JP2006121816A - Inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize an internal power conversion loss in accordance with an output setting voltage, an output current, or an AC power supply voltage, in an inverter device that converts power to the AC power of an arbitrary voltage and an arbitrary frequency by receiving the power from an AC power supply. <P>SOLUTION: This inverter device comprises an AC-DC conversion means 2 that converts the power of the AC power supply 1 to an optimum DC voltage, a DC-AC conversion means 3 that converts the DC power converted by the AC-DC conversion means 2 to the AC power, and a DC-voltage optimizing means 4 that controls the DC-AC conversion means 3 so as to minimize the power conversion loss, and by this, the AC power of the arbitrary voltage and the arbitrary frequency can be output, thus obtaining an effect that the power conversion loss can be minimized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a high efficiency inverter using power conversion technology.

  In recent years, fossil fuel depletion and global warming have occurred due to an increase in the load on ordinary households, and there has been a demand for effective use of energy by energy-saving devices such as power-saving devices or reduction of standby power for various electrical devices. Yes.

  Conventionally, as this type of energy-saving technology and apparatus, there are known ones for home use or business use that have a function of reducing excessive voltage of AC voltage and reducing power consumption (for example, see Patent Document 1). .

  The power saving device will be described below with reference to FIG.

  As shown in the figure, a power saving apparatus 101 includes a series transformer 104 disposed between an AC power supply 102 and a load 103, and a regenerative inverter 105 whose output side is connected to the secondary winding of the series transformer 104. As a result, the voltage applied to the load 103 is controlled. Also, with this configuration, the voltage applied to the load 103 can be continuously controlled by continuously controlling the output of the regenerative inverter 105, and stable power saving power can be supplied to the load 103 side.

  Conventionally, a general-purpose inverter equipped with high-efficiency technology that reduces power consumption is also known (see, for example, Patent Document 1).

  In addition, in a grid-connected inverter using inverter technology, as a grid-connected power converter that links the power generated by the power generator to the grid side, the voltage fluctuation of the DC power supply is detected, and the DC power supply is detected based on the detected voltage fluctuation amount. The one that operates at the maximum power point is known (for example, see Patent Document 2).

  Hereinafter, the grid interconnection inverter will be described with reference to FIG.

As shown in FIG. 10, the voltage of the DC power supply 106 is smoothed by the input capacitor 107 and then boosted to a voltage higher than the system voltage by the boost converter 108. The output of boost converter 108 is smoothed by intermediate capacitor 109 and input to inverter 110. Inverter 110 converts the output of boost converter 108 into alternating current power, and injects alternating current synchronized with system 111. Further, the voltage fluctuation of the DC power supply 106 within a half cycle of the system 111 is detected by the input voltage fluctuation detecting means 112 and output to the control circuit 113. The control circuit 113 determines the ON time of the switching elements constituting the boost converter 108 and the inverter 110 so that the power drawn from the DC power supply 106 is maximized.
JP 2002-270884 A (FIG. 1) JP 2004-135409 A (FIG. 1)

  In such a power saving device using the conventional inverter technology, the power supply voltage supplied to the load is lowered, and as a result, a power saving effect can be obtained for a load close to a pure resistance typified by lighting or the like. As a device for promoting energy saving, internal consumption of the power saving device occurs, so when the load power is small, the loss inside the device becomes larger than the power saving power of the load, resulting in a problem of increasing the power consumption. There is a demand to suppress the power consumption of the device itself for promoting energy saving.

  In addition, in the grid-connected inverter using the conventional inverter technology, when the generated power from the DC power source, for example, the solar battery is particularly small, the optimal control for following the maximum power of the generated power is performed. As a result, there is a problem that the power loss ratio increases and the effective utilization rate of the generated power decreases, and it is required not only to maximize the generated power but also to minimize the internal loss of the grid-connected inverter.

  The present invention solves such conventional problems, and an object of the present invention is to provide an inverter device that can minimize power loss during power conversion in the inverter device and maximize conversion efficiency. .

  In order to achieve the above object, the inverter device of the present invention has AC-DC converting means for converting an AC power source into an optimum DC voltage, and DC-- which converts DC power converted by the AC-DC converting means into AC power. An AC conversion means and a DC voltage optimization means for controlling the AC-DC conversion means so as to minimize the power conversion loss are provided.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  The DC voltage optimizing means is configured to control so as to minimize the power conversion loss of the AC-DC converting means.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  Further, the DC voltage optimizing means is configured to control so as to minimize the power conversion loss of the DC-AC converting means.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  Further, the DC voltage optimizing means is configured to control so as to minimize the sum of the power conversion losses of the AC-DC converting means and the DC-AC converting means.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  Further, the DC voltage optimization means is configured to change the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss in accordance with the output AC command voltage.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  Further, the DC voltage optimization means is configured to change the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss according to the load current connected to the DC-AC conversion means.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  Further, the DC voltage optimization means is configured to change the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss in accordance with the input current of the DC-AC conversion means.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  Further, the DC voltage optimization means is configured to change the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss in accordance with the input power of the DC-AC conversion means.

  With this means, in a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion can be performed in accordance with the output conditions, and the loss inside the device can be minimized. An inverter device is obtained.

  According to the present invention, AC-DC conversion means for converting an AC power source into an optimal DC voltage, DC-AC conversion means for converting DC power converted by the AC-DC conversion means into AC power, and power conversion loss In a general-purpose inverter device for supplying an arbitrary load, when outputting an arbitrary voltage and frequency, by including a DC voltage optimizing unit that controls the AC-DC converting unit so as to minimize the It is possible to provide an inverter device that can perform optimum conversion in accordance with output conditions and minimize the loss inside the device.

  Further, the DC voltage optimizing means is configured to control so as to minimize the power conversion loss of the AC-DC converting means, so that in the general-purpose inverter device that supplies an arbitrary load, the output of an arbitrary voltage and frequency Therefore, it is possible to provide an inverter device that can perform optimum conversion according to the output condition and minimize the loss inside the device.

  Further, the DC voltage optimizing means is configured to control so as to minimize the power conversion loss of the DC-AC converting means, so that in the general-purpose inverter device that supplies an arbitrary load, the output of an arbitrary voltage and frequency Therefore, it is possible to provide an inverter device that can perform optimum conversion according to the output condition and minimize the loss inside the device.

  Further, in the general-purpose inverter device for supplying power to an arbitrary load, the DC voltage optimizing unit is configured to control so as to minimize the total power conversion loss of the AC-DC converting unit and the DC-AC converting unit. When outputting an arbitrary voltage and frequency, it is possible to provide an inverter device that can perform optimum conversion according to the output conditions and minimize the loss inside the device.

  Further, the DC voltage optimizing means supplies an arbitrary load by changing the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the output AC command voltage. In the general-purpose inverter device, when outputting an arbitrary voltage and frequency, it is possible to provide an inverter device that can perform optimum conversion according to the output condition and minimize the loss inside the device.

  Further, the DC voltage optimizing means is arbitrarily configured by changing the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the load current connected to the DC-AC converting means. In general-purpose inverter devices that supply power to a load, an inverter device can be provided that performs optimum conversion according to output conditions when outputting an arbitrary voltage and frequency, and can minimize loss inside the device. .

  Further, the DC voltage optimizing means is configured to change the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the input current of the DC-AC converting means, so that an arbitrary load can be obtained. In the general-purpose inverter device supplied to the device, when outputting an arbitrary voltage and frequency, an optimal conversion can be performed in accordance with the output conditions, and an inverter device capable of minimizing the loss inside the device can be provided.

  Further, the DC voltage optimizing means is configured to change the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the input power of the DC-AC converting means, so that any load can be obtained. In the general-purpose inverter device supplied to the device, when outputting an arbitrary voltage and frequency, an optimal conversion can be performed in accordance with the output conditions, and an inverter device capable of minimizing the loss inside the device can be provided.

  The invention according to claim 1 of the present invention is an AC-DC conversion means for converting an AC power source into an optimum DC voltage, and a DC-AC conversion means for converting DC power converted by the AC-DC conversion means into AC power. And a DC voltage optimizing means for controlling the AC-DC converting means so as to minimize the power conversion loss. In the general-purpose inverter device for supplying an arbitrary load, an arbitrary voltage and frequency When outputting, an optimum conversion is performed according to the output conditions, and the loss inside the apparatus can be minimized.

  The DC voltage optimizing means is configured to control so as to minimize the power conversion loss of the AC-DC converting means. In the general-purpose inverter device that supplies an arbitrary load, the DC voltage optimizing means has an arbitrary voltage and frequency. When outputting, an optimum conversion is performed according to the output conditions, and the loss inside the apparatus can be minimized.

  Furthermore, the DC voltage optimizing means is configured to control so as to minimize the power conversion loss of the DC-AC converting means. In the general-purpose inverter device that supplies an arbitrary load, the DC voltage optimizing means has an arbitrary voltage and frequency. When outputting, an optimum conversion is performed according to the output conditions, and the loss inside the apparatus can be minimized.

  Further, the DC voltage optimizing means is configured to control so as to minimize the total power conversion loss of the AC-DC converting means and the DC-AC converting means, and is a general-purpose inverter device that supplies an arbitrary load. In this case, when outputting an arbitrary voltage and frequency, optimum conversion is performed in accordance with the output condition, and the loss inside the apparatus can be minimized.

  Furthermore, the DC voltage optimizing means is configured to change the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the output AC command voltage, and is supplied to an arbitrary load. In the general-purpose inverter device, when outputting an arbitrary voltage and frequency, an optimum conversion is performed according to the output condition, and the loss inside the device can be minimized.

  Further, the DC voltage optimization means is configured to change the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss according to the load current connected to the DC-AC conversion means, In a general-purpose inverter device that supplies an arbitrary load, when outputting an arbitrary voltage and frequency, an optimum conversion is performed according to the output conditions, and the loss inside the device can be minimized. .

  Further, the DC voltage optimizing means is configured to change the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the input current of the DC-AC converting means. In the general-purpose inverter device supplied to the load, when outputting an arbitrary voltage and frequency, optimum conversion is performed according to the output condition, and the loss inside the device can be minimized.

  Further, the DC voltage optimizing means is configured to change the input voltage of the DC-AC converting means up and down so as to minimize the power conversion loss according to the input power of the DC-AC converting means. In the general-purpose inverter device supplied to the load, when outputting an arbitrary voltage and frequency, optimum conversion is performed according to the output condition, and the loss inside the device can be minimized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a configuration diagram of an inverter device according to the first embodiment.

  As shown in the figure, the inverter device includes an AC-DC converter 2 that converts an AC power source 1 into an optimum DC voltage, and a DC-AC converter that converts the DC power converted by the AC-DC converter 2 into AC power. Means 3 and DC voltage optimizing means 4 for controlling the DC-AC converting means 3 so as to minimize the power conversion loss are provided. The AC-DC converter 2 controls switching of the diodes 2e to 2h, the reactors 2i and 2j, the filter circuit 2k, the smoothing capacitor 2L, and the switching elements 2a to 2d that are anti-parallel to the switching elements 2a to 2d. The full-bridge type boost chopper circuit is configured. Further, the DC-AC conversion means 3 boosts the AC-DC conversion means 2 and converts the power converted into DC into AC, and switching elements 3a to 3d and anti-parallel diodes 3e to 3h The output ripple voltage reduction filter 3i and the inverter control unit 3j for controlling the switching of the switching elements 3a to 3d are provided to constitute a full bridge type inverter circuit. Here, the basic operation of the full bridge type boost chopper circuit and the full bridge type inverter is a known technique, and thus detailed description thereof is omitted.

  Next, the DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG. As shown in the figure, the DC voltage optimization unit 4 calculates the power conversion loss of the AC-DC conversion unit 2. As shown in Formula 1, the calculation method is the static loss of the switching elements 2a to 2d (the AC / DC SW (static loss) and the dynamic loss when the switching elements 2a to 2d are turned on) (the AC / DC SW (dynamic loss: when ON)), and A dynamic loss at the time of off (AC / DC SW (dynamic loss: OFF)) and a loss of 2h from the antiparallel diode 2e (AC / DC D (loss)) are calculated.

  In the static loss in Equation 1, Ipeak indicates the peak value of the instantaneous current during switching, and Vce indicates the voltage between the collector and the emitter when the switching element 1b is on. Also, in the dynamic loss in Equation 1, Esw (ON) indicates the loss at the time of on, Esw (OFF) indicates the loss at the time of off, fsw indicates the switching frequency, and duty is the switching element 2a to 2d. Indicates the value obtained by dividing the on-time by the switching period. Further, in the loss of the diodes 2e to 2h for preventing the backflow, DVec indicates the forward voltage of the diodes 2e to 2h, and Idc_in indicates the current flowing from the diodes 2e to 2h.

  Next, the DC voltage optimization unit 4 calculates the power conversion loss of the DC-AC conversion unit 3. As shown in Formula 2, the calculation method is as follows: static loss of switching elements 3a to 3d (orthogonal SW (static loss)) and dynamic loss when switching elements 3a to 3d are on (orthogonal SW (dynamic loss: when ON)), Calculation of dynamic loss at OFF (orthogonal SW (dynamic loss: OFF)), loss from diode 2e to 2h (orthogonal D (loss)), and loss of output ripple voltage reduction filter 3i (output filter (loss)) To do.

  In the static loss in Equation 2, Ipeak indicates the peak value of the instantaneous current at the time of switching, and Vce indicates the voltage between the collector and the emitter when the switching elements 3a to 3d are on. Also, in the dynamic loss in Equation 2, Esw (ON) indicates the loss at the time of on, Esw (OFF) indicates the loss at the time of off, fsw indicates the switching frequency, and duty indicates the switching elements 3a to 3d. Indicates the value obtained by dividing the on-time by the switching period. In addition, in the loss of the diodes 3e to 3h that are antiparallel, DVec indicates the forward voltage of the diodes 3e to 3h, and Idc_in indicates the current that flows from the diodes 3e to 3h. Further, the loss of the output ripple voltage reduction filter 3i is approximated as A% of the uniform output capacitance Pout.

  Further, the instantaneous voltage of the power supply voltage of the AC power supply 1 is Vac (t), the intermediate DC voltage is Vdc, the instantaneous value of the inverter output voltage is Vout (t), and the ON time of the switching elements 3a to 3d is divided by the switching period T. The value is duty, the off time is Toff, the forward voltage of the diodes 3e to 3h is DVec, the inductance of the output ripple voltage reduction filter 3i is L, and the differential value of the current flowing through the output ripple voltage reduction filter 3i is di / Assuming that dt is given, the relational expression is as shown in Equation 3.

  Here, the total loss of each circuit, that is, the total loss at the time of power conversion of the apparatus, is the loss of the AC-DC conversion means 2 (Σ (AC / DC loss)) and the loss of the DC-AC conversion means 3 (Σ ( This is the sum of orthogonal loss)), as shown in Equation 4.

  At this time, Vdc that minimizes Equation 4 can be calculated by differentiating Vdc and inputting the value determined by each component and each value one hour before. A deviation from the actual intermediate DC voltage Vdc (t) is calculated using Vdc calculated here as a target value, and proportional-integral control is performed to calculate the output command current of the DC-AC converter 3. By outputting the calculated output command current to the DC-AC converter 3, the DC voltage Vdc (t) can be controlled to the command voltage, that is, the target voltage Vdc.

  As described above, according to the first embodiment, the AC-DC converting means 2 that converts the AC power source 1 into the optimum DC voltage, and the DC power converted by the AC-DC converting means 2 are converted into AC power. General-purpose inverter for supplying to an arbitrary load, comprising a DC-AC converting means 3 for performing DC and an AC-DC converting means 2 for controlling the AC-DC converting means 2 so as to minimize power conversion loss In the apparatus, when outputting an arbitrary voltage and frequency, optimal conversion is performed according to the output condition, and the loss inside the apparatus can be minimized.

(Embodiment 2)
The DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG.

  As shown in the figure, the DC voltage optimizing means 4 inputs the power supply voltage of the AC power supply 1 one time before. Next, the DC voltage optimization unit 4 calculates the power conversion loss of the AC-DC conversion unit 2. The calculation method is as shown in Equation 1. The DC voltage Vdc that minimizes the power conversion loss is calculated and used as the Vdc command voltage. By calculating a deviation between the command voltage Vdc and the actual intermediate DC voltage Vdc (t) and performing proportional integral control, the AC-DC conversion means 2 is controlled.

  As described above, according to the second embodiment, the DC voltage optimizing unit 4 is configured to change the input voltage of the DC-AC converting unit 3 so that the power conversion loss is minimized according to the power supply voltage of the AC power source 1. When the AC-DC converter 2 that boosts the power supply voltage of the AC power supply 1 outputs an arbitrary voltage and frequency, it performs optimal conversion in accordance with the output conditions by adopting a configuration in which the power supply voltage of the AC power supply 1 is boosted. Loss can be minimized.

(Embodiment 3)
The DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG.

  As shown in the figure, the DC voltage optimizing means 4 inputs the output voltage of the inverter. An optimum DC voltage Vdc that minimizes the conversion loss of the DC-AC conversion means 3 is calculated from the input output voltage of the inverter. The optimal DC voltage Vdc calculation method is as shown in Equation 5.

  Here, Vec indicates the voltage between the collector and the emitter when the switching elements 3a to 3d are on, ω is the angular velocity, L is the inductance of the output ripple voltage reduction filter 3i, and Ipeak is the peak value of the instantaneous current at the time of switching. Vk indicates a margin voltage for current output. By using Vdc calculated by Equation 5 as a target voltage and calculating a deviation from the actual intermediate DC voltage Vdc (t) and performing proportional-integral control, the AC-DC conversion means 2 is controlled.

  As described above, according to the third embodiment, the DC voltage optimizing unit 4 is configured to change the input voltage of the DC-AC converting unit 3 so that the power conversion loss is minimized according to the level of the output command voltage of the inverter. By adopting a configuration in which the value is changed up and down, the conversion efficiency of the DC-AC conversion means 3 can be improved, that is, the power conversion loss can be minimized and the effective utilization rate of the power of the AC power supply 1 can be improved.

(Embodiment 4)
The DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG.

  As shown in the figure, the DC voltage optimizing means 4 inputs the output command voltage of the inverter. An optimum DC voltage Vdc that minimizes the conversion loss of the DC-AC converter 3 is calculated from the input output command voltage of the inverter. The optimal DC voltage Vdc calculation method is as shown in Equation 6.

  The deviation from the actual intermediate DC voltage Vdc (t) is calculated using Vdc calculated by Equation 6 as a target voltage, and proportional-integral control is performed, thereby controlling the AC-DC converter 2. Here, Vec indicates the voltage between the collector and the emitter when the switching elements 3a to 3d are on, ω is the angular velocity, L is the inductance of the output ripple voltage reduction filter 3i, and Ipeak is the peak value of the instantaneous current at the time of switching. Vk indicates a margin voltage for current output.

  As described above, according to the fourth embodiment, the DC voltage optimization unit 4 is configured to change the input voltage of the DC-AC conversion unit 3 up and down according to the level of the output command voltage of the inverter. Thus, the conversion efficiency of the DC-AC conversion means 3 can be improved, that is, both the minimization of power conversion loss and the improvement of the effective power utilization rate of the AC power supply 1 can be achieved.

(Embodiment 5)
The DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG.

  As shown in the figure, the DC voltage optimizing means 4 inputs a current command value output from the inverter one time before. Next, the input power of the AC power supply 1 one hour before is input, and the target voltage Vdc of the intermediate DC voltage is calculated from the input power of the AC power supply 1 and the current command value output from the inverter. The calculation method of the target voltage Vdc of the intermediate DC voltage is as shown in Equation 7.

  By calculating the deviation between the target voltage Vdc and the actual intermediate DC voltage Vdc (t) and performing proportional integral control, the AC-DC conversion means 2 is controlled.

  As described above, according to the fifth embodiment, the DC voltage optimizing means 4 is configured to change the intermediate DC voltage up and down according to the output current command value of the DC-AC converting means 3 that is linked. Thus, it is possible to achieve both minimization of power conversion loss and improvement of the effective utilization rate of input power of the AC power supply 1.

(Embodiment 6)
The DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG.

  As shown in the figure, the DC voltage optimizing means 4 inputs the input current of the DC-AC converting means 3 one hour before. Next, the power loss of the AC-DC converting means 2 can be calculated by Equation 1 based on the input current that has been input. Furthermore, the power conversion loss of the DC-AC conversion means 3 can be calculated by the formula 2. The total power loss of the AC-DC conversion means 2 and the DC-AC conversion means 3 is the sum of the formulas 1 and 2. Become. The optimum operating point of Vdc can be calculated by differentiating the sum of Equations 1 and 2 with a DC voltage and calculating the minimum point of power loss.

  As described above, according to the sixth embodiment, the DC voltage optimization unit 4 can change the input voltage of the DC-AC conversion unit 3 up and down in accordance with the input current of the DC-AC conversion unit 3. Thus, minimization of power conversion loss and improvement of the effective utilization rate of input power of the AC power source 1 can be achieved at the same time.

(Embodiment 7)
The DC voltage optimizing means 4 is shown in FIG. A control flowchart of the DC voltage optimizing means 4 will be described with reference to FIG.

  As shown in the figure, the DC voltage optimizing means 4 inputs the input current of the DC-AC converting means 3 one hour before. Next, the input DC power is calculated from the input current and the DC voltage one hour before. By dividing the calculated DC power by the output command voltage of the inverter, the output command current can be calculated, and the power loss of the DC-AC conversion means 3 can be calculated by Equation 2. Since the power conversion loss of the AC-DC converting means 2 can be calculated by Equation 1, the total power conversion loss is the sum of Equations 1 and 2. The optimum operating point of Vdc can be calculated by differentiating the sum of Equations 1 and 2 with a DC voltage and calculating the minimum point of power loss.

  As described above, according to the seventh embodiment, the DC voltage optimization unit 4 can change the input voltage of the DC-AC conversion unit 3 up and down according to the input power of the DC-AC conversion unit 3. Thus, minimization of power conversion loss and improvement of the effective utilization rate of input power of the AC power source 1 can be achieved at the same time.

  This is an optimal control technique for improving the efficiency of an inverter using AC-DC conversion and DC-AC conversion techniques, and can also be applied to a general-purpose inverter device that can output any frequency and voltage used for motor control and the like.

Configuration diagram of the grid interconnection inverter of Embodiment 1 of the present invention Control flow chart of the DC voltage optimizing means 4 Control flowchart of DC voltage optimizing means 4 according to the second embodiment of the present invention. Control flowchart of DC voltage optimizing means 4 according to Embodiment 3 of the present invention. Control flowchart of DC voltage optimizing means 4 according to Embodiment 4 of the present invention. Control flowchart of DC voltage optimizing means 4 according to Embodiment 5 of the present invention. Control flowchart of DC voltage optimizing means 4 according to Embodiment 6 of the present invention. Control flowchart of DC voltage optimizing means 4 according to Embodiment 7 of the present invention Configuration diagram of power saving device using conventional inverter technology Configuration diagram of a grid-connected inverter using conventional inverter technology

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 AC-DC converting means 2a-2d Switching element 2e-2h Diode 2i-2j Boosting reactor 2k Filter circuit 2L Smoothing capacitor 2m Boosting chopper control part 3 DC-AC converting means 3a-3d Switching element 3e-3h Diode 3i Output ripple voltage reduction filter 3j Inverter controller 4 DC voltage optimization means 101 Power saving device 102 AC power supply 103 Load 104 Series transformer 105 Regenerative inverter 106 DC power supply 107 Input capacitor 108 Boost converter 109 Intermediate capacitor 110 Inverter 111 System 112 Input voltage fluctuation detection means 113 Control circuit

Claims (8)

AC-DC conversion means for converting an AC power source into an optimal DC voltage, DC-AC conversion means for converting DC power converted by the AC-DC conversion means into AC power, and minimizing power conversion loss An inverter device comprising DC voltage optimizing means for controlling AC-DC converting means. 2. The inverter apparatus according to claim 1, wherein the DC voltage optimizing means controls so as to minimize the power conversion loss of the AC-DC converting means. 2. The inverter apparatus according to claim 1, wherein the DC voltage optimizing means controls so as to minimize the power conversion loss of the DC-AC converting means. 2. The inverter apparatus according to claim 1, wherein the DC voltage optimizing means controls so as to minimize the total power conversion loss of the AC-DC converting means and the DC-AC converting means. 2. The inverter apparatus according to claim 1, wherein the DC voltage optimization means changes the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss in accordance with the output AC command voltage. The DC voltage optimization means changes the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss according to the load current connected to the DC-AC conversion means. The described inverter device. The DC voltage optimization means changes the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss according to the input current of the DC-AC conversion means. Inverter device. The DC voltage optimization means changes the input voltage of the DC-AC conversion means up and down so as to minimize the power conversion loss according to the input power of the DC-AC conversion means. Inverter device.

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