A Virtual Series Compensation Control of Virtual Synchronous Generator for Improving Energy Transmission Efficiency

Presently, the series-compensated capacitor is a common way to improve ac energy transmission efficiency. However, the series-compensated grid-connected system of virtual synchronous generator (VSG) is prone to cause impedance resonance, which can lead to sub-synchronous oscillation (SSO). First, the characteristics and mechanism of this SSO are revealed by the impedance method. With the series compensation level increase, the energy transmission efficiency increases, but the SSO risk increases too. To address this issue, a virtual series compensation control of VSG is proposed by analyzing the working mechanism of the series-compensated capacitor method. Meanwhile, the operating limits of the inverter with the proposed control are investigated. Compared with the series-compensated capacitor method, the proposed virtual series compensation control requires no additional hardware devices and has better stability. Finally, the proposed control and its corresponding theoretical analysis are verified by simulations and experiments.