Multifunctional Control Algorithm for VSC-Based Grid-Connected Microgrid for Compensation Operation Modes

In some configurations, microgrid is connected to an AC grid via voltage source converters (VSCs), supplying local non-linear loads (NLLs) of the microgrid connected to the output of the VSC. In such condition, the produced current distortions of the NLLs may flow through the AC grid due to low impedance. Hence, the microgrid should compensate the current distortions, which have been generated by the NLLs. On the other hand, when the AC grid has voltage harmonics, they amplify the produced distortions of the NLLs. To harness these distortions, this paper proposes a new multifunctional control method of the grid connecting microgrid VSC, which can decompose the current distortions into two components originated by the NLLs, and other one by the AC grid voltage harmonics. Then, VSC-based grid-connected microgrid can operate in two compensation modes. The first operation mode includes the compensation of distortions only with considering NLLs contribution. While in the second mode, VSC tries to compensate the distortions with considering contributions of both NLLs and AC grid voltage harmonics. In this mode, the proposed method is able to limit the total harmonic distortion level of AC grid side current in the standard limitation (less than 5%). The effectiveness of the proposed control method is studied using the simulations and experiments.