Voltage regulator control system with multiple control programs

A voltage regulator controller is provided with multiple control programs. At any given time, one of the control programs is selected to be "active" depending on the existing operating conditions. An operator (user) configures the voltage regulator control to change its active control program based on a number of factors, which can include, for example, demand metering values, the time and/or date, external inputs such as the measured transformer oil temperature, commands received via a serial communications port and fault/maintenance status. In a preferred embodiment, the configuration settings for activation are handled in accordance with a priority scheme when more than one of the conditions occur simultaneously.

BACKGROUND OF THE INVENTION 
This invention relates to voltage regulators and related control systems. 
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, which is covered with a waterproof housing, and 
external bushings S, SL, L for access. 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. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a voltage regulator controller is 
provided with multiple control programs. At any given time, one of the 
control programs is selected to be "active" depending on the existing 
operating conditions. An operator (user) configures the voltage regulator 
control to change its active control program based on a number of factors, 
which can include, for example, demand metering values, the time and/or 
date, external inputs such as the measured transformer oil temperature, 
commands received via a serial communications port and fault/maintenance 
status. 
In a preferred embodiment, the configuration settings for activation are 
handled in accordance with a priority scheme when more than one of the 
conditions occur simultaneously.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will now be described by reference 
to FIGS. 2 through 8. 
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 set-points 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 connector 328. A user interface task 
(usint) 330 running under the processor section's 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. 
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 a microprocessor (.mu.P) 334. The microprocessor 334 is 
coupled to a serial electrically erasable read only programmable memory 
(EEPROM) 336 which stores the operations count and operator programmed 
configuration data including "control program selection parameters". 
In operation, high voltage signals are generated by the voltage regulator 
transformer 304. 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. 
The processor board monitors tap changes by sensing an "Operations Counter" 
signal from the transformer assembly 304. The Operations Counter signal is 
generated by an electronic switch 338 (FIG. 5) located on the tap changer 
mechanism 306. Each time the tap position changes, the switch is toggled 
from one position to the other. If the switch is open before the tap 
change, it closes as the tap change occurs; and vice-versa. 
In accordance with the present invention, the processor section stores a 
plurality of tap control programs A-E in its non-volatile memory as well 
as a default control program. At any given time, only one of the tap 
control programs is active (i.e. controls changes in the tap position). 
Which control program is active depends on how the regulator's operating 
conditions compare to the operator programmed selection parameters. 
Another program task, the "switching task" 340 periodically (e.g. once a 
second) monitors the regulator's operating conditions and causes the mcp 
to activate (use as the sole executing tap control program) the 
appropriate control program (A-E or default) for the set of conditions 
that is occurring at the monitoring time. 
Examples of the stimuli (particular operating conditions) that can be 
monitored is shown in Table 1. For each stimuli, a different tap control 
program operating in accordance with a different control algorithm is 
selected as being "active". When more than one of the stimuli occurs 
simultaneously, the active tap control program is chosen in accordance 
with a priority scheme as shown in table 1, where 1 is the highest 
priority and 5 is the lowest priority. 
TABLE 1 
______________________________________ 
ACTIVE CONTROL 
STIMULUS PRIORITY PROGRAM 
______________________________________ 
Demand/ 2 A 
Metering Values 
Time/Date 5 B 
External Input 
3 C 
Serial Port Command 
4 D 
Fault/Maintenance 
1 E 
Status 
______________________________________ 
When the operator selects multiple control mode (by way of the from panel 
and keypad) the processor section displays a list of operator selectable 
stimuli (such as shown in FIG. 1) on the display. For each of the stimuli 
selected, the operator is first prompted to identify the particular 
control program which will be associated with occurrence of the stimuli. 
Once the control program is identified, the operator is presented with a 
submenu of configuration settings. Optionally, the operator can also be 
prompted to select the priority for the selected stimuli although in the 
presently described embodiment the stimuli are assigned preprogrammed 
priorities. 
Those of skill in the art will recognize that the multiple tap position 
control algorithms need not be implemented by completely independent 
program tasks. As an alternative, programs A-E can modify the operation of 
the default control task by, for example, setting bits in a control 
register which cause the default task to behave differently. In such an 
embodiment, what the operator is actually specifying is an active control 
algorithm which is implemented by a combination of the default control 
program and control program parameters set by way of executing programs 
A-E. In any event, it should be understood that a change in the selection 
of a control program A-E represents a change in the algorithm that 
controls the positioning of regulator tap. 
When the operator selects Demand/Metering Values, a menu of selectable 
metered parameters is displayed and the operator is prompted to select one 
of metered parameters to control the activation of program A. For example 
the operator can select from metered parameters including KVAR demand, 
Power Factor, Load Current and any other parameters monitored by the 
metering task. Once a metered parameter is selected, the operator is 
prompted to enter a range which will activate the corresponding control 
program. For example, where a power factor is selected, the operator also 
selects a power factor range (a high threshold and a low threshold) during 
which program A is invoked by the switching task. 
When the operator selects Time/Date, a prompt is displayed requesting the 
operator to specify a starting and ending time and date or a periodic 
interval over which program C is to be activated. 
When the operator selects external input, a menu of external inputs is 
displayed and the operator is prompted to select one or more which will 
trigger program C. These can include, for example, analog and discrete 
external inputs brought in through the I/O expansion chassis and external 
trigger sources. 
When the operator selects serial port, the mcp commences monitoring of the 
serial port 328 for algorithm switching commands received by way of the 
port's serial communication lines. 
When Fault/Maintenance Status is selected, a menu of diagnostic test 
results and maintenance status is displayed and the operator is prompted 
to select one which will cause the control program to change. Preferably, 
the control algorithm associated with program E will be of a type that 
minimizes tap control activities until the fault/maintenance issue had 
been resolved. 
It should be understood that the active program could also be selected upon 
a combination of conditions. For example, the Demand/Metering Values can 
be enabled to change the control tasks only when the Time/Data settings 
are within a selected range. 
A flow chart of the switching task is shown in FIG. 6. The configuration 
settings are periodically monitored by the main control program in step 
602. 
In step 604 the switching task determines if multiple control algorithm 
(MCA) mode is "OFF". If MCA mode is "OFF" in step 605 the switching task 
selects the default tap control algorithm. If MCA mode is "ON" the 
switching task proceeds to test the particular control mode settings (in 
priority order) to determine which settings are selected. 
In step 606 the switching task determines whether Fault/Maintenance mode 
has been selected. If yes, in step 607 the switching task compares the 
present fault/maintenance state with the operator selected state and 
switches the tap control program to task E if they match. Otherwise the 
control program remains as currently selected. 
If Fault/Maintenance mode has not been selected, in step 608 the switching 
task determines whether Demand/Metering mode has been selected. If yes, in 
step 609 the switching task compares the selected metered values with the 
operator selected submenu ranges and, if the metered values are in range, 
the switching task informs the mcp to change the tap control program to 
task A. Otherwise, the control program remains as currently selected. 
If Demand/Metering has not been selected, in step 610 the switching task 
determines whether External Input mode has been selected. If yes, in step 
611 the switching task compares the present state of the external inputs 
with the operator selected external input states and switches the tap 
control program to task C if they match. Otherwise, the control program 
remains as currently selected. 
If External Input mode has not been selected, in step 612 the switching 
task determines whether Serial Port mode has been selected. If yes, in 
step 613 the switching task checks for algorithm switching commands 
received via the serial communication(s) port(s) and switches the tap 
control program to task D if the serial port switching command has been 
received. Otherwise, the control program remains as currently selected. 
If Serial Port mode has not been selected, in step 614 the switching task 
determines whether Time/Date mode has been selected. If yes, in step 615 
the switching task compares the present time and date with the pre-set 
time and date or periodic interval. If the time/date is in the user 
selected range, the switching task informs the mcp to change the tap 
control program to task B. Otherwise, the control program remains as 
currently selected. 
An example of the external input algorithm operating mode is oil 
temperature variamp (OTV). A flow chart of the operation of this mode is 
shown in FIG. 2. When Oil Temperature Variamp mode is selected the 
processor section monitors the oil temperature by way of a transducer 350 
disposed inside the oil within the transformer assembly 302. If External 
Input-OTV mode has been selected, in step 202 the switching task reads the 
oil temperature measured by the temperature transducer 350. In step 204 
the oil temperature is compared against a first temperature threshold T3. 
If the oil temperature exceeds the first temperature threshold (e.g. 115 
degrees Centigrade) in step 206 switching task compares the present tap 
position with a new tap position excursion range to be used when T3 has 
been exceeded (this range is referred to hereinafter as the "T3 range"). 
In the present embodiment, this range is one-quarter the full tap 
excursion range. If the tap position is not within T3 new range, in step 
208 the processor section moves the tap position into range and then, in 
step 210, the switching task activates a first tap position control 
program which causes the regulator to run towards the neutral position 
(raise or lower direction) to below one-third the full range. If the 
present tap position is in the T3 range, step 210 is executed directly 
following step 206. The maximum range of the tap position excursions 
remains one-quarters of the full range until such time as the oil 
temperature drops below T3--10 degrees C. 
If the oil temperature does not exceed the first temperature threshold, in 
step 212 the switching task compares the oil temperature to a second, 
lower, temperature threshold. If the oil temperature exceeds the second 
threshold (e.g. 105 degrees Centigrade), in step 214 switching task 
compares the present tap position with the new tap position excursion 
range to be used when T2 (but not T3) has been exceeded (this range is 
referred to hereinafter as the "T2 range"). In the present embodiment, 
this range is one-half of the full tap excursion range. If the tap 
position is not within the T2 range, in step 216 the processor section 
moves the tap position into the T2 range and then, in step 218, the 
switching task activates a second tap position control program which 
causes the regulator to run towards the neutral position (raise or lower 
direction) to below one-half of the full range. If the present tap 
position is in the T2 range, step 218 is executed directly following step 
214. The maximum range of the tap position excursions remains one-half of 
the full range until such time as the oil temperature reaches the first 
threshold T3 or drops below T2--10 degrees C. 
If the oil temperature does not exceed the first or second temperature 
thresholds (T3, T2), in step 220 the switching task compares the oil 
temperature to a third, lower, temperature threshold T1. If the oil 
temperature exceeds the third threshold (e.g. 90 degrees Centigrade), in 
step 222 switching task compares the present tap position with the new tap 
position excursion range to be used when T1 (but not T2) has been exceeded 
(this range is referred to hereinafter as the "T1 range"). In the present 
embodiment, this range is three quarters the full tap excursion range. If 
the tap position is not within the T1 range, in step 224 the processor 
section moves the tap position into the T1 range and then, in step 226, 
the switching task activates a third tap position control program which 
causes the regulator to run towards the neutral position (raise or lower 
direction) to below three-quarters of the full range. If the present tap 
position is within the T1 range, step 226 is executed directly following 
step 222. The maximum range of the tap position excursions remains 
three-quarters of the full range until such time as the oil temperature 
reaches the second threshold T2 or drops below T1--10 degrees C. 
For example, assume settings are: T1=90.degree. C., T2=105.degree. C. and 
T3=115.degree. C.; The current tap position is at 16 raise; and the oil 
temperature sensor indicates a 90.degree. C. reading. The external 
Input-OTV algorithm responds by forcing tap lower operations until the tap 
position is below 12 raise. The algorithm then limits the tap position to 
between 12 lower and 12 raise. Subsequently, the oil temperature sensor 
reads 105.degree. C. or higher. External Input-OTV algorithm responds by 
forcing tap lower operations until the tap position is below 8 raise. The 
algorithm then limits the tap position to between 8 lower and 8 raise. 
Note that if the third temperature threshold were exceeded, the External 
Input-OTV algorithm would force limiting of the tap position range to 
between 4 raise and 4 lower. 
The thresholds T1, T2, T3 are operator programmable and default to preset 
limits (e.g. 90.degree. C., 105.degree. C. and 115.degree. C. 
respectively) in the absence of operator programmed thresholds. 
The tap changing mechanism, transformer and switch are shown in more detail 
in FIG. 5. The components of FIG. 5 are part of a conventional voltage 
regulator transformer assembly and thus, most will not be described in 
detail here. The tap changing mechanism 306 is operated by a stepper motor 
502 which is in turn operated by way of raise (J) and lower (K) control 
signals. The operations counter switch 338 is operated by a cam 504 which 
rotates half a turn each time a tap change is made. One side of the switch 
338 is connected to AC return ("E" ground). The Operations Counter signal 
that is input to the controller is thus alternately (1) open circuit (2) 
closed to ground, each time a tap change occurs. 
The present invention may be embodied as an improvement to the base 
circuitry and programming of an existing microprocessor based voltage 
regulator controller. 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., USA. 
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. 
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 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 328 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 a 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 a real time 
clock 432 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, the look-up tables 336a, 336b and the operations 
count. 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 432 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 (including scaled 
versions of I, Vin and Vout) are provided to an A/D converter port 34c 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 506, 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 to the SPI bus 318 when they are plugged into the chassis. 
The processor section 312 can communicate with the personality module 310 
by way of an I/O module (SPI BUS R/T) in the I/O expansion chassis. 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. The external stimuli and serial 
port commands used to change the tap control algorithm can also be input 
to the processor board by way of I/O modules (e.g. a serial communications 
controller for the serial communications commands or a digital and/or 
analog input module for the external stimuli). 
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.