DC-Link Current Harmonic Mitigation via Phase-Shifting of Carrier Waves in Paralleled Inverter Systems

Silpa Baburajan, Haoran Wang, Dinesh Kumar, Qian Wang and Frede Blaabjerg
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Silpa Baburajan: Department of Energy and Technology, Aalborg University, 9220 Aalborg, Denmark
Haoran Wang: Department of Energy and Technology, Aalborg University, 9220 Aalborg, Denmark
Dinesh Kumar: Global Research and Development Centre, Danfoss Drives A/S, 6300 Gråsten, Denmark
Qian Wang: Department of Energy and Technology, Aalborg University, 9220 Aalborg, Denmark
Frede Blaabjerg: Department of Energy and Technology, Aalborg University, 9220 Aalborg, Denmark

Energies, 2021, vol. 14, issue 14, 1-17

Abstract: DC-connected parallel inverter systems are gaining popularity in industrial applications. However, such parallel systems generate excess current ripple (harmonics) at the DC-link due to harmonic interactions between the inverters in addition to the harmonics from the PWM switching. These DC-link harmonics cause the failure of fragile components such as DC-link capacitors. This paper proposes an interleaving scheme to minimize the current harmonics induced in the DC-link of such a system. First, the optimal phase-shift angle for the carrier signal is investigated using the analytical equations, which provides maximum capacitor current ripple cancellation (i.e., at the main switching frequency harmonic component). These optimally phase-shifted switching cycles lead to variations of the output current ripples, which, when summed together at the DC-link, result in the cancellations of the DC-link current ripples. The results show that when the carrier waves of the two inverters are phase-shifted by a 90° angle, the maximum high-frequency harmonic ripple cancellation occurs, which reduces the overall root-mean-square (RMS) value of the DC-capacitor current by almost 50%. The outcome of this proposed solution is a cost-effective DC-harmonics mitigating strategy for the industrial designers to practically configure multi-inverter systems, even when most of the drives are not operating at rated power levels. The experimental and simulation results presented in this paper verify the effectiveness of the proposed carrier-based phase-shifting scheme for two different configurations of common DC connected multi-converter systems.

Keywords: DC-link current; harmonic mitigation; voltage source inverters; multi-converter systems; carrier wave interleaving scheme; DC-grid; phase-shifting; capacitor current ripple; unipolar sinusoidal pulse width modulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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