For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging ...For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.展开更多
With the development and utilization of renewable energy,the scaling of microgrid composed of distributed generation systems and energy storing devices,e.g,photovoltaic(PV),wind power,micro gas turbine,fuel cell,are b...With the development and utilization of renewable energy,the scaling of microgrid composed of distributed generation systems and energy storing devices,e.g,photovoltaic(PV),wind power,micro gas turbine,fuel cell,are becoming much lager.Research on control of multi-inverter parallel is the focus as the key technique,which can improve the reliability of microgrids.The inverters in the microgrid operate in parallel,which not only facilitates the expansion of the microgrid but also improves the reliability of the operation of the microgrid system in off-grid mode.The key to the parallel operation of the inverter is to achieve even distribution of the load current.In this paper,a comprehensive review on the control strategies of parallel-operated inverters is presented.Also,the detailed analysis,comparison,and discussion on the existing parallel control strategies are investigated.展开更多
The increasing use of power electronic devices can deteriorate the power quality by introducing voltage and current harmonics.In islanded microgrids,the presence of nonlinear loads can distort the point of common coup...The increasing use of power electronic devices can deteriorate the power quality by introducing voltage and current harmonics.In islanded microgrids,the presence of nonlinear loads can distort the point of common coupling(PCC)voltage,while the dead-time effect can also bring additional circulating current harmonics among parallel inverters.To simultaneously attenuate the PCC voltage harmonics and suppress the dead-time induced circulating current harmonics,this paper proposes a coordinated control strategy for harmonic mitigation of parallel inverters.The proposed control strategy allows inverter impedances to be properly reshaped at selective harmonic frequencies.As a consequence,the PCC voltage harmonics are filtered by the inverter operating in the harmonic compensation mode(HCM),whereas the dead-time induced circulating current harmonics are suppressed by the inverter operating in the harmonic rejection mode(HRM).Experimental results from an islanded microgrid prototype with two parallel inverters are provided to validate the effectiveness of the proposed control strategy.展开更多
Ⅰ. INTRODUCTION MULTILEVEL inverters are increasingly being used in high-power medium voltage applications due to their superior performance compared to two-level inverters, such as lower common-mode voltage, lower d...Ⅰ. INTRODUCTION MULTILEVEL inverters are increasingly being used in high-power medium voltage applications due to their superior performance compared to two-level inverters, such as lower common-mode voltage, lower dv/dt, lower harmonics in output voltage and current, and reduced voltage on the power switches.展开更多
Parallel converter can significantly increase the capacity of the converter and improve the power quality of AC side, but the circulation which can lead to high switching loss and even damage the devices will easily e...Parallel converter can significantly increase the capacity of the converter and improve the power quality of AC side, but the circulation which can lead to high switching loss and even damage the devices will easily exist in the direct parallel converters. In this paper, the average model of parallel interleaved inverters system to analyze the circulation current is shown, and the cross current is relevant to DC-bus voltage and the overlap time of zero vectors in the switching period. Based on this observation, a discontinuous space vector modulation without using zero vectors (000) is eliminate and suppress the zero-sequence current to entire system. Finally, the effectiveness of modulation strategy is verified by the simulations in this paper.展开更多
A deconpling control strategy of inverter parallel system is proposed based on the equivalent output impedance of single phase voltage source SPWM (sinusoidal pulse width modulation) inverter. The active power and r...A deconpling control strategy of inverter parallel system is proposed based on the equivalent output impedance of single phase voltage source SPWM (sinusoidal pulse width modulation) inverter. The active power and reactive power are calculated in terms of output voltage and current of the inverter, and sent to the other inverters in the parallel system via controller area network (CAN) bus. By calculating and decoupling the circumfluence of the active power and reactive power, the inverters can share load current via the regulation of the reference-signal phase and amplitude. Experimental results of an 110V/2kVA inverter parallel system show the feasibility of the decoupling control strategy.展开更多
The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial p...The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial power equipment at high switching frequencies. This paper presents an adaptive composite soft switching configuration which combines snubber functions and resonant ZCS circuits for switches in inverters using power bridge leg modules. Simulation and experimental results are included.展开更多
An adaptive stable observer with output current online identification strategy for the auxiliary inverters applied in advanced electric trains, such as high speed railway, urban rail, subway and maglev trains, is prop...An adaptive stable observer with output current online identification strategy for the auxiliary inverters applied in advanced electric trains, such as high speed railway, urban rail, subway and maglev trains, is proposed. The designed observer is used to estimate the state variables, i.e. controllable duty ratio and current components in d-q-o rotary reference frame. The convergence of the observer estimation error is analyzed with consideration of uncertain level variation of input voltage at direct current(DC) side and sufficient conditions are given to prove its practical stability. Experimental results are shown to confirm the effectiveness of the proposed observer.展开更多
This paper proposes a new concept of synthesized voltage vector to address dead-time effect issue for Finite Control Set Model Predictive Control(FCS-MPC)technique.For a voltage source inverter(VSI),dead-time is inevi...This paper proposes a new concept of synthesized voltage vector to address dead-time effect issue for Finite Control Set Model Predictive Control(FCS-MPC)technique.For a voltage source inverter(VSI),dead-time is inevitably inserted between the turn off and turn on instants of power devices to avoid short circuit phenomenon.The influence of dead-time leads to output voltage vector error of three-phase inverters.Furthermore,it will result in computing deviation in cost function,and will deteriorate the performance of the system if not properly dealt with.In this paper,the problem is clearly analyzed,and the solution to this issue is proposed by introducing a synthesized voltage vector.The proposed solution is verified by Hardware-in-the-loop(HiL)test in real time,and results validate the effectiveness of the proposed solution.展开更多
This paper proposes a robust dichotomy-based model predictive control(DS-MPC)with a fixed switching frequency for the grid-connected inverter(GCI).The proposed fast dichotomy algorithm can select and deduce the optima...This paper proposes a robust dichotomy-based model predictive control(DS-MPC)with a fixed switching frequency for the grid-connected inverter(GCI).The proposed fast dichotomy algorithm can select and deduce the optimal voltage vector dynamically through the space vector plane.Therefore,the proposed DS-MPC strategy could ensure dynamic performance and steady-state performance as well.Also,the current control robustness can be improved through DS-MPC with disturbance observer(DO)based on the extended Kalman filter(EKF).The novelty of this control is that the current control with fast dynamic response can be realized in the weak grid,even if the grid voltages are greatly distorted.Simulation and hardware experiments on the weak grid validate the effectiveness of the proposed DS-MPC with the EKF observer approach.展开更多
Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used t...Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.展开更多
Fuzzy logic control(FLC)systems have found wide utilization in several industrial applications.This paper proposes a fuzzy logic-based fault detection and identification method for open-circuit switch fault in grid-ti...Fuzzy logic control(FLC)systems have found wide utilization in several industrial applications.This paper proposes a fuzzy logic-based fault detection and identification method for open-circuit switch fault in grid-tied photovoltaic(PV)inverters.Large installations and ambitious plans have been recently achieved for PV systems as clean and renewable power generation sources due to their improved environmental impacts and availability everywhere.Power converters represent the main parts for the grid integration of PV systems.However,PV power converters contain several power switches that construct their circuits.The power switches in PV systems are highly subjected to high stresses due to the continuously varying operating conditions.Moreover,the grid-tied systems represent nonlinear systems and the system model parameters are changing continuously.Consequently,the grid-tied PV systems have a nonlinear factor and the fault detection and identification(FDI)methods based on using mathematical models become more complex.The proposed fuzzy logic-based FDI(FL-FDI)method is based on employing the fuzzy logic concept for detecting and identifying the location of various switch faults.The proposed FL-FDI method is designed and extracted from the analysis and comparison of the various measured voltage/current components for the control purposes.Therefore,the proposed FL-FDI method does not require additional components or measurement circuits.Additionally,the proposed method can detect the faulty condition and also identify the location of the faulty switch for replacement and maintenance purposes.The proposed method can detect the faulty condition within only a single fundamental line period without the need for additional sensors and/or performing complex calculations or precise models.The proposed FL-FDI method is tested on the widely used T-type PV inverter system,wherein there are twelve different switches and the FDI process represents a challenging task.The results shows the superior and accurate performance of the proposed FL-FDI method.展开更多
This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power osci...This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power oscillations and current distortions are inevitable.In the proposed strategy,the extended power theory is introduced to compute the power feedbacks together with the classical power theory.Based on the combination of the classical and extended power theory,the proposed strategy can achieve the sinusoidal current provision and the flexible regulation between three common targets,i.e.,constant active power,balanced current,and constant reactive power.Meanwhile,the proposed strategy is associated with a power limiter,which is capable to keep the currents under the pre-defined threshold and to compute the maximum apparent power for better utilization of the inverter capacity.With this power limiter,the rated inverter capacity is fully used for both the active and reactive power provisions under unbalanced grid faults.Using the proposed power regulation and limitation,the VSI can avoid overcurrent tripping and flexibly regulate its power under unbalanced grid faults.All the conclusions are verified by the real-time hardware-in-loop tests.展开更多
Capacitor voltage imbalance is a significant problem for three-level inverters.Due to the mid-point modulation of these inverter topologies,the neutral point potential moves up or down depending on the neutral point c...Capacitor voltage imbalance is a significant problem for three-level inverters.Due to the mid-point modulation of these inverter topologies,the neutral point potential moves up or down depending on the neutral point current direction creating imbalanced voltages among the two capacitors.This imbalanced capacitor voltage causes imbalanced voltage stress among the semiconductor devices and causes increase output voltage and current harmonics.This paper introduces a modified voltage balancing strategy using two-level space vector modulation.By decomposing the three-level space vector diagram into two-level space vector diagram and redistributing the dwell times of the two-level zero space vectors,the modified voltage balancing method ensures minimal NP voltage ripple.Compared to the commonly used NP voltage control method(using 3L SVM[9]),the proposed modified NP voltage control method offers a slightly higher neutral-point voltage ripple and output voltage harmonics but,it has much lower switching loss,code size and execution time.展开更多
Battery energy storage systems,fuel cells,and photovoltaic generators are being adopted in distribution networks to achieve CO;emission reduction.These power sources require inverters to connect to AC networks.However...Battery energy storage systems,fuel cells,and photovoltaic generators are being adopted in distribution networks to achieve CO;emission reduction.These power sources require inverters to connect to AC networks.However,sub-networks,such as a microgrids containing inverter power sources,may be disconnected from the utility network and operated in a standalone mode during extended blackouts.This study focuses on a standalone microgrid supplied by inverter power sources without a synchronous generator and proposes a new microgrid inverter control.In this inverter control,a single grid forming inverter is operated as a master power source to determine frequency and voltage,and other inverters,called grid following inverters,are operated as subordinate power sources with active and reactive power control.The necessary functions in the energy management system are examined,and the coordinated operation of all inverters in the microgrid is demonstrated via simulation.展开更多
Excellent electrical properties and the impact of latest power devices for improving the efficiency of photovohaic(PV) inverters are presented.Power modules using SiC-MOSFET and SBD exhibit the possibility to realiz...Excellent electrical properties and the impact of latest power devices for improving the efficiency of photovohaic(PV) inverters are presented.Power modules using SiC-MOSFET and SBD exhibit the possibility to realize PV inverters with peak efficiency beyond 99%.Si-IGBT modules using reverse-blocking(RB)-IGBT have enabled to massproduce PV inverters with peak efficiency of 98.4%.Si superjunction(SJ)-MOSFET and discrete IGBT have enabled to improve the efficiency of small power PV inverters by 0.5 point.展开更多
The overall performance of photovoltaic (PV) inverter imphes many different technical issues.One of the key criterias is based on the measurement of the conversion and the maximum power point tracking (MPPT) effic...The overall performance of photovoltaic (PV) inverter imphes many different technical issues.One of the key criterias is based on the measurement of the conversion and the maximum power point tracking (MPPT) efficiency and its applicable evaluation in practice.Intense work has been done in the last few years to formulate applicable standards for measuring static and dynamic efficiencies worldwide.Besides that,this work is presenting on novel methods of analysis on non-trivial system characteristics impacting the final evaluation on the overall performance of the PV inverter.The elaborated testing procedures for complex system behavior under highly nonlinear conditions (unintentional partial shading, mismatching of DC strings) are explained and characterized.With the help of experimental results, the exclusive impact on the overall efficiency is illustrated and helpful statements are given on the resulting technical characteristics of MPP strategies.展开更多
This work reports on the integration of organic and inorganic semiconductors as heterojunction active layers for high-performance ambipolar transistors and complementary metal-oxide-semiconductor(CMOS)-like inverters....This work reports on the integration of organic and inorganic semiconductors as heterojunction active layers for high-performance ambipolar transistors and complementary metal-oxide-semiconductor(CMOS)-like inverters.Pentacene is employed as a p-type organic semiconductor for its stable electrical performance,while the solution-processed scandium(Sc)substituted indium oxide(ScInO)is employed as an n-type inorganic semiconductor.It is observed that by regulating the doping concentration of Sc,the electrical performance of the n-type semiconductor could be well controlled to obtain a balance with the electrical performance of the p-type semiconductor,which is vital for achieving high-performance inverters.When the doping concentration of Sc is 10 at.%,the CMOS-like logic inverters exhibit a voltage gain larger than 80 and a wide noise margin(53%of the theoretical value).The inverters also respond well to the input signal with frequency up to 500 Hz.展开更多
In this paper, signal distortions caused by spectral inverters which are used in 10Gb/s optical fiber communication systems with mid span spectrum inversion in terms of dispersion shift fibers are analyed numerically....In this paper, signal distortions caused by spectral inverters which are used in 10Gb/s optical fiber communication systems with mid span spectrum inversion in terms of dispersion shift fibers are analyed numerically. It is shown that there exist the optimal input signal power, fiber length and fiblter bandwidth for the spectral in verters. System transmission penalty can be minimized by optimizing these parameters.展开更多
基金funded by Tsinghua University-Weichai Power Intelligent Manufacturing Joint Research Institute (WCDL-GH-2022-0131)。
文摘For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.
文摘With the development and utilization of renewable energy,the scaling of microgrid composed of distributed generation systems and energy storing devices,e.g,photovoltaic(PV),wind power,micro gas turbine,fuel cell,are becoming much lager.Research on control of multi-inverter parallel is the focus as the key technique,which can improve the reliability of microgrids.The inverters in the microgrid operate in parallel,which not only facilitates the expansion of the microgrid but also improves the reliability of the operation of the microgrid system in off-grid mode.The key to the parallel operation of the inverter is to achieve even distribution of the load current.In this paper,a comprehensive review on the control strategies of parallel-operated inverters is presented.Also,the detailed analysis,comparison,and discussion on the existing parallel control strategies are investigated.
基金This research was supported by the National Research Foundation,Prime Minister’s Office,Singapore under the Energy Programme and administrated by the Energy Market Authority(EP Award No.NRF2015EWT-EIRP002-007)。
文摘The increasing use of power electronic devices can deteriorate the power quality by introducing voltage and current harmonics.In islanded microgrids,the presence of nonlinear loads can distort the point of common coupling(PCC)voltage,while the dead-time effect can also bring additional circulating current harmonics among parallel inverters.To simultaneously attenuate the PCC voltage harmonics and suppress the dead-time induced circulating current harmonics,this paper proposes a coordinated control strategy for harmonic mitigation of parallel inverters.The proposed control strategy allows inverter impedances to be properly reshaped at selective harmonic frequencies.As a consequence,the PCC voltage harmonics are filtered by the inverter operating in the harmonic compensation mode(HCM),whereas the dead-time induced circulating current harmonics are suppressed by the inverter operating in the harmonic rejection mode(HRM).Experimental results from an islanded microgrid prototype with two parallel inverters are provided to validate the effectiveness of the proposed control strategy.
文摘Ⅰ. INTRODUCTION MULTILEVEL inverters are increasingly being used in high-power medium voltage applications due to their superior performance compared to two-level inverters, such as lower common-mode voltage, lower dv/dt, lower harmonics in output voltage and current, and reduced voltage on the power switches.
文摘Parallel converter can significantly increase the capacity of the converter and improve the power quality of AC side, but the circulation which can lead to high switching loss and even damage the devices will easily exist in the direct parallel converters. In this paper, the average model of parallel interleaved inverters system to analyze the circulation current is shown, and the cross current is relevant to DC-bus voltage and the overlap time of zero vectors in the switching period. Based on this observation, a discontinuous space vector modulation without using zero vectors (000) is eliminate and suppress the zero-sequence current to entire system. Finally, the effectiveness of modulation strategy is verified by the simulations in this paper.
基金supported by the National Natural Science Foundation of China under Grant No 50677056
文摘A deconpling control strategy of inverter parallel system is proposed based on the equivalent output impedance of single phase voltage source SPWM (sinusoidal pulse width modulation) inverter. The active power and reactive power are calculated in terms of output voltage and current of the inverter, and sent to the other inverters in the parallel system via controller area network (CAN) bus. By calculating and decoupling the circumfluence of the active power and reactive power, the inverters can share load current via the regulation of the reference-signal phase and amplitude. Experimental results of an 110V/2kVA inverter parallel system show the feasibility of the decoupling control strategy.
基金Supported by the Zhejiang Province Natural Science Foundationthe Royal Society of U.K.
文摘The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial power equipment at high switching frequencies. This paper presents an adaptive composite soft switching configuration which combines snubber functions and resonant ZCS circuits for switches in inverters using power bridge leg modules. Simulation and experimental results are included.
基金Project(61273158)supported by the National Natural Science Foundation of China
文摘An adaptive stable observer with output current online identification strategy for the auxiliary inverters applied in advanced electric trains, such as high speed railway, urban rail, subway and maglev trains, is proposed. The designed observer is used to estimate the state variables, i.e. controllable duty ratio and current components in d-q-o rotary reference frame. The convergence of the observer estimation error is analyzed with consideration of uncertain level variation of input voltage at direct current(DC) side and sufficient conditions are given to prove its practical stability. Experimental results are shown to confirm the effectiveness of the proposed observer.
文摘This paper proposes a new concept of synthesized voltage vector to address dead-time effect issue for Finite Control Set Model Predictive Control(FCS-MPC)technique.For a voltage source inverter(VSI),dead-time is inevitably inserted between the turn off and turn on instants of power devices to avoid short circuit phenomenon.The influence of dead-time leads to output voltage vector error of three-phase inverters.Furthermore,it will result in computing deviation in cost function,and will deteriorate the performance of the system if not properly dealt with.In this paper,the problem is clearly analyzed,and the solution to this issue is proposed by introducing a synthesized voltage vector.The proposed solution is verified by Hardware-in-the-loop(HiL)test in real time,and results validate the effectiveness of the proposed solution.
文摘This paper proposes a robust dichotomy-based model predictive control(DS-MPC)with a fixed switching frequency for the grid-connected inverter(GCI).The proposed fast dichotomy algorithm can select and deduce the optimal voltage vector dynamically through the space vector plane.Therefore,the proposed DS-MPC strategy could ensure dynamic performance and steady-state performance as well.Also,the current control robustness can be improved through DS-MPC with disturbance observer(DO)based on the extended Kalman filter(EKF).The novelty of this control is that the current control with fast dynamic response can be realized in the weak grid,even if the grid voltages are greatly distorted.Simulation and hardware experiments on the weak grid validate the effectiveness of the proposed DS-MPC with the EKF observer approach.
文摘Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.
基金supported by the Deanship of Scientific Research at Prince Sattam Bin Abdulaziz University under the research project No.2020/01/11742.
文摘Fuzzy logic control(FLC)systems have found wide utilization in several industrial applications.This paper proposes a fuzzy logic-based fault detection and identification method for open-circuit switch fault in grid-tied photovoltaic(PV)inverters.Large installations and ambitious plans have been recently achieved for PV systems as clean and renewable power generation sources due to their improved environmental impacts and availability everywhere.Power converters represent the main parts for the grid integration of PV systems.However,PV power converters contain several power switches that construct their circuits.The power switches in PV systems are highly subjected to high stresses due to the continuously varying operating conditions.Moreover,the grid-tied systems represent nonlinear systems and the system model parameters are changing continuously.Consequently,the grid-tied PV systems have a nonlinear factor and the fault detection and identification(FDI)methods based on using mathematical models become more complex.The proposed fuzzy logic-based FDI(FL-FDI)method is based on employing the fuzzy logic concept for detecting and identifying the location of various switch faults.The proposed FL-FDI method is designed and extracted from the analysis and comparison of the various measured voltage/current components for the control purposes.Therefore,the proposed FL-FDI method does not require additional components or measurement circuits.Additionally,the proposed method can detect the faulty condition and also identify the location of the faulty switch for replacement and maintenance purposes.The proposed method can detect the faulty condition within only a single fundamental line period without the need for additional sensors and/or performing complex calculations or precise models.The proposed FL-FDI method is tested on the widely used T-type PV inverter system,wherein there are twelve different switches and the FDI process represents a challenging task.The results shows the superior and accurate performance of the proposed FL-FDI method.
基金This work is supported by the National Key Research and Development Program of China under Project 2021YFB2601600。
文摘This paper develops a flexible power regulation and limitation strategy of voltage source inverters(VSIs)under unbalanced grid faults.When the classical power theory is used under unbalanced grid faults,the power oscillations and current distortions are inevitable.In the proposed strategy,the extended power theory is introduced to compute the power feedbacks together with the classical power theory.Based on the combination of the classical and extended power theory,the proposed strategy can achieve the sinusoidal current provision and the flexible regulation between three common targets,i.e.,constant active power,balanced current,and constant reactive power.Meanwhile,the proposed strategy is associated with a power limiter,which is capable to keep the currents under the pre-defined threshold and to compute the maximum apparent power for better utilization of the inverter capacity.With this power limiter,the rated inverter capacity is fully used for both the active and reactive power provisions under unbalanced grid faults.Using the proposed power regulation and limitation,the VSI can avoid overcurrent tripping and flexibly regulate its power under unbalanced grid faults.All the conclusions are verified by the real-time hardware-in-loop tests.
文摘Capacitor voltage imbalance is a significant problem for three-level inverters.Due to the mid-point modulation of these inverter topologies,the neutral point potential moves up or down depending on the neutral point current direction creating imbalanced voltages among the two capacitors.This imbalanced capacitor voltage causes imbalanced voltage stress among the semiconductor devices and causes increase output voltage and current harmonics.This paper introduces a modified voltage balancing strategy using two-level space vector modulation.By decomposing the three-level space vector diagram into two-level space vector diagram and redistributing the dwell times of the two-level zero space vectors,the modified voltage balancing method ensures minimal NP voltage ripple.Compared to the commonly used NP voltage control method(using 3L SVM[9]),the proposed modified NP voltage control method offers a slightly higher neutral-point voltage ripple and output voltage harmonics but,it has much lower switching loss,code size and execution time.
文摘Battery energy storage systems,fuel cells,and photovoltaic generators are being adopted in distribution networks to achieve CO;emission reduction.These power sources require inverters to connect to AC networks.However,sub-networks,such as a microgrids containing inverter power sources,may be disconnected from the utility network and operated in a standalone mode during extended blackouts.This study focuses on a standalone microgrid supplied by inverter power sources without a synchronous generator and proposes a new microgrid inverter control.In this inverter control,a single grid forming inverter is operated as a master power source to determine frequency and voltage,and other inverters,called grid following inverters,are operated as subordinate power sources with active and reactive power control.The necessary functions in the energy management system are examined,and the coordinated operation of all inverters in the microgrid is demonstrated via simulation.
文摘Excellent electrical properties and the impact of latest power devices for improving the efficiency of photovohaic(PV) inverters are presented.Power modules using SiC-MOSFET and SBD exhibit the possibility to realize PV inverters with peak efficiency beyond 99%.Si-IGBT modules using reverse-blocking(RB)-IGBT have enabled to massproduce PV inverters with peak efficiency of 98.4%.Si superjunction(SJ)-MOSFET and discrete IGBT have enabled to improve the efficiency of small power PV inverters by 0.5 point.
文摘The overall performance of photovoltaic (PV) inverter imphes many different technical issues.One of the key criterias is based on the measurement of the conversion and the maximum power point tracking (MPPT) efficiency and its applicable evaluation in practice.Intense work has been done in the last few years to formulate applicable standards for measuring static and dynamic efficiencies worldwide.Besides that,this work is presenting on novel methods of analysis on non-trivial system characteristics impacting the final evaluation on the overall performance of the PV inverter.The elaborated testing procedures for complex system behavior under highly nonlinear conditions (unintentional partial shading, mismatching of DC strings) are explained and characterized.With the help of experimental results, the exclusive impact on the overall efficiency is illustrated and helpful statements are given on the resulting technical characteristics of MPP strategies.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61574003 and 61774010)Shenzhen Municipal Scientific Program,China(Grant Nos.GGFW20170728163447038 and JCYJ20180504165449640).
文摘This work reports on the integration of organic and inorganic semiconductors as heterojunction active layers for high-performance ambipolar transistors and complementary metal-oxide-semiconductor(CMOS)-like inverters.Pentacene is employed as a p-type organic semiconductor for its stable electrical performance,while the solution-processed scandium(Sc)substituted indium oxide(ScInO)is employed as an n-type inorganic semiconductor.It is observed that by regulating the doping concentration of Sc,the electrical performance of the n-type semiconductor could be well controlled to obtain a balance with the electrical performance of the p-type semiconductor,which is vital for achieving high-performance inverters.When the doping concentration of Sc is 10 at.%,the CMOS-like logic inverters exhibit a voltage gain larger than 80 and a wide noise margin(53%of the theoretical value).The inverters also respond well to the input signal with frequency up to 500 Hz.
文摘In this paper, signal distortions caused by spectral inverters which are used in 10Gb/s optical fiber communication systems with mid span spectrum inversion in terms of dispersion shift fibers are analyed numerically. It is shown that there exist the optimal input signal power, fiber length and fiblter bandwidth for the spectral in verters. System transmission penalty can be minimized by optimizing these parameters.