equal to a low side voltage of a substation that supplies voltage to the segment of the electrical distribution system.
determining, using a first substation application platform associated with a first segment of an electrical distribution system or a second substation application platform associated with a second segment of the electrical distribution system, an estimated cost of generating power at a current or future time period on the first segment of an electrical distribution system or the second segment of the electrical distribution system, or both; and
determining to run, using the first substation application platform or the second substation application platform:
a voltage control function to cause a voltage deviation of the first segment or the second segment, or both, to most closely approach a first desired value without causing voltage violations or power factor to fall beneath a power factor threshold;
a Volt/VAR control function to cause the voltage deviation of the first segment or the second segment, or both, to more closely approach the first desired value than otherwise and active power losses of the first segment or the second segment, or both, to more closely approach a second desired value than otherwise without causing voltage violations or power factor to fall beneath the power factor threshold;
a power loss reduction function to cause the active power losses of the first segment or the second segment, or both, to most closely approach the second desired value without causing voltage violations or power factor to fall beneath the power factor threshold; or
a power factor control function to cause the power factor to most closely approach a desired power factor value; or
based at least in part on the estimated cost of generating power during the current or future time period.
14. The method of claim 13, wherein the power loss reduction function is determined to be run when the estimated cost of generating power is less than a first threshold and a second threshold, the Volt/VAR control function is determined to be run when the estimated cost of generating power is equal to or greater than the first threshold and less than the second threshold, and the voltage control function is determined to be run when the estimated cost of generating power is equal to or greater than the second threshold.
15. The method of claim 13, comprising controlling the first segment and the second segment while the first segment is providing power to a recovered portion of the second segment by:
running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, on the second segment using the second substation application platform;
while the second application platform is running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, on the second segment, running a violation check function on the first segment using the first substation application platform, wherein the violation check function is configured to prevent or mitigate a voltage violation on the first segment; and
after running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, on the second segment using the second substation application platform, running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, on the first segment using the first substation application platform.
16. The method of claim 15, comprising communicating a minimum voltage of the second segment from the second substation application platform to the first substation application platform while the first substation application platform is running the violation check function on the first segment or while the first substation application platform is running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, on the first segment, or both.
17. The method of claim 15, comprising communicating from the second substation application platform to the first application platform an indication that the second substation application platform has finished running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, when the second substation application platform for has finished running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, and communicating from the first substation application platform for to the second substation application platform an indication that the first substation application platform has finished running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, when the first substation application platform has finished running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof.
18. The method of claim 15, comprising, while the first substation application platform is running the voltage control function, the Volt/VAR control function, the power loss reduction function, or the power factor control function, or the combination thereof, on the first segment, running a violation check function on the second segment using the second substation application platform, wherein the violation check function is configured to prevent or mitigate a voltage violation on the second segment.
instructions to receive measurements associated with a feeder of an electrical distribution system;
instructions to determine an expected load on the feeder at a present or future time period;
instructions to simulate a distribution power flow of the feeder according to various capacitor switching configurations of at least one capacitor of the feeder using the measurements;
instructions to determine an expected voltage deviation, reduction in power loss, and power factor associated with the various capacitor switching configurations based at least in part on the simulated distribution power flow of the feeder;
instructions to select a non-dominated capacitor switching configuration from among the various capacitor switching configurations:
a first capacitor switching configuration that is expected to cause a voltage deviation of the segment of the electrical distribution system to most closely approach a first desired value without causing voltage violations or power factor to fall beneath a power factor threshold;
a second capacitor switching configuration that is expected to cause the voltage deviation of the segment of the electrical distribution system to more closely approach the first desired value than otherwise and active power losses of the segment of the electrical distribution system to more closely approach a second desired value than otherwise without causing voltage violations or power factor to fall beneath the power factor threshold; or
a third capacitor switching configuration that is expected to cause the active power losses of the segment of the electrical distribution system to most closely approach the second desired value without causing voltage violations or power factor to fall beneath the power factor threshold;
wherein the first, second, or third capacitor switching configuration is selected based at least in part on the expected load on the feeder at the present or future time period; and
instructions to control capacitors of the feeder according to the non-dominated capacitor switching configuration during the present or future time period.
20. The article of manufacture of claim 19, comprising instructions to transmit at least one of the measurements to another electronic device associated with another feeder of the electrical distribution system.
The subject matter disclosed herein relates to decentralized, coordinated control of equipment associated with an electrical distribution system to optimize voltage and active power losses in light of one another (Volt/VAR) while keeping power factor within a desired range
In a first embodiment, a controller includes a network interface and data processing circuitry. The network interface may receive first measurements associated with a segment of an electrical distribution system and transmit a control signal configured to control equipment of the segment of the electrical distribution system. The data processing circuitry may determine a total load on the segment of the electrical distribution system and run a first simulation of the segment of the electrical distribution system simulating various equipment configurations based at least in part on the first measurements. The data processing circuitry may select from among the various equipment configurations, depending at least in part on the total load, one of several different equipment configurations. The data processing circuitry also may generate the control signal, which may cause the equipment of the segment of the electrical distribution system to conform to the selected equipment configuration. By way of example, a first equipment configuration may cause a voltage deviation of the segment of the electrical distribution system to most closely approach a first desired value without causing voltage violations or power factor to fall beneath a power factor threshold. A second equipment configuration may cause the voltage deviation of the segment of the electrical distribution system to more closely approach the first desired value than otherwise and active power losses of the segment of the electrical distribution system to more closely approach a second desired value than otherwise without causing voltage violations or power factor to fall beneath the power factor threshold. A third equipment configuration may cause the active power losses of the segment of the electrical distribution system to most closely approach the second desired value without causing voltage violations or power factor to fall beneath the power factor threshold.
In a second embodiment, a method may involve determining, using a first substation application platform associated with a first segment of an electrical distribution system or a second substation application platform associated with a second segment of the electrical distribution system, an estimated cost of generating power at a current or future time period on the first segment of an electrical distribution system or the second segment of the electrical distribution system, or both. Additionally, the method may involve determining to run a voltage control function, a Volt/VAR control function, a power loss reduction function, a power factor control function, or a combination thereof, based at least in part on the estimated cost of generating power. By way of example, the voltage control function to cause a voltage deviation of the first segment or the second segment, or both, to most closely approach a first desired value without causing voltage violations or power factor to fall beneath a power factor threshold. The Volt/VAR control function to cause the voltage deviation of the first segment or the second segment, or both, to more closely approach the first desired value than otherwise and active power losses of the first segment or the second segment, or both, to more closely approach a second desired value than otherwise without causing voltage violations or power factor to fall beneath the power factor threshold. The power loss reduction function to cause the active power losses of the first segment or the second segment, or both, to most closely approach the second desired value without causing voltage violations or power factor to fall beneath the power factor threshold. The power factor control function to cause the power factor to most closely approach a desired power factor value.
In a third embodiment, an article of manufacture includes one or more tangible, machine-readable storage media having instructions encoded thereon for execution by a processor of an electronic device. The instructions include instructions to receive measurements associated with a feeder of an electrical distribution system, instructions to determine an expected load on the feeder at a present or future time period, instructions to simulate a distribution power flow of the feeder according to various capacitor switching configurations of at least one capacitor of the feeder using the measurements, and instructions to determine an expected voltage deviation, reduction in power loss, and power factor associated with the various capacitor switching configurations based at least in part on the simulated distribution power flow of the feeder. In addition, the instructions include instructions to select a non-dominated capacitor switching configuration from among various capacitor switching configurations that causes a voltage deviation to most closely approach a first desired value, that causes the voltage deviation of the segment of the electrical distribution system to more closely approach the first desired value than otherwise and active power losses of the segment of the electrical distribution system to more closely approach a second desired value than otherwise, or that causes the active power losses of the segment of the electrical distribution system to most closely approach the second desired value based at least in part on the expected load on the feeder at the present or future time period. The instructions may further include instructions to control capacitors of the feeder according to the selected non-dominated capacitor switching configuration during the present or future time period.
FIGS. 1 and 2 are one-line drawings of an electrical distribution system that can be optimized for a desired operational parameter such as power factor, active power losses, voltage, and/or voltage and active power losses in light of one another (Volt/VAR) while keeping power factor within a desired range via decentralized coordinated control, in accordance with an embodiment;
FIG. 3 is a block diagram of an application platform of a substation that can optimize a desired operational parameter of the electrical distribution system of FIGS. 1 and/or 2 via decentralized coordinated control, in accordance with an embodiment;
FIG. 12 is a schematic diagram representing a manner of switching distribution capacitor banks to vary a desired operational parameter of a segment of an electrical distribution system, in accordance with an embodiment;
FIG. 13 is a plot representing a change in load across a segment of an electrical distribution system over time, in accordance with an embodiment;
FIGS. 14 and 15 are flowcharts describing embodiments of methods for selecting and applying various decentralized coordinated control schemes to optimize a desired operational parameter of an electrical distribution system, in accordance with an embodiment;
FIG. 16 is a flowchart describing an embodiment of a method for decentralized coordinated control of an electrical distribution system to optimize a desired operational parameter, in accordance with an embodiment;
FIG. 17 is a plot modeling voltage over a segment of an electrical distribution system before and after adjusting voltage regulators in the method of the flowchart of FIG. 16, in accordance with an embodiment;
FIG. 18 is a one-line diagram illustrating a manner of supplying power from a first segment of an electrical distribution system to a restored segment of the electrical distribution system, in accordance with an embodiment;
FIG. 19 is a one-line diagram representing an equivalent circuit of the one-line diagram of FIG. 18, in accordance with an embodiment;
FIG. 20 is a flowchart describing an embodiment of a method for optimizing a desired operational parameter across a first segment of an electrical distribution system and a restored segment of the electrical distribution system via decentralized coordinated control;
FIG. 21 is a flowchart describing an embodiment of a method for determining a combination of capacitors of an electrical distribution system that may be switched on or off to optimize a desired operational parameter;
FIG. 22 is a flowchart describing an embodiment of a method for determining a capacitor that may be switched on or off to optimize a desired operational parameter;
FIG. 23 is a plot representing a number of solutions that optimize various operating parameters in 3-D space;
FIG. 24 is a plot representing a non-dominated solution from among the solutions of FIG. 22, which represents a compromise between loss reduction and voltage difference, in accordance with an embodiment;
FIG. 25 is a flowchart describing an embodiment of a method for determining and responding when switching is expected to cause a voltage violation on the segment of the electrical distribution system;
FIG. 26 is a flowchart describing an embodiment of a method for detecting and/or correcting any voltage violation that occurs when a capacitor is switched on or off;
FIG. 27 is a flowchart describing an embodiment of a method for adjusting voltage regulators across a segment of an electrical distribution system after a desired operational parameter has been optimized;
FIG. 28 is a flowchart describing an embodiment of a method for reducing the voltage supplied by a substation to various segments of an electrical distribution system after the voltage has been flattened across the segments;
FIG. 29 is a plot illustrating the reduction of the voltage across the segments of the electrical distribution system, in accordance with an embodiment;
FIG. 30 is a flowchart describing an embodiment of a method for optimizing power factor at a substation after the feeder segments of the electrical distribution system have been optimized for power factor; and
FIG. 31 is a flowchart describing an embodiment of a method for performing a distribution power flow simulation of a feeder of an electrical distribution system.
where {tilde over (Z)}=R+jX is the impedance 52 of the line segment. The current vector Ĩ appears in FIG. 4 alongside the equivalent circuit, and represents the sum of both real and reactive current components Ĩ=IR+jIX. The voltage drop, Vdrop, across the line segment is defined as a difference between the magnitudes of the source voltage {tilde over (V)}S and the load voltage {tilde over (V)}R:
ΔV rise ≈XI C.
It should be understood that the equation above may approximate the effect of a capacitor 22 switching on on the feeder 14 voltage profile. From this equation, it may be seen that if the capacitor 22 is the capacitor is oversized (i.e., IX−IC<0), the system may be overcompensated and the voltage drop in the line segment ΔVdrop may become negative. Consequently, the load voltage, VR, may become higher than the source voltage, VS. This condition may occur if capacitors 22 installed on the feeder 14 were not adequately located or sized, or when certain sections of the feeder 14 need to be overcompensated to achieve better voltage flattening along the feeder 14 and its laterals. The effect of switching the capacitor 22 on or off in the circuit of FIG. 6 may also effect power losses. The active power loss on the line segment of the circuit of FIG. 6 while the capacitor 22 is switched off (e.g., the condition illustrated by FIG. 4), may depend on the impedance 52 of the line segment and the square of the current, I, flowing through it:
P loss = R V R 2 ( P 2 + Q 2 ) or P loss = Δ V 2 R Z 2 ≈ Δ V drop 2 R Z 2
P loss new = R ( I R 2 + ( I X - I C ) 2 ) , or P loss new = R V R 2 ( P 2 + ( Q - Qc ) 2 ) , or P loss ≈ ( Δ V drop - Δ V rise ) 2 R Z 2 .
Δ P LOSS = ∑ i , j ( R i , j I X i , j 2 - R i , j ( I X i , j - I C k ) 2 ) ,
pf = cos ( θ ) = P P 2 + Q 2 .
pf new = P - Δ P LOSS ( P - Δ P LOSS ) 2 + ( Q - Δ Q LOSS - Q C ) 2 ≈ P P 2 + ( Q - Q C ) 2 ,
Δ P LOSS = ∑ i , j Δ P loss i , j ,
Δ Q LOSS = ∑ i , j Δ Q loss i , j ,
ΔQ loss i,j =X i,j I X i,j 2 −X i,j(I X i,j −I C k ),
Δ V drop total = Re { 1 2 Z ~ I ~ t ( 1 + 1 n ) } ,
V drop total = Re { 1 2 Z ~ I ~ t } .
P loss total = 3 RI t 2 ( 1 3 + 1 2 n + 1 6 n 2 ) .
Determining the distribution power flow for a feeder 14 without laterals may occur as illustrated by a flowchart 600 of FIG. 31. The flowchart 600 may begin when the application platform for Volt/Var optimization 18 sorts buses of the feeder 14 according to their distance to the substation 12 and initializes the end node voltage as {tilde over (V)}n B={tilde over (V)}S, where {tilde over (V)}S is the specified voltage at the substation bus LS and the superscript “B” stands for “backward sweep” (block 602). The application platform for Volt/Var optimization 18 may start from the end bus and perform a backward sweep using KCL and KVL to calculate voltage of each upstream bus and the line currents (block 604). The backward sweep may take place as follows:
Ĩ n-1,n B =Ĩ n B.
{tilde over (V)} n-1 B ={tilde over (V)} n B +{tilde over (Z)} n Ĩ n-1,n B.
Ĩ n-2,n-1 B =Ĩ n-1 B +Ĩ n-1,n B.
{tilde over (V)} n-2 B ={tilde over (V)} n-1 B +{tilde over (Z)} n-1 Ĩ n-2,n-1 B.
V ~ S B = V ~ 1 B + Z ~ 1 I ~ t B , where : I ~ t B = ∑ i = 1 n I ~ i B .
V ~ i F = V ~ i - 1 F - Z ~ i ( I ~ t B - ∑ j = 1 i - 1 I ~ j B ) .
After completing the forward sweep of block 610, the backward sweep may be repeated (block 604) using the new end voltages (i.e., {tilde over (V)}n B={tilde over (V)}n F) rather than the assumed voltage {tilde over (V)}S as carried out in the first iteration of the backward sweep. The forward and backward sweeps of blocks 604 and 610 may be repeated as shown in the flowchart 600 until the calculated voltage at the source is within the tolerance ε of the specified source voltage {tilde over (V)}S.
Δ P LOSS C 2 = Δ P loss C 2 S , 1 + Δ P loss C 2 1 , 2 ,
Δ P LOSS C 4 = Δ P loss C 4 S , 1 + Δ P loss C 4 1 , 2 + Δ P loss C 4 2 , 3 + Δ P loss C 4 3 , 4 Δ P LOSS C 3 , 1 = Δ P loss C 3 , 1 S , 1 + Δ P loss C 3 , 1 1 , 2 + Δ P loss C 3 , 1 2 , 3 + Δ P loss C 3 , 1 3 , 31 Δ P LOSS C 5 , 1 = Δ P loss C 5 , 1 S , 1 + Δ P loss C 5 , 1 1 , 2 + Δ P loss C 5 , 1 2 , 3 + Δ P loss C 5 , 1 3 , 4 + Δ P loss C 5 , 1 4 , 5 + Δ P loss C 5 , 1 5 , 51
pf C 2 ≈ P t - Δ P LOSS C 2 ( P t - Δ P LOSS C 2 ) 2 + ( Q t - Δ Q LOSS C 2 - Q C 2 ) 2 , where Δ Q LOSS C 2 = Δ Q loss C 2 S , 1 + Δ Q loss C 2 1 , 2 .
Selection of the Operational Parameter to Optimize
The total load on a feeder 14 may vary over time, impacting the amount of real and reactive power drawn across the feeder 14. As more power is drawn by the loads 26 of the feeder 14, more power may be generated by various electrical generation facilities. The amount of power drawn by the loads 26 on the feeder 14 may vary predictably over time. One example of this variation appears in a plot 70 of FIG. 13, in which the power demand across a feeder 14 varies over the period of one day. In the plot 70, an ordinate 72 represents the total load demand in units of kW from the loads 26 on a feeder 14, and an abscissa 74 represents time in units of hours over a 24-hour period.
As can be seen in the plot 70, the total load demand by the loads 26 on a feeder 14 may be relatively low at certain parts of the day, namely at night, when residential and commercial loads are usually relatively low. These nighttime hours may be represented by time segments 0-t1 and t4-24. During these hours, substantially only baseload generation 76 facilities may be generating power. The cost of power generated using baseload generation 76 facilities may be relatively low (e.g., $0.05-$0.06/kWh), as baseload power generation 76 facilities provide some power at all times. At other times, such as between time segments t1-t2 and t3-t4, intermediate load generation 78 facilities may provide additional power in combination with the baseload generation 76 facilities. Intermediate load generation 78 facilities may be more costly to supply power than the baseload generation 76 facilities, but may be used less often. Finally, during relatively short periods of particularly high demand, the total load demand by the loads 26 of the feeder 14 may reach peak 80 levels. During the peak load generation 80, illustrated in FIG. 13 as occurring between time segments t2-t3, the baseload power generation 76 facilities, the intermediate power generation 78 facilities, and peak load generation 80 facilities may supply power. The cost of supplying additional power via the peak load generation 80 facilities may be quite high (e.g., $150/kWh). The peak load generation 80 conditions may last for a relatively short period of time, sometimes occurring only a few hours per year.
Because the quantity and quality of the loads 26 of the feeder 14 may vary over time, the supervisory station controller 38 may optimize different operational parameters of the feeder 14 as these power demand conditions change. For example, the supervisory station controller 38 may optimize the voltage output across the feeder 14 during peak load generation 80 conditions (e.g., between time segments t2-t3) using a “Voltage optimization function.” As will be discussed below, this voltage optimization function may involve both voltage flattening across the feeders 14 and a voltage reduction across the feeders 14, such that the voltage across the feeders 14 may be reduced while remaining within the prescribed minimum and maximum boundaries. In particular, on the consumer side, all loads 26 may be built to operate within a certain voltage range. For example, according to current standards, each phase voltage on the customer side should be within the range of 120V plus or minus 5% or, equivalently, 114V-126V. Many electrical devices may operate more efficiently and use less power at a lower voltage (assuming a constant impedance load, constant current load and so forth). In other words, during the peak load generation 80 hours (e.g., between times t2-t3), a lower voltage can result in significant demand reduction and energy conservation. Operating at a lower voltage may also extend appliance life. Examples of carrying out the voltage optimization function are described below.
During baseload generation 76 conditions (e.g., between time segments 0-t1 and t4-24 of the plot 70, and typically occurring at night), a reduction in voltage to force a reduction in demand may be less desirable than reducing active power losses. As such, during such a time when substantially only baseload 76 generation facilities are employed, the supervisory station controller 38 may undertake an “active power loss reduction function,” also referred to as a “VAR optimization function,” to optimize the active power losses of the feeders 14. The active power loss reduction function may considerably improve the efficiency of the feeders 14 of an electrical distribution system 10, since active power losses from generation to distribution to a customer can reach 75% or more. Specifically, because line active power losses depend on the resistance of the line and the magnitude of the current, reducing the current across the feeders 14 may lead to an overall active power loss reduction. The supervisory station controller 38 may carry out the active power loss reduction function, for example, as discussed below.
During intermediate load generation 78 conditions (e.g., between time segments t1-t2 and t3-t4) a combination of a reduction in voltage and a reduction in power losses throughout the feeders 14 may be warranted. Accordingly, during intermediate load generation 78 conditions, the supervisory station controller 38 may apply a “Volt/VAR optimization function” that balances these operational parameters. In particular, it is noted that voltage flattening and VAR optimization may be competing objectives. Achieving the lowest possible voltage profile with the smallest voltage deviation ΔV may come at the expense of higher active power losses. Likewise, achieving the smallest power losses may come at the expense of a greater voltage deviation ΔV across the feeders 14. As such, a balance between the voltage and VAR optimization according to the Volt-VAR function may attempt to balance these concerns during intermediate load generation 78 conditions. Examples of carrying out the Volt-VAR optimization function are discussed below.
If, at any time, the power factor of a feeder 14 is excessively undesirable (e.g., falling beneath some threshold), the supervisory station controller 38 may perform a “power factor optimization function” to improve the power factor. The supervisory station controller 38 may seek to optimize the power factor at the substation 12 and/or the feeders 14. Examples for carrying out the power factor optimization function are discussed below.
Before continuing further, various objective functions (i.e., operational parameter targets sought by the supervisory station controller 38) respectively associated with the voltage optimization function, the active power loss reduction function, the Volt-VAR optimization function, and the power factor optimization function are presented below.
Voltage Optimization Objective Function
As will be discussed below, the application platform for Volt/VAR optimization 18 may optimize the voltage across the feeders 14 first by flattening the voltage and then by reducing it. The application platform for Volt/VAR optimization 18 may attempt to flatten the voltage profile along the feeders 14 and enable the feeders 14 to use deeper voltage reduction modes by minimizing the voltage deviations ΔV according to the following objective:
Min Δ V subject to V min ≤ V j ≤ V max , j = 1 , … , N pf min ≤ pf ≤ pf max
In the equation above, ΔV is the difference between the maximum and the minimum voltage on the feeder 14, N is the total number of feeder 14 voltage measurement points, Vmin is the minimum allowable voltage on the feeder 14 (e.g., 120V−5%, or 114V), Vmax is the maximum allowable voltage on the feeder 14 as defined in the voltage flattening (VF) function (e.g., 120V+5%, or 126V), pf is the power factor measured at the head of the feeder 14, and pfmin and pfmax are its lower and upper permissible limits as desired. As will be described further below, the application platform for Volt/VAR optimization 18 may determine which capacitor 22 or combinations of capacitors 22 may satisfy the above relationship. Once the application platform for Volt/VAR optimization 18 has caused the voltage deviation ΔV across the feeders 14 to be reduced, the application platform for Volt/VAR optimization 18 may cause the source voltage VS at the outset of the feeders 14 to be reduced.
Active Power Loss Reduction Objective Function
The application platform for Volt/Var optimization 18 may optimize the active power losses across the feeders 14 using the active power loss reduction function. This active power loss reduction function may involve seeking the objective described by the following objective:
Max Δ P loss subject to V min ≤ V j ≤ V max , j = 1 , … , N pf min ≤ pf ≤ pf max
where is ΔPloss is active power loss reduction on the feeder 14, N is the total number of feeder 14 voltage measurement points, Vmin is the minimum allowable voltage on the feeder 14 (e.g., 120V−5%, or 114V), Vmax is the maximum allowable voltages on the feeder 14 as defined in the active power loss reduction function as desired (e.g., 120V+5%, or 126V), pf is the power factor measured at the head of the feeder 14, while pfmin and pfmax are its lower and upper permissible limits as desired.
Max Δ P loss and Min Δ V subject to V min ≤ V j ≤ V max , j = 1 , … , N pf min ≤ pf ≤ pf max
In the equation above, the objective is to simultaneously minimize voltage deviation ΔV on the feeder 14, and maximize active power loss reduction ΔPloss on the feeder 14. N is the total number of feeder 14 voltage measurement points, Vmin is the minimum allowable voltage on the feeder 14 (e.g., 120V−5%, or 114V), Vmax is the maximum allowable voltage on the feeder 14 as defined in the Volt-VAR optimization function (e.g., 120V+5%, or 126V), pf is the power factor measured at the head of the feeder 14, and pfmin and pfmax are lower and upper permissible limits for power factor as desired. Since Min ΔV and Max ΔPloss are two competing objectives, there will be no single optimal solution. Instead, the optimization will result in a number of solutions that represent trade-offs between the two objectives. Finding an appropriate trade-off between voltage deviation on the feeder ΔV and loss reduction ΔPloss will be described in greater detail below with reference to FIGS. 23 and 24.
Min  pf - pf des  subject to V min ≤ V j ≤ V max pf , j = 1 , … , N pf min ≤ pf ≤ pf max
Optimization Function for a Desired Operational Parameter
When a feeder 14 has a normal configuration (i.e., no anomalous conditions on the feeder 14 or restored feeder 14 segments feed from the normally configured source feeder 14), the application platform for Volt/Var optimization 18 may carry out an optimization function for a desired operational parameter, such as power factor optimization, active power loss reduction optimization, voltage optimization, and/or Volt/VAR optimization, in the manner represented by a flowchart 130 of FIG. 16. The flowchart 130 may begin as the application platform for Volt/Var optimization 18 starts the desired parameter optimization function (block 132). As such, the application platform for Volt/Var optimization 18 may obtain measurements 48, which may include LTC transformer 16, voltage regulator (VR) 28, and capacitor 22 status and voltage information directly from remote terminal units (RTUs), from a database 49 that contains such data, or from the field (block 134).
Having obtained the measurements 48, the application platform for Volt/Var optimization 18 may carry out a capacitor control function that optimizes the desired parameter (block 136). This capacitor control function will be discussed in greater detail below with reference to FIGS. 21 and 22 below. Essentially, the capacitor control function of block 136 may return a combination of capacitors 22 or a single capacitor 22 that, when switched on or off, may optimize the desired parameter of the feeder 14. As will be discussed below, the capacitor control function may involve simulating the feeder 14 in various configurations to determine a configuration that best matches the objective relationship presented above associated with optimizing the desired parameter.
If the capacitor control function block 136 outputs a capacitor-switching configuration that switches on or off at least one capacitor 22 in the feeder 14 (decision block 138), the application platform for Volt/Var optimization 18 may simulate the effects of these capacitor-switching configurations via distribution power flow simulations or by using the approximate equations. Thus, as will be discussed below, selecting from the next capacitor 22 that is available for switching in the capacitor-switching configuration (block 140), the application platform for Volt/Var optimization 18 may perform a first voltage regulator function (block 142). An example of such a first voltage regulator function 142 is discussed in greater detail below with reference to FIG. 25. Essentially, the first voltage regulator function of block 142 involves simulating the effect on the feeder 14 of switching on or off the selected capacitor 22 to ensure that no voltage violations are expected to result. If the first voltage regulator function of block 142 indicates that the selected capacitor 22 is expected to produce a voltage violation (decision block 144), it will calculate tap point and the application platform for Volt/Var optimization 18 may issue control signals 50 to the equipment of the feeder 14 to enact the determined configurations.
In particular, the application platform for Volt/Var optimization 18 may first move taps of voltage regulators (VRs) 28 to new positions, as may have been calculated during the first voltage regulator function (block 142), starting from the head of the feeder 14 (block 146). The application platform for Volt/Var optimization 18 may continue to move taps of the voltage regulators (VRs) 28 Tdr intervals, which may last, for example, approximately 10 s to 15 s. Next, the application platform for Volt/Var optimization 18 may cause the selected capacitor 22 to be switched on or off and may start a timer of duration Tc (block 148). The duration Tc represents a capacitor switching time delay, during which time the selected capacitor 22 will not be considered available for switching. In some embodiments, Tc may last at least 5 minutes. Additionally or alternatively, Tc may become progressively longer as the number of times the capacitor 22 has been switched increases. For example, once the capacitor 22 has been switched on or off five times in a particular 24-hour period, the time Tc may be set such that the capacitor 22 can no longer be switched for some extended duration (e.g., 24 more hours). The timer Tc may be a user-defined value. For instance, the there may be two timers that can be set from 0 s to any suitable desired value—a capacitor 22 may be allowed to be switched ON after a timer Tc expires and may be allowed to be switched OFF after another timer Td has expired.
To ensure that the simulations performed by the application platform for Volt/Var optimization 18 accurately predicted the effect of switching on the selected capacitor 22 on the voltage of the feeder 14, the application platform for Volt/Var optimization 18 next may run a violation check function (block 150). The violation check function may involve monitoring the actual measurements 48 of the feeder 14 following the changes in configuration of the equipment on the feeder 14, and taking corrective measures, if appropriate. An example of such a violation check function as carried out at block 150 is described in greater detail below with reference to FIG. 24. The violation check function of block 150 may be carried out until a time delay Td1 has passed, in which Tc>>Td1. After the time delay Td1, the active power loss reduction optimization function may start again, with the application platform for Volt/Var optimization 18 obtaining new measurements at block 174.
Returning to decision block 138, it should be appreciated that any time the list of available capacitors 22 from a capacitor-switching configuration of the capacitor control function of block 136 is empty, there are no capacitors 22 of the feeder 14 that can be switched on or off to optimize active power losses without causing a voltage violation (i.e., the capacitor list is empty). Under such conditions, the active power losses may be considered optimized and the application platform for Volt/Var optimization 18 may carry out a second voltage regulator function 154. The second voltage regulator function of block 154 may be used to flatten the overall voltage across the length of the feeder 14. An example of such a second voltage regulator function as carried out at block 154 is described in greater detail below with reference to FIG. 25. If the parameter being optimized is wholly or entirely voltage (e.g., the voltage optimization function or the Volt/VAR optimization function) (decision block 155), a voltage reduction function may be carried out (block 156). An example of the voltage reduction function as carried out in block 156 is described in greater detail below with reference to FIG. 28. The application platform for Volt/Var optimization 18 may thereafter continue to optimize active power loss reduction according to the flowchart 130.
Before continuing further, the effect of carrying out the second voltage regulator function of block 154 of FIG. 16 is briefly described with reference to FIG. 17. Specifically, FIG. 17 illustrates a plot 160, which includes an ordinate 162 representing the voltage across the length of a feeder 14, as depicted above the plot 160. The voltages are delineated as falling within 120V±5%, or 126V (line 164) and 114V (line 166). An abscissa 168 represents a length of the feeder 14. As shown in FIG. 17, the feeder 14 includes two voltage regulators (VRs) 28. A curve 172 represents the voltage across the feeder 14 before the second voltage regulator function of block 154 of FIG. 16 is carried out, and a curve 174 illustrates the voltage across the length of the feeder 14 afterward. Thus, the second voltage regulator function of block 154 causes the voltage regulators (VRs) 28 to generally output the same supply voltage VS as provided at the outset of the feeder 14 on their respective high side (HS) buses.
The active power loss reduction optimization function of FIG. 16 may also be employed to optimize active power losses of a normally configured feeder and a restored segment of a different feeder 14 that had been subject to a fault. For example, as shown in FIG. 18, a first feeder 14A having power supplied by a first substation 12A may supply power to a restored segment 180 of a second feeder 14B that is usually supplied by a substation 12B. As seen in FIG. 18, a breaker 24 adjoining the first feeder 14A and the restored segment 180 of the second feeder 14B is illustrated as closed. Thus, it may be understood that the first feeder 14A is supplying power to the restored segment 180 of the second feeder 14B in FIG. 15. The breaker 24 and switch 124 on the other side of the restored segment 180 of the second feeder 14B are depicted as being open. A first application platform for Volt/Var optimization 18A may be associated with the first feeder 14A, and a second application platform for Volt/Var optimization 18B may be associated with the second feeder 14B.
FIG. 19 represents the circuit of FIG. 18 in equivalent form. Namely, from the perspective of the first feeder 14A, restored segment 180 of the second feeder 14B may be seen as a load 27. From the perspective of the restored segment 180 of the second feeder 14B, disconnect switch 124A is a source point that is supplying power to the restored segment 180.
The equivalent circuit of FIG. 19 may form a basis upon which to simulate operational parameters of the feeders 14A and/or 14B for purposes of optimizing a desired parameter. Indeed, a flowchart 190 of FIG. 20 illustrates one manner in which the desired parameter may be optimized on both the first feeder 14A and the restored segment 180 of the second feeder 14B. The flowchart 190 of FIG. 17 may include two processes 192 and 194 that are respectively carried out by different application platforms for Volt/Var optimization 18. That is, the process 192 may be carried out by the first application platform for Volt/Var optimization 18A that is associated with the first feeder 14A, and the process 194 may be carried out by the second application platform for Volt/Var optimization 18B that is associated with the second feeder 14B. The processes 192 and 194 may respectively begin with blocks 196 and 198 as the two application platforms for Volt/Var optimization 18 carry out active power loss reduction optimization.
The first application platform for Volt/Var optimization 18A associated with the first feeder 14A may carry out a process 200 while the second application platform for Volt/Var optimization 18B associated with the second feeder 14B carries out a process 202. Specifically, the second application platform for Volt/Var optimization 18B may obtain measurements 48 pertaining to the equipment of the feeder 14B, including the restored segment 180. The application platform for Volt/Var optimization 18B may also set an indicator IN (block 206) (e.g., IN=0) to indicate that the active power loss reduction optimization function is being carried out on the feeder 14B (block 208). The active power loss reduction optimization function of block 208 may be substantially the same as discussed above with reference to flowchart 130 of FIG. 16. After the application platform for Volt/Var optimization 18B has completed the active power loss reduction optimization function of block 208, the application platform for Volt/Var optimization 18B may set the indicator IN to indicate that the active power loss reduction optimization is complete (block 210), (e.g., IN=1). Meanwhile, the application platform for Volt/Var optimization 18B may occasionally publish data 212 and 214 to the application platform for Volt/Var optimization 18A, representing a minimum voltage Vmin across the second feeder 14B and the indicator IN.
While the second application platform for Volt/Var optimization 18B is carrying out the active power loss reduction optimization function in process 202, the first application platform for Volt/Var optimization 18A may obtain measurements associated with the first feeder 14A (block 216) and carry out a violation check function (block 218) to ensure that the desired parameter optimization carried out by the second application platform for Volt/Var optimization 18B does not cause any voltage violations on the first feeder 14A. The violation check function of block 218 may be substantially the same as the violation check function of block 150 of FIG. 16, which is discussed in greater detail below with reference to FIG. 26. If the indicator 214 indicates that the second application platform for Volt/Var optimization 18A has not completed the desired parameter optimization function (decision block 220), the first application platform for Volt/Var optimization 18A may continue to receive new measurements 48 and run the violation check function 218. Otherwise, when the second application platform 18B has completed the desired parameter optimization function on the second feeder 14B, the processes 192 and 194 both may progress to respectively carry out processes 222 and 224.
Namely, the second application platform for Volt/Var optimization 18B may continue to provide the minimum voltage of the second feeder 14B, shown as data 226 while the first application platform for Volt/Var optimization 18A carries out the process 222. That is, the first application platform for Volt/Var optimization 18A may set an indicator IN (e.g., IN=0) (block 228) before carrying out the desired parameter optimization function on the first feeder 14A (block 230). When the desired parameter optimization function of block 230 has completed, the first application platform for Volt/Var optimization 18A may change the indicator IN to note that the desired parameter optimization function of block 230 has completed (e.g., IN=1) (block 232).
Meanwhile, in the process 224, the second application platform for Volt/Var optimization 18B may receive the indicator IN as data 234 published by the first application platform for Volt/Var optimization 18A. As long as the data 234 suggests that the first application platform for Volt/Var optimization 18A has not completed the desired parameter optimization function (e.g., IN=0) (decision block 236), the second application platform for Volt/Var optimization 18B may continue to wait (block 238). When the data 234 indicates that the first application platform for Volt/Var optimization 18A has completed the desired parameter optimization function (e.g., IN=1) (decision block 236), both the feeder 14A and the restored segment of the feeder 14B may be understood to be optimized for the desired parameter. The flowchart 190 of FIG. 20 may repeat as desired.
FIGS. 21 and 22 represent examples of methods for carrying out the capacitor control function for active power loss reduction of block 136 of FIG. 16. As mentioned above, carrying out the method of FIG. 20 may produce a list of capacitors 22 of a feeder 14 that, when switched on or off, are expected to optimize active power losses on the feeder 14. In particular, FIG. 21 represents a flowchart 240 that may begin when the application platform for Volt/Var optimization 18 simulates the taps of the voltage regulators (VRs) 28 of the feeder 14 as being in a neutral position (block 242). Under such conditions, the application platform for Volt/Var optimization 18 may run a distribution power flow simulation in the manner discussed above with reference to FIG. 31 (block 244). Using such a distribution power flow simulation, the application platform for Volt/Var optimization 18 may determine an initial voltage deviation ΔV0, representing a baseline voltage deviation that may be used for comparison purposes later (block 246).
Next, the application platform for Volt/Var optimization 18 may iteratively test various capacitor-switching configurations, each of which may include a particular combination of capacitors 22 of the feeder 14 switched on and/or off. Thus, the application platform for Volt/Var optimization 18 may set a loop variable i=1 (block 248) and simulate the effect of each ith of 2M capacitor-switching configurations of combinations of capacitors 22 (block 250), where M represents number of capacitors available for switching (note that the total number of capacitors on the circuit in N). In simulating the feeder 14 with each ith capacitor-switching configuration, the application platform for Volt/Var optimization 18 may determine the voltage deviation ΔV across the feeder 14, active power losses PLOSS, and the power factor pf of the feeder 14 (block 252). The application platform for Volt/Var optimization 18 may increment i (block 254) and, while i is not greater than the total number of capacitor-switching configurations (i.e., 2M) (decision block 256), the application platform for Volt/Var optimization 18 may continue to simulate the effect of various capacitor-switching configurations on the feeder 14. After the voltage deviation ΔV, active power losses PLOSS and power factors have been calculated for all of the capacitor-switching configurations, the application platform for Volt/Var optimization 18 may determine a non-dominated solution that optimizes the desired parameter (block 258).
A variation of the flowchart of FIG. 21 for determining a capacitor switching solution that optimizes the desired parameter appears as a flowchart 290 of FIG. 22. The flowchart 290 may take place in substantially the same manner as FIG. 21, with certain exceptions. In general, blocks 292-308 of FIG. 22 may take place in the same manner as blocks 242-258 of FIG. 21, except that blocks 300 and 306 of FIG. 22 are different from blocks 250 and 256 of FIG. 21. Specifically, in block 300 of the example of FIG. 22, the effect of a change in a single capacitor 22, rather than a combination of capacitors 22, may be determined Thus, as indicated by decision block 306 of FIG. 22, the number of tests may be reduced to M iterations rather than 2M iterations, where M represents the number of capacitors 22 that can be switched in the feeder 14 (note that N is the total number of the capacitors installed on the feeder).
A 3-D plot 260 shown in FIG. 23 represents various solutions for voltage deviation ΔV, power loss PLOSS, and power factor for various capacitor-switching configuration combinations, as generally may be determined in blocks 252 of the flowchart 240 of FIGS. 21 and 302 of the flowchart 290 of FIG. 22. In the 3-D plot 260, a first axis 262 represents power loss PLOSS, a second axis 264 represents voltage deviation ΔV, and a third axis 266 represents power factor. A 3-D solution space 268 represents a 3-D boundary, within which various solutions for capacitor-switching configurations may produce acceptable results. It should be appreciated that, from such a range of acceptable solutions as may be found within the 3-D solution space 268 a non-dominated solution may be determined that optimizes the desired parameter while other operational parameters of the feeder 14 remain as desirable as may be possible.
When the application platform for Volt/Var optimization 18 attempts to optimize both voltage deviation ΔV while also optimizing active power losses PLOSS to the greatest extent, which are in tension with one another, the application platform for Volt/Var optimization 18 may select a capacitor-switching configuration that offers the best voltage deviation ΔV in view of the active power loss PLOSS. For example, as shown by a plot 284 of FIG. 24, in which an ordinate 286 represents active power losses PLOSS, and an abscissa 288 represents a voltage deviation ΔV, and optimal non-dominated solution optimizing both voltage deviation ΔV and active power loss PLOSS may occur when a distance 289 from the origin to the solution reaches a minimum, as illustrated. This consideration may be made when carrying out a Volt/VAR optimization.
As described above with reference to FIG. 16, the application platform for Volt/Var optimization 18 may carry out a first voltage regulator function at block 142, a violation check function at block 150, and a second voltage regulator function at block 154. These functions will now be described in greater detail below.
One example of the first voltage regulator function that may be carried out at block 142 of FIG. 16 appears as a flowchart 350 in FIG. 25. To carry out the first voltage regulator function of block 142 of FIG. 16, the application platform for Volt/Var optimization 18 may begin the function (block 352), and set an indicator IN to a default value (e.g., IN=1) (block 354). The application platform for Volt/Var optimization 18 then may run a distribution power flow simulation of the feeder 14 that simulates when a particular capacitor 22 is switched on or off and simulating the voltage regulators (VRs) 28 at their current taps (block 356) or use approximate equations to estimate the new voltage profile. If a maximum voltage on the feeder 14 exceeds a desired value (e.g., Vmax>126V) (decision block 358), the voltage regulators (VRs) 28 may be adjusted to cause the maximum voltage to be reduced, if possible. In particular, the application platform for Volt/Var optimization 18 may iteratively adjust the voltage regulators (VRs) 28, starting with the first voltage regulator (VR) 28 that has a maximum voltage violation, starting from the head of the feeder 14 (block 360). The application platform for Volt/Var optimization 18 may calculate a different tap position for the first voltage regulator (VR) 28 such that the new voltage of the first voltage regulator (VR) 28 is less than the maximum allowable voltage Vmax (block 362).
A flowchart 390 of FIG. 26 represents an example of the violation check function of block 150 in FIG. 16, which represents a component of the active power loss reduction optimization function. Recalling that the violation check function of FIG. 26 may take place after a capacitor 22 has been switched at block 148 of FIG. 16, the violation check function of flowchart 390 may verify that no voltage violations have occurred after the capacitor 22 has been switched or, if a voltage violation has occurred occur, the violation check function of flowchart 390 may take corrective action to mitigate the violations. The flowchart 390 may begin when the application platform for Volt/Var optimization 18 starts to carry out the violation check function (block 392) and obtains a new set of measurements 48 of the feeder 14 (block 394). The new set of measurements 48 obtained by the application platform for Volt/Var optimization 18 at block 394 may be used by the application platform for Volt/Var optimization 18 to search for any voltage regulators (VRs) 28 that exhibit a maximum voltage or minimum voltage violation (block 396). If no voltage violation is found (decision block 398), the application platform for Volt/Var optimization 18 may end the violation check function (block 400).
In the event that switching the capacitor 22 at block 148 of FIG. 16, the flowchart 390 of FIG. 24 that represents an example of the block 150 of FIG. 16 may cause the application platform for Volt/Var optimization 18 to undertake corrective measures. If a maximum voltage violation has occurred (decision block 398), the application platform for Volt/Var optimization 18 first may identify the voltage regulator (VR) 28 nearest to the substation 12 exhibiting a maximum voltage violation (block 402). The application platform for Volt/Var optimization 18 may calculate a new, lower tap position associated with the voltage regulator (VR) 28 (block 404). If the calculated tap position is feasible (i.e., the calculated tap position is not lower than the minimum tap position available at the voltage regulator (VR) 28) (decision block 406), the application platform for Volt/Var optimization 18 may output a control signal 50 to cause the voltage regulator (VR) 28 to lower its tap to that calculated at block 404 (block 408). The application platform for Volt/Var optimization 18 then may continue to verify that no other voltage violations exist on the feeder 14, beginning again by obtaining a new set of measurements 48 (block 394). On the other hand, if the calculated tap position is not feasible (i.e., the calculated tap position is lower than a minimum available tap position of the voltage regulator (VR) 28) (decision block 406), the application platform for Volt/Var optimization 18 may output a controller signal 50 to turn off the largest capacitor 22 of the feeder 14 and/or furthest capacitor 22 from the substation 12 (block 410).
A flowchart 430 of FIG. 27 represents an example of the second voltage regulator function carried out by the application platform for Volt/Var optimization 18 at block 154 of FIG. 16. As discussed above, this second voltage regulator function may cause the voltage regulators (VRs) 28 across the feeder 14 to maintain, to a great extent, a low-side (LS) bus output that is equal to the source voltage VS. The flowchart 430 of FIG. 27, which represents an example of this second voltage regulator function, may begin when the application platform for Volt/Var optimization 18 starts the second voltage regulator function (block 432) and considers each voltage regulator (VR) 28 of the feeder 14 iteratively (block 434). In particular, the application platform for Volt/Var optimization 18 may begin with a first voltage regulator (VR) 28 (e.g., VRi), where initially i=1.
As noted above, when the optimization function of FIG. 16 is run to optimize the voltage of the feeder 14, the voltage across the feeder 14 may be reduced after it has been flattened via the voltage reduction function of block 156 of FIG. 16. A flowchart 470 of FIG. 28 represents one example of this voltage reduction function undertaken at block 156 of FIG. 16. The flowchart 470 of FIG. 28 may begin as the application platform for Volt/VAR optimization 18 starts the voltage reduction function (block 472), waiting until the application platform for Volt/VAR optimization 18 has performed the voltage flattening function as to all feeders associated with the substation 12 (block 474). Once the voltage flattening function applied across the feeders 14 have completed, the application platform for Volt/VAR optimization 18 may determine the maximum and minimum voltages of all the feeders using measurements 48 (block 476). If any of the maximum voltages of the feeders 14 exceeds a maximum acceptable voltage (decision block 478), the application platform for Volt/VAR optimization 18 may cause the LTC 16 to tap down (block 480), and may wait for the violation check function for all of the feeders 14 to complete (block 482). Otherwise, the application platform for Volt/VAR optimization 18 may determine whether the minimum voltage of any of the feeders 14 falls beneath a minimum acceptable voltage Vmin (decision block 484). If so, the application platform for Volt/VAR optimization 18 may cause the LTC 16 to tap up (block 486), before waiting for the violation check function for all of the feeders 14 to complete (block 482). Note that any successive tap changes should not exceed a predefined number of taps (e.g., 8 taps which is equivalent to 5% voltage change).
To optimize power factor at both the substation level 12 and the feeder levels 14, the application platform for Volt/Var optimization 18 may adjust substation 12 capacitor banks 22 after optimizing the power factor on the feeders 14. A flowchart 570 of FIG. 30 represents one such example of a method for improving power factor at the substation level 12. The flowchart 570 of FIG. 30 may begin when the application platform for Volt/Var optimization 18 obtains new measurements 48 (block 572). The application platform for Volt/Var optimization 18 may perform the power factor optimization function for each feeder 14, resulting in power factor on the feeder to be in the desired range without causing a voltage violation (block 574).
To ensure no new voltage violations have occurred, the application platform for Volt/Var optimization 18 may run the violation check function (e.g., as discussed above for each of the feeders 14 (block 592). The application platform for Volt/Var optimization 18 also may obtain new measurements 48 (block 594) and return to block 578.
Technical effects of the present disclosure include, among other things, improved voltage flattening and reduction, improved reduction in active power losses, and/or improved power factor on a segment of an electrical distribution system. These improvements may occur at opportune times most appropriate given the power generation constraints currently impacting the electrical distribution system. Thus, according to embodiments of the present disclosure, loads of an electrical distribution system may consume less power from the segment of the electrical distribution system when demand or generation costs are high. In some examples, the electrical distribution system may then reduce power losses when demand or generation costs are not excessively high. In addition, the control of a restored segment of an electrical distribution system can also be undertaken using the same control functions used to control a normally configured segment.
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Clasificación de EE.UU. 700/298, 700/297, 700/291, 700/295, 703/18, 700/286
Clasificación internacional G05D17/00, G05D5/00, G06G7/54, G05D3/12, G05D11/00, G05D9/00
Clasificación cooperativa H02J3/14, Y02B70/3225, Y04S20/222
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