TWI516011B - Solar inverter and voltage transformation method thereof - Google Patents

Description

Solar inverter and voltage conversion method thereof

The present invention relates to a solar inverter, and more particularly to a single stage solar inverter having a buck mode and a boost mode.

With the vigorous development of industry and technology, human consumption of petrochemical energy is increasing day by day, while the earth's natural resources are limited. In order to avoid the lack of energy and the serious damage to the environment and ecology caused by excessive use of petrochemical energy, governments have begun to promote energy conservation. In addition to saving energy, people are also actively looking for alternative energy solutions. Solar energy, wind energy and biomass energy are all research goals. Among them, solar energy is most favored by everyone. Because the inexhaustible use of solar energy, the process of converting electrical energy is clean and pollution-free, so naturally the most people invest in research.

A typical solar photovoltaic system consists of a solar cell module and an inverter. The solar cell module converts the sun's rays into electric energy in the form of a direct current voltage; the inverter converts the direct current voltage generated by the solar cell module into an alternating voltage that can be sent to the grid.

In the high-wattage specification of solar photovoltaic systems, multiple solar cell modules are connected in series to achieve the output specifications required by the solar cell module, and the back-end inverters convert the direct current into alternating current output. . The traditional multi-string inverter (Multi-String Inverter) can be divided into two stages. The first stage is to convert the DC voltage converted by the solar cell module to a boost converter or a buck converter. Is going to solar energy The DC output from the battery module is converted into the input voltage required by the second stage to obtain the required input voltage. The second stage then controls the full bridge circuit with a sinusoidal pulse width modulation (Sinusoidal Pulse Width Modulation) signal. The voltage is converted into a square wave whose width does not depend, and finally the AC voltage is output through the filter circuit.

Since the traditional inverter requires two stages of circuits to achieve the AC voltage value required by the city grid circuit, the more components the circuit loop passes through, the greater the total loss on the components, which is the efficiency of the conventional inverter. The main reason for not being high, and the number of circuit components is large, the cost is certainly increased, and the price of the solar photovoltaic system cannot be effectively reduced.

In view of this, the present disclosure provides a solar inverter with a pseudo DC link, and the solar inverter performs maximum power tracking and modulation output through a DC/DC converter for full-wave rectification. Wave wave. After that, the AC/DC inverter (or polarity selector) of the latter stage is simply restored to a positive and negative half-cycle sine wave output to the AC grid.

Embodiments of the present invention provide a solar inverter including a buck-boost converter, an isolation transformer, a full-wave rectifier, and a polarity selector. The buck-boost converter receives the input voltage, the buck modulation signal and the boost modulation signal, wherein the buck-boost converter modulates the input voltage according to the buck modulation signal and the boost modulation signal, and outputs a waveform adjustment signal accordingly When the buck-boost converter is stepping down the input voltage according to the buck modulation signal in the buck mode, when the buck-boost converter is in boost mode according to the boost modulation The signal boosts the input voltage step by step. The isolation transformer has a primary side and a secondary side, and the isolation transformer is electrically connected to the buck-boost converter. The isolation transformer is used for electrical isolation, receives the waveform adjustment signal, and outputs the isolated waveform adjustment signal. The full-wave rectifier is electrically connected to the isolation transformer, and the full-wave rectifier rectifies the isolated waveform adjustment signal, and outputs a full-wave pulse signal accordingly. The polarity selector is electrically connected to the full-wave rectifier, and the polarity selector reverses the polarity of the waveform of the half-cycle of the full-wave pulse signal, and outputs a commercial sine wave signal accordingly.

In one of the embodiments of the present invention, wherein the buck-boost converter is in the boost mode, the duty cycle of the buck modulation signal is 100% and the duty cycle of the boost modulation signal is greater than 50%.

In one embodiment of the present invention, wherein when the buck-boost converter is in the buck mode, the duty cycle of the buck modulation signal is less than 100% and the duty cycle of the boost modulation signal is equal to the threshold duty cycle, wherein the threshold responsibility The period is the minimum duty cycle for the buck-boost converter to function properly.

In one embodiment of the present invention, wherein the buck-boost converter is more electrically connected to the digital signal processing chip, when the voltage of the preset sine wave is greater than the boundary voltage, the buck-boost converter is in the boost mode when the sine is preset. When the voltage of the wave is less than the boundary voltage, the buck-boost converter is in the buck mode.

In one embodiment of the present invention, in the boost mode, when the voltage of the first triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a boost signal of the high level voltage to the rise and fall. The voltage converter; when the voltage of the first triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs a boost modulation signal of the low level voltage to the buck-boost converter.

In one embodiment of the present invention, in the step-down mode, when the voltage of the second triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a step-down modulated signal of the high level voltage to the rise and fall. The voltage converter; when the voltage of the second triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs a step-down modulation signal of the low level voltage to the buck-boost converter.

In one embodiment of the invention, wherein the polarity selector operates at a mains frequency and the sine wave signal it outputs is a mains frequency, wherein the polarity selector is electrically coupled to the AC grid.

In one embodiment of the invention, the buck-boost converter includes a first transistor, a second transistor, a third transistor, and a fourth transistor. The gate of the first transistor receives the first pulse width modulation signal, and the source of the first transistor is connected to the winding of the primary side of the isolation transformer. The gate of the second transistor receives the second pulse width modulation signal, and the drain of the second transistor is coupled to the source of the first transistor. The gate of the third transistor receives the third pulse width modulation signal, and the drain of the third transistor is connected to the first end of the first transistor and the first end of the buck-boost inductor, and the source connection of the third transistor is isolated The winding on the primary side of the transformer. The gate of the fourth transistor receives the fourth pulse width modulation signal, the drain of the fourth transistor is connected to the source of the third transistor, and the source of the fourth transistor is connected to the source of the second transistor and the first Ground voltage. The first to fourth pulse width modulation signals are boost modulation signals, and when in the boost mode, the duty cycle corresponding to the first to fourth pulse width modulation signals is greater than 50% to gradually input the input voltage Boost; when in the buck mode, the duty cycle corresponding to the first to fourth pulse width modulation signals is equal to the threshold duty cycle to maintain the buck-boost converter in normal operation.

In one embodiment of the invention, the buck-boost converter further includes a drop Piezoelectric crystals and a step-down diode. The gate of the step-down transistor receives the step-down modulation signal, the drain of the step-down transistor is connected to the input voltage, and the source of the step-down transistor is connected to the second end of the step-up and step-down inductor. The anode of the step-down diode is connected to the first ground voltage, and the cathode of the step-down diode is connected to the source of the step-down transistor. When in the boost mode, the duty cycle of the buck modulation signal is 100% to turn on the buck transistor. When in the buck mode, the duty cycle of the buck modulation signal is less than 100% to gradually reduce the input voltage. Pressure.

In one embodiment of the invention, the full wave rectifier includes a first diode, a second diode, a third diode, a fourth diode, and a capacitor. The anode of the first diode is connected to the second ground voltage. The anode of the second diode is connected to the anode of the first diode. The anode of the third diode is connected to the cathode of the first diode and the winding of the secondary side of the isolation transformer. The anode of the fourth diode is connected to the cathode of the second diode and the winding of the secondary side of the isolation transformer, and the cathode of the fourth diode is connected to the cathode of the third diode. The first end of the capacitor is connected to the cathode of the third diode, and the second end of the capacitor is connected to the second ground voltage. The first to fourth diodes are used for full-wave rectifying the isolated waveform adjustment signal, and thereby outputting a full-wave pulse signal.

In one embodiment of the invention, the polarity selector comprises a first tamper switch, a second tamper switch, a third tamper switch and a fourth tamper switch. The first end of the first switch is connected to the first end of the capacitor, and the control end of the first switch receives the first control signal and determines the on or off state accordingly. The first end of the second control switch is connected to the second end of the first control switch and the positive end of the AC power grid, the second end of the second control switch is connected to the second ground voltage, and the control end of the second control switch receives The second control signal determines the on or off state accordingly. The first end of the third tamping switch is connected to the first end of the capacitor, and the control end of the third tamping switch receives the third control signal and determines the conduction according to the third end Or disconnected state. The first end of the fourth tamper switch is connected to the second end of the third tamper switch and the negative end of the AC power grid, and the second end of the fourth tamper switch is connected to the second ground voltage, and the control end of the fourth tamper switch receives The fourth control signal determines the on or off state accordingly. The first and the fourth switch are in the same state of being turned on or off, the second and the third switch are in the same state of being turned on or off, and the first and the second switch are turned on. Or the reverse state is reversed.

Another embodiment of the present invention provides a voltage conversion method for a solar inverter. The voltage conversion method includes the steps of: receiving an input voltage, a step-down modulation signal, and a step-up modulation signal, wherein the input voltage is modulated according to the step-down modulation signal and the step-up modulation signal, and the waveform adjustment signal is output according to the signal; The isolated waveform adjustment signal is full-wave rectified, and the full-wave pulse signal is output according to this; and the waveform of the half-cycle of the full-wave pulse signal is reversed, and the commercial sine wave signal is output accordingly. In the buck mode, the input voltage is stepped down according to the buck modulation signal, and in the boost mode, the input voltage is stepped up according to the boost modulation signal.

In summary, the solar inverter and the voltage conversion method thereof according to the embodiments of the present invention can convert the input voltage received by the solar inverter into a boost mode and a buck mode through the buck-boost converter. The mains sine wave signal achieves excellent conversion efficiency at high power. Moreover, the present disclosure can reduce the complexity of circuit design to further save component count and circuit design cost.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims Scope Any restrictions.

Various illustrative embodiments are described more fully hereinafter with reference to the accompanying drawings. However, the inventive concept may be embodied in many different forms and should not be construed as being limited to the illustrative embodiments set forth herein. Rather, these exemplary embodiments are provided so that this invention will be in the In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Similar numbers always indicate similar components.

It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, such elements are not limited by the terms. These terms are used to distinguish one element from another. Thus, a first element discussed below could be termed a second element without departing from the teachings of the inventive concept. As used herein, the term "and/or" includes any of the associated listed items and all combinations of one or more.

[Embodiment of Solar Inverter]

Please refer to FIG. 1. FIG. 1 is a block diagram of a solar inverter according to an embodiment of the invention. As shown in FIG. 1, the solar inverter 100 includes a buck-boost converter 110, an isolation transformer 120, a full-wave rectifier 130, and a polarity selector 140. The buck-boost converter 110 is electrically connected to the isolation transformer 120. The isolation transformer 120 is electrically connected between the buck-boost converter 110 and the full-wave rectifier 130. The full wave rectifier 130 is electrically connected to the polarity selector 140.

Regarding the boost converter 110, the buck-boost converter 110 receives the input voltage VIN, the buck modulation signal BU, and the boost modulation signal BST, where The buck converter 110 modulates the input voltage VIN according to the buck modulation signal BU and the boost modulation signal BST, and accordingly outputs the waveform adjustment signal WS, wherein the buck-boost converter 110 is in the buck mode, according to the buck. The modulation signal BU gradually steps down the input voltage VIN, and the step-up and step-down converter 110 gradually boosts the input voltage VIN according to the boost modulation signal BST in the boost mode. In this embodiment, the input voltage VIN is the output voltage of the solar panel.

Regarding the isolation transformer 120, the isolation transformer 120 has a primary side and a secondary side, the isolation transformer 120 is used for electrical isolation for safety purposes, and the isolation transformer 120 receives the waveform adjustment signal WS and correspondingly outputs the isolated waveform adjustment signal. WS'.

Regarding the full-wave rectifier 130, the full-wave rectifier 130 fully-wave rectifies the isolated waveform adjustment signal WS', and accordingly outputs the full-wave pulse signal AS.

Regarding the polarity selector 140, the polarity selector 140 reverses the polarity of the waveform of the half-cycle of the full-wave pulse signal AS, and outputs the commercial sine wave signal VOUT to an AC power grid (not shown in FIG. 1), wherein the polarity is selected. The device 140 operates at the mains frequency and switches when the zero crossing occurs.

What is to be taught next is to further explain the working principle of the solar inverter 110.

Referring to FIG. 1 , when the buck-boost converter 110 receives the output voltage of the solar panel, that is, when the buck-boost converter 110 receives the input voltage VIN, the buck-boost converter 110 uses a voltage modulation conversion mechanism to input the voltage. The voltage VIN is modulated. Further, in the buck mode, the buck-boost converter 110 gradually steps down the input voltage VIN through the buck modulation signal BU it receives. In addition, in the boost mode, the buck-boost converter The 110 will gradually boost the input voltage VIN through the boost modulation signal BST it receives. It is worth mentioning that, in this embodiment, in order to enable the solar inverter 100 to operate normally, when the step-up/down converter 110 is in the boost mode, the duty cycle of the step-down modulation signal BU is 100% and rises. The duty cycle of the pressure modulation signal BST is greater than 50%. When the buck-boost converter 110 is in the buck mode, the duty cycle of the buck modulation signal BU is less than 100% and the duty cycle of the boost modulation signal BST is equal to the threshold duty cycle, wherein the threshold duty cycle is to enable buck-boost conversion The minimum duty cycle for the device 110 to function properly.

It is worth mentioning that, in this embodiment, the step-down converter 110 is more electrically connected to the digital signal processing chip (not shown in FIG. 1). The digital signal processing chip receives the input voltage VIN and the input current, and the output voltage VOUT and the output current of the output of the full-wave rectifier 130 to further adjust the mechanism inside the buck-boost converter 110 and correspondingly output the buck modulation signal. BU and boost modulation signal BST, designers can use the firmware to design the needs of the actual application. In the digital signal processing chip, when the voltage of the preset sine wave is greater than the boundary voltage, it means that the buck-boost converter 110 enters a so-called boost mode; when the voltage of the preset sine wave is less than the boundary voltage, it means that the buck-boost conversion The device 110 enters a so-called buck mode.

In the boost mode, when the voltage of the first triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a boost signal BST of the high level voltage to the buck-boost converter 110. When the voltage of the first triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs the boost modulation signal BST of the low level voltage to the buck-boost converter 110. In the buck mode, when the voltage of the second triangular wave signal is greater than the voltage of the preset sine wave, the digital signal is The chip outputs a step-down modulation signal BU of the high-level voltage to the buck-boost converter 110; when the voltage of the second triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs a low-level voltage step-down The signal BU is modulated to the buck-boost converter 110.

It should be noted that the boundary voltage, the voltage of the preset sine wave, the voltage of the first triangular wave and the voltage of the second triangular wave are all designed by the firmware design to be built into the table inside the digital signal processing chip. Can be further modified according to actual application needs.

Next, the buck-boost converter 110 outputs a waveform adjustment signal WS to the isolation transformer 120 for electrical isolation through the isolation transformer 120. The isolation transformer 120 correspondingly outputs the isolated waveform adjustment signal WS' to the full-wave rectifier 130 to perform full-wave rectification of the isolated waveform adjustment signal WS' through the full-wave rectifier 130, and output a full-wave according thereto. Pulse signal AS. Thereafter, the polarity selector 140 reverses or reverses the waveform of the half-cycle of the full-wave pulse signal, and accordingly outputs the commercial sine wave signal VOUT to the AC grid to be incorporated into the energy supply system of the AC grid. Accordingly, the present disclosure can simultaneously generate a sine wave waveform during the voltage level increase, thereby achieving excellent conversion efficiency at high power, that is, voltage conversion of the voltage generated by the solar panel and generating a sine wave signal to Energy supply system into the AC grid. Therefore, the disclosure can reduce the complexity of the circuit design to further save component count and circuit design cost.

In order to explain in more detail the operational flow of the solar inverter 100 of the present invention, at least one of the following embodiments will be further described.

In the following various embodiments, an embodiment different from the above FIG. 1 will be described. Portions, and the remaining omitted portions are the same as those of the embodiment of Fig. 1 described above. In addition, for the sake of convenience, like reference numerals or numerals indicate similar elements.

[Another embodiment of a solar inverter]

Please refer to FIG. 2. FIG. 2 is a block diagram of a solar inverter according to an embodiment of the present invention. Different from the above embodiment of FIG. 1, in the present embodiment, the buck-boost converter 110 includes a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth transistor Q4, and a step-down transistor. Qb, step-down diode Db and buck-boost inductor Lb. The full-wave rectifier 130 includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, and a capacitor Cr. The polarity selector 140 includes a first switch S1, a second switch S2, a third switch S3 and a fourth switch S4. The solar inverter 200 further includes a coupling capacitor Cin connected in parallel to the input voltage VIN.

Wherein, the first transistor Q1, the second transistor Q2, the third transistor Q3, the fourth transistor Q4, and the step-up and step-down inductor Lb are main components for completing the boost mode in this embodiment, and The step-down transistor Qb, the step-down diode Db, and the step-up and step-down inductor Lb are the main components for completing the buck mode in this embodiment.

The gate of the first transistor Q1 receives the first pulse width modulation signal BST1, and the source of the first transistor Q1 is connected to the winding of the primary side of the isolation transformer 120. The gate of the second transistor Q2 receives the second pulse width modulation signal BST2, and the drain of the second transistor Q2 is connected to the source of the first transistor Q1. The gate of the third transistor Q3 receives the third pulse width modulation signal BST3, and the drain of the third transistor Q3 is connected to the first end of the first transistor Q1 and the first end of the step-up and step-down inductor Lb, the third transistor The source is connected to the winding of the primary side of the isolation transformer 120. The gate of the fourth transistor Q4 receives the fourth pulse width modulation signal BST4 The drain of the fourth transistor Q4 is connected to the source of the third transistor Q3, and the source of the fourth transistor Q4 is connected to the source of the second transistor Q2 and the first ground voltage GND1. Wherein, the first pulse width modulation signal to the fourth pulse width modulation signal BST1~BST4 are the boost modulation signal BST, and when in the boost mode, the first to fourth pulse width modulation signals BST1~BST4 The corresponding duty cycle is greater than 50% to gradually increase the input voltage VIN; when in the buck mode, the duty cycle corresponding to the first to fourth pulse width modulation signals BST1 to BST4 is equal to a threshold duty cycle, The normal operation of the buck-boost converter 110 is maintained.

The gate of the step-down transistor Qb receives the step-down modulation signal BU, the drain of the step-down transistor Qb is connected to the input voltage VIN, and the source of the step-down transistor Qb is connected to the second end of the step-up and step-down inductor Lb. The anode of the step-down diode Db is connected to the first ground voltage GND1, and the cathode of the step-down diode Db is connected to the source of the step-down transistor Qb. When in the boost mode, the duty cycle of the buck modulation signal BU is 100% to turn on the buck transistor Qb, and when in the buck mode, the duty cycle of the buck modulation signal BU is less than 100% to input the voltage. VIN gradually steps down.

The anode of the first diode D1 is connected to the second ground voltage GND2. The anode of the second diode D2 is connected to the anode of the first diode D1. The anode of the third diode D3 is connected to the cathode of the first diode D1 and the winding of the secondary side of the isolation transformer 120. The anode of the fourth diode D4 is connected to the cathode of the second diode D2 and the winding of the secondary side of the isolation transformer 120, and the cathode of the fourth diode D4 is connected to the cathode of the third diode D3. The first end of the capacitor Cr is connected to the cathode of the third diode D3, and the second end of the capacitor Cr is connected to the second ground voltage GND2. The first to fourth diodes D1 to D4 are used for full-wave rectifying the isolated waveform adjustment signal WS', and according to the output of the full-wave pulse Wave signal AS.

The first end of the first switch S1 is connected to the first end of the capacitor Cr, and the control end of the first switch S1 receives the first control signal CS1 and determines the on or off state accordingly. The first end of the second switch S2 is connected to the second end of the first switch S1 and the positive end of the AC power grid, and the second end of the second switch S2 is connected to the second ground voltage GND2, the second switch The control terminal of S2 receives the second control signal CS2 and determines the on or off state accordingly. The first end of the third switch S3 is connected to the first end of the capacitor Cr, and the control end of the third switch S3 receives the third control signal CS3 and determines the on or off state accordingly. The first end of the fourth control switch S4 is connected to the second end of the third control switch S3 and the negative end of the AC power grid, and the second end of the fourth control switch S4 is connected to the second ground voltage GND2, the fourth control switch The control terminal of S4 receives the fourth control signal CS4 and determines the on or off state accordingly. The first switch S1 and the fourth switch S4 are in the same state of being turned on or off, and the second switch S2 and the third switch S3 are in the same state of being turned on or off, and the first switch S1 is It is opposite to the on or off state of the second switch S2.

What is to be taught next is to further explain the working principle of the solar inverter 200, and assume that all switching elements are ideal components.

Please refer to FIG. 2 to FIG. 5 at the same time. FIG. 3 is a schematic diagram of driving waveforms according to an embodiment of the present invention. 4 is a circuit diagram of a solar inverter in a boost mode according to an embodiment of the invention. FIG. 5 is a circuit diagram of a solar inverter in a buck mode according to an embodiment of the invention. When the voltage of the preset sine wave Vg is greater than the boundary voltage Vb, the step-up and step-down converter 110 is in the boost mode. At this time, when the voltage of the first triangular wave signal VT1 is greater than the voltage of the preset sine wave Vg, the digital signal processing chip outputs a high output. The first to fourth pulse width modulation signals BST1 to BST4 of the level voltage are corresponding to the first to fourth transistors Q1 to Q4; when the voltage of the first triangular wave signal VT1 is less than the voltage of the preset sine wave Vg, The digital signal processing chip outputs first to fourth pulse width modulation signals BST1 to BST4 of the low level voltage to the corresponding first to fourth transistors Q1 to Q4.

When the voltage of the preset sine wave Vg is less than the boundary voltage Vb, the step-up and step-down converter 110 is in the buck mode. At this time, when the voltage of the second triangular wave signal VT2 is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a step-down modulation signal BU of the high level voltage to the step-down transistor Qb, when the second triangular wave signal When the voltage of VT2 is less than the voltage of the preset sine wave, the digital signal processing chip outputs the step-down modulation signal BU of the low level voltage to the step-down transistor Qb. It should be noted that, in the buck mode, the duty cycle δbuck of the buck modulation signal BU is less than 100% and is transmitted to the first to fourth pulse width modulation signals BST1 of the first to fourth transistors Q1 to Q4. ~BST4's duty cycle δboos is a threshold duty cycle δmin, and this threshold duty cycle δmin is the minimum duty cycle for the buck-boost converter 110 to operate normally.

Next, a detailed description of the solar inverter 200 in the boost mode will be described.

Please refer to FIG. 6 to FIG. 10 simultaneously. FIG. 6 is a driving waveform diagram of first to fourth pulse width modulation signals according to an embodiment of the present invention. 7 to 10 are circuit diagrams of a solar inverter in a boost mode according to an embodiment of the present invention. Before the following description is made, it should be noted that a switching cycle is taken as an example to facilitate the understanding of the disclosure, but the disclosure is not limited by one switching cycle. Furthermore, in the boost mode, the duty cycle δbuck of the buck modulation signal BU is 100%, so the buck transistor Qb It is always in the on state, and the duty cycle δboost of the first to fourth pulse width modulation signals BST1 to BS4 is greater than 50%.

As shown in FIG. 7, in the time interval from time t0 to t1, the first to fourth transistors Q1 to Q4 are all turned on according to the received first to fourth pulse width modulation signals BST1 to BST4, and thus the buck-boost Inductor Lb will begin to work on energy storage. At this time, the primary side of the isolation transformer 120 is due to the fact that the first to fourth transistors Q1 to Q4 are all turned on so that no energy is transmitted to the secondary side of the isolation transformer 120, so the energy of the load is all paid to the whole. The capacitance Cr in the wave rectifier 130 is provided. As shown in FIG. 8, in the time interval from time t1 to t2, at time t1, the second transistor Q2 and the third transistor Q3 are modulated according to the second and third pulse width modulation signals BST2, BST3 received therefrom. It will be turned off, and the first transistor Q1 and the fourth transistor Q4 will remain in an on state. Therefore, the energy stored in the step-up and step-down inductor Lb charges the capacitor Cr through the isolation transformer 120 and the second diode D2 and the third diode D3 in the full-wave rectifier 130 to store energy. Next, as shown in FIG. 9, in the time interval from time t2 to time t3, the first to fourth transistors Q1 to Q4 are all turned on according to the received first to fourth pulse width modulation signals BST1 to BST4. Therefore, the buck-boost inductor Lb will start the energy storage work again. At this time, the primary side of the isolation transformer 120 is due to the fact that the first to fourth transistors Q1 to Q4 are all turned on so that no energy is transmitted to the secondary side of the isolation transformer 120, so the energy of the load is all paid to the whole. The capacitance Cr in the wave rectifier 130 is provided, wherein the current path is the same as in the embodiment of FIG. Thereafter, as shown in FIG. 10, in the time interval from time t3 to t4, at time t3, the first transistor Q1 and the fourth transistor Q4 are modulated according to the first and fourth pulse width modulation signals received therefrom. BST1 and BST4 are turned off, while the second transistor Q2 and the third transistor Q3 are kept on. state. Therefore, the energy stored in the buck-boost inductor Lb reversely charges the capacitor Cr through the isolating transformer 120 and the fourth diode D4 and the first diode D1 in the full-wave rectifier 130 to store energy. In the next switching cycle, it should be understood that the solar inverter 200 will continuously repeat the operation of the boost mode as shown in FIG. 7 to FIG. 10 above to modulate the input voltage VIN, and will not be described herein.

Next, a detailed description of the solar inverter 200 in the step-down mode will be described.

Referring to FIG. 11 to FIG. 17, FIG. 11 is a driving waveform diagram of first to fourth pulse width modulation signals and step-down modulation signals according to an embodiment of the present invention. 12 to 17 are circuit diagrams of a solar inverter in a buck mode according to an embodiment of the invention. Before the following description is made, it should be noted that a switching cycle is taken as an example to facilitate the understanding of the disclosure, but the disclosure is not limited by one switching cycle. In the buck mode, the duty cycle δbuck of the buck modulation signal BU is less than 100%, and the duty cycle δboost of the first to fourth pulse width modulation signals BST1 to BST4 is the threshold duty cycle δmin, wherein the threshold duty cycle δmin is Defined as the minimum duty cycle for the buck-boost converter 110 to function properly.

As shown in FIG. 12, in the time interval from time t0 to t1, the step-down transistor Qb, the first transistor Q1 and the fourth transistor Q4 are respectively controlled by the step-down modulation signal BU and the first pulse width modulation signal. The BST1 is turned on with the fourth pulse width modulation signal BST4, and the second diode D2 and the third diode D3 are turned on. Therefore, the step-up and step-down inductor Lb is charged via the isolation transformer 120 with a capacitance Cr to store energy. Next, as shown in FIG. 13, during the time interval from time t1 to t2, the step-down transistor Qb controlled by the buck modulation signal BU is turned off, and is controlled by the first pulse width modulation signal BST1 and Fourth pulse The first transistor Q1 and the fourth transistor Q4 of the wide modulation signal BST4 are continuously turned on, and the second diode D2 and the third diode D3 are also continuously turned on. Therefore, the step-up and step-down inductor Lb continues to store the capacitor Cr through the isolation transformer 120. Next, as shown in FIG. 14, in the time interval from time t2 to t3, the step-down transistor Qb and the first to fourth transistors Q1 to Q4 are respectively controlled by the step-down modulation signal BU and the first to fourth The pulse width modulation signal BST1~BST4 is turned on. Therefore, the input voltage VIN (that is, the energy on the solar panel) will store the buck-boost inductor Lb through the step-down transistor Qb. At this time, the primary side of the isolation transformer 120 is short-circuited because the first to fourth transistors Q1 to Q4 are all turned on, so that no energy is transmitted to the secondary side of the isolation transformer 120, and the load energy is obtained by the capacitance. Cr to provide. Thereafter, as shown in FIG. 15, during the time interval from time t3 to time t4, the step-down transistor Qb controlled by the buck modulation signal BU is turned on, and is controlled by the first pulse width modulation signal BST1 and The fourth pulse width modulation signal BST4 is turned off, and the first diode D1 and the fourth diode D4 are turned on. Therefore, the step-up and step-down inductor Lb reversely charges the capacitor Cr via the isolation transformer 120 to store energy. Next, as shown in FIG. 16, during the time interval from time t4 to t5, the step-down transistor Qb controlled by the buck modulation signal BU is turned off, and is controlled by the second pulse width modulation signal BST2 and The second transistor Q2 and the third transistor Q3 of the three-pulse width modulation signal BST3 are still turned on, and the fourth diode D4 and the first diode D1 are continuously turned on. Therefore, the step-up and step-down inductor Lb continues to store the capacitor Cr through the isolation transformer 120. Finally, as shown in FIG. 17, in the time interval from time t5 to t6, the step-down transistor Qb and the first are controlled by the step-down modulation signal BU and the first to fourth pulse width modulation signals BST1 B BST4, respectively. Until the fourth transistor Q1~Q4, all of them will be turned on. Therefore, enter The voltage VIN (ie, the energy on the solar panel) will store the buck-boost inductor Lb via the buck transistor Qb. At this time, the primary side of the isolation transformer 120 is short-circuited due to the all-on relationship of the first to fourth transistors Q1 to Q4, so that no energy is transmitted to the secondary side of the isolation transformer 120. Therefore, the load energy is provided by the capacitor Cr, wherein the current path is the same as in the embodiment of Fig. 14. In the next switching cycle, it should be understood that the solar inverter 200 will repeatedly repeat the operation of the buck mode as shown in the above-mentioned FIG. 12 to FIG. 17 to modulate the input voltage VIN, which will not be described herein.

Further detailed next is the related detailing of the polarity selector 140.

Please refer to FIG. 18 to FIG. 20 simultaneously. FIG. 18 is a driving waveform diagram of a control signal according to an embodiment of the present invention. 19 to 20 are circuit diagrams showing the operation of a polarity selector according to an embodiment of the present invention. Before the following description is made, it should be noted that a switching cycle is taken as an example to facilitate the understanding of the disclosure, but the disclosure is not limited by one switching cycle.

As shown in FIG. 19, during the time interval from time t0 to t1, the first control switch S1 and the fourth control switch S4 controlled by the first control signal CS1 and the fourth control signal CS4 are turned on, and are controlled. The second control switch S2 and the third control switch S3 of the second control signal CS2 and the third control signal CS3 are turned off. Therefore, the energy on the capacitor Cr is transmitted to the AC grid through the current path as shown in FIG. 19 to be incorporated into the energy supply system of the AC grid. Next, as shown in FIG. 20, during the time interval from time t1 to t2, the second switch S2 and the third switch S3 controlled by the second control signal CS2 and the third control signal CS3 are turned on, and The first switch S1 and the fourth switch controlled by the first control signal CS1 and the fourth control signal CS4 are controlled to open Off S4 will be closed. Therefore, the energy on the capacitor Cr is transmitted to the AC grid through the current path as shown in FIG. 20 to be incorporated into the energy supply system of the AC grid. It is worth mentioning that the operating frequencies of the first to fourth tamper switches S1 S S4 are the mains frequency (eg 60 Hz) and are switched at the zero crossing, so the loss of the polarity selector 140 can be ignored, thus Can be considered a single-level architecture.

In view of the above, the single-stage solar inverter proposed by the present disclosure can convert the input voltage VIN received by the solar inverter into a commercial sine wave signal VOUT through the boost mode and the buck mode of the buck-boost converter. , achieve excellent conversion efficiency at high power. Moreover, the present disclosure can reduce the complexity of circuit design to further save component count and circuit design cost.

[An embodiment of the voltage conversion method]

Please refer to FIG. 21. FIG. 21 is a flowchart of a voltage conversion method according to an embodiment of the present invention. The exemplary step flow described in this embodiment can be implemented by using the solar inverter 100 shown in FIG. 1 or the solar inverter 200 shown in FIG. 2, so please refer to FIG. 1 or FIG. 2 for explanation and understanding. . The voltage conversion method includes the steps of: receiving an input voltage, a step-down modulation signal, and a step-up modulation signal, wherein the input voltage is modulated according to the step-down modulation signal and the step-up modulation signal, and the waveform adjustment signal is output according to the Step S10). The isolated waveform adjustment signal is full-wave rectified, and a full-wave pulse signal is outputted accordingly (step S20). The waveform of the half-cycle of the full-wave pulse signal is inverted in polarity, and the commercial sine wave signal is outputted accordingly (step S30). In the buck mode, the input voltage is stepped down according to the buck modulation signal, and in the boost mode, the input voltage is stepped up according to the boost modulation signal.

The details of the steps of the voltage conversion method of the solar inverter are described in detail in the above embodiments of FIGS. 1 to 20, and will not be described herein.

It should be noted that the steps of the embodiment of FIG. 21 are only for convenience of description, and the embodiments of the present invention do not take the steps of the steps as a limitation of implementing various embodiments of the present invention.

[Possible effects of the examples]

In summary, the single-stage solar inverter and the voltage conversion method thereof according to the embodiments of the present invention can input the input of the solar inverter through the boost mode and the buck mode of the buck-boost converter. The voltage is converted to a commercial sine wave signal, achieving excellent conversion efficiency at high power. Moreover, the present disclosure can reduce the complexity of circuit design to further save component count and circuit design cost.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

100,200‧‧‧ solar inverter

110‧‧‧ buck-boost converter

120‧‧‧Isolation transformer

130‧‧‧Full-wave rectifier

140‧‧‧Polar selector

AS‧‧‧ full wave signal

BU‧‧‧Buck modulation signal

BST‧‧‧Boost modulation signal

BST1‧‧‧First pulse width modulation signal

BST2‧‧‧Second pulse width modulation signal

BST3‧‧‧3rd pulse width modulation signal

BST4‧‧‧4th pulse width modulation signal

Cin‧‧‧Coupling Capacitor

Cr‧‧‧ capacitor

CS1‧‧‧First control signal

CS2‧‧‧second control signal

CS3‧‧‧ third control signal

CS4‧‧‧ fourth control signal

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

Db‧‧‧Bucking diode

GND1‧‧‧First ground voltage

GND2‧‧‧second ground voltage

Lb‧‧‧Buck-boost inductor

Qb‧‧‧Buck transistor

Q1~Q4‧‧‧Optoelectronics

S10~S30‧‧‧Steps

S1‧‧‧First control switch

S2‧‧‧Second control switch

S3‧‧‧ third control switch

S4‧‧‧fourth control switch

T0~t6‧‧‧Time

Vb‧‧‧ boundary voltage

Vg‧‧‧preset sine wave

VIN‧‧‧ input voltage

VT1‧‧‧first triangular wave signal

VT2‧‧‧second triangular wave signal

VOUT‧‧‧ City electric sine wave signal

WS, WS’‧‧‧ waveform adjustment signal

Δbuck, δboost‧‧ ‧ duty cycle

Δmin‧‧‧ threshold responsibility cycle

The present invention has been described in detail with reference to the accompanying drawings, in which FIG. Block diagram.

2 is a block diagram of a solar inverter according to an embodiment of the present invention.

3 is a schematic diagram of a driving waveform in accordance with an embodiment of the present invention.

4 is a circuit diagram of a solar inverter in a boost mode according to an embodiment of the invention.

FIG. 5 is a solar inverter in a buck mode according to an embodiment of the present invention. Schematic diagram of the circuit.

FIG. 6 is a driving waveform diagram of first to fourth pulse width modulation signals according to an embodiment of the present invention.

7 to 10 are circuit diagrams of a solar inverter in a boost mode according to an embodiment of the present invention.

11 is a driving waveform diagram of first to fourth pulse width modulation signals and a step-down modulation signal according to an embodiment of the present invention.

12 to 17 are circuit diagrams of a solar inverter in a buck mode according to an embodiment of the invention.

Figure 18 is a diagram showing driving waveforms of a polarity selector control signal according to an embodiment of the present invention.

19 to 20 are circuit diagrams showing the operation of a polarity selector according to an embodiment of the present invention.

21 is a flow chart of a voltage conversion method in accordance with an embodiment of the present invention.

200‧‧‧ solar inverter

110‧‧‧ buck-boost converter

120‧‧‧Isolation transformer

130‧‧‧Full-wave rectifier

140‧‧‧Polar selector

BU‧‧‧Buck modulation signal

BST1‧‧‧First pulse width modulation signal

BST2‧‧‧Second pulse width modulation signal

BST3‧‧‧3rd pulse width modulation signal

BST4‧‧‧4th pulse width modulation signal

CS1‧‧‧First control signal

CS2‧‧‧second control signal

CS3‧‧‧ third control signal

CS4‧‧‧ fourth control signal

Cin‧‧‧Coupling Capacitor

Cr‧‧‧ capacitor

D1‧‧‧First Diode

D2‧‧‧ second diode

D3‧‧‧ third diode

D4‧‧‧ fourth diode

Db‧‧‧Bucking diode

GND1‧‧‧First ground voltage

GND2‧‧‧second ground voltage

Lb‧‧‧Buck-boost inductor

Qb‧‧‧Buck transistor

Q1~Q4‧‧‧Optoelectronics

S1‧‧‧First control switch

S2‧‧‧Second control switch

S3‧‧‧ third control switch

S4‧‧‧fourth control switch

VIN‧‧‧ input voltage

VOUT‧‧‧ City electric sine wave signal

Claims (16)

A solar inverter includes: a buck-boost converter receiving an input voltage, a step-down modulation signal, and a step-up modulation signal, wherein the step-up and step-down converter converts the voltage according to the step-down signal Modulating the signal to modulate the input voltage, and outputting a waveform adjustment signal accordingly; an isolation transformer having a primary side and a primary stage side, the isolation transformer being electrically connected to the buck-boost converter, the isolation transformer being used for electrical Isolating, receiving the waveform adjustment signal and outputting the isolated waveform adjustment signal; a full-wave rectifier electrically connected to the isolation transformer, the full-wave rectifier rectifying the isolated waveform adjustment signal and outputting accordingly a full-wave pulse signal; and a polarity selector electrically connected to the full-wave rectifier, the polarity selector inverts a polarity of the waveform of the full-wave pulse signal after the half-cycle, and outputs a mains sine wave signal accordingly The buck-boost converter gradually steps down the input voltage according to the buck modulation signal in a buck mode, and the buck-boost converter is In the boost mode, the input voltage is stepwise boosted according to the boost modulation signal, whereby the sine wave waveform can be simultaneously generated during the voltage level increase, wherein the buck-boost converter is electrically connected to a digital position. a signal processing chip, when a voltage of a preset sine wave is greater than a boundary voltage, the buck-boost converter is in the boost mode, and when the voltage of the preset sine wave is less than the boundary voltage, the buck-boost converter In this buck mode. The solar inverter of claim 1, wherein when the buck-boost converter is in the boost mode, the duty cycle of the buck modulation signal is 100% and the duty cycle of the boost modulation signal is greater than 50%. The solar inverter of claim 1, wherein when the buck-boost converter is in the buck mode, the duty cycle of the buck modulation signal is less than 100% and the boost modulation signal is The duty cycle is equal to a threshold period of responsibility, where the threshold duty cycle is the minimum duty cycle for the buck-boost converter to function properly. The solar inverter of claim 1, wherein in the boost mode, when the voltage of a first triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a high standard The step-up modulation signal of the bit voltage is applied to the buck-boost converter; when the voltage of the first triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs the boosting tone of the low-level voltage The signal is changed to the buck-boost converter. The solar inverter of claim 1, wherein in the step-down mode, when the voltage of a second triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a high standard The step-down modulation signal of the bit voltage is applied to the buck-boost converter; when the voltage of the second triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs the buck tone of the low level voltage The signal is changed to the buck-boost converter. The solar inverter of claim 1, wherein the polarity selector operates at a mains frequency, and the sine wave signal outputted by the polarity selector is the mains frequency, wherein the polarity selector is more electrically Connected to an AC grid. The solar inverter of claim 1, wherein the buck-boost converter comprises: a first transistor, the gate receiving a first pulse width modulation signal, and the source thereof Connected to the winding of the primary side of the isolation transformer; a second transistor whose gate receives a second pulse width modulation signal, the drain of which is connected to the source of the first transistor; a third transistor, The gate receives a third pulse width modulation signal, the drain is connected to the first end of the first transistor and the first end of a step-up and step-down inductor; the source is connected to the winding of the primary side of the isolation transformer; And a fourth transistor, the gate receiving a fourth pulse width modulation signal, the drain is connected to the source of the third transistor, and the source is connected to the source of the second transistor and a first ground a voltage, wherein the first to the fourth pulse width modulation signals are the boost modulation signals, and when in the boost mode, the duty cycle corresponding to the first to the fourth pulse width modulation signals More than 50% to gradually boost the input voltage; when in the buck mode, the duty cycle corresponding to the first to the fourth pulse width modulation signals is equal to a threshold duty cycle to maintain the buck-boost conversion The device works normally. The solar inverter of claim 7, wherein the step-up and step-down converter further comprises: a step-down transistor, wherein the gate receives the step-down modulation signal, and the drain thereof is connected to the input voltage, a source connected to the second end of the buck-boost inductor; and a step-down diode having an anode connected to the first ground voltage and a cathode connected to a source of the buck transistor, wherein when in the boost mode The duty cycle of the buck modulation signal is 100% to turn on the buck transistor. When in the buck mode, the duty cycle of the buck modulation signal is less than 100% to step down the input voltage. The solar inverter according to claim 1, wherein the full wave is integrated The flow device comprises: a first diode having an anode connected to a second ground voltage; a second diode having an anode connected to the anode of the first diode; and a third diode connected to the anode a cathode of the first diode and a winding of the secondary side of the isolation transformer; a fourth diode having an anode connected to the cathode of the second diode and the winding of the secondary side of the isolation transformer, a cathode connected to the cathode of the third diode; and a capacitor having a first end connected to the cathode of the third diode and a second end connected to the second ground voltage, wherein the first to the fourth pole The body is used for full-wave rectifying the isolated waveform adjustment signal, and the full-wave pulse signal is output accordingly. The solar inverter of claim 9, wherein the polarity selector comprises: a first switch, the first end of which is connected to the first end of the capacitor, and the control end receives a first control signal And determining a conduction or disconnection state; a second control switch, the first end of which is connected to the second end of the first control switch and the positive end of an AC power grid, and the second end is connected to the second ground voltage The control terminal receives a second control signal and determines an on or off state according to the second control switch, the first end of which is connected to the first end of the capacitor, and the control end receives a third control signal according to Determining the on or off state; and a fourth switch, the first end of which is connected to the second end of the third switch and the negative end of the AC grid, and the second end is connected to the second ground voltage, The control terminal receives a fourth control signal and determines the on or off state according to the control terminal. The first and the fourth switch are in the same state of being turned on or off, the second and the third switch are in the same state of being turned on or off, and the first and the second switch are turned on. Or the reverse state is reversed. A voltage conversion method includes: receiving an input voltage, a step-down modulation signal, and a step-up modulation signal, wherein the input voltage is modulated according to the step-down modulation signal and the step-up modulation signal, and The output is a waveform adjustment signal; the isolated waveform adjustment signal is full-wave rectified, and a full-wave pulse signal is output according to the waveform; and the waveform of the full-wave pulse signal is reversed in the second half of the waveform, and The output is a mains sine wave signal; wherein in a buck mode, the input voltage is stepped down according to the buck modulation signal, and in a boost mode, the input voltage is given according to the boost modulation signal Step-up boosting, wherein the voltage conversion method is used in a solar inverter as described in claim 1, wherein the buck-boost converter is more electrically connected to a digital signal processing chip when a pre-set sine wave When the voltage is greater than a boundary voltage, the buck-boost converter is in the boost mode, and when the voltage of the preset sine wave is less than the boundary voltage, the buck-boost converter is in the Buck mode. The voltage conversion method of claim 11, wherein when the buck-boost converter is in the boost mode, the duty cycle of the buck modulation signal is 100% and the boost modulation signal is responsible The period is greater than 50%. The voltage conversion method of claim 11, wherein when the buck-boost converter is in the buck mode, the duty cycle of the buck modulation signal is less than 100% and the step of the boost modulation signal is Cycle equals one responsibility The cycle, wherein the threshold duty cycle is the minimum duty cycle for the buck-boost converter to function properly. The voltage conversion method of claim 11, wherein in the boost mode, when the voltage of a first triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a high level voltage. The step-up modulation signal is sent to the buck-boost converter; when the voltage of the first triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs the boost modulation signal of the low level voltage To the buck-boost converter. The voltage conversion method according to claim 11, wherein in the step-down mode, when the voltage of a second triangular wave signal is greater than the voltage of the preset sine wave, the digital signal processing chip outputs a high level voltage. The step-down modulation signal is sent to the buck-boost converter; when the voltage of the second triangular wave signal is less than the voltage of the preset sine wave, the digital signal processing chip outputs the buck modulation signal of the low level voltage To the buck-boost converter. The voltage conversion method of claim 11, wherein the polarity selector operates at a mains frequency, and the sine wave signal outputted by the polarity selector is the mains frequency, wherein the polarity selector is electrically connected. To an AC grid.