Research On DC Double Input Power Supply For Relay Protection

With the rapid development of science and technology and widespread use of modern high-end equipment, people put forward higher demand to the continuity and reliability of the power supply.In the power system field,for example,power generation,transmission and distribution,dc power system is very important, because it provides power for the power system of control circuit, signal circuit, relay protection and automatic device and lighting device of accident,so whether dc power system can work reliablely, relates directly to the whole unit or the generator, and even the security and stable operation of whole power system.The double input device of common power supply and spare power supply is used for improving reliability of the power supply,which has an important role. In actual use, dc double input power supply require electrical isolation, and when common power supply breaks down, the spare power supply can provide normal dc voltage within10millisecond. But the current power supply system, simply make double input power in parallel through mechanical switch or after diodes in parallel.Because the minimum reaction time of the mechanical switch is50milliseconds, so when one power supply breaks down, it is unable to realize uninterrupted power supply for the electrical equipment for the former, in addition, the mechanical switch exist limited use life and big noise,while the latter violated25item countermeasures in the power system that double input power supply must be independent. So thus device will carry serious impact on the reliability and safety of electric equipment.In view of the shortcomings of the above power supply device,by making use of the advantages of high frequency switching power supply, this paper puts forward a new double input voltage dc power supply device, due to the advantages of the electrical isolation and rapid response of dc-dc converter, it can satisfy the demand of electrical isolation of the double power and fast cutting. This paper analyzes the design of spare power supply chiefly, and make a detailed analysis of main circuit topology which is ZVS PSC-FB converter, and then based on TMS320LF2407A digital microcontroller, we have completed a220V/50A dc double input power supply device, and we also make detailed description and instructions on the main circuit device parameters design and selection, hardware design and software control strategy design of the control circuit, finally through the PSIM simulation software and concrete experimental results, we verify the principle analysis of the whole system and parameter design, the results show that the double power supply device have realized electrical isolation of the double input power supply, and when single power supply fails, the cutting time will be less than10milliseconds,which has a important practical significance to the safe, reliable and stable operation of the electrical equipment.