An active distribution network voltage control method considering the operation potential of centralized energy stations

Abstract

The present invention discloses a method for controlling the voltage of an active distribution network taking into account the operating potential of a centralized energy station. Step 1: According to the selected active distribution network-centralized energy station system, read the initial values ​​of variables or parameters such as the equipment composition of the centralized energy station, the equipment operating parameters, and the current stored heat of the thermal storage device; Step 2: According to the structure and parameters of the active distribution network-centralized energy station system provided in step 1, establish an active distribution network voltage control model taking into account the operating potential of the centralized energy station; Step 3: Perform a second-order cone transformation on the relevant non-convex constraints in the active distribution network-centralized energy station system optimization scheduling model obtained in step 2, establish a second-order cone programming model and call the relevant solver for solving; Step 4: Output the solution result of step 3. Advantages of the present invention: Fully consider the potential of the thermal storage device and the thermal inertia of the building in the centralized energy station to improve the voltage level.

Description

Technical Field

[0001] The present invention relates to an active distribution network voltage control method, and in particular to an active distribution network voltage control method taking into account the operation potential of a centralized energy station. Background Art

[0002] Distributed power sources represented by wind turbines / photovoltaics and centralized energy stations with electricity as the core are important means for clean energy utilization on the supply side and energy efficiency improvement on the consumer side. Therefore, the energy architecture that uses active distribution networks as energy transmission channels and uses centralized energy stations to achieve coordinated supply of multiple energies can achieve green and clean distributed energy integration and efficient utilization of multiple energy sources, and has been widely used.

[0003] With the increasing penetration of distributed energy and the demand for centralized energy stations, the safe and stable operation of distribution networks faces huge challenges, including changes in power flow direction and voltage deviation. Common distribution network voltage regulation devices include traditional on-load tap-changing transformers, capacitor banks, etc., as well as intelligent soft switches (SOPs) that can realize active power transmission and reactive power compensation between different feeders. At the same time, centralized energy stations contain a variety of energy supply and energy storage devices, and the demand side also has strong flexibility; through the reasonable energy supply and storage of energy supply and energy storage devices and the thermal management of cold and hot loads on the demand side, the energy demand can be transferred on the time axis, thereby changing the distribution network flow and achieving the improvement of the distribution network operation goals. Therefore, giving full play to the flexible potential of various adjustable resources of centralized energy stations, through reasonable management strategies, can effectively support the operation of distribution networks and improve voltage quality. It should be pointed out that the resource behavior characteristics and response characteristics that can be used by the regulation equipment at the distribution network level and the centralized energy station are quite different, and reasonable control strategies are needed to realize the complementary synergy of controllable equipment / resources at the energy distribution and energy consumption levels.

[0004] At present, the operation optimization of active distribution network mostly only uses its own regulating equipment to improve voltage quality, and there is no voltage control method that considers the operation potential of centralized energy stations. Therefore, there is an urgent need for an active distribution network voltage control method that considers the operation potential of centralized energy stations, fully utilizes the flexibility of centralized energy station supply and demand equipment and demand response resources, and coordinates the operation of distribution network and energy station to improve the voltage operation level of active distribution network. Summary of the invention

[0005] The technical problem to be solved by the present invention is to establish an active distribution network voltage control method that takes into account the operating potential of a centralized energy station, aiming at the voltage optimization problem of an active distribution network including a centralized energy station, comprehensively consider the coordination of multiple constraints and multiple resources of the distribution network-energy station, and finally formulate a voltage optimization adjustment plan.

[0006] The technical solution adopted by the present invention is:

[0007] Step 1: Input the known active distribution network and centralized energy station structure and parameter information;

[0008] Step 2: Based on the structures and parameters of the active distribution network and centralized energy station provided in step 1, establish an active distribution network voltage control model that takes into account the operation potential of the centralized energy station;

[0009] Step 3: Perform a second-order cone transformation on the relevant non-convex constraints in the active distribution network-central energy station system optimization scheduling model obtained in step 2, establish a second-order cone programming model and call the relevant solver for solving it.

[0010] Step 4: Generate an active distribution network voltage optimization control scheme considering the operation potential of the centralized energy station.

[0011] The active distribution network voltage control method considering the operating potential of the centralized energy station proposed in the present invention is based on solving the voltage regulation problem of the active distribution network, fully considering the potential for improving the voltage level by the heat storage device and the thermal inertia of the building in the centralized energy station, and establishing an active distribution network voltage optimization control model considering the operating potential of the centralized energy station. Through the second-order cone transformation of non-convex constraints, the relevant solver is called to solve and the system day-ahead optimization control plan is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flow chart of the active distribution network voltage control method considering the operation potential of the centralized energy station of the present invention;

[0013] Figure 2 It is a structural diagram of an active distribution network including multiple centralized energy stations;

[0014] Figure 3 Energy variation curve of heat storage device in centralized energy station;

[0015] Figure 4 It is the curve diagram of indoor temperature change of the building;

[0016] Figure 5 This is the graph of the output of the centralized energy station and the indoor temperature changes in Scheme 2 and Scheme 3;

[0017] Figure 6 The maximum and minimum value variation curves of node voltages for Scheme 1 and Scheme 3 are shown in Figure 2. DETAILED DESCRIPTION

[0018] The active distribution network voltage control method considering the operating potential of the centralized energy station proposed in the present invention is described in detail below with reference to implementation cases and drawings.

[0019] The active distribution network voltage control method of the present invention taking into account the operation potential of the centralized energy station is as follows: Figure 1As shown, the following steps are included:

[0020] 1) According to the selected active distribution network-centralized energy station system, input the distribution network parameters, read the predicted values ​​of the electric load, outdoor temperature, and distributed energy output, and read the initial values ​​of variables or parameters such as the equipment composition of the centralized energy station, equipment operating parameters, and the current stored heat of the thermal storage device;

[0021] 2) Based on the structure and parameters of the active distribution network-centralized energy station system provided in step 1), an active distribution network voltage control model considering the operation potential of the centralized energy station is established, including: setting the system energy consumption and the minimum distribution network voltage deviation as the optimization target, and considering the distribution network operation constraints (including distribution network flow constraints, distributed power supply operation constraints, soft switch operation constraints), centralized energy station operation constraints (including energy supply equipment operation constraints, hot water storage tanks, building thermal inertia operation potential constraints and supply and demand balance constraints);

[0022] (1) The optimization objectives of the system energy consumption and the minimum voltage deviation of the distribution network can be expressed as

[0023] minF′=W C (f L +f CES )+W V f V (1)

[0024]

[0025]

[0026]

[0027] In the formula, f L 、f CES 、f V are the distribution network loss, the energy consumption of the centralized energy station and the voltage deviation target, respectively. C and W V are the system energy consumption and voltage over-limit weight coefficients, N T is the total number of scheduling intervals in a scheduling cycle, N N is the number of distribution network nodes, Ω b is the set of system branches, r ij is the resistance of branch ij, I t，ij is the current of branch ij at time t, is the loss caused by the SOP connected to node i during period t, Δt is the scheduling time interval, V t，i is the voltage of node i at time t, and V thrare the upper and lower limits of the node voltage amplitude optimization interval, is the interconnection line power of centralized energy station i at time t.

[0028] (2) The distribution network operation constraints are expressed as

[0029] Distribution network flow constraints:

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036] Where P t，ij , Q t，ij is the active and reactive power flowing from node i to node j at time t, I t，ij is the current of line ij at time t, r ij 、x ij are the resistance and reactance of line ij, V t，i is the voltage of node i at time t, are the active and reactive power injected by distributed generation j at time t, are the active power and reactive power of the load at node j at time t, is the energy consumption of the centralized energy station m at time t, Ω b , are the set of lines and the set of centralized energy stations connected to node j, are the active power and reactive power injected by the distributed generation at node i at time t respectively.

[0037] Distributed power generation operation constraints:

[0038]

[0039]

[0040] In the formula, is the corresponding predicted power; is the power factor of the distributed generation at node i.

[0041] Soft switching operation constraints

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] In the formula, are the active and reactive powers injected into node j by the intelligent soft switch at time t, are the active power and reactive power injected by SOP on node i at time t, is the active power loss of SOP at node i, is the loss coefficient of SOP at node i; is the capacity of SOP on node i.

[0048] (3) The operation constraints of the centralized energy station

[0049] Energy supply equipment operation constraints:

[0050]

[0051]

[0052]

[0053]

[0054] In the formula, are the power supply of the ground source heat pump and electric boiler in the centralized energy station i at time t, are their power consumption, is the corresponding performance coefficient and efficiency, is the upper and lower limits of the ground source heat pump power, The upper and lower limits of electric boiler power.

[0055] Hot water storage tank operation potential constraints:

[0056]

[0057]

[0058]

[0059] In the formula, The heat stored in the hot water storage tank in the centralized energy station i at time t, Heat loss rate of hot water storage tank in centralized energy station i, The heat storage and heat release power of the hot water tank are respectively is the maximum heat storage capacity of the hot water storage tank in the centralized energy station i.

[0060] Building thermal inertia potential constraints:

[0061]

[0062]

[0063]

[0064] Where, T i，t is the indoor temperature of building i in the centralized energy station at time t, The energy injection power of building i in energy station at time t, C air , air The ratio is the specific heat capacity and density of air, V i is the building volume in energy station i, T out，t is the outdoor temperature at time t, K i 、F i are the average heat dissipation coefficient and surface area of ​​building i of energy station, T are the upper and lower limits of the building temperature, T ave，min 、T ave，max They are the upper and lower limits of the average room temperature of the building respectively.

[0065] Supply and demand balance constraints:

[0066]

[0067]

[0068]

[0069] In the formula, It is the upper limit of operating power of interconnection lines of centralized energy stations.

[0070] 3) Performing second-order cone transformation on the relevant non-convex constraints in the active distribution network-central energy station system optimization scheduling model obtained in step 2), establishing a second-order cone programming model and calling the relevant solver for solving;

[0071]

[0072]

[0073]

[0074]

[0075] For the square of the voltage amplitude in the distribution network flow and current squared Use v t，i and l t，ij Substitute, then equations (5)-(7) become equations (31)-(33). Perform a second-order cone relaxation transformation on equation (8) and transform it into a standard second-order cone form such as equation (34).

[0076] The SOP constraint is transformed into a rotating cone to simplify the solution model, and then equations (14)-(17) are transformed into

[0077]

[0078]

[0079]

[0080]

[0081] 4) Output the solution results of step 3), including the voltage level of the distribution network, the energy supply power of the energy supply and demand equipment of the centralized energy station, the heat storage / heating power of the heat storage device, the stored energy and the indoor temperature of the building.

[0082] The present invention establishes an active distribution network voltage control method that takes into account the operating potential of centralized energy stations. After the second-order cone model is transformed, a related solver is used to obtain a system voltage regulation scheme within the scheduling period.

[0083] Example analysis:

[0084] For this embodiment, firstly, according to the selected active distribution network including multiple centralized energy stations, the distribution network and centralized energy station equipment parameters, electrical load, and outdoor temperature forecast value are input. Figure 2 As shown. In this system, the distribution network is connected to three centralized energy stations (the access locations are divided into nodes 11, 13 and 32). The centralized energy station equipment includes ground source heat pump units, electric boiler units, and hot water storage tanks. Assuming that the equipment parameters remain consistent, the rated power of the ground source heat pump and electric boiler units are 1500KW and 1000kW respectively, and the maximum storage capacity of the hot water storage tank is 20000kWh. The system is installed with 3 photovoltaic systems and 1 wind turbine unit. The parameters are shown in Table 1. Without considering the reactive support role of distributed power sources, it is assumed that all distributed power sources operate according to a fixed power factor of 0.9. The upper and lower limits of the building temperature are set to 18 and 22℃ respectively, the standard temperature is 20℃, the upper and lower limits of the daily average temperature are 19℃ and 21℃ respectively, and the air density and specific heat capacity are 1.2kg / m 3, 1.007kJ / (kg℃); the building parameters of the energy station are shown in Table 2. Two groups of SOPs with a capacity of 1000kVA are installed at nodes 12-22 and 18-33 respectively. The loss coefficient of each SOP converter is 0.02, and the SOP power injection node direction is set to the positive direction. The scheduling cycle is 1 day, the scheduling interval is 30min, and the system node voltage allowable range and expected range are [0.95,1.05] and [0.97,1.03] respectively. The system energy consumption and voltage offset weights are set to 0.7 and 0.3.

[0085] The computer hardware environment for performing optimization calculations is Intel I9-10900K, with a main frequency of 3.70GHz, a memory of 32GB, and a software environment of Windows 10 operating system.

[0086] For this embodiment, the energy storage device energy output from the centralized energy station and the building temperature change under the proposed strategy are shown in Figure 3 , Figure 4 . Comparing the system operation results of considering or not considering the operation potential of the centralized energy station, Scheme 1 only considers the optimization of the distribution network itself (i.e., not considering the regulation of the energy station heat storage device and the building thermal inertia), Scheme 2 further considers the regulation potential of the centralized energy station thermal storage, and Scheme 3 considers the regulation of the heat storage device and the building thermal inertia at the same time. The system operation results of different schemes are shown in Table 3. The output of the centralized energy station and the indoor temperature in Scheme 2 and Scheme 3 are shown in Table 3. Figure 5 , Scheme 6 is the node maximum and minimum voltage curves of Schemes 1 and 3.

[0087] Comparing the operation results of Scheme 1 and Scheme 2 in Table 3, it can be seen that after considering the flexible storage-release characteristics of the thermal storage device, based on the timing characteristics of distributed power sources and energy efficiency consumption, the energy storage and energy release of the thermal storage device at different times can effectively change the energy consumption curve of the energy station and thus optimize the distribution network flow distribution. The maximum and minimum voltages of the nodes are closer to the reference values. Figure 5 Comparing the operation results of Scheme 2 and Scheme 3 in Table 3, considering the thermal demand response characteristics of the building, the indoor temperature of the building is kept high when the output of the distributed power source is large, absorbing more DG output nearby, improving the voltage level and reducing energy loss. Figure 6 By comparing Scheme 1 and Scheme 3 in Table 3, it can be seen that after considering the operating potential of the heat storage device of the centralized energy station and the thermal inertia of the building, the voltage deviation can be effectively reduced through the orderly storage and release of energy by the heat storage device and the regulation of the building temperature, and better voltage quality and operating economy can be obtained.

[0088] Table 1 Distributed power supply parameters

[0089]

[0090] Table 2 Building parameters of central energy station

[0091]

[0092] Table 3. Operation results of different schemes

[0093]

Claims

1. An active distribution network voltage control method considering the operation potential of a centralized energy station, characterized in that: The steps include: Step 1: According to the selected active distribution network-central energy station system, input the distribution network parameters, read the predicted values ​​of the electric load, outdoor temperature, and distributed energy output, and read the initial values ​​of variables or parameters such as the equipment composition of the central energy station, equipment operating parameters, and the current stored heat of the heat storage device; Step 2: Based on the structure and parameters of the active distribution network-centralized energy station system provided in step 1, establish an active distribution network voltage control model that takes into account the operating potential of the centralized energy station, including: setting the system energy consumption and the minimum distribution network voltage deviation as the optimization objectives, and considering the distribution network operation constraints, including power flow constraints, distributed power generation operation constraints, soft switch operation constraints, and centralized energy station operation constraints, including energy supply equipment operation constraints, hot water storage tanks, building thermal inertia operation potential constraints, and supply and demand balance constraints; Step 3: Perform a second-order cone transformation on the relevant non-convex constraints in the active distribution network-central energy station system optimization dispatching model obtained in step 2, establish a second-order cone programming model and call the relevant solver to solve it; Step 4: Output the solution results of step 3, including the voltage level of the distribution network, the energy supply power of the energy supply and demand equipment of the centralized energy station, the heat storage / heating power of the heat storage device, the stored energy and the indoor temperature of the building.

2. The active distribution network voltage control method considering the operation potential of the centralized energy station according to claim 1 is characterized in that: The optimization goal described in step 2 is to minimize the system energy consumption and the distribution network voltage deviation, which can be expressed as: min F′=W C (f L +f CES )+W V f V In the formula, f L 、f CES 、f V are the distribution network loss, the energy consumption of the centralized energy station and the voltage deviation target, respectively. C and W V are the system energy consumption and voltage over-limit weight coefficients, N T is the total number of scheduling intervals in a scheduling cycle, N N is the number of distribution network nodes, Ω b is the set of system branches, r ij is the resistance of branch ij, I t，ij is the current of branch ij at time t, is the loss caused by the SOP connected to node i during period t, Δt is the scheduling time interval, V t，i is the voltage of node i at time t, and V thr are the upper and lower limits of the node voltage amplitude optimization interval, is the interconnection line power of centralized energy station i at time t.

3. The active distribution network voltage control method considering the operation potential of the centralized energy station according to claim 1 is characterized in that: The potential constraints of the hot water storage tank operation and the building thermal inertia operation described in step 2 can be expressed as: Hot water storage tank operation constraints In the formula, The heat stored in the hot water tank in the centralized energy station i at time t, Heat loss rate of hot water storage tank in centralized energy station i, The heat storage and heat release power of the hot water storage tank in the centralized energy station i at time t, are the heating power of the ground source heat pump and electric boiler of the centralized energy station i at time t, The maximum storage heat of the hot water storage tank of the centralized energy station i; Building thermal inertia operation constraints Where, T i，t is the indoor temperature of building i in the centralized energy station at time t, The energy injection power of building i in energy station at time t, C air , air The ratio is the specific heat capacity and density of air, V i is the building volume in energy station i, T out，t is the outdoor temperature at time t, K i 、F i are the average heat dissipation coefficient and surface area of ​​building i of energy station, T are the upper and lower limits of the building temperature, T ave，max , T ave ，min They are the upper and lower limits of the average room temperature of the building respectively.

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