JPH04236129A - Higher harmonic preventing/suppressing device - Google Patents

Abstract

PURPOSE:To efficiently prevent/suppress higher harmonic components generated from a rectifier load. CONSTITUTION:The first reactor 6 connected in series with a rectifier load 1 and system 3 and a II type LC circuit which is constituted by connecting in parallel two series circuits respectively constituted by connecting in series parallel circuits of braking resistances and reactors for by-passing basic waves with capacitors to the load 1 and system 3 are provided between the load 1 and system 3 and, in addition, the second reactor 7 for relieving the influence of commutation vibrations is provided between the LC circuit and system 3. Namely, the sweeping of a notching voltage to the system 3 is relieved without deteriorating the operational characteristic of the load 1 by means of the first reactor 6 and capacitor 4 of the LC circuit and a resonance high frequency is damped by preventing the occurrence of a loss caused by a basic-wave current by means of the braking resistance 10 having a reactor 8 for by-passing basic waves connected in series with the capacitor 4. A capacitor 5 is also provided on the system side of the reactor 6 so as to confine the commutation vibrations.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention deals with theoretical harmonics caused by a rectangular load current in the operation of a rectifier load, and harmonics caused by commutation vibration caused in a power system by a notching voltage generated with commutation operation. The present invention relates to a harmonic prevention and suppression device for comprehensively preventing or suppressing waves.

0002

2. Description of the Related Art A depression in line voltage, so-called notching voltage, which occurs with the commutation of a rectifier load such as a thyristor rectifier, is caused by the adjacent power factor correction capacitor and line inductance in, for example, a 6.6 KV power distribution system. Free oscillations are caused in the constructed LC closed circuit, and harmful harmonics are generated in the system due to this. Such a phenomenon is called commutation vibration. Due to the recent increase in the number and capacity of rectifier loads installed in power distribution systems, such commutation vibration has become a problem that cannot be ignored. Conventional countermeasures against harmonics include AC filters that absorb harmonics by setting a resonance order for specific harmonics, harmonic compensators (also called active filters: AF) that perform compensation control, and filters between rectifier loads and grids. Buffer reactors and the like are being considered, which connect a reactor in series with the power supply to reduce the electrical coupling between the two, thereby preventing the notching voltage from flowing into the system. However, in the case of the above-mentioned AC filter, there is a problem that it lacks versatility in power distribution systems where system configuration changes are complicated, since the harmonic suppression function is degraded or lost due to system configuration changes. Further, in the case of an active filter, its application is limited because its length is short and compensation can only be made up to about the 20th order in response to the requirement for extremely high resonance frequencies up to about the 50th order. Furthermore, in the case of a buffer reactor, if you try to sufficiently prevent the notching voltage from flowing into the grid, it will worsen the commutation characteristics of the rectifier load,
In extreme cases, there is a problem that commutation failure may occur.

On the other hand, in order to reduce the electrical coupling between the rectifier load and the grid in order to solve commutation vibration, a reactor is connected in series between the rectifier load transformer and the grid, and the A capacitor is connected in parallel to the terminals of the rectifier load transformer to prevent deterioration of the operating characteristics of the rectifier load, and a braking resistor is inserted and connected in series to the reactor or the capacitor to quickly attenuate resonance harmonics. There is also a harmonic prevention/suppression device that includes a fundamental wave bypass reactor connected in parallel to the braking resistor. However, when the resonant harmonics change due to a change in the system configuration, this device not only may not have a sufficient prevention function, but also cannot prevent and suppress theoretical harmonics. Therefore, the problem of the present invention is to
The object of the present invention is to provide a harmonic prevention and suppression device that can overcome these problems in the prior art.

0004

[Means for Solving the Problems] In order to solve such problems, the present invention connects a first reactor in series between the rectifier load and the grid for reducing the electrical coupling between the two, and , inserting a Π-shaped LC circuit in which a series circuit in which a parallel circuit of a braking resistor and a fundamental wave bypass inductance is connected in series to a capacitor are connected in parallel to the rectifier load side and the system side of this first reactor, Moreover, a second reactor is inserted in series between this Π-type LC circuit and the system side to reduce electrical coupling between the two. Also, a series circuit in which a parallel circuit of a braking resistor and a fundamental wave bypass inductance is connected in series to a capacitor is on the system side of the Π-type LC circuit, or
Alternatively, it may be provided only on one side of the load, and a capacitor may be connected to the other side. Furthermore, in addition to these configurations, in order to prevent and suppress theoretical harmonics, an AC filter may be connected between the Π type LC circuit and the buffer reactor, or a Π type filter may be connected between the Π type LC circuit and the buffer reactor. A harmonic compensator may be connected in parallel with the LC circuit.

[0005]

[Operation] Π type LC connected between rectifier load and grid
The first reactor in the circuit acts as a buffer reactor that reduces the electrical coupling between the grid and the load, and serves to alleviate the leakage of notching voltage into the grid. The problem of deterioration of operating characteristics can be solved by having the load-side capacitor function to supply short-circuit current during commutation. In other words, since the load-side capacitor supplies a short-circuit current during commutation, the accumulated charge decreases and the terminal voltage decreases, resulting in a notching voltage. Conventionally, the reduced charge is supplemented by power factor improvement capacitors of other consumers in the system, which causes commutation vibration to spread within the system, but with this device, a capacitor is also installed on the system side. Vibration is contained inside,
Moreover, the generated resonance harmonics are quickly attenuated by the braking resistance. In order to prevent the resonance frequency from decreasing due to a change in the system configuration and the current passing through the braking resistor from decreasing, the vibration prevention and suppression function of the Π-shaped LC circuit described above is reduced.
A second reactor is inserted in series between the LC circuit and the system to reduce the electrical coupling between them. In addition, in order to prevent theoretical harmonics, an AC filter or a harmonic compensator (
active filter). Furthermore, in order to reduce the number of circuit elements, a series circuit in which a parallel circuit of a braking resistor and a fundamental wave bypass inductance is connected in series to a capacitor is installed on either the load side or the grid side of the Π-type LC circuit. It is possible to provide only one.

[0006]

Embodiment FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In the figure, 1 is a rectifier load, 2 is a rectifier load transformer, 3 is a system, 4, 5 are capacitors, 6, 7, 8,
9 is a reactor, and 10 and 11 are resistors. That is,
A reactor 6 is connected in series to the system 3 side of the rectifier load transformer 2, and a capacitor 4 is connected in parallel to this. A braking resistor 10 is connected in series to this capacitor 4, and a fundamental wave bypass reactor 8 is connected in parallel to the braking resistor 10. Thus, a series circuit in which a capacitor 5 is connected in series to a parallel circuit consisting of a reactor 6, a resistor 11, and a reactor 9, and a resistor 10
A Π-type LC circuit is constituted by a series circuit in which a capacitor 4 is connected in series with a parallel circuit consisting of a reactor 8 and a parallel circuit. The rectifier load 1 generates a commutation depression, that is, a notching voltage, with the commutation operation. A reactor 6 (inductance L) connected in series between the system 3 and the transformer 2
1) acts as a buffer reactor, which weakens the electrical coupling between the load 1 and the system 3, thereby alleviating the flow of notching voltage from the load side to the system. On the other hand, since there is a concern that the presence of this inductance L1 will deteriorate the operating characteristics such as a drop in the terminal voltage of the load, a capacitor is connected in parallel to the high voltage side terminal of the rectifier load transformer 2 to supply short circuit current during commutation. A capacitor 4 of C1 is connected. Since this capacitor 4 has a power factor improving effect,
It can also be used as a power factor correction capacitor. By the way, it is necessary to replenish the discharged charge of capacitor C1 after commutation, but if this is replenished from system 3, vibrations will spread to the system, so to prevent this, capacitor C1
A capacitor 5 of 2 is connected to the system side for charge replenishment, and a reactor 7 having a value of L2 as a buffer reactance is connected in series to the system side from the Π-type LC circuit of C1-L1-C2. The resonance frequency fr of the commutation vibration confined in this closed circuit C1-L1-C2 is approximately given by the following equation. fr=1/2π{C1・C2・L1/(C1+C2
)}1/2...(1)

[0007] However,
If this fr is too low, the amount of resonant current passing through the braking resistors 10 and 11 will be reduced, preventing the vibration from quickly damping; if it is too high, the values of the reactor and capacitor will be too small, resulting in a loss of notching voltage in the system. As the prevention function decreases,
fr is the order in which commutation vibration does not occur under ideal operating conditions in the range of 700 to 2000 Hz, for example, avoid the 17th to 19th orders for a 6-pulse rectifier, and the 2nd order for a 12-pulse rectifier.
3rd to 25th orders must be avoided. Next, the resistance values RS1 and RS2 of the braking resistors 10 and 11 are determined according to the following conditions for the purpose of speeding up vibration. e-(RS1+RS2)T0/2L1=ε

(2) However, the vibration damping rate ε is empirically selected to be approximately 0.01. Further, T0 is the commutation interval of the 6-pulse rectifier, and is given by the following equation, where f0 is the commercial frequency. T0=1/6f0

...(3) Also, reactor 8 for fundamental wave bypass
, 9 are given by the following conditions. RS1/2πf0・LS1=RS2/2πf0・L
S2=1/α...(4) Here, the constant α is empirically 0
．． 2 to 0.25 is selected.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. This is different from the AC filter 12 shown in FIG.
The feature is that the LC circuit and the system 3 are connected in parallel, which makes it possible to suppress theoretical harmonics. In other words, with such a configuration, it is possible to prevent and suppress both commutation vibration and theoretical harmonics.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention. In the configuration of FIG. 2, when the system configuration of the AC filter 12 is changed and the inflow of theoretical harmonics from the system increases, it becomes overloaded and there is a risk of burnout. Therefore, as shown in FIG. 3, an active filter 13 is used instead of the AC filter.
By connecting the LC circuit in parallel with the system 3, it is possible to cope with changes in the system configuration.

FIG. 4 is a circuit diagram showing a modification of FIG. 1. This embodiment differs from the one shown in FIG. 1 in that the R-L parallel circuit, which was inserted in series with the capacitor 4 in FIG. 1, is concentrated on the capacitor 5 side. This not only simplifies the circuit configuration by reducing the number of components, but also improves the ability of the capacitor 4 to supply short-circuit current during commutation, and therefore the ability to prevent notching voltage from being lost to the system.

FIG. 5 is a circuit diagram showing a modification of FIG. 4. In other words, R-L inserted in series with capacitor 4
The parallel circuit is concentrated on the capacitor 5 side, which is the same as that shown in FIG.
is connected in parallel between the Π-type LC circuit and system 3. By doing so, a function for suppressing theoretical harmonics can be added to the structure shown in FIG. 1.

FIG. 6 is a circuit diagram showing a modification of FIG. 5. This is because when the system shown in Figure 5 suppresses theoretical harmonics, if the system configuration is changed and the inflow of theoretical harmonics from the system increases, the AC filter will be overloaded and there is a risk of burnout. Instead, by connecting the active filter 13 in parallel between the Π-type LC circuit and the system 3, the theoretical harmonic suppression function is improved.

FIG. 7 is a circuit diagram showing another modification of FIG. 1. That is, the R-L parallel circuit, which was inserted in series with the capacitor 5 in FIG. 1, is concentrated on the capacitor 4 side. By doing so, the number of constituent elements can be reduced and the circuit configuration can be simplified.

FIG. 8 is a circuit diagram showing a modification of FIG. 7. This is similar to FIG. 7 in that the R-L parallel circuit that was inserted in series with capacitor 4 is concentrated on the capacitor 5 side, reducing the number of components and simplifying the circuit configuration. A feature is that an AC filter 12 consisting of a series circuit of a reactor and a capacitor similar to the case of FIG. 5 is connected in parallel between the Π-type LC circuit and the system 3. By doing so, it is possible to add a function to further suppress theoretical harmonics to that shown in FIG.

FIG. 9 is a circuit diagram showing a modification of FIG. 8. In other words, when the system shown in Figure 8 suppresses theoretical harmonics, if the system configuration is changed and the inflow of theoretical harmonics from the system increases, the AC filter will become overloaded and there is a risk of burnout, so it is necessary to replace it with an AC filter. By connecting the active filter 13 in parallel between the Π-type LC circuit and the system 3, the theoretical harmonic suppression function is improved.

[0016]

According to the present invention, a series reactor between the grid and the rectifier load and a parallel capacitor on the load side of the series reactor reduce notching voltage to the grid without deteriorating the operating characteristics of the rectifier load. By using a braking resistor with a reactor for bypassing the fundamental wave inserted in series with the capacitor, it is possible to quickly attenuate the resonance high frequency while preventing loss due to the fundamental wave current. In addition, in order to prevent the resonant frequency from changing due to the system configuration and reducing the effectiveness of the braking resistance, a capacitor is also installed on the system side of the reactor to form a Π-type LC circuit to contain vibrations and to The influence of this Π
This can be prevented by adding a buffer reactor to the system side of the LC circuit. Furthermore, by adding an AC filter or an active filter, it is possible to provide a comprehensive harmonic prevention and suppression device that also has a theoretical harmonic suppression function.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a sixth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a seventh embodiment of the present invention.

FIG. 8 is a circuit diagram showing an eighth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a ninth embodiment of the present invention.

[Explanation of symbols]

1 Rectifier load 2　Rectifier transformer 3 Load 4 Capacitor 5 Capacitor 6 Reactor 7 Reactor 8 Reactor 9 Reactor 10 Braking resistance 11 Braking resistance 12 AC filter

Claims (5)

[Claims] 1. A first reactor is connected in series between the rectifier load and the grid for reducing electrical coupling between the two, and a braking resistor is provided on the rectifier load side and the grid side of the first reactor. Insert a Π-type LC circuit in which a series circuit consisting of a parallel circuit with a fundamental wave bypass inductance and a capacitor are connected in parallel, respectively.
A harmonic prevention and suppression device characterized in that a second reactor is inserted in series between this Π-shaped LC circuit and the system side for reducing electrical coupling between the two. 2. A first reactor is connected in series between the rectifier load and the grid for reducing electrical coupling between the two, and a capacitor is connected on the rectifier load side of the first reactor, and a capacitor is connected in series between the rectifier load and the grid. On the side, there is a Π-shaped L in which a parallel circuit of a braking resistor and a fundamental wave bypass inductance is connected in series with a capacitor, and a series circuit is connected in parallel with each other.
1. A harmonic prevention and suppression device characterized in that a C circuit is inserted, and a second reactor is inserted in series between this Π-shaped LC circuit and the system side for reducing electrical coupling between the two. 3. A first reactor is connected in series between the rectifier load and the grid for reducing electrical coupling between the two, and a braking resistor and a fundamental waveform are connected on the rectifier load side of the first reactor. Π type L with a series circuit in which a parallel circuit with a bypass inductance is connected in series with a capacitor, and a capacitor is connected in parallel on the grid side.
1. A harmonic prevention and suppression device characterized in that a C circuit is inserted, and a second reactor is inserted in series between this Π-shaped LC circuit and the system side for reducing electrical coupling between the two. 4. An AC filter is connected in parallel between the Π-type LC circuit and the second reactor to prevent and suppress theoretical harmonics. Harmonic prevention and suppression device. 5. A harmonic compensator is connected between the Π type LC circuit and the second reactor in parallel with the Π type LC circuit to prevent and suppress theoretical harmonics.
The harmonic prevention and suppression device according to any one of claims 1 to 3.