Abstract
Commutation failure (CF) is an inherent drawback of line-commutated converter high-voltage DC (LCC-HVDC) system. And CF prevention (CFPREV) control is widely applied in UHVDC lines to mitigate the subsequent CF. However, the formation of a multi-infeed UHVDC system induces power exchange and voltage interaction between AC buses during the transient process, making the behaviors and mitigation of CFs more complex. Consequently, exploring the impact of CFPREV control on adjacent stations and optimizing the CFPREV control to adapt to the interaction characteristics in a multi-infeed system is necessary. Considering the interaction characteristics, the impact of CFPREV control on the commutation process of inverters in a multi-infeed system is analyzed through formula derivation and simulation verification. It is found that although CFPREV control can effectively mitigate the CFs of the inverter near the fault, it will further increase the risk of concurrent CF (CCF) of remote inverters due to the interaction on the AC side. To solve this problem, a coordinated control scheme of CFPREV controls in a multi-infeed UHVDC system is proposed. The output of the CFPREV control of the inverter near the fault can be adjusted adaptively according to the commutation margins of remote inverters. And the probability of CCF caused by CFPREV control is consequently decreased. Case studies are conducted based on Henan provincial multi-infeed UHVDC system in China to verify the analysis result and the effectiveness of the coordinated control scheme of CFPREV controls.
Highlights
Ultra-HVDC (UHVDC) transmission technology has been extensively utilized around the world due to its well-known advantage of long-distance bulk power transmission and lower operating power losses [1]
To cope with the two research tasks introduced above, this paper investigates the impact of CF prevention (CFPREV) control on the commutation processes in multi-infeed UHVDC systems considering the interaction between adjacent inverter stations
Due to the reactive power exchanged between the stations, CFPREV control further decreases the voltages of adjacent AC buses and leads to the concurrent commutation failure (CF) (CCF) in the multi-infeed system
Summary
Ultra-HVDC (UHVDC) transmission technology has been extensively utilized around the world due to its well-known advantage of long-distance bulk power transmission and lower operating power losses [1]. To cope with the two research tasks introduced above, this paper investigates the impact of CFPREV control on the commutation processes in multi-infeed UHVDC systems considering the interaction between adjacent inverter stations. The mechanism of CFPREV control determines that it will increase the probability of CCFs in remote stations due to the reactive power exchange and voltage interaction on the AC side To address this problem, a coordinated control scheme of CFPREV controls in a multiinfeed UHVDC system is proposed to prevent the CCFs. is coordinated controller can adaptively adjust the output of CFPREV control according to the extinction angle drop of the inverters in other UHVDC lines, so as to reduce the adverse effect on the commutation processes in remote inverter stations.
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