Study On Transient Process Monitoring Method Of Frequency Conversion Starting In Pumped Storage Power Unit

With the accelerated construction of energy Internet,clean energy power generation will occupy an increasing proportion in the grid.Wind,light,nuclear and other large-scale development of new energy and special high-voltage power grid construction of the overall speed provides a new vitality to the development of pumped storage.At the same time,the development of pumped storage also provides a strong support for optimizing and configuring resources of high-voltage power grid as well as promoting clean energy consumption.At present,large-scale domestic and foreign large-scale pump storage units use static frequency starting as the main starting mode.When the transient voltage and current of the synchronous motor are measured,the frequency of the measured signal changes with time.The DFT phasor measurement method based on the traditional zero-crossing detection method is to measure the frequency signal instead of this kind of frequency conversion signal.It is necessary to study the measurement of such signals.In this paper,the frequency conversion starting process of pumped storage unit is studied.Firstly,the static frequency control system composed of SCR is taken as the research object.The starting principle of the unit is introduced and the working characteristics of the system are analyzed.It shows that the static frequency control system has the similar speed characteristics of the DC motor,and has good control characteristics and Wide speed range.Secondly,the mathematical model of the frequency conversion starting process in the two-phase synchronous coordinate system is established,which lays the theoretical foundation for the digital simulation.Then,the frequency conversion starting process of the pumped storage unit is analyzed,and the process of the excitation process and the control process are analyzed,and the design of the double current closed loop regulator is completed.Then,the voltage and current waveforms of the frequency conversion starting process of the pumped storage unit are introduced.It shows that the existing power quality tester has a large error in measuring the voltage waveform of the unit,and then leads to the large value based on the extreme value of the zero crossing method and the frequency conversion Time domain analysis method of frequency conversion system monitoring method,taking into account the advantages and disadvantages of the two detection methods,choose to use the extreme value of the first cross-zero method to measure the frequency,transient value,attenuation coefficient,the use of time domain analysis of voltage and current Value,power factor and three-phase power.Finally,the simulation results show that the correctness of the monitoring method is proved by using the frequency conversion system monitoring method to simulate the simulation process.In order to further verify the algorithm performance,the performance of the frequency conversion system monitoring method and the traditional DFT algorithm are analyzed and analyzed in four cases:frequency linear variation,frequency sine change,amplitude slow fluctuation and frequency oscillation.Aiming at the problems existing in the transient process monitoring of the frequency conversion starting of the unit,a unit start transient process monitoring system based on the frequency conversion system monitoring method is set up.And the monitoring process of a certain unit is carried out.The monitoring results show that the frequency conversion system monitoring method can measure the change of the main physical quantity of the starting process.