JP2008092720A - Charging device of instantaneous drop compensation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To conduct stable high-speed charging to an electric double-layer capacitor. <P>SOLUTION: This charging control device for charging the electric double-layer capacitor generates a PWM output command of an inverter by proportionally integrates (PI) and operates deviation between a charging power command value and a charging power detection value by a proportional integration operation part 11, and corrects the charging power command value by proportionally integrates and operates a charging voltage command value and its voltage detection value by a proportional integration operation part 12. A switch 16 is on-controlled when a charging voltage of the electric double-layer capacitor reaches a full-charging voltage, and outputs an output of the proportional integration operation part 12 as a correction signal for lowering the charging power command value. The device includes a limiter which prevents discharging control from the electric double-layer capacitor caused by an effect that the corrected charging power command value is brought into negative polarity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a voltage sag compensator that compensates for power supply to a load by using an electric double layer capacitor as a power storage unit at the time of voltage sag (instantaneous voltage drop and power failure) due to lightning strikes and accidents, etc. It relates to recovery charging of the electric double layer capacitor later.

  This type of uninterruptible power supply, for which many uninterruptible power supplies have been proposed as devices for compensating for power supply to a load during a power failure of the system, is shown in FIG. In addition to this, a power supply path to the load 3 is formed, and separately from this, DC power from the power storage unit 4 such as a storage battery is converted into AC power by the inverter 5, and power to the load 3 is output via the output transformer 6. A supply path is formed.

  In this configuration, power is supplied from the commercial power source 1 to the load 3 in normal times, the change-over switch 2 is opened in the event of a power failure of the commercial power source 1, and the general load is disconnected to make only the important load. Switch to power supply from the inverter 5 to the load 3.

  In the uninterruptible power supply configured as described above, the functional configuration as the voltage sag compensator is an electric double layer capacitor that is small in size and capable of high-speed response, although the stored power amount is smaller than that of the storage battery. Use it to compensate only for instantaneous voltage drop of commercial power. In addition, a charging device 8 is provided for quickly charging the electric double layer capacitor in preparation for the next instantaneous voltage drop after the recovery from the voltage drop.

  Here, the charging device 8 uses a charger composed of an inverter, a step-up transformer and a rectifier or a DC-DC converter (buck-boost chopper), and charges the electric double layer capacitor to a voltage higher than the power supply voltage. Increases the amount of power that can be discharged during sag compensation. As for the charging method, the electric double layer capacitor is charged with constant power at the beginning of charging, and when it reaches a certain voltage, it is switched to constant voltage control. Charging is prevented (see, for example, Patent Document 1).

  FIG. 3 shows a control block diagram of a conventional charging apparatus, in which the inverter as the charging power conversion means is PWM-controlled, constant power charging is performed at the initial stage, and constant voltage charging is performed at the end stage. The PI calculation unit 11 generates an inverter output voltage command by performing a proportional integral (PI) calculation on the deviation between the charge power command value of the electric double layer capacitor and the charge power detection value. PI calculation unit 12 generates an inverter output voltage command by performing a proportional integral calculation on the deviation between the DC voltage command value of the electric double layer capacitor and the DC voltage detection value. The switch 13 switches from the output of the PI calculation unit 11 to the output of the PI calculation unit 12 when the charging voltage of the electric double layer capacitor reaches the full charge voltage. The PWM modulation unit 14 obtains a PWM modulated wave according to the deviation between the output voltage command from the switch 13 and the base voltage, and uses this as a gate signal for the inverter. The base voltage (1 p.u) is calculated by the base voltage calculation unit 15 from the detected DC voltage.

  As the actual control by the above charge control block diagram, the recovery charge power is 75 kW, the standby voltage is 640 V, the internal resistance of the electric double layer capacitor is 0.3Ω, first, constant power charge is performed at 75 kW, and the capacitor voltage reaches 673 V Switch to DC voltage constant control. Charging to a voltage higher than the standby voltage is due to consideration of the internal resistance of the capacitor.

  For example, when constant power charging is performed up to 640 V at 75 kW, the current that flows when the capacitor voltage reaches 640 V is 75000 [W] ÷ 640 [V] = 117 [A]. When the internal resistance is 0.3 [Ω], a voltage of about 35 V is applied to the internal resistance from 117 [A] × 0.3 [Ω] = 35.1 [V], and is actually applied to the capacitor. The voltage is about 605 [V]. If the DC voltage constant control is performed from this state, the charging current becomes small and it takes a long charging time.

Therefore, the capacitor voltage is charged up to 673V with constant power. When constant power charging is performed up to 673 V at 75 kW, the current that flows when the capacitor voltage reaches 673 V is 75000 [W] ÷ 673 [V] = 111 [A]. If the internal resistance is 0.3 [Ω], the voltage actually applied to the capacitor is about 639.7 [V] from 111 [A] × 0.3 [Ω] = 33.3 [V], The battery can be fully charged.
JP 2003-199332 A

  In the conventional charging method, after the capacitor voltage reaches 673 [V], the constant charge power control is switched to the constant DC voltage control, so that the PWM command value may change stepwise and the charge control may become unstable. There is.

  Further, in the constant voltage control, when the detected DC voltage value is 640 [V] or more, the charging current is reduced, so that the charging power is made negative (minus) and stored in the electric double layer capacitor. There is a risk of discharging electric power, and there is a risk that the charging time will be extended.

  An object of the present invention is to provide a charging device for a voltage sag compensator that solves the above-described problems.

  In order to solve the above-mentioned problem, the present invention performs constant power charging control by a proportional-integral calculation unit based on a charging power command value and a detection value until the electric double layer capacitor is fully charged, and a direct current voltage command when full charging is reached. The charging power command value is corrected and controlled by a proportional-integral operation unit based on the value and the detected value, and has the following configuration.

(1) In a voltage sag compensator that compensates for power supply to a load by using an electric double layer capacitor as a power storage unit in the event of an instantaneous voltage drop or a power failure,
A charging device for charging the electric double layer capacitor after the compensation,
A first proportional integration for generating a charging power output command of the charging power output means of the electric double layer capacitor by performing a proportional integration (PI) operation on a deviation between the charging power command value of the electric double layer capacitor and a charging power detection value. An arithmetic unit;
A second proportional-integral calculation unit that generates a correction signal of the charge power command value by performing a proportional-integral calculation of a deviation between the charge voltage command value of the electric double layer capacitor and the detected voltage value;
A switch that is turned on when the charge voltage of the electric double layer capacitor reaches a full charge voltage, and that outputs the output of the second proportional-integral calculation unit as a correction signal that lowers the charge power command value; Features.

  (2) A limiter is provided for preventing the corrected charging power command value from becoming negative and controlling discharge from the electric double layer capacitor.

  As described above, according to the present invention, constant power charging control is performed by the proportional-plus-integral calculation unit based on the charging power command value and the detected value until the electric double layer capacitor is fully charged. Since the charging power command value is corrected and controlled by the proportional-plus-integral calculation unit based on the detected value, the following effects are obtained.

  ・ High-speed charging is possible compared to conventional charging by switching to constant DC voltage control.

  -Since charging current changes continuously, stable control can be performed.

  -By providing a limiter that suppresses the charging power command value from becoming negative, discharging from the electric double layer capacitor can be eliminated and the charging time can be shortened.

  FIG. 1 is a control block diagram of a charging apparatus showing an embodiment of the present invention. The PI calculation unit 11 performs a proportional integral (PI) calculation on the deviation between the charging power command and the detected charging power value to generate an output voltage command for the inverter. The PI calculation unit 12 performs a proportional integral calculation on the deviation between the DC voltage command and the DC voltage detection value to generate a correction signal for the charging power command value. The switch 16 is turned on when the charge voltage of the electric double layer capacitor reaches the full charge voltage, and is output as a correction signal that lowers the charge power command value at the output of the PI calculation unit 12.

  The PWM modulation unit 14 obtains a PWM modulation wave according to the deviation between the output voltage command from the PI calculation unit 11 and the base voltage, and makes this a gate signal of the inverter. The base voltage (1 p.u) is calculated by the base voltage calculation unit 15 from the detected DC voltage.

  According to the above control circuit configuration, at the initial stage of charging of the electric double layer capacitor, the switch 16 is controlled to be off, and the electric power of the electric double layer capacitor is charged by the PI calculation unit 11. After that, when the electric double layer capacitor is charged to a full charge voltage (for example, 673 V in the above example), the switch 16 is turned on.

  As a result, until the DC voltage of the electric double layer capacitor reaches the command value, the charging power drooping control is performed with the charging power command value greatly reduced as the deviation increases, and charging by switching to the conventional DC voltage constant control is performed. Compared to, high-speed charging is possible.

  In addition, when shifting from the constant power charging state to the correction of the charging power command value, it is predicted that the charging power command value changes stepwise by the on-control of the control switch 16. The PWM command value changes smoothly. That is, the PWM command value changes continuously, and stable control can be performed.

  By adding a limiter circuit to the corrected output that corrects the charge power command value, the current command value can be prevented from becoming negative (so as not to be discharged), and the electric power stored in the electric double layer capacitor can be reduced. There is no discharge.

  In addition, although the case of the charging power control by an inverter was shown in embodiment, it can apply to the charging power control by other charging circuits, such as a DC-DC converter, and can obtain an equivalent effect.

The control block diagram of the charging device which shows embodiment of this invention. The structural example of an uninterruptible power supply. The control block diagram of the conventional charging device.

Explanation of symbols

11 PI Calculation Unit 12 PI Calculation Unit 13 Changeover Switch 14 PWM Modulation Unit 15 Base Voltage Calculation Unit 16 Switch

Claims (2)

In the voltage sag compensator that compensates the power supply to the load using the electric double layer capacitor as a power storage unit at the time of instantaneous voltage drop or power failure
A charging device for charging the electric double layer capacitor after the compensation,
A first proportional integration for generating a charging power output command of the charging power output means of the electric double layer capacitor by performing a proportional integration (PI) operation on a deviation between the charging power command value of the electric double layer capacitor and a charging power detection value. An arithmetic unit;
A second proportional-integral calculation unit that generates a correction signal of the charge power command value by performing a proportional-integral calculation of a deviation between the charge voltage command value of the electric double layer capacitor and the detected voltage value;
A switch that is turned on when the charge voltage of the electric double layer capacitor reaches a full charge voltage, and that outputs the output of the second proportional-integral calculation unit as a correction signal that lowers the charge power command value; A charging device for a sag compensation device as a feature.   2. The charging device of the sag compensation device according to claim 1, further comprising a limiter that prevents the corrected charging power command value from becoming negative and causing discharge control from the electric double layer capacitor. .

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