Smart Solar PV Inverters with Advanced Grid Support Functionalities. Rajiv K. Varma

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      LIST OF ABBREVIATIONS

AGCautomatic generation controlANSIAmerican National Standards InstituteAPCactive power curtailmentAPSArizona Public ServiceAVRautomatic voltage regulatorBESSbattery energy storage systemBOSbalance of systemBPSbulk power systemCAISOCalifornia Independent System OperatorCIGREConseil International des Grands Réseaux Electriques, translated as, International Council on Large Electric SystemsCPUCCalifornia Public Utilities CommissionDERdistributed energy resourceDERMSdistributed energy resource management systemDFIGdoubly fed induction generatorDGdistributed generator/generationDMSdistribution management systemDVARdynamic VAREHVextra high voltageEPCengineering, procurement, and constructionEPRIElectric Power Research InstituteEPSelectric power systemERCOTElectric Reliability Council of TexasESSenergy storage systemFACTSFlexible AC Transmission SystemFERCFederal Energy Regulatory CommissionFFRfast frequency responseFROfrequency response obligationHChosting capacityHFRThigh frequency ride throughHVhigh voltageHVDChigh voltage direct currentHVRThigh voltage ride throughIBRinverter based resourceIEAInternational Energy AgencyIEEEInstitute of Electrical and Electronics EngineersIGBTinsulated gate bipolar transistorILCinverter level controllerIMinduction motorLBNLLawrence Berkeley National LaboratoryLFRTlow frequency ride throughLTCload tap changerLVlow voltageLVRTlow voltage ride throughMPPTmaximum power point trackingMVmedium voltageMVAmega volt ampereMVARmega volt ampere reactiveMWmegawattNERCNorth American Electric Reliability CorporationNRELNational Renewable Energy LaboratoryOLTCon load tap changerOPFoptimal power flowp.u.per unitPCCpoint of common couplingPFpower factorPFRprimary frequency responsePIproportional–integralPIIpermitting, inspection, and interconnectionPLLphase locked loopPMUphasor measurement unitPoCpoint of connectionPOIpoint of interconnectionPPCpower plant controllerPQpower qualityPSDCpower swing damping controllerPSSpower system stabilizerPVphotovoltaicPVPSphotovoltaic power systemsPV‐STATCOMphotovoltaic static synchronous compensatorPWMpulse width modulationQSTSquasi static time seriesRMSroot mean squareROCOFrate of change of frequencyRPCreactive power controlRTDSreal time digital simulatorSCADAsupervisory control and data acquisitionSCESouthern California EdisonSEIGself‐excited induction generatorSFsolar PV farmSGsmart gridSIsmart inverterSILsurge impedance loadingSIRsynchronous inertial responseSIWGSmart Inverter Working GroupSLGsingle line to ground faultSOCstate of chargeSPWMsinusoidal pulse width modulationSRPSalt River ProjectSSDCsubsynchronous damping controllerSSOsubsynchronous oscillationsSSRsubsynchronous resonanceSTATCOMstatic synchronous compensatorSVCstatic var compensatorTCRthyristor‐controlled reactorTHDtotal harmonic distortionTOVtransient overvoltageTSCthyristor‐switched capacitorUFLSunder-frequency load sheddingUPFunity power factorVARvolt amp reactiveVCOvoltage controlled oscillatorVSCvoltage source converterVSIvoltage source inverterVVCvolt–var controlWAMSwide area measurement systemWECCWestern Electricity Coordinating CouncilWFwind farmWTGwind turbine generator

1 IMPACTS OF HIGH PENETRATION OF SOLAR PV SYSTEMS AND SMART INVERTER DEVELOPMENTS

      Solar Photovoltaic (PV) power systems are being integrated at an unprecedented rate in both bulk power systems and distribution systems worldwide. It is expected that by 2050, solar PV systems will provide about 35% of global electricity generation [1]. Different countries, and their provinces and states, are setting up ambitious targets for PV system installations up to 100% renewables with substantial share of solar PV systems. Several grid impact studies with 100% Inverter Based Resources (IBRs) and Distributed Energy Resources (DERs) with a major component of solar PV systems have already been performed [2, 3]. While these systems significantly help in reducing overall greenhouse gas emissions, they present unique integration challenges which need to be understood and mitigated to derive full benefits from their applications. The solar PV systems are based on inverters. Power electronics technology provides new “smart” capabilities to the inverters in addition to their primary function of active power generation. These capabilities not only help solar PV systems mitigate different adverse impacts of their integration but also provide several valuable grid support functions.

      This chapter presents the concepts of reactive power and active power control, which form the basis of smart inverter operation. The impact of such controls on system voltage and frequency is explained. The different challenges of integrating solar PV systems on a large scale in transmission and distribution systems are briefly described [4]. The evolution of smart inverter technology is then presented.

1.1 Concepts of Reactive and Active Power Control

      1.1.1 Reactive Power Control

      1.1.1.1 Voltage Control

Injection of reactive power at a bus causes the voltage to rise whereas absorption of reactive power causes the bus voltage to decline. Figure 1.1 illustrates a simple power system having an equivalent voltage E and equivalent network short circuit impedance with reactance X and resistance R. An inductor X_L is connected as load at a bus termed Point of Common Coupling (PCC) to show the effect of reactive power absorption. The PCC voltage and inductor current are denoted by V and I, respectively. The impact of reactive power absorption by the inductor on the PCC voltage is examined through phasor diagrams for three cases of network impedance. The phasor diagrams for cases (a) R = 0 (purely inductive network), (b) X/R = 3 (substantially reactive network), and (c) X/R = 1/3 (substantially resistive network) are depicted in Figure 1.2a–c, respectively. The phasor diagrams are drawn with the phasor V as reference, which has same magnitude in all the three cases. The phasor diagrams can also be drawn with equivalent voltage E as reference phasor having the same magnitude, although the conclusions will be the same in both cases.

Figure 1.1 A simple power system with an inductor connected at PCC.

Figure 1.2 Phasor diagrams for network with inductive load; (a) network with R = 0; (b) network with X/R = 3; (c) network with X/R = 1/3.

      In the absence of inductor X_L, the PCC voltage is E. The lagging inductor current causes a voltage drop IR + jIX across the network impedance, thereby reducing the PCC voltage to V. Stated alternately, the reactive power absorption by the inductor reduces PCC voltage by an amount |E| − |V |.

      For case (a) R = 0, it is evident from Figure 1.2a that the change in voltage is directly proportional to network reactance and the СКАЧАТЬ