JP2010028942A - Power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion apparatus for suppressing that a high-requency current accompanying switching of a converter via a floating capacity existing between the converter and a storage battery, and a grounding point flows through a grounding point of a power supply system-side and a grounding point of a load side. <P>SOLUTION: The power conversion apparatus is provided with the converter 1 receiving power from an AC power supply, obtaining DC voltage and converting DC voltage into AC voltage, a filter 2 connected to an input-side of the converter 1 and a filter 3 connected to the output-side of the converter 1. A common connection point of a capacitor 22, constituting the filter 2 of the input-side and a common connection point of a capacitor 32 constituting the filter 3 of the output-side, are electrically connected. A bypass capacitor 5 is connected between the connection point and the grounding point. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power converter that receives an AC power supply and outputs an AC voltage having an arbitrary frequency, and in particular, noise generated in a converter that converts a DC voltage into an AC voltage or an AC voltage into a DC voltage. It is related with the technique for reducing.

  In general, in a power converter that receives an AC power supply and outputs an AC voltage having an arbitrary frequency, the converter includes a converter and an inverter, and the converter temporarily converts the AC voltage of the power supply system into a DC voltage. The obtained DC voltage is converted into a stable AC voltage by an inverter and supplied to a load.

  In such a power conversion device, a filter is provided on the input side of the converter so that the influence of the carrier frequency component generated by switching of the switching elements constituting the converter is not transmitted to the power supply system side, and the inverter is installed. A filter is provided on the output side of the inverter so that the influence of the carrier frequency component generated along with the switching of the constituting switching element is not transmitted to the load side, and the carrier frequency is reduced by each of these filters.

  Thus, when filters are provided on the input side and output side of the converter respectively, it is possible to remove the carrier frequency component, but the DC bus voltage viewed from the ground point is caused by the carrier frequency component. There is a problem that voltage fluctuations occur.

  For this reason, in the conventional power conversion device, the common connection point of the capacitor constituting the input side filter and the common connection point of the capacitor constituting the output side filter are electrically connected to each other, so that The thing which suppressed the fluctuation | variation of the seen DC bus-line voltage is proposed (for example, refer the following patent document 1).

JP-A-9-294381

  Thus, in the conventional power conversion device described in Patent Document 1, by electrically connecting the common connection points of the capacitors constituting the filter on the input side and the filter on the output side that receive AC power, It is possible to reduce input / output potential fluctuations accompanying switching of the converter.

  However, since a stray capacitance inevitably exists between the converter or inverter constituting the converter and the grounding point, in a conventional power converter, high-frequency current generated by switching of the converter passes through the stray capacitance. Leaks to the ground point, and the current flows from the ground point on the power system side through the input side filter to the converter again and circulates, or the high frequency leaked to the ground point through the stray capacitance Current flows again from the load-side ground point to the converter via the output-side filter and circulates. Since the high frequency current leaking from the converter through the stray capacitance in this way is higher in frequency than the current of the carrier frequency component of the converter, the filters are provided on the input side and the output side of the converter, respectively. It is not possible to prevent the circulation sufficiently.

  The high-frequency current circulating in this way becomes a radiation noise source, which causes problems such as inducing interference to other devices connected to the power supply system and affecting the radio frequency band. Further, even when a storage battery is connected to the DC bus of the converter, a high frequency current flows through a stray capacitance generated between the storage battery and the grounding point, so that the same problem occurs.

  The present invention has been made to solve the above-described problems, and a high-frequency current accompanying switching of a converter is supplied to a power supply system via a stray capacitance existing between the converter or a storage battery and a grounding point. An object of the present invention is to provide a power conversion device that suppresses the flow of noise current through a grounding point on the side and a grounding point on the load side.

  A power converter according to the present invention includes a converter that receives a DC voltage from an AC power source and converts the DC voltage into an AC voltage, and a filter that is connected to the input side and the output side of the converter. In the power converter provided, the common connection point of the capacitor constituting the filter on the input side and the common connection point of the capacitor constituting the filter on the output side are electrically connected to each other, and the connection point and the grounding point are A bypass capacitor is connected between the two.

  According to the present invention, even if a high-frequency current flows through the stray capacitance existing between the converter or the storage battery and the ground point in accordance with switching of the converter, the high-frequency current passes through the bypass capacitor. Then, it flows from the filter on the input side or the filter on the output side toward the converter. For this reason, as in the prior art, the high-frequency current leaked from the converter to the grounding point via the stray capacitance flows again from the grounding point on the power supply system side to the converter via the input-side filter and circulates. Alternatively, it is possible to reduce the high-frequency current leaking to the grounding point from flowing again from the load-side grounding point to the converter via the output-side filter and circulating. For this reason, it is possible to prevent inconveniences such as inductive failure caused by leaked high-frequency current as noise current to other devices connected to the power supply system, and influence on the radio frequency band.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a power conversion apparatus according to Embodiment 1 of the present invention.
In FIG. 1, reference numeral 1 denotes a converter that converts an AC voltage received from an AC power source into a DC voltage, and converts the obtained DC voltage into a stable AC voltage. 2 is a filter provided on the input side of the converter 1. Reference numeral 3 denotes a filter provided on the output side of the converter 1. Reference numeral 4 denotes a stray capacitance existing between the converter 1 and the grounding point.

  The converter 1 includes a converter 11 that receives power from an AC power source and temporarily converts it to a DC voltage, and an inverter 12 that converts the DC voltage obtained by the converter 11 into a stabilized AC voltage and supplies the stabilized AC voltage to a load. Between the converter 11 and the inverter 12, a voltage smoothing circuit 13 including a capacitor C0 is provided.

  Converter 11 is formed of a three-phase full bridge circuit having switching element Tr1 and diode D1, and inverter 12 is formed of a three-phase full bridge circuit having switching element Tr2 and diode D2. Each switching element Tr1, Tr2 is switched by a control circuit (not shown).

  Further, the above-mentioned filter 2 on the input side is configured so that the influence of the carrier frequency component generated by switching of the switching element Tr1 constituting the converter 11 is not transmitted to the power supply system side. The carrier frequency is reduced so that the influence of the carrier frequency component generated in association with switching of the switching element Tr2 constituting the inverter 12 is not transmitted to the load side. The filter 2 on the input side includes a reactor 21. Similarly, the output-side filter 3 is also composed of a reactor 31 and a capacitor 32.

  As a feature of the first embodiment, the common connection point of the capacitor 22 constituting the input-side filter 2 and the common connection point of the capacitor 32 constituting the output-side filter 3 are electrically connected to each other, A bypass capacitor 5 is connected between the connection point and the ground point. In this case, as will be described later, since it is necessary to reduce the impedance so that the high-frequency current leaking from the converter 1 via the stray capacitance 4 bypasses the bypass capacitor 5 and flows preferentially, The capacitor 5 is set so as to have a capacitance equal to or greater than the stray capacitance 4 generated between the converter 1 and the grounding point.

  In the power conversion device configured as described above, the high-frequency current generated by switching of the switching elements Tr1 and Tr2 of the converter 11 and the inverter 12 constituting the converter 1 is a stray capacitance that exists between the converter 1 and the grounding point. 4, the high-frequency current immediately flows from the filter 2 on the input side or the filter 3 on the output side toward the converter 1 via the bypass capacitor 5. Therefore, as in the prior art, the high-frequency current leaked to the grounding point via the stray capacitance 4 flows again from the grounding point on the power supply system side to the converter 1 via the input-side filter 2 and circulates. This suppresses the occurrence of a phenomenon in which the high-frequency current leaked to the grounding point via the stray capacitance 4 flows again from the load-side grounding point to the converter 1 via the output-side filter 3 and circulates. .

  Thus, in this Embodiment 1, since it can suppress that the high frequency current accompanying the switching of the converter 1 flows as a noise current via the grounding point on the power supply system side or the grounding point on the load side, It is possible to prevent inconveniences such as inducing interference to other devices connected to the system side and affecting the radio frequency band.

  Further, since the wiring electrically connecting the common connection point of the capacitor 22 of the filter 2 on the input side and the common connection point of the capacitor 32 of the filter 3 on the output side is grounded via the bypass capacitor 5, Compared with the case where the common connection point of the capacitors 22 and 32 of the filters 2 and 3 is directly grounded, the overall capacitance can be easily adjusted. That is, since the bypass capacitors 5 are connected in series to the filters 2 and 3, respectively, by setting the capacitance of the bypass capacitor 5 appropriately, a relatively high frequency leakage desired to be bypassed. Only the current flows through the bypass capacitor 5, and the low frequency leakage current can be made difficult to flow. Thereby, an unnecessary leakage current flowing from the apparatus to the power supply system side or the load side can be efficiently reduced.

Embodiment 2. FIG.
FIG. 2 is a circuit diagram showing a power conversion apparatus according to Embodiment 2 of the present invention, and components corresponding to those in Embodiment 1 shown in FIG.

  The power converter according to the second embodiment is characterized in that common mode cores 6 and 7 through which wirings for three phases are inserted are respectively provided in the front stage of the input side filter 2 and the rear stage of the output side filter 3. It is that. The common mode cores 6 and 7 are, for example, ring-shaped ferrite cores. Since the other configuration is the same as that of the first embodiment shown in FIG. 1, detailed description is omitted here.

In the second embodiment, a common mode core 6 is provided in front of the input-side filter 2 in addition to the bypass capacitor 5, so that the bypass capacitor 5 is not bypassed, In addition, it is possible to increase the impedance with respect to the path of the partially remaining high-frequency current flowing through the ground point on the load side. As a result, the circulation of these remaining high-frequency currents can be further suppressed, and problems such as inducing interference to other devices connected to the power supply system and affecting the radio frequency band can be prevented. This can be prevented more effectively.
Since other operations and effects are the same as those in the first embodiment, detailed description thereof is omitted here.

  In the second embodiment, the common mode cores 6 and 7 are provided on both the input side and the output side. However, only one of them may be provided as necessary.

Embodiment 3 FIG.
FIG. 3 is a circuit diagram showing a power conversion device according to Embodiment 3 of the present invention, and the same reference numerals are given to the components corresponding to those of Embodiment 1 shown in FIG.

  A feature of the power conversion device of the third embodiment is that a storage battery 14 is connected in parallel to a DC bus between the voltage smoothing circuit 13 and the inverter 12 constituting the converter 1.

  The storage battery 14 serves as an uninterruptible power supply (UPS). When the AC power supply is normal, the switching element Tr1 of the converter 11 is switched and the storage battery 14 is charged by the DC voltage from the voltage smoothing circuit 13. On the other hand, at the time of a power failure of the AC power source, the operation of the converter 11 is stopped and power is supplied from the storage battery 14 to the inverter 12 to supply stable and stable AC power to the load.

Even when the storage battery 14 is provided, stray capacitance is generated between the storage battery 14 and the grounding point (particularly, when the distance between the wirings of the converter 1 and the storage battery 14 becomes long), and therefore, via this stray capacitance, A high-frequency current generated by switching of the converter 1 leaks and flows. However, even in this case, the electrostatic capacitance of the bypass capacitor 5 is larger than the sum of the stray capacitance generated between the converter 1 and the ground point and the stray capacitance generated between the storage battery and the ground point. Since the leaked high-frequency current can be bypassed by the bypass capacitor 5, the high-frequency current associated with the switching of the converter 1 is passed through the grounding point on the power system side or the grounding point on the load side. Flow can be suppressed. As a result, it is possible to prevent inconveniences such as inducing disturbance to other devices connected to the power supply system side or affecting the radio frequency band.
Other configurations and operational effects are the same as those of the first embodiment, and thus detailed description thereof is omitted here.

The present invention is not limited to the configurations of the first to third embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in each of the first to third embodiments, when the converter 1 converts the AC voltage of the power supply system into a DC voltage, the switching element is configured by an IGBT (Insulated Gate Bipolar Transistor) in the figure. However, the present invention is not limited to this, and the same effect can be obtained even if it is replaced with a transistor or MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

  Further, in each of the first to third embodiments, except for the bypass capacitor 5, the wiring that electrically connects the common connection points of the capacitors 22 and 32 of the filters 2 and 3 on the input side and the output side is connected. However, the present invention is not limited to this. For example, as shown in FIG. 4, the same effect can be obtained by simultaneously connecting the bypass capacitor 5 to the DC bus of the converter 1. In addition, as shown in FIG. 5, the same effect can be obtained by simultaneously connecting the bypass capacitor 5 to the midpoint between the two capacitors C1 and C2 constituting the voltage smoothing circuit 13.

It is a circuit diagram which shows the power converter device in Embodiment 1 of this invention. It is a circuit diagram which shows the power converter device in Embodiment 2 of this invention. It is a circuit diagram which shows the power converter device in Embodiment 3 of this invention. It is a circuit diagram which shows the modification of the power converter device of this invention. It is a circuit diagram which shows the modification of the power converter device of this invention.

Explanation of symbols

1 converter, 11 converter, 12 inverter, 13 voltage smoothing circuit,
14 storage battery, 2 input filter, 3 output filter, 4 stray capacitance,
5 Capacitor for bypass, 6, 7 Common mode core.

Claims (5)

A converter that receives power from an AC power source to obtain a DC voltage and converts the DC voltage into an AC voltage, a filter connected to the input side of the converter, and a filter connected to the output side of the converter In the power converter provided,
The common connection point of the capacitor constituting the filter on the input side and the common connection point of the capacitor constituting the filter on the output side are electrically connected to each other, and the bypass is connected between the connection point and the ground point. A power converter characterized by connecting a capacitor. The power converter according to claim 1, wherein a common mode core is provided on at least one of an input side and an output side of the converter. 3. The bypass capacitor according to claim 1, wherein the bypass capacitor is set to have a capacitance equal to or greater than a stray capacitance generated between the converter and the grounding point. Power converter. The power converter according to claim 1, further comprising a storage battery connected to a DC bus of the converter. The bypass capacitor is set to have a capacitance equal to or greater than the sum of the stray capacitance generated between the converter and the ground point and the stray capacitance generated between the storage battery and the ground point. The power converter according to claim 4, wherein the power converter is provided.

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