A distributed low-carbon control method for isolated AC / DC hybrid microgrids

Abstract

The present invention relates to the technical field of operation control of an AC / DC hybrid microgrid group, and provides a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group, wherein the carbon emission of a distributed power source is derived from the active output to obtain a carbon emission micro-increase rate; a distributed low-carbon control target is formulated according to an equal carbon emission micro-increase rate criterion; a hierarchical distributed low-carbon control architecture is constructed according to the distributed low-carbon control target; distributed power sources are controlled based on a leader-follower framework, secondary control items are obtained, and low-carbon droop control is introduced to achieve distributed low-carbon control at the microgrid level, and the deviation of the carbon emission micro-increase rate between microgrids is introduced into an interconnected converter and brought into a PI controller to achieve low-carbon control at the microgrid group level. The present invention can significantly reduce the carbon emissions of the system, and can be reduced by about 2.6% under different load conditions.

Description

Technical Field

[0001] The present invention relates to the field of low-carbon control of microgrid groups, and in particular to a distributed low-carbon control method for isolated island AC / DC hybrid microgrid groups. Background Art

[0002] With the gradual shortage of fossil energy, distributed generation (DGs) based on photovoltaic, wind turbines and energy storage are widely used in new power systems due to their advantages of flexible access points, low environmental pollution and high energy supply. However, the unstable output and diverse structures of distributed generation also bring severe challenges to the operation and control of power systems.

[0003] In order to solve the above problems and further improve energy utilization, the concept of microgrid clusters has been proposed. Among the various types of microgrid clusters, AC / DC hybrid microgrid clusters can integrate geographically adjacent microgrids with different power supply forms. It has the advantages of low investment, high power quality, and strong power supply capacity, and has gradually become the main development direction of microgrid clusters.

[0004] In the existing research on the operation and control of AC / DC hybrid microgrid groups, it can be roughly divided into two categories: power coordination control method and distributed collaborative control method. In the power coordination control method, by designing appropriate control strategies for the microgrid layer and the microgrid group layer, the reasonable distribution of power between DGs in each microgrid and the stable operation of bus voltage can be achieved under low communication / no communication conditions. In the distributed collaborative control method, the microgrid group and each distributed power controller are based on a consistency algorithm to ensure that the frequency and voltage of each microgrid are restored to the rated value, and the reasonable distribution of the output power of each DG in the system is achieved to ensure its safe and stable operation.

[0005] For carbon emission reduction regulation of microgrid groups, existing studies mostly adopt upper-level optimization scheduling and energy management methods. For example, a multi-objective optimization scheduling method for multi-energy microgrids, a multi-objective optimization configuration method based on cloud energy storage, and a two-level robust optimization scheduling model are proposed, which take into account the economy and environmental friendliness of system operation. As for the introduction of carbon emission rights trading mechanism, existing studies have proposed a microgrid low-carbon economic configuration method involving step-by-step carbon trading, a multi-microgrid power sharing operation optimization method, and an electricity-heat-carbon emission rights sharing method based on master-slave game.

[0006] In the existing research on the operation and control of AC / DC hybrid microgrids, for the power coordination control method, when heavy loads are connected to the system, the frequency and voltage will deviate from the rated value, affecting the stable operation of the system. For the distributed collaborative control method, although the recovery of system frequency and voltage and the reasonable allocation of output power of each power source are achieved, the control of system carbon emissions is ignored.

[0007] For carbon emission reduction control, existing methods are mostly used for DG power generation scheduling. By establishing a DG carbon emission model, the carbon emissions are converted into carbon emission costs and included in the total power generation cost. This method belongs to the upper-level optimization scheduling and energy management. There is a large time scale difference between this layer and the control layer, which is not conducive to the low-carbon control of isolated AC / DC hybrid microgrid groups at multiple time scales. Summary of the invention

[0008] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention provides a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group. By introducing a carbon emission micro-increase rate in the secondary control link of the distributed power source, it not only ensures the recovery of the AC microgrid frequency and the common DC bus voltage, but also realizes distributed low-carbon control at the microgrid level. By introducing the deviation of the carbon emission micro-increase rate of each microgrid in the control link of the inter-grid interconnection converter, low-carbon control at the microgrid group level is realized. The present invention can significantly reduce the carbon emissions of the system, which can be reduced by about 2.6% under different load conditions.

[0009] The present invention provides a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group, comprising:

[0010] S1: The carbon emission micro-increase rate is obtained by differentiating the carbon emission of distributed power sources in the isolated AC / DC hybrid microgrid group with respect to the active output;

[0011] S2: Formulate the distributed low-carbon control target of the isolated AC / DC hybrid microgrid group according to the equal carbon emission micro-increase rate criterion;

[0012] S3: Construct a hierarchical distributed low-carbon control architecture based on the distributed low-carbon control objectives;

[0013] S4: Based on the leader-follower framework, distributed power sources are controlled to obtain secondary control items, which are introduced into low-carbon droop control to achieve low-carbon control of the microgrid converter control layer in the hierarchical distributed low-carbon control architecture;

[0014] S5: By introducing the deviation of the carbon emission micro-increase rate between microgrids into the interconnected converter and bringing it into the PI controller, low-carbon control of the control layer of the interconnected converter between microgrids in the hierarchical distributed low-carbon control architecture is realized;

[0015] S6: Low-carbon and stable operation of the microgrid group is achieved through low-carbon control of the microgrid converter control layer and low-carbon control of the interconnected converter control layer.

[0016] Furthermore, the isolated AC / DC hybrid microgrid group generates carbon emissions through the power generation link of distributed power sources. The isolated AC / DC hybrid microgrid group includes an AC microgrid, a DC microgrid and an inter-grid interconnection converter.

[0017] Furthermore, in step S1, the carbon emission micro-increase rate of the distributed power source is expressed as:

[0018]

[0019] in, is the slight increase rate of carbon emissions from distributed power sources, It is the active power output of distributed power sources. is the carbon emission coefficient of the first distributed power source, is the carbon emission coefficient of the second distributed power source;

[0020] According to the Lagrange multiplier method, when the carbon emission increment rate of all distributed power sources in the isolated AC / DC hybrid microgrid group is equal, the carbon emissions reach the minimum.

[0021] Furthermore, in the step S2,

[0022] The low-carbon control target of the AC microgrid is to restore the frequency of the AC microgrid to its rated value and to allocate active power to the grid-forming units and grid-following units in the AC microgrid according to the principle of equal carbon emission micro-increase rate;

[0023] The low-carbon control target of the DC microgrid is to restore the common DC bus voltage of the DC microgrid to its rated value and to allocate active power to the dispatchable units and power units in the DC microgrid according to the principle of equal carbon emission micro-increase rate;

[0024] The low-carbon control target of the inter-grid interconnected converter is to realize the active power interaction between the microgrids through the inter-grid interconnected converter, so as to ensure the consistency of the carbon emission micro-increase rate of each microgrid in the isolated AC / DC hybrid microgrid group.

[0025] Furthermore, in the step S3, the distributed low-carbon control architecture of the isolated AC / DC hybrid microgrid group includes a microgrid converter control layer and an inter-grid interconnection converter control layer.

[0026] Furthermore, in the step S4, the distributed low-carbon control method of the microgrid converter control layer is:

[0027] By replacing the output active power with the carbon emission micro-increase rate of the distributed power source, the traditional droop control is improved to low-carbon droop control, so that each distributed power source in the microgrid can distribute the output active power according to the equal carbon emission micro-increase rate principle;

[0028] The outer loop of the AC microgrid obtains the bus voltage reference value or the carbon emission micro-increase rate reference value of the distributed power source through a consistency algorithm, and the inner loop adopts a voltage and current double closed-loop control structure to achieve zero-static error tracking of the reference value;

[0029] The outer loop of the DC microgrid converts the carbon emission micro-increase rate into a power reference value, and the inner loop adopts a current single-loop control structure to achieve zero-static error tracking of the reference value.

[0030] Furthermore, the interconnected converter control outer loop receives information from the connected local microgrid and adjacent interconnected converters, adjusts the transmission power reference value, coordinates the mutual power between microgrids, and achieves the low-carbon control goal of the interconnected converters between networks.

[0031] After obtaining the reference value of the transmission power of the interconnected converters through the outer loop, the inner loop adopts a current single-loop control structure to achieve rapid tracking of the reference value.

[0032] Furthermore, the AC microgrid is based on a leader-follower framework, with the grid-building unit as the leader and the grid-following unit as the follower, to construct a distributed low-carbon control method of the grid-building-grid-following unit, including:

[0033] Primary control of the grid-forming units and grid-following units of the AC microgrid;

[0034] The low carbon droop control expression of GFMU converter is:

[0035]

[0036] in, is the frequency collected by the nbth grid-forming unit GFMU-nb in the nth AC microgrid, is the frequency rating of the nbth grid-forming unit GFMU-nb in ACMG-n; is the carbon emission increment rate of the nbth grid-type unit in ACMG-n, is the droop coefficient of GFMU-nb;

[0037] The low carbon droop control expression of GFLU converter is:

[0038]

[0039] in, is the frequency collected by the nwth grid-type unit GFLU-nw, The frequency rating value collected for the nwth grid-following unit GFLU-nw, is the carbon emission slight increase rate of GFLU-nw, is the droop coefficient of GFLU-nw;

[0040] The secondary control expression of GFMU converter is:

[0041]

[0042] in, It is the consistency control input of GFMU-nb. is a positive gain of GFMU-nb, is the PI controller transfer function of GFMU-nb, is the communication weight between node nb and its neighboring node nw, is the set of adjacent nodes of node nb, is the secondary control quantity of the output frequency of GFMU-nb;

[0043] The secondary control expression of GFLU converter is:

[0044]

[0045] in, is the consistency control input of GFLU-nw, is a positive gain of GFLU-nw, is the PI controller transfer function of GFLU-nw, is the set of adjacent nodes of node nw, is the communication weight between node nw and its neighboring node nb, is the secondary control amount of GFLU-nw;

[0046] The secondary control variable is introduced into the low-carbon droop control to achieve the low-carbon control target of the AC microgrid.

[0047] Furthermore, the DC microgrid is based on the leader-follower framework, with the dispatchable unit as the leader and the power unit as the follower, to build a dispatchable-power unit distributed low-carbon control, including:

[0048] Primary control of dispatchable units and power units of DC microgrid:

[0049] The primary control of DU converter, the low carbon droop control expression of DU converter is:

[0050]

[0051] in, is the carbon emission slight increase rate of the oth dispatchable unit in DCMG, is the low carbon droop coefficient of DU-o, is the common DC bus voltage, is the rated value of the common DC bus voltage;

[0052] The primary control of PU converter, the low carbon droop control expression of PU converter is:

[0053]

[0054] in, is the slight increase rate of carbon emission of PU-z, is the low carbon droop coefficient of PU-z,

[0055] The main goal of the secondary control of the DC microgrid converter is to restore the voltage of the common DC bus while achieving the output of active power by each power source according to the equal carbon emission micro-increase rate criterion;

[0056] The secondary control expression of DU converter is:

[0057]

[0058] in, is the output voltage value of DU-o, is the secondary control quantity of DU-o, It is the consistency control input of DU-o. is a positive gain of DU-o, is the communication weight between node o and its neighboring node z, is the PI controller transfer function of DU-o, The set of adjacent nodes of node o;

[0059] The secondary control expression of PU converter is:

[0060]

[0061] in, is the secondary control quantity of PU-z, is the consistency control input of PU-z, is a positive gain of PU-z, is the communication weight between node z and its neighboring node o, is the PI controller transfer function of PU-z, The set of neighboring nodes of node PU-z;

[0062] The secondary control variable is introduced into the low-carbon droop control to achieve the low-carbon control target of the DC microgrid.

[0063] Furthermore, the grid-forming unit of the AC microgrid and the dispatchable unit of the DC microgrid respectively transmit the average value information of the carbon emission micro-increase rate of the power supply of their microgrids to the inter-grid interconnection converter. The interconnection converter makes a difference between the average values ​​of the carbon emission micro-increase rate of the two connected microgrids and brings it into the PI controller. When the system enters a steady state, the input of the PI controller is 0, realizing a low-carbon control between microgrids.

[0064] The secondary control expression of the interconnected converter is:

[0065]

[0066] in, is the power reference value of IC-r, is the secondary control quantity of IC-r, is the communication weight between the interconnected converter node r and its adjacent node s, is the carbon emission micro-increase rate deviation of the microgrids on both sides of IC-r, is the carbon emission slight increase rate of the neighboring node s of node r, is a positive gain of IC-r, is the set of adjacent nodes of IC-r, is the PI controller transfer function of IC-r secondary control, is the PI controller transfer function of IC-r.

[0067] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects:

[0068] The present invention provides a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group. By introducing a carbon emission micro-increase rate in the secondary control link of the distributed power source, it not only ensures the recovery of the AC microgrid frequency and the common DC bus voltage, but also realizes distributed low-carbon control at the microgrid level. By introducing the deviation of the carbon emission micro-increase rate of each microgrid in the control link of the inter-grid interconnection converter, low-carbon control at the microgrid group level is realized. The present invention can significantly reduce the carbon emissions of the system, which can be reduced by about 2.6% under different load conditions.

[0069] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0071] Figure 1 It is a flow chart of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group provided by the present invention.

[0072] Figure 2 The invention provides a distributed low-carbon control block diagram of a GFMU converter of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0073] Figure 3The invention provides a distributed low-carbon control block diagram of a GFLU converter of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0074] Figure 4 The invention provides a distributed low-carbon control block diagram of a DU converter of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0075] Figure 5 The invention provides a distributed low-carbon control block diagram of a PU converter of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0076] Figure 6 The invention provides a distributed low-carbon control block diagram of interconnected converters of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0077] Figure 7 It is an AC microgrid frequency curve and a common DC bus voltage curve diagram of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group provided by the present invention.

[0078] Figure 8 It is a carbon emission micro-increase rate curve of each DG of the AC microgrid in the distributed low-carbon control method of an isolated AC / DC hybrid microgrid group provided by the present invention.

[0079] Fig. 9 It is a carbon emission micro-increase rate curve of each DG of the AC microgrid under normal working conditions of the communication link of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group provided by the present invention.

[0080] Fig.10 It is a carbon emission micro-increase rate curve of each DG of the AC microgrid under the communication link failure condition of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group provided by the present invention.

[0081] Fig.11 The present invention provides a frequency curve of each DG of an AC microgrid and a common DC bus voltage curve under a traditional method of a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0082] Fig.12 It is a carbon emission micro-increase rate curve of each DG of the AC microgrid under the traditional method of the distributed low-carbon control method of the isolated AC / DC hybrid microgrid group provided by the present invention.

[0083] Fig.13 The invention provides a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group, and provides a frequency curve of each DG of the AC microgrid and a common DC bus voltage curve under the method of the invention.

[0084] Fig.14It is a carbon emission micro-increase rate curve of each DG of the AC microgrid under the method of the present invention of the distributed low-carbon control method of an isolated AC / DC hybrid microgrid group provided by the present invention.

[0085] Fig.15 The present invention provides a method for distributed low-carbon control of an isolated AC / DC hybrid microgrid group according to a traditional method and a system carbon emission curve under the method of the present invention. DETAILED DESCRIPTION

[0086] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0087] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0088] Combine the following Figures 1 to 15 The present invention describes a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group.

[0089] like Figure 1 As shown, a distributed low-carbon control method for an isolated AC / DC hybrid microgrid group includes:

[0090] S1: The carbon emission micro-increase rate is obtained by differentiating the carbon emission of distributed power sources in the isolated AC / DC hybrid microgrid group with respect to the active output;

[0091] The isolated AC / DC hybrid microgrid group includes multiple AC microgrids (ACMG), multiple DC microgrids (DCMG) and multiple interlinking converters (ICs). The ACMG is connected to the DC bus of the DCMG through ICs to achieve DC side coupling of multiple microgrids.

[0092] In an isolated AC / DC hybrid microgrid group, the distributed generation sources (DGs) in the AC microgrid include grid-forming units (GFMUs) and grid-following units (GFLUs). Among them, GFMUs usually use droop control characteristics to simulate voltage sources and provide voltage support for the AC microgrid bus. GFLUs use droop control characteristics to simulate current sources and participate in the power regulation of the system by collecting bus frequency. The distributed generation sources in the DC microgrid include dispatchable units (DUs) and power units (PUs). DUs use droop control characteristics to simulate voltage sources and provide voltage support for the common DC bus. PUs simulate current sources and respond to DC voltage changes by adjusting their own output power. DGs in the AC microgrid and DGS in the DC microgrid can directly participate in the power management of the system. DGS includes fuel cells (FC), micro gas turbines (MGT), etc. Clean renewable energy based on distributed photovoltaics generally adopts maximum power point tracking control to achieve maximum energy utilization by tracking the power reference value. The present invention regards such DG as a load with negative power characteristics.

[0093] The microgrid group contains N AC microgrids, the nth AC microgrid is ACMG-n, It contains nb grid-forming units and nw grid-following units. The AC microgrid realizes power interaction between microgrids through the connected ICs; the DC microgrid contains o dispatchable units and z power units. The converters and ICs of each unit in the AC microgrid adopt two-level voltage source converters, and each unit in the DC microgrid adopts conventional bidirectional DC / DC converters.

[0094] The communication network of the AC / DC hybrid microgrid group consists of a microgrid communication layer and an interconnected converter communication layer. In the microgrid communication layer, each unit in the microgrid is equipped with an intelligent agent; in the interconnected converter communication layer, each IC is equipped with an intelligent agent. A networking unit in each AC microgrid establishes a communication link with the connected IC, and a dispatchable unit in the DC microgrid establishes a communication link with each IC.

[0095] The carbon emissions generated by the isolated AC / DC hybrid microgrid group are mainly generated by the power generation link of its distributed power sources. For DG such as fuel cells, the relationship between output and carbon emissions is calculated as follows:

[0096]

[0097] in, It is the active power output of distributed power sources. is the carbon emissions of distributed power generation, is the carbon emission coefficient of the first distributed power source, is the carbon emission coefficient of the second distributed power source, is the carbon emission coefficient of the third distributed power source; , , It can be calculated from the fuel consumption coefficient.

[0098] The main goal of low-carbon control of microgrid groups is to minimize the total carbon emissions of the system. The calculation expression is:

[0099]

[0100] in, is the total carbon emissions of the system, is the minimum value of the total carbon emissions of the system, ACMG-n Carbon emissions per DG, ACMG-n The active contribution of each DG, ACMG-n The maximum active output of a DG, ACMG-n The minimum active output of a DG, For the first time in DCMG Carbon emissions per DG, For the first time in DCMG The active contribution of each DG, For the first time in DCMG The maximum active output of a DG, For the first time in DCMG The minimum active output of a DG, is the local load of ACMG-n, is the local load of DCMG, Delivers power to the IC connected to the ACMG-n.

[0101] In some embodiments of the present invention, the carbon emission micro-increase rate of DG is defined with reference to the concept of cost micro-increase rate proposed in economics. The carbon emission micro-increase rate of DG is calculated as follows:

[0102]

[0103] in, is the slight increase rate of carbon emissions from distributed power sources,

[0104] According to the Lagrange multiplier method, when the carbon emission increment rate of all DGs in the isolated AC / DC hybrid microgrid group is equal, the carbon emissions of the system will be minimized.

[0105] In some embodiments of the present invention, nodes represent intelligent agents in reality, and each layer of the communication network is an undirected graph. ,in For the picture The node set of For the picture The edge set of is the set of neighboring nodes of the ith node; the communication weight between adjacent nodes is the adjacency matrix When hour, ,otherwise, , undirected graph The degree matrix of , where the elements is the sum of the communication weights between node i and its adjacent nodes. The communication network can be represented by its Laplace matrix:

[0106]

[0107] in, is the Laplace matrix elements.

[0108] In some embodiments of the present invention, a leader-follower consensus (LFC) framework is adopted, where a part of the intelligent agents in the communication network are regarded as leaders, and while performing the consensus protocol, additional control objectives are achieved; the other part of the intelligent agents are regarded as followers, and perform the consensus protocol;

[0109] Setting up a node set The first nl nodes in the group are leaders, and the last N-nl nodes are followers. Then the leader node set for , follower node set Can be defined as , the follower's consistency protocol is:

[0110]

[0111] in, For Node The control input, For Node The state quantity of

[0112] The leader's consistency protocol is based on the follower's consistency protocol, introducing an external input, expressed as:

[0113]

[0114] in, For external input,

[0115] It can guide all agents in the system to reach a consensus agreement in a predetermined manner.

[0116] S2: Formulate the distributed low-carbon control target of the isolated AC / DC hybrid microgrid group according to the equal carbon emission micro-increase rate criterion;

[0117] S21: Low-carbon control objectives of AC microgrids:

[0118] To restore the frequency of the AC microgrid to its rated value:

[0119]

[0120] in, is the AC bus frequency of ACMG-n, is the AC bus frequency rating of ACMG-n;

[0121] The active power of the grid-forming units and the grid-following units in the AC microgrid is allocated according to the principle of equal carbon emission micro-increase rate:

[0122]

[0123] in, ACMG-n The carbon emission rate of each grid-type unit increases slightly. is the carbon emission increment rate of the nbth grid-type unit in ACMG-n, is the carbon emission slight increase rate of the first grid-type unit in ACMG-n, is the carbon emission micro-increase rate of the nwth grid-type unit in ACMG-n;

[0124] S22: Low-carbon control objectives of DC microgrids:

[0125] To restore the common DC bus voltage of the DC microgrid to its rated value:

[0126]

[0127] in, is the common DC bus voltage, is the rated value of the common DC bus voltage;

[0128] The dispatchable units and power units in the DC microgrid are allocated active power according to the principle of equal carbon emission micro-increase rate:

[0129]

[0130] in, is the carbon emission slight increase rate of the first dispatchable unit DG in DCMG, is the carbon emission slight increase rate of the oth dispatchable unit in DCMG, is the carbon emission slight increase rate of the first power unit in DCMG, is the carbon emission slight increase rate of the zth power unit in the DCMG.

[0131] S23: Low-carbon control objectives of interconnected converters:

[0132] Active power interaction between microgrids is achieved through inter-grid interconnected converters, ensuring that the carbon emission micro-increase rate of each microgrid in the isolated AC / DC hybrid microgrid group is consistent:

[0133]

[0134] in, is the carbon emission increase rate of DG in the first AC microgrid, is the carbon emission increase rate of DG in the rth AC microgrid, is the carbon emission increase rate of DG in the DC microgrid.

[0135] S3: Construct a hierarchical distributed low-carbon control architecture based on the distributed low-carbon control objectives;

[0136] The distributed low-carbon control architecture of the isolated AC / DC hybrid microgrid group includes the microgrid converter control layer and the grid interconnected converter control layer.

[0137] S4: Based on the leader-follower framework, distributed power sources are controlled to obtain secondary control items, which are introduced into low-carbon droop control to achieve low-carbon control of the microgrid converter control layer in the hierarchical distributed low-carbon control architecture;

[0138] In the microgrid converter control layer, the AC microgrid and the DC microgrid control the DG devices therein based on the LFC framework, obtain the secondary control quantity, and introduce it into the low-carbon droop control to achieve the low-carbon control target of the AC microgrid and the low-carbon control target of the DC microgrid;

[0139] The outer loop of the AC microgrid obtains the bus voltage reference value or the carbon emission micro-increase rate reference value of the distributed power source through a consistency algorithm, and the inner loop adopts a voltage and current double closed-loop control structure to achieve zero-static error tracking of the reference value;

[0140] The outer loop of the DC microgrid converts the carbon emission micro-increase rate into a power reference value, and the inner loop adopts a current single-loop control structure to achieve zero-static error tracking of the reference value;

[0141] Outer loop control includes primary control and secondary control.

[0142] S41: Distributed low-carbon control of AC microgrids;

[0143] like Figure 2 Shown and Figure 3 As shown, based on the LFC framework, the present invention regards GFMUs as leaders and GFLUs as followers, and designs a distributed low-carbon control of the grid-building and grid-following type units.

[0144] S411: Low carbon control of GFMU converter;

[0145] S4111: GFMU converter primary control;

[0146] As the primary control of the GFMU converter, the low-carbon droop control improves the traditional droop control and introduces the carbon emission micro-increase rate of DGs instead of the output active power into the droop formula to ensure that under no communication conditions, each DG in the microgrid can distribute the output active power according to the equal carbon emission micro-increase rate criterion. The low-carbon droop control expression of the GFMU converter is:

[0147]

[0148] in, is the frequency of the nbth meshing unit GFMU-nb in ACMG-n, is the frequency rating of the nbth grid-forming unit GFMU-nb in ACMG-n; is the carbon emission slight increase rate of GFMU-nb, is the droop coefficient of GFMU-nb;

[0149] S4112: GFMU converter secondary control;

[0150] Although the primary control can ensure that each power source in the microgrid outputs active power according to the equal carbon emission micro-increase rate principle, it will cause the bus frequency to deviate from the rated value. Therefore, a secondary control structure needs to be designed to achieve the low-carbon control goal of the AC microgrid.

[0151] like Figure 2 As shown, the secondary control expression of GFMU converter is:

[0152]

[0153] in, It is the consistency control input of GFMU-nb. is a positive gain of GFMU-nb, is the PI controller transfer function of GFMU-nb, is the communication weight between node nb and its neighboring node nw, is the set of adjacent nodes of node nb, is the secondary control quantity of the output frequency of GFMU-nb;

[0154] One of the neighboring nodes of GFMU-nb is GFLU-nw, and the set of neighboring nodes of GFMU-nb is determined according to the actual communication topology of the system;

[0155] The secondary control quantity is introduced into the low-carbon droop control to achieve the low-carbon control target of the AC microgrid.

[0156] The calculation expression is:

[0157]

[0158] in, is the output frequency reference value of GFMU-nb.

[0159] S4113: GFMU converter inner loop control;

[0160] The inner control loop of the GFMU converter adopts the voltage and current control loop. The voltage and current loop expressions are:

[0161]

[0162] in, is the d-axis component of the inductor current reference value, is the q-axis component of the inductor current reference value, is the d-axis component of the voltage reference value, are the q-axis components of the voltage reference value, is the d-axis component of the bus voltage, is the q-axis component of the bus voltage, is the PI controller transfer function of the GFMU-nb voltage loop, is the filter capacitor, is the electrical angular velocity;

[0163]

[0164] in, is the d-axis component of the carrier voltage reference value, is the q-axis component of the carrier voltage reference value, is the d-axis component of the inductor current reference value, is the q-axis component of the inductor current reference value, is the d-axis component of the inductor current, is the q-axis component of the inductor current; is the PI controller transfer function of the GFMU-nb current loop, is the filter inductor,

[0165] S412: Low carbon control of GFLU converter;

[0166] S4121: primary control of GFLU converter;

[0167] As the primary control of the GFLU converter, low-carbon droop control improves the traditional droop control and introduces the carbon emission micro-increase rate of DGs instead of the output active power into the droop formula to ensure that under no communication conditions, each DG in the microgrid can distribute the output active power according to the equal carbon emission micro-increase rate criterion. The low-carbon droop control expression is:

[0168]

[0169] in, is the frequency collected by the nwth grid-type unit GFLU-nw, The frequency rating value collected for the nwth grid-following unit GFLU-nw, is the carbon emission slight increase rate of GFLU-nw; is the droop coefficient of GFLU-nw;

[0170] like Figure 3 As shown, S4122: The secondary control expression of the GFLU converter is:

[0171]

[0172] in, is the consistency control input of GFLU-nw, is a positive gain of GFLU-nw, is the PI controller transfer function of GFLU-nw, is the set of adjacent nodes of node nw, is the communication weight between node nw and its neighboring node nb, is the secondary control amount of GFLU-nw;

[0173] One of the neighboring nodes of GFLU-nw is GFMU-nb, and the neighboring node set of GFLU-nw is determined according to the actual communication topology of the system.

[0174] The secondary control quantity is introduced into the low-carbon droop control to achieve the low-carbon control target of the AC microgrid.

[0175] The calculation expression is:

[0176]

[0177] in, is the reference value of carbon emission micro-increase rate of GFLU-nw;

[0178] S4123: GFLU converter inner loop control;

[0179] After the outer loop obtains the reference value of the GFLU carbon emission micro-increase rate, the inner loop uses the current loop control to obtain the carrier voltage reference value;

[0180]

[0181] in, is the d-axis component of the carrier voltage reference value, is the q-axis component of the carrier voltage reference value, is the d-axis component of the inductor current reference value, is the q-axis component of the inductor current reference value, is the d-axis component of the inductor current, is the q-axis component of the inductor current; is the PI controller transfer function of the GFLU-nw current loop, For the filter inductor.

[0182] S42: Distributed low-carbon control of DC microgrids;

[0183] like Figure 4 and Figure 5 As shown, based on the LFC framework, the present invention regards DUs as leaders and PUs as followers, and designs a dispatchable-power type unit distributed low-carbon control;

[0184] S421: Low carbon control of DU converter;

[0185] S4211: DU converter primary control;

[0186] As the primary control of DU converter, low carbon droop control is expressed as:

[0187]

[0188] in, is the carbon emission slight increase rate of the oth dispatchable unit in DCMG, is the low carbon droop coefficient of DU-o;

[0189] S4212: DU converter secondary control;

[0190] The main goal of the secondary control of the DC microgrid converter is to ensure that each power source outputs active power according to the equal carbon emission micro-increase rate criterion while achieving the restoration of the common DC bus voltage;

[0191] like Figure 4 As shown, the secondary control expression of DU converter is:

[0192]

[0193] in, is the output voltage value of DU-o, is the secondary control quantity of DU-o, It is the consistency control input of DU-o. is a positive gain of DU-o, is the communication weight between node o and its neighboring node z, is the PI controller transfer function of DU-o, The set of neighboring nodes of node DU-o;

[0194] One of the neighboring nodes of DU-o is the power unit PU-z, and the real neighboring node set of DU-o depends on the actual communication topology of the system.

[0195] Introducing the secondary control amount into the low carbon droop control, the calculation expression is:

[0196]

[0197] in, is the output voltage reference value of DU-o,

[0198] S4213: DU converter inner loop control;

[0199] The inner loop control of DU converter adopts voltage and current loop control, and the calculation expression is:

[0200]

[0201] in, is the inductor current reference value, is the PI controller transfer function of the DU-o voltage loop.

[0202]

[0203] in, is the duty cycle reference value; is the inductor current, is the inductor current reference value; is the PI controller transfer function of the DU-o current loop.

[0204] S422: Low carbon control of PU converter;

[0205] S4221: primary control of PU converter;

[0206]

[0207] in, is the slight increase rate of carbon emission of PU-z, is the low carbon droop coefficient of PU-z,

[0208] like Figure 5 As shown, S4222: The secondary control expression of the PU converter is:

[0209] in, is the secondary control quantity of PU-z, is the consistency control input of PU-z, is a positive gain of PU-z, is the communication weight between node z and its neighboring node o, is the PI controller transfer function of PU-z, The set of neighboring nodes of node PU-z;

[0210] One of the neighboring nodes of PU-z is the schedulable unit DU-o. The real neighboring node set of PU-z depends on the actual communication topology of the system.

[0211] Introducing the secondary control amount into the low carbon droop control, the calculation expression is:

[0212]

[0213] in, is the reference value of the carbon emission slight increase rate of PU-z, is the output voltage value of PU-z;

[0214] S4223: inner loop control of PU converter;

[0215] After the outer loop obtains the reference value of the PU carbon emission micro-increase rate, the inner loop adopts the current loop control to obtain the reference value of the duty cycle.

[0216]

[0217] in, is the duty cycle reference value, is the inductor current, and is the inductor current reference value; is the PI controller transfer function of the PU-z current loop.

[0218] S5: By introducing the deviation of the carbon emission micro-increase rate between microgrids into the interconnected converter and bringing it into the PI controller, low-carbon control of the control layer of the interconnected converter between microgrids in the hierarchical distributed low-carbon control architecture is achieved.

[0219] like Figure 6 As shown, in the control layer of the interconnected converter, each ICs control outer loop adjusts its transmission power reference value by receiving information from the connected local microgrid and the adjacent IC, coordinates the mutual power between microgrids, and achieves the low-carbon control goal of the above-mentioned interconnected converter;

[0220] After the outer loop obtains the reference value of ICs transmission power, the inner loop adopts a current single-loop control structure to achieve rapid tracking of the reference value;

[0221] Since in the distributed low-carbon control of the microgrid converter, the DGs in the microgrid have allocated active power according to the equal carbon emission micro-increase rate criterion, the grid-forming unit and the dispatchable unit respectively transmit the average carbon emission micro-increase rate information of the power source of their microgrids to the inter-grid interconnected converter. The IC takes the difference of the average carbon emission micro-increase rate of the two connected microgrids and brings it into the PI controller. When the system enters a steady state, the PI controller input is "0", and a low-carbon control between microgrids can be achieved:

[0222]

[0223] in, is the average carbon emission increase rate of the AC microgrid connected to IC-r, is the average carbon emission increase rate of the DC microgrid connected to IC-r, is the carbon emission micro-increase rate deviation of the microgrids on both sides of IC-r, is the PI controller transfer function of IC-r,

[0224] In the above-mentioned primary low-carbon control method, each IC only collects the information of the connected local microgrid for control. This method is easy to cause different ICs to compete for the power of the same microgrid, which in turn causes power fluctuations of DGs in the microgrid, which seriously affects the normal operation of the system. To solve this problem, a secondary control method of IC is designed, and the calculation expression is:

[0225]

[0226] in, is the power reference value of IC-r, is the secondary control quantity of IC-r, is the communication weight between the interconnected converter node r and its adjacent node s, is the carbon emission micro-increase rate deviation of the microgrids on both sides of the adjacent nodes of node r, is a positive gain of IC-r, is the set of adjacent nodes of IC-r, is the PI controller transfer function of IC-r secondary control;

[0227] Inner loop control of interconnected converters;

[0228] The inductor current reference value is obtained according to the power calculation formula in the dq coordinate system, and the inner loop adopts the current loop control to obtain the carrier voltage reference value;

[0229]

[0230] in, is the d-axis component of the carrier voltage reference value, is the q-axis component of the carrier voltage reference value, is the d-axis component of the inductor current reference value, is the q-axis component of the inductor current reference value, is the d-axis component of the inductor current, is the q-axis component of the inductor current; is the PI controller transfer function of the IC-r current loop, For the filter inductor.

[0231] S6: The low-carbon and stable operation of the microgrid group is ensured through the low-carbon control of the microgrid converter control layer and the low-carbon control of the interconnected converter control layer.

[0232] In order to verify the effectiveness of the distributed low-carbon control method proposed in the present invention, an island AC / DC hybrid microgrid group model was built in the MATLAB / Simulink simulation platform. The system simulation parameters are shown in Table 1, and the carbon emission coefficient of each DG in the system is shown in Table 2.

[0233] Table 1 System simulation parameters

[0234]

[0235] Table 2 Carbon emission coefficient of each microgrid distributed power source

[0236]

[0237] The model contains two AC microgrids and one DC microgrid. Each AC microgrid contains a GFMU and two GFLUs, and the DC microgrid contains a DU and two PUs.

[0238] Example 1: Simulation verification under the scenario of continuous load increase

[0239] In order to verify the effectiveness of the distributed low-carbon control method for the isolated AC / DC hybrid microgrid group proposed in the present invention, the present invention sets a scenario of continuous load increase. The load of the microgrid in each period is shown in Table 3.

[0240] Table 3 Load of microgrid in each period

[0241]

[0242] Figure 7 Figure (a) shows the frequency curve of AC microgrid ACMG-1. Figure 7 Figure (b) shows the frequency curve of AC microgrid ACMG-2. Figure 7 Figure (c) in the figure is the common DC bus voltage curve, as shown in Figure 7 As shown in the figure, under different load conditions, the distributed low-carbon control method can restore the frequency of each AC microgrid and the common DC bus voltage to their rated values. The physical quantities fluctuate slightly during the load jump process and can quickly recover to the steady-state value, ensuring the stable and reliable operation of the system.

[0243] Figure 8 Figure (a) shows the carbon emission micro-increase rate curve of each DG of ACMG-1. Figure 8 Figure (b) shows the carbon emission micro-increase rate curve of each DG of ACMG-2. Figure 8 Figure (c) shows the carbon emission micro-increase rate curve of each DG of DCMG. Figure 8 As shown in the figure, under different load conditions, the distributed low-carbon control method can realize the distribution of output active power of each microgrid DGs according to the equal carbon emission micro-increase rate criterion, thereby ensuring the low-carbon control of the AC / DC hybrid microgrid group under different load conditions.

[0244] Example 2: Simulation verification in a communication link failure scenario

[0245] In order to verify the reliability of the distributed low-carbon control method of the isolated island AC / DC hybrid microgrid group under the condition of communication link failure, the present invention is At s, the communication link between PU1 and PU2 in DCMG is disconnected, and the communication weight between PU2 and DU is reduced by 60%; thereafter, s, a system load jump is set, and the microgrid load in each time period is shown in Table 4.

[0246] Table 4 Microgrid load in each time period

[0247]

[0248] At the same time, the simulation results under normal working conditions of the communication link are as follows Fig. 9 As shown, Fig. 9Figure (a) shows the slight increase in carbon emissions of ACMG-1 DGs under normal operating conditions of the communication link. Fig. 9 Figure (b) shows the slight increase in carbon emissions of ACMG-2 DGs under normal operating conditions of the communication link. Fig. 9 Figure (c) shows the carbon emission increase rate of DCMG DGs under normal communication link conditions. The simulation results under communication link failure conditions are shown in Figure 2. Fig.10 As shown, Fig.10 Figure (a) shows the slight increase in carbon emissions of ACMG-1 DGs under the condition of communication link failure. Fig.10 Figure (b) shows the slight increase in carbon emissions of ACMG-2 DGs under the condition of communication link failure. Fig.10 Figure (c) shows the carbon emission micro-increase rate of DCMG DGs under the condition of communication link failure. After the communication link between PU1 and PU2 is disconnected, the system load jumps. Since the communication topology of DCMG still maintains connectivity at this time, the present invention can still ensure that the DGs in the microgrid group allocate active power according to the equal carbon emission micro-increase rate criterion to achieve low-carbon control of the system.

[0249] contrast Fig. 9 Figure (c) and Fig.10 As can be seen from Figure (c), before and after the load jump, the present invention can achieve the system control target under both working conditions. However, the DCMG under the communication link failure has a change in the communication topology and the communication weight of the normal link is reduced. Therefore, the convergence speed of the carbon emission micro-increase rate of each distributed power source is significantly reduced, and the system takes longer to enter a steady state.

[0250] Example 3: Simulation verification in different comparison scenarios

[0251] In order to verify the superiority of the distributed low-carbon control method of the isolated AC / DC hybrid microgrid group of the present invention, the present invention compares it with the traditional AC / DC hybrid microgrid group distributed cooperative control method that only considers power distribution. The load conditions of the system in each period are the same as those in Example 2. The simulation results of the two methods are as follows: Figures 11 to 14 shown.

[0252] Fig.11 The middle (a) figure is the ACMG-1 frequency curve under the traditional method. Fig.11 The middle (b) figure is the ACMG-2 frequency curve under the traditional method. Fig.11 Figure (c) shows the common DC bus voltage curve under the traditional method. Fig.13 Figure (a) is the ACMG-1 frequency curve under the method of the present invention. Fig.13 Figure (b) is the ACMG-2 frequency curve under the method of the present invention. Fig.13 Figure (c) shows the voltage curve of the common DC bus under the method of the present invention. Fig.11 and Fig.13 Both the conventional method and the method of the present invention can achieve the recovery of the frequency and the common DC bus voltage relative to their rated values ​​when the load changes.

[0253] Fig.12 The middle figure (a) shows the carbon emission increment rate of each DG in ACMG-1 under the traditional method. Fig.12 The middle (b) figure shows the carbon emission increment rate of each DG in ACMG-2 under the traditional method. Fig.12 Figure (c) shows the carbon emission increment rate of each DG in DCMG under the traditional method. Fig.12 As shown in the figure, the carbon emission micro-increase rates of each microgrid DGs under the traditional method are not consistent, indicating that it is necessary to reduce the output of DGs with higher carbon emissions while appropriately increasing the output of DGs with lower carbon emissions to reduce the total carbon emissions of the system.

[0254] Fig.14 Figure (a) shows the carbon emission increment rate of each DG in ACMG-1 under the method of the present invention. Fig.14 Figure (b) shows the carbon emission increment rate of each DG in ACMG-2 under the method of the present invention. Fig.14 Figure (c) shows the carbon emission increment rate of each DG in DCMG under the method of the present invention; Fig.14 The figure shows the carbon emission micro-increase rate of each DG in the microgrid group under the method of the present invention. The DGs under the method of the present invention fully consider their own carbon emissions when allocating power, and the carbon emission micro-increase rate of each microgrid DGs remains consistent under different load conditions, indicating that the method can adaptively promote DGs with lower carbon emission micro-increase rate in the microgrid group to give priority to powering the load and realize low-carbon control of the system.

[0255] Fig.15 The carbon emission curves of the system under the traditional method and the method of the present invention are shown in the figure. It can be seen from the figure that the method of the present invention can significantly reduce the carbon emission of the system. According to calculations, compared with the traditional method, the carbon emission of the method proposed by the present invention can be reduced by about 2.6% under different load conditions.

[0256] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A distributed low-carbon control method for an isolated AC / DC hybrid microgrid group, characterized in that: include: S1: The carbon emission micro-increase rate is obtained by differentiating the carbon emission of distributed power sources in the isolated AC / DC hybrid microgrid group with respect to the active output; S2: Formulate the distributed low-carbon control target of the isolated AC / DC hybrid microgrid group according to the equal carbon emission micro-increase rate criterion; S3: Construct a hierarchical distributed low-carbon control architecture based on the distributed low-carbon control objectives; S4: Based on the leader-follower framework, distributed power sources are controlled to obtain secondary control items, which are introduced into low-carbon droop control to achieve low-carbon control of the microgrid converter control layer in the hierarchical distributed low-carbon control architecture; The distributed low-carbon control method of the microgrid converter control layer is: By replacing the output active power with the carbon emission micro-increase rate of the distributed power source, the traditional droop control is improved to low-carbon droop control, so that each distributed power source in the microgrid can distribute the output active power according to the equal carbon emission micro-increase rate principle; The outer loop of the AC microgrid obtains the bus voltage reference value or the carbon emission micro-increase rate reference value of the distributed power source through a consistency algorithm, and the inner loop adopts a voltage and current double closed-loop control structure to achieve zero-static error tracking of the reference value; Based on the leader-follower framework, the AC microgrid takes the grid-building unit as the leader and the grid-following unit as the follower to construct a distributed low-carbon control method for the grid-building-grid-following unit, including: Primary control of the grid-forming units and grid-following units of the AC microgrid; The low carbon droop control expression of GFMU converter is: in, is the frequency collected by the nbth grid-forming unit GFMU-nb in the nth AC microgrid, is the frequency rating of the nbth grid-forming unit GFMU-nb in ACMG-n; is the carbon emission increment rate of the nbth grid-type unit in ACMG-n, is the droop coefficient of GFMU-nb; The low carbon droop control expression of GFLU converter is: in, is the frequency collected by the nwth grid-type unit GFLU-nw, The frequency rating value collected for the nwth grid-following unit GFLU-nw, is the carbon emission slight increase rate of GFLU-nw, is the droop coefficient of GFLU-nw; The secondary control expression of GFMU converter is: in, It is the consistency control input of GFMU-nb. is a positive gain of GFMU-nb, is the PI controller transfer function of GFMU-nb, is the communication weight between node nb and its neighboring node nw, is the set of adjacent nodes of node nb, is the secondary control quantity of the output frequency of GFMU-nb; The secondary control expression of GFLU converter is: in, is the consistency control input of GFLU-nw, is a positive gain of GFLU-nw, is the PI controller transfer function of GFLU-nw, is the set of adjacent nodes of node nw, is the communication weight between node nw and its neighboring node nb, is the secondary control amount of GFLU-nw; The secondary control variable is introduced into the low-carbon droop control to achieve the low-carbon control target of the AC microgrid; The outer loop of the DC microgrid converts the carbon emission micro-increase rate into a power reference value, and the inner loop adopts a current single-loop control structure to achieve zero-static error tracking of the reference value; The DC microgrid is based on the leader-follower framework, with the dispatchable unit as the leader and the power unit as the follower, to build a dispatchable-power unit distributed low-carbon control, including: Primary control of dispatchable units and power units of DC microgrid: The primary control of DU converter, the low carbon droop control expression of DU converter is: in, is the carbon emission slight increase rate of the oth dispatchable unit in DCMG, is the low carbon droop coefficient of DU-o, is the common DC bus voltage, is the rated value of the common DC bus voltage; The primary control of PU converter, the low carbon droop control expression of PU converter is: in, is the slight increase rate of carbon emission of PU-z, is the low carbon droop coefficient of PU-z, The main goal of the secondary control of the DC microgrid converter is to restore the voltage of the common DC bus while achieving the output of active power by each power source according to the equal carbon emission micro-increase rate criterion; The secondary control expression of DU converter is: in, is the output voltage value of DU-o, is the secondary control quantity of DU-o, It is the consistency control input of DU-o. is a positive gain of DU-o, is the communication weight between node o and its neighboring node z, is the PI controller transfer function of DU-o, The set of adjacent nodes of node o; The secondary control expression of PU converter is: in, is the secondary control quantity of PU-z, is the consistency control input of PU-z, is a positive gain of PU-z, is the communication weight between node z and its neighboring node o, is the PI controller transfer function of PU-z, The set of neighboring nodes of node PU-z; The secondary control variable is introduced into the low-carbon droop control to achieve the low-carbon control target of the DC microgrid; S5: By introducing the deviation of the carbon emission micro-increase rate between microgrids into the interconnected converter and bringing it into the PI controller, low-carbon control of the control layer of the interconnected converter between microgrids in the hierarchical distributed low-carbon control architecture is realized; S6: Low-carbon and stable operation of the microgrid group is achieved through low-carbon control of the microgrid converter control layer and low-carbon control of the interconnected converter control layer.

2. A distributed low-carbon control method for an isolated AC / DC hybrid microgrid group according to claim 1, characterized in that: The isolated AC / DC hybrid microgrid group generates carbon emissions through the power generation link of distributed power sources. The isolated AC / DC hybrid microgrid group includes AC microgrid, DC microgrid and inter-grid interconnection converter.

3. The distributed low-carbon control method for an isolated AC / DC hybrid microgrid group according to claim 1 is characterized in that: In step S1, the carbon emission micro-increase rate of distributed power sources is expressed as: in, is the slight increase rate of carbon emissions from distributed power sources, It is the active power output of distributed power sources. is the carbon emission coefficient of the first distributed power source, is the carbon emission coefficient of the second distributed power source; According to the Lagrange multiplier method, when the carbon emission increment rate of all distributed power sources in the isolated AC / DC hybrid microgrid group is equal, the carbon emissions reach the minimum.

4. The distributed low-carbon control method for an isolated AC / DC hybrid microgrid group according to claim 2 is characterized in that: In the step S2, The low-carbon control target of the AC microgrid is to restore the frequency of the AC microgrid to its rated value and to allocate active power to the grid-forming units and grid-following units in the AC microgrid according to the principle of equal carbon emission micro-increase rate; The low-carbon control target of the DC microgrid is to restore the common DC bus voltage of the DC microgrid to its rated value and to allocate active power to the dispatchable units and power units in the DC microgrid according to the principle of equal carbon emission micro-increase rate; The low-carbon control target of the inter-grid interconnected converter is to realize the active power interaction between the microgrids through the inter-grid interconnected converter, so as to ensure the consistency of the carbon emission micro-increase rate of each microgrid in the isolated AC / DC hybrid microgrid group.

5. The distributed low-carbon control method for an isolated AC / DC hybrid microgrid group according to claim 1 is characterized in that: In the step S3, the distributed low-carbon control architecture of the isolated AC / DC hybrid microgrid group includes a microgrid converter control layer and an inter-grid interconnection converter control layer.

6. The distributed low-carbon control method for an isolated AC / DC hybrid microgrid group according to claim 1 is characterized in that: The interconnected converter control outer loop receives information from the connected local microgrid and adjacent interconnected converters, adjusts the transmission power reference value, coordinates the mutual power between microgrids, and achieves the low-carbon control goal of the interconnected converters between networks. After obtaining the reference value of the transmission power of the interconnected converters through the outer loop, the inner loop adopts a current single-loop control structure to achieve rapid tracking of the reference value.

7. A distributed low-carbon control method for an isolated AC / DC hybrid microgrid group according to claim 6, characterized in that: The grid-forming unit of the AC microgrid and the dispatchable unit of the DC microgrid respectively transmit the average value information of the carbon emission micro-increase rate of the power supply of their microgrids to the inter-grid interconnection converter. The interconnection converter makes a difference between the average values ​​of the carbon emission micro-increase rate of the two connected microgrids and brings it into the PI controller. When the system enters a steady state, the input of the PI controller is 0, realizing a low-carbon control between microgrids. The secondary control expression of the interconnected converter is: in, is the power reference value of IC-r, is the secondary control quantity of IC-r, is the communication weight between the interconnected converter node r and its adjacent node s, is the carbon emission micro-increase rate deviation of the microgrids on both sides of IC-r, is the carbon emission slight increase rate of the adjacent node s of node r, is a positive gain of IC-r, is the set of adjacent nodes of IC-r, is the PI controller transfer function of IC-r secondary control, is the PI controller transfer function of IC-r.

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