JP2004320888A - Noise suppression device for power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, because the trend toward high speed of a power conversion switching device increases high-frequency leak current and surge voltage to exert an adverse effect, although there is the conventional embodiment is which can reduce such an adverse effect by attaching a resonance circuit consisting of reactors and capacitors , some loss is generated due to resistance contained in the resonance circuit. <P>SOLUTION: A series circuit of the reactors L1 to L3 and the capacitors C1 to C3 is connected between output terminals Vu to Vw of an inverter 3 consisting of switching devices Q1 to Q6 and negative side VN of DC output. Diodes D1 to D6 are connected between VP and VN, and resistors R1 to R3 are connected between a junction point of the reactor and the capacitor and a diode junction point. With this constitution, the loss due to resistance can be restrained from increasing by excluding resistance in a charging/discharging path of the capacitors C1 to C3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a noise reduction device in a power conversion device including a switching element such as an inverter device.
[0002]
[Prior art]
FIG. 7 shows an induction motor drive system for driving a three-phase induction motor by a three-phase inverter. This is shown, for example, in FIG. 1 in Japanese Patent Application Laid-Open No. 2002-247836, and FIG. 7 in which the current detector 5 is removed from FIG. 1 corresponds to FIG.
In FIG. 7, the input of the rectifier 2 is provided to the AC power supply 1, the capacitor C0 is provided to the output of the rectifier 2, the three-phase inverter 3 including the semiconductor switches Q1 to Q6 is provided to the capacitor C0, and the output of the three-phase inverter 3 is provided. The motors 4 are respectively connected. The switches Q1 to Q6 of the three-phase inverter 3 are turned on and off by pulse width modulation (PWM) pulses, and the motor 4 is driven by the output voltage of the output of the three-phase inverter 3.
[0003]
By the way, the semiconductor switches Q1 to Q6 have higher element characteristics from the viewpoints of reduction of switching loss and noise reduction, and as the dv / dt, which is a voltage change rate at the time of switching, becomes steeper, harmonic leakage occurs. Problems such as deterioration of motor winding insulation due to increase in current and surge voltage have occurred.
Therefore, a circuit as shown in FIG. 8 shown in Non-Patent Document 1 has been proposed as suppressing the dv / dt of the voltage applied to a load such as a motor while keeping the merit of increasing the element characteristics.
[0004]
FIG. 8 will be described.
It is assumed that a current flows from the inverter 3 to the load side in the reactor L1. When the switch Q1 is turned on in this state, a resonance current i1 flows as indicated by an arrow in FIG. 9 and the capacitor C1 is charged. Due to the resonance phenomenon between the reactor L1 and the capacitor C1, the voltage of the capacitor C1 rises more slowly than the voltage change of the switch Q1. When the capacitor C1 is charged to the DC intermediate voltage Ed, the diode D1 becomes conductive and a current i2 flows as shown by an arrow in FIG. 9, and the energy stored in the reactor L1 by the resonance phenomenon is changed from the reactor L1 to the diode. D1 → resistor R1 → switch Q1 → reactor L1 is consumed in the resistor. When the energy stored by the resonance phenomenon is consumed by the resistor R1, only the load current iL flows through the reactor L1, and a normal state is set. By this circuit operation, the voltage applied to the motor 4 is suppressed from changing, and is clamped by the diode to a DC intermediate voltage value, so that the surge voltage is suppressed and the high-frequency noise is reduced.
[0005]
Next, consider the case where the switch Q1 is turned off and the switch Q2 is turned on. In this case, the resonance current i3 flows as indicated by the arrow in FIG. 10, and the capacitor C1 is discharged. Due to the resonance phenomenon between the reactor L1 and the capacitor C1, the voltage of the capacitor C1 falls more slowly than the voltage change of the switch Q1 (or the switch Q2).
When the capacitor C1 is discharged to zero, the diode D2 becomes conductive, a current i4 flows as shown by an arrow in FIG. 10, and the energy stored in the reactor L1 by the resonance phenomenon is changed from the reactor L1, the switch Q2, and the resistor R2. → Diode D2 → Dissipated to resistor R2 via reactor L1. When the energy stored by the resonance phenomenon is consumed by the resistor R2, only the load current iL flows through the reactor L1, and a normal state is set.
[0006]
Therefore, as in the case where the switch Q1 is turned on, the voltage applied to the motor 4 is suppressed from changing, and is clamped to almost zero (the negative potential of the DC output) by the diode, so that the surge voltage is suppressed. And high-frequency noise is reduced. Although the U phase has been described above, the operations and effects of the other phases are exactly the same.
[0007]
[Non-patent document 1]
"Design and Implementation of an Inverter Output LC Filter Used for DV / DT Reduction", "IEEE TRANSACTION ONPOWER ELECTRONICS" VOL. 17, NO. 3, p. 327-331, MAY, 2002
[0008]
[Problems to be solved by the invention]
In the configuration of FIG. 8, since the resistor R2 is on the path where the capacitor C1 discharges when the switch Q1 is turned off and the switch Q2 is turned on, the resistor R2 causes an extra loss. As a result, a component having a large allowable loss must be used for the resistor, which causes a problem that the device becomes large.
Accordingly, an object of the present invention is to reduce the loss of a resistor, reduce leakage current and surge voltage, and realize a smaller device.
[0009]
[Means for Solving the Problems]
In order to solve such a problem, the invention according to claim 1 includes a rectifier circuit connected to an AC power supply, and a power converter in which a DC output of the rectifier circuit is connected to a smoothing circuit and an inverter circuit.
A series circuit of a reactor and a capacitor is connected between the output terminal of each phase of the inverter circuit and the positive bus or the negative bus of the DC output unit, respectively, and the positive bus and the negative bus of the DC output unit are connected. A series circuit of diodes is connected by the same number as the number of output phases, and a resistor is connected between a connection point of the reactor and the capacitor and a connection point of the series circuit of the diode. I do.
[0010]
According to a second aspect of the present invention, there is provided a power converter in which a rectifier circuit connected to an AC power supply and a DC output of the rectifier circuit are connected to a smoothing circuit and an inverter circuit.
A series circuit in which a series circuit of a reactor and a capacitor is connected between the output terminal of each phase of the inverter circuit and the negative bus of the DC output unit, and a diode is connected in series with a connection point between the reactor and the capacitor. A connection point of the circuit is individually connected to each phase, a resistor is connected between a cathode side of the series circuit of the diode and a positive bus of the DC output unit, and an anode side of the series circuit of the diode and the capacitor of the capacitor. A resistor is connected between the reactor and one end that is not connected.
[0011]
According to a third aspect of the present invention, there is provided a power converter in which a rectifier circuit connected to an AC power supply and a DC output of the rectifier circuit are connected to a smoothing circuit and an inverter circuit.
A series circuit in which a series circuit of a reactor and a capacitor is connected between the output terminal of each phase of the inverter circuit and the positive bus of the DC output unit, and a diode is connected in series with a connection point between the reactor and the capacitor. A connection point of the circuit is individually connected to each phase, a resistor is connected between a cathode side of the series circuit of the diode and one end of the capacitor not connected to the reactor, and an anode side of the series circuit of the diode. A resistor is connected between the DC output unit and the negative bus.
[0012]
According to a fourth aspect of the present invention, there is provided a power converter in which a rectifier circuit connected to an AC power supply and a DC output of the rectifier circuit are connected to a smoothing circuit and an inverter circuit.
The smoothing circuit comprises a series connection circuit of smoothing capacitors having the same capacity, and a series circuit of a reactor and a capacitor is connected between a series connection point of the smoothing capacitors and an output terminal of each phase of the inverter circuit. A connection point of a series circuit in which a diode is connected in series to a connection point between the reactor and the capacitor is individually connected to each phase, and a resistance is provided between a cathode side of the series circuit of the diode and a positive bus of a DC output unit. And a resistor connected between the anode side of the series circuit of the diode and the negative bus of the DC output unit.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a configuration diagram showing a first embodiment of the present invention. This is obtained by changing the connection position of the resistor in FIG. 8, and the operation will be described below. As shown in FIG. 2, it is assumed that a current flows from the inverter 3 to the load side in the reactor L1. When the switch Q1 is turned on in this state, the resonance current il shown in FIG. 2 flows, and the capacitor C1 is charged. Due to the resonance phenomenon between the reactor L1 and the capacitor C1, the voltage of the capacitor C1 rises more slowly than the voltage change of the switch Q1.
[0014]
When the capacitor C1 is charged to the DC intermediate voltage value Ed, the diode D1 becomes conductive, a current i2 flows as shown in FIG. 2, and the energy stored in the reactor L1 by the resonance phenomenon is changed from the reactor L1 to the resistor R1 to the resistor R1. It is consumed by the resistor R1 through the path of the diode D1, the switch Q1, and the reactor L1. When the energy stored by the resonance phenomenon is consumed by the resistor R1, only the load current iL flows through the reactor L1, and a normal state is set. By this operation, the voltage applied to the motor 4 is suppressed from changing, and is clamped by the diode to a DC intermediate voltage value, so that the surge voltage is suppressed and the high-frequency noise is reduced.
[0015]
Next, consider the case where the switch Q1 is turned off and the switch Q2 is turned on. In this case, the resonance current i3 flows as shown in FIG. 3, and the capacitor C1 is discharged. Due to the resonance phenomenon between the reactor L1 and the capacitor C1, the voltage of the capacitor C1 falls more slowly than the voltage change of the switch Q1 (or the switch Q2).
When the capacitor C1 is discharged to zero, the diode D2 becomes conductive, a current i4 flows as shown in FIG. 3, and the energy stored in the reactor L1 by the resonance phenomenon is changed from the reactor L1, the switch Q2, the diode D2, and the resistor. R1 is consumed by the resistor R1 through the reactor L1. When the energy stored by the resonance phenomenon is consumed by the resistor R1, only the load current iL flows through the reactor L1, and a normal state is set.
[0016]
Therefore, as in the case where the switch Q1 is turned on, the voltage applied to the motor 4 is suppressed from changing, and is clamped to almost zero (the negative potential of the DC output) by the diode, so that the surge voltage is suppressed. And high-frequency noise is reduced. Although the U phase has been described above, the operation and effects of the other phases are the same.
That is, although the basic functions and operations are the same as those of the conventional circuit of FIG. 8, the circuit of FIG. 1 forms a path that does not pass through the resistor when charging and discharging the capacitor, so that the resistor is unnecessary. There is an advantage that no loss occurs. The connection point of the load is a connection point between the reactor L1 and the capacitor C1 so that the load current does not flow through the resistor. In FIG. 1, the capacitors C1 to C3 are connected to the negative side of the DC bus, but may be connected to the positive side of the DC bus.
[0017]
FIG. 4 is a circuit diagram showing a second embodiment of the present invention, in which connection points of capacitors C1 to C3 are connected to the negative side of a DC bus.
Similarly, FIG. 5 is a circuit diagram showing a third embodiment of the present invention, in which connection points of capacitors C1 to C3 are connected to the positive side of a DC bus.
FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention, in which a connection point of capacitors C1 to C3 is connected to a series connection point of capacitors C01 and C02, that is, a neutral point of a DC intermediate voltage. is there.
Note that the functions and operations of FIGS. 4 to 6 are completely the same as those of FIG.
[0018]
【The invention's effect】
According to the present invention, the leakage current and the surge voltage can be reduced without increasing the loss due to the resistor, so that there is an advantage that the size and efficiency of the device can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention; FIG. 2 is an explanatory diagram of a current path when Q1 is turned on in FIG. 1; FIG. 3 is an explanatory diagram of a current path when Q1 is turned off in FIG. FIG. 5 is a circuit diagram showing a second embodiment of the present invention. FIG. 5 is a circuit diagram showing a third embodiment of the present invention. FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention. 7 is a circuit diagram showing a conventional example of an induction motor drive system. FIG. 8 is a circuit diagram showing a conventional example for suppressing dv / dt. FIG. 9 is an explanatory diagram of a current path when Q1 is turned on in FIG. For explaining the current path when Q1 is turned off.
DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Rectifier, 3 ... Inverter circuit, 4 ... Induction motor (motor), Q1-Q6 ... Switching element, L1-L3 ... Reactor, C0-C3, C01, C02 ... Capacitor, R1-R3 ... Resistance Vessels, D1 to D6 ... diodes.

Claims (4)

In a rectifier circuit connected to an AC power supply, and a power converter in which a smoothing circuit and an inverter circuit are connected to a DC output of the rectifier circuit,
A series circuit of a reactor and a capacitor is connected between the output terminal of each phase of the inverter circuit and the positive bus or the negative bus of the DC output unit, respectively, and the positive bus and the negative bus of the DC output unit are connected. A series circuit of diodes is connected by the same number as the number of output phases, and a resistor is connected between a connection point of the reactor and the capacitor and a connection point of the series circuit of the diode. Noise reduction device for power converters. In a rectifier circuit connected to an AC power supply, and a power converter in which a smoothing circuit and an inverter circuit are connected to a DC output of the rectifier circuit,
A series circuit in which a series circuit of a reactor and a capacitor is connected between the output terminal of each phase of the inverter circuit and the negative bus of the DC output unit, and a diode is connected in series with a connection point between the reactor and the capacitor. A connection point of the circuit is individually connected to each phase, a resistor is connected between a cathode side of the series circuit of the diode and a positive bus of the DC output unit, and an anode side of the series circuit of the diode and the capacitor of the capacitor. A noise reduction device for a power conversion device, wherein a resistor is connected between a reactor and one end that is not connected. In a rectifier circuit connected to an AC power supply, and a power converter in which a smoothing circuit and an inverter circuit are connected to a DC output of the rectifier circuit,
A series circuit in which a series circuit of a reactor and a capacitor is connected between the output terminal of each phase of the inverter circuit and the positive bus of the DC output unit, and a diode is connected in series with a connection point between the reactor and the capacitor. A connection point of the circuit is individually connected to each phase, a resistor is connected between a cathode side of the series circuit of the diode and one end of the capacitor not connected to the reactor, and an anode side of the series circuit of the diode. A noise reduction device for a power converter, wherein a resistor is connected between the DC output unit and a negative bus. In a rectifier circuit connected to an AC power supply, and a power converter in which a smoothing circuit and an inverter circuit are connected to a DC output of the rectifier circuit,
The smoothing circuit comprises a series connection circuit of smoothing capacitors having the same capacity, and a series circuit of a reactor and a capacitor is connected between a series connection point of the smoothing capacitors and an output terminal of each phase of the inverter circuit. A connection point of a series circuit in which a diode is connected in series to a connection point between the reactor and the capacitor is individually connected to each phase, and a resistance is provided between a cathode side of the series circuit of the diode and a positive bus of a DC output unit. And a resistor connected between the anode side of the series circuit of the diode and the negative bus of the DC output unit.

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