Harmonic Analysis and Mitigation of Low-Frequency Switching Voltage Source Inverter With Auxiliary VSI

Abstract

The output currents of high-power Voltage Source Inverters (VSIs) are distorted by the switching harmonics and the background harmonics in the grid voltage. This paper presents an active harmonic filtering scheme for high-power, low-frequency switching VSIs with an additional auxiliary VSI. In the approach, the auxiliary low-power, high-frequency switching VSI is used to compensate both the switching harmonics of the high-power VSI and the low-order harmonics introduced by the distorted grid voltage. Impedance modeling and analysis are implemented for the hybrid VSI system, where the impacts of the grid impedance are analyzed. Different control targets are then formulated based on the analysis, and the corresponding control strategies are proposed. Lastly, simulations and experimental results are provided to validate the theoretical analysis and the performance of the proposed control strategy.

Harmonic Analysis of Single-Phase Neutral-Point-Clamped Cascaded Inverter in Advanced Traction Power Supply System Based on the Big Triangular Carrier Equivalence Method

“…Nevertheless, this is typically inaccurate for non-integer ratios of the carrier and modulating signal frequencies [11]. A 3-D Fourier integral has been proposed in [12][13][14] for output to input voltage ratio limited to 0.5, but the construction of 3-D unit cell and mentions the limits of the Fourier integral for higher ratios are unclear. Ref.…”

“…The simulation results of an eight modules cascaded inverter with carrier phase shifted phase opposition disposition SPWM is shown in Figure 8. According to Equations (10) and (13), with different values of m and n, the ratio of i-th harmonic amplitude to fundamental amplitude can be calculated, which is represented as HRUi. When output waveforms are of 5-level, 9-level and 13-level, HRUi of first, third and fifth harmonics in side-frequency band of characteristic harmonic are counted in Table 4.…”

Control Scheme and Performance Analysis of Dual-Frequency Single-Phase Grid-Connected Inverter Interfaced With Weak and Distorted Grids

“…Therefore, it is not trivial to design the LCL filter at a low switching frequency [30]. The current control bandwidth of the inverter is also limited by the low resonant frequency of the LCL filter [32], [33], which reduces the ability to suppress the influence of the grid background harmonics [5], [6]. In addition, for LCLtype inverter with low switching frequency, the low resonant frequency of the LCL filter can reduce the performance of frequency-selective current control scheme proposed in [34].…”

“…The switching ripple caused by the power inverter is eliminated by the auxiliary converter which operates at high switching frequency (60 kHz). Like the active trap filter [36], [37], the current of the auxiliary converter is much smaller than the rated current, so its loss is also much smaller than the rated power of the inverter [17], [32], [35], [38]− [40].…”

Analysis and design of L + LCL‐filtered dual‐frequency single‐phase grid‐connected inverter

“…However, the impedance shaping ATF technology is sensitive to the background harmonics of the grid voltage and cannot compensate for the low‐order harmonics caused by the grid. Therefore, additional APF technology is also required to suppress the low‐order harmonics [25].…”