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
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
In this manuscript it is proposed and demonstrated that how an ANFIS (Adaptive Neuro Fuzzy Inference System) can be used in the control of a Voltage Source Inverter (VSI) connected to the grid. Volatile changes in the...In this manuscript it is proposed and demonstrated that how an ANFIS (Adaptive Neuro Fuzzy Inference System) can be used in the control of a Voltage Source Inverter (VSI) connected to the grid. Volatile changes in the gird parameters rising by its variable demands and other related issues may humiliate the efficiency with which power can be injected into the grid. The system becomes a higher order one with the filters used at the terminal of the Voltage Source Inverter (VSI) along with the parameters of the grid which change from time to time. Single time tuned mathematical controllers like the PID variants are not suitable for such applications. Considering the increased order of the system and the associated non-linearity we have to look out for intelligent controllers. An ANFIS based control is found to be promising;the development and implementation of one such are demonstrated in this paper using the MATLAB SIMULINK platform and through experimental verification using the Reduced Instruction Set Computer (RISC) Microcontroller Advanced RISC Machine (ARM) processor as the central controller for the VSI.展开更多
Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circu...Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circuit is made up of the parasitic capacitance of the power semiconductors and the leakage inductor of the transformer primary. In this paper two saturable inductors as magnetic switches are added to secondary, so output inductor is always reflected to primary and assists resonant transition. Full ZVS is achieved under lower load current. The above mentioned investigated results are validated by the computerized simulation and hardware circuit experiment.展开更多
The full bridge zero voltage zero current switching ( FB-ZVZCS ) , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circu...The full bridge zero voltage zero current switching ( FB-ZVZCS ) , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.展开更多
The application of LCL filters has become popular for inverters connected to the power grid due to their advantages in harmonic current reductions. However,the power grid in a distribution system is non-ideal, present...The application of LCL filters has become popular for inverters connected to the power grid due to their advantages in harmonic current reductions. However,the power grid in a distribution system is non-ideal, presenting itself as a voltage source with significant impedance. This means that an inverter using an LCL filter may interact with other grid-connected inverters via the nonideal grid. In this paper, damping optimization of LCLfilters to reduce this interaction is studied for a three-phase voltage source inverter(VSI). Simulation results show that resonant oscillation occurs in a distributed power grid, even if the VSI with an LCL filter is well designed for standalone applications. A small-signal analysis is performed to predict this stability problem and to locate the boundary of the instability using an impedance approach. Based on these analytical results, optimized damping of the LCLfilter can be designed. The oscillation phenomena and optimized damping design are verified by simulations and experimental measurements.展开更多
An inverter type power source system for robot arc welding is considered. The power source includes several isolated gate bipolar transistor (IGBT) inverter power units. The output current of every individual power un...An inverter type power source system for robot arc welding is considered. The power source includes several isolated gate bipolar transistor (IGBT) inverter power units. The output current of every individual power unit is regulated by an identical single chip microcomputer to enable the whole power source system to work over a wide range of continuous output current with good dynamic properties. This inverter type power source satisfies robotic welding requirements.展开更多
Current source inverter(CSI)is a class of power electronic converters that,thanks to the inherent boost capability and ease of control,is investigated for grid-tied photovoltaic power conversion applications.Tradition...Current source inverter(CSI)is a class of power electronic converters that,thanks to the inherent boost capability and ease of control,is investigated for grid-tied photovoltaic power conversion applications.Traditional CSI and CSI7 topologies are here analyzed and compared with two kind of space vector modulation strategies mainly in terms of ground leakage current both in simulations and experiments.Furthermore,THD of the injected grid current and the computation of conduction and switching semiconductor power losses are also carried out in numerical simulations.The topology comparison is carried out with the use of a different number of PV modules,to analyze the robustness of the topologies to different size of the PV strings.Simulation and experimental results show that the CSI7 topology,with respect to conventional CSI,allows to strongly reduce ground leakage current,phase current THD and semicondutor power losses,at the price of an additional power device.展开更多
In order to improve maximum power point tracking(MPPT) performance, a variable and adaptive perturb and observe(P&O)method with current predictive control is proposed. This is applied in three-phase threelevel neu...In order to improve maximum power point tracking(MPPT) performance, a variable and adaptive perturb and observe(P&O)method with current predictive control is proposed. This is applied in three-phase threelevel neutral-point clamped(NPC) photovoltaic(PV)generation systems. To control the active power and the reactive power independently,the decoupled power control combined with a space vector modulation block is adopted for three-phase NPC inverters in PV generation systems.To balance the neutral-point voltage of the three-phase NPC grid-connected inverter, a proportional and integral control is used by adj usting the dwell time of small voltage vectors. A three-phase NPC inverter rated at 12 kVA was established. The performance of the proposed method was tested and compared with the fixed perturbation MPPT algorithm under different conditions. Experimental results confirm the feasibility and advantages of the proposed method.展开更多
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In this manuscript it is proposed and demonstrated that how an ANFIS (Adaptive Neuro Fuzzy Inference System) can be used in the control of a Voltage Source Inverter (VSI) connected to the grid. Volatile changes in the gird parameters rising by its variable demands and other related issues may humiliate the efficiency with which power can be injected into the grid. The system becomes a higher order one with the filters used at the terminal of the Voltage Source Inverter (VSI) along with the parameters of the grid which change from time to time. Single time tuned mathematical controllers like the PID variants are not suitable for such applications. Considering the increased order of the system and the associated non-linearity we have to look out for intelligent controllers. An ANFIS based control is found to be promising;the development and implementation of one such are demonstrated in this paper using the MATLAB SIMULINK platform and through experimental verification using the Reduced Instruction Set Computer (RISC) Microcontroller Advanced RISC Machine (ARM) processor as the central controller for the VSI.
文摘Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circuit is made up of the parasitic capacitance of the power semiconductors and the leakage inductor of the transformer primary. In this paper two saturable inductors as magnetic switches are added to secondary, so output inductor is always reflected to primary and assists resonant transition. Full ZVS is achieved under lower load current. The above mentioned investigated results are validated by the computerized simulation and hardware circuit experiment.
文摘The full bridge zero voltage zero current switching ( FB-ZVZCS ) , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.
基金supported by National Natural Science Foundation of China(No.51507118)by Open Fund of State Key Laboratory of Operation and Control of Renewable Energy and Storage Systems,China Electric Power Research Institute(Research on renewable energy power generation grid-connected converter fault tolerance evaluation method
文摘The application of LCL filters has become popular for inverters connected to the power grid due to their advantages in harmonic current reductions. However,the power grid in a distribution system is non-ideal, presenting itself as a voltage source with significant impedance. This means that an inverter using an LCL filter may interact with other grid-connected inverters via the nonideal grid. In this paper, damping optimization of LCLfilters to reduce this interaction is studied for a three-phase voltage source inverter(VSI). Simulation results show that resonant oscillation occurs in a distributed power grid, even if the VSI with an LCL filter is well designed for standalone applications. A small-signal analysis is performed to predict this stability problem and to locate the boundary of the instability using an impedance approach. Based on these analytical results, optimized damping of the LCLfilter can be designed. The oscillation phenomena and optimized damping design are verified by simulations and experimental measurements.
文摘An inverter type power source system for robot arc welding is considered. The power source includes several isolated gate bipolar transistor (IGBT) inverter power units. The output current of every individual power unit is regulated by an identical single chip microcomputer to enable the whole power source system to work over a wide range of continuous output current with good dynamic properties. This inverter type power source satisfies robotic welding requirements.
基金Supported by the Ningbo Science&Technology Beauro(2017D10031,2018A-08-C)(3315 Innovation Team).
文摘Current source inverter(CSI)is a class of power electronic converters that,thanks to the inherent boost capability and ease of control,is investigated for grid-tied photovoltaic power conversion applications.Traditional CSI and CSI7 topologies are here analyzed and compared with two kind of space vector modulation strategies mainly in terms of ground leakage current both in simulations and experiments.Furthermore,THD of the injected grid current and the computation of conduction and switching semiconductor power losses are also carried out in numerical simulations.The topology comparison is carried out with the use of a different number of PV modules,to analyze the robustness of the topologies to different size of the PV strings.Simulation and experimental results show that the CSI7 topology,with respect to conventional CSI,allows to strongly reduce ground leakage current,phase current THD and semicondutor power losses,at the price of an additional power device.
基金supported in part by the National Young Natural Science Foundation of China (No. 51407124)in part by China Postdoctoral Science Foundation (No. 2015M581857)in part by Suzhou prospective applied research project (No. SYG201640)
文摘In order to improve maximum power point tracking(MPPT) performance, a variable and adaptive perturb and observe(P&O)method with current predictive control is proposed. This is applied in three-phase threelevel neutral-point clamped(NPC) photovoltaic(PV)generation systems. To control the active power and the reactive power independently,the decoupled power control combined with a space vector modulation block is adopted for three-phase NPC inverters in PV generation systems.To balance the neutral-point voltage of the three-phase NPC grid-connected inverter, a proportional and integral control is used by adj usting the dwell time of small voltage vectors. A three-phase NPC inverter rated at 12 kVA was established. The performance of the proposed method was tested and compared with the fixed perturbation MPPT algorithm under different conditions. Experimental results confirm the feasibility and advantages of the proposed method.