JP3818155B2 - Power converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power conversion apparatus that charges a battery with electric power generated by a solar cell or a fuel cell and converts the electric power of the battery into a power form that can be used as a power source for home appliances and in-vehicle devices.
[0002]
[Prior art]
FIG. 13 is a block diagram showing a configuration of a power conversion device that is conventionally used. Here, the power generation means is the solar cell 1. The DC power generated by the solar cell 1 is boosted and charged to the battery 3 by the converter 2. The output of the battery 3 is connected to an inverter 4 that converts a DC voltage into an AC voltage, and the inverter 4 includes four switching elements each having a diode connected in parallel, a reactor, and a capacitor. The output of the inverter 4 is output through an AC output outlet 5. Reference numeral 6 denotes a control circuit.
[0003]
The operation will be described below with reference to FIG. The converter 2 performs boosting control to match the electric power of the solar cell 1 whose voltage fluctuates by sunshine with the voltage of the battery 3 that is a voltage source, and charges the battery 3. Next, by performing a switching operation on the basis of the pulse pattern obtained by comparing the DC voltage of the battery 3 with the triangular wave in the control circuit 6 and the sine wave reference wave, the inverter 4 converts the DC voltage of the battery 3 to a high frequency. Convert to pulse voltage train. Since the obtained pulse voltage train passes through the reactor and the capacitor to remove high-frequency ripple, a sinusoidal voltage waveform is generated as the output of the inverter 4. Here, when the output of the inverter 4 is a sinusoidal AC 100V, the peak voltage is 141V. Therefore, considering the voltage drop of the reactor in the inverter 4, at least the battery voltage (= inverter input voltage) needs to be 150V or more. It is. Finally, the output of the inverter 4 supplies electric power to an electric device used at home as an AC voltage of 50 Hz or 60 Hz (usually 100 V) via an AC output outlet 5.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, since the inverter performs switching at a high frequency in the entire region in order to always generate a sine wave, many switching losses occur in addition to the conduction loss. In particular, in the case of a device with low power consumption, the ratio of the switching loss is larger than the conduction loss. Therefore, when a battery with a limited amount of electric power is an input power source of an inverter, the usage time of the connected device is significantly shortened compared to a rectangular wave output in which a DC voltage is AC-converted at a commercial frequency. Further, since the loss is large, the space required for cooling is increased, and there is a problem that there is a limit to downsizing of the product.
[0005]
An object of the present invention is to provide a power conversion device that can be used for a long time by enabling selection of a waveform that reduces inverter loss within a range in which malfunction does not occur in a connected device.
[0006]
[Means for Solving the Problems]
In order to solve the conventional problems, a power conversion device according to the present invention includes a DC power supply, a battery, a converter that boosts the voltage of the DC power supply and charges the battery, and converts the output voltage of the battery to AC. And a control circuit that compares the reference wave and the triangular wave to determine the pulse width based on the size of the inverter, and is set so that the amplitude of the reference wave is greater than or equal to the amplitude of the triangular wave. Without performing high-frequency switching, the battery voltage is directly output, and the inverter is a power converter characterized by performing sinusoidal modulation only for a certain period of time between AC valleys, so that the inverter does not malfunction. It is an object of the present invention to provide a high-efficiency power conversion device that can reduce the loss of the device and use the device for a long time.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The invention described in claim 1 includes a DC power supply, a battery, a converter that boosts the voltage of the DC power supply and charges the battery, an inverter that converts the output voltage of the battery into AC , a reference wave, and a triangular wave And a control circuit that determines the pulse width based on the magnitude of the voltage and setting the amplitude of the reference wave to be equal to or greater than the amplitude of the triangular wave, so that the battery does not perform high-frequency switching near the peak of the AC waveform. A voltage is directly output, and the inverter performs sinusoidal modulation only for a certain period of time between the valleys of the AC output voltage, so that a high-efficiency power conversion device with reduced high-frequency switching operation is obtained.
[0008]
According to a second aspect of the invention, in the first aspect of the invention, there is provided first switching means that can be set from the outside of the main body, and the first switching means performs inverter output control at all times in a sine. By switching to either a wave modulation operation or a sinusoidal modulation operation only for a certain period of time between AC valleys, a power conversion device that can reliably achieve high efficiency in a device that can operate without a sine wave is obtained.
[0009]
The invention described in claim 3 has, in particular, the first phase setting means that can be set from outside the main body in the invention of claim 1 or 2, wherein the first phase setting means has a sine wave modulation period. By making it variable, the power conversion device realizes high efficiency over a wide range by generating an optimal waveform according to the connected device.
[0010]
According to a fourth aspect of the present invention, in particular, in the first aspect of the present invention, the second switching means that can be set from outside the main body is provided, and the second switching means is a commercial switch. By switching between power supply control for the entire period of one cycle or control for supplying power only for a certain period, a highly efficient power conversion device capable of controlling the power of the connected device is provided.
[0011]
The invention described in claim 5 is the invention described in any one of claims 1 to 4, particularly, having second phase setting means that can be set from the outside of the main body, and the second phase setting means. Is a highly efficient power conversion device that improves the degree of freedom of power control of connected devices by varying the power supply period.
[0012]
The invention described in claim 6 is the invention described in any one of claims 1 to 5, in particular, having output current detection means, third switching means, and resistance, and the third switching. The means and the resistor are arranged in series and are arranged in parallel with the inverter output, and when the load current detected by the output current detecting means is below a certain value, the third switching means is brought into a connected state. As a result, the inverter output voltage does not vibrate when the power consumption of the connected device is small.
[0013]
The invention described in claim 7 has an output voltage detection means and a phase difference detection means for detecting a phase difference obtained from the output voltage detection means in the invention described in claim 6, wherein the phase difference If the phase difference obtained by the detection means is greater than or equal to a certain value, the third switching means can be connected to cause the inverter output voltage to vibrate even if the connected device is an inductive load or a capacitive load. There are no high quality power converters.
[0014]
【Example】
Example 1
A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. In the power conversion apparatus of this embodiment, the power generated by the solar cell (DC power supply) 11 is boosted by the converter 12 and input to the battery 13 and the inverter 14. The DC voltage of the battery 13 is converted into an AC voltage by the inverter 14. The inverter 14 is composed of a full bridge, a reactor, and a capacitor by four switching elements Q1, Q2, Q3, and Q4, and a reactor and a capacitor that function as a high-frequency filter are connected to an intermediate terminal of the full bridge. Here, the output of the inverter 14 is supplied to an AC output outlet 15 and can be connected to a plug of a home appliance. The inverter 14 performs a switching operation based on the drive signal of the control circuit 16.
[0015]
The operation of the power converter configured as described above will be described with reference to the waveform diagram of FIG. The converter 12 converts the DC power obtained from the solar cell 11 as a generator into stable DC power and at the same time the peak value of the AC output voltage that requires a sine wave (for example, the peak when the AC output voltage is AC100V) The voltage is increased to 141 V) or more, and the battery 13 as the power storage means is charged. The inverter 14 compares the reference wave and the triangular wave in the control circuit 16 and determines the pulse width according to the magnitude relationship. By setting the amplitude of the sine wave to be equal to or larger than the amplitude of the triangular wave, the inverter 14 In the vicinity of the peak, the battery voltage is output as it is without performing high-frequency switching. In the valley of the AC waveform, the average value is converted into a high-frequency pulse voltage having a sine wave shape. The obtained pulse voltage passes through the reactor and the capacitor, thereby removing high-frequency ripple, generating a sinusoidal voltage waveform, and the combined voltage with the output voltage near the peak is 50 Hz or It is output as a 60 Hz AC voltage (usually 100 V).
[0016]
As described above, according to this embodiment, the inverter performs sinusoidal modulation only in the valley of the AC output voltage, so that the high-frequency switching operation can be stopped for a certain period of one commercial cycle, and at the same time, the loss can be reduced. By generating a waveform that does not affect the zero voltage detection of the connected device, it is possible to realize a highly efficient and highly reliable power conversion device.
[0017]
(Example 2)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of this embodiment. 3 is different from the circuit configuration of FIG. 1 in the first embodiment in that a first switching means 17 is added to the control circuit 16 so that the amplitude of the triangular wave that determines the operation of the inverter 4 can be selected. Is a point. Components other than those described above are the same as those in the first embodiment, and a detailed description thereof will be omitted.
[0018]
The operation of the power converter configured as described above will be described with reference to the waveform diagram of FIG. When the connected device requires a sine wave, such as a measuring instrument, the reference wave inside the control circuit 16 becomes less than the amplitude of the triangular wave in the entire region by selecting the sine wave with the first switching means 17. The output of the inverter 4 is a complete sine wave. If the connected device does not necessarily require a sine wave, such as a thermal device, the first switching means 17 selects other than a sine wave, and the amplitude of the sine wave is made larger than the amplitude of the triangular wave near the peak. Thus, the inverter 4 is always turned on to output the battery 3 voltage as it is. At this time, since the voltage is a sinusoidal voltage in the valley of the AC waveform, zero voltage detection is reliably performed even when the connected device performs phase control, for example, and power control is performed without malfunction.
[0019]
As described above, according to the present embodiment, the operation of the control circuit 16 is switched by the first switching means 17 so that the inverter output control can be performed at any time by the sine wave modulation operation or the sine wave modulation only during a certain period of the AC valley. It is possible to switch to any one of the operations, and it is possible to realize a power conversion device that can surely achieve high efficiency in a device that can operate without a sine wave.
[0020]
Example 3
Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing the configuration of this embodiment. 5 is different from the circuit configuration of FIG. 3 in the second embodiment in that the first phase setting means 18 is added to the control circuit 16 so that the amplitude of the triangular wave that determines the operation of the inverter 4 can be arbitrarily adjusted. This is the point. Components other than those described above are the same as those in the second embodiment, and a detailed description thereof will be omitted.
[0021]
The operation of the power converter configured as described above will be described with reference to the waveform diagram of FIG. The first phase setting means 18 can be adjusted from the outside, and the high-frequency switching region of the inverter 4 is changed by changing the amplitude of the triangular wave with respect to the reference wave in the control circuit 16 while confirming the operation of the connected device. It is changing. For example, even if the motor characteristics are different, such as a connected device such as a refrigerator or a fan, the start-up and operation are ensured and the high-frequency switching area of the inverter 4 is adjusted to the maximum value by the first phase setting means. is doing. Of course, since the voltage is a sinusoidal voltage in the valley of the AC waveform, zero voltage detection is reliably performed even when the connected device performs phase control, for example, and power control is performed without malfunction.
[0022]
As described above, according to the present embodiment, since the high-frequency switching region of the control circuit 16 can be linearly changed by the first phase setting means 18, it is possible to always ensure normal operation even when the load changes. It is possible to provide a highly efficient power conversion device that keeps the switching loss of the inverter to a minimum.
[0023]
Example 4
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing the configuration of this embodiment. 7 differs from the circuit configuration of FIG. 5 in the third embodiment in that a second switching means 19 is added to the control circuit 16 to supply power to the inverter 4 in addition to the normal sine wave output operation. It is a point that an operation for partially stopping the operation in one commercial cycle can be additionally selected. Components other than those described above are the same as those in the third embodiment, and a detailed description thereof will be omitted.
[0024]
The operation of the power converter configured as described above will be described with reference to the waveform diagram of FIG. When the connected device requires a sine wave, such as a measuring instrument, the sine wave is selected by the second switching means 19 so that the reference wave, which is a sine wave inside the control circuit 16, becomes a triangular wave in the entire region. In comparison, the input of the inverter 4 is switched at a high frequency, and the output becomes a complete sine wave. On the other hand, when the connected device wants to perform power control like a thermal device, the second switching means 19 selects something other than a sine wave, and sets the reference wave to zero in a certain period of the commercial cycle. In, the inverter output becomes zero and the power supply to the connected equipment is stopped. In FIG. 8, the power supply is stopped from the rising edge of the AC waveform. However, when the connected device detects zero voltage at the rising edge, the power supply stop may be moved 180 degrees to avoid malfunction. Needless to say.
[0025]
As described above, according to the present embodiment, the operation of the control circuit 16 is switched by the second switching means 19, so that the inverter output control is always performed with the sine wave modulation operation and the power supply stop control for a certain period between the AC valleys. By switching between the two, it is possible to realize a power conversion device that can surely control power in a device that can operate without a sine wave.
[0026]
(Example 5)
The fifth embodiment of the present invention will be described below with reference to the drawings. FIG. 9 is a block diagram showing the configuration of this embodiment. 9 is different from the circuit configuration of FIG. 7 in the fourth embodiment in that the second phase setting means 20 is added to the control circuit 16 to arbitrarily set the zero period of the reference wave for limiting the power supply of the inverter 4. It is a point that can be adjusted to. Components other than those described above are the same as those in the fourth embodiment, and a detailed description thereof will be omitted.
[0027]
The operation of the power converter configured as described above will be described with reference to the waveform diagram of FIG. The second phase setting means 20 can be adjusted from the outside so that the reference wave zero command in the control circuit 16 is arbitrarily changed while confirming the operation of the connected device, so that the inverter 4 in one commercial cycle can be controlled. The output duty is changed. For example, when it is desired to finely control the number of revolutions and the heater temperature, such as a motor device such as a refrigerator or a fan, or a thermal device such as an electric carpet, electric power is continuously generated at the level set by the second phase setting means 20. Take control. Therefore, when performing power control of the connected device, there is no need to perform phase control on the connected device side, and no power loss occurs.
[0028]
As described above, according to this embodiment, the second phase setting unit 20 can arbitrarily change the power control by providing the reference signal in the control circuit with a zero period arbitrarily. It is possible to provide a power converter with good quality.
[0029]
(Example 6)
The sixth embodiment of the present invention will be described below with reference to the drawings. FIG. 11 is a block diagram showing the configuration of this embodiment. 11 differs from the circuit configuration of FIG. 9 in the fifth embodiment in that the output current value of the inverter 4 is taken into the control circuit 16 by the output current detection means 21 and the first configuration configured in series. The third switching means 22 and the resistor 23 are arranged in parallel with the output of the inverter 4. Components other than those described above are the same as those in the fifth embodiment, and a detailed description thereof will be omitted.
[0030]
The operation of the power conversion device configured as described above will be described with reference to the drawings. The cut-off frequency of the reactor and capacitor arranged at the inverter output is usually about 1 kHz, and when the rated power of the connected device is small (light load), the reactor and capacitor arranged at the output part of the inverter 4 Resonance occurs, the output voltage vibrates and noise is generated. Here, the current value detected by the output current detection means 21 is compared with a threshold value inside the control circuit 16. 3 is turned on, and the connected device and the resistor 23 are connected in parallel when viewed from the output of the inverter 4. Then, the resistor 23 acts as a damping element and acts to suppress output voltage vibration and noise.
[0031]
As described above, according to the present embodiment, when the rated power of the connected device is small, the power conversion device capable of always supplying high-quality output by inserting the resistor 23 as a damping element in parallel to the inverter output. Can be provided.
[0032]
(Example 7)
The seventh embodiment of the present invention will be described below with reference to the drawings. FIG. 12 is a block diagram showing the configuration of this embodiment. 12 differs from the circuit configuration of FIG. 11 in the sixth embodiment in that the value of the phase difference detection means 25 for detecting the phase difference from the output current by providing the output voltage detection means 24 is taken into the control circuit 16. The connection device determination process is performed. Components other than those described above are the same as those in the sixth embodiment, and a detailed description thereof will be omitted.
[0033]
The operation of the power conversion device configured as described above will be described with reference to the drawings. When the connected device is an inductive or capacitive load, the output voltage of the inverter 4 often vibrates greatly at a frequency determined by the reactor and the capacitor disposed at the output of the connected device and the inverter 4. The current waveform detected by the output current detection means 21 and the voltage waveform detected by the output voltage detection means 24 are taken into the control circuit 16 as a phase difference by the phase difference detection means 25, and this value is the difference between the delay phase and the advance phase. If it is equal to or greater than the threshold value, it is determined in the control circuit 16 as an inductive load or a capacitive load. Further, the control circuit 16 turns on the third switching means 22 arranged at the output of the inverter 4 to connect the connecting device and the resistor 23 in parallel as viewed from the output of the inverter 4. Then, the resistor 23 acts as a damping element and acts to suppress output voltage vibration and noise.
[0034]
As described above, according to the present embodiment, when the connected device is an inductive load or a capacitive load, the resistor 23 as a damping element is inserted in parallel to the inverter output, so that a high-quality output can always be supplied. A possible power conversion device can be provided.
[0035]
【The invention's effect】
As described above, according to the first to seventh aspects of the present invention, a high-efficiency power conversion device that does not cause a malfunction in a connected device by maintaining a sine wave near the zero point of the inverter output AC voltage. Can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of a power conversion device according to a first embodiment of the present invention. FIG. 2 is a waveform diagram showing the operation of each part of the power conversion device. FIG. FIG. 4 is a waveform diagram showing the operation of each part of the power conversion apparatus. FIG. 5 is a block diagram showing the configuration of the power conversion apparatus according to the third embodiment of the present invention. FIG. 6 is a waveform diagram showing the operation of each part of the power conversion apparatus. FIG. 7 is a block diagram showing the configuration of the power conversion apparatus according to the fourth embodiment of the invention. FIG. 9 is a block diagram showing the configuration of the power conversion apparatus according to the fifth embodiment of the present invention. FIG. 10 is a waveform chart showing the operation of each section of the power conversion apparatus. The block diagram which shows the structure of the power converter device which is the 6th Example of this invention. FIG. 13 is a block diagram showing the configuration of a conventional power conversion device. FIG. 14 is a waveform diagram showing the operation of each part of the power conversion device. Explanation】
11 Solar cell (DC power supply)
12 converter 13 battery 14 inverter 15 AC output outlet 16 control circuit 17 first switching means 18 first phase setting means 19 second switching means 20 second phase setting means 21 output current detection means 22 third switching means 23 Resistance 24 Output voltage detection means 25 Phase difference detection means

Claims (7)

A DC power supply, a battery, a converter that boosts the voltage of the DC power supply and charges the battery, an inverter that converts the output voltage of the battery to AC , a reference wave and a triangular wave are compared, and the pulse width is large and small And a control circuit that determines the reference wave amplitude so that the amplitude of the reference wave is equal to or greater than the amplitude of the triangular wave, the battery voltage is directly output without performing high-frequency switching near the peak of the AC waveform, and the inverter A power conversion device that performs sine wave modulation for a certain period of time in an AC valley.   First switching means that can be set from the outside of the main body, and the first switching means controls the output of the inverter to either a sine wave modulation operation that is always performed or a sine wave modulation operation that is performed only during a certain period between AC valleys. The power converter according to claim 1, wherein the power converter is switched.   3. The power conversion apparatus according to claim 1, further comprising a first phase setting unit that can be set from outside the main body, wherein the first phase setting unit varies a sine wave modulation period.   And a second switching unit that can be set from the outside of the main body, wherein the second switching unit switches between power supply control for all periods of one commercial cycle or control for supplying power only for a certain period. The power converter according to any one of claims 1 to 3.   5. The power conversion according to claim 1, further comprising a second phase setting unit that can be set from outside the main body, wherein the second phase setting unit varies a power supply period. apparatus.   The output current detection means, the third switching means, and a resistor, wherein the third switching means and the resistor are configured in series and arranged in parallel with the inverter output, and the output current detection means 6. The power conversion device according to claim 1, wherein when the load current detected in step 1 is equal to or less than a predetermined value, the third switching unit is connected.   An output voltage detecting means; and a phase difference detecting means for detecting a phase difference obtained from the output voltage detecting means, and a third switching means if the phase difference obtained by the phase difference detecting means is a predetermined value or more. The power conversion device according to claim 6, wherein the power conversion device is in a connected state.

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