WO2017097379A1 - Load shedding in a microgrid - Google Patents

Load shedding in a microgrid Download PDF

Info

Publication number
WO2017097379A1
WO2017097379A1 PCT/EP2015/079441 EP2015079441W WO2017097379A1 WO 2017097379 A1 WO2017097379 A1 WO 2017097379A1 EP 2015079441 W EP2015079441 W EP 2015079441W WO 2017097379 A1 WO2017097379 A1 WO 2017097379A1
Authority
WO
WIPO (PCT)
Prior art keywords
microgrid
load
loads
power
load shedding
Prior art date
Application number
PCT/EP2015/079441
Other languages
French (fr)
Inventor
Ritwik MAJUMDER
Antonis MARINOPOULOS
Original Assignee
Abb Schweiz Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Abb Schweiz Ag filed Critical Abb Schweiz Ag
Priority to PCT/EP2015/079441 priority Critical patent/WO2017097379A1/en
Publication of WO2017097379A1 publication Critical patent/WO2017097379A1/en

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
    • H02J3/144—Demand-response operation of the power transmission or distribution network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/10—The network having a local or delimited stationary reach
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/50—The network for supplying or distributing electric power characterised by its spatial reach or by the load for selectively controlling the operation of the loads
    • H02J2310/56—The network for supplying or distributing electric power characterised by its spatial reach or by the load for selectively controlling the operation of the loads characterised by the condition upon which the selective controlling is based
    • H02J2310/58—The condition being electrical
    • H02J2310/60—Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
    • Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/20—End-user application control systems
    • Y04S20/222—Demand response systems, e.g. load shedding, peak shaving

Definitions

  • At least one load of the plurality of loads in the microgrid is prioritized for receiving power in relation to at least one the other load of lower priority
  • the selection includes exempting the at least one load that is prioritized for receiving power, from selection provided the power level of the at least one other load of lower priority for receiving power fulfils the determined need for load shedding .
  • the loads are selected in view of their location within the microgrid , however one or more loads may be exempted from selection .
  • the load shedding need determi ner 43 determines the need for load shedding based on the received i nformation .
  • the load selector 44 is configured to select loads to be shed based on the location of the loads in relation to the PCC and the voltage and frequency regulating power source 2, and also configured to determine the sequence of disconnection.
  • the disconnector 45 is configured to disconnect the selected loads in the determined sequence using the communication means 40.
  • the microgrid controller is provided for performning the method, which includes: monitoring 202, 302 the power balance in the microgrid 1; determining 204, 302 a need for load shedding in view of the power balance; and selecting 206, 306 at least one load to be disconnected, in view of the need for load shedding.

Abstract

A method and a microgrid controller (4) for controlling load shedding in a microgrid (1), which microgrid (1) comprises a plurality of loads (12:1-12:5, 13:1-13:5), a plurality of power sources (2, 2A), and a point of common coupling (3) for selectively connecting the microgrid (1) to a main grid (30). The microgrid controller is provided for performing the method, which includes: - monitoring (202, 302) the power balance in the microgrid (1); - determining (204, 302) a need for load shedding in view of the power balance; and - selecting (206, 306) at least one load to be disconnected, in view of the need for load shedding. Especially, the selecting (206, 306) is performed in view of the locations of the plurality of loads (12:1-12:5, 13:1-13:5) within the microgrid (1) in relation to at least one microgrid system voltage and microgrid system frequency controlling entity (2, 3, 30) of the microgrid (1), wherein the loads (12:1-12:3; 13:1-13:2) that are closest to the microgrid system voltage and microgrid system frequency controlling entity, or entities, (2, 30) are prioritized for disconnection, and subsequently disconnecting (208) the selected load, or loads (12:1-12:3; 13:1-13:2).

Description

Load Shedding in a Microg rid
Tech nical Field
The i nvention relates to a method of load shedding i n a microgrid , and a microgrid controller for performing the method .
Backg round
A microgrid is a network that includes loads and power sources, and that may operate connected to, and exchange power with a main grid , but may also operate disconnected from a main grid . When the microgrid is not connected to the main grid , the power sources of the microgrid supply the power needed for the loads. If the supply and demand of power within the microgrid is not balanced , one or more of the loads may be disconnected , so called load shedding . A typical method of load shedding in a main grid is to monitor the frequency and upon detecting a fall of the frequency perform load shedding .
In the prior art, methods and systems for load shedding in microgrids are descri bed . For example, the article "Enhancement of Power System Stability Using Adaptive Combinational Load Sheddi ng Methods" by Saffarian et al describes load shedding in a microgrid (see chapter I I I ) where the voltage and/or frequency is measured at each load , and wherein the loads that experience the largest disturbances i n voltage/frequency are shed (see Saffarian , A. and Sanaye-Pasand , M . (201 1 ). "Enhancement of Power System Stability Using Adaptive Combinational Load Sheddi ng Methods". IEEE Trans. Power Syst. , 26(3), pp.1 010- 1020). Instead of performing load shedding based on deviations of frequency and/or voltage, it has been suggested to monitor the power balance of a microgrid i n order for the system to react faster and more accurate. WO2015003729 describes a method of load shedding when the microgrid is suddenly disconnected from the mai n grid , and moves i nto islandi ng and the subsequent island operation . In WO2015003729 the load shedding is based on monitoring the power balance and the load shedding is determi ned prior to islanding in order to speed up the load sheddi ng and stabilize the microgrid quickly if the microgrid becomes disconnected from the main grid .
It has also been suggested to excl ude critical loads from disconnection , if possible. For example, patent document GB2519753, A, shows a system where the power balance is monitored to determine a need for load shedding . The loads of GB251 9753 are shed based on priority (see abstract, page 23, line 24-26, claim 4 and claim 1 1 of GB2519753). Another example can be found in patent document US2012/0283888, A1 , which describes a method for connecting and disconnecting a microgrid to/from a main grid . The method of US2012/0283888 monitors the power balance (see step 430 in figure 4, and §0040 of US2012/0283888). The loads i n this microgrid can be labelled as regular loads, su b-critical loads and critical loads, to provide a priority for shedding (see §0029 of US2012/0283888). The load that has the highest power level among the regular loads are selected for shedding (see §0051 of US2012/0283888, where "regular loads" are referred to as "first level loads").
A method of load shedding in a microgrid may therefore incl ude monitoring the power balance of the microgrid , i .e. the balance between supply and consumption , and shed loads when the consumption exceeds the supply, wherein the loads are disconnected to minimize the difference between the power supply and the power consumption . Load shedding may be performed when the microgrid is connected to a main grid , as well as in island operation. Load shedding methods may prioritize some of the loads of the microgrid .
It should be noted that load shedding is important in order to stabilize the microgrid into a new steady state operation . The load sheddi ng should be performed in order to match the available power and the consumed power at a desired frequency and desired voltage level of the microgrid . The actual process of disconnecting loads may however infl uence how quickly the microgrid stabilizes. There is a risk that the process of load sheddi ng leads to further destabilization when the power flow i n the microgrid changes.
Summary of invention
The present i nvention concerns load shedding i n a microgrid based on monitoring the power balance when the microgrid is connected and receives power from a main grid , i .e. in "grid connected" operation , as well as when the microgrid operates disconnected from the main grid , in island operation.
An aim of the present i nvention is to improve the stability within a microgrid when loads are disconnected .
Accordi ng to a first aspect, the present i nvention provides a method for controlling load shedding in a microgrid . The microgrid comprises a plurality of loads, a plurality of power sources, and a point of common coupling for selectively connecting the microgrid to a main grid , wherein the point of common coupling , the power sources and the loads are interconnected . The method includes:
- monitoring the power balance in the microgrid ;
- determining a need for load shedding in view of the power balance; and
- selecting at least one load to be disconnected , which at least one load is selected among the pl urality of loads in view of the need for load shedding .
The method especially includes that
- the selecting of at least one load is performed in view of the locations of the plurality of loads within the microgrid relative to at least one microgrid system voltage and microgrid system frequency controlling entity of the microgrid , wherein the loads that are closest to any of said at least one microgrid voltage and microgrid frequency controlling entity are prioritized for disconnection , and - disconnecting the selected at least one load .
Thus the sol ution of the i nvention includes that the specific loads that are selected for shedding , are selected in view of their location within the microgrid .
In an embodiment of the first aspect of the present invention , the disconnecting of the selected loads is performed i n sequence when more than one load is selected , wherei n the selected load that is closest to any of said at least one microgrid system voltage and microgrid system frequency controlling entity is disconnected first.
Preferably, the selected load that is furthest away from said at least one microgrid system voltage and microgrid system frequency controlling entity is disconnected last.
In an embodiment of the first aspect of the present i nvention, at least one load of the plurality of loads in the microgrid is prioritized for receiving power in relation to at least one the other load of lower priority, and the selection includes exempting the at least one load that is prioritized for receiving power, from selection provided the power level of the at least one other load of lower priority for receiving power fulfils the determined need for load shedding . Thus, the loads are selected in view of their location within the microgrid , however one or more loads may be exempted from selection . A load that is prioritized for receiving power has higher importance, and may be referred to as a critical load The at least one prioritized load can for example be a power plant, an industrial facility or hospital and is in general a load that is considered more important than the other loads and therefore more important to supply power to.
In an embodiment of the first aspect of the present invention, the at least one microgrid voltage and microgrid frequency controlling entity is: - at least one power source of the power sources, which at least one power source is provided to regulate the microgrid system voltage and the microgrid system frequency when the microgrid is disconnected from the main grid , and is
- the point of common coupling to the main grid when the microgrid is connected to the main grid .
Accordi ng to a second aspect, the present i nvention provides a microgrid controller for performing load shedding in a microgrid , which microgrid controller is configured to perform the method steps of the first aspect of the present invention.
Accordi ng to a third aspect, the present i nvention provides a computer program product for controlling load shedding i n a microgrid , which computer program product is storable on a computer medi um, and which computer program product when executed by a microgrid controller enables the controller to perform the method of the first aspect of the invention. An exception to this rule is that some loads may have a high importance. However, among the least and equally important loads, those loads are selected that are electrically close to, i .e. located near, the one or more power sources that control/regulate the frequency and the voltage of the microgrid .
Brief description of the drawings
Figure 1 is a schematic illustration of main parts of a microgrid connected to a main grid ;
Figure 2 1 is a schematic illustrations of the microgrid operating as an island , i .e. when not connected to the main grid ;
Figure 3 is a schematic flow chart describing grid-connected operation of the microgrid ;
Figure 4 is a schematic flow chart describing island operation of the microgrid ; Figure 5 is a schematic illustration of a microgrid controller includi ng functional components of the microgrid controller, and a computer program product for a microgrid controller. Detailed description of embodiments
Figure 1 illustrates a microgrid 1 comprising a plurality of loads 13: 1 -13:5, a pl urality of distributed power sources 2 , 2A and electrical connections 5 that are arranged to connect the power sources 2, 2A to the loads 13: 1 -13:5. The microgrid 1 also includes a microgrid controller 4 configured to monitor the power flow in the microgrid 1 and configured to selectively control connection and disconnection of the loads 13: 1 -13:5. The microgrid 1 also comprises a point of common coupling , PCC 3, which provides a connection point to a mai n grid 30 for the microgrid 1 .
Each power source 2, 2A may comprise a distributed generator and a voltage source converter, wherein the voltage source converter is arranged to supply the power from the distri buted generator to the microgrid 1 . The voltage source converter may convert the power from a DC generator to AC, or from the voltage level of a DC generator to the AC voltage of the microgrid . Alternatively, or additionally, a transformer may be used for transforming the AC level of a power source to the AC level of the microgrid 1 . The distributed generators may include photovoltaic DC generators, fuel cell DC generators, wind power AC generators, water power AC generators, or AC gas turbi nes. Other types of power sources 2, 2A may also be provided in the microgrid , especially one or more electric energy storages, such as a battery or capacitor storage and/or a fly-wheel storage. In island operation of the microgrid at least one of the power sources 2, 2A will be assigned to control the system voltage and the system frequency of the microgrid . One power source 2 may be used to control/regulate both the system frequenc7y and the system voltage. Figure 1 illustrates a situation where the microgrid 1 is connected to exchange power with a main grid via the point of common coupling, PCC 3. In this grid connected situation, the stability of the microgrid depends mainly on the power from the main grid 30, wherein the voltage level and frequency of the power from the main grid 30 is the main entity for controlling and regulating the voltage level and frequency in the microgrid 1.
Figure 2 illustrates the microgrid 1 in a situation wherein the microgrid 1 has been disconnected from the main grid 30 by means of a switch 7 arranged at the point of common coupling 3. In figure 2, a first power source 2 of the power sources 2, 2A is configured to regulate the voltage level and regulate the frequency of the microgrid 1, when the microgrid 1 is in island operation, i.e. when the microgrid 1 is not connected to the main grid 30.
Figures 1 and 2 illustrate basically the same microgrid 1, but the loads are numbered 13:1-13:5 in figure 1 and are numbered 12:1- 12:5 in figure 2. Thus, the microgrid 1 of figure 2 comprises a microgrid controller 4, a point of common coupling 3, a switch 7 to the main grid 30, a plurality of loads 12:1-12:5, a plurality of distributed power sources 2, 2A and electrical connections 5 that are arranged to connect the power sources 2, 2A to the loads 12:1-12:5.
The reason for this re-numbering of the loads 13:1-13:5, 12:1- 12:5 is to illustrate the location of each load in relation to the system voltage and system frequency regulating entity, i.e. the main grid 30, via PCC 3, in figure 1 and the first power source 2 in figure 2. In figure 1 the load closest to the PCC 3 is numbered "13:1", the second closest is denoted "13:2", the third closest "13:3", the fourth closest "13:4", and the fifth closest "13:5". In figure 2 the load closest to the first power source 2, which regulates the voltage level and frequency of the microgrid 1, is denoted "12:1", the second closest to the first power source 2 is denoted "12:2", the third closest "12:3", the fourth closest "12:4", and the fifth closest "12:5".
The microgrid controller 4 is arranged and configured to monitor the power balance in the microgrid 1, by monitoring the power flow at the PCC 3, the power produced by the power sources 2, 2A and the power consumed by the loads 12:1-12:5, 13:1-13:5. The microgrid controller 4 monitors the power flow to each one of the loads 12:1-12:5, 13:1-13:5 and at the PCC 3 e.g. by receiving measurements of voltage and current, or power, from measuring units 6 arranged at each of the loads 12:1-12:5, 13:1-13:5 and the PCC 3. The microgrid controller 4 also monitors the power supplied from the power sources 2, 2A, by means of being communicatively connected to the power sources 2, 2A and receive voltage and current information, or power information from each power source 2, 2A. A reduction of power from the main grid 30 or a sudden loss of a power source 2A may lead to a power imbalance that may require load shedding. The microgrid controller 4 is configured to determine a need for load shedding based on the power balance of the microgrid 1. The microgrid controller 4 is further configured to select loads to be disconnected among said loads 12:1-12:5, 13:1-13:5, wherein the loads to be disconnected are selected in view of their respective location within the microgrid 1. The microgrid controller 4 is further configured to disconnect the selected loads in sequence by disconnecting the closest load first, then the second closest load and so on. The microgrid controller 4 is in the illustrated embodiments operatively connected to switches and/or breakers 8, one switch/breaker at each load one of the loads 12:1-12:5, 13:1-13:5, and disconnects the selected loads by opening said switch and/or breaker 8.
For example, in the grid connected state of figure 1 , the controller 4 may determine a certain need for load shedding upon monitoring the power balance, and then select to disconnect loads corresponding to the need, such as the load 13:1 closest to the PCC 3, and the load 13:2 second closest to the PCC 3. Thus, the loads 13: 1 , 13:2 are selected for disconnection since these are the loads 13: 1 , 13:2 that are closest to the PCC 3, and since the power consumption of these loads 13: 1 , 13:2 corresponds to the determined need . The microgrid 4 will subsequently disconnect the selected loads 13: 1 , 13:2 in sequence starting with the load 13: 1 that is closest to the PCC, and after a short delay disconnect the second closest load 13:2. In the island state of figure 2, the microgrid controller 4 may determi ne that the closest load 12 : 1 , the second closest load 12:2, and third closest load 12:3, i .e. closest to the voltage level and frequency regulating first power source 2, should be disconnected in order to balance the power since the consumption of these three loads fulfill the load shedding need . The microgrid 4 will then disconnect the selected loads 12 : 1 , 12:2, 12:3 in order of closeness to the voltage and frequency regulating first power source 2. Figure 3 illustrates grid-connected operation 200 of the microgrid controller 4 whereas figure 4 illustrates island operation 300 of the microgrid controller 4.
When the microgrid 1 is connected to the main grid 30, the main grid 30 provides the stability of the voltage and frequency for the microgrid 1 . The grid-connected operation 200 of figure 3 comprises monitoring 202 the power balance of the microgrid 1 , which means that the power production of each power source 2, 2A, the power consumption by each load 13: 1 - 13:5, and the power exchange at the PCC, primarily the power flow from the main grid 30, is monitored . By the monitoring of the power balance, changes in power production , power exchange or power consumption can be utilized to predict that load shedding is needed and the amount of the need for load shedding . The method uses the monitored power balance to determine 204 a need for load shedding . With knowledge of the consumption of each load , one or more loads can be selected for disconnection . The method further i ncludes primarily selecting 206 the loads closest to the main grid 30, i .e. closest to the PCC 3, for shedding . However, it is possible to exclude one or more of the loads from selection , especially avoiding disconnection of critical loads by excludi ng selection of one or more such loads. Thus, the selecting 206 of loads for the load shedding may include exempting one or more critical loads.
In the example of figure 1 , load 13:5 is marked "crit", indicating a critical load , and this load 1 3:5 is excluded from disconnection if possible. When load shedding is needed , the method 200 will select 206 the closest load 13: 1 for load shedding and if, in view of the monitored power balance, the power of load 13: 1 is not enough , the second closest load 13:2 will be selected for sheddi ng. However, if the second closest load 13:2 is a critical load it should be excluded from the selection and the method 200 will select (in step 206) the first 13: 1 and third 1 3:3 closest load for the load shedding .
The selected loads are preferably shed sequentially by means of disconnecting 208 the selected loads in order of closeness to the PCC 3, since the main grid 30 provides the stability of system voltage and frequency for the microgrid 1 .
When, i n the example of figure 1 , loads 1 3: 1 and 13:2 have been selected for the load sheddi ng, load 13: 1 is disconnected first and then load 13:2 is disconnected , since load 13: 1 is closest to the PCC 3, and since load 13:2 is furthest away from the PCC 3 among the selected loads 13: 1 , 13:2. The grid-connected operation 200 may also incl ude determining whether the microgrid is disconnected from the main grid 30, in which case the method switch to island operation 300 of figure 4, while otherwise continuing with monitoring 202 the power i n the microgrid . Thus, the method 200 is looped back and repeated . The island operation 300 illustrated in figure 4 , may start 301 with assigni ng one of the power sources 2 to regulate the system voltage and frequency of the microgrid , and with performing an initial load shed in view of the power balance when entering from grid-connected , i .e. when islanding . The initial load shed is based on the lost power flow from the main grid 30. The loads shedded is preferably selected in order of closeness to the power source 2 assigned for system voltage and system frequency regulation , in accordance with steps 306, 308 that will be descri bed in the following .
The island operation 300 is similar to the grid-connected operation 200, but do not select 206 and disconnect 208 the loads in view of their closeness to the PCC 3. Instead , the loads are selected 306 and disconnected 308 in view of their closeness to the one or more power sources that is responsi ble for regulating the system voltage and/or system frequency of the microgrid 1 .
Island operation incl udes monitoring 302 the power balance of the microgrid , including monitoring the production of each of the power sources 2, 2A and the consumption of each of the loads 12: 1 -12:5. The island operation 300 continues with determining 304 a need for loads shedding based on the power balance. The method conti nues with selecting 306 loads for sheddi ng based on the need and on the closeness of the loads to the power source 2, or alternatively power sources, used for regulating the system voltage and frequency. The loads that have been selected are subsequently disconnected 308, which disconnection 308 is preferably made in order of closeness to the system voltage and system frequency regulating power source 2, or power sources. If the microgrid becomes connected to the main grid 30, the island operation is ended and the method returns to controlling the microgrid 1 in accordance with the grid-connected operation 200. Otherwise, the method conti nues in island operation 300 and continues with and repeats monitoring 302 the power, determine 304 need for load shedding , selecting 306 loads for the load sheddi ng and disconnect 308 the selected loads in order of closeness to the system voltage and frequency regulating power source 2 or power sources.
As in grid-connected operation 200, the island operation 300 may include excluding one or more loads, such as critical loads, from selection 306 and disconnection 308. In the illustrated example of figure 2 , load 13:4 is marked as a critical ("crit") load . Load 13:4 is the fourth closest load to the regulating power source 2, but load 13:4 will be excluded from disconnection , if possible, and load 13:5, which is the fifth closest to the regulating power source
2 will be selected prior to the forth closest load 13:4.
Figure 5 illustrates functions of the microgrid controller 4, which preferably consists of a combi nation of hardware and software for performi ng its functions i n accordance with the methods of figures
3 and 4. The microgrid controller includes communication means 40 for receiving measurements and information , especially information about voltage, currents and power of the power sources 2 , loads 12 , 13 and the power flow at the PCC 3. The communication means 40 is also configured for sendi ng commands to the breakers 8. The microgrid controller 4 further includes a power balance monitorer 42 , a load shedding need determi ner 43, a load selector 44 , and a disconnector 45. Power balance monitorer 42 is configured for monitoring the power balance of the microgrid 1 by means of receiving power information , and/or voltage and current information from the microgrid power sources, loads and the PCC as received by means of the communication means. The load shedding need determi ner 43 determines the need for load shedding based on the received i nformation . The load selector 44 is configured to select loads to be shed based on the location of the loads in relation to the PCC and the voltage and frequency regulating power source 2, and also configured to determine the sequence of disconnection. The disconnector 45 is configured to disconnect the selected loads in the determined sequence using the communication means 40. The functions can be provided as a computer program product 46 and stored for example on a CD disc, or provided via a network, such as Internet or a LAN (local area network) of the microgrid The present invention has been described in embodiments that describe a method, and a microgrid controller 4, for controlling load shedding in a microgrid 1, which microgrid 1 comprises a plurality of loads 12:1-12:5, 13:1-13:5, a plurality of power sources 2, 2A, and a point of common coupling 3 for selectively connecting the microgrid 1 to a main grid 30. The microgrid controller is provided for performning the method, which includes: monitoring 202, 302 the power balance in the microgrid 1; determining 204, 302 a need for load shedding in view of the power balance; and selecting 206, 306 at least one load to be disconnected, in view of the need for load shedding. Especially, the selecting 206, 306 is performed in view of the locations of the plurality of loads 12:1-12:5, 13:1-13:5 within the microgrid 1 in relation to at least one microgrid system voltage and microgrid system frequency controlling entity 2, 3, 30 of the microgrid 1, wherein the loads 12:1-12:3; 13:1-13:2 that are closest to the microgrid system voltage and microgrid system frequency controlling entity, or entities, 2, 30 are prioritized for disconnection, and subsequently disconnecting 208 the selected load, or loads 12:1-12:3; 13:1-13:2. In the embodiments, a computer program 46 product for enabling a microgrid controller to perform the steps of the method has been described. However, as is readily appreciated by a person skilled in the art, other embodiments than those herein described are equally possible within the scope of the present invention, as defined by the appended patent claims.

Claims

Claims
1. A method for controlling load shedding in a microgrid (1), which microgrid (1) comprises a plurality of loads (12:1-12:5, 13:1-13:5), a plurality of power sources (2, 2A), and a point of common coupling (3) for selectively connecting the microgrid (1) to a main grid (30), wherein the point of common coupling (3), the power sources (2, 2A) and the loads (12:1-12:5, 13:1-13:5) are interconnected, said method includes:
- monitoring (202, 302) the power balance in the microgrid (1); - determining (204, 302) a need for load shedding in view of the power balance; and
- selecting (206, 306) at least one load to be disconnected, which at least one load (12:1-12:3; 13:1-13:2) is selected among the plurality of loads (12:1-12:5, 13:1-13:5) in view of the need for load shedding,
characterized in that
- the selecting (206, 306) of at least one load is performed in view of the locations of the plurality of loads (12:1-12:5, 13:1- 13:5) within the microgrid (1) in relation to at least one microgrid system voltage and microgrid system frequency controlling entity (2, 3, 30) of the microgrid (1), wherein the loads (12:1-12:3; 13:1- 13:2) that are closest to any of said at least one microgrid system voltage and microgrid system frequency controlling entity (2, 30) are prioritized for disconnection, and
- disconnecting (208) the selected at least one load (12:1-12:3; 13:1-13:2).
2. A method for controlling load shedding in a microgrid (1) according to claim 1, wherein when more than one load is selected, the disconnecting (208) of the selected loads (12:1- 12:3; 13:1-13:2) is performed in sequence wherein the selected load (12:1, 13:1) that is closest to any of said at least one microgrid system voltage and microgrid system frequency controlling entity (2, 30) is disconnected first.
3. A method for controlling load shedding i n a microgrid (1 ) accordi ng to claim 2, wherein the selected load (1 2:3, 13:2) that is furthest away from said at least one microgrid system voltage and microgrid system frequency controlling entity (2, 30) is disconnected last.
4. A method for controlling load shedding i n a microgrid (1 ) accordi ng to any of claims 1 -4, wherein at least one load (1 2:4 , 13:5) of the pl urality of loads (12 : 1 -12:5, 13: 1 -13:5) i n the microgrid (1 ) is prioritized for receiving power in relation to at least one the other load (12 : 1 -12 :3, 12:5, 13: 1 -13:4) of lower priority, and wherein the selection (206, 306) includes exempting the at least one load (12:4, 13:5) that is prioritized from selection provided the power level of the at least one other load (12 : 1 -12 :3, 12:5, 13: 1 -13:4) of lower priority fulfils the need for load shedding .
5. A method for controlling load shedding according to any of claims 1 to 4, wherein :
- when the microgrid is disconnected from the main grid (30) said at least one microgrid system voltage and microgrid system frequency controlling entity (2 , 3) is at least one power source (2) of the power sources (2, 2A), which at least one power source (2) is provided to regulate the microgrid system voltage and the microgrid system frequency when the microgrid is disconnected from the main grid (30), and wherein
- when the microgrid is connected to the main grid (30) said at least one microgrid system voltage and microgrid system frequency controlling entity (2, 30) is the point of common coupling (3) to the main grid (30).
6. A microgrid controller (4) for performing load shedding in a microgrid , which microgrid controller (4) is configured to perform the method steps of any of claims 1 to 5.
7. A computer program product (46) for controlling load sheddi ng in a microgrid (1 ), which computer program product (46) is storable on a computer medium, and which computer program product (46) when executed by a microgrid controller (4), enables the microgrid controller (4) to perform the method of any of claims 1 to 5.
PCT/EP2015/079441 2015-12-11 2015-12-11 Load shedding in a microgrid WO2017097379A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2015/079441 WO2017097379A1 (en) 2015-12-11 2015-12-11 Load shedding in a microgrid

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2015/079441 WO2017097379A1 (en) 2015-12-11 2015-12-11 Load shedding in a microgrid

Publications (1)

Publication Number Publication Date
WO2017097379A1 true WO2017097379A1 (en) 2017-06-15

Family

ID=54849629

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2015/079441 WO2017097379A1 (en) 2015-12-11 2015-12-11 Load shedding in a microgrid

Country Status (1)

Country Link
WO (1) WO2017097379A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3522324B1 (en) 2018-02-05 2019-12-25 Beegy GmbH Method and arrangement for load management of electrical devices
FR3112637A1 (en) * 2020-07-15 2022-01-21 Total Sa Method of controlling an electrical micro-grid

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120283888A1 (en) 2011-05-05 2012-11-08 State Grid Corporation Of China (Sgcc) Seamless Transition Method and Apparatus for Micro-grid Connect/Disconnect from Grid
WO2015003729A1 (en) 2013-07-08 2015-01-15 Abb Technology Ltd Controlling power in a micro-grid
GB2519753A (en) 2013-10-29 2015-05-06 Bae Systems Plc Controlling power distribution within a microgrid

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120283888A1 (en) 2011-05-05 2012-11-08 State Grid Corporation Of China (Sgcc) Seamless Transition Method and Apparatus for Micro-grid Connect/Disconnect from Grid
WO2015003729A1 (en) 2013-07-08 2015-01-15 Abb Technology Ltd Controlling power in a micro-grid
GB2519753A (en) 2013-10-29 2015-05-06 Bae Systems Plc Controlling power distribution within a microgrid

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
LINFENG WU ET AL: "A Novel Dynamic Partitioning and Active-Splitting Strategy in Power System Emergency Control", POWER AND ENERGY ENGINEERING CONFERENCE (APPEEC), 2010 ASIA-PACIFIC DATE OF CONFERENCE: 28-31 MARCH 2010, IEEE, PISCATAWAY, NJ, USA, 28 March 2010 (2010-03-28), pages 1 - 6, XP031658713, ISBN: 978-1-4244-4812-8 *
M. SANAYE-PASAND ET AL: "Centralized adaptive load shedding methods to enhance power system voltage stability margins", IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, vol. 3, no. 6, 30 November 2008 (2008-11-30), US, pages 669 - 679, XP055244149, ISSN: 1931-4973, DOI: 10.1002/tee.20329 *
SAFFARIAN, A.; SANAYE-PASAND, M.: "Enhancement of Power System Stability Using Adaptive Combinational Load Shedding Methods", IEEE TRANS. POWER SYST., vol. 26, no. 3, 2011, pages 1010 - 1020, XP011336028, DOI: doi:10.1109/TPWRS.2010.2078525
SAFFARIAN, ENHANCEMENT OF POWER SYSTEM STABILITY USING ADAPTIVE COMBINATIONAL LOAD SHEDDING METHODS
TAKUMI KATO ET AL: "Multiagent System for Priority-Based Load Shedding in Microgrid", 2013 IEEE 37TH ANNUAL COMPUTER SOFTWARE AND APPLICATIONS CONFERENCE WORKSHOPS, 31 July 2013 (2013-07-31), pages 540 - 545, XP055243861, ISBN: 978-1-4799-2159-1, DOI: 10.1109/COMPSACW.2013.133 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3522324B1 (en) 2018-02-05 2019-12-25 Beegy GmbH Method and arrangement for load management of electrical devices
FR3112637A1 (en) * 2020-07-15 2022-01-21 Total Sa Method of controlling an electrical micro-grid

Similar Documents

Publication Publication Date Title
CN106537717B (en) Method for controlling a wind power plant, wind power plant system and storage medium
Wang et al. Coordinated control of distributed energy-storage systems for voltage regulation in distribution networks
Boroyevich et al. Future electronic power distribution systems a contemplative view
EP2469681B1 (en) Methods and systems for operating a power generation system
EP2072813A2 (en) Control system and method for operating a wind farm
EP2704282A2 (en) Voltage control for wind turbine generators
CA2839813C (en) A method in an electric power system, controller, computer programs, computer program products and electric power system
EP2600479A1 (en) Controlling an electrical grid with islanded operation
KR101566296B1 (en) Frequency Control System in Power System
US20160239034A1 (en) Methods and apparatus for detecting and correcting instabilities within a power distribution system
JP2012249500A (en) Power system management system, and management method for power system
US10389123B2 (en) Power control of microgrid wherein detecting a need for overloading a transformer based on power balance within the microgrid
JP6410696B2 (en) System control device and system stabilization system
Cvetkovic Modeling, analysis and design of renewable energy nanogrid systems
WO2017097379A1 (en) Load shedding in a microgrid
EP3176901A1 (en) Controller for a multiphase inverter
WO2018051684A1 (en) Microgrid operation device and microgrid operation method
Khederzadeh Frequency control of microgrids by demand response
JP2016144229A (en) Power system operation device, power system operation method and power system operation system
JP5497216B1 (en) Distribution system control method and information processing apparatus
Nanou et al. Evaluation of DC voltage control strategies for multi-terminal HVDC grids comprising island systems with high RES penetration
CN110649629B (en) STATCOM and UPFC coordinated control method
KR101698267B1 (en) Method of Controlling Energy Storage System
CN115699494A (en) System and method for connecting multiple power sources in parallel
KR20160118640A (en) Method of controlling Energy Storage System

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15808397

Country of ref document: EP

Kind code of ref document: A1

DPE1 Request for preliminary examination filed after expiration of 19th month from priority date (pct application filed from 20040101)
NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15808397

Country of ref document: EP

Kind code of ref document: A1