Model-free Voltage Control for Inverter-based Energy Resources: Algorithm, Simulation and Field Test Verification

Dynamic voltage support is a type of critical ancillary service in electric power networks. With the increasing penetration of inverter-based renewable energy resources, utilizing their idle capacity to provide dynamic voltage support is becoming essential. However, the performance of traditional control methods is ofter limited due to the frequently changing operating point and network parameters, which are tuned only in a specific condition and suffer performance deterioration in others. This paper presents a model-free dynamic voltage control method for inverter-based energy resources to supply dynamic voltage support. This method can dynamically estimate the system with pseudo gradients, in which a continuous parameter function is proposed to adaptively approximate the optimal intermediate parameters. It guarantees the performance when the host system operating states vary without tuning the controller's parameters, while in comparison the PID controllers require the parameters being tuned repeatedly. Both numerical simulation and field tests demonstrate that the proposed method significantly outperforms the classic PI and adaptive PI controllers, especially in the case when the host system varies over time.