Abstract
As the latest generation of flexible AC transmission system (FACTS) devices, the unified power flow controller (UPFC) has comprehensive control capability and has played an important role in modern power systems. Research on UPFC steady-state power flow regulation capability is valuable for the design and operation of UPFC projects. To analyze the UPFC regulation capability, in this paper, the interaction between the UPFC and the external system is studied and the key factors of UPFC regulation capability are analyzed. It is demonstrated that the changes in the voltage magnitude and phase angle difference of UPFC-embedded line terminals will hinder the UPFC from regulating the power flow and decrease the UPFC regulation capability. Therefore, the UPFC power flow regulation capability is not only related to the parameters of the UPFC and its installation line, but also related to grid parameters. To analyze the UPFC active power flow regulation capability in practical power grids, the relationship between the UPFC regulation capability and grid parameters is deduced, and an estimation method is proposed to calculate the regulation range. Then, the estimation method is applied in the Chuxiong Power Grid and compared with power flow calculations. The results verify the UPFC power flow regulation characteristics given by the analysis and the effectiveness of the estimation method. Besides, it is shown that the estimation method can lower the requirements for the power flow calculation program, and reduce computation load.
Highlights
A variety of flexible AC transmission system (FACTS) devices, including the thyristor controlled series capacitor (TCSC), thyristor controlled phase shifter (TCPS), static synchronous series compensator (SSSC), unified power flow controller (UPFC), etc., have the function of adjusting line power flows [1].They provide an effective means to enhance the efficiency and security of power systems [2,3].Among them, the UPFC has received extensive attention in recent years
The range of ∆pkm is independent of the voltage magnitude of bus l and the phase angle difference between line terminals, but it is proportional to the magnitude of the UPFC series converter output voltage, and is inversely proportional to the line impedance
The research on UPFC power flow regulation capability is of great significance for the design and operation of UPFC projects
Summary
A variety of flexible AC transmission system (FACTS) devices, including the thyristor controlled series capacitor (TCSC), thyristor controlled phase shifter (TCPS), static synchronous series compensator (SSSC), unified power flow controller (UPFC), etc., have the function of adjusting line power flows [1]. The above literature investigates the power flow regulation capability of the UPFC in small power systems and assumes that the operating states of the external system (such as bus voltage magnitudes and phase angles) are unchanged under different UPFC output scenarios. The above articles present different theoretical methods for analyzing the impact of the UPFC on system operating states, but they have not studied the power flow regulation capability of the UPFC. 2020, 13, 4419 capability of the Nanjing Western Power Grid (NWPG) UPFC is studied, and 3 of it is demonstrated that the actual power flow control range obtained by the power flow calculation is much smaller than the theoretical value due to the change in the external network operating states. In Section the relationship between the UPFCthe active power flow regulation capability capability and grid parameters is studied, and themethod estimation method The is proposed.
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