摘要:Because of its advantages such as small size and light weight,power electronic transformers(PET)are increasingly used in power transmission and distribution systems.The traditional centralized control method requires each cascaded power module to communicate with the central controller through a high-speed communication link,which increases the computational and communication burden of the central controller and reduces the expandability and modularity of a PET system.In this paper,a distributed feedforward control method for a cascaded H-bridge(CHB)converter-based PET is proposed.The pulse width modulation,input current regulation,voltage balance control,power balance control,output voltage regulation and output current regulation are assigned to the distributed local controllers.Therefore,the computational and communication burden of the central controller can be significantly reduced.The number of fibers connected to the central controller can be significantly reduced.Meanwhile,the proposed control method can greatly improve the dynamic response of the load disturbance,and a smooth start-up process of the PET system can be achieved.Simulation results are given to show the effectiveness of the proposed method.
摘要:At present,power electronic transformers(PETs)have been widely used in power systems.With the increase of PET capacity to the megawatt level.the problem of increased losses need to be taken seriously.As an important indicator of power electronic device designing,losses have always been the focus of attention.At present,the losses are generally measured through experiments,but it takes a lot of time and is difficult to quantitatively analyze the internal distribution of PET losses.To solve the above problems,this article first qualitatively analyzes the losses of power electronic devices and proposes a loss calculation method based on pure simulation.This method uses the Discrete State Event Driven(DSED)modeling method to solve the problem of slow simulation speed of large-capacity power electronic devices and uses a loss calculation method that considers the operating conditions of the device to improve the calculation accuracy.For the PET prototype in this article,a losses model of the PET is established.The comparison of experimental and simulation results verifies the feasibility of the losses model.Then the losses composition of PET was analyzed to provide reference opinions for actual operation.It can help pre-analyze the losses distribution of PET,thereby providing a potential method for improving system efficiency.
摘要:Modular multilevel resonant converter is an promising candidate for high voltage applications since it has advantageous features,such as high efficiency,high voltage capability and easy fault-tolerant operation.However,the inequality of arm inductance in practice will lead to imbalance between the upper and lower arm voltages,which will induce large ripples in the circulating current and a dc bias on the voltage generated by modular circuits.To compensate for the voltage imbalance,effects of arm duty cycle changes on arm voltages are discussed.An arm voltage balancing control method is proposed:adjust arm duty cycle according to arm voltage deviation in every switching cycle.Simulation and experimental results are presented to validate the theoretical analysis and the proposed control method.