Design And Implementation Of Control Parts For De-excitation System Of Large-scale Generator Sets

With the sustained and rapid growth of the national economy,the demand for electrical energy is getting larger and larger,and the problem of environmental pollution is getting worse.To solve the dual problems of electricity consumption and environmental pollution,large-scale generator sets have been constructed and applied on a large scale.Self-shunt excitation system has many advantages such as less equipment,simple principle,fast system response,small maintenance workload and high economical efficiency.It has been widely used in large-scale generator sets.The de-excitation device is one of the core equipments of the excitation system and is responsible for transferring and consuming the rotor energy.It is also the only device that limits and prevents the failure and further expands the protection of the generator.The de-excitation device of a large-scale self-stimulated generator set should be able to meet the requirements for safe and reliable degaussing under various operating conditions.In this paper,the problem of demagnetization in the case of erroneous excitation is studied.A de-excitation circuit with inverter controller involved in accidental de-excitation is proposed.The hardware and software of the inverter controller are designed.For the shortcomings of poor reliability and slow movement of mechanical crowbar,electronic crowbar components with high redundancy,quick action,and fault indication are studied.The control circuit of electronic crowbar is studied and designed to meet large-scale power generation.Firstly,the energy removal and de-excitation circuits commonly used in the de-excitation system of large-scale generating units are analyzed,and the commutation conditions for the successful de-excitation of de-excitation circuits are deduced.In addition,the arc voltage requirement of field circuit breaker has been analyzed and studied when large-scale generator units are mistakenly forced excitation.In view of the limited arc voltage value and high cost of field circuit breakers at present,inverter controller is designed.The inverter controller uses a Field-Programmable Gate Array(FPGA)as the control chip.Using its rich hardware resources and parallel execution of the program,the controller hardware circuit design and software design are performed.Secondly,the redundant self diagnosis electronic crowbar is designed to replace the mechanical crowbar in the linear resistance or silicon carbide(SiC)nonlinear resistance demagnetization circuit,which is the control board without fault monitoring or the slow motion of the mechanical crowbar and the aging of mechanical parts.Finally,the test platform and design test method are established,and the function verification and system test of the control parts are completed,and satisfactory results are obtained.The test results show that the control parts for de-excitation system of large-scale generator sets are beneficial to the demagnetization and commutation of the accident shutdown,and the rapidity,reliability,and economy of the extinction device are improved.