Interaction Between Coordinated and Droop Control PV Inverters

Abstract

Autonomous droop control PV inverters have improved voltage regulation compared to the inverters without grid support functions, but more flexible control techniques will be required as the number of solar photovoltaic (PV) installations increases. This paper studies three inverter future deployment scenarios with droop control inverters, non-exporting inverters, and coordinated inverter control (CIC). The network operation and the interaction between various inverter control methods are studied by simulating inverter operation on two low-voltage networks. Considering 30% PV penetration as the base case, we demonstrate that coordinated inverters can mitigate overvoltages and voltage fluctuations caused by the tripping of passive inverters in 85% of PV location cases when at least as many coordinated as passive inverters are deployed on the 114-node test feeder. However, this rate reduced to 37% with the IEEE 906-node network demonstrating that the deployment of coordinated inverter control may not be able to reverse passive inverter-related voltage disturbances when the build-up of passive inverters has reached a certain threshold.The aggregated PV output from coordinated inverters can be also used to provide grid support services. When the low-voltage networks operate close to the upper voltage limits, the change in the power output from coordinated inverters following a regulation request may be partially offset by passive inverters. Considering an equal number of passive and coordinated inverters, this paper shows that for each unit of the down-regulation request delivered by coordinated inverters, passive inverter output may increase by up to 0.2 units and decrease by up to 0.45 units during coordinated inverter up-regulation.

Support Matrix Regression for Learning Power Flow in Distribution Grid With Unobservability

“…Besides, many customers can own ancillary devices with active controllers to support reactive power for voltage regulation, but the dynamic model and control rules may be unavailable to the utility [2]. For example, the Volt/VAr droop control of a smart inverter follows a combined curve of several piece-wise linear sections [40], which is different from the function types in basic power flow model.…”

Adaptive coordination of sequential droop control for PV inverters to mitigate voltage rise in PV-Rich LV distribution networks

“…This power fluctuation can result in voltage oscillation in the network [2]. To damp the voltage oscillation, there are several techniques available in the literature, such as applying a low-pass filter represented by a continuous-time transfer function with a time constant for PV power output [2] and limiting the rate of changes of PV power outputs [41]. For this paper, the investigation of the voltage oscillation due to the interaction between PV droop controls is left for future researches.…”