Small Disturbance Stability Analysis And Control Of Power Electronic Power Systems

Under the background of alleviating the global energy shortage and encouraging the development of new energy,a large number of photovoltaic,wind power and other new energy power generation devices are connected to the power grid through power electronic equipment.Meanwhile,converter equipment containing a large number of power electronic components has been widely used in long distance HVDC transmission,which makes the trend of electric power electronization increasingly prominent in the power system.The electronization of power system makes the system operation state more complicated and the influence on the stability of the system with small disturbance is increasingly prominent.In recent years,the problem of small disturbance stability with unknown mechanism has appeared in power systems in many places.In order to clarify the small disturbance stability mechanism of power electronic power systems and improve its stability under disturbance by control measures,related researches are carried out in this paper,the main research contents are described as follows:Firstly,the model and principle of the traditional generator,wind power generation and photovoltaic power generation on the generating side of the system are established and analyzed.The control model of the converter on the transmission side,the model of the DC transmission line,the model of the static load on the load side and the model of the dynamic load of the induction motor are introduced.Then,from the perspective of theoretical analysis,the small disturbance stability of the simple power electronic power system is analyzed when the load types are respectively constant power load constant current load constant impedance load and induction motor load.The simulation model was established in MATLAB by eigenvalue analysis method based on lyapunov stability analysis theory.The eigenvalues of the corresponding state equation of the system under different load types are calculated,the results of theoretical analysis are verified,and the small disturbance stability of the power electronic power system under different load types is analyzed.Then,in the voltage source converter at both ends of the HVDC transmission,taking the active power control link on the inverter side of the converter as an example,the mathematical expression of the output current change on the inverter side of the voltage source converter is derived,and the derived result is compared with the expression of the spring motion process in the typical spring mass damping system.It is concluded that the change of the output current on the inverter side of the HVDC transmission of the voltage source converter has an inertia characteristic similar to the movement process of the spring.The existence of this characteristic in the electric power electronic systems has brought adverse effects on the stability of the system with small disturbance.Simulation verification is done in the traditional simple three-machine system and IEEE14-node system as well as their corresponding power electronic power systems.The variation of the output current in the inverter side of the voltage source converter and the small disturbance stability of the system are analyzed,and the correctness of the theoretical analysis is verified.Finally,the influence of power on the stability of the system with small disturbance is summarized in the previous theoretical analysis,and the influence of power variation in the system on the system frequency is analyzed.Frequency is also a key factor that affects the power quality and system stability.On this basis,a system-level power control strategy is proposed to achieve the optimal balance between the total power emitted and the total power absorbed in the system.This strategy can effectively improve the stability of the system with small disturbance.At the same time,the traditional bald eagle search algorithm was improved by introducing Gaussian variation and dynamic inertia weight in the form of concave function to improve the global search ability and the ability to jump out of the local optimal.The improved bald eagle search algorithm is used to solve the function model,and the effectiveness of the proposed system level power control measures is verified.