This paper proposes a novel SVPWM (space vector pulse width modulation) strategy for the three-level neutral-point-clamped voltage source inverter, based on the particular disposition of all the redundant voltage ve...This paper proposes a novel SVPWM (space vector pulse width modulation) strategy for the three-level neutral-point-clamped voltage source inverter, based on the particular disposition of all the redundant voltage vectors. The new modulation approach shows superior performance for harmonic voltage and balancing control of neutral-point potential compared to the popular eight-stage centered SVPWM. It realizes suppression of inverter neutral-point potential variation by accurately modifying redundant factor of small vectors pairs, only requiring information of DC-link capacitor voltages and three-phase load currents. This is convenient to apply and is compatible of digital computer realization. Feasibility of the proposed control approach is verified by simulation and experimental results.展开更多
The four-level active neutral point clamped(ANPC)inverter has become increasingly widely used in the renewable energy indus-try since it offers one more voltage level without increasing the total number of active swit...The four-level active neutral point clamped(ANPC)inverter has become increasingly widely used in the renewable energy indus-try since it offers one more voltage level without increasing the total number of active switches compared to the three-level ANPC inverter.The model predictive current control(MPCC)is a promising control method for multi-level inverters.However,the conven-tional MPCC suffers from high computational complexity and tedious weighting factor tuning in multi-level inverter applications.A low-complexity MPCC without weighting factors for a four-level ANPC inverter is proposed in this paper.The computational burden and voltage vector candidate set are reduced according to the relationship between voltage vector and neutral point voltage balance.The proposed MPCC shows excellent steady-state and dynamics performances while ensuring the neutral point voltage balancing.The efficacy of the proposed MPCC is verified by simulation and experimental results.展开更多
With the acceleration of agricultural electrification,a lot of nonlinear and shock loads appear in the rural power grid,and the resulting harmonic and reactive currents pollute the rural power grid more and more serio...With the acceleration of agricultural electrification,a lot of nonlinear and shock loads appear in the rural power grid,and the resulting harmonic and reactive currents pollute the rural power grid more and more seriously.To solve the above problem,three-level neutral point clamped(NPC)inverters have been widely used,but their development is greatly restricted by the defect of neutral point voltage imbalance.In this paper,an improved virtual space vector pulse width modulation(VSVPWM)was proposed.Firstly,the mathematical models of various space vectors were established,and the influence of various space vectors on neutral point voltage was analyzed.The sum of the vector current at the neutral point was zero and the voltage control at the neutral point was completed by.introducing the time offset into different switching times of the redundant small vector.This method was simple in design and avoided the redundant calculation of the traditional VSVPWM method and tedious switch sequence design.This balancing control strategy could greatly reduce the influence of virtual vectors on neutral point voltage and effectively control the low-frequency oscillation of neutral point voltage.The validity of the method was verified by establishing a matlab simulation model.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
The presence of an integrator in a reference model of a rotor flux-based model reference adaptive system(RF-MRAS)and non-linearity of the inverter in the output voltage degrade the speed response of the sensorless ope...The presence of an integrator in a reference model of a rotor flux-based model reference adaptive system(RF-MRAS)and non-linearity of the inverter in the output voltage degrade the speed response of the sensorless operation of the electric drive system in terms of DC drift,initial value issues,and inaccurate voltage acquisition.To improve the speed response,a compensating voltage component is supplemented by an amending integrator.The compensating voltage is a coalition of drift and offset voltages,and reduces DC drift and initial value issues.During low-speed operation,inaccurate voltage acquisition distorts the stator voltage critically,and it becomes considerable when the stator voltage of the machine is low.Implementing a three-level neutral point clamped inverter in speed-sensorless decoupled control of an induction motor improves the performance of the drive with superior quality of inverter output voltage.Further,the performance of the induction motor drive is improved by replacing the proportional-integral(PI)controller in the adaption mechanism of RF-MRAS with an adaptive neuro-fuzzy inference system(ANFIS)controller.A prototype model of the three-level neutral point clamped inverter(3L-NPC)-fed induction motor drive is fabricated in a laboratory,and its performance for a RF-MRAS,modified RFMRAS,and modified RFMRAS using ANFIS are compared using different benchmark tests.展开更多
针对三相LCL并网逆三电平中点钳位(Neutral Point Clamped,NPC)逆变器中有限集模型预测控制(Finite Control Set-Model Predictive Control,FCS-MPC)计算量大和控制速度慢导致NPC逆变器性能变差的问题,设计了一种快速模型预测控制方法...针对三相LCL并网逆三电平中点钳位(Neutral Point Clamped,NPC)逆变器中有限集模型预测控制(Finite Control Set-Model Predictive Control,FCS-MPC)计算量大和控制速度慢导致NPC逆变器性能变差的问题,设计了一种快速模型预测控制方法。通过改变快速模型预测控制中参考电流电角度控制逆变器输出电流的相位,实现入网电流与电网同步;通过在冗余短矢量中选择合适的短矢量,实现直流侧中点电压平衡,减少计算量;通过缩小计算扇区,使快速模型预测控制仅在当前最优输出电压矢量附近进行寻优计算,进一步减少计算量。在MATLAB/SIMULINK中搭建了三相LCL并网NPC逆变器仿真模型,仿真结果验证了上述控制方法的快速性和可行性,运算速度提高了18.31%,入网电流总谐波失真(Total Harmonic Distortion,THD)值减少了2.38%。展开更多
In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control se...In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control set-model predictive control(FCS-MPC)with low switching frequency for three-level neutral point clamped-active front-end converters(NPC-AFEs)is proposed.With this approach,the prediction model of three-level NPC-AFEs is established inα-βreference frame,and the control objective of low average switching frequency is introduced into a cost function.The proposed method not only achieves the desired control performance under low switching frequency,but also performs the efficient operation for the three-level NPC-AFEs.The simulation results are provided to verify the effectiveness of proposed control scheme.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
The interaction between grid-connected inverters and the grid may cause stability issues,and compromise the reliable operation of the inverters.This study investigates the stability of a three-level neutral point clam...The interaction between grid-connected inverters and the grid may cause stability issues,and compromise the reliable operation of the inverters.This study investigates the stability of a three-level neutral point clamped(NPC)inverter connected to the grid using impedance-based methods.Because the impedance model of a three-phase three-level NPC inverter has not yet been reported,this study fills the literature gap by analyzing the influence of three-level DC-side neutral point control on the impedance characteristics.By fully considering the DC bus dynamics and DC voltage control loop,and the current loop and phase-locked loop(PLL),the admittance model of a three-phase three-level NPC inverter is established and verified by simulation.Additionally,in the stability analysis of a threelevel NPC inverter grid-connected system,the frequency coupling introduced by the PLL and DC bus dynamics is included with the help of an established admittance model.The stability of the grid-connected system under different grid short circuit ratios(SCR)and operating power levels is analyzed according to the Nyquist stability criterion.The experimental results revealed that the established impedance model of the three-phase three-level NPC inverter can properly represent the stability of this system.展开更多
文摘This paper proposes a novel SVPWM (space vector pulse width modulation) strategy for the three-level neutral-point-clamped voltage source inverter, based on the particular disposition of all the redundant voltage vectors. The new modulation approach shows superior performance for harmonic voltage and balancing control of neutral-point potential compared to the popular eight-stage centered SVPWM. It realizes suppression of inverter neutral-point potential variation by accurately modifying redundant factor of small vectors pairs, only requiring information of DC-link capacitor voltages and three-phase load currents. This is convenient to apply and is compatible of digital computer realization. Feasibility of the proposed control approach is verified by simulation and experimental results.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB4201602)the National Natural Science Foundation of China(Grant No.52002409).
文摘The four-level active neutral point clamped(ANPC)inverter has become increasingly widely used in the renewable energy indus-try since it offers one more voltage level without increasing the total number of active switches compared to the three-level ANPC inverter.The model predictive current control(MPCC)is a promising control method for multi-level inverters.However,the conven-tional MPCC suffers from high computational complexity and tedious weighting factor tuning in multi-level inverter applications.A low-complexity MPCC without weighting factors for a four-level ANPC inverter is proposed in this paper.The computational burden and voltage vector candidate set are reduced according to the relationship between voltage vector and neutral point voltage balance.The proposed MPCC shows excellent steady-state and dynamics performances while ensuring the neutral point voltage balancing.The efficacy of the proposed MPCC is verified by simulation and experimental results.
基金Supported by Application Technology Research and Development of Harbin City(2017RAXXJ075)。
文摘With the acceleration of agricultural electrification,a lot of nonlinear and shock loads appear in the rural power grid,and the resulting harmonic and reactive currents pollute the rural power grid more and more seriously.To solve the above problem,three-level neutral point clamped(NPC)inverters have been widely used,but their development is greatly restricted by the defect of neutral point voltage imbalance.In this paper,an improved virtual space vector pulse width modulation(VSVPWM)was proposed.Firstly,the mathematical models of various space vectors were established,and the influence of various space vectors on neutral point voltage was analyzed.The sum of the vector current at the neutral point was zero and the voltage control at the neutral point was completed by.introducing the time offset into different switching times of the redundant small vector.This method was simple in design and avoided the redundant calculation of the traditional VSVPWM method and tedious switch sequence design.This balancing control strategy could greatly reduce the influence of virtual vectors on neutral point voltage and effectively control the low-frequency oscillation of neutral point voltage.The validity of the method was verified by establishing a matlab simulation model.
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The presence of an integrator in a reference model of a rotor flux-based model reference adaptive system(RF-MRAS)and non-linearity of the inverter in the output voltage degrade the speed response of the sensorless operation of the electric drive system in terms of DC drift,initial value issues,and inaccurate voltage acquisition.To improve the speed response,a compensating voltage component is supplemented by an amending integrator.The compensating voltage is a coalition of drift and offset voltages,and reduces DC drift and initial value issues.During low-speed operation,inaccurate voltage acquisition distorts the stator voltage critically,and it becomes considerable when the stator voltage of the machine is low.Implementing a three-level neutral point clamped inverter in speed-sensorless decoupled control of an induction motor improves the performance of the drive with superior quality of inverter output voltage.Further,the performance of the induction motor drive is improved by replacing the proportional-integral(PI)controller in the adaption mechanism of RF-MRAS with an adaptive neuro-fuzzy inference system(ANFIS)controller.A prototype model of the three-level neutral point clamped inverter(3L-NPC)-fed induction motor drive is fabricated in a laboratory,and its performance for a RF-MRAS,modified RFMRAS,and modified RFMRAS using ANFIS are compared using different benchmark tests.
文摘针对三相LCL并网逆三电平中点钳位(Neutral Point Clamped,NPC)逆变器中有限集模型预测控制(Finite Control Set-Model Predictive Control,FCS-MPC)计算量大和控制速度慢导致NPC逆变器性能变差的问题,设计了一种快速模型预测控制方法。通过改变快速模型预测控制中参考电流电角度控制逆变器输出电流的相位,实现入网电流与电网同步;通过在冗余短矢量中选择合适的短矢量,实现直流侧中点电压平衡,减少计算量;通过缩小计算扇区,使快速模型预测控制仅在当前最优输出电压矢量附近进行寻优计算,进一步减少计算量。在MATLAB/SIMULINK中搭建了三相LCL并网NPC逆变器仿真模型,仿真结果验证了上述控制方法的快速性和可行性,运算速度提高了18.31%,入网电流总谐波失真(Total Harmonic Distortion,THD)值减少了2.38%。
文摘In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control set-model predictive control(FCS-MPC)with low switching frequency for three-level neutral point clamped-active front-end converters(NPC-AFEs)is proposed.With this approach,the prediction model of three-level NPC-AFEs is established inα-βreference frame,and the control objective of low average switching frequency is introduced into a cost function.The proposed method not only achieves the desired control performance under low switching frequency,but also performs the efficient operation for the three-level NPC-AFEs.The simulation results are provided to verify the effectiveness of proposed control scheme.
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。
基金This work was supported in part by the National Natural Science Key Foundation of China under Grant 51937001the Natural Science Foundation Key Project of Chongqing Province under Grant cstc2019jcyj-zdxmX0005National Grid Project under Grant 5200-201958248A-0-0-00.
文摘The interaction between grid-connected inverters and the grid may cause stability issues,and compromise the reliable operation of the inverters.This study investigates the stability of a three-level neutral point clamped(NPC)inverter connected to the grid using impedance-based methods.Because the impedance model of a three-phase three-level NPC inverter has not yet been reported,this study fills the literature gap by analyzing the influence of three-level DC-side neutral point control on the impedance characteristics.By fully considering the DC bus dynamics and DC voltage control loop,and the current loop and phase-locked loop(PLL),the admittance model of a three-phase three-level NPC inverter is established and verified by simulation.Additionally,in the stability analysis of a threelevel NPC inverter grid-connected system,the frequency coupling introduced by the PLL and DC bus dynamics is included with the help of an established admittance model.The stability of the grid-connected system under different grid short circuit ratios(SCR)and operating power levels is analyzed according to the Nyquist stability criterion.The experimental results revealed that the established impedance model of the three-phase three-level NPC inverter can properly represent the stability of this system.