With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as...With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.展开更多
Three-level neutral point clamped(NPC)inverters have been widely applied in the high voltage and high power drive fields.The capacitance voltage balancing algorithm is a hot topic that many specialists and scholars ha...Three-level neutral point clamped(NPC)inverters have been widely applied in the high voltage and high power drive fields.The capacitance voltage balancing algorithm is a hot topic that many specialists and scholars have been working on.V arious capacitance voltage balancing strategies have been studied,in which the redundant short vectors are not fully utilized.In order to increase the capacitance voltage control effect of the short vectors,a new algorithm is proposed.展开更多
在三相两电平逆变器中,虚拟空间矢量调制(virtual space vector modulation,VSVM)因其能降低共模电压的幅值和三次谐波而受到广泛关注,但还存在共模电压的谐波成分丰富,且幅值变化和方向变化的发生率较高的问题,为此提出一种改进型VSVM...在三相两电平逆变器中,虚拟空间矢量调制(virtual space vector modulation,VSVM)因其能降低共模电压的幅值和三次谐波而受到广泛关注,但还存在共模电压的谐波成分丰富,且幅值变化和方向变化的发生率较高的问题,为此提出一种改进型VSVM方法。该方法通过分析经典VSVM的矢量合成和共模电压特点,对虚拟矢量和虚拟零矢量所对应的基本矢量进行优化排序,使每个开关周期的共模电压波形相同,均为单个矩形波。进一步分析了所提方法的共模谐波、死区补偿和开关损耗。在逆变器-永磁同步电机系统中进行仿真和实验。结果表明:与经典VSVM相比,所提方法在保持共模电压低幅值的同时,使幅值变化和方向变化的发生率都降低3倍,完全消除基带谐波和边带谐波分量,并使共模电压的高频段峰值平均减小6 dB,且线电流、线电压、转矩和转速等性能依然良好。该方法在不增加系统体积和成本的情况下,能更有效抑制共模干扰,有利于共模滤波器的设计,并为其他共模抑制脉冲宽度调制(pulse width modulation,PWM)方法的研究提供了借鉴。展开更多
Space-vector modulation (SVM) is widely used in multilevel inverters because of its ability to improve DC bus utilization, reduce harmonic distortion, and enhance operational flexibility. However, the increasing compl...Space-vector modulation (SVM) is widely used in multilevel inverters because of its ability to improve DC bus utilization, reduce harmonic distortion, and enhance operational flexibility. However, the increasing complexity of multilevel inverter topologies, such as neutral-point clamped, cascaded H-bridge, and modular multilevel converters, presents challenges in terms of computational efficiency, neutral-point voltage balancing, and common-mode voltage suppression. A detailed review of SVM techniques is provided, including traditional methods and advanced variants such as carrier-based SVM, selective harmonic elimination SVM, and virtual SVM. Additionally, recent hybrid approaches that combine multiple strategies to address specific performance requirements are discussed. The findings highlight advancements in improving the modulation performance, reducing switching losses, and achieving better harmonic attenuation. A discussion of the future challenges and opportunities for multilevel inverter modulation strategies is concluded.展开更多
文摘With the rapid integration of renewable energy sources,modern power systems are increasingly challenged by heightened volatility and uncertainty.Doubly-fed variable-speed pumped storage units(DFVS-PSUs)have emerged as promising technologies for mitigating grid oscillations and enhancing system flexibility.However,the excitation converters in DFVS-PSUs are prone to significant issues such as elevated common-mode voltage(CMV)and neutral-point voltage(NPV)fluctuations,which can lead to electromagnetic interference and degrade transient performance.To address these challenges,an optimized virtual space vector pulse width modulation(OVSVPWM)strategy is proposed,aiming to suppress CMV and NPV simultaneously through coordinated multi-objective control.Specifically,a dynamic feedback mechanism is introduced to adjust the balancing factor of basic vectors in the synthesized virtual small vector in real-time,achieving autonomous balancing of the NPV.To address the excessive switching actions introduced by the OVSVPWM strategy,a phase duty ratio-based sequence reconstruction method is adopted,which reduces the total number of switching actions to half of the original.A zero-level buffering scheme is employed to reconstruct the single-phase voltage-level output sequence,achieving peak CMV suppression down to udc/6.Simulation results demonstrate that the proposed strategy significantly improves electromagnetic compatibility and operational stability while maintaining high power quality.
文摘Three-level neutral point clamped(NPC)inverters have been widely applied in the high voltage and high power drive fields.The capacitance voltage balancing algorithm is a hot topic that many specialists and scholars have been working on.V arious capacitance voltage balancing strategies have been studied,in which the redundant short vectors are not fully utilized.In order to increase the capacitance voltage control effect of the short vectors,a new algorithm is proposed.
文摘光伏等新能源及储能系统基于电力电子接口融入微电网,其低惯量问题显著,面临严峻的频率稳定风险。为了改善微电网频率动态特性,利用模型预测控制(model predictive control,MPC)协同优化外环与内环,提出了一种基于级联模型预测(cascaded model predictive control,CMPC)的虚拟同步机(virtual synchronous generator,VSG)控制策略。在外环,利用MPC的滚动优化,对输入VSG的有功功率参考值进行实时修正。在内环,优化通过两个阶段寻找最优电压矢量(voltage vector,VV)的离散空间矢量模型预测控制(discrete space vector model predictive control,DSVM-MPC)方法,减少跟踪外环输出误差,使频率控制更为精确。仿真结果表明,所提策略能够提升频率响应和限流效果,避免频率过冲。
文摘Space-vector modulation (SVM) is widely used in multilevel inverters because of its ability to improve DC bus utilization, reduce harmonic distortion, and enhance operational flexibility. However, the increasing complexity of multilevel inverter topologies, such as neutral-point clamped, cascaded H-bridge, and modular multilevel converters, presents challenges in terms of computational efficiency, neutral-point voltage balancing, and common-mode voltage suppression. A detailed review of SVM techniques is provided, including traditional methods and advanced variants such as carrier-based SVM, selective harmonic elimination SVM, and virtual SVM. Additionally, recent hybrid approaches that combine multiple strategies to address specific performance requirements are discussed. The findings highlight advancements in improving the modulation performance, reducing switching losses, and achieving better harmonic attenuation. A discussion of the future challenges and opportunities for multilevel inverter modulation strategies is concluded.
