Analysis And Suppression Measures Of Sub-synchronous Oscillation Based On Doubly-Fed Induction Generator In Wind Farm

Since fossil fuels have been put into use,various problems have emerged in an endless stream.At the top of the list is the energy shortage problem.Coal,oil and natural gas are nonrenewable energy sources,over excessive exploitation lead to their depletion of adverse and the shortage of energy will have an immeasurable impact on future generations.Secondly,in the process of using fossil fuels,it will inevitably produce environmental problems.Air pollution,water pollution,solid waste pollution have become serious in many countries and even the entire human society.Therefore,the development of renewable energy is a common theme in the world.solar energy is inexhaustible clean energy,the wind energy is solar energy of another form of transformation,is mainly used to wind power.The wind turbine generator based on doubly fed induction generator(DFIG)has become one of the most popular models at present because of its good economy,high efficiency,high reliability and flexible control.However,the DFIG may cause the system sub synchronous oscillation(SSO),which is similar to the traditional thermal power through the series compensation capacitors in the long distance transmission process.Due to the essential difference between the wind turbine structure,grid with conventional thermal power units,and the wind farm machine of all kinds and diverse,so the SSO problem of large-scale wind power in the delivery becomes especially complex.The SSO system can cause the fan off the network,reduce the shaft life,even make it fracture,affect the safe and stable operation of the grid.In this paper,the IGE of the SSO of the DFIG with series compensation capacitor is studied.1)This paper based on the study of the impact of series compensation capacitor line transmission characteristics of the deduced it evoked SSO phenomenon.Then introduce the popular three types of mainstream fans on the current market and discuss their respective,which DFIG triggered the highest probability of SSO.Four basic types of SSO in the traditional power system are described in terms of the mathematical derivation of the circuit.2)Highlight the characteristics of wind farm by contrast the type of SSO of the wind farm with the traditional power system.In the SSO caused by the use of series compensation capacitors in the DFIG,the possibility of the occurrence of the sub-synchronous resonance(SSR)is great.Among them,it is mainly the induction generator effect.The sub-synchronous control interaction(SSCI)is the form of special SSR in the wind farm.3)Five main methods used to analyze the SSR are described in detail.The unit interaction factor method is mainly used in high voltage direct current transmission system.The characteristic value analysis method and time domain simulation are used to analyze the SSO phenomenon of DFIG wind farm.4)To establish a suitable system to the study of the DFIG through series compensated transmission wind power.Build the detailed mathematical model,including the model of wind speed,shaft,doubly-fed induction generator,inverter,series compensation capacitor,lines grid etc.Using small interfering eigenvalue stability analysis method to obtain the system state equation,to get sub-synchronous oscillation influencing factors.5)To investigate the traditional SSO suppression method,according to the characteristics of doubly fed wind power generation unit,improve the electrical damping system to suppress SSO.Add damping controller in the generator rotor side converter current loop,through a band-pass filter,phase compensation,and gain limiter to suppress SSR.