B2B-VSC 3-phase 4-leg output voltage stabilization in stand-alone microgrid

The article describes the structure of a mathematical model of an automatic control system (ACS) of a 2-level 4-wire voltage source inverter (VSI) as part of a back-to-back voltage source converter (B2B-VSC). The main task of the control is to maintain the set voltage at the output filter. Note that the power part of the VSI is made according to a four-wire circuit with eight transistors connected to the LC output filter. The VSI control system is represented in a Cartesian coordinate system d-q with an orientation along the vector of the output voltage, the position of which is set by the ACS. The control system consists of a channel for regulating the output current and VSI voltage. The proposed model allows to provide the required voltage on the load when working in an autonomous network. The installation of such a B2B-VSC will eliminate the dependence of the load voltage on the frequency of rotation of the generator and ensure the operation of the drive mechanism in optimal mode. In addition, the influence of the zero conductor reactor parameters on the duration of transients of the zero component and the overall effect on the total harmonic distortion coefficient (THD) of the current is considered.