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The control of inverters with output LC filter has a special importance in applications where a high quality voltage is needed. However, the controller design becomes more difficult. A model predictive control (MPC) is used for voltage control of a three-phase inverter with output LC filter. The controller uses a model of the system to predict the behaviour of the variables for a given voltage vector sequence until a certain horizon of time, then a cost function is used as a criterion for selecting the switching state that will be applied during the next sampling interval. This paper presents the effect of considering different number of prediction steps in terms of THD and the number of cycles or the settling time to reach steady state operation. The simulation results for MPC with only one prediction step and the improved MPC with two prediction steps are presented and compared, under linear and nonlinear loads, using MATLAB/Simulink tools. The simulation results show that the improved MPC improves the THD for nonlinear loads and make it constant for different resistive loads. Moreover, the settling time can be considered constant for various linear and nonlinear loads.

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Grid-connected photovoltaic (PV) systems are now a common part of the modern power network. A recent development in the topology of these systems is the use of transformerless inverters. Although they are compact, cheap, and efficient, transformerless inverters suffer from chronic leakage current. Various researches have been directed toward evolving their performance and diminishing leakage current. This paper introduces the application of a model predictive control (MPC) algorithm to govern and improve the performance of a grid-tied neutral-point-clamped (NPC) 3-φ transformerless inverter powered by a PV panel. The transformerless inverter was linked to the grid via an inductor/capacitor (LC) filter. The filter elements, as well as the internal impedance of the grid, were considered in the system model. The discrete model of the proposed system was determined, and the algorithm of the MPC controller was established. Matlab’s simulations for the proposed system, controlled by the MPC and the ordinary proportional–integral (PI) current controller with sinusoidal pulse width modulation (SPWM), were carried out. The simulation results showed that the MPC controller had the best performance for earth leakage current, total harmonic distortion (THD), and the grid current spectrum. Also, the efficiency of the system using the MPC was improved compared to that using a PI current controller with SPW modulation.

This paper presents a method for the performance improvement of a shunt active power filter (SAPF) using the indirect current control (ICC) scheme. Compared to the conventional direct current control (DCC) scheme, the ICC gives better performance with a lower number of sensors. A simplified and efficient control algorithm using a low cost Intel 80C196KC microcontroller is implemented using only two current sensors for the source current and one voltage sensor for the DC-link voltage of the SAPF circuit. The objective is to eliminate harmonics and to compensate the reactive power produced by non-linear loads such as an uncontrolled rectifier feeding an inductive load. The APF is realized using a three phase voltage source inverter (VSI) with a dc bus capacitor. Experimental results are presented to prove the better performance of the ICC method over the DCC one.