Model predictive control with constant switching frequency for four-leg DSTATCOM using three-dimensional space vector modulation

In this study, model predictive control (MPC) with constant switching frequency is proposed for four-leg distribution static compensator (FL-DSTATCOM) to compensate the current related power quality issues. MPC techniques having many advantages compared to conventional pulse width modulation and hysteresis control techniques. In MPC, the future behaviour of the controlled variable is predicted using the model of the system and a cost function is formed using reference and predicted variable. MPC for DSTATCOM applications consider the difference between the reference and actual DSTATCOM current as a cost function and selects the switching state which minimises the cost function. However, while using MPC, the switches of DSTATCOM operate in variable switching frequency and sometimes the values are also very high. Due to this reason higher switching losses, unequal stress appear across the inverter switches and it also reduces the lifetime of the switch. Therefore, in this study, the concept of three-dimensional space vector modulation is adopted to achieve a constant and user-defined switching frequency MPC for FL-DSTATCOM to conquer the limitations of conventional variable switching frequency MPC. The validation of the proposed work is achieved using simulation and experimental studies.