Hybrid UP-PWM Scheme for HERIC Inverter to Improve Power Quality and Efficiency

Zhongting Tang, Mei Su, Yao Sun, Bin Cheng, Yongheng Yang, Frede Blaabjerg, Lina Wang

Research output: Contribution to journalJournal articleResearchpeer-review

11 Citations (Scopus)
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The Highly Efficient and Reliable Inverter Concept (HERIC) inverter is a cost-effective topology, which has low leakage currents and a relatively high efficiency. Thus, it is very suitable for transformerless PV systems. However, with the reported modulation methods, it is difficult to simultaneously maintain the high efficiency, good power quality, and reactive power injection of the HERIC inverter. In this paper, a hybrid unipolar pulse width modulation (UP-PWM) scheme is thus proposed to achieve those performances. The hybrid scheme adopts the conventional UP-PWM in the case of generating the positive power. When generating the negative power, a modulation scheme, which only requires the operation of freewheeling switches, is specifically proposed. Additionally, in the region of the output voltage and current zero-crossing points (ZCP), an UP-PWM with modified dead time is introduced. In order to validate the effectiveness of the proposed scheme, simulations and experiments are performed on a 4-kW HERIC inverter system with a 20-kHz switching frequency. The results demonstrate that the proposed hybrid UP-PWM method achieves a better performance in terms of reactive power injection than the conventional UP-PWM scheme, and a higher efficiency than the UP-PWM with dead time. In addition, the proposed UP-PWM scheme also enables a better power quality.
Original languageEnglish
Article number8418796
JournalI E E E Transactions on Power Electronics
Issue number5
Pages (from-to)4292-4303
Number of pages12
Publication statusPublished - May 2019


  • HERIC Inverter
  • Pulse Width Modulation (PWM)
  • Hybrid Unipolar PWM
  • Reactive Power Capability
  • Efficiency
  • Zero-crossing Distortion
  • Power Quality
  • Photovoltaic Systems

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