| In order to reduce the adverse impact of the traditional power generation,the DC distributed power system based on new energy generation is developing rapidly.The DC distributed power system has the characteristics of high energy efficiency,low economic cost,flexible structure and regional power supply,and it is generally composed of new energy power generation devices,the DC bus,hybrid energy storage system and load converters.In this paper,the front-end power converter in the DC distributed power system,the DC bus stability control technology and the topology and the control strategy of the integrated hybrid storage system are investigated respectively.The double-switch Buck-Boost(DSBB)converter is suitable for the front-end power converter in distributed power system.There have been proposed several modulation schemes for this converter,such as synchronization modulation(SM),interleaved modulation(IM)and combined control mode.The synchronization is simple in control and easy to implement.Using the interleaved modulation,the inductor ripple current of this converter is relatively small so that the power loss is low.The combined control mode has high-power density and conversion efficiency.However,the requirements of the converter are not only limited in the aforementioned metrics,but the related complexity of control system design,implementation and control performance sometimes also play important roles in industry applications.A new modulation method is used in the paper,and the double-switch Buck-Boost converter can obtain balanced performance between the inductor current ripple and the average value,and a unified small-signal model for controller design is derived,as well as the dual-loop control system is designed.Comparison of the inductor average current and conversion efficiency versus the new modulation,synchronization modulation and interleaved modulation by the specific formulas and curve diagrams is described in this paper.Finally,simulation and experimental results are presented to verify the effectiveness.The cascaded structure is a common connection in distributed power systems,and the high-bandwidth closed-loop controlled load converter collected to the DC bus shows negative impedance constant power characteristic,which might cause the voltage oscillation in DC bus.By sharing the magnetic core of the phase shift full bridge(PSFB),an extra port is introduced to integrate into the load converter in this paper,which can stabilize the DC bus voltage of the cascaded system.The control strategy which introduces the ripple component of DC bus voltage to modify the phase-shift in the voltage control loop of the extra port is used in this paper.Small-signal of the extra port is presented in this paper and simulation results show the validation of the method.The hybrid energy storage system in the distributed power system might be a backup power source,as there is insufficient power which the new energy power generation device generates,the hybrid energy storage can make the power supply of the system to be uninterrupted.Separated bidirectional DC/DC converter is used in conventional hybrid energy storage systems,using more power switches and leading to low power density.An integrated hybrid energy storage system is introduced in this paper,which is using the switches multiplexing technology,and the capacitor energy storage and inductor current dual control loop is constituted in this system.The linear current filter is introduced to divide the inductor current,so that the current is distributed to different energy storage components to process.The controller of load power feedforward is designed to improve the dynamic performance of DC bus voltage during load changing.Finally,it is verified by simulation and experiment. |
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