Compound Power Synchronization Control for Voltage Source Converters

As the most common interface between renewable energy and power grid (or load), it is important for Voltage Source Converters (VSCs) to keep close synchronization with connected system so that active and reactive power can be controlled independently under the dq frame. Traditionally, this synchronization is maintained through Phase Locked Loop (PLL) or interaction between active power and frequency. In this paper, a compound control approach for VSC synchronization is proposed where active and reactive power are combined in adaptive proportions. The dynamic coupling of active and reactive power is taken into consideration in this paper, thereby the tracking accuracy under power fluctuation is improved and additional synchronization unit could be ignored. Analytic models and experiment results are presented to validate the feasibility of the strategy.