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Interleaving Impact on AC Passive Components of Paralleled Three-Phase Voltage-Source Converters

Year: 2008
Fig. 1. Definition of interleaving angle (κ).
Higher power density and lower weight is very attractive for applications seeking to minimize the weight and volume of power electronics systems. For three phase AC-DC converter, the AC passive components such as the boost inductor and EMI filter are one of the most bulky and heavy parts of the whole system. How to reduce the AC passive components is very important to increase power density and reduce weight of the whole system.

Interleaving, as a PWM technique used in parallel converter system, can help reduce output harmonic currents and voltages by phase shifting the real or equivalent carrier waveforms a certain angle (shown in Fig.1). As a result, interleaving has the potential to reduce the value of AC passive components of paralleled three-phase voltage-source converters (VSCs). However, how to maximize the benefit of interleaving is still not clear without an insightful understanding of the principle of interleaving.

A comprehensive study of the impact of interleaving on AC passive components is carried out in CPES. Based on the analysis, a topology with inter-phase inductor limiting circulating current is proposed shown in Fig.2. A physical design of the inductor for the system is done with optimized interleaving angle. The specifications of the system include: 10kW power, 230V rms AC voltage, 650 V DC voltage, 70 kHz switching frequency and DO 160E EMI standards. The design results confirmed that interleaving can reduce the weight of AC passive components. For this specific system, the total weight can be reduced to 60%. All key conclusions are verified by experimental results. The PWM waveforms and AC currents are shown in Fig. 3 for the cases without and with interleaving.

Fig. 2. Sample System under study.
Fig. 3. Experimental results without interleaving.
Fig. 4. Experimental results with interleaving.

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