JPH0746073Y2 - Power converter - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a power converter using a battery and an AC / DC converter as a DC power supply, and particularly to a power converter suitable for absorbing regenerative energy from a load.

B. Outline of the Invention The present invention is a power converter having a battery and an AC / DC converter as a DC power source. By absorbing the regenerative current to the battery side when the DC voltage rises due to the regenerative current from the load, the regenerative energy is absorbed. This is to ensure the prevention of overvoltage.

C. Conventional Technology Generally, DC or AC power of current or voltage controlled by a power converter such as a chipper or an inverter is obtained from DC power, and this power is supplied to an inductive load such as a DC machine or an induction motor. In the power converter, DC power is obtained from an AC power supply such as a commercial power supply by a rectifier or an AC / DC converter such as a forward converter, and a battery is provided in parallel with the AC / DC converter as a backup DC power supply.

Then, in order to process the regenerative current from the load generated at the time of switching the forward / reverse rotation with respect to the inductive load or at the time of turning off the switch element of the power conversion unit, conversion to DC by the rectifier and resistance consumption or regeneration to AC power supply are performed. I am trying.

D. Problems to be Solved by the Invention The conventional regenerative energy processing method has problems that the power efficiency is lowered and a complicated and expensive processing circuit is required.

E. Means and Actions for Solving Problems The present invention has been made in view of the above problems, and is a power converter that supplies AC power to a load from a power conversion unit that uses a battery and an AC / DC converter as a DC power supply. In the DC power supply, the DC output end of the battery and the DC output end of the AC / DC converter are connected in parallel via diodes for preventing backflow to supply DC to the power converter, and the AC / DC converter is provided. A voltage detection circuit for detecting that the DC voltage of the electric power converter exceeds the voltage of the comparison reference by the regenerative current from the load with the voltage of the DC output terminal of the comparison reference, and the detection signal of the voltage detection circuit. A switch circuit for conducting the diode in the reverse direction provided between the DC output terminal of the battery and the DC power source, and the DC voltage of the power conversion unit is likely to rise due to the regenerative current from the load side. In Rutoki absorbs regenerative current as a charging current to the battery output voltage of the AC-DC converter unit as a detection reference voltage.

F. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention, which is applied to a power converter that drives an induction motor by a transistor type voltage source inverter. The DC power supply is composed of a battery 1 and a rectifier 2 connected in parallel via diodes 3 and 4. This DC power supply has a smoothing capacitor 5 and supplies DC power to the inverter unit 6. The inverter unit 6 includes power transistors U, V, W, X, Y, Z connected in bridges, and regenerative diodes D _U , D _V , in antiparallel with these transistors.
D _W , D _X , D _Y , and D _Z are provided, and AC power is supplied to the induction motor 7 by on / off control such as P _W M control of the transistors U to _Z.

In such a power converter, the current energy flowing through the winding of the electric motor 7 at the time of forward / reverse switching of the electric motor 7 and deceleration is regenerated to the DC side through the diodes D _{U to} D _Z. This regenerative current becomes the charging current of the capacitor 5, but since the capacitor 5 is made to absorb the voltage surge from the electric motor side caused by the high-speed switch in the inverter unit 6, the capacitor 5 is charged by the regenerative current. If the voltage is left as it is, it will be overvoltage. Further, when the mechanical system coupled to the electric motor 7 has a driving ability, when the electric motor speed increases to the maximum rotation, there is no regenerative ability, which causes an overspeed.

Therefore, in this embodiment, the circuit means for absorbing the regenerative energy in the battery 1 is provided. A current limiting resistor 9 and a reverse voltage blocking diode 19 are connected in series to the input side light emitting diode of the photocoupler 8, and this series connection circuit is provided between the voltage end of the capacitor 5 and the output end of the rectifier 2.
The output side phototransistor of the photocoupler 8 is connected in series with the resistor 11 so as to obtain an output current from the voltage terminal of the capacitor 5. This photocoupler and its peripheral circuits constitute a voltage detection circuit, and it is detected that the charging voltage of the capacitor 5 exceeds the output voltage of the rectifier 2 by the regenerative current from the electric motor 7 side as an ON output of the phototransistor on the output side of the photocoupler 8. To do.

Next, a power transistor 12 in Darlington connection is connected in antiparallel to the diode 3, and the output signal of the photocoupler 8 is applied as a base current to the power transistor 12 for on / off control thereof. This power transistor
A switch circuit 12 is on-driven by the detection output of the photocoupler 8 and forms a current path by using the regenerative current from the electric motor 7 side as the charging current to the battery 1.

By providing such a circuit, when the regenerative current from the electric motor 7 tries to overcharge the capacitor 5, the power transistor 12 is turned on by the ON output of the photocoupler 8, and the regenerative current is regenerated as a battery charging current to regenerate the power of the capacitor 5. The voltage is limited to the output voltage of the rectifier 2.

In this embodiment, the detection circuit is simplified by detecting the overcharge of the capacitor by using the DC output voltage of the rectifier 2 as a reference. In addition, the control means of the transistor 12 is easily established by providing the voltage detection with the insulating means by the photocoupler.

The above embodiment shows the case where the invention is applied to the transistor type voltage source inverter, but it can be applied to other types of inverters in the same manner, and can be applied to other power converters such as a direct current motor controller by a chip. Of course.

G. Effect of the Invention As described above, according to the present invention, the regenerative current is converted to the battery by detecting the increase in the DC voltage due to the regenerative current from the load side in the power converter using the battery and the AC / DC converter as the DC power source. Since it is absorbed as the charging current, it is possible to reliably prevent the DC overvoltage of the power conversion unit and improve the power efficiency with a configuration having a relatively small number of circuit elements. Further, in the present invention, the AC / DC converter and the battery are connected in parallel via the pair of diodes, and the terminal voltage of the AC / DC converter is used as the comparison reference voltage to detect the regeneration state. Therefore, during regeneration (battery charging). Since the voltage of the DC portion is always higher than the voltage of the AC / DC converter, the diode 4 is brought into a non-conducting state for regenerative operation, and it is possible to prevent current from flowing from the AC / DC converter to the battery. As a result, the regenerative energy absorption margin on the battery side does not decrease during regeneration.

Further, according to the present invention, since the AC / DC converter and the battery are completely separated by the pair of diodes 3 and 4, even when the AC / DC converter is short-circuited, the capacitor 5 side, the AC / DC converter and the diode 4 are disconnected, and the switch is used. There is an effect that the circuit becomes conductive and the drive by the battery and the regenerative operation can be continued.

[Brief description of drawings]

The drawing is a circuit diagram showing an embodiment of the present invention. 1 ... Battery, 2 ... Rectifier, 5 ... Smoothing capacitor, 6 ... Inverter section, 7 ... Induction motor, 8 ... Photocoupler, 12 ... Power transistor.

Claims (1)

[Scope of utility model registration request] 1. A power converter for supplying AC power to a load from a power conversion unit using a battery and an AC / DC converter as a DC power supply, wherein the DC power supply has a DC output end of the battery and a DC output end of the AC / DC converter. Are connected in parallel to each other through diodes for preventing backflow to supply direct current to the power converter, and the power converter with the regenerative current from the load using the voltage at the DC output end of the AC / DC converter as a comparison reference. A reverse voltage of the diode provided between the DC output end of the battery and the DC power supply by a detection signal of the voltage detection circuit for detecting that the DC voltage of And a switch circuit that conducts to the battery, and absorbs a regenerative current from the load as a charging current to the battery.