Method for performing intelligent compensation and actively intervening and avoiding resonance in intelligent power grid

Abstract

The invention provides a method for performing intelligent compensation and actively intervening and avoiding resonance in an intelligent power grid, which comprises an ASG (Automatic Static Var Generator) and a plurality of capacitors. The input priority of the capacitors is determined according to the judgment conditions of first input of common compensation and second input of separate compensation, first input of large capacity and second input of small capacity, and first input of small switching times, and finally accurate compensation is completed by the ASVG; recording the method as an input compensation method; when resonance occurs, the ASVG starts to be cut off and adjusted from the input capacitor with the minimum capacity, and the impedance in the system is changed by changing the switching sequence, the switching number and the switching interval of the input capacitor; the sum of the capacities of the cut-off capacitors is recorded as a Q cut total, the Q cut total is subjected to input compensation, capacitors with other capacities are adopted for input compensation, the capacitors with the other capacities refer to capacities different from the capacities of the cut-off capacitors, and input compensation is carried out according to the input compensation method; and power grid quality treatment is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid quality management, and in particular to a method for performing intelligent compensation in a smart grid while also actively intervening and avoiding resonance. Background Art

[0002] In the operation of the power grid, due to the existence of nonlinear loads, harmonics and reactive power are inevitably generated. Capacitors are currently widely used to control reactive power. However, when using capacitors, resonance is very likely to occur when harmonics exist, which will have an impact on the power grid and cause serious impact.

[0003] In view of the above problems, the applicant intends to conduct further research on the hybrid compensation system of the power grid composed of ASVG+capacitor (ASVG is a static VAR generator), aiming to propose a method to solve compensation and resonance, so as to achieve the purpose of improving the quality of the power grid. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for performing intelligent compensation in a smart grid while actively intervening and avoiding resonance, which is beneficial to the quality management of the power grid.

[0005] In order to solve the above technical problems, the present invention proposes a method for performing intelligent compensation in a smart grid while actively intervening and avoiding resonance. During compensation, capacitors are put into operation according to the judgment conditions such as common compensation first and divided compensation later, large capacity first and small capacity later, and less switching times first to determine the priority of the input and put into operation in order of priority, and finally the ASVG completes the precise compensation; the above method is recorded as the input compensation method;

[0006] When resonance occurs, ASVG starts to cut off the smallest capacitor and changes the impedance of the system by changing the switching order, number and interval of the capacitors. The total capacity of the capacitors cut off is Q. 切总 , for Q 切总 The input compensation is carried out using capacitors of other capacities, where the capacitors of other capacities refer to the capacities other than the capacity of the cut-off capacitors, and the input compensation is carried out according to the aforementioned input compensation method.

[0007] As an improvement, the reactive component of the system current is detected by sampling the CT on the system side and recorded as Q 总 , let the compensation capacity required by ASVG be Q SVG , the minimum compensation capacity of a single capacitor is recorded as Q C , when Q 总 >Q CWhen the reactive power required for compensation is greater than the maximum compensation capacity of a single capacitor, ASVG first controls the capacitor Q with the largest capacity and the least switching times. C共·MAX Priority is given to inputting the common compensation capacitor Q C共·MAX Afterwards, if the current Q 总 >Q C If the required reactive power compensation is greater than the maximum compensation capacity of a single common compensation capacitor among the remaining common compensation capacitors, then ASVG controls the common compensation capacitor with the largest current compensation capacity and the least switching times to continue to be put into operation, and repeats the above process until the investment conditions are no longer met. Or, when the common compensation capacitors are put into operation and the reactive power compensation is still not met, the separate compensation capacitors are put into operation until the investment conditions are no longer met.

[0008] As an improvement, the process of switching on the split compensation capacitor includes: ASVG first controls the split compensation capacitor Q with the largest capacity and the least switching times among the split compensation capacitors. C分·MAX Input, when inputting the common compensation capacitor Q C共·MAX Afterwards, if the current Q 总 >Q C分 If the required reactive power compensation is greater than the maximum compensation capacity of the remaining sub-compensation capacitors, then ASVG controls the sub-compensation capacitor with the largest current compensation capacity and the least switching times to continue to be put into operation, and repeats the above process until the input conditions are no longer met.

[0009] As an improvement, when the input conditions are not met, if Q 总 -Q C >0, ASVG is put into fine compensation, and the capacity of the fine compensation is the remaining capacity to be compensated.

[0010] As an improvement, fine compensation means that ASVG performs stepless compensation within the rated capacity range.

[0011] As an improvement, the method for determining the capacitor with fewer switching times is as follows: the switching times of the capacitor refers to the number of times the capacitor is switched on and off by the relay during actual operation. The switching times are recorded in the program during the capacitor switching process and accumulated. By reading the switching times of each capacitor and comparing them, the capacitor with fewer switching times can be determined.

[0012] As an improvement, the capacitors that have been put into use have M capacities, so the capacitors of various capacities are recorded as Q from small to large. c1 , Q c2 , Q c3 ,......Q cM , corresponding to the above different capacities, the number of capacitors of various capacities is recorded as N c1 、N c2 、Nc3 、.....N cM When cutting, first cut off a Q c1 , and then judge Δ n > Is A true? If true, continue to remove the second Q c1 , and then judge Δ n >A is true, and so on, if Q c1 After all the resection is completed, there is no Q available for resection. c1 , and Δ n > A still holds, so continue to remove one Q c2 , and judge Δ n > Is A true? If true, continue to remove the second Q c2 , and then judge Δ n >A is true, and so on, if Q c2 After all the resection is completed, there is no Q available for resection. c2 , Δ n >A still holds true, then continue to remove the capacitor of Qc3 and repeat the above process until it is judged that Δ n >When A is not true, stop cutting; Δ n It is the rate of change of the amplitude of the nth harmonic on the system side, where n is a positive integer, A is the set value, and its value range is 100~1000A / S.

[0013] As an improvement, Δ n The definition is as follows:

[0014] The amplitude of the nth harmonic current component on the system side at time T is recorded as Then there is in Δ T Within time, Δ n for:

[0015]

[0016] Δ T =T2-T1

[0017] Where T1 and T2 represent the time in the unit period of 20ms, Δ n The unit is A / S.

[0018] As an improvement, the quantity ratio of capacitors with different capacities corresponding to harmonic amplification is recorded, and this quantity ratio is avoided in subsequent switching compensation.

[0019] After adopting the above structure, compared with the prior art, the present invention has the following advantages: after the above improvement, the linkage timing of reactive power compensation and harmonic control can be unified and coordinated, which is conducive to simple, effective and rapid active intervention in the generation of harmonic current amplification, and the harmonic current can be curbed when it shows a trend of amplification. The compensation order and quantity are greatly optimized, and a chaotic and disordered compensation order will not be generated. In applications with fast reactive power change rate, large change amplitude and large harmonics, large-capacity and intelligent switching of capacitor groups can be performed quickly and accurately, thereby coordinating reactive power and harmonic changes. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below:

[0021] In this example, the capacitor adopts an intelligent capacitor, which mainly includes a control unit, a circuit breaker, a capacitor, a reactor and a magnetic latching relay. The intelligent capacitor can adopt a commercially available low-voltage reactive power compensation device with suppressed resonance, such as the products produced and sold by Zhejiang Shengtai Electric Co., Ltd.

[0022] The plurality of capacitors include a plurality of intelligent co-compensation capacitors and a plurality of intelligent separate compensation capacitors.

[0023] This example uses a static VAR generator. Of course, an APF with reactive power compensation capability can also be used. APF is called an active filter. Static VAR generator and APF can be used equivalently. In this case, APF is equivalent to a static VAR generator. Each smart capacitor communicates with ASVG. The smart capacitor sends its own status information to ASVG. ASVG learns the switching status of each smart capacitor based on the status information sent. ASVG controls multiple capacitors to switch according to compensation needs.

[0024] The present invention provides a method for performing intelligent compensation in a smart grid while actively intervening and avoiding resonance, comprising an ASVG and a plurality of capacitors. During compensation, the capacitors are put into use according to the judgment conditions such as common compensation first and divided compensation later, large capacity first and small capacity later, and less switching times first to determine the priority of the capacitors and put them into use in order of priority, and finally the ASVG completes the precise compensation.

[0025] When resonance occurs, ASVG starts to cut and adjust from the capacitor with the smallest capacity that has been put into operation, and uses one or more of the three methods of changing the switching order, switching quantity, and switching interval of the capacitor to change the impedance in the system. For example, the current switching order of capacitors is "first common compensation and then separate compensation, first large capacity and then small capacity", so changing the switching order of capacitors means not switching according to the switching order of "first common compensation and then separate compensation, first large capacity and then small capacity", such as first small capacity, and giving priority to cutting off small capacity common compensation capacitors and separate compensation capacitors, so that the switching order is different from the original switching order; the switching quantity refers to the number of capacitors that have been put into operation and the number of capacitors that have not been put into operation, that is, the switching quantity is two data, one data is the number of capacitors that have been put into operation, and the other data is the number of capacitors that have not been put into operation. Changing the switching quantity means changing the number of capacitors that have been put into operation and the number of capacitors that have not been put into operation. The ratio of the number of capacitors to the number of switches, for example, the current switching number is 10:5, 10 is the number of capacitors that have been put into use, and 5 is the number of capacitors that have not been put into use. If the switching number needs to be changed to adjust the impedance, one capacitor can be removed, and the switching number becomes 9:6; the switching interval includes two time intervals, namely, the switching time interval and the removal time interval. Specifically, the switching time interval is the time interval between the Nth switch and the N+1th switch, such as the 1st and the 2nd, the 2nd and the 3rd, and so on. Similarly, the removal time interval is the time interval between the Nth removal and the N+1th removal, such as the 1st and the 2nd, the 2nd and the 3rd, and so on.

[0026] Method for judging the capacitor with fewer switching times: The switching times of the capacitor refers to the number of times the capacitor is switched on and off by the relay during actual operation. The switching times are recorded in the program during the switching process of the capacitor and accumulated. By reading the switching times of each capacitor and comparing them, the capacitor with fewer switching times can be judged.

[0027] The number of capacitors required for each compensation can be determined by the following method:

[0028] The reactive component of the system current is detected by sampling the CT on the system side and recorded as Q 总 , let the compensation capacity required by ASVG be Q SVG , the capacitor capacity is recorded as Q c1 <Q c2 <Q c3 ...<Q cM ;

[0029] When Q 总 <Q C1 When the required reactive power is less than the minimum capacity of a single capacitor, there is no need to switch the capacitor, and the ASVG will compensate for all capacitive reactive power.

[0030] When Q 总 =Q C , then the number of capacitors with the minimum capacity required is 1;

[0031] When Q 总 >Q C1 When the total reactive power of the capacitor required for compensation is ∑Q C =λ 1 Q c1 +λ 2 Q c2 +λ 3 Q c3 ……+λ M Q cM (λ M is a positive integer, indicating the number of capacitors put into use), and ∑Q C <Q 总 , at this time the ASVG compensation capacity is Q SVG =Q 总 -∑Q C .

[0032] After determining the number of capacitors to be put into use, the priority of capacitors can be determined by the following method, and they can be put into use in order of priority:

[0033] When Q 总 >Q C1 When the reactive power required for compensation is greater than the maximum compensation capacity of a single capacitor, ASVG first controls the capacitor Q with the largest capacity and the least switching times. C共MAX Priority is given to inputting the common compensation capacitor Q C共MAX Afterwards, if the current Q 总 >Q C1 If the required reactive power compensation is greater than the maximum compensation capacity of a single common compensation capacitor among the remaining common compensation capacitors, then ASVG controls the common compensation capacitor with the largest current compensation capacity and the least switching times to continue to be put into operation, and repeats the above process until the investment conditions are no longer met. Or, when the common compensation capacitors are put into operation and the reactive power compensation is still not met, then the separate compensation capacitors are put into operation until the investment conditions are no longer met.

[0034] The process of switching on the split compensation capacitor includes: ASVG first controls the split compensation capacitor Q with the largest capacity and the least switching times among the split compensation capacitors. C分MAX Input, when inputting the common compensation capacitor Q C共MAX Afterwards, if the current Q 总 >Q C分If the required reactive power compensation is greater than the maximum compensation capacity of a single remaining sub-compensation capacitor, then ASVG controls the sub-compensation capacitor with the largest remaining compensation capacity and the least switching times to continue to be put into operation, and repeats the above process until the input conditions are no longer met.

[0035] When the input conditions are not met, if Q 总 -Q C >0, ASVG is put into fine compensation, and the capacity of the fine compensation is the remaining capacity to be compensated.

[0036] Fine compensation means that ASVG performs stepless compensation within the rated capacity range. For example, if the capacity of ASVG is 50Kvar, its compensation range can be 0 to 50, with a minimum of 0.1Kvar. Therefore, the compensation accuracy of ASVG is refined.

[0037] Through the above process, the input compensation of the power grid is realized.

[0038] When resonance occurs, ASVG starts to cut off and adjust from the capacitor with the smallest capacity that has been put into operation, and changes the impedance in the system by changing the switching order, switching quantity and switching interval of the capacitors that have been put into operation.

[0039] The capacitors that have been put into use have M capacities, so the capacitors of various capacities are recorded as Q from small to large. c1 , Q c2 , Q c3 ,......Q cM , corresponding to the above different capacities, the number of capacitors of various capacities is recorded as N c1 、N c2 、N c3 、.....N cM , first remove a Q c1 , and then judge Δ n > Is A true? If true, continue to remove the second Q c1 , and then judge Δ n >A is true, and so on, if Q c1 After all the resection is completed, there is no Q available for resection. c1 , and Δ n > A still holds, so continue to remove one Q c2 , and judge Δ n > Is A true? If true, continue to remove the second Q c2 , and then judge Δ n >A is true, and so on, if Q c2 After all the resection is completed, there is no Q available for resection. c2 , Δ n>A still holds true, then continue to remove the capacitor of Qc3 and repeat the above process until it is judged that Δ n >When A is not true, stop cutting; Δ n is the rate of change of the nth harmonic amplitude on the system side, n is a positive integer, A is the set value, and the value range is 100~1000A / S. In this example, A is 100.

[0040] If M is 3, then there are three types of capacitors, Q c1 , Q c2 , Q c3 , and has a capacity relationship of Q c1 <Q c2 <Q c3 , Q c1 , Q c2 , Q c3 The number of c1 、N c2 、N c3 When cutting, first cut off a Q c1 , and then judge Δ n > Is A true? If true, continue to remove the second Q c1 , and then judge Δ n >A is true, and so on, if Q c1 After all the resection is completed, there is no Q available for resection. c1 , and Δ n > A still holds, so continue to remove one Q c2 Otherwise, stop the removal and compensate the removed capacity; remove a Q c2 After that, we need to judge Δ n > Is A true? If true, continue to remove the second Q c2 , and then judge Δ n > Is A true? If not, then there is no need to remove the remaining Q c2 There is no need to continue removing Qc3, and the next step is to compensate for the removed volume.

[0041] Δ n The definition is as follows:

[0042] The amplitude of the nth harmonic current component on the system side at time T is recorded as Then there is in Δ T Within time, Δ n for:

[0043]

[0044] Δ T =T2-T1

[0045] Where T1 and T2 represent the time in the unit period of 20ms, Δ n The unit is A / S.

[0046] The following method can be used to compensate for the removed capacity: the total capacity of the removed capacitors is Q 切总 , for Q 切总 The compensation is carried out by using capacitors of other capacities. The capacitors of other capacities refer to the capacity different from the capacity of the capacitors removed. Taking the above example of M being 3, the compensation Q c1 , Q c2 capacitors outside.

[0047] When harmonics are amplified, the quantity ratio of capacitors with different capacities at that moment is recorded, and in the subsequent switching compensation, this quantity ratio is avoided. In this way, the probability of harmonic amplification can be actively reduced, which is a further active intervention, which is of great significance to the power quality.

[0048] Through the above process, intelligent compensation for the smart grid is achieved while actively intervening and avoiding resonance.

[0049] The above description is only a preferred embodiment of the present invention, so all equivalent changes or modifications made according to the structure, characteristics and principles described in the scope of the patent application of the present invention are included in the scope of the patent application of the present invention.

Claims

1. A method for performing intelligent compensation in a smart grid while also actively intervening and avoiding resonance, comprising an ASVG and a plurality of capacitors, characterized in that: During compensation, capacitors are put into operation according to the judgment conditions such as common compensation first and divided compensation later, large capacity first and small capacity later, and less switching times first to determine the priority of input and put into operation in order of priority, and finally the ASVG completes the accurate compensation; the above method is recorded as the input compensation method; When resonance occurs, ASVG starts to cut off and adjust from the capacitor with the smallest capacity that has been put into use, and changes the impedance in the system by changing the switching order, switching quantity, and switching interval of the capacitors that have been put into use; The total capacitance of the removed capacitors is Q 切总 , for Q 切总 The input compensation is carried out using capacitors of other capacities, where the capacitors of other capacities refer to the capacities other than the capacity of the cut-off capacitors, and the input compensation is carried out according to the aforementioned input compensation method.

2. The method for performing intelligent compensation while actively intervening and avoiding resonance in a smart grid according to claim 1, characterized in that: The reactive component of the system current is detected by sampling the CT on the system side and recorded as Q 总 , let the compensation capacity required by ASVG be Q SVG , the minimum compensation capacity of a single capacitor is recorded as Q C , when Q 总 >Q C When the reactive power required for compensation is greater than the maximum compensation capacity of a single capacitor, ASVG first controls the capacitor Q with the largest capacity and the least switching times. C共·MAX Priority is given to inputting the common compensation capacitor Q C共·MAX Afterwards, if the current Q 总 >Q C If the required reactive power compensation is greater than the maximum compensation capacity of a single common compensation capacitor among the remaining common compensation capacitors, then ASVG controls the common compensation capacitor with the largest current compensation capacity and the least switching times to continue to be put into operation, and repeats the above process until the investment conditions are no longer met. Or, when the common compensation capacitors are put into operation and the reactive power compensation is still not met, the separate compensation capacitors are put into operation until the investment conditions are no longer met.

3. The method for performing intelligent compensation and active intervention and avoiding resonance in a smart grid according to claim 2, characterized in that: The process of switching on the split compensation capacitor includes: ASVG first controls the split compensation capacitor Q with the largest capacity and the least switching times among the split compensation capacitors. C分·MAX Input, when inputting the common compensation capacitor Q C共·MAX Afterwards, if the current Q 总 >Q C分 If the required reactive power compensation is greater than the maximum compensation capacity of the remaining sub-compensation capacitors, then ASVG controls the sub-compensation capacitor with the largest current compensation capacity and the least switching times to continue to be put into operation, and repeats the above process until the input conditions are no longer met.

4. The method for performing intelligent compensation while actively intervening and avoiding resonance in a smart grid according to claim 2 or 3, characterized in that: When the input conditions are not met, if Q 总 -Q C >0, ASVG is put into fine compensation, and the capacity of the fine compensation is the remaining capacity to be compensated.

5. The method for performing intelligent compensation and active intervention and avoiding resonance in a smart grid according to claim 1, characterized in that: Fine compensation refers to the stepless compensation of ASVG within the rated capacity range.

6. The method for performing intelligent compensation while actively intervening and avoiding resonance in a smart grid according to claim 1, characterized in that: Method for judging the capacitor with fewer switching times: The switching times of the capacitor refers to the number of times the capacitor is switched on and off by the relay during actual operation. The switching times are recorded in the program during the switching process of the capacitor and accumulated. By reading the switching times of each capacitor and comparing them, the capacitor with fewer switching times can be judged.

7. The method for performing intelligent compensation and active intervention and avoiding resonance in a smart grid according to claim 1, characterized in that: The capacitors that have been put into use have M capacities, so the capacitors of various capacities are recorded as Q from small to large. c1 , Q c2 , Q c3 ,......Q cM , corresponding to the above different capacities, the number of capacitors of various capacities is recorded as N c1 、N c2 、N c3 、.....N cM When removing, first remove a Q c1 , and then judge Δ n > Is A true? If true, continue to remove the second Q c1 , and then judge Δ n >A is true, and so on, if Q c1 After all the resection is completed, there is no Q available for resection. c1 , and Δ n > A still holds, so continue to remove one Q c2 , and judge Δ n > Is A true? If true, continue to remove the second Q c2 , and then judge Δ n >A is true, and so on, if Q c2 After all the resection is completed, there is no Q available for resection. c2 , Δ n >A still holds true, then continue to remove the capacitor of Qc3 and repeat the above process until it is judged that Δ n >When A is not true, stop cutting; Δ n It is the rate of change of the amplitude of the nth harmonic on the system side, where n is a positive integer, A is the set value, and its value range is 100~1000A / S.

8. The method for performing intelligent compensation and active intervention and avoiding resonance in a smart grid according to claim 7, characterized in that: Δ n The definition is as follows: The amplitude of the nth harmonic current component on the system side at time T is recorded as Then there is in Δ T Within time, Δ n for: D T =T2-T1 Where T1 and T2 represent the time in the unit period of 20ms, Δ n The unit is A / S.

9. The method for performing intelligent compensation and active intervention and avoiding resonance in a smart grid according to claim 1, characterized in that: Record the quantity ratio of capacitors of different capacities during harmonic amplification, and avoid this quantity ratio in subsequent switching compensation.

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