JPH10146060A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce leakage currents by providing a power converter with a high-frequency filter where a reactor is inserted and connected to an AC line and load is connected to the AC line on opposite side of a bridge and also series circuits consisting of capacitors and resistors are connected severally to both positive and negative electrodes of the AC line. SOLUTION: One end point A of a reactor LA1 is connected to the AC line of an inverter INV. For the other end point A', the series circuit of a capacitor CA1 and a resistor RA1 and the series circuit of a capacitor CA2 and a resistor RA2 are connected, respectively, to the positive electrode side and the negative electrode side of an inverter INV so as to form a high frequency filter 4. Hereby, high-frequency voltage where the rate of change of the voltage at switching start and trail of switching elements Q1 and Q2 is suppressed is obtained from the AC line of the high-frequency filter 4, and leak currents flowing through the stray capacitor between the parts of a power converter, wiring, a casing or the like and the earth can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forward conversion (converter) or reverse conversion (inverter) power converter.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration example of a conventional power converter. V _IN is an input AC power supply, which is rectified by a rectifier REC and converted into a DC voltage E. The control circuit CONT (for example, FIG. 8 of JP-A-6-351256) drives the inverter INV in which the semiconductor switches Q1 and Q2 are assembled in a half-bridge so that the output _VOUT becomes a sine wave, and turns the DC voltage E into a high-frequency AC voltage. Convert to Semiconductor switch Q
Diodes D1 and D2 provided in antiparallel to Q1 and Q2 are provided for regeneration and circulation of reactive power on the AC output side of the inverter INV. The high-frequency AC voltage converted by the inverter INV is removed by a low-pass filter including reactors LF and CF to remove a high-frequency component, and a sine-wave AC voltage _VOUT is output. RL is an AC load. Here, the high-frequency AC voltage converted by the inverter INV constituted by the semiconductor switch is a rectangular wave voltage containing many high-frequency components. As shown in FIG. 8, a stray capacitance (CS) exists between the ground, the components, wiring, housing, and the like of the power conversion device, and when a high-frequency AC voltage converted by the inverter INV is applied thereto, the stray capacitance is generated. There is a problem that high-frequency leakage current (ig) flows between the power converter and the ground through (CS). Further, since this high-frequency leakage current is a leakage current flowing through the ground line, if there is an earth leakage breaker in the AC line, it trips, which is also a problem in equipment security.

FIG. 9 shows a power converter using a high-frequency filter for suppressing noise due to these high-frequency AC voltages. 4 is a reactor LA1, a capacitor CA1,
This is a high-frequency filter made of CA2. This second-order lag type LC filter has an amplifying action near the cutoff frequency, so that the reactor LA1, the capacitors CA1, C
Free oscillation determined by the constant of A2 is likely to occur, making the output voltage control unstable. This free vibration is likely to occur when the so-called damping coefficient is small in control theory. For this reason, it is necessary to provide a voltage sensing transformer including a lead element in order to stably perform voltage control, and to suppress the occurrence of free vibration of the filter by the phase transition effect, to operate the voltage control system stably, etc. The control circuit becomes complicated and the cost of the apparatus increases. (For details, refer to Japanese Patent Application No. 5-28592, registration number 25552230, "Inverter Device.")

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed to improve the above-mentioned problem, and has as its object the leakage current flowing to the ground caused by the high-frequency switching of a semiconductor switch element constituting a power converter. And to reduce the cost of the power converter.

[0005]

SUMMARY OF THE INVENTION In order to achieve these objects, the present invention provides high-frequency switching of a switch element bridge-connected between an AC line and a DC line to perform any one of orthogonal power conversion. In the power conversion device to be performed, a reactor is inserted and connected to the AC line, a load is connected to the AC line on the opposite side of the bridge of the reactor, and in addition, a series circuit including a capacitor and a resistor is connected to the positive and negative electrodes of the DC line. The present invention is characterized in that a power conversion device is provided with a high-frequency filter connected to the power converter. Further, the present invention provides a power converter for performing any one of orthogonal power conversion by high-frequency switching a switch element bridge-connected between an AC line and a DC line, wherein the AC line includes a series circuit of a reactor and a resistor. Insert and connect
A power conversion device is provided, wherein a high-frequency filter is provided in which a load is connected to an AC line on the opposite side of the bridge of the series circuit and a capacitor is connected to each of the positive and negative electrodes of the DC line. It is a feature of. Further, the present invention, in a power conversion device that performs orthogonal power conversion by high-frequency switching a switch element bridge-connected between an AC line and a DC line, a reactor is inserted and connected to the AC line, A high-frequency filter was provided by connecting a load to an AC line on the opposite side of the bridge of the reactor and additionally connecting a resistor, and connecting a capacitor to the opposite side of the resistor and to both the positive and negative poles of the DC line. A feature of the present invention is a power conversion device characterized by the above.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a power converter for performing orthogonal power conversion by switching a switching element bridge-connected between an AC line and a DC line at high frequency, a reactor is inserted and connected to the AC line. By connecting a load to the AC line on the opposite side of the bridge of the reactor, and by providing a high-frequency filter by connecting a series circuit consisting of a capacitor and a resistor to both the positive and negative poles of the DC line, A high-frequency voltage in which the rate of change dV / dt of the voltage at the rise and fall of the switching of the switching element is suppressed is obtained from the AC line of the high-frequency filter and leaks through the stray capacitance between the power conversion device parts, wiring, housing, and the ground. The current can be reduced.

[0007]

Next, an embodiment of the present invention will be described. FIG.
Is a configuration example of an inverter device as a first embodiment to which the present invention is applied. In the figure, 1 is an AC power supply, 2 is a rectifier, 3 is an inverter circuit, 4 is a high-frequency filter, 5 is a low-pass filter, 6 is an AC load, and 7 is a control circuit. An inverter INV in which the semiconductor switches Q1 and Q2 are combined in a half bridge is driven by an on / off signal given from a control circuit, and a DC voltage E obtained by rectifying an AC voltage.
To a high frequency AC voltage. Here the semiconductor switch Q
Although an example in which a transistor is used as Q1 and Q2 has been described, it goes without saying that a semiconductor switch element such as a power MOS FET or IGBT can be used. Transistor Q
Diodes D1 and D2 provided in antiparallel to Q1 and Q2 are provided for regeneration and circulation of reactive power on the AC output side of the inverter INV. One end (point A) of reactor LA1
Is connected to the AC line of the inverter INV, and the other end (A ′
(Point) connects a series circuit of the capacitor CA1 and the resistor RA1 and a series circuit of the capacitor CA2 and the resistor RA2 to the positive and negative sides of the DC line of the inverter INV, respectively, to form a high frequency filter. The cut-off frequency of the filter is set by the reactor (LA1) and the capacitors (CA1, CA2), the attenuation at the resonance frequency of the high-frequency filter is set by the resistors (RA1, RA2), and the oscillation of the current flowing through the LCR circuit is suppressed. One end of a low-pass filter composed of a series circuit of a reactor LF and a capacitor CF is connected to the reactor LA1 (AC line side opposite to the inverter INV), and the other end is connected to the midpoint potential (E / 2) of the input DC voltage. Connecting. An AC voltage V _OUT from which high-frequency components have been removed is output to both ends of the capacitor CF.

FIG. 2 shows voltage and current waveforms at various parts of the inverter. The current i _a1 has a positive direction from the point A to the point A ', the currents i _a1 and i _a2 have a positive direction for charging the capacitor, and the current i _lf has a positive direction from the point A' to the reactor LF. In addition, the inductance value of reactor LF is larger than that of reactor LA1, and the current _{iff of} reactor LF can be regarded as a substantially constant value during the switching period, and is shown as a level value. The current i _la1 flowing through the reactor LA1 is shown as i _la1 = i _lf -i _a1 + i _a2 . The control circuit CONT outputs a drive signal d1 for the transistor Q1 and a drive signal d2 for the transistor Q2. The transistor is turned on when the drive signal is at a high level, and turned off when the drive signal is at a low level. Therefore, the voltage waveform at the point A is a rectangular wave having a voltage E level when the drive signal d1 is at a high level and a voltage zero level when the drive signal d2 is at a high level. The rate of change dV / dt of the voltage at the rise and fall of this rectangular wave switching is a very large value and is a waveform including many high-frequency components.

FIG. 3 shows a current flow in each state of the transistors Q1 and Q2. When the current _lf flowing through the reactor LF is positive, when the transistor Q1 is turned on and the transistor Q2 is turned off, the voltage at the point A changes from the zero level to the E level, and the reactor LA1-the resistance R
The circuit of A1-capacitor CA1 is short-circuited by transistor Q1, and the charge charged in capacitor CA1 is changed to capacitor CA1-transistor Q1-reactor LA.
Discharging the path of 1- resistor RA1 current -i _a1 flows. The reactor LA1- resistance RA2- the circuit of a capacitor CA2 applied voltage E, the capacitor CA2 transistors Q1- reactor LA1- is charged through a path of the capacitor CA2- resistor RA2 current i _a2 flows. The voltage of the capacitor CA1 becomes zero level, the voltage of the capacitor CA2 becomes E level, and the currents _ia1 and _ia2 become zero (FIG. 3A).

When the transistor Q1 is turned off and the transistor Q2 is turned on, the voltage at the point A changes from the E level to the zero level, the circuit of the reactor LA1, the resistor RA2 and the capacitor CA2 is short-circuited by the transistor Q2, and the capacitor CA2 is charged. which do charges discharged current -i _a2 through a path of the capacitor CA2- transistor Q2- reactor LA1- resistor RA2. Voltage E is applied to the circuit of the reactor LA1, the resistor RA1, and the capacitor CA1, and the capacitor CA1 is connected to the transistor Q2.
- reactor LA1- it is charged through a path of the capacitor CA1- resistor RA1 current flows i _a2. The voltage of the capacitor CA2 becomes zero level, the voltage of the capacitor CA1 becomes E level, and the currents _ia1 and _ia2 become zero (FIG. 3B).

Next, similarly, also when the current _iff flowing through reactor LF is negative, when transistor Q1 is turned on and transistor Q2 is turned off, the voltage at point A changes from zero level to E level, and reactor LA1- The circuit of the resistor RA1 and the capacitor CA1 is short-circuited by the transistor Q1, and the electric charge charged in the capacitor CA1 is changed to the capacitor CA1 and the transistor Q1 and the reactor L.
A1- discharged current -i _a1 flows through the path of the resistor RA1.
Also, the reactor LA1, the resistor RA2, and the capacitor CA2
The circuit of the voltage is applied E, the capacitor CA2 transistors Q1- reactor LA1- is charged through a path of the capacitor CA2- resistor RA2 current i _a2 flows. The voltage of the capacitor CA1 becomes zero level, the voltage of the capacitor CA2 becomes E level, and the currents _ia1 and _ia2 become zero (FIG. 3c).

When the transistor Q1 is turned off and the transistor Q2 is turned on, the voltage at the point A changes from the E level to the zero level, the circuit of the reactor LA1, the resistor RA2 and the capacitor CA2 is short-circuited by the transistor Q2, and the capacitor CA2 is charged. which do charges discharged current -i _a2 through a path of the capacitor CA2- transistor Q2- reactor LA1- resistor RA2. Voltage E is applied to the circuit of the reactor LA1, the resistor RA1, and the capacitor CA1, and the capacitor CA1 is connected to the transistor Q2.
- reactor LA1- it is charged through a path of the capacitor CA1- resistor RA1 current flows i _a2. The voltage of the capacitor CA2 becomes zero level, the voltage of the capacitor CA1 becomes E level, and the currents _ia1 and _ia2 become zero (FIG. 3D).
A 'voltage of point A' is represented as voltage _{= RA2 * i a2 + ∫i a2} dt / CA2 points, change of rise and fall of the voltage of the switching to the second-order lag response to the voltage at point A Rate dV /
A switching waveform in which dt is suppressed (high-frequency components equal to or higher than the cut-off frequency set value of the filter are removed) is obtained. As a result, the current flows through a loop consisting of the stray capacitance existing between the AC line including the wiring from the low-pass filter to the AC load and the ground and the stray capacitance existing between the DC line of the inverter circuit and the ground. High frequency leakage current is A '
Since it is proportional to the product of the stray capacitance and the rate of change dV / dt of the voltage at the point, it is possible to provide a power converter in which the high-frequency leakage current is reduced by the suppression of the rate of change dV / dt of the voltage.

FIG. 4A shows a second embodiment of the present invention. The second embodiment differs from the first embodiment in the configuration of the high frequency filter. Resistor R in series with reactor LA1
A1 is connected to form a series circuit including the reactor LA1 and the resistor RA1, one end (point A) of the series circuit is connected to the AC line of the inverter INV, and the other end (point A ') is connected to the capacitor CA1 and the capacitor CA2. And the other ends of the capacitors are connected to the positive and negative sides of the DC line of the inverter INV, respectively, to form a high frequency filter. This reactor (LA1) and capacitor (CA1,
CA2) sets the cutoff frequency of the filter, the resistor (RA1) sets the attenuation at the resonance frequency of the high frequency filter, suppresses the oscillation of the current flowing through the LCR circuit, and achieves the same filter effect as in the first embodiment. It can be obtained with few parts. Furthermore, if the resistance of the winding of the reactor LA1 is used, the resistance RA1 can be omitted.

FIG. 4B shows a third embodiment of the present invention. The third embodiment differs from the first embodiment in the configuration of the high frequency filter. One end (point A) of reactor LA1
Is connected to the AC line of the inverter INV, and the other end (A ′
Point) is connected to the resistor RA1. The other end of the resistor RA1 is connected to the capacitors CA1 and CA2, and the other end of the capacitor is connected to the positive and negative sides of the DC line of the inverter INV to form a high frequency filter. This reactor (LA1) and capacitor (CA1,
CA2) sets the cutoff frequency of the filter, the resistor (RA1) sets the attenuation at the resonance frequency of the high frequency filter, suppresses the oscillation of the current flowing through the LCR circuit, and achieves the same filter effect as in the first embodiment. It can be obtained with few parts. Therefore, FIGS.
The configuration of the high-frequency filter of (b) can obtain the necessary filter effect with a small number of components, and has a great effect of reducing the cost of the power converter.

FIG. 5A shows a configuration example in which the present invention is applied to a three-phase full-bridge inverter circuit. Each of the UVW-phase AC lines of the bridge-connected switch elements (U
A reactor is inserted and connected to the points (points V, W, W), and terminals (U ', V',
At point W '), a series circuit of a capacitor and a resistor is connected from the positive and negative poles of the DC line, respectively, and the input of a three-phase low-pass filter is connected. As a result, U ′ point, V ′ point,
The switching waveform at the point W 'is obtained by removing a high-frequency component equal to or higher than the cut-off frequency set value of the filter in which the rate of change of the voltage dV / dt is suppressed, and including the wiring from the low-pass filter to the AC load. A high-frequency leakage current flowing through a loop composed of a stray capacitance existing between the line and the ground and a stray capacitance existing between the DC line of the inverter circuit and the ground can be reduced by an amount corresponding to the suppression of the dV / dt value. . Although the power converter (UPS, inverter, etc.) having a low-pass filter has been described, the effect of the present invention can also be obtained with a power converter (motor driver) having a motor indicated by 10 in FIG. Needless to say. Although the three-phase full-bridge inverter circuit has been described, the same effect can be obtained with the single-phase full-bridge inverter circuit of FIG. Needless to say, the configuration of the high-frequency filter (filter configuration using a common resistor) shown in FIGS. 4A and 4B can be used for these inverters.

FIG. 6A shows a configuration example of a converter device to which the present invention is applied. In the figure, 1 is an AC power supply, 2 is a reactor, 3 is a high frequency filter, 4 is an inverter circuit, 5 is a rectifier diode, 6 is a smoothing capacitor, 7 is a DC load, and 8 is a control circuit. An inverter INV in which the semiconductor switches Q1 and Q2 are combined in a half-bridge so as to be a sine wave having a rate of 1 and a DC output voltage is maintained at a target value is driven by an on / off signal given from a control circuit 8, The operation of accumulating energy in the reactor and discharging to a smoothing capacitor through diodes D1 and D2 provided in antiparallel to transistors Q1 and Q2 and a rectifier diode is performed at a high frequency. Here, an example in which transistors are used as the semiconductor switches Q1 and Q2 has been described.
It goes without saying that a semiconductor switch element such as BT can be used. The control for improving the waveform of the input current is publicly known, and a detailed description thereof will be omitted (Reference: Technical Report of the Institute of Electrical Engineers of Japan (Part II) No. 372: “Trends in Uninterruptible Power Supplies”, p20 to p21).

One end (point A) of the reactor LA1 is connected to the AC line of the inverter INV, and the other end (point A ') includes a series circuit of the capacitor CA1 and the resistor RA1 and a series circuit of the capacitor CA2 and the resistor RA2. A high frequency filter is formed by connecting the positive and negative sides of the DC line of INV. The cut-off frequency of the filter is set by the reactor (LA1) and the capacitors (CA1, CA2), the attenuation at the resonance frequency is set by the resistors (RA1, RA2), and the current of the current flowing through the LCR circuit is set to 2
The next vibration state is suppressed. The voltage at the point A 'responds to the voltage at the point A in a second-order lag system, the rate of change dV / dt of the voltage at the rise and fall of the switching is suppressed, and high-frequency components higher than the cut-off frequency set value of the filter are removed. Obtain a switching waveform. As a result, the voltage of the high-frequency leakage current A 'flowing through a loop composed of the stray capacitance existing between the AC line including the wiring and the ground and the stray capacitance existing between the DC line of the inverter circuit and the ground is determined. Since the rate of change is proportional to the product of the rate of change dV / dt and the stray capacitance, it is possible to provide a power converter in which the high-frequency leakage current is reduced by an amount corresponding to the suppression of the rate of change dV / dt of the voltage. Although the half-bridge converter circuit has been described, the same effect can be obtained with the three-phase full-bridge converter circuit of FIG. 6B and the single-phase full-bridge converter circuit of FIG. 6C. It goes without saying that the configuration of the high-frequency filter (filter configuration using a common resistor) shown in FIGS. 4A and 4B can be used for these converters.

[0018]

According to the present invention, there is provided a power converter for performing orthogonal power conversion by performing high-frequency switching on a switch element bridge-connected between an AC line and a DC line. A reactor is inserted and connected, and a load is connected to an AC line on the opposite side of the bridge of the reactor, and a high-frequency filter is provided in which a series circuit including a capacitor and a resistor is connected to each of the positive and negative electrodes of the DC line. As a result, a high-frequency voltage in which the rate of change dV / dt of the voltage at the rise and fall of the switching of the switching element is suppressed can be obtained from the AC line of the high-frequency filter, and the floating between the parts, wiring, housing, etc. of the power converter and the ground. This has the effect of reducing leakage current flowing through the capacitor. In addition, since a high-frequency filter in which free vibration is suppressed can be configured with a small number of components, there is an effect of reducing the cost of the power conversion device.

[Brief description of the drawings]

FIG. 1 shows a configuration of a power converter according to an embodiment of the present invention.

FIG. 2 shows operation waveforms of respective units according to the embodiment of the present invention.

FIG. 3 shows a current flow path according to the embodiment of the present invention.

FIG. 4A shows a configuration of a power converter according to a second embodiment of the present invention. (B) A configuration of a power converter according to a third embodiment of the present invention is shown.

FIGS. 5A and 5B show a configuration of a power converter according to a fourth embodiment of the present invention, wherein FIG. 5A shows a three-phase full-bridge inverter and FIG. 5B shows a single-phase full-bridge inverter.

FIG. 6 shows a configuration of a power converter according to a fifth embodiment of the present invention, where (a) is a half-bridge converter,
(B) shows a three-phase full-bridge converter, and (c) shows a single-phase full-bridge converter.

FIG. 7 shows a configuration of a conventional power converter.

FIG. 8 is a simplified circuit diagram showing a problem of the conventional power converter.

FIG. 9 is a power converter using a high-frequency filter for suppressing noise due to a high-frequency AC voltage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter 3 Inverter 4 Inverter 5 High frequency filter 6 High frequency filter 7 High frequency filter 8 Low pass filter 9 AC load 10 DC load

Claims (9)

[Claims] 1. A power conversion device for performing one of orthogonal power conversions by performing high-frequency switching on a switch element bridge-connected between an AC line and a DC line, wherein a reactor is inserted and connected to the AC line.
A high-frequency filter is provided in which a load is connected to an AC line on the opposite side of the bridge of the reactor, and a series circuit including a capacitor and a resistor is connected to both the positive and negative poles of the DC line. Power converter. 2. A power converter for performing orthogonal power conversion by performing high-frequency switching on a switch element bridge-connected between an AC line and a DC line, wherein a series circuit of a reactor and a resistor is connected to the AC line. And a high-frequency filter provided by connecting a load to the AC line on the opposite side of the bridge of the series circuit and additionally connecting a capacitor to both the positive and negative poles of the DC line. Power converter. 3. A power conversion device that performs one of orthogonal power conversions by performing high-frequency switching on a switch element bridge-connected between an AC line and a DC line, wherein a reactor is inserted and connected to the AC line.
A high-frequency filter was provided by connecting a load to an AC line on the opposite side of the bridge of the reactor and additionally connecting a resistor, and connecting a capacitor to the opposite side of the resistor and to both the positive and negative poles of the DC line. A power converter characterized by the above-mentioned. 4. The power conversion device according to claim 1, wherein the power conversion main circuit is an inverter. 5. The power conversion device according to claim 1, wherein the power conversion main circuit is a converter. 6. The power conversion device according to claim 2, wherein the power conversion main circuit is an inverter. 7. The power converter according to claim 2, wherein the power conversion main circuit is a converter. 8. The power conversion device according to claim 3, wherein the power conversion main circuit is an inverter. 9. The power converter according to claim 3, wherein the power conversion main circuit is a converter.