| East China Power Grid has formed a dense DC multi-feed system,and HVDC transmission system has a significant impact on the stability of the system with the application of new technologies such as hierarchical connection and hybrid flexibility.Faced with the current power grid development trend,this paper presents the control characteristics of HVDC transmission system,strategies to suppress commutation failure and the application effect of new type synchronous condenser in actual engineering.The main content is as follows.(1)The influence of technical routes of HVDC control strategies on commutation failure and system stability is studied.At present,the actual operating HVDC transmission system generally adopts or inherit the two technical routes of SIEMENS and ABB,and the main difference between them is the control mode of the inverter stations.One is to use constant voltage control in normal operation,and the other is to use mathematical model to predict and control the extinction angle,along with emergent phase shifting when necessary.Their electromagnetic transient simulation models are built in detail in this chapter to draw the steady-state operation curves and study the commutation failure of the inverter side under typical faults.Using the linearization model,the influence of key parameters on the dynamic stability of the overall system was studied analytically in the category of small-signal stability,and the simulation model was used to verify the influence of control parameters on commutation failure.(2)The performance of dynamic reactive power compensation strategies to suppress commutation failure are studied.HVDC inverters are prone to commutation failure when disturbances occur,resulting in power loss at the receiving end.During the recovery period of commutation failure,a large amount of reactive power is consumed.If the reactive power reserve of the system is insufficient,there is the risk of continuous commutation failures or even cascading failure.This paper studies the impact and effect of installing dynamic reactive power equipment in the inverters.Additionally,this paper compares their operating characteristics and economic performance in view of the detailed electromagnetic transient model and manufacturing data of synchronous condenser,SVC and STATCOM.It is concluded that the dynamic performance of the three devices is similar.However,the synchronous condensers are mature in manufacturing and rich in operating experience,and can be used on a large scale in improving the reactive voltage stability of AC/DC hybrid power systems.Combining with the construction project of the synchronous condensers put into operation at the inverter station of the State Grid Corporation of China in East China,this paper compares the East China Power Grid’s response characteristics to faults when there are or not synchronous condensers.(3)The effect of reactive power adjustment with synchronous condensers to suppress commutation failure in actual engineering is studied.The synchronous condenser has been built and put into use in 11 converter stations,and it has played a effient role in reactive power support in the case of voltage fluctuations,commutation failures,and near-zone failures,which suppresses the occurrence of commutation failure or further commutation failure.This paper counts the movements of the synchronous condenser nationwide from January to October 2020,and collects and analyzes the waveforms of the synchronous condenser under typical conditions such as strong excitation,magnetization,and demagnetization. |
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