報(bào)告ptt7dg ctrl分布式發(fā)電控制

1、分布式發(fā)電控制Dr. Wenzhong GaoIntegration of Alternative EnergyOn-site distributed generation (DG): small-scale, close to loads.Integration challenges for renewable energy DG: intermittent, variable.Microgrid: multiple renewable energy sources, locally controlled to serve loads; can run in parallel with gr

2、id or stand-alone; dispatchable (controllable)Three types of integration busses: dc, ac, high-freq ac. (Fig 12.12)Integration of multiple renewable energy sources. (Fig 12.11)Power Electronics: enabling technology! Figure 12.12 Varieties of energy integration: (a) dc-link integration; (b) ac-link in

3、tegration; (c) HFAC-link integrationFigure 12.11 General schemes for integration of electrical sources and loads and thermal dissipationPower flow theory: flow of active power P and reactive power Q between two sources can be controlled by adjusting the power angle and voltage magnitude of each syst

4、em.Active Power flow P is controlled predominantly by the power angle; Reactive power flow Q is controlled predominantly by the voltage magnitude.Parallel connection of two power converters with a common load.The Complex power at the load because of the two inverters (VSI):SoSo active and reactive p

5、ower flowing from each VSI:Independent control of real and reactive Power.(Sensitivity is more significantis small since)Variation of active power is strongly coupled with power angle and frequency variation; reactive power is strongly coupled with voltage magnitude.Because controlling frequency dyn

6、amically controls the power angle , real power flow control can be achieved equivalently by controlling the frequency of the voltage generated by DG VSI.DG control: each DG unit supply real and reactive power in proportion to its power ratings, so that DG units share the load power demand in a prede

7、termined manner among themselves within the microgrid after islanding.分布式發(fā)電控制Distributed Generation Control (fuel cell control as example)Control of distributed generation systemsPower converter systems for distributed resourcesApproach to control reactive and active powerPower quality issues and mi

8、tigation technologiesControl of PEMFC DGFuel cell output voltage is a function of load current. DC/DC converter adapts fuel cell output voltage to desired inverter input voltage and smooth the fuel cell output current (reduce ripple current drawn from fuel cells).PWM VSI is used to interconnect fuel

9、 cell to utility grid for real and reactive power control purposes.LC filter: reduce the harmonics of the inverter output voltage (see block diagram)Controller for DC/DC boost converter: keep the DC bus voltage within an acceptable range.PQ Controller:Control the VSI output voltage to synchronize wi

10、th grid (amplitude, angle, frequency)Control real power, reactive power according to reference values.The real power and reactive power delivered to the grid is determined by the amplitude and angle of the sending end voltage source; i.e. inverter output voltage , For reference real power Pref, reac

11、tive power Qref,So, three phase of (in abc frame): (utility grid voltage)voltagesdq reference transformation: transform a stationary (abc) system to a rotating (dq0) system. So 60Hz quantity es DC quantity in dq frame. This eases controller design. Also control variables are reduced from 3 to 2.Sinu

12、soidal PWM is used to control the VSI.(Space vector PWM can also be used!)SPWM generates square wave ON/OFF signal to control IGBT switches, by comparing a sinusoidal reference modulation signal with a high frequency carrier waveform (triangular).The frequency of the modulation signal must be the sa

13、me as grid frequency, 60Hz.The angle and magnitude of the modulation signal control the real power and reactive power.Block diagram of the overall control system of the inverterFiring Signal to IGBTModulation Ref. SignalControlSignalInnerloopouterloopIdqLoadfollowercontroller1/SPLLSo, in dq frame, t

14、he reference voltage:dq Reference Signal Computation BlockDecouple the dynamicsTwo control loops: inner current control loop is much faster than outer voltage control loop.The two loop controllers can be designed independently.Use PI compensatorsController design for power electronics converters are

15、 based on small-signal linearized models.Simulation results:Power management How controller performs for given Pref and QrefLoad following capabilitiesStability during faults.Simulation DataOuter voltage control loopController performance for boost converterDC/DCVfcVinPI480V +- VdPWMUsing a constant

16、 utilization factor (via control), Fuel cell output voltage Vdc will be within the limits with small variations, which can be handled by VSI. Thus, a DC/DC boost converter can be avoided.VSI output voltage: Taking rated values as the base value,VSI output in per unit:so, Another TopologyFuelCellVSIm

17、Grid Busso, three phase delivered real and reactive power from fuel cell to grid:(fuel cell output power)Control of VSI for constant power operation, (Pref, )i.e. constant real power Pref and constant p.f. cos .so, the two control variables of VSI:Control real powerm depends on fControl voltagebutDe

18、sired DC output voltage from boost converterPoint of common couplingPLL structures. General structure of the three-phase dq PLL methoddq/abcutility=0Power Flow ControlDG(e.g. PV, Fuel Cell)VSIViVsIsLsGridISVsViIsXsResynchronization ControlWhen the utility grid returns to normal operating conditions, the islanded micro grid has to resynchronize with the grid for reconnection.Real Power ControllerReactive Power ControllerSpace Vector to ABC ModulatorInner Voltage andCurrent Closed LoopControlPIPIVSI ControllerVSIPWMvReferences1Felix A. Farret