reference frame. The bus voltage is converted to the individual LC reference frameusing reverse transformation, given bywhere•In case of multiple LCs, the LC whosedqframe is taken as the common referenceframe has to provide its reference frequency change∆ωcomto all the sub-modules.For simplicity, thedqframe of the 1-st inverter is chosen as the common referenceframe. Accordingly, output variables of the 1-st inverter include the operatingfrequency and the output current, while all the other inverters affect the microgridoperation only by the current flowing into the microgrid network.•A complete state-space model of thei-th LC is given below by combining the state-space models of the power controller, voltage controller, current controller andoutput LCL filter.(0)(0)1(0)(0)sincoscossinbDbQVbDbQVVTVV= 11bdqSbDQVvTvTD=DD
58LC Model in a MicrogridwhereINVωinvINVciiioDQiiCxiCwD=DDcominvINVinvINVcomiiiibDQiixAxBvBwwD=DDD.invTiiiidqidqildqiodqiodqixPQiviD=DDDDDDDD12111122INV111121111122313 13000000 0PiPiV iPviViC iV iPviC iViC iViCiiLCL iC iV iPviLCLiLCL iViLCL iC iViLCL iCiLCL iC iViCiLCL iP iABBCBBDCBCBDBABDDCABTBDCBCBDDDBCw= comcominvINV1213 213 1000, 000TPiiiLCLSBxBBBTwwD===1 13INVω1 130001 00001 PiCiCiw==INVc2 13000000iCSCTT=
59•LCs are coordinated for maintaining V/f and sharing power. The LC cooperationin a MGcan be realized by communication links, but they will make the systemmore expensive and less reliable.•In this chapter, control techniques based on local measurements which do notrequire expensive communication facilities have been proposed.•The LC modeling approach presented in this chapter divides the whole systeminto three major sub-modules; inverter, network and loads (see Fig 28).State Space Representation of MGFig 27. Structure of inverter-based microgrid with LCs
60•Each inverter is modeled on its individual reference frame whose rotation frequency is set by its local power sharing controller.
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