A capacitor overcurrent protection method for a reactive power compensation controller

Abstract

This invention relates to a capacitor overcurrent protection method for a reactive power compensation controller. First, the rated capacitance and series reactance K of the capacitor are obtained. The theoretical output current Ie of the capacitor is calculated, and the actual output current Is1 of the current capacitor is measured. The capacitor is then switched on, and the actual output current Is2 of the current capacitor is measured again. If Is3 > I1 within a time period T1, the capacitor is considered to be in an overcurrent situation, and the capacitor is immediately disconnected. If Is3 < Ie within a time period T1, the switching process ends. If Is3 > Ie, Is3 is measured again after a waiting time T2. This invention determines the risk of overcurrent by detecting the capacitor's output current, effectively avoiding capacitor damage, slowing capacity decay, and extending the capacitor's service life, thereby making the compensation effect of the capacitor bank more reliable.

Description

Technical Field

[0001] This invention relates to the field of reactive power compensation technology in low-voltage power distribution, and in particular to a capacitor overcurrent protection method for a reactive power compensation controller. Background Technology

[0002] With the rapid development of modern industry and the surge in electricity consumption, the large amount of reactive power generated by inductive loads in the power grid will lead to a decline in power quality and an increase in power loss, seriously threatening the safe operation of the power system. Therefore, reactive power compensation equipment has been widely used, especially reactive power compensation capacitor banks.

[0003] Capacitor banks require reactive power compensation controllers to monitor the power grid status in real time, determine the required reactive power compensation amount, and switch capacitors of appropriate capacity for accurate and real-time reactive power compensation. However, most existing controllers only focus on the reactive power compensation effect on the power grid, often neglecting the usage of the capacitors. This leads to a significant reduction in capacitor lifespan or even damage. Even when a capacitor is damaged, it cannot be identified, and the damaged capacitor may still be switched on, requiring short-circuit protection devices such as fuses to disconnect it.

[0004] Capacitor damage and reduced lifespan are often caused by overcurrent, therefore there is an urgent need for a capacitor overcurrent protection method for reactive power compensation controllers. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a capacitor overcurrent protection method for a reactive power compensation controller. By detecting the output current of the capacitor, the method can determine whether there is an overcurrent risk, effectively avoid capacitor damage, slow down capacity decay, and extend the service life of the capacitor.

[0006] The objective of this invention is achieved as follows:

[0007] A capacitor overcurrent protection method for a reactive power compensation controller includes the following:

[0008] Step SS1: Obtain the rated capacitance Q of the capacitor e ,

[0009] Before the controller can connect the capacitor, it is necessary to first obtain the rated capacitance Q of the capacitor. e The series reactance K of a series capacitor;

[0010] Step SS2: Calculate the theoretical output current I of the capacitor. e ,

[0011] U s This is the actual voltage across the capacitor.

[0012] Ue This is the rated voltage across the capacitor.

[0013] Step SS3: Measure the actual output current I of the current capacitor. s1 ;

[0014] Step SS4: The controller selects the appropriate capacitor capacity to be connected based on the actual reactive power demand;

[0015] Step SS5: Measure the actual output current I of the capacitor being connected. s2 ;

[0016] Step SS6: Calculate I s3 I s3 =I s2 -I s1 ;

[0017] Step SS7: Determine if there is an overcurrent.

[0018] S7.1, if I during time interval T1 s3 >I1, where I1 is the set threshold of 1;

[0019] If this is the case, the capacitor is considered to be experiencing an overcurrent, and the capacitor should be disconnected immediately.

[0020] S7.2, if I during time interval T1 s3 <I e ,

[0021] No action will occur, and the current input process will end.

[0022] S7.3, if I during time interval T1 s3 >I e ,

[0023] Then proceed to waiting time T2;

[0024] S7.31, After waiting time T2, check I again. s3 , if I s3 >I2, where I2 is the set threshold of 2;

[0025] If this is the case, the capacitor is considered to be experiencing an overcurrent, and the capacitor should be disconnected immediately.

[0026] S7.32, If I s3 <I2,

[0027] If the capacitor is not overcurrent, the detection is stopped.

[0028] Preferably, in step SS2, K is the series reactance of the capacitor, typically 7% or 14%.

[0029] Preferably, threshold 1 is greater than threshold 2, i.e., I1 > I2.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention employs a capacitor overcurrent protection method for reactive power compensation controllers. This method provides more accurate overcurrent detection, monitors the output status of connected capacitors in real time, locates defective capacitors, and avoids the problem of usable capacitors being mistakenly identified as damaged and thus failing to compensate, resulting in poor compensation performance of the capacitor bank. This invention determines the risk of overcurrent by detecting the capacitor's output current, effectively preventing capacitor damage, slowing capacity decay, and extending capacitor lifespan, thereby making the compensation effect of the capacitor bank more reliable. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process of the present invention.

[0033] Figure 2 This is a logic diagram of the method of the present invention. Detailed Implementation

[0034] To better understand the technical solution of the present invention, a detailed description will be provided below in conjunction with relevant figures. It should be understood that the following specific embodiments are not intended to limit the specific implementation of the technical solution of the present invention, but are merely implementations that can be adopted by the technical solution of the present invention.

[0035] Example 1:

[0036] See Figure 1 , Figure 1 A flowchart illustrating the present invention has been drawn. As shown in the figure, the present invention relates to a capacitor overcurrent protection method for a reactive power compensation controller, which includes the following:

[0037] Step SS1: Obtain the rated capacitance Q of the capacitor e ,

[0038] Before the controller can connect the capacitor, it is necessary to first obtain the rated capacitance Q of the capacitor. e The series reactance K of a series capacitor;

[0039] Step SS2: Calculate the theoretical output current I of the capacitor. e ,

[0040] U s This is the actual voltage across the capacitor.

[0041] U e The rated voltage across the capacitor.

[0042] K is the series reactance of the capacitor, which is typically 7% or 14%.

[0043] Step SS3: Measure the actual output current I of the current capacitor. s1 ;

[0044] Step SS4: The controller selects the appropriate capacitor capacity to be connected based on the actual reactive power demand;

[0045] Step SS5: Measure the actual output current I of the capacitor being connected. s2 ;

[0046] Step SS6: Calculate I s3 I s3 =I s2 -I s1 ;

[0047] Step SS7: Determine if there is an overcurrent.

[0048] S7.1, if I during time interval T1 s3 >I1, where I1 is the set threshold of 1;

[0049] If this is the case, the capacitor is considered to be experiencing an overcurrent, and the capacitor should be disconnected immediately.

[0050] S7.2, if I during time interval T1 s3 <I e ,

[0051] No action will occur, and the current input process will end.

[0052] S7.3, if I during time interval T1 s3 >I e ,

[0053] Then proceed to waiting time T2;

[0054] S7.31, After waiting time T2, check I again. s3 , if I s3 >I2, where I2 is the set threshold of 2;

[0055] If this is the case, the capacitor is considered to be experiencing an overcurrent, and the capacitor should be disconnected immediately.

[0056] S7.32, If I s3 <I2,

[0057] If the capacitor is not overcurrent, the detection is stopped.

[0058] Throughout the process of determining whether a capacitor is overcurrent, if threshold 1 is greater than threshold 2, and the actual output current measured during time period T1 is greater than the maximum threshold 1, it is assumed that the capacitor has experienced resonant overcurrent and is immediately disconnected. The measurement after time period T2 mainly considers that after switching the capacitor, the power grid may fluctuate, and this fluctuation causes the current change to be less than threshold 1. After time T2, the power grid tends to stabilize, and the capacitor output current measured at this time is more accurate. If the measured current is greater than threshold 2 at this time, it is determined to be overcurrent, and the capacitor is disconnected; if it is less than threshold 2, it is determined that the capacitor is outputting normally, and the detection is terminated.

[0059] Comparative Example 1:

[0060] Comparative Example 1 uses an existing general-purpose controller;

[0061] The reactive power and harmonics are generated to simulate the continuous changes in the field load, and the reactive power compensation capacitor cabinet compensates for reactive power by switching capacitors.

[0062] The following table compares the data from Comparative Example 1 and Example 1:

[0063] Reactive power compensation cabinet 1 (the controller with overcurrent protection used in Example 1)

[0064] Capacitor Number capacity Initial capacity decay Compensated capacity attenuation 1 10Kvar 0.1％ 5.7％ 2 30Kvar 0.1％ 5.1％ 3 50Kvar 0.1％ 3.8％ 4 50Kvar 0.2％ 3.8％ 5 50Kvar 0.1％ 3.7％ 6 50Kvar 0.2％ 3.8％ 7 50Kvar 0.1％ 3.6％ 8 50Kvar 0.1％ 3.8％

[0065] Reactive power compensation cabinet 2 (using the same ordinary controller as in comparative model 1)

[0066]

[0067]

[0068] The above two sets of data show that by using a controller with overcurrent protection, the capacity attenuation is greatly reduced after compensation.

[0069] The above are merely specific application examples of the present invention and do not constitute any limitation on the scope of protection of the present invention. All technical solutions formed by equivalent transformations or substitutions fall within the scope of protection of the present invention.

Claims

1. A capacitor overcurrent protection method for a reactive power compensation controller, characterized in that, It includes the following: step SS1: Obtain the rated capacitance Q of the capacitor e , Before the controller can connect the capacitor, it is necessary to first obtain the rated capacitance Q of the capacitor. e The series reactance K of a series capacitor; Step SS2: Calculate the theoretical output current I of the capacitor. e , U s This is the actual voltage across the capacitor. U e This is the rated voltage across the capacitor. Step SS3: Measure the actual output current I of the current capacitor. s1 ; Step SS4: The controller selects the appropriate capacitor capacity to be connected based on the actual reactive power demand; Step SS5: Measure the actual output current I of the capacitor being connected. s2 ; Step SS6: Calculation I s3 , I s3 =I s2 -I s1 ; Step SS7: Determine if there is an overcurrent. S7.1, if I during time interval T1 s3 >I1, where I1 is the set threshold of 1; If this is the case, the capacitor is considered to be experiencing an overcurrent, and the capacitor should be disconnected immediately. S7.2, if I during time interval T1 s3 <I e , No action will occur, and the current input process will end. S7.3, if I during time interval T1 s3 >I e , Then proceed to waiting time T2; S7.31, After waiting time T2, check I again. s3 , if I s3 >I2, where I2 is the set threshold of 2; If this is the case, the capacitor is considered to be experiencing an overcurrent, and the capacitor should be disconnected immediately. S7.32, If I s3 <I2, If the capacitor is not overcurrent, the detection is stopped.

2. The capacitor overcurrent protection method for a reactive power compensation controller according to claim 1, characterized in that: In step SS2, K is the series reactance of the capacitor, which is 7% or 14%.

3. The capacitor overcurrent protection method for a reactive power compensation controller according to claim 1, characterized in that: Threshold 1 is greater than threshold 2, i.e., I1 > I2.

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