Abstract
In this paper, a new three-phase grid-connected inverter system is proposed. The proposed system includes two inverters. The main inverter, which operates at a low switching frequency, transfers active power to the grid. The auxiliary inverter processes a very low power to compensate for the grid current ripple. Thus, no active power is processed by the auxiliary inverter. The goal is to produce a grid current with a low total harmonic distortion (THD) and to obtain the highest efficiency from the inverter system. The main inverter is controlled via a space-vector pulse-width modulation owing to its optimum switching pattern, and the auxiliary inverter is controlled via a hysteresis current-control technique owing to the technique’s fast dynamic response. The proposed system is analyzed in terms of different DC-link voltage, switching frequency, and filter inductance values. The optimum system parameters are selected that provide a THD value of less than 5%. A prototype inverter system at a 10-kW output power has been implemented. The main inverter operates at a 3-kHz switching frequency, and the auxiliary inverter compensates for the grid-current ripple. In total, a THD of 4.33% and an efficiency of 97.86% are obtained using the proposed inverter system prototype.
Highlights
The energy obtained from alternative energy sources is transferred to power grids through inverters
No active power is processed by the auxiliary inverter, and the current is lower compared with the main inverter
The auxiliary inverter is controlled via the hysteresis current control (HCC)
Summary
The energy obtained from alternative energy sources is transferred to power grids through inverters. The widely used synchronization technique, which has synchronous rotating frame phase-locked loops (SRF-PLLs), has been utilized It has good performance when the grid voltage is balanced and not polluted by harmonics. The main inverter operates at low switching frequency and transfers active power to the grid, while the auxiliary inverter compensates for the grid-current ripple. The main purpose of utilizing the auxiliary inverter that is different from the active filter is an increased system efficiency compared to a single sixswitch three-phase inverter with an L filter. The proposed system is modelled in MATLAB and analyzed in terms of the DC-link voltage, switching frequency, and filter inductance values for a 10-kW output power. The main inverter and auxiliary inverter are controlled via the dSPACE real-time controller and analogue controller, respectively
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