JP2016178744A - Electric power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power converter capable of displaying the conversion efficiency in an easily recognizable manner.SOLUTION: An electric power converter 2 converts DC power generated by a solar cell 3 into AC power. The electric power converter has a display unit 1 that calculates the conversion efficiency of the electric power converter 2 based on the DC power input into the electric power converter 2 and the AC power output from the electric power converter 2, and displays according to a difference between the calculated conversion efficiency and the conversion efficiency of the electric power converter 2 in rating output operation.SELECTED DRAWING: Figure 3

Description

The present invention relates to display of conversion efficiency of a power conversion device that converts DC power generated by a solar cell into AC power and can be superimposed on a system or supplied to an AC load.

2. Description of the Related Art There is known a power conversion device that converts DC power generated by a solar cell into AC power and can be superimposed on a system or supplied to an AC load. The total amount of output power (AC power) of this power converter or the remaining surplus power consumed on the use side can be sold to an electric power company. Since the power conversion device uses a structure that periodically turns on / off semiconductor switching elements when converting DC power to AC power, heat loss occurs during conversion. For this reason, the conversion efficiency of the power conversion device often shows a value in the latter half of 90%.

However, since the conversion efficiency when the power conversion device is actually operating varies depending on the amount of solar radiation, it is necessary to calculate from the input power (DC power) and output power (AC power) each time, which is troublesome. . Patent Document 1 describes that conversion efficiency is calculated from input power and output power of a power converter.

JP 2000-3224 A

Patent Document 1 has a description of calculating the conversion efficiency, but the calculated conversion efficiency is used to determine the failure or abnormal state of the solar cell or the power conversion device from the comparison with the normal value, and the conversion efficiency itself is determined. It was not displayed. Even if the value of the conversion efficiency itself is displayed on the display unit or the like, normally, the state that the value means cannot be easily determined.
For example, even if the power generation efficiency is displayed as 96%, it is not easy for the user to determine whether the state is normal or abnormal, whether the solar radiation amount is reduced due to clouds.

The present invention makes it possible to visually recognize the operating state by changing the design based on the difference between the conversion efficiency during rated output operation and the conversion efficiency during actual operation of the power converter.

The present invention relates to a power converter for converting DC power generated by a solar cell into AC power, based on DC power input to the power converter and AC power output from the power converter. A conversion unit of the power conversion device is calculated, and a display unit is provided that performs display according to the difference between the calculated conversion efficiency and the conversion efficiency at the rated output operation of the power conversion device. In addition, the display can be performed by changing the design.

In the power converter of the present invention, since the display is performed based on the conversion efficiency at the rated output operation, the current power generation state can be easily determined. Further, if the display state with low conversion efficiency continues, the abnormality can be easily determined.

It is explanatory drawing which shows the Example of this invention. It is explanatory drawing which shows the outline of this invention. It is explanatory drawing which shows the display of the display part of this invention.

The present invention is used for a power conversion device having a display unit and a power conversion device capable of display.

FIG. 1 is an explanatory diagram showing an embodiment of the present invention. A display unit (remote controller) 1 and a power conversion device 2 are configured to be able to transmit and receive control signals and data. The display unit 1 and the power conversion device 2 are connected by wired connection or wireless connection, and transmit and receive control signals and data using a predetermined protocol. 3 is a solar cell, and the generated DC power is the power converter 2
To the power line. 4 is a system, which is superimposed after the DC power generated by the solar cell 3 is converted into AC power by the power converter 2.

As shown in FIG. 1, the display unit 1 is not only configured separately from the power conversion device 2 via communication means, but may be configured integrally with the power conversion device 2. Furthermore, a terminal (such as an information terminal) connected via a wired or wireless communication network may be operated as a display unit.

FIG. 2 is an explanatory diagram showing an outline of the power conversion device 2, and the DC generated power generated by the solar cell 3 is superimposed on the system 4 via the booster unit 21, the inverter unit 22, and the filter unit 23. The step-up unit 21 forms a step-up chopper circuit using, for example, a step-up reactor, a semiconductor switching element, a diode, and a smoothing capacitor. The step-up ratio of the step-up unit 21 can be controlled by changing the on-duty when the switching element is turned on / off at a predetermined cycle. This step-up ratio is obtained by inputting the generated power generated by the solar cell 3 through the open / close switch and then detecting the DC power value detected by the DC power detector 21a (the DC power detector 21a includes a voltage detector, a current detector, And the product of these detection values is used as the DC power value) to be maximized. This step-up ratio is controlled by MPPT (Maximum Po
This is a control that follows the optimum operating point (corresponding to the maximum power generation amount) of the solar cell, which is referred to as a “Wer Point Tracking” method and constantly fluctuates due to changes in weather conditions and the like. The rated output of the power conversion device 2 is the output (AC power) at or near the optimum operating point, and the conversion efficiency during rated output operation is the conversion efficiency of the power conversion device 2 when operating at this rated output. It can be.

Note that the step-up unit 21 is not limited to the step-up chopper circuit, and a step-down chopper circuit may be used when the output voltage of the solar cell is high, and a step-up ratio (such as an insulation type forward type or flyback type using a transformer). Alternatively, any device capable of controlling the step-down ratio) may be used.

The DC power having the intermediate voltage at the point 21b boosted by the booster unit 21 is converted into a pseudo sine wave by the inverter unit 22 based on a PWM (Pulse Width Modulation) system and turned on / off by a plurality of switching elements and output. The The inverter unit 22
When outputting a single-phase pseudo sine wave, connect at least four switching elements in a single-phase bridge, and when outputting a three-phase pseudo sine wave, connect at least six switching elements in a three-phase bridge. do it. Further, different circuit connections such as a neutral point clamp method may be used for the inverter unit, and a pseudo sine wave may be generated by multi-stage output by gradation.

The pseudo sine wave output from the inverter unit 22 is superposed on the system 4 after the high frequency component is removed or attenuated by the filter unit 23 (reactor and capacitor constitute a low pass filter). The DC power generated by the solar cell 3 is mainly generated by the booster unit 21 and the inverter unit 22.
The power is reduced when it is output from the power conversion device 2 due to the heat loss generated during the operation of the plurality of switching elements constituting the. It should be noted that the loss of the reactor and other electrical components, the operating power in the control unit 24, and the like also lead to a reduction in the output power.

On / off signals of a plurality of switching elements constituting the inverter unit 22 are generated by the control unit 24. The control unit 24 is configured using a microcomputer (an arithmetic device such as a microprocessor, MPU, or CPU), and has an interface circuit (not shown because a general-purpose system corresponding to a wired system or a wireless system can be used). It is possible to transmit / receive control signals and data to / from the display unit 1.

The control unit 24 and the display unit 1 can be connected to each other by transmitting and receiving control signals and data via a communication network in addition to a dedicated signal line and radio.

25 is an AC power detector, a DC voltage detector and C.I. T.A. It consists of an alternating current detector by (current transformer). It is obtained from the voltage waveform due to the time change of the DC voltage in the control unit 24 (
The product of the effective value of the current detected by the AC detector as well as the effective value (according to the moving average) is substantially the AC power value output from the power converter 2. The calculation of the AC power value includes a method using the square root of the square average of the voltage value and current value, a method of obtaining from the integration of the AC current value, etc., and is not limited in the present invention. Also, even in the case of three-phase AC, if the loads connected to the three phases are equal for each phase, the line current x the phase voltage x 1.732 (square root of 3) can be obtained. If the load is unbalanced or reactive power is considered However, it can be calculated by a predetermined calculation.

26 is for switching the AC power output from the power converter 2 between the grid 4 and the AC load. The state shown in FIG. 2 is a state in which AC power is supplied to the grid 4 using a single pole double head switch. In a state opposite to that shown in the figure, AC power can be supplied to an AC load connected to the terminal.

The control unit 24 determines the AC power value obtained from the output of the AC power detector 25 and the DC power detector 21a.
The conversion efficiency A is calculated using the DC power value obtained from the output. (A = AC power value / DC power value)

Next, the control unit 24 obtains a difference C (= A−B) of the conversion efficiency A with respect to the conversion efficiency (rated efficiency) B at the rated output operation of the power converter 2 and when this difference is positive (the conversion efficiency A is converted). In the case of efficiency B or higher), it means that the converter is operating at a conversion efficiency that is higher than the rated efficiency, and the symbol 31 is displayed. If the difference C is less than 0 to minus 10, the symbol 32 is displayed. If it is between minus 10 and minus 30, the symbol 33 is displayed. When the difference C is less than minus 30, no display is made.

FIG. 3 is an explanatory diagram of the display unit 1, and the symbols 31 to 32 are set by combining the symbol indicating the sun and the symbol indicating the cloud. FIG. 3 shows a state in which all symbols 31 to 32 are displayed for easy understanding, but one symbol 31 to 32 is displayed during normal operation. However, there is a case where the symbol is not displayed.

By performing such display, if the power generation amount of the solar cell 3 is equal to or higher than the rated output, the conversion efficiency of the power conversion device 2 becomes the conversion efficiency during the rated output operation, and sufficient power generation is performed. In addition, when the electric power generation amount of the solar cell 3 becomes more than a rated output, the conversion efficiency of the power converter device 2 may become higher than the conversion efficiency at the time of rated output operation.

When the solar cell 3 is covered with clouds, or at sunrise or sunset, the amount of solar radiation decreases and the output of the solar cell 3 does not reach the rated output. Even in this case, since the heat loss in the switching element and the amount of operating power in the control unit are not substantially changed, the conversion efficiency of the power conversion device 2 is lower than the conversion efficiency during rated output operation. Therefore, it can be easily inferred that a cloud is applied from the pattern 32 and the amount of solar radiation is reduced. Similarly, if the amount of solar radiation further decreases, it can be inferred from the pattern 33 that the amount of solar radiation has further decreased.

If the display and the actual outdoor weather (irradiation amount) do not match for a long time, the solar cell 3
Or since the abnormality of the power converter device 2 is considered, the user can easily perform the inspection or request the inspection.

Reference numerals 34a to 34d are operation switches for switching display, display mode, display items, and the like. Further, when the frequency used for the on / off operation of the switching elements of the booster 21 and the inverter 22 can be changed, the conversion efficiency at the rated output operation for each frequency may be displayed. This frequency switching operation switch can be used.

The display is not limited to the design shown in FIG. 3. For example, when the display space is insufficient, the color of one design is changed to blue-yellow-red, etc. to effectively use the display unit. Similarly, a combination of turning on / off the LED lamp may be used. Furthermore, the symbol is not limited to the symbol shown in FIG. 3 such as a bar graph or a pie graph.

The present invention is used for a power conversion device having a display unit and a power conversion device capable of display.

As mentioned above, although one Embodiment of this invention was described, the above description is for making an understanding of this invention easy, and does not limit this invention. It goes without saying that the present invention can be changed and improved without departing from the gist thereof, and that the present invention includes equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Display part 2 Power converter 3 Solar cell 4 System | strain 21 Booster part 22 Inverter part 23 Filter part 24 Control part 31 thru | or 33

Claims (3)

In a power converter for converting DC power generated by a solar cell into AC power, the power converter based on DC power input to the power converter and AC power output from the power converter A power conversion apparatus comprising: a display unit configured to calculate a conversion efficiency of the power conversion apparatus, and to perform display in accordance with a difference between the calculated conversion efficiency and the conversion efficiency at the rated output operation of the power conversion apparatus. The power conversion apparatus according to claim 1, wherein the display corresponding to the difference is a display based on a change in color, and uses at least two kinds of colors. The power conversion apparatus according to claim 1, wherein the display corresponding to the difference is a display based on a difference in display symbols, and at least two types of symbols are used.

Images