Study On Sending-end Angle Transient Stability For Wind-thermal-bundled Power Based On D-PMSG Transmitted By DC System

The scheme of Wind-thermal bundled power transmitted by DC system is the main solution to the problem that power consumptive of energy rich base and energy shortage of load center.The centralized access of large-scale wind power,long-distance transmission and wind turbine's control characteristics and it's output,have decided that connectwind power to the grid will have a greater impact on the grid operation,and this impact is different from the conventional power supply.The Direct-drive Permanent Magnet Synchronous Generator(D-PMSG)is connected to the grid through converter,the structure and operation characteristics of D-PMSG are different from conventional synchronous generator.Therefore,the research on the angle transient stability of wind-thermal bundled power based on D-PMSG transmitted by DC system not only has theoretical research value,but also has practical engineering significance.This paper mainly studies the sending-end angle transient stability of the system when the wind farm based on the D-PMSG is bundled with the nearby thermal power plant transmitted by UHVDC.In this paper,the basic mathematical model of wind-thermal bundled power transmitted by UHVDC systemwas built by using Digsilent/Power Factory software.The influence of integratingD-PMSGsin the systemangle transient stability was analyzed by using Extended Equal Area Criteria(EEAC),when the power system under the situation that wind power input of D-PMSG was balanced by severely disturbed group reduced their mechanical power.Then,the influence of UHVDC transmission mode on the angle transient stability of wind-thermal bundled system was analyzed.Then,for improvethe sending-end angle transient stability for thermal-bundled power,atransient reactive power support control strategy is proposed for the full-scale frequency converter of the D-PMSG.When the voltage of the power network is reduced due to the fault of the power network,the transient reactive power control strategy is used in the reactive power control of the inverter;the reference value of reactive power is set by low voltage controller.D-PMSG needs to provide certain reactive power to support the grid voltage.Finally,the influence of integratingD-PMSGs with transient reactive power support control modein the system angle transient stability was analyzed by using EEAC.At the same time,the angle transient stability of wind-thermal bundled system based on D-PMSGs with different control strategies were compared.Simulationresults show that,when the power system under the situation that wind power input of D-PMSGswere balanced by severely disturbed group reduced their mechanical power,the connection of D-PMSGis beneficial to the angle transient stability of the system,and the UHVDC transmission mode can improve the angle transient stability of the wind-thermal bundled system compared with the AC transmission mode.The D-PMSGs with transient reactive power support control strategy is also beneficial to the angle transient stability of the system.When the D-PMSGs adopt transient reactive power support control strategy,the system angle transient stability will be better compared with the situation of D-PMSGs adopting unity power factor control strategy.