Frequency Synchronization of Three-Phase Grid-Connected Inverters Controlled as Current Supplies

Zhenbin Fu; Zhihua Feng; Xi Chen; Xinxin Zheng; Jing Yin

Frequency Synchronization of Three-Phase Grid-Connected Inverters Controlled as Current Supplies

Vol. 18, No. 5, pp. 1347-1356, Sep. 2018

10.6113/JPE.2018.18.5.1347

Current control

Frequency locked loops

Pulse width modulation inverters

Space vector pulse width

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Abstract

In a three-phase system, three-phase AC signals can be translated into two-phase DC signals through a coordinate transformation. Thus, the PI regulator can realize a zero steady-state error for the DC signals. In the control of a three-phase grid-connected inverter, the phase angle of grid is normally detected by a phase-locked loop (PLL) and takes part in a coordinate transformation. A novel control strategy for a three-phase grid-connected inverter with a frequency-locked loop (FLL) based on coordinate transformation is proposed in this paper. The inverter is controlled as a current supply. The grid angle, which takes part in the coordinate transformation, is replaced by a periodic linear changing angle from ?π to π. The changing angle has the same frequency but a different phase than the grid angle. The frequency of the changing angle tracks the grid frequency by the negative feedback of the reactive power, which forms a FLL. The control strategy applies to non-ideal grids and it is a lot simpler than the control strategies with a PLL that are applied to non-ideal grids. The structure of the FLL is established. The principle and advantages of the proposed control strategy are discussed. The theoretical analysis is confirmed by experimental results.

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Cite this article

[IEEE Style]

Z. Fu, Z. Feng, X. Chen, X. Zheng, J. Yin, "Frequency Synchronization of Three-Phase Grid-Connected Inverters Controlled as Current Supplies," Journal of Power Electronics, vol. 18, no. 5, pp. 1347-1356, 2018. DOI: 10.6113/JPE.2018.18.5.1347.

[ACM Style]

Zhenbin Fu, Zhihua Feng, Xi Chen, Xinxin Zheng, and Jing Yin. 2018. Frequency Synchronization of Three-Phase Grid-Connected Inverters Controlled as Current Supplies. Journal of Power Electronics, 18, 5, (2018), 1347-1356. DOI: 10.6113/JPE.2018.18.5.1347.