A multi-energy power distribution network voltage control method

Abstract

The application discloses a kind of multi-energy distribution network voltage control methods, comprising the following steps, define local voltage control rule;Analysis distributed power output causes voltage fluctuation upper and lower limit;Build global voltage control function;Algorithm is solved to objective function, the local voltage control rule is acquisition control point voltage u, determine whether to satisfy the following constraint, set the reactive power output of voltage compensation device.The multi-energy distribution network voltage control method, considering the uncertainty fluctuation of distributed power supply, improve the accuracy of voltage fluctuation analysis, formulate the localized voltage adjustment rule and global voltage optimization function, realize passive control and active control combination, reduce fluctuation rate, using interval number to express the uncertainty of distributed power supply, less computing resource demand, control reaction speed is fast.

Description

Technical Field

[0001] The present invention relates to the field of multi-energy distribution network technology, and in particular to a voltage control method for multi-energy distribution networks. Background Technology

[0002] Large-scale distributed photovoltaic (PV) grid connection transforms traditional distribution networks into multi-energy distribution networks. Due to fluctuations in PV output power, voltage fluctuations occur at and near grid-connected nodes. These fluctuations typically last for minutes. To ensure the supply voltage to users and reduce voltage fluctuations, multi-energy distribution networks require fast-adjusting voltage control devices, such as on-load tap changers, dynamic voltage regulators, and capacitor banks.

[0003] Current voltage control methods can pre-set voltage adjustment strategies, determine whether a threshold is exceeded based on voltage measurement data from observation points, and then control local adjustment equipment or photovoltaic inverters via serial communication and Modbus protocol. This method mainly utilizes local voltage information and can achieve local optimization, but the adjustment speed is slow. Current technology ignores the output uncertainty of distributed power sources, resulting in the superposition of voltage fluctuations and distributed power source fluctuations, which poses a risk of voltage fluctuations exceeding limits. In order to reduce the impact of uncertainty, a short-interval control strategy is required, which necessitates a high-bandwidth data acquisition system, faster voltage sensitivity factor estimation, and short-term renewable energy prediction algorithms, leading to higher costs. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the current voltage control methods for multi-energy distribution networks, this invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a voltage control method for multi-energy distribution networks, which aims to: globally optimize voltage control, reduce volatility, and improve analysis accuracy.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution, which includes the following steps: defining local voltage control rules; analyzing the upper and lower limits of voltage fluctuations caused by distributed power source output; constructing a global voltage control function; and solving the objective function using an algorithm.

[0008] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, the local voltage control rule is to collect the control point voltage u, determine whether the following constraints are met, and set the reactive power output of the voltage compensation device.

[0009] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, wherein: when u ≤ V Then set the reactive power output to Q′. V The lower voltage limit specified by national standards; when it meets the requirements V ≤u≤ V Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to... Here, q0 is the lower limit warning value of the voltage, q′ is the initial reactive power of the voltage compensation device, and q′ is the upper limit reactive power of the voltage compensation device; when the following conditions are met... Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to q0. This is the upper limit warning value for voltage; when it is met... Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to... This refers to the upper limit of voltage required by national standards.

[0010] In a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, the voltage disturbance of the i-th node caused by the output fluctuation of the distributed power source can be expressed as: In the formula Δu i,t p represents the voltage fluctuation at time t. j,t p j,t-1 For the predicted output of the distributed generation at time t and time t-1, Δp j,t This indicates fluctuations in the output of distributed power sources.

[0011] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, when the distributed power source is an intermittent distributed power source such as photovoltaic or wind turbine, which relies on natural resources, the fluctuation range of the distributed power source output is: Δ p j,t = p j,t - p j,t-1 In the formula Indicates the upper limit of fluctuation, Δ p j,t Indicates the lower limit of fluctuation. This indicates the predicted upper limit of output power from distributed generation sources; p j,t This represents the lower limit of the predicted output of distributed generation.

[0012] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, wherein: when the distributed power source is a freely adjustable type such as a gas turbine, the fluctuation range of the distributed power source output is:

[0013] In the formula λ is the upper limit of expectation. t To control variables, This represents the lower bound of the expectation.

[0014] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, the voltage fluctuation range is known to be:

[0015] In the formula Indicates the upper limit of voltage fluctuation, Δ u i,t is the lower limit of voltage fluctuation, pou represents the rate of change of voltage relative to power, and sgn() is the sign function.

[0016] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, the method for constructing the global voltage control function is to comprehensively consider voltage fluctuation rate and voltage limit constraint to construct the objective function.

[0017] In the formula, Δq j Φ represents the reactive power change of the voltage compensation device. t Δvc represents the loss after the voltage exceeds the limit, and Δvc represents the expenditure to reduce voltage fluctuation rate.

[0018] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, the constraint condition for constructing the global voltage control function is:

[0019] In the formula, d represents the expenditure coefficient for the lower limit of the unit voltage warning, e represents the expenditure coefficient for the lower limit of the unit voltage warning, and q tc q represents the reactive power output of the compensation device. dg This indicates the reactive power of distributed power sources. This represents the lower limit of node voltage fluctuations caused by distributed generation fluctuations. Indicates the lower limit of the node voltage. This represents the upper limit of node voltage fluctuations caused by distributed power source fluctuations.

[0020] As a preferred embodiment of the multi-energy distribution network voltage control method of the present invention, the step of solving the objective function using an algorithm includes: analyzing the local voltage fluctuation range; determining the local voltage value based on the current voltage and voltage fluctuation range; controlling the reactive power compensation device based on the local voltage control; formulating a global voltage optimization function; and realizing the optimized adjustment of multiple reactive power compensation devices.

[0021] The beneficial effects of this invention are: it takes into account the uncertainty fluctuations of distributed power sources, improves the accuracy of voltage fluctuation analysis, formulates localized voltage adjustment rules and global voltage optimization functions, realizes the combination of passive and active control, reduces volatility, uses interval numbers to represent the uncertainty of distributed power sources, requires less computing resources, and has a fast control response speed. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0023] Figure 1 This is a schematic diagram of the algorithm flow for the multi-energy distribution network voltage control method of the present invention.

[0024] Figure 2 This is a schematic diagram of the distribution network used in the example analysis of the multi-energy distribution network voltage control method of the present invention. Detailed Implementation

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0028] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0029] Example 1

[0030] Reference Figure 1This is the first embodiment of the present invention, which provides a voltage control method for a multi-energy distribution network, comprising the following steps:

[0031] Define local voltage control rules; analyze the upper and lower limits of voltage fluctuations caused by distributed power generation output; construct a global voltage control function; and solve the objective function using an algorithm.

[0032] 1. Define local voltage control rules, which is a passive method.

[0033] The local voltage control rule is to collect the control point voltage u, determine whether the following constraints are met, and set the reactive power output of the voltage compensation device.

[0034] 1.1 When u≤ V Then set the reactive power output to Q′. V This refers to the lower voltage limit specified by national standards.

[0035] 1.2, when satisfied Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to... q0 is the lower limit warning value of the voltage, q′ is the initial reactive power of the voltage compensation device, and q′ is the upper limit reactive power of the voltage compensation device.

[0036] 1.3, when satisfied Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to q0. This is the upper limit warning value for voltage.

[0037] 1.4 When satisfied Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to... This refers to the upper limit of voltage required by national standards.

[0038] To achieve global voltage optimization, it is possible to optimize and coordinate the voltage of multiple regions. One approach is passive judgment, which involves pre-defining the constraints, operating conditions, and priorities of control variables such as tap changers, reactive power compensation, and active power reduction. The actual collected voltage determines the control action based on the judgment.

[0039] Example 2

[0040] Reference Figure 1 This is the second embodiment of the present invention, which differs from the first embodiment in that it uses a different active prediction method:

[0041] 1. Analyzing the upper and lower limits of voltage fluctuations caused by distributed power generation output is an active control method.

[0042] 1.1 The voltage disturbance caused by the output fluctuation of the distributed power source at the i-th node can be expressed as: In the formula Δu i,t p represents the voltage fluctuation at time t. j,t p j,t-1 Let Δp be the time t and t-1. j,t =p j,t -p j,t-1

[0043] Predicted output of distributed power sources at time Δp j,t This indicates fluctuations in the output of distributed power sources.

[0044] 1.2 When the distributed power source is an intermittent distributed power source such as photovoltaic or wind turbine, which relies on natural resources, the fluctuation range of the distributed power source output is:

[0045] Δ p j,t = p j,t - p j,t-1 In the formula Indicates the upper limit of fluctuation, Δ p j,t Indicates the lower limit of fluctuation. This indicates the predicted upper limit of output power from distributed generation sources; p j,t This represents the lower limit of the predicted output of distributed generation.

[0046] 1.3 When the distributed power source is a freely adjustable type such as a gas turbine, the fluctuation range of the distributed power source output is:

[0047] In the formula λ is the upper limit of expectation. t To control variables, This represents the lower bound of the expectation.

[0048] 1.4 Therefore, the voltage fluctuation range can be determined as follows:

[0049]

[0050]

[0051]

[0052] In the formula Indicates the upper limit of voltage fluctuation, Δ u i,t is the lower limit of voltage fluctuation, pou represents the rate of change of voltage relative to power, and sgn() is the sign function.

[0053] Active forecasting involves developing and optimizing measures based on the output of distributed power sources predicted in the day-ahead or ultra-short-term forecasts, with the point voltage qualification rate or equipment cost as the optimal objective function.

[0054] Example 3

[0055] Reference Figure 1 This is the third embodiment of the present invention, which differs from the second embodiment in that it constructs a global voltage control function:

[0056] 1. Objective function: Taking into account both voltage fluctuation rate and voltage over-limit constraints, an objective function is constructed.

[0057] min(Δq j Δq j T +Φ t +Δvc)

[0058] In the formula, Δq j Φ represents the reactive power change of the voltage compensation device. t Δvc represents the loss after the voltage exceeds the limit, and Δvc represents the expenditure to reduce voltage fluctuation rate.

[0059] 2. Constraints

[0060]

[0061] In the formula, d represents the unit voltage warning lower limit expenditure coefficient.

[0062]

[0063] In the formula, e represents the unit voltage warning lower limit expenditure coefficient.

[0064]

[0065] In the formula, q tc q represents the reactive power output of the compensation device. dg This indicates the reactive power of distributed power sources. This represents the lower limit of node voltage fluctuations caused by distributed generation fluctuations. This indicates the lower limit of the node voltage.

[0066]

[0067] This represents the upper limit of node voltage fluctuations caused by distributed power source fluctuations.

[0068] By solving the objective function using genetic algorithms, particle swarm optimization, or similar methods, the following results can be obtained: Figure 1The steps shown involve analyzing the local voltage fluctuation range; determining the local voltage value based on the current voltage and voltage fluctuation range; controlling the reactive power compensation device based on the local voltage control; formulating a global voltage optimization function; and achieving optimized adjustment of multiple reactive power compensation devices.

[0069] One approach is to perform day-ahead offline optimization using predicted PV power generation and load demand to minimize losses and tap change frequency.

[0070] Combined with Examples 1-3

[0071] By combining active and passive control, local voltage adjustment rules are predefined, and the upper and lower limits of voltage fluctuations caused by distributed power generation are estimated. A global voltage optimization control function is established to ensure that the voltage fluctuation rate of the multi-energy distribution network meets the requirements.

[0072] Reference Figure 2 To verify the effectiveness of the voltage control method proposed in this patent, a distribution network with a 110kV / 380V distribution transformer at the beginning was constructed based on PSACD. The system has a total of 20 nodes, with distributed photovoltaic power connected at nodes 7 and 13 respectively. The rated power is 30kW, the load power of each node is 2.5kW, the power factor is 0.85, the line type is overhead line, and the distance between each node is 500m.

[0073] Low voltage is likely to occur in the power distribution network during cloudy or rainy weather or at dusk when there is insufficient sunlight and the user load is high.

[0074] At 15:00, the load on nodes 12 and 13 doubled, and the voltage at node 16 fell below the lower limit, reaching 0.9 of the rated voltage. First, according to the local voltage control rules, the reactive power compensation device at node 15 was adjusted to increase the reactive power output and raise the voltage level. At 16:00, the voltage at node 16 returned to the rated level. That is, when the voltage is below the limit, the localized voltage adjustment rules can be used first, and the voltage can be adjusted by calling the reactive power compensation device near the load point.

[0075] At 17:00, due to significant fluctuations in photovoltaic output, node 16 experienced another period of low voltage, reaching 0.85% of the rated voltage. At this point, the reactive power compensation device at node 15 could no longer meet the compensation requirements. Therefore, an active control method was needed. Distributed photovoltaic output was represented by an interval, with the output fluctuation range being [2kW, 10kW]. A probabilistic model was not required to describe the distributed power output; according to this patent, the voltage fluctuation range [-0.04, -0.10] could be calculated. Based on the control model of this patent, the output of the reactive power compensation devices at nodes 15, 5, and 17 was adjusted. Combined with the reactive power of the distributed power sources at nodes 13 and 7, the voltage at node 16 was increased, reducing the voltage fluctuation rate. The entire adjustment process took 10 minutes, demonstrating rapid control response.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A voltage control method for a multi-energy distribution network, characterized in that: Includes the following steps, Define local voltage control rules; Analyze the upper and lower limits of voltage fluctuations caused by distributed power generation output; Construct a global voltage control function; An algorithm is used to solve the objective function; The global voltage control function is constructed by comprehensively considering voltage fluctuation rate and voltage limit constraints, and then constructing the objective function. ; In the formula, This represents the reactive power change of the voltage compensation device. This indicates the loss after the voltage exceeds the limit. This indicates a reduction in expenditure related to voltage fluctuations; The constraints for constructing the global voltage control function are: In the formula, represents the expenditure coefficient for the upper limit of the unit voltage warning, and 'e' represents the expenditure coefficient for the lower limit of the unit voltage warning. This indicates the reactive power output of the compensation device. This indicates the reactive power of distributed power sources. This represents the lower limit of node voltage fluctuations caused by distributed generation fluctuations. Indicates the lower limit of the node voltage. This represents the upper limit of node voltage fluctuations caused by distributed power source fluctuations.

2. The multi-energy distribution network voltage control method according to claim 1, characterized in that: The local voltage control rule is to collect the control point voltage. Determine whether the following constraints are met, and set the reactive power output of the voltage compensation device.

3. The multi-energy distribution network voltage control method according to claim 2, characterized in that: When satisfied Then set the reactive power output to , The lower voltage limit specified by national standards; When satisfied Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set as follows: This is the lower limit warning value for point voltage. This is the initial reactive power of the voltage compensation device. This is the upper limit of reactive power for voltage compensation devices; When satisfied Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set to... , This is the upper limit warning value for voltage; When satisfied Based on the maximum reactive power value and the voltage regulation target value, the reactive power output is set as follows: This refers to the upper limit of voltage required by national standards.

4. The multi-energy distribution network voltage control method according to claim 3, characterized in that: The voltage disturbance at the i-th node caused by the power output fluctuation of the distributed power source can be expressed as: In the formula This represents the voltage fluctuation at time t. , Predict the output of distributed power sources at time t and time t-1. This indicates fluctuations in the output of distributed power sources.

5. The multi-energy distribution network voltage control method according to claim 4, characterized in that: When the distributed power source is an intermittent distributed power source such as photovoltaic or wind turbine, and relies on natural resources, the fluctuation range of the distributed power source output is: In the formula Indicates the upper limit of fluctuation. Indicates the lower limit of fluctuation. This indicates the upper limit of the predicted output of distributed power sources. This represents the lower limit of the predicted output of distributed generation.

6. The multi-energy distribution network voltage control method according to claim 1, characterized in that: The steps for solving the objective function using an algorithm include: Analyze the range of local voltage fluctuations; Determine the local voltage value based on the current voltage and voltage fluctuation range; Control the reactive power compensation device according to the local voltage control; Define a global voltage optimization function; To achieve optimized adjustment of multiple reactive power compensation devices.

Images