JP2012039825A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise which accompanies fast switching of a power converter having a switching element and severely hinders loss reduction of the power converter because increase of dv/dt in order to reduce element loss generates noise with higher and larger power.SOLUTION: A voltage-type power converter with a pulse width modulation reduces high-frequency noise by connecting a DC midpoint potential of the power converter and a load output point via a capacitor.

Description

  The present invention is a power conversion device using a power semiconductor element, and particularly reduces high-frequency common mode noise.

  The background art will be described with reference to FIG.

  In general, a power conversion device that converts DC power into arbitrary power has a DC power source 5 and its DC voltage converted to an arbitrary voltage and frequency as shown in FIG. 2 using a power conversion circuit 6 such as an inverter circuit or a chopper circuit. A configuration in which the electrical device of the load 7 is converted is generally used. This power conversion circuit uses a power semiconductor element and operates by switching at high speed.

JP-A-9-294381 JP 2000-315929 A

Fujimoto, Morimoto et al. "Reduction of leakage current of PWM inverter in integrated grounding system" 2007 IEEJ National Conference 4-154

  In the power converter, a common mode voltage generated when the power semiconductor element is switched is reduced.

  FIG. 3 shows a circuit of a conventional power converter. This circuit is the same for both DC choppers and inverters. The circuit has a parasitic inductance and stray capacitance that do not appear in the circuit diagram, and when the switching element 1 or 2 operates, a steep rise and fall of the voltage occurs. At this time, the output waveform vibrates due to the parasitic component. This vibration component may have a peak several times the DC power supply voltage and a frequency of several tens of MHz.

  In response to this problem, a common mode filter is generally provided to reduce common mode noise generated when the power conversion element is switched.

  For example, in Patent Document 1, as a common mode filter, a common mode filter including a reactor and a capacitor is inserted on the output side of the circuit.

  In Patent Document 2, the common mode current is reduced by connecting a Y capacitor to the feeder line.

  In Non-Patent Document 1, the common mode current is reduced by connecting the neutral point of the motor as a load and the DC intermediate potential of the inverter via a capacitor.

  According to the first aspect of the present invention, in the device for converting from direct current to arbitrary power using a switching element, a capacitor is connected to the load output point, and the direct current intermediate potential of the capacitor and the power conversion device is connected. A power converter.

  According to claim 2, the power converter according to claim 1, wherein the capacitor connected to the load side is connected immediately after the power converter.

  According to Claim 3, the capacitor connected to the load side is connected immediately before the power converter, The power converter according to Claim 1 characterized by the above-mentioned.

  According to claim 4, in the power conversion device according to claim 1, a multi-phase output is provided, and a three-phase Y-connected capacitor is connected immediately after the multi-phase output point. A power conversion device connected to a direct current intermediate potential of the device.

  The present invention can suppress a high-frequency common mode voltage only by adding a simple passive element.

It is an example of the power converter device of this invention. It is a block diagram of an example of the conventional power converter device. It is a circuit diagram of 1 arm of the conventional power converter. It is an example of the power converter device of this invention in Example 2. FIG. It is an example of the power converter device of the present invention in Example 3.

  Preferred embodiments of the invention are illustrated using the following examples.

  Claims 1 and 2 of the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram in which a circuit under the following conditions is added to the circuit of FIG.

  A capacitor of the same capacity for creating the intermediate potential 3 of the DC link is connected in the immediate vicinity of the switching element, and a capacitor 4 for connecting the output point and the intermediate potential 3 is added. In this case, a smoothing reactor and a common mode choke are not required, but even if connected, there is no effect.

  By creating the intermediate potential 3, the parasitic component from the power source to the switching element becomes invisible from the switching element side, so that the generation of high frequency components can be suppressed.

  In addition, by adding the capacitor 4, a high-frequency component feedback circuit that has been generated can be formed, so that outflow of the high-frequency component to the load side can be prevented.

  Claim 3 will be described with reference to FIG.

  In the circuit of FIG. 3, the capacitor 4 is connected immediately before the load 8. Even in this case, since the high frequency component can be effectively fed back to the intermediate potential 3, the inflow of the high frequency component to the load can be prevented. In this case, a smoothing reactor and a common mode choke are not required, but even if connected, there is no effect.

  Claim 4 will be described with reference to FIG.

  FIG. 5 shows a three-phased example of FIG. Even if there are a plurality of output points, it is possible to suppress the generation of high frequency components. In this case, a smoothing reactor and a common mode choke are not required, but even if connected, there is no effect.

  The present invention is effective for a power circuit using a power switching semiconductor element. Moreover, since only a few passive elements are attached to the existing hardware, it is extremely effective.

DESCRIPTION OF SYMBOLS 1 Upper arm element 2 Lower arm element 3 DC intermediate potential 4 Capacitor 5 DC power supply 6 Power conversion circuit 7 Load 8 Load

Claims (4)

  An apparatus for converting from direct current to arbitrary power using a switching element, wherein a capacitor is connected to a load output point, and a direct current intermediate potential of the capacitor and the power conversion apparatus is connected.   The power converter according to claim 1, wherein the capacitor connected to the load side is connected immediately after the power converter.   The power converter according to claim 1, wherein the capacitor connected to the load side is connected immediately before the power converter. 2. The power converter according to claim 1, having a multi-phase output, and a three-phase Y-connected capacitor is connected immediately after the multi-phase output point, and a neutral point of the capacitor is connected to a DC intermediate potential of the power converter. The power converter characterized by being made.

Images