JP2004297851A - Power supply for controlling motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply with high power conversion efficiency which is equipped with a backup battery for power outage and operates a load for driving a motor, capable of maintaining a battery capacitance at power outage with high reliability, and also capable of corresponding when the power outage extends. <P>SOLUTION: A power storage means to which fuel cell equipped with a counter flow blocking means is connected to a DC bus line, parallel to a storage battery, for energization only in the direction from the fuel cell to the storage battery side. In order to realize the equipment of high power conversion efficiency by reducing the power loss of a switching element, a bidirectional converter is interposed between the DC bus line and the storage battery which comprises a converter function for stepping up the discharging from the storage battery side to the DC bus line but stepping down the charging in the reverse direction. A battery management unit which always monitors the storage battery to detect the capacitance of the storage battery for commanding refresh charging and a control circuit that receives the signal from the unit for automatic charge control, constitute the bidirectional converter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
When receiving commercial AC power, convert the AC to DC and supply the battery to the inverter in front of the motor while charging the battery. When the commercial AC power fails, supply DC power to the inverter from the battery without interruption without interruption for a long time. The present invention also relates to a power supply device that supplies DC power from a fuel cell in an auxiliary manner, and automatically recovers power while monitoring a battery when a power failure recovers, and supplies power to a motor while maintaining a fully charged state.
[0002]
[Prior art]
In the electric drive system using the voltage of a storage battery or a power storage device, the following patent document discloses a technology for improving the reliability of the storage battery and providing a device capable of improving performance and reducing cost. Patent Literature 2 discloses a technology of an apparatus for supplying power without interruption in response to a long-term power failure.
[Patent Document 1]
[Patent Document 1] Japanese Unexamined Patent Application Publication No. Hei 6-276609. As a conventional technology of an electric drive system, a paragraph (0003) describes that "power semiconductors, which are expensive parts in an inverter, are cost-effective by increasing the DC voltage. However, the number of storage batteries connected in series is increased, for example, the reliability and life of the storage batteries are reduced due to mismatch in capacity of each 2 V unit cell (cell). " (0010) states that "there is a disadvantage that the capacity of the storage battery is significantly deteriorated." As an improvement, the paragraph (0020) in the description of the embodiment may be such that "a connection body of three storage batteries and three corresponding DC / DC converters is connected in parallel and has tolerance to failure". There is a description that "when a short circuit or an open circuit is detected, the circuit is disabled (disabled) and operated with a capacity of 2/3 (two out of three parallels)."
[0003]
FIG. 4 is a circuit diagram (FIG. 4) of an embodiment of the electric drive system disclosed in Japanese Patent Application Laid-Open No. Hei 6-276609 which is expressed as a block diagram for easy understanding. DC / DC converters 63, 64, 65 and storage batteries 60, 61, 62 are connected in parallel to form a DC power supply, and a capacitor Cdc is connected to the output terminal of the DC / DC converter. The voltage Vdc across the capacitor is a DC link voltage. It is. This direct current is converted to alternating current by the inverter 10 and connected to the motor M1.
[0004]
There is a patent document described below as a disclosure of a technique aiming at maintaining the private power generation function for a long time.
[Patent Document 2]
[Patent Document 1] Japanese Patent Application Laid-Open No. H10-144327 discloses a prior art of a hybrid power supply system. In paragraph (0015), a “polymer electrolyte fuel cell module and a storage battery such as a lithium ion battery or a silver zinc oxide battery are described. Power is supplied to the motor and other operating systems via the charge / discharge management device. " In paragraph (0021), there is a description that "the secondary battery supplies power even in an emergency such as when the power generation of the fuel cell suddenly stops." In paragraph (0022), "the output of the fuel cell falls below a predetermined value. Then, the power generation of the fuel cell is stopped and only the secondary battery is connected as the power supply of the operating system. " In Patent Document 2, the function of a secondary battery for complementing the weak points of a fuel cell is emphasized, and the secondary battery plays a role as a backup of the fuel cell. However, the means for maintaining the charged capacity of the secondary battery in a fully charged state is described as “float charging from the fuel cell” (paragraph 0004) and “provided to be chargeable from an external power supply”. (Paragraph 0007), it remains unknown whether the secondary battery has reached the end of its life or its capacity has been reduced in the float charging use state. SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply device which has a risk of causing a risk and has a means for ensuring reliability.
[0005]
[Problems to be solved by the invention]
In the technique for improving the reliability of a DC power supply according to Patent Document 1, parallel connection which is the basis of a redundant design of an electric connection circuit is specifically shown. The performance of a lead-acid battery using dilute sulfuric acid as an electrolyte is as follows: as long as the system is improved by combining lead-acid batteries with a cell voltage of 2 V, "parallel connection of batteries that are undergoing deterioration is dangerous, The shortcoming inherent in lead-acid batteries, which will be faster, remains inherent and must be eliminated. Eliminating the above drawbacks, the power is supplied from the power storage means to the load without any interruption during a power failure, and when the power is restored, the power is automatically supplied while monitoring the power storage means and the power is supplied to the load while maintaining the fully charged state It is an object of the present invention to provide a control power supply device for a motor and to cope with a long-term power failure in which the electric capacity of a battery or an electric double layer capacitor is completely discharged.
[0006]
[Means for Solving the Problems]
As a means of realizing a power supply device by making full use of technology to make a battery stand by in the best condition, a lead compound electrode immersed in dilute sulfuric acid as an electrolyte is charged with sulfation (crystallized lead sulfate and charged. A system in which a battery other than a lead-acid battery is connected as a power storage means, instead of a lead-acid battery that has the principle that its capacity does not recover forever even when charged. I focused on what to do.
[0007]
According to claim 1, a bidirectional converter having a battery management unit and a control circuit is connected between the rectifier and the battery connected to the commercial AC power supply, and the control circuit for driving the bidirectional converter is provided by the battery management unit. And intervene between the rectifier and the battery to control charging. In the event of a commercial AC power failure, DC power is supplied from the battery to the load, and at the same time that the power failure is restored, the bidirectional converter automatically charges the battery by the optimal amount of charge, and then keeps the battery condition in the best charged state. A power supply device characterized by this.
[0008]
According to claim 2, the power storage means, which is a parallel connection of the battery and the fuel cell, is a power storage means in which the battery is connected in parallel to the fuel cell in which the reverse current blocking means to the fuel cell is connected in series. The power supply device according to claim 1 is provided.
[0009]
According to claim 3, the battery is a storage battery other than a lead storage battery and does not require a rechargeable capacity called sulfation, which does not require electrolyte replenishment, and is sealed, for example, a nickel hydrogen storage battery, or The power supply device according to claim 1 or 2, which is an electric double layer capacitor.
[0010]
According to claim 4, the battery management unit is connected to the detection lead wire for each single cell or for each unit cell in which a plurality of single cells are assembled, and monitors the electrical characteristics such as the measured discharge capacity. The power supply device according to any one of claims 1 to 3, wherein the power supply device is a battery management unit that supplies a command signal such as refresh charge to the control circuit when a predetermined limit is exceeded.
[0011]
According to claim 5, the battery management unit includes a single cell so that it can be checked on a daily basis that the recovery of the battery capacity has significantly decreased compared to the rated capacity even when the battery is nearing the end of its life and charged. A detection lead wire for terminal voltage measurement, internal impedance measurement, etc. is connected for each unit cell or for each unit cell in which a plurality of single cells are assembled, and the measured electrical characteristics are monitored to exceed a predetermined limit. 5. The battery management unit according to claim 1, wherein when the battery management unit is determined to indicate the end of battery life, a warning is issued or a command signal for controlling or stopping the charging current to a very small current is given to a control circuit. Power failure power supply.
[0012]
According to claim 6, the battery management unit is connected to a temperature sensor for each single cell, for each unit cell obtained by assembling a plurality of single cells, or for a representative cell. 6. A battery management unit which, when exceeding a predetermined limit and determines that the storage battery is in an abnormal state, sends a warning to the control circuit or issues a command signal for stopping the charging current or controlling the charging current to a very small current to the control circuit. The uninterruptible power supply described.
[0013]
According to claim 7, the bidirectional converter forms an energizing circuit as a boost converter when discharging the battery, and forms an energizing circuit as a step-down converter when charging the battery, so that the current direction increases from the battery side to the load side. The uninterruptible power supply device according to any one of claims 1 to 6, wherein the bidirectional converter is an electric characteristic that is stepped down from the rectifier side to the battery side and that operates by contactlessly switching the electric characteristic in both directions without contact.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment according to the present invention will be described. FIG. 1 is a circuit diagram illustrating an embodiment according to the present invention. In FIG. 1, a rectifier 2 is connected to a commercial AC power supply terminal 1 to rectify AC into DC, convert DC to AC through a DC bus 3 and supply AC to a motor M2 as a load. I have. As described above, the alternating current is supplied to the load while the commercial alternating current power is being received. For example, the load is driven by a motor and the speed of the motor is often controlled by an inverter. When a commercial AC power failure occurs during motor operation, the battery 4 having a capacity that compensates for a short-time power failure discharges and supplies electric power to the motor without interruption, so that the motor 4 is connected so that operation can be continued. I have. The switch 9 is closed except when the battery 4 is replaced. The fuel cell F is connected in parallel to the battery 4 via the reverse blocking means 12. As shown in FIG. 2, the reverse direction blocking means 12 charges only the direction of the arrow C and does not supply current in the opposite direction, that is, the direction from the battery 4 to the fuel cell F, and charges the battery 4 from the fuel cell F. A reverse blocking means such as a semiconductor switch element that energizes only when the voltage of the fuel cell F is higher than the battery 4 so that the DC bus 3 can be energized. After the control circuit 102 detects the power failure and issues a fuel cell start command signal and the output voltage of the fuel cell reaches a steady value, the reverse blocking means 12 conducts in the forward direction and supplies DC to the battery side. However, the operation of the fuel cell for a predetermined time until the output voltage of the fuel cell reaches a predetermined value may not be performed due to deterioration of the battery. In order to economically supply a reliable, lightweight, and uninterruptible power supply with high reliability by preventing such troubles beforehand, as a means for always keeping the battery 4 in the best charge-completed state, both means described below are used. The battery 4 is connected to the DC bus 3 via the bidirectional converter.
[0015]
The bidirectional converter 5 is configured as follows. A smoothing capacitor 6 is connected between the output terminal P (positive) and the output terminal N (negative) of the rectifier to smooth the output voltage of the rectifier. The voltage between PN is selected to be higher than the terminal voltage of the battery 4. For example, the battery 4 is composed of 72 cells of a nickel-metal hydride storage battery such that the terminal voltage of the battery 4 changes from 79 V to 165 V during charging. On the other hand, the voltage between PN can be controlled between 130 V and 180 V. This voltage is called a link voltage. The terminal voltage of the smoothing capacitor 7 is reduced from 79 V to 115 V during charging of the battery 4 by the PWM control of the switching element 51 by the PWM control of the switching element 51. This is performed by a signal, and the end of charging is detected to control to a very small current.
[0016]
The operation of stepping down the direct current by the switching elements 51 and 52 will be described. The switching element 52 is turned off, and the pulse 51 is changed (by PWM control) to change the ratio between the on-period and the off-period of the switching, so that a wide pulse or a narrow pulse can be generated. The battery 4 is charged in a state where the battery switch 9 is closed by smoothing by the smoothing capacitor 7 to lower the average value of DC.
[0017]
The operation of boosting the direct current by the switching elements 51 and 52 will be described. When discharging from the battery 4 to the DC bus 3, the switching element 51 is turned off, and the switching element 52 changes the ratio of the switching conduction period to the non-conduction period (by performing PWM control) to change the magnitude of the discharge current average value. . When the switching element 52 is turned on and a discharge current flows through the smoothing reactor 8, energy is accumulated in the smoothing reactor 8. Next, while the switching element 52 is off, the energy stored in the smoothing reactor 8 is released. The current at this time passes through the diode 53 connected in anti-parallel to the switching element 51 to charge the smoothing capacitor 6. The voltage between the terminals of the smoothing capacitor 6 is increased to approximately twice the discharge voltage of the battery 4. This is because a voltage substantially equal to the voltage between the terminals of the smoothing capacitor 7 is accumulated in the smoothing reactor 8, and the voltage accumulated in both is charged between the terminals of the smoothing capacitor 6 by the added voltage. When a large current, for example, 50 A is applied to the load, the voltage becomes 130 V, which is slightly lower than twice the battery voltage (79 V in a single cell of 1.1 V in series with 72 cells). Is output between the output terminal P (positive) and the output terminal N (negative).
[0018]
The bidirectional converter 5 has a characteristic of switching between a step-up operation and a step-down operation without contact in the direction in which current flows from the battery 4 to the DC bus 3 and in the opposite direction. It is also effective to replace the battery 4 with an electric double layer capacitor having an extremely large capacitance.
[0019]
The bidirectional converter 5 includes a battery management unit 101 and a control circuit 102, and has an operation shown in the flowchart of FIG. Referring to FIG. 1, the operation of FIG. 3 will be described. In the power failure recovery (step 150) of FIG. 3, constant current charging of the battery 4 is started (step 151). A case of a hydrogen storage battery, which is used in series with 72 cells as described above, will be described. The temporal change of the battery voltage at which constant-current charging was started at a charging current of 2 A continued to increase gradually from 79.2 V (single cell 1.1 V), and then to 115.2 V (single cell 1.6 V) at the end of charging. I do. This end-of-charge voltage (single cell 1.6 V) has a characteristic (-4 mV / ° C. cell) that the lower the battery temperature, the lower the value. At a certain voltage of 1.6 V or less, the maximum value is reached. It gradually decreases through voltage. Therefore, the difference-[Delta] V between the maximum voltage value and the lowered voltage value is detected (step 152), and it is determined that the charging is near the end. The value of −ΔV is approximately −10 mV to −20 mV per single cell. To be more precise, it is necessary to pay attention to the time at which the voltage −ΔV is detected. When the storage battery immediately after discharging is switched to the start of constant current charging, the voltage may drop from a charging voltage of around 1.4 V per cell for several minutes. This is because the resistance inside the battery immediately after discharge is high and gradually decreases during energization. Taking such a phenomenon into consideration, -ΔV after 10 minutes from the start of charging is detected.
[0020]
When it is determined that the charging is near the end, the charging is switched to trickle charging (step 153), and the charging is continued with a small current sufficient to compensate for the self-discharge. For example, in many cases, trickle charging is performed with a current of 0.2 to 0.5 A in a sealed nickel-metal hydride storage battery having a rated capacity of 10 Ah.
[0021]
When the battery temperature is normal (Y determination in step 202) during a period in which the battery has not reached the end of charging (-ΔV cannot be detected (N determination in step 152)), constant current charging is continued. To detect the battery temperature, a thermistor is fixed to each single cell or to each unit cell in which a plurality of single cells are assembled, and a lead wire is connected to the battery management unit 101. For example, assuming four cells as a battery pack, a temperature detector is brought into contact with the center of the battery pack, 72 cells are formed into 18 battery packs, and 18 sets of lead wires are connected to the battery management unit 101. The temperature data between the assembled batteries is compared by sequentially switching and measuring the temperatures of the assembled batteries, and the protruding assembled battery is determined to be “abnormal battery”.
[0022]
When -ΔV of the battery cannot be detected (N determination in step 152) and the battery temperature is not normal (N determination in step 202), the charging current is controlled to intermittent charging or a small current, or charging is stopped (step 203). Then, an alarm (step 204) is issued. This is to prevent internal deterioration from progressing more and more with constant current charging in a normal case. In the simplified device, for example, if the temperature of the single cell exceeds 48 ° C., it is determined that the temperature is not normal (N determination).
[0023]
In place of battery temperature detection, wiring is connected from the battery management unit 101 so as to measure the internal impedance of the battery with an electric signal for each single cell or for each unit cell obtained by combining a plurality of single cells. If a certain unit cell protrudes as compared to the other, it is determined that the unit cell is not normal and an alarm is displayed.
[0024]
The battery capacity inspection command (step 154) is issued, for example, every six months from the battery management unit 101, and the current detector 11 for detecting the discharge current (step 155) is connected. The time to reach a voltage of 144 V (discharge end voltage) corresponding to 144 times the cell / time (discharge end voltage) is measured, and the current value × time is calculated by the control circuit 102 to integrate the battery capacity (step 156). The integrated capacity value is compared with the rated battery capacity stored in the battery management unit 101 (step 157), and it is determined whether the rated capacity is 50% or more. 151). It is determined whether the capacity is 50% of the rated capacity. If the capacity is not more than 50% (N determination), a notification is issued (step 158) and a refresh charge (step 159) is commanded. In this way, a command signal is issued every six months and the discharge capacity of the battery is confirmed. If the discharge capacity does not reach the predetermined capacity, refresh charge and discharge capacity confirmation are repeated to recover the battery capacity. For example, the number of times the discharge capacity integration is repeated and the value of the discharge capacity are displayed in the notification (step 158), so that the history of the capacity recovery of the battery can be known, so that it is possible to know whether the time to replace the battery is near or not. A device with high backup reliability was obtained. It is only necessary to ensure the battery capacity for the time required to start the fuel cell connected in parallel with the battery, so the capacity and size of the battery can be reduced, and the preliminary discharge current during refresh charge can be small. Parts can be downsized.
[0025]
It is also effective to connect the battery in parallel or use an electric double layer capacitor instead of the battery.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the fault that the battery which should be backed up by an unexpected power failure due to the shortage of the dischargeable capacity of the battery, which cannot be achieved by the conventional technology, and the motor stops can be eliminated. did it. Since the fuel cell was connected via the reverse current blocking means, the rated capacity of the battery could be reduced to cope with a long-term power failure. Since the history of battery capacity recovery can be known, it is possible to know in advance when battery replacement is necessary, and backup reliability in the event of a power failure has been improved. Since the battery is maintained and managed in the best condition by the battery management unit, the number of batteries in series can be increased. As a result of being able to increase the DC voltage, the power loss of the switching circuit was reduced because the current could be reduced. Since the voltage has been increased, the inverter may be a switching element with a small current, and the dimensions of the element and the radiation fin may be small. Therefore, the whole device is small and lightweight, which contributes to resource and energy saving and has a large industrial value.
[Brief description of the drawings]
FIG. 1 is a circuit diagram illustrating an embodiment according to the present invention.
FIG. 2 is a main part circuit diagram illustrating an embodiment according to the present invention. FIG. 3 is a flowchart illustrating an embodiment according to the present invention.
FIG. 4 is a configuration diagram of a conventional device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Commercial AC power supply terminal 2 Rectifier 3 DC bus 4 Battery 5 Bidirectional converter 6 Smoothing capacitor 7 Smoothing capacitor 8 Smoothing reactor 9 Battery switch 10 Inverter 11 Current detector 12 Reverse current blocking means F Fuel cell M1 Motor M2 Motor 51 Switching element (For step-down)
52 Switching element (for boosting)
53, 54 Diodes 60, 61, 62 Storage batteries 63, 64, 65 DC / DC converter 101 Battery management unit 102 Control circuit Cdc Capacitor P Output terminal (plus terminal)
N output terminal (minus terminal)
Vdc DC link voltage

Claims (7)

A power storage means, which is a parallel connection of a battery and a fuel cell, to which a voltage detection means is connected is connected to a DC bus to which a rectifier connected to a commercial AC and a motor inverter are connected. In a power supply device that continuously supplies power to a motor inverter without a momentary interruption, a bidirectional converter having a battery management unit and a control circuit is interposed between the DC bus and the battery, and when a commercial AC power failure occurs, the bidirectional converter is disconnected from the battery. When the DC bus is energized through a bidirectional converter, and the power failure is long, the control circuit detects the voltage of the battery and issues a power generation start command. The control circuit detects the recovery of the power failure and issues a stop command at the same time as the recovery from the power failure. The battery is started to be charged from the rectifier by the bidirectional converter, the battery management unit, and the control circuit, and the automatic charge is controlled by an optimum amount of charge. A motor control power supply device, wherein a control circuit for judging performance is integrated. 2. The motor according to claim 1, wherein the power storage means, which is a parallel connection of the battery and the fuel cell, is a power storage means in which a battery is connected in parallel to a fuel cell in which reverse current blocking means to the fuel cell is connected in series. Power supply for control. The motor control power supply device according to claim 1 or 2, wherein the battery is a sealed storage battery that does not require dipping and replenishment of an electrolytic solution other than a lead storage battery, or an electric double layer storage device. The battery management unit monitors the data such as the electrical characteristics measured by connecting the detecting means for each single cell or for each unit cell in which a plurality of single cells are aggregated. 4. The motor control power supply device according to claim 1, wherein the power supply device is a battery management unit that transmits a command signal for refresh charging or the like to the control circuit when the charge amount exceeds the limit. The battery management unit detects abnormal conditions such as a condition in which the data measured for each single cell or for each unit cell in which a plurality of single cells are aggregated exceeds a predetermined limit and the end of life of the storage battery is approaching. 5. The motor control power supply device according to claim 1, wherein the battery control unit is a battery management unit that notifies the control circuit when the determination is made or supplies a control signal to control or stop the charging current to a very small current. The battery management unit is in an abnormal state because the cell temperature data measured for each single cell, for each unit cell obtained by assembling a plurality of single cells, or for the representative cell exceeds a predetermined limit. 6. The motor control power supply device according to claim 1, wherein the battery management unit is a battery management unit that gives an alarm or a command signal for controlling or stopping the charging current to a very small current to the control circuit when it is determined that the charging current is small. In the bidirectional converter, an energizing circuit as a boost converter is formed during discharging from the battery to the DC bus side, and an energizing circuit as a step-down converter is formed during charging of the battery from the DC bus side. 7. The motor control power supply device according to claim 1, wherein the bidirectional converter has a characteristic in which an electric characteristic is switched in a step-up direction to a step-up voltage and in a direction from a DC bus side to a battery in a step-down direction.

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