Reactive compensation control method and system

Abstract

The invention discloses a reactive compensation control method and system, the system comprises a data acquisition unit, a data storage unit, a data processing unit, a switching unit and a control unit, the data acquisition unit is in communication connection with the data storage unit, the data storage unit is in communication connection with the data processing unit, and the switching unit is in communication connection with the data processing unit. The data processing unit is respectively in communication connection with the control module and the control unit, the control unit is in communication connection with the control module, and the control module is arranged in the switching unit. According to the invention, a plurality of capacitors are combined into a capacitor bank which is the same as or similar to the capacitance needing to be put into operation or meets the batch put into operation requirement through different connection modes according to the capacitance needing to be put into operation, so that relatively large inrush current brought to a power grid when a large-capacity reactive power compensation device is put into operation is reduced; and meanwhile, the power factor of the power grid after being put into operation does not exceed a reasonable threshold range.

Description

Technical Field

[0001] The present invention relates to the technical field of reactive power compensation of electric power system, and more particularly to a reactive power compensation control method and system. Background Art

[0002] In order to improve power supply efficiency, reduce losses in power transformers and transmission lines, and improve the power supply environment, when the power factor of the power grid is low, people usually use reactive power compensation to improve the power factor of the power grid. When the power factor of the power grid is too high, it may cause problems such as uneven circuit load or equipment damage. Therefore, when the power factor of the power grid is high, people usually remove the reactive power compensation device in operation in the power grid to keep the power factor of the power grid within a reasonable range.

[0003] However, when it is necessary to put the reactive power compensation device into operation, there is often a certain gap between the capacity that needs to be put into operation and the actual capacity of the reactive power compensation device. In order to avoid the large inrush current brought to the power grid by the commissioning of large-capacity reactive power compensation devices, people usually put the smaller capacity into operation first, and then the larger capacity into operation. At this time, reactive power compensation devices with different capacities need to be configured, which will bring higher equipment costs. Summary of the invention

[0004] To this end, the technical problem to be solved by the present invention is to provide a reactive power compensation control method and system, which combines multiple capacitors into a capacitor group with the same or similar capacity as the capacity to be put into operation or meets the requirements for batch operation through different connection methods according to the capacity to be put into operation, thereby reducing the large inrush current brought to the power grid by the commissioning of a large-capacity reactive power compensation device, and at the same time, it can also ensure that the power factor of the power grid after commissioning will not exceed a reasonable threshold range.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: A reactive power compensation control method is applicable to a reactive power compensation system in which more than three capacitors are provided in a switching unit of a reactive power compensation device, and comprises the following steps: (S1) Collect data information related to the power factor of the power grid and calculate the capacity C required to be put into operation t0 Or the cut-off capacitance C q0 , using the redundancy coefficient to calculate C t0 and C q0 Adjust the adjusted C t1 and the adjusted C q1 To ensure the power factor cosφ of the power grid after the switching unit is put into operation or removed 1 The following inequality is satisfied: (1+α)×cosφ 0 ≤cosφ 1≤(1-β)×cosφ 2 Where, α and β are adjustable parameters, the value range of α is [0.01, 0.05], and the value range of β is [0.01, 0.05]; cosφ 0 is the controllable lower limit of the power factor of the power grid; cosφ 2 It is the controllable upper limit of the power factor of the power grid; (S2) Based on the C calculated in step (S1), t1 or C q1 The switching units are put into operation or removed according to the following strategies: (CL1) When it is necessary to put the unit into operation, first t1 The capacitors in the switching unit are connected in series, in combination with series and parallel, or in parallel to form a capacitor bank, and then the switching unit is put into operation; (CL2) When it is necessary to cut off the switching unit, according to C q1 The strategy of first-in, first-out will cut off the online switching units.

[0006] The above reactive power compensation control method uses the following formula to calculate C t0 and C q0 Make adjustments: C t1 =C t0 ×(1-γ 1 ) C q1 =C q0 ×(1-γ 2 ) In the formula, C t1 is the adjusted capacity to be put into operation; 1 is the redundancy factor when reactive power compensation power needs to be increased, and its value range is [0.05, 0.08]; C q1 is the capacitance to be removed after adjustment; γ 2 The redundancy factor when the reactive compensation power needs to be reduced is in the range of [0.11, 0.17]; γ 1 and γ 2 Satisfy the following inequalities respectively: (1+α)×(1-γ 1 )≥1 (1-β)×(1-γ 1 )≥0.8 (1+α)×(1-γ 2 )≥1 (1-β)×(1-γ 2 )≥0.8.

[0007] The above reactive power compensation control method, γ 1 and γ 2 The ratio is: 0.4~1.

[0008] In the reactive power compensation control method, in step (S2), when the switching unit is cut off, after the switching unit is cut off, the connection state between the capacitors in the switching unit is disconnected.

[0009] In the above reactive power compensation control method, in step (S2), it is necessary to continuously switch and after the nth switching unit is put into operation or removed, calculate the expected change of power factor Δcosφ n , and use the collected data information related to the power factor of the power grid to calculate the actual change in power factor , where the power factor of the power grid is calculated with an accuracy of 0.0001; when Δcosφ n and Any value in is zero or Δcosφ n and When they are equal, the preset delay switching time interval t 0 Put into operation or cut off, otherwise, according to Δcosφ n and The time difference Δt between the time point when the n+1th switching unit is put into operation or removed and the time point when the nth switching unit is put into operation or removed is calculated, and the n+1th switching unit is put into operation or removed at a time Δt after the time point when the nth switching unit is put into operation or removed; wherein Δt is calculated by the following formula: Where, t 0 The value ranges from 4 to 8 seconds.

[0010] In the above reactive power compensation control method, in step (S1), the capacity C required to be put into operation is calculated. t0 Or the cut-off capacitance C q0 When the power factor change during the switching unit operation or removal period is predicted based on historical data , and then calculate C using the following formula t0 or C q0 : Where C is C t0 or C q0 ; P is the active power of the power grid; It is the power factor of the power grid before the switching unit is put into operation or removed; is the power factor of the grid after the switching unit is put into operation or removed; ω is the voltage angular frequency, ω=2πf, where f is the AC frequency; V is the grid voltage; δ is an adjustable parameter with a value range of [0.8,0.95]. The f in is the first letter of future.

[0011] In the above reactive power compensation control method, the value range of δ is [0.87, 0.93].

[0012] A system for performing reactive power compensation control using the reactive power compensation control method comprises: A data acquisition unit is used to collect data information related to the power factor of the power grid and the switching time of the switching unit; A data storage unit, used for storing data collected by the data collection unit; A data processing unit, used for processing the data collected by the data collection unit; A switching unit is used to provide reactive compensation power for reactive compensation; the switching unit includes more than or equal to 3 capacitors and a control module, and the control module is used to connect the capacitors in the switching unit in series, in parallel, or in series and parallel according to the processing result of the data processing unit; A control unit, used for performing a switching operation of the switching unit according to a data processing result output by the data processing unit; The data acquisition unit is communicatively connected with the data storage unit, the data storage unit is communicatively connected with the data processing unit, the data processing unit is communicatively connected with the control module and the control unit respectively, and the control unit is communicatively connected with the control module.

[0013] In the above system, the control unit is communicatively connected with the display unit.

[0014] In the above system, the control unit is connected to the handheld terminal for communication via the wireless communication unit.

[0015] The technical solution of the present invention achieves the following beneficial technical effects: 1. The present invention combines multiple capacitors into a capacitor bank based on the capacitance required for operation, so that after the capacitor bank is put into operation, the power factor of the power grid can still be within a preset range, thereby avoiding frequent switching on and off of the reactive power compensation device and improving the power quality of the power grid.

[0016] 2. Considering that the power factor of the power grid may fluctuate due to various reasons, in order to ensure that the power factor of the power grid after the reactive compensation device is put into operation or removed is still within the preset threshold range as much as possible after fluctuations occur, a redundancy factor is introduced to adjust the capacity that needs to be put into operation or removed, so that the power factor of the power grid after the completion of the operation or removal is still within the preset threshold range when the power factor of the power grid fluctuates.

[0017] 3. There is a certain difference between the actual increase in the power factor of the power grid after the reactive compensation device is put into operation or removed and the expected value. The present invention uses this difference to adjust the time interval of the delayed switching, so that the power factor of the power grid can be adjusted to the correct position as soon as possible without causing a large inrush current in the power grid due to the switching of the reactive compensation device.

[0018] 4. Predict the fluctuation of power factor of power grid based on historical data, and adjust the capacity to be put into operation or removed based on the fluctuation of power factor of power grid due to the access or exit of power equipment in the near future time point, so as to realize the change of power factor of power grid caused by the switching operation of reactive power compensation device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the working principle of the reactive power compensation control system; Figure 2 Flow chart of reactive power compensation control method. DETAILED DESCRIPTION

[0020] In order to ensure that the power factor of the power grid can remain stable above the limit specified by the industry after some power-consuming equipment in the power grid is started and stopped, users or power suppliers will adjust the power factor of the power grid by investing reactive compensation devices into the power grid or removing reactive compensation devices from the power grid. However, in order to avoid the shutdown of power-consuming equipment after the removal of reactive compensation devices, which may cause the power factor of the power grid to be lower than the limit specified by the industry, users or power suppliers usually keep the power factor of the power grid within a preset threshold range, even if the power grid supplies power within a preset threshold range of the power factor of the power grid, to ensure the quality of the power grid electricity. In order to avoid the shutdown of power equipment after the reactive compensation device is removed, causing the power factor of the power grid to be lower than the limit specified by the industry, and to avoid the startup of power equipment after the reactive compensation device is put into operation, causing the power factor of the power grid to be higher than the limit of stable power supply of the power grid (for example, the power factor of the power grid is 1), the present invention uses redundancy rules to reduce the capacity that needs to be put into operation or removed, even if the actual capacity put into operation is lower than the capacity that needs to be put into operation, or the actual capacity removed is lower than the capacity that needs to be removed, so as to cope with the changes in the power factor of the power grid caused by the start and stop of some power equipment in the power grid, thereby reducing the switching frequency of the reactive compensation device.

[0021] Specifically, Figure 1As shown, the reactive power compensation control system in the present invention includes a data acquisition unit, a data storage unit, a data processing unit, a switching unit, a control unit, a display unit and a handheld terminal. The data acquisition unit is communicatively connected to the data storage unit, the data storage unit is communicatively connected to the data processing unit, the data processing unit is communicatively connected to the control module and the control unit respectively, the control unit is communicatively connected to the control module and the display unit respectively, and the control unit is communicatively connected to the handheld terminal via a wireless communication unit.

[0022] In the present invention, a data acquisition unit is used for data information related to the power factor of the power grid and the switching time of the switching unit; a data storage unit is used to store the data collected by the data acquisition unit; a data processing unit is used to process the data collected by the data acquisition unit; a switching unit is used to provide reactive compensation power for reactive compensation; the switching unit includes more than or equal to 3 capacitors and a control module, and the control module is used to connect the capacitors in the switching unit in series, in parallel, or in series and parallel according to the processing result of the data processing unit; a control unit is used to perform the switching operation of the switching unit according to the data processing result output by the data processing unit; a display unit is used to display the working status of the switching unit; and a handheld terminal is used for user management personnel to remotely perform the switching operation of the reactive compensation device.

[0023] Since the capacitance of a single capacitor is fixed, and the capacitance required when the power factor of the power grid needs to be adjusted through a reactive compensation device is not necessarily equal to or close to the fixed capacitance of the capacitor, this will cause the following situation: after the reactive compensation device off the grid is connected to the power grid for operation, the power factor of the power grid will run at a high level, which is prone to problems such as uneven circuit load or equipment damage. If the reactive compensation device is not put into operation in the power grid, the power factor of the power grid will run at a low level, the power quality of the power grid is not high, and the losses of the power supply transformer and the transmission line will also be relatively high. Therefore, the present invention adopts a method of combining multiple capacitors into a capacitor group that meets the requirements through different connection methods according to the reactive compensation requirements of the power grid to solve the above problems.

[0024] Specifically, Figure 2 As shown, reactive power compensation can be performed by using the reactive power compensation control system of the present invention through the following steps: (S1) Collect data information related to the power factor of the power grid and calculate the capacity C required to be put into operation t0 Or the cut-off capacitance C q0 , using the redundancy coefficient to calculate C t0 and C q0 Adjust the adjusted C t1 and the adjusted C q1 To ensure the power factor cosφ of the power grid after the switching unit is put into operation or removed 1 The following inequality is satisfied: (1+α)×cosφ 0 ≤cosφ 1 ≤(1-β)×cosφ 2 Where, α and β are adjustable parameters, the value range of α is [0.01, 0.05], and the value range of β is [0.01, 0.05]; cosφ 0 is the controllable lower limit of the power factor of the power grid; cosφ 2 It is the controllable upper limit of the power factor of the power grid; Among them, use the following formula to calculate C t0 and C q0 Make adjustments: C t1 =C t0 ×(1-γ 1 ) C q1 =C q0 ×(1-γ 2 ) In the formula, C t1 is the adjusted capacity to be put into operation; 1 It is the redundancy factor when the reactive power compensation power needs to be increased. The value range is [0.05, 0.08] and can be adjusted and set according to the actual situation; C q1 is the capacitance to be removed after adjustment; γ 2 The redundancy factor when the reactive compensation power needs to be reduced has a value range of [0.11, 0.17] and can be adjusted and set according to actual conditions; And γ 1 and γ 2 Satisfy the following inequalities respectively: (1+α)×(1-γ 1 )≥1 (1-β)×(1-γ 1 )≥0.8 (1+α)×(1-γ 2 )≥1 (1-β)×(1-γ 2 )≥0.8 (S2) Based on the C calculated in step (S1), t1 or C q1 The switching units are put into operation or removed according to the following strategies: (CL1) When it is necessary to put the unit into operation, first t1The capacitors in the switching unit are connected in series, in combination of series and parallel, or in parallel to form a capacitor bank, and then the switching unit is put into operation; multiple capacitors are combined together by connecting in series, first in parallel and then in series, first in series and then in parallel, or in other connection methods, so that capacitor banks with different capacitances can be constructed using the same type of capacitors to meet the needs of reactive compensation switching; (CL2) When it is necessary to cut off the switching unit, according to C q1 The strategy of first-in, first-out will cut off the online switching units.

[0025] Given that the grid can supply power at a larger grid power factor within the preset grid power factor threshold, in order to apply the redundancy factor to C t0 and C q0 When making adjustments, the power factor of the power grid can be allowed to fluctuate upward to prevent the power factor of the power grid from fluctuating downward beyond the lower limit allowed by the industry, that is, to prevent electricity users from using electricity for a long time at a lower power factor of the power grid. 1 and γ 2 The association, specifically, is 1 and γ 2 The ratio is: 0.4~1, which can also prevent the power factor of the power grid from falling to the lower limit allowed by the industry due to the shutdown of some power-consuming equipment, thereby reducing the switching frequency of the switching unit.

[0026] In order to facilitate the combination and operation of the capacitors in the switching unit, when the switching unit is cut off, the connection state between the capacitors in the switching unit is disconnected, so that the capacitors can be recombined as needed.

[0027] As the capacitor is used for a long time, its performance will decline. When a capacitor with declining performance is put into operation or removed from the grid, the expected change in power factor generated by the capacitor is Δcosφ. n The actual change in power factor of the power grid due to the commissioning or removal of the capacitor There are certain differences. This difference is reflected in the fact that the power factor of the power grid has not been adjusted after the capacitor is put into operation. This requires other capacitors to be put into operation or removed from the power grid. At the same time, considering the power factor fluctuation caused by the start and stop of electrical equipment, if the time point for putting other capacitors into operation or removing them from the power grid is to be adjusted. Specifically, in step (S2), continuous switching is required and after the nth switching unit is put into operation or removed, the expected change in power factor Δcosφ is calculated. n , and use the collected data information related to the power factor of the power grid to calculate the actual change in power factor , where the power factor of the power grid is calculated with an accuracy of 0.0001; when Δcosφ n and Any value in is zero or Δcosφ n and When they are equal, the preset delay switching time interval t 0 Put into operation or cut off, otherwise, according to Δcosφ n and The time difference Δt between the time point when the n+1th switching unit is put into operation or removed and the time point when the nth switching unit is put into operation or removed is calculated, and the n+1th switching unit is put into operation or removed at a time Δt after the time point when the nth switching unit is put into operation or removed; wherein Δt is calculated by the following formula: Where, t 0 The value ranges from 4 to 8 seconds.

[0028] In actual production, some electrical equipment in the power grid will start and stop regularly, that is, start and stop within a fixed time period. In this case, with the start and stop of these electrical equipment, the power factor of the power grid will fluctuate regularly. In order to reduce the impact of this fluctuation on the reactive power compensation operation and avoid the power factor of the power grid exceeding the preset threshold range after the reactive power compensation device is switched on, it is necessary to take the impact of the start and stop of these electrical equipment on the power grid into account. Specifically, in step (S1), the capacity C required to be put into operation is calculated. t0 Or the cut-off capacitance C q0 When the power factor change during the switching unit operation or removal period is predicted based on historical data , and then calculate C using the following formula t0 or C q0 : Where C is C t0 or C q0 ; P is the active power of the power grid; It is the power factor of the power grid before the switching unit is put into operation or removed; is the power factor of the power grid after the switching unit is put into operation or removed; ω is the voltage angular frequency, ω=2πf, where f is the AC frequency; V is the power grid voltage; δ is an adjustable parameter, and the value range is [0.8, 0.95]. Preferably, the value range of δ is [0.87, 0.93].

[0029] When the reactive compensation control method of the present invention is used to control the reactive compensation operation of the power grid, a preset threshold range is set. Even if the power factor of the power grid is within the preset threshold range, when it is lower than the lower limit of the preset threshold range, the reactive compensation device (switching unit) is put into operation in the power grid. When the power factor of the power grid is higher than the upper limit of the preset threshold range, a part of the reactive compensation devices in operation in the power grid is cut off. The redundancy principle can effectively avoid excessive commissioning or cutting of capacitance. Compared with the switching operation of the reactive compensation device based on the existing reactive compensation control method, the switching operation frequency of the reactive compensation device based on the reactive compensation control method of the present invention is reduced by about 30%. Moreover, the power factor change during the switching unit commissioning or cutting period is predicted based on historical data. The application of can effectively avoid invalid switching operations when the power factor of the power grid fluctuates regularly, thereby enabling the power grid to provide more stable power supply.

[0030] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. A reactive power compensation control method, applicable to a reactive power compensation system in which more than three capacitors are provided in a switching unit of a reactive power compensation device, characterized in that: The steps include: (S1) Collect data information related to the power factor of the power grid and calculate the capacity C required to be put into operation t0 Or the cut-off capacitance C q0 , using the redundancy coefficient to calculate C t0 and C q0 Adjust the adjusted C t1 and the adjusted C q1 To ensure that the power factor cosφ1 of the power grid after the switching unit is put into operation or removed satisfies the following inequality: (1+α)×cosφ0≤cosφ1≤(1-β)×cosφ2 Wherein, α and β are adjustable parameters, the value range of α is [0.01, 0.05], and the value range of β is [0.01, 0.05]; cosφ0 is the controllable lower limit of the power factor of the power grid; cosφ2 is the controllable upper limit of the power factor of the power grid; (S2) Based on the C calculated in step (S1), t1 or C q1 The switching units are put into operation or removed according to the following strategies: (CL1) When it is necessary to put the unit into operation, first t1 The capacitors in the switching unit are connected in series, in combination with series and parallel, or in parallel to form a capacitor bank, and then the switching unit is put into operation; (CL2) When it is necessary to cut off the switching unit, according to C q1 The strategy of first-in, first-out will cut off the online switching units.

2. The reactive power compensation control method according to claim 1, characterized in that: Use the following formula to calculate C t0 and C q0 Make adjustments: C t1 =C t0 ×(1-γ1) C q1 =C q0 ×(1-γ2) In the formula, C t1 is the capacity to be put into operation after adjustment; γ1 is the redundancy factor when reactive power compensation power needs to be increased, and its value range is [0.05, 0.08]; C q1 is the capacity to be removed after adjustment; γ2 is the redundancy factor when the reactive compensation power needs to be reduced, and its value range is [0.11, 0.17]; γ1 and γ2 satisfy the following inequalities respectively: (1+α)×(1-γ1)≥1 (1-β)×(1-γ1)≥0.8 (1+α)×(1-γ2)≥1 (1-β)×(1-γ2)≥0.

8.

3. The reactive power compensation control method according to claim 2, characterized in that: The ratio of γ1 and γ2 is: 0.4~1.

4. The reactive power compensation control method according to claim 1, characterized in that: In step (S2), when the switching unit is cut off, after the switching unit is cut off, the connection state between the capacitors in the switching unit is disconnected.

5. The reactive power compensation control method according to claim 1, characterized in that: In step (S2), continuous switching is required and after the nth switching unit is put into operation or removed, the expected change in power factor Δcosφ is calculated n , and use the collected data information related to the power factor of the power grid to calculate the actual change in power factor , where the power factor of the power grid is calculated with an accuracy of 0.0001; when Δcosφ n and Any value in is zero or Δcosφ n and If they are equal, they are put into operation or removed according to the preset delay switching time interval t0. Otherwise, they are switched on or off according to Δcosφ n and The time difference Δt between the time point when the n+1th switching unit is put into operation or removed and the time point when the nth switching unit is put into operation or removed is calculated, and the n+1th switching unit is put into operation or removed at a time Δt after the time point when the nth switching unit is put into operation or removed; wherein Δt is calculated by the following formula: In the formula, t0 is 4 to 8s.

6. The reactive power compensation control method according to claim 1, characterized in that: In step (S1), the capacity C required to be put into operation is calculated t0 Or the cut-off capacitance C q0 When the power factor change during the switching unit operation or removal period is predicted based on historical data , and then calculate C using the following formula t0 or C q0 : Where C is C t0 or C q0 ; P is the active power of the power grid; It is the power factor of the power grid before the switching unit is put into operation or removed; is the power factor of the grid after the switching unit is put into operation or removed; ω is the voltage angular frequency; V is the grid voltage; δ is an adjustable parameter with a value range of [0.8, 0.95].

7. The reactive power compensation control method according to claim 6, characterized in that: The value range of δ is [0.87,0.93].

8. A system for performing reactive power compensation control using the reactive power compensation control method according to any one of claims 1 to 7, characterized in that: include: A data acquisition unit is used to collect data information related to the power factor of the power grid and the switching time of the switching unit; A data storage unit, used for storing data collected by the data collection unit; A data processing unit, used for processing the data collected by the data collection unit; A switching unit is used to provide reactive compensation power for reactive compensation; the switching unit includes more than or equal to 3 capacitors and a control module, and the control module is used to connect the capacitors in the switching unit in series, in parallel, or in series and parallel according to the processing result of the data processing unit; A control unit, used for performing a switching operation of the switching unit according to a data processing result output by the data processing unit; The data acquisition unit is communicatively connected with the data storage unit, the data storage unit is communicatively connected with the data processing unit, the data processing unit is communicatively connected with the control module and the control unit respectively, and the control unit is communicatively connected with the control module.

9. The system according to claim 8, characterized in that The control unit is communicatively connected with the display unit.

10. The system according to claim 8, characterized in that The control unit is connected to the handheld terminal for communication via the wireless communication unit.

Images