JPH0315230A - Operation of active filter for electric power - Google Patents

Abstract

PURPOSE:To effect efficient compensation with a small compensating capacity regardless of the opening and closing of a system by a method wherein a harmonic removing active filter, connected to a plurality (N) of power source systems, is operated at all times to compensate 1/N of total harmonic capacity. CONSTITUTION:Power source systems 101-103 of N (positive integer and N=3 in a diagram) branches connected to a power source are connected to a common bus C through breakers 201-203, active filters 501-503 and current transformers 401-403. Loads 301-303 are connected to the bus C. The active filters 501-503 compensate 1/3 of a total higher harmonic capacity, which is required to compensate. The active filters 501-503 and connected at all times except a time when all of the breakers 201-203 are cut OFF whereby compensating operation is effected. According to this method, efficient compensation may be effected with a small compensating capacity regardless of the opening and closing of the systems.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an operation method of an active filter for power, which is applied to a receiving end of a power source and is comprised of a power conversion device for compensating harmonic current required by a load. Regarding. (Prior Art) FIG. 3 shows an active filter AF of this type in a three-branch power supply system 101, 102, 103. , AF3 is connected, and in the figure, 20l, 2
02, 203 are circuit breakers connected to each power supply system 101, 102, 103. 301, 302, 303 are loads, 4
01, 402, 403 are load currents iL8g l L2p
l Current detector for detecting L3, 501, 502, 5
03 is a current detector that detects the output currents (compensation currents) ic, icz, and ic3 of the active filters AF, AF2, and AF. Further, FIG. 4 shows the control circuit 60 of the active filter.
Although not shown, this control circuit 600 is connected to each active filter AF. ，
AF. , A F, individually (i.e., 3 units)
Those with the same structure are provided. stomach? , the configuration of this control circuit 600 will be explained as one provided corresponding to active filter AF■. That is, as shown in FIG. 4, this control circuit 600 includes a fundamental wave component arithmetic unit 601 that calculates the fundamental wave component ito from the load current i5, and a fundamental wave component arithmetic unit 601 that calculates the fundamental wave component ito from the load current i5.
an adder 602 for calculating the compensation current command value 10.4 which is the deviation from L0, and an adder 603 for calculating the deviation between this compensation current command value i c1g and the output current (compensation current) ic■ of the active filter AFL. , a comparator 604 that compares this deviation with a predetermined reference level, and a pulse distributor 605 that generates a firing pulse based on the output signal of the comparator 604. is active filter AF1
It is sent to the residence circuit. The harmonic current required by the loads 301, 302, and 303 is generated by operating each active filter AF, AF2, and AF so that the output current of the active filter matches the compensation current command value using the control circuit configured as described above. can be compensated instead of the power supply systems 101, 1.02, 103.

In the conventional operation method described above, the compensation capacity of each of the active filters AF, AF, AF is 1/3 of the total amount of harmonics caused by the loads 301 to 303, taking into consideration the operation of the power supply system. By making it more than that, 1
Even when one power supply system is open or inactive, care is taken to maintain the desired compensation effect by an active filter connected to other power supply systems that are turned on, or
Measures were taken to stop the operation of one active filter while keeping the individual compensation capacity at 1/3 of the above total harmonic amount, and to operate the remaining two filters, taking it for granted that the compensation effect would worsen. It was getting worse.

In other words, it is necessary to adopt a method of controlling each active filter individually, such as suspending the operation of active filters that depend on the operation of the power supply system, and operating only the active filters of the system that are in the on state. I didn't get it.

(Problem to be solved by the invention) Therefore, in the conventional operation method, the harmonic compensation equipment has a compensation capacity higher than necessary, or the compensation effect is greatly reduced depending on the operation of the power supply system. There was a problem. The present invention was proposed in order to solve the above problems, and its purpose is to provide a power active active that uses a small compensation capacity and can provide a large compensation effect regardless of the operational status of the power supply system. The purpose of the present invention is to provide a method for operating a filter.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a system for each power supply system, even in an operation where a part of the power supply system consisting of N branches (N is a natural number of 2 or more) is opened or suspended. The control circuit is designed so that the compensating current command value of each active filter is set to 1/N of the total harmonic amount without stopping any of the active filters connected to the active filters. be.

That is, the present invention provides power receiving equipment in which loads are connected to N-branch power supply systems, in which each of the power supply systems has:
A power active filter having a compensation capacity of 1/N of the total amount of harmonics required by the load is connected to each, and when all of the power supply systems are turned on, the amount of harmonics generated in each power supply system is calculated. All active filters are operated as compensation targets for the active filters connected to each power supply system individually, and unless all of the power supply systems are open, if even one system is open, the total amount of generated harmonics will be reduced. All active filters are operated with 1/N as the compensation target for each active filter.

(Operation) In FIG. 3, the power supply systems M 101 , 102 , 103 are referred to as the first, second,
Let us consider a case where the circuit breaker 201 of the third system (referred to as the third system) is opened and the lth system lot is opened/suspended. At this time, the active filter AFX is connected to the other second and third systems 102,
103, these systems M10
2, 103 as one of the loads. At this time, all harmonics taken by the loads 301 to 303 are supplied from the power supply via the second and third systems 102 and 103. . For this reason, active filter AF. ~The total harmonics to be compensated for by AF3 are the 2nd and 3rd systems 102, 10
It is detected by the current detectors 402 and 403 of No. 3.

In this case, all active filters AF■~AF,
Assuming that the active filter is operated, the compensation capacity of each active filter should be 1/3 of the above total harmonics, but if it is actually operated with this amount of harmonics as the command value. lineage l 1
01 active filter AF. loads the harmonics 301
~303, the current detectors 402,4
The harmonics detected by active filter AF. The compensation target will be reduced from the original value by the compensation amount.

In view of this point, in the present invention, for example, the closing/opening status signals of the circuit breakers (201 to 203 in FIG. 3) of the three-branch power supply system are inputted to the control system to turn on/off the multiple power supply systems. Detect conditions. Then, all systems are open and
Unless it is in a dormant state, if even one system is open or in a dormant state, the current detector of the system in the interconnected state (402, 403 when the 1st system?01 is in a dormant state in Figure 3)
The total harmonics of the loads 301 to 303 are detected by adding the outputs of the current detectors (same < 401) of the system that is inactive as well as the outputs of the current detectors (same < 401) of the system that is in the inactive state. Then, 173 of this total harmonic amount is applied to each active filter AF1~
AF, and all active filters AF. -This is for driving AF3. The above will be explained using mathematical formulas. Now, let the harmonic currents taken by the loads 301 to 303 be l Lh1t l Lh and i Lh3, respectively, and
The harmonic currents detected by the current detectors 401 to 403 are
If E h, i D, h, i T, h, the load 301~
The total harmonic amount ih taken by 303 is as shown in the following equation.

i h= i L fly+i th2 + i Ll+,
・・・・・・(1) This IH is the first engineering system
When 01 is in rest state, current detectors 402 and 403
flows to the load through. Therefore, ih= it,h+ iy,h (it■h=0)
...(2).

Here, if the compensation target IC of each of the three active filters AF-AF3 is set to 173 of the total harmonic amount ih, then the following equation is obtained. Suppose that the harmonics of this value are applied to each active filter AF. ~AF, is to be supplied by the current detector 4
The harmonics supplied through active filter AF. Compared to before operation, ih'= i
h − ic= i T, h+ i T3h −
i Ding. h --- --- (4), and the active filter AF. will decrease by the amount supplied.

Therefore, it is not possible to calculate the compensation current command value only from the current detectors 402 and 403 installed in the system that is in the interconnected state, and the amount of harmonic current detected by the current detection II 401 of the system that is in the idle state is also I have to take it into consideration.

Therefore, the total harmonic amount ih is: i h= i r1h+ i d. h+ir, h
= i Lh1+ i Lhz + i Lhi
...(5), and 1/3 of this value is applied to each active filter AF. ~ A F z was set as the compensation current command value.

In this way, the present invention determines whether each system is all connected, or whether one or more systems are in an open/dormant state, depending on the state of the circuit breakers in the power system, Select whether to set the compensation current command value for each active filter as the value from each current detector, or divide the total harmonic amount detection value into N/l and use it as the compensation current command value for each active filter. decide.

In this way, even if the N-branch power supply system is partially stopped, the operation of all active filters will be compensated, and each compensation capacity will be 1/N of the total harmonic amount to compensate for harmonics. There is no risk of increasing the capacity of the equipment.

(Example) DESCRIPTION OF THE PREFERRED EMBODIMENTS A practical example of the present invention will be described below with reference to the drawings.

First, the first drawing shows an active filter control circuit 700 used in this embodiment. Note that this embodiment has a three-branch power supply system M101 as shown in FIG.
, 102, 103 This is for when operating the motors AF, AF2, AF3. Here, the control circuit 700 controls each power supply system M101.102.
．． Three status signals indicating whether the circuit breakers 201, 202, 203 of No. 103 are closed or open;
The load currents iL, iJ, iL, of each system detected by the current detectors 401, 402, 403 in the figure are input, and the active filters AF, AF. ．． AF. a current command calculator 710 that calculates and outputs compensation current command values ic, , io2, i-c3'' according to Each active filter AF, AF, AF. adders 751, 752, 753 that calculate the deviations from the output currents i c11 1 QzH l 03, respectively, and a comparator 761 that compares these deviations with a predetermined reference level.
762, 763 and their comparators 761, 76
The main components are pulse distributors 771, 772, and 773, which generate ignition pulses based on the output signals of No. 2,763. Next, FIG. 2 shows the internal structure of the current command calculator 710. In the figure, load current iL, iL2, i
L, are input to fundamental wave component calculators 711, 712, and 713, respectively, and a fundamental wave component is calculated, and this fundamental wave component and load current i t. ,, i L. , i L, is detected by adders 721, 722, and 723.

Furthermore, the load current LL111L2ylL3 is calculated by the adder 7.
41, and the addition result has a gain of 173.
The signal is applied to an adder 743 via a gain amplifier 742.

Further, SW1 is an analog switch, and this switch SW1 connects the a contact S air provided on the input side of the fundamental wave component calculator 713, the output side of the gain amplifier 742, and the input of the fundamental wave component calculator 713. b contact S1b provided between the output side of the fundamental wave arithmetic unit 713 and the adder 7
43, and a b contact Sib.
Here, each contact is interlocked. Note that the output of the fundamental wave component calculator 713 is sent to the adder 7 via the b contact Sb.
43 with negative polarity.

Also, the gain of the gain amplifier 742 is 1/N depending on the power supply system or the number N of analog filters. It is set. On the other hand, each output of the adders 721, 722, 723 is transmitted to each a contact S. of the analog switch SW2. a, S, a,
The output of the adder 743 is added to each b contact s2b, s, b, s of the analog switch SW2.
, b to adders 731, 732, 733, respectively, and these adders 731, 732
, 733 is the compensation current command value "LylC2, lc)
”.

Next, this operation will be explained. First, in this embodiment, the state of the circuit breakers 201, 202, and 203 of each power supply system is explained.
(Turning on/off) In other words, the analog switch s w. , S.W. By controlling the opening and closing of the individual current detectors 401, 402,
Load current iL■, iLi, iL3 detected by 403
Determine whether to use the harmonic current based on the compensation current command value as the compensation current command value or to use 173 of the total harmonic amount taken by the load as the compensation current command value. For example, as shown in Table 1 below, if all systems are in the on state and are linked, is there an error? switch S
By turning on both SW and SW, all the a contacts S in the current command calculator 710 are turned on. a, S 2a is closed, and the load current of each system i L. , i L,, it2
are input to the individual fundamental wave component calculators 711, 712, 713, and each compensation current command value ic, ic2, ic3''
is obtained. This is normal operating condition.

Further, for example, if the first system Milot is in an open/dormant state, all the b contacts Sb, s, and b in the current command calculator 710 are closed by turning off the analog switches sw1 and sw2. As a result, each load current i
After L, iL,, iL, are added in an adder 741, 1/3 of the combined amount is obtained by a gain amplifier 742 and inputted to a fundamental wave component calculator 713, where a fundamental wave component is calculated. Ru. This fundamental wave component is subtracted from the output of the gain amplifier 742 in an adder 743, and then passed through each b contact S2b and adders 731, 732, 733 to the compensation current command value i of the active filters AF, ~AF,
c1, i c2, i c3''.

As is clear from Table 1, this operation is exactly the same as long as the single system is in the open/dormant state, except when the system in κ is in the open/dormant state.

Therefore, regardless of the operation status of the power supply system, it is possible to operate and compensate for all active filters, including the active filters in the suspended system, and the compensation capacity of each active filter is sufficient to be 1/3 of the total amount of harmonics. It turns out.

In addition, in this Table 1, "Breaker status" number 1 is "
``Nage'' indicates input, and ``Open'' indicates release.

In addition, in the above embodiment, the three-branch power system Mt (knotsuri)
As explained above, the present invention can be applied to a general 1-N branch power supply system. (Effects of the Invention) As described above, according to the present invention, the amount of harmonics generated in each power supply system is compensated for by the active filter of each system, depending on the on/off state of the N-branch power supply system. Alternatively, since all active filters are operated with 1/N of the total amount of generated harmonics being compensated for each active filter individually, it is possible to install it in a suspended system regardless of how the power system is operated. It is now possible to operate and compensate for all active filters, including active filters that have been modified, and the compensation capacity of each active filter only needs to be 1/N of the total amount of harmonics, so there is no risk of increasing the capacity of the compensation equipment. This has the effect that the compensation effect does not decrease.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a control circuit used in an embodiment of the present invention, FIG. 2 is a configuration diagram of a current command calculator in FIG. 1,
Figure 3 is a configuration diagram of a three-branch power supply system to which the present invention is applied. FIG. 4 is a configuration diagram of a control circuit in the prior art. 101-103... Power supply system 201-203...
- Breakers 301 to 303...Loads 401 to 403, 501 to 503...Current detector 700
...Control circuit 710...Current command calculator 71
1 to 713...fundamental wave fraction calculators 721 to 723, 7
31-733, 741, 743, 751-753...
Adders 761-763...Comparators 771-773...Pulse distributor

Claims (1)

[Claims] In a power receiving facility in which a load is connected to each of N branch power supply systems (N is a natural number of 2 or more), each power supply system has a compensation capacity of 1/N of the total harmonic amount required by the load. Connect each power active filter,
When all of the power supply systems are turned on, all active filters are operated to compensate for the amount of harmonics generated in each power supply system by the active filters connected to each power supply system, and all of the power supply systems are open. The active filter for electric power is characterized in that, if even one system is in an open state except when the system is in the state of Filter operation method.