Integral voltage control of a distribution feeder to avoid voltage violations
A method for controlling voltage in a feeder of a distribution system having a plurality of DERs includes executing a feedback control using an integral controller. A voltage signal is generated using measured or estimated voltages at multiple locations along the feeder. An error is determined between the voltage signal and a defined voltage limit. The error is input to a controller including an integrator to generate a control action to counteract the error. The control action is distributed among at least some controllable DERs, from the plurality of DERs, that are capable of responding to the control action by generating actuation signals for absorbing reactive power from or injecting reactive power into the feeder, and/or for reducing active power or increasing active power in the feeder. The control action continues to increase until the voltage signal reaches the defined voltage limit, to thereby control voltage in the feeder.
1 . A method for controlling voltage in a feeder of a distribution system including a plurality of DERs by executing a feedback control, comprising:
generating a voltage signal using measured or estimated voltages at multiple locations along the feeder,
determining an error between the voltage signal and a defined voltage limit,
inputting the error to a controller comprising an integrator to generate a control action to counteract the error, and
distributing the control action among at least some controllable DERs, from the plurality of DERs, that are capable of responding to the control action by generating actuation signals for absorbing reactive power from or injecting reactive power into the feeder, and/or for reducing active power or increasing active power in the feeder,
wherein the control action continues to increase until the voltage signal reaches the defined voltage limit, to thereby control voltage in the feeder.
2 . The method according to claim 1 , wherein the voltage signal is a maximum measured or estimated voltage along the feeder, for overvoltage control, or a minimum measured or estimated voltage along the feeder, for undervoltage control.
3 . The method according to claim 1 , wherein the voltage signal includes a weighted sum of the measured or estimated voltages, wherein weights are defined based on the locations of the measured or estimated voltages.
4 . The method according to claim 1 , wherein the control action is distributed equally among the controllable DERs.
5 . The method according to claim 4 , wherein the control action is communicated to the controllable DERs by way of broadcasting.
6 . The method according to claim 1 , wherein the control action is distributed based on defined weights among the controllable DERs.
7 . The method according to claim 1 , wherein the response to the control action per controllable DER comprises initially responding in a first mode by generating actuation signals to absorb reactive power from or inject reactive power into the feeder until a defined reactive power limit of the DER is reached, and subsequently responding in a second mode by generating actuation signals to respectively reduce active power or increase active power in the feeder.
8 . The method according to claim 1 , wherein the response to the control action is determined locally at individual controllable DERs.
9 . The method according to claim 1 , wherein the response to the control action comprises implementing a decision to delay or prevent the start of a load process by one or more controllable DERs.
10 . The method according to claim 1 , wherein the controller is provided with output saturation at “0” and includes an anti-windup feedback loop that stops the integrator when the saturation is active, such that the controller outputs either only a positive control action or only a negative control action.
11 . The method according to claim 1 , comprising adjusting a gain of the integrator based on a learned sensitivity of the measured or estimated voltages along the feeder to the control action.
12 . The method according to claim 1 , comprising using separate controllers respectively for an overvoltage control based on a defined upper voltage limit and for an undervoltage control based on a defined lower voltage limit.
13 . The method according to claim 1 , comprising:
combining the control action with a further control action generated by a further controller based on an error between a power signal derived from measured or estimated active power at one or more critical assets of the distribution system and a defined power limit, to generate a combined control action, and
distributing the combined control action over the controllable DERs to generate actuation signals to control voltage and power along the feeder.
14 . A non-transitory computer-readable storage medium including instructions that, when processed by a computing system, configure the computing system to perform the method according to claim 1 .
15 . A computing system for voltage control in a distribution system, comprising:
one or more processors, and
memory storing instructions executable by the one or more processors to carry out a method according to claim 1 .