JP3371718B2 - Charging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a secondary battery with electric power from an AC power source, and more particularly to refresh discharge for discharging a residual portion of the previously charged electric power before charging.

[0002]

2. Description of the Related Art A secondary battery is used as a power source for portable electric devices and electric vehicles. In particular, the development of electric vehicles has been promoted in consideration of the environment. The biggest challenge in the development of this electric vehicle is a secondary battery, which has a large capacity and a short charging time.

In such a secondary battery, Ni-M
It is known that the initial electric power cannot be stored if the electric power from the previous charging remains during charging, such as H (hydrogen storage alloy) or Ni-Cd battery. This substantial decrease in capacity is called the memory effect. In order to prevent this memory effect, refresh discharge is conventionally performed in which residual power is supplied to a load resistor provided in parallel with the secondary battery before charging. Japanese Unexamined Patent Publication No. 4-261338 discloses a charging circuit that performs such refresh discharge.

[0004]

In the conventional refresh discharge, as described above, the remaining electric power is passed through the resistor and converted into heat energy. There is a problem that the generated heat energy is wasted because it is released into the atmosphere without doing work. Of course, this is not in line with the trend of energy saving.

Further, there is a problem that the heat generated by the resistance may cause the surrounding electric equipment to be heated and cause a failure.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a charging device that does not waste power during refresh discharge.

[0007]

In order to achieve the above-mentioned object, a charging device according to the present invention provides a secondary battery for supplying power to a three-phase alternating current permanent magnet motor with power supplied from a power supply. A charging device for charging, when performing a refresh discharge for discharging the residual power stored in the secondary battery before charging,
Comprising a power return means for returning the discharge power to the power supply, the power return means includes a coil of the motor, the reflation
During the discharge, the neutral point of the motor and the secondary
The two terminals of the commercial power supply are connected to the pole of the pond.
Power is returned to the power supply through all three-phase coils of the motor . Furthermore, during refresh discharging, the amount of current flowing through each phase of the discharge current from each phase of the current is controlled so as to balance the torque generated preferable. In order to balance the torques of the three phases, for example, it is possible to control so that equal currents simultaneously flow in the respective phases.

By discharging the electric power remaining in the secondary battery before charging, the memory effect can be suppressed, and the discharged electric power is returned to the power source, so that the electric power wasted can be reduced. Further, it is not necessary to take measures against heat generated when the discharge power is consumed by the resistor, and the configuration of the entire device is simplified. In addition, three-phase AC permanent magnet
Current is applied to the three-phase coil of the motive, and the amount of current at this time is
Control so that the torque generated by the current of each phase is balanced
This prevents the electric motor from rotating.
Wear. In order to balance the torque as described above
Would, for example, pass equal currents through three-phase coils at the same time.
You can do it.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment (hereinafter, referred to as an embodiment) of a charging device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of this embodiment. The present embodiment is mounted on an electric vehicle, and an inverter 16 and an inverter that convert electric power of a field coil 12 of a motor 10 for driving the vehicle and a secondary battery 14 into a three-phase alternating current and supply the three-phase alternating current to the drive motor 10. A control circuit 18 for controlling 16 transistors is included. These configurations have been conventionally adopted as drive system circuits for electric vehicles. Furthermore, the present embodiment includes a discharge circuit 20 used during refresh discharge. The state shown in FIG. 1 shows a state in which the commercial power source 24 for single-phase AC is connected via the connector 22, one terminal of the commercial power source 24 is at the neutral point of the motor 10, and the other terminal is the secondary battery. 1
4 are connected to the positive electrode and the negative electrode via diodes 26a and 26b, respectively. Transistors 28a, 28b, 30a, 30b, 32a, 3 included in the inverter 16
2b and the base terminals of the transistors 34a and 34b of the discharge circuit are connected to the control signal terminal 36 of the control circuit 18, but the control signal line is omitted in FIG. In addition, diodes 38a, 38b, 40a, 40b, 4 are provided in parallel with each of the transistors 28a-32b.
2a and 42b are provided. As shown, the transistor 34a of the discharge circuit 20 is provided between one terminal of the commercial power source 24 and the positive electrode of the secondary battery 14, and the transistor 34b is the terminal of the same commercial power source and the negative electrode of the secondary battery 14. It is provided in between.

When the electric vehicle is running, the main switch 44
a, 44b are connected, the DC power from the secondary battery 14 is converted into a three-phase AC by the inverter 16, and the motor 1
Supplied to zero. At this time, the electric power supplied to the motor 10 is detected by the current sensor 46, and the actual current signal Iact
Is sent to the control circuit 18 and is feedback-controlled. Further, the inverter 16 is controlled so that the electric power generated by the motor 10 is regenerated to the secondary battery 14 during braking. The inrush limiting switch 50 connected in series with the resistor 48 and arranged in parallel with the main switch 44a is
This is for gradually supplying electric charge to the capacitor 52 at the time of startup. Then, the rush control switch 50 is opened when a predetermined amount of electric charge is stored in the capacitor 52, and the main switch 44a is connected.

In the present embodiment, when charging the secondary battery 14, first, the electric power remaining in the secondary battery 14 is discharged. This is so-called refresh discharge. This suppresses the memory effect found in secondary batteries, especially nickel-based secondary batteries. In the refresh discharge, the transistor 34 of the discharge circuit 20 is changed according to the phase of the commercial power supply.
a, 34b and the transistor 32 of the inverter 16
a and 32b are controlled.

FIG. 2 shows a commercial power source and a transistor 32.
The relationship of the control signals a, 32b, 34a, 34b is shown. In the control circuit 18, based on the input signal Vac1 indicating the commercial power source voltage, a discharge current command value I that is a sine wave of the same phase as this and has an amplitude of a predetermined battery discharge current I
ref is calculated. The commercial power supply voltage signal Vac1 is a signal having the same phase as the voltage of the line of the two power lines connected to the secondary battery via the diodes 26a and 26b. As for the discharge current command value Iref, the actual discharge current signal Iact detected by the current sensor 46 is sent to the control circuit 18 and is feedback-controlled thereby.

The discharge current command value Iref is pulse-width modulated (PWM) and then the transistors 32a, 32b, 34 are discharged.
The control signals T32a, T32b, T34a, T34b of a and 34b are calculated. The transistors 32a and 34b are PWM-controlled when the discharge current command value Iref is positive, and
b, 34a PWM control is performed when the discharge current command value Iref is negative. As a result, the remaining electric power of the secondary battery 14 is returned to the commercial power source 24. Therefore, in the case of this embodiment, the power returning means includes the transistors 32a, 32b,
34a, 34b and a control circuit 18 for controlling these transistors are included.

The terminal voltage of the secondary battery 14 needs to be larger than the amplitude of the commercial power supply voltage in consideration of the modulation rate of the transistor. In the secondary battery 14 of this embodiment, 24 cells are connected in series. Assuming that the secondary battery has deteriorated, when each cell generates 11V, the modulation rate of the transistor is about 0.612, and the discharge voltage is about 161V. Therefore, the amplitude of the commercial power supply voltage in Japan becomes about 141 V or more, and even when the secondary battery is deteriorated to some extent, the discharged power can be sufficiently returned to the commercial power supply.

After the refresh discharge is completed, the charge is performed. The control at this time will be described for the phase connected to the transistors 32a and 32b among the three phases of the motor.
When the voltage at the neutral point of the motor 10 connected to the commercial power source 24 is positive, the transistor 32b is on / off controlled, and the transistor 32a is off. When the transistor 32b is turned off, the field coil 1
The voltage is boosted by 2, current flows through the diodes 42a and 26b, and the secondary battery 14 is charged. On the contrary, when the voltage at the neutral point becomes negative, the transistor 32a is controlled to be turned on / off and the transistor 32b is controlled to be turned off. When the transistor 32a is switched from on to off, the field coil 1
The voltage is boosted by 2 and current flows through the diodes 26a and 42b to charge the secondary battery 14. Similar control is performed and charging is performed for the other phases.

In the above-described embodiment, the refresh discharge is performed only by the phases related to the transistors 32a and 32b, but the transistors 28a, 28b, 30a and 30b related to the other phases can be simultaneously controlled. . In particular, when the motor 10 is a permanent magnet motor having a rotor having magnetic poles made of permanent magnets, the discharge current is passed through all three phases to balance the torques generated by the respective phase currents, and the motor 10 rotates. Can be prevented.

Further, in the above-described embodiment, the transistors 32a and 34b are synchronously turned on / off, but when the discharge current command value Iref is positive, one of the transistors 34a is controlled to be turned on and the other 32a is turned on. PWM
It can also be controlled. Similarly, the transistors 32b and 3
4a, when the discharge current command value Iref is negative, one of the transistors 4a is controlled to be turned on, and the other 3a is controlled.
2b can be PWM-controlled.

As described above, according to the present embodiment, since the discharged power can be returned to the AC power supply when performing the refresh discharge of the secondary battery, it is possible to reduce the waste of power. Further, as compared with the case where refresh discharge is performed by a resistor as in the above publication, measures against heat generated by the resistor,
For example, it is not necessary to add a heat shield plate or adopt a circuit element having high heat resistance. Therefore, a simpler and cheaper device can be provided.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment according to a charging device of the present invention.

FIG. 2 is a time chart showing control of the present embodiment.

[Explanation of symbols]

10 drive motor, 12 field coil, 14 secondary battery, 16 inverter, 18 control circuit, 20 discharge circuit, 24 commercial power source.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-292304 (JP, A) JP-A-8-163787 (JP, A) JP-A-8-126121 (JP, A) JP-A-8- 186907 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02J ⁷ /00-7/36 B60L 11/18

Claims (3)

(57) [Claims] 1. A charging device for charging a secondary battery, which supplies electric power to a three-phase alternating current permanent magnet motor, with electric power from a power supply, wherein the residual electric power stored in the secondary battery is charged before charging. when performing refresh charge discharging comprises power conversion means for converting the discharge power to the power supply, the power return means includes a coil of the motor, the
At the time of refresh discharge, the neutral point and the front of the motor
The two terminals of the commercial power source are connected to the secondary battery poles respectively.
A power generator that converts electric power to a power supply through all three-phase coils of this electric motor . 2. A charging device according to claim 1, before Symbol power return means, when the refresh discharge, the amount of current flowing through the coil of the three <br/> phase, each phase current is generated A charging device that controls the torque to be balanced. 3. The charging device according to claim 2, wherein the power return means controls such that equal currents simultaneously flow through the three-phase coils during refresh discharge.