JP2014176254A - AC power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to keep highly reliable power supply to as many electric loads L as possible by effectively using limited power supply ability.SOLUTION: An overload time amplitude reduction amount setting unit 110 calculates an amplitude adjustment amount ΔA by PI operation using an undervoltage value ΔVdcdown that is a value obtained by subtracting DC voltage Vdc from preset target DC voltage Vdcdown, when the DC voltage Vdc decreases because of an overload. An amplitude adjustment unit 120 calculates final target amplitude A* by subtracting the amplitude adjustment amount ΔA from basic target amplitude A'*. A PI control unit 124 calculates an inverter output voltage instruction Vinv* that is a target value of output voltage of an inverter circuit 50, by the PI operation on the basis of a deviation ΔVac between target output voltage Vac* calculated using the target amplitude A* and output voltage Vac.

Description

  The present invention relates to an AC power supply apparatus that converts DC power into AC by an inverter and supplies power.

  2. Description of the Related Art Conventionally, an AC power supply device that supplies power in place of a commercial power supply even when the commercial power supply is stopped is known. For example, it is proposed in Patent Document 1 and the like. For example, such an AC power supply device receives power supply from a generator or a battery, converts the DC power into DC power having a constant voltage by a converter, and then converts the DC power into AC having the same voltage waveform as that of a commercial power supply by an inverter.

  The commercial power supply has an allowable voltage range. For example, in a 200V system power supply, an allowable range of ± 10% is set with reference to 202V. Therefore, it is necessary for the AC power supply apparatus to supply power at a voltage within the specified range. For example, when the output voltage of the AC power supply apparatus is set to 202 V, the amplitude of the AC voltage is 286 V (= 202 × √2), so the output of the converter is set so that the input voltage of the inverter is 286 V or more. The voltage is set. If the input voltage of the inverter is 286 V or higher (for example, 300 V, 350 V, etc.), an AC voltage having a sine waveform with an amplitude of 286 V can be output by PWM control of the switching element of the inverter.

  In addition, an electrical device that receives power supply from an AC power supply apparatus is originally designed on the assumption that power is supplied from a commercial power source. Therefore, it is desirable that the voltage waveform of the power output from the AC power supply device is a sine wave shaped to the same extent as the commercial power supply and has a low distortion rate.

JP 2005-86870 A

(Problems to be solved by the invention)
If the amount of power supplied to the electric load increases and exceeds the rated output of the converter, the converter cannot maintain the output of a constant set voltage regardless of its own voltage control. As a result, when the output voltage of the converter falls below 286V, the inverter can output the target AC voltage despite executing the PWM control targeting the output of the AC voltage of 202V (effective value). Disappear. In this case, as shown in FIG. 4, the output voltage waveform of the AC power supply apparatus is not a sine wave but a mountain-shaped waveform with the top cut off, and the distortion rate of the output voltage increases. This distortion of the voltage waveform is not preferable particularly in a capacitor input type electric device.

  Moreover, although there is a user's need to use as many electrical loads as possible, such a need cannot be met due to a decrease in the output voltage of the AC power supply device and an increase in the distortion rate.

  Further, in the device proposed in Patent Document 1, when the output current of the inverter exceeds a predetermined value due to overload, a configuration is adopted in which the gate switching is performed for a predetermined time with respect to the switching element of the inverter. However, there is a problem that the output voltage of the inverter becomes discontinuous and the output voltage of the inverter is greatly distorted.

  The present invention has been made to address the above-described problems, and is intended to maintain a reliable power supply for as many electrical loads as possible by effectively using the limited power supply capability. Objective.

(Means for solving the problem)
A feature of the present invention that solves the above problems is that a DC power output unit (30, 40) that inputs power output from a power source (20), converts the power into DC power controlled to a constant set voltage, and outputs the DC power. An inverter circuit (50) that inputs DC power output from the DC power output unit and converts it into AC, and the inverter circuit so that the device output voltage (Vac) becomes a sine wave having a preset amplitude. AC power supply apparatus comprising inverter control means (100) for controlling the operation of
DC voltage detection means (41) for detecting a DC voltage (Vdc) supplied from the DC power output unit to the inverter circuit, and based on the DC voltage detected by the DC voltage detection means, the DC voltage is An overload state detecting means (111) for detecting an overload state that is below an overload determination threshold value (Vdc1) lower than a set voltage, and a target of the device output voltage when the overload state is detected. The value is changed to a sine wave voltage having an amplitude (A ′ * − ΔA) smaller than the set amplitude (A ′ *), and the inverter voltage command ( Overload control means (110, 120 to 124) for setting Vinv *).

  In the present invention, the DC power output unit inputs the power output from the power supply, converts the DC power to a constant set voltage, and outputs the DC power to the inverter circuit. As a power source, a power source other than a commercial power source, for example, a generator or a battery can be used. The DC power output unit can be constituted by, for example, a converter circuit that converts AC power output from the generator into DC, and converter control means that controls the output voltage of the converter circuit to a constant set voltage. Alternatively, a DC / DC converter circuit that converts the voltage of DC power output from a DC power source such as a battery and converter control means that controls the output voltage of the DC / DC converter circuit to a constant set voltage can be used.

  The inverter circuit inputs the DC power output from the DC power output unit and converts it into AC. The inverter control means controls the operation of the inverter circuit so that the device output voltage (output voltage of the AC power supply device) becomes a sine wave having a preset amplitude.

  The DC power output unit has a drooping characteristic that when the power supply amount to the electric load is in an overload state exceeding the rated output, the DC output voltage greatly decreases as the power supply amount exceeds the rated output. For this reason, when the AC power supply device is in an overload state, it cannot output a sine wave voltage having a set amplitude, and the distortion rate of the device output voltage increases. In view of this, the present invention includes DC voltage detection means, overload state detection means, and overload control means. The DC voltage detection means detects a DC voltage supplied from the DC power output unit to the inverter circuit. The overload state detection unit detects an overload state in which the DC voltage is below an overload determination threshold that is lower than the set voltage, based on the DC voltage detected by the DC voltage detection unit.

  When an overload condition is detected, the overload control means changes the target value of the device output voltage to a sine wave voltage having an amplitude smaller than the set amplitude at the time of non-overload, and the target value after the device output voltage is changed Set the inverter voltage command to follow the value. Therefore, AC power having a sinusoidal voltage with a small distortion rate can be supplied. Further, since the amount of power supplied to the electric load is reduced, the output voltage of the DC power output unit can be increased, and as a result, a drop in the device output voltage can be suppressed. As a result, it is possible to maintain a reliable power supply to as many electrical loads as possible by effectively using the limited power supply capability.

  Another feature of the present invention is that the overload control means has an amount (ΔVdown) in which the DC voltage (Vdc) detected by the DC voltage detection means is lower than a preset reference voltage (Vdcdown). Amplitude adjustment amount calculation means (112, 113) for calculating an amplitude adjustment amount (ΔA) for reducing the amplitude of the device output voltage as the value increases, and a target value of the device output voltage, the set amplitude as the amplitude adjustment amount. And an amplitude adjusting means (120) for setting the sine wave voltage of the adjusted amplitude (A ′ * − ΔA) adjusted in step (1).

  In the present invention, the amplitude adjustment amount calculation means that the amplitude adjustment amount calculation means decreases the amplitude of the device output voltage as the amount by which the DC voltage detected by the DC voltage detection means is lower than a preset reference voltage is larger. Is calculated. Then, the amplitude adjusting means sets the target value of the device output voltage to a sine wave voltage having an adjusted amplitude obtained by adjusting the set amplitude with the amplitude adjustment amount. Therefore, it is possible to set the target value of the device output voltage having an appropriate amplitude according to the input voltage of the inverter circuit.

  Another feature of the present invention is that the amplitude adjustment amount calculation means sets the reference voltage (Vdcdown) as a target value in feedback control so that the DC voltage (Vdc) follows the reference voltage. The purpose is to control the amplitude of the device output voltage.

  In the present invention, the reference voltage is set as a target value in feedback control, and the amplitude of the device output voltage is controlled so that the DC voltage follows the reference voltage. Therefore, it is possible to easily control the amplitude of the device output voltage.

  In the above description, in order to help the understanding of the invention, the reference numerals used in the embodiment are attached in parentheses to the configuration of the invention corresponding to the embodiment. It is not limited to the embodiment defined by the reference numerals.

It is a schematic block diagram of the alternating current power supply apparatus which concerns on this embodiment. It is a functional block diagram of an inverter controller. It is a graph showing the apparatus output voltage waveform by which the amplitude was adjusted by output suppression control. It is a graph showing the apparatus output voltage waveform at the time of an overload when not implementing output suppression control.

  Hereinafter, an AC power supply apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an AC power supply device 1 that supplies AC power to an electric load. The AC power supply device 1 converts the engine 10, the generator 20 connected to the engine 10 to generate three-phase AC power by the operation of the engine 10, and the three-phase AC power output from the generator 20 into DC power. Converter circuit 30, converter controller 40 that controls the operation of converter circuit 30, inverter circuit 50 that converts DC power output from converter circuit 30 into AC power, inverter controller 100 that controls the operation of inverter circuit 50, And a filter circuit 60 for smoothing the output of the inverter circuit 50.

  The AC power supply device 1 of this embodiment is provided in an outdoor unit of an engine-driven air conditioner (not shown). The engine-driven air conditioner includes a compressor that is driven by the power of the engine 10 and compresses the refrigerant by the compressor. The engine-driven air conditioner includes the AC power supply device 1 so that the electric equipment in the air conditioner can be operated even during a power failure when the supply of commercial power is stopped. At the time of a power failure, by starting the engine 10 with a battery, the generator 20 is driven by the power of the engine 10 to supply electric power to an electrical device (for example, a fan) in the air conditioner. In addition, the AC power supply device 1 includes external output terminals 70 and 71 so that the AC power supply device 1 can be used not only as an electric device in the air conditioner but also as an emergency power source for electric appliances used in homes, offices, factories, and the like. . For this reason, the AC power supply device 1 is a power supply source to the electric load in an emergency in which power cannot be supplied from the commercial power supply.

  The generator 20 outputs the generated three-phase AC power to the converter circuit 30. The converter circuit 30 is a three-phase bridge circuit in which semiconductor switching elements 31 to 36 such as MOS-FETs (Metal-Oxide-Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors) are bridge-connected. According to the output gate signal, the on / off states of the switching elements 31 to 36 are switched to convert the three-phase AC power into DC power. The converter circuit 30 is connected to the inverter circuit 50 via the two DC lines 37 and 38, and outputs the converted DC power to the inverter circuit 50.

  A smoothing capacitor 39 is provided between the two DC lines 37 and 38. In addition, a DC voltage sensor 41 for detecting a voltage between the DC lines 37 and 38 is provided. The DC voltage sensor 41 supplies the DC voltage Vdc, which is the detected value, to the converter controller 40 and the inverter controller 100. Converter controller 40 feeds back DC voltage Vdc and outputs a gate signal in which the duty ratio is set so that DC voltage Vdc matches target DC voltage Vdc * to switching elements 31 to 36 of converter circuit 30. Thereby, the output DC voltage of the converter circuit 30 is maintained at the target DC voltage Vdc *.

  The inverter circuit 50 is an H-bridge circuit in which semiconductor switching elements 51 to 54 such as MOS-FETs and IGBTs are bridge-connected, and the switching elements 51 to 54 are turned on / off according to a gate signal output from the inverter controller 100. Is switched to convert DC power into single-phase AC power. An AC line 55 is connected to the connection between the switching element 51 serving as the upper arm and the switching element 52 serving as the lower arm, and an AC is connected to the connection between the switching element 53 serving as the upper arm and the switching element 54 serving as the lower arm. Line 56 is connected.

  In the inverter circuit 50, the switching element 51 and the switching element 54 are turned on, and the switching element 52 and the switching element 53 are turned off so that a current flows in the direction of arrow a. Is turned on, and the switching element 51 and the switching element 54 are turned off to allow current to flow in the direction of the arrow b. By switching on and off the switching elements 51 to 54 and controlling the duty ratio, an AC voltage is generated between the AC line 55 and the AC line 56.

  A filter circuit 60 is provided on the output side of the inverter circuit 50. The filter circuit 60 includes a reactor 61 provided in series with the AC line 55 and a capacitor 62 provided between the AC lines 55 and 56, and reduces output current ripple.

  External output terminals 70 and 71 are provided on the output side of the filter circuit 60. A plurality of electrical loads L that receive AC power supply are connected to the external output terminals 70 and 71. Further, an output voltage sensor 43 that detects a voltage between the external output terminals 70 and 71 is provided. The output voltage sensor 43 detects the output voltage Vac of the AC power supply device 1 and supplies the output voltage Vac, which is the detected value, to the inverter controller 100. Hereinafter, the voltage output from the AC power supply device 1 is referred to as a device output voltage.

  The inverter controller 100 includes a microcomputer and a drive circuit that outputs a gate signal to the switching elements 51 to 54 as main parts, and the output voltage Vac detected by the output voltage sensor 43 is a preset target output voltage Vac *. The switching elements 51 to 54 of the inverter circuit 50 are controlled so as to coincide with.

  In the AC power supply device 1 of the present embodiment, the target output voltage is set to AC 202V so that power can be supplied to the 200V electric load L. Therefore, the waveform of the target output voltage Vac * of the AC power supply apparatus 1 is set to a sine wave having an amplitude of 286 V (= 202 × √2) and the same frequency f as that of the commercial power supply. Further, the 100V electric load L is configured such that the 200V power supply is stepped down by a transformer (not shown) to be converted into a 100V power supply and supplied.

  Thus, in order to supply 202V AC power to the electric load L, the input voltage of the inverter circuit 50 needs to be equal to or larger than the amplitude value (286V) of the device output voltage. Here, in order to simplify the explanation, numerical values are shown assuming that the voltage drop of the reactor 61 and the switching elements 51 to 54 of the filter circuit 60 is zero. In the present embodiment, the target DC voltage Vdc *, which is the target value of the output voltage of the converter circuit 30, is set to a value of 286V or higher, for example, 340V. Therefore, the converter controller 40 controls the duty ratio of the gate signals of the switching elements 31 to 36 so that the DC voltage Vdc detected by the DC voltage sensor 41 follows the target DC voltage Vdc *.

  In the AC power supply device 1, AC power input from the generator 20 is converted to DC by the converter circuit 30, and further converted to AC by the inverter circuit 50. When the amount of power supplied to the electric load L increases and exceeds the rated output of the converter circuit 30, the converter circuit 30 has a drooping characteristic that the DC output voltage greatly decreases as the degree of exceeding the rated output increases. For this reason, regardless of the voltage feedback control of the converter controller 40, the output voltage of the converter circuit 30 cannot be maintained at a constant target DC voltage Vdc *. In this case, there is no problem if the output voltage of the converter circuit 30 is 286V or higher, but if it falls below 286V, the AC output voltage of the inverter circuit 50 decreases. If the voltage feedback control by the inverter controller 100 is continued in this state as it is, the output voltage waveform of the inverter circuit 50 will not be a sine wave but a chevron waveform with the top cut off as shown in FIG. . In this case, not only does the distortion rate of the AC voltage increase, but also the power supply to the electric load L is not suppressed. .9 × √2).

  Therefore, in the AC power supply apparatus 1 according to the present embodiment, the amplitude of the target output voltage Vac * of the apparatus output voltage is defined by effectively utilizing that the voltage regulation of the AC power supply is in a range of ± 10% with reference to 202V. By reducing the power supply within the range, the power supply amount is narrowed down so that power supply with an appropriate voltage can be continued for as many electrical loads L as possible. Hereinafter, the process of the inverter controller 100 performed for that purpose will be described.

  FIG. 2 is a functional block diagram showing functions of the inverter controller 100. The inverter controller 100 includes an overload amplitude reduction amount setting unit 110, an amplitude adjustment unit 120, an output waveform command unit 121, a target output voltage setting unit 122, an output voltage deviation calculation unit 123, and a PI control unit 124. PWM controller 125. The overload amplitude reduction amount setting unit 110 includes an output suppression control determination unit 111, a DC voltage deviation calculation unit 112, a PI control unit 113, a limiter 114, and a control switching unit 115. Further, the inverter controller 100 converts the detection signal representing the DC voltage Vdc output from the DC voltage sensor 41 and the output voltage Vac output from the output voltage sensor 43 into a digital value at a predetermined sampling period. The sensor value converted into the digital value represents an instantaneous value.

  First, the basic process in the normal time, that is, when the DC voltage input to the inverter circuit 50 is an appropriate value will be described. The amplitude adjustment unit 120 includes a basic target amplitude A ′ * of a preset device output voltage (output voltage of the AC power supply device 1) and an amplitude adjustment amount ΔA set by the overload amplitude reduction amount setting unit 110. Is read. The basic target amplitude A ′ * represents the amplitude of the original target output voltage Vac * of the AC power supply device 1 (when not overloaded). In the present embodiment, since the target output voltage Vac * is set to the effective value 202V, the basic target amplitude A ′ * is 286V (= 202 × √2). The amplitude adjustment unit 120 calculates the final target amplitude A * by subtracting the amplitude adjustment amount ΔA from the basic target amplitude A ′ *. The amplitude adjustment amount ΔA is calculated by the overload amplitude reduction amount setting unit 110, and is set to zero (ΔA = 0) in a normal time that is not an overload state. Accordingly, at the normal time, the basic target amplitude A ′ * becomes the final target amplitude A * (A * ← A * ′). The amplitude adjustment unit 120 outputs the calculated target amplitude A * to the target output voltage setting unit 122.

  The output waveform command unit 121 generates a sine wave setting signal for setting the sine waveform of the AC voltage output from the AC power supply device 1. The sine wave setting signal is a signal represented by sin (2πf × t). Here, f is the frequency of the target output voltage Vac *, and the same value as the frequency of the commercial power supply is set. T represents time. The sine wave used here represents a waveform shape without any intention to distinguish between a sine wave and a cosine wave. Further, the frequency f is not necessarily the same as the frequency of the commercial power source. The output waveform command unit 121 outputs the generated sine wave setting signal to the target output voltage setting unit 122.

  The target output voltage setting unit 122 calculates the final target output voltage Vac * by multiplying the target amplitude A * by the sine wave setting signal (sin (2πf × t)). The target output voltage setting unit 122 outputs the calculated target output voltage Vac * (= A * × (sin (2πf × t)) to the output voltage deviation calculation unit 123.

  The output voltage deviation calculation unit 123 reads the output voltage Vac detected by the output voltage sensor 43 and calculates a deviation ΔVac (= Vac * −Vac) between the target output voltage Vac * and the output voltage Vac. The output voltage deviation calculation unit 123 outputs the calculated deviation ΔVac to the PI control unit 124.

  The PI control unit 124 calculates an inverter output voltage command Vinv * that is a target value of the output voltage of the inverter circuit 50 by PI calculation (proportional integration calculation) based on the deviation ΔVac. The PI control unit 124 outputs the calculated inverter output voltage command Vinv * to the PWM control unit 125.

  The PWM control unit 125 generates a gate signal that sets the on / off switching timing of the switching elements 51 to 54 of the inverter circuit 50 based on the inverter output voltage command Vinv *. The PWM control unit 125 outputs the generated gate signal to the switching elements 51 to 54 of the inverter circuit 50. As a result, a voltage following the inverter output voltage command Vinv * is output from the inverter circuit 50. Thereby, the AC power controlled to the target amplitude A * is output from the AC power supply device 1.

  Next, the overload amplitude reduction amount setting unit 110 will be described. Even when the device output voltage falls below the specified range due to overload, the power supply to the electrical load L is reduced by lowering the target amplitude A * within the specified range, and the power supply set to a sinusoidal voltage is set. Can be continued. As a result, the DC voltage (output voltage of the converter circuit 30) input to the inverter circuit 50 can be increased. With such a principle, it is possible to suppress the input voltage of the inverter circuit 50 from falling below a limit voltage 257 V (= 202 × 0.9 × √2) that can output the specified lower limit value of the AC voltage, and a sine with a low distortion rate. Enables the continuation of power supply with wavy AC voltage. Hereinafter, controlling the target amplitude A * to be lower than the basic target amplitude A ′ * is referred to as output suppression control.

  The output suppression control determination unit 111 is a functional unit that determines the timing for starting and ending the output suppression control. The output suppression control determination unit 111 reads the DC voltage Vdc output from the DC voltage sensor 41, and sets the output suppression determination flag F to “0” when the DC voltage Vdc is equal to or greater than the output suppression control start threshold Vdc1. Set. When the output suppression determination flag F is set to “0” and the DC voltage Vdc falls below the output suppression control start threshold Vdc1, the output suppression determination flag F is changed from “0” to “1”. Switch. When the output suppression determination flag F is set to “1” and the DC voltage Vdc exceeds the output suppression control end threshold Vdc2, the output suppression determination flag F is changed from “1” to “0”. Switch. The output suppression control determination unit 111 outputs the set output suppression control flag F to the control switching unit 115.

  The output suppression control start threshold value Vdc1 is a preset threshold value for determining an overload state, and is a value lower than the target DC voltage Vdc * of the converter circuit 30 and the device output voltage becomes a specified lower limit value. The voltage value is set to be equal to or higher than the input voltage of the inverter circuit 50. For example, the output suppression control start threshold value Vdc1 is set to the input voltage of the inverter circuit 50 when the device output voltage becomes the specified lower limit value (202 × 90%). In this case, the output suppression control start threshold value Vdc1 is 257 V (= 202 × 0.9 × √2). Further, the output suppression control end threshold value Vdc2 is set with hysteresis in order to prevent control chattering, and is set to a voltage higher than the output suppression control start threshold value Vdc1 by a predetermined value. Note that it is not always necessary to provide hysteresis. In this case, the output suppression control end threshold Vdc2 may be the same as the output suppression control start threshold Vdc1.

  The DC voltage deviation calculation unit 112 reads the DC voltage Vdc output from the DC voltage sensor 41 and subtracts the DC voltage Vdc from the target DC voltage Vdcdown preset for output suppression control. The undervoltage value ΔVdcdown (= Vdcdown−Vdc) is calculated. The target DC voltage Vdcdown is such that the AC voltage output from the inverter circuit 50 is lower than the target value (effective value 202V) in a normal (non-overloaded state) and is not less than the specified lower limit value (effective value 202 × 0.9V). Is set to a value that falls within the range. In the present embodiment, the target DC voltage Vdcdown is set to 257 V (= 202 × 0.9 × √2), which is the same as the output suppression control start threshold Vdc1. The target DC voltage Vdcdown is a calculated setting value in the inverter controller 100 for controlling the amplitude of the device output voltage, and is not the target value of the output voltage of the converter circuit 30 in the converter controller 40. To the last, the output voltage of the converter circuit 30 is controlled by the converter controller 40 using the constant target DC voltage Vdc * as a target value regardless of the overload state. The DC voltage deviation calculation unit 112 outputs the calculated undervoltage value ΔVdcdown to the PI control unit 113.

  The PI control unit 113 calculates the amplitude adjustment amount ΔA by PI calculation (proportional integration calculation) based on the deviation ΔVdcdown. This amplitude adjustment amount ΔA sets a reduction width for reducing the amplitude of the device output voltage from the basic target amplitude A ′ *. By this PI calculation, the larger the deviation ΔVdcdown, the larger the amplitude adjustment amount ΔA is calculated. The PI control unit 113 outputs the calculated amplitude adjustment amount ΔA to the limiter 114.

  The limiter 114 sets the amplitude adjustment amount ΔA to zero (ΔA ← 0) when the input amplitude adjustment amount ΔA is equal to or less than zero (ΔA ← 0), and when the amplitude adjustment amount ΔA is a positive value, The value is set to the amplitude adjustment amount ΔA. The limiter 114 outputs the set amplitude adjustment amount ΔA to the control switching unit 115.

  The control switching unit 115 receives the output suppression determination flag F from the output suppression control determination unit 111. When the output suppression determination flag F is “1”, the control switching unit 115 selects the amplitude adjustment amount ΔA input from the limiter 114 and outputs it. When the suppression determination flag F is “0”, the amplitude adjustment amount ΔA set to the value zero is selected. Then, the selected amplitude adjustment amount ΔA is output to the amplitude adjustment unit 120. As described above, the amplitude adjustment unit 120 subtracts the amplitude adjustment amount ΔA from the basic target amplitude A ′ * to calculate the final target amplitude A *. Therefore, in an overload state where the output suppression control is executed, the target amplitude A * becomes smaller as the input voltage of the inverter circuit 50 (the output voltage of the converter circuit 30) is lower than the target DC voltage Vdcdown. Is set. Thereby, the amplitude of the sine wave of the target output voltage Vac * is adjusted to be small. Therefore, the power supplied to the electric load L is reduced. The narrowing of power supply to the electric load L works to increase the input voltage of the inverter circuit 50 (the output voltage of the converter circuit 30). For this reason, in an overload state, the input voltage of the inverter circuit 50 follows the target DC voltage Vdcdown within the range of power supply capability. When the electric power used by the electric load L decreases, the DC voltage output from the converter circuit 30 is increased by the voltage control of the converter controller 40, and the normal control state is restored.

  According to the AC power output apparatus 1 of the present embodiment described above, when the amount of power supplied to the electric load L increases and the input voltage of the inverter circuit 50 falls below the output suppression control start threshold Vdc1, the AC power supply The target amplitude A * of the device output voltage is reduced by effectively utilizing the voltage regulation range of Therefore, as shown in FIG. 3, AC power having a sinusoidal voltage with a small distortion rate can be supplied. In this case, since the amount of power supplied to the electric load L is reduced, it is possible to suppress a drop in the device output voltage. Further, in the overload state, the amplitude adjustment amount ΔA is set by the PI control using the deviation between the target DC voltage Vdcdown and the input voltage of the inverter circuit 50. Therefore, an appropriate target corresponding to the input voltage of the inverter circuit 50 is set. The amplitude A * can be set. Further, the amplitude control of the device output voltage can be easily performed. As a result, it is possible to maintain a reliable power supply to as many electrical loads L as possible by effectively using the limited power supply capability. In addition, since the distortion rate of the device output voltage can be suppressed to a low level, the influence on the capacitor input type electric device can be suppressed.

  Further, the AC power supply device 1 of the present embodiment is provided in an engine-driven air conditioner, operates a generator 20 by an engine 10 that drives a compressor, and converts the power generated by the generator 20 into a converter circuit 30. Is converted to direct current, and the direct current power is converted to alternating current by the inverter circuit 50. Therefore, the engine 10 can be used effectively.

  Although the AC power supply device 1 according to the present embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the present embodiment, the generator 20 is used as the power source of the AC power supply apparatus 1, but a battery may be used instead. In that case, the converter circuit 30 and the converter controller 40 may be configured by a DC / DC converter (a DC / DC converter circuit and a DC / DC converter controller).

  In the present embodiment, the DC power is converted into single-phase AC power by the inverter circuit 50 using the H bridge circuit, but the DC power is converted into three-phase AC power by the inverter circuit using the three-phase bridge circuit. It may be configured to be converted and supplied.

  The AC power supply device 1 of the present embodiment is provided in an engine-driven air conditioner. For example, the AC power supply device 1 is applied to a cogeneration device that uses engine exhaust heat to extract power, heat, and cold. Also good.

  DESCRIPTION OF SYMBOLS 1 ... AC power supply device, 10 ... Engine, 20 ... Generator, 30 ... Converter circuit, 40 ... Converter controller, 41 ... DC voltage sensor, 43 ... Output voltage sensor, 50 ... Inverter circuit, 51, 52, 53, 54 DESCRIPTION OF SYMBOLS ... Switching element, 60 ... Filter circuit, 70, 71 ... External output terminal, 100 ... Inverter controller, 110 ... Overload amplitude reduction amount setting part, 111 ... Output suppression control determination part, 112 ... DC voltage deviation calculation part, 113 DESCRIPTION OF SYMBOLS ... PI control part 114 ... Limiter 115 ... Control switching part 120 ... Amplitude adjustment part 121 ... Output waveform command part 122 ... Target output voltage setting part 123 ... Output voltage deviation calculation part 124 ... PI control part, 125: PWM control unit, A *: target amplitude, A '*: basic target amplitude, Vac *: target output voltage.

Claims (3)

DC power output unit that inputs the power output from the power supply, converts it to DC power controlled to a constant set voltage, and outputs it,
An inverter circuit that inputs DC power output from the DC power output unit and converts it into AC,
An AC power supply apparatus comprising: inverter control means for controlling the operation of the inverter circuit so that the apparatus output voltage becomes a sine wave having a preset set amplitude;
DC voltage detecting means for detecting a DC voltage supplied from the DC power output unit to the inverter circuit;
Based on the DC voltage detected by the DC voltage detection means, overload condition detection means for detecting an overload condition in which the DC voltage is below an overload determination threshold lower than the set voltage;
When the overload condition is detected, the target value of the device output voltage is changed to a sine wave voltage having an amplitude smaller than the set amplitude, and the inverter is set so that the device output voltage follows the changed target value. And an overload control means for setting the voltage command of the AC power supply device. The overload control means includes:
Amplitude adjustment amount calculation means for calculating an amplitude adjustment amount for reducing the amplitude of the device output voltage, as the amount by which the DC voltage detected by the DC voltage detection means is lower than a preset reference voltage is larger.
2. The AC power supply according to claim 1, further comprising: an amplitude adjusting unit that sets a target value of the device output voltage to a sine wave voltage having an adjusted amplitude obtained by adjusting the set amplitude by the amplitude adjustment amount. apparatus.   The amplitude adjustment amount calculation means sets the reference voltage as a target value in feedback control, and controls the amplitude of the device output voltage so that the DC voltage follows the reference voltage. Item 3. The AC power supply device according to Item 2.

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