JPH063566B2 - Power adjustment method - Google Patents

Description

The present invention relates to a power adjustment method for a three-phase AC circuit for preventing voltage flicker, improving power factor, reducing harmonic components, and the like.

[Conventional technology]

It is well known to connect a lead power supply circuit composed of a capacitor, or a parallel circuit of a capacitor and a reactor, between the three-phase AC power supply lines for the purpose of preventing flicker and / or improving the power factor. Also, JP-A-56-159936
(Japanese Patent Application No. 55-61600), the instantaneous effective current,
And determining the instantaneous reactive current and controlling the power fault compensation circuit based on this. Furthermore, Japanese Patent Application Sho 6
In 0-137499, the Applicant proposed a method for easily achieving power factor correction of a three-phase unbalanced load based on line current detection. In addition, three-phase P composed of transistors
A method of controlling a reactive component using a WM converter has already been proposed.

[Problems to be solved by the invention]

However, the above-mentioned Japanese Patent Application No. 60-137499 does not disclose a method for removing harmonic components. Further, the method of using the transistor three-phase PWM converter has a drawback that it is difficult to increase the capacity.

Therefore, it is an object of the present invention to provide a method capable of easily achieving medium or large capacity power adjustment.

[Means for solving problems]

The present invention for solving the above problems and achieving the above objects will be described with reference to the reference numerals of the drawings showing the embodiments.The three-phase load (2) connected to the three-phase AC power supply line One phase,
Detecting currents I _U , I _V , and I _W of the second and third phases, and detecting the first and second currents I _U , I _V , and I _W of the first, second, and third phases. Instantaneous reactive current I _Uq , I _Vq , I _{Wq of} 2nd and 3rd phase
The first, second and third instantaneous reactive currents
Obtaining the effective values a, b, c of the fundamental wave components of I _Uq , I _Vq , and I _Wq or a value proportional _thereto , and the effective value of the fundamental wave component of the instantaneous reactive current of each phase represented by the line current. a, b, c or a value proportional thereto is converted into phase currents x, y, z, and the fundamental wave component of the reactive current of the three-phase load (2) is converted based on the phase currents x, y, z. Control the reactive current fundamental wave component supply circuit (3) so as to compensate for each of the instantaneous reactive currents based on the instantaneous reactive currents I _q or I _Uq , I _Vq , and I _Wq for all three phases or for each phase. phase of the harmonic components [Delta] I _qU, [Delta] I _qV, to obtain the [Delta] I _QW, wherein the first three-phase load (2), the current I _U of the second and third phase, I _V, disabling instant based on the I _{W Obtaining} the harmonic components ΔI _pU , ΔI _pV , ΔI _pW of each phase of the current, the harmonic components ΔI _qU , ΔI _qV , ΔI _qW of each phase of the instantaneous reactive current and the harmonics of each phase of the instantaneous active current Component ΔI _pU , ΔI _pV , and ΔI _pW are added to _obtain the harmonic addition signals I _Uh , I _Vh , and I _Wh , the three-phase pulse width modulation conversion circuit (10) connected to the three-phase AC power line, The harmonic addition signal so as to remove the invalid and effective harmonic components of the three-phase AC power supply line.
The present invention relates to a power adjustment method characterized by performing control based on I _Uh , I _Vh , and I _Wh .

[Action]

According to the above invention, the fundamental wave component of the reactive current and the harmonic components of the reactive current and the active current are substantially separated and compensated based on the detection of the load current. Since the harmonic components of the reactive current and the active current have higher frequencies than the fundamental wave component, they are compensated by the pulse width modulation (PWM) conversion circuit (10). At this time, if necessary, some of the fundamental wave components are PWM
It may be compensated by the conversion circuit (10). The PWM conversion circuit (10) has a function of compensating for the fundamental wave component, but if it is configured to compensate for all of the fundamental wave component here, the semiconductor switch becomes unavailable in the case of a large capacity, or High cost. Therefore, in the present invention, all or most of the fundamental wave component of the reactive current is supplied by the reactive current fundamental wave component supply circuit (3). As a result, it is possible to easily and satisfactorily achieve suppression of ineffective and effective harmonic currents, prevention of flicker, and improvement of power factor.

〔Example〕

Next, a power adjustment system for a three-phase AC circuit according to an embodiment of the present invention will be described with reference to the drawings.

[Overall explanation]

In FIG. 1, the three-phase unbalanced load (2) is applied to the power supply lines (1u, 1v, 1w) of the first phase (U phase), the second phase (V phase), and the third phase (W phase). Are connected. This three-phase unbalanced load (2)
For example, a single-phase load (2a) (2b) such as a welder with almost the same power factor
(2c) is connected between each line, load between each line (2a)
(2b) and (2c) are not fixed loads, but their sizes change. Therefore, if power factor compensation is not performed, voltage fluctuations (flicker) of the power supply lines (1u) (1v) (1w) occur due to fluctuations of the load (2), and the power factor deteriorates. (3) is a fundamental wave component supply circuit of the lead reactive current for power factor adjustment, and is composed of first, second and third circuits (3a) (3b) (3c),
It is connected to the three-phase power lines (1u) (1v) (1w). This invalid fundamental component supply circuit current (3) a plurality of capacitors C _1a -C _1n between each line, C _2a ~C _2n, thyristors S _1a to S _1n as the AC switch C _3a ~C _3n, S _2a to S _2n, and is configured by connecting through the S _3a to S _3n. If the leading current supplied by the fundamental wave component supply circuit (3) of the reactive current is adjusted according to the fluctuation of the load (2), the power factor of the three-phase AC circuit is compensated and the voltage fluctuation (flicker) is also prevented. To be done. In addition,
In this embodiment, since four capacitors having a capacitance ratio of 1: 2: 4: 8 are provided as the capacitors C _{1a to} C _1n , a capacity of 15 stages can be obtained by combining these 4 capacitors. . The capacitors C _{2a to} C _2n and C _{3a to} C _3n have the same configuration.

In this example, the load (2a) between the lines as a three-phase load (2)
Since (2b) and (2c) consist of many groups, it is difficult to directly detect the phase current. Therefore, the line currents I _U , I _V , I _W
In order to detect the current, current detectors (4a) (4b) (4c), which are current transformers, are connected to the respective power supply lines (1u) (1v) (1w).

Signal processing circuit connected to current detectors (4a) (4b) (4c)
(5) calculates the fundamental wave component of the instantaneous reactive current, sends control signals x ₁ , y ₁ , z ₁ for compensating for it to the gate control circuit (7) with three lines 6, and Of the harmonic component of the effective current and the harmonic component of
I _Uh , I _Vh , and I _Wh are sent to the control signal forming circuit (9) of the next stage through three lines (8).

The gate control circuit (7) is based on the control signals x ₁ , y ₁ , z ₁ sent from the signal processing circuit (5) that indicate the number of stages of capacitor input for each phase, and the fundamental wave component of the load (2) and reactive current. It is a circuit that generates a gate signal for controlling the thyristors S _{1a to} S _3n so that the total power factor with the supply circuit (3) becomes 1.

The PWM conversion circuit (10) for supplying harmonic compensation current includes transistors Q _{1 to} Q ₆ as bridge-connected self-extinguishing type semiconductor switching elements, and an AC is applied to the connection point of each pair of transistors Q _{1 to} Q _6. The power supply lines (1u, 1v, 1w) are connected, and the reactor (11) is connected as a load to the transistors Q _{1 to} Q ₆ of each pair. Bases of the transistors Q ₁ to Q ₆ is connected to the control signal forming circuit (9), the transistors Q ₁ to Q ₆ is driven pulse width modulation (PWM), and supplies a controlled harmonic compensation current. Note that capacitors C ₁₁ , C ₁₂ , and C ₁₃ are connected between the input lines of the PWM conversion circuit (10). Further, current detectors (12), (13) and (14) are connected, and their outputs are connected to the control signal forming circuit (9).

The control signal forming circuit (9) provides the invalid and effective harmonic addition signals I _Uh , I _Vh , I _Wh provided by the signal processing circuit (5) and the current provided by the current detectors (12) (13) (14). And based on the power line
A signal for controlling on / off of the transistors Q _{1 to} Q ₆ is formed so that the harmonic components of (1u), (1v), and (1w) become zero.

[Explanation of FIG. 2] The details of the signal processing circuit (5) are as shown in FIG. The first arithmetic circuit (15) for obtaining the instantaneous imaginary current I _q connected to the current detectors (4a) (4b) (4c) shown in Fig. 1 outputs the instantaneous reactive current component of the three-phase as a direct current. It is a circuit to do. The instantaneous imaginary current I _q means an instantaneous reactive current for all three phases.

Reference numeral (16) is a second arithmetic circuit for obtaining the instantaneous reactive current of each phase, which is connected to the first arithmetic circuit (15) and is based on the instantaneous imaginary current I _q and the line currents I _U , I of each phase. Outputs the instantaneous reactive current I _Uq , I _Vq , and I _Wq of each phase corresponding to _V and I _W. This arithmetic circuit (16)
The specific configuration of will be described later.

(17) is a fundamental wave component extraction circuit, and a second arithmetic circuit (16)
The effective value of the fundamental wave component of the instantaneous reactive current I _Uq , I _Vq , and I _Wq obtained from the line current a of the fundamental wave component of the instantaneous reactive current,
It is configured to output b and c (effective value) as direct current. The fundamental wave component extraction circuit (17) will be described later in detail.

(18) is a third arithmetic circuit for converting a line current into a phase current. That is, it is a circuit for converting the line currents a, b, c (effective value) of each phase of the fundamental wave component of the instantaneous reactive current into the phase currents x, y, z (effective value) of each phase. The third arithmetic circuit (18) will be described in detail later.

(19) is a capacitor stage number determination circuit, which is required to compensate the phase currents x, y, z (effective value) of the fundamental wave component of the instantaneous reactive current obtained from the third arithmetic circuit (18) in the preceding stage. Control signals x ₁ , y ₁ , z ₁ indicating the number of stages of capacitors C _{1a to} C _3n
Are formed and sent to the gate control circuit (7). Signals x ₁ , y ₁ , z ₁ indicating the number of capacitor stages are phase currents x, y,
It is a signal corresponding to z.

(20) is a three-phase batch instantaneous reactive current harmonic component extraction circuit. The instantaneous imaginary current I _q output from the first arithmetic circuit (15) is composed of a fundamental wave component and a harmonic wave component. The fundamental wave component is compensated by the fundamental wave component supply circuit (3), but the harmonic component is not compensated, so in order to compensate for this, the three-phase batch instantaneous reactive current harmonic component extraction circuit (20) The harmonic component of the instantaneous reactive current (instantaneous imaginary current) is extracted. By the way, if all of the fundamental wave components can be compensated by the fundamental wave component supply circuit (3), the harmonic component represented by direct current can be obtained by subtraction of the instantaneous imaginary current I _q and the direct current signal indicating the fundamental wave component. You can ask. Alternatively, the AC harmonic component can be obtained by subtracting the AC instantaneous reactive current and the AC instantaneous fundamental wave component. However, in this embodiment, the fundamental wave component is compensated stepwise, and the shortage or excess of compensation occurs. Therefore, the shortage or excess is compensated by the PWM conversion circuit (10). In order to enable this compensation, a fundamental wave compensation amount signal generation circuit (21) is provided between the capacitor stage number determination circuit (19) and the harmonic component extraction circuit (20).

The fundamental wave compensation amount signal generation circuit (21) is a sine wave conversion circuit (22) connected to the capacitor stage number determination circuit (19) for converting a DC level into a sine wave, and a phase current converted into a line current. The fourth arithmetic circuit (23) and the fifth arithmetic circuit (24) for obtaining the fundamental wave component of the compensated instantaneous imaginary current. Since the fundamental wave compensation amount signal generation circuit (21) outputs a DC signal, it can also be called a circuit that generates a compensated instantaneous imaginary current I _qc . The harmonic component extraction circuit (20) is a first and a fifth arithmetic circuit.
Since it is connected to (15) and _performs the operation of I _q −I _qc , it can be called a circuit for _obtaining an instantaneous imaginary current ΔI _q of _{undercompensation} or overcompensation. The PWM conversion circuit (10) compensates for the instantaneous imaginary current that is under-compensated or over-compensated.

(26) is a sixth arithmetic circuit for obtaining the instantaneous actual current I _p , which is connected to the current detectors (4a) (4b) (4c). Instantaneous actual current I _p
Is a DC signal that means an instantaneous active current for all three phases. In this embodiment, since the harmonic component of the active current is also compensated by the PWM conversion circuit (10), the sixth arithmetic circuit (26) detects the instantaneous actual current and detects the harmonic component contained therein. Extract.

(27) is an average value circuit for calculating the average value of the commercial (power) frequency of the instantaneous actual current I _p in one cycle, and the arithmetic circuit (23) in FIG.
It is connected to the. The average value I _pa obtained from this is a DC signal corresponding to the fundamental wave component of the instantaneous active current.

(28) is an instantaneous real current harmonic component extraction circuit, which is connected to the sixth arithmetic circuit (26), the average value circuit (27) and the seventh arithmetic circuit (29), Output the harmonic component ΔI _P of the batch instantaneous active current). If no instantaneous real current is supplied based on the capacitor fundamental wave component supply circuit (3), the instantaneous real current I _pc obtained from the seventh arithmetic circuit (29) is zero, so It is not necessary to connect the output of the calculation circuit (29) to the instantaneous real current harmonic component extraction circuit (28), but if the load (2) is unbalanced, the fundamental component supply circuit (3a) ( 3b) and (3c) also become unbalanced and instantaneous real current flows. Therefore, this instantaneous actual current is compensated by the PWM conversion circuit (10). The seventh arithmetic circuit (29) is connected to the fourth arithmetic circuit (23), and instantaneously based on I _Uc , I _Vc , and I _Wc obtained from the line currents of the fundamental wave component supply circuit (3). The actual current I _pc is obtained.

The eighth arithmetic circuit (30) is an instantaneous reactive current harmonic component arithmetic circuit
(31) and instantaneous active current harmonic component calculation circuit (32) and addition circuit
(33) Including and. The instantaneous reactive current harmonic component calculation circuit (31) is connected to the instantaneous imaginary current harmonic component extraction circuit (20), and the instantaneous imaginary current harmonic component ΔI, which is a DC signal supplied from this circuit.
_q is the instantaneous reactive current harmonic component of three-phase alternating current ΔI _qU , Δ
Convert to I _qV and ΔI _qW . The instantaneous active current harmonic component calculation circuit (32) is connected to the instantaneous actual current harmonic component extraction circuit (28) and converts the instantaneous actual current harmonic component ΔI _p , which is a DC signal, into the three-phase AC instantaneous active current AC ΔI. Convert to _pU , ΔI _pV , and ΔI _pW . The adder circuit (33) uses the instantaneous reactive current harmonic component Δ
I _qU , ΔI _qV , ΔI _qW and instantaneous active current harmonic component Δ
I _pU , ΔI _pV , and ΔI _pW are added to _obtain an AC control signal.
Outputs I _Uh , I _Vh , and I _Wh .

[Instantaneous imaginary current, instantaneous reactive current]

The instantaneous reactive current is described in the above-mentioned JP-A-56-159936.

The three-phase AC power supply voltages V _U , V _V , and V _W have maximum values V _m and angular frequency ω
If the balanced three-phase AC voltage is expressed by the following equation.

Now, when the three-phase load currents I _U , I _V , and I _W are coordinate-transformed with a transformation matrix that rotates by ω and expressed by I _p and I _q , the following equation is generally established when there is no zero-phase current. To do.

Here, since only the instantaneous reactive current I _q of the three-phase is calculated, if I _p = 0 in the equation (2), the following equation is obtained.

In the present invention, the instantaneous reactive current I _q of the above-mentioned equation (4) for all three phases is defined as the instantaneous imaginary current.

FIG. 3 shows in detail the first and second arithmetic circuits (15) and (16) of FIG. The lines (41) (42) (43) connected to the current detectors (4a) (4b) (4c) in Fig. 1 are the coefficients Multiplier (50) (51) via coefficient multipliers (44) (45) (46)
Each of them is connected to one of the input terminals of (52). The sin ωt generation circuit is connected to the other input terminal of the multiplier (50) (51) (52).
(47), sin (ωt-2π / 3) generation circuit (48) and sin (ωt-4π / 3) generation circuit (49) are connected. Each multiplier (50) (5
1) The output of (52) is connected to the adder (53). Adder (5
A DC signal corresponding to the instantaneous imaginary current I _q is obtained on the output line of 3).

The second operational circuit (16) for obtaining the instantaneous reactive current component converts the DC instantaneous imaginary current I _q into the instantaneous reactive currents I _Uq , I _Vq and I _Wq of each phase as shown in FIG. , Multiplier (54) (55) (5
6) and coefficient units (57) (58) (59). First arithmetic circuit (15)
The output of the sine wave signal generation circuit (47) (48) (49) that also serves as the output of the adder (53) is multiplied by each multiplier (54) (55) (56), and this is multiplied by the coefficient Is multiplied by the instantaneous reactive current I _{Uq of} each phase,
I _Vq and I _Wq are obtained. Instantaneous reactive current of each phase I _Uq , I _Vq , I
The relational expression between _Wq and the instantaneous imaginary current _Iq is as follows.

[Fundamental wave component extraction circuit] The fundamental wave component extraction circuit (17) of the instantaneous reactive current is a low-pass filter (61) connected to the lines of the instantaneous reactive currents I _Uq , I _Vq , and I _Wq of each phase as shown in FIG. ) (62) (63) and RMS converters (64) (65) (66) connected to these output lines. The low-pass filters (61) (62) (63) remove the harmonic components from the instantaneous reactive current of each phase including the harmonic components and output the fundamental wave of the power supply frequency. Each RMS converter (64) (65) (66)
Is, for example, R of AD536A of Analog Devices Co., Ltd.
The MS / DC converter outputs a DC voltage corresponding to an AC effective value. Therefore, the fundamental wave extraction circuit (17) outputs the line voltages a, b, and c representing the effective value.

[Line current-phase current conversion]

Next, a method of converting the line currents (instantaneous reactive currents) a, b, c into phase currents (instantaneous reactive currents) x, y, z will be described with reference to FIGS. 5 and 6.

Third operation circuit (18) for converting line current to phase current in FIG.
Is configured to convert the line currents a, b and c into phase currents x, y and z based on the following equations (6), (7) and (8).

However, A is shown by the following equation.

It will be described that the phase currents x, y, and z are approximately obtained by the equations (6), (7), and (8). If only the reactive current components of the loads (2a) (2b) (2c) in FIG. 1 are extracted, the phase currents x, y, z converted into each phase have a phase difference of 120 degrees, and It can be represented by a vector diagram. Then, each phase current x, y, z
Since the relationship between the line currents and the line currents a, b and c is also as shown in FIG. 6, the following equation (9) is established between them.

Since θ = 2/3, The following equation (11) is established by the equation (10).

2 (x + y + z) ² -3 (xy + yz + zx) ＝ b ² + c ² + a ² (11) On the other hand, the following formula (12) is established by the formula.

3 (xy + yz + zx) ² = 2 (b ² c ² + c ² a ² + a ² b ² )-(b ⁴ + c ⁴ + a ⁴ ) ... (12) From equation (12), The formula is obtained.

Substituting Eq. (13) into Eq. (11), we obtain

Hereafter, let Eq. (14) be A. Further, the following equation is established from the equation (10).

The following equation is established from the equation (16) and the relation of x + y + z = A.

From the equation (17), the above equations (6), (7) and (8) are obtained. Therefore, equations (6), (7), and (8) represent the phase current of each phase.

The operation circuit (18) of FIG. 5 is connected to the fundamental wave component extraction circuit (17) of FIG. 2 in order to execute the operations of equations (6), (7) and (8). 71, (72) and (73) have square calculators (74), (75) and (76) for obtaining square values of line currents a, b and c. The output stage of the square operation unit (74) (75) (76), (6) (7) (8) of ^{a 2 + b 2, b 2} + c 2, c 2 + a 2 in Adders (77), (78), and (79) are provided to perform the calculation of the part, and 2c ² in the equations (6), (7), and (8),
To obtain 2a ² and 2b ² , double value calculators (80), (81) and (82) are provided. (83) (84) (85) is a subtracter, which subtracts the output of the computing unit (80) (81) (82) from the output of the previous stage adder (77) (78) (79) 6) (7) (8) of ^{a 2 + b 2 -2c 2,} b 2 + c 2 -2a 2, c 2 +
You get a ² -2b ² . (86) is an adder,
The output c ² + a ² (79), the square operation unit (75) outputs b ² and addition of (6) (7) (8 ) a 2 + b 2 + c 2 included in A of Formula I will get it.

(87) (88) (89) are dividers, and subtractors (83) (84) (8
The output of 5) is divided by the separately obtained 3A to obtain the second term of the equations (6), (7) and (8). (90) (91) (92) are adders, which were calculated separately from the outputs of the dividers (87) (88) (89) in the previous stage (6)
This is to add the value A / 3 of the first term of the equations (7) and (8) and output the phase currents x, y and z of the equations (6), (7) and (8).

Adder connected to line current input line (71) (72) (73)
(93) (94) (95) is a + in the formula showing A of the formulas (6) (7) (8).
b, b + c, c + a are obtained. Adder (96)
Is for adding (c) of the line (73) to the output (a + b) of the adder (93) to obtain (a + b + c) in the expression indicating A. The subtracter (97) subtracts the output of the line (73) from the output of the adder (93) to obtain a + bc of the expression indicating A. The subtractor (98) is a circuit that subtracts the output of the line (71) from the output of the adder (94) to obtain (-a + b + c) of the expression indicating A. The subtractor (99) is a circuit that subtracts the output of the line (72) from the output of the adder (95) to obtain (ab + c) of the expression indicating A. The multiplier (100) multiplies the output of the adder (96) by the output of the subtractor (97) to obtain (a + b +
c) A circuit for obtaining (a + b-c). The multiplier (101) multiplies the output of the subtractor (98) and the output of the subtractor (99) to obtain A
Is a circuit that obtains (-a + b + c) (a-b + c) in the equation. The multiplier (102) is the former two multipliers (100) (101)
Of the output of (a + b + c)
(-A + b + c) (a-b + c) (a + b-c) (hereinafter, referred to as B) is obtained. Multiplier (103)
Is a circuit for obtaining B × 3 based on the output B of the multiplier (102) in the previous stage. The square root calculator (104) is the multiplier (103) in the previous stage.
Output square root of 3B Is a circuit to obtain. The adder (105) adds the output of the arithmetic unit (104) at the previous stage and the output of the adder (86) Is a circuit to obtain. The 1/2 divider (106) is the adder (10
This is a circuit that obtains 1/2 the output of 5). Square root calculator
(107) is the square root of the output of the 1/2 divider (106) in the previous stage, that is, A
To obtain the output of the expression. The multiplier (108) multiplies the output A of the preceding stage arithmetic unit (107) by 3 to obtain 3A, and supplies this to the dividers (87) (88) (89) of each phase. The multiplier (109) calculates 1/3 of the output A of the square root calculator (107),
This is supplied to the adders (90) (91) (92).

[Sine wave conversion circuit]

The sine wave conversion circuit (22) connected to the capacitor stage number determination circuit (19) has a capacitor stage number control signal x ₁ , which is a DC signal,
A circuit that converts y ₁ and z ₁ into a sine wave (fundamental wave) with an amplitude corresponding to this level. The sine wave voltage of each phase x ₁₁ , y
_11, sends the z _11. If the fundamental wave component supply circuit (3) completely compensates the phase currents x, y, z, then x ₁₁ , y
₁₁ and z ₁₁ are equal to x, y and z.

[Circuit that converts phase current to line current]

Between the phase currents x, y, z and the line currents a, b, c Have a relationship. Therefore, the output line currents a ₁ , b ₁ , c ₁ corresponding to the input phase currents x ₁₁ , y ₁₁ , z ₁₁ of the fourth arithmetic circuit (23) can be obtained by the following equation.

FIG. 7 shows a fourth arithmetic circuit (23) for the equation (19). The fourth arithmetic circuit (23) includes three squarers (110) (111) (11
2), three multipliers (113) (114) (115), and six adders
(116) (117) (118) (119) (120) (121) and arithmetic units (122) (123) (124) for obtaining three square roots. When the fundamental wave component is ideally compensated by the capacitor, the output currents a, b and c of the fundamental wave component extraction circuit (17) and the output line currents a ₁ and b of the fourth arithmetic circuit (24). ₁ and c ₁ are equal.

[Compensated fundamental wave component]

The fifth arithmetic circuit (2) connected to the fourth arithmetic circuit (23)
In 4), the compensated fundamental wave component is obtained in the form of instantaneous imaginary current. The instantaneous imaginary current I _qc and the instantaneous real current I _pc of the line currents a ₁ , b ₁ , c ₁ can be expressed by the following equations.

Therefore, the instantaneous imaginary current I _qc indicating the fundamental wave component compensated by the capacitor is obtained by the following equation.

The calculation of the equation (21) is performed by the fifth calculation circuit (24) shown in FIG. The fifth arithmetic circuit (24) is a sine wave generating circuit (13
1) (132) (133), multipliers (134) (135) (136), and adder (13
It consists of 7) and a coefficient unit (138). The sine wave generator (13
1) (132) (133) are the sine wave generating circuits (47) (48) (49) of FIG.
May also be combined. Instantaneous imaginary current harmonic component extraction circuit (20)
In the above, by calculating I _qc indicating the compensated fundamental wave component output from the fifth arithmetic circuit (24) and the instantaneous imaginary current I _q before compensation, the instantaneous imaginary current Δ of under-compensation or over-compensation is calculated.
I _q is required. This instantaneous imaginary current ΔI _q represents the sum of the harmonic component of the instantaneous reactive current and the fundamental wave component that could not be compensated by the capacitor or was overcompensated by DC.
If the fundamental wave can be completely compensated by the fundamental wave component supply circuit (3), ΔI _q represents only the harmonic component.

[Instantaneous actual current of capacitor current]

When the capacitors of the fundamental wave component supply circuit (3) in FIG. 1 are connected unbalanced, an effective current (instantaneous actual current) flows. This instantaneous real current I _pc is expressed by equation (20). Therefore, the instantaneous actual current I _pc can be _calculated by the following equation.

FIG. 9 shows a seventh arithmetic circuit for the equation (22), which has three phases.
cos wave generator (141) (142) (143) and multiplier (144) (145) (1
46), an adder (147), and a coefficient unit (148).

[Instantaneous Actual Current of Load Current] The three-phase batch instantaneous effective current of the load currents I _U , I _V , and I _W , that is, the instantaneous actual current I _p is expressed by equation (2). Therefore, it can be calculated by the following equation.

FIG. 10 shows a sixth arithmetic circuit for obtaining the instantaneous actual current I _p of the equation (23), which is a three-phase cos wave generation circuit (151) (152) (153).
Multipliers (154) (155) (156), adder (157), coefficient unit (15
8) and. The cos wave generation circuits (151), (152) and (153) may be configured so as to also serve as the cos wave generation circuits (141), (142) and (143) of FIG.

[Instantaneous current average value circuit]

As shown in FIG. 11, an average value circuit (27) for obtaining the average value of one cycle of the commercial (power) frequency is composed of an integrating circuit (160) and a sample hold circuit (161). Integrator circuit
(160) is connected to the sixth arithmetic circuit (26), and the power supply line (1u) (1
v) (1w) is reset in response to the power source zero-point pulse indicating the start of one cycle of the commercial AC voltage, and integrates the one-cycle instantaneous actual current I _p of the commercial frequency. The sample-hold circuit (161) samples and holds the integrated value of one cycle in response to the power source zero-point pulse, and outputs it as an average value I _pa .
This average value I _pa corresponds to the fundamental wave component of the instantaneous active current.

[Instantaneous real current harmonic component extraction circuit]

The instantaneous real current harmonic component extraction circuit (28) is a sixth arithmetic circuit.
A subtractor that subtracts the average value I _pa given by the average value circuit (27) from the instantaneous actual current I _p given by (26) to obtain I _p −I _pa , and the result of this subtraction with the seventh arithmetic circuit. (29) and the adder that adds the instantaneous real current I _pc , and ΔI _p
= I _p −I _pa + I _pc . The harmonic component is extracted by subtracting the average value I _pa corresponding to the fundamental wave component of the instantaneous real current from the instantaneous real current I _p containing the harmonic component. In this embodiment, the instantaneous actual current I supplied by the fundamental wave component supply circuit (3) including the capacitor is
This I _pc is added to compensate for _pc at the same time.

[Eighth Arithmetic Circuit (30)] The eighth arithmetic circuit (30) is configured as shown in FIG. The instantaneous reactive current harmonic component operation circuit (31) included here is a coefficient unit (170) and a three-phase sine wave generation circuit (171) (1
72) (173) and multipliers (174) (175) (176) .The instantaneous imaginary current harmonic component ΔI _q given from the instantaneous imaginary current harmonic component extraction circuit (20) is used as the three-phase instantaneous reactive current. Harmonic component Δ
The following calculation is performed to convert to I _qU , ΔI _qV , and ΔI _qW .

Instantaneous active current harmonic component operation circuit (32) is a coefficient unit (177)
And a three-phase cos wave generator (178) (179) (180) and a multiplier (1
81) (182) (183) and the instantaneous real power source harmonic component ΔI _p
The three-phase instantaneous active current harmonic components ΔI _pU , ΔI _pV , ΔI _pW
The following calculation is performed to convert to.

The adder circuit (33) outputs the added signals I _Uh , I _Vh , and I _Wh of the instantaneous reactive current harmonic component and the instantaneous active current harmonic component as shown in the following equation.

The addition signals I _Uh , I _Vh , and I _Wh are harmonic component signals of the instantaneous reactive current and the instantaneous active current.

[Control Signal Forming Circuit (9)] The control signal forming circuit (9) includes a phase inverting circuit (9c), a hysteresis comparator (9a), and a logic circuit (9b). The harmonic component signal of the third arithmetic circuit (30) is applied to one input terminal of the hysteresis comparator (9a) via the phase inverting circuit (9c).
The output line of I _Uhb is connected, and the AC harmonic component signal I _Uhb illustrated in FIG. 14 (A) is input to the output line. The other input terminal of the comparator (9a) has the current detector shown in Fig. 1.
(12) is connected, and the detected current value I _CT shown in FIG. 13 (A) is input. The comparator (9a) obtains two hysteresis levels V _L and V _H based on the harmonic component signal I _Uhb , compares these with the current detection value I _CT, and I _Uhb reaches V _L and V _H. The output is inverted every time, and the comparison output shown in FIG. 13 (B) is obtained. That is, I _Uhb goes from level V _H to level V _L t ₂ ~
The comparison output is low level in the t ₃ section, and becomes high level in the period of t ₃ to t ₄ where I _Uhb goes from the level V _L to the level V _H.

The logic circuit (9b) uses the transistor Q ₁ ,
It is a circuit that forms the control signal of Q ₂ . The control signal of the transistor Q ₁ shown in FIG. 14 (C) selects the comparison output of FIG. 14 (B) as it is from t ₁ to t ₅ of the _first half cycle of the harmonic component signal I _Uhb , and the control signal of the latter half cycle is selected. 14th from t _{5 to} t ₆
It is formed by inverting the comparison output of FIG. The control signal for the transistor Q _{2 in} FIG.
This is an inversion of the control pulse in FIG. Harmonic component signal I _Vh, the control signals of the transistor Q ₃ to Q ₆ of the second and third phases corresponding to I _Wh also be formed in exactly the same way as the first phase.

〔motion〕

Line current I including harmonic components and reactive components in load (2) in Fig. 1
_{When U} , _IV and _IW are flowing, current detectors (4a) (4b)
It is detected in (4c) and sent to the signal processing circuit (5). The signal processing circuit (5) forms capacitor stage number control signals x ₁ , y ₁ and z ₁ for compensating the fundamental wave component of the reactive current and sends them to the gate control circuit (7). The gate control circuit (7) controls ON of the thyristors S _{1a to} S _3n so as to connect the selected capacitors of the fundamental wave component supply circuit (3). As a result, the fundamental wave component is supplied by the capacitor. By the way, the thyristors S _{1a to} S _3n cannot supply the higher harmonic components because the current is not immediately interrupted even when the supply of the gate signal is stopped.

On the other hand, the PWM conversion circuit (10) for harmonic compensation compensates for the component that cannot be compensated by the fundamental wave component supply circuit (3) of the reactive current. That is, the reactive current fundamental wave component supply circuit (3)
Is for compensating the fundamental wave component of the reactive current, and is not for compensating the harmonic component.Therefore, the transistor Q is used to remove the instantaneous reactive and effective harmonic component addition signals I _Uh , I _Vh , and I _{Wh. The} PWM conversion circuit (10) composed of _{1 to} Q ₆ is driven. Since the transistor Q ₁ to Q ₆ is a self-extinguishing semiconductor switch, it is possible to perform the on-off at a commercial frequency or frequencies, it is possible to compensate for the harmonic components. Therefore, according to the method of FIG. 1, flicker prevention, power factor improvement, and harmonic current suppression are achieved.

[Modification]

The present invention is not limited to the above-described embodiments, and the following modifications are possible, for example.

(1) Output signal of the capacitor stage number determination circuit (19) in FIG.
Instead of making line currents a ₁ , b ₁ and c ₁ showing the compensation fundamental wave component by the sine wave conversion circuit (22) and the fourth operation circuit (23) based on x ₁ , y ₁ and z ₁ , Fundamental wave component supply circuit as shown in FIG.
Connect the current detector C to the line that connects (3) to the power line (1u, 1v, 1w).
T ₁ , CT ₂ , CT ₃ are connected, and the signal detected by these is a ₁ ,
It may be used as b _1, c _1.

(2) Fig. 16 shows fundamental wave component supply circuit for reactive current (3a) (3b)
A modification of (3c) is shown. In this circuit, capacitors between each line
Reactors L ₁ , L ₂ and L ₃ are connected in parallel to C ₁ , C ₂ and C ₃ ,
Thyristors S ₁ , S ₂ and S ₃ are connected in series with reactors L ₁ , L ₂ and L ₃ . The thyristors S ₁ , S ₂ , and S ₃ are phase-controlled (conduction angle control) so that the power factor becomes 1. Therefore, an effect equivalent to continuously controlling the capacitor capacity can be obtained.

The phase control angles of the thyristors S ₁ , S ₂ and S ₃ are determined based on the phase currents x, y and z of the instantaneous reactive current.

(3) A mechanical switch such as an electromagnetic contactor may be connected instead of the thyristors S _{1a to} S _3n shown in FIG. It may also be used GTO instead of the transistor Q ₁ to Q _6.

(4) Instead of configuring each arithmetic circuit with an analog arithmetic unit, a digital arithmetic circuit with a microcomputer may be used.

(5) The thyristors S _{1a to} S _3n and S _{1 to} S ₃ may not be triacs, but SCRs may be connected in antiparallel.

(6) A capacitor may be connected instead of the reactor (11) in FIG. When this capacitor is connected in this way, a reactor is connected in series to the three-phase input line of the PWM conversion circuit (10) instead of the capacitors C ₁₁ , C ₁₂ , and C ₁₃ .

(7) Instead of obtaining the compensation shortage or excess of the fundamental wave component, if the shortage of compensation or excess is already known,
The deficiency or excess may be added to the fundamental wave component to obtain the instantaneous imaginary current harmonic component ΔI _q .

(8) Instead of obtaining the harmonic component based on the instantaneous imaginary current I _q , the instantaneous reactive current obtained from the second arithmetic circuit (16)
From I _Uq , I _Vq , and I _Wq , the low-pass filter (6
The outputs of 1), (62) and (63) may be analog-subtracted to extract the harmonic components of each phase. Similarly, for the harmonic component of the instantaneous active current, instead of the instantaneous real current I _p , a three-phase instantaneous active current is obtained, and the fundamental component is analog-subtracted from this instantaneous active current to extract the harmonic component. You may do it.
That is, Japanese Patent Application Nos. 61-169322 and 61-1713.
The harmonic components can be extracted by various methods as described in the specification of No. 35 and the drawings.

(9) If it is not necessary to compensate the fundamental wave compensation shortage or overcompensation by the fundamental wave component supply circuit (3) with the PWM conversion circuit (10),
The output of the fundamental wave component extraction circuit (17) may be input to the fifth arithmetic circuit (24).

〔The invention's effect〕

As is apparent from the above, in the present invention, the fundamental wave component and the harmonic component are separately compensated, so that a large reactive component can be optimally controlled to suppress the harmonic component, prevent flicker, and improve the power factor. . Further, since the harmonic component of the active current is also compensated for, high quality power supply becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a three-phase power regulator according to a first embodiment of the present invention, FIG. 2 is a block diagram showing a signal processing circuit of FIG. 1, and FIG. 3 is a first diagram of FIG. And a block diagram showing the second arithmetic circuit, FIG. 4 is a block diagram showing the fundamental wave component extracting circuit of FIG. 2, FIG. 5 is a block diagram showing the third arithmetic circuit, and FIG. FIG. 7 is a block diagram showing the fourth arithmetic circuit, FIG. 8 is a block diagram showing the fifth arithmetic circuit, and FIG. 9 is a seventh diagram. FIG. 10 is a block diagram showing a sixth arithmetic circuit, FIG. 11 is a block diagram showing an average value circuit, FIG. 12 is a block diagram showing an eighth arithmetic circuit, and FIG. The figure is a block diagram showing one phase of the control signal forming circuit (9), and Fig. 14 is the wave of each part of the circuit of Fig. 13. FIG. 15 is a block diagram showing a modified fundamental wave signal generating circuit of the modified example, and FIG. 16 is a block diagram showing a fundamental wave component supply circuit of the modified example. (1u) (1v) (1w) ... power supply line, (2) ... load, (3) ... fundamental wave component supply circuit, (4a) (4b) (4c) ... current detector, (5) ... signal processing circuit , (10) ... PWM conversion circuit, (15) ... First arithmetic circuit for obtaining instantaneous imaginary current, (17) ... Fundamental wave component extraction circuit, (21) ... Fundamental wave compensation amount signal generation circuit, (26) ... A sixth arithmetic circuit for obtaining an instantaneous actual current, (28) ... An instantaneous actual current harmonic component extraction circuit.

Claims (1)

[Claims] 1. A first-phase, second-phase and third-phase current (I _U , _IV ) of a three-phase load (2) connected to a three-phase AC power line.
I _W ), and based on the currents (I _U , I _V , I _W ) of the first, second and third phases, the instantaneous reactive currents (I) of the first phase, the second phase and the third phase.
_Uq , I _Vq , I _Wq ), the first, second and third instantaneous reactive currents (I _Uq , I _Vq ,
I _Wq ) to obtain an effective value (a, b, c) of the fundamental wave component or a value proportional _{thereto, and} the effective value (a, b) of the fundamental wave component of the instantaneous reactive current of each phase represented by a line current. b, c) or a value proportional thereto is converted into a phase current (x, y, z), a reactive current composed of a capacitor or a reactor and a controllable switching element connected to a three-phase AC power line. The fundamental wave component supply circuit (3) is connected to the phase current (x,
control so as to compensate the fundamental wave component of the reactive current of the three-phase load (2) based on y, z), and the instantaneous reactive current (I _q or I _Uq , I for all three phases or for each phase).
_Determining the harmonic components (ΔI _qU , ΔI _qV , ΔI _qW ) of each phase of the instantaneous reactive current on the basis of _Vq , I _Wq ), the first, second and third phases of the three-phase load (2) The harmonic components (ΔI _pU , ΔI _pV , ΔI _pW ) of each phase of the instantaneous active current based on the currents (I _U , I _V , I _W ) of the instantaneous active current, and the harmonic components of each phase of the instantaneous reactive current. (ΔI _qU , Δ
I _qV , ΔI _qW ) and the harmonic component (ΔI _pU , ΔI _pV , ΔI _pW ) of each phase of the instantaneous active current, to obtain a harmonic added signal (I _Uh , I _Vh , I _Wh ), A three-phase pulse width modulation conversion circuit (10), which is connected to the three-phase AC power supply line and is composed of a reactor or a capacitor and a controllable switching element, is used to detect ineffective and effective harmonic components of the three-phase AC power supply line. A power adjusting method comprising: controlling based on the harmonic addition signals (I _Uh , I _Vh , I _Wh ) so as to be removed.