Uneven power distribution,transient voltage,and frequency deviations are observed in the photovoltaic storage hybrid inverter during the switching between grid-connected and island modes.In response to these issues,th...Uneven power distribution,transient voltage,and frequency deviations are observed in the photovoltaic storage hybrid inverter during the switching between grid-connected and island modes.In response to these issues,this paper proposes a grid-connected/island switching control strategy for photovoltaic storage hybrid inverters based on the modified chimpanzee optimization algorithm.The proposed strategy incorporates coupling compensation and power differentiation elements based on the traditional droop control.Then,it combines the angular frequency and voltage amplitude adjustments provided by the phase-locked loop-free pre-synchronization control strategy.Precise pre-synchronization is achieved by regulating the virtual current to zero and aligning the photovoltaic storage hybrid inverter with the grid voltage.Additionally,two novel operators,learning and emotional behaviors are introduced to enhance the optimization precision of the chimpanzee algorithm.These operators ensure high-precision and high-reliability optimization of the droop control parameters for photovoltaic storage hybrid inverters.A Simulink model was constructed for simulation analysis,which validated the optimized control strategy’s ability to evenly distribute power under load transients.This strategy effectively mitigated transient voltage and current surges during mode transitions.Consequently,seamless and efficient switching between gridconnected and island modes was achieved for the photovoltaic storage hybrid inverter.The enhanced energy utilization efficiency,in turn,offers robust technical support for grid stability.展开更多
To improve the fault diagnosis accuracy of a PV grid-connected inverter,a PV grid-connected inverter data diagnosis method based on MPA-VMD-PSO-BiLSTM is proposed.Firstly,unlike the traditional VMD algorithm which rel...To improve the fault diagnosis accuracy of a PV grid-connected inverter,a PV grid-connected inverter data diagnosis method based on MPA-VMD-PSO-BiLSTM is proposed.Firstly,unlike the traditional VMD algorithm which relies on manual experience to set parameters(e.g.,noise tolerance,penalty parameter,number of decompositions),this paper achieves adaptive optimization of parameters through MPA algorithmto avoid the problemof feature information loss caused by manual parameter tuning,and adopts the improved VMD algorithm for feature extraction of DC-side voltage data signals of PV-grid-connected inverters;and then,adopts the PSO algorithm for theThen,the PSO algorithm is used to optimize the optimal batch size,the number of nodes in the hidden layer and the learning rate of the BiLSTM network,which significantly improves the model’s ability to capture the long-term dependent features of the PV inverter’s timing signals,to construct the PV grid-connected inverter prediction model of PSO-BiLSTM,and predict the capacitance value of the PVgrid-connected inverter.Finally,diagnostic experiments are carried out based on the expected capacitance value and the capacitance failure criterion.The results showthat compared with the traditional VMD algorithm,the MPA-optimised VMD improves the signal-to-noise ratio(SNR)of the signal decomposition from 28.5 to 33.2 dB(16.5%improvement).After combining with the PSO-BiLSTM model,the mean absolute percentage error(MAPE)of the fault diagnosis is reduced to 1.31%,and the coefficient of determination(R2)is up to 0.99.It is concluded that the present method has excellent diagnostic performance of PV grid-connected inverter data signals and effectively improves the accuracy of PV grid-connected inverter diagnosis.展开更多
The development of renewable energy power generation for carbon neutrality and energy transition has been increasing worldwide,leading to an increasing demand for high-power conversion.Compared with traditional interl...The development of renewable energy power generation for carbon neutrality and energy transition has been increasing worldwide,leading to an increasing demand for high-power conversion.Compared with traditional interleaved paralleling,the integrated paralleling of three-level inverters can further reduce the output harmonics.Moreover,a well-designed switching sequence ensures that the average circulating current is zero,which provides a superior and feasible solution to satisfy the demands of high-power operations.However,a large instantaneous loop current exists between shunt converters,which leads to disadvantages such as higher switching device stress and loss.In this study,by utilizing the state-distribution redundancy provided by the integrated modulation process,a new design for switch-ing sequences is suggested for the integrated modulation of shunt three-level converters.This design aims to reduce the circulating current while better preserving the same output current harmonics than traditional parallel methods.The proposal includes an in-depth analysis and explanation of the implementation process.Finally,the proposed method is validated through simulations and prototype experi-ments.The results indicate that compared with traditional methods,the adoption of the improved switching sequence presented in this study leads to an average reduction of 3.2%in the total harmonic distortion of the inverter’s output and an average decrease of 32%in the amplitude of the circulating current.Both the output harmonics and circulating currents are significantly suppressed across various modulation indices.展开更多
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
The use of high-permittivity(high-k) thin films as gate dielectrics is essential in the development of lowpower electronics,In this work,rare-earth thulium oxide(Tm_(2)O_(3)) thin films were prepared by a facile solut...The use of high-permittivity(high-k) thin films as gate dielectrics is essential in the development of lowpower electronics,In this work,rare-earth thulium oxide(Tm_(2)O_(3)) thin films were prepared by a facile solution process and annealed at various temperatures from 400 to 700℃.The evolution of the physical and dielectric properties of Tm_(2)O_(3) thin film with annealing temperature was investigated.It is demonstrated that the Tm_(2)O_(3) thin film annealed at 600℃ exhibits the optimal performance,including a low leakage current of 3×10^(-10) A/cm^(2),a large areal capacitance of 250 nF/cm^(2) at 100 Hz,and a high permittivity value of 14.2.The Tm_(2)O_(3) thin film as a gate insulator was integrated into the thin film transistor(TFT) employing In_(2)O_(3)-based semiconducting channels.The In_(2)O_(3) TFT with 600℃-annealed Tm_(2)O_(3) dielectric exhibits the superior perfo rmance,with a high I_(on)/I_(off) of 1.65×10^(7),a small subthre shold swing(SS) value of 0.2 V/dec,a V_(TH) of+1.8 V,and a mobility of 1.68 cm^(2)/(V·s).Furthermore,an inverter constructed by connecting the TFT with a resistor exhibits full-swing characteristics.This work provides a facile and appealing method for preparing the high-k Tm_(2)O_(3) thin films as alternative gate dielectrics with the potential for use in low-power electronics and logic circuit applications.展开更多
The pulse width modulation (PWM) scheme is used in the staircase waveform inverters. The control strategy and system characteristics are analyzed. While the single pulse width modulation is used, the 12 stairs wavefo...The pulse width modulation (PWM) scheme is used in the staircase waveform inverters. The control strategy and system characteristics are analyzed. While the single pulse width modulation is used, the 12 stairs waveform inverter can achieve the output voltage regulated in a wide range of input voltage as well as the perfect output waveform. A 1 500 V input 80 kVA inverter has been deve loped. Experiments of the 80kVA inverter resulted in that the scheme is a perfect method for the development of high power converters with high efficiency.展开更多
Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width mo...Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.展开更多
Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation o...Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation of the photovoltaic system. To overcome the problems mentioned above, the mathematical model of the parallel photovoltaic inverters is established. Several factors including the impact of the reference current of the grid-connected inverter, the grid voltage interference and the current disturbance between the photovoltaic inverters in parallel with the grid-connected inverters are analyzed. The grid impedance and the LCL filter of the photovoltaic inverter system are found to be the key elements which lead to existence of resonance peak. This paper presents the branch voltage and current double feedback suppression method under the premise of not changing the topological structure of the photovoltaic inverter, which effectively handles the resonance peak, weakens the harmonic content of the grid current of the photovoltaic grid-connected inverter and the voltage at the point of common coupling, and improves the stability of the parallel operation of the photovoltaic grid-connected inverters in weak grid. At last, the simulation model is established to verify the reliability of this suppression method.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
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
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
Security and reliability of inverter are an indispensable part in power electronic system. Faults of inverter are usually caused by switch elements’ operating fault. Taking the inverter with hysteresis current contro...Security and reliability of inverter are an indispensable part in power electronic system. Faults of inverter are usually caused by switch elements’ operating fault. Taking the inverter with hysteresis current control as the research object, a universal open-circuit fault location method which can be applied to multiple control strategies is proposed in the paper. If the switch open-circuit fault happens in inverter, the output phase current will inevitably change, which can be used as a characteristic for diagnosis, combined with the comparison of phase-current direction before and after the fault occurrence, to diagnose and locate the open-circuit fault in a half cycle. Moreover, this method requires neither system control signals nor sensor. The validity, reliability and limitation of the fault location method in the paper are verified and analyzed through dSPACE-based experiment platform.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
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
Cascade multilevel inverters have been developed for electric utility applications. A cascade M level inverter consists of (M 1)/2 H bridges in which each bridge's dc voltage is supported by its own dc capacito...Cascade multilevel inverters have been developed for electric utility applications. A cascade M level inverter consists of (M 1)/2 H bridges in which each bridge's dc voltage is supported by its own dc capacitor. The new inverter can: (1) generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle; (2) dispense with multi pulse inverters' transformers used in conventional utility interfaces and static var compensators; (3) enables direct parallel or series transformer less connection to medium and high voltage power systems. In short, the cascade inverter is much more efficient and suitable for utility applications than traditional multi pulse and pulse width modulation (PWM) inverters. The authors have experimentally demonstrated the superiority of the new inverter for power supply, (hybrid) electric vehicle (EV) motor drive, reactive power (var) and harmonic compensation. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, var compensation, and harmonic filtering in power systems. Analytical, simulated, and experimental results demonstrated the superiority of the new inverters.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
基金received funding from the Postgraduate Research&Practice Innovation Program of Jiangsu Province(SJCX23_1633)2023 University Student Innovation and Entrepreneurship Training Program(202311463009Z)+1 种基金Changzhou Science and Technology Support Project(CE20235045)Open Project of Jiangsu Key Laboratory of Power Transmission&Distribution Equipment Technology(2021JSSPD12).
文摘Uneven power distribution,transient voltage,and frequency deviations are observed in the photovoltaic storage hybrid inverter during the switching between grid-connected and island modes.In response to these issues,this paper proposes a grid-connected/island switching control strategy for photovoltaic storage hybrid inverters based on the modified chimpanzee optimization algorithm.The proposed strategy incorporates coupling compensation and power differentiation elements based on the traditional droop control.Then,it combines the angular frequency and voltage amplitude adjustments provided by the phase-locked loop-free pre-synchronization control strategy.Precise pre-synchronization is achieved by regulating the virtual current to zero and aligning the photovoltaic storage hybrid inverter with the grid voltage.Additionally,two novel operators,learning and emotional behaviors are introduced to enhance the optimization precision of the chimpanzee algorithm.These operators ensure high-precision and high-reliability optimization of the droop control parameters for photovoltaic storage hybrid inverters.A Simulink model was constructed for simulation analysis,which validated the optimized control strategy’s ability to evenly distribute power under load transients.This strategy effectively mitigated transient voltage and current surges during mode transitions.Consequently,seamless and efficient switching between gridconnected and island modes was achieved for the photovoltaic storage hybrid inverter.The enhanced energy utilization efficiency,in turn,offers robust technical support for grid stability.
基金supported by Science and Technology Projects of Jiangsu Province(No.BE2022003)Science and Technology Projects of Jiangsu Province(No.BE2022003-5).
文摘To improve the fault diagnosis accuracy of a PV grid-connected inverter,a PV grid-connected inverter data diagnosis method based on MPA-VMD-PSO-BiLSTM is proposed.Firstly,unlike the traditional VMD algorithm which relies on manual experience to set parameters(e.g.,noise tolerance,penalty parameter,number of decompositions),this paper achieves adaptive optimization of parameters through MPA algorithmto avoid the problemof feature information loss caused by manual parameter tuning,and adopts the improved VMD algorithm for feature extraction of DC-side voltage data signals of PV-grid-connected inverters;and then,adopts the PSO algorithm for theThen,the PSO algorithm is used to optimize the optimal batch size,the number of nodes in the hidden layer and the learning rate of the BiLSTM network,which significantly improves the model’s ability to capture the long-term dependent features of the PV inverter’s timing signals,to construct the PV grid-connected inverter prediction model of PSO-BiLSTM,and predict the capacitance value of the PVgrid-connected inverter.Finally,diagnostic experiments are carried out based on the expected capacitance value and the capacitance failure criterion.The results showthat compared with the traditional VMD algorithm,the MPA-optimised VMD improves the signal-to-noise ratio(SNR)of the signal decomposition from 28.5 to 33.2 dB(16.5%improvement).After combining with the PSO-BiLSTM model,the mean absolute percentage error(MAPE)of the fault diagnosis is reduced to 1.31%,and the coefficient of determination(R2)is up to 0.99.It is concluded that the present method has excellent diagnostic performance of PV grid-connected inverter data signals and effectively improves the accuracy of PV grid-connected inverter diagnosis.
基金supported by the National Natural Science Foundation of China(Grant No.51977046)Wuxi University Research Start-up Fund for Introduced Talent(2022r021).
文摘The development of renewable energy power generation for carbon neutrality and energy transition has been increasing worldwide,leading to an increasing demand for high-power conversion.Compared with traditional interleaved paralleling,the integrated paralleling of three-level inverters can further reduce the output harmonics.Moreover,a well-designed switching sequence ensures that the average circulating current is zero,which provides a superior and feasible solution to satisfy the demands of high-power operations.However,a large instantaneous loop current exists between shunt converters,which leads to disadvantages such as higher switching device stress and loss.In this study,by utilizing the state-distribution redundancy provided by the integrated modulation process,a new design for switch-ing sequences is suggested for the integrated modulation of shunt three-level converters.This design aims to reduce the circulating current while better preserving the same output current harmonics than traditional parallel methods.The proposal includes an in-depth analysis and explanation of the implementation process.Finally,the proposed method is validated through simulations and prototype experi-ments.The results indicate that compared with traditional methods,the adoption of the improved switching sequence presented in this study leads to an average reduction of 3.2%in the total harmonic distortion of the inverter’s output and an average decrease of 32%in the amplitude of the circulating current.Both the output harmonics and circulating currents are significantly suppressed across various modulation indices.
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.
基金supported by the National Natural Science Foundation of China (21978142,52005277)。
文摘The use of high-permittivity(high-k) thin films as gate dielectrics is essential in the development of lowpower electronics,In this work,rare-earth thulium oxide(Tm_(2)O_(3)) thin films were prepared by a facile solution process and annealed at various temperatures from 400 to 700℃.The evolution of the physical and dielectric properties of Tm_(2)O_(3) thin film with annealing temperature was investigated.It is demonstrated that the Tm_(2)O_(3) thin film annealed at 600℃ exhibits the optimal performance,including a low leakage current of 3×10^(-10) A/cm^(2),a large areal capacitance of 250 nF/cm^(2) at 100 Hz,and a high permittivity value of 14.2.The Tm_(2)O_(3) thin film as a gate insulator was integrated into the thin film transistor(TFT) employing In_(2)O_(3)-based semiconducting channels.The In_(2)O_(3) TFT with 600℃-annealed Tm_(2)O_(3) dielectric exhibits the superior perfo rmance,with a high I_(on)/I_(off) of 1.65×10^(7),a small subthre shold swing(SS) value of 0.2 V/dec,a V_(TH) of+1.8 V,and a mobility of 1.68 cm^(2)/(V·s).Furthermore,an inverter constructed by connecting the TFT with a resistor exhibits full-swing characteristics.This work provides a facile and appealing method for preparing the high-k Tm_(2)O_(3) thin films as alternative gate dielectrics with the potential for use in low-power electronics and logic circuit applications.
文摘The pulse width modulation (PWM) scheme is used in the staircase waveform inverters. The control strategy and system characteristics are analyzed. While the single pulse width modulation is used, the 12 stairs waveform inverter can achieve the output voltage regulated in a wide range of input voltage as well as the perfect output waveform. A 1 500 V input 80 kVA inverter has been deve loped. Experiments of the 80kVA inverter resulted in that the scheme is a perfect method for the development of high power converters with high efficiency.
文摘Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.
基金supported by National Natural Science Foundation of China (No. 61573303)Natural Science Foundation of Hebei Province (No. E2016203092)
文摘Obvious resonance peak will be generated when parallel photovoltaic grid-connected inverters are connected to the weak grid with high grid impedance, which seriously affects the stability of grid-connected operation of the photovoltaic system. To overcome the problems mentioned above, the mathematical model of the parallel photovoltaic inverters is established. Several factors including the impact of the reference current of the grid-connected inverter, the grid voltage interference and the current disturbance between the photovoltaic inverters in parallel with the grid-connected inverters are analyzed. The grid impedance and the LCL filter of the photovoltaic inverter system are found to be the key elements which lead to existence of resonance peak. This paper presents the branch voltage and current double feedback suppression method under the premise of not changing the topological structure of the photovoltaic inverter, which effectively handles the resonance peak, weakens the harmonic content of the grid current of the photovoltaic grid-connected inverter and the voltage at the point of common coupling, and improves the stability of the parallel operation of the photovoltaic grid-connected inverters in weak grid. At last, the simulation model is established to verify the reliability of this suppression method.
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.
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Projects(2016YFB1200401,2017YFB1200801)supported by the National Key R&D Program of China
文摘Security and reliability of inverter are an indispensable part in power electronic system. Faults of inverter are usually caused by switch elements’ operating fault. Taking the inverter with hysteresis current control as the research object, a universal open-circuit fault location method which can be applied to multiple control strategies is proposed in the paper. If the switch open-circuit fault happens in inverter, the output phase current will inevitably change, which can be used as a characteristic for diagnosis, combined with the comparison of phase-current direction before and after the fault occurrence, to diagnose and locate the open-circuit fault in a half cycle. Moreover, this method requires neither system control signals nor sensor. The validity, reliability and limitation of the fault location method in the paper are verified and analyzed through dSPACE-based experiment platform.
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Cascade multilevel inverters have been developed for electric utility applications. A cascade M level inverter consists of (M 1)/2 H bridges in which each bridge's dc voltage is supported by its own dc capacitor. The new inverter can: (1) generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle; (2) dispense with multi pulse inverters' transformers used in conventional utility interfaces and static var compensators; (3) enables direct parallel or series transformer less connection to medium and high voltage power systems. In short, the cascade inverter is much more efficient and suitable for utility applications than traditional multi pulse and pulse width modulation (PWM) inverters. The authors have experimentally demonstrated the superiority of the new inverter for power supply, (hybrid) electric vehicle (EV) motor drive, reactive power (var) and harmonic compensation. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, var compensation, and harmonic filtering in power systems. Analytical, simulated, and experimental results demonstrated the superiority of the new inverters.
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.
