JPH03103045A - Uninterruptible power supply - Google Patents

Abstract

PURPOSE:To obtain an uninterruptible power supply, which can feed power from a power converter to a load even under overload state, by lowering the level of target voltage command or stopping generation of switching signal when overload is applied. CONSTITUTION:When an overload 16 is applied, overload current flows to the output of an inverter 26 and when the output level of a current detector 28 exceeds an overcurrent level, output level from an operational amplifier 38 is inverted from high to low thus inverting the output level of a comparator 42 from low to high. Consequently, the amplitude of a target voltage command, i.e., the output signal from a multiplier 54, is limited low by the output signal from the operational amplifier 38, whereby the output voltage of the inverter 26 is constricted. By such arrangement, abrupt increase of output current from the inverter 26 can be suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an uninterruptible power supply, and particularly relates to an uninterruptible power supply suitable for supplying AC power to a load even if the AC power supply is in an abnormal state. .

[Conventional technology]

Magazine OHM is the conventional control method for uninterruptible power supplies.
As described on pages 22-23 of the November 1986 issue, there are continuous use systems in which a storage battery is placed between the rectifier and inverter, or continuous use systems in which a storage battery is placed between the storage battery and the inverter, and the storage battery and inverter are connected. A standby method is known in which a bypass circuit is provided to bypass the inverter, and the bypass circuit and the inverter output are connected to the load via a changeover switch. The standby type is Mitsubishi Electric Technical Report V
oQ. As described in page 14 of 62 Na6, 1988, if the output side of the inverter becomes overloaded and excessive current flows, the inverter should be disconnected from the load by switching the changeover switch. A method is adopted in which AC power is directly supplied to the load via a changeover switch, and when overload current stops generating, the changeover switch is switched again to supply power from the inverter to the load.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, no consideration is given to cases in which the AC power supply that supplies power to the bypass circuit experiences a power outage or the voltage of the AC power supply drops, resulting in an overload state on the load side of the inverter. Sometimes, when the AC power supply that supplies power to the bypass circuit experiences a power outage or the voltage of the AC power supply drops, there is a risk that the equipment on the load side may stop due to power failure detection. In addition, in the case of a power supply device that uses a continuous use method, there is a risk that an overload current will flow through the inverter and the semiconductor elements that make up the inverter will deteriorate.

An object of the present invention is to provide an uninterruptible power supply that can supply power from a power converter to a load even if the load is overloaded.

[Means to solve the problem]

In order to achieve the above object, the present invention includes, as a first device, a rectifier that converts AC power from an AC power source into DC power, and a power converter that converts the output power of the rectifier into AC power in response to a switching signal. A converter, a DC power source that supplies DC power to the input side of the power converter, an overload detector that detects when the output side of the power converter is overloaded, and an output voltage and target of the power converter. conversion output adjustment means for adjusting the conversion output of the power converter by applying a switching signal to the power converter to suppress deviation from the voltage command value; This constitutes an uninterruptible power supply that has a command value control means for lowering the command value. The second device includes a rectifier that converts AC power from an AC power supply into DC power, a power converter that receives a switching signal and converts the output power of the rectifier into AC power, and an input side of the power converter that converts DC power. DC power supply supplied to the power converter, an overload detector to detect when the output side of the power converter is overloaded, and an overload detector to suppress the deviation between the output voltage of the power converter and the target voltage command value to zero. conversion output adjustment means for applying a switching signal to the power converter to adjust the conversion output of the power converter; and switching signal control for stopping generation of the switching signal to the conversion output adjustment means based on the detection output of the overload detector. This constitutes an uninterruptible power supply having means.

A third device including the first or second device is a main switch that is inserted into a circuit connecting the output side of the power converter and the load and opens and closes the circuit in response to a switching command, and a main switch that connects the output side of the power converter and the load, and A sub switch is inserted into the circuit connecting the load on the output side and opens and closes the circuit in response to a switching command, a power status detector detects whether the AC power supply is in a normal state, and a power status detector detects whether the AC power supply is in a normal state. A switching command is output to open the main switch and close the sub switch when the power supply is detected to be in a normal state and an overload is detected by the overload detector.If the above conditions are not met, the main switch is output. The switch control means outputs a switching command to close the switch and open the sub-switch.

A fourth device includes a rectifier that converts AC power from an AC power source into DC power, a power converter that receives a switching signal and converts the output power of the rectifier into AC power, and a DC power source that generates DC power. A charger that rectifies AC power from an AC power source to charge the DC power source, a power status detector that detects whether the AC power source is in a normal state, and a power status detector that detects an abnormality in the AC power source. a DC power supply control means for supplying the output power of the DC power supply to the input side of the power converter when the output side of the power converter is overloaded; a conversion output adjustment means that adjusts the conversion output of the power converter by applying a switching signal to the power converter to suppress the deviation between the output voltage and the target voltage command value to zero; The present invention includes an uninterruptible power supply having command value command means for lowering the S voltage command value.

A fifth device includes a rectifier that converts AC power from an AC power source into DC power, a power converter that receives a switching signal and converts the output power of the rectifier into AC power, and a DC power source that generates DC power. A charger that rectifies AC power from an AC power source to charge the DC power source, a power status detector that detects whether the AC power source is in a normal state, and a power status detector that detects an abnormality in the AC power source. a DC power supply control means for supplying the output power of the DC power supply to the input side of the power converter when the output side of the power converter is overloaded; Conversion output adjustment means adjusts the conversion output of the power converter by applying a switching signal to the power converter to suppress the deviation between the output voltage and the target voltage command value to zero, and the conversion is performed using the detection output of the overload detector. The uninterruptible power supply includes switching signal control means for causing the output adjustment means to stop generating a switching signal.

A sixth device including the fourth or fifth device is a main switch that is inserted into a circuit connecting the output side of the power converter and the load and opens and closes the circuit according to a switching command, and a main switch that connects the output side of the power converter and the load, and a main switch that connects the AC power source and the power converter. A sub switch is inserted into the circuit connecting the load on the output side and opens and closes the circuit in response to a switching command, and a power status detector detects that the AC power supply is in a normal state, and an overload detector detects an overload. switch control means that outputs a switching command to open the main switch and close the auxiliary switch on the condition that the condition is detected, and outputs a change-over switch that closes the main switch and opens the auxiliary switch when the condition is not satisfied. This is a power outage power supply system.

[Effect]

If the load becomes overloaded while the output power of the power converter is being supplied to the load, the output voltage of the power converter can be reduced by lowering the target voltage command value or stopping the generation of the switching signal. is narrowed down, and the output power of the power converter is supplied to the load with the output voltage level suppressed. The time the output voltage is narrowed down is several milliseconds when the overcurrent flows.
ec or less, and the load on the output side of the power converter will not stop. [Example] Hereinafter, an example of the present invention will be described based on the drawings.

In FIG. 1, the uninterruptible power supply is comprised of a main circuit 10 and a control circuit 12, each of which is inserted between an AC power supply 4 and a load 16.

The main circuit 10 includes a rectifier 18, a charger 20, a switching element (thyristor) 22, a battery 24, a PWM inverter 26, a current detector 28, and an AC switch 30.32.
The input side of 2 is connected to the AC power supply 14, and the AC switch 3
The output side of 0.32 is output to load 16. The II current flow device 18 has a rectifying element such as a diode, and the AC power supply 1
4. Rectify the AC power from 4, and convert the rectified DC power to pwM.
It is designed to be supplied to the inverter 26. Charger 2
0 rectifies the AC power from the AC power supply 14 and supplies the rectified DC power to the battery 24 to charge the battery 24.

The switching element 22 is turned on when the control circuit 12 detects a power outage of the AC power source 14 or a drop in the output voltage of the AC power source 14, and is a DC power source that supplies DC power from the battery 24 to the inverter 26. It is configured as a control means.

The PWM inverter 26 has a switching element such as a transistor, and is configured as a power converter that receives a switching signal and converts DC power from the rectifier 18 or battery 24 into AC power. The current detector 28 detects the output current of the inverter 26 and outputs the detected output to the control circuit 12. This current detector 28
is used as a load detector that detects from the output current of the inverter 26 that the output side of the inverter 26 is in a loaded state. The AC switches 30 and 32 are each made of a semiconductor element. The AC switch 30 switches between the inverter 26 and the load l6 according to a switching command from the control circuit 12.
It is configured as a main switch that opens and closes the circuit connecting the

On the other hand, the AC switch 32 is configured as a sub switch that opens and closes a circuit connecting the AC power source 14 and the load 16 by bypassing the rectifier 18, the inverter 26, and the AC switch 30 in response to a switching command from the control circuit 12. These switches are configured such that the AC switch 30 closes the circuit and the AC switch 32 opens the circuit during normal operation or power outage, and the AC switch is activated only when the AC power supply 14 is in a normal state and the load 16 is in an overload state. 30 opens the circuit, and AC switch 32 closes the circuit.

The control circuit 12 includes a bypass voltage detection circuit N34, an analog switch 36, an operational amplifier 38, an overcurrent level signal generator 40, a comparator 42, and an overcurrent level signal generator 44.
, an AND gate 46, a switching control circuit 48, a reference sine wave generator 50, a triangular wave generator 52, a multiplier 54, an operational amplifier 56, and a converter 58, and a bypass voltage detection circuit 34 is connected to the AC power supply 14. A switching control circuit 48 is connected to the AC switch 30.32, and a comparator 58 is connected to the inverter 26.

The bypass voltage detection circuit 34 inputs AC power from the AC power supply 14, outputs a high level signal when the AC power supply 14 is in a normal state, and outputs a high level signal when the AC power supply 14 is in a power outage or when the voltage of the AC power supply 14 is input. It is used as a power supply status detector that outputs a low level signal when the voltage drops below a set level. The analog switch 36 takes in the signal from the bypass voltage detection circuit 34 and outputs the signal from the detection circuit 34.
When the output level of the detection circuit 34 is at a high level, contacts C and A are connected, and when the output level of the detection circuit 34 is inverted to a low level, contacts C and B are connected. The operational amplifier 38 compares the overcurrent level signal with the output signal of the analog switch 36 (ground potential or the output level of the current detector 28), and outputs a DC signal to the multiplier 54 according to the comparison result. There is. The signal from the reference sine wave generator 50 is supplied to the multiplier 54, and the multiplier 54 outputs a sine wave whose amplitude is limited by the output level of the operational amplifier 38. This sine wave is the target voltage command value (Vref
) is supplied to the non-inverting input terminal of the operational amplifier 56. That is, the analog switch 36 and the operational amplifier 3
Reference numeral 8 is configured as command value control means for reducing the amplitude of the target voltage command value in accordance with the output level of the current detector 28 when the AC power supply 14 is in an abnormal state. Note that the output level of the overcurrent level signal generator 40 is . Like the overcurrent level signal generator 44, it is set in correspondence with the maximum allowable current that can flow through the switch elements of the inverter 26, and when the ground potential is selected by the analog switch 36, a constant voltage is output from the operational amplifier 38. A DC signal is output, and the sine wave is controlled to a constant amplitude signal.

The operational amplifier 56 is configured to output a signal to the converter 58 for suppressing the deviation between the output signal (target voltage command value) of the multiplier 54 and the output voltage of the inverter 26 to zero. The comparator 58 separates the signal from the operational amplifier 56 and the signal from the triangular wave generator 52 (several KHz to several tens of KHz).
z), and a switching signal (PMW signal) corresponding to the comparison result is output to each switching element of the inverter 26. That is, the operational amplifier 56, the comparator 58, and the triangular wave generator 52 are configured as conversion output adjusting means for controlling the output voltage of the inverter 26 to a constant voltage and constant frequency.

Further, the comparator 42 receives the signal from the current detector 28 and the signal from the overcurrent level signal generator 44, and outputs a high level signal when the output level of the current detector 28 exceeds the overcurrent level. At other times, it outputs a low level signal. The AND gate 46 receives the output signal of the comparator 42 and the output signal of the bypass voltage detection circuit 34, and outputs a gate signal according to these signals to the switching control circuit 48. As shown in FIG. 2, when the output level of the AND gate 46 is at a low level, the switching control circuit 48 outputs a switching signal that turns off the AC switch 32 and turns on the AC switch 30. When the output level of 46 is reversed to a high level, the AC switch 32 is turned on and the AC switch 30 is turned off.

In the above configuration, when both the AC power source l4 and the load 16 are in a normal state, the AC switch 30 is closed and the AC switch 32 is opened, and the AC power from the AC power source 14 is converted to DC power by the rectifier l8, and then the inverter 26, it is converted back into AC power and supplied to the load l6 via the AC switch 30. At this time, the output signal of the inverter 26 is controlled to a constant voltage and constant frequency by a PWM signal, and the battery 24 is charged by the charger 20. . At this time, when the load 16 becomes overloaded and an overcurrent flows through the inverter 26, and the output level of the current detector 28 exceeds the overcurrent level, the output level of the comparator 42 is reversed from low level to high level, and the AND The level of the gate 46 is inverted from low level to high level. As a result, a switching signal is output from the switching control circuit 48, and the AC switch 3
0 is switched from a closed state to an open state, and the AC switch 32 is switched from an open state to a closed state.

Then, the AC power from the AC power supply 14 is supplied to the AC switch 32.
is supplied to the load 16 via.

Next, with the AC switch 30 in the closed state, the AC switch 3
When AC power supply 1 is in the open state due to a power outage etc.
4 is detected, the analog switch 36 is switched and DC power from the battery 24 is supplied to the inverter 26 via the switching element 22. During such operation, if the load 16 becomes overloaded and an overload current flows to the output side of the inverter 26, and the output level of the current detector 28 exceeds the overcurrent level, the operational amplifier The output level of comparator 38 is inverted from high level to low level, and the output level of comparator 42 is inverted from low level to high level. As a result, the amplitude of the target voltage command value, which is the output signal of the multiplier S4, is limited to a low amplitude by the output signal of the operational amplifier 38, and the output voltage of the inverter 26 is narrowed down. As a result, a sudden increase in the output current of the inverter 26 is suppressed.

Further, at this time, the output level of the AND gate 46 is maintained at a low level, so the AC switch 30 is maintained in a closed state. That is, when an overcurrent occurs, the output voltage of the inverter 26 is reduced, so instead of supplying AC power to the load l6 via the AC switch 32, the output power of the inverter 26 is transferred to the AC switch 30.
can be supplied to the load 16 via.

Next, another embodiment of the present invention will be described based on FIG.

In this embodiment, an OR gate 60 and a comparator 39 are provided in place of the analog switch 36, multiplier 54, and operational amplifier 38 shown in FIG. AND gates 64, 66, 68, and 70 are provided on the output side of the circuit, and the PWM signal is controlled by the signal from the OR gate 60. , the same parts are given the same reference numerals and their explanation will be omitted.

The OR gate 60 outputs a high level signal when the AC power supply 14 or the load 16 is in a normal state, and
4 becomes abnormal due to a power outage, etc., and when the load 16 becomes overloaded and the overcurrent exceeds the overcurrent level, a low level signal is sent to the AND gates 64, 66, 68, 7.
It is designed to output to 0. AND gate 64-7
0 is connected to the switching element of the inverter 26 and inputs the PWM signal from the gate signal distributor 62, and when a low level signal is output from the OR gate 60, the output of the PWM signal is stopped. That is, the overcurrent signal generator 40, the comparator 39, the OR gate 60, and the AND gates 64 to 70 are configured as switching signal control means. In the above structure, when the AC switch 30 is closed,
When the AC switch 32 is in the open state, the AC power source 14
becomes abnormal, the output level of the bypass voltage detection circuit 34 is reversed from high level to low level, and the DC power of the battery 24 is transferred to the inverter 2 via the switching element 22.
6. As a result, even when the power supply 14 is abnormal, AC power is supplied from the inverter 26 to the load 16 based on the DC power from the battery 24. In this state, the load l6 becomes overloaded and the inverter 26
An overcurrent flows through the circuit, and when this current exceeds the overload level,
As shown in FIG. 5, the output level of the OR gate 60 becomes low level, and the supply of the PWM signal to the inverter 26 is stopped. As a result, the output voltage of the inverter 26 is reduced, and the current of the inverter 26 is suppressed below the allowable current level. At this time, the output level of the AND gate 46 is at a low level, so the AC switch 30 is maintained in a closed state. Therefore, even if the load 16 becomes overloaded when AC power cannot be supplied to the load 16 via the AC switch 32 during a power outage of the AC power supply 14,
By temporarily reducing the output voltage of the inverter 26, AC power from the inverter 26 can be supplied to the load 16 via the AC switch 30. Moreover, if the time during which the overload current flows is short, the time during which the output voltage of the inverter 26 decreases is also shortened, and AC power from the inverter 26 can be supplied to the load 16 in a more stable state.

Further, in each of the above embodiments, the AC switches 30, 32
Although the AC switch 30.3
It is also possible to apply the present invention to a power supply device that does not have a switch having the same function as 2. In addition to the battery 24, it is also possible to use a DC power source driven by an internal combustion engine or the like as the DC power source. Furthermore, it is possible to apply the present invention to a power supply device that does not have a charger for charging a DC power supply. [Effects of the Invention] As explained above, according to the present invention, the conversion output of the power converter is narrowed down when the load becomes overloaded, so that even if the load becomes overloaded, the power conversion continues. It becomes possible to supply the output power of the device to the load, and it is possible to supply power to the load regardless of whether there is an abnormality in the AC power supply, contributing to improved reliability.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of an AC switch, and FIG.
4 is an overall configuration diagram showing another embodiment of the present invention, and FIG. 5 is a waveform diagram for explaining the action of the device shown in FIG. 4. It is a diagram. 10... Main circuit, 12... Control circuit, 14... AC power supply, 16... Load, 18... Rectifier, 20...
- Charger, 22... Switching element, 24... Battery, 26... PWM inverter, 28... Current detector, 30. 32... AC switch, 34... Bypass voltage detection circuit, 36...Analog switch, 38.56...Operation amplifier, 40.44...Overcurrent level signal generator, 39,42
, 58... comparator, 46... AND gate,
48... Switching control circuit, 50... Reference sine wave generator, 52... Triangular wave generator, 54... Multiplier. Figure 2 Figure 3

Claims (1)

[Claims] 1. A rectifier that converts AC power from an AC power supply into DC power, a power converter that receives a switching signal and converts the output power of the rectifier into AC power, and a power converter that converts DC power into DC power. A DC power supply that supplies to the input side, an overload detector that detects when the output side of the power converter is overloaded, and a device that suppresses the deviation between the output voltage of the power converter and the target voltage command value. An uninterruptible power supply having a conversion output adjustment means for applying a switching signal to a power converter to adjust the conversion output of the power converter, and a command value control means for lowering the target voltage command value based on the detection output of an overload detector. Device. 2. A rectifier that converts AC power from an AC power supply into DC power, a power converter that receives a switching signal and converts the output power of the rectifier into AC power, and a DC power supply that supplies DC power to the input side of the power converter. A power supply, an overload detector that detects when the output side of the power converter is overloaded, and a switching signal that suppresses the deviation between the output voltage of the power converter and the target voltage command value to zero. A conversion output adjustment means for adjusting the conversion output of the power converter by applying it to the converter, and a switching signal control means for stopping generation of a switching signal to the conversion output adjustment means based on the detection output of the overload detector. Outage power supply. 3. inserted into a circuit that connects the output side of the power converter and the load, and inserted into the circuit that connects the main switch that opens and closes the circuit according to a switching command, and the AC power source and the load on the output side of the power converter; a sub-switch that opens and closes the circuit according to a switching command;
A power status detector detects whether the AC power supply is in a normal state, and a power status detector detects that the AC power supply is in a normal state, and an overload detector detects that an overload is detected. 3. Switch control means for outputting a switching command to open the main switch and close the auxiliary switch when a condition is met, and outputting a switching command to close the main switch and open the auxiliary switch when the condition is not met.
Uninterruptible power supply as described. 4. A rectifier that converts AC power from an AC power source into DC power, a power converter that converts the output power of the rectifier into AC power in response to a switching signal, a DC power source that generates DC power, and a power converter that converts AC power from an AC power source into AC power. A charger that rectifies AC power to charge a DC power supply, a power supply status detector that detects whether the AC power supply is in a normal state, and a power supply status detector that detects whether the AC power supply is in a normal state. DC power supply control means that supplies the output power of the power supply to the input side of the power converter, an overload detector that detects when the output side of the power converter is in an overload state, and an output voltage and target of the power converter. a conversion output adjustment means that adjusts the conversion output of the power converter by applying a switching signal to the power converter to suppress the deviation from the voltage command value to zero; An uninterruptible power supply having a command value command means for lowering the command value. 5. A rectifier that converts AC power from an AC power source into DC power, a power converter that receives a switching signal and converts the output power of the rectifier into AC power, a DC power source that generates DC power, and a power converter that converts AC power from an AC power source. A charger that rectifies AC power to charge a DC power supply, a power supply status detector that detects whether the AC power supply is in a normal state, and a power supply status detector that detects whether the AC power supply is in a normal state. DC power supply control means that supplies the output power of the power supply to the input side of the power converter, an overload detector that detects when the output side of the power converter is in an overload state, and an output voltage and target of the power converter. Conversion output adjustment means for adjusting the conversion output of the power converter by applying a switching signal to the power converter to suppress the deviation from the voltage command value to zero, and conversion output adjustment means for adjusting the conversion output of the power converter using the detection output of the overload detector An uninterruptible power supply having a switching signal control means for stopping generation of a switching signal. 6. inserted into a circuit connecting the output side of the power converter and the load, and inserted into the circuit connecting the main switch that opens and closes the circuit according to a switching command, and the AC power source and the load on the output side of the power converter; a sub-switch that opens and closes the circuit according to a switching command;
If the power status detector detects that the AC power supply is in a normal state and the overload detector detects an overload, a switching command is output to open the main switch and close the sub switch, and the above conditions are met. 6. The uninterruptible power supply according to claim 4, further comprising switch control means for outputting a changeover switch that closes the main switch and opens the auxiliary switch when the condition is not satisfied.