CN117458631A - Multi-scene coordination control method for AC/DC hybrid micro-grid group - Google Patents
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
一种交直流混合微电网群多场景协调控制方法，包括：面向交直流混合微电网群整体经济运行的场景，构建基于等成本微增量原则的子微网群间控制目标；面向交直流混合微电网群中交流子微网的频率波动场景，构建频率恢复控制目标；面向交直流混合微电网群中直流子微网的电压波动场景，构建电压恢复控制目标；构建控制器基本架构；针对单个ILC，构建各ILC控制器的本地控制项、各ILC控制器的交流侧频率辅助控制项、各ILC控制器的直流侧电压辅助控制项及各ILC控制器的协调辅助控制项；根据ILC控制器的本地控制项和辅助控制项，构建ILC控制策略。实现各子微网成本微增量收敛一致及维持各子微网频率电压稳定。
A multi-scenario coordinated control method for an AC/DC hybrid microgrid group, including: oriented to the overall economic operation scenario of the AC/DC hybrid microgrid group, constructing inter-microgrid control objectives based on the equal-cost micro-increment principle; oriented to the AC/DC hybrid microgrid group For the frequency fluctuation scenario of the AC sub-microgrid in the microgrid group, construct the frequency recovery control target; for the voltage fluctuation scenario of the DC sub-microgrid in the AC-DC hybrid microgrid group, construct the voltage recovery control target; construct the basic architecture of the controller; for a single ILC constructs the local control items of each ILC controller, the AC side frequency auxiliary control items of each ILC controller, the DC side voltage auxiliary control items of each ILC controller, and the coordination auxiliary control items of each ILC controller; according to the ILC controller local control items and auxiliary control items to build an ILC control strategy. Achieve consistent convergence of micro-incremental cost of each sub-microgrid and maintain frequency and voltage stability of each sub-microgrid.
Description
Technical Field
The invention belongs to the field of micro-grid group control, and particularly relates to a multi-scene coordination control method for an alternating current-direct current hybrid micro-grid group.
Background
Micro-grids have become an important way of grid-connected consumption of distributed power sources as an effective means of accommodating distributed power sources. The main function of the micro-grid is to effectively integrate distributed power supplies with dispersed geographic positions, centralize surfing, promote clean energy consumption, greatly lighten the running load of the power grid, ensure the running stability and safety of an external power grid and ensure more flexibility and intelligence of a power system. In addition, the micro-grid can be closely connected with the clean energy system, thereby being beneficial to the management of a user on the demand side and realizing the maximum utilization of the current energy and resources. The absorption and utilization of the scattered energy are the most remarkable characteristics of the micro-grid, which are different from the large power grid, and the micro-grid can run in a grid-connected mode, so that reliable high-level power supply is realized. As such, the flexibility and efficient use of the characteristics of the decentralized energy source makes it very useful in industrial, commercial, urban and remote areas. However, a single micro-grid has the defects of limited working capacity, weak disturbance rejection capability and the like, so how to interconnect a plurality of micro-grids to form an alternating current-direct current hybrid micro-grid group, realize the economic control of the micro-grid group and become an important development direction and research content of the micro-grid.
At present, research has important significance for realizing economic mutual control of micro-grid groups, but the defects still exist, and the method is specifically expressed as follows:
first, the existing research often adopts droop control to distribute the power of each DG unit to perform primary control on the frequency and the voltage of the micro-grid, however, the droop control is poor control, and cannot realize economic control on the micro-grid, and secondary control needs to be performed on the micro-grid, and the secondary control can be classified into centralized control, distributed control and distributed control according to the communication topology and the control structure. Most of the prior researches adopt centralized control to carry out secondary control on a micro-grid, however, the centralized control is required to have a central controller, the fault of the central controller or the fault of a node in the system can affect the stable operation and even breakdown of the system, the expandability and redundancy of the system adopting the centralized control are low, the dependency of the centralized control on communication is high, and complex communication links and high bandwidth support are required, so that the reliability of the system is low.
Secondly, the research of the control direction of the existing micro-grid group mostly only considers the economic dispatch of the micro-grid group or only considers the single target of frequency voltage tracking, and does not realize the multi-target coordination of the economic dispatch and stable frequency and bus voltage at the same time.
Disclosure of Invention
Aiming at the defects or improvement demands of the prior art, the invention aims to provide a multi-scene coordination control method for an AC/DC hybrid micro-grid group, which adopts a limited time consistency algorithm as a secondary control method based on an equal cost micro-increment principle, considers the influence of time delay on system stability, finally realizes power economic distribution between AC/DC sub-micro-grids, ensures consistent convergence of the cost micro-increment of each sub-micro-grid and maintains stable frequency and voltage of each sub-micro-grid.
In order to achieve the above purpose, the invention discloses a multi-scene coordination control method for an AC/DC hybrid micro-grid group, which comprises the following steps:
1) Constructing a system structure of an alternating current-direct current hybrid micro-grid group comprising an alternating current sub-micro-grid, a direct current sub-micro-grid and an interconnection device controller (Interlocking Controller, ILC);
2) Constructing a control target among sub-micro-grid groups based on an equal-cost micro-increment principle facing to a scene of overall economic operation of an AC/DC hybrid micro-grid group;
3) Constructing a frequency recovery control target for a frequency fluctuation scene of an alternating current sub-micro-grid in an alternating current-direct current hybrid micro-grid group;
4) Constructing a voltage recovery control target facing to a voltage fluctuation scene of a direct current sub-micro network in an alternating current-direct current hybrid micro network group;
5) Constructing a controller basic framework based on a finite time consistency algorithm;
6) Aiming at a single ILC and facing to the scene of overall economic operation of an AC/DC hybrid micro-grid group, based on a controller basic framework, constructing a local control item of each ILC controller by taking a cost micro-increment as a decision variable;
7) Aiming at a single ILC and facing the frequency fluctuation scene of an alternating current sub-micro network in an alternating current-direct current hybrid micro grid group, based on a controller basic framework, the alternating current sub-micro network frequency is taken as a decision variable, and an alternating current side frequency auxiliary control item of each ILC controller is constructed;
8) Aiming at a single ILC and facing to a voltage fluctuation scene of a direct current sub-micro network in an alternating current-direct current hybrid micro grid group, based on a controller basic framework, taking the voltage of the direct current sub-micro network as a decision variable, and constructing a direct current side voltage auxiliary control item of each ILC controller;
9) Aiming at all ILCs, to avoid power contention among different ILCs, constructing a coordination auxiliary control item of each ILC controller based on a controller basic framework by taking a cost micro increment as a decision variable;
10 According to the local control item of the ILC controller, the alternating-current side frequency auxiliary control item, the direct-current side voltage auxiliary control item and the coordination auxiliary control item, constructing an ILC control strategy.
In the step 2), a control target among sub-micro-grid groups based on an equal-cost micro-increment principle is constructed facing to a scene of overall economic operation of an alternating current-direct current hybrid micro-grid group, and the control target is specifically as follows:
in the method, in the process of the invention,the cost micro increment mean value of the mth alternating current sub-micro network; />The cost micro increment mean value of the nth direct current sub-micro network;
the control target among the sub-micro network groups is realized by controlling the transmission power of the ILC, the control target of the control target among the sub-micro network groups is divided into 2 parts, and the 1 st part is to make the cost micro increment of an alternating current sub-micro network and a direct current sub-micro network which are directly connected with the ILC the same, namely:
in the method, in the process of the invention,the average cost micro increment of the m-number alternating current sub-micro network connected with the bi-directional converter ILCg at the moment t is set; />Average cost micro for n-th direct current sub-micro-network connected with ILCg at time tAn increment; f (f) g A difference value that is a cost micro increment between the 2 sub-micro networks;
part 2 of the control target is to make the difference of the cost micro increment of the double-side sub-micro-network at each ILC consistent and finally substitute 0, namely:
in the step 3), a frequency recovery control target is constructed facing to a frequency fluctuation scene of an alternating current sub-micro-grid in an alternating current-direct current hybrid micro-grid group, and specifically comprises the following steps:
stabilizing the frequency of each AC sub-micro-network to a frequency reference value, and constructing a frequency recovery control target as follows:
wherein omega is i Frequency measurement for the ith ac sub-microgrid; omega * Is the frequency reference value of the ac sub-microgrid.
In the step 4), a voltage recovery control target is constructed facing to a voltage fluctuation scene of a direct current sub-micro-grid in an alternating current-direct current hybrid micro-grid group, and specifically comprises the following steps:
stabilizing the voltage of the common bus of each direct current sub-micro network to a voltage reference value, and constructing a voltage recovery control target as follows:
in U PCC,pu,n The method comprises the steps that a normalized measured value of the voltage of a bus commonly connected with the direct current side of an nth direct current sub-micro network is obtained;and the normalized reference value of the bus voltage is commonly connected to the direct current side of the nth direct current sub-micro network.
In step 5), a controller basic architecture based on a finite time consistency algorithm is constructed, specifically:
the finite time consistency control is adopted to improve the convergence speed and the convergence performance, and the control protocol is as follows:
wherein u is i (t) is a coherence protocol; a, a ij Is the communication weight between the distributed nodes; x is x i And x j The state quantity of the nodes i and j is respectively represented and used for representing information such as frequency, voltage, power and the like in the micro-grid; alpha is more than 0 and less than 1 as control factors, and is used for adjusting control parameters of convergence speed; sign (x) is a sign function;
the frequency of the alternating current sub-micro network is converged to 50Hz, the voltage of each sub-micro network is converged to a rated value, a leading node is introduced to receive reference value information on the basis of a limited time consistency protocol aiming at a voltage and frequency control target, after information interaction is carried out between the leading node and adjacent nodes, the states of all nodes are converged to the reference value, and the control protocol is as shown in the formula:
wherein b is i A reference input weight representing an i-th node; x is x ref A given reference value to which the system state needs to converge;
the control protocol for the limited time consistency of the AC/DC hybrid micro-grid group considering the time delay is as follows:
wherein τ ij The communication time delay from the node j to the node i is set; t (T) i Is a self-delay, corresponding to the computation delay or reaction delay of the DG unit itself.
In the step 6), a local control item of an ILC controller is constructed aiming at a certain ILC and facing to a scene of overall economic operation of an AC/DC hybrid micro-grid group, specifically:
the cost micro increment of the AC/DC sub-micro-network directly connected with the single ILC is equal, the difference value of the cost micro-increment of the AC/DC sub-micro-network is taken as a decision variable, and the decision variable is substituted into the (6) to obtain the control strategy of the local control item, wherein the control strategy is as follows:
in the method, in the process of the invention,the local control item is a local control item of the ILCg and is used for realizing that the cost micro increment of an alternating current sub-micro network m and a direct current sub-micro network n which are directly connected with the ILCg is the same; in the formula, subscripts m and n respectively correspond to an alternating current sub-micro network and a direct current sub-micro network which are connected with the ILCg; />The average cost micro increment of an m-number alternating current sub-micro network connected with the bi-directional converter ILCg is set; />Is the average cost micro increment of the n-number direct current sub-micro network connected with the ILCg;
wherein N is m Is the whole of AC sub-micro network, N n Is the whole of the DC sub-micro network; g i For the link weight of node i and common connection bus, if node i and ILC have communication link, g i =1, otherwise 0; τ mi Representing communication delay in the communication process of the ith DG unit in the mth alternating current sub-micro network and the mth alternating current sub-micro network controller; τ ni Representing communication delay in the communication process of an ith DG unit in an nth direct current sub-micro network and an nth direct current sub-micro network controller; i Ci For forming the ith DG unit in the sub-micro-networkThe expression of the micro increment is as follows:
I Ci ＝2α i P i +β i (11)
wherein alpha is i And beta i Representing cost coefficients for each distributed power supply; p (P) i Representing the active power output by each distributed power source.
In step 7), aiming at a certain ILC and facing to a frequency fluctuation scene of an alternating current sub-micro network in an alternating current-direct current hybrid micro grid group, an alternating current side frequency auxiliary control item of an ILC controller is constructed, specifically:
the frequency of an alternating current sub-micro network directly connected with a single ILC is restored to a rated value, the frequency of the alternating current sub-micro network is used as a decision variable, and the decision variable is substituted into the variable (8) to obtain the control strategy of the alternating current side frequency auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,is an AC side frequency auxiliary control item; />And omega pu,m The normalized values are respectively the reference frequency of the AC side public connection bus and the actual measurement frequency of the AC side public connection bus; τ gm A communication delay between the ILCg and the AC sub-micro-network m; t is time; alpha is a control factor for adjusting convergence speed;
the normalized frequency is defined as:
wherein omega is pu A normalized value representing frequency; ω represents ac microgrid frequency; omega max And omega min Is the upper and lower limits of the ac microgrid frequency.
In the step 8), for a certain ILC and for a voltage fluctuation scene of a dc sub-microgrid in the ac/dc hybrid microgrid group, a dc side voltage auxiliary control item of the ILC controller is constructed, specifically:
and (3) restoring the voltage of the direct current sub-micro network directly connected with the single ILC to a rated value, substituting the voltage of the direct current sub-micro network into the direct current sub-micro network serving as a decision variable into the direct current sub-micro network (8) to obtain a control strategy of the direct current side voltage auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,is a DC side voltage auxiliary control item; />And U PCC,pu,n The reference frequency of the direct current side public connection bus and the normalized value of the actual measurement voltage of the direct current side public connection bus are respectively obtained; τ gn Is the communication delay between ILCg and dc subnetwork n.
The normalized dc voltage is defined as:
in U pu A normalized value representing the dc voltage; ω represents dc microgrid voltage; u (U) max And U min Is the upper and lower limits of the dc microgrid voltage.
In step 9), for all ILCs, to avoid power contention among different ILCs, a coordination auxiliary control item of the ILC controller is constructed, specifically:
and (3) enabling the difference value of the cost micro increment of the two-side sub-micro network at all ILCs to be consistent and finally to be substituted into 0, taking the difference value of the cost micro increment of the two-side sub-micro network as a decision variable, substituting the decision variable into the formula (8) to obtain a control strategy of the coordination auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,a coordination auxiliary control item for the cost micro increment difference value of the double-side sub-micro network at all ILCs; o is a set of ILCs; a, a gh The communication weight between the ILC double-side sub-micro-network difference value and the ILCh is calculated; />The average cost micro increment of a p-type alternating current sub-micro network connected with the bi-directional converter ILCg is set; />Average cost micro increment of the q-number direct current sub-micro network connected with the ILCg; τ gh A communication delay between the ILC double-sided sub-microgrid difference value and ILCh; t (T) g Communication self-delay of each AC/DC sub-micro-network; subscripts p and q correspond to an ac subnetwork and a dc subnetwork, respectively, which are connected to the ILCh.
The ILC is controlled secondarily, and the operation information of other ILCs is basically introduced on the basis of the ILC local control, so that the development of the cost micro-increment of the sub-micro-grid to the cost micro-increment average value of the AC/DC hybrid micro-grid group can be promoted, and the economic distribution of the active power among all sub-micro-grids can be realized.
In step 10), an ILC control strategy is constructed according to a local control item and an auxiliary control item of the ILC controller, specifically:
in the method, in the process of the invention,an active power reference value for flow through ILCg; />Integration for ILCg local control term; />Integrating the auxiliary control term for the alternating-current side frequency; />Integration as a direct-current side voltage auxiliary control term; />And integrating the coordination auxiliary control items of the cost micro increment difference value of all the double-side sub-micro networks at the ILC.
The system structure of the AC/DC hybrid micro-grid group comprises a plurality of AC sub-micro-grids, a plurality of DC sub-micro-grids and a plurality of interconnection device controllers ILC, wherein the AC sub-micro-grids and the DC sub-micro-grids are used for interconnecting the sub-micro-grids through the interconnection device controllers ILC;
the AC sub-micro-grid comprises an AC load, a distributed AC power generation system and an AC energy storage system;
the direct current sub-micro-grid comprises: direct current load, distributed direct current power generation system, direct current energy storage system.
In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:
the invention considers the AC/DC hybrid micro-grid group economy mutual aid control method, based on the principle of equal cost micro-increment, adopts a finite time consistency algorithm as a secondary control method, considers the influence of time delay on system stability, finally realizes the power economy distribution between AC/DC sub-micro-grids, ensures that the cost micro-increment convergence of each sub-micro-grid is consistent, and maintains the frequency voltage stability of each sub-micro-grid. The problems of low reliability and single control target of the traditional AC/DC hybrid micro-electric cluster centralized control are well solved.
Drawings
FIG. 1 is a flow chart of a control method of the present invention;
fig. 2 is a schematic diagram of an ac/dc hybrid micro-grid group structure implemented in the present invention;
FIG. 3 is a schematic diagram of a distributed autonomous economic control strategy for an AC/DC hybrid micro-grid cluster implemented by the present invention;
FIG. 4 is a schematic diagram of an AC/DC hybrid micro-grid group simulation model implemented by the present invention;
fig. 5 is a schematic diagram of simulation results of an ac/dc hybrid microgrid group under a variable load condition implemented by the present invention, a is a cost micro-increment allocation result of each DG, b is a cost micro-increment allocation result of each subnetwork, c is a frequency fluctuation condition of an ac subnetwork, d is a PCC voltage fluctuation condition of the ac subnetwork, e is a reactive allocation condition of the ac DG, and f is a PCC voltage fluctuation condition of the dc subnetwork;
fig. 6 is a schematic diagram of a simulation result of an ac/dc hybrid microgrid group under a "plug and play" condition implemented in the present invention, where a is a cost micro-increment allocation result of each DG, b is a cost micro-increment allocation result of each subnetwork, c is a frequency fluctuation condition of the ac subnetwork, d is a PCC voltage fluctuation condition of the ac subnetwork, e is a reactive allocation condition of the ac DG, and f is a PCC voltage fluctuation condition of the dc subnetwork.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to the drawings and specific embodiments of the present invention.
As shown in fig. 1, the multi-scene coordination control method for the ac/dc hybrid micro-grid group comprises the following steps:
1) Constructing a system structure of an alternating current-direct current hybrid micro-grid group comprising an alternating current sub-micro-grid, a direct current sub-micro-grid and an interconnection device controller (Interlocking Controller, ILC);
2) Constructing a control target among sub-micro-grid groups based on an equal-cost micro-increment principle facing to a scene of overall economic operation of an AC/DC hybrid micro-grid group;
the step 2) is specifically as follows:
in the method, in the process of the invention,the cost micro increment mean value of the mth alternating current sub-micro network; />Is the cost micro increment mean value of the nth direct current sub-micro network.
The control objective among the sub-micro network groups is realized by controlling the transmission power of the ILC, the ILC control objective can be divided into 2 parts, and the 1 st part is to make the cost micro increment of an alternating current sub-micro network and a direct current sub-micro network which are directly connected with the ILC the same, namely:
in the method, in the process of the invention,the average cost micro increment of the m-number alternating current sub-micro network connected with the bi-directional converter ILCg at the moment t is set; />The average cost micro increment of the n-number direct current sub-micro network connected with the ILCg at the moment t is set; f (f) g Is the difference in cost micro-increment between these 2 sub-micro-networks. When calculating the average cost micro increment of the sub-micro networks, DG of a communication link with the ILC in each sub-micro network transmits the cost micro increment of the current sampling moment to a converter station, and the average value is calculated.
Part 2 of the ILC control objective is to make the difference of the cost micro increment of the two-side sub-micro-net at each ILC consistent and finally substitute 0, namely:
3) Constructing a frequency recovery control target for a frequency fluctuation scene of an alternating current sub-micro-grid in an alternating current-direct current hybrid micro-grid group;
the step 3) is specifically as follows:
stabilizing the frequency of each AC sub-micro-network to a frequency reference value, and constructing a frequency recovery control target as follows:
wherein omega is i Frequency measurement for the ith ac sub-microgrid; omega * Is the frequency reference value of the ac sub-microgrid.
4) Constructing a voltage recovery control target facing to a voltage fluctuation scene of a direct current sub-micro network in an alternating current-direct current hybrid micro network group;
the step 4) is specifically as follows:
stabilizing the voltage of the common bus of each direct current sub-micro network to a voltage reference value, and constructing a voltage recovery control target as follows:
in U PCC,pu,n The method comprises the steps that a normalized measured value of the voltage of a bus commonly connected with the direct current side of an nth direct current sub-micro network is obtained;and the normalized reference value of the bus voltage is commonly connected to the direct current side of the nth direct current sub-micro network.
5) Constructing a controller basic framework based on a finite time consistency algorithm;
the step 5) is specifically as follows:
the finite time consistency control is adopted to improve the convergence speed and the convergence performance, and the control protocol is as follows:
wherein u is i (t) is a coherence protocol; a, a ij Is a distributed nodeThe communication weight between the two; x is x i And x j The state quantity of the nodes i and j is respectively represented and used for representing information such as frequency, voltage, power and the like in the micro-grid; alpha is more than 0 and less than 1 as control factors, and is used for adjusting control parameters of convergence speed; sign (x) is a sign function;
in the invention, the frequency of an alternating current sub-micro network is required to be controlled to be converged to 50Hz, the voltage of each sub-micro network is converged to a rated value, so that a leading node is introduced to receive reference value information on the basis of a limited time consistency protocol, all node states are converged to a reference value after information interaction is carried out with adjacent nodes, and the control protocol is as shown in the formula:
wherein b is i Reference input weight, x, representing the i-th node ref Indicating a given reference value to which the system state needs to converge.
The control protocol in the equation does not take into account the effect of time delay. In a practical distributed control environment, time delays in the communication process are unavoidable. In general, time delays may affect the convergence and stability of a coherency algorithm. The traditional distributed control based on the consistency algorithm mostly considers time delay caused by interaction among different nodes, and less considers time delay in the state measurement of the nodes. Two time delays are comprehensively considered, and a limited time consistency control method of the AC/DC hybrid micro-grid group considering the time delays is researched. Considering the influence of two time delays, the control protocol is:
wherein τ ij The communication time delay from the node j to the node i is set; t (T) i Is a self-delay, corresponding to the computation delay or reaction delay of the DG unit itself.
Specifically, in this embodiment, the control factor α takes a value of 0.9, and the communication delay τ ij And self-delay T i Take 5ms.
6) Aiming at a single ILC and facing to the scene of overall economic operation of an AC/DC hybrid micro-grid group, based on a controller basic framework, constructing a local control item of each ILC controller by taking a cost micro-increment as a decision variable;
the step 6) is specifically as follows:
the cost micro increment of the AC/DC sub-micro-network directly connected with the single ILC is equal, the difference value of the cost micro-increment of the AC/DC sub-micro-network is taken as a decision variable, and the decision variable is substituted into the (6) to obtain the control strategy of the local control item, wherein the control strategy is as follows:
in the method, in the process of the invention,the local control item is a local control item of the ILCg and is used for realizing that the cost micro increment of an alternating current sub-micro network m and a direct current sub-micro network n which are directly connected with the ILCg is the same; in the formula, subscripts m and n respectively correspond to an alternating current sub-micro network and a direct current sub-micro network which are connected with the ILCg. />The average cost micro increment of an m-number alternating current sub-micro network connected with the bi-directional converter ILCg is set; />Is the average cost micro increment of the n-type direct current sub-micro network connected with the ILCg. The expressions of the two are:
wherein N is m Is the whole of AC sub-micro network, N n Is the whole of the DC sub-micro network; g i For the link weight of node i and common connection bus, if node i and ILC have communication link, g i =1, otherwise 0; τ mi Representing communication delay in the communication process of the ith DG in the mth alternating current sub-micro network and the mth alternating current sub-micro network controller; τ ni Representing communication delay in the communication process of the ith DG in the nth direct current sub-micro network and the nth direct current sub-micro network controller; i Ci The expression of the cost micro increment of the ith DG in the sub-micro network is as follows:
I Ci ＝2α i P i +β i (11)
wherein alpha is i And beta i Representing cost coefficients for each distributed power supply; p (P) i Representing the active power output by each distributed power source.
7) Aiming at a single ILC and facing the frequency fluctuation scene of an alternating current sub-micro network in an alternating current-direct current hybrid micro grid group, based on a controller basic framework, the alternating current sub-micro network frequency is taken as a decision variable, and an alternating current side frequency auxiliary control item of each ILC controller is constructed;
the step 7) is specifically as follows:
the frequency of an alternating current sub-micro network directly connected with a single ILC is restored to a rated value, the frequency of the alternating current sub-micro network is used as a decision variable, and the decision variable is substituted into the variable (8) to obtain the control strategy of the alternating current side frequency auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,is an AC side frequency auxiliary control item; />And omega pu,m The normalized values are respectively the reference frequency of the AC side public connection bus and the actual measurement frequency of the AC side public connection bus; τ gm A communication delay between the ILCg and the AC sub-micro-network m; t is time; alpha is a control factor for adjusting convergence speed;
the normalized frequency is defined as:
wherein omega is pu A normalized value representing frequency; ω represents ac microgrid frequency; omega max And omega min Is the upper and lower limits of the ac microgrid frequency.
8) Aiming at a single ILC and facing to a voltage fluctuation scene of a direct current sub-micro network in an alternating current-direct current hybrid micro grid group, based on a controller basic framework, taking the voltage of the direct current sub-micro network as a decision variable, and constructing a direct current side voltage auxiliary control item of each ILC controller;
the step 8) is specifically as follows:
and (3) restoring the voltage of the direct current sub-micro network directly connected with the single ILC to a rated value, substituting the voltage of the direct current sub-micro network into the direct current sub-micro network serving as a decision variable into the direct current sub-micro network (8) to obtain a control strategy of the direct current side voltage auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,is a DC side voltage auxiliary control item; />And U PCC,pu,n The reference frequency of the direct current side public connection bus and the normalized value of the actual measurement voltage of the direct current side public connection bus are respectively obtained; τ gn Is the communication delay between ILCg and dc subnetwork n.
The normalized dc voltage is defined as:
in U pu A normalized value representing the dc voltage; ω represents dc microgrid voltage; u (U) max And U min Is the upper and lower limits of the dc microgrid voltage.
9) Aiming at all ILCs, to avoid power contention among different ILCs, constructing a coordination auxiliary control item of each ILC controller based on a controller basic framework by taking a cost micro increment as a decision variable;
the step 9) is specifically as follows:
and (3) enabling the difference value of the cost micro increment of the two-side sub-micro network at all ILCs to be consistent and finally to be substituted into 0, taking the difference value of the cost micro increment of the two-side sub-micro network as a decision variable, substituting the decision variable into the formula (8) to obtain a control strategy of the coordination auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,a coordination auxiliary control item for the cost micro increment difference value of the double-side sub-micro network at all ILCs; o is a set of ILCs; a, a gh The communication weight between the ILC double-side sub-micro-network difference value and the ILCh is calculated; />The average cost micro increment of a p-type alternating current sub-micro network connected with the bi-directional converter ILCg is set; />Average cost micro increment of the q-number direct current sub-micro network connected with the ILCg; τ gh A communication delay between the ILC double-sided sub-microgrid difference value and ILCh; t (T) g Communication self-delay of each AC/DC sub-micro-network; subscripts p and q correspond to an ac subnetwork and a dc subnetwork, respectively, which are connected to the ILCh.
The ILC is controlled secondarily, and the operation information of other ILCs is basically introduced on the basis of the ILC local control, so that the development of the cost micro-increment of the sub-micro-grid to the cost micro-increment average value of the AC/DC hybrid micro-grid group can be promoted, and the economic distribution of the active power among all sub-micro-grids can be realized.
10 According to the local control item of the ILC controller, the alternating-current side frequency auxiliary control item, the direct-current side voltage auxiliary control item and the coordination auxiliary control item, constructing an ILC control strategy.
The step 10) is specifically as follows:
in the method, in the process of the invention,an active power reference value for flow through ILCg; />Integration for ILCg local control term; />Integrating the auxiliary control term for the alternating-current side frequency; />Integration as a direct-current side voltage auxiliary control term; />And integrating the coordination auxiliary control items of the cost micro increment difference value of all the double-side sub-micro networks at the ILC.
The structure of the AC/DC hybrid micro-grid group implemented by the invention is shown in figure 2. The ac/dc hybrid microgrid group structure comprises an ac sub-microgrid, a dc sub-microgrid and an interconnection device controller (Interlocking Controller, ILC):
the ac subnetwork comprises:
a. ac load: the load characteristics of the lamp, the television, the refrigerator, the fan, the computer, the electric tool and the like relate to parameters such as voltage, frequency, power factor and the like.
b. A distributed power generation system: it is composed of a plurality of renewable energy power generation devices, such as solar photovoltaic power generation devices, wind power generation devices, etc., which convert the direct current output into an alternating current power supply required in the micro-grid through an inverter.
c. An energy storage system: the storage device such as super capacitor, lithium ion battery is included, can store and release the electric quantity of DG system to satisfy electric power system's demand.
The direct current sub-micro-grid comprises:
a. direct current load: the direct-current electric vehicle charging pile comprises direct-current illumination, a direct-current air conditioner, a direct-current electric vehicle charging pile and the like, and the load characteristics of the direct-current electric vehicle charging pile relate to parameters such as voltage and current.
b. DC power generation system: the solar energy power generation system consists of a plurality of renewable energy power generation devices, such as a solar photovoltaic power generation device, a wind power generation device and the like, and the devices directly output a direct current power supply.
c. An energy storage system: the storage device comprises a super capacitor, a lithium ion battery and the like, and can store and release the electric quantity of the direct current system so as to meet the requirements of an electric power system.
The interconnection device controller (Interlocking Controller, ILC) is a device for realizing connection between the AC sub-micro-network and the DC sub-micro-network, and has the functions of real-time monitoring, coordination control and the like. The interconnect controller (Interlocking Controller, ILC) includes:
hardware equipment: the system comprises a hardware system formed by a computer, communication equipment, a sensor, an actuator and the like, and is used for carrying out real-time communication, remote monitoring and control on each equipment in an alternating current sub-micro network, a direct current sub-micro network and a micro-grid.
Software system: a software system comprising an operating system, an application program, a database, an algorithm and the like and used for analyzing and processing various parameters and states of the micro-grid so as to realize the optimized running and management of the micro-grid
Specifically, in the present embodiment, a distributed autonomous economic control strategy of the ac/dc hybrid micro grid group based on the limited time consistency is shown in fig. 3.
The invention considers the AC/DC hybrid micro-grid group economy mutual aid control method, based on the principle of equal cost micro-increment, adopts a finite time consistency algorithm as a secondary control method, considers the influence of time delay on system stability, finally realizes the power economy distribution between AC/DC sub-micro-grids, ensures that the cost micro-increment convergence of each sub-micro-grid is consistent, and maintains the frequency voltage stability of each sub-micro-grid. The problems of low reliability and single control target of the traditional AC/DC hybrid micro-electric cluster centralized control are well solved.
In order to check the correctness of the proposed economic mutual aid control scheme of the AC/DC hybrid micro-grid group, the invention establishes a simulation model in PSCAD/EMTDC, and the simulation model of the AC/DC hybrid micro-grid group is shown in figure 4 to carry out the simulation verification of the economic mutual aid control of the AC/DC hybrid micro-grid group.
The invention designs 2 working conditions, namely a variable load working condition and a plug and play working condition.
Working condition 1: and (5) changing load working conditions. And (3) closing the ILC at 2.5s, inputting an inter-group control strategy, and enabling the active load of the DC sub-micro-grid to be suddenly increased from 100kW to 210kW at 4s, wherein the operation simulation result of the AC/DC hybrid micro-grid group is shown in figure 5. From the simulation results, as can be seen from fig. 5 (a) and (b), each DG unit can converge and agree under the action of the control strategy in the sub-micro-network, so as to realize the power economic allocation in the micro-network. After 2.5s of input of the inter-group control strategy, each bidirectional converter rapidly adjusts the exchange power among the sub-micro networks to enable the cost micro increment of each sub-micro network to be converged. In the process, each DG unit can still well realize the economic distribution of the internal power of the micro-grid and is matched with the adjustment of the inter-group control strategy. In the process of the subsequent sudden load increase, the AC/DC hybrid micro-grid group can still quickly adjust the output of each sub-micro-grid, so that the system meets the economic operation requirement. As can be seen from the simulation results in fig. 5 (c) and (d), the frequency of the ac sub-microgrid and the PCC voltage of the dc sub-microgrid can be quickly recovered to the reference level, so as to ensure the power balance of the ac/dc hybrid microgrid group. As can be seen from the simulation results in fig. 5 (e) and (f), DG units in each sub-micro-grid can distribute reactive power according to the equal-proportion distribution principle, and rapidly track the reactive power when the load suddenly increases, and simultaneously, restore the PCC voltage of each sub-micro-grid to the reference level.
Working condition 2: "plug and play" operating mode. The simulation duration is 6s, ILC is closed at 2.5s, inter-group control strategy is put into, DG13 in the AC sub-micro-grid MG1 is taken out of operation at 3.5s, and put into again at 5s, and the simulation result of the operation of the AC/DC hybrid micro-grid group is shown in FIG. 6. From the simulation results, as can be seen from fig. 6 (a) and (b), each DG unit can converge and agree under the action of the control strategy in the sub-micro-network, so as to realize the power economic allocation in the micro-network. After 2.5s of input of the inter-group control strategy, each bidirectional converter rapidly adjusts the exchange power among the sub-micro networks to enable the cost micro increment of each sub-micro network to be converged. In the process, each DG unit can still well realize the economic distribution of the internal power of the micro-grid and is matched with the adjustment of the inter-group control strategy. In the subsequent DG switching process, the AC/DC hybrid micro-grid group can still quickly adjust the output of each sub-micro-grid, so that the system meets the economic operation requirement. As can be seen from the simulation results in fig. 6 (c) and (d), the frequency of the ac sub-microgrid and the PCC voltage of the dc sub-microgrid can be quickly recovered to the reference level, so as to ensure the power balance of the ac/dc hybrid microgrid group. As can be seen from the simulation results in fig. 6 (e) and (f), the DG units in each sub-micro-grid can distribute reactive power according to the equal-proportion distribution principle, and rapidly track the reactive power when DG is switched, and simultaneously, restore the PCC voltage of each sub-micro-grid to the reference level.
The invention provides an economic mutual-aid control method for an AC/DC hybrid micro-grid group, which adopts a finite time consistency algorithm, considers the influence of time delay on system stability, controls the AC/DC hybrid micro-grid group, and realizes the economic operation, power tracking and frequency voltage stabilization of the AC/DC hybrid micro-grid group.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (11)
1. A multi-scene coordination control method for an AC/DC hybrid micro-grid group is characterized by comprising the following steps:
1) Constructing a system structure of an alternating current-direct current hybrid micro-grid group comprising an alternating current sub-micro-grid, a direct current sub-micro-grid and an interconnection device controller (Interlocking Controller, ILC);
2) Constructing a control target among sub-micro-grid groups based on an equal-cost micro-increment principle facing to a scene of overall economic operation of an AC/DC hybrid micro-grid group;
3) Constructing a frequency recovery control target for a frequency fluctuation scene of an alternating current sub-micro-grid in an alternating current-direct current hybrid micro-grid group;
4) Constructing a voltage recovery control target facing to a voltage fluctuation scene of a direct current sub-micro network in an alternating current-direct current hybrid micro network group;
5) Constructing a controller basic framework based on a finite time consistency algorithm;
6) Aiming at a single ILC and facing to the scene of overall economic operation of an AC/DC hybrid micro-grid group, based on a controller basic framework, constructing a local control item of each ILC controller by taking a cost micro-increment as a decision variable;
7) Aiming at a single ILC and facing the frequency fluctuation scene of an alternating current sub-micro network in an alternating current-direct current hybrid micro grid group, based on a controller basic framework, the alternating current sub-micro network frequency is taken as a decision variable, and an alternating current side frequency auxiliary control item of each ILC controller is constructed;
8) Aiming at a single ILC and facing to a voltage fluctuation scene of a direct current sub-micro network in an alternating current-direct current hybrid micro grid group, based on a controller basic framework, taking the voltage of the direct current sub-micro network as a decision variable, and constructing a direct current side voltage auxiliary control item of each ILC controller;
9) Aiming at all ILCs, to avoid power contention among different ILCs, constructing a coordination auxiliary control item of each ILC controller based on a controller basic framework by taking a cost micro increment as a decision variable;
10 According to the local control item of the ILC controller, the alternating-current side frequency auxiliary control item, the direct-current side voltage auxiliary control item and the coordination auxiliary control item, constructing an ILC control strategy.
2. The method for coordinated control of multiple scenes of an ac/dc hybrid micro grid group according to claim 1, wherein in step 2), a scene of overall economic operation of the ac/dc hybrid micro grid group is oriented, and a control target between sub micro grid groups based on an equal cost micro increment principle is constructed, specifically:
in the method, in the process of the invention,the cost micro increment mean value of the mth alternating current sub-micro network; />The cost micro increment mean value of the nth direct current sub-micro network;
the control target among the sub-micro network groups is realized by controlling the transmission power of the ILC, the control target of the control target among the sub-micro network groups is divided into 2 parts, and the 1 st part is to make the cost micro increment of an alternating current sub-micro network and a direct current sub-micro network which are directly connected with the ILC the same, namely:
in the method, in the process of the invention,the average cost micro increment of the m-number alternating current sub-micro network connected with the bi-directional converter ILCg at the moment t is set;the average cost micro increment of the n-number direct current sub-micro network connected with the ILCg at the moment t is set; f (f) g A difference value that is a cost micro increment between the 2 sub-micro networks;
part 2 of the control target is to make the difference of the cost micro increment of the double-side sub-micro-network at each ILC consistent and finally substitute 0, namely:
3. the method for coordinated control of multiple scenes of an ac/dc hybrid micro-grid group according to claim 1, wherein in step 3), frequency recovery control targets are constructed for frequency fluctuation scenes of ac sub-micro-grids in the ac/dc hybrid micro-grid group, specifically:
stabilizing the frequency of each AC sub-micro-network to a frequency reference value, and constructing a frequency recovery control target as follows:
wherein omega is i Frequency measurement for the ith ac sub-microgrid; omega * Is the frequency reference value of the ac sub-microgrid.
4. The method for coordinated control of multiple scenes of an ac/dc hybrid micro grid group according to claim 1, wherein in step 4), voltage fluctuation scenes of dc sub micro-grids in the ac/dc hybrid micro grid group are oriented, and a voltage recovery control target is constructed specifically as follows:
stabilizing the voltage of the common bus of each direct current sub-micro network to a voltage reference value, and constructing a voltage recovery control target as follows:
in U PCC,pu,n The method comprises the steps that a normalized measured value of the voltage of a bus commonly connected with the direct current side of an nth direct current sub-micro network is obtained;is common to the DC side of the nth DC sub-micro-networkAnd connecting a normalized reference value of the bus voltage.
5. The method for coordinated control of multiple scenes of an ac/dc hybrid micro grid group according to any one of claims 1 to 4, wherein in step 5), a controller basic architecture based on a finite time consistency algorithm is constructed, specifically:
the finite time consistency control is adopted to improve the convergence speed and the convergence performance, and the control protocol is as follows:
wherein u is i (t) is a coherence protocol; a, a ij Is the communication weight between the distributed nodes; x is x i And x j The state quantity of the nodes i and j is respectively represented and used for representing information such as frequency, voltage, power and the like in the micro-grid; alpha is more than 0 and less than 1 as control factors, and is used for adjusting control parameters of convergence speed; sign (x) is a sign function;
the frequency of the alternating current sub-micro network is converged to 50Hz, the voltage of each sub-micro network is converged to a rated value, a leading node is introduced to receive reference value information on the basis of a limited time consistency protocol aiming at a voltage and frequency control target, after information interaction is carried out between the leading node and adjacent nodes, the states of all nodes are converged to the reference value, and the control protocol is as shown in the formula:
wherein b is i A reference input weight representing an i-th node; x is x ref A given reference value to which the system state needs to converge;
the limited time consistency control protocol of the AC/DC hybrid micro-grid group considering the time delay is as follows:
wherein τ ij The communication time delay from the node j to the node i is set; t (T) i Is a self-delay, corresponding to the computation delay or reaction delay of the DG unit itself.
6. The method and apparatus for coordinated control of multiple scenes of an ac/dc hybrid micro grid group according to claim 5, wherein in step 6), a local control item of an ILC controller is constructed for a scene of overall economic operation of the ac/dc hybrid micro grid group, specifically:
the cost micro increment of the AC/DC sub-micro-network directly connected with the single ILC is equal, the difference value of the cost micro-increment of the AC/DC sub-micro-network is taken as a decision variable, and the decision variable is substituted into the (6) to obtain the control strategy of the local control item, wherein the control strategy is as follows:
in the method, in the process of the invention,the local control item is a local control item of the ILCg and is used for realizing that the cost micro increment of an alternating current sub-micro network m and a direct current sub-micro network n which are directly connected with the ILCg is the same; in the formula, subscripts m and n respectively correspond to an alternating current sub-micro network and a direct current sub-micro network which are connected with the ILCg; />The average cost micro increment of an m-number alternating current sub-micro network connected with the bi-directional converter ILCg is set; />Is the average cost micro increment of the n-number direct current sub-micro network connected with the ILCg;
wherein N is m Is the whole of AC sub-micro network, N n Is the whole of the DC sub-micro network; g i For the link weight of node i and common connection bus, if node i and ILC have communication link, g i =1, otherwise 0; τ mi Representing communication delay in the communication process of the ith DG unit in the mth alternating current sub-micro network and the mth alternating current sub-micro network controller; τ ni Representing communication delay in the communication process of an ith DG unit in an nth direct current sub-micro network and an nth direct current sub-micro network controller; i Ci The expression of the cost micro increment of the ith DG unit in the sub-micro network is as follows:
I Ci ＝2α i P i +β i (11)
wherein alpha is i And beta i Representing cost coefficients for each distributed power supply; p (P) i Representing the active power output by each distributed power source.
7. The method for coordinated control of multiple scenes of an ac/dc hybrid micro grid group according to claim 6, wherein in step 7), for a certain ILC, and for a frequency fluctuation scene of an ac sub-micro grid in the ac/dc hybrid micro grid group, an ac side frequency auxiliary control item of the ILC controller is constructed, specifically:
the frequency of an alternating current sub-micro network directly connected with a single ILC is restored to a rated value, the frequency of the alternating current sub-micro network is used as a decision variable, and the decision variable is substituted into the variable (8) to obtain the control strategy of the alternating current side frequency auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,is an AC side frequency auxiliary control item; />And omega pu,m The normalized values are respectively the reference frequency of the AC side public connection bus and the actual measurement frequency of the AC side public connection bus; τ gm A communication delay between the ILCg and the AC sub-micro-network m; t is time; alpha is a control factor for adjusting convergence speed;
the normalized frequency is defined as:
wherein omega is pu A normalized value representing frequency; ω represents ac microgrid frequency; omega max And omega min Is the upper and lower limits of the ac microgrid frequency.
8. The method for controlling the economic mutual aid of the ac/dc hybrid micro-grid group according to claim 7, wherein in the step 8), for a certain ILC, and for a voltage fluctuation scene of a dc sub-micro-grid in the ac/dc hybrid micro-grid group, a dc side voltage auxiliary control item of the ILC controller is constructed, specifically:
and (3) restoring the voltage of the direct current sub-micro network directly connected with the single ILC to a rated value, substituting the voltage of the direct current sub-micro network into the direct current sub-micro network serving as a decision variable into the direct current sub-micro network (8) to obtain a control strategy of the direct current side voltage auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,is a DC side voltage auxiliary control item; />And U PCC,pu,n Ginseng respectively as public connecting bus of DC sideThe normalized value of the actual measured voltage of the common connection bus of the test frequency and the direct current side; τ gn Is the communication delay between the ILCg and the DC sub-micro network n;
the normalized dc voltage is defined as:
in U pu A normalized value representing the dc voltage; ω represents dc microgrid voltage; u (U) max And U min Is the upper and lower limits of the dc microgrid voltage.
9. The method for coordinated control of multiple scenes of an ac/dc hybrid microgrid group according to claim 8, wherein in step 9), for all ILCs, in order to avoid power contention among different ILCs, a coordinated auxiliary control item of an ILC controller is constructed, specifically:
and (3) enabling the difference value of the cost micro increment of the two-side sub-micro network at all ILCs to be consistent and finally to be substituted into 0, taking the difference value of the cost micro increment of the two-side sub-micro network as a decision variable, substituting the decision variable into the formula (8) to obtain a control strategy of the coordination auxiliary control item, wherein the control strategy is as follows:
in the method, in the process of the invention,a coordination auxiliary control item for the cost micro increment difference value of the double-side sub-micro network at all ILCs; o is a set of ILCs; a, a gh The communication weight between the ILC double-side sub-micro-network difference value and the ILCh is calculated; />The average cost micro increment of a p-type alternating current sub-micro network connected with the bi-directional converter ILCg is set; />Average cost micro increment of the q-number direct current sub-micro network connected with the ILCg; τ gh A communication delay between the ILC double-sided sub-microgrid difference value and ILCh; t (T) g Communication self-delay of each AC/DC sub-micro-network; subscripts p and q correspond to an ac subnetwork and a dc subnetwork, respectively, which are connected to the ILCh.
The ILC is controlled secondarily, and the operation information of other ILCs is basically introduced on the basis of the ILC local control, so that the development of the cost micro-increment of the sub-micro-grid to the cost micro-increment average value of the AC/DC hybrid micro-grid group can be promoted, and the economic distribution of the active power among all sub-micro-grids can be realized.
10. The method for coordinated control of multiple scenes of an ac/dc hybrid microgrid group according to any one of claims 6 to 9, wherein in step 10), an ILC control strategy is constructed according to a local control item and an auxiliary control item of an ILC controller, specifically:
in the method, in the process of the invention,an active power reference value for flow through ILCg; />Integration for ILCg local control term; />Integrating the auxiliary control term for the alternating-current side frequency; />Integration as a direct-current side voltage auxiliary control term; />And integrating the coordination auxiliary control items of the cost micro increment difference value of all the double-side sub-micro networks at the ILC.
11. The method for coordinated control of multiple scenes of an ac/dc hybrid micro-grid group according to claim 1, wherein the system structure of the ac/dc hybrid micro-grid group comprises a plurality of ac sub-micro-grids, a plurality of dc sub-micro-grids and a plurality of interconnection device controllers ILC, and the ac sub-micro-grids and the dc sub-micro-grids are interconnected through the interconnection device controllers ILC;
the AC sub-micro-grid comprises an AC load, a distributed AC power generation system and an AC energy storage system;
the direct current sub-micro-grid comprises: direct current load, distributed direct current power generation system, direct current energy storage system.
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