Model Predictive Control of Four Level NNPC DSTATCOM for Power Quality Improvement in Distribution System

Two level Voltage Source Inverters (VSI) are the viable solution for Distribution Static Compensator (DSTATCOM) applications in secondary distribution system, where the voltage levels are either 415 V or 230 V. However, the limitations of two level VSIs in primary distribution system (3.3 kV - 33 kV) are the requirement of higher rating switches or series connection of lower rating switches, which motivates the replacement two level VSIs with multi-level inverters (MLI). Therefore, in this paper Model Predictive Control (MPC) of four level Nested Neutral Point Clamped (NNPC) MLI based DSTATCOM is proposed. In the proposed work cost function is framed as a combination of DSTATCOM currents and capacitor voltages which can compensate the current related power quality issues as well as eliminate the requirement of additional PI controllers for voltage regulation of flying capacitors. Weighting factors Tuning during multi constraint case is a tedious task. To overcome this limitation, a Multi-Criteria Decision Making (MCDM) method namely simple additive weighting method is used in the proposed work which reduces the difficulties in the weighting factor tuning. The performance of the proposed control algorithm is evaluated using simulation which shows the efficacy of the proposed control algorithm.