JP2001045746A - Circuit for controlling harmonic current constituent of power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the harmonic current to zero that is superimposed on the input and output currents of a power converter without having to use a filter incorporating capacitors as main constituents. SOLUTION: A DC-DC converter structured by parallel connection of a first voltage raise chopper that operates at the control factor of 50% to a second voltage raise chopper part operates with reverse phase against a first chopper which a control factor of 50% is connected to the pre-stage of an inverter device functioning as a power converter. Also, a second chopper circuit 30, a DC-DC converter 40 and third chopper circuit 60 are added to a first chopper circuit 20 which functions as the power converter. The harmonic current outputted by the first chopper circuit 20 is calculated from the constant of the circuit constituents of the first chopper circuit 20 and the third chopper circuit 60 and the control factor of the first transistor 21 of the first chopper circuit 20. A reverse-phase harmonic current that cancels this harmonic current is outputted from the third chopper circuit 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic current component suppressing circuit for a power converter, which suppresses a harmonic current component included in an input current or an output current thereof in accordance with a switching operation of the power converter.

[0002]

2. Description of the Related Art Power conversion can be freely performed by turning on / off a semiconductor switching element such as a transistor or a thyristor. A harmonic current component is generated in the current flowing to the load side, and the harmonic current causes various inconveniences. Therefore, it is important to suppress the harmonic current generated in the power converter.

FIG. 5 is a circuit diagram showing a conventional example of an input current harmonic suppression circuit for suppressing a harmonic component of a current input to a power conversion device. Shows the case.

In FIG. 5, DC power from a DC power supply 1 is input via an input impedance 2 to an inverter device 3 as a power converter. This inverter device 3 comprises a smoothing capacitor 5 and a DC / AC converter 6,
The input DC power is converted into AC power to drive the induction motor 7. In order to suppress a harmonic current component included in the input current to the inverter device 3, an input filter 4 is provided upstream of the inverter device 3. Is provided.

[0005] Figure 6 is a waveform diagram showing a state of the respective portions of the conventional circuit shown in FIG. 5, FIG. 6 is the change in the input current I ₃ of the DC / AC converter 6, 6 a smoothing capacitor change in the input current I ₂ to 5, FIG. 6 is a I ₁ (input current ie inverter 3) the output current of the input filter 4 change, FIG. 6 is the change in the input current I ₀ of the input filter 4, the each Is shown.

In FIG. 6, the input current of the DC / AC converter 6 greatly pulsates with the operation of the converter 6 (see FIG. 6).
Is a smoothing capacitor 5 installed before the DC / AC converter 6
This pulsating current shunts (see FIG. 6),
The harmonic current I _1rip included in the input DC current I _DC to the inverter device 3 is considerably suppressed (see FIG. 6). However, in order to further reduce the harmonic current, an input filter 4 composed of a reactor and a capacitor is provided in a stage preceding the inverter device 3. As a result, the harmonic current I _0rip included in the input current I ₀ of the input filter 4 becomes
It is _smaller than the above-mentioned harmonic current I _1rip (see FIG. 6).

FIG. 7 is a circuit diagram showing a conventional example of an output current harmonic suppression circuit for suppressing a harmonic component of a current output from a power conversion device, and is a circuit diagram of a power conversion device for converting DC power to DC power. Shows the case.

In FIG. 7, DC power from a DC power supply 1 is input to a first chopper circuit 20 as a power conversion device via an input capacitor 11, and the first chopper circuit 20 Transistor 21, diode 22, first reactor 23, and capacitor 24
It consists of. The output side of the first chopper circuit 20 is provided with a first voltage detector 25, and the voltage adjuster 77 sets the voltage detected by the first voltage detector 25 by the voltage setting unit 26 by the adjustment operation. The drive signal is supplied to the drive circuit 78 so as to match the voltage to be applied. The first transistor 21 is turned on and off at a control rate determined by a control signal output from the voltage regulator 77, so that the voltage of the load 8 is controlled to the value set by the voltage setter 26.

FIG. 8 is an operation waveform diagram showing the state of each part of the conventional circuit shown in FIG. 7, FIG. 8 shows the on / off operation of the first transistor 21, and FIG.
Change in the current I ₁₁ flowing in 3, 8 is the change in current I ₁₂ flowing through the capacitor 24, current flows in Figure 8 the load 8 I
Each shows ₁₃ changes. With the on / off operation of the first transistor 21, a large harmonic current I
_Although a current I _{11 including 11 rip} flows through the first reactor 23 (see FIG. 8), since the impedance of the capacitor 24 is generally smaller than the impedance of the load 8,
_Most of the harmonic current I _11rip flowing through the first reactor 23 is shunted to the capacitor 24. This is the harmonic current I _12rip (see FIG. 8). Therefore, the harmonic current I _13rip flowing to the load 8 (see FIG. 8) is the remaining portion of the generated harmonic current. However, if the impedance of the load 8 is small, the shunt ratio with the capacitor 24 changes, and the harmonic current I _13rip to the load 8 may become large.

[0010]

As is apparent from FIGS. 5 and 6 described above, in order to suppress the harmonic current contained in the input current of the power converter, conventionally, a reactor, a capacitor and a In order to further suppress the harmonic current component, the filter capacity must be increased. Also, as the installed capacity of the power converter increases, the filter capacity also needs to be increased. However, no matter how large the filter capacity is, the harmonic current cannot be completely reduced to zero, and the installation of the filter results in an increase in the size of the entire apparatus and a decrease in the operating efficiency of the apparatus. Further, when an external short circuit occurs, the filter may become a current supply source, and the accident may be expanded.

Conventionally, a capacitor is installed on the output side of the power converter in order to suppress a harmonic current contained in the output current. However, the capacity of the capacitor increases as the installed capacity of the power converter increases. However, when the impedance of the load is small, the capacitor capacity must be increased regardless of the installed capacity of the power conversion device. Cannot be completely reduced to zero, and the installation of the capacitor makes the entire device larger,
There is a disadvantage that the operation efficiency of the device is also reduced. Further, when an external short circuit occurs, the filter may become a current supply source, and the accident may be expanded.

An object of the present invention is to suppress a harmonic current superimposed on an input / output current of a power converter to zero without using a filter having a capacitor as a main component.

[0013]

In order to achieve the above-mentioned object, a harmonic current component suppressing circuit of a power converter according to the present invention is connected to a DC power supply and supplies power to a load by switching operation. In the device, control rate 50%
And a second boost chopper operating at a control rate of 50% in the opposite phase to the first boost chopper, and connecting this boost chopper parallel circuit to the DC power supply and the power converter. Insert between

N sets of booster choppers, each operating at a control rate of 100 / n% and maintaining the phase difference between the booster choppers at 2π / n, are connected in parallel. It is inserted between the DC power supply and the power converter.

A harmonic current component of the output current of the power conversion device is calculated from the circuit constant of the power conversion device and the switching operation, and an anti-phase harmonic current component having an opposite phase and the same magnitude as the harmonic current component is calculated. An output side of the separate power conversion device is provided, and an output side of the separate power conversion device is connected to an output side of the power conversion device.

[0016]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, which suppresses a harmonic current component contained in a current input to a power converter for converting DC power into AC power. It represents the case to do.

In the circuit of the first embodiment shown in FIG. 1, a DC / DC converter 10 is installed in front of an inverter device 3 as a power conversion device composed of a smoothing capacitor 5 and a DC / AC converter 6. . This DC / DC converter 10 includes a reactor A12
First consisting of a diode A13 and a transistor A14
Boost chopper, reactor B15 and diode B1
6 and a second step-up chopper comprising a transistor B17 are connected in parallel, and an input capacitor 11 is provided on the input side thereof. Both step-up choppers are operated at a control rate of 50% and in mutually opposite phases.

FIG. 2 is an operation waveform diagram showing the operation state of each part of the circuit of the first embodiment shown in FIG. 1. FIG. 2 shows the operation of the transistor A14, FIG. 2 shows the operation of the transistor B17, and FIG. changes in I ₁ (input current ie inverter 3) the output current of the DC / DC converter 10, FIG. 2 is a change in flowing current I _a reactor A12, 2 is the change in flowing current I _B of the reactor B15 2 shows the change in the input current I ₀ of the DC / DC converter 10.

Transistor A14 and transistor B17
DOO is, in both 50% of the control rate, and by operating in opposite phases, and the harmonic current contained in the flowing current I _A reactor A12, harmonic current contained in the flowing current I _B of the reactor B15 Means that the magnitudes are opposite to each other and have the same magnitude, so that when the two currents are summed, the respective harmonic currents are canceled and become zero. The input capacitor 11 provided in the DC / DC converter 10 can be downsized because its purpose is to suppress the input voltage fluctuation when the load fluctuates.
There is no need to provide a structure that can withstand the passage of harmonic current. Also, the input impedance 2 can be reduced in size because it is not necessary to consider the harmonic current.

In the circuit of the first embodiment already described with reference to FIG.
The DC converter 10 is configured by connecting two sets of step-up choppers in parallel. However, in the circuit according to the second embodiment, n sets (n> 2, such as n = 3) is different from the circuit of the first embodiment in that the booster chopper is connected in parallel with the circuit of the first embodiment, but is otherwise the same, so that the illustration of the circuit of the second embodiment is omitted. In the circuit of the second embodiment, each of the boost choppers has a control rate of 100 / n% (when n = 3,
33.3%) and the phase difference between each boost chopper is kept at 2π / n (2π / 3 when n = 3),
The pulsation component contained in the current input to the n sets of boost chopper parallel circuits can be suppressed to zero as in the case of the circuit of the first embodiment described above.

In the circuits of the first and second embodiments described above, the inverter device 3 (the smoothing capacitor 5 and the D
Although the case where the pulsating component of the current input to the C / AC converter 6 is suppressed has been described above, if the converter generates a current ripple on the input side, it is not limited to the DC / AC converter. Of course, the present invention can be applied.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention, in which a harmonic current component contained in a current output from a power converter for converting DC power into another DC power is suppressed. Is represented.

In the circuit of the third embodiment shown in FIG. 3, the DC power of the voltage V ₀ supplied from the power supply composed of the DC power supply 1 and the input capacitor 11 is converted to V ₁ by the first chopper circuit 20 as a power converter. This is a case where the voltage is reduced to a certain voltage and supplied to the load 8.
Transistor 21, diode 22 and first reactor 2
3 and the capacitor 24. by the way,
When the first chopper circuit 20 is operated alone, as described above in FIGS. 7 and 8, a large harmonic current included in the output current I _13. Therefore, the second chopper circuit 30 including the second transistor 31, the diode 32, the reactor 33, and the capacitor 34, the third transistor 41, the fourth transistor 44, the diodes 42, 43, 46, the insulating transformer 45, and the capacitor 47 Insulated type D
A C / DC converter 40 and a third chopper circuit 60 including a fifth transistor 61, a diode 62, and a second reactor 63 are added.

The first voltage regulator 27 controls the first chopper circuit 2 detected by the first voltage detector 25 by the regulating operation.
In order to make the output voltage of 0 coincide with the value set by the voltage setting device 26, a control signal having a control rate α is output. As a result, the first drive circuit 28 sets the first transistor 21 to the control rate α.
To work with. Since the power supply voltage is V ₀ , the output voltage (that is, load voltage) V ₁ of the first chopper circuit 20 detected by the first voltage detector 25 is as shown in Expression 1.

[0025]

V ₁ = α · V ₀ Assuming that the difference voltage between the power supply voltage V ₀ and the load voltage V ₁ is V ₄ ,

[0026]

V ₄ = V ₀ −V ₁ = (1−α) · V ₀ The second voltage adjuster 37 adjusts the output voltage of the second chopper circuit 30 detected by the second voltage detector 35. V
₂ to the second drive circuit 38 to output a control signal that causes the second drive circuit 38 to match the value calculated by the first calculation circuit 36.
8 operates the second transistor 31. Here, the first arithmetic circuit 36 receives the voltage V ₁ from the first voltage detector 25 and the control rate α from the first voltage regulator 27, and calculates the value of the inductance L ₁₁ of the first reactor 23, and a value of the inductance L ₁₂ of the second reactor 63 constituting the third chopper circuit 60, calculates a voltage V ₂ to the second chopper circuit 30 is output according to equation 3 below.

[0027]

(Equation 3) The third voltage regulator 51 adjusts the output voltage V ₃ of the isolated DC / DC converter 40 detected by the third voltage detector 48 to the value calculated by the second calculation circuit 49 by the adjustment operation. Is output to the third drive circuit 52, and the third drive circuit 52 operates the third transistor 41 and the fourth transistor 44 to convert DC power into AC power. After the AC power is insulated by the insulating transformer 45, it is again converted to DC power by the diode 46. Here, the second arithmetic circuit 49 inputs the voltage V ₁ from the first voltage detector 25 and the control rate α from the first voltage regulator 27, and calculates the value of the inductance L ₁₁ of the first reactor 23, and a value of the inductance L ₁₂ of the second reactor 63 constituting the third chopper circuit 60, calculates a voltage V ₃ to be output is insulated DC / DC converter 40 according to equation 4 below.

[0028]

(Equation 4) Fifth transistor 61 forming third chopper circuit 60
Operates in a phase opposite to that of the first transistor 21, that is, at a control rate of “1−α” by a drive signal from the same first drive circuit 28 as the first transistor 21 described above. As a result, the harmonic current component I _11Rip the current I ₁₁ flowing through the first reactor 23, because the second reactor 63 is opposite phase to the harmonic current component I _12Rip the current I ₁₂ flowing through, both Are summed, the harmonic current is canceled and becomes zero. Therefore the current I ₁₃ flowing to the load 8 does not include a harmonic current.

FIG. 4 is an operation waveform diagram showing the operation state of each part of the circuit of the third embodiment shown in FIG. 3, and FIG.
4 shows the operation of the transistor 21, FIG.
The change in the flowing current I ₁₁ of the first reactor 23, FIG. 4 shows each change in the flowing current I ₁₂ of the second reactor 63, a is.

While the first transistor 21 is on, the harmonic current of the current I ₁₁ flowing through the first reactor 23 is defined as i _1a (see FIG. 4), and the current I ₁₁ flowing through the second reactor 63 is Assuming that the _twelve harmonic currents are i _2a (see FIG. 4), i _1a is represented by Expression 5 and i _2a is represented by Expression 6. Here, T is the operation cycle of the first transistor 21.

[0031]

(Equation 5)

(Equation 6) The condition for canceling the harmonic current is i _1a = i
_2a . Therefore, when Equations 5 and 6 are applied to this condition and arranged, the output voltage set value V ₂ of the second chopper circuit 30 is expressed by Equation 7 below.

[0032]

(Equation 7) Equation 7 is the same as the equation (Equation 3) calculated by the first arithmetic circuit 36 to set the output voltage of the second chopper circuit 30. Further, the current I ₁₂ flowing through the second reactor 63 during the period in which the first transistor 21 is off.
Assuming that the harmonic current of i _2b (see FIG. 4) is i _2b
Is represented by Equation 8 below.

[0033]

(Equation 8) The output voltage set value V ₃ of the insulated DC / DC converter 40 is obtained from Expression 8 and Expression 7 described above, and the value is represented by Expression 9.

(Equation 9) Equation 9 is the same as the equation (Equation 4) calculated by the second arithmetic circuit 49 to set the output voltage of the insulated DC / DC converter 40.

[0034]

In a power converter for performing power conversion by switching operation of a semiconductor switch element, various problems occur due to the superposition of a harmonic current on an input current and an output current. Therefore, conventionally, a filter having a capacitor as a main component is added to the input side and the output side of the power converter to suppress the harmonic current, but when the impedance of the load is small, the power converter is However, there is a disadvantage that a large filter capacitance is required even if the capacitance is small. Also,
No matter how large the filter capacitance, it is difficult to completely eliminate the harmonic current, and there is a disadvantage that the filter reduces the efficiency of the entire device. Further, when an external short circuit occurs, the filter may become a current supply source, and the accident may be expanded. On the other hand, according to the present invention, no filter is used to suppress the harmonic current, so that the efficiency of the device is not reduced, and the input current and the output current are reduced without using a large capacitor or a filter. The effect of suppressing the harmonic current component included in the device to zero can be obtained, and the effect of avoiding an increase in the size of the device can also be obtained. Furthermore,
Since a large-capacity capacitor is not used, the effect of avoiding the possibility of generating an excessive short-circuit current at the time of an accident can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an operation waveform diagram showing an operation state of each part of the circuit of the first embodiment shown in FIG.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is an operation waveform diagram showing an operation state of each part of the circuit of the second embodiment shown in FIG. 3;

FIG. 5 is a circuit diagram showing a conventional example of an input current harmonic suppression circuit for suppressing harmonic components of a current input to a power converter.

FIG. 6 is an operation waveform diagram showing a state of each part of the conventional circuit shown in FIG. 5;

FIG. 7 is a circuit diagram showing a conventional example of an output current harmonic suppression circuit for suppressing harmonic components of a current output from a power conversion device.

8 is an operation waveform diagram showing a state of each part of the conventional circuit shown in FIG. 7;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Input impedance 3 Inverter apparatus as a power converter 4 Input filter 6 DC / AC converter 7 Induction motor 8 Load 10 DC / DC converter 11 Input capacitor 12 Reactor A 13 Diode A 14 Transistor A 15 Reactor B 16 Diode B 17 Transistor B 20 First chopper circuit as power converter 23 First reactor 25 First voltage detector 26 Voltage setting device 27 First voltage regulator 28 First drive circuit 30 Second chopper circuit 35 Second voltage detection Device 36 First arithmetic circuit 37 Second voltage regulator 38 Second drive circuit 40 Insulated DC / DC converter 45 Insulation transformer 48 Third voltage detector 49 Second arithmetic circuit 51 Third voltage regulator 52 Third drive Circuit 60 Third chopper circuit 63 Second reactor

Claims (3)

[Claims] 1. A power converter connected to a DC power supply and supplying power to a load by a switching operation, comprising: a first step-up chopper operating at a control rate of 50%;
0%, the second step-up chopper operates in the opposite phase to the first step-up chopper.
A boost current chopper is connected in parallel, and the boost chopper parallel circuit is inserted between the DC power supply and the power converter. 2. A power converter connected to a DC power supply and supplying power to a load by a switching operation, wherein each of n sets of booster choppers connected in parallel has a control rate.
100 / n% and the phase difference between each boost chopper is 2π
A harmonic current component suppression circuit for a power conversion device, wherein an n-stage parallel circuit of n sets of boost choppers operated while maintaining at / n is inserted between the DC power supply and the power conversion device. 3. A power converter connected to a DC power supply and supplying power to a load by a switching operation, wherein a harmonic current component of the output current of the power converter is calculated from a circuit constant of the power converter and the switching operation. A power conversion device for calculating and outputting an antiphase harmonic current component having the same phase and the opposite phase as the harmonic current component, and outputting the power conversion device on the output side of the power conversion device. A harmonic current component suppressing circuit for a power converter, wherein the output side of the power converter is connected.