A novel three-level zero-voltage zero-current switching(ZVZCS)DC/DC converter is proposed in this paper.A tapped-inductor is used to replace the normal out-put filter inductor,so that the circulating current in the ze...A novel three-level zero-voltage zero-current switching(ZVZCS)DC/DC converter is proposed in this paper.A tapped-inductor is used to replace the normal out-put filter inductor,so that the circulating current in the zero-state can be reset to zero.The reset voltage and the re-set time can be set conveniently just by simply changing the winding ratio of the tapped inductor.The converter achieves a zero-current tuning off for inner switching,and a zero-voltage tuning on for outer switching.No circulating current exists in the zero state,so that the loss in the on-state is reduced,and the efficiency can be improved.The experimental results verify that the ZVZCS has low voltage stress,zero-voltage and zero-current switching.展开更多
The traditional PI controller for a hybrid energy storage system(HESS)has certain drawbacks,such as difficult tuning of the controller parameters and the additional filters to allocate high-and low-frequency power flu...The traditional PI controller for a hybrid energy storage system(HESS)has certain drawbacks,such as difficult tuning of the controller parameters and the additional filters to allocate high-and low-frequency power fluctuations.This paper proposes a model predictive control(MPC)method to control three-level bidirectional DC/DC converters for grid-connections to a HESS in a DC microgrid.First,the mathematical model of a HESS consisting of a battery and ultra capacitor(UC)is established and the neutral point voltage imbalance of a three-level converter is solved by analyzing the operating modes of the converter.Secondly,for the control of the grid-connected converters,an MPC method is proposed for calculating steady-state reference values in the outer layer and the dynamic rolling optimization in the inner layer.The outer layer ensures the voltage regulation and establishes the current predictive model,while the inner layer,using the model predictive current control,makes the current follow the predictive value,thus reducing the system current ripple.This cascaded topology has two independent controllers and is free of filters to realize the high-and low-frequency power allocation for a HESS.Therefore,it allows two types of energy storage devices to independently regulate the voltage and realizes the power allocation of the battery and UC.Finally,simulation studies are conducted in PSCAD/EMTDC,and the effectiveness of the proposed HESS control strategy is verified in a case,such as a controller comparison and fault scenario.展开更多
文摘A novel three-level zero-voltage zero-current switching(ZVZCS)DC/DC converter is proposed in this paper.A tapped-inductor is used to replace the normal out-put filter inductor,so that the circulating current in the zero-state can be reset to zero.The reset voltage and the re-set time can be set conveniently just by simply changing the winding ratio of the tapped inductor.The converter achieves a zero-current tuning off for inner switching,and a zero-voltage tuning on for outer switching.No circulating current exists in the zero state,so that the loss in the on-state is reduced,and the efficiency can be improved.The experimental results verify that the ZVZCS has low voltage stress,zero-voltage and zero-current switching.
基金supported in part by the State Grid Corporation of China under Grant No.521500190017.
文摘The traditional PI controller for a hybrid energy storage system(HESS)has certain drawbacks,such as difficult tuning of the controller parameters and the additional filters to allocate high-and low-frequency power fluctuations.This paper proposes a model predictive control(MPC)method to control three-level bidirectional DC/DC converters for grid-connections to a HESS in a DC microgrid.First,the mathematical model of a HESS consisting of a battery and ultra capacitor(UC)is established and the neutral point voltage imbalance of a three-level converter is solved by analyzing the operating modes of the converter.Secondly,for the control of the grid-connected converters,an MPC method is proposed for calculating steady-state reference values in the outer layer and the dynamic rolling optimization in the inner layer.The outer layer ensures the voltage regulation and establishes the current predictive model,while the inner layer,using the model predictive current control,makes the current follow the predictive value,thus reducing the system current ripple.This cascaded topology has two independent controllers and is free of filters to realize the high-and low-frequency power allocation for a HESS.Therefore,it allows two types of energy storage devices to independently regulate the voltage and realizes the power allocation of the battery and UC.Finally,simulation studies are conducted in PSCAD/EMTDC,and the effectiveness of the proposed HESS control strategy is verified in a case,such as a controller comparison and fault scenario.
