JP5589771B2 - Charger current control device - Google Patents

Description

  The present invention relates to a current control device for a charger, and more particularly to a device for preventing an overcurrent of a battery charger mounted on an electric vehicle such as a battery forklift.

  FIG. 8 shows a circuit configuration of a charger mounted on an electric vehicle such as a battery forklift. AC is an AC power source, RF1 is a first rectifier, and a diode bridge converts AC to DC. C1 is a smoothing capacitor for smoothing the voltage obtained by full-wave rectifying the AC voltage AC and converting it to DC, and TR1 is an inverter, which is composed of a semiconductor element such as a transistor or IGBT and converts DC to AC. CS1 is a current detector, which is used to detect the current of the inverter TR1 and protect the semiconductor elements constituting the inverter from overcurrent.

The electric power converted into alternating current by the inverter TR1 is converted into alternating current by the second rectifier RF2 through the transformer TF, and the battery B is charged through the smoothing circuit including the smoothing reactor DCL and the smoothing capacitor C2. The battery B is controlled at a constant voltage and a constant current by changing the on / off ratio of the switching element T1.
D2 is a freewheeling diode, which protects T1 from overvoltage by returning the current of the reactor L1 to the battery B when the switching element T1 is turned off. CS2 is a current detector that detects battery current.

  As shown in FIG. 8, Patent Document 1 is known as a device that takes out a predetermined voltage and current from an AC power supply via a rectifier and supplies them to a battery at a predetermined timing.

JP 2002-142381 A

  In Patent Document 1, since the circuit setting before the start of charging corresponds to charging under constant current control, the charging current before starting charging is 0, and the output of the PWC control circuit is output at the maximum duty ratio. It is under the state to be. When charging from constant current control is started in this state, in order to solve the problem that a large inrush current occurs immediately after the start of charging, the peak value of the inrush charging current at the start of charging is reduced, and the inrush immediately after starting charging An inrush current prevention switch for preventing current is provided.

  However, in a charger that takes out and charges a predetermined constant voltage and constant current from an AC power source via a rectifier, an external load having a large capacity is connected to the same AC power source as the AC power source to which the charger is connected. In such a case, an overcurrent phenomenon occurs in the charging circuit when the power supply voltage drops instantaneously, for example, when the external load is turned on.

  An object of the present invention is to provide a current controller for a charger that prevents an overcurrent due to an external factor of the charger.

Claim 1 of the present invention converts an alternating voltage converted to direct current into an alternating voltage by an inverter, converts the converted alternating voltage into direct current by a rectifier, smoothes it by a smoothing circuit, and controls it by a switching element. While in the charger that controls the charging voltage and charging current of the battery,
A deviation signal between the detection voltage Vdet of the smoothing circuit and a preset voltage command Vref is amplified by a proportional integration voltage amplifier, and the output voltage of the inverter is controlled via the PWM control unit based on the amplified signal. A current detector for detecting a battery current, and a current control unit for amplifying a deviation signal between a detected current Idet detected by the current detector and a current command Iref preset in the current setter by a current amplifier; The switching element is configured to be turned on / off via a pulse width converter based on the output signal of the current controller.

According to a second aspect of the present invention, the current control unit receives the detection current Idet detected by the current detector and calculates an average current Iav, and a change rate of increase / decrease in battery current. Each of the change rate setting unit set in advance and the average current Iav and the current value set by the current setting unit are compared. When the average current Iav is larger than the current set value, the average current Iav and the change rate setting unit A difference signal from the set current value is set as a current command Iref, and when the average current Iav is smaller than the current set value, a sum signal of the average current Iav and the current value set by the change rate setting unit is set as a current command Iref. The present invention is characterized in that a set current switching unit comprising a comparing means is provided.

  According to a third aspect of the present invention, the current control unit receives a deviation signal between the detection current Idet and the current command Iref, and a current amplifier having a function of switching the polarity of the output signal according to the input difference signal polarity; A rate-of-change setting unit connected to the output side, an averaging unit that calculates the average current Iav by inputting the detected current Idet detected by the current detector, an output of the average current Iav and the rate-of-change setting unit The sum signal is output to the pulse width converter.

  As described above, according to the present invention, the overcurrent phenomenon that occurs in the charging circuit when the power supply voltage drops instantaneously, such as when the external load is turned on, is suppressed. Further, since the control circuit itself directly controls the inverter and the switching element, a photocoupler and a detection circuit for converting a feedback signal as in Patent Document 1 are unnecessary, and the size can be reduced.

The block diagram of the control apparatus of the charger which shows the Example of this invention. The time chart of the voltage and electric current at the time of the instantaneous voltage fall by this invention. The block diagram of the control apparatus of the charger which shows the other Example of this invention. The block diagram of the current control part of this invention. The flowchart of an electric current control part operation | movement. The time chart of the voltage and electric current at the time of the instantaneous voltage fall by this invention. The block diagram of the current control part by the other Example of this invention. The block diagram of the control apparatus of the conventional charger.

  FIG. 1 is a block diagram showing a first embodiment of the present invention. The same or corresponding parts as those in FIG. A voltage control unit 1 includes a voltage setting unit 11, a proportional amplifier 12, and a voltage amplifier 13. A current control unit 2 includes a current setting unit 21, a proportional amplifier 22, and a current amplifier 23. Reference numeral 3 denotes a pulse width converter.

  The voltage setting unit 11 sets the voltage command Vref. The detection voltage Vc2 of the smoothing capacitor C2 is amplified to a predetermined value by the proportional amplifier 12 and then output to the subtraction unit 14 as Vdet. The subtraction unit 14 performs a difference calculation between the set voltage Vref and the detection voltage Vdet, and the calculated difference signal is output to the PWM control unit 4 via the proportional-integral voltage amplifier 13 so that the difference signal becomes 0 so that the difference signal becomes zero. Is controlled.

  On the other hand, the battery current Id2 detected by the current detector CS2 is output to the subtraction unit 24 through the proportional amplifier 22, and a difference signal from the current command Iref set by the current setting unit 21 is obtained. . The difference signal is output to the pulse width conversion unit 3 through the proportional-integral current amplifier 23, and the pulse width conversion unit 3 performs on / off ratio control of the switching element T1 so that the difference signal becomes zero.

FIG. 2 shows a time chart of the present invention. When an instantaneous voltage drop occurs at time t1 due to an external factor, and the voltage is restored at time t2, the voltages Vc1 and Vc2 of the smoothing capacitors C1 and C2 also drop. Accordingly, a difference signal between the voltage command Vref and the detected voltage Vdet is generated in the subtracting unit 14 of the voltage control unit 1, and the voltage amplifier 13 outputs 100% voltage to raise the voltage until the time t2 when the instantaneous voltage drop is restored. Then, the inverter TR1 is controlled via the PWM control unit 4.
The current controller 2, the output current of the current amplifier 23 by the instantaneous voltage drop at the time t1 Furikireru to 100% since it becomes less current command, but battery current Id2 is the supply voltage to the battery Vc2 <V _B becomes Since it becomes lower than the battery voltage V _B, it does not flow until time t2 after the instantaneous voltage drop is restored.

  Therefore, according to the first embodiment, the overcurrent phenomenon that occurs in the charging circuit when the power supply voltage drops instantaneously, such as when the external load is turned on, is suppressed. Further, since the control circuit itself directly controls the inverter TR1 and the switching element T1, the control circuit itself does not require a photocoupler or a detection circuit for converting a feedback signal as in Patent Document 1, and can be miniaturized.

  FIG. 3 is a block diagram showing the second embodiment. The difference from the first embodiment shown in FIG. 1 is the current control unit 2a, which is configured as shown in FIG. In the first embodiment, when the instantaneous voltage drop is restored, the voltage amplifier 13 and the current amplifier 23 are in the output state of 100%, so that the maximum voltage and the maximum current are output. For this reason, the battery current Id2 does not completely suppress the overcurrent phenomenon at time t3 shown in FIG. The second embodiment eliminates this overshoot.

In FIG. 4, reference numeral 25 denotes an averaging unit, and an average value of the detection current Idet output via the proportional amplifier 22 is obtained by a moving average means or the like. 26 is a positive direction change rate setting unit, 27 is a negative direction change rate setting unit, and the set current of each setting unit 26, 27 is set to about 10% positive or negative change rate of the charging current when the increase / decrease current is 100%. Has been. 28 and 29 are switching units, and the switching unit 28 switches to the terminal a1 (increase side) when the current command Iref> Iav + ΔI set by the current setting unit 21, and the terminal b1 (decrease side) when the current command Iref <Iav−ΔI. Switch to. The switching unit 29 switches to the terminal b2 side when the average value Iav of the charging current is within ± ΔI with respect to the current command Iref. And these 25-29 comprise a setting current switching part.

FIG. 5 shows an operation flow of the set current switching unit. The battery current Id2 is amplified to a predetermined value by the proportional amplifier 22 and is input to the averaging unit 25 as a detected current value Idet. The averaging unit 25 converts the average value Iav to the average value Iav in step S1, compares the average value Iav with the current set value set by the current setting unit 21 in step S2, and determines the difference between the current set value and the change rate set value ±. It is compared whether it is greater than ΔI. Here, when | Iav−Iref |> ± ΔI is exceeded, the switching unit 28 is turned on in step S3, and it is further determined in step S4 whether Iav−Iref> 0. As a result, when the average value Iav is larger than the current set value, Iav−ΔI is output as the current command Iref in step S5. When the average value Iav is smaller than the current command Iref, Iav + ΔI is output as the current command Iref in step S6.
On the other hand, when the difference between the average value Iav and the current set value is smaller than the change rate set value ± ΔI in step S2, the switching units 28 and 29 are turned off (step S7), and the set value in the current set unit 21 in S8. Is a current command Iref.

  FIG. 6 shows a time chart of the second embodiment. At time t3 after time t2 when the instantaneous voltage drop is restored, the current command Iref becomes Iav + ΔI. Therefore, when the battery current Id2 increases rapidly, Idet> Iref Therefore, since the current amplifier 23 starts to limit the current increase, the current increase is limited, and the battery current Id2 is continuously charged without becoming an overcurrent.

  Therefore, according to this embodiment, the increase in the battery current Id2 at the time of recovery from the instantaneous voltage drop is suppressed more than in the first embodiment, and overcurrent can be prevented based on external factors. Others are the same as in the first embodiment.

FIG. 7 is a block diagram of the current control unit 2b according to the third embodiment, and the rest is the same as FIG. A change rate setting unit 30 is connected to the output side of the current amplifier 23, and its output ± ΔI is added to the average value Iav by the addition unit 31 and then input to the pulse width conversion unit 3.
The operation of FIG. 7 will be described.
The detected battery current Id2 is amplified to a predetermined value by the proportional amplifier 22 and output to the subtractor 24 as a detected current value Idet, and a difference calculation with the current command Iref is executed. Is input. The current amplifier 23 has a function of a changeover switch that changes the polarity of the output signal according to the polarity of the input difference signal. When the detected current value Idet becomes larger than the current command Iref, the output of the current amplifier 23 becomes negative. When the detected current value Idet becomes smaller than the current command Iref, the output of the current amplifier 23 becomes positive. Therefore, when the output of the current amplifier 23 is negative, the change rate signal ΔI preset by the change rate setting unit 30 is negative, and the signal input to the pulse width conversion unit 3 is Iav−ΔI. Further, when the output of the current amplifier 23 is positive, the change rate signal ΔI is positive, and the signal input to the pulse width converter 3 is Iav + ΔI.

  According to this embodiment, even if the detected current value Idet suddenly changes greatly, the signal input to the pulse width conversion unit 3 changes to ± ΔI or less, so that the overcurrent of the battery current Id2 is prevented and implemented. The same effect as in Example 2 is achieved.

DESCRIPTION OF SYMBOLS 1 ... Voltage control part 2 ... Current control part 3 ... Pulse width conversion part 4 ... PWM control part 11 ... Voltage setting part 12, 22 ... Proportional amplifier 13 ... Voltage amplifier 21 ... Current setting part 23 ... Voltage amplifier 25 ... Averaging part

Claims (3)

The AC voltage converted to DC is converted to AC voltage by an inverter, the converted AC voltage is converted to DC by a rectifier, smoothed by a smoothing circuit, and controlled by a switching element, and the battery charging voltage and charging current are controlled. In the charger that controls
A deviation signal between the detection voltage Vdet of the smoothing circuit and a preset voltage command Vref is amplified by a proportional integration voltage amplifier, and the output voltage of the inverter is controlled via the PWM control unit based on the amplified signal. ,
A current detector for detecting the battery current is provided, and a current control unit for amplifying a deviation signal between the detected current Idet detected by the current detector and a current command Iref preset in the current setting device by a current amplifier is provided. A current control device for a charger, wherein the switching element is controlled to be turned on / off via a pulse width converter based on an output signal of the current controller. The current control unit inputs an detection current Idet detected by the current detector, calculates an average current Iav, and a rate-of-change setting unit that presets the rate of increase / decrease in battery current. And when the average current Iav is larger than the current setting value, the difference between the average current Iav and the current value set by the change rate setting unit is compared with the current value set by the current setting unit. A set current comprising a comparison means using the current command Iref as the current command Iref, and when the average current Iav is smaller than the current set value, the sum signal of the average current Iav and the current value set by the change rate setting unit. The current control device for a charger according to claim 1, further comprising a switching unit. The current control unit receives a deviation signal between the detection current Idet and the current command Iref, and a current amplifier having a polarity switching function of an output signal according to the input difference signal polarity, and a change connected to the output side of the current amplifier A rate setting unit, an averaging unit that inputs the detection current Idet detected by the current detector and calculates an average current Iav, and a pulse width conversion of a sum signal of the average current Iav and the output of the change rate setting unit The current control device for a charger according to claim 1, wherein the current control device is configured to output to a power supply unit.

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