A method and controller for optimizing control of reactive power compensation of a capacitor bank

Abstract

The application discloses a kind of optimization control method and controller of capacitor bank reactive power compensation, control method includes: step (1), calculate power factor of power grid;Step (2), according to target power factor and the number of configured capacitor with switching authority determines the capacitor to be put into;Step (3), judge whether the reactive power demand change frequency is lower than the switching rotation frequency of capacitor bank;Step (4), start capacitor forced removal function, judge whether capacitor input duration is greater than set value;Step (5), forced removal capacitor, mark as "prohibit input", start forced rest time countdown;Step (6), when forced rest time countdown is zero, re-mark as "allow input".The above process is realized by reactive power compensation controller, including timing module and control module;The application can solve the problem of capacitor, loop switch life excessive consumption caused by unbalanced compensation processing distribution when load is stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of reactive power compensation, and particularly to a method and a controller for optimizing the reactive power compensation of a capacitor bank. BACKGROUND

[0002] The use of electrical equipment in a power system generates reactive power, which is usually inductive, and reduces the capacity utilization efficiency of the power source. This can be improved by adding appropriate capacitors to the system. Power capacitor compensation, also known as power factor compensation, aims to compensate for the phase difference between voltage and current in the system.

[0003] Currently, most ordinary reactive power compensation controllers support equal-capacity cycling switching, i.e., in the case of changes in load, the controller switches the capacitor bank in the same capacity sequence. However, in some specific applications, such as stable loads, the reactive power changes little. At this time, part of the capacitor bank of the reactive power compensation device is in the state of being put into operation for a long time, while the remaining part of the capacitor is in the state of being idle and not put into operation for a long time. This great imbalance in the allocation of compensation processing causes excessive wear and tear on some capacitors and circuit switches, while some capacitors and switches are often not used, which is an embarrassing and unbalanced situation.

[0004] Therefore, it is necessary to optimize the existing switching control method of the capacitor bank reactive power compensation to improve the balance of the allocation of compensation processing and prolong the service life of the capacitors and circuit switches. SUMMARY

[0005] To this end, the technical problem to be solved by the present application is to provide a method and a controller for optimizing the reactive power compensation of a capacitor bank to solve the problem of excessive wear and tear on capacitors and circuit switches caused by the great imbalance in the allocation of compensation processing when the existing capacitor bank reactive power compensation is stable.

[0006] To solve the above technical problems, the present application provides the following technical solutions:

[0007] A method for optimizing the reactive power compensation of a capacitor bank, comprising the following steps:

[0008] Step (1), sampling three-phase voltage and current signals, calculating the effective value of voltage, the effective value of current, active power and power factor;

[0009] Step (2), calculating the compensation capacitor capacity according to the target power factor, and determining the capacitors to be put into according to the number of capacitors with switching authority configured;

[0010] Step (3), determining whether the frequency of change in system reactive power demand is lower than the switching rotation frequency of the capacitor bank;

[0011] Step (4), when the system reactive power demand change frequency is lower than the switching frequency of the capacitor bank, the capacitor forced removal function is started, and it is judged whether the capacitor has been put into the capacitor for more than or equal to the set value;

[0012] Step (5), when the capacitor has been put into the capacitor for more than or equal to the set value, the capacitor is forced to be removed, marked as "prohibit input", and the forced rest time countdown is started;

[0013] Step (6), when the forced rest time countdown of the forced removed capacitor is cleared, it is re-marked as "allow input", and the capacitor is added to the end of the non-input capacitor queue.

[0014] The above-mentioned optimization control method of capacitor bank reactive power compensation, in step (2), the configuration method of the number of switched-in capacitors is:

[0015] (2-1), according to the capacity of the capacitor, the capacitor is divided into small capacity capacitor, medium capacity capacitor and large capacity capacitor; Small capacity capacitor group into small group capacity sequence, medium capacity capacitor group into medium group capacity sequence, large capacity capacitor group into large group capacity sequence;

[0016] (2-2), when there are available capacitors in the large group capacity sequence, the capacitors in the large group capacity sequence are preferentially put in; When the capacitors in the large group capacity sequence cannot meet the input demand, it is judged whether there are available capacitors in the medium group capacity sequence, if so, the capacitors in the medium group capacity sequence are put in; When the capacitors in the medium group capacity sequence cannot meet the input demand, it is judged whether there are available capacitors in the small group capacity sequence, if so, the capacitors in the small group capacity sequence are put in;

[0017] (2-3), if the capacitors in the small group capacity sequence also cannot meet the input demand, then wait until the forced rest time of the forced removed capacitor reaches the set value before putting in.

[0018] In the above-mentioned optimization control method of capacitor bank reactive power compensation, in (2-1), the capacity of the large capacity capacitor is 2 times that of the medium capacity capacitor, and the capacity of the medium capacity capacitor is 2 times that of the small capacity capacitor; In (2-2), when the system reactive power demand is greater than the capacity of the available large capacity capacitor in the large group capacity sequence, a group of large capacity capacitors is put in; When all the capacitors in the large group capacity sequence have been put into use, a group of medium group capacity capacitors is put in to replace them to achieve the maximum degree of approaching the target power factor.

[0019] The optimization control method of the capacitor bank reactive power compensation, in step (3), when the system reactive power demand change frequency is higher than or equal to the switching frequency of the capacitor bank, the capacitor input time is set to zero, that is, the capacitor forced removal function is closed, at this time, the capacitor is normally switched according to the system reactive power demand change.

[0020] The optimization control method of the capacitor bank reactive power compensation, in step (5), when a group of capacitors is forced to be removed, the un-input capacitors in the same capacity sequence as the forced removal group are selected for use; if no suitable capacity is matched, the un-input capacitors in the lower capacity sequence are selected for use until all the input capacitors are input.

[0021] The optimization control method of the capacitor bank reactive power compensation, in step (6), after the forced rest time countdown is cleared, the forced removal capacitor recovers the switching permission and is added to the end of the corresponding un-input capacitor sequence.

[0022] The optimization control method of the capacitor bank reactive power compensation, in step (4), the setting value of the capacitor input time is set according to the switch type and load characteristics; in step (5), the setting value of the forced rest time is set according to the switch type and load characteristics; the setting time precision of the capacitor input time and the forced rest time is 0.1 hour.

[0023] The optimization control method of the capacitor bank reactive power compensation, in step (4), for contact switches, the maximum input time of the capacitor is set to 12h, and for thyristor switches, the maximum input time of the capacitor is set to 10h.

[0024] The optimization control method of the capacitor bank reactive power compensation, in step (1), the signal with a period T is sampled at a frequency of N points per period to obtain the voltage sampling sequence and the current sampling sequence ; then:

[0025] The calculation method of the voltage effective value U is: ;

[0026] The calculation method of the current effective value I is: ;

[0027] The calculation method of the active power P is: ;

[0028] The calculation method of the apparent power S is: ;

[0029] The calculation method of the power factor cos is: cos = (P2+Q2) / (P2-Q2) P / S ;

[0030] The method for calculating the compensation capacitor capacity in step (2) of the optimization control method of the capacitor bank reactive power compensation is: Q c ;

[0031] In the formula, phi1 and phi2 are the power factor angles before and after compensation respectively.

[0032] An optimization controller for capacitor bank reactive power compensation is used to implement the optimization control method of the capacitor bank reactive power compensation described above; it includes a control module and a timing module; the timing module is used to monitor the input duration of the input capacitor and the forced rest time of the forced removal of the capacitor; the control module is used to automatically adjust the switching output combination of the capacitor bank, so that the idle and unused capacitor can be put into use in time.

[0033] The technical solution of the application achieves the following beneficial technical effects:

[0034] 1. The optimization control method of the capacitor bank reactive power compensation uses the timing method to monitor the input capacitor bank, adjusts the switching output combination of the capacitor bank when the use duration of the input capacitor reaches the set time, so that the idle and unused capacitor can be put into use in time, and this process can be automatically implemented by the reactive power compensation controller.

[0035] 2. The optimization control method of the capacitor bank reactive power compensation increases the input timer of all capacitor banks, the timing unit is hour, and the set time accuracy is 0.1 hour. When the input compensation capacitor reaches the set time and the capacitor is forced to be removed, the controller detects that the system reactive power demand has changed, and selects the remaining and allowed input capacitor from the same capacity sequence as the forced removal capacitor. The controller supports three kinds of compensation capacities, i.e. 1x, 2x and 4x. When a group of capacitors is removed, a group of capacitors is selected from the remaining and allowed input capacitors of the same capacity; if no suitable capacity is matched, two groups of capacitors are selected from the lower capacity. The removed capacitor group regains the switching right after the delay (discharge time + forced rest time) time reaches, and is added to the sequence of the capacitor to be (not) input. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The flowchart of the optimization control method of the capacitor bank reactive power compensation;

[0037] Figure 2 The configuration process flowchart of the capacitor input use. ​DETAILED DESCRIPTION

[0038] As Figure 1 shown, the optimization control method of the capacitor bank reactive power compensation of the embodiment includes the following steps:

[0039] Step (1), sampling three-phase voltage and current signals, calculating voltage effective value, current effective value, active power and power factor; sampling signals with a period of T at a frequency of N points per cycle to obtain voltage sampling sequence and current sampling sequence ; then:

[0040] The calculation method of the voltage effective value U is: ;

[0041] The calculation method of the current effective value I is: ;

[0042] The calculation method of the active power P is: ;

[0043] The calculation method of the apparent power S is: ;

[0044] The calculation method of the power factor cosφ is: P / S .

[0045] Step (2), calculating the compensation capacitor capacity according to the target power factor, and determining the capacitor to be put in according to the number of capacitors with switching authority configured; reducing inductive reactive power after the capacitor is put in, thereby improving the system power factor;

[0046] The method for calculating the compensation capacitor capacity Q c is:

[0047] ;

[0048] In the formula, φ1 and φ2 are the power factor angles before and after compensation, respectively.

[0049] As Figure 2 shown, the configuration method of the number of capacitors with switching authority is:

[0050] (2-1), according to the capacity of the capacitor, the capacitors are divided into small capacity capacitors, medium capacity capacitors and large capacity capacitors; the capacity of the large capacity capacitor is 2 times that of the medium capacity capacitor, and the capacity of the medium capacity capacitor is 2 times that of the small capacity capacitor; the small capacity capacitors form a small group capacity sequence, the medium capacity capacitors form a medium group capacity sequence, and the large capacity capacitors form a large group capacity sequence;

[0051] (2-2), when the system reactive demand is greater than the capacity of the large-capacity capacitor that can be put into the large-capacity capacitor sequence, then a group of large-capacity capacitors is put into; when all the capacitors in the large-capacity capacitor sequence have been put into use, then a group of medium-capacity capacitors is put into to replace it to achieve the maximum degree of approaching the target power factor; that is, when there are capacitors that can be put into the large-capacity capacitor sequence, the capacitors in the large-capacity capacitor sequence are preferentially put into; when the capacitors in the large-capacity capacitor sequence cannot meet the input demand, it is determined whether there are capacitors that can be put into the medium-capacity capacitor sequence, if so, the capacitors in the medium-capacity capacitor sequence are put into; when the capacitors in the medium-capacity capacitor sequence cannot meet the input demand, it is determined whether there are capacitors that can be put into the small-capacity capacitor sequence, if so, the capacitors in the small-capacity capacitor sequence are put into;

[0052] (2-3), if the capacitors in the small-capacity capacitor sequence also cannot meet the input demand, then wait until the forced rest time of the forced removed capacitor reaches the set value before being put into.

[0053] Step (3), determine whether the system reactive demand change frequency is lower than the switching frequency of the capacitor bank; when the system reactive demand change frequency is higher than or equal to the switching frequency of the capacitor bank, the capacitor input time is set to zero, that is, the capacitor forced removal function is not triggered and is in the closed state, at this time, the controller normally switches the capacitor according to the system reactive demand change.

[0054] Step (4), when the system reactive demand change frequency is lower than the switching frequency of the capacitor bank, the forced removal function is triggered; after the capacitor forced removal function is started, it is determined whether the input time of the put-in capacitor is greater than or equal to the set value; the set value of the capacitor input time is flexibly adjusted according to the switch type and the load characteristics, and the parameter can be set; the time accuracy of the capacitor input time is 0.1 hours; for contact switches, the maximum input time of the capacitor is set to 12h, and for thyristor switches, the maximum input time of the capacitor is set to 10h; in other embodiments, the maximum input time of the capacitor can be appropriately adjusted according to the user site environment temperature and the switching switch brand, quality and other conditions;

[0055] Step (5), when the input time of the put-in capacitor is greater than or equal to the set value, the capacitor is forced to be removed, marked as "prohibited input", and the forced rest time countdown is started; when a group of capacitors is forced to be removed, the capacitors in the same group are removed at the same time, and the forced rest time of the removed capacitors is started. Figure 2The configuration process is as follows: firstly, the un-used capacitor is selected from the same capacity sequence as the forcedly removed capacitor; if no suitable capacity is matched, the un-used capacitor is selected from the lower capacity sequence until all the available capacitors are used. The set value of the forced rest time is flexibly adjusted according to the switch type and load characteristics, and the parameter can be set; the set time precision of the forced rest time is 0.1 hour.

[0056] Step (6), when the forced rest time of the forcedly removed capacitor is cleared, the forcedly removed capacitor resumes the right to be switched, is marked as "allowed to be used" again, and is added to the end of the corresponding un-used capacitor sequence.

[0057] The above control method is realized by a reactive power compensation controller in the embodiment, which comprises a control module and a timing module; the timing module is used to monitor the use time of the used capacitor and the forced rest time of the forcedly removed capacitor; the control module is used to automatically adjust the switching output combination of the capacitor bank, so that the un-used capacitor can be used in time, and the problem that the compensation processing distribution is greatly unbalanced when the load is stable can be solved, thereby the service life of the capacitor and the circuit switch is significantly improved.

[0058] Obviously, the above embodiment is only an example for clear illustration, and is not a limitation on the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. All the embodiments do not need to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the patent application claims.

Claims

1. A method for optimal control of reactive power compensation of a capacitor bank, characterized in that, It comprises the following steps: Step (1), sampling three-phase voltage and current signals, calculating voltage effective value, current effective value, active power and power factor; Step (2), calculating compensation capacitor capacity according to target power factor, and determining the capacitor to be put into according to the number of capacitors with switching authority configured; The configuration method of the number of capacitors with switching authority is: (2-1), according to the capacity of the capacitor, the capacitor is divided into small capacity capacitor, medium capacity capacitor and large capacity capacitor; Small capacity capacitor forms a small group capacity sequence, medium capacity capacitor forms a medium group capacity sequence, and large capacity capacitor forms a large group capacity sequence; The capacity of large capacity capacitor is 2 times that of medium capacity capacitor, and the capacity of medium capacity capacitor is 2 times that of small capacity capacitor; (2-2), when there is a capacitor that can be put into in the large group capacity sequence, the capacitor in the large group capacity sequence is preferentially put into; When the capacitor in the large group capacity sequence cannot meet the input requirement, it is judged whether there is a capacitor that can be put into in the medium group capacity sequence, if there is, the capacitor in the medium group capacity sequence is put into; When the capacitor in the medium group capacity sequence cannot meet the input requirement, it is judged whether there is a capacitor that can be put into in the small group capacity sequence, if there is, the capacitor in the small group capacity sequence is put into; When the system reactive demand is greater than the capacity of the large capacity capacitor that can be put into in the large group capacity sequence, a group of large capacity capacitors is put into; When all the capacitors in the large group capacity sequence have been put into use, a group of medium group capacity capacitors is put into to replace them to achieve the maximum proximity to the target power factor; (2-3), if the capacitor in the small group capacity sequence also cannot meet the input requirement, wait until the forced rest time of the forced removal capacitor reaches the set value before putting it into; Step (3), when the system reactive demand change frequency is higher than or equal to the switching frequency of the capacitor bank, set the capacitor input time to zero, i.e. the capacitor forced removal function is closed, at this time, according to the system reactive demand change, the capacitor is normally switched; Step (4), when the system reactive demand change frequency is lower than the switching frequency of the capacitor bank, start the capacitor forced removal function, and judge whether the input time of the put-in capacitor is greater than or equal to the set value; The set value of the capacitor input time is set according to the switch type and load characteristics; Step (5), when the input time of the put-in capacitor is greater than or equal to the set value, the capacitor with input time greater than or equal to the set value is forced to be removed, marked as "prohibited to put in", and the forced rest time countdown is started; When a group of capacitors is forced to be removed, if no suitable capacity is matched, the unput-in capacitor is selected for use until all the put-in capacitors are put into; Step (6), when the forced rest time countdown of the forced removed capacitor is cleared, it is re-marked as "allowed to put in", and the capacitor re-marked as "allowed to put in" is added to the end of the corresponding unput-in capacitor queue.

2. The method of claim 1, wherein, The setting time precision of capacitor input time and forced rest time is 0.1 hour.

3. The method of claim 2, wherein, In step (1), a signal with a period T is sampled at a frequency of N points per period, to obtain a voltage sample sequence and a current sample sequence ; then: Voltage effective value U The calculation method is: ; Current effective value I The calculation method is: ; Active power P The calculation method is: ; apparent power S The method of calculation is: ; The calculation method of the power factor cosφ is: cosφ = P / (U * I) P / S .

4. The method of claim 2, wherein, In step (2), the compensation capacitance capacity is calculated Q c The method is as follows: ； In the formula, φ1 and φ2 are power factor angles before and after compensation, respectively.

5. An optimal controller for capacitor bank reactive power compensation, characterized by, The application discloses a method for realizing the optimal control of the reactive power compensation of a capacitor bank, and belongs to the technical field of power system optimization control. The application discloses a method for realizing the optimal control of the reactive power compensation of a capacitor bank, and belongs to the technical field of power system optimization control.

Images