TY - JOUR
T1 - Hybrid UP-PWM Scheme for HERIC Inverter to Improve Power Quality and Efficiency
AU - Tang, Zhongting
AU - Su, Mei
AU - Sun, Yao
AU - Cheng, Bin
AU - Yang, Yongheng
AU - Blaabjerg, Frede
AU - Wang, Lina
PY - 2019/5
Y1 - 2019/5
N2 - 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.
AB - 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.
KW - HERIC Inverter
KW - Pulse Width Modulation (PWM)
KW - Hybrid Unipolar PWM
KW - Reactive Power Capability
KW - Efficiency
KW - Zero-crossing Distortion
KW - Power Quality
KW - Photovoltaic Systems
UR - http://www.scopus.com/inward/record.url?scp=85050583159&partnerID=8YFLogxK
U2 - 10.1109/TPEL.2018.2858784
DO - 10.1109/TPEL.2018.2858784
M3 - Journal article
SN - 0885-8993
VL - 34
SP - 4292
EP - 4303
JO - I E E E Transactions on Power Electronics
JF - I E E E Transactions on Power Electronics
IS - 5
M1 - 8418796
ER -