JP2601422B2 - Harmonic compensator - Google Patents

Description

The present invention relates to an improvement of a harmonic compensator provided in a system line between a power supply system and a load facility.

[Conventional technology]

A harmonic compensator based on a three-phase PWM converter composed of high-speed switching elements, an AC reactor provided on the AC side of the three-phase PWM converter, a DC capacitor of the three-phase PWM converter, and the like is disclosed in August 1986. "System and Control" Vol.30, No.8
As described in "Principles and Control Methods of Active Filters for Electric Power" published in U.S. Pat.

Hereinafter, the conventional harmonic compensator will be described.
FIG. 2 is a main circuit configuration diagram of a three-phase AC system including a conventional harmonic compensator, and FIG. 3 is a block diagram of a control device of the harmonic compensator.

The three-phase AC system power supply 11 supplies power to a load 12 such as Leonard, and a harmonic current flows in the system line. In this system line, an AC reactor 14 is inserted in series with each phase on the AC side, and a three-phase PWM converter 15 is connected.
The DC capacitor 13 is connected to the DC side of the converter 15.

3-phase PWM converter 15 is turned on, consists off Switching element S ₁ to S ₆ and the diode D ₁ to D _6, each of the switching elements S ₁ to S ₆ are connected in parallel with the diode D ₁ to D _6, respectively Above, connected as a three-phase bridge circuit,
Switching element S ₁ to S ₆ by the trigger signal V _G generated by the controller shown in FIG. 3 is turned on, performs a harmonic compensation is turned off.

The AC reactor 14 inserted into the DC side on the AC side of the three-phase PWM converter 15 is for limiting the rise of the current of the three-phase PWM converter 15, and the DC capacitor 13 connected to the DC side is This is for stabilizing the voltage on the DC side of the three-phase converter, and is usually charged to about twice the voltage of the three-phase AC system power supply 1.

That is, the harmonic compensator is a three-phase PWM converter 15,
It comprises the control device shown in FIG. 3 for turning on and off the switching elements of the AC reactor 14, the DC capacitor 13 and the three-phase PWM converter 15.

Now, in the main circuit configuration shown in FIG. 2, the load current flowing into the load 12 is represented by i _LU , i _LV , i _LW, and the compensation current flowing into the harmonic compensator is represented by i _U , i _V , i _W. Then, a current i _LU + i _U , i _LV + i _V , i _LW + i _W obtained by adding the load current and the compensation current vectorwise in each phase flows through the system power supply 11. Therefore, the compensation currents i _U , i _V , i _W flowing into the harmonic compensator only need to have components that cancel the harmonic components of the load currents i _LU , i _LV , i _LW , respectively.

In order to perform the above-described harmonic compensation, three-phase to two-phase conversion as described below is performed, and the concepts of real power and imaginary power are introduced. This concept is based on three-phase load currents i _LU , i _LV , i _LW using the following equations (1) to (3).
And system voltages e _U , e _V , and e _W are converted into two-phase currents i _Lα , i _Lβ and voltages e _α , e _β .

Here, [C] is a three- or two-phase transformation matrix.

Using the two-phase voltage and current obtained by the above equations (1) to (3), the instantaneous real power p and imaginary power q are obtained by the following equation (4).

The instantaneous real power p and the imaginary power q correspond to the conventional active power and reactive power, and the instantaneous real power p and the imaginary power q are expressed by the following equations (5) and (6), respectively. Decomposed into minutes.

p = + ...... (5) q = + ...... (6) where two-phase load current _{I L [alpha,} the fundamental wave component of _{I L?} DC component, the harmonic component is transformed AC components, in, These DC and AC components can generally be separated through a high-pass filter.

Next, an example of a control device configured based on the above-described principle will be described with reference to FIG.

The power calculation circuit 1 includes a system voltage e _U , e _V , e _W and a load current i _LU , i _W
The instantaneous real power p and the imaginary power q are calculated from the detected values of _LV and i _LW according to the equations (1) to (4), and are sent to the high-pass filter 2.

Hypal filter 2 removes the DC component from these,
The AC component of the instantaneous real power and the AC component of the instantaneous imaginary power are sent to the sign inversion circuit 3. The sign inverting circuit 3 inverts these signs and outputs them to the current command value calculating circuit 4 as the real power command signal p ^* and the imaginary power command signal q ^* .

p ^* = − (7) q ^* = − (8) These are the original forms of the current command signal generated in the current command value calculation circuit 4. That is, the harmonic active power is controlled based on the actual power command signal p ^* obtained by the equation (7), and the harmonic reactive power is controlled based on the imaginary power command signal q ^* obtained by the equation (8). .

The current command value calculation circuit 4 receives the real power command signal p ^* , the imaginary power command signal q ^*, and the system voltages e _U , e _V , e _W and receives the equation (1) and the following equations (9) to (11). according) type, two-phase current command signal i _alpha ^*, to obtain a i _beta ^*, current signal three-phase for 2-phase to 3-phase conversion i _U ^*, i _V ^*, to generate a i _W ^*, current Output to the control circuit 5.

[C] ^-1 is the inverse transformation matrix of [C].

The current control circuit 5 includes a hysteresis comparator,
Current _{^{i U *, i V *,}} i W * with compensation current i _U, compares the detected value of i _V, i _W, for example, and i _U ≦ i _U ^* made when at i _U ^* ≧ 0, 3-phase PWM Switching element S _{4 of} converter 15
I was on and i _U> i _U ^* made when at i _U ^* ≧ 0, turns off the switching element S _4, also and i _U ≦ i _U ^* made when at i _U ^* <0, the switching element S ₁ is intended to generate a trigger signal V _G as off, the switching element S ₁ to S ₆ by the trigger signal V _G is turned on, is turned off, the current instantaneous value of each phase of the harmonic compensator is controlled.

[Problems to be solved by the invention]

In the harmonic compensator that operates as described above, the capacity of the harmonic compensator also increases when the load capacity increases, so that the switching current of the switching element of the three-phase PWM converter increases, which leads to thermal destruction. There is a problem.

The present invention has been made to solve the above problems, and when the compensation capacity of a load is equal to or larger than the rated capacity of a harmonic compensator, the calculated actual power p and imaginary power q of the load are reduced. The current command value is calculated by setting the new command real power p 'and command imaginary power q'.

By these operations, the harmonic compensating device 3
An object of the present invention is to provide a harmonic compensator that prevents thermal destruction of a switching element in a phase PWM converter.

[Means for solving the problem]

Therefore, a 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 each of an AC side of the three-phase PWM converter. An AC reactor provided for the three-phase PWM converter, a DC capacitor provided on the DC side of the three-phase PWM converter, and a control device for controlling the three-phase PWM converter. Means for calculating real power and imaginary power; means for generating an AC component of instantaneous real power and imaginary power from the instantaneous real power and imaginary power; and calculating a compensation capacity from the instantaneous real power and imaginary power. Means for calculating a compensating device operation command from the compensation capacity and the compensating device designated capacity; a real power command signal and an imaginary power command based on the compensating device operation command and the instantaneous real power and imaginary power. Means for calculating a current command value from the real power command signal, the imaginary power command signal and the power supply voltage, and a switching element for each phase of the three-phase PWM converter based on the current command value and the compensation current. Means for generating a trigger signal.

[Action]

In the harmonic compensator according to the present invention, the compensation capacity KVA is obtained from the AC component of the instantaneous real power and the AC component of the imaginary power by the following equation (12).

The compensator operation command R ^* is determined by comparing the compensation capacity KVA with a preset compensator designated capacity KVA ^*, and the actual power command p is determined from this and the instantaneous real power AC component and imaginary power AC component. And an imaginary power command q ', and a current value to be compensated is calculated from these.

For example, when KVA ≧ KVA ^* , the compensator operation command R ^* is R ^* = KVA ^* / KVA (13). If KVA <KVA ^* , the compensator operation commands R ^* and R ^* = 1.
By multiplying the instantaneous real power p and the imaginary power q by the compensator operation command R ^* , the real power command p ′ and the imaginary power command q ′ are calculated, and these are subjected to a high-pass filter to extract only the AC component. inverts its sign and the actual power command signal p ^* and imaginary power command signal q ^*, these and the system voltage e _U, e _V, e _W current and a command signal i _U ^*, i _V ^*, the i _W ^* Can be calculated.

This is an example, and the sign of the instantaneous real power AC component and the imaginary power AC component is inverted by directly multiplying them by the direct compensator operation command R ^* to obtain the real power command signal p ^* and the imaginary power command signal q ^*. Good.

〔Example〕

Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a control device of a harmonic compensator according to the present invention, and the same reference numerals as those in FIG. 3 denote parts having the same functions.

As in the case of the conventional device, the power operation circuit 1 includes the system voltages e _U and e
_V, e _W and the load current i _LU, i _LV, from the detected value of i _LW (1) ~
The instantaneous real power p and the imaginary power q are calculated according to the equation (4).

The high-pass filter 2 removes a DC component from the instantaneous real power p and the imaginary power q, respectively, and generates an AC component of the instantaneous real power and an AC component of the instantaneous imaginary power.

The compensation capacity calculation circuit 6 calculates the compensation capacity KVA from the AC component of the instantaneous real power and the AC component of the instantaneous imaginary power according to equation (12).
Is calculated.

The comparison circuit 7 generates a compensating device operation command R ^* from the compensating capacitance KVA and a preset compensating device designated capacitance KVA ^* as follows.

First, when KVA ≧ KVA ^*, R ^* = KVA ^* / KVA. Then, when KVA <KVA ^*, R ^* = 1.

The command power calculation circuit 8 multiplies the instantaneous real power p and the imaginary power q calculated by the power calculation circuit 1 by the compensator operation command R ^* to calculate a command real power p 'and a command imaginary power q'.

p ′ = R ^* × p (14) q ′ = R ^* × q (15) The command actual power p ′ and the command imaginary power q ′ are input to the high-pass filter 2 ′ to remove the DC component. Thus, an AC component 'of the command actual power and an AC component' of the command imaginary power are generated.

The sign inverting circuit 3 inverts the sign of the AC component of the commanded real power and the AC component of the commanded imaginary power to obtain the real power command signal p ^*.
And an imaginary power command signal q ^* .

The current command value calculation circuit 4 calculates the current from the actual power command signal p ^* , the imaginary power command signal q ^*, and the system voltages e _U , e _V , and e _{W according} to the above equations (1) and (9) to (11). Command signal i _U
^* , I _V ^* , i _W ^* are calculated.

The current control circuit 5 is the current command signal _{^{i U *, i V *,}} i W * with compensation current i _U, i _V, and compares the detected value of i _W, for example, i _U ^* ≧ 0 and with i _U ≦ i _U ^* When the switching element S ₄ of the three-phase PWM converter 15
I was on and i _U> i _U ^* made when at i _U ^* ≧ 0, to turn on the switching element S _4, also and i _U ≦ i _U ^* made when at i _U ^* <0, the switching element S ₁ each switching element of the trigger signal V _G to 3-phase PWM converter 15 so as to turn off S ₁
The ~S ₆ on and off.

As described above, the compensation capacity KVA becomes the compensator designated capacity K
When the voltage exceeds VA ^* , the compensation effect is reduced in proportion to KVA ^* / KVA by compensating only this capacitance, but it is possible to prevent the switching element from being thermally destroyed.

In the present embodiment, the instantaneous real power p and the imaginary power q output from the power calculation circuit 1 are used as inputs to the command voltage calculation circuit 8, but the AC component and the instantaneous imaginary power of the instantaneous real power output from the high-pass filter 2 are used. By using the AC component, the same effect can be obtained by omitting the high-pass filter 2 '.

〔The invention's effect〕

As described above in detail using one embodiment, according to the magnitude of the harmonic current to be compensated, the compensation is completely compensated for within the rated capacity of the compensator, and is compensated for when the rated capacity is exceeded. By stopping the compensation current with only one pole of the capacitance and preventing the thermal destruction of the switching element, it is possible to continue the effective and safe operation.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control device of a harmonic compensator according to the present invention, FIG. 2 is a main circuit connection diagram of a three-phase AC system including the harmonic compensator, and FIG. It is a block diagram of a compensating device. 1 ... power calculation circuit, 2, 2 '... high-pass filter, 3
…… Sign inversion circuit, 4 …… Current command value calculation circuit, 5…
Current control circuit, 6 Compensation capacity calculation circuit, 7 Comparison circuit, 8 Command power calculation circuit, 11 3-phase AC system power supply, 12 Load, 13 DC capacitor, 14 AC reactor, 15 ...... 3-phase PWM converter, S ₁ to S ₆ ...... switching element, D ₁ to D ₆ ...... diode.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-165926 (JP, A) JP-A-60-168224 (JP, A) JP-A-58-72377 (JP, A) 36809 (JP, B2) JP 5-78844 (JP, B2)

Claims (1)

(57) [Claims] 1. A harmonic compensator provided in a system line between a power supply system and load equipment, comprising: a three-phase PWM converter; and an AC reactor provided in each phase on the AC side of the three-phase PWM converter. A DC capacitor provided on the DC side of the three-phase PWM converter, and a control device for controlling the three-phase PWM converter. The control device calculates instantaneous real power and imaginary power from a power supply voltage and a load current. Means, means for generating an AC component of instantaneous real power and imaginary power from the instantaneous real power and imaginary power, means for calculating a compensation capacity from the AC component of the instantaneous real power and imaginary power, and the compensation capacity and compensation Means for calculating a compensating device operation command from the device-specified capacity; means for calculating a real power command signal and an imaginary power command signal from the compensating device operation command and the instantaneous real power and imaginary power; Means for calculating a current command value from a signal, an imaginary power command signal, and a power supply voltage; and means for generating a trigger signal for a switching element of each phase of the three-phase PWM converter from the current command value and the compensation current. A harmonic compensator.