EV charging station with cascaded low-pass filtering scheme-based control of unified power quality conditioner

摘要

This paper proposes a cascaded low-pass filter (CLPF) scheme for the control of a unified power quality conditioner (UPQC) installed for enhancing the power quality of an electric vehicle (EV) charging station. With the incorporation of UPQC, the EV charging station draws sinusoidal currents at unity power factor and the supply voltage is maintained at the nominal value at the charger input. In the CLPF scheme, the alpha-beta components of the load current are individually processed through a cascade connection of two LPFs to determine the corresponding fundamental orthogonal components. Based on thus determined components, the instantaneous and peak value and phase angle of the fundamental positive sequence component (FPSC) of the load current are computed. Similarly, the corresponding quantities related to the load and supply voltages are also computed with the CLPF scheme. With the computations related to the load current and supply voltage, the unit voltage templates (UVTs), power factor and fundamental active component (FAC) of the load current are calculated. For the control of shunt compensation, reference currents are generated based on the FAC of the load current and UVTs. Alternately, the control of series compensation is employed with the help of UVTs and peak amplitude of the FPSC of the load voltage. The performance of CLPF scheme-based extraction is compared with that of the earlier reported schemes through simulation and experimental studies. The performance comparison reveals a faster dynamic and more accurate steady-state response with the proposed scheme. The performance analysis of the proposed CLPF scheme-based control of a UPQC deployed at the EV charging station for different operating conditions demonstrates station operation with requisite reactive power compensation and mitigation of voltage sag/swell, and prevention of propagation of harmonic and unbalanced currents into the grid. This results in increased reliability of charger operation, energy savings and increased efficiency of the distribution network.