Voltage control method for buck-boost conversion circuit of photovoltaic module, inverter and photovoltaic module

Abstract

The invention provides a voltage control method for a buck-boost conversion circuit of a photovoltaic module, and the method comprises the steps: comparing an input voltage inputted to an input end with an output voltage outputted from an output end, obtaining a first comparison result, comparing a difference value between the input voltage and the output voltage with a specified threshold value, obtaining a second comparison result, and outputting the second comparison result. And the control circuit is used for controlling the buck-boost conversion circuit based on the first comparison result and the second comparison result, so that the expected constant output current can be detected at the output end, and the output voltage matched with the load is output.

Description

Technical Field

[0001] The present invention relates to the field of household photovoltaic energy storage, specifically the field of balcony photovoltaic energy storage, and in particular to a voltage control method, an inverter and a photovoltaic module for a buck-boost conversion circuit of a photovoltaic module. Background Art

[0002] On balcony photovoltaics, the battery pack is charged through photovoltaic panels. A common DC-DC converter problem is that the input voltage from the photovoltaic panels may be higher, lower or equal to the battery voltage, so a constant current source needs to be generated at the output for maximum power point tracking (MPPT), that is, the DC-DC converter must perform operations such as step-up and step-down. Summary of the invention

[0003] Technical problem to be solved by the invention

[0004] In existing photovoltaic modules, the photovoltaic modules need to be connected to the battery through a buck-boost conversion circuit. Since the voltage of the electric energy generated by the photovoltaic module is unstable, it is necessary to output a stable voltage matching the battery through a certain boost or buck.

[0005] When the difference between the output voltage of the photovoltaic module and the battery voltage is too large, the conventional step-up or step-down operation control can make the PWM control power switch of the Buck-boost circuit to make the output voltage meet the voltage requirements of the battery. However, when the above difference is very small, the voltage difference is often ignored and the step-up or step-down operation is not performed, which will have a certain impact on the battery.

[0006] The object of the present invention is to provide a voltage control method, an inverter and a photovoltaic module for a buck-boost conversion circuit of a photovoltaic module, which can perform a precise boost or buck operation when the above-mentioned difference is very small.

[0007] Technical solutions to technical problems

[0008] According to a first aspect of the present invention, there is provided a voltage control method for a buck-boost conversion circuit for a photovoltaic component, the buck-boost conversion circuit comprising: a first switch and a second switch connected in series, the first switch having an input terminal connected to the photovoltaic component, the second switch having a ground terminal; and a third switch and a fourth switch connected in series, the third switch having a ground terminal, the fourth switch having an output terminal for connecting a load, an inductor being connected between a first connection point where the first switch and the second switch are connected in series and a second connection point where the third switch and the fourth switch are connected in series, the voltage control method is characterized in that an input voltage input to the input terminal and an output voltage output from the output terminal are compared to obtain a first comparison result, a differential value between the input voltage and the output voltage and a specified threshold are compared to obtain a second comparison result, and based on the first comparison result and the second comparison result, the buck-boost conversion circuit is controlled so as to detect a desired constant output current at the output terminal, thereby outputting an output voltage matching the load.

[0009] Furthermore, in the voltage control method of the present invention, when the first comparison result is that the input voltage is greater than the output voltage, and the second comparison result is that the difference between the input voltage and the output voltage is less than a specified threshold, the buck-boost conversion circuit is controlled to a peak buck current mode, and in each control cycle, at the beginning of the control cycle, the first switch and the third switch are turned on and the second switch and the fourth switch are turned off, and the value of the input current at the input end is detected, and when it is detected that the input current is stable, the third switch is turned off and the fourth switch is turned on, and when the value of the current flowing through the inductor reaches a first threshold, the first switch is turned off and the second switch is turned on until the end of this control cycle.

[0010] Furthermore, in the voltage control method of the present invention, the turning off of the third switch and the turning on of the fourth switch are performed according to the proportion of the time when the third switch is turned on in the control period.

[0011] Furthermore, in the voltage control method of the present invention, the duration of turning on the third switch and turning off the fourth switch is 15%±3 of the duration of one control cycle.

[0012] Furthermore, in the voltage control method of the present invention, during the first stage from turning on the first switch and the third switch and turning off the second switch and the fourth switch to turning off the third switch and turning on the fourth switch, the inductor stores energy and is charged, and the current flowing through the inductor increases; during the second stage from turning off the third switch and turning on the fourth switch to turning off the first switch and turning on the second switch, the inductor releases the stored energy to the load, and the current of the inductor increases ramp-wise; in the third stage from turning off the first switch and turning on the second switch until the end of this control cycle, the inductor releases the stored energy to ground.

[0013] Furthermore, in the voltage control method of the present invention, the first threshold is obtained based on the input current, the input voltage and the maximum power tracking of the photovoltaic component.

[0014] Furthermore, in the voltage control method of the present invention, when the first comparison result is that the input voltage is less than the output voltage, and the second comparison result is that the difference between the input voltage and the output voltage is less than a specified threshold, the buck-boost conversion circuit is controlled to a peak boost current mode. In each control cycle, at the beginning of the control cycle, the first switch and the third switch are turned on and the second switch and the fourth switch are turned off. When the value of the current flowing through the inductor reaches a second threshold, the third switch is turned off and the fourth switch is turned on until the end of this control cycle. When it is detected that the output current at the output end is the desired constant output current value, the first switch is turned off and the second switch is turned on.

[0015] Furthermore, in the voltage control method of the present invention, the first switch is turned off and the second switch is turned on according to the proportion of the time when the first switch is turned on in the control period.

[0016] Furthermore, in the voltage control method of the present invention, the duration of turning on the first switch and turning off the second switch is 85%±3 of the duration of one control cycle.

[0017] Furthermore, in the voltage control method of the present invention, during a first stage from turning on the first switch and the third switch and turning off the second switch and the fourth switch to turning off the third switch and turning on the fourth switch, the inductor stores energy and is charged, and a current flowing through the inductor increases; during a second stage from turning off the third switch and turning on the fourth switch to turning off the first switch and turning on the second switch, the inductor releases the stored energy to the load, and the current of the inductor decreases at an angle; and in a third stage from turning off the first switch and turning on the second switch until the end of this control cycle, the inductor releases the stored energy to ground.

[0018] Furthermore, in the voltage control method of the present invention, the second threshold is obtained based on the input current, the input voltage and maximum power tracking.

[0019] Furthermore, in the voltage control method of the present invention, when the input voltage is greater than the sum of the output voltage and the specified threshold value, the buck-boost conversion circuit is controlled to a peak buck current mode, and in each control cycle, the third switch is always disconnected and the fourth switch is always turned on, and at the beginning of the control cycle, the first switch is turned on and the second switch is disconnected, the inductor stores energy and is charged, and the current flowing through the inductor increases, and when the value of the current flowing through the inductor reaches a first threshold value, the first switch is disconnected and the second switch is turned on.

[0020] Furthermore, in the voltage control method of the present invention, when the input voltage is greater than the sum of the output voltage and the specified threshold value, the buck-boost conversion circuit is controlled to a peak boost current mode, and in each control cycle, the first switch is always turned on and the second switch is always turned off, and at the beginning of the control cycle, the third switch is turned on and the fourth switch is turned off, the inductor stores energy and is charged, and the current flowing through the inductor increases. When the value of the current in the inductor reaches the second threshold value, the third switch is turned off and the fourth switch is turned on.

[0021] Furthermore, in the voltage control method of the present invention, the prescribed threshold value is a value greater than 0V and less than 3V.

[0022] According to a second aspect of the present invention, an inverter is provided, comprising a buck-boost conversion circuit using any one of the voltage control methods described above.

[0023] According to a third aspect of the present invention, there is provided a photovoltaic assembly, comprising a buck-boost converter circuit using any one of the voltage control methods described above.

[0024] Effects of the Invention

[0025] According to the present invention, a voltage control method, an inverter and a photovoltaic module for a buck-boost conversion circuit of a photovoltaic module can be provided, which can perform a precise boost or buck operation when the difference between the input voltage and the output voltage is very small. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure may be better understood by describing exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0027] Description of labels:

[0028] 10 buck-boost conversion circuit, 11, 11a photovoltaic module, 111 photovoltaic module unit, 12, 12a inverter, 121 inverter unit, IN input terminal, OUT output terminal, Vin input voltage, Vout output voltage, A first switch, B second switch, C third switch, D fourth switch, SW1 first connection point, SW2 second connection point, L inductor, Rsense resistor sensor, IL inductor current.

[0029] Figure 1 This is the circuit diagram of the currently used step-up and step-down conversion circuit (Buck-boost circuit).

[0030] Figure 2 It is a schematic diagram showing a voltage control method of the present invention in which the buck-boost converter circuit uses a peak buck current mode to perform a buck operation when the input voltage Vin is much higher than the output voltage Vout.

[0031] Figure 3 It is a schematic diagram showing a voltage control method of the present invention in which the buck-boost conversion circuit uses a peak buck current mode to perform a boost-buck operation when the input voltage Vin is slightly higher than the output voltage Vout.

[0032] Figure 4 It is a schematic diagram showing a voltage control method of the present invention in which the buck-boost conversion circuit uses a peak boost current mode to perform a boost-buck operation when the input voltage Vin is slightly lower than the output voltage Vout.

[0033] Figure 5 It is a schematic diagram showing a voltage control method of the present invention in which the buck-boost converter circuit uses a peak boost current mode to perform a boost operation when the input voltage Vin is much lower than the output voltage Vout.

[0034] Figure 6 The invention is a block diagram showing a micro inverter including a step-up / step-down conversion circuit (Buck-boost circuit) to which the voltage control method of the present invention is applied.

[0035] Figure 7The block diagram shows a photovoltaic module including a buck-boost conversion circuit (Buck-boost circuit) to which the voltage control method of the present invention is applied. DETAILED DESCRIPTION

[0036] The embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0037] In the description of the present disclosure, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", etc. indicate directions or positional relationships only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present disclosure. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0038] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of the present disclosure. In the description of the present disclosure, it should also be noted that, unless otherwise clearly specified and limited, the terms "connected", "connected", "relative", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances.

[0039] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present disclosure. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] Figure 1This is a general circuit diagram of the currently applied buck-boost conversion circuit (hereinafter referred to as Buck-boost circuit). The Buck-boost circuit is a synchronous buck-boost controller, a current mode DC / DC converter that can operate in pass-through mode to help eliminate EMI and switching losses and maximize efficiency (up to 99.9%). Optional options include continuous conduction mode (CCM), pulse skipping or burst mode (Burst Mode) operation, or in pass-through mode, the output voltage can be adjusted. When the input voltage is directly transmitted to the output without actively switching MOS, the operating current is extremely low and there is no switching noise. The circuit can be made MPPT-enabled through software control. Since the Buck-boost circuit combines the advantages of buck and boost circuits, it is possible to select boost or buck mode according to the input voltage and load requirements to output the required voltage.

[0041] The input terminal IN of the Buck-boost circuit is connected as follows Figure 1 The PV module shown in the figure has its output terminal OUT connected to a battery pack or Figure 1 The loads such as the inverter shown are controlled by a processor such as an MCU not shown, so that the input voltage from the photovoltaic module can be provided to the battery with a stable output voltage and a desired constant current after conversion by the Buck-boost circuit.

[0042] The circuit structure of the Buck-boost circuit is briefly described below. In addition, the load connected to the output terminal OUT is a rechargeable battery as an example. The load connected to the output terminal OUT may also be an inverter 11.

[0043] like Figure 1 As shown, the Buck-boost circuit mainly includes an inductor L and four switches A, B, C, and D. The inductor L is used to store energy when the switch is turned on, and release energy to the load when the switch is turned off. The four switches A, B, C, and D use MOS transistors, or other components or combinations of components that can be driven and controlled. The above four switches A, B, C, and D are used to control the on and off of the current to realize the charging and discharging of the inductor. More specifically, it is assumed that the four switches A, B, C, and D all use NMOS transistors as an example for explanation.

[0044] Switch A is used as the first switch of the Buck-boost circuit. Its gate acts as the control terminal TG1 of switch A. Its drain acts as the input terminal of switch A, that is, the input terminal IN of the Buck-boost circuit. Figure 1The photovoltaic module shown is connected to input the voltage or current from the photovoltaic module, and in addition, its source is connected to switch B. Switch B serves as the second switch of the Buck-boost circuit, its gate acts as the control terminal BG1 of switch B, its drain is connected to switch A, and its source is grounded as the ground terminal. The connection point where the source of switch A and the drain of switch B are connected serves as the first connection point SW1 of the Buck-boost circuit.

[0045] The switch C is used as the third switch of the Buck-boost circuit, and its gate functions as the control terminal BG2 of the switch C. Its drain is connected to the switch D, and its source is connected to the ground terminal. The switch D is used as the fourth switch of the Buck-boost circuit, and its gate functions as the control terminal TG2 of the switch D. Its drain functions as the output terminal of the switch D, i.e., the output terminal OUT of the Buck-boost circuit, and is connected to the battery pack or the like. Figure 1 The micro inverter 11 shown is connected to a load, thereby outputting a voltage obtained after being stepped up or stepped down by the Buck-boost circuit. The connection point where the drain of the switch C and the source of the switch D are connected serves as the second connection point SW2 of the Buck-boost circuit.

[0046] An inductor L is connected between the first connection point SW1 and the second connection point SW2. The inductor L can store energy. For example, when switches A and C are turned on and switches B and D are turned off, the voltage input from switch A is stored in the inductor L. When switch C is turned off and switch D is turned on, the energy stored in the inductor L is released to a load such as a battery, thereby charging the load such as a battery. In addition, a resistance sensor Rsense can also be connected between the first connection point SW1 and the second connection point SW2, and the resistance sensor Rsense detects the current IL flowing through the inductor L.

[0047] The Buck-boost circuit structure has been briefly described above. Although not illustrated, the switching control of the Buck-boost circuit can be controlled by an MCU or the like. Since the voltage input by the photovoltaic module may be higher than, lower than, or equal to the battery voltage or the voltage required by the inverter 11, therefore, usually we control through the MCU and divide the entire buck-boost process into four control regions. That is: 1. Peak bucking in the bucking region (Vin >> Vout); 2. Peak bucking in the buck-boost region (Vin ≈> Vout); 3. Peak boosting in the buck-boost region (Vin <≈ Vout); 4. Peak boosting in the boosting region (Vin << Vout). In the above, Vin is the input voltage input by the photovoltaic module to the Buck-boost circuit, Vout is the output voltage at the output end of the Buck-boost circuit, Vin >> Vout means the input voltage is much higher than the output voltage, Vin ≈> Vout means the input voltage is slightly higher than the output voltage, Vin <≈ Vout means the input voltage is slightly lower than the output voltage, and Vin << Vout means the input voltage is much lower than the output voltage.

[0048] <1. Peak voltage drop in the buck region (Vin>>Vout)>

[0049] Figure 2 It is a schematic diagram showing that when the input voltage Vin is much higher than the output voltage Vout, the Buck-boost circuit performs a bucking operation using the peak bucking current mode. As Figure 2 shown, the horizontal axis represents time. In addition, from top to bottom, it successively represents the switching actions of switches A, B, C, D, and the change in the current IL flowing through the inductor L. Figure 2 The changes in two control cycles are shown. In addition, during the (A + D) stage in the figure, it means that only switches A and D are conducting, and the (B + D) stage means that only switches B and D are conducting.

[0050] As Figure 2 shown, switch C is always off and switch D is always on. At the beginning of each control cycle, switch A is on and switch B is off, so that the inductor L stores energy and is charged, and the current IL flowing through the inductor L rises. When the current IL flowing through the inductor L reaches the specified peak bucking current threshold during the (A + D) stage, that is, Figure 2 the value of the current IL pointed by the downward arrow in

[0051] In addition, the peak buck current threshold as the first threshold can be calculated based on the input current, input voltage and maximum power tracking of the photovoltaic module. In addition, when the current IL reaches the specified peak buck current threshold, it can be detected at the output terminal OUT that the output current at this time is the desired stable output current.

[0052] <2. Peak Buck in Buck-Boost Region (Vin≈>Vout)>

[0053] In this case, since the difference between the input voltage and the output voltage is very small, a conventional step-down operation cannot be performed and a fine step-down operation is required. Figure 3 This is a schematic diagram showing that when the input voltage Vin is slightly higher than the output voltage Vout, the Buck-boost circuit uses the peak buck current mode to perform a step-up and step-down operation. In addition, here, slightly higher generally means that the difference is less than or equal to 3V. Depending on different system requirements, it sometimes also means that the difference is between 3V and 5V. Figure 3 As shown, the horizontal axis represents time, and the switching operations of switches A, B, C, and D and the change of the current IL flowing through the inductor L are shown from top to bottom. Figure 3 The changes in two control cycles are shown in the figure. In addition, during the (A+C) stage, only switches A and C are turned on, during the (A+D) stage, only switches A and D are turned on, and during the (B+D) stage, only switches B and D are turned on.

[0054] At the beginning of the control cycle, switches A and C are turned on, and switches B and D are turned off, and the value of the input current at the input terminal IN of the Buck-boost circuit is detected at regular intervals. When the value of the input current is detected to be stable, switch C is turned off and switch D is turned on. This stage is called the (A+C) stage. The (A+C) stage is relatively short. According to the actual detection results, it accounts for about 15%±3 of the entire control cycle. In this (A+C) stage, the inductor L stores energy and is charged, and the current IL flowing through the inductor L increases.

[0055] Next, when the current value of the current flowing through the inductor reaches the peak buck current threshold, switch A is turned off and switch B is turned on until the end of this control cycle. The period from turning off switch C and turning on switch D to turning off switch A and turning on switch B is called the (A+D) stage. During the (A+D) stage, the inductor L releases the stored energy to a load such as a battery, that is, discharges. At this time, the voltage from the inductor L and the input voltage Vin from the input terminal IN are superimposed and applied to a load such as a battery, thereby charging the battery, etc., and the current of the inductor rises ramp-wise.

[0056] In addition, the period from turning off switch A and turning on switch B until the end of this control cycle is called the (B+D) stage. In this (B+D) stage, when the current value of the current flowing through the inductor reaches the peak buck current threshold, the current at the output end has reached the desired output current value. At this time, there is no need to charge the battery anymore, and the excess energy in the inductor L needs to be released so that a stable output current can be obtained.

[0057] In addition, the third switch can be switched off and the fourth switch can be switched on according to the duration of turning on the third switch and turning off the fourth switch. The above duration can be controlled to be about 15%±3 of the duration of a cycle. For example, at the beginning of the control cycle, the duration of the third switch on and the duration of the fourth switch off are both controlled to be 15% of the duration of a cycle, and then the third switch is controlled to be turned off and the fourth switch is controlled to be turned on for the remaining duration of a cycle.

[0058] Thus, a stable and constant current can be detected at the output end of the Buck-boost circuit, and a voltage value matching the battery can be output. In addition, such control can also solve the problem of low efficiency of Buck-boost in a wide voltage range and the problem of charging the battery through maximum power tracking of photovoltaic modules under different lighting conditions.

[0059] 3. Peak boost in the buck-boost region (Vin <≈Vout)

[0060] In this case, since the difference between the input voltage and the output voltage is very small, a conventional boosting operation cannot be performed and a fine boosting operation is required. Figure 4 This is a schematic diagram showing that when the input voltage Vin is slightly lower than the output voltage Vout, the Buck-boost circuit uses the peak boost current mode to perform a step-up and step-down operation. In addition, here, slightly lower generally means that the difference is less than or equal to 3V. Depending on different system requirements, it sometimes also means that the difference is between 3V and 5V. Figure 4 As shown, the horizontal axis represents time, and the switching operations of switches A, B, C, and D and the change of the current IL flowing through the inductor L are shown from top to bottom. Figure 4 The changes in two control cycles are shown in the figure. In addition, during the (A+C) stage, only switches A and C are turned on, during the (A+D) stage, only switches A and D are turned on, and during the (B+D) stage, only switches B and D are turned on.

[0061] At the beginning of the control cycle, switches A and C are turned on, and switches B and D are turned off. When the current value IL of the current flowing through the inductor L reaches the peak boost current threshold, switch A is turned off and switch B is turned on until the end of this control cycle. This stage is called the (A+C) stage. In this (A+C) stage, the inductor L stores energy and is charged, and the current IL flowing through the inductor L increases.

[0062] When it is detected that the output current at the output end reaches the desired constant output current value, switch A is turned off and switch B is turned on. This stage is called the (A+D) stage. In this (A+D) stage, the inductor L releases the stored energy to the load such as the battery, that is, discharges. At this time, the voltage from the inductor L and the input voltage from the input end are superimposed and applied to the battery, etc., so as to charge the battery, and the current of the inductor L decreases obliquely.

[0063] In addition, the period from turning off switch A and turning on switch B until the end of this control cycle is called the (B+D) stage. In this (B+D) stage, since the current at the output end has reached the desired output current value, there is no need to charge the battery anymore. It is necessary to release the excess energy in the inductor L so that a stable output current can be obtained.

[0064] In addition, the first switch can be switched off and the second switch can be switched on according to the duration of turning on the first switch and turning off the second switch. The above duration can be controlled to be about 85%±3 of the duration of a cycle. For example, at the beginning of the control cycle, the duration of the first switch on and the duration of the second switch off are both controlled to be 85% of the duration of a cycle, and then the first switch is controlled to be turned off and the second switch is controlled to be turned on for the remaining duration of a cycle.

[0065] In addition, the peak boost current threshold, as the second threshold, can be obtained based on the input current, input voltage and maximum power tracking of the photovoltaic module.

[0066] Thus, a stable and constant current can be detected at the output end of the Buck-boost circuit, and a voltage value matching the battery can be output. In addition, such control can also solve the problem of low efficiency of Buck-boost in a wide voltage range and the problem of charging the battery through maximum power tracking of photovoltaic modules under different lighting conditions.

[0067] <4. Peak boost voltage in boost region (VIN<<VOUT)>

[0068] Figure 5 It is a schematic diagram showing that when the input voltage Vin is much lower than the output voltage Vout, the Buck-boost circuit uses the peak boost current mode to perform boost operation. Figure 4As shown, the horizontal axis represents time, and the switching operations of switches A, B, C, and D and the change of the current IL flowing through the inductor L are shown from top to bottom. Figure 5 The changes in two control cycles are shown in the figure. In addition, during the (A+C) stage in the figure, only switches A and C are turned on, and during the (A+D) stage, only switches A and D are turned on.

[0069] like Figure 5 As shown in the figure, switch A is always on and switch B is always off. At the beginning of each control cycle, switch C is on and switch D is off, and the value of the current IL of the inductor L rises. When the inductor current reaches the specified peak boost current threshold during the (A+C) stage, Figure 4 When the current IL reaches the value indicated by the downward arrow in FIG. 1 , the switch C is turned off and the switch D is turned on for the remaining time of the current control cycle. Thus, a voltage matching the battery voltage can be output.

[0070] In addition, for each control cycle of the above control zones, the current at the input end and the current at the output end need to be detected regularly, and then fed back to the MCU to adjust the disconnection time of each switch. In addition, the timing here is, for example, sending a 12.5ms PWM pulse signal as a detection signal for detection.

[0071] The voltage control method of the buck-boost converter circuit 10 is described above. In the above description, the buck-boost converter circuit 10 is used as an independent circuit to be connected to the photovoltaic module 11 and the load such as a rechargeable battery or an inverter 12. Figure 6 , 7 As shown, the buck-boost conversion circuit 10 using the voltage control method of the present invention can also be included in a photovoltaic module or in a micro inverter.

[0072] Figure 6 1 is a block diagram showing a micro inverter 12a including a step-up / step-down conversion circuit (Buck-boost circuit) 10 to which the voltage control method of the present invention is applied. Figure 6 As shown, the buck-boost conversion circuit 10 and the inverter unit 121 constitute a micro inverter 12a. The input terminal IN of the buck-boost conversion circuit 10 is connected to the photovoltaic module 11, and the output terminal of the buck-boost conversion circuit 10 is connected to the inverter unit 121. The inverter unit 121 is a component unit other than the buck-boost conversion circuit 10 in the micro inverter 12a.

[0073] Figure 7 1 is a block diagram showing a photovoltaic module including a buck-boost circuit to which the voltage control method of the present invention is applied. Figure 7As shown, the buck-boost conversion circuit 10 and the photovoltaic module unit 111 constitute a photovoltaic module 11a. The input terminal IN of the buck-boost conversion circuit 10 is connected to the photovoltaic module unit 11, and the output terminal of the buck-boost conversion circuit 10 is connected to the micro inverter 12. The photovoltaic module unit 111 is a component unit in the photovoltaic module 11a except the buck-boost conversion circuit 10. In addition, the present invention also provides a computer-readable storage medium, on which encoded instructions are recorded, and when the instructions are executed, the voltage control method of the buck-boost conversion circuit for the photovoltaic module of the present invention can be implemented. The computer-readable storage medium may include a hard disk drive, a floppy disk drive, a compact disk read / write (CD-R / W) drive, a digital versatile disk (DVD) drive, a flash memory drive and / or a solid-state storage device, etc.

[0074] The preferred embodiments of the present invention are described in detail above. However, it should be understood that the present invention can be implemented in various ways and variations without departing from its broad spirit and scope. A person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A voltage control method for a buck-boost conversion circuit of a photovoltaic module, The step-up / step-down conversion circuit comprises: A first switch and a second switch connected in series, wherein the first switch has an input terminal connected to the photovoltaic component, and the second switch has a ground terminal; as well as a third switch and a fourth switch connected in series, the third switch having a ground terminal, the fourth switch having an output terminal for connecting to a load, An inductor is connected between a first connection point where the first switch and the second switch are connected in series and a second connection point where the third switch and the fourth switch are connected in series, and the voltage control method is characterized in that: comparing an input voltage input to the input terminal and an output voltage output from the output terminal to obtain a first comparison result, comparing the difference between the input voltage and the output voltage with a predetermined threshold value to obtain a second comparison result, Based on the first comparison result and the second comparison result, the buck-boost conversion circuit is controlled so that a desired constant output current can be detected at the output end, thereby outputting an output voltage that matches the load.

2. The voltage control method according to claim 1, characterized in that: When the first comparison result is that the input voltage is greater than the output voltage, and the second comparison result is that the difference between the input voltage and the output voltage is less than a specified threshold, The buck-boost conversion circuit is controlled to a peak buck current mode. In each control cycle, At the beginning of the control cycle, the first switch and the third switch are turned on and the second switch and the fourth switch are turned off, and the value of the input current of the input terminal is detected, When it is detected that the input current is stable, the third switch is turned off and the fourth switch is turned on. When the value of the current flowing through the inductor reaches a first threshold value, the first switch is turned off and the second switch is turned on until the current control cycle ends.

3. The voltage control method according to claim 2, characterized in that: The turning off of the third switch and the turning on of the fourth switch are performed according to the proportion of the time when the third switch is turned on in the control period.

4. The voltage control method according to claim 2, characterized in that: The duration of turning on the third switch and turning off the fourth switch is 15%±3 of the duration of one control cycle.

5. The voltage control method according to claim 2, characterized in that: During the first stage from turning on the first switch and the third switch and turning off the second switch and the fourth switch to turning off the third switch and turning on the fourth switch, the inductor stores energy and is charged, and the current flowing through the inductor increases. During the second stage from turning off the third switch and turning on the fourth switch to turning off the first switch and turning on the second switch, the inductor releases the stored energy to the load, and the current of the inductor increases in a ramp. In the third stage of turning off the first switch and turning on the second switch until the current control cycle ends, the inductor releases the stored energy to the ground.

6. The voltage control method according to claim 2, characterized in that: The first threshold is obtained based on the input current, the input voltage, and maximum power point tracking of the photovoltaic component.

7. The voltage control method according to claim 1, characterized in that: When the first comparison result is that the input voltage is less than the output voltage, and the second comparison result is that the difference between the input voltage and the output voltage is less than a specified threshold, The buck-boost conversion circuit is controlled to a peak boost current mode. In each control cycle, At the beginning of the control cycle, the first switch and the third switch are turned on and the second switch and the fourth switch are turned off. When the value of the current flowing through the inductor reaches a second threshold, the third switch is turned off and the fourth switch is turned on until the current control cycle ends. When it is detected that the output current of the output end is a desired constant output current value, the first switch is turned off and the second switch is turned on.

8. The voltage control method according to claim 7, characterized in that: The first switch is turned off and the second switch is turned on according to the proportion of the time when the first switch is turned on in the control period.

9. The voltage control method according to claim 7, characterized in that: The duration of turning on the first switch and turning off the second switch is 85%±3 of the duration of one control cycle.

10. The voltage control method according to claim 7, characterized in that: During the first stage from turning on the first switch and the third switch and turning off the second switch and the fourth switch to turning off the third switch and turning on the fourth switch, the inductor stores energy and is charged, and the current flowing through the inductor increases. During the second stage from turning off the third switch and turning on the fourth switch to turning off the first switch and turning on the second switch, the inductor releases the stored energy to the load, and the current of the inductor decreases in an inclined manner. In the third stage of turning off the first switch and turning on the second switch until the current control cycle ends, the inductor releases the stored energy to the ground.

11. The voltage control method according to claim 7, characterized in that: The second threshold is obtained based on the input current, the input voltage, and maximum power tracking.

12. The voltage control method according to claim 1, characterized in that: When the input voltage is greater than the sum of the output voltage and the specified threshold, the buck-boost converter circuit is controlled to be in a peak buck current mode. In each control cycle, The third switch is always turned off, the fourth switch is always turned on, and, At the beginning of the control cycle, the first switch is turned on and the second switch is turned off, the inductor stores energy and is charged, and the current flowing through the inductor increases. When the value of the current flowing through the inductor reaches a first threshold, the first switch is turned off and the second switch is turned on.

13. The voltage control method according to claim 1, characterized in that: When the input voltage is greater than the sum of the output voltage and the specified threshold, the buck-boost converter circuit is controlled to a peak boost current mode. In each control cycle, The first switch is always turned on, the second switch is always turned off, and, At the beginning of the control cycle, the third switch is turned on and the fourth switch is turned off, the inductor stores energy and is charged, and the current flowing through the inductor increases. When the value of the current of the inductor reaches a second threshold, the third switch is turned off and the fourth switch is turned on.

14. The voltage control method according to any one of claims 1 to 13, characterized in that: The predetermined threshold value is a value greater than 0V and less than 3V.

15. An inverter, characterized in that: A buck-boost converter circuit comprising a voltage control method according to any one of claims 1 to 14.

16. A photovoltaic module, characterized in that: A buck-boost converter circuit comprising a voltage control method according to any one of claims 1 to 14.

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