弱受端交流电网下VSC-HVDC系统的功率解耦控制设计

Power decoupling control design of the VSC-HVDC underthe weak receiving AC grid conditions

针对弱受端交流电网下,采用矢量控制的VSC-HVDC系统功率耦合效应明显的问题,揭示弱受端交流电网引起功率耦合的原因,提出相应的改进解耦控制策略。首先,推导得出VSC输出功率与d、q轴电流间的线性化关系。然后,分析得出弱受端交流电网下有功与q轴电流、无功与d轴电流之间的耦合关系,从而揭示矢量控制下的功率耦合机理。同时,基于前馈补偿的思想,对矢量控制策略进行改进,实现更有效的功率解耦。理论分析和时域仿真结果表明,弱受端交流电网下功率强耦合的主要原因是有功功率与q轴电流强耦合、无功功率与d轴电流强耦合。此外,所提出的改进矢量控制能够改善系统的解耦性能、故障响应特性和稳定性。

The power coupling effect of the voltage source converter-based high voltage direct current(VSC-HVDC)system using the vector control is obvious under the weak receiving AC grid conditions.In view of this issue,the reason for the power coupling caused by the weak receiving AC grid is revealed,and a corresponding improved decoupling control strategy is proposed.Firstly,the linearized relationships between the output power and dq-axis currents of VSC were derived.Then,the coupling relationships between output active power and q-axis current,output reactive power and d-axis current were analyzed.The power coupling mechanism was revealed based on the coupling relationships.Meanwhile,based on the idea of feedforward compensation,the vector control strategy was improved to achieve more effective power decoupling.The theoretical analysis and time-domain simulation results show that the strong power coupling under the weak receiving AC grid results from the strong coupling of active power and q-axis current,and reactive power and d-axis current,respectively.Besides,the proposed improved vector control can improve the decoupling performance,fault response characteristics and stability of the system.