Development Of New All-Digital EPS

As society advanced，high requirements of power supplies are needed. Society havebecome increasingly dependent on power supply. However, sudden accidents occurring inpower supply still cannot be avoided. In spite of strict electric administration and advancedelectric equipments, power cuts still happen occasionally. Therefore，EPS as one kind ofemergency power supply equipments is widely used in such cases.First of all, this paper introduces the background and development trend of three-phaseemergency power supply. On the basis of analysis of the characteristics and limitations of thetraditional emergency power supply systems, from the view of simplifying the circuitstructure and reducing product cost, we proposed a new three-phase emergency powersystem with two basic components of EPS circuit：Bi-directional DC/DC circuit andbi-directional PWM converter.Secondly, a detailed analysis of bi-directional DC/DC circuit and bi-directional PWMconverter are carried out. For bi-directional DC/DC circuit, based on the comparative analysisof four typical non-isolated bi-directional DC/DC converter, a bi-directional half-bridge DC/DC converter which is suitable for battery application is introduced. The BUCK and BOOSTmode operation procedure of the converter are discussed separately in detail. In order to lay asolid foundation in closed-loop design, small signal models of BUCK and BOOST mode ofthe converter are established. The closed-loop stability is discussed and has given the electriccircuit related parameter design method.Regarding the bi-directional PWM converter, when the electrical network is normal, gridthrough the static transfer switch directly supply power to load, at the same time, activeenergy of the net side will be send for battery through bi-directional PWM converter andDC/DC circuit.When electrical network break down, the bi-directional PWM converter workin the invertor condition, will transform the DC voltage into AC voltage to provide a stablethree-phase sinusoidal voltage to the load after the low-pass filter. Analyzes the main circuit topology and mathematical model of the inverter,design double closed-loop control system ofinverter and gives the method to realize the digitization. Introduces the basic principle ofinverter sine pulse width modulation technology, which is used widely, and it’s controllingand sampling methods.Finally, according to the entire project of the control system, adopting DSP major corechip as the control system to design new three-phase emergency power control systemhardware circuit and software system which bases on TMS320F2812. Hardware mainlyincludes signal sampling regulate circuit, buffer circuit, power drive circuit and protectioncircuit. The software of adopting the modular programming methods gives flow chart of themain program and sub program. In the base of the theoretical analysis and system design,using computer simulation software Matlab, and building prototype to conduct the experimentin order to examine the correctness of the model system which is established through thesimulation results and the analysis of experimental.To sum up, this paper comes up with the new emergency power system, by usingtwo-way topological structure to realize all functions that usually by using the unidirectionalcircuit, in the meanwhile, to reach the greenization, intelligent and low-cost requirements ofEPS products.