An input-output signal selection based on Phillips-Heffron model of a parallel high voltage alternative current/high voltage direct current(HVAC/HVDC) power system is presented to study power system stability. It is w...An input-output signal selection based on Phillips-Heffron model of a parallel high voltage alternative current/high voltage direct current(HVAC/HVDC) power system is presented to study power system stability. It is well known that appropriate coupling of inputs-outputs signals in the multivariable HVDC-HVAC system can improve the performance of designed supplemetary controller. In this work, different analysis techniques are used to measure controllability and observability of electromechanical oscillation mode. Also inputs–outputs interactions are considered and suggestions are drawn to select the best signal pair through the system inputs-outputs. In addition, a supplementary online adaptive controller for nonlinear HVDC to damp low frequency oscillations in a weakly connected system is proposed. The results obtained using MATLAB software show that the best output-input for damping controller design is rotor speed deviation as out put and phase angle of rectifier as in put. Also response of system equipped with adaptive damping controller based on HVDC system has appropriate performance when it is faced with faults and disturbance.展开更多
A design scheme of variable structure model reference control systems using only input and output measurements is presented for the systems with unmodeled dynamics and disturbances in input and output channels. The mo...A design scheme of variable structure model reference control systems using only input and output measurements is presented for the systems with unmodeled dynamics and disturbances in input and output channels. The modeled part of the systems has relative degree greater than one and unknown upper bound of degree. By introducing some auxiliary signals and normalized signals with memory functions and appropriate choice of controller parameters, the developed variable structure controller guarantees the global stability of the closed-loop system and the arbitrarily small tracking error.展开更多
为研究电网换相换流器高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)控制链路延时对系统小信号稳定性的影响,首先,建立考虑控制链路延时后的LCC系统小信号模型,包括状态空间模型和单输入单输出...为研究电网换相换流器高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)控制链路延时对系统小信号稳定性的影响,首先,建立考虑控制链路延时后的LCC系统小信号模型,包括状态空间模型和单输入单输出反馈控制模型。然后,基于所建立的模型,研究不同交流系统强度下控制链路延时变化时系统的根轨迹移动特征,获得主导模态的振荡频率,定量评估控制链路延时对系统幅值和相位裕度的影响。最后,研究控制链路延时对系统临界运行短路比和控制参数可行域的影响,揭示控制链路延时、交流系统强度及控制系统之间的相互制约关系及交互作用机理。理论分析和仿真验证结果表明,随着控制链路延时的增加,为保证LCC系统稳定传输额定功率,交流系统强度不能过低;链路延时在一定程度上降低了控制参数的可行域,尤其是在弱系统工况,当LCC控制链路延时较大时,需适当降低定直流电压控制器或锁相环(phase-locked-loop,PLL)的带宽来保证系统稳定。展开更多
文摘An input-output signal selection based on Phillips-Heffron model of a parallel high voltage alternative current/high voltage direct current(HVAC/HVDC) power system is presented to study power system stability. It is well known that appropriate coupling of inputs-outputs signals in the multivariable HVDC-HVAC system can improve the performance of designed supplemetary controller. In this work, different analysis techniques are used to measure controllability and observability of electromechanical oscillation mode. Also inputs–outputs interactions are considered and suggestions are drawn to select the best signal pair through the system inputs-outputs. In addition, a supplementary online adaptive controller for nonlinear HVDC to damp low frequency oscillations in a weakly connected system is proposed. The results obtained using MATLAB software show that the best output-input for damping controller design is rotor speed deviation as out put and phase angle of rectifier as in put. Also response of system equipped with adaptive damping controller based on HVDC system has appropriate performance when it is faced with faults and disturbance.
文摘A design scheme of variable structure model reference control systems using only input and output measurements is presented for the systems with unmodeled dynamics and disturbances in input and output channels. The modeled part of the systems has relative degree greater than one and unknown upper bound of degree. By introducing some auxiliary signals and normalized signals with memory functions and appropriate choice of controller parameters, the developed variable structure controller guarantees the global stability of the closed-loop system and the arbitrarily small tracking error.
文摘为研究电网换相换流器高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)控制链路延时对系统小信号稳定性的影响,首先,建立考虑控制链路延时后的LCC系统小信号模型,包括状态空间模型和单输入单输出反馈控制模型。然后,基于所建立的模型,研究不同交流系统强度下控制链路延时变化时系统的根轨迹移动特征,获得主导模态的振荡频率,定量评估控制链路延时对系统幅值和相位裕度的影响。最后,研究控制链路延时对系统临界运行短路比和控制参数可行域的影响,揭示控制链路延时、交流系统强度及控制系统之间的相互制约关系及交互作用机理。理论分析和仿真验证结果表明,随着控制链路延时的增加,为保证LCC系统稳定传输额定功率,交流系统强度不能过低;链路延时在一定程度上降低了控制参数的可行域,尤其是在弱系统工况,当LCC控制链路延时较大时,需适当降低定直流电压控制器或锁相环(phase-locked-loop,PLL)的带宽来保证系统稳定。
