An Improved Sinusoidal (PWM) and Vector (SVPWM) Current Control for a Three-Phase Photovoltaic Inverter Connected to a Non-linear Load

Abstract

After improving the electrical performance of a single-phase photovoltaic inverter (previous article), this article aims to model the three-phase photovoltaic inverter of voltage connected to the grid, and the comparison of two improved methods of controlled of this inverter by the vector control PWM (SVPWM) and sinusoidal (SPWM) under non-linear load conditions (NLL). For this and after modeling the converter, we wish to apply the vector and sinusoidal control in order to minimize the losses of the current injected by this converter in the grid. After application of the Park transformations, the d-q components would not be time-invariant in situations where harmonics, resonances or unbalance is present. Control allows indirect control of the active and reactive powers injected into the grid. This strategy is based on decoupling the output currents of the inverter into active and reactive currents using the Park transformation. The PI controllers are implemented in the dq frame (synchronous reference frame SRF) to adjust the grid currents in the synchronous dq frame. To generate the reference current and maintain synchronism between the inverter and the grid, a Phase-locked loop technique (PLL) can be used. The main advantage and objective of this method is to effectively compensate the harmonic current content of the grid current without and with the use of compensation devices. The main objective is to address, in terms of cost, efficiency, power management and power quality, the problems found with Three-phase photovoltaic inverter connected to the grid controlled by SVPWM and SPWM, in order to compared the two methods and obtain a more reliable and flexible Three-phase inverter. The results of simulations of the new SPWM and SVPWM algorithm demonstrate its superior performance compared to the simple sinusoidal pulse width modulation which is previously used with single-phase photovoltaic inverters (previous article [1,2,3]). After comparing the results of the two methods vector and sinusoidal commands, we notice that the current THDi of the current for the vector control (SVPWM) is lower than that obtained with the sinusoidal command (SPWM). The effectiveness of these techniques proposed in this article is demonstrated by the simulation results using the MATLAB/ SIMULINK environment.