A Novel Frequency-changer Control Strategy Based on a Virtual Synchronous Motor

The use of frequency-changers is widespread in daily electric power generation. If a frequency-changer could automatically adjust its power output according to the load status and power network operation, it would have a positive impact on power system stability. To achieve this a novel control strategy based on virtual synchronous motors (VSM) is proposed in this paper. The frequency-changer consists of two main parts: the rectifier and the inverter. In the rectifier part, a UDC-Q control strategy is adopted to control the DC-link voltage and the reactive power. In the inverter part, a VSM control strategy is used; it includes a power-frequency controller and an excitation controller, and can change the inverter's output frequency and voltage with the variation of load, can adjust the active power with change of the power system frequency. The proposed control strategy is simulated using Simulink/Matlab. The simulation results show that the proposed control strategy can follow the mechanical inertia and electrical characteristics of the synchronous moto and can effectively improve the system power quality and system stability.