DC/AC power converting apparatus including DC component remover

• US 5,012,400 A
• Filed: 09/21/1989
• Issued: 04/30/1991
• Est. Priority Date: 09/26/1988
• Status: Expired due to Term

• Current Assignee: Toshiba Mitsubishi-Electric Industrial Systems Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yasuda, Nobuyuki
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): Voeltz, Emanuel T.
• Application Number:
  US07/410,057
• Time in Patent Office: 586 Days
• Field of Search: 363/16, 363/17, 363/20, 363/21, 363/24, 363/25, 363/26, 363/39, 363/40, 363/41, 363/95, 363/98, 363/97, 363/131, 363/132, 363/133, 363/134
• US Class Current: 363/95
• CPC Class Codes: H02M 1/12 Arrangements for reducing harmonics from ac input or output
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: H02M 7/4803 with means for reducing DC component from AC output voltage

Abstract

In a DC/AC power converting apparatus, a DC component is removed from an AC output. The DC/AC power converting apparatus includes: a DC source for supplying DC power; a DC/AC inverter circuit for inverting the DC power into AC power; a transformer for transforming the AC power to obtain desirable AC power; a detector for detecting an output signal derived from the DC/AC inverter circuit to produce an output detection signal; a calculation circuit for performing a control calculation to enable the output detection signal to follow a reference signal, whereby a first output instruction signal is derived; and, a DC component remover for removing a DC component from the first output instruction signal to derive a second output instruction signal inverting operation of the DC/AC inverter circuit is controlled based upon the second output instruction signal to prevent DC magnetization of the transformer.

Claims

1. A power converting apparatus comprising:

means for supplying DC (direct current) power;

DC-to-AC inverting means for inverting the DC power into AC (alternating current) power;

transformer means for transforming the AC power to obtain desirable AC power;

detecting means for detecting an output signal from the DC-to-AC inverting means to produce an output detection signal;

calculating means for performing a control calculation for the DC-to-AC inverting means to enable the output detection signal to follow a reference signal by generating a first output instruction signal; and

,

DC component removing means, located in a feedback loop between the calculating means and the DC-to-AC inverting means, for removing a DC component from the first output instruction signal to derive a second output instruction signal such that the inverting operation of the DC-to-AC inverting means is controlled based upon the second output instruction signal to prevent DC magnetization of the transformer means.

2. A power converting apparatus as claimed in claim 1, further comprising:

means for converting the second output instruction signal output from the DC component removing means into a pulsatory gate signal to control the inverting operation of the inverting means.

3. A power converting apparatus as claimed in claim 1, wherein the DC component removing means includes:

a low-pass filter filtering the first output instruction signal to obtain the DC component contained in the first output instruction signal;

an inverter inverting the DC component derived from the low-pass filter to output an inverted DC component; and

,

an adder adding the inverted DC component to the first output instruction signal to obtain the second output instruction signal.

4. A power converting apparatus as claimed in claim 3, wherein a cutoff frequency of the low-pass filter is selected to be considerably lower than a frequency of the AC power derived from the DC-to-AC inverting means.

5. A power converting apparatus as claimed in claim 4, wherein cutoff frequency of the low-pass filter is approximately 2 Hz and the frequency of the AC power is from 50 to 60 Hz.

6. A power converting apparatus as claimed in claim 1, wherein DC component removing means includes an integrator circuit and a subtracting circuit.

7. A power converting apparatus as claimed in claim 1, wherein the detecting means includes a current transformer.

8. A power converting apparatus as claimed in claim 1, wherein the detecting means includes a potential transformer.