Multiple setpoint configuration in a voltage regulator controller

A voltage regulator controller including means for creating multiple regulator setpoint configurations. Configurations can be selected upon demand, by time/date activation, or by an external trigger source.

I. BACKGROUND OF THE INVENTION 
a. Field of the Invention 
This invention relates to voltage regulators and related control systems. 
b. Related Art 
A step type voltage regulator is a device which is used to maintain a 
relatively constant voltage level in a power distribution system. Without 
such a regulator, the voltage level of the power distribution system could 
fluctuate significantly and cause damage to electrically powered 
equipment. 
A step-type voltage regulator can be thought of as having two parts: a 
transformer assembly and a controller. A conventional step-type voltage 
regulator transformer assembly 102 and its associated controller 106 are 
shown in FIG. 1. The voltage regulator transformer assembly can be, for 
example, a Siemens JFR series. The windings and other internal components 
that form the transformer assembly 102 are mounted in an oil filled tank 
108. A tap changing mechanism (not shown) is commonly sealed in a separate 
chamber in the tank 108. 
The various electrical signals generated by the transformer are brought out 
to a terminal block 110 and external bushings S, SL, L for access. The 
terminal block is preferably covered with a waterproof housing. An 
indicator 112 is provided so that the position of the tap as well as its 
minimum and maximum positions can be readily determined. 
A cabinet 114 is secured to the tank to mount and protect the voltage 
regulator controller 106. The cabinet 114 includes a door (not shown) and 
is sealed in a manner sufficient to protect the voltage regulator 
controller 106 from the elements. Signals carried between the transformer 
or tap changing mechanism and the voltage regulator controller 106 are 
carried via an external conduit 116. 
The tap changing mechanism is controlled by the voltage regulator 
controller 106 based on the controller's program code and programmed 
configuration parameters. In operation, high voltage signals generated by 
the transformer assembly 102 are scaled down for reading by the controller 
106. These signals are used by the controller 106 to make tap change 
control decisions in accordance with the configuration parameters and to 
provide indications of various conditions to an operator. 
The regulator control configuration parameters are commonly referred to as 
"setpoints". These setpoints typically include forward and reverse 
settings for voltage level thresholds, bandwidth and time delay. The 
setpoints can also include settings for upper and lower voltage limit 
control. 
II. SUMMARY OF THE INVENTION 
In accordance with the present invention, a voltage regulator controller 
includes means for defining a plurality of independent sets of regulator 
control parameters and means for defining a condition under which each 
particular set of the regulator control parameters will be used to control 
operation of the voltage regulator. In a preferred embodiment, the control 
parameter set can be selected upon demand, by time/date activation, or by 
an external trigger source.

IV. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will now be described by reference 
to FIGS. 2 through 5. 
A step-type voltage regulator and its associated controller according to an 
embodiment of the present invention are shown in FIG. 3. The voltage 
regulator transformer assembly 302 can be, for example, a Siemens JFR 
series but in any event is of a conventional type which includes a 
multi-tap transformer 304 and an associated tap changer (tap changing 
mechanism) 306. The tap changer 306 is controlled by the voltage regulator 
controller 308 which receives signals indicative of voltage and current in 
the windings of the transformer 304 and conventionally generates tap 
control signals in accordance with operator programmed setpoints and 
thresholds for these signals. The voltage regulator 302 can also be 
provided with a non-volatile memory (personality module) 310 which stores 
statistics and historical information relating to the voltage regulator. 
The voltage regulator controller 308 includes a processor section 
(processor board) 312, a high voltage interface 314, a PCMCIA memory card 
interface 315 (for receiving a conventional PCMCIA standard memory card 
316), an I/O expansion chassis (rack) 317 which is coupled to the 
processor section 312 by way of a bus 318 and a front panel 320 which is 
coupled to the processor section. 
The front panel 320 provides an operator interface including a keypad 322, 
a character display 324, indicators 326 for various regulator conditions 
and a serial communications port (local port) connector 328. A user 
interface task (usint) 330 running under the processor sections main 
control program (mcp) 332 monitors activity on the keypad 322 and provides 
responses to the character display 324 as needed. The front panel 320, its 
associated operator interface and the user interface task 330 can be of 
the type described in U.S. patent application Ser. No. 07/950,402; filed 
on Sep. 23, 1992, which is incorporated by reference in its entirety as if 
printed in full below. 
Parametric data such as instantaneous values for the load voltage, load 
current, power factor, real power, reactive power, apparent power, source 
voltage and the instantaneous tap position; are monitored and updated 
periodically by a metering (mtr) task 333 running under the main control 
program 332. This parametric data is stored in a configuration and data 
memory 408 coupled to the processor section's microprocessor (uP) 334. In 
accordance with an embodiment of the present invention, the metering task 
333 also maintains in the data and configuration memory, separate tallies 
1-4 for forward lead Kilovolt-Ampere Reacted (KVAR) hours, forward lag 
KVAR hours, reverse lead KVAR hours and reverse lag KVAR hours. A separate 
KVAR hour total with a sign ("+" or "31") can also be determined from the 
separate tallies. The separate tallies 1-4 and the KVAR hour total (with 
sign) are accessible by a operator via the front panel display or the 
communications port. 
The processor section 312 generates digital control signals based on 
internal program code and operator selected parameters entered (by an 
operator) via the controllers front panel 320. The processor section 312 
is controlled by the microprocessor 334. An EEPROM 336 coupled to the up 
provides a non-volatile storage area for parametric data (including 
setpoints) and other working data. This data is downloaded to the 
configuration and data memory (which can be embodied as a static random 
access memory) by the microprocessor 334 when the processor section 312 is 
initialized. The SRAM copy is used, by the microprocessor, as the working 
copy of the configuration data. A real time clock (RTC) 337 provides the 
processor with data indicative of the time, date and day of the week. 
In operation, high voltage signals are generated by the voltage regulator 
transformer 304. These signals are scaled down via internal transformers 
(not shown) and provided to the high voltage interface 314. The high 
voltage interface 314, in turn, further scales the transformed down 
signals for reading by an analog to digital converter (shown in FIG. 4) 
within the processor section 312. The data fed back from the voltage 
regulator 302 is used by the processor section 312 to make tap change 
control decisions and to provide indication of various conditions to an 
operator. 
In accordance with an embodiment of the present invention, a setpoint 
control (spc) task 340 running under the main control program monitors 
operator selected operating conditions (setpoint modifying events) which, 
should they occur, cause the setpoint values to change. When the setpoint 
control task 340 detects the setpoint modifying events it causes the main 
control program to substitute one of a plurality of alternate groups of 
setpoint values for the currently used setpoint values. 
When the operator activates multiple setpoint control, the setpoint control 
task monitors controller activities and inputs for pre-defined setpoint 
modifying events. Depending on how the multiple setpoint control is 
configured, the spc task monitors one or more of the following activities: 
1) configuration changes that effect multiple setpoint control, 
2) the time and day of week, and 
3) external events which may be used to trigger the setpoint modifying 
algorithm to change the setpoints. 
In addition, other pre-defined setpoint modifying events can be identified. 
These can include pre-set values or ranges for metered parameters such as 
load voltage, source voltage, power factor, load current, and tap 
position. 
The operator enables multiple setpoint control by configuring the voltage 
regulator controller via the keypad 322 and the character display 324. The 
operator enters configuration data via the keypad 322 while viewing the 
configuration data on the character display 324. The user interface task 
330 monitors keypad activity and provides responses to the character 
display as needed. 
When the operator changes the configuration data (e.g., for the multiple 
setpoint control set-up), the user interface task 330 modifies the 
corresponding configuration data stored in the EEPROM 336. This revised 
configuration data is then accessible by the setpoint control task for 
determining which setpoint modifying events to monitor for changing the 
setpoint values. The setpoint group (SG) definitions and the corresponding 
setpoint modifying event (ME) definitions are copied into a table 342 in 
the configuration memory when the voltage regulator controller is 
initialized. The uP 334 (and the setpoint control task) then uses the 
configuration memory copy as the working copy. 
Similarly, the operator can enable multiple setpoint control by 
electronically configuring the voltage regulator controller via the 
communications port 328 or a communications port interface on the I/O 
Expansion Chassis 317. 
The operator sets the time and day of week for which new setpoint values 
are to be substituted. Several time/day-of-week values may be specified. 
For each time/day-of-week value entered, the operator also selects which 
group of setpoint parameters is to be substituted. Time and calendar dates 
can also be jointly used to specify the moment for changing the selected 
setpoint parameter group. Thus, the setpoint parameter substitutions can 
be repeated (by the controller) on the same date and time during 
subsequent years. 
Once the operator sets the time/day-of-week values for setpoint parameter 
substitutions, the setpoint modifying algorithm starts monitoring the real 
time and day-of-week using the real time clock 337. When the matching time 
and day-of-week occurs, the setpoint modifying algorithm causes the main 
control program to activate the new setpoint group specified in the 
multiple setpoint control configuration data. 
The specific setpoint modes are selected by way of the front panel using 
the keyboard and display. In accordance with an embodiment of the present 
invention, an operator selects configuration choices from a menu displayed 
on the front panel display. Specifically, the choices are: 
1. Multi-Setpoint Mode 
2. Local Setpoint Group Select 
3. Setpoint Group Definition 
4. Automatic Multi-Setpoint Control; 
5. Remote Multi-Setpoint Control. 
When "Multi-Setpoint Mode" is selected an option list is displayed which 
prompts the operator to select the operating mode of the multiple setpoint 
function from a number of displayed options. The options are: Off, Local, 
Automatic, and Automatic with Remote Override. When set to Off, single 
setpoint configuration (the default) is enabled. 
When "Local Setpoint Group Select" is selected the operator is prompted to 
select the active setpoint group for Local control. Choices are SG1-SGx. 
Local control can be used to quickly select one group of setpoints from a 
set of previously entered setpoint groups. 
When "Setpoint Group Definition" is selected the operator is prompted to 
define the SG parameters. A fixed number (x) SGs are allowed. (e.g. 6) 
The "Automatic Multi-Setpoint Control" option prompts the operator to enter 
one or more entries, each including a Day, Time and Setpoint Group. If the 
Multi-Setpoint Mode=Automatic, these settings enable programming of 
Multi-Setpoint control by time and day-of-week. A fixed number (x) of 
settings are allowed. (e.g. 6). 
When "Remote Multi-Setpoint Control" is selected the operator is prompted 
to specify an external trigger and a setpoint group. If Multi-Setpoint 
Mode=Auto with Remote Override, the regulator controller selects the 
specified setpoint group when the specified external trigger occurs. In 
this mode, if none of the operator specified signals are active, 
multi-setpoint control reverts to Automatic control (i.e., Time/Day based 
control). 
The setpoint control task 340 will now be described in more detail by 
reference to FIG. 2. 
In step 202, the setpoint control task monitors the configuration setting 
(stored in the controller's configuration memory) selected by an operator 
via the user interface task. In step 204 the setpoint control task 
examines the configuration setting to determine whether Multiple Setpoint 
Control Mode (MSCM) is ON. If Multiple Setpoint Control Mode is turned 
OFF, the multiple setpoint mode is not enabled and the setpoint control 
task remains dormant except for monitoring the configuration memory for 
Multiple Setpoint Control Mode to be turn ON. 
If, in step 204, the setpoint control task determines that MSCM is ON, in 
step 206 the setpoint control task determines whether MSCM is set to 
LOCAL. If yes, in step 208 the setpoint task gets the setpoint group 
number from the configuration parameter memory and informs the main 
control program of any changes in the setpoint group. If no, in step 210 
the setpoint control task determines whether MSCM is set for Auto with 
Remote Override. 
If Auto with Remote Override is not set, in step 212 the setpoint control 
task commences monitoring of the time and day of week and in step 214 
checks these against the multiple setpoint configuration parameters stored 
in the configuration memory 206. The time and day of the week can be 
determined by way of the real time clock 337 or by a time and day tracking 
mechanism internal to the processor. 
If, in step 214, the setpoint control task determines that the time and day 
of week match the configuration parameters, in step 216 the task signals 
the main control program to change to the new operator selected setpoint 
group (stored in the configuration memory) 
If Auto with Remote Override is set, in step 218 the setpoint task 
determines if any of the external setpoint control inputs defined in the 
configuration parameters are active. If no, the setpoint control task 
executes steps 212-216. If yes, in step 220 the setpoint control task 
determines the setpoint group to select based on the external control 
inputs and signals the main control program to change to the select 
setpoint group determined. 
An example of Auto with Remote Override setpoint group selection will now 
be described. Assume three external signals (A, B and C) are being 
monitored (for example three control signals generated by a remote 
computer). Also assume that the data shown in Table 1 has been stored in 
the configuration memory in response to an operator programming the 
controller. 
TABLE 1 
______________________________________ 
A B C Setpoint-Group 
______________________________________ 
0 0 1 SG1 
0 1 0 SG2 
0 1 1 SG3 
1 0 0 SG4 
1 0 1 SG5 
1 1 0 SG6 
1 1 1 SG7 
______________________________________ 
When Auto with Remote Override is set, the setpoint task will commence 
monitoring inputs A, B and C and select a setpoint group in accordance 
with Table 1. If, for example, only C is active (set to 1) setpoint group 
SG1 will be selected. If, for example, none of A, B or C are active (A=0, 
B=0 and C=0), the setpoint task will revert to Time/Day based control. 
As previously discussed, in contrast to conventional KVAR meters which 
accumulate and record the total KVAR hours (lead and lag) and do not keep 
separate tallies for forward and reverse KVAR hours, according to an 
embodiment of the present invention however, the voltage regulator 
controller maintains separate tallies for forward KVAR hours (lead), 
forward KVAR hours (lag), reverse KVAR hours (lead) and reverse KVAR hours 
(lag). A separate total with a sign (.+-.) can also be maintained. These 
totals are independently accessible by a user via the front panel display 
or a communications port. 
For power systems, the reactive component of the power represents losses in 
the system. Measuring this loss is a first step in helping to reduce it. 
Breaking the KVAR hour measurement into its constituent elements assures 
that, over time, the leading and lagging reactive energies accumulate 
rather than cancel each other out. Electric utilities can use the KVAR 
hour measurements to improve the design of their distribution systems. 
Power flow direction is determined by the sign of the real power (Watts.) 
When the real power is positive, the power flow direction is considered to 
be "Forward", while if the real power is negative, the power flow 
direction is "Reverse". In the voltage regulator controller of FIGS. 3 and 
4, the formulas for determining Watts, Reactive Power (VARs) and the Power 
Factor(PF) are shown below, where N is the number of samples taken per 
cycle and t is the total sampling time. 
##EQU1## 
The voltage-to-current phase angle is determined from the values of the 
real power (Watts) and the apparent power (VA). The apparent power, VA 
(Volt-Amperes), is the product of the Root-Mean-Square (RMS) Current and 
RMS voltage. From the phase angle, the quadrant of the voltage/current 
relationship can be determined as illustrated in FIG. 5. 
The direction of power flow in FIG. 5 is load referenced. That is to say 
that positive power flows into the load and negative power flows out of 
the load. FIG. 5 assumes that the voltage and current are sinusoidal, 50 
to 60 Hertz. In Quadrant I, Watts, VARs and the Power Factor (PF) are all 
positive. This condition is lagging and inductive (i.e. normal inductive 
load on the voltage regulator transformer 304). In Quadrant IV Watts are 
positive while VARs and the Power Factor are negative. This condition is 
leading and capacitive (i.e., normal capacitive load). In Quadrant II, 
Watts and the Power Factor are negative and VARs are positive. This 
condition is leading and capacitive (i.e. the load is a generator 
consuming VARs). In Quadrant III, Watts and VARs are negative and the 
Power Factor is positive. This condition is lagging and inductive (i.e. 
the load is a generator supplying VARs). For each of the quadrants, a 
separate location 1-4 is provided in the configuration and data memory to 
maintain the corresponding KVAR hour tallies). 
Typically, the reactive power runs in the 1000s to 100,000s, so it is 
represented as KVARs (Kilo-Volt-Ampere-Reactive). KVAR-Hours (KVARhr) are 
calculated by taking the product of the KVAR value and the time increment 
over which it is measured. For example, the KVARhr value can be updated 
once per second, using the formula: 
EQU KVARHRnew=KVARHRold+KVAR*1/3600 (hours) 
For each new KVARhr measurement, the regulator controller determines which 
of the four KVARhr memory locations 1-4 (referred to as "bins") to 
increment, based on the quadrant of the current/voltage phase angle. The 
bins for KVARhr parameters are accumulated as follows: 
______________________________________ 
Bin Parameter Quadrant 
______________________________________ 
1 Forward KVARhr lead 
IV 
2 Forward KVARhr lag I 
3 Reverse KVARhr lead 
II 
4 Reverse KVARhr lag III 
______________________________________ 
The present invention may be embodied as an improvement to the base 
circuitry and programming of an existing microprocessor based voltage 
regulator controllers. An example of a controller having suitable base 
circuitry and programming is the Siemens MJ-X voltage regulator 
controller, available from Siemens Energy and Automation, Inc. of Jackson, 
Miss., U.S.A. 
A more detailed block diagram of the processor section 312 and its 
interconnection to other elements of the voltage regulator controller is 
illustrated in FIG. 4. 
The processor section 312 includes the microprocessor 334 (for example, a 
Motorola 68HC16) which is coupled to the other processor elements by way 
of a common bus 404. An electrically erasable programmable read only 
memory (EEPROM) 406 includes the microprocessor's program instructions and 
default configuration data. The main control program, including the 
setpoint modifying software algorithm, reside in the EEPROM 406. The 
microprocessor 334 executes instructions from the EEPROM 406 to perform 
normal operations of the voltage regulator controller 308. 
A static type random access memory (SRAM) 408 stores operator programmed 
configuration data and includes areas for the microprocessor 334 to store 
working data and data logs. The working data includes parametric data such 
as load and source voltage, power factor, load current, tap position, etc. 
These parameters are updated periodically by the metering or other tasks 
running under the main control program. 
The microprocessor 334 also communicates with the alphanumeric character 
display 324, the keypad 322 and indicators 326 and the memory card 
interface 315 via the bus 404. 
The keypad 322 and indicators 326 are coupled to the bus 404 via a 
connector 414 and a bus interface 415. As previously described, a memory 
card 316 can be coupled to the bus 404 by way of a conventional PCMCIA 
standard interface 315 and connector 420. 
Operational parameters, setpoints and special functions including metered 
parameters, log enables, log configuration data and local operator 
interfacing are accessed via the keypad 322. The keypad is preferably of 
the membrane type however any suitable switching device can be used. The 
keypad provides single keystroke access to regularly used functions, plus 
quick access (via a menu arrangement) to all of the remaining functions. 
The microprocessor 334 includes an SCI port 334a which is connected to a 
communication port interface 422. The communication port interface 422 
provides the SCI signals to the external local port 338 on the 
controller's front panel 320. An isolated power supply for the 
communication port interface 422 is provided by the high voltage interface 
314 via a high voltage signal interface connector 426. 
The communication port interface 422 supports transfer of data in both 
directions, allowing the controller to be configured via a serial link, 
and also provides meter and status information to a connected device. In 
addition to supporting the configuration and data retrieval functions 
required for remote access, the communication port interface 422 supports 
uploading and/or downloading of the program code for the microprocessor 
334. 
The communication port interface 422 can be, for example, an RS-232 
compatible port. The local port connector 328 can be used for serial 
communication with other apparatus, for example a palmtop or other 
computer. The physical interface of the local port connectors 328 can be a 
conventional 9-pin D-type connector whose pin-out meets any suitable 
industry standard. 
The microprocessor 334 also includes an SPI port 334b which is connected to 
an expansion connector 428 by way of an SPI interface 430. The expansion 
connector brings the SPI bus 318 out to the I/O expansion chassis 317 via 
a cable. Other devices that reside on the SPI bus include the real time 
clock 337 and the serial EEPROM 336. The real time clock can be used to 
provide the time and date and data indicative of the passage of programmed 
time intervals. The serial EEPROM 336 stores operator programmed 
configuration data (including the setpoint configuration) and other 
working data. The operator programmed configuration data is downloaded to 
the SRAM 408 by the microprocessor 334 when the processor section 312 is 
initialized. The SRAM copy is used, by the microprocessor, as the working 
copy of the configuration data. The real time clock 337 is programmed and 
read by the microprocessor 334. 
The high voltage signal interface connector 426 provides a mating 
connection with a connector on the high voltage interface 314. Scaled 
analog signals from the high voltage interface 314 are provided to an A/D 
converter port 334c by way of an analog sense signal interface 436. The 
analog sense signal interface 436 low pass filters the scaled analog input 
signals prior to their provision to the A/D converter port 334c. Digital 
signals from the high voltage interface 314 are provided to the bus 404 
via a digital sense signal interface 438. The digital sense signal 
interface 438 provides the proper timing, control and electrical signal 
levels for the data. 
Control signals from the microprocessor's general I/O port 334d are 
provided to the high voltage signal interface connector 426 by way of a 
relay control signal interface 440. The relay control signal interface 
converts the voltage levels of the I/O control signals to those used by 
the high voltage interface 314. A speaker driver 442 is connected to the 
GPT port 334e of the microprocessor 334. The processor section 312 also 
includes a power supply 444 which provides regulated power to each of the 
circuit elements of the processor section 312 as needed. The high voltage 
interface 314 provides an unregulated power supply and the main 5 volt 
power supply for the processor section 312. 
The microprocessor 334 recognizes that a memory card 316 has been plugged 
into the memory card interface 315 by monitoring the bus 404 for a signal 
so indicating. In response, the microprocessor 334 reads operator selected 
control parameters entered via the controller's keypad 322. Depending on 
the control parameters, the microprocessor either updates the programming 
code in its configuration EEPROM 406, executes the code from the memory 
card 316 while it is present but does not update its EEPROM 406, or dumps 
selected status information to the memory card 316 so that it can be 
analyzed at a different location. As an alternative embodiment, the 
processor section 312 can be programmed to default to the memory card 
program when the presence of a memory card is detected. In this case, upon 
detection, the program code from the memory card would be downloaded to 
the SRAM 408 and executed by the microprocessor from there. 
The I/O expansion chassis (rack) 317 includes a number (e.g. 6) of 
connectors 450 for receiving field installable, plug-in I/O modules 452. 
The connectors 450 are electrically connected to the SPI bus 318 via a 
common processor section interface connector 454 and couple the I/O 
module(s) 452 (1), 452 (2) to the SPI bus 318 when they are plugged into 
the chassis. 
The processor section 312 can communicate with the personality module 310 
in a number of ways. For example, the microprocessor 334 can be provided 
with conventional RS-232 interface circuitry to the SCI bus. A 
conventional RS-232 cable can then be used to connect this RS-232 
interface to an RS-232 interface on the personality module. Alternatively, 
an I/O module (SPI BUS R/T) in the I/O expansion chassis can provide the 
physical and electrical interface between the SPI bus 318 and a cable 
connected to the personality module. An SPI R/T or other communications 
port can also be used to provide outside access to the controller's data 
logs and configuration parameters otherwise accessible on the front panel. 
For Multiple Setpoint control, the processor section receives discrete 
inputs for the Auto with Remote Override function by way of a Discrete 
Input Module 452 (2) plugged into the I/O Expansion Chassis 317. The 
Discrete Input Module is a parallel to serial converter that monitors the 
states of discrete signals a-d provided by one or more external sources 
and converts the state information into serial data for monitoring by the 
microprocessor 334 by way of the SPI bus 318. 
Now that the invention has been described by way of the preferred 
embodiment, various modifications, enhancements and improvements which do 
not depart from the scope and spirit of the invention will become apparent 
to those of skill in the art. Thus, it should be understood that the 
preferred embodiment has been provided by way of example and not by way of 
limitation. The scope of the invention is defined by the appended claims.