JP2010172047A - Apparatus to counter momentary drop - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a conventional system does not discharge energy efficiently, if it uses a detected voltage discharged from an accumulating device with an internal voltage and a recommended lower limit voltage as a terminal voltage and stops its discharge when this value comes to a recommended lower limit voltage. <P>SOLUTION: The voltage lower limit value to stop the discharge of the accumulating device is set to a value obtained by subtracting a drop voltage (the product of a discharge current and an internal resistance value) due to an internal resistance from the recommended lower limit voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an uninterruptible power supply device including a power conversion device and a power storage device such as a secondary battery or a large-capacitance capacitor, and more particularly to a voltage sag countermeasure device for the purpose of short-time compensation.

Conventionally, lead storage batteries have been generally used as power storage devices for uninterruptible power supplies.
In recent years, as a countermeasure against the instantaneous voltage drop phenomenon of AC power supply, the energy density is lower than that of lead-acid batteries, but the instantaneous voltage drop countermeasure device applying a capacitor that has a long charge / discharge cycle life and low internal resistance and high output density ( It is also called a voltage sag compensator. The voltage sag countermeasure device using a capacitor is suitable for power compensation for a few seconds or less.

As an example of a voltage sag countermeasure device to which a capacitor is applied, Patent Document 1 is a conventional example of a voltage sag countermeasure device to which an electric double layer capacitor (hereinafter referred to as EDLC) is applied.
FIG. 4 shows a circuit configuration of the voltage sag countermeasure device proposed in Patent Document 1. The circuit includes a commercial power source (AC power source) 1, an instantaneous voltage drop detection unit 7 that detects an instantaneous voltage drop (hereinafter referred to as “instantaneous voltage drop”), a high-speed switch 2 that shuts off the power supply from the commercial power source 1 during an instantaneous voltage drop, a load 3, EDLC 4 as an electricity storage device, power converter 5 for converting AC power and DC power to each other, power conversion input circuit breaker for supplying AC power obtained by converting DC power from EDLC 4 by the power converter 5 to the load 3 6 is composed. The power converter 5 includes an inverter circuit using a semiconductor switch element, a diode, and the like that can perform an inverse conversion operation (inverter operation) and a forward conversion operation (converter operation). Moreover, EDLC4 as an electrical storage device is represented by the series circuit of the internal resistance 4r and the electrostatic capacitance 4c.

When the commercial power source is healthy, commercial power is supplied from the commercial power source 1 to the load 3 through the high-speed switch 2, while the DC power obtained by converting the AC power from the commercial power source 1 by the power converter 5 is set to the rated voltage in the EDLC 4. Charge the battery and wait.
When the voltage sag detector 7 detects a voltage sag, the high-speed switch 2 is opened and the power conversion input circuit breaker 6 is turned on, and AC power obtained by converting DC power from the EDLC by the power converter is supplied to the load 3.

JP 2006-246609 A

  A case where a hybrid capacitor that can sustain energy from EDLC as an electricity storage device is applied to a voltage sag countermeasure device will be described as an example. A hybrid capacitor is a capacitor that uses a Faraday reaction at one of the positive electrode and the negative electrode and a non-Faraday reaction at the other. Moreover, since the lower limit voltage exists, it is necessary to control the lower limit voltage.

Since the hybrid capacitor has an internal resistance, a voltage drop corresponding to the discharge current occurs. As a result, the observed capacitor voltage is a value obtained by subtracting the voltage drop value generated by the discharge current from the capacitance voltage value depending on the remaining capacity. Therefore, as shown in FIG. 2 (upper stage), when the discharge is stopped when the capacitor voltage Vb reaches the lower limit voltage V ₂ , this corresponds to a voltage drop ΔV _r determined by the discharge current and the internal resistance at the time of reaching the end. The energy indicated by ΔJ below remains. The larger the internal resistance, the more this residual amount becomes, causing a decrease in the subsequent releasable energy.

  As countermeasures, there are a method of selecting a capacitor having a low internal resistance and a method of decreasing the internal resistance by increasing the number of parallel connections. In the former, the capacitance decreases as the internal resistance decreases, so the number of parallel increases in order to obtain the capacitance that is originally required for energy release. On the other hand, in the latter case, when the parallel number is increased, the electrostatic capacity becomes excessive with respect to the required capacity. Therefore, both methods increase the size of the capacitor group.

In order to solve the above-mentioned problem, in the first invention, the power conversion device and a power storage device having a recommended lower limit voltage are provided. When the AC power source is healthy, AC power is supplied from the AC power source to the load. When the voltage or frequency of the power supply deviates from a predetermined range, in the uninterruptible power supply that supplies AC power to the load from the power storage device via the power converter,
When the voltage of the power storage device reaches a determination value determined based on a recommended lower limit voltage, the power supply operation from the power converter to the load is stopped.

  In the second invention, the determination value determined based on the recommended lower limit voltage is a voltage drop estimated from a discharge current from the power storage device and an internal resistance value of the power storage device from the recommended lower limit voltage of the power storage device. The voltage value is obtained by subtracting the amount.

  In a third aspect of the invention, the determination value determined based on the recommended lower limit voltage is a recommended lower limit voltage of the power storage device, a discharge current from the power storage device, an internal resistance value of the power storage device, and the power storage device. The voltage value is obtained by subtracting the estimated voltage drop from the temperature measurement value.

  In a fourth invention, the power storage device is a hybrid capacitor in which one of the positive electrode and the negative electrode uses a Faraday reaction and the other uses a non-Faraday reaction.

In the present invention, the remaining capacity stored in the electrostatic capacity can be reduced to 0% by correcting the voltage drop due to the internal resistance downward from the original discharge end level.
As a result, the energy stored in the capacitor can be used to the maximum, and the capacitors can be downsized.

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is an operation diagram showing the relationship between the capacitor voltage Vb during discharge and the voltage drop ΔVr due to the internal resistance. FIG. 1 is a circuit diagram showing a second embodiment of the present invention. FIG. 4 is a circuit diagram for explaining the prior art.

  The main point of the present invention is that the terminal voltage of the hybrid capacitor is conventionally measured as a method for determining the discharge lower limit voltage when discharging the hybrid capacitor. In the present invention, however, the internal voltage is taken into account from the terminal voltage. This is a point obtained by subtracting the voltage drop corresponding to the internal resistance.

  FIG. 1 shows a first embodiment of the present invention. Fig. 2 (lower) shows the operating waveforms of the discharge voltage and current. FIG. 1 shows an example of a circuit that performs arithmetic processing for correcting a voltage drop due to internal resistance downward from the original discharge end level when the hybrid capacitor is applied to a voltage drop countermeasure device. The circuit of FIG. 1 is different from the circuit of the prior art of FIG. 4 in that the multiplier 10 that multiplies the discharge current Ic detected by the current detector 8 and the resistance value Rc of the internal resistance 4r of the capacitor 4 and the voltage of the capacitor voltage Vb. This is a circuit in which an arithmetic circuit composed of a voltage detector 9 for detecting the voltage and a switch 11 that is turned on when the capacitor voltage Vb reaches the lower limit voltage V2 is added.

  First, the multiplier 10 multiplies the discharge current Ic and the internal resistance value Rc of the capacitor 4 to calculate a voltage drop ΔVr due to the internal resistance. When the capacitor voltage Vb reaches the lower limit voltage V2, the switch 11 is turned on, and ΔVr ′ at that time is calculated. By subtracting ΔVr ′ from the lower limit voltage V2, a new lower limit voltage V2 ′ is calculated. The voltage V2 'is used as a stop determination criterion. When discharging to the lower limit voltage V2 ', the capacitor voltage Vb after the end of discharge becomes the lower limit voltage V2 of the conventional control, and the remaining energy of the capacitor can be set to 0%. At that time, even if the hybrid capacitor 4 is transiently discharged to the lower limit voltage V2 ', the characteristics and life of the capacitor are not affected.

  As a result, it is possible to take measures against a decrease in the amount of energy that can be released, which has been a problem in the conventional method, and the energy held by the capacitor can be used to the maximum, so that the capacitor group can be downsized.

  FIG. 3 shows a second embodiment of the present invention. The difference from the first embodiment is that the hybrid capacitor 4 is provided with a temperature detector 4T, the internal resistance value Rc is corrected by the temperature correction circuit 14, and the multiplication result of the correction result Rc ′ and the discharge current Ic is the internal value of the hybrid capacitor. This is a voltage drop due to resistance.

Since the internal resistance value of the hybrid capacitor varies depending on the temperature, this temperature characteristic can be realized by preparing the temperature correction circuit in advance. By using this method, even when the environmental change is large, the energy held by the capacitor can be used to the maximum, and the capacitor group can be downsized.
In addition, although the example of the hybrid capacitor was shown as an electrical storage device in the said Example, if it is an electrical storage device with an internal resistance, it is realizable.

  The present invention is not limited to the voltage drop countermeasure device, but can be applied to an electric vehicle, a grid interconnection compensation device, and the like to which a large-capacitance capacitor having an internal resistance is applied.

DESCRIPTION OF SYMBOLS 1 ... Commercial power supply (AC power supply) 2 ... High-speed switch 3 ... Load 4 ... Power storage device 5 ... Power converter 6 ... Power conversion input circuit breaker 7 ... Instantaneous voltage drop detection 8 ... Current detector 9 ... Voltage detector 10 ... Multiplier 11 ... Switch 12 ... Adder 13 ... Stop determination circuit

Claims (4)

When the power converter has an electricity storage device with a recommended lower limit voltage and the AC power source is healthy, AC power is supplied from the AC power source to the load, and the voltage or frequency of the AC power source deviates from a predetermined range An uninterruptible power supply that supplies AC power to the load from the power storage device via the power converter,
When the voltage of the said electrical storage device reaches the determination value determined based on a recommendation lower limit voltage, the power supply operation | movement from the said power converter device to the said load is stopped, The instantaneous voltage drop countermeasure apparatus characterized by the above-mentioned.   The determination value determined based on the recommended lower limit voltage is a voltage value obtained by subtracting a voltage drop amount estimated from a discharge current from the power storage device and an internal resistance value of the power storage device from the recommended lower limit voltage of the power storage device. The voltage sag countermeasure device according to claim 1.   The determination value determined based on the recommended lower limit voltage is estimated from the recommended lower limit voltage of the power storage device, the discharge current from the power storage device, the internal resistance value of the power storage device, and the temperature measurement value of the power storage device. The voltage drop countermeasure device according to claim 1, wherein the voltage value is obtained by subtracting the voltage drop amount. The power storage device according to claim 1, wherein one of the positive electrode and the negative electrode is a hybrid capacitor using a Faraday reaction and the other using a non-Faraday reaction.

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