Abstract
Distributed power inverters with inductive capacitive–inductive (LCL) filters have become popular in distributed power generation system. However, due to unknown grid impedance, the inverters are confronted with challenges of local filter resonance, poor power quality, and multiple interactive resonance. This paper proposes a low-loss active compensator that can counteract effects of the grid impedance on the current control performance of single-phase grid-connected inverter with an LCL filter. The compensator utilizes dual unit point-of-common-coupling voltage feedforward control mechanisms (VFFC), in which one is integrated with the inverter controller, and the other is generated through an extra low voltage source converter (LV-VSC) in series with the filter capacitor. The LV-VSC has no additional passive inductive-capacitive filtering elements and provides very low volt-ampere. To confirm its validity, a single-phase inverter testbed integrated with the compensator was built. The experimental results validate the current-controlled performance enhancement of the proposed inverter system operating under different grid conditions.
Highlights
Distributed renewable energy resources are commonly connected to the power grid through a current-controlled voltage source inverter (VSI) via an output power filter, such as inductive capacitive–inductive (LCL) filter [1,2]
At Lg = 0.04 pu (4 mH), the total harmonic distortion (THD) of grid current is sustained at THDi = 1.69%, which benefits from the unit PCC voltage feedforward control mechanisms (VFFC) and PR+HC current regulator
At L =0.04 pu (4 mH), the total harmonic distortion (THD) of grid current is sustained at THDi = 1.69%, which benefits from the unit PCC VFFC and
Summary
Distributed renewable energy resources are commonly connected to the power grid through a current-controlled voltage source inverter (VSI) via an output power filter, such as inductive capacitive–inductive (LCL) filter [1,2]. Due to the filter resonance, the grid current regulation of these VSIs faces a critical challenge of system stability To alleviate such concerns, the prior arts aimed to reshape the inverter equivalent output impedance by passive or active damping approaches. A well-known method is to utilize the PCC between inverters and thethe grid andand improve the feedforward control controlto toease easesuch suchdynamic dynamicinteraction interaction between inverters and grid improve power quality of the inverter. It has been the power quality of the inverter.
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