JPH01218334A - Uninterruptible power system - Google Patents

Abstract

PURPOSE:To reduce the size and the cost of an uninterruptible power system, by feeding voltage boosted through a booster type DC converter to an inverter circuit. CONSTITUTION:When a commercial power source 10 is normal, AC commercial source voltage is rectified through a diode bridge 20 and a booster type DC converter 60 is controlled such that the input signal is sinusoidal, then DC voltage is boosted to a predetermined level with input higher harmonics being reduced. DC current is fed to the load 50 of an inverter circuit 30 in the form of AC power. Furthermore, a battery 40 is charged through a charger 70. Upon interruption of the commercial power source 10, a DC switch 45 is turned ON to feed power from the battery 40, and the voltage is boosted to a predetermined level through the booster type DC converter 60. The DC power is inverted through the inverter circuit 30 into AC power and fed to the load 50. Upon recovery of power, the DC switch 45 is turned OFF to separate the battery 40.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an uninterruptible power supply device supplied with power from a battery.

"Prior Art" Conventionally, the rectifier circuit of an uninterruptible power supply has been composed of either a diode element or a thyristor element, or a combination of both, or a bridge circuit and a DC output smoothing LC. A rectifier circuit consisting of a filter is used.

FIG. 6 is an example of an uninterruptible power supply using a conventional rectifier circuit, in which 10 is a commercial power supply, 20 is a diode bridge, 21 is a smoothing reactor, 22 is a smoothing capacitor, and 25 is a A charger, 30 an inverter circuit, 31 a reactor for an output stage filter, 32 a capacitor for an output stage filter, 40 a battery, 45 a DC switch, and 50 a load.

When the commercial power supply 10 is normal, the AC power source AC power is converted into smooth DC power by a rectifier circuit consisting of a diode bridge 20, a smoothing reactor 21, and a smoothing capacitor 32, and the DC power is converted into AC power by an inverter circuit 30. Then, harmonic components contained in the AC power are removed by output stage filters 31 and 32, and the AC power is supplied to the load 50 as a low distortion sine wave AC power. Also, charger 2
5, the battery 40 is constantly charged.

When the commercial power supply 1G is out of power, the DC switch 45 is turned on to supply DC power from the battery 40 to the inverter circuit 30, thereby supplying AC power to the load 50, thereby achieving uninterrupted operation.

Figure 7 shows an uninterruptible power supply device designed to reduce input harmonics using a conventional configuration method.In Figure 0, 10 is a commercial power supply, 20 is a diode bridge, 25 is a charger,
3 is an inverter circuit, 31 is an output stage filter reactor, 32 is an output stage filter capacitor, 40 is a battery, 45 is a DC switch, 50 is a load, and 60 is a step-up DC conversion circuit.

When the commercial power supply 10 is normal, the AC power from the AC power source is full-wave rectified by the diode bridge 20 and supplied to the step-up DC converter 60 . The step-up DC conversion circuit is
The input current waveform of the diode bridge 20 is controlled to be a sine waveform, and the output voltage of the conversion circuit is made constant. The output voltage of the conversion circuit is converted into AC power by an inverter circuit 30 and supplied to a load 50. Further, the battery is constantly charged by the charger 25.

When the commercial power supply 10 is out of power, the battery 40 supplies power, which is converted to AC power by the inverter circuit 30 and supplied to the load 50, thereby achieving uninterrupted power.

"Problem to be solved by the invention" The input voltage and current waveforms in the uninterruptible power supply using the conventional rectifier circuit shown in Fig. 6 are as shown in Fig. 8.
In the figure, (a) shows the input voltage, (b) shows the input current waveform when the smoothing reactor 21 is sufficiently large, and (C) shows the input current waveform when the smoothing reactor 21 has a small value. The input current of the conventional rectifier circuit shown in FIG. 8 contains many harmonics. These harmonics flow into the commercial power system and adversely affect other equipment. As a means to solve this problem in the rectifier circuit, multiplexing of rectifiers, a PWM converter, etc. have been used, but this inevitably increases the size and cost of the device.

Further, when an uninterruptible power supply device designed to reduce input current harmonics is constructed as shown in FIG. 7, the following problem occurs.

As the DC voltage increases, the total voltage of the battery increases accordingly, the number of battery cells does not increase, and the battery voltage increases, making it necessary to use a step-up charger. Therefore, the circuit and control are more complex than conventional chargers.

Therefore, compared to the conventional circuit system shown in FIG. 6, the reduction in input harmonics results in an increase in the size and cost of the device. Also, a device using a conventional rectifier circuit (Figure 6) and an input harmonic reduction type device with a conventional configuration (Figure 7)
In both cases, when the battery voltage decreases, it becomes necessary to compensate for the variation with the inverter circuit, and a margin must be provided for the inverter rating accordingly, and the design of the output stage filter becomes complicated and large.

From the above points, in the conventional uninterruptible power supply device of input harmonic reduction type as shown in FIG. 7, it is inevitable that the device becomes larger, the cost increases, and the control method becomes more complicated.

"Means for Solving the Problems" An example of the basic configuration of the input current harmonic reduction type uninterruptible power supply according to the present invention is shown in FIG.
11.12 is a reactor and capacitor for the input stage filter, 20 is a diode bridge, 30 is an inverter circuit, 31.32 is a reactor and capacitor for the output stage filter, 40 is a battery, 45 is a DC switch, 50 is a load, 60 70 is a step-up DC converter circuit, and 70 is a charger. The commercial power supply 10 is connected to a diode bridge 20 via an input stage filter reactor 11 and a capacitor 12, and the output end of the diode bridge 20 is input to an inverter circuit 3G via a step-up DC conversion circuit 60. The output end of the inverter circuit 30 is connected to a load 50 via an output stage filter reactor 31 and a capacitor 32. On the other hand, the battery 40g is connected to the output stage of the diode bridge 20 via the tDC switch 45, and is also connected to the input stage or output stage of the inverter circuit 30 via the charger 70.

An example of the control circuit configuration of the step-up DC converter circuit according to the present invention is shown in FIG. 2, 150 is a current detector, 160a, 160b
are the input and output voltage detectors of the conversion circuit, respectively;
00 is the reference voltage generator, 110 is the difference device, 120 is the PI
130 is a multiplier, 14G is a comparator, and 180 is a distribution circuit for providing a signal to each switching element according to the step-up DC conversion circuit.

The output voltage is detected by a voltage detector 160b, and the output of the detector and the output of the reference voltage generator are connected to a differentiator 110, and the output of the differentiator 110 is connected to one input of the multiplier 130 via a PI compensator. connected to the terminal. The output of a voltage detector 160a that detects input voltage is connected to the other input terminal. The output of the multiplier 13G is sent to the comparator 14
0, and the output of the current detector 150 is connected to the other input terminal. The output of the comparator 14G is connected to the circuit switching element via the distribution circuit 180 as required as a drive signal for the step-up DC conversion circuit.

"Operation" The operation of the uninterruptible power supply configured according to the present invention will be explained using FIG. 1.

When the commercial power supply 10 is normal, the commercial power supply AC power is rectified by the diode bridge 20 and the step-up DC conversion circuit 6
0 so that the input current becomes a sine wave, and boosts the voltage to a predetermined DC voltage while reducing input harmonics.

This DC current is supplied by the inverter circuit 30 to the load 50 as AC power.

Also, the battery 40 is charged by the charger 70.

When the commercial power supply 10 is out of power, the DC switch 45 is turned on to supply power from the battery, and the step-up DC conversion circuit 6
0, the voltage is increased to a predetermined voltage. This DC power is converted into AC power by the inverter circuit 30 and supplied to the load 50 in the same way as during normal commercial operation. When the power is restored, the battery 40 is disconnected by turning off the DC switch 45, and the charger 70 is operated so that it is turned off at the time of a power outage and turned on when the power is restored.

On the other hand, regarding the control circuit, the control of the inverter circuit 30 is the same as the conventional one, and the control of the step-up DC converter circuit 60 will be explained with reference to FIG.

The same operation occurs whether the commercial power supply 10 is normal or during a power outage. The input and output voltages of the step-up DC conversion circuit 60 are detected by an input voltage detector 160a and an output voltage detector 160b, respectively. The output signal of the input voltage detection circuit 160a has a full-wave rectified waveform when the commercial power supply 10 is normal, and has a DC waveform during a power outage. The difference between the value detected by the output voltage detection circuit 160b and the indicated value of the reference voltage generator 10G is detected by the differentiator 110, and the output value of the differentiator 110 is detected by the PI compensator 1.
20, it becomes the sole power of the multiplier 130. On the other hand, the other input of the multiplier 130 is input to the input power voltage detector 160a.
Therefore, the input voltage waveform proportional to the error in the output voltage of the step-up DC converter becomes the output of the multiplier 13G, and when the commercial power supply 10 is normal, it becomes a full-wave rectified waveform, while during a power outage, it becomes a DC waveform. The output of the multiplier 130 is connected to one output of the comparator 140, and becomes a reference waveform according to the error in the output voltage. A signal obtained by comparing the reference waveform and the input radio waveform of the step-up DC converter circuit detected by the current detector 150 by the comparator 14G is sent to the distribution circuit 18 as necessary.
By outputting through 0, the step-up DC converter circuit is controlled.

With the above operation, when the commercial power supply 10 is normal, the input current waveform of the diode bridge becomes a sine wave, and the input voltage of the inverter circuit 30 becomes a boosted and stable DC voltage. On the other hand, in the event of a power outage, the voltage value of the battery 40 is boosted to a predetermined input voltage of the inverter circuit 30 and stabilized.

``Embodiment'' An embodiment of the present invention is shown in FIG. 3. 10 is a commercial power supply, 11.12 is an input filter handle, a capacitor, 20 is a diode bridge, 30 is an inverter circuit, 31.32 is an inverter. Reactor and capacitor for the output stage filter, 45 is a thyristor, 40 is a battery, 50 is a load, 60 is a boost chopper circuit, 61 is a DC reactor for the boost chopper, 62 is a SW for the boost chopper,
63 is a voltage separation diode, 63 is a step-up chopper output stage capacitor, 70 is a charging DC/DC converter, 8
0 is a power failure detection circuit, 100 is a reference voltage generator, 110 is a differentiator, 120 is a PI compensator, 130 is a multiplier, 140
is a comparator (hysteresis type), 150 is a current detector, 1
60a and 60b are voltage dividers, and 170 is a driver circuit.

When the commercial power supply 10 is normal, the AC power source AC power is rectified by the diode bridge 20, and the boost chopper circuit 60 converts the input current into a sine wave and boosts the input current to a predetermined voltage. The control method will be explained next. The voltage at the output stage of the boost chopper is divided by the voltage divider 160b, and the difference from the reference voltage is detected by the difference device 110. The error in the output voltage detected by the difference device 110 is controlled and compensated by the PI compensator 120.

On the other hand, the input voltage is divided by a voltage divider 160a and multiplied by the control compensated error. This human power.

The waveform obtained by multiplying the divided voltage waveform by the error voltage is a half-sine wave like the input voltage waveform, and it increases or decreases in proportion to the error in the output voltage.

A hysteresis comparator compares the half-sine reference signal multiplied by the output voltage error with the current flowing through the boost chopper reactor 61. The current flowing through the reactor 61 increases as the boost chopper SW is turned on and off.
Since the current decreases, the on state is maintained until a certain upper limit value of the reference signal is reached, and when the current exceeds the upper limit value, the current is shifted to the off state.

The current decreases and the off state is maintained up to a certain lower limit of the reference value, but when it falls below that lower limit, the operation of shifting to the on state is repeated, and the current flowing through the reactor becomes the reference value. It follows the wave and becomes a sine wave.

This reduces input harmonics. Further, the magnitude of the reference signal wave is changed so that the output voltage matches a predetermined voltage value, and a certain boosted predetermined voltage is output. The inverter circuit 30 supplies this DC output voltage to the load 50 as AC power. Further, the battery 40 is charged by the charging DC/DC converter 70. At this time, the battery is charged below the commercial power supply voltage peak value.

When the commercial power supply 10 is out of power, the power outage detection circuit 80 detects the power outage, turns on the thyristor 45, and turns off the charging DC/DC converter. If the battery voltage is equal to or higher than the commercial power supply voltage value, the thyristor 45 maintains the on state, the battery 40 and the boost chopper 60 are connected, and power is supplied from the battery. The reference signal waveform during normal commercial operation only changes from a sine half wave to a direct current, and a step-up operation is performed to output a predetermined voltage. At this time, even when the battery voltage decreases, the inverter input voltage remains constant, improving the utilization rate of the inverter elements, and making the harmonic content of the output voltage constant, which facilitates filter design.

When the commercial power supply 10 is restored, the thyristor automatically turns off when the commercial power supply voltage becomes higher than the battery voltage.

Further, the charging DC/DC converter 70 is turned on and starts charging the battery.

The operational waveforms of the boost chopper section of the device of this embodiment are as shown in FIGS. 4 and 5. FIG. 4 shows (a) the input voltage when the commercial power supply 10 is normal, (b) the reference signal waveform and actual accelerator current value, and (C) the output voltage. Further, FIG. 5 shows waveforms corresponding to FIG. 4 when the commercial power supply 10 is out of power.

[Effects of the Invention] The uninterruptible power supply according to the present invention can easily reduce input harmonics, and compared to the conventional method of reducing input harmonics, the battery voltage is reduced, and the charger can be easily installed. configuration can be used. Furthermore, even when the battery voltage drops, the inverter input voltage remains constant, which improves the utilization rate of the inverter elements and facilitates filter design. On the other hand, in a boost chopper circuit that achieves input harmonic reduction, an isolated type is used to operate at high frequency,
By using an insulated charger, etc., the insulating inverter and transformer included in the inverter circuit can be omitted, and a high-frequency link type uninterruptible power supply can be easily realized.

Overall, with the uninterruptible power supply of the present invention, it is easier to
Moreover, it is possible to realize an input harmonic reduction type uninterruptible power supply device that is small and low cost.

[Brief explanation of the drawing]

Figure 1 is an example of the basic configuration of an uninterruptible power supply according to the present invention, Figure 2 is an example of the control configuration of a step-up DC converter circuit according to the present invention, Figure 3 is an example of an embodiment of the present invention, and Figure 4 is during normal commercial operation. 5 is an example of the operating waveforms of the chopper section in an embodiment of the present invention, FIG. 5 is an example of the operating waveforms of the chopper section during a commercial power outage, FIG. 6 is an uninterruptible power supply ZS diagram using a conventional rectifier circuit, and FIG. FIG. 8, a block diagram of an uninterruptible power supply with a conventional configuration designed to reduce input harmonics, shows the input voltage and current waveforms of a conventional rectifier circuit. In the drawing, 10... commercial power supply, 20... diode bridge, 30...
...Inverter, 40...Battery 45.
...DC switch, 50...Load, 60
・・・・・・DC conversion circuit, 70・old charger.

Claims (1)

[Claims] A full-wave rectifier circuit that connects diodes in a bridge to convert commercial AC power into DC power; a battery; a DC switch that connects the battery and the full-wave rectifier circuit; It receives power from the commercial power supply through a rectifier circuit, operates so that the current waveform becomes a sine wave, and boosts the battery DC voltage via the DC switch during a power outage, when the commercial power supply is normal and during a power outage. A step-up DC converter circuit that maintains a constant output voltage regardless of the voltage, an inverter circuit that inversely converts the output DC power of the step-up DC converter circuit to AC power, and an output voltage of the step-up DC converter circuit or the inverter circuit 30.
a charger for charging the battery from an output voltage of the battery;
An uninterruptible device comprising means for detecting a power outage and power restoration, and a power outage detection circuit that turns the DC switch on at the time of a power outage and off at the time of power restoration, and turns the charger off at the time of a power outage and turns on at the time of power restoration. power supply.