JPS6380721A - Harmonic compensator - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a harmonic compensation device provided in a system line between a power supply system and load equipment.

[Conventional technology]

Conventionally, LO filters (passive filters) have often been adopted as harmonic countermeasures for power transmission and distribution systems.

This is a shunt that has a lower impedance than the system impedance for specific harmonics, and suppresses harmonics flowing into the power transmission and distribution system.It is installed near the source of harmonics. It is.

However, the LO filter has the following problems.

That is, the harmonic suppression effect by the LO filter is affected by the impedance of the system. Depending on the constants of the LC filter, it may even form a parallel resonant circuit with the system impedance, causing an increase in harmonics.

Further, when the LO filter becomes overloaded, the LO filter must be cut off from the grid, and the harmonic suppression function may be completely lost.

In recent years, with the development of semiconductor elements with switching functions, load equipment using these elements has come into widespread use.As a result, harmonic compensation devices have become important, and active filters have been developed and used. It has become.

An active filter that is basically composed of a three-phase bridge type PWM converter using high-speed switching elements, an AC reactor provided on the AC side of this PWM converter, and a capacitor provided on the DC side is described in, for example, Journal of the Institute of Electrical Engineers of Japan 60- 865 "Active filter for harmonic suppression using multiple voltage type PWM converter".

[Problem that the invention seeks to solve]

- (If you try to suppress harmonics by the method shown in the above paper, for example, you will not be able to follow Leonard's commutation sufficiently due to the AC reactor installed on the AC side of the PWM converter. First, there was a drawback that low-order harmonics could not be suppressed sufficiently.

[Means for solving problems]

The harmonic compensator according to the present invention is a harmonic compensator provided in a system line between a power supply system and load equipment, and includes a three-phase PWM converter, and a harmonic compensator provided on the input side of each phase of the three-phase PWM converter. reactor and the three-phase P
The control device includes a DC capacitor provided in parallel on the output side of the WM converter, and a control device that controls the three-phase PWM converter. means for generating a phase voltage;
means for calculating n-th harmonic instantaneous real power and imaginary power from the harmonic three-phase voltage and the load current of the load equipment, and removing a harmonic liquid component from the n-th harmonic instantaneous real power and imaginary power to obtain a DC component. means for inverting the signs of the DC components of the n-th harmonic instantaneous real power and imaginary power to generate real power and imaginary power command signals; means for generating a current command signal from an imaginary power command signal;
Three-phase PWM is performed by comparing the current command signal and the compensation current value.
The present invention is characterized by comprising means for generating trigger signals for switching elements of each phase of the converter.

[For production]

The operation of the harmonic compensator of the present invention will be explained by taking the fifth harmonic compensator as an example. This device R performs three-phase to two-phase conversion as described below, and introduces the concepts of real power and imaginary power.

This concept first uses the following equations (1) to (4) to calculate the sinusoidal waveform fifth harmonic three-phase voltage euI ey + ew and the non-sinusoidal load current ILU + tt, v j ILW
around the voltage of the two phases α and β, eβ and the current 11n *
Convert to tLβ.

Using the two-phase voltages and currents obtained from equations (2) and (3) above, the fifth harmonic instantaneous real power and imaginary power are as follows. These fifth harmonic instantaneous real power p and imaginary power q are as follows (6),
Like the C force, it is decomposed into a DC component p+q and an alternating current component p, q.

p=1)+I) ・・・・・・・・・
・・・・・・・・・(6)q”q+q
・・・・・・・・・・・・・・・・・・(7) Here, the 5th harmonic components of the load currents iLα, iLβ are DC components i, i
can be separated through a low-pass filter.

Therefore, from the 5th Taiha wave instantaneous real power p and imaginary power q, 8-- ・・・・・・・・・・・・
・・・・・・(8) −−p 8−− ・・・・・・・・・・・・
(9) A real power command signal p and an imaginary power command signal q of q −″q can be obtained by the sign inversion circuit.

* * From these real power and imaginary power command signals p+Q, a two-phase current command signal Iα is obtained according to the following equations (10) to (12).

I is obtained, 2-phase to 3-phase conversion is performed, and the 5th harmonic compensator is converted to the above current signal + 1 ÷ (If the PWM converter is controlled, the compensation current is the 5th harmonic in the load current. The flow cancels out the harmonics.

As a result, harmonic compensation, which is the purpose of this device, can be achieved.

Although the above description has been made regarding the fifth harmonic order, the harmonic compensator of the present invention is not limited to the fifth order, but can be applied to all n-order orders. In this case, n may be substituted for 5 in the above explanation.

〔Example〕

Hereinafter, one embodiment will be described with reference to the drawings. 1st
The figure is a block diagram showing an embodiment of a control device when the harmonic compensator according to the present invention is a fifth harmonic compensator,
FIG. 2 is a diagram showing the main circuit configuration of a three-phase AC system equipped with a harmonic compensator.

In the figure, 1 is a fifth harmonic generation circuit, 2 is a fifth harmonic power calculation circuit, 3 is a low-pass filter, 4 is a sign inversion circuit, 5 is a current command value calculation circuit, 6 is a current control circuit, 11 is 3 12 is a load, 13 is an AC reactor, 14 is a three-phase PWM converter, and 15 is a DC converter. Further, the subscripts U, V, and W indicate the U, V, and W phases of the three-phase AC system power supply, respectively, and the subscripts indicate the load components.

As shown in Figure 2, the harmonic compensator is connected to AC reactor 1.
3, 3-phase PWM converter 14. It is composed of the DC capacitor 15 and the control device shown in FIG.

Of these, the three-phase PWM converter 14 is operated by switching elements 81 to S6 in response to a switching command vG supplied from the device control circuit 6, which is composed of six diodes D1 to D6 and switching elements 81 to S6 that can be turned on and off.
6 is on. turned off, compensation current iU + IV + I
It controls W.

Note that the AC reactor 13 is a three-phase PWM converter 14.
The DC capacitor 15 is used to stabilize the voltage on the DC side of the three-phase PWM converter 14.

Now, in the main circuit configuration shown in FIG.
Compensation current 'U + IV + IW flowing into the harmonic compensator section consisting of and load current 'LU + lL
The 5th fA is added to the power supply current obtained by vectorial addition of V+iLW.
To avoid including wave components, the compensation current IU + lV
+iw is the load current 'LU + ILV + I
It is sufficient to have a component that cancels the fifth harmonic component of LW.

Next, an example of a control device constructed based on the principle described above will be explained with reference to FIG. In FIG. 1, a fifth harmonic generation circuit 1 generates a sinusoidal fifth harmonic three-phase voltage having a frequency five times that of a three-phase AC power supply 11. In FIG. The fifth harmonic power calculation circuit 2 calculates the load current 'LU + iLV +
From tt, w and the fifth harmonic three-phase relaxation pressure, the above (2),
Equation (5) is calculated to calculate the fifth harmonic instantaneous real power p and imaginary power q.

The low-pass filter 3 removes the alternating current from the fifth harmonic instantaneous real power p and imaginary power q.

The sign inverting circuit 4 receives the fifth signal which is the output of the low-pass filter 3.
By inverting the signs of the DC components i and i of the harmonic instantaneous real power p and imaginary power q, we obtain the real power command signal p and the imaginary power command signal q* shown in equations (8) and (9). Output.

The current command value calculation circuit 5 is based on the above equation (2) and (10) to
* *Current control circuit that calculates the two-phase current command values iα and iβ according to equation (12), performs two-phase to three-phase conversion, and generates the current command signal i♂+IV'+tw of the harmonic compensator. 6
is equipped with hysteresis comparators *, *, *, and the current command signal IU + consideration V + IW and compensation current I
For example, when *, *ig≧O and IU≦iU, the switching element S4 shown in FIG. 2 is turned on, and when *IU≧O and iU>iU, the switching element S4 is turned on. A trigger signal VG that turns off S1 is generated, and the switching elements 81 to S6 are controlled on and off by this trigger signal vG, and the instantaneous value of each phase current of the harmonic compensator is changed to each phase current command signal. It is controlled as if it were chased.

In the above explanation, reference was made to the fifth harmonic compensator, but
For example, if you want to compensate for the 7th harmonic, the 5th harmonic generation circuit 1, the 5th harmonic power calculation circuit 2, the low-pass filter 3,
Each circuit of the sign inversion circuit 4 and the current command value calculation circuit 5 is configured also for the 7th harmonic, and a similar 7th harmonic is generated.
By sending the harmonic current command signal and the fifth harmonic current command signal to the current control circuit 6, it is possible to compensate for the seventh harmonic as well as the fifth harmonic.

Further, in the above explanation, the three-phase to two-phase conversion matrix uses equation (4), but similar compensation can also be performed by using equation (13) shown below.

Here, ωt=2πft (f is the fundamental frequency).

At this time, the inverse transformation matrix for 2-phase to 3-phase conversion is [Effects of the Invention] As explained in detail above, according to the harmonic compensator according to the present invention, among the harmonics included in the load current, One harmonic is detected as DC components i, i of the harmonic's open effective power p and imaginary power q, and the DC component P+Q
Since the current command signal is obtained by inverting the sign of , and converting it from 2-phase to 3-phase, the current command signal becomes smooth, and the target low-order harmonics can be sufficiently suppressed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a control device when the harmonic compensator according to the present invention is a fifth harmonic compensator, and FIG. 2 is a block diagram of a three-phase AC system equipped with a harmonic compensator. FIG. 3 is a diagram showing the main circuit configuration. 1...Fifth harmonic generation circuit, 2...Fifth
Harmonic power calculation circuit, 3...Low pass filter,
4... Sign inversion circuit, 5... Current command value calculation circuit, 6... Group current control circuit, 11...
・3-phase AC power supply system, 12...Load, 13...
...AC reactor, 14...3 phase PWM
Core bar 9.15...DC capacitor.

Claims (1)

[Claims] In a harmonic compensator installed in a system line between a power supply system and load equipment, a three-phase PWM converter and a three-phase PWM converter,
A reactor provided on the input side of each phase of the three-phase PWM converter, a DC capacitor provided in parallel on the output side of the three-phase PWM converter, and a control device for controlling the three-phase PWM converter, the control device comprising: The device is powered by
means for generating an n-th harmonic three-phase voltage of a sinusoidal waveform having twice the frequency; and calculating n-th harmonic instantaneous real power and imaginary power from the n-th harmonic three-phase voltage and the load current of the load equipment. means for removing harmonic components from the n-th harmonic instantaneous real power and imaginary power to extract a DC component; and means for generating an imaginary power command signal; means for generating a current command signal from the nth harmonic three-phase voltage and the real power and imaginary power command signals; and comparing the current command signal and the value of the compensation current. and means for generating trigger signals for switching elements of each phase of a three-phase PWM converter.