Applying Supercapacitor To The DC Power Supply System Of The Smart Substation

With continuous development and long-term applied in practice of smart grid, the DC power supply of the smart substation with integrated power supply has gradually exposed its some disadvantages. Firstly, battery pack is applied in the integrated power as backup power. But the batteries has some disadvantages, for example, the battery cell affects the performance of the whole pack, different batteries are difficult to match each other’s performance very well, abandoned batteries are harmful to environment and the cost of checking, maintaining and exchanging battery pack is also very high. Besides, the integrated power adopts centralized power supply mode. There are some questions, for example, too many wire connections of DC power box, complicated layout of DC power screen, serious interference of loads, the distant transmission distance of DC bus cable and the high construction cost. The other question is that the whole power station may be out of work when the DC power supply is broken down.This paper puts forward a distributed DC supply system based on supercapacitor, which aims at solving the shortage of the DC power supply system of the smart substation. It also makes referencing research on this system.Firstly, this paper summarizes the current situation of DC power supply system of substation in domestic and foreign research. It also outlines the achievement of research about supercapacitor applied in energy storage systems. It puts forward a distributed DC supply system based on supercapacitor and designs it. Meanwhile, it illustrates the structure of standard modules of supercapacitor applied in distributed DC power supply system and make parallel design of multi-module power.Secondly, the designed system is demonstrated available on aspects of advanced technology, power supply reliability, cost, environmental protection and scalability. It has an advantage on technology and cost over traditional centralized DC power supply system. The theory of supercapacitor and bidirectional DC-DC power converter are illustrated, and the DC load of substation is computed. The capacity of supercapacitor is matched to the designing requirement and the type and parameters of bidirectional DC-DC power converter is also confirmed.Finally, the load and supercapacitor of DC system are modeled. The bidirectional DC-DC power converter is modeled based on state space averaging method. Double closed loop control system of supercapacitor energy storage system is designed. This system is simulated with MATLAB/SIMULINK module. The result of both simulation and experiment verifies the availability and reliability of designed system. Parallel current sharing technology is presented in the paper, and the current sharing control unit is also designed.