Frequency support control of two‐stage photovoltaic grid‐connected system based on virtual governor

Abstract

Abstract Given the urgent need for photovoltaic (PV) energy to participate in grid frequency regulation, a control strategy of the DC/DC converter of a two‐stage PV system based on the virtual governor (PV‐VG) is proposed in this paper. First, a one‐step PV maximum power point estimation (MPPE) method is proposed, which can obtain the reference voltage corresponding to the maximum power point and the power deload point, and some complex iterative calculations and sampling processes are circumvented. Then, based on the constant DC bus voltage of the two‐stage PV system, the coupling mathematical model of boost circuit duty cycle (D) and PV output power is established. According to the power setting and frequency deviation, the D is taken as the direct control target to reflect the direct coupling characteristics of D and grid frequency (f‐D) so that the PV system can adjust the output power reference independently according to the grid frequency deviation. Finally, a simulation model is built in Matlab/Simulink and RT‐LAB, and the results show that the accuracy of the proposed one‐step MPPE method is over 99.8%, and the correctness and efficiency of the PV‐VG control strategy are verified in some case study.

Keywords

• Solar power stations and photovoltaic power systems
• Voltage control
• Frequency control
• Control of electric power systems
• DC‐DC power convertors
• Power convertors and power supplies to apparatus