JPS61173694A - Power converter - Google Patents

Abstract

PURPOSE:To obtain a power converter having an extremely small transient variation and stable converter unit in a simple circuit configuration by providing a power source phase detector and a self-extinguishing element drive circuit for obtaining the output of the detector. CONSTITUTION:In a controller 9, a phase detector 91 generates signals of outputs 901-906 by the voltages of 3-phase AC power source 1. The outputs 901-906 are signals of 180 deg. of firing phase angle and 120 deg. of conducting period for the AC power source voltage. The output of the detector 91 is amplified by a driver 92 as it is, applied as a drive signal to self-extinguishing elements S1-S6 of a converter 3, and the elements S1-S6 are fired or extinguished. Thus, a DC voltage unit is connected through diodes D1-D6 and the elements S1-S6 always so that the voltage between the lines of 3-phase AC power source 1 are fed through AC reactors 2, 2', 2'' to the maximum 2-phases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a static power converter that converts AC power into DC power and regenerates DC power into AC power.

[Conventional technology]

In power converters that obtain AC power and perform AC/DC conversion, it has recently become increasingly desirable to regenerate DC power to AC power from the standpoint of energy conservation.In general, AC motor drive devices reduce the load during deceleration. Since the kinetic energy is regenerated to the DC voltage section as electrical energy, the DC voltage increases. Here, an excessive rise in DC voltage may lead to damage to the semiconductor element. Therefore, a conventional method has been adopted in which a resistor is connected between the positive and negative electrodes of the DC voltage section, and the resistor consumes the power regenerated from the motor to suppress the rise in the DC voltage.

Furthermore, an AC motor drive device as shown in FIG. 3 is known as one that uses a conventional method of regenerating the electric power regenerated from the electric motor to the DC voltage section to the AC power supply.

FIG. 3 shows the configuration of main parts of a conventional power converter, in which 1 is a three-phase AC power supply, 2.2', 2' are AC reactors, 3 is a self-extinguishing element 5. , S, , Ss * 8
4 eSs, a diode Dr e D2 + connected in antiparallel to Sg and the self-extinguishing element S5-8m, respectively.
The converter section is bridge-connected from Da e Da t Ds e Da, 4 is a DC smoothing capacitor,
Similarly to the converter section 3, the inverter section is composed of a self-extinguishing element and a diode connected in a bridge manner, and the numeral 6 is an alternating current.
-There is an electric motor. Here, the converter section 3 shows an example in which transistors are used as self-extinguishing elements 5l-8s, and functions as a forward converter that obtains DC voltage from an AC power source when the AC motor 6 is in motion, and converts DC power during regeneration. It works as an inverse converter that regenerates AC power. Further, the inverter section 5 converts the DC voltage into an arbitrary AC voltage when the motor is in power operation, and during regeneration, rectifies the regenerated power and returns it to the DC voltage section.

Furthermore, 7 is a control circuit section of the converter section 3, and 8 is a current detector. Here, the control circuit section 7 includes a phase detector 71.
Voltage setting device 72. Subtractor 73. Pulse control circuit 74. Power regeneration determination circuit 75. It consists of an AND circuit 76 and a drive circuit 77. Note that the control circuit section of the inverter section 5 is omitted since it is not the gist of the present invention.

The function of such a connection configuration is as follows.

Now, the direct fL voltage section, that is, the -voltage voltage of the capacitor 4 is output. Further, the pulse control circuit 74 determines the distribution of the ignition signal to be applied to the self-extinguishing cords 81 to 86 in accordance with the output of the subtracter 73 and the output of the phase detector 71 so as to make the DC voltage match the DC voltage setting voltage. On the other hand, the power regeneration determination circuit 75 determines whether the AC lIC1Ib horizontal 6 is in the power state based on the DC voltage section voltage and the current polarity signal of the current detection a8 output.
It determines whether it is in the regeneration state and outputs "0" when it is in the 9th regeneration state and "1" when it is in the 9th regeneration state.

Here, the AND circuit 76 indicates that the row-raw discrimination circuit 75 indicates rl.
The output of the pulse control circuit 74 is sent to the drive circuit 77 only when the AC motor 6 is outputting J, that is, when the AC motor 6 is regenerating. The drive circuit 77 amplifies the output of the AND circuit 76 and connects the self-extinguishing cable Sx e Ss of the converter section 3.
* Sm * 84 e vortex, ignites or extinguishes 8.

Therefore, in the device for driving the AC motor shown in FIG. 3, when the motor is running, the drive signal to the self-extinguishing elements S1 to S6 is blocked by the regeneration determination circuit 75 and the AND circuit 76, so that the self-extinguishing elements S1 to S6 are self-extinguishing. All the arc elements 5s-8s remain extinguished, and power is supplied from the three-phase AC power supply l to the AC reactors 2.2', 2', the diodes D1 to Ds of the converter section 3, and the DC voltage section.

It is supplied to an AC motor 6 via an inverter section 5.

During motor regeneration, the power emitted by the AC motor 6 is regenerated from the inverter section 6 to the DC voltage section. 74 output is the power regeneration discrimination circuit 7
5 and the AND circuit 76 to the drive circuit 77, the self-arc-extinguishing element S5-8m is controlled, and the resulting power of the DC voltage section is regenerated to the three-phase AC power supply l.

Therefore, such a conventional AC motor drive device is provided with a control circuit section 7 as shown in the figure, which controls the flow of power according to the state of power regeneration of the motor.

[Problem that the invention seeks to solve]

Conventional power conversion devices, like the AC motor drive device shown in Figure 3, detect that the motor is in a regenerative state and then control the DC voltage to a constant level. The control circuit section has a complicated configuration, requiring a circuit section for detecting whether the motor is in the 9 regeneration state or the 9 regeneration state, and a pulse control circuit section.

Further, since both the DC voltage and the AC power source transfer power between circuits with low impedance, it is not easy to keep the DC voltage constant while stably controlling the flow of power between the two. Furthermore, transient fluctuations in the DC voltage due to sudden changes in load cannot be avoided, and the system may become unstable depending on the response speed and gain of the control system. In particular, when switching between F-row and regeneration, the transient fluctuation becomes even larger due to the detection delay of the F-row regeneration discrimination circuit and the sudden change in the state of the main circuit due to the start or end of switching of the semiconductor element. Therefore, it has become necessary to provide a margin for the voltage rating and current rating of the semiconductor element, and it has become necessary to provide a separate current limiting unit.

[Means for solving problems and their effects]

In view of the above-mentioned points, the present invention has been developed to provide a converter unit capable of forward conversion and inverse conversion, which incorporates a simple control circuit unit to provide a converter unit in which direct current and voltage are stable and transient fluctuations are extremely small even when the load suddenly changes. The converter section does not perform control to keep the DC voltage constant, nor does it detect whether the motor is in a power running state or a regeneration state. Therefore, it is possible to provide a device with a simple configuration that can perform power running regeneration without performing any process. Hereinafter, the present invention will be explained based on the drawings.

〔Example〕

FIG. 1 shows the main part configuration of an embodiment according to the present invention, and 9 is a control circuit section. In the figure, the same reference numerals as in FIG. 3 indicate the same components. Here, the control circuit section 9 includes a phase detector 91 and a drive circuit 92.

If this connection configuration is compared with FIG. 3, the difference is that the control circuit section 7 shown in FIG. 3 is replaced with the control circuit section 9 as shown.

Furthermore, FIG. 2 is a waveform diagram shown for explanation of FIG. 1, and VRI! l * VsTe VTRGi Three-phase AC power supply voltage of source 1, VRF is virtual rectified voltage of three-phase AC-IIL source 1 power supply voltage, vDo is DC voltage in DC voltage section, 901 , 902 , 903 , 904 , 90
5, 906 is the output of the phase detector 91 of the control circuit section 9;
IDO indicates the DC current of the converter section 3, and IR indicates the 8-phase current of the three-phase AC power supply 1.

Next, the functions of the connection configuration shown in FIG. 11g1 will be explained in detail with reference to FIG. 2.

In the control circuit section 2, the phase detector 91 generates output signals 901 to 906 to the drive circuit 92 based on the voltage of the three-phase AC power supply 1. Here, the outputs 901 to 906 have an ignition phase angle of 180° with respect to the AC power supply voltage as shown in the example.
, is a signal with a conduction period of 120°. Then, the output of the phase detector 91 is directly amplified by the drive circuit 92, and the self-extinguishing elements Ss, S2.
As, SaqSs*Ss are given as drive signals, so that the self-extinguishing elements S1 to S6 are turned on or off. Here, the way the drive signal is given to the above-mentioned self-extinguishing element is AC'dim.
It does not change whether the machine 6 is in the running state or in the regeneration state, and is always given.

In this way, according to the first factor and FIG. 2, when the AC motor 6 is in the power state, the electric power is
The current flows from the AC reactors 2.2', 2' to the diodes Dl-Ds of the converter section 3, to the DC voltage section, to the inverter section 5, and to the AC motor 6. In this case, during the period when the self-extinguishing elements S1 to S6 are turned on, the diode D! Since it is included in the period in which current is flowing through D6, the fact that the self-extinguishing elements S1 to S6 are turned on has no effect on the forward conversion operation of the converter unit 3. Therefore, the DC current IDO and the R-phase current generator 8 are the same as when the converter section 3 is composed of only diodes Dl=Ds as shown before time To in FIG. When in the regenerative state, the regenerated power from the AC motor 6 passes through the diode section of the inverter section 5 and is regenerated to the DC voltage section, attempting to increase the DC '1 voltage, but the average value of the virtual rectified waveform of the AC/power supply That is, when the DC voltage VDO becomes higher than the virtual rectified voltage Vat, the self-extinguishing elements S1 to S6 of the converter section 3 and the AC reactors 2 and 2'.

A current flows through 2' and is returned to the three-phase AC power supply 1. At this time, the diodes D1 to D of the converter section 3
6, a reactive current flows only during the overlap period necessary for commutation. Therefore, this DC current IDO and the 8-phase current IR
The situation is shown at time T in Figure 2.

The result will be as shown below.

In other words, the firing phase angle of the self-extinguishing elements 81 to 86 of the converter section 3 is 180 degrees, and the conduction period is 120 degrees.
Due to the ignition caused by Always three-phase AC power supply 1 via elements 5s-8s
AC reactors 2.2', 2 are connected to the two phases with the maximum line voltage.
This means that the DC voltage section is connected to the power source of the DC voltage vno with the waveform shown by the broken line in Fig. 2 via the AC reactors 2, 2', and 2'. Therefore, when the AC motor 6 is running, the voltage of the DC voltage section is reduced by the voltage drop due to the AC reactors 2.2' and 2' due to the virtual rectification of the AC power supply and the average value of the waveform. Furthermore, during regeneration of the AC motor 6, the voltage of the DC voltage section is determined to be a voltage that is higher than the average value of the virtual rectified waveform of the AC power supply by the voltage drop caused by the AC reactors 2.2', 2'.

As described above, in this embodiment, the control circuit section 9, which includes only the phase detector 91 and the drive circuit 92, is capable of responding to the power running and regenerative operation of the AC motor 6.

Furthermore, it is clear that with such a system, the fluctuations in the DC voltage part are only caused by the AC reactor part, and there are no transient fluctuations or instability caused by the response speed or gain of the control system. Therefore, even with sudden changes in load conditions, only transient fluctuations due to the main circuit impedance, ie, the AC reactor portion, occur, and a transition due to switching and response of the control system occurs as shown at time To in FIG.

In this way, whether the motor is in the power regeneration state or in the first regeneration state is automatically determined by the magnitude of the average value of the voltage of the DC voltage section and the virtual rectified waveform of the AC power supply, and any sudden changes in power regeneration are automatically determined. , load conditions, etc., it can be assumed that only transient fluctuations limited by the AC reactor section will not occur.

〔Effect of the invention〕

As explained above, according to the present invention, a special power conversion device capable of forward conversion and inverse conversion is provided, which can realize a converter section of an AC motor drive device with extremely small transient fluctuations and stability using a control circuit section with a simple configuration. can be provided.

Although this explanation has been made using an AC motor drive device as an example, the power converter device capable of forward conversion and inverse conversion according to the present invention generally applies to all systems that require power transfer between a DC voltage and an AC power source. It can be applied to

For example, it is suitable for regenerating reactive power generated during commutation in a current source inverter.

Further, although the example uses a transistor as the self-extinguishing element, it is of course possible to use any semiconductor element having self-extinguishing ability, such as a gate turn-off thyristor.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing the main part configuration of an embodiment of the present invention, Fig. 2 is a waveform diagram shown for explanation of Fig. 1, and Fig. 3 shows the main part structure of a conventional power conversion device. FIG. 1...Three-phase AC' power supply, 3...Converter section, 4...Capacitor, 5...Inverter section, 6...AC Electric motor, 7.9...
...Control circuit section, Vas e VIIT #V'rR
...Power supply voltage, YAF...Virtual rectified voltage, VDO...DC voltage, IDO...
DC current, IR...R phase current.

Claims (1)

[Claims] In a power conversion device capable of forward and reverse conversion, which has a converter section with a bridge connection configuration using an anti-parallel circuit of a self-extinguishing element and a diode, converts AC power into DC, and regenerates DC power into AC power. , a power supply phase detection circuit and a self-arc-extinguishing element drive circuit for obtaining the output of the power supply phase detection circuit are provided, and the self-arc-extinguishing element is set at a constant phase angle of 180° and a conduction period of 120° with respect to the AC power supply. A power converter device characterized in that the power converter always fires regardless of whether a forward conversion operation or an inverse conversion operation is being performed.