Control of Three-Phase Buck-Type Dynamic Capacitor Using the Model Predictive Control Method for Dynamic Compensation of the Reactive Power and Load Current Harmonics

Dynamic capacitor (DCAP), as a shunt power quality device, corrects the power factor of the load and reduces the total harmonic distortion (THD) of the source current. A novel control method was presented based on the model predictive control (MPC) to control a three-phase three-wire buck-type DCAP. The injected current of DCAP is the control variable, which must be controlled by two power electronic switches of DCAP. MPC controller minimized the absolute value of the difference between a reference current and a DCAP current in the prediction horizon. The reference current consisted of two distinct parts, i.e., reactive power compensator (RPC), and harmonic current eliminator (HCE), based on the fundamental component of the load current. Also, a prediction model (PM) was proposed to calculate state variables of the DCAP based on their previous values, state of the switches, and prediction values of the grid voltage. The proposed PM was extracted from the linearized differential equations of the DCAP. All DCAP components, such as capacitors and inductors of the inner and outer filters, were modeled in the proposed PM. Unlike the PI controller, the proposed MPC has fewer control parameters and can use in extensive operational conditions. The simulation results in MATLAB software showed the superiority of the proposed method compared with the even harmonic modulation (EHM) method on a three-phase DCAP.