Study Of Signal Detection Based On PWM For High Voltage And Large Current And Its MCR Application

Today,power electronics has become one of the supporting technologies for power systems.It has been used in the field of power transmission: HVDC(High Voltage DC Transmission),and Flexible Alternative Current Transmission System(FACTS).Photovoltaic power plants and wind power generation used in the field of new energy grid-connected power generation have been carried out on a large scale.The real-time monitoring of power electronic equipment is an important guarantee to ensure the safe operation of equipment and improve the safety of the system.Since the equipment is usually operated at a high voltage of 10 k V or higher,high current of k A or higher,it is different from the common load level in terms of voltage level and current level.some conventional measurement and control methods for small and medium power applications,may no longer be suitable.The detection unit must adapt to the harsh electromagnetic environment such as high electric field and strong magnetic field on the site,and the system background equipment monitoring equipment needs to take into account personal safety insulation,which requires special design considerations.This paper combines engineering design and development tasks to study a new high current sampling method,a high voltage isolated transmission,good anti-interference,small size,high precision,good consistency,low-cost solution for signal modulation and demodulation and transmission.Design and manufacture current monitoring systems for rapid excitation of MCR and complete laboratory and field testing.The paper combines the research and development tasks of the fast-excited MCR(Magnetic Controllable Reactor)power loop monitoring system received by the unit.On the basis of investigating various current and voltage detection technologies,the following research work is mainly carried out for the application characteristics of high voltage and high current:1)Analyze and study the large current detection method based on micro-ohmic resistance,design a conductive bus row-micro-ohmic resistance signal acquisition structure and a large current sampling circuit of precision amplification circuit;2)Based on the analysis of various signal isolation techniques,including conventional PWM modulation and demodulation principles,an adaptive PWM modulation and demodulation scheme is proposed,which illustrates due to the use of partial closed loop the elimination the main source of error of PWM modulation and demodulation.It can achieve higher measurement accuracy,providing a new method and technical means for high voltage isolated sampling transmission technology.3)The paper designs high-voltage and high-current sampling and signal transmitting module and receiving module circuit,analyzes the system transfer function,and evaluates the overall error of the whole signal detecting circuit caused by the parameter deviation of the circuit components.Explain that the technical solutions adopted can meet the technical requirements of the project.Through the transfer function simulation on MATLAB platform and circuit simulation on Plecs platform,the author has evaluated the feasibility of the proposed scheme,designed parameters,and built a specific circuit module to verify the correctness of the scheme through experiments.The author also used the signal detection transmission/reception module to establish a fast excitation MCR main loop monitoring system.The trial of the commissioning site shows that the system can meet the monitoring requirements of the main loop.