Generalised average modelling of grid‐connected three‐phase VSC with closed‐loop vector control and regular‐sampled modulation

Abstract

Based on the generalised averaging method, a comprehensive mathematical model for a three-phase grid-connected voltage source converter (VSC) with closed-loop vector control and symmetrical regular-sampled modulation is proposed here. The double Fourier series of switching functions is presented to construct the state average vectors in this model. To involve the conventional vector current control strategy, the coordinate transformation method of the state average vector is derived. The multiplication properties are also illustrated to calculate the product average vector for state variables. The proposed model is validated in both MATLAB simulations and hardware experiments. The results show that both the fundamental and the switching behaviours of the converter as well as the closed-loop dynamics of the controller can be accurately demonstrated by the derived model with fast simulation speed. The steady-state harmonic distribution can also be directly achieved by computing the equilibrium point of the system. The proposed model is appropriate for system-level studies of power electronic-based power systems and can provide a beneficial reference for the practical design and the performance assessment of the closed-loop VSC system, which indicates the broad prospect of the application of generalised average models in power system and power electronics fields.