Inverter control circuit and solar photovoltaic three-phase grid-connected system

Abstract

The present application discloses an inverter control circuit and a solar photovoltaic three-phase grid-connected system, comprising: a control unit, a first switching tube, and a second switching tube; the first end of the first switching tube is connected to the positive electrode of the power supply, the second end of the first switching tube is connected to the first end of the second switching tube, and the second end of the second switching tube is connected to the negative electrode of the power supply to obtain a voltage signal. The control unit is connected to the common end of the first switching tube and the second switching tube, and the first control end of the first switching tube and the second control end of the second switching tube. The control unit obtains a second control signal based on the voltage signal at the common end and the first control signal at the first control end and the second control end, and controls the first switching tube and the second switching tube to be turned on or off by the second control signal to achieve zero voltage turn-on of the switching tube. In the inverter control circuit using this solution, the control unit controls the switching tube based on the common end and the control end signal of the switching tube, so that the switching tube is turned on at zero voltage, thereby improving conversion efficiency.

Description

Technical Field

[0001] The present application relates to the photovoltaic field, and in particular to an inverter control circuit and a solar photovoltaic three-phase grid-connected system. Background Art

[0002] In solar photovoltaic power generation systems, it is necessary to directly input electric energy into the public grid through a grid-connected inverter to reduce energy consumption. Commonly used grid-connected inverters are three-phase three-bridge-arm grid-connected inverters, such as Figure 1 As shown, this inverter operates in discontinuous mode, offering advantages such as zero-current turn-on, low harmonic distortion, and high stability when connected in parallel. Furthermore, the inverter's switching devices resonate during the dead time, enabling soft switching. However, since the switching devices cannot achieve zero-voltage turn-on, conversion efficiency is low and electromagnetic interference (EMI) noise may be a concern.

[0003] It can be seen that how to control the switching tube devices of the inverter to be turned on at zero voltage is a problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0004] The purpose of this application is to provide an inverter control circuit and a solar photovoltaic three-phase grid-connected system to improve the inverter conversion efficiency and reduce electromagnetic interference.

[0005] In order to solve the above technical problems, the present application provides an inverter control circuit, comprising: a control unit 1, a first switch tube, and a second switch tube;

[0006] The first end of the first switching tube is connected to the positive electrode of the power supply, the second end of the first switching tube is connected to the first end of the second switching tube as a common end, and the second end of the second switching tube is connected to the negative electrode of the power supply;

[0007] The control unit 1 is connected to the common end and the first control end of the first switch tube and the second control end of the second switch tube, and is used to obtain a second control signal based on the voltage signal of the common end and the first control signals of the first control end and the second control end, and control the first switch tube and the second switch tube to be turned on or off through the second control signal.

[0008] Preferably, the inverter control circuit further includes: an analog signal processor 4;

[0009] The input terminal of the analog signal processor 4 is connected to the common terminal to obtain the voltage signal and convert the voltage signal into an analog signal;

[0010] An output terminal of the analog signal processor 4 is connected to the control unit 1 to send the analog signal to the control unit 1 .

[0011] Preferably, the inverter control circuit further includes: a Schmitt trigger;

[0012] The input end of the Schmitt trigger is connected to the analog signal processor 4 to obtain the analog signal and convert the analog signal into a first digital signal;

[0013] The output end of the Schmitt trigger is connected to the control unit 1 to send the first digital signal to the control unit 1 .

[0014] Preferably, the inverter control circuit further includes: a digital signal processor 3;

[0015] The input end of the digital signal processor 3 is connected to the Schmitt trigger to obtain the first digital signal;

[0016] The output end of the digital signal processor 3 is connected to the control unit 1 to obtain the control signal and generate a second digital signal according to the control signal and the first digital signal.

[0017] Preferably, the control unit 1 is a DSP.

[0018] Preferably, the first switching tube and the second switching tube are MOS tubes.

[0019] Preferably, the inverter control circuit further includes a first resonant capacitor and a second resonant capacitor;

[0020] The first resonant capacitor is connected in parallel with the first end and the second end of the first switch tube, and the second resonant capacitor is connected in parallel with the first end and the second end of the second switch tube.

[0021] Preferably, the inverter control circuit further comprises: a filter circuit, wherein the filter circuit comprises a filter capacitor and a filter inductor;

[0022] The first end of the filter inductor is connected to the common end, the second end of the filter inductor is connected to the first end of the filter capacitor, and the second end of the filter capacitor is connected to the analog signal processor 4 .

[0023] Preferably, the inverter control circuit further includes: an alarm circuit, wherein a first end of the alarm circuit is connected to the common end, and a second end of the alarm circuit is connected to the control unit 1;

[0024] When it is detected that the current in the circuit is greater than the threshold current, the control unit 1 is controlled to turn off the first switch tube and the second switch tube.

[0025] In order to solve the above technical problems, the present application also provides a solar photovoltaic three-phase grid-connected system, including the inverter control circuit described above.

[0026] The inverter control circuit provided in this application includes: a control unit, a first switching tube, and a second switching tube; the first end of the first switching tube is connected to the positive electrode of a power supply, the second end of the first switching tube is connected to the first end of the second switching tube, and the second end of the second switching tube is connected to the negative electrode of the power supply, so as to obtain a voltage signal to be processed. The control unit is connected to the common end of the first and second switching tubes and the first control end of the first switching tube and the second control end of the second switching tube, and obtains a second control signal based on the voltage signal at the common end and the first control signal at the first and second control ends. The control unit controls the first and second switching tubes to be turned on or off using the second control signal, thereby achieving zero-voltage turn-on of the switching tube devices.

[0027] It can be seen that, by using the inverter control circuit provided in this application, the control unit controls the switch tube according to the common end and the control end signal of the switch tube device, so that the switch tube is turned on at zero voltage, thereby improving conversion efficiency and reducing EMI noise.

[0028] In addition, the present application also provides a solar photovoltaic three-phase grid-connected system, including the above-mentioned inverter control circuit, with the same effect as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] Figure 1 This is a structural diagram of a commonly used three-phase three-leg grid-connected inverter;

[0031] Figure 2 A structural diagram of an inverter control circuit provided in an embodiment of the present application;

[0032] Figure 3 a is a schematic diagram of the common terminal voltage after the first switch tube is turned off provided in an embodiment of the present application;

[0033] Figure 3 b is a schematic diagram of the common terminal voltage after the second switch tube is turned off according to an embodiment of the present application;

[0034] Figure 4 A schematic diagram of a common terminal signal provided in an embodiment of the present application after being processed by a Schmitt trigger;

[0035] Figure 5A schematic diagram of the common terminal and control signal during the dead zone of the first switching tube provided in an embodiment of the present application;

[0036] The reference numerals are as follows: 1 is a control unit, 2 is a switch tube driving circuit, 3 is a digital signal processor, and 4 is an analog signal processor. DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0038] The core of this application is to provide an inverter control circuit and a solar photovoltaic three-phase grid-connected system.

[0039] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0040] Figure 2 A structural diagram of an inverter control circuit provided in an embodiment of the present application is shown in FIG. Figure 2 As shown, the present application provides an inverter control circuit, comprising: a control unit 1, a first switch tube Q1, and a second switch tube Q2;

[0041] The first end of the first switch tube Q1 is connected to the positive electrode of the power supply, the second end of the first switch tube Q1 is connected to the first end of the second switch tube Q2 as a common end, and the second end of the second switch tube Q2 is connected to the negative electrode of the power supply;

[0042] The control unit 1 is connected to the common terminal and the first control terminal of the first switch tube Q1 and the second control terminal of the second switch tube Q2, and is used to obtain a second control signal based on the voltage signal of the common terminal and the first control signal of the first control terminal and the second control terminal, and control the first switch tube Q1 and the second switch tube Q2 to be turned on or off through the second control signal.

[0043] Specifically, the structure of the inverter control circuit provided in this application is first introduced. This application improves the structure of the traditional grid-connected inverter. In this application, a single bridge arm of the inverter is used as an example to illustrate the solution. It can be understood that the number of bridge arms of the grid-connected inverter can be one or more, and there is no limitation here.

[0044] It should be noted that the first switch Q1 and the second switch Q2 can be MOS transistors or triodes. In a specific implementation, the first switch Q1 and the second switch Q2 are connected in series, and the connection point between the two is a common terminal; the control unit 1 is connected to the common terminal to obtain the voltage signal to be processed.

[0045] In this embodiment, the control circuit of a three-phase three-leg inverter is used for illustration. Figure 1 or Figure 2 As shown, the first switch tube Q1 and the second switch tube Q2 constitute the first bridge arm of the three-phase three-bridge-arm grid-connected inverter, the third switch tube Q3 and the fourth switch tube Q4 constitute the second bridge arm of the three-phase three-bridge-arm grid-connected inverter, and the fifth switch tube Q5 and the sixth switch tube Q6 constitute the third bridge arm of the three-phase three-bridge-arm grid-connected inverter; the midpoints of the three bridge arms are set as the first common terminal Ua, the second common terminal Ub, and the third common terminal Uc, respectively, and an output inductor is connected in series to each common terminal.

[0046] The circuit also includes a resonant capacitor connected in parallel with the switch tube to generate resonance, reduce the voltage across the switch tube, and achieve zero-voltage switching. This embodiment is described assuming that all the switch tubes are MOS tubes. The first end of the first resonant capacitor C1 is connected to the drain of the first switch tube Q1, and the second end is connected to the first common terminal Ua. The first end of the third resonant capacitor C3 is connected to the drain of the third switch tube Q3, and the second end is connected to the second common terminal Ub. The first end of the fifth resonant capacitor C5 is connected to the drain of the fifth switch tube Q5, and the second end is connected to the third common terminal Uc. The first end of the second resonant capacitor C2 is connected to the source of the second switch tube Q2, and the second end is connected to the first common terminal Ua. The first end of the fourth resonant capacitor C4 is connected to the source of the fourth switch tube Q4, and the second end is connected to the second common terminal Ub. The first end of the sixth resonant capacitor C6 is connected to the source of the sixth switch tube Q6, and the second end is connected to the third common terminal Uc.

[0047] The control unit 1 is also connected to the control terminals of the first and second switching transistors Q1 and Q2 to control the on and off of the first and second switching transistors Q1 and Q2 via a pulse width modulation (PWM) signal. In a specific implementation, the control unit 1 collects the voltage signal at the common terminal and converts it into a digital signal.

[0048] When the switch tube resonates during the dead zone, the common point potential will rush to the DC power supply voltage value or drop to 0V. At this time, the switch tube is in a zero voltage state. Take one of the bridge arms as an example: when the first switch tube Q1 is turned off and the second switch tube Q2 stops freewheeling, if Figure 3As shown in a, the waveform of the potential change of the first common terminal Ua is shown in the figure. After time t1, the switch tube is in the dead zone and resonance occurs. At the peak times t2 and t4, the voltage of the first common terminal Ua is equal to the power supply voltage Vdc. At this time, the first switch tube Q1 is at zero voltage. When the second switch tube Q2 is turned off and the freewheeling of the first switch tube Q1 ends, the waveform of the potential change of the first common terminal Ua is shown in Figure 3 As shown in b, after the moment t1, the switch tube is in the dead zone and resonance occurs. At the valley moments t2 and t4, the voltage of the first common terminal Ua is 0, and the second switch tube Q2 is in a zero voltage state. The solution provided in the present application judges the working state of the circuit by integrating the drive signal of the switch tube and the voltage signal of the common terminal, thereby controlling the on and off of the switch tube. The control unit 1 uses the drive signals PWM1~PWM6 of each switch tube and the voltage signals U1, U2, and U3 of the common terminal as inputs for digital signal processing, D1, D2, and D3 as outputs, and controls the on and off of the switch tube according to the values ​​of D1, D2, and D3. Taking the bridge arm where the first switch tube Q1 and the second switch tube Q2 are located as an example, the truth table of input and output is shown in Table 1:

[0049] Table 1 Control unit input and output truth table

[0050] PWM1 PWM2 <![CDATA[U1 a ]]> D1 0 0 0 0 0 0 1 1 0 1 0 0 0 1 1 0 1 0 0 1 1 0 1 1

[0051] Among them, U1 a It is the signal output by U1 after being processed by control unit 1. a Waveform Figure 4 As shown, U1 drops to VT - When U1 a From 1 to 0; U1 rises to VT + When U1 a From 0 to 1.

[0052] In a specific implementation, the control unit 1 controls the on / off of the switch tube by detecting the changes of D1, D2, and D3, so that the switch tube can be turned on at zero voltage. Taking one of the bridge arms as an example, during the dead zone of the first switch tube Q1 and the second switch tube Q2, U a And the waveform of D1 is as follows Figure 5 As shown. a When it approaches the peak, D1 changes from 0 to 1. a When D1 changes from 1 to 0 as it approaches the valley, the control unit 1 detects that D1 changes from 0 to 1 and sets PWM1 to 1 at times t2 and t4 to turn on the first switch Q1. Alternatively, when D1 changes from 1 to 0, the control unit 1 sets PWM2 to 1 at times t1 and t3 to turn on the second switch Q2. This allows the zero-voltage turn-on of the switch to be achieved.

[0053] In a specific implementation, the control unit 1 can be an external computer or an embedded chip such as a DSP or FPGA. Due to the complex working environment of the inverter circuit, an embedded chip is usually used as the control unit. Among them, the DSP chip has strong control and digital signal processing capabilities, so this application selects a DSP chip as the control unit 1.

[0054] It is understood that due to the varying application scenarios of different inverter circuits, the current signal values ​​in the inverter circuit vary widely. To protect the safety of the control unit 1, the voltage value at the common terminal needs to be proportionally reduced by the analog signal processor 4. For example, the voltage signal at the common terminal, which ranges from 0 to 800 V, needs to be converted into a voltage signal with a consistent waveform but a value range of 0 to 3.3 V. This voltage conversion can be achieved using the analog signal processor 4 built into the control unit 1, or an external analog signal processor 4 can be connected between the common terminal and the control unit 1.

[0055] The process of generating a new control signal based on the voltage signal at the common terminal and the voltage signal at the control terminal of the switch tube can be completed by the control unit 1 or by the external digital signal processor 3. Furthermore, when the control signal is generated by the external digital signal processor, the analog voltage signal at the switch point can also be converted into a digital voltage signal by an external Schmitt trigger.

[0056] It is understandable that in order to improve the harmonic suppression capability of the inverter circuit, an output inductor and a filter capacitor can be connected in series between the common end and the control unit 1 to form a harmonic bypass channel, thereby improving the harmonic suppression capability and achieving high-quality grid-connected current at low power.

[0057] In order to improve the safety of the inverter control circuit, the inverter control circuit also includes an alarm circuit. When it is detected that the current in the circuit is greater than the threshold current, the control unit 1 turns off the first switch tube Q1 and the second switch tube Q2 and sends an alarm to the management personnel.

[0058] In this embodiment, an inverter control circuit is provided, comprising: a control unit, a first switch tube, and a second switch tube; the first end of the first switch tube is connected to the positive electrode of the power supply, the second end of the first switch tube is connected to the first end of the second switch tube, and the second end of the second switch tube is connected to the negative electrode of the power supply to obtain a voltage signal to be processed. The control unit is connected to the common end of the first switch tube and the second switch tube and the first control end of the first switch tube and the second control end of the second switch tube, obtains a second control signal based on the voltage signal of the common end and the first control signal of the first control end and the second control end, and controls the first switch tube and the second switch tube to be turned on or off by the second control signal to realize zero voltage turn-on of the switch tube device. It can be seen that, using the inverter control circuit provided by the present application, the control unit controls the switch tube according to the common end and the control end signal of the switch tube device, so that the switch tube is turned on at zero voltage, thereby improving conversion efficiency and reducing EMI noise.

[0059] In specific implementations, due to different application scenarios of different inverter circuits, in some scenarios, the value of the voltage signal in the inverter circuit is relatively large, and directly controlling the inverter circuit may damage the control unit 1 and cause danger.

[0060] In order to improve the application range and safety of the inverter control circuit, based on the above embodiment, it further includes: an analog signal processor 4;

[0061] The input terminal of the analog signal processor 4 is connected to the common terminal to obtain a voltage signal and convert the voltage signal into an analog signal;

[0062] An output terminal of the analog signal processor 4 is connected to the control unit 1 to send the analog signal to the control unit 1 .

[0063] In order to protect the control unit 1, an external analog signal processor 4 is used in this embodiment to proportionally reduce the voltage value at the common terminal through the analog signal processor 4. For example, the voltage signal of 0 to 800 V at the common terminal is converted into a voltage signal with a consistent waveform but a value range of 0 to 3.3 V.

[0064] Furthermore, when the inverter circuit is a high-voltage circuit, the voltage of the control unit 1 is too low and cannot control the switch tube well. Therefore, the switch tube drive circuit 2 can be connected to the control unit 1 and the switch tube control end, so that the control unit 1 can indirectly control the conduction and shutdown of the switch tube device in the inverter circuit.

[0065] In this embodiment, the voltage signal at the common terminal of the inverter is converted into a voltage signal with a smaller amplitude by an analog signal processor, thereby improving the application range and safety of the inverter control circuit.

[0066] Furthermore, since the voltage signal at the common terminal is an analog signal, in order to facilitate processing by the control unit 1, it is also necessary to convert the digital analog signal into a digital signal. Based on the above embodiment, the inverter control circuit further includes: a Schmitt trigger;

[0067] The input end of the Schmitt trigger is connected to the analog signal processor 4 to obtain the analog signal and convert the analog signal into a first digital signal;

[0068] The output end of the Schmitt trigger is connected to the digital signal processor 3 to send the first digital signal to the digital signal processor 3 .

[0069] In this embodiment, the analog signal is converted into a digital signal by a Schmitt trigger, thereby improving the speed at which the digital signal processor and the control unit process the voltage signal.

[0070] In practice, inverter circuits are often used in large-scale power generation or power supply equipment, such as solar photovoltaic power generation systems. To reduce equipment costs, the control unit 1 often needs to control multiple devices. When the inverter control circuit fails, an external digital signal processor 3 can be used to generate control signals to minimize interference from maintenance work on other devices.

[0071] On the basis of the above embodiment, it further includes a digital signal processor 3;

[0072] An input terminal of the digital signal processor 3 is connected to a Schmitt trigger to obtain a first digital signal;

[0073] An output terminal of the digital signal processor 3 is connected to the control unit 1 to obtain a control signal and generate a second digital signal according to the control signal and the first digital signal.

[0074] In this embodiment, an external digital signal processor is used to make the inverter control circuit easier to maintain.

[0075] In a specific implementation, the control unit 1 can be an external computer or an embedded chip such as a DSP or FPGA. Due to the harsh working environment of the inverter circuit, an embedded chip is usually used as the control unit 1. Among them, the DSP chip has strong control and digital signal processing capabilities, so this application uses a DSP chip as the control unit 1.

[0076] On the basis of the above embodiment, the control unit 1 of the inverter control circuit is a DSP.

[0077] In this embodiment, by selecting a DSP chip as the control circuit of the inverter control circuit, the ability of the control circuit to adapt to the environment is improved, and the digital signal processing capability of the control unit is improved.

[0078] In practice, switching transistors include MOS transistors and triodes. Triodes are often used in current-driven circuits, while MOS transistors are voltage-controlled devices and are commonly used in voltage-driven circuits. MOS transistors offer the advantages of low power consumption, high output impedance, and excellent temperature and noise characteristics, making circuits more stable. In practice, MOS transistors have a much higher upper frequency limit than triodes, making them safer and more stable. Therefore, MOS transistors are often used as switching devices.

[0079] Based on the above embodiment, the first switch transistor Q1 and the second switch transistor Q2 are MOS transistors. The MOS transistors used in this embodiment can be NMOS transistors or PMOS transistors. Users can choose the appropriate MOS transistor according to actual conditions. In this embodiment, NMOS transistors are used as switching devices.

[0080] It should be noted that the first switch tube Q1 and the second switch tube Q2 can be MOS tubes with built-in freewheeling diodes or MOS tubes requiring external freewheeling diodes, which is not limited here.

[0081] In this embodiment, MOS transistors are selected as switch transistors, which can reduce the power consumption of the circuit and make the circuit more stable and reliable.

[0082] On the basis of the above embodiment, the inverter control circuit further includes a first resonant capacitor C1 and a second resonant capacitor C2;

[0083] The first resonant capacitor C1 is connected in parallel with the first end and the second end of the first switch tube Q1 , and the second resonant capacitor C2 is connected in parallel with the first end and the second end of the second switch tube Q2 .

[0084] In this embodiment, the voltage across the switch tube is reduced by connecting a resonant capacitor in parallel with the switch tube to generate resonance, thereby enabling the switch tube to be turned on at zero voltage.

[0085] In a specific implementation, the voltage signal output at the common terminal contains signals of different frequencies. In order to filter the voltage signal to remove noise, based on the above embodiment, the inverter control circuit further includes: a filter circuit, the filter circuit including a filter capacitor Ca and a filter inductor L1;

[0086] A first end of the filter inductor L1 is connected to the common end, a second end of the filter inductor L1 is connected to a first end of the filter capacitor Ca, and a second end of the filter capacitor Ca is connected to the analog signal processor 4 .

[0087] In this embodiment, a filter circuit is connected in series to the common terminal to filter out clutter interference signals in the common terminal voltage signal.

[0088] In practice, the voltage signal in the inverter circuit is large, and if an accident occurs, it will cause serious consequences. In order to improve the safety of the inverter control circuit, it is also necessary to add an alarm circuit in the inverter control circuit.

[0089] In order to ensure the safety of the inverter control circuit, based on the above embodiment, the inverter control circuit further includes: an alarm circuit, wherein a first end of the alarm circuit is connected to the common end, and a second end of the alarm circuit is connected to the control unit 1;

[0090] When it is detected that the current in the circuit is greater than the threshold current, the control unit 1 controls the first switch tube Q1 and the second switch tube Q2 to be turned off.

[0091] It is understood that the alarm circuit includes an indicator light and a buzzer. When it is detected that the current in the circuit is greater than the threshold current, the indicator light is controlled to flash and the buzzer to sound an alarm, and the switching tube device in the circuit is turned off to prevent damage to the equipment.

[0092] In this embodiment, an alarm circuit is connected between the common end of the first switch tube and the second switch tube and the control unit. When it is detected that the current in the circuit is greater than the threshold current, the control unit is controlled to turn off each switch tube, thereby improving the safety of the inverter control circuit.

[0093] Finally, the present embodiment further provides a solar photovoltaic three-phase grid-connected system, which, in addition to the inverter control circuit described above, also includes solar panels, an AC power distribution cabinet, etc. Since each component has been described in detail above, it will not be repeated in this embodiment.

[0094] In this embodiment, a solar photovoltaic three-phase grid-connected system is provided, including the above-mentioned inverter control circuit, which includes: a control unit, a first switch tube, and a second switch tube; the first end of the first switch tube is connected to the positive electrode of the power supply, the second end of the first switch tube is connected to the first end of the second switch tube, and the second end of the second switch tube is connected to the negative electrode of the power supply to obtain a voltage signal to be processed. The control unit is connected to the common end of the first switch tube and the second switch tube and the first control end of the first switch tube and the second control end of the second switch tube, obtains a second control signal based on the voltage signal at the common end and the first control signal at the first control end and the second control end, and controls the first switch tube and the second switch tube to be turned on or off by the second control signal to achieve zero voltage turn-on of the switch tube device. Therefore, using the inverter control circuit provided by the present application, the control unit controls the switch tube based on the common end and the control end signal of the switch tube device, so that the switch tube is turned on at zero voltage, thereby improving conversion efficiency and reducing EMI noise.

[0095] The inverter control circuit and solar photovoltaic three-phase grid-connected system provided by the present application are introduced in detail above. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of this application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of this application.

[0096] It should also be noted that, in this specification, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

Claims

1. An inverter control circuit, characterized in that: include: A control unit (1), a first switching tube, and a second switching tube; The first end of the first switching tube is connected to the positive electrode of the power supply, the second end of the first switching tube is connected to the first end of the second switching tube as a common end, and the second end of the second switching tube is connected to the negative electrode of the power supply; The control unit (1) is connected to the common terminal and the first control terminal of the first switch tube and the second control terminal of the second switch tube, and is used to obtain a second control signal according to the voltage signal of the common terminal and the first control signals of the first control terminal and the second control terminal, and to control the first switch tube and the second switch tube to be turned on or off according to the second control signal; When the first switch tube is turned off and the second switch tube ends its freewheeling, D1 changes from 0 to 1 when Ua approaches the peak value. The control unit (1) detects that D1 changes from 0 to 1 and sets PWM1 to 1 to turn on the first switch tube at zero voltage. When the second switch tube Q2 is turned off and the first switch tube Q1 ends its freewheeling, D1 changes from 1 to 0 when Ua approaches the valley. The control unit (1) detects that D1 changes from 1 to 0 and sets PWM2 to 1 to turn on the second switch tube at zero voltage. D1 is the signal output by the digital signal processor corresponding to the bridge arm where the first switch tube and the second switch tube are located; Ua is the potential of the common terminal; PWM1 is the signal of the first control terminal of the first switch tube, and PWM2 is the signal of the second control terminal of the second switch tube; Also included: an analog signal processor (4); The input terminal of the analog signal processor (4) is connected to the common terminal to obtain the voltage signal and convert the voltage signal into an analog signal; The output end of the analog signal processor (4) is connected to the control unit (1) to send the analog signal to the control unit (1); Also included: Schmitt trigger; The input end of the Schmitt trigger is connected to the analog signal processor (4) to obtain the analog signal and convert the analog signal into a first digital signal; The output end of the Schmitt trigger is connected to the control unit (1) to send the first digital signal to the control unit (1); Also included: a digital signal processor (3); The input end of the digital signal processor (3) is connected to the Schmitt trigger to obtain the first digital signal; The output end of the digital signal processor (3) is connected to the control unit (1) to obtain the control signal and generate a second digital signal based on the control signal and the first digital signal.

2. The inverter control circuit according to claim 1, characterized in that: The control unit (1) is a DSP.

3. The inverter control circuit according to claim 1, wherein: The first switch tube and the second switch tube are MOS tubes.

4. The inverter control circuit according to claim 3, characterized in that: Also includes a first resonant capacitor and a second resonant capacitor; The first resonant capacitor is connected in parallel to two ends of the first switch tube except the control end, and the second resonant capacitor is connected in parallel to two ends of the second switch tube except the control end.

5. The inverter control circuit according to claim 1, wherein: Also includes: A filter circuit, comprising a filter capacitor and a filter inductor; The first end of the filter inductor is connected to the common end, the second end of the filter inductor is connected to the first end of the filter capacitor, and the second end of the filter capacitor is connected to the analog signal processor (4).

6. The inverter control circuit according to claim 1, characterized in that: Also includes: an alarm circuit, wherein a first end of the alarm circuit is connected to the common end, and a second end of the alarm circuit is connected to the control unit (1); When it is detected that the current in the circuit is greater than a threshold current, the control unit (1) is controlled to turn off the first switch tube and the second switch tube.

7. A solar photovoltaic three-phase grid-connected system, characterized in that: The inverter control circuit comprises the inverter control circuit according to any one of claims 1 to 6.

Images