Transactions of China Electrotechnical Society  2023, Vol. 38 Issue (16): 4366-4375    DOI: 10.19595/j.cnki.1000-6753.tces.221038
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A Modulation Strategy for Simultaneously Reducing High-Frequency Common-Mode Voltage of Indirect Matrix Converter
Lu Zijing1,2, Li Shanhu1,2, Cao Sunpeng1,2, Liu Xu1,2, Sun Qingguo1,2
1. State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin 300130 China;
2. Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei Province Hebei University of Technology Tianjin 300130 China

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Abstract  An indirect matrix converter (IMC) is a new generation of AC-AC converter with broad application prospects in ships, aerospace, and wind power. IMC is composed of a rectifier and an inverter stage. Affected by the pulse width modulation (PWM), a high-frequency and high-amplitude common mode voltage (CMV) will be generated at the output during IMC operation. The CMV will damage the insulation layer of the motor winding, increase the mechanical wear of the bearing and shorten the service life of the motor. Therefore, the CMV must be suppressed. Most of the CMV suppression strategies focus on reducing the peak value. The high-frequency CMV amplitude is inhibited by adding active or passive filters to the CMV path, which not only increases the mention and cost of the system but also reduces the compactness of the IMC. Based on the amplitude and positive/negative characteristics of CMV for IMC under the action of each active vector, this paper proposes a new modulation strategy to reduce the high-frequency CMV of IMC significantly. This method significantly reduces the high-frequency CMV amplitude by decreasing the positive and negative transition times and amplitude change range of the CMV in a carrier cycle.
Firstly, the rectifier and inverter stages are both divided into six sectors. The positive/negative characteristics of the CMV under the action of each active vector in each input sector are analyzed. Secondly, use active vectors that keep the direction of the CMV unchanged within an input sector for modulation. The rectifier stage selects two adjacent active current vectors in each input sector to synthesize the reference input current vector. The inverter stage selects active voltage vectors V2, V4, V6 in input sectors 1, 3, 5 and selects V1, V3, V5 in input sectors 2, 4, 6 to synthesize the reference output voltage vector. Thirdly, according to the three-phase output current direction of each inverter stage sector and the freewheeling characteristics of the freewheeling switching diodes, the switching sequence of the inverter stage active voltage vectors is arranged rationally to eliminate the CMV spikes caused by the dead zone effect. Fourthly, the traditional space vector modulation (SVM) method and two classical CMV suppression modulation strategies of IMC are selected to compare with the proposed method from the time and frequency domains. The time domain compares the CMV waveforms within one input sector and the switching sequences within one switching cycle. The CMV amplitude at n fc ( fc is the switching frequency of the IMC) is affected by the number of amplitude changes and the magnitude of the change in a switching cycle. The high-frequency amplitude of CMV for the other three strategies is larger than the proposed method because the direction of the three methods is constantly changing in an input sector. The frequency domain compares the CMV spectrum obtained by the triple Fourier transform of these four methods under the voltage transfer ratio (VTR) of 0.1~0.5. The CMV amplitude decreases under a specific VTR or frequency band, but it is still high in other cases. The CMV amplitude of the new method does not exceed 5% of the traditional SVM method in each high-frequency band and is almost unaffected by the VTR. Finally, simulations and experiments are carried out on the above four methods. The simulation and experiments confirm that the proposed strategy can suppress the CMV by 42.3% compared with the traditional method and greatly reduce the CMV amplitude of each high-frequency band.
Key wordsIndirect matrix converter (IMC)      high-frequency common-mode voltage      positive and negative characteristics      modulation strategy     
Received: 02 June 2022     
PACS: TM46  
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Lu Zijing
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Lu Zijing,Li Shanhu,Cao Sunpeng等. A Modulation Strategy for Simultaneously Reducing High-Frequency Common-Mode Voltage of Indirect Matrix Converter[J]. Transactions of China Electrotechnical Society, 2023, 38(16): 4366-4375.
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https://dgjsxb.ces-transaction.com/EN/10.19595/j.cnki.1000-6753.tces.221038     OR     https://dgjsxb.ces-transaction.com/EN/Y2023/V38/I16/4366
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