JPS6185065A - Inverter device - Google Patents

Abstract

PURPOSE:To reduce a ripple current and to suppress an induction defect by producing the ripple voltage component of a special frequency from a low pass filter, and connecting it with a transformer in the polarity to become reverse phase. CONSTITUTION:An output voltage of a DC filter is fed from both terminals of a capacitor 6 to an input filter 9, and input to an amplifier 11 through a band filter 10 for sorting the special frequency (the frequency of the commercial frequency band). The output of the amplifier 11 is applied in series with a reactor 5 by a transformer 12, and in reverse phase polarity to the ripple voltage of the special frequency of the capacitor 6. An input overvoltage suppressor 13 is connected with the input side of the filter 10, and an output overvoltage suppressor 14 is connected with the output side of the amplifier 11, and protected. Thus, the special frequency is sorted from the output voltage (the input voltage of the inverter 7) of the filter circuit, superposed on a DC circuit in the reverse polarity, thereby reducing the ripple current contained in the feedback current.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a DC filter circuit formed by connecting a series reactor and a shunt capacitor in an inverse manner from a DC iii #i, and a variable voltage/variable frequency inverter. The present invention relates to an inverter device that supplies power to an AC load via an inverter device, and particularly to an induction damage suppressing means in an N source circuit of an inverter that drives and controls an induction motor for driving an electric vehicle.

[Technical background of the invention and its problems]

FIG. 1 shows a typical main circuit configuration when an induction motor as a main motor in an electric vehicle is driven and controlled by a variable voltage/variable frequency inverter (hereinafter referred to as a VVVF inverter). In this main circuit, pantograph 1
A DC filter circuit consisting of a main fuse 2, a current breaker 3, a high-speed circuit breaker 4, a DC reactor 5, and a shunt capacitor 6 connected in reverse is connected to the DC power collected by V.
It is supplied to a VVF inverter 7, where it is converted into variable voltage/variable frequency three-phase alternating current to drive an induction motor 8.

In such electric vehicle main circuits, inductive disturbances due to the current controlled intermittently by the switching elements constituting the VVVF inverter, that is, 6 times the inverter frequency, occur when a wide range of frequency control operation from low frequency to high frequency is performed. A return current i containing frequency harmonics flows. The induction of this harmonic current may cause various safety equipment such as traffic lights and railroad crossings to malfunction. For this reason, for example, the ripple current component included in the return current i is specified to be suppressed to 0.7 A or less in the case of the 50H2 or 60H7 commercial frequency band.

The DC filter circuit consisting of the reactor 5 and the capacitor 6 originally has the function of reducing harmonic components contained in such return current. However, in order to reduce the harmonic current components to below the above-mentioned values with this DC filter circuit, the inductance of the rear coil 5 and the capacitance of the capacitor 6 must be set to considerably large values. In this case, even if a high-voltage and large-capacity filter is required, the filter circuit that satisfies such requirements is large in size and has a large ω, but there are severe constraints on the space for installation. For example, an inverted LC filter circuit reduces ripple current of 50Hz component by 10dB.
To attenuate, C=650 with C=10ml l-1
A large capacitor with a very large value of 0 μF is required.

On the other hand, it has conventionally been a problem to select from the voltage of the filter capacitor of the VVVF inverter a voltage component corresponding to a ripple at a specific frequency in the return current, which is problematic due to the above-mentioned inductive disturbance. In other words, the filter capacitor voltage is a distorted wave in which pulse-like voltages caused by switching of the inverter switching elements are superimposed in addition to the ripple component of the frequency 6 times the inverter output frequency.For example, when the DC voltage of the filter capacitor is 1500V, the above-mentioned Since the pulsed voltage reaches over 100V AC, approximately 1
It is difficult to selectively extract ripple voltages of commercial frequency components of 0 V or less from these distorted waves even when using a general bandpass filter.

As mentioned above, in the conventional reverse type C filter circuit, in order to attenuate the harmonic components contained in the return current, especially the components below the commercial frequency band, it is necessary to This poses a problem in that it is disadvantageous in terms of weight, space, and economy, especially when used in vehicles.

(Objective of the Invention) Therefore, an object of the present invention is to reduce harmonic current contained in the return current of an inverter, especially ripple current below the commercial frequency band, by a small and lightweight means, and to effectively eliminate inductive disturbances. An object of the present invention is to provide an inverter device that can suppress the above.

[Summary of the invention]

In order to achieve this object, the present invention provides, in the above-mentioned inverter device, a high-pass filter that extracts an AC component voltage from the output side voltage of the DC filter circuit, and an i! a low-pass filter that removes a pulse-like voltage component of a 2i voltage and a convex frequency; a bandpass filter that does not extract a ripple voltage component of a specific frequency from the output of the low-pass filter; and an amplifier that amplifies the output of the bandpass filter. Connect the primary winding to the output side of the amplifier,
The present invention is characterized by comprising a transformer in which a secondary winding is connected in series with the DC filter circuit accelerator with a polarity opposite to the ripple voltage of the specific frequency included in the output side voltage of the DC filter circuit. It is something to do.

Furthermore, in addition to the above, the present invention provides an overvoltage suppression device that protects the bandpass filter and amplifier from overvoltage generated on the secondary winding side of the transformer or overvoltage arriving at the primary winding side based on the overvoltage. This is a characteristic feature.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment in which the present invention is applied to the main circuit of an electric vehicle having the circuit configuration shown in FIG.

In FIG. 1, the voltage on the output side of the DC filter circuit is derived across capacitor 6 and introduced into input filter 9. In FIG. The input filter 9 is an RC filter formed by connecting a capacitor 16 and a resistor 17 in an inverted manner, as shown in FIG.
It consists of a high-pass filter and an RC low-pass filter formed by connecting a resistor 18 and a capacitor 19 in an inverted manner.

A bandpass filter 10'/fi using an operational amplifier is provided on the output side of the input filter 9 to select a specific frequency (in this embodiment, a frequency in the commercial frequency band), and an amplifier is further provided on the output side of the input filter 9. 11 are provided. It is assumed that the amplifier 11 has no phase between its input and output. The output side of amplifier 11 is connected to the primary winding of transformer 12 .

The secondary winding of this transformer 12 is connected to the power supply side of the capacitor 6,
It is arranged so as to be in series with the reactor 5 in terms of circuit, and so that a voltage having a polarity opposite in phase to the ripple voltage of a specific frequency of the capacitor 6 is applied. An input overvoltage suppression device 1 for suppressing overvoltage from the input filter 9 is provided on the input side of the bandpass filter 10 including active circuit elements.
Similarly, a transformer 1 is connected to the output side of the amplifier 11.
An output overvoltage suppressor 14 for suppressing overvoltage from 2 is connected. Both overvoltage suppression devices 13 and 14 include overvoltage absorbing capacitors, and receive control power from the control power source 15.

Now, in the circuit of FIG. 1, the output voltage of the filter circuit, that is, the input terminal of the inverter 70 is input to the input filter 9, and here the capacitor 16 and the resistor 1
A high-pass filter consisting of a resistor 18 and a capacitor 19 removes the direct current component and extracts only the alternating current component, and a low-pass filter consisting of a resistor 18 and a capacitor 19 removes pulse-like high voltages with a frequency of 5001-1 z or higher. Set constants for . - That is, the frequency characteristics of the input filter 9 are like the phase characteristics shown by curve (a) and the amplitude characteristics shown by curve (b). The output voltage of the input filter 9 from which DC components and pulsed voltages with a frequency of 500 Hz or more have been removed in this way is input to the bandpass filter 10, where an operational amplifier is used to calculate the phase (a) as shown in FIG. ) and amplitude (b), ripple voltages in the commercial frequency band (here, 50 Hz) are selectively extracted from the input voltage, and ripple voltages at other frequencies are attenuated. The output of the bandpass filter 10 is amplified by the amplifier 11 and superimposed on the DC circuit via the transformer 12 with the polarity as described above. That is, as shown in FIG. 5, the ripple voltage (a) in the commercial frequency band included in the output side voltage of the DC filter circuit has the opposite phase and the same voltage value superimposed from the secondary side of the transformer 12. is canceled out by the voltage (b). Thereby, the ripple current included in the return current can be reduced.

By introducing the voltage to the bandpass filter 10 through the input filter 9, high voltages that cannot be sufficiently attenuated by the bandpass filter 10 alone, such as DC voltages of 15 V or more and high frequency pulses, can be removed in advance by the input filter 9, and the entire circuit can be removed. The amplitude and phase can be easily adjusted. Furthermore, because the bandpass filter 10 does not need to handle high voltages for the above-mentioned reasons, a dedicated amplifier can be used, and excellent attenuation characteristics can be obtained with a simple circuit configuration.

On the other hand, the input overvoltage suppression device 13 and the output overvoltage suppression device 14 absorb overvoltage when an overvoltage occurs in the main circuit (power circuit consisting of elements 1 to 8) at the time of startup or during a transient phenomenon such as an accident. The bandpass filter 10 and amplifier 11 including the operational amplifier are protected from overvoltage.

As described above, in the device of the present invention, the attenuation characteristics of the harmonic ripple current included in the return current of the main circuit are determined by the frequency characteristics of the input filter 9 and the bandpass filter 10. Input filter 9 and band filter 10 also for harmonic ripple current other than the band? I) This can be addressed by changing the frequency characteristics by changing circuit constants or combining multiple sets of filters.

Although the above embodiment is an example of an inverter that supplies power to an induction motor for driving an electric vehicle, the present invention is not limited thereto and can be applied to other AC loads.

〔Effect of the invention〕

As described above, according to the present invention, the ripple current of a specific frequency included in the return current generated by the operation of the VVVF inverter can be removed without using a large filter reactor or capacitor in the main circuit. , can be efficiently reduced by a small and lightweight circuit device, and highly reliable suppression of inductive disturbances can be achieved.

[Brief explanation of drawings]

Fig. 1 is a circuit connection diagram showing an embodiment of the present invention, Fig. 2 is a connection diagram showing a specific example of the input filter of Fig. 1, and Fig. 3 shows the frequency characteristics of the input filter of Fig. 1. FIG. 4 is a characteristic diagram showing the frequency characteristics of the bandpass filter in FIG. 1, FIG. 5 is a voltage waveform diagram for explaining the canceling effect of ripple current in the device in FIG. 1, and FIG. is the induction motor V
1 is a connection diagram of a known electric vehicle main circuit whose drive is controlled by a VVF inverter. 5... Series reactor, 6... Shunt capacitor, 7
...VVVF inverter, 8...Induction motor, 9.
...Input filter, 10...Band filter, 11...
・Amplifier, 12...Transformer, 13.14...Overvoltage suppressor, 16.19...Capacitor, 17.18・
··resistance. Applicant's agent Kiyoshi Inomata Figure 2 Figure 3 Frequency (Hz) Figure 4 Figure 5

Claims (1)

[Claims] 1. An inverter that supplies power from a DC power source to an AC load via a DC filter circuit formed by connecting a series reactor and a shunt capacitor in an inverted L shape, and a variable voltage/variable frequency inverter. In the apparatus, a high-pass filter extracts an AC component voltage from the output side voltage of the DC filter circuit, and a low-pass filter removes high-voltage and high-frequency pulse-like voltage components from the AC component voltage extracted by the high-pass filter. A bandpass filter that extracts a ripple voltage component of a specific frequency from the output of this low-pass filter, an amplifier that amplifies the output of this bandpass filter, a primary winding connected to the output side of the amplifier, and a secondary winding connected to the output side of the amplifier. An inverter device comprising: a transformer connected in series with the series reactor with a polarity opposite to the ripple voltage of the specific frequency included in the output side voltage of the DC filter circuit. 2. In an inverter device that supplies power from a DC power source to an AC load via a DC filter circuit formed by connecting a series reactor and a shunt capacitor in an inverted L shape, and a variable voltage/variable frequency inverter, the DC filter A high-pass filter that extracts an AC component voltage from the output side voltage of the circuit, a low-pass filter that removes high-voltage and high-frequency pulse-like voltage components from the AC component voltage extracted by this high-pass filter, and this low-pass filter. a bandpass filter for extracting a ripple voltage component of a specific frequency from the output of the bandpass filter, an amplifier for amplifying the output of the bandpass filter, a primary winding connected to the output side of the amplifier, and a secondary winding connected in series to the series reactor. A transformer connected with a polarity opposite to the ripple voltage of the specific frequency included in the output side voltage of the DC reactor circuit, and an overvoltage generated on the secondary winding side of this transformer or the primary An inverter device comprising: an overvoltage suppression device that protects the bandpass filter and the amplifier from overvoltage arriving at the winding side.