| Compared with the AC power distribution network,the DC power distribution network has superior performance in terms of distributed power access,controllability,distribution capacity and so on.The DC power distribution network has become the direction of future power distribution.However,terminals of the DC power distribution network are numerous and dispersed,and how to coordinate them is a problem to be solved urgently.Moreover,due to the isolation caused by power electronic converters,the DC power distribution network is a low-inertia system and satisfactory power quality is hard to be acquired by capacitive inertia.In order to realize the secure,stable and high-efficiency operation of the DC power distribution network,as well as improve the reliability of control strategies,decentralized autonomous control of the DC power distribution network is studied in this paper based on the droop control.The main research results are as follows:(1)A multi-mode voltage regulation strategy based on droop control is proposed.According to DC voltage deviation and voltage regulation capacity of the terminals,voltage regulation of the DC poewr distribution network is divided into main voltage regulation mode,reserve voltage regulation mode and emergency voltage regulation mode.Decentralized and autonomous control of the DC voltage under various operating conditions is realized by the strategy.Grid-connected converter and energy storage regulate DC voltage with droop control respectively under main voltage regulation mode and reserve voltage regulation mode.The emergency voltage regulation mode includes new energy sources’ power-down operation and load-off operation.Moreover,state of charge of the battery and voltage deviation are considered,and relative solutions are proposed.A six-terminal ring-structure DC power distribution network simulation platform is established on Matlab/Simulink and effectiveness of the proposed voltage regulation strategy is verified by simulation results.(2)An adaptive droop control strategy with virtual inertial response is proposed.Based on the definition of inertia and the concept of virtual inertia for DC power distribution network,the principle of virtual inertial response acquired by swing of the droop curve is studied and an adaptive droop coefficient is proposed.By replacing the fixed droop coefficient with the adaptive one,the converter can supply virtual inertia to the DC bus voltage when disturbances occur.The supplied inertia can be adjusted by virtual inertia coefficient.Small signal stability analysis of the DC power distribution nerwrok with the proposed control strategy is carried out and value range of the vritual inertia coefficient is obtained.The effectiveness of the proposed control strategy on improving inertial response of the DC power distribution network is verified by related simulation examples.(3)A scheme of multi-level and multi-time-scale hardware in-the-loop simulation(HILS)system is designed to test operation and control strategies of the DC power distribution network.According to control levels and control time scales,primary control,secondary control and tertiary control are implemented in different processors.Local key units and system-level control methods can be both tested in the proposed scheme.According to the proposed scheme and processors’ computing ability and characteristics,a HILS platform including an actual controller DSP,a real-time simulation machine RT-LAB,a processer cRIO and a host computer is built.Feasibility and flexibility of the designed HILS platform are verified by related tests. |
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