Modulation for the AVC-HERIC Inverter to Compensate for Deadtime and Minimum Pulsewidth Limitation Distortions

Abstract

With the superiority in leakage current suppression, the active voltage clamping highly efficient and reliable inverter concept (AVC-HERIC) has become a promising candidate in low-and medium-power PV systems. In addition, the high power density and low system costs have been attained in the AVC-HERIC due to the removal of the isolation transformers. However, to maintain high efficiency and good power quality under reactive power injection, prior-art modulation methods for the AVC-HERIC should be modified. In this paper, a simple modulation scheme is proposed for the AVC-HERIC, which ensures bidirectional current flow at any time. An improved modulation scheme is implemented according to the reference voltage polarity, and it is integrated into the proposed scheme to enable flexible reactive power injection. Moreover, the improved modulation scheme can maintain the same high efficiency as adopting the unipolar pulse width modulation (UP-PWM) strategy. More importantly, the deadtime and minimum pulse width limitation (MPWL) distortions are compensated effectively by the proposed modulation, leading to a good power quality. Simulations and experimental tests are performed on a 3-kW AVC-HERIC, and the results verify the effectiveness of the proposed modulation.

An Interlinking Converter for Renewable Energy Integration Into Hybrid Grids

“…5, all the full-bridge switches are used as a boost switch during the ST period, leading to lower switching losses of S 1-4 (i.e., the turn-ON losses of S 1-4 are eliminated in the DC-AC conversion) and lower conduction losses of S SR (i.e., the power diode in the twostage inverter). Therefore, the efficiency can become higher than the conventional two-stage inverter [14].…”

“…(2) During the period of m tri ∈ [0, 1 − d), the synchronous rectifier switch S SR is ON, and the HERIC adopts an improved modulation method in [14] to achieve a constant CMV (i.e., being half of V L ). In this case, S 1-6 operate following a sinusoidal pulse width modulation (PWM) scheme (i.e., by comparing m tri with |m AC |), as shown in Fig.…”

“…Since the proposed interlinking conversion architecture has no ST protection, deadtime should be added between the switching mode transitions. The deadtime insertion is the same as that in [14]. Nevertheless, according to the above, the DC gain can be obtained as…”

“…In addition, it employs a symmetrical impedance network that is beneficial to system efficiency, leakage current suppression and power density. A dedicated modulation scheme is exemplified, which can further improve the power quality and flexible control [14], while maintaining efficiency. Experimental tests in Section III have demonstrated the efficacy of the proposed interlinking converter.…”

Efficiency-Prioritized Droop Control Strategy of AC Microgrid

“…Operation efficiency is one of important concerns for power conversion system. The efforts toward efficiency improvement for individual inverter have been frequently performed in [5]- [12], where high-efficient modulation methods [5]- [8], topologies design and passive component optimization [9]- [12] are proposed. However, efficiency issue in microgrid with multiple paralleled inverters has been paid very limited concerns.…”