The Power Flow Detection And Control Strategies Research For Cophase Traction Power System

The approach of single-phase industry frequency AC power supply is used in China electrified railway.It has lots of advantages such as high voltage level, good capability of powering,low loss and so on.But the problems of power quality such as harmonies,reaetive power,negative and of crossing neutral sections still exists.With the development of high-speed and heavy-duty electrified railway,these problems are getting worse and worse,which directly influences the safety and reliable operation of trains.Traditional solution, separately to rise power quality and to get crossing neutral sections automaticlly,rusults in a large investment and complex systems. Cophase supply, to solve two problems above at the same time,is able to solve the problems exist in modern traction power supply system.The skill open up a new direction for the develop of high-speed and heavy-duty electrified railway in the future. Key skills like system structure of cophase supply, detection technology, control strategy are researched in this paper based on cophase power supply system.And the following aspects are mainly completed.1. The system structure of cophase power supply system and the theory of active compensation are analized,and the structure of the active phase power supply system adapt to different types of traction transformers and AC-DC converters are put forward,which provide a reference for implementation of the project of cophase supply system.2. The advantages and disadvantages of average active power theory and instantaneous reactive power theory are analized and a method of current and power detection is put forward applied to cophase supply system of structure of balancing transformer and V-connection transformer,which is basic on instantaneous reactive power theory,for cophase supply system needs to compensate for the negative sequence.3. The traditional control method of voltage and current of converter in cophase supply system are studied. That designing controller using the theory of direct power control will improve the static and dynamic effects of converter is proposed and the design in control system structure are completed based on the research above. A constrained control strategy is proposed in converter meeting power quality indicators,which will greatly reduce the capacity of converter and improve the economics of the system under the terms of meeting power quality indicators in cophase power supply system.4. The structure and principles of cophase continuous power supply system are studied, a direct power control strategy is proposed in single traction substation and the corresponding controller structure is designed. Simulation results show that the method can coordinate the active power in three-phase side and single-phase side in the case of output power mutation in single-phase side,and reactive power in single-phase side does not influence the power factor in three-phase side.Then a scheme about multiple substation capacity and location optimization is proposed in-cophase continuous supply system. Example shows that the optimization ones can reduce the loss in cophase continuous power supply system,which provides a theoretical basis for capacity design and site selection of high-power AC-DC-AC Substation.