JP4569596B2 - Uninterruptible power supply, AC power supply device, and AC voltage switching method according to load equipment - Google Patents

Description

  The present invention relates to an uninterruptible power supply apparatus, an AC power supply apparatus, and an AC voltage switching method according to a load device.

  Patent document 1 discloses an uninterruptible power supply. In this uninterruptible power supply, a trapezoidal wave reference signal is generated by a reference wave generation circuit, and the PWM signal generation circuit compares the trapezoidal wave with the triangular wave generated by the triangular wave generation circuit to generate a drive signal to the inverter. Generate. Thereby, trapezoidal AC power is supplied from the uninterruptible power supply to the load, the reactive current of the power supplied to the capacitive load is suppressed, and the power factor is improved.

Japanese Patent Laid-Open No. 2001-8462 (FIG. 2, paragraph 0029, detailed description of the invention, etc.)

  By the way, an uninterruptible power supply supplies electric power to load equipment with alternating current power. The power supply circuit of the load equipment connected to the uninterruptible power supply includes, for example, an input transformer, a capacitive one having a capacitor, and a capacitor input type rectifier using a rectifier and a capacitor. There are circuits. And the uninterruptible power supply of patent documents 1 is suitable for capacitive load equipment by making the AC voltage applied to load equipment into a trapezoidal wave.

  However, the AC voltage of trapezoidal waves contains many harmonic components such as the third harmonic and the fifth harmonic. Therefore, when this trapezoidal wave AC voltage is applied to a load device equipped with an input transformer, harmonic loss may occur in the transformer of the power supply circuit and the like, which may cause a rise in temperature of the transformer. It is better to operate such a load device with a sinusoidal AC voltage.

  For load equipment that uses a capacitor input type rectifier circuit as a power supply, applying a trapezoidal wave or, in extreme cases, a square wave improves the power factor of the power supply rather than applying a sinusoidal AC voltage. It is convenient because it is done.

  The present invention supplies optimum power to all types of load devices regardless of the load devices, particularly to load devices that use a capacitor input type rectifier circuit as a power source and load devices that use other methods as a power source. An object of the present invention is to provide an uninterruptible power supply apparatus, an AC power supply apparatus, and an AC voltage switching method according to load equipment.

The uninterruptible power supply according to the present invention is switched based on a triangular wave generating means for generating a triangular wave, a sine wave generating means for generating a sine wave that can be changed to an amplitude larger than the triangular wave, and a level comparison between the triangular wave and the sine wave. A switching signal generating means for generating a signal, a switching element that is turned on and off by the switching signal, an inverter circuit that generates AC voltage power to be supplied to the load device by the switching operation, and the uninterruptible power supply from the load device A detection member for detecting the load current supplied to the load device, and the load device detected when the crest factor value of the load current detected when AC power is supplied to the load device is smaller than a predetermined threshold, the load device When it is determined that the load is not an input rectifier load and the crest factor value is greater than the specified threshold A determination unit load device is determined to be a capacitor input type rectifier loads, to produce a sine wave amplitude is larger than the triangular wave by the sine wave generating means when the load device is determined to be a capacitor input type rectifier loads, And control means for generating a sine wave having an amplitude smaller than the triangular wave by the sine wave generating means when it is determined that the load device is not a capacitor input type rectifier load.

If this configuration is adopted, the uninterruptible power supply can automatically determine the type of the load device, and can appropriately supply sine wave or trapezoidal power to the load device according to the determination. When the load device is a capacitor input type rectifier load, trapezoidal AC power can be supplied, and when the load device is not a capacitor input type rectifier load, sinusoidal AC power can be supplied. Therefore, optimal power can be supplied to all types of load devices without bothering the uninterruptible power supply and the user. In particular, whether or not the load device is a capacitor input type rectifier load can be appropriately determined based on detection of the load current. In addition, since the sine wave AC power is supplied to the load device in the detection of the load current, there is no problem with the load device during the detection. Furthermore, since power supply to the load device is started at the time of detection, the start of power supply to the load device is not delayed because of such detection.

  Another uninterruptible power supply according to the present invention has the following features in addition to the above-described components of the present invention. That is, when it is determined that the load device is a capacitor input type rectifier load, the control means determines that the amplitude of the sine wave is at least four times the amplitude of the triangular wave and that the load device is not a capacitor input type rectifier load. If so, the amplitude of the sine wave is made smaller than one time the amplitude of the triangular wave.

  If this configuration is adopted, the uninterruptible power supply can supply AC power of the same sine wave as a general uninterruptible power supply to a load that is not a capacitor input rectifier, and a capacitor input rectifier load. Can be supplied with trapezoidal AC power. When supplying the trapezoidal wave AC power, the switching loss of the inverter can be greatly reduced because the number of on / off times of the switching elements of the inverter circuit is significantly reduced.

  Another uninterruptible power supply according to the present invention has the following features in addition to the above-described components of the present invention. That is, the control means outputs a clock signal for outputting a sine wave and a modulation factor designation signal for designating the maximum amplitude of the sine wave to the sine wave generating means. Further, the sine wave generating means generates a sine wave whose frequency changes according to the clock signal and whose maximum amplitude is specified by the modulation factor specifying signal.

  Thereby, the control unit can control the amplitude of the sine wave generated by the sine wave generation circuit. The sine wave generation circuit can generate a sine wave whose maximum amplitude is that of the modulation factor designated by the modulation factor designation signal.

The AC power supply device according to the present invention switches based on a triangular wave generating means for generating a triangular wave, a sine wave generating means for generating a sine wave that can be changed to an amplitude larger than the triangular wave, and a level comparison between the triangular wave and the sine wave. A switching signal generating means for generating a signal; a switching element that is turned on and off by the switching signal; an inverter circuit that generates AC voltage power supplied to the load device by the switching operation; and the load device from the AC power supply device A detection member for detecting the load current supplied to the load device, and the load device detected when the crest factor value of the load current detected when AC power is supplied to the load device is smaller than a predetermined threshold, the load device When it is determined that the load is not an input rectifier load and the crest factor value is greater than the specified threshold Generating a determination unit load device is determined to be a capacitor input type rectifier loads, the sine wave amplitude is larger than the triangular wave by the sine wave generating means when the load device is determined to be a capacitor input type rectifier loads the And control means for generating a sine wave having an amplitude smaller than that of the triangular wave by the sine wave generating means when it is determined that the load device is not a capacitor input type rectifier load.

  If this configuration is adopted, the AC power supply apparatus can automatically determine the type of the load device, and can appropriately supply sine wave or trapezoidal power to the load device according to the determination. When the load device is a capacitor input type rectifier load, trapezoidal AC power can be supplied, and when the load device is not a capacitor input type rectifier load, sinusoidal AC power can be supplied. Therefore, this AC power supply apparatus can supply optimal power to all types of load devices without bothering the user.

An AC voltage switching method according to a load device according to the present invention is an AC voltage switching method according to a load device executed by an AC power supply device, the step of supplying AC power from the AC power supply device to the load device; When the load current supplied from the AC power supply device to the load device is detected, and the load current crest factor value detected when the AC power is supplied as a sine wave to the load device is smaller than a predetermined threshold value Determining that the load device is not a capacitor input type rectifier load, and determining that the load device is a capacitor input type rectifier load if the crest factor value is greater than a predetermined threshold; and When switching the inverter circuit that generates AC voltage power when it is determined to be a load For the switching signal generating means for generating the switching signal, the amplitude of the sine wave supplied for level comparison with the triangular wave is controlled to be larger than the triangular wave, and it is determined that the load device is not a capacitor input rectifier load. The step of controlling the amplitude of the sine wave to be smaller than that of the triangular wave.

  An AC power supply apparatus that employs this method can automatically determine the type of load device, and can appropriately supply sine wave or trapezoidal power to the load device according to the determination. When the load device is a capacitor input type rectifier load, trapezoidal AC power can be supplied, and when the load device is not a capacitor input type rectifier load, sinusoidal AC power can be supplied. Therefore, this AC power supply device can efficiently supply power to all types of load devices without bothering the user.

  In the present invention, optimal power can be supplied to all types of load devices regardless of the load devices.

  Hereinafter, an AC voltage switching method according to an uninterruptible power supply apparatus, an AC power supply apparatus, and a load device according to an embodiment of the present invention will be described with reference to the drawings. The AC power supply apparatus will be described as a part of the uninterruptible power supply apparatus. The AC voltage switching method according to the load device will be described as a part of the operation of the uninterruptible power supply.

  FIG. 1 is a block diagram showing an uninterruptible power supply 1 according to an embodiment of the present invention. The uninterruptible power supply 1 supplies power from a built-in battery 12 to a load device when, for example, a commercial AC power supply is out of power. Therefore, the uninterruptible power supply 1 has a pair of power receiving terminals 2 and 3 and a pair of power feeding terminals 4 and 5. The uninterruptible power supply 1 may have a plurality of sets of power supply terminals.

  An AC power supply such as a commercial AC power supply (not shown) is connected to the pair of power receiving terminals 2 and 3 of the uninterruptible power supply 1. An AC power source such as a commercial AC power source outputs AC power having a frequency of 50 Hz or 60 Hz and an effective value of 100 volts or 200 volts, for example.

  A load device (not shown) is connected to the pair of power supply terminals 4 and 5. Examples of the power supply circuit of the load device include a device having an input transformer, a capacitive device having a capacitor, and a capacitor input type rectifier circuit using a rectifier and a capacitor. In particular, load devices such as computer terminals often have capacitor input type rectifier circuits using rectifier elements and capacitors.

  FIG. 2 is a circuit diagram illustrating a configuration example of the input stage of the power supply circuit of the load device. 2A is a power supply circuit in which the transformer 51 is used as an input stage, and FIG. 2B is a power supply circuit in which a capacitor input type rectifier circuit is used. When the power supply circuit of FIG. 2A is connected as a load device, the primary coil of the transformer 51 is connected to the pair of power supply terminals 4 and 5. When the power supply circuit of FIG. 2B is connected as a load device, the rectifying element 62 and the capacitor 63 are connected to the pair of power supply terminals 4 and 5.

  Inside the uninterruptible power supply 1, the pair of power receiving terminals 2 and 3 are connected to the converter circuit 11. The converter circuit 11 converts the AC voltage input to the pair of power receiving terminals 2 and 3 into a DC voltage. A battery 12 and an inverter circuit 13 are connected to the output of the converter circuit 11. The converter circuit 11 supplies DC power to the inverter circuit 13 and charges the battery 12.

  The inverter circuit 13 has a pair of input terminals 21 and 22, a pair of output terminals 23 and 24, four switching elements 25, 26, 27, and 28, and four free-wheeling diodes 29, 30, 31, and 32. . One input terminal 21 is connected to the positive electrode of the battery 12. The other input terminal 22 is connected to the negative electrode of the battery 12.

  As the switching elements 25, 26, 27, and 28, for example, an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor FET), or the like is used. In these switching elements 25, 26, 27, and 28, a switching loss accompanying a switching operation occurs. As the number of switching operations increases, the power loss due to the switching operation of the inverter circuit 13 increases.

  Of the four switching elements 25, 26, 27, and 28, the collector of the first switching element 25 is connected to one input terminal 21, and the emitter is connected to one output terminal 23. The collector of the second switching element 26 is connected to one input terminal 21, and the emitter is connected to the other output terminal 24. The collector of the third switching element 27 is connected to one output terminal 23, and the emitter is connected to the other input terminal 22. The collector of the fourth switching element 28 is connected to the other output terminal 24, and the emitter is connected to the other input terminal 22.

  The four free-wheeling diodes 29, 30, 31, and 32 have a direction in which a current opposite to that of each switching element 25, 26, 27, 28 flows between the collectors and emitters of the four switching elements 25, 26, 27, 28. Connected to.

  In the four switching elements 25, 26, 27, and 28 of the inverter circuit 13, the first switching element 25 and the fourth switching element 28 are simultaneously controlled to be in an ON state, and the second switching element 26 and three The eye switching elements 27 are simultaneously controlled to be in the on state. Each set of switching elements is basically controlled to be turned on alternately.

  When the pair of switching elements 25 and 28 are turned on, one output terminal 23 of the inverter circuit 13 is connected to the positive electrode of the battery 12, and the other output terminal 24 is connected to the negative electrode of the battery 12. When the other sets of switching elements 26 and 27 are turned on, one output terminal 23 of the inverter circuit 13 is connected to the negative electrode of the battery 12, and the other output terminal 24 is connected to the positive electrode of the battery 12. By such a switching operation, the positive and negative electrodes of the battery are alternately connected to the pair of output terminals 23 and 24 of the inverter circuit 13.

  An LPF (Low Pass Filter) circuit 14 is connected to the inverter circuit 13. The LPF circuit 14 is connected to a pair of power supply terminals 4 and 5. The LPF circuit 14 includes a reactor 36 and a capacitor 37. The reactor 36 is connected between one output terminal 23 of the inverter circuit 13 and one power supply terminal 4. One end of the capacitor 37 is connected between the reactor 36 and one power supply terminal 4. The other output terminal 26 of the inverter circuit 13 and the other power supply terminal 5 are connected to the other end of the capacitor 37.

  With the above configuration, the pair of power receiving terminals 2 and 3 and the pair of power feeding terminals 4 and 5 are connected, and a power supply path between the AC power source and the load device via the uninterruptible power supply 1 is configured. In addition to this, the uninterruptible power supply 1 has a control circuit for supplying sinusoidal AC power or trapezoidal AC power to the load device from the pair of power supply terminals 4 and 5. Specifically, the uninterruptible power supply 1 includes a setting switch 41 as a setting member, a load current detection circuit 42 as a detection member, a control unit 43 as control means and determination means, and a sine wave generation as sine wave generation means. A circuit 44, a clock generation circuit 45, a triangular wave generation circuit 46 as a triangular wave generation unit, a comparator circuit 47 as a switching signal generation unit, and the like.

  The clock generation circuit 45 generates a clock signal having a predetermined frequency. The clock generation circuit 45 generates a clock signal having a frequency of, for example, several kilohertz to several tens of kilohertz.

  A clock signal is input to the triangular wave generation circuit 46. The triangular wave generation circuit 46 outputs a triangular wave synchronized with the clock signal. The amplitude of the triangular wave generated by the triangular wave generation circuit 46 is constant.

  The sine wave generation circuit 44 outputs a sine wave having an amplitude corresponding to the setting. The frequency of the sine wave may be the same as the AC power input to the pair of power receiving terminals 2 and 3 (for example, 50 hertz or 60 hertz). In particular, the sine wave generation circuit 44 of this embodiment can output the sine wave with the amplitude changed from 0 to about 4 A or more when the amplitude of the triangular wave is A. Unlike this embodiment, in an uninterruptible power supply that supplies sine wave AC power, the sine wave generation circuit outputs a sine wave having an amplitude smaller than the amplitude of the triangular wave.

  The comparator circuit 47 receives a triangular wave having a predetermined amplitude generated by the triangular wave generating circuit 46 and a sine wave having an arbitrary amplitude generated by the sine wave generating circuit 44. The comparator circuit 47 compares the sine wave level with the triangular wave level. Then, for example, the comparator circuit 47 generates a switching signal that becomes a high level during a period in which the sine wave level is higher than the triangular wave level, and becomes a low level in a period during which the sine wave level is lower than the triangular wave level.

  In FIG. 1, this switching signal is supplied to one set of switching elements, that is, the gate of the first switching element 25 at the upper left and the gate of the fourth switching element 28 at the lower right. Further, the switching signal is inverted by the inverting element 48, and in FIG. 1, to the other set of switching elements, that is, the gate of the third switching element 27 at the lower left and the gate of the second switching element 26 at the upper right. Supplied. These switching elements 25, 26, 27, and 28 are turned on when the gate is at a high level, and are turned off when the gate is at a low level.

  Thereby, in the inverter circuit 13, the switching signal generated by the comparator circuit 47 simultaneously controls the first switching element 25 at the upper left and the fourth switching element 28 at the lower right in FIG. The second switching element 26 in the upper right and the third switching element 27 in the lower left are controlled to be turned on simultaneously. In addition, each set of switching elements is controlled to be turned on alternately.

  FIG. 3 is a waveform diagram showing signal waveforms when sinusoidal AC power is supplied from the pair of power supply terminals 4 and 5. FIG. 3A shows a sine wave generated by the sine wave generation circuit 44 when a sine wave AC power is supplied and a triangular wave generated by the triangular wave generation. When sine wave AC power is supplied, the amplitude of the sine wave is smaller than the amplitude of the triangular wave. The comparator circuit 47 compares these levels and generates the switching signal of FIG. FIG. 3C shows a switching signal inverted by the inverting element 48. These switching signals are PWM (pulse width modulation) signals whose pulse width changes according to the amplitude of the sine wave.

  And the four switching elements 25-28 of the inverter circuit 13 perform switching operation by the switching signal of FIG. 3 (B) and FIG. 3 (C). Thus, the sinusoidal AC power shown in FIG. 3D is supplied from the LPF circuit 14 to the pair of power supply terminals 4 and 5. This AC power is supplied to a load device connected to the pair of power supply terminals 4 and 5.

  FIG. 4 is a waveform diagram showing signal waveforms when trapezoidal AC power is supplied from the pair of power supply terminals 4 and 5. FIG. 4A shows a sine wave generated by the sine wave generation circuit 44 when a trapezoidal wave AC power is supplied, and a triangular wave generated by the triangular wave generation. In the case of supplying trapezoidal AC power, the amplitude of the sine wave is larger than that of the triangular wave. The sine wave in FIG. 4A has an amplitude that is approximately twice that of a triangular wave. The comparator circuit 47 compares these levels and generates the switching signal shown in FIG. FIG. 4C shows a switching signal inverted by the inverting element 48. These switching signals are a kind of PWM (pulse width modulation) signals.

  Then, the four switching elements 25 to 28 of the inverter circuit 13 perform a switching operation by the switching signals of FIG. 4B and FIG. 4C. Thereby, the trapezoidal AC power of FIG. 4D is supplied from the LPF circuit 14 to the pair of power supply terminals 4 and 5. This AC power is supplied to a load device connected to the pair of power supply terminals 4 and 5.

  The setting switch 41 in FIG. 1 is for selecting the voltage waveform of the electric power that the uninterruptible power supply 1 supplies to the load device from the pair of power supply terminals 4 and 5, and includes a sine wave selection position and a trapezoidal wave selection position. It can be set to one of the three positions of the automatic selection position. The setting switch 41 outputs a signal corresponding to the setting to the control unit 43.

  The load current detection circuit 42 in FIG. 1 detects an instantaneous current supplied from the pair of power supply terminals 4 and 5 to the load device. The load current detection circuit 42 outputs the detected instantaneous load current to the control unit 43.

  The control unit 43 in FIG. 1 outputs a setting signal to the sine wave generation circuit 44. For example, the control unit 43 outputs a clock signal and a modulation factor designation signal to the sine wave generation circuit 44. The control unit 43 outputs, for example, a clock signal for causing the sine wave generation circuit 44 to output a sine wave synchronized with the received voltage and a modulation factor designation signal for designating the maximum amplitude of the sine wave. The sine wave generation circuit 44 generates a sine wave whose frequency changes according to the clock signal and whose maximum amplitude is designated by the modulation factor designation signal. That is, the sine wave generation circuit 44 generates a sine wave having the maximum amplitude in synchronization with the received voltage and corresponding to the specified modulation rate. The modulation factor specified by the control unit 43 to the sine wave generation circuit 44 may be a value from 0 to 4, for example. When a modulation factor of 1 or more is designated, the maximum amplitude of the sine wave is larger than that of the triangular wave.

  The control unit 43 is realized, for example, when a CPU (not shown) executes a program (not shown) stored in a memory (not shown) of the microcomputer 50. The unillustrated program may be stored in the memory before the uninterruptible power supply 1 is shipped, or may be stored in the memory after the uninterruptible power supply 1 is shipped. A part of the program stored in the memory may be stored after the uninterruptible power supply 1 is shipped. Thus, even if the program stored in the memory after shipment is an installed program stored in a computer-readable recording medium such as a CD-ROM (Compact Disc Read Only Memory) or a semiconductor memory, It may be downloaded from a server device or the like via a transmission medium such as the Internet.

  In addition to the control unit 43, a sine wave generation circuit 44, a clock generation circuit 45, a triangular wave generation circuit 46, a comparator circuit 47, an inverting element 48, etc. are stored in a memory (not shown) of the microcomputer 50. The uninterruptible power supply 1 may be realized by executing a program (not shown) by a CPU (not shown).

  Next, the operation of the uninterruptible power supply 1 according to this embodiment having the above configuration will be described. In the following description, an operation for selecting a waveform of AC power supplied from the pair of power supply terminals 4 and 5 to the load device will be mainly described.

  FIG. 5 is a flowchart showing a flow of output waveform selection processing executed by the control unit 43 when the uninterruptible power supply 1 is started, for example. In the output waveform selection process, the control unit 43 first reads a signal input from the setting switch 41 and determines the setting position of the setting switch 41 (step ST1). The setting position of the setting switch 41 includes a sine wave selection position, a trapezoidal wave selection position, and an automatic selection position.

  And the control part 43 will select a sine wave output, if the setting switch 41 is set to the sine wave selection position. The control unit 43 outputs to the sine wave generation circuit 44 a clock signal that is synchronized with the received voltage and a modulation rate designation signal that designates a modulation rate smaller than 1 (step ST2).

  As a result, the sine wave generation circuit 44 generates a sine wave having an amplitude smaller than that of the triangular wave in synchronization with the received voltage. The uninterruptible power supply 1 supplies sinusoidal AC power as shown in FIG.

  If the setting switch 41 is set to the trapezoidal wave selection position, the control unit 43 selects the trapezoidal wave output. The control unit 43 outputs to the sine wave generation circuit 44 a clock signal synchronized with the received voltage and a modulation rate designation signal designating “4” as the modulation rate (step ST3).

  As a result, the sine wave generation circuit 44 generates a sine wave having an amplitude four times that of the triangular wave in synchronization with the received voltage. The uninterruptible power supply 1 supplies trapezoidal wave AC power as shown in FIG.

  When the setting switch 41 is set to the automatic selection position, the control unit 43 starts a process for determining whether or not the load device is a capacitor input type rectifier load. First, the control unit 43 outputs a clock signal synchronized with the received voltage and a modulation rate designation signal for designating a modulation rate smaller than 1 to the sine wave generation circuit 44. The sine wave generation circuit 44 generates a sine wave having an amplitude smaller than the triangular wave in synchronization with the received voltage. Further, uninterruptible power supply 1 starts to supply sinusoidal AC power as shown in FIG. 3D to the load device (step ST4).

  The load current detection circuit 42 detects an instantaneous current when the sinusoidal AC power is supplied from the pair of power supply terminals 4 and 5 to the load device. The control unit 43 accumulates an instantaneous current value for a predetermined period (for example, several periods) of the AC power of the sine wave (step ST5).

  After accumulating the instantaneous current value, the control unit 43 calculates the current peak value and the effective value using the accumulated instantaneous current value for a predetermined period (step ST6). The current peak value has the largest absolute value among the accumulated instantaneous current values. The effective value can be obtained, for example, by calculating the root mean square value of the accumulated instantaneous current values for one period and further calculating the square root thereof.

  After calculating the current peak value and effective value of the load current, the control unit 43 further calculates a crest factor value (step ST7). The crest factor value can be calculated by dividing the peak value of the waveform by the effective value.

  Thereafter, the control unit 43 determines whether or not the load device is a capacitor input type rectifier load by using the calculated crest factor value. Specifically, the control unit 43 determines that the load device is a capacitor input type rectifier load when the crest factor value is equal to or larger than a predetermined threshold (here, 1.8, for example), and is smaller than the predetermined threshold. In this case, it is determined that the load device is not a capacitor input type rectifier load (step ST8).

  FIG. 6 is an explanatory diagram illustrating a current waveform according to the type of the load device. FIG. 6A shows an example of a current waveform when a sinusoidal AC voltage is applied to a resistive load as a case where the load is not a capacitor input type rectifier load. In the case of a resistive load, the load current waveform is also a sine wave. In contrast, FIG. 6B is an example of a current waveform when a sinusoidal AC voltage is applied to the capacitor input rectifier load. In the case of a capacitor input type rectifier load, the load current has a discrete waveform that flows only when the absolute value of the AC voltage exceeds a predetermined voltage. In these figures, a dotted line indicates a voltage waveform of a sine wave applied to the load device.

  In the case of a substantially sinusoidal load current as shown in FIG. 6A, the crest factor value is about 1.41. In the case of a load current having a waveform separated into a mountain-shaped waveform and a groove-shaped waveform as shown in FIG. B (A), the crest factor value is about 2. As described above, the crest factor value of the load current varies depending on whether or not the load device is a capacitor input rectifier load. Therefore, the control unit 43 appropriately determines whether the load device is a capacitor input rectifier load by determining whether or not the crest factor value is equal to or greater than a predetermined threshold (e.g., 1.8 in this case). Judgment can be made.

  When the crest factor value is smaller than a predetermined threshold (here, 1.8, for example) and it is determined that the load device is not a capacitor input rectifier load, the control unit 43 selects a sine wave output. The control unit 43 outputs to the sine wave generation circuit 44 a clock signal that is synchronized with the received voltage and a modulation rate designation signal that designates a modulation rate smaller than 1. As a result, the sine wave generation circuit 44 generates a sine wave having an amplitude smaller than that of the triangular wave in synchronization with the received voltage. The uninterruptible power supply 1 supplies sinusoidal AC power as shown in FIG.

  When it is determined that the load device is not a capacitor input rectifier load based on this automatic measurement, the uninterruptible power supply 1 has already supplied sine AC power to the load device. Therefore, when it is determined that the load device is not a capacitor input rectifier load, the control unit 43 does not actually perform the switching operation and maintains the clock signal and the modulation factor designation signal so far and maintains the sine wave generation circuit 44. To supply.

  When the crest factor value is equal to or greater than a predetermined threshold (e.g., 1.8 in this case) and the load device is determined to be a capacitor input rectifier load, the control unit 43 performs control to switch from sine wave output to trapezoidal wave output. Execute. The control unit 43 outputs to the sine wave generation circuit 44 a clock signal synchronized with the power reception voltage and a modulation rate designation signal designating “4” as the modulation rate. Accordingly, the sine wave generation circuit 44 switches the sine wave to be generated to a sine wave having an amplitude four times that of the triangular wave in synchronization with the received voltage. The AC voltage supplied to the load device by the uninterruptible power supply 1 is switched from a sine wave as shown in FIG. 3D to a trapezoidal wave as shown in FIG.

  FIG. 7 is a waveform diagram showing a waveform of AC power supplied from the uninterruptible power supply 1 to the load device.

  FIG. 7A is a waveform of AC power output when the setting switch 41 selects the sine wave selection position and when it is determined that the load device is not a capacitor input rectifier load in automatic selection. . The alternating current in this case is supplied to the load device by a sine wave voltage waveform as shown by a solid line in FIG. In addition, since the load device is substantially linear, the load current is also a substantially sine wave, the crest factor value of the load current is about 1.41, and power is supplied to the load device.

  FIG. 7B is a waveform of AC power output when the trapezoidal wave selection position is selected in the setting switch 41 and when it is determined that the load device is a capacitor input rectifier load in automatic selection. . The alternating current in this case is supplied to the load device by a trapezoidal voltage waveform as shown by a solid line in FIG. Further, since the load device is a capacitor input type rectifier load, the load current also becomes a trapezoidal wave, the crest factor value of the load current is about 1.1, and power is supplied to the load device. The waveform shown in FIG. 7B is obtained when the control unit 43 designates, for example, 4 as the modulation factor in the sine wave generation circuit 44.

  As described above, the uninterruptible power supply 1 of this embodiment can supply a sine wave AC voltage or a trapezoidal wave AC voltage to the load device based on the setting of the setting switch 41. Therefore, the uninterruptible power supply 1 can efficiently supply power to all types of load devices regardless of whether the load devices are capacitor input rectifier loads.

  Further, the uninterruptible power supply 1 of this embodiment is configured such that when the setting switch 41 is set to the automatic selection position, the load current in a state where a sine wave AC voltage is supplied to the load device is used as the load current detection circuit 42. Further, the control unit 43 calculates the crest factor value of the load current to determine whether the load device is a capacitor input type rectifier load. Further, when the control unit 43 determines that the load device is a capacitor input rectifier load, the control unit 43 generates a sine wave having an amplitude larger than the triangular wave by the sine wave generation circuit 44 and supplies a trapezoidal wave AC voltage to the load device. When it is determined that the load device is not a capacitor input type rectifier load, the sine wave generation circuit 44 generates a sine wave having an amplitude smaller than that of the triangular wave and supplies the AC voltage of the sine wave to the load device.

  Therefore, this uninterruptible power supply 1 can supply optimal power to all types of load devices without bothering the user. Further, the uninterruptible power supply 1 can appropriately determine whether or not the load device is a capacitor input type rectifier load. Therefore, the user does not need to determine whether the load device is a capacitor input rectifier load. In addition, since the sine wave AC voltage is supplied to the load device in the detection of the load current, there is no problem in the load device during the detection.

  In particular, when it is determined that the load device is a capacitor input type rectifier load, the control unit 43 causes the amplitude of the sine wave to be four times the amplitude of the triangular wave or more and the load device is not a capacitor input type rectifier load. If it is determined, the amplitude of the sine wave is made smaller than one times the amplitude of the triangular wave.

  Therefore, the uninterruptible power supply 1 can supply a sine wave AC voltage similar to that of the general uninterruptible power supply 1 to a load that is not a capacitor input rectifier load, and also to the capacitor input rectifier load. On the other hand, a trapezoidal AC voltage can be supplied. Also, the crest factor value of the load current for the capacitor input type rectifier load can be improved to about half, for example, from about 2 to about 1.1. Moreover, when the trapezoidal wave AC power is supplied, the number of on / off operations of the switching elements 25 to 28 of the inverter circuit 13 is greatly reduced, so that not only the crest factor value is improved, but also the switching loss is reduced. It is greatly reduced. The effect of improving these crest factor values and the effect of reducing switching loss are high. For example, the improvement effect is not limited by the waveform supplied to the comparator circuit 47 as in the case where a trapezoidal wave having the same amplitude as the triangular wave is supplied to the comparator circuit 47 instead of the sine wave. Will be expensive.

  The above embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications and changes can be made without departing from the scope of the invention. It is.

  For example, in the above-described embodiment, the control unit 43 specifies “4” as the modulation factor when outputting trapezoidal AC power. In addition to this, for example, when outputting the trapezoidal wave AC power, the control unit 43 may designate a modulation rate that is extremely larger than 1, for example, “100”. As a result, a rectangular wave can be output as the output voltage, and the switching frequency of the inverter can be 50 Hz or 60 Hz, so that the loss of the inverter can be significantly reduced.

  In the above embodiment, the load current detection circuit 42 detects the load current, and the control unit 43 determines the type of the load device based on the crest factor value of the load current. In addition to this, for example, the frequency characteristic of the impedance of the load device is detected as a physical quantity that changes according to the load device fed from the uninterruptible power supply 1, and the control unit 43 is based on the frequency characteristic of the impedance. The type of the load device may be determined.

  However, when detecting the frequency characteristic of the impedance of the load device, it takes time because it is necessary to examine the impedance of the load device in a predetermined frequency range. And in the period for the measurement and judgment, since it is necessary to isolate | separate the LPF circuit 14 etc. of the uninterruptible power supply 1 from a pair of electric power feeding terminals 4 and 5, feeding to load equipment may be started. Can not. On the other hand, when making a determination based on the crest factor value of the load current as in this embodiment, not only does it take a long time for the measurement and the determination, but also the load device for the measurement. Since it is necessary to supply AC power, power supply to the load device can be started by power supply for measurement. In addition, power can be continuously supplied by switching the waveform as necessary thereafter.

  In the above embodiment, in the uninterruptible power supply 1, the output power is switched between a sine wave and a trapezoidal wave. The present invention is not limited to the uninterruptible power supply 1, and for example, in an AC power supply apparatus such as a power supply apparatus such as a generator or a power quality improvement apparatus for improving the waveform quality of AC power, the output power is a sine wave. It may be used to switch between trapezoidal waves.

  The present invention can be suitably used in an uninterruptible power supply or the like to efficiently supply AC power.

FIG. 1 is a block diagram showing an uninterruptible power supply according to an embodiment of the present invention. FIG. 2 is a circuit diagram illustrating a configuration example of the input stage of the power supply circuit of the load device. FIG. 3 is a waveform diagram showing signal waveforms when sinusoidal AC power is supplied. FIG. 4 is a waveform diagram showing signal waveforms when trapezoidal AC power is supplied. FIG. 5 is a flowchart showing output waveform selection processing by the control unit. FIG. 6 is an explanatory diagram illustrating a current waveform according to the type of the load device. FIG. 7 is a waveform diagram showing the waveform of the AC voltage supplied to the load device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Uninterruptible power supply 13 Inverter circuit 25-28 Switching element 41 Setting switch (setting member)
42 Load current detection circuit (detection member)
43 Control unit (control means, judgment means)
44 Sine wave generation circuit (sine wave generation means)
46 Triangular wave generating circuit (Triangular wave generating means)
47 Comparator circuit (switching signal generating means)

Claims (5)

A triangular wave generating means for generating a triangular wave;
Sine wave generating means for generating a sine wave that can be changed to an amplitude larger than the triangular wave;
Switching signal generating means for generating a switching signal based on a level comparison between the triangular wave and the sine wave;
An inverter circuit that has a switching element that is turned on and off by the switching signal, and generates AC voltage power to be supplied to the load device by the switching operation;
A detection member for detecting a load current supplied from the uninterruptible power supply to the load device ;
When the crest factor value of the load current detected when supplying AC power with a sine wave to the load device is smaller than a predetermined threshold, the load device is determined not to be a capacitor input rectifier load, A judging means for judging that the load device is a capacitor input type rectifier load when the crest factor value is larger than a predetermined threshold;
When it is determined that the load device is a capacitor input type rectifier load, the sine wave generating means generates the sine wave having an amplitude larger than the triangular wave, and it is determined that the load device is not a capacitor input type rectifier load. Control means for generating the sine wave having an amplitude smaller than the triangular wave by the sine wave generating means,
An uninterruptible power supply comprising: When it is determined that the load device is a capacitor input type rectifier load, the control means sets the amplitude of the sine wave to four times or more of the amplitude of the triangular wave, and the load device is a capacitor input type rectifier load. not equal uninterruptible power supply of claim 1, wherein the, to less than one times the amplitude of the triangular wave amplitude of the sine wave when it is determined. The control means outputs a clock signal for outputting a sine wave as an inverter output voltage to the sine wave generating means and a modulation factor designation signal for designating the maximum amplitude of the sine wave,
The sine wave generating means generates a sine wave whose frequency changes according to the clock signal and whose maximum amplitude is specified by the modulation factor specifying signal. The uninterruptible power supply according to claim 2 or 3 . A triangular wave generating means for generating a triangular wave;
Sine wave generating means for generating a sine wave that can be changed to an amplitude larger than the triangular wave;
Switching signal generating means for generating a switching signal based on a level comparison between the triangular wave and the sine wave;
An inverter circuit that has a switching element that is turned on and off by the switching signal, and generates AC voltage power to be supplied to the load device by the switching operation;
A detection member for detecting a load current supplied from the AC power supply device to the load device ;
When the crest factor value of the load current detected when supplying AC power with a sine wave to the load device is smaller than a predetermined threshold, the load device is determined not to be a capacitor input rectifier load, A judging means for judging that the load device is a capacitor input type rectifier load when the crest factor value is larger than a predetermined threshold;
When it is determined that the load device is a capacitor input type rectifier load, the sine wave generating means generates the sine wave having an amplitude larger than the triangular wave, and it is determined that the load device is not a capacitor input type rectifier load. Control means for generating the sine wave having an amplitude smaller than the triangular wave by the sine wave generating means,
An AC power supply device comprising: An AC voltage switching method according to a load device executed by an AC power supply apparatus,
Supplying AC power from the AC power supply device to the load device;
The load current supplied to the load device from the AC power supply device is detected, and the crest factor value of the load current detected when the sine wave AC power is supplied to the load device is greater than a predetermined threshold value. Determining that the load device is not a capacitor input type rectifier load if small, and determining that the load device is a capacitor input type rectifier load if the crest factor value is greater than a predetermined threshold;
When it is determined that the load device is a capacitor input type rectifier load, the level is compared with the triangular wave for the switching signal generating means for generating the switching signal for switching the inverter circuit that generates the AC voltage power. Controlling the amplitude of the sine wave supplied to be larger than the triangular wave and controlling the amplitude of the sine wave to be smaller than the triangular wave when it is determined that the load device is not a capacitor input rectifier load; ,
An AC voltage switching method according to a load device.

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