Power system and method of operating the same

Abstract

A power system and its operating method are disclosed. The power system includes: a mains network connected to a first switch; and a microgrid connected to the mains network via the first switch. The microgrid includes: a converter device connected to a bus; a controller connected to the first switch and the converter device and used to transmit a first signal; and a load connected to the converter device via the bus. The mains network is connected to the bus via the first switch and used to supply power to the load. The controller is further used to detect a first line connecting the mains network and the microgrid, and to determine whether the first line is abnormal. When the controller determines that the first line is abnormal, the controller disconnects the first switch and switches a first part of the converter device to operate as a voltage source via the first signal.

Description

Technical Field

[0001] This disclosure relates to a power system, and more particularly to a microgrid system with a converter device for switching power supply operation modes and its operation method. Background Technology

[0002] In existing power systems, microgrids within a grid-connected network or mains grid architecture primarily define their geographical scope as feeders, receiving power from the mains grid to supply loads. When an anomaly occurs in the upstream mains power supply, power can only be supplied to the loads via the downstream microgrid operating off-grid until the anomaly is resolved and it can then reconnect to the mains grid. In this case, the power distribution and supply volume within the off-grid microgrid need further consideration to ensure sufficient power supply. Summary of the Invention

[0003] This disclosure includes a power system comprising: a mains network connected to a first switch; and a microgrid connected to the mains network via the first switch, the microgrid including a plurality of converter devices connected to a bus; a controller connected to each of the first switch and the converter devices and used to transmit a plurality of first signals; and a plurality of loads connected to the converter devices via the bus, wherein the mains network is connected to the bus via the first switch and used to supply power to the loads, the controller further being used to detect a first line connecting the mains network and the microgrid and to determine whether the first line is abnormal, and when the controller determines that the first line is abnormal, the controller disconnects the first switch and switches a first portion of the converter devices to operate as a voltage source via the first signals.

[0004] This disclosure includes a method for operating a power system, comprising: connecting a mains power grid to multiple microgrids via multiple lines through multiple switches; detecting multiple voltages of the switches and determining whether the lines are abnormal based on the voltages; when a first line of the lines is determined to be abnormal, disconnecting the first switch of the switches and switching a first portion of multiple converter devices in the first microgrid connected to the first line to operate as a voltage source; and when the first line is determined to be normal, maintaining the first switch connected, and each of the converter devices operating as a current source, different from the voltage source mode, wherein when the first line is determined to be abnormal, a second portion of the converter devices operates as a current source, and the second portion is different from the first portion. Attached Figure Description

[0005] The embodiments disclosed herein can be best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with industry standard practice, the various features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various features may be arbitrarily increased or decreased.

[0006] Figure 1 This is a schematic diagram of a power system shown according to some embodiments of the present disclosure;

[0007] Figure 2 This is a schematic diagram of a power system shown according to some embodiments of the present disclosure;

[0008] Figure 3 This is a flowchart illustrating a method of operating a power system according to some embodiments of the present disclosure;

[0009] Figure 4 This is a schematic diagram of a power system shown according to some embodiments of the present disclosure;

[0010] Figure 5 This is a schematic diagram of a power system shown according to some embodiments of the present disclosure.

[0011] Explanation of icon numbers

[0012] 100: Power System

[0013] 110: Microgrid

[0014] 111: Controller

[0015] 112~116: Converter equipment

[0016] 120: Power Distribution System

[0017] 122, 123: Power converter

[0018] 124, 125, 126: Inverters

[0019] 130: Mains power network

[0020] 132, 133: Energy storage system

[0021] 134, 135, 136: Renewable Energy Devices

[0022] 200: Power System

[0023] 210: Microgrid

[0024] 211: Controller

[0025] 212~216: Converter equipment

[0026] 222, 223: Power converters

[0027] 224, 225, 226: Inverters

[0028] 232, 233: Energy storage system

[0029] 234, 235, 236: Renewable Energy Devices

[0030] 300: Operating Instructions

[0031] 301~312: Operation

[0032] A, A(t): parameters

[0033] BS110, BS210: Bus

[0034] B_j, B_j(t): Parameters

[0035] CB10~CB15: Switches

[0036] CB20~CB25: Switches

[0037] CBN11, CBN12: Switches

[0038] CBN21, CBN22: Switches

[0039] F_CB10, F_CB20: Frequency

[0040] F_limL: Lower frequency limit

[0041] F_limH: Upper limit frequency

[0042] I_CB10, I_CB20: Current

[0043] I_lim: Threshold current level

[0044] i: a positive integer

[0045] j: a positive integer

[0046] L1, L2: Lines

[0047] N11, N12: Load

[0048] N21, N22: Load

[0049] Ni, Nj: Positive integers

[0050] PCC: Common Coupling Point

[0051] P112~P116, P212~P216: Actual power

[0052] Q112~Q116, Q212~Q216: Virtual Power

[0053] S1~S10: Signals

[0054] ST_GFL, ST_GFL(t): Total capacity

[0055] S_PCS_GFL_i(t): Capacity

[0056] S_PV_GFL_j(t): Capacity

[0057] S_GFM, S_GFM(t): Capacity

[0058] S_GFL, S_GFL(t): Capacity

[0059] S_Load, S_Load(t): Loading capacity

[0060] SC_Load, SC_Load(t): Critical load extraction capacity

[0061] SNC_Load, SNC_Load(t): Non-critical load capacity

[0062] ST1_GFL, ST2_GFL: Total capacity

[0063] S1_GFM, S2_GFM: Capacity

[0064] S1_GFL, S2_GFL: Capacity

[0065] S1_Load, S2_Load: Load extraction capacity

[0066] SC1_Load, SC2_Load: Critical load extraction capacity

[0067] SNC1_Load, SNC2_Load: Non-critical load extraction capacity

[0068] S_N11, S_N12: Loading capacity

[0069] S112_GFL~S116_GFL: Capacity

[0070] S212_GFL~S216_GFL: Capacity

[0071] t: time

[0072] V112~V116: Output voltage

[0073] V212~V216: Output voltage

[0074] V_DEF: Rated output voltage level

[0075] V_limL: Low limit voltage level

[0076] V_limH: Upper limit voltage level

[0077] V_CB10, V_CB20: Voltage Detailed Implementation

[0078] The following disclosure provides numerous different embodiments or examples for implementing various features of the provided subject matter. Specific examples of components and configurations are described below to simplify this disclosure. Of course, these components and configurations are merely examples and are not intended to be limiting. For example, in the following description, forming a first feature on or above a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which an additional feature may be formed between the first and second features such that the first and second features are not in direct contact. Additionally, reference numerals and / or letters may be repeated in various instances of this disclosure. This repetition is for simplicity and clarity and does not in itself determine the relationship between the various embodiments and / or configurations discussed.

[0079] In this document, when an element is referred to as a “connection” or “coupled,” it may mean an “electrical connection” or “electrical coupling.” “Connection” or “coupled” can also be used to indicate the operation or interaction between two or more elements. Furthermore, although terms such as “first,” “second,” etc., are used herein to describe different elements, these terms are merely used to distinguish elements or operations described using the same technical terminology. Unless the context clearly indicates otherwise, these terms do not specifically refer to or imply any order or sequence, nor are they intended to limit the invention.

[0080] Additionally, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” “upper,” “top,” “bottom,” and similar terms may be used herein to describe the relationship between one element or feature illustrated in the figures and one or more other elements or features. Besides the orientation depicted in the figures, spatial relative terms are intended to cover different orientations of elements in use or operation. Devices may be oriented in other ways (rotated 90 degrees or otherwise), and the spatial relative descriptive terms used herein will be interpreted accordingly.

[0081] Figure 1 This is a schematic diagram of a power system 100 shown according to an embodiment of the present disclosure. Figure 1 As shown, the power system 100 includes a microgrid 110, a power distribution system 120, and a mains grid 130. In some embodiments, the microgrid 110, the power distribution system 120, and the mains grid 130 are separated into a mains end and a grid end by a common coupling point PCC.

[0082] like Figure 1As shown, the microgrid 110 includes a controller 111, multiple converter devices 112-116, multiple loads N11 and N12, and multiple switches CB10-CB15, CBN11, and CBN12. In some embodiments, converter device 112 includes a power converter 122 and an energy storage system 132. Converter device 113 includes a power converter 123 and an energy storage system 133. Converter device 114 includes an inverter 124 and a renewable energy device 134. Converter device 115 includes an inverter 125 and a renewable energy device 135. Converter device 116 includes an inverter 126 and a renewable energy device 136.

[0083] like Figure 1 As shown, power converter 122 is connected to energy storage system 132 and to bus BS110 via switch CB11. Power converter 123 is connected to energy storage system 133 and to bus BS110 via switch CB12. Inverter 124 is connected to renewable energy unit 134 and to bus BS110 via switch CB13. Inverter 125 is connected to renewable energy unit 135 and to bus BS110 via switch CB14. Inverter 126 is connected to renewable energy unit 136 and to bus BS110 via switch CB15. Load N11 is connected to bus BS110 via switch CBN11. Load N12 is connected to bus BS110 via switch CBN12.

[0084] In some embodiments, the mains network 130 is connected to the power distribution system 120. The power distribution system 120 is connected to switch CB10 via line L1, and switch CB10 is connected to bus BS110 to distribute power to the microgrid 110. Controller 111 is connected to switch CB10 to detect parameters at the mains end and control the switching on and off of switch CB10. Further details regarding the detection of mains parameters and the control of switch CB10 will be provided later. Figure 3 Detailed explanations are provided in the corresponding paragraphs.

[0085] In some scenarios, when the mains grid 130 is operating normally and switch CB10 is engaged, the mains grid 130 distributes power to the microgrid 110 and supplies power to loads N11 and N12, or charges energy storage systems 132 and 133. The mains grid 130 supplies power to the loads or charges the energy storage systems based on the current operating state of the microgrid 110. In other scenarios, when the mains grid 130 malfunctions and switch CB10 is disengaged, the mains grid 130 is disconnected from the microgrid 110, and energy storage systems 132 and 133, along with renewable energy devices 134-136, supply power to loads N11 and N12. Further details regarding the determination of normal and abnormal operation of the mains grid 130, and the power supply of the microgrid 110 to loads N11 and N12, will be provided later. Figure 3 Detailed explanations are provided in the corresponding paragraphs.

[0086] In some embodiments, when the mains network 130 is operating normally, each of the inverter devices 112-116 operates in grid-following (GFL) mode. Specifically, when the inverter devices 112-116 operate in GFL mode, they function as current sources. At this time, the power converters 122-123 and the inverters 124-126 operate according to the voltage and frequency provided by the mains network 130.

[0087] In some embodiments, when the mains network 130 malfunctions, or when the microgrid 110 operates off-grid, a portion of the converter devices 112-116 switch to grid-forming (GFM) mode. Specifically, when one or more of the converter devices 112-116 operate in GFM mode, the converter devices 112-116 operate as voltage sources. At this time, power converters 122-123 and inverters 124-126 independently generate voltage and frequency to supply power to each of loads N11 and N12. In some embodiments, off-grid operation refers to the independent operation of the microgrid 110 to supply power to each of loads N11 and N12 when the switch CB10 connecting the microgrid 110 and the mains network 130 is disconnected.

[0088] like Figure 1As shown, controller 111 controls converter devices 112-116 via signals S1-S5 respectively, and uses these signals to switch the operating modes of converter devices 112-116. Specifically, controller 111 switches converter devices 112-116 from GFL mode to GFM mode and / or from GFM mode to GFL mode via signals S1-S5 respectively. In some embodiments, each of signals S1-S5 can be implemented via a fiber optic network or cable, and controller 111 transmits signals S1-S5 to power converters 122-123 and inverters 124-126 respectively via a virtual channel for power interconnection. In some embodiments disclosed herein, signals S1-S5 can be implemented using GOOSE (Generic Object Oriented Substation Event) virtual channel communication technology.

[0089] In some embodiments, the power distribution system 120, the mains network 130, the controller 111, the converter devices 112-116, the loads N11 and N12, and each of the plurality of switches CB10-CB15, CBN11, and CBN12 in the power system 100 are interconnected via power lines. In some embodiments, the controller 111 transmits signals S1-S5 to the converter devices 112-116 via GOOSE communication lines.

[0090] In the embodiments disclosed herein, each of switches CB11-CB15, CBN11, and CBN12 is in the active state. In other words, when the microgrid 110 is operating, each of switches CB11-CB15, CBN11, and CBN12 is turned on.

[0091] In some embodiments, converter devices 112-116 may be implemented using inverter-based resources (IBRs). Power converters 122-123 may be implemented using a power conversion system (PCS). Energy storage systems 132-133 may be implemented using a battery energy storage system (BESS). Inverters 124-126 may be implemented using a solar photovoltaic inverter (PV inverter). Renewable energy devices 134-136 may be implemented using a solar photovoltaic array (PV array). In some embodiments, renewable energy devices 134-136 may also be implemented using a generator or renewable energy source, such as a solar power system, a wind power system, a hydropower system, and a geothermal power system; however, this disclosure is not limited to the aforementioned power generation systems.

[0092] In some embodiments, the power distribution system 120 may be located in a substation or related facility and is used to distribute the power provided by the mains network 130 to multiple different microgrids.

[0093] In some embodiments, loads N11-N12 may be general-purpose power supplies with low instantaneous power withdrawal. In other embodiments, loads N11-N12 may be power supplies for electric vehicles (EVs) with higher instantaneous power withdrawal. For example, general-purpose power supplies may have an instantaneous power withdrawal of 0.05-5.0 kWh, while electric vehicle power supplies may have an instantaneous power withdrawal of 20-400 kWh.

[0094] Figure 2 This is a schematic diagram of a power system 200 according to some embodiments of the present disclosure. Figure 2 As shown, power system 200 includes various devices found in power system 100. Power system 200 further includes microgrid 210.

[0095] In some embodiments, power system 200 is another variation of power system 100. In various embodiments, power systems 100 and 200 may include one or more microgrids, such as microgrids 110 and 210, however, this disclosure is not limited thereto.

[0096] like Figure 2 As shown, microgrid 210 includes a controller 211, multiple converter devices 212-216, multiple loads N21 and N22, and multiple switches CB20-CB25, CBN21, and CBN22. In some embodiments, converter device 212 includes a power converter 222 and an energy storage system 232. Converter device 213 includes a power converter 223 and an energy storage system 233. Converter device 214 includes an inverter 224 and a renewable energy device 234. Converter device 215 includes an inverter 225 and a renewable energy device 235. Converter device 216 includes an inverter 226 and a renewable energy device 236. In some embodiments, the connection relationships and operation modes of the various devices in microgrid 210 are similar to those in microgrid 110. For the sake of brevity, some similarities between microgrids 210 and 110 will not be repeated.

[0097] like Figure 2As shown, power converter 222 is connected to energy storage system 232 and to bus BS210 via switch CB21. Power converter 223 is connected to energy storage system 233 and to bus BS210 via switch CB22. Inverter 224 is connected to renewable energy device 234 and to bus BS210 via switch CB23. Inverter 225 is connected to renewable energy device 235 and to bus BS210 via switch CB24. Inverter 226 is connected to renewable energy device 236 and to bus BS210 via switch CB25. Load N21 is connected to bus BS210 via switch CBN21. Load N22 is connected to bus BS210 via switch CBN22.

[0098] In some embodiments, the power distribution system 120 is connected to switch CB20 via line L2, and switch CB20 is connected to bus BS210 to distribute power to microgrid 210. Controller 211 is connected to switch CB20 to detect parameters at the mains power supply and control the switching on and off of switch CB20. Further details regarding the detection of mains power parameters and the control of switch CB20 will be provided later. Figure 3 This will be explained in detail in the corresponding paragraphs. In some embodiments, the independent operation of microgrid 210 is similar to that of microgrid 110. For the sake of brevity, the similarities in operation between microgrids 210 and 110 will not be repeated.

[0099] In some scenarios, when the mains network 130 is functioning properly and each of switches CB10 and CB20 is engaged, the mains network 130 is used to distribute power to each of microgrids 110 and 210 and to supply power to loads N11, N12, N21 and N22.

[0100] In other scenarios, when the mains network 130 malfunctions and each of switches CB10 and CB20 is disconnected, the mains network 130 is disconnected from each of the microgrids 110 and 210. Energy storage systems 132 and 133 and renewable energy devices 134-136 are used to supply power to loads N11 and N12. Energy storage systems 232 and 233 and renewable energy devices 234-236 are used to supply power to loads N21 and N22.

[0101] In other scenarios, when the mains grid 130 is operating normally and one of the switches CB10 and CB20 is disconnected, the microgrid corresponding to the disconnected switch operates off-grid. The microgrid corresponding to the one with switches CB10 and CB20 still connected is powered by the mains grid 130. For example, when the mains grid 130 is operating normally, switch CB10 is disconnected, and switch CB20 is engaged, the mains grid 130 is used to distribute power to the microgrid 210 and to power loads N21 and N22. Simultaneously, the mains grid 130 is disconnected from the microgrid 110, and the microgrid 110 operates off-grid. Energy storage systems 132 and 133 and renewable energy devices 134-136 are used to power loads N11 and N12.

[0102] like Figure 2 As shown, controller 211 controls converter devices 212-216 via signals S6-S10, respectively, to switch the operating modes of converter devices 212-216. Specifically, controller 211 switches converter devices 212-216 from GFL mode to GFM mode and / or from GFM mode to GFL mode via signals S6-S10. In some embodiments, signals S6-S10 can be implemented using GOOSE virtual channel communication technology.

[0103] In some embodiments, when the mains network 130 is operating normally, each of the converter devices 112-116 and 212-216 operates in GFL mode. At this time, each of the converter devices 112-116 and 212-216 operates as a current source.

[0104] In other embodiments, when the mains power network 130 malfunctions, a portion of converter devices 112-116 and 212-216 switch to GFM mode. In this mode, converter devices 112-116 and 212-216 operate as voltage sources. In some embodiments, a portion of converter devices 112-116 and 212-216 comprises one or more of converter devices 112-116 and / or one or more of converter devices 212-216.

[0105] In some embodiments, the controller 211, the converter devices 212-216, the loads N21 and N22, and each of the plurality of switches CB20-CB25, CBN21, and CBN22 are interconnected via power lines. In some embodiments, the controller 211 transmits signals S6-S10 to the converter devices 212-216 via GOOSE communication lines.

[0106] In the embodiments disclosed herein, each of switches CB21-CB25, CBN21, and CBN22 is in the active state. In other words, when the microgrid 210 is operating, each of switches CB21-CB25, CBN21, and CBN12 is turned on.

[0107] In some embodiments, converter devices 212-216 can be implemented via an IBR. Power converters 222-223 can be implemented via a PCS. Energy storage systems 232-233 can be implemented via a BESS. Inverters 224-226 can be implemented via solar photovoltaic inverters. Renewable energy devices 234-236 can be implemented via solar cell arrays.

[0108] In some embodiments, loads N21 to N22 may be general power supplies with low instantaneous power withdrawal. In other embodiments, loads N11 to N12 may be power supplies for electric vehicles (EVs) with higher instantaneous power withdrawal.

[0109] Figure 3 This is a flowchart illustrating an operation method 300 of power systems 100 and 200 according to some embodiments of this disclosure. For example... Figure 3 As shown, operation method 300 includes operations 301 to 312. In some embodiments, operation method 300 can be applied to power systems 100 and 200. The following various embodiments will use power system 200 as an example to illustrate operation method 300.

[0110] In operation 301, when the power system 200 is running, the mains network 130 is connected to each of the microgrids 110 and 210.

[0111] Specifically, when the power system 200 is operating, microgrids 110 and 210 respectively switch CB10 and CB20. At this time, the mains network 130 distributes power to each of microgrids 110 and 210 through the power distribution system 120 to supply power to loads N11, N12, N21, and N22. After completing operation 301, the power system 200 proceeds to operation 302.

[0112] In operation 302, controllers 111 and 211 measure and calculate the parameters of the mains terminals of lines L1 and L2, respectively.

[0113] Specifically, controller 111 measures multiple parameters between power distribution system 120 and switch CB10 via line L1. Controller 211 measures multiple parameters between power distribution system 120 and switch CB20 via line L2. These parameters include voltages V_CB10 and V_CB20, currents I_CB10 and I_CB20, and frequencies F_CB10 and F_CB20 between switches CB10 and CB20 and power distribution system 120, respectively. However, this disclosure is not limited to the parameters described above.

[0114] In some embodiments, controllers 111 and 211 may measure multiple parameters of lines L1 and L2 via relays and voltmeters. Power system 200 performs operation 303 after completing operation 302.

[0115] In operation 303, controllers 111 and 211 monitor multiple initial state parameters of converter devices 112-116 and 212-216, respectively.

[0116] Specifically, converter devices 112 to 116 transmit their initial state parameters to controller 111 via signals S1 to S5, respectively. Converter devices 212 to 216 transmit their initial state parameters to controller 211 via signals S6 to S10, respectively.

[0117] In some embodiments, the initial state parameters of converter devices 112-116 include the operating state of converter devices 112-116 and the capacities S112_GFL to S116_GFL of converter devices 112-116 operating in GFL mode. The initial state parameters of converter devices 212-216 include the operating state of converter devices 212-216 and the capacities S212_GFL to S216_GFL of converter devices 212-216 operating in GFL mode. In some embodiments, each of the capacities S112_GFL to S116_GFL and S212_GFL to S216_GFL may have a capacity unit of kilowatt-hours (kWh) or megawatt-hours (MWh). Power system 200 performs operation 304 after completing operation 303.

[0118] In operation 304, controllers 111 and 211 calculate the total capacity of microgrids 110 and 210, respectively.

[0119] Specifically, controller 111 calculates the total capacity ST1_GFL of microgrid 110 when converter devices 112-116 operate in GFL mode, and the capacity S1_GFM of microgrid 110 when converter devices 112-116 operate in GFM mode. Similarly, controller 211 calculates the total capacity ST2_GFL of microgrid 210 when converter devices 212-216 operate in GFL mode, and the capacity S2_GFM of microgrid 210 when converter devices 212-216 operate in GFM mode.

[0120] In some embodiments, the total capacity ST1_GFL and ST2_GFL can be calculated according to the following formula.

[0121]

[0122] Where Ni, Nj, i, and j are positive integers greater than zero.

[0123] In formula (1), the total capacity ST_GFL(t) is used to represent the total capacity of the microgrid at time t and when it is operating in GFL mode, for example, the total capacity ST1_GFL and ST2_GFL.

[0124] In formula (1), the capacity S_PCS_GFL_i(t) represents the total capacity of the PCS-implemented converter devices in the microgrid at time t, operating in GFL mode. The positive integer Ni represents the number of PCS-implemented converter devices in the microgrid, such as converter devices 112 and 113. The positive integer i represents the i-th converter device; for example, i equals 1 to represent converter device 112, and i equals 2 to represent converter device 113.

[0125] In formula (1), the capacity S_PV_GFL_j(t) represents the total capacity of inverter-implemented converter devices in the microgrid at time t, operating in GFL mode. The positive integer Nj represents the number of inverter-implemented converter devices in the microgrid, for example, converter devices 114 to 116. The positive integer j represents the j-th inverter-implemented converter device; for example, j equals 1 to represent converter device 114, j equals 2 to represent converter device 115, and j equals 3 to represent converter device 116. In some embodiments, the capacity S_PV_GFL_j can be used to represent the capacity of the solar photovoltaic inverter.

[0126] In some embodiments, the parameter B_j(t) in formula (1) indicates the maximum power percentage capacity of the j-th solar photovoltaic inverter at time t. In some embodiments, the parameter B_j can be expressed as a percentage value or a decimal, such as 20% or 0.2. However, this disclosure is not limited to this value or representation.

[0127] In some embodiments, the capacities S1_GFM and S2_GFM can be calculated based on the total capacities ST1_GFL and ST2_GFL. Specifically, the capacities S1_GFM and S2_GFM are calculated using the following formulas.

[0128] S_GFM(t)=ST_GFL(t)×A(t)...(2).

[0129] In formula (2), the capacity S_GFM(t) is used to represent the capacity of the microgrid at time t and when it is operating in GFM mode, for example, the capacities S1_GFM and S2_GFM.

[0130] In some embodiments, parameter A(t) indicates the percentage of multiple converter devices that can switch from GFL mode to GFM mode at time t. In some embodiments, parameter A can be expressed as a percentage value or a decimal, such as 20% or 0.2. However, this disclosure is not limited to this value or representation.

[0131] In some embodiments, the percentage value of parameter A is directly proportional to the number of converter devices operating in GFM mode. Specifically, the percentage value of parameter A increases when the number of converter devices switching from GFL mode to GFM mode increases, and the percentage value of parameter A decreases when the number of converter devices switching from GFL mode to GFM mode decreases.

[0132] For example, in formula (2), when each of the converter devices 112-116 operates in GFL mode, the total capacity ST1_GFL of microgrid 110 is 50 MWh. In some scenarios, when one of the converter devices 112-116 switches from GFL mode to GFM mode, parameter A has a conversion percentage of 20%. In this case, the capacity S1_GFM of microgrid 110 is equal to 50 MWh multiplied by 20%, which is 10 MWh. In other scenarios, when multiple of the converter devices 112-116 switch from GFL mode to GFM mode, parameter A has a conversion percentage of 90%. In this case, the capacity S1_GFM of microgrid 110 is equal to 50 MWh multiplied by 90%, which is 45 MWh.

[0133] In some embodiments, the calculation methods for the total capacity ST2_GFL and capacity S2_GFM of microgrid 210, and the relationship between the operating modes of converter devices 212-216 and the calculation of the total capacity ST2_GFL and capacity S2_GFM, are similar to those of microgrid 110. For the sake of simplicity, the calculation of the total capacity ST2_GFL and capacity S2_GFM will not be described again with examples. After completing operation 304, power system 200 performs operation 305.

[0134] In operation 305, controllers 111 and 211 calculate the capacity of converter devices 112-116 and 212-216 operating in GFM mode and GFL mode, respectively.

[0135] Specifically, controller 111 calculates the capacity S1_GFM of a portion of the converter devices 112-116 operating in GFM mode, and the capacity S1_GFL of another portion of the converter devices 112-116 maintained in GFL mode. Controller 211 calculates the capacity S2_GFM of a portion of the converter devices 212-216 operating in GFM mode, and the capacity S2_GFL of another portion of the converter devices 212-216 maintained in GFL mode.

[0136] In some embodiments, the capacities S1_GFM and S2_GFM can be calculated using formula (2). The capacities S1_GFL and S2_GFL can be calculated using the following formula.

[0137] S_GFL(t)=ST_GFL(t)×(1-A(t))...(3).

[0138] In formula (3), the capacity S_GFL(t) is used to represent the capacity of the microgrid at time t, when one or more of the converter devices are still operating in GFL mode, for example, the capacities S1_GFL and S2_GFL.

[0139] In some embodiments, the operating modes of multiple converter devices can be switched according to the required load capacity S_Load. Specifically, when a portion of the multiple converter devices operates in GFL mode, the microgrid has a capacity S_GFL. When another portion of the multiple converter devices operates in GFM mode, the microgrid has a capacity S_GFM. In this case, the sum of the capacities S_GFL and S_GFM must be greater than or equal to the load capacity S_Load and satisfy the following formula.

[0140] S_GFL(t)+S_GFM(t)≥S_Load(t)...(4)

[0141] As shown in formula (4), the sum of the capacities S_GFL and S_GFM at time t is greater than or equal to the load capacity S_Load required by the load at time t.

[0142] For example, at time t, loads N11 and N12 have withdrawn capacities S_N11 and S_N12, respectively. When a portion of converter devices 112-116 operates in GFL mode and another portion operates in GFM mode, microgrid 110 has capacities S1_GFL and S1_GFM. In this case, the sum of each of the capacities S1_GFL and S1_GFM must be greater than or equal to the sum of each of the withdrawn capacities S_N11 and S_N12. Microgrid 210 operates similarly to microgrid 110; for simplicity, the withdrawn capacity of microgrid 210 will not be described again.

[0143] In some embodiments, a portion of the multiple loads may be further divided into critical loads, and another portion may be further divided into non-shutdown loads. Accordingly, the load extraction capacity S_Load of the multiple loads may be further divided into critical load extraction capacity SC_Load of critical loads and non-critical load extraction capacity SNC_Load of non-critical loads, satisfying the following formula.

[0144] S_Load(t)=SC_Load(t)+SNC_Load(t)...(5)

[0145] As shown in Equation (5), the load capacity S_Load required by the load in the microgrid at time t is equal to the sum of the critical load capacity SC_Load and the non-critical load capacity SNC_Load at time t.

[0146] For example, in microgrids 110 and 210, a portion of loads N11, N12, N21, and N22 can be classified as critical loads, such as loads N11 and N21. Another portion of loads N11, N12, N21, and N22 can be classified as non-critical loads, such as loads N12 and N22. However, this disclosure is not limited to this example.

[0147] In some embodiments, the critical load capacity SC_Load represents the load capacity required for a critical load. Critical loads may include hospitals, city centers, military facilities, banks, or other similar electrical installations; however, this disclosure is not limited to these critical installations. The non-critical load capacity SNC_Load represents the load capacity required for a non-critical load. Non-critical loads may include general household electricity, charging stations, or other similar electrical installations; however, this disclosure is not limited to these non-critical installations. After completing operation 305, the power system 200 proceeds to operation 306.

[0148] In operation 306, controllers 111 and 211 determine whether the mains power network 130 and the lines L1 and L2 connected to the mains power network are abnormal.

[0149] Specifically, controller 111 determines whether line L1 is abnormal based on voltage V_CB10, current I_CB10, and frequency F_CB10. Similarly, controller 211 determines whether line L2 is abnormal based on voltage V_CB20, current I_CB20, and frequency F_CB20.

[0150] In some embodiments, when the voltage level of voltage V_CB10 is less than or equal to the lower limit voltage level V_limL, or when the voltage level of voltage V_CB10 is greater than or equal to the upper limit voltage level V_limH, the controller 111 determines that line L1 is abnormal. When the current level of current I_CB10 is greater than the threshold current level I_lim, the controller 111 determines that line L1 is abnormal. When the frequency F_CB10 is less than or equal to the lower limit frequency F_limL, or when the frequency F_CB10 is greater than or equal to the upper limit frequency F_limH, the controller 111 determines that line L1 is abnormal.

[0151] Correspondingly, when the voltage level of voltage V_CB20 is less than or equal to the lower limit voltage level V_limL, or when the voltage level of voltage V_CB20 is greater than or equal to the upper limit voltage level V_limH, controller 211 determines that line L2 is abnormal. When the current level of current I_CB20 is greater than the threshold current level I_lim, controller 211 determines that line L2 is abnormal. When the frequency F_CB20 is less than or equal to the lower limit frequency F_limL, or when the frequency F_CB20 is greater than or equal to the upper limit frequency F_limH, controller 211 determines that line L2 is abnormal.

[0152] In some embodiments, when controllers 111 and 211 determine that lines L1 and L2 are abnormal, controllers 111 and 211 determine that the mains power network 130 is operating abnormally, and the power system 200 performs operation 307 after completing operation 306.

[0153] In some embodiments, when controllers 111 and 211 determine that lines L1 and L2 are normal, controllers 111 and 211 determine that the mains power network 130 is operating normally, and the power system 200 repeats operation 302 after completing operation 306.

[0154] In operation 307, controllers 111 and 211 disconnect switches CB10 and CB20 connected to the mains network 130 and send commands to multiple converter devices.

[0155] Specifically, when controllers 111 and 211 disconnect switches CB10 and CB20 connected to the mains network 130, microgrids 110 and 210 operate off-grid. At this time, controller 111 transmits commands to converter devices 112-116 via signals S1-S5 respectively. Controller 211 transmits commands to converter devices 212-216 via signals S6-S10 respectively.

[0156] In some embodiments, the above instructions may include switching converter devices 112-116 and 212-216 from GFL mode to GFM mode, and setting converter devices 112-116 and 212-216 to their corresponding rated output voltage levels V_DEF. However, the instructions may include other similar parameters and settings, and this disclosure is not limited to the above instructions. After completing operation 307, the power system 200 proceeds to operation 308.

[0157] In operation 308, controllers 111 and 211 switch a portion of the converter equipment to GFM mode and GFL mode.

[0158] Specifically, controller 111 switches one or more of converter devices 112-116 from GFL mode to GFM mode via signals S1-S5 respectively. Controller 211 switches one or more of converter devices 212-216 from GFL mode to GFM mode via signals S6-S10 respectively.

[0159] In some embodiments, due to differences in the modules or configurations of the converter devices, the capacity that the converter devices can supply under GFM mode varies. Therefore, the capacity S_GFM that the microgrid can provide to the loads also differs. For example, in some scenarios, the capacity S1_GFM that microgrid 110 can provide under GFM mode is less than the load capacity S1_Load required by loads N11 and N12. In other scenarios, the capacity S2_GFM of microgrid 210 is greater than the capacity that microgrid 210 can provide to loads N21 and N22 under GFM mode.

[0160] In the above scenario, the controllers 111 and 211 disclosed herein can switch a portion of the converter devices 112-116 and 212-216 from GFL mode to GFM mode to supply power to loads N11, N12, N21 and N22 by the methods of total load determination, critical load determination in GFM mode, and critical load determination in both GFM and GFL modes.

[0161] In the method for determining the total load, when the controller's calculated capacity S_GFM is greater than the load's required tap-out capacity S_Load, one or more of the converter devices switch to GFM mode and are used to supply power to the load. The method for determining the total load satisfies the following formula.

[0162] S GFM(t) ≥S Load(t)

[0163] S_GFL(t)=ST_GFL(t)×(1-A(t))

[0164] Specifically, when the microgrid's capacity S_GFM at time t is greater than the load-discharge capacity S_Load, the converter's capacity S_GFM operating in GFM mode can supply the load within the microgrid. At this time, the converter's capacity S_GFL operating in GFL mode is equal to the total capacity ST_GFL minus the capacity switched to GFM mode, i.e., the total capacity ST_GFL multiplied by parameter A.

[0165] For example, when controller 111 calculates that the capacity S1_GFM of microgrid 110 at time t is greater than the required load capacity S_Load of each of loads N11 and N12, a portion of converter devices 112-116 operate in GFM mode to supply power to each of loads N11 and N12.

[0166] In the method for determining the critical load supply in GFM mode, when the controller's calculated capacity S_GFM is greater than the critical load's critical load capacity SC_Load, one or more converter devices switch to GFM mode operation and are used to supply power to the critical load. The method for determining the critical load supply in GFM mode satisfies the following formula.

[0167] S GFM(t) ≥SC Load(t)

[0168] S_GFL(t)=ST_GFL(t)×(1-A(t))

[0169] Specifically, when the microgrid's capacity S_GFM at time t is greater than the critical load capacity SC_Load, the capacity S_GFM of one or more converter devices operating in GFM mode can supply the critical load within the microgrid. In this case, the capacity S_GFL of the converter devices operating in GFL mode is equal to the total capacity ST_GFL minus the capacity switched to GFM mode, i.e., the total capacity ST_GFL multiplied by parameter A.

[0170] For example, when load N11 is a critical load and load N12 is a non-critical load, and when controller 111 calculates that the capacity S1_GFM of microgrid 110 at time t is greater than the critical load capacity SC_Load required by load N11, a portion of converter devices 112-116 switches to GFM mode, and another portion of converter devices 112-116 operates in GFL mode to jointly supply power to loads N11 and N12. In the above example, when the capacity required by load N11 changes (e.g., the required capacity increases), the converter devices operating in GFM mode output power according to the changed capacity required by load N11 to absorb the change in the required capacity of load N11. At this time, the converter devices operating in GFM and GFL modes maintain joint power supply to loads N11 and N12.

[0171] In some scenarios, when microgrid 110 is operating, converter devices 112-114 operate in GFM mode, and the capacity of converter devices 112-114 is sufficient to cover load variations of load N11. Conversely, converter devices 115-116 operate in GFL mode. In this mode, converter devices 115-116 operate in maximum power point tracking (MPPT), and their output power can also be scheduled according to the converter devices operating in GFM mode.

[0172] In other scenarios, when microgrid 110 is operating and the capacity of converter devices 112-114 operating in GFM mode is insufficient to cover load changes in load N11, converter devices 115-116 can further switch to GFM mode operation to absorb load changes in load N11. In the method for determining critical load in GFM mode, converter devices 112-116 are used together to supply power to each of loads N11 and N12.

[0173] In some embodiments, whether a converter device (e.g., converter devices 112-116) can switch to GFM mode operation depends on the actual device function.

[0174] In the method for determining the critical load supply in GFM and GFL modes, when the controller-calculated capacity S_GFM is less than the critical load's critical load capacity SC_Load, but the sum of the capacities S_GFM and S_GFL is greater than the critical load's critical load capacity SC_Load, each of the converter devices switches to GFM or GFL mode to supply power to the critical load. The method for determining the critical load supply in GFM mode satisfies the following formula.

[0175] S GFM(t) +S GFL(t) ≥SC Load(t)

[0176] S_GFL(t)=ST_GFL(t)×(1-A(t))

[0177] Specifically, when the sum of the microgrid's capacity S_GFM and capacity S_GFL at time t exceeds the critical load capacity SC_Load, each converter device operates in both GFM and GFL modes, jointly supplying power to the critical load within the microgrid. In this case, the converter device's capacity S_GFL operating in GFL mode is equal to the total capacity ST_GFL minus the capacity switched to GFM mode, i.e., the total capacity ST_GFL multiplied by parameter A.

[0178] For example, when load N11 is a critical load and load N12 is a non-critical load, and when controller 111 calculates that the capacity S1_GFM of microgrid 110 at time t is less than the critical load capacity SC_Load required by load N11, a portion of converter devices 112-116 operates in GFM mode, while another portion of converter devices 112-116 maintains GFL mode to provide capacity S1_GFL to jointly power loads N11 and N12. In some embodiments, since the capacities S1_GFM and S1_GFL are only sufficient to provide power to loads N11 and N12, when the power required by critical load N11 changes, the change in the power required by load N11 cannot be absorbed by converter devices 112-114.

[0179] In some scenarios, when the change in the amount of electricity required by the load N11 cannot be absorbed by the converter devices 112-114 operating in GFM mode, and the converter devices 112-114 cannot adjust the output voltage in a timely manner according to the change in electricity, the bus BS110 may experience voltage imbalance.

[0180] In other scenarios, when the power required by the changes in loads N11 and N12 exceeds the power that converter devices 112-116 can provide, the microgrid 110 can also maintain a stable power supply from converter devices 112-116 to the critical load N11 by offloading the non-critical load N12. However, this disclosure is not limited to the above-mentioned operating scenarios.

[0181] In some embodiments, the above-described discrimination method only provides some implementations of the operation of microgrids 110 and 210 disclosed herein; however, the content of this disclosure is not limited thereto. In various embodiments, microgrids 110 and 210 can still control the operating mode of converter devices through different discrimination methods. Power system 200 performs operation 309 after completing operation 308.

[0182] In operation 309, each of the multiple converter devices 112-116 and 212-216 sends back the status parameters after switching to GFM mode and GFL mode to controllers 111 and 211.

[0183] Specifically, the aforementioned state parameters include the output voltages V112-V116 and V212-V216 of each of the converter devices 112-116 and 212-216, the actual power P112-P116 and P212-P216, the virtual power Q112-Q116 and Q212-Q216, and the operating mode. Converter devices 112-116 and 212-216 respectively transmit their respective output voltages V112-V116 and V212-V216 back to controllers 111 and 211. Converter devices 112-116 and 212-216 further transmit their respective operating modes back to controllers 111 and 211. After completing operation 309, the power system 200 performs operation 310.

[0184] In operation 310, controllers 111 and 211 determine whether the status parameters of converter devices 112-116 and 212-216 after switching operating modes are the same as the instructions.

[0185] Specifically, controller 111 determines whether the voltage levels of output voltages V112 to V116 are equal to the rated output voltage level V_DEF, whether the real power P112 to P116 and the virtual power Q112 to Q116 are the same as the power output command values, and whether the operating modes of converter devices 112 to 116 and 212 to 216 are the same as the command. Controller 211 determines whether the voltage levels of output voltages V212 to V216 are equal to the rated output voltage level V_DEF, and whether the operating modes of converter devices 112 to 116 and 212 to 216 are the same as the command.

[0186] In some embodiments, when controllers 111 and 211 determine that the output voltages V112-V116 and V212-V216 of converter devices 112-116 and 212-216, the actual power P112-P116 and P212-P216, the virtual power Q112-Q116 and Q212-Q216, and the operating mode are the same as the command, the power system 200 performs operation 311. When controllers 111 and 211 determine that the output voltages V112-V116 and V212-V216 of converter devices 112-116 and 212-216, and the operating mode are different from the command, the power system 200 performs operation 312.

[0187] For example, when controller 111 sends a command to converter device 112 in operation 307 that includes a rated output voltage level V_DEF and GFM mode, and the rated output voltage level V_DEF is 50 volts, controller 111 determines whether the output voltage V112 is equal to 50 volts, whether the real power P112 and virtual power Q112 are the same as the command values, and whether converter device 112 is operating in GFM mode. When controller 111 determines that the output voltage V112 is equal to 50 volts and converter device 112 is operating in GFM mode, controller 111 determines that the output voltage V112 and operating mode of converter device 112 are the same as the command. Conversely, when controller 111 determines that the output voltage V112 is not equal to 50 volts, and / or converter device 112 is not operating in GFM mode, controller 111 determines that the output voltage V112 and / or operating mode of converter device 112 are different from the command.

[0188] In operation 311, microgrids 110 and 210 operate off-grid and supply power to loads N11, N12, N21 and N22.

[0189] Specifically, when controller 111 determines that the output voltages V112-V116 of converter devices 112-116 and the operating mode are the same as the command, switch CB10 remains disconnected, and microgrid 110 supplies power to loads N11 and N12. When controller 211 determines that the output voltages V212-V216 of converter devices 212-216 and the operating mode are the same as the command, switch CB20 remains disconnected, and microgrid 210 supplies power to loads N21 and N22. After completing operation 311, power system 200 completes operation method 300.

[0190] In operation 312, converter devices 112-116 and 212-216 perform parameter compensation.

[0191] Specifically, when controller 111 determines that the output voltage V112-V116, actual output power P112-P116, virtual output power Q112-Q116, and operating mode of converter devices 112-116 are different from the instructions, controller 111 retransmits the instructions to converter devices 112-116 via signals S1-S5 respectively. When controller 211 determines that the output voltage V212-V216 and operating mode of converter devices 212-216 are different from the instructions, controller 211 retransmits the instructions to converter devices 212-216 via signals S6-S10 respectively. After completing operation 312, power system 200 repeats operation 309.

[0192] In some approaches, the architecture of the mains grid and microgrid primarily uses feeders as the power supply and distribution path for the microgrid. Power is typically supplied to the microgrid from the mains grid to power the loads. When an anomaly occurs in the upstream line or the mains power supply, power can only be supplied to the loads through the downstream microgrid operating off-grid until the anomaly is resolved and it can then reconnect to the mains grid. However, when the capacity provided by the microgrid operating off-grid is insufficient, the only solution is to offload the load to reduce power demand. This can lead to power outages for some emergency or critical facilities.

[0193] Compared to the methods described above, in the embodiments disclosed herein, power systems 100 and 200 can control converter devices 112-116 and 212-216 to switch operating modes via signals S1-S10 using the GOOSE communication protocol. When an anomaly occurs in lines L1 and L2 connected to the mains network 130, converter devices 112-116 and 212-216 switch from GFL mode to GFM mode according to signals S1-S10, respectively, enabling microgrids 110 and 210 to continuously supply power to loads N11, N12, N21, and N22 during off-grid operation. The power systems 100 and 200 disclosed herein further prevent emergency or critical facilities from losing power due to mains anomalies.

[0194] Figure 4 This is a schematic diagram of a power system 200 according to some embodiments of the present disclosure. Figure 4 As shown, switch CB10 in microgrid 110 is in the off state, and switch CB20 in microgrid 210 is in the on state.

[0195] Also refer to Figure 4 and Figure 3 ,exist Figure 4 In the scenario described, controller 111 determines an anomaly in line L1 during operation 306 and disconnects switch CB10. At this time, controller 111 transmits commands to converter devices 112-116 via signals S1-S5 respectively, switching each of converter devices 112-114 to GFM mode and maintaining each of converter devices 115-116 in GFL mode. When converter devices 112-114 operate in GFM mode, microgrid 110 has the capacity S1_GFM provided by converter devices 112-114. When converter devices 115-116 operate in GFL mode, microgrid 110 has the capacity S1_GFL provided by converter devices 115-116.

[0196] In some scenarios, when load N11 is a critical load and load N12 is a non-critical load, load N11 has a critical load withdrawal capacity SC_Load, and load N12 has a non-critical load withdrawal capacity SNC_Load. In this case, when the capacity S1_GFM is greater than the sum of the critical load withdrawal capacity SC_Load and the non-critical load withdrawal capacity SNC_Load, converter devices 112-114 are used to supply power to each of loads N11 and N12. Specifically, the capacity S1_GFM provided by converter devices 112-114 is used to supply power to each of loads N11 and N12.

[0197] In some embodiments, when the capacity S1_GFM is greater than the critical load removal capacity SC_Load but less than the load removal capacity S_Load, converter devices 112-114 operate in GFM mode, and converter devices 115-116 operate in GFL mode to supply power to loads N11 and N12. Converter devices 112-114 can absorb changes in the capacity required by load N11. Specifically, when converter devices 112-114 operate in GFM mode, the capacity S1_GFM provided by microgrid 110 is greater than the capacity required by load N11. At this time, converter devices 112-116 jointly supply power to each of loads N11 and N12. When the capacity required by load N11 changes, converter devices 112-114 can absorb the changed capacity of load N11.

[0198] In other embodiments, when the capacity S1_GFM is less than the critical load capacity SC_Load, each of the converter devices 112-116 supplies power to loads N11 and N12. When the power required by the loads N11 and N12 changes exceeds the power that the converter devices 112-116 can provide, a voltage drop occurs. The controller 111 disconnects the switch CBN12, causing the microgrid 110 to stop supplying power to load N12, ensuring that the capacity generated by each of the converter devices 112-116 is sufficient to supply power to load N11. Specifically, the capacity S1_GFM provided by converter devices 112-114 operating in GFM mode and the capacity S1_GFL provided by converter devices 115-116 operating in GFL mode are used to supply power to each of loads N11 and N12. When the capacity required by load N11 changes, converter devices 112-114 cannot adjust the provided capacity S1_GFM to absorb the change in the capacity required by load N11. At this time, the controller 111 unloads the load N12, so that the capacity S1_GFM is sufficient to power the critical load N11.

[0199] In other scenarios, when load N11 is a non-critical load and load N12 is a critical load, load N12 has a critical load withdrawal capacity SC_Load, and load N11 has a non-critical load withdrawal capacity SNC_Load. In this case, the microgrid 110 operates similarly to the previous scenario, only requiring the replacement of loads N11 and N12. Therefore, for the sake of brevity, the similarities will not be repeated.

[0200] Also refer to Figure 4 and Figure 3 ,exist Figure 4 In this scenario, controller 211 determines that line L2 is normal during operation 306. At this time, switch CB20 remains on, and the mains network 130 continues to supply power to microgrid 210 to supply power to loads N21 and N22.

[0201] Figure 5 This is a schematic diagram of a power system 200 according to some embodiments of the present disclosure. Figure 5 As shown, each of the switches CB10 in microgrid 110 and CB20 in microgrid 210 is in a disconnected state.

[0202] Also refer to Figure 5 and Figure 3 ,exist Figure 5 In the scenario described, controller 111 determines that line L1 is abnormal in operation 306 and disconnects switch CB10. Controller 211 determines that line L2 is abnormal in operation 306 and disconnects switch CB20.

[0203] At this time, controller 111 transmits commands to converter devices 112-116 via signals S1-S5 respectively, switching each of converter devices 112-114 to GFM mode and maintaining each of converter devices 115-116 in GFL mode. Correspondingly, controller 211 transmits commands to converter devices 212-216 via signals S6-S10 respectively, switching each of converter devices 212-214 to GFM mode and maintaining each of converter devices 215-216 in GFL mode.

[0204] In some embodiments, when each of inverter devices 112-114 and 212-214 operates in GFM mode, microgrid 110 has the capacity S1_GFM provided by inverter devices 112-114, and microgrid 210 has the capacity S2_GFM provided by inverter devices 212-214. When each of inverter devices 115-116 and 215-216 operates in GFL mode, microgrid 110 has the capacity S1_GFL provided by inverter devices 115-116, and microgrid 210 has the capacity S2_GFL provided by inverter devices 215-216.

[0205] In some scenarios, when loads N11 and N21 are critical loads and loads N12 and N22 are non-critical loads, loads N11 and N21 have critical load withdrawal capacities SC1_Load and SC2_Load, respectively, and loads N12 and N22 have non-critical load withdrawal capacities SNC1_Load and SNC2_Load, respectively.

[0206] At this time, when the capacity S1_GFM is greater than the sum of the critical load capacity SC1_Load and the non-critical load capacity SNC1_Load, converter devices 112-114 supply power to each of loads N11 and N12. Specifically, the capacity S1_GFM provided by converter devices 112-114 is used to supply power to each of loads N11 and N12. Correspondingly, when the capacity S2_GFM is greater than the sum of the critical load capacity SC2_Load and the non-critical load capacity SNC2_Load, converter devices 212-214 supply power to each of loads N21 and N22. Specifically, the capacity S2_GFM provided by converter devices 212-214 is used to supply power to each of loads N21 and N22.

[0207] In some embodiments, when the capacity S1_GFM is greater than the critical load withdrawal capacity SC1_Load but less than the load withdrawal capacity S1_Load, converter devices 112-114 operate in GFM mode, and converter devices 115-116 operate in GFL mode, jointly supplying power to loads N11 and N12. Specifically, the capacity S1_GFM provided by converter devices 112-114 and the capacity S1_GFL provided by converter devices 115-116 are jointly supplied to loads N11 and N12. In this case, when the required capacity of load N11 changes, the operation of converter devices 112-114 in GFM mode can further absorb the change in the required capacity of load N11. Correspondingly, when the capacity S2_GFM is greater than the critical load extraction capacity SC2_Load but less than the load extraction capacity S2_Load, converter devices 212-214 operate in GFM mode, and converter devices 215-216 operate in GFL mode to jointly supply power to loads N21 and N22. Specifically, the capacity S2_GFM provided by converter devices 212-214 and the capacity S2_GFL provided by converter devices 215-216 are jointly supplied to loads N21 and N22. At this time, when the capacity required by load N21 changes, the operation of converter devices 212-214 in GFM mode can further absorb the change in the capacity required by load N21.

[0208] In other embodiments, when the capacity S1_GFM is less than the critical load capacity SC1_Load, each of converter devices 112-116 supplies power to loads N11 and N12. When the power required by the changes in loads N11 and N12 exceeds the power that converter devices 112-116 can provide, causing a voltage drop, controller 111 disconnects switch CBN12, causing microgrid 110 to stop supplying power to load N12. Specifically, the capacity S1_GFM provided by converter devices 112-114 and the capacity S1_GFL provided by converter devices 115-116 are used to supply power to loads N11 and N12. When the capacity S1_GFM provided by converter devices 112-114 is insufficient to absorb the changes in capacity required by load N11, controller 111 unloads load N12, allowing microgrid 110 to maintain power supply to load N11. Correspondingly, when the capacity S2_GFM is less than the critical load capacity SC2_Load, each of the converter devices 212-216 is used to supply power to loads N21 and N22. At this time, if the converter devices 212-214 operating in GFM mode are insufficient to absorb changes in the capacity required by load N21, the controller 211 will disconnect the switch CBN22, causing the microgrid 210 to stop supplying power to load N22. Specifically, the capacity S2_GFM provided by converter devices 212-214 and the capacity S2_GFL provided by converter devices 215-216 are used to supply power to loads N21 and N22. When the capacity S2_GFM provided by converter devices 212-214 is insufficient to absorb changes in the capacity required by load N21, the controller 211 will unload load N22, allowing the microgrid 210 to maintain power supply to load N21.

[0209] In other scenarios, when loads N11 and N21 are non-critical loads, and loads N12 and N22 are critical loads, loads N12 and N22 have critical load removal capacities SC1_Load and SC2_Load, respectively, while loads N11 and N21 have non-critical load removal capacities SNC1_Load and SNC2_Load, respectively. In this case, the operation of microgrids 110 and 210 is similar to the previous scenario, only requiring the replacement of loads N11 and N21 with loads N12 and N22, respectively. Therefore, the similarities will not be repeated.

[0210] Also refer to Figure 5 and Figure 4 In the embodiments disclosed herein, the switching of converter devices 112-114 and 212-214 to GFM mode is not limited to. In various variations, each of converter devices 112-116 and 212-216 can switch between GFM mode and GFL mode.

[0211] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of this art, the content of this disclosure, and the specific content thereof. Certain terms used to describe this disclosure will be discussed elsewhere in this specification to provide additional guidance to those skilled in the art in describing this disclosure.

[0212] While specific embodiments of the present disclosure have been disclosed in relation to the above embodiments, these embodiments are not intended to limit the present disclosure. Various alternatives and modifications can be made by those skilled in the art without departing from the principles and spirit of the present disclosure. Therefore, the scope of protection of the present disclosure is determined by the scope of the appended claims.

Claims

1. An electric power system, comprising: The mains power network is connected to the first switch; as well as A microgrid, connected to the mains network via the first switch, the microgrid comprising: Multiple converter devices are connected to the bus; A controller is connected to each of the first switch and each of the plurality of converter devices, and is used to transmit a plurality of first signals; as well as Multiple loads are connected to the multiple converter devices via the bus. The mains power network is connected to the bus via the first switch and is used to supply power to the plurality of loads. The controller is further configured to detect the first line connecting the mains power network and the microgrid, and to determine whether the first line is abnormal. When the controller determines that the first line is abnormal, the controller disconnects the first switch and switches the first part of the multiple converter devices to operate as a voltage source through the multiple first signals.

2. The power system according to claim 1, wherein When the controller determines that the first line is normal, the controller keeps the first switch on, and each of the plurality of converter devices operates as a current source, different from the voltage source. When the controller determines that the first line is abnormal, the second part of the plurality of converter devices operates in the form of the current source, and the second part is different from the first part.

3. The power system according to claim 2, wherein the plurality of converter devices comprises: Multiple converters are connected to the bus; and Multiple energy storage systems are connected to the multiple converters, respectively. in, When the first portion of the plurality of converter devices operates as the voltage source, the plurality of energy storage systems corresponding to the first portion of the plurality of converters are used to supply power to the plurality of loads.

4. The power system according to claim 2, wherein the controller is further configured to: Calculate the first capacity of the first portion of the plurality of converter devices when the first portion operates in the form of the voltage source, and Calculate the second capacity of the second portion when the second portion of the plurality of converter devices operates in the form of the current source.

5. The power system according to claim 4, wherein When the first capacity is greater than the third capacity of the plurality of loads, the first portion of the plurality of converter devices is used to supply power to each of the plurality of loads. When the first capacity is less than the third capacity, and the first capacity is greater than the fourth capacity of the third portion of the plurality of loads, the first and second portions of the plurality of converter devices are used to supply power to the fourth capacity of the plurality of loads, and when the fourth capacity changes, the first portion of the plurality of converter devices is used to absorb the capacity change. When the first capacity is less than the fourth capacity, and when the sum of the first capacity and the second capacity is greater than the fourth capacity, each of the first portion and the second portion of the plurality of converter devices supplies power to the third capacity of the plurality of loads.

6. The power system according to claim 4, wherein When the voltage level of the first switching voltage is lower than the lower limit voltage level or higher than the upper limit voltage level, the controller determines that the first line is abnormal, and When the first part of the plurality of converter devices switches to the voltage source mode, each of the first parts sends back a plurality of status parameters to the controller, the plurality of status parameters including at least the output voltage of each of the first parts.

7. The power system according to claim 2, wherein the plurality of converter devices further comprises: Multiple inverters are connected to the bus; and Multiple renewable energy devices are connected to the multiple inverters, respectively. in, When the first portion of the plurality of converter devices operates as the voltage source, the plurality of regenerative energy devices corresponding to the first portion of the plurality of inverters are used to supply power to the plurality of loads.

8. A method for operating a power system, comprising: The mains power network is connected to multiple microgrids via multiple lines through multiple switches; Detect multiple voltages of the multiple switches, and determine whether the multiple circuits are abnormal based on the multiple voltages; When it is determined that the first line of the plurality of lines is abnormal, the first switch of the plurality of switches is disconnected, and the first part of the multiple converter devices in the first microgrid of the plurality of microgrids connected to the first line is switched to voltage source mode operation. as well as When the first line is determined to be normal, the first switch remains engaged, and each of the plurality of converter devices operates as a current source, different from the voltage source type. When the first line is determined to be abnormal, the second part of the plurality of converter devices operates in the form of the current source, and the second part is different from the first part.

9. The method for operating a power system according to claim 8, further comprising: When it is determined that the second line of the plurality of lines is abnormal, and the first line is normal, the second switch of the plurality of switches is disconnected, and the third part of the plurality of converter devices in the second microgrid of the plurality of microgrids connected to the second line is switched to the voltage source mode for operation; and When the second line is determined to be normal, the second switch remains engaged, and each of the plurality of converter devices operates as a current source, different from the voltage source. in, When an anomaly is detected in the second line, the fourth section of the plurality of converter devices operates as a current source, and the fourth section differs from each of the first, second, and third sections. When the second line is determined to be abnormal and the first line is normal, each of the first and second parts of the plurality of converter devices operates as the current source.

10. The method of operating a power system according to claim 9, further comprising: Calculate the first capacity of the first part operating in the form of the voltage source, and the second capacity of the second part operating in the form of the current source; Calculate the third capacity of the third part operating in the form of a voltage source, and the fourth capacity of the fourth part operating in the form of a current source. in, When the first capacity is greater than the fifth capacity of the plurality of loads in the first microgrid, the first portion is used to supply power to each of the plurality of loads. When the third capacity is less than the sixth capacity of the plurality of loads of the second microgrid, and the third capacity is greater than the seventh capacity of the seventh portion of the plurality of loads of the second microgrid, each of the plurality of converter devices is used to supply power to each of the plurality of loads.

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