Performance Improvement for Reduction of Resonance in a Grid-Connected Inverter System Using an Improved DPWM Method

Abstract

This paper proposes discontinuous pulse width modulation (DPWM) for a grid-connected inverter system using an LCL-filter which consists of two inductors and a capacitor that is connected in parallel per phase. The modulation signal is discontinuously changed, and the harmonic voltages are generated in the wide frequency range at the output terminal of the inverter when the conventional DPWM is used. If these harmonic voltages are present in the resonance frequency band by an LCL-filter, then the resonance problem of the grid current occurs. To suppress the resonance problem, the proposed DPWM injects the sixth harmonic to the modulation signal. Therefore, in the improved DPWM, harmonic voltages at the output terminal of the inverter are sufficiently reduced because the discontinuous change of the modulation signal disappears. The proposed DPWM method is verified by a Powersim (PSIM) simulation (Powersim Inc., Rockville, MD, USA) and experiments with a 3-kW neutral-point clamped (NPC)-type grid-connected inverter system.

Resonance Suppression Method for Grid-Connected Converter With LCL Filter Under Discontinuous PWM

“…In [19] and [20], the resonance problem from DPWM was discussed through a frequency domain analysis. The loworder harmonics under a half of the switching frequency were triggered when the offset voltage is abruptly changed.…”

Design of Robust Higher-Order Repetitive Controller Using Phase Lead Compensator

“…The zero-phase tracking error compensator It is proved by simulations as well as validated experimentally that the disturbances are completely rejected by the proposed design. Repetitive controllers have been proposed in recent works [8]- [12], with many notable results on the area, they have improved results in terms of frequency changes in the exogenous signal but a computational burden.…”

Parallel Resonance Mechanism Analysis and Suppression of Inductance-Capacitance-Inductance Grid-Connected Inverters

“…In [13], the interaction under weak grid conditions was discussed, the concepts of interactive current and common current are proposed, and the stability of the system into interactive stability and common stability is also analyzed; discontinuous pulse width modulation (DPWM) for a grid-connected inverter system using an LCL-filter was proposed [14], and a virtual impedance-based bandwidth control method for multi-parallel harmonic-compensation grid-connected inverters is proposed [15]. On the basis of references [12][13][14][15], reference [16] revealed the resonance phenomenon caused by the interactive current, and analyzes the influence of the interactive resonance between inverters on the resonance and dynamic characteristics of the system. However, in [12][13][14][15][16] it was assumed that the parameters and control strategies of all grid-connected inverters are the same.…”

“…On the basis of references [12][13][14][15], reference [16] revealed the resonance phenomenon caused by the interactive current, and analyzes the influence of the interactive resonance between inverters on the resonance and dynamic characteristics of the system. However, in [12][13][14][15][16] it was assumed that the parameters and control strategies of all grid-connected inverters are the same. In practical applications, due to the difference of grid-connected capacity, output current and LCL filter parameters, the resonance frequency and the number of resonance peaks of grid-connected systems with multiple grid-connected inverters will be directly affected, which makes it difficult to analyze the resonance characteristics of parallel systems with multiple inverters.…”