JP3104492B2 - Power harmonic / reactive power compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power harmonic and reactive power compensating device such as an active power filter or a reactive power compensating device (also referred to as SVG) having an inverter as a main component. .

[0002]

2. Description of the Related Art A method for deriving a compensation current of a conventional reactive power compensator using instantaneous power / instantaneous reactive power theory is disclosed in
Kanazawa, Fujita, Nambae: "Generalized Theory of Instantaneous Reactive Power and Its Application" IEEJ Transactions on Electronics, B, 103, 7, pp48
The explanation is based on 3-490, July 1983. Instantaneous power p and instantaneous reactive power q are α voltage e _α , β voltage e _β , α current
It is represented by the following equation using i _α and β current i _β .

[0003]

(Equation 1)

FIG . 7 is a diagram showing a configuration of a conventional reactive power compensator provided in a three-phase three-wire power system. Instantaneous power p, the instantaneous reactive power q can be determined in each part of the system of FIG. Also, the instantaneous power p and the instantaneous reactive power q
Is obtained, the current flowing through that portion can be obtained from the following equation.

[0005]

(Equation 2)

[0006] The suffix S indicates the power supply side of the system, and the suffix L indicates the load side.
The reactive power compensator is represented by a subscript C, and the following equation is obtained from the equation (4).

[0007]

(Equation 3)

When the reactive power compensator supplies the harmonic component of the load current, the instantaneous power p _C and the instantaneous reactive power q _C supplied by the reactive power compensator are expressed by the following equations. The subscript AC represents an AC component, and the subscript DC represents a DC component. p _C = p _LAC (8-1) q _C = q _LAC (8-2) Note that the equations (8-1) and (8-1) (hereinafter, both equations are simply referred to as equation (8)) are load currents. Is supplied from the reactive power compensator.

As can be seen from the equation (6), the instantaneous load power p _L can be derived from the measured values of the voltages e _α and e _β and the load currents i _Lα and i _Lβ . p _LAC is the AC component and can be extracted from the instantaneous load power p _L by an appropriate circuit. As can be seen from equation (6), the instantaneous load reactive power q _L can also be derived using the measured values of the voltages e _α and e _β and the load currents i _Lα and i _Lβ . Therefore, the instantaneous power p _C and the instantaneous reactive power q _C can be derived from the equation (8). Therefore, as can be seen from equation (7), the compensation currents i _Cα and i _Cβ
Are these instantaneous power p _C , instantaneous reactive power q _C and voltage e _α ,
It can be derived by using the measured value of e _β. further,
The instantaneous compensation current commands i _Ca , i _Cb , i _Cc for each phase can be derived from the currents i _Cα , i _Cβ using the equation (3).

In FIG. 7, reference numeral 1 denotes a power source of a three-phase three-wire power system, 2 denotes a load, 3 denotes a three-phase three-wire inverter which is a component of the reactive power compensator, and 41 detects a phase voltage of the system. A system voltage detector, 22 is a load current detector for detecting a system phase current, and 5 is an α voltage from each phase voltage of the detector 41.
The first αβ conversion circuit 6 for deriving e _α and β voltage e _β is configured to calculate α currents i _Lα and β from the negative current of each phase of the load current detector 22.
A second αβ conversion circuit 7 for deriving the current i _Lβ , 7 is a load instantaneous power derivation circuit for deriving an instantaneous load power p _L from the outputs of the first and second αβ conversion circuits 5 and 6, and 8 is a first and a second 2 is a load instantaneous reactive power deriving circuit that derives instantaneous load reactive power q _L from the outputs of the αβ conversion circuits 5 and 6; 9 is a Δ derivation circuit that derives Δ from the output of the first αβ conversion circuit 5; A first AC component extraction circuit for extracting an AC component p _LAC from the output of the instantaneous load power derivation circuit 7; a second AC component extraction circuit 27 for extracting an AC component q _LAC from the output of the instantaneous load reactive power derivation 8; 10 is a circuit that derives α, β compensation currents i _Cα and i _Cβ from the outputs of the first αβ conversion circuit 5, the Δ derivation circuit 9, the AC component extraction circuit 26, and the AC component extraction circuit 27. α, β compensation current i
_Cα, i to derive the _i Cβ Cα · i Cβ derivation circuit, 11
Is a phase component conversion circuit for deriving each phase compensation current command value i _Ca , i _Cb , i _Cc from the output of the i _Cα · i _Cβ derivation circuit 10.

[0011]

When a compensation current deriving circuit using a conventional instantaneous power / instantaneous reactive power theory is adopted in a reactive power compensator, Kirchhoff's first law and (5), (6), From equations (7) and (8), the current flowing from the power supply side of the system , that is, the system current _isa ,
_i sβ becomes the following equation.

[0012]

(Equation 4)

When the system voltage is a sine wave (when only the fundamental wave component exists), the voltages e _α and e _β are sine wave alternating currents. In the steady state, the DC component p _LDC of the instantaneous power on the load side is a constant value. Therefore, if the delta is only the DC component, 1 / delta becomes DC, i _sa, i _{S [beta} is a sine wave. Naturally, the system phase currents _isa , _isb , and _isc also have a sine wave. However, if Δ contains an AC component,
The AC component is also included in 1 / Δ, i _sα , i
_The harmonic component is included in _sβ . This harmonic component is not preferable because it causes an induction failure. The case where the AC component is included in Δ is the following case. (1) Harmonic components are included in the system voltage. (2) Even if the system voltage is a sine wave, it is asymmetric. That is, a negative-phase component and a zero-phase component are included in addition to the positive-phase component. The latter case is common. The conventional scheme eventually gives the desired result only in the case of sinusoidally symmetric three-phase voltages. Furthermore, from the equations (1), (2) and (3), the instantaneous reactive power q is

[0014]

(Equation 5)

When the system has a symmetric three-phase voltage, (e)
_c− e _b ) / √3 is a voltage obtained by advancing e _a by 90 °, (e _a
-E _c) / √3 the voltage is advanced 90 ° with e _b, (e _b -
e _a) / √3 becomes a voltage which is advanced 90 ° to e _c, the mean value of the instantaneous reactive power q is the reactive power (however, have a reactive power by leading current to positive). But asymmetric 3
In the case of the phase voltage, the average value of the instantaneous reactive power q does not represent the reactive power. The above is the problem of the conventional reactive power compensating device for power using instantaneous power and instantaneous reactive power.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. If the system voltage is a sine wave, it is possible to use not only a symmetric three-phase voltage but also an asymmetric three-phase voltage. It is another object of the present invention to provide a reactive power compensator that supplies a harmonic current flowing to a load, a reactive current and a negative-phase current if necessary, and that does not generate a harmonic component in a system current.

[0017]

A power harmonic / reactive power compensator according to claim 1 of the present invention uses a conventional method .
Instantaneous reactive power defined differently from the definition of instantaneous reactive power
To derive the instantaneous reactive power based on this new definition
Phase shifting means for delaying 90 ° each phase instantaneous voltage in order, the
Instantaneous reactive power calculation circuit, the instantaneous reactive power to derive the instantaneous reactive power of phase segregated from the output and the phase current of the phase shifting means
Extracts the AC component from the output of the arithmetic circuit and shifts the phase to the AC component
Compensation current finger that derives the compensation current command value by multiplying the output of the circuit
It is provided with a price calculation circuit .

According to the second and third aspects , the phase shift means is provided.
In this case , a phase delay circuit or a memory is used.

(Delete)

According to a fourth aspect of the present invention, in a three-phase three-wire power system, an instantaneous reactive power calculation circuit is configured using two-phase current signals of the three-phase three-wire power system .

[0021] pertaining to claim 5, 6, 7, 8 term, complement
In deriving the compensation current command value , a voltage obtained by delaying each phase voltage by an arbitrary angle θ other than 90 ° is used.

[0022]

According to the present invention, there is provided a power harmonic according to claim 1 of the present invention.
As long as the system voltage does not contain harmonic components, the power compensator has a new constant whose true value represents the true reactive power not only when the system voltage is symmetric but also when it is asymmetric.
The instantaneous reactive power based on the right is used. That is, in the present invention, the instantaneous reactive power q is set to 90
° Defined as the sum of three phases of the product of the delayed voltage instantaneous value.
The reason for using the phase voltage delayed by 90 ° instead of the phase voltage advanced by 90 ° is to make the reactive power due to the delayed current positive. When the instantaneous reactive power q is expressed by an equation, it is as follows. _{q = e a 'i a +} e b' i b + e c 'i c (10) However, e _a': e _a a 90 ° delayed voltage e _b ': voltage of e _b delayed 90 ° e _c': Voltage at which e _c is delayed by 90 ° On the other hand, instantaneous power p is expressed by the following equation as in the conventional case. _{p = e a i a + e} b i b + e c i c (11) to be considered a three-phase four-wire power system. Neutral current i ₀ is given by the following equation. _{i 0 = i a + i b} + i c (12) (10), (11), the following equation is obtained from equation (12).

[0023]

(Equation 6)

The following equation is obtained from the equation (13).

[0025]

(Equation 7)

Equations (13) and (14) hold for each part of the system. The instantaneous power p _C and the instantaneous reactive power q _C supplied by the reactive power compensator are determined as shown in Expression (8), and the neutral current i
_{If C0 is set} to i _L0 , the compensation current command i _Ca ,
i _Cb and i _Cc are represented by the following equations.

[0027]

(Equation 8)

Similarly, from the equation (14), the system current _isa ,
_isb and _isc are represented by the following equations.

[0029]

(Equation 9)

In the method of the present invention, (13) and (1)
Equations 4), (15), and (16) correspond to equations (1), (4), (7), and (9) in the conventional method, respectively. When the system voltage is asymmetric, an AC component occurs in addition to the DC component in Δ in equation (9) in the conventional method.
Δ ₄ ′ in equation (16) in the present invention is only a DC component. Therefore, as can be seen from equation (16), the present invention
According to this, each of the system phase currents _isa , _isb , and _isc does not include a harmonic component, and a good operation is performed.

The method using the phase delay circuit according to the second aspect or the method using the memory according to the third aspect uses the phase amounts directly without using the αβ conversion used in the conventional method. Becomes easier. Further, since the circuit is simplified, a highly accurate output current command value can be obtained.

(Delete)

In the three-phase three-wire circuit according to the fourth aspect , the following equation is satisfied. _{i c = - (i a +} i b) (17) (17) Equation (10) are substituted into Equation (11), the following equation is obtained.

[0034]

(Equation 10)

The following equation is obtained from the equation (18).

[0036]

[Equation 11]

Equations (18) and (19) hold for each part of the system. When the instantaneous power p _C and the instantaneous reactive power q _C are determined as shown in Expression (8), the compensation current commands i _Ca and i _Cb are expressed by the following expressions from Expressions (8) and (19).

[0038]

(Equation 12)

Similarly, from equations (8) and (19), system currents _isa and _isb are expressed by the following equations.

[0040]

(Equation 13)

The definitive to the present invention (18), (19),
Equations (20) and (21) are conventional equations (1),
This corresponds to equations (4), (7) and (9). If the system voltage is asymmetrical, the Δ conventional (9) is an AC component in addition to the DC component is generated, corresponding in the present invention (21)
Δ ₃ ′ in the equation is only a DC component. Therefore, (21)
As can be seen from the equation , according to the present invention, each system phase current i
_sa and _isb do not include harmonic components. Therefore, the current i
_{The sc} contains no harmonic components. This departure from the above
According to the description, better operation is possible.

According to claim 5, θ is used instead of 90 °.
A circuit that derives a phase voltage delayed only by 90 degrees has better transient response characteristics than a circuit that derives a phase voltage delayed by 90 degrees if θ is set to less than 90 °. By selection, the AC component of f defined by the equation (22) is reduced, and the AC component of f is separated from the above f.
The transient response characteristics of the extracted circuit can be improved. _{f = e a "i a +} e b" i b + e c "i c (22) _{However, e a", e b "} , e c": Each e _a, e _b, e _c
(11), (12), (22) obtained by delaying the phase angle θ by
The following equation is obtained from the equation.

[0043]

[Equation 14]

The following equation is obtained from the equation (23).

[0045]

(Equation 15)

Δ ₄ "has only a DC component. For example, e _a " is expressed by the following equation using e _a 'and e _a . e _a "= e _a 'sin θ + e _a cos θ Therefore, the above f is expressed as follows using the instantaneous power p and the instantaneous reactive power q: f = pcos θ + q sin θ (25) (23), (24), ( Equation (25) is established in each part of the system: the instantaneous power p _C and the instantaneous reactive power q _C supplied by the reactive power compensator are determined as in Equation (8), and the current i _C0 is equal to the current i _L0. For example, the following equation is obtained from the equations (8), (24), and (25).

[0047]

(Equation 16)

Similarly, (8), (24), (25)
From the equations, the system currents _isa , _isb , and _isc are expressed by the following equations.

[0049]

[Equation 17]

When the system voltage is asymmetric, the conventional equation (9)
In Δ at , an AC component occurs in addition to the DC component,
Delta ₄ "of the corresponding (27) in the present invention is only the DC component. Accordingly, harmonic strain phase currents i _sa, i _sb, i _sc according to the invention, as seen from (27) No components are included and better operation is possible.

The method using the phase delay circuit described in claim 5 or the method using the memory described in claim 6 simplifies the circuit because αβ conversion is not used. Further, since the circuit is simplified, a highly accurate output current command value can be obtained.

(Delete)

In the three-phase three-wire circuit according to the eighth aspect, equation (17) holds. Equation (17) is replaced by (11), (2)
2) Substituting into the equation, the following equation is obtained.

[0054]

(Equation 18)

The following equation is obtained from the equation (28).

[0056]

[Equation 19]

Δ ₃ "has only a DC component (2).
Equations (8) and (29) hold for each part of the system. When the instantaneous power p _C and the instantaneous reactive power q _C are determined as in equation (8),
From equations (8), (25) and (29), the compensation current command i _Ca ,
i _Cb is represented by the following equation.

[0058]

(Equation 20)

As can be seen from equation (30), p _LAC , f
The output current of the reactive power compensator can be derived using the _LAC . Similarly, from equations (8), (25) and (29), the system currents _isa and _isb are expressed by the following equations.

[0060]

(Equation 21)

Δ ₃ "in equation (31) is only a DC component.
Therefore, as can be seen from equation (31), the system phase currents _isa and _isb do not include harmonic components, and a better operation is achieved.
Will be possible .

[0062]

[Embodiment 1] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the three-phase three-wire system of FIG. 1, 1 is a power supply, 2 is a load,
Is a three-phase three-wire inverter, 21 is a system voltage detector, 22
Is a load current detector, 23 is a load instantaneous power deriving circuit that derives load instantaneous power p _L from detection results of the system voltage detector 21 and the load current detector 22, and 24 is a phase of the detected instantaneous voltage of the system voltage detector 21. 90 ° delay circuit for delaying 90 °
25 load instantaneous reactive power deriving circuit for deriving the load instantaneous reactive power q _L from the output of the load current detector 22 and 90 ° delay circuit 24, the first 26 for extracting an AC component p _LAC from the load instantaneous power deriving circuit 23 Is an AC component extraction circuit for extracting an AC component q _LAC from the instantaneous load reactive power deriving circuit 25, and 28 is a system voltage detector 2
1 and delta ₃ from the output of the 90 ° delay circuit 24 'outputs the delta _3'
The deriving circuit 29 is provided with a compensation current command i _Ca based on the output of the system voltage detector 21, the 90 ° delay circuit 24, the first AC component extracting circuit 26, the second AC component extracting circuit 27, and the Δ ₃ ′ deriving circuit 28. i _Ca · i _Cb derivation circuit for outputting a i _Cb, 30 is i _Ca
An i _Cc deriving circuit that outputs a compensation current command i _Cc from the output of the i _Cb deriving circuit 29; The output current of the three-phase three-wire inverter 3 is made to follow the compensation current commands i _Ca , i _Cb and i _Cc .

Next, the operation will be described. In the system voltage detector 21 between lines instantaneous voltage _{(e a -e c), (} e b -e
_c ) Detect. In the load current detector 22, the load a, b
The phase instantaneous currents i _La and i _Lb are detected. The instantaneous load power deriving circuit 23 calculates the instantaneous load power p _L using the following equation obtained from the equation (18). _{p L = (e a -e c} ) i La + (e b -e c) the i _Lb (32) 90 ° delay circuit _{24 (e a -e c),} (e b -e
the phase of _c) delayed _{90 ° (e a -e c)} ', (e b
−e _c ) ′, which are respectively (e _a ′ −
e _c ′), (e _b ′ −e _c ′). The instantaneous load reactive power deriving circuit 25 derives the instantaneous load reactive power q _L according to the following equation obtained from equation (18). extracts _{q L = (e a '-e} c') i La + (e b '-e c') i Lb (33) AC component p _LAC from the first AC component extracting circuit 26 in the load instantaneous power p _L And a second AC component extraction circuit 27
Then, an AC component q _LAC is extracted from the instantaneous load reactive power q _L. Delta ₃ derived 'from the detected voltage and the 90 degree phase voltage which is delayed 90 ° in the delay circuit 24 of the derivation circuit 28 in system voltage detector 21 (19) △ ₃ according expression' a. The i _Ca · i _Cb derivation circuit 29 performs the operation of the equation (20). That is, a function consisting of the detection voltage of the system voltage detector 21 and a voltage obtained by delaying the phase of the 90 ° delay circuit 24 by 90 ° is represented by q _LAC output from the second AC component extraction circuit 27 or the first AC component extraction circuit. The compensation current commands i _Ca and i _Cb are derived by multiplying by p _LAC which is the output of 26 and adding both of them.
In i _Cc derivation circuit 30 derives the i _Cc according to the following formula. i _Cc = − (i _Ca + i _Cb ) (34) The outputs of the i _Ca · i _Cb derivation circuit 29 and the i _Cc derivation circuit 30 are compensation current commands, and follow the output current of the three-phase three-wire inverter 3.

Embodiment 2 FIG. In the first embodiment, the 90 ° delay circuit 24
Although the description has been given of the case where the delayed line voltage instantaneous value is obtained from the line voltage instantaneous value passed through the phase delay circuit, the AD converter 6 is used instead of the 90 ° delay circuit 24 as shown in FIG.
0, a memory 61 and a DA converter 62 are provided to output the instantaneous line voltage value stored in the past for a time corresponding to 90 °. In this way, errors caused by temperature changes are reduced as compared with the first embodiment.

Embodiment 3 FIG. In the first and second embodiments, the case where the second AC component extraction circuit 27 extracts the AC component q _LAC from the instantaneous load reactive power q _L output from the instantaneous load reactive power derivation circuit 25 has been described. As shown in FIG. 3, the AC component extraction circuit 27 is removed, and the output q _L of 25 is directly input to 29 to derive the compensation current commands i _Ca and i _Cb . That is, in equation (20), the compensation current commands i _Ca and i _Cb are derived using the instantaneous load reactive power q _L instead of q _LAC . In this case, the reactive power compensator supplies a harmonic current and a reactive current.

Embodiment 4 FIG. Although the first, second, and third embodiments deal with the case of a three-phase three-wire system, as shown in FIG.
The three-phase four-wire system uses a three-phase four-wire inverter 4 unlike 3 in FIG. 1, and differs from the system voltage detector 21 in FIG.
Instantaneous voltage of each phase was measured from the neutral line in the system voltage detector 41 e _a, e _b, detects a e _c. Further, unlike the load current detector 22 of FIG. 1, the load current detector 42 detects three-phase load currents i _La , i _Lb , and i _Lc . In the 90 ° delay circuit 34, the phase is output from the output of the system voltage detector 41 by 90 °.
° derive e _a ′, e _b ′, and e _c ′. The load instantaneous power deriving circuit 43 derives the load instantaneous power p _L from the outputs of the system voltage detector 41 and the load current detector 42 according to the following expression obtained from Expression (11). _{p L = e a i La +} e b i Lb + e c i Lc (35) 90 ° in accordance with the following formula obtained from the load in the instantaneous reactive power derivation circuit 45 (10) delay circuit 34, the output of the load current detector 42 The instantaneous load reactive power q _L is derived. q _L = e _a 'i _La + e _b ' i _Lb + e _c 'i _Lc (36) Δ ₄ ' In the derivation circuit 48, the 90 ° delay circuit 34 and the output of the system voltage detector 41 are Δ ₄ 'in accordance with the equation (14). Is derived. The adder circuit 46 derives a load neutral line current i _L0 from the output of the load current detector 42 according to equation (12). The compensating current deriving circuit 49 converts the compensating current commands i _Ca , i _Cb , i _Cc into the first AC component extracting circuit 2 based on equation (15).
6. Second AC component extraction circuit 27, 90 ° delay circuit 3
4. Derived from the outputs of the system voltage detector 41, the adding circuit 46, and the Δ ₄ 'deriving circuit 48. These compensation current commands have three phases and four
The output current of the linear inverter 4 is made to follow.

Embodiment 5 FIG. In the first embodiment, the 90 ° delay circuit 24 derives a voltage obtained by delaying the system line voltage by 90 °, and the load instantaneous reactive power deriving circuit 25 determines the load instantaneous reactive power from the output of the 90 ° delay circuit 24 and the load current. Although the case of deriving the power q _L has been described, as shown in FIG. 5, the line voltage instantaneous value e _a "− delayed by an arbitrary angle θ instead of the 90 ° delay circuit 24 is used.
e _c ", e _b" provided θ delay circuit 54 for deriving a -e _c ".
The following f is obtained from the output of the θ delay circuit 54 and the outputs i _La and i _{Lb of the} load current detector 22 according to the following equation obtained from the equation (28).
_The circuit that outputs _L is the same as the instantaneous load reactive power deriving circuit 25 in FIG. _{f L = (e a "-e} c") i La + (e b "-e c") i Lb (37) Therefore, theta delay circuit 54 based on the output from (28) of the load current detector 22 Load instantaneous reactive power derivation circuit 2
At 5, the above f _L is derived. Incidentally, (29) e _a -e _c according _{equation, e b -e c, e a} "-e c", e b "-e c"
Deriving a delta ₃ "from is the same as the delta ₃ 'deriving circuit 28 in FIG. 1. Accordingly, the system voltage detector 21,
deriving a delta ₃ "in delta ₃ 'deriving circuit 28 according to the output (29) of θ delay circuit 54. compensation current command i _Ca,
i _Cb is a system voltage detection circuit 21, a first AC component extraction circuit 26, a second AC component extraction circuit 27, a Δ ₃ ′ derivation circuit 2
8. From the output of the θ delay circuit 54, i
It is derived in the _Ca · i _Cb derivation circuit 29. The i _Cc deriving circuit 30 derives a compensation current command i _Cc from the output of the i _Ca · i _Cb deriving circuit 29. These compensation current commands have three phases and three
The output current of the linear inverter 3 is made to follow. A circuit that derives a line voltage delayed by θ is less than a circuit that derives a line voltage delayed by 90 ° if θ is less than 90 °.
Transient response is improved, it is possible to further AC component f _LAC of the f _L is reduced by appropriately choosing θ according to the load, to improve the transient response characteristics of the circuit for extracting the f _LAC from f _L .

Embodiment 6 FIG. In the fourth embodiment, at 34, the system line voltage 9
Deriving the voltage delayed by 0 °, the load instantaneous reactive power deriving circuit 4
5, the instantaneous reactive power q _{L based on} the output of the 90 ° delay circuit 34 and the load current output from the load current detector 42.
Has been described, but as shown in FIG.
Instead of the delay circuit 34, there is provided a θ delay circuit 64 that outputs instantaneous values e _a , e _b , and e _{c of} voltages delayed by an arbitrary angle θ from each phase voltage, which is obtained from Expression (22). A circuit that derives the following f _L from the output of the θ delay circuit 64 and the outputs i _La , i _Lb , and i _{Lc of the} load current detector 42 according to the following equation is shown in FIG.
, The same as the instantaneous load reactive power deriving circuit 45. f _L = e _a "i _La + e _b " i _Lb + e _c "i _Lc (37) Therefore, in the instantaneous reactive power deriving circuit 45, the output of the load current detector 42 and the output of the θ delay circuit 64 are (22)
The above f _L is derived based on the equation. It should be noted that e _a , e _b , e _c and e _a ", e _b ", e _c "to Δ ₄ "
Delta ₄ "derivation circuit for deriving a is the same as the delta ₄ 'deriving circuit 48 in FIG. 4. Thus, the system voltage detector 41,
deriving a delta ₄ "in delta ₄ 'deriving circuit 48 in accordance with the output from (24) of θ delay circuit 64. compensation current command i _Ca,
i _Cb and i _Cc are a first AC component extraction circuit 26, a second AC component extraction circuit 27, a system voltage detector 41, and an addition circuit 4.
6, derived from the output of the θ delay circuit 64 in the compensation current deriving circuit 49 according to the equation (26). The output current of the three-phase four-wire inverter 4 is made to follow these compensation current commands. The circuit that derives the phase voltage delayed by θ is 90 °
If it is less than 90%, the transient response characteristic is better than that of a circuit that derives a phase voltage delayed by 90 °, and the AC component f _{LAC of} f _L is reduced by appropriately selecting θ according to the load, and f Transient response characteristics of a circuit that extracts f _LAC from _L can be improved. Further, in the above embodiment, a case is considered in which a capacitor or a reactor is present on the DC side of the inverter. However, a case where a storage battery or a superconducting energy storage device is present may be provided, and the same effects as those in the above embodiment can be obtained. .

[0069]

As described above, according to the present invention, even when a negative phase component and a negative phase component exist in the system voltage, a new instantaneous value different from the conventional definition is obtained in which the average value is correct reactive power. Since the compensation current derivation circuit using this amount is adopted by adopting the definition of reactive power, good power with good characteristics such that the system current becomes a sine wave even when there is a negative phase component or a zero phase component in the system voltage Harmonic / reactive power compensator can be obtained.
Further, since the αβ conversion conventionally used is not used, the output current deriving circuit is simplified, and as a result, an output current command value with high accuracy can be obtained.

The output current command value required to derive the
In the method of obtaining an instantaneous voltage obtained by delaying each phase voltage of the three-phase power supply by 90 ° using a phase delay circuit, the apparatus can be inexpensive because the phase delay circuit can be formed only from an operational amplifier, a capacitor, and a resistor.

The output current command value required to derive the
In a method of using a memory to obtain an instantaneous voltage obtained by delaying each phase voltage of the three-phase power supply by 90 °, an error due to a temperature change is reduced.

A circuit that derives a voltage delayed by θ less than 90 ° has a better transient response characteristic than a circuit that derives a voltage delayed by 90 °, and furthermore, by appropriately selecting θ according to the load, f _L Since the AC component f _LAC becomes smaller and the transient response characteristic of the circuit that extracts f _LAC from f _L can be improved, the output current command value is derived based on the instantaneous voltage obtained by delaying the voltage by an arbitrary angle θ. A device provided with such a circuit has improved transient response characteristics.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a block diagram showing Embodiment 5 of the present invention.

FIG. 6 is a block diagram showing Embodiment 6 of the present invention.

FIG. 7 is a block diagram of a conventional reactive power compensator based on the instantaneous power / reactive power theory.

[Explanation of symbols]

Reference Signs List 1 power supply 2 load 3 three-phase three-wire inverter 4 three-phase four-wire inverter 5 αβ component conversion circuit 6 αβ component conversion circuit 7 load instantaneous power derivation circuit 8 load instantaneous reactive power derivation circuit 9 Δ derivation circuit 10 i _Cα , i _Cβ derivation circuit 11 Each phase component conversion circuit 21 System voltage detector 22 Load current detector 23 Load instantaneous power derivation circuit 24 90 ° delay circuit 25 Load instantaneous reactive power derivation circuit 26 AC component extraction circuit 27 AC component extraction circuit 28 Δ ' Derivation circuit 29 i _Ca , i _Cb derivation circuit 30 i _Cc derivation circuit 34 90 ° delay circuit 41 System voltage detector 42 Load current detector 43 Load instantaneous power derivation circuit 44 Phase angle θ delay circuit 45 Load instantaneous reactive power derivation circuit 46 summing circuit 48 delta ₄ 'deriving circuit 49 compensation current derived circuit 54 theta delay circuit 60 AD converter 61 memory 62 DA converter 64 theta Re circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomohiro Kobayashi 1-2-1, Wadazakicho, Hyogo-ku, Kobe-shi, Mitsubishi Electric Corporation Kobe Works (56) References JP-A-55-125035 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J 3/18 G05F 1/70

Claims (8)

(57) [Claims] 1. A harmonic of a load current in a three-phase power system.
High for power to supply current or reactive current or negative phase current
In harmonic and reactive power compensator, phase shifting means, the output of該移phase means and said 3 to derive a voltage phase and the delayed 90 ° in phase instantaneous voltage of the three-phase power system
Instantaneous reactive power calculating circuit for deriving the instantaneous reactive power of phase segregated from the product of the phase instantaneous current phase power system, disable conductive when instantaneous
An AC component is extracted from the output of the force calculation circuit, and the AC component is
Compensation for deriving a compensation current command value by multiplying the output of the phase shift circuit
A harmonic / reactive power compensating device for electric power, comprising a compensation current command value calculating circuit . 2. A phase delay circuit is used as said phase shift means.
2. The power harmonic / reactive power compensator according to claim 1, wherein: As claimed in claim 3 wherein said phase shifting means, writing a value of each phase instantaneous voltage in the memory, claim 1, characterized by being configured to determine by reading after a time determined it
The harmonic / reactive power compensator for power described. 4. A three-phase three-wire electric power system, the 3-phase 3
The instantaneous reactive power using the two-phase current signal of the wire power system
4. An arithmetic circuit according to claim 1, wherein:
The power harmonic / reactive power compensator according to any one of the above. 5. A high-frequency power supply for supplying a harmonic current or a reactive current or a negative-phase current of a load current of a three-phase power system.
In the reactive power compensator , the phase of the instantaneous voltage of each phase of the three-phase power system is set to an arbitrary angle θ
Phase shift means for deriving a delayed voltage, an output of the phase shift means ,
From the product of the instantaneous current of each phase of the three-phase power system, a function pcos θ +
function arithmetic circuit for deriving a value of qsinθ, the function number of operation times
Extract the AC component from the output of the road, and
Compensation current to derive compensation current command value by multiplying output of phase means
A power harmonic / reactive power compensator comprising a command value calculation circuit . 6. A phase delay circuit is used as said phase shift means.
Power harmonics and reactive power compensation device according to claim 5, characterized in that the. 7. The phase shifting means according to claim 5, wherein a value of the instantaneous voltage of each phase is written in a memory and read out after a predetermined time to obtain the value.
The harmonic / reactive power compensator for power described. 8. The three-phase three-wire electric power system, the 3-phase 3
Function calculation circuit using two-phase current signals of a wire power system
Power harmonics and reactive power compensator according to <br/> any one of claim 5, wherein 7 that constitute the.