JP2022119184A - Active disconnection control method for multi-energy cooperative power grid - Google Patents

Abstract

To provide an active disconnection control method for a multi-energy cooperative power grid.SOLUTION: In a method, after a reasonable control policy is selected on the basis of a system structure, the goal is to maximize the energy supply recovery of a power grid, an active disconnection model for multi-energy coupling power grid is constructed by considering load priority and controllability comprehensively to obtain active parallel-off control for power grid considering multi-energy coupling by using a greedy algorithm, and the energy supply recovery effect of the power grid is improved by considering the multi-energy coupling effect of the system to ensure the safety and reliability of the energy supply to the system.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to the field of electric power system, and more particularly to an active disconnection control method for multi-energy cooperative power grid.

Active disconnection for distribution networks is one of the most effective power restoration policies [1], as it can ensure continuous power supply to some critical loads in the event of failure, reduce threats to personal safety and loss of economic property due to When a failure occurs inside the distribution network or in the upper transmission network, active disconnection is realized by adjusting the open/closed state of the division switch and contact switch, and the island of power supplied by the distributed power supply (Distribution Generation, DG) is created. form and improve the recovery speed of critical load feeds in the system, on the premise of ensuring the safety of supplying energy to the system. By rationally setting the position of the disconnection point for the distribution network including distributed power sources, in the event of a failure, it operates in an isolated island mode to reduce the adverse effects of the failure on the distribution network, reduce the power outage range, It has important implications for improving the energy supply quality, energy supply safety and reliability of distribution networks (Non-Patent Documents 2-4).

Currently, I am researching the power supply recovery policy of distribution networks including distributed power sources. However, distributed generation is characterized by uncertainties and susceptibility to external environmental influences, which have limited impact on grid energy supply restoration. Also, some loads in the distribution network are energy conversion devices driven by electricity, the function of which is to convert electrical energy into various forms of energy such as heat, cold, etc., and in case of failure the part electrical load will be supplied by the corresponding subsystem. In order to improve the energy supply recovery capacity of the distribution grid, we should not only consider from the power source side of the distribution grid, but also start from the viewpoint of the flexibility of the multi-type load of the distribution grid, and the energy conversion equipment in the distribution grid. By regulating special flexible loads such as , further exploit the potential resilience of the grid.

In the energy background of multi-energy coupling, the conventional power grid has the power grid as the core, and the multi-energy coupling energy system (non-patent document 5), whose flexible operation mode and multi-energy complementary characteristics provide a better and more rational solution for active grid paralleling on the one hand, and on the other hand the grid provide new opportunities for the safety control of Compared to traditional active disconnection policies, elements such as gas turbines, Combine Heat and Power (CHP), etc. have better stability and controllability, so the supporting action on the grid is more solar, Significantly stronger than conventional distributed power sources such as wind power generation, active disconnection for electrical grids can provide strong power support by means of quantitatively increasing the output of coupling elements. Second, the power-driven energy conversion device can reduce the load on the grid by reducing power or directly stopping operation, etc., and the missing energy support such as hot and cold can be replaced by the corresponding energy system. supply, thereby reducing the amount of load waiting to be restored on the grid. In summary, after considering the complementary effect of multi-energy, in case of failure, the energy system of multi-energy coupling provides power supply support to the distribution grid by coordinating multi-type energy, and heat, cold, etc. It has an important role in reducing the distribution network load and improving the recovery effect of system failure by converting the energy supply method of the network, but there are few studies in this aspect.

Therefore, it is of particular importance to research and develop active parallel-off control methods for multi-energy cooperative power grids.

IEEE standard for interconnection distributed resources with electric power system: IEEE Std 1547 [S]. Iscataway, NJ, USA: IEEE Press, 2003 Microgrids for service restoration to critical load in a resilient distribution system [J], Xu Y, Liu C, Schneider K P, et al, IEEE Transactions on Smart Grid, 2018, 624-9(1) Reliability evaluation for distribution system with renewable distributed generation during islanded mode of operation [J], Atwa Y.; M. , El-Saadany E.; F. , IEEE Trans on Power Systems, 2009, 24(2): 572-581 Review and Prospects of Power Distribution Network Fault Recovery in Toughness Background [J], Huh Yin, Ho Gyeonghan, Wang Ying et al., Electrical Engineering Technical Journal, 2019, 34(16): 3416-3429 User-level integrated energy system planning for engineering applications [J], Zhou Changcheng, Makiyuan, Guo Zuogang et al., Electrical Engineering Technical Bulletin, 2020, 35(13): 2843-2854

The present invention provides an active parallel-off control method for multi-energy cooperative power grid.

By constructing a network model of electric-gas-thermal coupling multi-energy streams, the present invention proposes active parallel-off alternative control and cooperative control policies for power grids that apply to multi-energy coupling. After selecting a reasonable control policy based on the system structure, the goal is to maximize the energy supply recovery of the distribution network, comprehensively consider the load priority and controllability, and for the multi-energy coupling distribution network An active paralleling model is constructed, and a greedy algorithm is used to obtain active paralleling control for a distribution network that considers multi-energy coupling. It improves the supply recovery effect and ensures the safety and reliability of energy supply to the system, the details of which are explained below.

1. An active parallel-off control method for a multi-energy cooperative power grid, the method comprising:
constructing a network model of multi-energy streams for a power grid that takes multi-energy coupling into account and using an alternating iteration method to obtain an initial multi-energy stream;
Based on the initial multi-energy stream, according to the type of coupling element, propose an alternative control policy and coordinated control policy, obtain multi-energy stream, load distribution in the coupling element, the output of each distributed generation and the distribution network. obtaining a status;
A step of constructing an active parallel-off model for a distribution network that adopts an alternative control policy and a cooperative control policy, targets the maximum amount of load recovery, constrains safe operation conditions, and considers multi-energy coupling;
Using a greedy algorithm to find an active paralleling model for a distribution network, obtain a means of dividing an isolated distribution network island in a fault situation, and perform active paralleling to realize continuous power supply to a distribution network load in a fault situation. and a step.

Among them, the alternative control policy uses the multi-energy coupling effect to convert the load of the node where the supply type coupling element is located to the corresponding energy subsystem for energy supply, on the premise of satisfying the safety constraints. , the output of the non-electrical coupling element or the electrical acquisition type coupling element replaces the load of the electrical supply type coupling element.

Further, the mathematical model of said alternative control policy is:

In the equation, ΔP _ri represents the power of the alternative electrical energy, δ _e represents the step size by which the output of the electrically fed coupling element is reduced, η _i represents the conversion efficiency, and Δφ _r represents the alternative electrical energy sub represents the output that the balance node of the system needs to increase, ∂φ _r /∂φ _node represents the sensitivity of the output of the node where the non-electronic system electrically driven coupling element is located to the output of the balance node, n _t represents the number of iterations.

Wherein, the cooperative control policy is to increase the electric output of the electric gain coupling element to provide power support for the active disconnection for the power grid under the premise of meeting the safety constraints.

Furthermore, the mathematical model of said cooperative control policy is:

In the _formula , _{a =} 1, 2, . represents the step size of the power increase on the element feed side, ΔΩ _a represents the increased output of the other subsystems, ζ is the conversion ratio, and Δr _a is the non-electrical type to be changed to cancel ΔΩ _a . Represents the output of the coupling element.

Wherein, the step of determining the initial multi-energy stream distribution of the system using the alternative control policy includes the following steps.

Specifically, the alternative control policy is:
selecting (1) a coupling element with regulating capability in a load side system of electrically driven coupling elements as a balance node;
step (2) of determining the reduction step size δ _e of the node load at which the electrically fed coupling element is located in the distribution network and calculating the power increase Δφ _r of the balancing node;
Calculate the multi-energy streams of the system, determine whether the system at this time satisfies all the constraints, and if so, the electrically-fed coupling element will continue to reduce the output, and move to step (2). , otherwise obtaining alternative electrical loads (3).

Further, the step of determining the distribution of the initial multi-energy streams of the system using the cooperative control policy specifically comprises:
step (1) of selecting and marking the most efficient coupling element among the electrical acquisition type coupling elements;
step (2) of determining the step size δ of the power increase on the supply side of the electrical harvesting type coupling element and gradually increasing the power on the supply side according to the step size to obtain an increased power on the load side of the coupling element; When,
Determine if the system at this time satisfies all the constraints, if so, go to step (2) and continue to increase the output, else step (3) to execute step (4). )When,
Adjust the output of the non-electrical coupling element, determine that the system can be restored to a safe operating state, if satisfied, continue to execute step (2), otherwise continue to step (5). performing step (4);
Mark the coupling element, if still no electricity-obtained coupling element is marked, continue to perform step (2), else step (5) to obtain the final operating state of the coupling element ) and including.

1. The present invention considers the multi-energy cooperative effect of the system, and by coordinating multiple forms of energy, fully explores the energy supply potential of the multi-energy coupling system, and effectively increases the energy supply recovery amount of the system. , and compared with the traditional distributed power supply only to restore power supply, the isolated island formed by this method has fewer switching operations, which helps the system to restore normal operation after the fault is cleared. .

2. The present invention builds an active paralleling model that comprehensively considers the load priority, controllability and network topology structure of the distribution network, and the system topology structure and load characteristics and flexible soft open point , SOP) can be fully utilized to improve the amount of load recovery of the distribution network in the event of a fault, and at the same time to ensure the continuous and reliable supply of critical loads on a priority basis. reduce threats to personal safety and loss of economic property due to

3. The present invention takes the angle of multi-energy cooperation as a starting point for the distribution network that considers multi-energy coupling, and proposes an alternative control policy and a cooperative control policy that apply to the multi-energy coupling power distribution network. It improves the energy supply recovery level of the distribution grid from both transition and power support, can rationally select the control policy based on the system structure, and has relatively strong versatility.

Fig. 4 is a flow chart of an active parallel-off control method for multi-energy cooperative power grid; FIG. 4 is a schematic diagram of an alternative control policy realization process; 1 is a schematic diagram of a distribution network topology structure considering multi-energy coupling; FIG. 1 is a schematic diagram of an active parallel-off for an electrical grid; FIG.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the following describes the embodiments of the present invention in more detail.

(Example 1)
An active parallel-off control method for a distribution network considering multi-energy coupling, the method includes steps 101-104, as shown in FIG.

In step 101, build a network model of the multi-energy streams of the distribution grid considering multi-energy coupling, and obtain the initial multi-energy streams of the system by using alternating iteration method.

In step 102, based on the initial multi-energy stream of the system, according to the type of coupling elements in the system, propose an alternative control policy and a coordinated control policy, dig deep into the multi-energy cooperation effect of the system, and make an active Provide power support for disconnection, improve the power recovery of the power grid, and based on this, determine the multi-energy stream of the system, the coupling elements in the system, the output of each distributed power source and the load distribution in the power grid. Get status.

In step 103, after adopting an alternative control policy and a cooperative control policy, an active disconnection model for a power distribution network is created with the goal of maximizing the amount of load recovery, with the safe operating conditions of the system as constraints, and considering multi-energy coupling. To construct.

In step 104, a greedy algorithm is used to obtain an active paralleling model for the distribution network, a means for dividing the distribution network island in case of failure is obtained, active paralleling is performed according to the obtained means, and a distribution network is obtained in case of failure. Provides continuous power to the load.

As described above, the embodiment of the present invention realizes the active grid disconnection control considering the multi-energy coupling effect through the above steps 101 to 104, and the flexible angles of the power supply side and the load of the power grid. Considering from the above, fully explore the potential power supply recovery capacity of the power grid, effectively improve the power supply recovery level of the power grid, and provide a new way of thinking about the fault recovery of the power grid.

(Example 2)
In the following, specific calculation formulas and examples are combined to further introduce the solution means in Example 1, and the details are shown in the following description.

In step 201, construct and obtain a network model of the multi-energy streams of the power grid that considers the multi-energy coupling.

Here, the step 201 includes:
1) Distribution network model a) Topological structure model of the distribution network Represent the topological structure of the distribution network in the form of a node authorization tree, namely T(V, E, W), where V, E, W are respectively Represents a set of nodes, edges, and node weights. The node weight W can be represented by the following equation (1),

In the equation, ω is the weight of node v _i , S _Gi , S _Li represent the sum of the injected power of the sources and the sum of the power of the loads connected to node v _i , respectively.

b) Distribution grid power flow model The distribution grid is the core of the multi-energy coupling energy system and the hinge connecting other energy subsystems. An embodiment of the present invention describes a power system using a classical AC power flow model, whose node power equations are:

In the equation, P _i , Q _i are the active and reactive powers of node i respectively, Y _ij is the admittance between nodes i, j, U _i is the voltage phasor of node i, U _j is the node is the voltage phasor of j, "." is the phasor operation, "*" is the conjugate operation, Re is the real part operation, and Im is the imaginary part operation.

2) Thermal system model A thermal system can be constructed into a hydraulic model and a thermal model, respectively, depending on the type of variables to be obtained. The hydraulic model includes a nodal flow equation and a head loss equation that hot water flowing through the network must satisfy, i.e.

In the formula, A _s is the node-branch association matrix of the heat supply network, m is the flow rate of each pipe, m _q is the flow rate out of each node, and B _h is the circuit-branch of the heat supply network. is the association matrix and h _f is the head loss vector.

The thermal model includes a thermal power equation, a supply-recovery heat temperature equation and a nodal temperature mixing equation, i.e.

In the equation, T _s is the heat supply temperature, T ₀ is the output temperature, Φ is the nodal heat output, T _end is the end temperature, T _start is the start temperature, and _Ta is the ambient temperature. where l is the length of the pipe, m _out , T _out and min , T _in are the flow rate and temperature of the water _in the outflow and inflow pipes respectively, C _p is the specific heat capacity of the water, and λ is the pipe is the thermal conductivity of

3) Natural gas system model The relationship between pipe flow rate and node pressure in a natural gas network without compressors is:

In the equation, f _r is the steady-state flow rate of natural gas pipe r, K _r is a pipe parameter, and s _mn is a sign function indicating the flow direction of natural gas in pipe r, whose value is 1 or − 1 and p _m , p _n represent the pressure at nodes m, n.

The equation for nodal flow in a natural gas system is

where A _g is the node-branch association matrix of the natural gas system, f is the pipeline natural gas flow rate, and L is the flow rate out of each node.

4) Coupling element model Coupling element is an important energy conversion device in multi-energy coupling energy system. be. The multi-energy coupling energy system includes multiple types of coupling elements such as micro gas turbines, CHP plants, gas boilers, electric boilers, etc., and can be represented by the following models.

The power equation for a CHP plant is

In the equation, C _CHP is the thermoelectric ratio of the CHP plant, P _CHP,e is the electrical power produced by the CHP plant, and Φ _CHP,h is the thermal power produced by the CHP plant.

The gas boiler power equation is

In the equation, _ΦGB represents the thermal power produced by the gas boiler, _LGB represents the flow rate at which the natural gas system injects natural gas, α represents the efficiency of the gas boiler, and _Hg represents the calorific value of the natural gas.

The power equation for an electric boiler is

In the equation, Φ _EB represents the heat output produced by the electric boiler, PE _EB represents the power consumed by the electric boiler, and β represents the efficiency of the electric boiler.

The gas turbine power equation is

In the equation, _PGT represents the power produced by the gas turbine, γ represents the efficiency of the gas turbine, and _LGT represents the flow rate at which the natural gas system injects natural gas.

5) Multi-Energy Stream Determination Method When determining the multi-energy stream of the system, the coupling element is equivalent to the source point or load point in the corresponding energy subsystem based on the energy types of its energy supply side and load side. SOPs can be equated with load nodes, generator nodes or balance nodes based on different operating regimes to facilitate determination of system power flow. The embodiment of the present invention adopts the alternating solution method to obtain the multi-energy streams of the multi-energy coupling distribution network, which is computationally efficient, has a flexible solution method, and analyzes and controls the operating state of the coupling elements. For simplicity, we base ourselves on the following control policy proposals.

At step 202, an alternative control policy and a cooperative control policy are proposed according to the system architecture and the type of coupling element.

Here, the step 202 includes:

Coupling elements are divided into three types according to the energy types on the energy supply side and the load side. The first is an electric coupling element typified by gas turbines, CHP plants and the like, and the third is a non-electrical coupling element typified by gas boilers and the like. Alternative control policies and coordinated control policies are proposed for different types of coupling elements, thereby improving the power restoration quality of the distribution network and the safety and reliability of the system.

1) Alternate control policy The alternate control policy uses the multi-energy coupling effect to convert the load of the node where the electric boiler or other electric supply type coupling element is located to the corresponding energy subsystem to supply energy. is to do. Under the premise that system safety constraints are satisfied, by increasing the output of non-electrical coupling elements such as gas boilers or electrical acquisition type coupling elements such as CHP plants, the load of electric supply type coupling elements such as electric boilers can be replaced. and, for example, a gas boiler to replace an electric boiler to power the heat system, increase the load on the natural gas system, reduce the load on the grid, thereby realizing the effect of replacing the load on the grid, reduce the load waiting to be restored, improve the rate of load restoration, and improve the load restoration effect of the distribution network.

The process of implementing the alternative control policy is as shown in FIG. reduces the unit load ΔP _r , the operating point is changed from a to a ^′ , so the system on the load side of coupling element A suffers a unit power shortage of η _i ΔP _r , and the safe operation of the system In order to _ensure

In general, non-electrical coupling elements or electrical harvesting coupling elements such as electric boilers, CHP plants, etc. that can supply energy to multiple energy systems are selected as balancing nodes of the system. When coupling element B becomes the balance node of the load side system, its operating point changes from point b to point b'. After multiple iterations, when the output of coupling element B reaches a threshold, a coupling element such as coupling element C can be selected as the balance node of the load side system to continue executing the alternate control policy. The replacement process ends when coupling element A is completely replaced or the output of all coupling elements reaches the upper limit.

If an electrically powered coupling element is present in the energy network, an alternative control policy can be used to restore the energy supply. A mathematical model of the alternative control policy for any electrically-fed coupling element is

In the equation, ΔP _ri represents the power of the alternative electrical energy, δ _e represents the step size by which the output of the electrically fed coupling element is reduced, η _i represents the conversion efficiency, and Δφ _r represents the alternative electrical energy sub represents the output that the balance node of the system needs to increase, ∂φ _r /∂φ _node represents the sensitivity of the output of the node where the non-electronic system electrically driven coupling element is located to the output of the balance node, n _t represents the number of iterations.

2) Coordinated control policy Coordinated control policy increases the electrical output of electricity harvesting coupling elements such as gas turbines, CHP plants, etc., and provides power support for active disconnection for the grid, subject to network safety constraints. It is to be. In the energy system, if the load side is only an electric power load, the electric power output can be increased on the premise that the system safety constraints are satisfied, as opposed to the electric power acquisition type coupling element that can increase electric power. When there are multiple types of loads on the load side (for example, CHP plants, etc.), the electrical output is increased and the output of the non-electronic system load side is increased accordingly, and the non-electric type cup in the non-electronic system is increased. A ring element is selected as the balance node and used to balance the increased power of the electric gain coupling element. As the electrical output of a CHP plant increases, the thermal output of the CHP plant also increases accordingly, requiring a reduction in the thermal output of non-electrical coupling elements such as gas boilers in order to meet the safe operation constraints of the thermal system. be.

Coordinated control policies can be used when there is an electrical gain coupling element in the system that can increase the electrical output. For any electrical acquisition type coupling element, the mathematical model of its cooperative control policy is as shown in equation (12),

In the _formula , _{a =} 1, 2, . If ΔΩ a represents the step size of the power increase on the element supply side, ΔΩ _a represents the increased output of the other subsystems, and there is only the grid on the load side, then ΔΩ _a =0 and ζ is the conversion ratio. , Δr _a represents the output of the non-electrical coupling element to be modified to cancel ΔΩ _a .

In step 203, the grid active paralleling model considering multi-energy coupling is mainly composed of the active paralleling target function and safe driving conditions.

Here, step 203 includes:

1) Goal function of active paralleling model The goal of active paralleling for power distribution networks considering multi-energy coupling is to maximize the amount of power restoration load, which can be expressed as follows:

In the equation, Π is the island finally formed, b is the node in the island, ω _b is the weight of node b, and P _i represents the load power connected to node b.

2) Constraints of the active disconnection model As the distribution network is the basis of the multi-energy coupling energy system, its operation method is flexible and the operation equipment is complicated. In addition, power system safety constraints can be divided into island power balance constraints, node voltage constraints, thermal stability constraints and SOP operating condition constraints.

The power balance constraint within the isolated island is

In the formula, P _Gi , Q _Gi , P _Li , Q _Li represent the active and reactive power of the source node and the active and reactive power of the load node in the formed island respectively, and n is the number of distributed power sources in the island. , where k is the number of load nodes in the island.

The node voltage constraint is

In the equation, U _c is the voltage _amplitude of node c, U _cmin , U _cmax are the upper and lower _bounds of the node voltage amplitude, c=1, 2, . is.

The thermal stability constraint is

In the equation, P _min , P _max , Q _min , Q _max are the maximum and minimum values of active and reactive power in power line transmission, P _xy , Q _xy are transmitted from node x to node y. , where x, _y =1, 2, . . . , ne.

Thermal system safety constraints include piping flow constraints and supply and recovery temperature constraints.

Constraints on piping flow are

In the equation, m _pq represents the mass flow rate of transporting water from node p to node q, m _min , m _max represent the upper and lower limits of the mass flow rate of the thermal system piping, p, q=1, 2, , _nh , where _nh is the total number of nodes in the thermal system.

In a practically operating thermal power system, the node heat supply and recovery temperature drop is small and both are within safety limits, where temperature safety constraints can be ignored.

Natural gas system safety constraints include pipe flow constraints, node pressure constraints, and the like.

The node pressure constraint is

In the equation, f _mn is the flow rate of gas transported from node c to node n, f _min , f _max represent the upper and lower limits of the gas flow rate in the natural gas pipeline, c, n=1, 2, . , _ng .

The node pressure constraint is

In the equation, p _t represents the pressure at node o, p _min , p _max represent the upper and lower limits of the natural gas node pressure, o=1, 2, . . . , _ng .
At step 204, a multi-energy coupling active grid model constructed using a greedy algorithm is determined.

Here, step 204 includes S1-S4.

S1: Obtain the initial multi-energy stream distribution of the system.

Based on the coupling elements in the multi-energy coupling energy system, it is determined whether to adopt an alternative control policy or a coordinated control policy. Employing the alternating solution algorithm mentioned in sub-step 5) of step 201 to calculate the multi-energy streams taking into account the multi-energy coupling grid, the output of the coupling element, the capacity of the distributed generation and the load of the grid get the distribution.

An algorithmic flow that employs an alternative control policy is
selecting (1) a coupling element with regulating capability in a load side system of electrically driven coupling elements as a balance node;
step (2) of determining the reduction step size δ _ee of the node load at which the electrically fed coupling element is located in the distribution network and calculating the power increase Δφ _r of the balancing node;
Calculate the multi-energy streams of the system and determine if the system at this time satisfies all the constraints mentioned in step 203; Step (3) of moving to (2), otherwise suspending the previous operation result;
and (4) obtaining an alternative electrical load quantity.

An algorithmic flow that employs a cooperative control policy is
step (1) of selecting and marking the most efficient coupling element among the electrical acquisition type coupling elements;
step (2) of determining the step size δ of the power increase on the supply side of the electrical harvesting type coupling element and gradually increasing the power on the supply side according to the step size to obtain an increased power on the load side of the coupling element; When,
Determine if the system at this time satisfies the constraints mentioned in step 203, and if so, go to step (2) and continue increasing the output, else execute step (4). a step (3) of
Adjust the output of the non-electrical coupling element, determine that the system can be restored to a safe operating state, if satisfied, continue to execute step (2), otherwise continue to step (5). performing step (4);
step (5) of marking the coupling element and continuing to perform step (2) if there is still no electrified coupling element marked; otherwise continuing to perform step (5);
and (6) obtaining the final operating state of the coupling element.

S2: Determine the initial island dividing means.

(1) A greedy algorithm is used to find sub-means for splitting islands, and the flow for finding them is as follows.

i) Isolate fault points, build a topology model of distribution network considering multi-energy coupling based on node type, system structure, weight and load demand of each node are w _i and P _i respectively.

ii) Let the DG that is not marked in the system and the node with the maximum output be the initial node, write Z={v ₀ }, and mark the DG.

iii) Calculate the sum P _Z of power of all nodes in the isolated island, the sum B _Z of weights of all nodes in the isolated island, and the remaining power supply capacity C _R according to formulas (20) to (22) at this time. , and check whether the system at this time satisfies the safe operation conditions of the power system; if so, continue running; otherwise, go to step (7);

iv) Compute the weight w _i (j) of the node element i and the node element j connected to it in the isolated island Z that has already been formed.

v) Choose the node with the largest weight, denote m, and add node m into the island if B _m is not 0, denote Z={Z, m}. Otherwise, go to step (7).

vi) If P _z <C _R , go to step (3). Otherwise, continue with the next step.

vii) Calculate P _Z , B _Z to obtain the initial island partitioning means.

(2) reconstructing the topology structure diagram, compressing the nodes in the formed island means into one new node, and denoting the node with n _e +i _c number (i _c is the number forming the island);

(3) If there is an unmarked power point in the system, go back to step (2) and continue creating isolated islands. Otherwise, move to the next step.

S3: Calculate the surplus power of all the isolated islands in the initial island dividing means, and if there is an isolated island whose surplus power is not 0, select a part of the controllable load at the node adjacent to the isolated island and add it to the isolated island. do.

S4: Perform multi-energy stream calculation using the alternate solution method, and if the multi-energy stream calculation result does not meet the system safety constraint or the power of the balance node in the island exceeds the limit, the part of the island pruning controllable loads with low priority to obtain the final island partitioning means of the grid. According to the load addition order in each isolated island, the open/close state of each switch is determined, the system is reconfigured, and the final active disconnection policy for the distribution network is obtained.

As described above, according to the above steps 201 to 204, the embodiment of the present invention considers the cooperative effect of multi-energy in the system and coordinates multiple forms of energy, thereby obtaining energy of the multi-energy coupling system. The supply potential is fully explored, and the energy supply recovery amount of the system is effectively improved. Compared with the traditional distributed power supply only, the switch operation times of the isolated island formed by the mentioned method are more. less and helps restore normal operation of the system after the fault is cleared. Considering the stationary model of the multi-energy coupling distribution network, from the perspective of multi-energy cooperation, we propose alternative control policies and coordinated control policies applied to the multi-energy coupling distribution network, both for load shifting and power supply support. It is of great significance to improve the energy supply recovery level of the power distribution grid and improve the system's energy supply safety and reliability.

(Example 3)
In the following, specific examples are combined to verify the feasibility of the solutions in Examples 1 and 2, and the details are shown in the following description.

The method considers a multi-energy coupling consisting of a PG&E 69-node power distribution system, a 32-node thermal system, and an 11-node natural gas system connected to an IEEE 33-node power distribution system via SOPs, as shown in Figure 3. A network is taken as an example to verify the accuracy and effectiveness of the proposed active disconnection policy for distribution networks. The coupling elements in the system shown in FIG. 3 include gas turbines, CHP plants, electric boilers and gas boilers, and their distribution is shown in Table 1 below. Nodes 5 and 36 in the PG&E 69 node distribution system are connected to the solar power supply. Safety constraints in the system are such that the voltage constraint of the power system is between 0.95 and 1.05 p.s. u. , the pressure constraint of the natural gas system is 20-75 mBar, the piping flow constraint is 1400 m ³ /h, the mass flow constraint of the thermal system piping is 5 kg/s, and the nodal temperature change of the thermal system is is also within the safe bounds, so the node temperature constraint can be ignored.

PG&E69 node power distribution system 2-3 line failure occurs, at this time the upper power source can not supply power to the distribution network, causing a large amount of power shortage in the distribution network, can not operate safely, will be solved It is necessary to line up to ensure that some loads remain powered, and the system's load waiting to be restored is 3802.19 kW. The load priorities and controllability in the PG&E 69 node distribution system are shown in Table 2 below. The photovoltaic power output at this time is 250 kW and 50 kW.

The following five scene power restoration policies are analyzed respectively.

Scene 1: Active parallel control policy analysis for distribution network based on conventional distributed generation.

Scene 2: Active parallel control policy analysis for distribution grid considering multi-energy coupling effects of the system.

Scene 3: Active parallel-off control policy analysis for distribution networks that comprehensively considers multi-energy coupling effects and SOP distribution.

In order to verify the accuracy of the method provided by the present invention, the method is applied to find the active paralleling means for the distribution network in scenes 1 and 2, and the specific isolated island dividing means is shown in FIG. 4 below. , the output state of the coupling element and the recovery state of the load in the two scenes are shown in Table 3, respectively.

It can be seen from the comparison of the above paralleling solutions that, after comprehensively considering the multi-energy complementary effect, the multi-energy coupling energy system realizes grid load transfer by coordinating multiple forms of energy, Realize 566.18 kW of electric energy substitution, reduce the energy supply pressure of the power grid, and adjust the output of the electricity acquisition type coupling element, the increase of the electric output of the coupling element is 156.77 kW. , which provides power support for the electrical grid.

Scene 3 utilizes an SOP installed between 22 in an IEEE 33 node system and 35 in a PG&E 69 node system to provide power recovery for an outage area including distributed power sources, and with such a load recovery policy, node 39 only powers down all loads, node 38 restores the 218 kW load, and all remaining loads can be restored.

As can be seen from FIG. 4 and Table 4 above, scene 1 restores power supply only by the distributed generators, and the restored load is low due to the output and load distribution constraints of the distributed generators. In addition, the number of switches that need to be operated is large, which affects the service life of the switches, is unfavorable to the safe operation of the system, and increases operating costs. Scenario 2 shows that after comprehensively considering the complementary effects of multi-energy, the multi-energy coupling energy system can coordinate multiple forms of energy to realize the load shift of the grid and the energy supply of the grid. Relieving pressure and regulating the output of the electric gain type coupling element, providing power supply support to the power grid, comprehensively considering the complementary effect of multi-energy to significantly improve the load recovery amount of the power grid. can increase the load recovery rate by about 19%. Scene 3, after considering SOPs, has a positive impact on the grid's paralleling solution. When considering the SOP, the power flow on both sides of it can be controlled, so the power flow distribution of the distribution network can be improved, providing voltage support for the distribution network islands, and at the same time providing some active power to the distribution network. and play the role of power supply support.

As explained above, after considering the multi-energy cooperation effect of the system, by coordinating multiple forms of energy, the energy supply potential of the multi-energy coupling system can be fully explored, and the energy supply recovery amount of the system can be effectively achieved. and play an important role in improving the safety and reliability of the system's energy supply. Taking into account the multi-energy coupling effect of the distribution network, the SOP can further improve the power supply recovery capability of the distribution network and improve the load recovery level of the distribution network.

Embodiments of the present invention do not limit the model numbers of other devices, as long as they are capable of completing the above functions, except that the model number of each device is specifically described.

It should be understood by those skilled in the art that the drawings are only schematic diagrams of one preferred embodiment, and the numbers of the above embodiments of the present invention are for illustrative purposes only and do not represent the superiority or inferiority of the embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. is also included in the protection scope of the present invention.

Claims (7)

An active disconnection control method for a multi-energy cooperative power grid, comprising:
constructing a network model of multi-energy streams for a power grid that takes multi-energy coupling into account and using an alternating iteration method to obtain an initial multi-energy stream;
Based on the initial multi-energy stream, according to the type of coupling element, propose an alternative control policy and coordinated control policy, obtain multi-energy stream, load distribution in the coupling element, the output of each distributed generation and the distribution network. obtaining a status;
A step of constructing an active parallel-off model for a distribution network that adopts an alternative control policy and a cooperative control policy, targets the maximum amount of load recovery, constrains safe operation conditions, and considers multi-energy coupling;
The greedy algorithm is used to find the active paralleling model for the distribution network, the method for dividing the isolated islands of the distribution network under fault conditions is obtained, and active paralleling is performed to realize continuous power supply to the distribution network load under fault conditions. An active parallel-off control method for a multi-energy cooperative power grid, comprising the steps of: The alternative control policy is
Utilizing the multi-energy coupling effect, the load of the node where the supply type coupling element is located is converted to the corresponding energy subsystem for energy supply, and on the premise of satisfying the safety constraints, the non-electrical coupling element or The active parallel-off control method for multi-energy cooperative power grid as claimed in claim 1, wherein the output of the electricity-obtaining coupling element replaces the load of the electricity-supplying coupling element. A mathematical model of the alternative control policy is:

(ΔP _ri represents the power of the alternative electrical energy, δ _e represents the step size by which the output of the electrically fed coupling element is reduced, η _i represents the conversion efficiency, and Δφ _r represents the power of the alternative electrical energy subsystem. represents the output that the balance node needs to increase, ∂φ _r /∂φ _node represents the sensitivity of the output of the node where the non-electronic system electrically driven coupling element is located to the output of the balance node, and n _t is the iteration number of times)
The active parallel-off control method for multi-energy cooperative power grid according to claim 1 or 2. The cooperative control policy is
The active solution for multi-energy cooperative grid according to claim 1, which is to increase the electrical output of the electrical gain coupling element to provide power support for the active grid disconnection, subject to safety constraints. Column control method. A mathematical model of the cooperative control policy is:

(a = 1, 2, ..., n _p-e , where n _p-e is the number of electric gain coupling elements, ΔP _a represents the power to be generated, and δ is the electric power acquisition coupling element supply represents the step size of the side output increase, ΔΩ _a represents the increased output of the other subsystems, ζ is the conversion ratio, and Δr _a is the non-electrical coupling to be changed to cancel ΔΩ _a . element output)
The active parallel-off control method for multi-energy cooperative power grid according to claim 1 or 4, wherein: The step of determining an initial multi-energy stream distribution for the system using an alternative control policy comprises:
selecting (1) a coupling element with regulating capability in a load side system of electrically driven coupling elements as a balance node;
step (2) of determining the reduction step size δ _e of the node load at which the electrically fed coupling element is located in the distribution network and calculating the power increase Δφ _r of the balancing node;
Calculate the multi-energy streams of the system, determine whether the system at this time satisfies all the constraints, and if so, the electrically-fed coupling element will continue to reduce the output, and move to step (2). , otherwise obtaining the alternative electric load quantity (3). The step of determining an initial multi-energy stream distribution of the system using a cooperative control policy comprises:
step (1) of selecting and marking the most efficient coupling element among the electrical acquisition type coupling elements;
step (2) of determining the step size δ of the power increase on the supply side of the electrical harvesting type coupling element and gradually increasing the power on the supply side according to the step size to obtain an increased power on the load side of the coupling element; When,
Determine if the system at this time satisfies all the constraints, if so, go to step (2) and continue to increase the output, else step (3) to execute step (4). )When,
Adjust the output of the non-electrical coupling element, determine that the system can be restored to a safe operating state, if satisfied, continue to execute step (2), otherwise continue to step (5). performing step (4);
Mark the coupling element, if still no electricity-obtained coupling element is marked, continue to perform step (2), else step (5) to obtain the final operating state of the coupling element ).

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