A Seamless Transfer Control Strategy for Three-phase Grid-tied Inverters Switching Between Current Control Mode and VSG Mode

In the presence of ongoing renewable energy penetration, future grid-tied inverters should be able to operate in both grid-following and grid-forming modes to meet diverse grid conditions and operating requirements. This paper introduces a seamless transfer control strategy for three-phase grid-tied inverters to switch between the traditional phase-locked loop based current control mode (CCM) and the virtual synchronized generator (VSG) mode. The basic principle of seamless transfer between CCM and VSG mode is described and the detailed implementation methods are presented as well. The effectiveness of the proposed seamless transfer strategy applied in potential applications is validated by the simulation results.