Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Patent
1999-06-09
2000-12-05
Wong, Peter S.
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
363 53, 363 80, H02M 112, H02M 114
Patent
active
061575542
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electric power unit with a condenser input type rectification circuit which converts an alternating current power source to a direct current voltage, and more particularly, to an electric power unit for inverter-controlled refrigerators, etc.
PRIOR ART
While a condenser input type rectification circuit has been widely used to convert an alternating current to a direct current in inverters of refrigerating systems such as refrigerators, air conditioners and the like, or in switching power sources, etc., a current waveform of the condenser input type rectification circuit is not a sine wave, but includes many higher harmonics, particularly higher harmonic components of odd orders of a fundamental frequency, thus causing various troubles. For lessening the current of higher harmonics, therefore, more and more development has been proceeded, one of which is realized as a passive filter. The passive filter is adapted generally to soften the current waveform with the use of a reactor thereby to suppress higher harmonics. However, the reactor of the passive filter should be of a considerably large capacity in order to completely suppress the higher harmonics only thereby. In the meantime, another type of proposals has been made to control the higher harmonics, in which an auxiliary means is employed. For instance, Unexamined Japanese Patent Laid-Open Publication No. H7-274515 describes an effective method for the purpose.
BACKGROUND TECHNOLOGY OF THE INVENTION AND ITS PROBLEM
In order to understand features of the present invention, an electric power unit adopting a conventional higher harmonics control method will be described with reference to FIGS. 19 and 20. FIG. 19 is a circuit diagram of an example of a conventionally used electric power unit. An electric power unit 100 in FIG. 19 is constituted of an alternating current power source 101 which is, for example, a commercial power source of 100V 50 Hz to general household, a bridge-type rectifier 102 for rectifying the alternating current power source 101, a first reactor 103, a diode 104, a second reactor 105, a capacitor 106 and a smoothing capacitor 107. The bridge-type rectifier 102 consists of four diodes D101, D102, D103, D104 in bridge connection.
The first reactor 103 has its one end connected to a + output of the bridge-type rectifier 102 and the other end connected to an anode of the diode 104. The second reactor 105 has its one end connected to the + output of the bridge-type rectifier 102 and the other end connected to one end of the capacitor 106. A cathode of the diode 104 is connected with the other end of the capacitor 106, and connected also to one end of the smoothing capacitor 107. The other end of the smoothing capacitor 107 is connected to a - output of the bridge-type rectifier 102. A load 108 of the power unit 100 is connected to both ends of the smoothing capacitor 107.
Now, the operation of the electric power unit 100 will be described. FIG. 20 is a diagram of waveforms of a half cycle in the electric power unit 100 shown in FIG. 19. An input voltage Vin from the alternating current power source 101 is a sine wave as indicated in FIG. 20. A current I101 running in the first reactor 103 shows a bent waveform because a charging current to the smoothing capacitor 107 is smoothed at the first reactor 103. A current I102 running in the second reactor 105 shows a waveform oscillating with a resonant frequency of the second reactor 105 and capacitor 106. An input current Iin becomes a sum of I101 and I102, assuming a waveform as shown in FIG. 20. Since the waveform of the input power is softened and a peak value of the current is lowered as above, higher harmonics are suppressed further.
The aforementioned arrangement has drawbacks, though. As described hereinabove, in the prior art, such current is supplied that supplements higher harmonics with the utilization of the resonance of the second reactor 105 and capacitor 106 and consequently, the resonant frequency is required to
REFERENCES:
patent: 3660787 (1972-05-01), Mahmoud et al.
patent: 5399955 (1995-03-01), Glaser et al.
patent: 5535087 (1996-07-01), Puckett et al.
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patent: 5687070 (1997-11-01), Jacobs et al.
patent: 5777866 (1998-07-01), Jacobs et al.
patent: 5883502 (1999-03-01), Spitaler
Patent Abstracts of Japan, vol. 11, No. 367 (E-561), Nov. 28, 1987 & JP 62 138058 A (Matsushita Seiko), Jun. 20, 1987.
Patent Abstracts of Japan, vol. 11, No. 355 (E-558), Nov. 19, 1987 & JP 62 131757 A (Hitachi Metals), Jun. 15, 1987.
Endo Katsumi
Hamaoka Koji
Kurimoto Kazunori
Matsushita Refrigeration Company
Vu Bao Q.
Wong Peter S.
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