Hybrid control approach of PV-Fed two-leg three-phase active power filter with harmonic compensation and reactive power injection

Power converter controllers are conventionally based on linearized averaged models, which have significant errors in capturing the large signal behavior of the system when there are wide changes in the input voltage, load, and reference voltages as happens in photovoltaic systems. The present paper proposes a hybrid approach for controlling a three-phase two-leg grid connected PV-fed reduced switch shunt active power filter. The control goal encompasses three aspects: (i) it is aimed to control the PV voltage so that to extract the maximum power available in the PV source regardless the weather conditions; (ii) the system should mitigate undesired harmonic currents generated by nonlinear loads and (iii) if desired the system must be able to inject additional reactive power into the grid in order to avoid a possible deterioration in grid stability, voltage drop and additional losses. The addressed control problem entails many complexities such as: the high dimension and strong nonlinearity of the system; The output voltage regulation should achieve a good precision in the case of a varying voltage reference at steady state and transient regime. To deal with the previous objectives, a cascaded two-loop controller is designed. The inner loop is formulated using a hybrid automaton approach to guarantee both harmonic compensation and reactive power injection. Meanwhile, the outer loop predominantly employs a proportional-integral regulator to ensure regulation of the PV voltage. Simulation results obtained using MATLAB/SimPowerSystems environment are presented to demonstrate the effectiveness of the approach in achieving the control objectives.