Design and HIL Validation of Van der Pol-based Virtual Oscillator Control for Two Parallel Inverters

Abstract

Islanded AC microgrids with parallel inverters require coordinated voltage formation and load sharing. This study presents a Van der Pol-based virtual oscillator controller for two parallel single-phase voltage-source inverters. The voltage reference of each inverter is generated from its local output-current measurement, and no communication channel is used between the two control units. The controller parameters are selected from the inverter power rating, nominal voltage and frequency, allowable frequency variation, transient requirement, and third-harmonic constraint. The proposed method is evaluated in a MATLAB/Simulink model and then executed on a TMS320F28379D DSP connected to a Typhoon HIL 402 real-time simulator. The test cases include resistive-load operation with equal 1:1 and unequal 1:2 current-sharing conditions, resistive load steps, and a nonlinear rectifier-load case. For the tested conditions, the inverter voltages settle near 220 V RMS, and the current waveforms follow the selected sharing settings in both the simulation and Controller-Hardware-in-the-Loop (CHIL) results. Under the nonlinear load, the inverter currents are distorted, whereas the inverter voltages remain synchronized and nearly sinusoidal. The results show that the controller can be implemented on the selected DSP-HIL platform for communication-free parallel-inverter operation.