JPH11313449A - Single conversion UPS - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate an uninterruptible power unit with the same control system in both cases where commercial power supply is used and interrupted, by subtracting the output of a limiter which limits the fluctuation range of a phase error generated from the phase of the output voltage of the power unit, and driving an inverter with a sine wave generated from the phase obtained from the results of the subtraction. SOLUTION: When a commercial AC power source 1 supplies a rated voltage, a single conversion type UPS device 28 supplies electric power from the power source 1 to a load 5 via a reactor 3 by turning on an input relay 2. When the power supply is made to the load 5, an inverter 4 controls the output voltage of the device 28 to a fixed value by performing PWM control on its built-in switching element and outputting reactive power. A change-over switch 15 is normally connected to an output voltage detecting value 14 side, and a phase detector 20 detects and outputs the phase of the output voltage. In a subtractor 25A the output of a first-order time delay filter 24a is subtracted from the phase of the output voltage. The output of the subtractor 25A becomes the phase for the inverter 4, and a standard sine wave is generated by inputting the phase of the inverter 4 to a limited wave generating means 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an uninterruptible power supply (U)
PS: Abbreviation for Uninterruptible Power Systems).

[0002]

2. Description of the Related Art An uninterruptible power supply (UPS) has a constant inverter power supply system in which power is always supplied from an inverter to a load regardless of the state of a power supply system, and a commercial AC power supply to a load when the power supply system is normal. There is a device of a continuous commercial power supply system in which power is supplied. Among the latter, there is a UPS of a type in which an inverter is operated even when power is supplied from a commercial system and has additional functions such as voltage compensation and an active filter. Various configurations are conceivable, but single conversion type UPS
Is also one of the forms. In general, the Institute of Electrical Engineers of Japan / Semiconductor Power Conversion Study Group / SPC-87-3 "Reactive Power Compensation Type Three-Phase Uninterruptible Uninterruptible Power Supply" or SPC-88-8
This is a configuration such as that found in “Multi-function inverters connected in parallel with power supply type UPS”. These connect an AC power supply and a load via a reactor, and also connect an inverter to the load side of the reactor. That is, a commercial power supply and an inverter are connected in parallel as viewed from the load. This single conversion UPS has four functions: a constant voltage control function by reactive power control, an active filter function for load harmonics, a DC voltage control function as a charger, and a sine wave inverter control function at the time of a power failure. It is known.

[0003]

FIG. 2 shows an example of a conventional single conversion type UPS. In FIG. 2, 1 is a commercial AC power supply, 2 is an input relay, 3 is a reactor, 4 is an inverter, 5 is a load, 6 is a ground point, 7 is a capacitor, 9 is a storage battery, 28 is a single-conversion UPS device, 43 is PWM signal generator, 46 is an output voltage compensation control system, 47 is an active filter control system, 3
8 is a DC voltage control system, 39 is a sine wave inverter control system,
Reference numeral 42 denotes a changeover switch. Next, the operation of FIG. 2 will be described. When the commercial AC power supply 1 is healthy, the single conversion UPS shown in FIG. 2 operates with the input relay 2 turned ON and the changeover switch 42 connected to the output voltage compensation control system 46 side. At this time, the inverter 4 outputs reactive power from the inverter by the output voltage compensation control system 46, and performs compensation control of the output voltage. In addition, the harmonic control of the load by the active filter control system 47 and the DC voltage control system 38 for charging the storage battery 9 are simultaneously operated. On the other hand, when a power failure occurs, the input relay 2 on the input side of the main circuit is opened to disconnect the commercial AC power supply 1 and switch the changeover switch 42 to switch the sine wave inverter control system 3
9 is operated. For this reason, two times are required for commercial power supply and power outage.
Different types of control systems are required, and there is a problem that the scale of the control circuit is large and complicated, and the control system also needs to be switched immediately by the changeover switch 42.

[0004] This is the same in the case of a digital control system constructed by software, and a switch means for switching a control algorithm is required. At this time, in order to prevent the adverse effect on the load, the output voltage fluctuation due to the switching of the control system must be minimized.
There is a problem that the switching sequence is very difficult and a high-speed operation is required.

Further, the conventional single conversion type UPS has a rated voltage of ± 10% of the rated voltage required for practical use.
Alternatively, in order to perform voltage compensation such that the output voltage becomes constant in a range of about ± 15%, it is necessary to output a reactive current equivalent to the rated current from the inverter 4.
There is a problem that the loss of the switching element forming the inverter 4 is large.

The single conversion system U
As a feature of PS, boost compensation is compared with step-up compensation, which raises the voltage when the voltage of the commercial power supply falls below the rating, and step-down compensation, which lowers the voltage when the voltage of the commercial power supply rises above the rating. In this case, since the reactive power borne by the inverter 4 becomes larger, there is a problem that the loss in the inverter 4 at the time of boost compensation is larger.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a UPS according to the present invention has means for calculating the active power of an inverter and setting upper and lower limits of a phase error. And first limiter means. Then, the output of the first limiter is subtracted from the phase of the output voltage, and the inverter operates with the sine wave created from the phase resulting from the subtraction as a command value. As a result, the inverter delicately controls the phase of the inverter so that the active power calculation result becomes zero. This control system can have not only a constant voltage controller by reactive power control during commercial power supply and an active filter function for harmonics of a load, but also a sine wave inverter control function at the time of power failure. Therefore, when a power failure occurs, simply disconnecting the commercial input by opening a switch or relay on the input side of the main circuit switches the UPS from voltage compensation control and active filter control to sine wave inverter control.

[0008] When a power failure occurs, the active power of the inverter rapidly increases from 0 to the rated power, but the phase error for controlling the phase of the inverter is limited by the first limiter means. The phase does not change suddenly. In addition, the first limiter means is a variable limiter, and the upper limit and the lower limit are reduced to 0 at the time of power failure, so that it is possible to smoothly shift to the sine wave inverter control at the time of power failure, and a sudden change in voltage occurs. do not do.

When the power is restored, the upper limit value and the lower limit value of the first limiter are gradually increased from 0 to predetermined values, so that no sudden voltage fluctuation occurs even when the power is restored.

As described above, according to the present invention, the UPS is always used by using the same control system at the time of commercial power supply and at the time of power failure.
Can be operated, and the switching sequence at the time of the occurrence of a power failure can be a simple configuration only for opening a switch or relay on the input side of the main circuit.

In the present invention, the DC voltage control system at the time of commercial power supply can be realized by adding an output obtained by amplifying a comparison error between the DC voltage and the DC voltage command value to a result of calculating the active power of the inverter.

Further, in the present invention, in order to reduce the loss in the inverter at the time of voltage compensation, no voltage compensation is performed while the input voltage is within a predetermined range centered on the rating, and the output voltage is the same as the input voltage. A control is proposed in which an effective value is output and voltage compensation is performed only when the input voltage is out of a predetermined range and is in a voltage range between a voltage determined as a power failure or an overvoltage. Means for realizing this control can be simply configured by means for calculating the effective value of the input voltage and the second limiter means. If the upper limit value and the lower limit value of the second limiter are set to an input voltage range in which voltage compensation is not performed, and the UPS is operated using the output of the second limiter as the voltage command value of the inverter,
The above control becomes possible.

For example, if the upper and lower limits of the second limiter are set to + 10% and -10% of the rated voltage, respectively,
When the input voltage is within the range of ± 10% of the rated voltage, the voltage compensation does not operate, the inverter is controlled only by the active filter function for the harmonics of the load, and the loss of the inverter can be suppressed to a relatively small value. At this time, even if the input voltage suddenly changes, if a filter is inserted after the second limiter, the output voltage command value changes only gradually, and does not adversely affect the load. Even if the input voltage changes between a range in which voltage compensation is not performed and a range in which voltage compensation is performed, a change in output voltage is suppressed within a predetermined range.

Further, if the second limiter means is a variable limiter, and the range of the limiter is gently narrowed during a power failure, and the upper limit value and the lower limit value are operated so as to be rated voltage values,
At the time of a power failure, it is possible to smoothly shift to inverter control for outputting a rated voltage. Further, at the time of power recovery, the output voltage at the time of power recovery does not fluctuate sharply by performing an operation of gradually returning the upper limit value and the lower limit value of the second limiter means to a steady value.

As means for reducing the inverter loss at the time of boost compensation, as described above, in addition to not performing voltage compensation when the commercial power supply voltage is about ± 10% of the rated voltage, for example, For the input voltage from -10 to -15%, the output voltage is compensated to -10%. For the input voltage from + 10% to + 25% of the rated voltage, the buck compensation is compensated to + 10%. When such control is used, the input allowable voltage range is from -15 to + 25%, and the maximum voltage required for boost compensation is about 5% at the maximum, so that the inverter loss can be reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. 1, 3, 4, 5, and 6. FIG. In FIG. 1, 1 is a commercial AC power supply, 2 is an input relay, 3 is a reactor, 4 is an inverter, 5 is a load, 6 is a ground point,
7 is a capacitor, 8 is input voltage detecting means, 9 is a storage battery,
10 is an inverter current detecting means, 11 is an output current detecting means, 12 is a capacitor current detecting means, 13 is an output voltage detecting means, 14 is an output voltage detected value, 15 is a changeover switch,
16 is an inverter current detection value, 17 is an input voltage detection value,
18 is an output current detection value, 19 is a capacitor current detection value,
20 is a phase detector, 21 is a power calculator, 22a and 22b
Is an error amplifier, 23a and 23b are limiters, 24a is a first-order lag filter, 25a, 25b and 25c are subtractors, 26
Is a sine wave generating means, 27 is an output voltage command value, 28 is a single conversion type UPS device, 29a is an adder,
0 is a power failure determination means, 31 is a multiplier, 32 is an output voltage waveform distortion compensation control system, 41 is a capacitor current compensation gain,
3 is a PWM signal generator, 44 is a differentiating means, and 45 is a reactor voltage compensation gain.

Next, the configuration of FIG. 1 will be described. In FIG. 1, one end of a commercial AC power supply 1 is grounded by a grounding point 6 and the other terminal is connected to one terminal of a reactor 3 via an input relay 2. The other terminal of reactor 3 is connected to one terminal of load 5, and the other terminal of load 5 is connected to ground 6 of commercial AC power supply 1. One output terminal of inverter 4 is connected in parallel between reactor 3 and load 5, and the other output terminal of inverter 4 is connected to ground point 6. A capacitor 7 is connected between the two output terminals of the inverter. Both ends of the storage battery 9 are also connected to the inverter 4. An input voltage detecting means 8 is connected between a connection point between the commercial AC power supply 1 and the input relay 2 and the ground point 6, and an input voltage detection value 17 as an output thereof is connected to the changeover switch 15 and the power failure judging means 30. . The inverter current detection means 10 is connected to one of the output terminals of the inverter 4, and the output of the inverter current detection value 16 is input to the power calculator 21. The capacitor current detection means 12 is connected to one terminal of the capacitor 7, and the output of the capacitor current detection value 19 is input to the capacitor current compensation gain 41 inside the output voltage waveform distortion compensation control system 32. The output current detecting means 11 is connected to one of the outputs of the single conversion type UPS device 28 connected to the load 5, and the output current detection value 18 as the output is output voltage waveform distortion compensation control system 32
Is input to the differentiating means 44 inside. The output voltage detecting means 13 is connected between two output terminals of the single conversion type UPS device 28 connected to the load 5, and the output voltage detection value 14 as the output thereof is switched by the changeover switch 15, the subtractor 25b, and the power calculator. 21.

The output of the power calculator 21 is the error amplifier 22
a, a limiter 23a, and a first-order lag filter 24a. The changeover switch 15 is connected to the phase detector 20, and the output of the phase detector 20 is
5a. The output of the subtractor 25a is connected to the multiplier 31 via the sine wave generating means 26. The output voltage command value 27 is multiplied by √2 and input to the multiplier 31. The output of the multiplier 31 is connected to the subtractor 25b and the adder 29a. The output of the subtractor 25b is connected to the adder 29a via the error amplifier 22b and the limiter 23b.

In the output voltage waveform distortion compensation control system 32, the output of the differentiating means 44 is connected to a subtractor 25c via a reactor voltage compensation gain 45. The output of the capacitor current compensation gain 45 is connected to the subtractor 25c. The output of the subtractor 25c is connected to the adder 29a. The output of the adder 29a is connected to the inverter 4 via the PWM signal generator 43.

Next, the operation of FIG. 1 will be described. When the commercial AC power supply 1 is supplying the rated voltage, the single conversion UPS device 28 turns on the input relay 2 and supplies the power from the commercial AC power supply 1 to the load 5 via the reactor 3. At this time, the inverter 4 performs an operation of performing PWM control on the internal switching element and controlling the output voltage to be constant by outputting a reactive current.

In this control, first, the inverter current detection value 16 detected by the inverter current detection means 10 and the output voltage detection value 1 detected by the output voltage detection means 13
4 is input to the power calculator 21. The power calculator 21 calculates the product of the inverter current detection value 16 and the output voltage detection value 14, performs time integration of the product, and calculates the active power output from the inverter. The obtained active power is input to the error amplifier 22a and amplified. The error amplifier 22a can be configured using an operational amplifier in an analog circuit, and can be configured as a proportional integrator in a digital circuit. The output amount of the error amplifier 22a is
By a, a value equal to or greater than a predetermined upper limit value and a value equal to or less than the lower limit value are cut. The output of the limiter 23a is input to the first-order lag filter 24a, and the change in the input value is reduced by a predetermined time constant.

On the other hand, the changeover switch 15 is usually connected to the output voltage detection value 14, and as a result, the phase detector 20 detects the phase of the output voltage and outputs the phase. In the subtracter 25a, the first order lag filter 2
4a is subtracted. At this time, the output of the first-order lag filter 24a becomes a phase error amount with respect to the output voltage phase. The output of the subtractor 25a becomes the phase of the inverter, and this phase is input to the sine wave generation means 26 to create a reference sine wave. The reference sine wave is multiplied by the voltage peak value that is √2 times the output voltage command value by the multiplier 31 to calculate the inverter instantaneous voltage command value. This inverter instantaneous voltage command value is compared with the output voltage detection value 14 by the subtractor 25b, and the voltage error is input to the error amplifier 22b. Similarly to the error amplifier 22a, the error amplifier 22b can be configured using an operational amplifier in an analog circuit, and can be configured as a proportional integrator in a digital circuit.

The output of the error amplifier 22b is a limiter 23b
Thus, a value equal to or greater than a predetermined upper limit value and a value equal to or less than the lower limit value are cut. The output of the limiter 23b is the adder 2
9a.

Next, in the output voltage waveform distortion compensation control system 32, the output current detection value 18 is time-differentiated by the differentiating means 44, and the load current change amount is calculated. The amount of change in the load current is multiplied by the reactor voltage compensation gain 45, and the amount of output voltage compensation by the current flowing through the reactor inside the inverter 4 is output. The output voltage compensation amount due to a change in the current of the capacitor 7 is calculated by multiplying the capacitor current detection value 19 by a capacitor current compensation gain 41. Subtractor 25
In c, the difference between these two output voltage compensation amounts is calculated and input to the adder 29a.

The adder 29a adds the instantaneous voltage command value of the inverter, the voltage error control amount which is the output value of the limiter 23b, and the output voltage compensation amount output from the output voltage waveform distortion compensation control system 32 to perform PWM. The signal is input to the signal generator 43 to drive the inverter 4. With this control,
The inverter 4 uses the active power of the inverter as the power calculator 21.
, And changes the output voltage phase according to the active power. Therefore, as a result, the inverter 4 operates in the phase where the active power is 0.

With the above configuration, it is possible to perform output voltage compensation control for input voltage fluctuations, harmonic reduction for non-linear loads, that is, active filter control and sine wave inverter control when a power failure occurs.

First, the output voltage compensation control for the input voltage fluctuation will be described with reference to FIG. FIG. 3 shows that the input voltage of the commercial AC power supply 1 is rated at 100 V, and the input voltage, output voltage, and output voltage at a linear load of 1 kVA when the input voltage is changed to 90 V and 110 V corresponding to ± 10%.
3 shows an inverter current and an inverter modulation wave.

FIG. 3A shows a case where the input voltage is reduced to 90 V, and the inverter 4 sets the output voltage command value 27 to 100 V.
In order to operate as V, the inverter modulation rate has an effective value of 10
It is equivalent to 0 V, and the output voltage is also 100 V. At this time, the inverter 4 controls the inverter phase with respect to the output voltage phase output from the phase detector 20 so that the active power output from the power calculator 21 becomes 0. As a result, the inverter current becomes The phase is delayed by 90 degrees with respect to the inverter modulation rate.

(B) shows a case where the input voltage is the rated voltage of 100 V. Since there is no need for voltage compensation, the current flowing from the inverter may be zero, and the inverter current is zero. Also, (c) is a waveform when the input voltage rises to 110 V. Since the inverter 4 operates with the output voltage command value 27 being 100 V as in (a), the inverter modulation rate is equivalent to an effective value of 100 V. And the output voltage is 100V
It is suppressed to. However, in the case of (c), since the direction of voltage compensation is opposite to that of (a), the phase of the current to be passed by the inverter is reversed. As a result, the inverter current becomes
The phase is advanced by 90 degrees with respect to the inverter modulation rate.

As described above, the output voltage can be compensated to a constant value even when the input voltage fluctuates by the circuit configuration of FIG.

Next, harmonic reduction control for a non-linear load will be described with reference to FIG. FIG. 4 shows waveforms at various points when the input voltage is rated at 100 V and the load is a linear load and a 100% rectifier load. In the case of the linear load shown in FIG. 3A, the output voltage is the same sine wave as the input voltage, so that no distortion compensation is required. As a result, the current flowing from the inverter becomes zero. However, at the time of the 100% rectifier load in (b), the output current becomes non-linear, so that the output voltage waveform distortion compensation control system 32 operates. First, since the output current detection value 18 greatly changes in such a nonlinear load, the time differential value is obtained by the differentiating means 44 and multiplied by the reactor voltage compensation gain 45 to compensate for the reactor voltage drop inside the inverter 4. I do. On the other hand, since the voltage of the capacitor 7 fluctuates due to the non-linear load, the capacitor current detection value 1
2 is multiplied by the capacitor current compensation gain 41 to calculate the amount of compensation for the capacitor voltage. By taking these differences and adding them to the PWM command value of the inverter, FIG.
Can be generated. Due to this inverter operation, the inverter current flows in the form as shown. As a result, a harmonic component of the load flows between the inverter 4 and the load 5, and the input current becomes substantially a sine wave. In this case, also in this case, the subtracter 25
Since the phase control up to “a” is operating, the power output from the inverter 4 is zero.

As described above, the input current of the UPS device can be compensated in a sinusoidal manner even in the case of a non-linear load by the circuit configuration of FIG.

Next, sine wave inverter control when a power failure occurs will be described with reference to FIGS. In the UPS of the present embodiment, when a power failure occurs, the voltage compensation function automatically operates, and operates so as to maintain the output voltage. FIG. 5 shows waveforms of respective parts before and after the occurrence of a power failure in a linear load. In the commercial power supply state, as described above, voltage compensation is not necessary and the load is linear, so that the inverter current is almost zero.
It has become. However, when a power failure occurs, the output voltage tends to sharply decrease, so that harmonic reduction control for a non-linear load operates. That is, as the voltage of the capacitor 7 decreases, the capacitor current detection value 19 increases, and the output of the capacitor current compensation gain 41 in the output voltage waveform distortion compensation control system 32 increases. At the same time, since the output current detection value 18 changes abruptly, the output of the reactor voltage compensation gain 45 also changes abruptly. As a result, the inverter modulation rate changes abruptly to compensate for a decrease in the input voltage.

For this reason, the output voltage is maintained without a sudden change, and the inverter current takes over the load current from this point. The power failure detection has a time lag from the actual power failure occurrence using any means, but this control system is characterized in that the output voltage does not drop or fluctuate in principle until the power failure detection.

FIG. 6 shows a sequence after a power failure occurs.
There is a slight time difference between when the commercial AC power supply 1 enters the power failure state and when the power failure determination means 30 outputs the power failure determination signal. At this time, the output voltage is maintained as described above,
The input relay 2 is turned off by a power failure determination signal output from the power failure determination means 30. The output of the power calculator 21 that is the active power of the inverter 4 is controlled to 0 before the power failure, but has the active power to supply the power to the load after the power failure. Since this power calculator 21 outputs the integration result for each period of the fundamental wave, the active power of the inverter is output until about one cycle after the power failure. However, because of the limiter 23a and the first-order lag filter 24a, more time is required for the change in power to be transmitted to the subtractor 25a as a phase control amount. Since the maximum value of the phase control amount, which is the upper limit value and the lower limit value of the limiter 23a, is sufficiently small with respect to one cycle, there is no problem even if the inverter operation is continued even during a power failure. At this time, as shown in the figure, the upper limit value and the lower limit value of the limiter 23a are narrowed and gradually changed to 0, so that the phase control amount, which is the output amount of the primary delay filter 24a, hardly changes as shown in FIG. The effect on No. 5 is also very small.

On the other hand, when the commercial AC power supply 1 is restored, the following operation is performed. First, the input voltage is detected by the input voltage detecting means 8, and the input voltage detection value 17 is detected by the power failure judging means 30 to recover the power. The changeover switch 15 is normally connected to the output voltage detection value 14 side.
Is switched to the input voltage detection value 17 side. With this operation, the phase detector 20 detects the input voltage detection value 1
4 phase and frequency. When the phase detector 20 completely matches the phase of the input voltage, the input relay 2 is turned on to start commercial power supply. After the input relay 2 is turned on, the changeover switch 15 is connected to the output voltage detection value 17 side.
That is, the phase detector 20 is connected to the input voltage side only when the power is restored, and is switched to the output voltage side after synchronization, and operates based on the output voltage phase. At this time, the upper limit value and the lower limit value of the limiter 23a are gradually changed to predetermined values by the power recovery determination of the power failure determination means 30 in reverse to the power failure,
No rapid fluctuation of the output voltage occurs.

As described above, in the present embodiment, control for constantly compensating the output voltage with respect to input voltage fluctuation, active filter control for a non-linear load such as a rectifier load,
In addition, the sine wave inverter can be controlled when a power failure occurs, and the fluctuation of the output voltage waveform from the occurrence of the power failure to the detection of the power failure is extremely small, and the influence on the load is small.

Next, a second embodiment of the present invention will be described with reference to FIG. 7, the same components and functions as those in FIG. 1 are denoted by the same reference numerals. In addition, 22c is an error amplifier, 23c is a limiter, 25d is a subtractor, 29b is an adder, 33 is a reactor, 34a and 34b are switching elements, 35a and 35b are DC smoothing capacitors, 36 is DC voltage detecting means, and 37 is DC The voltage command value 40 is a DC voltage detection value.

Next, the configuration of FIG. 7 will be described. 7 differs from FIG. 1 in the following parts. First, inside inverter 4, DC smoothing capacitors 35 a and 35 b are connected in series and connected to storage battery 9. Switching elements 34a and 34b are connected in series and connected to storage battery 9 in the same manner as DC smoothing capacitors 35a and 35b. Switching elements 34a and 3
One terminal of the reactor 33 is connected to the midpoint of 4b. The other terminal of reactor 33 is reactor 3
And the load 5 and to one terminal of the capacitor 7. The other terminal of the capacitor 7 is connected to the ground 6
And the DC smoothing capacitors 35a and 35b. DC voltage detecting means 36 is connected to both ends of DC smoothing capacitors 35a and 35b connected in series.
DC voltage detection value 4 which is the detection value of DC voltage detection means 36
0 is connected to the subtractor 25d. The DC voltage command value 37 is also connected to the subtractor 25d. The output of the subtractor 25d is connected to the adder 29b via the error amplifier 22c and the limiter 23c. The adder 29b is inserted between the power calculator 21 and the error amplifier 22a. Other configurations are the same as those in FIG.

Next, the operation of FIG. 7 will be described. In FIG. 7, when the commercial AC power supply 1 is healthy, the inverter 4 performs PWM control on the switching elements 34a and 34b to perform control for compensating the output voltage to be constant with respect to the input voltage fluctuation and active filter control for the nonlinear load. At this time, the active power of the inverter 4 is controlled to 0 by the configuration of FIG. 1, but control for keeping the voltage of the DC smoothing capacitors 35a and 35b constant is realized by the following operation.

The DC voltage detection value 40 detected by the DC voltage detection means 36 is subtracted from the DC voltage command value 37 by the subtractor 25d.
And the error voltage is input to the error amplifier 22c. The output of the error amplifier 22c is cut off by a limiter 23c at a value exceeding the upper and lower limits, and the output of the limiter 23c is input to an adder 29b. In the adder 29b,
The output of the power calculator 21 and a value corresponding to the DC voltage error from the limiter 23c are added and input to the error amplifier 22a. As a result, the inverter 4 operates at the phase of outputting or inputting only the active power for controlling the DC voltage to be constant.

Also in this embodiment, the other functions of the single-conversion UPS device 28, namely, the output voltage suppression control system in the event of a power failure and the control system capable of shifting to a sine wave inverter without instantaneous interruption, are the same as those in FIG. It functions in the same manner as in the embodiment.

As a configuration of the inverter 4, a configuration of a full-bridge inverter may be considered in addition to the illustrated half-bridge inverter. A configuration is also conceivable in which a step-up / step-down chopper circuit is inserted between the storage battery 9 and the DC smoothing capacitors 35a and 35b to reduce the voltage of the storage battery 9. Further, a method is conceivable in which a transformer is inserted between the inverter 4 and the capacitor 7 to lower the voltage of the entire inverter 4.

Next, a third embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIGS. 8, the same components and functions as those in FIGS. 1 and 7 are denoted by the same reference numerals. In addition, 23d is a limiter, 24b is a first-order lag filter, 48 is an effective value calculating means, and 49 is a reference pulse creating means.

Next, the configuration of FIG. 8 will be described. The input voltage detection value 17 is connected to the effective value calculation means 48. The output of the sine wave generator 26 is connected to the reference pulse generator 49, and the output of the reference pulse generator 49 is connected to the effective value calculator 48. The output of the effective value calculating means 48 is supplied to the √2 through the primary delay filter 24b and the limiter 23d.
After being multiplied, it is connected to the multiplier 31. The other circuit configuration is the same as the configuration in FIG. 1 or FIG.

Next, the operation of FIG. 8 will be described. The effective value calculating means 48 receives the input voltage detection value 17 and calculates the effective value. The calculation method includes a method of taking the root mean square of one cycle of the input voltage instantaneous value, and a method of calculating the absolute value of the input voltage instantaneous value by one.
For example, a method of adding a period, taking an average, and multiplying by a constant is conceivable. In either method, a calculation reference pulse of a fundamental frequency is required. In this embodiment, the reference sine wave which is the output amount of the sine wave
9 and outputs a reference pulse when the reference sine wave changes from a negative value to a positive value. The effective value calculating means 48 can calculate the effective value of the input voltage using the reference pulse. The effective value of the input voltage, which is the output amount of the effective value calculating means 48, is input to the first-order lag filter 24b and, when there is a sudden change, the change is reduced. The output of the first-order lag filter 24b is input to a limiter 23d. When a value exceeding a predetermined upper limit and lower limit is input, the output of the limiter 23d is limited.

FIG. 9 shows the relationship between the input voltage and the output voltage. The input / output voltage is rated at 100V, and the upper and lower limits of the limiter 23d are set to 110V and 90V, respectively. In this case, the effective value of the input voltage is from 90 V to 110 V
In this case, the output voltage has the same value as the input voltage, and the input / output characteristics are the characteristics of a straight line ascending to the right in the center of FIG. That is, under this condition, the inverter 4 operates only as an active filter without performing voltage compensation. On the other hand, when the input voltage is in the range of 85 V to 90 V, the output of the effective value calculation means 48 is
Since the output is lower than the lower limit of 3d, the output of the limiter 23d is 90V, and the voltage compensation control is performed so that the output voltage becomes constant at 90V. Similarly, when the input voltage is 110 V to 11
In the range of 5 V, since the output of the effective value calculating means 48 is higher than the upper limit of the limiter 23d, the limiter 2
The output of 3d becomes 110V, and the voltage compensation control is performed so that the output voltage becomes constant at 100V. That is, by performing this control, the input / output characteristics as shown in FIG. 9 can be realized. If the input voltage drops to 85 V or less, the power failure determination means 30 determines that a power failure has occurred, and switches to inverter operation. This is the same when the input voltage rises to 115 V or more. Also,
The power restoration judgment voltage when the power is restored from the inverter operation is 82
V and 113 V have hysteresis characteristics.

Next, a sequence when a power failure occurs will be described with reference to FIG. When the commercial AC power supply 1 fails, the power failure is determined by the power failure determining means 30 and the input relay 2 is turned off. The operation up to this point is the same as in the embodiment of FIG.
The reference pulse output from the reference pulse creating means 49 is
The output of the sine wave generator 26 is output in synchronization with the phase that changes from negative to positive. Since the effective value calculating means 48 calculates the effective value of the input voltage between the adjacent reference pulses, the output of the effective value calculating means 48 changes in synchronization with the reference pulse.
Therefore, after the power failure occurs, the effective value of the input voltage decreases when the first reference pulse is output, and if the power failure continues, the effective value of the input voltage decreases when the next reference pulse is output. Drops to zero. At this time, the upper limit value and the lower limit value of the limiter 23d are set to 110 V and 90 V, respectively, up to the time of the power failure determination as shown in the figure, and are changed to 100 V for a predetermined time from the power failure determination time. By changing the limiter 23d in this way and selecting an appropriate time constant for the temporary delay filter 24b, the output voltage command value, which is the output amount of the limiter 23d, can be kept to a minute change as shown.

On the other hand, when the power is restored, the upper limit value and the lower limit value of the limiter 23d are gradually decreased from the rated 100 V by 1 according to the power failure determination by the power failure determination means 30, respectively.
Change to 10V, 90V. This operation does not cause a sudden change in the output voltage even when the power is restored.

As described above, in the present embodiment, the range in which the voltage compensation control is performed is limited between 85 V and 90 V and between 110 V and 115 V, so that the inverter current during voltage compensation is suppressed and the loss is reduced. Can be reduced.
As a result, the output voltage fluctuation can be suppressed to ± 10%. Further, since the control in the range of the input voltage from 85 V to 115 V is realized by the control that only changes the voltage command value with a certain time constant, there is no operation such as switching between control for performing voltage compensation and control for not performing voltage compensation. Abrupt changes in the output voltage can be suppressed, and the adverse effects on the load can be minimized.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS.

FIG. 11 is a graph showing the relationship between the voltage compensation range and the capacity (% impedance) of reactor 3. In this graph, the load power factor is delayed by 0.
It shows the characteristics from 7 to 0.9. Further, the area where the input apparent power exceeds the rating when performing voltage compensation is indicated by hatching.

From this graph, it can be seen that, for example, when performing 10% step-down compensation, about 17% of the reactor is required in consideration of the excess of the apparent power. On the other hand, when it is attempted to perform a 10% boost compensation, it is shown that a reactor of about 60% is necessary to allow a load power factor delay of 0.7.

Therefore, in the present embodiment, the reactor 3
Is selected to be about 25%. In this case, the step-up compensation range is 5%, but the step-down compensation range can be expanded to 15%.

Next, FIG. 12 shows input / output voltage characteristics of the present embodiment. In this figure, as in FIG. 9, the horizontal axis represents the input voltage, and the vertical axis represents the output voltage, showing the control characteristics of the present embodiment. First, when the input voltage is 90% to 110%
%, The voltage compensation is not performed, and the output voltage is the same as the input voltage. When the input voltage falls below 90%, voltage compensation in the boosting direction is performed to keep the output voltage constant at 90%. When the input voltage drops to about 85%, the inverter operation starts.

On the other hand, when the input voltage rises above 110%, voltage compensation in the step-down direction is performed to reduce the output voltage to 1%.
Keep constant at 10%. When the input voltage further rises to about 125% or more, the operation is switched to the inverter operation.

This control can be realized only by selecting the reactor 3 to 25% in the circuit shown in FIG. 8 and changing the set value for switching to the inverter operation.

As a result, in the present embodiment, it becomes possible to widen the allowable range of the input voltage as compared with the characteristics of FIG.
The usability of the UPS is improved.

[0059]

According to the present invention, the operation of the UPS at the time of commercial power supply and at the time of power failure can be performed by the same control system.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a single conversion type UPS representing a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a conventional single conversion type UPS.

FIG. 3 is an operation waveform when an input voltage changes according to the first embodiment of the present invention.

FIG. 4 is an operation waveform at the time of a linear load and under a non-linear load according to the first embodiment of the present invention.

FIG. 5 is an operation waveform when a power failure occurs according to the first embodiment of the present invention.

FIG. 6 is a sequence when a power failure occurs according to the first embodiment of this invention.

FIG. 7 is a circuit configuration diagram of a single conversion type UPS representing a second embodiment of the present invention.

FIG. 8 is a circuit configuration diagram of a single conversion type UPS representing a third embodiment of the present invention.

FIG. 9 shows a relationship between an input voltage and an output voltage according to the third embodiment of the present invention.

FIG. 10 is a sequence when a power failure occurs according to the third embodiment of the present invention.

FIG. 11 shows a relationship between a voltage compensation range and a reactor.

FIG. 12 is a characteristic diagram showing a relationship between an input voltage and an output voltage according to the fourth embodiment of the present invention.

[Explanation of symbols]

1: Commercial AC power supply, 2: Input relay, 3: Reactor,
4 ... Inverter, 5 ... Load, 6 ... Grounding point, 7 ... Capacitor, 8 ... Input voltage detecting means, 9 ... Storage battery, 10 ... Inverter current detecting means, 11 ... Output current detecting means, 12 ... Capacitor current detecting means, 13 ... Output voltage detecting means, 14
... output voltage detection value, 15 ... changeover switch, 16 ... inverter current detection value, 17 ... input voltage detection value, 18 ... output current detection value, 19 ... capacitor current detection value, 20 ... phase detector, 21 ... power calculator , 22a, 22b, 22c ... error amplifier, 23a, 23b, 23c, 23d ... limiter, 24a, 24b ... primary delay filter, 25a, 25
b, 25c, 25d: subtractor, 26: sine wave generating means,
27 ... Output voltage command value, 28 ... Single conversion UPS device, 29a, 29b ... Adder, 30 ... Power failure judgment means, 31 ... Multiplier, 32 ... Output voltage waveform distortion compensation control system, 33 ... Reactor, 34a, 34b ... Switching elements, 35a and 35b ... DC smoothing capacitors, 36
... DC voltage detecting means, 37 ... DC voltage command value, 38 ... DC voltage control system, 39 ... sine wave inverter control system, 40 ...
DC voltage detection value, 41: capacitor current compensation gain, 4
2 switch, 43 PWM signal generator, 44 differentiating means, 45 reactor voltage compensation gain, 46 output voltage compensation control system, 47 active filter control system, 4
8 ... effective value calculating means, 49 ... reference pulse creating means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyasu Umezu 3-1-1, Sachimachi, Hitachi-City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Works (72) Inventor Hideaki Kunisada 3-Chome, Sachimachi, Hitachi-City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Yoshihiro Taniguchi 3-1-1, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (11)

[Claims] A first line connected to a power supply line between a commercial power supply and a load;
Switch means and the first reactor are inserted in series,
In a single-conversion UPS having an inverter having an AC output terminal connected between the first reactor and the load, means for calculating an active power of the inverter, a phase error varying according to the active power And first limiter means for limiting a range of variation of the phase error.
Wherein the output of the limiter is subtracted by a subtractor to operate as a phase of the inverter. 2. A voltage reference value created by multiplying the inverter phase by a sine wave having an output of the subtractor as an inverter phase and a predetermined voltage peak value as an amplitude, and the output voltage. A single-conversion UPS wherein a value obtained by adding a control amount obtained by amplifying the compared error voltage by an amplifying unit and the voltage reference value is used as a modulation factor of the inverter. 3. An output voltage distortion compensating control according to claim 1, wherein the configuration detects an output current supplied from the UPS to the load and calculates a time derivative thereof.
At least one of a configuration in which a value multiplied by a constant is added to the modulation factor, and a configuration in which a current of a filter capacitor on the output side of the inverter is detected and a value obtained by multiplying the current value by a constant is subtracted from the modulation factor. A single conversion type UPS having one configuration. 4. The apparatus according to claim 1, wherein said means for detecting a DC voltage of said inverter and means for calculating a DC voltage control amount by amplifying a voltage error obtained by comparing said DC voltage with a reference value. A single-conversion UPS comprising: a DC voltage control unit that controls the DC voltage to be constant by adding the DC voltage control amount to the active power. 5. A power supply system according to claim 1, further comprising a first delay means between said first limiter and said subtracter, wherein when a power failure occurs, the power failure determination means determines the power failure. The input relay is turned off, and the upper and lower limits of the first limiter are gradually changed to 0.
Characterized in that the upper limit and lower limit of the limiter are gradually changed to predetermined values. 6. The method according to claim 2, wherein when the input voltage is within a predetermined voltage range including a rated voltage, a value obtained by multiplying an effective value of the input voltage by a square root of 2 is used as the predetermined value. A single-conversion-type UPS that operates as a voltage peak value. 7. An apparatus according to claim 6, wherein said means for calculating an effective value of said input voltage, a second delay means, and a second limiter means are connected in series, and said upper limit value of said second limiter means. And setting the second limiter so as to include the rated voltage effective value between the first limiter and the lower limit, and operating the output of the second limiter as the effective value of the inverter voltage. UPS. 8. The power supply system according to claim 7, wherein when a power failure occurs in said commercial power supply, a power failure determination means determines a power failure and turns off said first switch means, and gradually lowers an upper limit value and a lower limit value of said second limiter. Single conversion type UP characterized by changing to the rated voltage effective value
S. 9. The UPS according to claim 1, wherein the means for detecting the phase of the output voltage of the UPS comprises the UPS.
The phase of the commercial power supply is detected and synchronized with the phase of the commercial power supply only when the power supply is started and when the commercial power supply is restored, and the phase of the output voltage is detected after the first switch is turned on. Conversion method UPS. 10. A first switch means and a first reactor are inserted in series in a power supply line between a commercial power supply and a load, and an AC output terminal is connected between the first reactor and the load. In a single-conversion UPS having an inverter, a power supply from the inverter to the load is not supplied when the commercial power supply is healthy, and a period from the occurrence of a power failure of the commercial power supply to the interruption of the first switch means. Wherein the active power supply from the inverter to the load is started. 11. A first switch means and a first reactor are inserted in series in a power supply line between a commercial power supply and a load, and an AC output terminal is connected between the first reactor and the load. A single-conversion UPS having an inverter that outputs the same voltage as the input voltage when the voltage of the commercial power supply is between a first voltage lower than a predetermined rated voltage and a second voltage higher than the rated voltage. When the voltage of the commercial power supply is between the first voltage and a third voltage lower than the first voltage, a voltage compensation operation is performed so that the output voltage becomes the first voltage. When the voltage is between the second voltage and a fourth voltage higher than the second voltage, the voltage compensating operation is performed so that the output voltage becomes the second voltage. 4th than the voltage difference of 3 Wherein the difference between the first voltage and the second voltage is larger.