Research On The Structure Configuration Of Distributed Synchronous Condenser And Its Damping Evaluation Of Low-frequency Oscillation

At present,the proportion of new energy in China is rapidly increasing,and the scale of ultra-high voltage direct current transmission is increasingly expanding,resulting in insufficient inertia and reactive power in some systems.On the other hand,the synchronous condenser can improve the voltage and reactive power support level sent by new energy sources,provide a certain amount of inertia,and improve system stability.Therefore,centralized and distributed synchronous condensers will be widely installed in actual systems,especially distributed synchronous condensers will be configured near new energy stations.However,research on the role of distributed synchronous condensers mainly focuses on reactive voltage,inertia,and other aspects,and there is no research on the impact of dynamic stability damping.In view of this,this article mainly studies the impact of the integration of distributed synchronous condensers on the low-frequency oscillation damping characteristics of power systems containing wind power.The main work of the paper is as follows:(1)Combining the eigenvalue method,the damping characteristics of distributed synchronous condensers with different configurations were analyzed,and a distributed synchronous condenser configuration suitable for damping low-frequency oscillations was determined.Firstly,mathematical models of distributed synchronous condensers using different types of rotors,excitation systems,and PSS are established;Secondly,the damping characteristics of distributed synchronous condensers with different configurations are analyzed and compared in a single machine system;Finally,the damping characteristics of distributed synchronous condensers with different configurations are analyzed and compared in a four-machine two-area system.The results show that distributed synchronous condensers have better damping enhancement effects when using salient pole type rotors and FM type excitation systems,and the type of PSS should be selected based on the actual needs of the system.(2)The extended Heffron-Phillips model of wind-thermal bundled system with the distributed synchronous condenser with recommended configuration is constructed,and combined with the damping torque method,the influence characteristics of the parameters of the distributed synchronous condenser on the low-frequency oscillation damping of the wind-thermal bundled system are analyzed.Firstly,the mathematical model of the wind-thermal bundled system connected to the distributed synchronous condenser is established;Secondly,combined with the linearization model of the system,an extended Heffron-Phillips model for low-frequency oscillation analysis of thermal power units is established;Thirdly,combined with the damping torque method,the calculation formula of the damping coefficient of the thermal power unit is deduced;Finally,the influence of the parameters of the distributed synchronous condenser and its excitation system on the damping coefficient of the thermal power unit is analyzed.(3)A multi-dimensional index system reflecting the damping effect of distributed synchronous condensers on new energy is constructed and applied to different systems to evaluate the damping effect of distributed synchronous condensers with recommended configurations.Firstly,combined with the response characteristics of the dynamic system,an evaluation index system that can be used to evaluate the damping effect of the synchronous condenser is constructed,including the damping ratio,adjustment time,the minimum static stability limit deviation rate and the damping calculation method based on the oscillation energy consumption;Secondly,using the above index system,in a single-machine system and a four-machine two-area system,the effect of the distributed synchronous condenser on the damping improvement of the new energy area was evaluated,and the change of the system damping when the operating conditions of the generator changed;Finally,in the actual system,the change of system damping is evaluated after the configuration of the synchronous condenser and when the number of configured synchronous condensers is changed.