JPH01148024A - Higher harmonic compensator - Google Patents

Abstract

PURPOSE:To reduce the capacity of a device, by cutting fundamental wave voltage applied to a three-phase PWM converter with the working of a parallel resonance circuit. CONSTITUTION:In a higher harmonic compensator, to the line respective-phases of a three-phase AC system power source 1 for feeding power to the load 2 of a thyristor Leonard device and the like, the primary side of a YY-connection transformer 7 is connected, and to a space between respective-phase terminals on the secondary side and the respective-phase AC reactor 4 of the higher harmonic compensator, the parallel resonance circuit 3 of a first reactor 22 and a capacitor 21 is connected, and between neutral points, a second reactor 23 is parallel-set. Besides, to the direct current side of a three-phase PWM converter 5, a DC capacitor 6 is connected, and by trigger signal created by a controller, a switching element is turned ON/OFF. Then, the parallel resonance circuit 3 is tuned in to the fundamental wave frequency of the system power source 1, and at both the ends of the second reactor 23, only frequency voltage except the fundamental wave frequency is found. Accordingly, in order to correct compensating current flowing through the ends, the output of its command is directed to a correcting circuit 16 for the compensation.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in an active filter type harmonic compensator that is connected in parallel to load equipment of a power supply system and compensates for harmonic current flowing into the load equipment into the power supply system. [Prior Art] A three-phase PWM converter composed of high-speed switching elements, an AC reactor connected to a power supply system in series on the AC side of the three-phase PWM converter, and an AC reactor connected between DC terminals of the three-phase PWM converter. The harmonic compensator, whose basic configuration is a DC capacitor, etc., was published in August 1985 by the Japan Automatic Control Association, "System Control J vof, 30. N.
It is well known as explained in "Principle and control method of power active filter" published in Vol. 8, Vol. The conventional harmonic compensation device described above will be explained below. Figure 3 is a main circuit configuration diagram of a three-phase AC system equipped with a conventional harmonic compensation device, and Figure 4 is a block diagram of a control device for the harmonic compensation device.The three-phase AC system power supply 1 is a thyristor Power is supplied to load 2 such as Leonard equipment, and harmonic current flows in the system line. AC reactor 4 is inserted in series in each phase on the AC side of this system line to create a 3-phase PW.
M converter 5 is connected, and the three-phase PWM converter 5
A DC capacitor 6 is connected to the DC side. The three-phase PWM converter 5 is composed of switching elements S1 to S@ and diodes D1 to Ds that can be turned on and off, and each of the switching elements S1 to S6 is connected in parallel with the diodes D1 to D. The switching elements S6 are turned on by the trigger signal vG, which is connected as a circuit and generated by the control device shown in FIG.
It is turned off to perform harmonic compensation. The AC reactor 4 inserted in series on the AC side of the 3-phase PWM converter 5 is for limiting the rise of current in the 3-phase PWM converter 5, and the DC capacitor 6 connected to the 1 DC side is 3 phase PWM converter 5
This is to stabilize the voltage on the DC side of the AC power supply 1, and is normally charged to a voltage about twice that of the three-phase AC system power supply 1. That is, the harmonic compensator is a three-phase PWM converter 5.
．． AC reactor 4. DC capacitor 6 and 3 phase PW
It consists of a control device shown in FIG. 4 for turning on and off the switching elements of the M converter 5. Now, in the main circuit configuration shown in Fig. 3, the load current flowing into the load 2 is iLυ + ILV + ILW, and the current flowing into the harmonic compensator is 'U + iv + i
When w, the grid power supply 1 has a current iLU+1t, which is the sum of the load current and the compensation current in each phase in a vectorial manner.
r t ihv+iv * it, w+iw flow. Therefore, the compensation current t, flowing into the harmonic compensator, I
tv l IW is the load current ILU s IL
It suffices if it is a component that cancels out the harmonic components of V s ILW. In order to perform harmonic compensation as described above, we perform three-phase to two-phase conversion as described below, and introduce the concepts of real power and imaginary power.
Three-phase load current ILU * tt, v l using formula 0
ILW and grid voltage eH* eV * eV are expressed as two-phase current ha t ILβ and voltage e6. This is to convert it into eβ. Using the two-phase voltage and current obtained from the above equations 0 to 0, the instantaneous real power p and the instantaneous real power p and imaginary power q correspond to the conventional active power and reactive power using the following equation 0. Yes, the instantaneous real power p and imaginary power q are calculated by the following formulas ■ and ■, respectively: DC components p, q and alternating current components p, q
Decomposed into 0 p=p+p ・Pa・・・・・・・・・・・・
・・・・・・・・・・・・・・・■q = q + q
”' ”’ ”” ”’ ”’ ”’ ”'°
°°°°°゛°■ Here, the two-phase load current iLα, IL
The fundamental distribution of β is the DC component p, q, and the harmonic component is the alternating current p,
q, and these DC components and AC components can generally be separated through a bypass filter. Next, an example of a control device constructed based on the principle described above will be explained with reference to FIG. 4. The power calculation circuit 11 calculates the system voltage eU * ey I ey
From the detected values of load current tt, tr l 'LV * ILW, instantaneous real power p and imaginary power q according to formula 0 to 0.
The bypass filter 2 removes the DC component from these and sends it to the raw bypass filter 2.
The AC component p of the instantaneous real power and the AC component q of the instantaneous imaginary power are sent to the sign inversion circuit 13. The sign inverting circuit 13 inverts these signs and outputs them to the power command value calculation circuit 14 as a real power command signal ♂ and an imaginary power command signal q. p=−p・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・■＊〜q＝−q ”'”'”'”' ””
”” ”’ ”’ ”’ ”’■These are the original form of the current command signal generated in the current command value calculation circuit 14. That is, the harmonic active power is controlled based on the real power command signal p obtained by the 0 formula, and the harmonic reactive power is controlled based on the imaginary power command signal q obtained by the 0 formula. *The current command value calculation circuit 14 receives the actual power command signal p. * Imaginary power command signal q and grid voltage eTJ * 4! V
# Upon receiving eW, obtain two-phase current command signals la*, i/* according to the above formula 0 and the following formulas 0 to ■, and
Perform phase conversion *** and generate three-phase current command signal iυ e iv I t
In addition, w.

[0] is

It is an inverse transformation matrix of [0]. The current control circuit 15 has a hysteresis comparator*
* Compare the detected value of the current command signal IU e IV @ IW and the compensation current member 11V t tw, and when, for example, 1υ≧0 and IU≦member *, turn on the switching element S4 of the three-phase PWM converter 5. When lυ≧0 and iv>itr* *, the switching element S4 is turned off, and the member 〈
0 and lυ≦lυ*, a trigger signal vG is generated that turns off one switching element S1, and this trigger signal Vo
The switching elements 81 to S6 are turned on. is turned off, and the instantaneous current values of each phase of the harmonic compensator are controlled. [Problems to be solved by the invention] In the conventional harmonic compensator shown in FIG. It was determined by the magnitude of the harmonic components. The rated voltage of the three-phase PWM converter 5 must be sufficiently higher than the maximum value of the fundamental wave voltage of the power supply system 1, and in order to lower this rated voltage, a transformer is installed between the harmonic compensator and the power supply system. It is also possible to insert a power supply, but in this case, there is a problem that the current to be handled increases in inverse proportion to the voltage drop. [Means for solving the problem] Harmonic compensation according to the present invention The device utilizes a parallel resonant circuit that resonates with the power system frequency so as to cut unnecessary fundamental wave voltage applied to the AC side of the three-phase PWM converter that constitutes the device. That is, the harmonic compensator according to the present invention is connected to a power supply system in parallel with load equipment, and is a three-phase PWM
a converter, an AC reactor inserted in series with each phase on the AC side of the three-phase PWM converter, and the three-phase PWM converter.
It consists of a DC capacitor connected between the DC terminals of the converter and a control device that controls the three-phase PWM converter, and the three-phase current and each phase voltage flowing into the load equipment are expressed as d and q2 on orthogonal coordinate axes, respectively. In a harmonic compensator that decomposes the power into shaft components, calculates the power on both shafts, converts only the alternating current component into a three-phase compensation current command as a harmonic component, and compensates the power supply system, a YY connection transformer is installed in the power supply system. A circuit configured such that the first reactor and the capacitor resonate in parallel with the power frequency is connected in series between the AC reactor of the harmonic compensator and each phase terminal on the secondary side of the transformer. , a second reactor is connected between the connection point of the parallel resonant circuit and the AC reactor and a neutral point on the secondary side of the transformer, and the leakage impedance of the transformer, the impedance of the parallel resonant circuit, and the second reactor are The transfer function is obtained by dividing the sum of impedances by the impedance of the second reactor.The above compensation current command is input, and the corrected compensation current command is obtained by the above transfer function, and the above three-phase PWM
It is characterized by switching the converter, and a circuit in which the first reactor and the capacitor are configured to resonate in parallel with the power system frequency is inserted in series on the power system side of the accelerator, so that the voltage of the power system is hardly appears between the terminals of the second reactor connected closer to the harmonic compensator than the parallel resonant circuit. In other words, the three-phase PW connected via the AC reactor
The fundamental wave voltage of the power supply system is no longer applied between the AC terminals of the M converter, and the voltage value of the DC capacitor connected between the DC terminals of the three-phase PWM converter can also be significantly reduced. In this way, the rated voltage of the three-phase PWM converter is reduced to an extent commensurate with the harmonics included in the grid line, and the current handled is only the harmonics in the load current.
The capacity of the phase PWM converter can be significantly reduced. However, since there is a second reactor connected to stabilize the phase-to-phase voltage on the AC side of the harmonic compensator, a part of the compensation current that is the output of the harmonic compensator flows through this and flows to the power system side. No inflow. To this end, the compensation current is corrected using the transfer function 1 as described below. Leakage inductance Lt of the transformer and the first of the parallel resonant circuit
The first impedance consisting of the inductance Lh of the reactor and the capacitance Oh of the capacitor is Z
l, second impedance consisting of the inductance Lg of the second reactor, the power supply impedance is zs, the load current harmonic is 1, and the output compensation current of the 13-phase PWM converter is IC, then 1 power supply current harmonic In order to make the wave component zero, the following equation must hold. Therefore, the compensation current IC is expressed by the following equation. This can be expressed in the form of a transfer function as shown in the following equation. , * 1w is the [phase] formula. Therefore, for the previous current command signal, the transfer function in parentheses on the right side of the [phase] equation is
In other words, the sum of the leakage impedance of the transformer, the impedance of the parallel resonant circuit, and the impedance of the second reactor divided by the second impedance is taken as a transfer function, and the compensation current command is input into this transfer function for correction. By obtaining a compensation current command and controlling the three-phase PWM inverter using this command, appropriate harmonic compensation can be performed. [Example] Hereinafter, an example will be described with reference to the drawings. 1st
The figure is a main circuit configuration diagram of one embodiment of the harmonic compensator according to the present invention, FIG. 2 is a professional diagram of the control device for the harmonic compensator according to the present invention, and FIGS. The same reference numerals as in the figure indicate parts having the same function. The primary side of the YY connection transformer 7 is connected to each phase of the line of the three-phase AC power supply 1 that supplies power to the load 2 such as a thyristor Leonard device, and the secondary side of each phase of the YY connection transformer 7 is A parallel resonant circuit 3 configured such that the first reactor 22 and the capacitor 21 resonate in parallel with the power frequency is connected in series between the terminal and each phase AC reactor 4 of the harmonic compensator, and this parallel resonance A second reactor 23 is connected in parallel between the connection point between the circuit 3 and the AC reactor 4 and the secondary neutral point of the transformer 7. A DC capacitor 6 is connected between the terminals on the DC side of the three-phase PWM converter 5, which is composed of switching elements and diodes in the same way as explained in FIG. The switching elements of the three-phase PWM converter 5 are turned on and off by the trigger signal vG. Regarding the operation of the harmonic compensator configured in this way,
The following description assumes that each circuit component is in an ideal state. Since the parallel resonant circuit 3 in which the first reactor 22 and the capacitor 21 are connected in parallel is a parallel resonant circuit tuned to the fundamental frequency of the three-phase AC power supply 1, the parallel resonant circuit 3 and the second reactor 23 The impedance of the circuit consisting of is infinite for the fundamental wave, and 3
The fundamental frequency voltage of the phase AC system power supply 1 is the parallel resonant circuit 3.
The voltage appears at both ends of the second reactor 23, and only voltages of frequencies other than the fundamental wave frequency appear at both ends of the second reactor 23. Generally, the harmonic components generated by the load 2 are composed of third-order or higher harmonic components, so the impedance of the parallel resonant circuit 3 with respect to these harmonic components decreases, and the impedance of the second reactor 23 increases. Current Ip flowing out from the AC reactor 4 due to the harmonic compensator
Only a small amount of υ+ IPV + ”PW flows into the second reactor 23, and most of it flows through the parallel resonant circuit 3 to the three-phase AC power supply! In order to correct the current, a compensation current command IU*+i expressed by the [phase] formula, which is the output of the current command value calculation circuit 14 in FIG.
V”, iw* is shown in parentheses of the [phase] formula fL; 6
The correction circuit 16 outputs a correction circuit 16 containing a transfer function, and the correction circuit 16 outputs a correction compensation current command IU'*IV'·l W / corrected based on the [phase] formula to the current control circuit 15. In this manner, in the harmonic compensator according to the present invention, since the fundamental wave voltage of the three-phase AC power supply 1 is not applied to the three-phase PWM converter 5, even if the charging voltage of the DC capacitor 6 is low, the second The three-phase PWM
Appropriate harmonic compensation can be performed by turning on and off the switching elements that constitute the converter 5. In the present invention, a YY connection is used as the three-phase transformer, but substantially the same effect can be obtained by using a ΔΔ connection. [Effects of the Invention] As described above in detail with reference to the embodiments, the harmonic compensator according to the present invention has three
Since the fundamental wave voltage applied to the phase PWM converter 5 is cut, the DC capacitor 6 should be operated with low voltage and voltage, and the three-phase PWM converter 5
equipment capacity can be reduced. Furthermore, a compensation circuit 16 having a built-in compensation transfer function controls the compensation current to be slightly shunted to the second reactor 23 inserted in order to stabilize the AC side voltage of the three-phase PWM converter 5.
Complete harmonic compensation can be achieved by correcting by .

[Brief explanation of the drawing]

Fig. 1 is a main circuit configuration diagram of an embodiment of the harmonic compensator according to the present invention, Fig. 2 is a schematic diagram of the control device thereof, and Fig. 3 is a diagram of the main circuit of an embodiment of the harmonic compensator according to the present invention. FIG. 4 is a block diagram of the main circuit configuration of the three-phase AC system and its control device. 1... Three-phase AC power supply, 2... Load, 3... Parallel resonant circuit, 4... AC reactor, 5... 3-phase PWM converter, 6.
...DC capacitor, 7... Three-phase transformer, 16... Correction circuit with built-in correction transfer function,
21... Capacitor, 22... First reactor, 23... Second reactor.

Claims (1)

[Claims] A harmonic compensation facility connected in parallel to a load facility in a power supply system, comprising a three-phase PWM converter, an AC reactor inserted in series with each phase on the AC side of the three-phase PWM converter, and the three-phase PWM converter. It consists of a DC capacitor connected between the DC terminals of the converter and a control device that controls the three-phase PWM converter, and the three-phase current and each phase voltage flowing into the load equipment are expressed as d on the orthogonal coordinate axes.
In the harmonic compensator, which decomposes into two axis components, q, calculates the power of both axes, and converts only the alternating current component into a three-phase compensation current command as a harmonic component to compensate for the power supply system, YY connection is used in the power supply system. The primary side of the transformer is connected, and a circuit configured such that the first reactor and the capacitor resonate in parallel with the power frequency is connected to the AC reactor of the harmonic compensator and the transformer 2.
A second reactor is connected between the connection point of the parallel resonant circuit and the AC reactor and a neutral point on the secondary side of the transformer, and the leakage impedance of the transformer and the The sum of the impedance of the parallel resonant circuit and the impedance of the second reactor divided by the impedance of the second reactor is in the form of a transfer function, the compensation current command is input, and a corrected compensation current command is obtained by the transfer function. A harmonic compensation device characterized in that it performs switching of the three-phase PWM converter.