摘要
Abstract
With the further advancement of the construction of"double-high"power system,the continuous phase change failure problem caused by transient voltage at the line commutated converter based high voltage direct current(LCC-HVDC)receiving end has become an important risk factor threatening the safe and stable operation of the power grid.Variable speed pumped storage(VSPS)units have the advantages of large single-machine capacity and fast response speed,which can participate in the transient voltage regulation of the power grid.The transient voltage regulation capability of VSPS can be further used to suppress the LCC-HVDC continuous phase change failure when VSPS is fed into the LCC-HVDC receiving end grid,however,there is still a gap in the domestic and international research in this area.
Firstly,from the structural characteristics of LCC-HVDC receiving end containing VSPS,the risk of phase-change failure faced by receiving end system is explained.Secondly,based on the mechanism of VSPS to inhibit the occurrence of continuous phase-change failure,a coordinated control strategy of VSPS to inhibit the continuous phase-change failure of LCC-HVDC is proposed,which takes the voltage of receiving end converter bus as the input signal,and acts on the reactive power outer loop of VSPS.Then,the reactive power regulation capability of the unit under different operating conditions is analysed by theoretical derivation,and the reactive power allocation scheme for VSPS transient voltage regulation is formulated by considering the maximum rotor current and the capacity limitation of the converter on the grid side.Finally,the reasonableness of the reactive power allocation scheme and the validity of the coordinated control strategy are verified based on the electromagnetic transient model of the VSPS feeder to the LCC-HVDC receiving end.
The validation results show that under different fault times and different fault degrees,the VSPS can reduce the probability of LCC-HVDC continuous phase change failure under most operating conditions by putting in the coordinated control strategy proposed in this paper.At the same time.Priority allocation of reactive power to grid side converter(GSC)can reduce the rotor over current to a certain extent without affecting the transient voltage support effect,ensuring the safe and stable operation of the unit.
The main conclusions of this paper are as follows:(1)The response time delay of the VSPS transient voltage regulation control is within the hundred milliseconds time scale,and for the LCC-HVDC continuous phase change failure fault it can function before the second dip of the bus voltage,which meets the response time requirement for suppressing the continuous phase change failure.(2)Both the stator side of the VSPS and the GSC have a certain amount of reactive power compensation capacity,and taking into account the demand for suppressing the rotor current during the fault increase demand,it is more reasonable to prioritise the assignment of reactive power to the GSC when the unit participates in transient voltage regulation.(3)The coordinated control strategy of VSPS proposed in this paper takes the voltage of the receiving end commutating bus as the input signal,and acts on the reactive power outer loop in the control part of the unit.This method enables the VSPS to respond in real time to the dynamic changes in the LCC-HVDC receiving end converter bus voltage,compensate the corresponding reactive power within the safe operating range of the unit,support the converter bus voltage,and thus effectively inhibit the occurrence of LCC-HVDC continuous phase change failure.关键词
连续换相失败/可变速抽水蓄能机组/无功特性/协调控制策略Key words
Continuous commutation failed/variable speed pump storage unit/reactive power characteristic/coordinated control strategy分类
动力与电气工程
