Abstract
At present, the reactive power distribution method considering the reactive power adjustment capacity of the inverter in the photovoltaic (PV) power plant will lead to the output voltage of the inverter exceeding the limit. In particular, the PV inverter adopts the constant reactive power control to support the voltage at point of common coupling (PCC), which has a good effect in the steady-state operation. However, when the system is subject to transient disturbance, the PV inverter cannot flexibly support the voltage level of the system by changing the reactive power output. Therefore, this paper proposes a source-network coordination control strategy aiming at the stability of bus voltage at PCC and inverter port voltage. Firstly, the paper introduced the advantages of constant voltage control of PV inverter. Then, the voltage and reactive power control objectives of the PV Inverter in the PV power plant were calculated by considering the PCC voltage, tie lines, power collection lines, the power of transformers and the voltage loss to realize the voltage and reactive power balance control between the inverters. Finally, an actual PV power plant simulation model was built to analyse the PCC voltage under the two conditions of PV output fluctuation and system fault to verify the effectiveness of the control strategy proposed in this paper. The proposed strategy has engineering application value for the realization of closed-loop voltage control between the power grid and PV power plant and the improvement of the active response ability to the PCC voltage.
Highlights
The large access of random and intermittent distributed PV to power grid makes the operation of the system more complex
With constant voltage control mode, the inverter can effectively adjust the reactive power output to stabilize the system voltage according to the real-time output, which makes the PV power plant adapt to the situation of point of common coupling (PCC) voltage fluctuation during the transient operation
In order to verify that the proposed coordination control strategy can effectively suppress the system voltage disturbance, dynamic simulation was carried out under the constant voltage control mode of PV inverter based on the actual operation data of PV power plant
Summary
The large access of random and intermittent distributed PV to power grid makes the operation of the system more complex. Large PV power plant should be equipped with reactive power capacity in accordance with the principle of basic balance in layers and zones, with the ability of automatic reactive power adjustment and voltage control [2, 3]. The reactive power distribution method considering the reactive power capacity of the inverter in the PV power plant is easy to cause the output voltage of the PV inverter to exceed the limit. Under the constant voltage control mode of the PV inverter, the voltage control objective of the PV inverter in the PV power plant was calculated by comprehensively considering the PCC voltage, tie lines, transformers, power collection lines and the voltage loss to realize the voltage and reactive power balance control between the inverters. The effectiveness of the control strategy proposed in this paper was verified by the analysis of the PCC voltage under the conditions of PV output fluctuation and system fault
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