Technology And Simulation Of Fault DFIG Crossing

Interaction between wind power system and grid is growing with the increasing installedcapacity of wind power, in which fault ride through capability of wind power system becomesone of the important factors that affects safe and stable operation of the power grid. Thispaper focuses on the fault ride-through capability of DFIG based wind power system,including low-voltage-ride-through (LVRT) capability and high-voltage-ride-through (HVRT)capability. The main research methods divided into control strategy improves and increaseprotection hardware devices; moreover the LVRT also contains symmetrically faultride-through and asymmetrically fault ride-through.To reach LVRT of DFIG wind power generator, this paper design a cooperativecontroller of GSC (grid-side-converter) and RSC (rotor-side-converter) in symmetrically faultupon mathematics modeling and fault transient analyzing; design a PD current regulatorcontroller of GSC and a PI-R current regulator controller of RSC in asymmetrically fault;design a controller of vector control when in steady-state and direct torque control when intransient-state, to solve asymmetrically fault and symmetrically fault in one time. About thecommon Crowbar and Chopper resistance, this paper researches its protective effect of lowvoltage fault.To work out HVRT of DFIG, this paper describes causes of voltage swell first, thenanalyzes the transient process of DFIG when high voltage fault; enumerates solutions ofHVRT, include increase Crowbar, improve control methods, increase var compensator(STATCOM) and super capacitor; design HVRT control strategies of GSC and RSC; designthe control method of STATCOM. Because of the poor feasibility of LVRT methods andHVRT methods in industrial production if it is separately designed, this paper conclusions thatthe ride-through problem should be operated by single control system which not onlyeffective for LVRT but also effective for HVRT. Furthermore, if in slight grid voltage fault,control strategy improves is the best way of ride-through, otherwise hardware devises should access.In order to prove the design control strategy in this paper, a simulation model of1.5MWDFIG wind power system is built in software Matlab/Simulink. After simulant of high voltagefault ride through and low voltage fault ride through, the results show that each controllerdesign in this paper is correct.