Rotor Loss And Temperature Field Analysis Under Abnormal Operations Of Large Capacity Synchronous Condensers

Synchronous condensers(SCs)have the advantages of wide reactive power adjustment range and strong voltage support capability.SC can be used for dynamic reactive power adjustment of the ultra high voltage direct current converter stations to maintain voltage stability to prevent commutation failure.However,the larger reactive power and current will cause the rotor loss and heat generation of SC to increase,thereby restricting its operation capability.Especially under the condition of asymmetrical system failure,the negative sequence magnetic field of SC will produce a lot of losses on the rotor,causing more serious heating.In this thesis,the loss and heating of the rotor core and slot wedges of the synchronous condenser under the asymmetrical operation of the system are studied.The main results are as follows:(1)The field-circuit-network coupling time-step finite element model of the 300Mvar synchronous condenser is established,and the dynamic process of the synchronous condenser is studied when the transmission line is asymmetrical short-circuit and the system is unbalanced operation.(2)By calculating the single-phase short-circuit and two-phase short-circuit faults of the transmission line,the law of the stator currents,excitation current and electromagnetic torque of the synchronous condenser with time is revealed.By calculating the single-phase step-down operation and the two-phase step-down operation of the system,the influence of different voltage drops on the stator current and excitation current is revealed,and the change rule of the stator current and excitation current with time is found.(3)The loss density of the rotor core and slot wedges of SC is studied when the transmission line is asymmetrical short-circuit and the system is unbalanced operation.The loss density of the rotor core and slot wedges with the radial depth is revealed,and the rotor position with greater loss density is obtained.(4)The two-dimensional transient temperature field model of the SC is stablished,and the rotor temperature distribution of the SC is studied under the above-mentioned fault conditions.The change law of the rotor slot wedge and iron core temperature with time is revealed,and the rotor position with the highest temperature rise is obtained.Taking into account the maximum allowable temperature of the rotor core,it reveals the ability of the synchronous condenser to withstand various asymmetric faults.