| Wind power is the main force of today’s new energy power generation,and wind power is often far away from the load center,requiring long-distance and cross-regional transmission.The wind and fire bundling method is used to transfer the thermal power together with the wind power to regulate the fluctuation,intermittent and randomness of the wind power output.On the other hand,series capacitor compensation is an effective means to improve system stability and transmission capability during long-distance AC transmission.However,in the Wind-Fire Bundling System with Series Compensation,the series compensation will bring about Sub-synchronous oscillation(SSO)problems,and the grid connection of wind power will have a non-negligible influence on the SSO characteristics of the system.In order to explore the SSO problem of the wind-fired baling and cross-feeding system,and propose corresponding suppression methods,the paper studies the following:The basic principle and implementation method of complex torque coefficient method are expounded.Based on the state space model of power system,the applicability of its multi-machine system is discussed.The results show that the system can be analyzed by the complex torque coefficient method when the system is stable viewed from the rotor side of the motor.It laid the foundation for the in-depth analysis of the SSO characteristics of the subsequent wind-fire baling system.Based on the first standard model of IEEE about subsynchronous oscillation.the system model of wind-fired bundling with direct-drive or double-fed wind turbine fan was added,and the corresponding model was built on PSCAD simulation software.The interaction between thermal power,wind power and series compensation in the system is analyzed by time domain simulation,and the applicability of the complex torque coefficient method is illustrated.Based on the electrical damping characteristics,the influence of wind power on the SSO characteristics of thermal power units is analyzed.The results show that after the double-fed fan is connected to the grid,the electrical damping of the thermal power unit is improved,and the smaller the series compensation is,the more effective the effect is.The direct-drive fan is integrated to weaken the electrical damping of the thermal power unit,but with the string compensation increasing,the electrical damping of the low frequency band will increase slightly.However,for both types of wind turbines,increasing the proportion of wind-fired bundling and the wind speed of the wind turbine will enhance their respective effects on the thermal power unit;increasing the inductive reactive power output can improve the electrical damping of the thermal power unit and improve its SSO.Finally,the analysis results of electrical damping are verified by time domain simulation.After theoretical derivation and analysis of damping characteristics,the results show that the fan output power will affect the electrical damping of the thermal power unit.In addition,the fan converter control link has the fast adjustment function of active and reactive decoupling.Therefore,this paper proposes a method for suppressing the thermal power unit SSO by the additional damping control of the fan converter,and the detailed analysis of the proposed SSDC suppression principle is carried out.After that,the multi-channel modal control active and reactive SSDC links are designed for the doubly-fed fan and the direct-drive fan,and the phase compensation parameters of each mode are optimized.Finally,the effectiveness of the proposed SSDC suppression effect is verified by electrical damping characteristics analysis and time domain simulation,and the suppression effects of different additional damping control types are compared. |
PDF Full Text Request