Receptacle power supply device

Abstract

To provide a simple, compact receptacle power supply device with less power loss which is capable of cooperation with an electric power system by feeding a receptacle with generated power of a solar battery.SOLUTION: The receptacle power supply device includes: a power conversion unit 1 that converts generated power of a solar battery 20; an inverter unit 2 for conversion into a sinusoidal voltage having the same frequency and phase with a system voltage; a plug 9 that can be inserted in a receptacle 30; and a control unit 3. The control unit 3 has a system voltage detection unit 5 that performs full-wave rectification of the system voltage, a generated power detection unit 6 that detects a voltage of the solar battery 20, a modulation wave generation unit 4 that outputs a modulation wave signal, and a PWM signal generation unit 7 that receives a high-frequency carrier signal and the modulation wave signal and outputs a PWM signal. A first semiconductor element 12 is controlled by an output voltage of the system voltage detection unit 5. A second semiconductor element 13 is controlled by an output voltage of the generated power detection unit 6. A current path resistance increases / decreases.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power conditioner that converts the generated power of a solar cell, and particularly to an apparatus that supplies power to an outlet of a commercial power system.

Background Art

[0002] A power conditioner that converts DC power obtained from a solar cell installed in a house or the like into AC power is known. Generally, the power conditioner is connected to an indoor distribution board. AC power from a commercial power system is also input to the distribution board. The distribution board supplies AC power to outlets (also referred to as "sockets") such as lighting fixtures and walls, and returns surplus power from the solar cell to the commercial power system if there is any.

[0003] Patent Documents 1 to 3 disclose an apparatus that converts DC power obtained from a solar cell into AC power, and connects to a commercial power system by inserting an AC plug, which is an output terminal of the apparatus, into a dedicated AC outlet in a house. The power supplied to the dedicated AC outlet is supplied to a general outlet via a distribution board or transmitted to the commercial power system.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, devices that connect to the commercial power grid by directly supplying power from a solar cell to a common electrical outlet without going through a distribution board have hardly been put into practical use. The power conditioner of a solar cell needs to be equipped with a mechanism to prevent single operation. There is a method of outputting reactive power to the grid for detecting single operation, but it will have an adverse effect on the grid when the phase or frequency of the grid changes or power loss occurs.

[0006] In a power conditioner of a solar cell, so-called MPPT control, i.e., maximum power point tracking control, is well known. MPPT control is a method of finding the maximum power point by stepwise changing the input current to the chopper section, such as the hill climbing method, and checking the increase and decrease of the input power, and it requires a CPU and a predetermined program. MPPT control causes power loss because it repeats trial and error. When the chopper section for performing DC-AC power conversion is configured with an isolated switching power supply, the inexpensive flyback method is often adopted, but the flyback method has a problem that the core of the transformer becomes large and it is difficult to increase the output power.

[0007] An object of the present invention is to solve the above problems and provide a simple and compact electrical outlet power supply device that can be connected to the power grid by directly supplying the generated power of a solar cell to a common electrical outlet and has little power loss.

Means for Solving the Problems

[0008] To achieve the above object, the present invention provides the following configuration. The reference numerals in parentheses are the reference numerals in the drawings described later and are attached for reference.

[0009] [1] An aspect of the present invention is an electrical outlet power supply device (10) for supplying the generated power of a solar cell (20) to an electrical outlet (30) connected to a grid power supply (40), To convert the generated power of the solar cell (20), a power conversion unit (1) including a transformer (T) and a switching element (S) for switching control of the primary coil (N1) of the transformer (T); an inverter unit (2) for converting the output voltage of the power conversion unit (1) into a sine wave voltage having the same frequency and phase as the grid voltage; a plug (9) which is an output terminal of the inverter unit (2) and can be inserted into the outlet (30); a control unit (3) for generating a PWM signal for controlling the switching element (S), and the control unit (3) includes a grid voltage detection unit (5) for full-wave rectifying the grid voltage obtained through the plug (9); a power generation voltage detection unit (6) including a constant voltage element (Z) and a resistance element (R1) connected in series between the output terminals of the solar cell (20), and outputting a voltage having a magnitude corresponding to the magnitude of the current flowing through the resistance element (R1); a modulation wave generation unit (4) including a first semiconductor element (12) and a second semiconductor element (13) each having current paths connected in series and a constant voltage applied across both ends thereof, and outputting the potential of the connection point (A) between the first semiconductor element (12) and the second semiconductor element (13) as a modulation wave signal; a PWM signal generation unit (7) which receives a high-frequency carrier signal and the modulation wave signal from the modulation wave generation unit (4) and outputs the PWM signal, and the first semiconductor element (12) is controlled by the output voltage of the grid voltage detection unit (5), wherein the AC impedance of the current path of the second semiconductor element (13) varies according to the magnitude of the output voltage of the power generation voltage detection unit (6). [2] In the above aspect, when the output voltage of the solar cell (20) increases or decreases, the output voltage of the power generation voltage detection unit (6) increases or decreases, the AC impedance of the current path of the second semiconductor element (13) increases or decreases, the pulse width of the PWM signal expands or contracts, and the current taken in by the power conversion unit (1) increases or decreases. [3] In the above aspect, the constant voltage (Vz) of the constant voltage element (Z) is set to the voltage at the minimum value of the shoulder portion, which is the control target range in the I-V characteristic curve of the solar cell (20). [4] In the above aspect, the transformer (T) of the power conversion unit (1) includes a first secondary coil (N21) configured to output in a forward manner with respect to the switching control of the primary coil (N1) and a second secondary coil (N22) configured to output in a flyback manner. The primary coil (N1) and the first secondary coil (N21) are loosely coupled. [5] In the above aspect, the power conversion unit (1) is characterized by outputting a pulsating current having the same frequency and phase as the pulsating current obtained by full-wave rectifying the utility voltage. [6] In the above aspect, the inverter unit (2) is characterized by converting the pulsating current output from the power conversion unit (1) into a sine wave by inverting every other one. [7] In the above aspect, the inverter unit (2) includes a first leg having an upper first switch element (Q1) and a lower second switch element (Q2) connected in series, and a second leg having an upper third switch (Q3) and a lower fourth switch element (Q4) connected in series. Each connection point of the first and second legs is an output terminal of the inverter unit (2). For each continuous pulsating current, a period in which the first and fourth switch elements (Q1, Q4) are on and the second and third switch elements (Q2, Q3) are off, and a period in which the first and fourth switch elements (Q1, Q4) are off and the second and third switch elements (Q2, Q3) are on are repeated. [8] In the above aspect, the on / off control of the first to fourth switches (Q1 to Q4) is performed using the pulsating current output from the power conversion unit (1) as a power source.

Advantages of the Invention

[0010] According to the present invention, by directly supplying the generated power of a solar cell to a general power outlet, it is possible to connect to the power grid, and a simple and compact power outlet power supply device with little power loss is realized.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the leakage detection device according to the present invention will be described in detail with reference to the drawings.

[0013] FIG. 1 is a diagram showing an overview of the overall configuration including the power outlet power supply device 10 according to the present invention. The utility power supply 40 of the commercial power grid is connected to the power outlet 30 via a distribution board (not shown) in a house or the like, and supplies AC 100V. The power outlet power supply device 10 is a device for supplying the generated power of the solar cell 20 to the power outlet 30 which is the output terminal of the utility power supply 40. The power outlet power supply device 10 serves as a simple power conditioner that converts the DC power of the solar cell 20 into AC power.

[0014] The solar cell 20 typically assumes a relatively small type installed, for example, on the roof of a house. The power generated by the solar cell 20 varies greatly depending on the weather and time of day. As an example, assume a solar cell with an open-circuit voltage of about 50V on a sunny day.

[0015] The socket power supply device 10 mainly includes a power conversion unit 1, an inverter unit 2, and a control unit 3. The power conversion unit 1 converts the power generated by the solar cell 20 so as to capture it at the maximum power point. Although details will be described later, the power conversion unit 1 includes a transformer and a switching element that switches and controls the primary coil of the transformer. The inverter unit 2 converts the output voltage of the power conversion unit 1 into a sine-wave voltage having the same frequency and phase as the voltage of the utility power supply 40. The control unit 3 generates a PWM signal for controlling the switching element of the power conversion unit 1. The socket power supply device 10 further includes a plug 9 which is an output terminal of the inverter unit 2. The plug 9 can be inserted into the socket 30.

[0016] Fig. 1 schematically shows the configuration of the control unit 3. The control unit 3 has a PWM signal generation unit 7 that generates a PWM signal to be transmitted to the power conversion unit 1. The PWM signal generation unit 7 generates a PWM signal, for example, by inputting a low-frequency modulation wave signal of about several tens of Hz and a high-frequency carrier wave signal of about several tens of kHz into a comparator. Such a PWM signal generation method is well known.

[0017] The modulation wave generation unit 4 generates a modulation wave signal to be output to the PWM signal generation unit 7. The modulation wave generation unit 4 receives signals from the utility voltage detection unit 5 and the generated voltage detection unit 6 respectively in order to generate the modulation wave signal.

[0018] The utility voltage detection unit 5 acquires the utility voltage (AC100V) of the utility power supply 40 from the output terminal of the inverter unit 2, performs a predetermined conversion, and outputs a predetermined signal to the modulation wave generation unit 4.

[0019] The power generation voltage detection unit 6 acquires the output voltage of the solar cell 2 from the output terminals of the solar cell 2, performs predetermined conversion, and outputs a predetermined signal to the modulation wave generation unit 4.

[0020] FIG. 2 is a diagram schematically showing a configuration example of the control unit 3 of the socket power supply device 10 in FIG. 1. FIG. 2 shows a state where the plug 9 in FIG. 1 is inserted into the socket 30. In the illustrated example, the control unit 3 converts the line voltage of the utility power supply 40 into a DC voltage of, for example, +24 V by the AC / DC converter 8 and is driven using this as a power source. For convenience of explanation, the potential of the negative terminal of the AC / DC converter 8 is taken as the reference potential of the control unit 3. When the plug 9 is pulled out from the socket 30, the power supply of the control unit 3 disappears, so the control unit 3 stops operating.

[0021] The line voltage detection unit 5 constitutes a diode bridge DB that full-wave rectifies the line voltage of the utility power supply 40. The input side of the line voltage detection unit 5 is connected to the utility power supply 40, and the resistor element R3 and the capacitor C4 connected in series to the utility power supply 40 serve as a high-pass filter that passes the line frequency. A pulsating current in which the positive half-wave of the line voltage continues is output to the output side of the line voltage detection unit 5. When a power outage occurs in the utility power supply 40 or when the plug 9 is pulled out from the socket 30, the input voltage of the line voltage detection unit 5 disappears, so the output voltage of the line voltage detection unit 5 also becomes 0 V. The line voltage detection unit 5 does not actively detect the utility power supply 40.

[0022] The power generation voltage detection unit 6 has a constant voltage element Z and a resistance element R1 connected in series between the output terminals of the solar cell 20. The constant voltage element Z maintains the voltage between both ends at a predetermined constant voltage. The negative terminal of the solar cell 20 has the same potential as the reference potential of the control unit 3. The constant voltage element Z is typically a Zener diode having a predetermined Zener voltage. The Zener voltage is set to be located near the shoulder portion of the I-V characteristic curve of the solar cell 20. For example, if the open-circuit voltage of the I-V characteristic curve is 50V, the Zener voltage is set to about 40V. Details will be described later with reference to FIG. 4. The control unit 3 performs a normal control operation when the output voltage of the solar cell 20 is higher than the Zener voltage. When the output voltage of the solar cell 20 is lower than the Zener voltage, the control unit 3 stops operating.

[0023] A voltage difference between the output voltage of the solar cell 20 and the Zener voltage is applied to the resistance element R1 of the power generation voltage detection unit 6, and a current corresponding to the resistance value flows. The current flowing through the resistance element R1 flows into the input-side diode of the photocoupler PV, and a voltage of a magnitude corresponding to the magnitude of the input-side current is output to the output side of the photocoupler PV. The photocoupler PV is connected such that its output voltage becomes a negative voltage with respect to the reference potential of the control unit 3. The output voltage of the photocoupler PV is used as a control voltage for controlling the second semiconductor element 13 of the modulation wave generation unit 4. A capacitor C3 for maintaining the output voltage and a discharge resistor R2 are connected in parallel to the output terminal of the photocoupler PV.

[0024] The modulation wave generation unit 4 includes a first semiconductor element 12 and a second semiconductor element 13. The first semiconductor element 12 is composed of a photocoupler, and the second semiconductor element 13 is composed of an n-channel JFET (junction field effect transistor). The current path between the collector and emitter of the output-side transistor of the photocoupler 12 and the current path between the drain and source of the JFET 13 are connected in series. The collector of the output-side transistor of the photocoupler 12 is connected to the positive terminal of the AC / DC converter 8, the emitter is connected to the drain of the JFET 13, and the source of the JFET 13 is connected to the negative terminal of the AC / DC converter 8. Therefore, a constant voltage is applied across both ends of the series-connected current path of the first semiconductor element 12 and the second semiconductor element 13.

[0025] The output voltage of the system voltage detection unit 5 is applied across both ends of the input-side diode of the photocoupler 12. Therefore, the current flowing through the output-side transistor of the photocoupler 12 (this current also flows through the current path of the DC-connected JFET 13) is controlled by a pulsating current obtained by full-wave rectifying the system voltage, and varies in accordance with the fluctuations of the pulsating current. As a result, the current flowing through the current path of the modulation wave generation unit 4 also becomes a pulsating current, whose frequency is twice the frequency of the system voltage and whose phase is the same.

[0026] The output voltage of the power generation voltage detection unit 6 is applied as the gate-source voltage for controlling the JFET 13. The n-channel JFET 13 is used between a negative pinch-off voltage (drain current 0 A) and 0 V (maximum drain current) of the gate-source voltage. Therefore, as the gate-source voltage increases (approaches the pinch-off voltage), the AC impedance of the current path of the JFET 13 increases, and as the gate-source voltage decreases (approaches 0 V), the AC impedance of the current path of the JFET 13 decreases.

[0027] Therefore, the potential at point A, which is the connection point between the photocoupler 12 and the JFET 13, becomes a potential divided by the ratio of the AC impedances of the current paths of the photocoupler 12 and the JFET 13, and the waveform of the flowing current is controlled to be a pulsating current. For example, when the output voltage of the power generation voltage detection unit 6 increases, the AC impedance of the current path of the JFET 13 increases, the potential at point A rises, and the amplitude of the pulsating current increases. Conversely, when the output voltage of the power generation voltage detection unit 6 decreases, the AC impedance of the current path of the JFET 13 decreases, the potential at point A drops, and the amplitude of the pulsating current decreases.

[0028] The PWM signal generation unit 7 includes a comparator 72 having two input terminals. The fluctuation of the potential at point A of the modulation wave generation unit 4 is input to one of the input terminals of the comparator 72 as a modulation wave signal. A carrier wave signal generated by the carrier wave generation unit 71 is input to the other input terminal of the comparator 72. Although the specific configuration of the carrier wave generation unit 71 is not shown, for example, a circuit that generates a high-frequency triangular wave of several tens of kHz is well known. Comparator 72 outputs a PWM signal having a pulse width corresponding to the amplitude of the modulated wave signal. When the amplitude of the modulated wave signal increases, the pulse width of the PWM signal becomes wider, and when the amplitude of the modulated wave signal decreases, the pulse width of the PWM signal becomes narrower. Since the modulated wave signal is pulsating current, the width of each pulse of the PWM signal is not constant. Therefore, the "pulse width" here refers to the average pulse width in one cycle of the pulsating current.

[0029] The PWM signal output by comparator 72 controls the gate of switching element S of power conversion unit 1 via an appropriate gate drive IC 73.

[0030] FIG. 3 is a diagram schematically showing a configuration example of power conversion unit 1 of the socket power supply device 10 in FIG. 1. A capacitor C1 for mitigating the output fluctuations of solar cell 20 is connected between the input terminals of power conversion unit 1.

[0031] In a preferred example, transformer T has a primary coil N1, a first secondary coil N21, and a second secondary coil N22. A switching element S is connected in series with primary coil N1. The switching element S is an n-channel MOSFET here, with its drain connected to primary coil N1 and its source connected to the negative input terminal. The gate is switched and controlled by the PWM signal output from the PWM signal generation unit 7 of the control unit.

[0032] Transformer T has the functions of both the forward method and the flyback method. The first secondary coil N21 is configured to output in the forward method with respect to the switching control of the primary coil N1. A diode D1 is connected in the forward direction with respect to the current flowing out from the start end (black dot) of the first secondary coil N21. On the other hand, the second secondary coil N22 is configured to output in the flyback method with respect to the switching control of the primary coil N1. A diode D2 is connected in the reverse direction with respect to the current flowing out from the start end (black dot) of the second secondary coil N22.

[0033] During the on-period of the switching element S, a forward current is output through the diode D1 due to the electromotive force generated in the first secondary coil N21. In order to prevent an excessive current like a short-circuit current from flowing through the first secondary coil N21 during the on-state, it is preferable to make the primary coil N1 and the first secondary coil N21 loosely coupled. For example, by providing a gap in the core or separating the two coils to generate leakage magnetic flux, the magnetic resistance of the magnetic circuit can be increased, and the excessive current during the on-state can be suppressed. On the other hand, in the second secondary coil N22, since the diode D2 is in the reverse direction, no current flows during the on-period, and magnetic energy is accumulated.

[0034] During the off-period of the switching element S, no current flows through the first secondary coil N21 because the diode D1 is in the reverse direction. On the other hand, in the second secondary coil N22, a flyback current flows through the diode D2 and is output. As a result, magnetic energy is released, so a magnetic reset circuit in a normal forward converter is unnecessary. Since magnetic saturation is less likely to occur, there is no need to use a large transformer.

[0035] Since current can be output during both the on-period and the off-period of the switching element S, a larger output can be obtained with a transformer of the same size compared to a power conversion unit using only the conventional flyback method.

[0036] A pulsating current is output between the output terminals of the power conversion unit 1 according to the control of the PWM signal from the control unit 3. The frequency of this pulsating current is twice the frequency of the utility voltage and the phases are the same. The amplitude of the output pulsating current varies according to the pulse width of the PWM signal. When the pulse width of the PWM signal becomes wider, the current taken in from the solar cell 20 becomes larger, and the amplitude of the pulsating current also becomes larger. When the pulse width of the PWM signal becomes smaller, the current taken in from the solar cell 20 becomes smaller, and the amplitude of the pulsating current also becomes smaller.

[0037] The capacitor C2 connected between the output terminals of the power conversion unit 1 is for removing high-frequency switching noise superimposed on the output low-frequency pulsating current.

[0038] Figure 4 is a diagram for explaining the control operation of the socket power supply device in FIG. 1. In FIG. 4, line L1 represents the I-V characteristic curve measured under the reference state (for example, the temperature of the solar cell is 25 °C and the irradiance is 1000 W / m 2 etc.), and it roughly corresponds to the sunshine situation on a sunny day. Line L2 is an example of the I-V curve on a cloudy day. The I-V characteristic curve has a portion that gradually decreases almost flatly from the short-circuit current Isc, a portion where the current rapidly decreases before the open-circuit voltage Voc, and a shoulder portion between these two. The maximum power point is at the point of V(Pmax) and I(Pmax) on line L1. The voltage of the maximum power point (not shown) of line L2 on a cloudy day is slightly lower than that on a sunny day.

[0039] The control unit 3 shown in FIG. 2 is set in accordance with the maximum power point of the I-V characteristic curve L1 in the reference state. The control unit 3 sets the shoulder portion centered around the maximum power point of the I-V characteristic curve as the control target range. The Zener voltage Vz of the Zener diode Z in FIG. 2 is set to the minimum voltage in the control target range of the control unit 3. Then, the resistance element R1 connected in series with the Zener diode Z is set in accordance with the maximum power point. That is, the voltage across the resistance element R1 is made to be V(Pmax) - Vz.

[0040] In the I-V characteristic curve of FIG. 4, for example, when the load becomes lighter and the output current increases from I(Pmax) to I1, the output voltage of the solar cell 20 decreases from V(Pmax) to V1, and the operating point deviates from the maximum power point. At this time, in the control unit 3 of FIG. 2, since the current flowing through the resistance element R1 decreases, the second semiconductor element (JFET) 13 has a smaller control voltage magnitude and the AC impedance of the current path decreases. As a result, the pulse width of the generated PWM signal is reduced, so the amount of current taken in by the power conversion unit 1 decreases. Thereby, the operating point returns toward the maximum power point.

[0041] Also, for example, when the load increases and the output current decreases from I(Pmax) to I2, the output voltage of the solar cell 20 increases from V(Pmax) to V2, and the operating point deviates from the maximum power point. At this time, in the control unit 3 of FIG. 2, since the current flowing through the resistance element R2 increases, the second semiconductor element 13 has an increased control voltage magnitude and an increased AC impedance of the current path. As a result, the pulse width of the generated PWM signal expands, so the amount of current taken in by the power conversion unit 1 increases. Thereby, the operating point will return toward the maximum power point.

[0042] When the sunlight changes, the shape of the I-V characteristic curve changes like the line L2 in FIG. 4, but the same control is performed within the control target range of the shoulder portion including the maximum power point.

[0043] In this way, maximum power point tracking control is simply realized without performing trial and error like the hill climbing method and without using a CPU or a program.

[0044] FIG. 5 is a diagram schematically showing a configuration example of the inverter unit 2 of the outlet power supply device of FIG. 1. The inverter unit 2 has a symmetric full-bridge configuration including a first leg and a second leg. In the first leg, the current paths of the upper first switch element Q1 and the lower second switch element Q2 are connected in series. In the second leg, the current paths of the upper third switch element Q3 and the lower fourth switch element Q4 are connected in series. In this example, each switch element is an n-channel MOSFET.

[0045] The connection point of the upper and lower switch elements in the first leg and the connection point of the upper and lower switch elements in the second leg are the output terminals of the inverter unit 2 and are connected to the plug 9. By the inverter unit 2, the pulsating current Vc input from the power conversion unit 1 is inverted every other one and converted into a sine wave alternating current vac. This sine wave alternating current vac has the same frequency and phase as the system voltage and has a voltage capable of being output to the system power supply. However, the sine wave alternating current vac is generated and output only when the plug 9 is connected to the outlet 30 of FIG. 1.

[0046] For this purpose, for each successive pulsating current, the period during which the first and fourth switch elements Q1 and Q4 are on and the second and third switch elements Q2 and Q3 are off (during which the current i1 shown by the solid line flows), and the period during which the first and fourth switch elements Q1 and Q4 are off and the second and third switch elements Q2 and Q3 are on (during which the current i2 shown by the dotted line flows) are repeated.

[0047] FIG. 6 is a diagram for schematically explaining the operation of the inverter section 2 in FIG. 5. Each of the switch elements Q1 to Q4 is configured such that each control terminal is driven using the pulsating current Vc input from the power conversion section 1 as a power source. Therefore, the inverter section 2 operates autonomously without an external control circuit. When the voltage of the pulsating current Vc is greater than the Zener voltages of the Zener diodes Z3 and Z4, each semiconductor element is driven using the voltage of the pulsating current Vc as a power source. During that time, the capacitors C3 and C4 are charged. When the voltage of the pulsating current Vc becomes less than the Zener voltages of the Zener diodes Z3 and Z4, each semiconductor element is driven using the voltages across the capacitors C3 and C4 as a power source.

[0048] FIG. 6(a) schematically shows waveforms for two cycles of the pulsating current Vc and the on and off states of each semiconductor element. FIG. 6(b) schematically shows the transition of the on and off switching of each semiconductor element at the X and Y time points in (a). The gray display indicates the off state or the transition to the off state. The switching is performed so that two switch elements on the same leg do not turn on simultaneously.

[0049] Since the power strip power supply device 10 of the present invention is configured to operate only when the utility power supply 40 is present, it does not output the generated power of the solar cell 20 when the voltage of the utility power supply 40 disappears. Therefore, single operation can be easily prevented. Also, the output stops immediately when the plug 9 is removed from the power strip 30.

[0050] As described above, the present invention has been described with reference to the configurations shown as examples. However, as long as it follows the principle of the present invention, various modified forms are also included in the scope of the present invention.

Description of Symbols

[0051] 1 Power conversion unit 2 Inverter unit 3 Control unit 4 Modulation wave generation unit 5 System voltage detection unit 6 Generated voltage detection unit 7 PWM signal generation unit 8 AC / DC converter 9 Plug 10 Outlet power supply device 20 Solar cell 30 Outlet 40 Utility power supply

Claims

1. A socket power supply device (10) for supplying the generated power of a solar cell (20) to a socket (30) connected to a utility power supply (40), comprising a power conversion unit (1) including a transformer (T) and a switching element (S) for switching control of the primary coil (N1) of the transformer (T) to convert the generated power of the solar cell (20), an inverter unit (2) for converting the output voltage of the power conversion unit (1) into a sine wave voltage having the same frequency and phase as the utility voltage, a plug (9) which is an output terminal of the inverter unit (2) and can be inserted into the socket (30), and a control unit (3) for generating a PWM signal for controlling the switching element (S). The control unit (3) includes a utility voltage detection unit (5) for full-wave rectifying the utility voltage acquired via the plug (9), a generated voltage detection unit (6) including a constant voltage element (Z) and a resistance element (R1) connected in series between the output terminals of the solar cell (20), and outputting a voltage having a magnitude corresponding to the magnitude of the current flowing through the resistance element (R1), a modulation wave generation unit (4) including a first semiconductor element (12) and a second semiconductor element (13) each having current paths connected in series and a constant voltage applied across both ends thereof, and outputting the potential at the connection point (A) between the first semiconductor element (12) and the second semiconductor element (13) as a modulation wave signal, and a PWM signal generation unit (7) which receives a high-frequency carrier signal and the modulation wave signal from the modulation wave generation unit (4) and outputs the PWM signal, wherein the first semiconductor element (12) is controlled by the output voltage of the utility voltage detection unit (5), and the AC impedance of the current path of the second semiconductor element (13) varies according to the magnitude of the output voltage of the generated voltage detection unit (6). The socket power supply device is characterized by this.

2. When the output voltage of the solar cell (20) increases or decreases, the output voltage of the generated voltage detection unit (6) increases or decreases, the AC impedance of the current path of the second semiconductor element (13) increases or decreases, the pulse width of the PWM signal expands or contracts, and the current taken in by the power conversion unit (1) increases or decreases. The socket power supply device according to Claim 1 is characterized by this.

3. The consent power supply device according to claim 1, wherein the constant voltage (Vz) of the constant voltage element (Z) is set to the voltage at the minimum value of the shoulder portion, which is the control target range in the I-V characteristic curve of the solar cell (20).

4. The transformer (T) of the power conversion unit (1) includes a first secondary coil (N21) configured to output in a forward manner with respect to the switching control of the primary coil (N1) and a second secondary coil (N22) configured to output in a flyback manner, The consent power supply device according to claim 1, wherein the primary coil (N1) and the first secondary coil (N21) are loosely coupled.

5. The consent power supply device according to claim 4, wherein the power conversion unit (1) outputs a pulsating current having the same frequency and phase as the pulsating current obtained by full-wave rectifying the utility voltage.

6. The consent power supply device according to claim 5, wherein the inverter unit (2) converts the pulsating current output by the power conversion unit (1) into a sine wave by inverting every other one.

7. The inverter unit (2) includes a first leg having an upper first switch element (Q1) and a lower second switch element (Q2) connected in series, and a second leg having an upper third switch (Q3) and a lower fourth switch element (Q4) connected in series, and connection points of the first and second legs are output terminals of the inverter unit (2), The consent power supply device according to claim 6, wherein for each continuous pulsating current, a period in which the first and fourth switch elements (Q1, Q4) are on and the second and third switch elements (Q2, Q3) are off and a period in which the first and fourth switch elements (Q1, Q4) are off and the second and third switch elements (Q2, Q3) are on are repeated.

8. The consent power supply device according to claim 7, wherein the on / off control of the first to fourth switches (Q1 to Q4) is performed using the pulsating current output by the power conversion unit (1) as a power source.

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