Treatment method and treatment system for transformer area user voltage imbalance out-of-limit

Abstract

The invention discloses a management method and management system for transformer area user voltage imbalance out-of-limit, and the method comprises the steps: S1, detecting the working power of a photovoltaic inverter through a sensor, and testing and calculating the active-voltage sensitivity of a grid-connected point of the photovoltaic inverter when the working power is close to the rated power of the photovoltaic inverter; s2, calculating an active-voltage sensitivity deviation of each inverter grid-connected node; s3, area division is carried out on the transformer area, and the area is divided in a segmented mode according to the electric pole number on each branch line; s4, monitoring voltage and current parameters of grid-connected points of the inverters, determining a voltage out-of-limit value, and determining a commutation sequence according to the calculated voltage sensitivity deviation of each node; according to the method, the problem of voltage imbalance out-of-limit caused by single-phase photovoltaic imbalance access or load imbalance is effectively solved, and the electric energy quality and the normal operation of user equipment are improved.

Description

Technical Field

[0001] The present invention discloses a method and system for managing voltage imbalance exceeding a limit for users in an area, and relates to the technical field of power systems, and in particular to a method and system for managing voltage imbalance exceeding a limit for users in an area caused by access to single-phase photovoltaic or single-phase new loads, using a power electronic commutation switch. Background Art

[0002] The current large-scale access of distributed photovoltaics to the distribution network has injected new vitality into the power system. However, the large-scale access of single-phase photovoltaics and the emergence of various new single-phase loads have brought certain challenges to the stable operation and power quality of the power system. The random access characteristics of single-phase photovoltaics and single-phase new loads often lead to unbalanced voltage exceeding the limit for users in the distribution network. This unbalanced voltage not only affects the user's normal power consumption experience, but may also damage power equipment, reduce its service life, and even threaten the safe and stable operation of the entire power system.

[0003] Traditional treatment methods, such as unbalanced control devices and transformer tap adjustment, have gradually revealed their limitations when dealing with this complex and changeable voltage imbalance problem. The unbalanced control device generates large line losses during the treatment process and cannot meet the line loss assessment requirements of the substation area; the transformer tap adjustment has problems such as limited adjustment accuracy and frequent operation that can easily lead to equipment aging. In addition, these methods often cannot accurately perform personalized treatment for each user's voltage conditions, resulting in unsatisfactory treatment results.

[0004] As a new type of power equipment, power electronic phase-changing switches provide new ideas and means to solve the problem of voltage imbalance and over-limit of users with their characteristics of fast response, high-precision control and flexible switching. However, how to give full play to the advantages of power electronic phase-changing switches and achieve efficient, accurate and reliable voltage management is still a difficult problem to be solved in current research and practice. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for controlling excessive voltage imbalance among users in a substation area. By adopting a power electronic phase-changing switch and combining advanced monitoring, analysis and control technologies, the problem of excessive voltage imbalance among users caused by the access of single-phase photovoltaic or single-phase new loads can be comprehensively solved.

[0006] The present invention is achieved by the following technical means:

[0007] A method for managing voltage imbalance exceeding the limit for users in a substation area, wherein the method is implemented by operating a photovoltaic inverter with a phase-changing switch, wherein the phase-changing switch includes a controller, a thyristor and a sensor, and includes the following steps:

[0008] S1, the sensor detects the working power of the photovoltaic inverter. When the working power is close to the rated power of the photovoltaic inverter, the active power-voltage sensitivity of the photovoltaic inverter grid connection point is calculated;

[0009] S2, calculate the active power-voltage sensitivity deviation of each inverter grid-connected node;

[0010] S3, dividing the substation area into regions, wherein the regions are divided into sections according to the pole numbers on each branch line;

[0011] S4, monitor the voltage and current parameters of each inverter grid connection point, determine the voltage over-limit value, and determine the commutation order based on the calculated voltage sensitivity deviation of each node.

[0012] Furthermore, the step S1 specifically includes the following steps:

[0013] S1-1, switch the single-phase photovoltaic to different access phase sequences, and record the voltage U of the node under each phase sequence an U bn U cn and active power P an P bn P cn ;

[0014] S1-2, calculate the active power change ΔP in each phase sequence n And the voltage change ΔU n ;

[0015] S1-3, calculate the active power-voltage sensitivity K of each single-phase photovoltaic inverter based on the active power change and voltage change n .

[0016] Furthermore, the step S2 specifically includes the following steps:

[0017] S2-1, monitor the voltage and current data in the area where the phase-changing switch is located;

[0018] S2-2, compare the voltage and current data with the commutation conditions. If the commutation conditions are met, the best commutation time is determined. At the best commutation time, the commutation switch is driven to perform commutation.

[0019] Active power change ΔP in each phase sequence n And the voltage change ΔU n , the calculation formula is:

[0020] ΔP n =P n '-P n

[0021] ΔU n =Un '-U n

[0022] Where P n ',U n ' is the active power and voltage of the phase after commutation, P n , U n is the active power and voltage before commutation;

[0023] Active power-voltage sensitivity K of single-phase photovoltaic inverter n , the calculation formula is:

[0024] Furthermore, in step S2, the active voltage sensitivity of each node is multiplied by the photovoltaic installed capacity of the node to obtain the voltage sensitivity deviation of each node, that is, the maximum voltage deviation that can be brought about by commutation, and the calculation formula is:

[0025] ΔU=K n S

[0026] Where ΔU is the voltage sensitivity deviation, and S is the photovoltaic installed capacity.

[0027] Furthermore, the area described in step S3 is divided according to the pole numbers of the electric poles, that is, the management intervals are divided according to 1#-2#, 2#-3#, ..., n-1#-n#, and when performing voltage deviation balancing, the end area of ​​the distribution station area is given priority, and the phase-to-phase voltage deviation balancing is performed in sequence towards the head end of the station area.

[0028] Furthermore, the specific steps for determining the commutation order in step S4 are as follows:

[0029] First, the voltage over-limit value of each photovoltaic inverter grid-connected node is determined, and the phase-changing distribution is performed based on the estimated regulated voltage generated by the commutative inverter in the substation area (usually the voltage deviation of the commutation regulation is proportional to the capacity of the inverter) to minimize the three-phase voltage deviation in the area.

[0030] Finally, the phases are switched from the end of the substation, i.e. the last pole number, forward in sequence until the voltage imbalance of each photovoltaic user exceeds the limit and meets the power supply voltage standard requirements.

[0031] The present invention also provides a system for managing voltage imbalance exceeding the limit for users in a transformer area, comprising the following modules:

[0032] The data collection and analysis module is used to analyze the voltage data of all users, and can count the duration and amplitude of the user voltage imbalance exceeding the limit;

[0033] The optimization calculation module is used to solve the optimal access position and number of power electronic phase-changing switches to achieve the goal of minimizing the number of phase-changing switches deployed in the substation area;

[0034] The phase-changing switch module is used to change the phase of the distribution network and transmit the voltage and current data in the substation area to the control module in a high-frequency and high-precision manner, providing real-time data guarantee for accurate phase-changing control;

[0035] A control module receives real-time monitoring data from the phase-changing switch module and quickly generates control instructions based on preset control strategies and algorithms; these instructions control the actions of the phase-changing switch module in real time to ensure that the voltage imbalance is effectively controlled in the shortest possible time, so that the voltage index of all users in the substation area reaches the highest level;

[0036] The monitoring and judgment module is used to monitor the user current zero-crossing information in real time and trigger the power electronic commutation action at the zero-crossing position, providing the best timing selection for the commutation operation and ensuring the safe and reliable operation of the power system.

[0037] Furthermore, the optimization calculation module uses intelligent optimization algorithms, such as particle swarm optimization algorithm and simulated annealing algorithm to solve.

[0038] Furthermore, the phase-changing switch module has a power electronic phase-changing switch, and a voltage detection unit and a current detection unit are integrated inside the power electronic phase-changing switch for real-time sensing of voltage and current changes in the transformer area.

[0039] The present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, a method for managing voltage imbalance exceeding a limit among users in an area is implemented.

[0040] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute a method for managing voltage imbalance exceeding a limit among users in a substation area.

[0041] Compared with the prior art, the present invention has the following technical advantages:

[0042] 1. The present invention effectively solves the problem of voltage imbalance exceeding the limit caused by unbalanced access of single-phase photovoltaic power generation or unbalanced load, thereby improving the power quality and the normal operation of user equipment.

[0043] 2. By testing the active voltage sensitivity and calculating the node voltage sensitivity deviation, the present invention can more accurately determine the nodes that need phase adjustment and the adjustment direction, thereby improving the control effect.

[0044] 3. The present invention balances voltage deviations based on the pole numbers in the substation area, which can better adapt to the structural characteristics of the low-voltage distribution network and improve the pertinence and effectiveness of the management.

[0045] 4. The present invention improves the stability and reliability of the system and reduces the maintenance cost by reducing the number of operations of the phase-changing switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The present invention will be further described below in conjunction with the accompanying drawings. The accompanying drawings are only used to illustrate preferred embodiments and are not to be considered as limiting the present application.

[0047] Figure 1 This is a flow chart of the three-phase unbalanced system treatment of the present invention;

[0048] Figure 2 This is a schematic diagram of the low voltage distribution station area of ​​the present invention;

[0049] Figure 3 This is a flow chart of the active power-voltage sensitivity test of the photovoltaic grid-connected node of the present invention. DETAILED DESCRIPTION

[0050] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0051] The present invention relates to a method for managing voltage imbalance exceeding a limit for users in a transformer area, which specifically comprises the following steps:

[0052] 1) Construct relevant models and calculate the models to obtain the optimal commutation switch access position, quantity information and optimal commutation conditions;

[0053] 2) Monitor the relevant data of the commutation switch, determine the commutation timing based on the data and commutation conditions, and achieve voltage balance;

[0054] Specifically, step 1 includes the following steps:

[0055] 1-1) Collect historical power data of all users in the substation area and filter and clean the data;

[0056] 1-2) Build an optimization model based on the acquired data;

[0057] 1-3) Solve the optimization model to calculate the optimal commutation switch access position, quantity and commutation conditions;

[0058] Step 2 specifically includes the following steps:

[0059] 2-1) Monitor the voltage and current data in the area where the phase-changing switch is located;

[0060] 2-2) Compare the voltage and current data with the commutation conditions. If the commutation conditions are met, the best commutation time is determined. At the best commutation time, the commutation switch is driven to perform commutation.

[0061] In the present invention, the historical voltage data collection interval is 15 minutes, and the power data includes three-phase voltage effective values ​​Ua(t), Ub(t), Uc(t), load current, power factor, active power and reactive power.

[0062] The voltage balance is calculated by the following formula:

[0063] Voltage unbalance degree=(maximum voltage effective value-minimum voltage effective value) / average voltage effective value×100%. By performing the above calculation on the voltage at each sampling point, a curve of voltage unbalance degree changing with time is obtained.

[0064] The over-limit duration and over-limit amplitude are calculated in the following manner:

[0065] Set a reasonable voltage threshold U th , usually a percentage of the rated voltage (such as +7%, -10%). When the absolute value of any phase voltage of the three-phase voltage |Ui(t)|>U th By accurately recording the start time t of the voltage exceeding the limit start and end time t end , first calculate the single limit-crossing duration T overlimit =t end -t start . If there are multiple over-limit durations, just add up the single over-limit durations;

[0066] The over-limit amplitude is defined as the maximum value of the voltage during the over-limit period, U max Or minimum value U min With threshold U th The difference between

[0067] The optimization model is as follows:

[0068] Objective function:

[0069] F=ω1N switch +ω2T total_overlimit +ω3A total_overlimit +ω4N action , U min ≤U i (t)≤U max ,

[0070] I i (t)≤I max , N action ≤N max , T interval ≥T min ;

[0071] N switchis the number of power electronic commutation switches, T total_overlimit The voltage over-limit duration of all users, A total_overlimit is the over-limit value, N action is the number of commutation switch actions, ω1, ω2, ω3, ω4 are weight coefficients;

[0072] U min and U max are the lower and upper limits of voltage, U i (t) is the voltage of the node at time t, I i (t) is the current of the node at time t;

[0073] I max is the maximum current carrying capacity of the line, N max is the maximum number of commutation times within the commutation switch unit time interval; T interval is the time interval between two commutation actions, T min It is the minimum interval of commutation action.

[0074] The optimal commutation timing is the zero-crossing point of the sine wave of each phase voltage. When a commutation operation is required, the commutation switch is controlled to be disconnected when the sine wave of the current phase voltage passes through the zero point. At the same time, the zero-crossing point of the sine wave of the target phase voltage to be switched to is calculated and waited for, and the commutation switch is turned on at the zero-crossing moment to achieve precise commutation.

[0075] The present invention also relates to a system for managing voltage imbalance exceeding a limit for users in a transformer area, comprising the following modules:

[0076] The data collection and analysis module is used to analyze the voltage data of all users, and can count the duration and amplitude of the user voltage imbalance exceeding the limit;

[0077] The optimization calculation module uses intelligent optimization algorithms, such as particle swarm optimization algorithm and simulated annealing algorithm, to solve the optimal access position and number of power electronic commutation switches, so as to achieve the goal of deploying the least number of commutation switches in the substation;

[0078] The phase-changing switch module has a power electronic phase-changing switch, which is used to change the phase of the distribution network. The power electronic phase-changing switch integrates a voltage and current detection unit, which can sense the voltage and current changes in the substation in real time, and transmit the data to the control module in a high-frequency and high-precision manner, providing real-time data guarantee for accurate phase-changing control;

[0079] The control module receives real-time monitoring data from the phase-changing switch module and quickly generates control instructions based on preset control strategies and algorithms. These instructions control the action of the phase-changing switch in real time to ensure effective control of voltage imbalance and over-limit in the shortest possible time, so that the voltage index of all users in the substation reaches the highest level.

[0080] The monitoring and judgment module is used to monitor the user current zero-crossing information in real time and trigger the power electronic commutation action at the zero-crossing position, providing the best timing selection for the commutation operation and ensuring the safe and reliable operation of the power system.

[0081] The following are some specific examples to explain in detail:

[0082] Example 1: Small-scale area management

[0083] Overview of Taiwan District:

[0084] Area type: Residential area

[0085] Transformer capacity: 315kVA

[0086] Single-phase photovoltaic access capacity: 20kW

[0087] Single-phase new load types: charging piles, air conditioners, etc.

[0088] Data collection and analysis:

[0089] One month of historical data is obtained from the marketing procurement system (or PMS3.0), and the three-phase voltage sampling frequency is one sampling point every 15 minutes.

[0090] Using data analysis technology, it was found that there was an obvious voltage imbalance problem. The longest over-limit duration reached 3 hours, the maximum over-limit amplitude was about 15%, and the average voltage imbalance was 8%.

[0091] Further analysis of the time distribution of limit-exceeding events revealed that they were mainly concentrated in the peak electricity consumption periods at noon and in the evening.

[0092] Optimized calculation and implementation:

[0093] Based on the collected and analyzed data, an optimization model is established, and the weight coefficients ω1 = 0.4, ω2 = 0.3, ω3 = 0.2, and ω4 = 0.1 are set to highlight the importance of reducing the number of commutation switches.

[0094] After solving the optimization algorithm, it was determined that the optimal phase-changing switch access positions are 7 and the number is 6.

[0095] According to the calculation results, power electronic phase-changing switches are installed at key nodes in the substation area, and parameter setting and debugging are carried out. Effect evaluation:

[0096] After the treatment, the data was continuously monitored for one month. The voltage imbalance improvement rate reached 80%, and the average imbalance dropped to 1.6%. The over-limit duration was reduced by 70%, and the over-limit duration was greatly shortened to 0.9 hours. The over-limit amplitude was reduced by 60%, and the maximum over-limit amplitude was reduced to 6%. The number of actions was reduced by 50%, and the phase-changing switch action was more accurate and efficient, and no instability occurred.

[0097] Example 2: Medium-sized area management

[0098] Overview of Taiwan District:

[0099] Area type: Industrial Park

[0100] Transformer capacity: 800kVA

[0101] Single-phase photovoltaic access capacity: 10kW

[0102] Single-phase new load types: industrial single-phase equipment, office air conditioners, etc.

[0103] Data collection and analysis:

[0104] Two months of high-resolution voltage data were collected with a sampling frequency of 20 times per second.

[0105] The analysis shows that the voltage imbalance problem is quite serious, with the longest over-limit duration being 6 hours, the maximum over-limit amplitude being as high as 20%, and the average voltage imbalance being 12%.

[0106] An in-depth study of the rules of exceeding the limit revealed that it is closely related to the factory production scheduling and equipment start-up and shutdown.

[0107] Optimized calculation and implementation:

[0108] When constructing the optimization model, the weight coefficients are adjusted to ω1=0.3, ω2=0.3, ω3=0.2, and ω4=0.2 to balance the optimization objectives.

[0109] The optimal number of commutation switch access positions is 5 and the number is 3.

[0110] Accurately install and debug the phase-changing switch to ensure its normal operation.

[0111] Effect evaluation:

[0112] Monitoring after two months of treatment showed that the voltage imbalance improved by 85%, and the average imbalance dropped to 1.8%. The over-limit duration was reduced by 75%, and the over-limit duration was shortened to 1.5 hours. The over-limit amplitude was reduced by 65%, and the maximum over-limit amplitude was reduced to 7%. The number of actions was reduced by 55%, and the system stability was significantly improved.

[0113] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for managing voltage imbalance exceeding the limit for users in a substation area, wherein the method is implemented by operating a photovoltaic inverter with a phase-changing switch, wherein the phase-changing switch includes a controller, a thyristor and a sensor, and is characterized in that: The steps include: S1, the sensor detects the working power of the photovoltaic inverter. When the working power is close to the rated power of the photovoltaic inverter, the active power-voltage sensitivity of the photovoltaic inverter grid connection point is calculated; S2, calculate the active power-voltage sensitivity deviation of each inverter grid-connected node; S3, dividing the substation area into regions, wherein the regions are divided into sections according to the pole numbers on each branch line; S4, monitor the voltage and current parameters of each inverter grid connection point, determine the voltage over-limit value, and determine the commutation order based on the calculated voltage sensitivity deviation of each node.

2. The method for controlling voltage imbalance exceeding the limit of users in the substation area according to claim 1 is characterized in that: The step S1 specifically includes the following steps: S1-1, switch the single-phase photovoltaic to different access phase sequences, and record the voltage U of the node under each phase sequence an , U bn , U cn and active power P an , P bn , P cn ; S1-2, calculate the active power change ΔP in each phase sequence n And the voltage change ΔU n ; S1-3, calculate the active power-voltage sensitivity K of each single-phase photovoltaic inverter based on the active power change and voltage change n .

3. The method for controlling voltage imbalance exceeding the limit of users in the substation area according to claim 2 is characterized in that: The step S2 specifically includes the following steps: S2-1, monitor the voltage and current data in the area where the phase-changing switch is located; S2-2, compare the voltage and current data with the commutation conditions. If the commutation conditions are met, the best commutation time is determined. At the best commutation time, the commutation switch is driven to perform commutation.

4. A method for controlling voltage imbalance exceeding the limit of users in a substation area according to claim 3, characterized in that: Active power change ΔP in each phase sequence n And the voltage change ΔU n , the calculation formula is: ΔP n =P n '-P n ΔU n =U n '-U n Where P n ',U n ' is the active power and voltage of the phase after commutation, P n , U n is the active power and voltage before commutation; Active power-voltage sensitivity K of single-phase photovoltaic inverter n , the calculation formula is:

5. The method for controlling voltage imbalance exceeding the limit of users in the substation area according to claim 2 is characterized in that: In step S2, the active voltage sensitivity of each node is multiplied by the photovoltaic installed capacity of the node to obtain the voltage sensitivity deviation of each node, that is, the maximum voltage deviation that can be brought about by phase switching. The calculation formula is: ΔU=K n S Where ΔU is the voltage sensitivity deviation, and S is the photovoltaic installed capacity.

6. The method for controlling voltage imbalance exceeding the limit of users in the substation area according to claim 1 is characterized in that: The area described in step S3 is divided according to the pole numbers of the electric poles, that is, the management intervals are divided according to 1#-2#, 2#-3#, ..., n-1#-n#. When performing voltage deviation balancing, the end area of ​​the distribution station area is given priority, and the phase-to-phase voltage deviation balancing is performed in sequence towards the head end of the station area.

7. The method for controlling voltage imbalance exceeding the limit of users in the substation area according to claim 1 is characterized by: The specific steps for determining the commutation order in step S4 are as follows: First, the voltage over-limit value of each photovoltaic inverter grid-connected node is determined, and the phase-changing distribution is performed based on the estimated regulated voltage generated by the commutative inverter in the substation area, so that the three-phase voltage deviation in this area is minimized; Finally, the phases are switched from the end of the substation, i.e. the last pole number, forward in sequence until the voltage imbalance of each photovoltaic user exceeds the limit and meets the power supply voltage standard requirements.

8. A management system for implementing the management method of voltage imbalance exceeding the limit of users in the substation area as described in claim 1, characterized in that: Includes the following modules: The data collection and analysis module is used to analyze the voltage data of all users, and can count the duration and amplitude of the user voltage imbalance exceeding the limit; The optimization calculation module is used to solve the optimal access position and number of power electronic phase-changing switches to achieve the goal of minimizing the number of phase-changing switches deployed in the substation area; The phase-changing switch module is used to change the phase of the distribution network and transmit the voltage and current data in the substation area to the control module in a high-frequency and high-precision manner, providing real-time data guarantee for accurate phase-changing control; A control module receives real-time monitoring data from the phase-changing switch module and quickly generates control instructions based on preset control strategies and algorithms; these instructions control the actions of the phase-changing switch module in real time to ensure that the voltage imbalance is effectively controlled in the shortest possible time, so that the voltage index of all users in the substation area reaches the highest level; The monitoring and judgment module is used to monitor the user current zero-crossing information in real time and trigger the power electronic commutation action at the zero-crossing position, providing the best timing selection for the commutation operation and ensuring the safe and reliable operation of the power system.

9. The treatment system according to claim 8, characterized in that: The optimization calculation module uses an intelligent optimization algorithm to solve the problem, and the intelligent optimization algorithm includes a particle swarm optimization algorithm and a simulated annealing algorithm.

10. The management system according to claim 8, characterized in that: The phase-changing switch module has a power electronic phase-changing switch, and a voltage detection unit and a current detection unit are integrated inside the power electronic phase-changing switch for real-time sensing of voltage and current changes in the station area.

11. A computer device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the method for controlling voltage unbalance exceeding a limit for users in an area as claimed in any one of claims 1 to 7 is implemented.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that: The storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the method for managing voltage imbalance exceeding the limit for users in the substation area according to any one of claims 1 to 7.

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