Distributed reactive power control in power distribution systems

A monitoring controller for monitoring a voltage violation on a monitored bus of a power distribution system, comprising:

• a sensor for measuring a voltage at the monitored bus;
• a memory for storing at least one threshold for values of the voltage and for storing equivalent impedances of a path of the power distribution system between a substation transformer and the monitored bus;
• a processor for determining a shift of phase angle on the path, for comparing the measured voltage with at least one threshold to determine the voltage violation, and for determining, upon detecting the voltage violation, a set of phase current adjustments required to compensate the voltage violation on the monitored bus, and determining an amount of reactive power required to generate the determined phase current adjustments required to compensate the voltage violation on the monitored bus using the equivalent impedances and the shift of phase angle;
• a transmitter for transmitting a request to provide the amount of reactive power into the power distribution system to compensate the voltage violation, such that the power distribution system requests from at least one distributed energy resource (DER) the amount of the requested reactive power;
• one or more DER controller operatively connected to the at least one DER for controlling an amount of the generated reactive power, such that there a plurality of DER units for the at least one DER to share generating reactive power, wherein each DER unit is controlled by a DER unit controller, wherein there are a plurality of DER unit controllers;
• and
• a preselected leading DER unit controller is preselected from the plurality of DER unit controllers of the DER and receives commands from the DER controller.

A method for regulating voltages of a power distribution system including a substation transformer for providing power to loads through a set of buses connected by line segments, wherein the power distribution system includes at least one distributed energy resource (DER) for generating reactive power into the power distribution system, at least one DER controller operatively connected to the DER for controlling an amount of the generated reactive power, a plurality of DER units for each DER to share generating reactive power and each DER unit is controlled by a DER unit controller, and a monitoring controller located in a region of the DER for monitoring a voltage violation on at least one phase of a monitored bus, the method comprising:

• determining, using a processor of the monitoring controller upon detecting the voltage violation, a set of phase current adjustments required to compensate the voltage violation on the monitored bus using equivalent impedances of a path of the power distribution system between the substation transformer and the monitored bus and a shift of phase angle on the path;
• determining, by the processor of the monitoring controller, an amount of reactive power required to generate the determined phase current adjustments required to compensate the voltage violation on the monitored bus;
• transmitting a request to the DER controller connected to the monitored bus to provide the determined reactive power to compensate the voltage violation;
• determining, by the DER controller in communication with neighboring DER controllers, an amount of reactive power for the DER to be controlled by the DER controller, wherein the amount of required reactive power for the DER is initialized with a summation of average reactive powers requests received from a cluster of monitored buses that are communicatively connected to the DER controller, and reactive power requests received from a set of DER controllers that are communicatively connected to the DER controllers;
• transmitting a request by the DER controller, to a preselected leading DER unit controller, such that the preselected leading DER unit controller is preselected from the plurality of DER unit controllers of the DER and receives commands from the DER controller, wherein the preselected leading DER unit controller is in communication with neighboring DER unit controllers to reach consensus on a sharing portion of determined reactive powers for each DER unit according to that DER unit capacity;
• and
• controlling the DER unit by the DER unit controller to generate the determined sharing portion of reactive power.