An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency e...An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency error caused by neutral point voltage ripple and high frequency error introduced by space vector synthesis were both taken into account,and the unified error model of output current ripple was established.By taking continuous and discontinuous modulation strategies as examples,the unified error model was validated through Fourier analysis of the experimental results.The proposed evaluation method will be helpful for the switching sequence optimization and the modulation strategy selection.展开更多
针对三电平中点钳位型NPC(neutral point clamped)变换器开关频率提高导致变换器电流纹波与电磁干扰噪声增大的问题,提出1种基于电流纹波预测的变开关频率调制策略,以降低三电平NPC变换器电流纹波、谐波噪声及电磁干扰噪声。根据电流纹...针对三电平中点钳位型NPC(neutral point clamped)变换器开关频率提高导致变换器电流纹波与电磁干扰噪声增大的问题,提出1种基于电流纹波预测的变开关频率调制策略,以降低三电平NPC变换器电流纹波、谐波噪声及电磁干扰噪声。根据电流纹波的要求计算出开关周期与采样周期并合成最新的开关周期,形成反馈,从而实现变频调制。使随机周期分布在期望周期的周围,从而使变换器的谐波噪声和电磁噪声更加均匀地分布在较宽的频段上,以达到减少变换器电磁噪声的目的,并改善输出电感上的电流纹波。相关仿真及实验结果表明,相较于传统的调制策略,所提调制策略共模噪声降低了约20 dB/μV,差模噪声降低了约10 dB/μV,其输出电感电流纹波幅值也有相应的减少。展开更多
This paper proposes a high performance three-level inverter Neutral Point Clamped (NPC) structure for photovoltaic system. The proposed configuration which can boost the low voltage of photovoltaic (PV) array, can als...This paper proposes a high performance three-level inverter Neutral Point Clamped (NPC) structure for photovoltaic system. The proposed configuration which can boost the low voltage of photovoltaic (PV) array, can also convert the photovoltaic DC power into high quality AC power. Attention has been paid to the problem of neutral point potential variation. In this way, a Direct Torque Control (DTC) technique has been applied and the estimated value of the Neutral Point Potential (NPP) is used, which is calculated by motor currents. This control strategy uses the redundancy presented by the inverter for selecting appropriate switching state through a switching table to achieve the control of NPP. This study shows the effect of the stability problem of the DC voltages and good static and dynamic performances were obtained in simulation of the proposed cascade “photovoltaic cell-three-level NPC VSI-induction motor”.展开更多
为降低中点箝位型(neutral point clamped,NPC)三电平整流器的电流谐波,在dq同步旋转坐标系下推导出带中点电压耦合项的NPC三电平整流器数学模型,并分析中点电压对电流控制的影响。对模型中的中点电压耦合项和交流侧等效电阻会增大电流...为降低中点箝位型(neutral point clamped,NPC)三电平整流器的电流谐波,在dq同步旋转坐标系下推导出带中点电压耦合项的NPC三电平整流器数学模型,并分析中点电压对电流控制的影响。对模型中的中点电压耦合项和交流侧等效电阻会增大电流谐波及无法通过常规方法进行准确估计的问题,设计一种混合参数自适应的迭代学习控制方法,以进行解耦控制并消除不确定参数的影响。通过构造Lyapunov函数和理论推导验证控制方法的稳定性。在整流器硬件平台上进行试验验证,结果表明,所设计的控制方法可有效降低电流谐波。展开更多
为进一步提高中点电压钳制(neutral point clamped,NPC)H桥级联五电平逆变器的动态响应、降低控制器计算负担的同时确保装置低损耗运行,文中在电压矢量矩形区域分类的基础上,提出一种以满足动态响应和降低开关损耗为目标的两级优化模型...为进一步提高中点电压钳制(neutral point clamped,NPC)H桥级联五电平逆变器的动态响应、降低控制器计算负担的同时确保装置低损耗运行,文中在电压矢量矩形区域分类的基础上,提出一种以满足动态响应和降低开关损耗为目标的两级优化模型预测电压控制策略。首先根据逆变器数学模型和期望电流进行目标电压矢量计算、修正,接着基于矩形区域分类对目标电压矢量进行定位;并以定位后的候选矢量为基础,设计了两级优化目标函数以输出满足要求的最优矢量。仿真和实验结果验证了该方法的有效性,与空间矢量脉宽调制以及传统模型预测电流、电压控制策略相比,该文所研究的两级优化模型预测电压控制策略,在确保逆变器动态响应的前提下既能降低控制器计算负担,还能有效减少器件开关损耗。展开更多
针对三电平中点钳位型(neutral point clamped,NPC)逆变器在实际应用中存在总谐波失真(total harmonic distortion,THD)值ηTHD高、开关损耗大、中性点电压漂移大等问题,提出一种基于矢量组合列的新型调制策略,将单个矢量组合成一组序列...针对三电平中点钳位型(neutral point clamped,NPC)逆变器在实际应用中存在总谐波失真(total harmonic distortion,THD)值ηTHD高、开关损耗大、中性点电压漂移大等问题,提出一种基于矢量组合列的新型调制策略,将单个矢量组合成一组序列,运用半波对称法对矢量序列进行组合,产生一种可以降低THD值、减少开关损耗、抑制中性点电压漂移、提高电压利用率和电能质量的调制策略。仿真和实验结果验证新型调制策略的优越性和可行性。展开更多
基金National Natural Science Foundation of China(Grant Nos.51807140 and 51690183).
文摘An analytical evaluation method for output waveform quality of space vector pulse width modulation(PWM)strategies applied in neutral⁃point⁃clamped three⁃level converter(3L⁃NPC)is proposed in this paper.Low frequency error caused by neutral point voltage ripple and high frequency error introduced by space vector synthesis were both taken into account,and the unified error model of output current ripple was established.By taking continuous and discontinuous modulation strategies as examples,the unified error model was validated through Fourier analysis of the experimental results.The proposed evaluation method will be helpful for the switching sequence optimization and the modulation strategy selection.
文摘针对三电平中点钳位型NPC(neutral point clamped)变换器开关频率提高导致变换器电流纹波与电磁干扰噪声增大的问题,提出1种基于电流纹波预测的变开关频率调制策略,以降低三电平NPC变换器电流纹波、谐波噪声及电磁干扰噪声。根据电流纹波的要求计算出开关周期与采样周期并合成最新的开关周期,形成反馈,从而实现变频调制。使随机周期分布在期望周期的周围,从而使变换器的谐波噪声和电磁噪声更加均匀地分布在较宽的频段上,以达到减少变换器电磁噪声的目的,并改善输出电感上的电流纹波。相关仿真及实验结果表明,相较于传统的调制策略,所提调制策略共模噪声降低了约20 dB/μV,差模噪声降低了约10 dB/μV,其输出电感电流纹波幅值也有相应的减少。
文摘This paper proposes a high performance three-level inverter Neutral Point Clamped (NPC) structure for photovoltaic system. The proposed configuration which can boost the low voltage of photovoltaic (PV) array, can also convert the photovoltaic DC power into high quality AC power. Attention has been paid to the problem of neutral point potential variation. In this way, a Direct Torque Control (DTC) technique has been applied and the estimated value of the Neutral Point Potential (NPP) is used, which is calculated by motor currents. This control strategy uses the redundancy presented by the inverter for selecting appropriate switching state through a switching table to achieve the control of NPP. This study shows the effect of the stability problem of the DC voltages and good static and dynamic performances were obtained in simulation of the proposed cascade “photovoltaic cell-three-level NPC VSI-induction motor”.
文摘为降低中点箝位型(neutral point clamped,NPC)三电平整流器的电流谐波,在dq同步旋转坐标系下推导出带中点电压耦合项的NPC三电平整流器数学模型,并分析中点电压对电流控制的影响。对模型中的中点电压耦合项和交流侧等效电阻会增大电流谐波及无法通过常规方法进行准确估计的问题,设计一种混合参数自适应的迭代学习控制方法,以进行解耦控制并消除不确定参数的影响。通过构造Lyapunov函数和理论推导验证控制方法的稳定性。在整流器硬件平台上进行试验验证,结果表明,所设计的控制方法可有效降低电流谐波。
文摘虚拟同步机VSG(virtual synchronous generator)通过模拟同步机特性为新能源并网提供惯性和阻尼。然而,电力电子开关器件高频开关过程中可能会发生断路故障,导致输出电流波形严重畸变,影响电网安全稳定运行。针对中点箝位型NPC(neutral point clamped)三电平VSG桥臂故障问题,提出一种中点电压均衡的VSG容错模型预测控制策略。分析NPC三电平VSG单相桥臂故障后运行机理,在开关器件故障后利用直流侧电容组成虚拟桥臂,重构为VSG桥臂故障容错结构。建立故障情况下预测电流模型,重构故障状态空间电压矢量,将直流侧中点电容电压引入容错模型代价函数,减小电容电压波动,实现VSG桥臂故障容错运行。实验结果表明,在开关器件发生故障后,NPC三电平VSG能容错连续运行,验证了所提模型预测容错控制策略的有效性,提高了VSG运行可靠性。
文摘为进一步提高中点电压钳制(neutral point clamped,NPC)H桥级联五电平逆变器的动态响应、降低控制器计算负担的同时确保装置低损耗运行,文中在电压矢量矩形区域分类的基础上,提出一种以满足动态响应和降低开关损耗为目标的两级优化模型预测电压控制策略。首先根据逆变器数学模型和期望电流进行目标电压矢量计算、修正,接着基于矩形区域分类对目标电压矢量进行定位;并以定位后的候选矢量为基础,设计了两级优化目标函数以输出满足要求的最优矢量。仿真和实验结果验证了该方法的有效性,与空间矢量脉宽调制以及传统模型预测电流、电压控制策略相比,该文所研究的两级优化模型预测电压控制策略,在确保逆变器动态响应的前提下既能降低控制器计算负担,还能有效减少器件开关损耗。
文摘针对三电平中点钳位型(neutral point clamped,NPC)逆变器在实际应用中存在总谐波失真(total harmonic distortion,THD)值ηTHD高、开关损耗大、中性点电压漂移大等问题,提出一种基于矢量组合列的新型调制策略,将单个矢量组合成一组序列,运用半波对称法对矢量序列进行组合,产生一种可以降低THD值、减少开关损耗、抑制中性点电压漂移、提高电压利用率和电能质量的调制策略。仿真和实验结果验证新型调制策略的优越性和可行性。
