Research On Excitation Power Supply For Superconducting Synchronous Condenser

The continues expansion of UHVDC Transmission Construction scale has brought a huge economic and environmental benefits,but problems such as insufficiency of reactive power reserves and voltage support capability are increasingly prominent.The synchronous condenser(SC)can effectively solve the above problems because of the output large reactive power capacity in short time.Moreover,with the application of superconductive technology in the SC,which makes the high temperature superconducting synchronous condenser(HTSSC)have excellent reactive compensation characteristics such as fast response time and small synchronous reactance.Same as the conventional SC,the HTS-SC condenser needs suitable excitation power supply.At present,there are few technical studies on the excitation power supply system of the HTS-SC.Therefore,based on the theoretical study of the 10 Mvar HTSSC,this paper designs the excitation power supply system of HTS-SC,and lays the foundation of theory and engineering for the follow-up development work.Firstly,reactive power compensation performance and structural characteristics of the10 Mvar HTS-SC is explained.The characteristics of HTS-SC’s excitation winding are clarified—large inductance and small resistance.Based on superconducting excitation winding,the HTS-SC mathematical model are established.The ANSYS simulation of HTSSC is constructed in combination with the existing parameters,which provides theoretical and model basis for subsequent design.It makes clear that when the HTS-SC runs in steady state,the system needs to provide low voltage and high precision DC current;when the HTSSC adjusts dynamically,the system needs to provide high voltage to change the magnetic field current quickly.Secondly,according to the above characteristics,a scheme of excitation power supply system of HTS-SC is proposed,including low voltage module,high voltage module,deexcitation and protection module and switching module.The system has the following functions: high voltage can be provided when excitation;low voltage and high precision current can be provided when condenser runs smoothly;rapid de-excitation.The power supply can switch high voltage and low voltage smoothly in advantage of the diode’s unilateral conduction,which makes it have engineering value.Then,the working principle of the supply system is described in detail by means of modal analysis.From the perspective of single module,the hardware parameters of single module are designed in order to achieve the performance requirements.Focusing on the high precision requirement,the four-phase interleaved buck converter is modeled,and a control strategy is proposed and designed later.Simulation results shows that the control system can achieve the ideal effect of high accuracy.Finally,the above design are verified by simulation and experiment.The simulation model of the excitation power supply system is established in Matlab/Simulink.The supply system and HTS-SC is simulated,proving the feasibility of the above design.Then,a 1k W low-power experimental platform containing all modules is established.The hardware circuit and the controller software is designed to complete the experimental verification.The feasibility and effectiveness of the proposed excitation power supply system is demonstrated.