Modern/distributed electric energy systems,with ever larger penetration of renewable(photovoltaic,wind,wave,and hydro)energy sources and time-variable outputs,are in need of stronger/higher frequency and alternating c...Modern/distributed electric energy systems,with ever larger penetration of renewable(photovoltaic,wind,wave,and hydro)energy sources and time-variable outputs,are in need of stronger/higher frequency and alternating current(AC)(direct current(DC))voltage control.In fact,faster and more stable active and reactive power in the presence of frequency and voltage sags and swells is needed.Power electronics-controlled variable speed generators do not have enough energy storage(inertia)for the scope(static synchronous compensators(STATCOMs)included).This is because power electronics tends to decouple the generator from the power system.While virtual inertia control in doubly fed induction generators(DFIGs)offers a partial solution to these problems,a more robust and comprehensive framework is required for advanced grid support.This is how,by extending the dual-excitation principles,the dualaxis excited electric synchronous generators(DE-SG)provide superior flexibility in two variants summarized here:as a multifunctional DFIG and dual-axis vs.single-axis excited synchronous generator(SG),and as a synchronous condenser(SC),with dual DC and AC excitation(as a no-load DFIG with inertia wheel),where variable speed is used to accelerate/decelerate the SC and thus provide additional assistance in frequency stabilization.These solutions,good for short-time transients,are not meant,however,to replace the large bidirectional energy storage systems(pump-hydro,hydrogen,batteries,etc.)which are crucial for the daily inherent variations of output energy in modern power systems with multiple power sources.The present paper offers a summary of techniques used in the dual-axis excited vs.single-axis excited SGs(SE-SGs),and SCs topologies,modeling,and control for better stability in modern multiple-source energy systems.This survey includes multiple case studies to shed light on prominent methods.展开更多
同步调相机可增强风电场短路比,但其面临着暂态功角失稳的挑战。首先,建立风电场-同步调相机联合系统的暂态稳定分析模型;其次,研究风电场低电压穿越(low voltage ride through,LVRT)控制对同步调相机转子动态的影响,据此揭示2种不同暂...同步调相机可增强风电场短路比,但其面临着暂态功角失稳的挑战。首先,建立风电场-同步调相机联合系统的暂态稳定分析模型;其次,研究风电场低电压穿越(low voltage ride through,LVRT)控制对同步调相机转子动态的影响,据此揭示2种不同暂态功角失稳场景,并推导出场景触发的临界条件。最后,基于反馈线性化方法设计附加控制器,通过动态调整故障后风电场的输出功率,在提升同步调相机暂态稳定性的同时确保风电场出力恢复。仿真结果表明:邻近新能源的同步调相机存在首摆、二摆失稳2种功角失稳形态,所提控制方法可有效抑制这2种失稳情况,并保障新能源电流在故障清除后快速恢复。展开更多
Large-scale synchronous condenser (LSC) has a broad application prospect in China's ultra-high voltage direct current (UHVDC) to provide dynamic reactive power. Loss of excitation (LOE) is an important grid-relate...Large-scale synchronous condenser (LSC) has a broad application prospect in China's ultra-high voltage direct current (UHVDC) to provide dynamic reactive power. Loss of excitation (LOE) is an important grid-related fault of LSC, resulting in uncontrolled reactive power consumption. However, due to the un obvious fault feature and UHVDC's diverse reactive power demands, LSC's LOE protection faces challenges in criterion and action mode configurations. Thus, this paper proposes a complete LOE protection strategy for the LSC used in UHVDC, including effective criterion and proper action mode. First, the defect of existing reverse reactive power-based protection is presented through an in-depth analysis of the LOE LSC's reactive power behavior. Then, excitation current difference between the measured value and equivalent actual value is identified as the new fault feature. Compared with existing reverse reactive power features which also appear in healthy LSC's leading phase conditions, this current difference feature only appears in the LO E process and thus is more typical. Since actual excitation current is unmeasurable in practice, an estimation model is built and validated by experiment and simulation. Moreover, the novel LOE protection strategy including current-based criterion and improved action mode is proposed. Through comparative simulation studies in PSCADIEMTDC, the novel protection exhibits superior performances compared to existing protection in LOE detection and commutation failure immunity improvement, as well as overvoltage suppression.展开更多
西藏电网与西北和西南电网联网后形成交直流并联格局和长链式通道弱交流连接,电压控制难度大。网内电网源荷分布不均,负荷中心缺乏电源支撑,随着负荷增长,网内重要断面故障后藏中地区电网电压不稳定问题突出。针对藏中地区负荷增长对西...西藏电网与西北和西南电网联网后形成交直流并联格局和长链式通道弱交流连接,电压控制难度大。网内电网源荷分布不均,负荷中心缺乏电源支撑,随着负荷增长,网内重要断面故障后藏中地区电网电压不稳定问题突出。针对藏中地区负荷增长对西藏电网电压稳定影响进行了深入分析,提出了在那曲和阿里地区分别配置构网型同步调相机的系统设计方案,用于解决藏中电网无功支撑不足引起的电压不稳定问题,并在电网故障后能够提供有功功率支撑,作为解决西藏那曲和阿里区域电网供电出现故障的过渡补充手段,并进行了仿真计算,验证了构网型静止无功发生器(static var generator,SVG)在电网故障瞬间,能够为系统提供无功支撑和短时有功输出。那曲和阿里电网构网型静止同步调相机投运后,为电网的稳定运行提供了无功和有功支撑。展开更多
文摘Modern/distributed electric energy systems,with ever larger penetration of renewable(photovoltaic,wind,wave,and hydro)energy sources and time-variable outputs,are in need of stronger/higher frequency and alternating current(AC)(direct current(DC))voltage control.In fact,faster and more stable active and reactive power in the presence of frequency and voltage sags and swells is needed.Power electronics-controlled variable speed generators do not have enough energy storage(inertia)for the scope(static synchronous compensators(STATCOMs)included).This is because power electronics tends to decouple the generator from the power system.While virtual inertia control in doubly fed induction generators(DFIGs)offers a partial solution to these problems,a more robust and comprehensive framework is required for advanced grid support.This is how,by extending the dual-excitation principles,the dualaxis excited electric synchronous generators(DE-SG)provide superior flexibility in two variants summarized here:as a multifunctional DFIG and dual-axis vs.single-axis excited synchronous generator(SG),and as a synchronous condenser(SC),with dual DC and AC excitation(as a no-load DFIG with inertia wheel),where variable speed is used to accelerate/decelerate the SC and thus provide additional assistance in frequency stabilization.These solutions,good for short-time transients,are not meant,however,to replace the large bidirectional energy storage systems(pump-hydro,hydrogen,batteries,etc.)which are crucial for the daily inherent variations of output energy in modern power systems with multiple power sources.The present paper offers a summary of techniques used in the dual-axis excited vs.single-axis excited SGs(SE-SGs),and SCs topologies,modeling,and control for better stability in modern multiple-source energy systems.This survey includes multiple case studies to shed light on prominent methods.
文摘同步调相机可增强风电场短路比,但其面临着暂态功角失稳的挑战。首先,建立风电场-同步调相机联合系统的暂态稳定分析模型;其次,研究风电场低电压穿越(low voltage ride through,LVRT)控制对同步调相机转子动态的影响,据此揭示2种不同暂态功角失稳场景,并推导出场景触发的临界条件。最后,基于反馈线性化方法设计附加控制器,通过动态调整故障后风电场的输出功率,在提升同步调相机暂态稳定性的同时确保风电场出力恢复。仿真结果表明:邻近新能源的同步调相机存在首摆、二摆失稳2种功角失稳形态,所提控制方法可有效抑制这2种失稳情况,并保障新能源电流在故障清除后快速恢复。
文摘Large-scale synchronous condenser (LSC) has a broad application prospect in China's ultra-high voltage direct current (UHVDC) to provide dynamic reactive power. Loss of excitation (LOE) is an important grid-related fault of LSC, resulting in uncontrolled reactive power consumption. However, due to the un obvious fault feature and UHVDC's diverse reactive power demands, LSC's LOE protection faces challenges in criterion and action mode configurations. Thus, this paper proposes a complete LOE protection strategy for the LSC used in UHVDC, including effective criterion and proper action mode. First, the defect of existing reverse reactive power-based protection is presented through an in-depth analysis of the LOE LSC's reactive power behavior. Then, excitation current difference between the measured value and equivalent actual value is identified as the new fault feature. Compared with existing reverse reactive power features which also appear in healthy LSC's leading phase conditions, this current difference feature only appears in the LO E process and thus is more typical. Since actual excitation current is unmeasurable in practice, an estimation model is built and validated by experiment and simulation. Moreover, the novel LOE protection strategy including current-based criterion and improved action mode is proposed. Through comparative simulation studies in PSCADIEMTDC, the novel protection exhibits superior performances compared to existing protection in LOE detection and commutation failure immunity improvement, as well as overvoltage suppression.
文摘西藏电网与西北和西南电网联网后形成交直流并联格局和长链式通道弱交流连接,电压控制难度大。网内电网源荷分布不均,负荷中心缺乏电源支撑,随着负荷增长,网内重要断面故障后藏中地区电网电压不稳定问题突出。针对藏中地区负荷增长对西藏电网电压稳定影响进行了深入分析,提出了在那曲和阿里地区分别配置构网型同步调相机的系统设计方案,用于解决藏中电网无功支撑不足引起的电压不稳定问题,并在电网故障后能够提供有功功率支撑,作为解决西藏那曲和阿里区域电网供电出现故障的过渡补充手段,并进行了仿真计算,验证了构网型静止无功发生器(static var generator,SVG)在电网故障瞬间,能够为系统提供无功支撑和短时有功输出。那曲和阿里电网构网型静止同步调相机投运后,为电网的稳定运行提供了无功和有功支撑。
