JPH0628926Y2 - Power converter - Google Patents

Description

Detailed Description of the Invention A. TECHNICAL FIELD The present invention relates to a power conversion device for charging and discharging a secondary battery.

B. SUMMARY OF THE INVENTION The present invention is a power conversion device that converts the output power of an AC power supply to DC and supplies it to a secondary battery, or converts the DC power of a secondary battery to AC and regenerates it to the AC power supply side in an antiparallel connection. A DC reactor is inserted between one of the DC terminals of the first and second power converters and the anode terminal of the secondary battery, and a series circuit including a switch and a capacitor between the DC terminals of the power converter. By connecting the switch and controlling the switch and the first and second power converters, it is possible to easily perform normal charging and discharging and complete discharging in the reverse charging mode, and to downsize the device and reduce the price. It is intended to be inexpensive.

C. 2. Description of the Related Art In a secondary battery (eg, zinc-bromine battery, zinc-chlorine battery, nickel-zinc battery, zinc-air battery, etc.) that uses zinc (Zn) as an active material of a cathode, in order to prolong the cycle life. In addition, a method of complete discharge for completely dissolving zinc in the cathode is adopted. FIG. 2 is a circuit diagram for realizing this method, and FIG. 3 is a waveform diagram showing an operation pattern. In FIG. 2, the secondary battery 1 is connected to a charging / discharging circuit (not shown), and in the complete discharge mode, a current flows through the load resistor 3 via the switch 2 to Complete discharge is performed until the battery voltage _ev and load current I _L shown in Figures (a) and (b) are almost zero. However, in such a method by complete discharge, even if the battery voltage e _v indicates zero, the zinc on the cathode remains undissolved,
When the next charge is performed, zinc is electrodeposited on the remaining zinc, and abnormal electrodeposition called dendrite occurs from that position, which extends to the anode and causes a battery short circuit. Also, as the battery scale increases, the amount of power wasted in the complete discharge mode becomes a problem. In order to solve this problem, another DC power source is used after battery discharge,
A complete discharge method in a reverse mode has been proposed in which the positive and negative polarities of the secondary battery are reversed by this power source to perform charging. FIG. 4 is a circuit diagram for realizing this, and FIG. 5 is a waveform diagram showing its operation pattern. In the reverse charging mode in FIG. 4, first, the polarity reversing switches 4A and 4B are used.
Are respectively connected to the contacts b and d, and then the switch 2 is turned on. In the reverse charging mode in such a connected state, the negative electrode end of the DC power supply 5 is connected to the anode side of the secondary battery 1, and the secondary battery 1 is reversely charged by the DC power supply 5. That is, the battery voltage e _v of the secondary battery 1 is the time t _{4 in} FIG.
Changes toward the negative polarity side as shown in ~t _6, reaches a certain preset negative voltage (-e _1). The battery current I _L is shown in Fig. 5 (b).
As shown in, a certain amount of reverse charge current flows in the same direction as the regular discharge current. Next, the battery voltage e _v is the specified negative voltage
At the time (-e ₁ ) is reached (time t ₆ ), the polarity reversing switch 4
A and 4B are connected to the contacts a and c, respectively, and the reverse discharge mode is set. In this reverse discharge mode, the positive electrode end of the DC power supply 5 is connected to the positive electrode side of the secondary battery 1, and the negative electrode end of the DC power supply 5 is connected to the negative electrode side of the secondary battery 1, whereby the secondary battery 1 is Start reverse discharge. In this state, the battery voltage e _v of the secondary battery 1 increases toward the positive polarity side as shown at time t _{6 to} t ₈ in FIG. It returns and eventually reaches the set positive voltage e _s . At this time, as the battery current I _L , a charging current flows as shown in FIG. Next, when the battery voltage e _v reaches the normal voltage e _s (time
Switch 2 is turned off at t ₈ ). After the reverse charging / discharging mode as described above, regular charging is performed.

The above is the complete discharge method in the reverse charge mode, but as an actual circuit for realizing this, a method in which two sets of three-phase bridge circuits of thyristors are connected in antiparallel with each other as shown in FIG. 6 is used. . In FIG. 6, reference numeral 6 denotes a power converter formed by connecting thyristors 7 to 12 in a three-phase bridge, and a power converter 19 formed by connecting thyristors 13 to 18 in a three-phase bridge is antiparallel. It is connected. The cathode sides of the thyristors 7, 8, 9 of the power converters 6, 19 and the anode sides of the thyristors 16, 17, 18 are connected to the anode side of the secondary battery 1 via the DC reactor 20. Thyristor 1 of power converters 6 and 19
Anode side of 0, 11, 12 and thyristor 13, 1
The cathode sides of 4, 15 are connected to the cathode side of the secondary battery 1. The AC sides of the power converters 6 and 19 are connected to a three-phase AC power source (not shown). In order to perform a complete discharge by the circuit configured as described above, first, the power converter 19 is put into an operating state and the power converter 6 is put into a stopped state at time t ₄ in FIG. In this state, the power converter 19 is operated in the γ control region, and the DC power of the secondary battery 1 is regenerated to the AC power supply (not shown) until time t ₅ . Further time
From t ₅ , the power converter 19 is operated in the α control region, and the secondary battery 1 is charged in the reverse direction with the power obtained by converting the AC power to DC. Next, at time t _{6 when} the battery voltage of the secondary battery 1 reaches the set negative voltage (−e ₁ ), the operation of the power converter 19 is stopped and the operation of the power converter 6 is started in the γ control region. . This power charged in the opposite direction to the secondary battery 1 from the time t ₆ is regenerated to the AC power supply side through the power converter 6. Further, from time t ₇ , the power converter 6 is switched to α
The secondary battery 1 is operated in the control region, and the secondary battery 1 is charged in the normal direction by the power obtained by converting the AC power to the DC. Then, to stop the operation of the power converter 6 at the time t ₈ to the battery voltage e _v has reached the normal voltage e _s.

D. Problems to be Solved by the Invention When the power converters 6 and 19 are controlled by the control method as described above, complete discharge can be easily performed, and the normal discharge shown in FIG. Can also be charged and discharged. However, in this method, the power factor when viewed from the AC power supply is not good. In addition, the power converter is a so-called separately-excited type in which the thyristor bridge is commutated by the AC power supply, so if there is a demand to disconnect the AC power supply and drive the battery and power converter independently to obtain AC power. I can't drive.

Therefore, recently, a large-capacity, high-voltage self-extinguishing type semiconductor element (gate turn-off thyristor, power transistor, etc.) is used to configure a power converter as shown in FIG. 7, for example, and shown in FIG. The charging and discharging modes have come to be carried out. FIG. 7 shows a power converter having a structure similar to that described in Japanese Patent Laid-Open No. 60-46773, in which 21 is a self-turn-off type semiconductor element, for example, gate turn-off thyristors 22 to 27 having polarities shown in the figure are bridged. It is a connected power converter. Feedback diodes 32 to 37 are respectively connected in antiparallel to the gate turn-off thyristors 22 to 27. The electrolytic capacitor 40 and the secondary battery 1 are connected in parallel between the positive and negative terminals of the power converter 21. The AC side of the power converter 21 is an AC reactor 4
It is connected to a three-phase AC power source (not shown) via 1, 42 and 43. The device configured in this way is a voltage-type PW.
It is driven as an M inverter.
As described in Japanese Patent No. 6773, the input current I _s supplied from the AC power supply is controlled so as to follow the input current command value L _s * created based on the sine wave current synchronized with the power supply voltage. As a result, not only can the secondary battery 1 be charged and discharged freely, but active power and reactive power can also be controlled (power factor control is also possible), and harmonics can also be generated by performing PWM control (pulse width modulation control). Since it can be reduced, it has been used as a converter for a recent power storage system. However, this circuit system cannot output a negative voltage (the polarity opposite to that in Fig. 7), so the circuit shown in Fig. 6 is required in addition to the circuit shown in Fig. 7 to perform complete discharge in the reverse charge mode. Becomes With such a structure, in addition to the normal charging / discharging device, a complete discharging device is required, resulting in a large number of boards and an increase in size and cost.

The present invention has been made in view of the above points, and its purpose is to:
An object of the present invention is to provide a power conversion device that can easily perform normal charging and discharging and complete discharging in a reverse charging mode, and also can downsize the device and reduce the price.

E. Means for Solving the Problems The present invention relates to a power converter for charging and discharging a secondary battery, in which first and second power converters each having a self-extinguishing type semiconductor element connected in a bridge are connected in antiparallel. A power conversion unit, a series circuit connected between one DC terminal and the other DC terminal of the power conversion unit, and including a switch and a capacitor, one DC terminal of the power conversion unit, and an anode of a secondary battery. A direct current reactor inserted in an electric path connecting the terminals, the power converter and the series circuit are operated as a voltage source inverter to charge and discharge the secondary battery, and the power converter and the series circuit are connected. It is characterized in that it is operated as a current source inverter to perform reverse charging and reverse discharging of the secondary battery.

F. Action In order to charge and discharge the secondary battery in the normal charge / discharge mode, the switch and the self-extinguishing type semiconductor element of the first power converter are turned on, and the second power converter is controlled by, for example, PWM (pulse width). Control). Then, the self-arc-extinguishing semiconductor element of the first power converter acts as a feedback diode for each self-arc-extinguishing semiconductor element on the second power converter side. Therefore, the power converter operates as a voltage source inverter, so that the secondary battery is charged when the power running operation is performed, and the secondary battery is discharged when the regenerative operation is performed.

Next, in order to perform complete discharge in the reverse charge mode, first, the switch is turned off, the operation of the first power converter is stopped, and the second power converter is PWM-controlled. Then, since the second power converter operates as a current source inverter, the secondary battery is reversely charged when the converter is regeneratively operated and then power-operated. When the battery voltage reaches the set negative voltage by the reverse charging, the operation of the second power converter is stopped and the first power converter is PWM-controlled. Then, since the first power converter operates as a current source inverter, the secondary battery is reversely discharged when the converter is regeneratively operated and then power-operated.

G. Embodiment An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as those in FIGS. 6 and 7 are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 51 is a self-extinguishing type semiconductor device, for example, a first power converter formed by connecting gate turn-off thyristors 61 to 66 in a three-phase bridge connection. A second power converter 52, which is a self-extinguishing type semiconductor device, for example, gate turn-off thyristors 71 to 76 connected in a three-phase bridge, is connected in antiparallel to the converter 51. The cathode side of the gate turn-off thyristors 61, 62, 63 of the power converters 51, 52 and the anode side of the gate turn-off thyristors 71, 72, 73 are connected to the anode side of the secondary battery 1 via the DC reactor 20. . The anode side of the gate turn-off thyristors 64, 65, 66 of the power converters 51, 52 and the cathode side of the gate turn-off thyristors 74, 75, 76 are connected to the cathode side of the secondary battery 1. The AC side of the power converters 51 and 52 is an AC reactor 4
It is connected to a three-phase AC power source (not shown) via 1, 42 and 43. A switch 53 and an electrolytic capacitor 40 are connected in series between the DC terminals of the power converters 51 and 52.

Next, the operation of the apparatus configured as described above will be described. First, in order to perform the operation in the normal charging and discharging modes shown in FIG. 5C, the control circuit (not shown) controls the switches 53 and the gate turn-off thyristors 61 to 66 of the first power converter 51 to be turned on, and The second power converter 52 is PWM-controlled, for example. Then, the gate turn-off thyristors 61 to 66 act as feedback diodes respectively connected in anti-parallel to the gate turn-off thyristors 71 to 76. Therefore, the device operates as a voltage source inverter and performs the same control as in the case of the circuit of FIG. As a result, the secondary battery 1 is charged when the second power converter 52 is operated for forward conversion, and is discharged when the second power converter 52 is operated for reverse conversion.

Next, in order to perform a complete discharge in the reverse charge / discharge mode shown in FIG. 5C, first, the switch 53 is turned off, the operation of the first power converter 51 is stopped, and the second power converter 52 is stopped. Is PWM controlled. Then, the device operates as a current source inverter, so from time t ₄ to time t _{5 in} FIG.
The second power converter 52 is operated in the γ control region until the above, and the DC power of the secondary battery 1 is regenerated to the AC power supply side.
Further from time t ₅ to operate the second power converter 52 in the α control region, it charges the secondary battery 1 in the reverse direction. Next, the time t when the battery voltage of the secondary battery 1 reaches the set negative voltage (-e ₁ ).
_{In 6} , the operation of the second power converter 52 is stopped and the operation of the first power converter 51 is started in the γ control region. This power charged in the opposite direction to the secondary battery 1 from the time t ₆ is regenerated to the AC power supply side. Further, from time t ₇ , the first power converter 51 is operated in the α control region, and the secondary battery 1 is charged in the normal direction by the power obtained by converting the AC power to the DC. The battery voltage e _v stops the operation of the first power converter 51 at time t ₈ has reached the normal voltage e _s.

The power converters 51 and 52 are not limited to the gate turn-off thyristors, but may be constituted by elements such as power transistors.

H. Effects of the Invention As described above, according to the present invention, the following effects can be obtained. That is, (1) the first and second power converters are connected in anti-parallel to configure the power converter, so that the current source inverter can be formed by simply switching the control method and controlling the on / off of the switch. It can also be driven as a voltage source inverter. Therefore, the secondary battery can be easily charged and discharged in the normal mode and completely discharged in the reverse charge / discharge mode.

(2) Since the main circuit can be commonly used, it is not necessary to provide both a device dedicated to the normal charge / discharge mode and a device dedicated to the reverse charge / discharge mode. Therefore, the device can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram for realizing a conventional complete discharge method, and FIG.
FIG. 4 is a waveform diagram showing the operation pattern of the complete discharge method, FIG. 4 is a circuit diagram for explaining the principle of the conventional complete discharge method in the reverse charge mode, and FIG. 5 is an operation pattern of the complete discharge method of FIG. FIG. 6 is a waveform diagram showing FIG. 6, FIG. 6 is a conventional circuit diagram for realizing the complete discharge method of FIG. 4, and FIG. 7 is a circuit diagram showing an example of a conventional power converter. 1 ... Secondary battery, 20 ... DC reactor, 40 ... Electrolytic capacitor, 41, 42, 43 ... AC reactor,
51 ... 1st power converter, 52 ... 2nd power converter, 53 ... Switch, 61-66, 71-76 ... Gate turn-off thyristor.

Claims (1)

[Scope of utility model registration request] 1. A power converter for charging and discharging a secondary battery, comprising: a power converter comprising first and second power converters each having a bridge connection of self-arc-extinguishing semiconductor elements and connected in antiparallel. A series circuit that is connected between one DC terminal and the other DC terminal of the power conversion unit and that includes a switch and a capacitor, and an electric path that connects one DC terminal of the power conversion unit and the anode terminal of the secondary battery. With the inserted DC reactor, the power converter and the series circuit are operated as a voltage source inverter to charge and discharge the secondary battery, and the power converter and the series circuit are operated as a current source inverter. A power conversion device characterized by performing reverse charging and reverse discharging of the secondary battery.