PV Charging Station with VSS-IMSAF and SOSMCC Disturbance Observer Based Controls to Enhance the Distribution Grid Capability

Abstract

This paper present a three-phase grid-tied (GT) charging station (CS) based on photovoltaic (PV) arrays. The purpose of the proposed CS is to support the distribution grid under heavy electric vehicles (EVs) loads with improved power quality. The variable step size improved multiband adaptive structured filter (VSS-IMSAF) technique is used to control voltage source converter (VSC). Due to the variable step size, the control regulates the grid currents and subjects to the proper step size selection to improve the performance of CS. Moreover, the charge/discharge operations of the electric vehicle battery (EVB) are also incorporated. For regulation of the DC bus voltage, second-order sliding mode cascaded control (SOSMCC) is used, which also controls the charge/discharge operations. The SOSMCC is equipped with the linear observer (LINO), second-order sliding mode observer (SOSMO), linear extended state observer (LESO), and nonlinear extended state observer (NESO), which reduce the overshoot, undershoot, and uncertainties in the voltage at DC link and EV battery current quickly and accurately. This charging station is also capable to operate under load unbalancing, unavailability and reduced insolation, and sudden change of the mode of operation (charging/discharging). The presented controls improve the performance of the CS and feed the reduced harmonic current to the grid under nonlinear load. The test results are presented using the OPAL-RT real-time simulator under various scenarios.