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    • 专利摘要:
    A method for operatively coupling a plurality of generating units in at least one micro-grid to a bulk grid, where the at least one micro-grid is configurable to be operatively coupled to the bulk grid via a point of interconnection breaker is presented. The method includes, using a control unit operatively coupled to the at least one micro-grid and the bulk grid, determining one or more bulk grid side parameters and one or more micro-grid side parameters, comparing one or more of the one or more micro-grid side parameters with corresponding one or more bulk grid side parameters, and synchronizing each of the plurality of generating units in the at least one micro-grid with the bulk grid based on the comparison. Further, the method includes connecting simultaneously, using the point of interconnection breaker, each of the plurality of generating units to the bulk grid based on the synchronization.
    公开号:SE1750731A1
    申请号:SE1750731
    申请日:2017-06-09
    公开日:2018-02-24
    发明作者:Sambamoorthy Veda Santosh；James Premerlani William
    申请人:Gen Electric；
    IPC主号:
    专利说明:

    [1] [0001] This invention was made with Government support under grant numberDE-OE0000728 awarded by the Government. The Govemment has certain rights in the invention.BACKGROUND
    [2] [0002] Embodiments of the present specif1cation relate generally to a system andmethod for interconnecting two grids, and more specif1cally to a system and method for synchronizing and connecting a micro-grid to a bulk grid.
    [3] [0003] A micro-grid is an electrical network with a well-defined boundary andtypically includes generating assets such as small distributed generators, local loads,inVerter-based distributed generation and other power systems equipment. Further,the micro-grid is generally coupled to the bulk grid (for example, an area electricpower system (AEPS)) through one or more Points of Interconnection (POIs). Incertain scenarios that arise from situations such as electrical disturbances, outage ofthe bulk grid, a request from an AEPS operator, and the like, the micro-grid mayoperate as an island by seVering its link to the bulk grid. In this island mode ofoperation, frequency and Voltage within the micro-grid are generally deterrnined bythe operating conditions of the micro-grid itself.
    [4] [0004] Further, it may be desirable to reconnect the micro-grid to the bulk grid.Currently, while reconnecting the micro-grid to the bulk grid, each of the multiplegenerating assets of the micro-grid is indiVidually connected back to the bulk grid.Disadvantageously, indiVidually connecting each generating asset of the micro-grid tothe bulk grid is a laborious task, since time required and number of interrnediate stepsfor resynchronizing with the bulk grid is greater. Typically, resynchronizing and eventually re-connecting generating assets necessiates use of equipment, such as 285773-1 synchronizing relays. Altematively, the generating assets need to be equipped Withadvanced controls for performing the resynchronization and reconnection. Inaddition, While reconnecting the micro-grid to the bulk grid, it is desirable to takeprecautions that ensure that reconnecting the micro-grid to the bulk grid by closing a POI breaker does not adversely impact the micro-grid assets.BRIEF DESCRIPTION
    [5] [0005] In accordance With aspects of the present specification, a method foroperatively coupling a plurality of generating units in at least one micro-grid to a bulkgrid, Where the at least one micro-grid is configurable to be operatively coupled to thebulk grid at a point of interconnection Via a point of interconnection breaker ispresented. The method includes deterrnining, using a control unit, one or more bulkgrid side parameters and one or more micro-grid side parameters, Where the controlunit is operatively coupled to the at least one micro-grid and the bulk grid. Further,the method includes comparing, using the control unit, one or more of the one or moremicro-grid side parameters With corresponding one or more bulk grid side parameters.The method also includes synchronizing, using the control unit, each of the pluralityof generating units in the at least one micro-grid With the bulk grid based on thecomparison. Moreover, the method includes connecting simultaneously, using thepoint of interconnection breaker, each of the plurality of generating units to the bulkgrid based on the synchronization. A non-transitory computer readable mediumincluding one or more tangible media, Where the one or more tangible media includecode adapted to perform the method for operatively coupling a plurality of generatingunits in at least one micro-grid to a bulk grid, Where the at least one micro-grid isconfigurable to be operatively coupled to the bulk grid at a point of interconnection via a point of interconnection breaker is presented.
    [6] [0006] In accordance With another aspect of the present specif1cation, a system foroperatively coupling a plurality of generating units in at least one micro-grid to a bulkgrid is presented. The system includes a point of interconnection breaker disposedbetween the bulk grid and the at least one micro-grid, Where the point of interconnection breaker is configured to operatively couple the at least one micro-grid 285773-1 to the bulk grid at a point of interconnection. Further, the system includes a controlunit operatively coupled to the bulk grid and the at least one micro-grid, where thecontrol unit is configured to deterrnine one or more bulk grid side parameters and oneor more micro-grid side parameters, compare the one or more micro-grid sideparameters with corresponding one or more bulk grid side parameters, synchronizeeach of the plurality of generating units with the bulk grid based on the comparison,and connect simultaneously each of the plurality of generating units to the bulk grid based on the synchronization.DRAWINGS
    [7] [0007] These and other features, aspects, and advantages of the present disclosurewill become better understood when the following detailed description is read withreference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
    [8] [0008] FIG. l is a diagrammatical representation of a system for synchronizing andreconnecting a micro-grid to a bulk grid, according to aspects of the present specification;
    [9] [0009] FIG. 2 is a flow chart representing an exemplary method for synchronizingand connecting a micro-grid to a bulk grid, according to aspects of the present specification; and
    [10] [0010] FIG. 3 is a control unit for use in the system of FIG. 1, according to aspects of the present specification.DETAILED DESCRIPTION
    [11] [0011] Unless defined otherwise, technical and scientific terms used herein havethe same meaning as is commonly understood by one of ordinary skill in the art towhich this specification belongs. The terms “f1rst”, “second”, and the like, as usedherein do not denote any order, quantity, or importance, but rather are used todistinguish one element from another. Also, the terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced 285773-1 items. The terrn “or” is meant to be inclusive and mean one, some, or all of the listed 77 CC items. The use of “including, comprising” or “having” and Variations thereof hereinare meant to encompass the items listed thereafter and equivalents thereof as well asadditional items. The terms ““connected” and “coupled” are not restricted to physicalor mechanical connections or couplings, and can include electrical connections orcouplings, whether direct or indirect. Furthermore, terms “circuit” and “circuitry”and “controlling unit” may include either a single component or a plurality ofcomponents, which are either active and/or passive and are connected or otherwisecoupled together to provide the described function. Also, the term operativelycoupled as used herein includes Wired coupling, wireless coupling, electrical coupling, magnetic coupling, radio communication, software based communication, or combinations thereof
    [12] [0012] As will be described in detail hereinafter, various embodiments of anexemplary method and system for connecting a smaller grid to a bulk grid arepresented. Specifically, systems and methods for synchronizing and connecting asmaller grid to a bulk grid are presented. The smaller grid may be a micro-grid or aportion of the bulk grid that has been disconnected from the bulk grid due to anelectrical disturbance, for instance. Use of the systems and methods presentedhereinafter aids in preventing any adverse impacts to the generating assets of themicro-grid and/or the smaller grids while reconnecting the generating assets of the micro-grid to the bulk grid.
    [13] [0013] Tuming now to the drawings and by way of example in FIG. 1, adiagrammatical representation 100 of a system for connecting a micro-grid to a bulkgrid, according to aspects of the present specification, is presented. In a presentlycontemplated configuration, the system 100 includes a bulk grid 102, a point ofinterconnection (POI) breaker 104, a micro-grid 106, and a control unit 108. In oneembodiment, reference numeral 103 may be representative of the point ofinterconnection (POI). The POI 103 is generally representative of the point at whichthe micro-grid 106 is operatively coupled to bulk grid 102. The POI breaker 104 maybe disposed at or about the POI 103. In one embodiment, the bulk grid 102 may be an area main electrical grid that includes a plurality of smaller grids. Although the 285773-1 example of FIG. 1 represents a single micro-grid coupled to a bulk grid, a system having a plurality of micro-grids coupled to the bulk grid is also anticipated.
    [14] [0014] The terrn “micro-grid,° as used herein, is used to refer to a small-scalepower grid with its own power resources, generators, loads, and def1nable boundariesthat are capable of operating independently or in conjunction with the bulk grid 102.In certain situations, it may be desirable to disconnect the micro-grid 106 from thebulk grid 102. Some examples of such situations include electrical disturbances in the bulk grid 102, outage of the bulk grid 102, and the like.
    [15] [0015] Further, the micro-grid 106 may include a plurality of generating units 110.The generating units 110 may in tum include a plurality of electrical generatorsconf1gured to generate electrical energy. Furthermore, the generating units 110 arecoupled to a plurality of loads. In one example, the generating unit 110 includes asynchronous generator and a non-synchronous generator. Also, each of the pluralityof generating units 110 has a corresponding switch 112. When all the switches 112are in a closed condition, the plurality of generating units 110 behaVes as a single unit.Furthermore, when all the switches 112 are in the closed condition, the plurality of generating units 110 forms a micro-grid 106.
    [16] [0016] It may be noted that the micro-grid 106 may be coupled to the bulk grid102 or may be disconnected from the bulk grid 102 at time t1. In the example whereat time t; the micro-grid 106 is coupled to the bulk grid 102, it may be desirable todisconnect the micro-grid 106 from the bulk grid 102 at time t1+At due to occurrenceof certain electrical disturbances. In such a scenario, it may be desirable to reconnectthe micro-grid 106 to the bulk grid 102 at time tg, where t2> t1+At. In accordancewith aspects of the present specif1cation, system 100 facilitates resynchronization andsimultaneous reconnection of each of the plurality of generating units 110 of the micro-grid 106 to the bulk grid 102.
    [17] [0017] In one embodiment, the micro-grid 106 may be reconnected to the bulk grid102 in real-time. In particular, the micro-grid 106 may be reconnected to the bulk grid 102 when the generating units 110 of the micro-grid 106 are operational and 285773-1 providing power to the loads. Implementing the system 100 as described hereinaboveadvantageously allows the micro-grid 106 to be reconnected to the bulk grid 102without the need for shutting down the bulk grid 102 and/or any other micro-gridcoupled to the bulk grid 102.
    [18] [0018] In situations where the micro-grid 106 is disconnected from the bulk grid102, the micro-grid 106 is configured to operate independent of the bulk grid 102. Inthis scenario, micro-grid side parameters, such as a frequency, a phase, and a voltagecorresponding to the micro-grid 106 are deterrnined based on the operating conditionof the micro-grid 106. Additionally, bulk grid side parameters such as a frequency, aphase, and a voltage corresponding to the bulk grid 102 may be deterrnined. It maybe noted that in certain scenarios, the parameters corresponding to the bulk grid 102and the micro-grid 106 may also be deterrnined when the micro-grid 106 and bulk grid 102 are connected to each other.
    [19] [0019] In one example, when the micro-grid 106 is decoupled from the bulk grid102 at a given instance of time t3, where t2>t3>t1+2lt, one or more of bulk grid sideparameters are different from the one or more micro-grid side parameters. Inparticular, voltage values, phase values, and/or frequency values corresponding to the micro-grid 106 are different from those corresponding to the bulk grid 102.
    [20] [0020] In one example, at time instance tg, the frequency of the micro-grid 106 isfy, while the frequency corresponding to the bulk grid 102 is fg, where f; is differentfrom fg. However, while reconnecting the micro-grid 106 to the bulk grid 102 at saytime tg, it is desirable to ensure that the frequency f; corresponding to the micro-grid106 is substantially equal to the frequency f; corresponding to the bulk grid 102.More particularly, it is desirable to minimize the difference between the frequenciesf;and f; that respectively correspond to the micro-grid 106 and the bulk grid 102 suchthat the difference is an optimal value. In one example, the optimal value ofdifference between frequencies of the micro-grid 106 and the bulk grid 102 may beabout 0.01 Hz. Similarly, while reconnecting the micro-grid 106 to the bulk grid 102,it is also desirable to achieve an optimal value of a difference in voltage values and/or phase values corresponding to the micro-grid 106 and the bulk grid 102. The scenario 285773-1 Where the micro-grid side parameters are substantially equal to the correspondingbulk grid side parameters is representative of a synchronized state of the micro-grid 106 With respect to the bulk grid 102.
    [21] [0021] In accordance With aspects of the present specification, the differencebetween the frequencies corresponding to the micro-grid 106 and the bulk grid 102may be reduced by modifying/altering one or more input parameters corresponding tothe generating units 110 of the micro-grid 106 to synchronize or resynchronize themicro-grid 106 With the bulk grid 102 prior to reconnecting the micro-grid 106 to thebulk grid 102. In the example of FIG. 1, the control unit 108 may be configured tomodify the one or more input parameters corresponding to the generating units 110.Some examples of the input parameters may include a mechanical speed, a field, atorque, and an excitation current When the generating unit 110 is an electrical generator.
    [22] [0022] In one embodiment, the control unit 108 may be an analog controller or adigital controller. In another embodiment, the control unit 108 may be proportional-integral (PI) controller. In yet another embodiment, the control unit 108 may includeone or more processing units and associated memory devices configured to execute atleast one control algorithm. As used herein, the term “processing unit” refers not onlyto integrated circuits referred to in the art as being included in a computer, but alsorefers to a controller, a microcontroller, a microcomputer, a programmable logiccontroller (PLC), an application specific integrated circuit, application-specificprocessors, digital signal processors (DSPs), Application Specific Integrated Circuits(ASICs), Field Programmable Gate Arrays (FPGAs), and/or any other programmablecircuits. Further, the memory deVice(s) may generally include memory element(s)including, but are not limited to, computer readable medium (e.g., random accessmemory (RAM)), computer readable non-Volatile medium (e.g., a flash memory), oneor more hard disk drives, a floppy disk, a compact disc-read only memory (CD-ROM), compact disk-read/Write (CD-MW) drives, a magneto-optical disk (MOD), adigital versatile disc (DVD), flash drives, optical drives, solid-state storage devices,and/or other suitable memory elements. Control steps that may be executed by the control unit 108 Will be described in greater detail With respect to FIG. 2. 285773-1
    [23] [0023] Implementing the system 100 as described hereinabove aids insynchronizing the micro-grid 106 with the bulk grid 102 prior to reconnecting themicro-grid 106 to the bulk grid 102. In particular, implementing the system 100 asdescribed hereinabove, allows the generating units 110 of the micro-grid 106 to besimultaneously connected to the bulk grid 102. The exemplary method ofsynchronization and connection of the micro-grid 106 with the bulk grid 102 will beexplained in greater detail with respect to FIG. 2.
    [24] [0024] FIG. 2 is a flow chart 200 representing an exemplary method forsynchronizing and connecting a micro-grid to a bulk grid, according to aspects of thepresent specif1cation. In the example of FIG. 2, a method for resynchronizing andreconnecting the micro-grid to the bulk grid is presented. The method of FIG. 2 willbe described with respect to the elements of FIG. 1.
    [25] [0025] As previously noted, certain scenarios call for the micro-grid to bedisconnected from the bulk grid, during which time the micro-grid operates in anindependent mode. Subsequently, it may be desirable to reconnect the micro-grid tothe bulk grid and hence, it may be desirable to resynchronize the micro-grid with thebulk grid. The term resynchronization is used to refer to the synchronization of the micro-grid 106 with the bulk grid prior to coupling the micro-grid to the bulk grid.
    [26] [0026] The method begins at block 202, where one or more bulk grid sideparameters and one or more micro-grid side parameters are deterrnined. It may benoted that at step 202 the bulk grid side parameters and micro-grid side parameters aredeterrnined when the micro-grid 106 is decoupled from the bulk grid 102. The bulkgrid side parameters and the micro-grid side parameters include a Voltage, afrequency, a phase angle, or combinations thereof. The term “bulk grid side,° as usedherein, refers to a point between the bulk grid 102 and the POI breaker 104.Similarly, the term “micro-grid side,° as used herein, refers to a point between themicro-grid 106 and the POI breaker 104. In one example, the bulk grid sideparameters and the micro-grid side parameters are deterrnined at the same instant oftime. In particular, the bulk grid side parameters and the micro-grid side parameters are deterrnined simultaneously. 285773-1
    [27] [0027] Moreover, in certain embodiments, the bulk grid side parameters and themicro-grid side parameters are deterrnined using the control unit 108. In anotherembodiment, the bulk grid side parameters and the micro-grid side parameters aredeterrnined using a voltage sensing device, a frequency deterrnination device, a phaseangle deterrnination device, or combinations thereof It may be noted that in certainexamples, the one or more bulk grid side parameters and one or more micro-grid sideparameters may also be deterrnined When the micro-grid 106 is coupled to the bulk grid 102.
    [28] [0028] Further, at block 204, one or more of the micro-grid side parameters arecompared With corresponding one or more of the bulk grid side parameters to identifyan occurrence of a deviation of one or more parameters corresponding to the micro-grid side from corresponding parameters of the bulk grid side. In one example, thevoltage corresponding to the micro-grid side is compared With the voltagecorresponding to the bulk grid side. Similarly, the phase angle corresponding to themicro-grid side is compared With the phase angle corresponding to the bulk grid side.In a similar manner, the frequency corresponding to the micro-grid side is compared With the frequency corresponding to the bulk grid side.
    [29] [0029] In certain scenarios, based on the comparison at block 204, no deviationbetween the micro-grid side parameters and the bulk grid side parameters may beidentified. In this scenario, the micro-grid 106 is in a synchronized or resynchronizedstate With reference to the bulk grid 102. In particular, When the voltage, frequency,and phase angle on the micro-grid side is substantially equal to the voltage, frequency,and phase angle on the bulk grid side, the micro-grid 106 is in a resynchronized stateor resynchronized With the bulk grid 102. In such a situation, control may be passedto block 214, Where the micro-grid 106 is instantly reconnected to the bulk grid 102.More particularly, each of the plurality of generating units 110 of the micro-grid 106 is simultaneously reconnected to the bulk grid 102.
    [30] [0030] HoWever, in certain other scenarios, based on the comparison of block 204,an occurrence of a deviation of one or more of the micro-grid side parameters from the corresponding one or more of the bulk grid side parameters may be identified, as 285773-1 indicated by block 206. In particular, if a value of one or more micro-grid sideparameters is different from corresponding one or more bulk grid side parameters, adeviation is identified. In this situation, it is desirable to reduce/minimize anydeviation of the micro-grid side parameters from the corresponding bulk grid side parameters prior to reconnecting the generating units 110 of the micro-grid 106 to thebulk grid 102.
    [31] [0031] In accordance With aspects of the present specification, the deviating micro-grid parameters are resynchronized With corresponding bulk grid side parametersprior to reconnecting the generating units 110 of the micro-grid 106 to the bulk grid102. In one embodiment, the deviating micro-grid parameters may be resynchronizedWith corresponding bulk grid side parameters by modifying values of one or moreinput parameters corresponding to one or more generating units 110 of the micro-grid106. As previously noted, some examples of the input parameters include amechanical speed, a field, a torque, an excitation current, a reactive power and an active power.
    [32] [0032] Accordingly, at block 208, a desired value for modifying one or more inputparameters corresponding to the plurality of generating units 110 of the micro-grid106 may be deterrnined based on the deviation deterrnined at block 206. In particular,the value for modifying the one or more input parameters corresponding to thegenerating units 110 of the micro-grid 106 to resynchronize the deviating micro-gridside parameters to the corresponding bulk grid side parameters may be deterrnined at block 208.
    [33] [0033] In one embodiment, the control unit 108 is employed to determine thevalues for modifying the input parameters of the generating units 110 to facilitateresynchronization of the micro-grid 106 With the bulk grid 102 prior to reconnectingmicro-grid 106 to the bulk grid 102. Accordingly, the deviation(s) deterrnined atblock 206 may be provided as an input to the control unit 108. The control unit 108 isconf1gured to determine the values for modifying the input parameters based on the deterrnined deviation. By Way of example, if the generating unit 110 is an electrical 285773-1 generator or an altemator, values for modifying input parameters such as a mechanical speed, a field, a torque, and/or an excitation current may be deterrnined.
    [34] [0034] Subsequent to the deterrnination of values for modifying the one or moreinput parameters corresponding to the generating units 110, the control unit 108 maybe configured to reduce/minimize the deterrnined deviation between one or moremicro-grid side parameters and the corresponding one or more bulk grid sideparameters to an optimal value, as indicated by block 210. In certain embodiments,the optimal value may be zero. The computation of the values for modifying the inputparameters based on the deterrnined deviation(s) of block 208 and the subsequentmodification of the input parameters based on the deterrnined values of block 210 will be described with reference to FIG. 3.
    [35] [0035] Referring now to FIG. 3, one example of a control unit 300 for use in thesystem of FIG. 1, according to aspects of the present specification is presented. FIG. 3 is described with reference to the components of FIGs. 1-2.
    [36] [0036] In the example of FIG. 3, the control unit 300 is a proportional integral (PI)controller. Also, the control unit 300 includes proportional subunits 302, 304 and asumming subunit 306. The proportional subunits 302, 304 may be configured tomodify any input provided to the proportional subunits 302, 304 by multiplying theinput by a constant value. In one example, the input includes a value of bulk grid sideand micro-grid side parameters acquired from simultaneous measurements. Thesumming subunit 306 may be configured to add at least two values that are providedas inputs to the summing subunit 306 from the proportional subunits 302, 304. Inaddition, the control unit 300 includes an integral subunit 308. The integral subunit308 is configured to generate an integral value of any input quantity provided to the integral subunit 308 by integrating the input quantity over a period of time.
    [37] [0037] As previously noted, the control unit 300 is configured to determine value(s)for modifying the input parameters corresponding to the generating units 110 toresynchronize the micro-grid 106 with the bulk grid based on the deviation(s) of the micro-grid side parameters from the corresponding bulk grid side parameters. Also, 11 285773-1 the micro-grid side parameters and the bulk grid side parameters include a frequency, a voltage, and/or a phase angle.
    [38] [0038] In the example of FIG. 3, a deviation in frequency Af and a deviation inphase angle A6 are provided as inputs to the proportional subunits 302, 304. Theseinputs are employed to determine a value for modifying an input parameter such asspeed corresponding to a plurality of generating units of the micro-grid 106.Accordingly, in one embodiment, if a deviation in phase angle A6 between the micro-grid side and the bulk grid side is identified at block 206, this deviation A6 is providedas an input to the proportional subunit 302. Similarly, if a deviation in frequency Afbetween the micro-grid side and the bulk grid side is identified at block 206, this deviation in frequency Af is provided as an input to the proportional subunit 304.
    [39] [0039] In the example of FIG. 3, Kpg is a proportional gain constant termcorresponding to a phase angle deviation. In particular, Kpg is the proportional gainconstant that is associated With the proportional subunit 302. Furthermore, thedeviation in phase angle A6 that is input to the proportional subunit 302 may bemultiplied by the proportional gain Kpg. Accordingly, the subunit 302 produces anoutput value that is proportional to the deviation in phase angle A6. The value of Kpgmay change With the configuration of the micro-grid 106 such as the number of generating units 110 in the micro-grid 106.
    [40] [0040] Similarly, Kf is a proportional gain constant corresponding to a frequencydeviation. In particular, Kf is the proportional gain constant that is associated With theproportional subunit 304. The deviation in phase angle Af that is provided as an inputto the proportional subunit 304 is multiplied by the proportional gain constant Kf. Theproportional subunit 304 produces an output value that is proportional to the deviationin frequency Af Further, output values from the proportional subunits 302, 304 are summed using the summing subunit 306.
    [41] [0041] Moreover, an output from the summing subunit 306 is provided to theintegral subunit 308. The output provided from the summing subunit 306 is reprersentative of an error signal. It may be noted that Kfg is an integral gain 12 285773-1 corresponding to integral subunit 308. The integral gain Kfg is inversely Weighted bymachine inertia Hi, Where i = I to n and is representative of the number of generatingunits 110. At the integral subunit 308, the output from the summing unit 306 isprocessed to obtain the speed variation ASpeedí, Where i = I to n, and n is representative of the number of generating units 1 10.
    [42] [0042] Further, in the example of FIG. 3, corresponding values for modifying thespeed ASpeedí may be provided to each of the plurality of generating units l 10. Uponreceiving the deterrnined values for modifying the speed, each generating unit ll0may vary the speed accordingly. This variation/modification of the speed by eachgenerating unit 110 aids in minimizing/reducing the deviation in the voltage, the frequency, and/or the phase angle between the micro-grid 106 and the bulk grid 102.
    [43] [0043] Particularly, modifying the input parameters of each generating unit 110,such as speed, results in a change in the voltage, frequency, and/or phase angle of anelectrical signal generated by that generating unit 110. This change in voltage,frequency, and phase angle of the electrical signal generated by individual generatingunits 110 results in a change in the values of the overall micro-grid side parameters,such as the voltage, frequency, and phase angle of the micro-grid 106. Further, thischange in overall micro-grid side parameters in tum causes the deviation between themicro-grid side parameters and the bulk grid side parameters to reduce to an optimalvalue, such as zero. Also, this reduction in the deviation of the voltage, frequency,and/or phase angle facilitates resynchronization of the micro-grid 106 With the bulk grid 102.
    [44] [0044] The example of FIG. 3 presents a control unit 300 conf1gured to determinethe value for varying speed corresponding to the plurality of generating units ll0. Ina similar manner, control unit 300 is conf1gured to determine values for modifyingother input parameters corresponding to the generating units 110 to minimize otherdeviations of one or more micro-grid side parameters, such as voltage. In oneexample, the input parameter may include an excitation current of a field Winding.Accordingly, a value for modifying the excitation current of a field Winding of each of the generating units ll0 is deterrnined by a control unit 300. Subsequently, the 13 285773-1 excitation current of the field winding of the generating units 110 may be modified tominimize a deviation in the value of voltage between the micro-grid 106 and the bulk grid 102 and resynchronize the micro-grid 106 with the bulk grid 102.
    [45] [0045] In addition, the control unit 300 may be configured to achieve acombination of objectives such as minimizing overshoot, minimizing steady stateerror, reducing time for synchronization, and the like. Minimizing overshoot aids inreducing any excess torque stress in a shaft of the generating units 110. Furthermore,minimizing steady state error aids in enhanced synchronization of the micro-grid 106having the plurality of generating units 110 with the bulk grid 102 prior to re-connection. Accordingly, electrical transients generated when the the micro-grid 106is re-connected with the bulk grid 102 is reduced. Moreover, for achieving thecombination of objectives, the control unit 300 may be tuned on-line. The onlinetuning of the control unit 300 may accordingly cause a change in the value of theconstants Kpg, Kf and Kfg corresponding to proportional subunits 302, 304, and theintegral subunit 308, respectively. Furthermore, the control unit 300 is configured toadapt to any change in the configuration of generating units 110 in the micro-grid106. Since the control unit 300 is conf1gured to adapt to any change in configurationof the generating units 110 such as the change in number of generating units, anymanual intervention for effective control operation using the control unit 300 is reduced considerably.
    [46] [0046] With retuming reference to FIG. 2, the deviation between one or moremicro-grid side parameters and the corresponding one or more bulk grid sideparameters is minimized to the optimal value, as depicted by block 210. Modifyingthe input parameters of the generating units 110 at block 210 based on the valuesdeterrnined at block 208 aids in reducing the deviation between one or more micro- grid side parameters and the corresponding one or more bulk grid side parameters.
    [47] [0047] Furthermore, at block 212, each of the plurality of generating units 110 ofthe micro-grid 106 is resynchronized with the bulk grid 102 based on the reduction ofthe deviation between the one or more micro-grid side parameters and the corresponding one or more bulk grid side parameters. As noted hereinabove, this 14 285773-1 deviation may be reduced such that an optimal value of the difference is achieved.The deviation between the one or more micro-grid side parameters and thecorresponding one or more bulk grid side parameters having a zero value isrepresentative of a resynchronized state of the micro-grid 106 With respect to the bulk grid 102.
    [48] [0048] Once the micro-grid 106 is synchronized/resynchronized With the bulk grid102, each of the plurality of generating units 110 is simultaneously reconnected to thebulk grid 102, as indicated by block 214. In one example, the simultaneousreconnection of each of the generating units 110 may include simultaneous closing ofthe corresponding sWitches 112 and the POI breaker 104. It may be noted that thePOI breaker 104 has a first state and a second state, Where the second state is differentfrom the first state. In one example, the first state of the POI breaker 104 is an openstate and the second state of the POI breaker 104 is a closed state. To effect thereconnection of the micro-grid 106 to the bulk grid 102, the control unit 108 isconfigured to transition the POI breaker 104 from the first state to the second state tooperatively couple the plurality of generating units 110 of the micro-grid 106 to thebulk grid 102.
    [49] [0049] In one example, each of the plurality of generating units 110 issimultaneously reconnected to the bulk grid 102 in real-time. In particular, each ofthe plurality of generating units 110 is simultaneously reconnected to the bulk grid102 Without having to shut down the bulk grid 102 or any other micro-grid 106connected to the bulk grid 102. Consequent to the simultaneous reconnection of thegenerating units 110 to the bulk grid 102, the micro-grid 106 is reconnected to thebulk grid 102. Although the method 200 is described With respect toresynchronization and reconnection of a single micro-grid to a bulk grid, a method forthe resynchronization and reconnection of a plurality of micro-grids to the bulk grid is also envisaged.
    [50] [0050] Furthermore, the foregoing examples, demonstrations, and process stepssuch as those that may be performed by the system may be implemented by suitable code on a processor-based system, such as a general-purpose or special-purpose 285773-1 computer. It should also be noted that different implementations of the presenttechnique may perforrn some or all of the steps described herein in different orders orsubstantially concurrently, that is, in parallel. Furthermore, the functions may beimplemented in a Variety of programming languages, including but not limited to C++or Java. Such code may be stored or adapted for storage on one or more tangible,machine readable media, such as on data repository chips, local or remote hard disks,optical disks (that is, CDs or DVDs), memory or other media, which may be accessedby a processor-based system to execute the stored code. Note that the tangible mediamay comprise paper or another suitable medium upon which the instructions areprinted. For instance, the instructions may be electronically captured Via opticalscanning of the paper or other medium, then compiled, interpreted or otherwiseprocessed in a suitable manner if necessary, and then stored in the data repository or memory.
    [51] [0051] Various embodiments of systems and methods for interconnecting twogrids, and more specifically systems and methods for resynchronizing andreconnecting a micro-grid to a bulk grid are presented. In particular, the systems andmethods presented herein allow a plurality of generating units corresponding to amicro-grid to be simultaneously reconnected to the bulk grid. The resynchronizing ofthe micro-grid with the bulk grid aids in aVoiding any adverse impact to thegenerating units in the micro-grid. Furthermore, simultaneously reconnectingmultiple generating units of the micro-grid to the bulk grid simplif1es the process ofreconnecting the micro-grid to the bulk grid. Also, simultaneous reconnection ofmultiple generating units aids in reducing the amount of time and the number ofinterrnediate steps for resynchonization and reconnection of the micro-grid to the bulkgrid. The methods and systems for resynchronizing and reconnecting the micro-gridto the bulk grid may also find application in resynchronizing and reconnecting any smaller grid to a bulk grid.
    [52] [0052] While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art that Various changesmay be made and equivalents may be substituted for elements thereof without departing from the scope of the inVention. In addition, many modif1cations may be 16 285773-1 made to adapt a particular situation or material to the teachings of the invention Without departing from the essential scope thereof. l7
    权利要求:
    Claims (20)
    [1] 1. l. A method for operatively coupling a plurality of generating units in atleast one micro-grid to a bulk grid, Wherein the at least one micro-grid is conf1gurableto be operatively coupled to the bulk grid at a point of interconnection via a point of interconnection breaker, the method comprising: deterrnining, using a control unit, one or more bulk grid side parameters andone or more micro-grid side parameters, Wherein the control unit is operatively coupled to the at least one micro-grid and the bulk grid; comparing, using the control unit, one or more of the one or more micro-grid side parameters With corresponding one or more bulk grid side parameters; synchronizing, using the control unit, each of the plurality of generating units in the at least one micro-grid With the bulk grid based on the comparison; and connecting simultaneously, using the point of interconnection breaker, each of the plurality of generating units to the bulk grid based on the synchronization.
    [2] 2. The method of claim l, Wherein the one or more bulk grid sideparameters and the one or more micro-grid side parameters comprise at least one of a Voltage, a frequency, and a phase angle.
    [3] 3. The method of claim l, Wherein connecting simultaneously each of theplurality of generating units to the bulk grid comprises transitioning the point ofinterconnection breaker from a first state to a second state to operatively couple theplurality of generating units to the bulk grid, and Wherein the second state is different from the first state.
    [4] 4. The method of claim 3, Wherein the first state of the point ofinterconnection breaker comprises an open state, and Wherein the second state of the point of interconnection breaker comprises a closed state.
    [5] 5. The method of claim l, Wherein comparing the one or more micro-grid side parameters to the one or more bulk grid side parameters comprises identifying an 18 285773-1 occurrence of a deviation of one or more of the one or more micro-grid sideparameters from corresponding one or more of the one or more bulk grid side parameters.
    [6] 6. The method of claim 5, further comprising deterrnining a Value formodifying one or more input parameters corresponding to the plurality of generating units based on the identified deviation.
    [7] 7. The method of claim 6, Wherein the one or more input parameterscomprise at least one of a mechanical speed, a field, a torque, an excitation current, or combinations thereof.
    [8] 8. The method of claim 6, Wherein synchronizing each of the plurality ofgenerating units With the bulk grid comprises reducing the deviation between the oneor more of the one or more micro-grid side parameters and the corresponding one or more of the one or more bulk grid side parameters to an optimal Value.
    [9] 9. The method of claim 8, Wherein the optimal value comprises a zero Value.
    [10] 10. l0. The method of claim l, Wherein connecting simultaneously each of theplurality of generating units to the bulk grid comprises coupling each of the plurality of generating units to the bulk grid in real-time.
    [11] 11. ll. A system for operatively coupling a plurality of generating units in at least one micro-grid to a bulk grid, comprising: a point of interconnection breaker disposed between the bulk grid and the atleast one micro-grid, Wherein the point of interconnection breaker is configured tooperatively couple the at least one micro-grid to the bulk grid at a point of interconnection; a control unit operatively coupled to the bulk grid and the at least one micro- grid, Wherein the control unit is configured to: 19 285773-1 determine one or more bulk grid side parameters and one or more micro-grid side parameters; compare the one or more micro-grid side parameters With corresponding one or more bulk grid side parameters; synchronize each of the plurality of generating units With the bulk grid based on the comparison; and connect simultaneously each of the plurality of generating units to the bulk grid based on the synchronization.
    [12] 12. The system of claim ll, Wherein the plurality of generating unitscomprises a non-synchronous generator, a synchronous generator, or a combination thereof.
    [13] 13. The system of claim ll, Wherein the point of interconnection breakerhas a first state and a second state, and Wherein the second state is different from the first state.
    [14] 14. The system of claim 13, Wherein the control unit is further conf1guredto transition the point of interconnection breaker from the first state to the second stateto operatiVely couple the plurality of generating units of the at least one micro-grid to the bulk grid.
    [15] 15. The system of claim 13, Wherein the control unit is further conf1guredto identify an occurrence of a deviation of one or more of the one or more micro-gridside parameters from corresponding one or more of the one or more bulk grid side parameters.
    [16] 16. The system of claim 15, Wherein the control unit is further conf1guredto determine a Value for modifying one or more input parameters corresponding to theplurality of generating units based on the identified deviation to reduce the identified deviation. 285773-1
    [17] 17. The system of claim 16, Wherein the one or more input parameterscomprise at least one of a mechanical speed, a field, a torque, an excitation current, or combinations thereof.
    [18] 18. The system of claim 11, Wherein the control unit comprises an analog controller, a digital controller, or a combination thereof.
    [19] 19. The system of claim 11, Wherein the one or more bulk grid sideparameters and the one or more micro-grid side parameters comprise at least one of a Voltage, a frequency, and a phase angle.
    [20] 20. A computer readable non-transitory medium comprising one or moretangible media, Wherein the one or more tangible media comprise code for causing a computer to perform the steps of: deterrnining one or more bulk grid side parameters and one or more micro-gridside parameters, Wherein a control unit is operatively coupled to at least one micro- grid and a bulk grid; comparing one or more of the one or more micro-grid side parameters With corresponding one or more bulk grid side parameters; synchronizing each of a plurality of generating units in the at least one micro- grid With the bulk grid based on the comparison; and connecting simultaneously each of the plurality of generating units to the bulk grid based on the synchronization. 21
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    同族专利:
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    MX2017008502A|2018-09-10|
    EP3288144A1|2018-02-28|
    CA2969995A1|2018-02-23|
    US10797488B2|2020-10-06|
    JP2018033295A|2018-03-01|
    CN107769243A|2018-03-06|
    US20180062394A1|2018-03-01|
    BR102017013495A2|2018-03-13|
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    法律状态:
    2019-09-17| NAV| Patent application has lapsed|
    优先权:
    申请号 | 申请日 | 专利标题
    US15/243,974|US10797488B2|2016-08-23|2016-08-23|Systems and methods for operatively coupling a micro-grid to a bulk grid|
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