1、The Research of Stand-alone DFIG Systems and Its Control StratagyOutline Applicable occasions and system components The research of fixed-pitch wind turbine Vector control strategies based on stator-flux orientation SimulationApplicable occasions and system componentsl Applicable occasions:l Stand-a
2、lone wind power systems are generally used in remote areas where are not covered by the conventional power grid.l In addition to regular grid,we should promote stand-alone wind power systems vigorously and supply the power of daily lives and production for remote area residents(such as remote rural,
3、pastoral area,island and so on).remote ruralApplicable occasions and system componentsAdvantages compared with general wind power generation:a.High mobility ;b.Diversification of energy use;c.Easy installation.Island pastoral areaApplicable occasions and system components system componentsDue to the
4、 characteristics of the wind energy instability,for the stable power supply to the regional load,wind power generation system is often combined with other forms of energy such as solar energy,fuel,or adding energy storage devices(batteries,fly wheels and so on),which can store up the wind energy.Whe
5、n wind energy is insufficient,energy storage devices supply to the loads together with wind power generation system.storage battery Comined energy supply systemsApplicable occasions and system components Structure of stand-alone DFIG systemsThe research of fixed-pitch wind turbineWind turbines are t
6、he primary energy conversion parts in wind power generation system i.Its used to intercept the air flowing with the kinetic energy,and the part of the kinetic energy of wind turbine blades wind swept area is converted into mechanical energy.It not only determines the effective output power of the wi
7、nd power generation system,but also directly affecting the safety of the crew and stable operation,which is one of the key components in the wind power generation system.According to the aerodynamics,the input power of the wind turbine:air density:airflow through the cross-sectional area of the wind
8、 wheel in unit time:wind SpeedTip speed ratio:：blade rotation angular speedThe research of fixed-pitch wind turbineMechanical power output of the wind turbine:R：blade radiusCp：Wind energy utilization factorFixed-pitch wind turbine Cp()curve:4.18)2.13131(73.0)(eCpThe research of fixed-pitch wind turb
9、ine A particular fixed pitch wind turbine has a unique optimaltip speed ratio that can get the maximum value of wind energy utilization factor.Fixed pitch variable speed wind power-speed curveopt:optimal tip speed ratioCpmax:maximum value of wind energy utilization factorPvCpPmaxmaxThe research of f
10、ixed-pitch wind turbineSimulation model of fixed-pitch wind turbineVector control strategies based on stator-flux orientationExcitation stator flux oriented control strategy is derived under the conditions of the grid voltage symmetry,the motor parameters symmetry,symmetrical line and transformer pa
11、rameters and symmetry load conditions,Therefore,each three-phase system of physical quantities(voltage,current,flux,etc.)contains only positive sequence component system in steady-state operation,active power,reactive power,electromagnetic torque,mechanical torque and speed are constants.DFIG coordi
12、nate transformation diagramVector control strategies based on stator-flux orientationDFIG voltage equation in a two-phase synchronous rotating coordinate system:(1-1)DFIG system flux equation under the two-phase synchronous rotating coordinate:(1-2)Vector control strategies based on stator-flux orie
13、ntationTo reduce the system order and simplify the mathematical model,directiing d-axis synchronous rotating coordinate system.with the following assumptions:a.Ignoring the transient process of the stator flux,that space vector s is in synchronous speed rotation,keeping the amplitude constant.And th
14、e s was defined in the d-axis synchronous coordinates;b.Ignoring the stator resistance Rs.By the previous equations(1-1)(1-2)and this equation(1-3):(1-3)(1-4)(1-6)Vector control strategies based on stator-flux orientationThe definition of the magnetizing current ims as follows:(1-5)By the previous e
15、quations(1-4):the stator flux orientation (1-6)(1-7)Control the amplitude of the stator voltage vector(1-8)Vector control strategies based on stator-flux orientationBy the previous equations(1-5)(1-7)(1-8),mathematical model of the DFIG in independent operation as shown below:By the mathematical mod
16、el of DFIG independent operation,which can get control block diagram as shown below:Vector control strategies based on stator-flux orientation DFIG in independent operationthe excitation vector control strategy diagram:decoupled controlCurrent inner loop PI controller:based on IMCVoltage outer loop
17、PI contorllerSimulationSimulation Figure:SimulationInitial conditions and requirements:Each phase resistance value of the load:R=5.45 ohmInput constant power:Pm=30 KWIn stable operation,the stator voltage Us maintained at 311v.The simulation results:The stator voltage UsSimulationStator side active power:the power size is determined by the load.Three phase stator voltages and three-phase stator currentsSimulationRotor speedA phase stator voltage and stator current
