JP2004289950A - Power supply system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system by which regenerative power can be effectively utilized without causing the waste consumption of the regenerative power, the complication of a device and the increase of maintenance work. <P>SOLUTION: A power supply main circuit comprises a converter 2 that converts the AC power of a commercial power supply 1, a smoothing capacitor 3 connected to the DC side of the converter 2, and an inverter 4 that converts the DC power of the smoothing capacitor 3 to AC power of a variable-voltage variable-frequency. A motor 5 is variable-speed driven based on an AC output of the inverter 4. A capacitor device 7 is arranged at a DC circuit between the converter 2 and the inverter 4 via a boosting and step-down chopper circuit 6. The boosting and step-down chopper circuit 6 stores the regenerative power or the like regenerated at the DE circuit side from the motor 5 to the capacitor device 7 by a step-down chopper operation, and feeds the power of the capacitor device 7 to the DC circuit side by a boosting chopper operation when the voltage of the DC circuit is lowered and so on. The motor 5 is constituted of a synchronous motor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply system for operating a motor at a variable speed, and more particularly to a power supply system configured to efficiently use regenerative power generated from the motor during regenerative operation.
[0002]
[Prior art]
For example, a power supply system that drives an elevator hoist or a vehicle electric motor obtains DC power from AC power of a commercial power supply via a converter, suppresses pulsation with a smoothing capacitor, and supplies the DC power to an inverter. It has a power supply main circuit that converts AC power of variable voltage and variable frequency by an inverter to operate the induction motor at a variable speed.
[0003]
In such a power supply system, when the motor is operated at a variable speed, if the operation is to be decelerated, or if the load of the motor acts in a direction in which the motor rotates without supply of commercial power, the torque generated by the motor Becomes negative (hereinafter referred to as regenerative operation). For example, the counterweight of the elevator is set to be lighter than the weight of the car, so that when the car rises, the motor enters a power running operation state in which electric power is supplied from the power supply main circuit. The regenerative operation state in which the kinetic energy of the load becomes regenerative power and returns to the DC circuit via the inverter. The vehicle motor enters a regenerative operation state when decelerating. When the regenerative power is sent to the DC circuit via the inverter, the DC circuit becomes overvoltage.
[0004]
As a countermeasure, a protection circuit consisting of a discharge resistor and a switching element is provided in the DC circuit, and when the DC voltage approaches the overvoltage level, the switching element is turned on and the discharge resistor is inserted into the DC circuit. There is a method (method 1) in which overvoltage is suppressed by converting to heat energy and consuming it.
[0005]
As another countermeasure, there is a method (method 2) in which a converter capable of bidirectionally (AC → DC, DC → AC) power conversion is used and the regenerative power generated from the motor side is regenerated to the commercial power supply side. .
[0006]
Further, there is a method (method 3) in which a battery is connected to the DC circuit, the battery is charged with regenerative power, and the electric power is supplied to the motor when necessary.
[0007]
[Problems to be solved by the invention]
In the method 1, since the regenerative electric power generated from the electric motor is consumed as heat energy by the discharge resistor, improvement is necessary from the viewpoint of energy saving.
[0008]
In method 2, since the regenerative electric power generated from the electric motor is regenerated to the commercial power supply, the waste of energy is reduced, but the configuration of the converter circuit and its control become complicated, which is disadvantageous in cost.
[0009]
In the method 3, there is a problem that the energy efficiency of the battery itself is low, the performance is accelerated due to repeated charging / discharging times and current burden, and the battery needs to be periodically replaced, which is inferior in terms of maintenance and economy.
[0010]
The present invention has been made in order to solve the above-described problems, and can efficiently generate regenerative power without wasting regenerative power, complicating the apparatus, or causing an increase in maintenance work. An object is to provide a power supply system that can be used.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a converter for converting commercial AC power to DC power, a smoothing capacitor connected to the DC side of the converter, Inverter, a motor that is operated at a variable speed based on the AC output of the inverter, a power storage device that is connected to a DC circuit between the converter and the inverter, and stores power, and that is connected between the power storage device and the DC circuit. DC power that is connected and regenerated by the converter or regenerated power regenerated from the motor to the DC circuit side is stored in the power storage device by the step-down chopper operation. And a step-up / step-down chopper circuit that discharges the electric power stored in the power storage device to the DC circuit side. Characterized in that configured in the machine.
[0012]
With this configuration, the regenerative power is generated by an efficient synchronous motor, stored in the power storage device from the DC circuit by the buck-boost chopper circuit, and supplied to the DC circuit side from the power storage device when necessary to effectively recycle the power. Since it is used, regenerative power can be used efficiently.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a circuit configuration diagram of a power supply system according to the present invention.
[0014]
1, a power supply system includes a converter 2 for converting commercial AC power from a commercial power supply 1 to DC power, a smoothing capacitor 3 for suppressing pulsation of a DC voltage converted by the converter 2, and a DC converted by the converter 2. A power supply main circuit including an inverter 4 for converting power into AC power having a variable voltage and a variable frequency is provided. An electric motor 5 is connected to an AC output side of the inverter 4 of the power supply main circuit. Variable speed operation. As the electric motor 5, for example, a permanent magnet type synchronous electric motor is used.
[0015]
The DC circuit between the converter 2 and the inverter 4 is provided with a power storage device 7 composed of an electric double-layer capacitor that charges and discharges power via a step-up / step-down chopper circuit 6 described later.
[0016]
The step-up / step-down chopper circuit 6 is connected between the DC circuit and the power storage device 7,
The DC power converted by the converter 2 or the regenerative power regenerated from the motor 5 to the DC circuit side is stored in the power storage device 7 by a step-down chopper operation, and the step-up chopper is operated when the motor 5 is operated in power mode or when the voltage of the DC circuit is reduced. The operation releases power from the power storage device 7 to the DC circuit side.
[0017]
That is, the step-up / step-down chopper circuit 6 connects the series circuit of the switching elements 10 and 11 in which the diodes 8 and 9 are connected in anti-parallel to the DC circuit, and connects the series connection point of the switching elements 10 and 11 and the power storage device 7. The reactor 12 is connected between them.
[0018]
The switching operation of the switching elements 10 and 11 is controlled by the control circuit 13. The control circuit 13 is connected to a voltage detection device 14 for detecting the DC voltage of the DC circuit and a voltage detection device 15 for detecting the voltage of the power storage device 7.
[0019]
In the power supply system having such a configuration, the DC power converted from the commercial AC power supply 1 by the converter 2 is charged by the smoothing capacitor 3 first, but when the capacitance of the power storage device 13 is insufficient (initial state). ), DC power is supplied to the power storage device 7 by stepping down (the smoothing capacitor 3 is discharged) via the switching element 10 and the reactor 12.
[0020]
Then, when the motor 5 starts operating and enters a regenerative operation state, regenerative power is supplied to the DC circuit, and the DC voltage increases. This DC voltage is detected by a voltage detection device 13 provided in the DC circuit, and the control circuit 12 turns on the switching element 10 when the DC voltage becomes equal to or higher than a preset value.
[0021]
Thereby, regenerative power is supplied from the DC circuit to power storage device 7 via switching element 10 and reactor 12. At this time, current energy is stored in the reactor 12. Thereafter, by turning off switching element 10, the current energy stored in reactor 12 flows through diode 9 connected in antiparallel to switching element 11, reactor 12 and closed loop of power storage device 7, and is stored in power storage device 7. Is done.
[0022]
FIG. 2 is a time chart showing the step-down chopper operation, and shows the relationship among the DC voltage of the DC circuit, the ON / OFF operation of the switching element 10, the current i flowing through the circuit, and the voltage of the power storage device 7.
[0023]
When the motor 5 is in the regenerative operation state, the regenerative power increases the DC voltage of the DC circuit, and the switching element 10 is turned on when the DC voltage becomes higher than a set value. Then, current i flows from the DC circuit through switching element 10 and reactor 12, and power is stored in power storage device 7. The switching element 10 is turned off when the current i is going to exceed the allowable current of the switching element 10 itself or when the DC voltage is going to be zero. After the switching element 10 is turned off, the current energy stored in the reactor 12 flows through the closed loop of the diode 9, the reactor 12, and the power storage device 7, attenuates with a time constant, and is stored in the power storage device 7.
[0024]
When the DC voltage rises again and becomes equal to or higher than the set value due to the switching element 10 being turned off, the switching element 10 is turned on and the power storage is started again, and thereafter the same operation is repeated.
[0025]
On the other hand, when the electric motor 5 is in the power running operation, the switching element 11 shown in FIG. 1 is turned on. As a result, power is discharged from power storage device 7 in closed loop of reactor 12, switching element 11, and power storage device 7, and current energy is stored in reactor 12. When the switching element 11 is turned off at this time, the current energy stored in the reactor 12 is discharged to the DC circuit through the reactor 12 and the diode 8, and the DC circuit is supplied with electricity.
[0026]
When the emitted power is attenuated, the switching element 11 is turned on again, current energy is accumulated in the reactor 12, and then power is released when the switching element 11 is turned off. Thereafter, the same operation is repeated.
[0027]
In performing the ON-OFF control of the switching elements 10 and 11, the power running operation and the regenerative operation of the electric motor 5 are detected by detecting whether the DC voltage of the DC circuit on the input side of the inverter 4 is sufficient or insufficient. The detection can be made by the control circuit 13 by detecting with the device 14, or can be performed by detecting the speed of the electric motor 5.
[0028]
According to the present embodiment, the regenerative electric power from electric motor 5 is stored in power storage device 7 without heat release (discarding), and when power running operation of electric motor 5 or the voltage of the DC circuit is insufficient, the electric power is stored in power storage device 7. Since the stored electric power is supplied, the amount of energy supplied from the commercial power supply can be effectively used, and an energy saving effect can be obtained. In addition, the cost and size of the apparatus can be reduced as compared with the method of returning the regenerative electric power to the commercial power supply 1, and maintenance work such as periodic replacement due to performance deterioration unlike the case of using a battery does not occur.
[0029]
Also, by using a permanent magnet type synchronous motor for the motor 5 as in the present embodiment, both the efficiency and the power factor are higher (about several%) and energy loss as compared with the case where an induction motor is used, for example. The regenerative electric power can be utilized by taking advantage of the characteristics with less power, and the control of the secondary magnetic field is not required, and the DC excitation can continuously generate a stable magnetic field by using the permanent magnet.
[0030]
Further, by using an electric double layer capacitor as the power storage device 7, it becomes possible to charge / discharge (supply current) more rapidly than when a battery is used, for example. In addition, since the electric double layer capacitor can be configured in the same volume and large capacity as compared with the aluminum electrolytic capacitor, the power storage device 7 can be reduced in size and weight, the life can be extended, and additional means such as temperature control is not required. It becomes.
[0031]
FIG. 3 is a circuit diagram showing a second embodiment of the present invention. This embodiment is different from the first embodiment in that a discharge resistor 16 and a protection circuit 18 for a switching element 17 are provided in parallel with a DC circuit. The switching element 17 is connected to the control circuit 13, and is turned on when the voltage between both ends of the power storage device 7 exceeds a set value.
[0032]
According to the present embodiment, when the power storing the regenerative power from motor 5 exceeds the allowable storage capacity of power storage device 7, the power is released to the DC circuit side and switching element 17 is turned on to discharge resistor 16. By converting the current to heat energy and radiating the heat, it is possible to prevent damage to the equipment due to an abnormal rise in the DC voltage value.
[0033]
Therefore, by combining the charge / discharge configuration with the step-up / step-down chopper circuit 6 and the power storage device 7 and the protection circuit 18 including the discharge resistor 16 and the switching element 17, energy can be effectively used.
[0034]
In this case, by arranging the discharge resistor 16 near the power storage device 7 and using it as a heating unit of the power storage device 7, the operation of the power storage device in a cold region can be efficiently performed.
[0035]
【The invention's effect】
As described above, according to the power supply system of the present invention, the regenerative power generated from the efficient synchronous motor is stored in the power storage device, and when the synchronous motor is in power running operation or when the DC voltage of the DC circuit is reduced. Since replenishing power is supplied, the operating efficiency can be improved without wasting regenerative power, without increasing the cost required for the converter circuit configuration and its control, and without requiring maintenance work.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of a power supply system according to the present invention.
FIG. 2 is a time chart illustrating a step-down chopper operation according to the first embodiment.
FIG. 3 is a circuit diagram showing a second embodiment of the power supply system according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Commercial power supply 2 ... Converter 3 ... Smoothing capacitor 4 ... Inverter 5 ... Electric motor 6 ... Step-up / step-down chopper circuit 7 ... Electric storage devices 8, 9 ... Diodes 10, 11, 17 ... Switching element 12 ... Reactor 13 ... Control circuits 14, 15 ... voltage detector 16 ... discharge resistor 18 ... protection circuit

Claims (4)

A converter for converting commercial AC power to DC power; a smoothing capacitor connected to the DC side of the converter; an inverter for converting the DC power of the smoothing capacitor to AC power of a variable voltage and variable frequency; and an AC output of the inverter. An electric motor that is operated at a variable speed based on, a power storage device that is connected to a DC circuit between the converter and the inverter and stores power, and that is connected between the power storage device and the DC circuit and is converted by the converter. DC power or regenerated power regenerated from the motor to the DC circuit side is stored in the power storage device by a step-down chopper operation, and the power storage device is operated by a power running operation of the motor or a step-up chopper operation when the voltage of the DC circuit is reduced. A step-up / step-down chopper circuit for discharging the electric power stored in the DC circuit to the DC circuit. The power supply system to be configured in the period an electric motor. The power supply system according to claim 1, wherein the power storage device is configured by an electric double layer capacitor. The power supply system according to claim 1, wherein a protection circuit including a discharge resistor and a switching element is provided in parallel with the DC circuit. The power supply system according to claim 3, wherein a discharge resistor of the protection circuit is used as a heating unit of the power storage device.

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