Inverter boost side circuit structure and photovoltaic system

Abstract

The utility model is applicable to the technical field of electronic circuits, and provides an inverter boost side circuit structure and a photovoltaic system, the circuit structure comprises a digital controller and an external peak current control circuit, the external peak current control circuit comprises a slope compensation module, a superposition module, a digital-to-analog conversion module, a comparison module and a trigger module, the external peak current control circuit is arranged in the inverter, limitation of chip resources is eliminated, current peak control is better achieved, the circuit can be flexibly placed on different single boards, and design optimization is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of electronic circuits, and particularly relates to a circuit structure on the boost side of an inverter and a photovoltaic system. Background Art

[0002] The boost module in a photovoltaic inverter generally adopts average current control because it is convenient for DSP (Digital Signal Processing) to implement. However, average current control usually requires a closed-loop control strategy, such as a PID (Proportion Integration Differentiation) controller, which makes the control algorithm more complex than simple peak current control. In addition, average current control focuses on the average value of current within a switching period, resulting in a slow response speed to transient load changes or power supply voltage fluctuations and requiring an additional per-cycle current limiting circuit.

[0003] With the development and cost reduction of SiC MOS (Metal Oxide Semiconductor Field Effect Transistor based on silicon carbide semiconductor material), its high-frequency characteristics are more suitable for peak current control, and peak current control is generally directly implemented by a chip. For string inverters, there are usually several or even more than a dozen boost main circuits converging on the boost side. Although current peak control can be directly implemented by a chip, limited by comparator resources, the number of boost circuits that can be supported is limited, and it is difficult to rely solely on the chip to implement current peak control. Summary of the Utility Model

[0004] An embodiment of the utility model provides a circuit structure on the boost side of an inverter, aiming to solve the problems of limited number of boost circuits using peak current control on the existing boost side of the inverter and the difficulty of implementing current peak control by a chip.

[0005] The embodiment of the utility model is implemented as follows. A circuit structure on the boost side of an inverter includes a digital controller and an external peak current control circuit. The external peak current control circuit includes a slope compensation module, a superposition module, a digital-to-analog conversion module, a comparison module, and a trigger module;

[0006] The digital controller is connected to the photovoltaic power circuit and is used to obtain the current and voltage information of the photovoltaic power circuit;

[0007] The slope compensation module is connected to the first output end of the digital controller and is used to convert the pulse signal output by the digital controller into a slope voltage signal with a preset slope and then output it;

[0008] The superposition module is connected to the slope compensation module and the photovoltaic power circuit and is used to superpose the slope voltage signal and the switching tube current signal of the photovoltaic power circuit and then output it;

[0009] The digital-to-analog conversion module is connected to the second output terminal of the digital controller and is configured to convert the digital signal output by the digital controller into a reference voltage signal and then output it.

[0010] The input terminal of the comparison module is connected to the superposition module and the digital-to-analog conversion module, and is configured to receive the signals output by the slope compensation module and the digital-to-analog conversion module, compare them, and then output.

[0011] The trigger module is connected to the output terminal of the comparison module and the first output terminal of the digital controller, and is configured to receive the pulse signal and the signal output by the comparison module, so as to output a driving signal to the switching tube of the photovoltaic power circuit.

[0012] Furthermore, the photovoltaic power circuit includes a photovoltaic string, a first inductor, a second inductor, a first diode, a second diode, a first capacitor, a first switching tube, and a second switching tube.

[0013] The first signal input terminal and the second signal input terminal of the digital controller are connected to the photovoltaic string, and are configured to obtain the photovoltaic current signal and the photovoltaic voltage signal of the photovoltaic string.

[0014] The first end of the photovoltaic string is connected to the positive electrode of the first diode and the second end of the first switching tube through the first inductor, and the first end of the photovoltaic string is also connected to the positive electrode of the second diode and the second end of the second switching tube through the second inductor.

[0015] The negative electrodes of the first diode and the second diode are both connected to the first end of the first capacitor.

[0016] The first end of the first switching tube, the first end of the second switching tube, and the second end of the first capacitor are all connected to the second end of the photovoltaic string.

[0017] The control terminals of the first switching tube and the second switching tube are both connected to the output terminal of the trigger module.

[0018] The third signal input terminal of the digital controller is connected to the first end of the first capacitor, and is configured to obtain the output voltage signal of the photovoltaic power circuit.

[0019] Furthermore, the inverter boost-side circuit structure further includes a Hall sampling circuit. The input terminal of the Hall sampling circuit is connected to the photovoltaic string, and the output terminal of the Hall sampling circuit is connected to the first signal input terminal of the digital controller.

[0020] Furthermore, the inverter boost-side circuit structure further includes a first voltage sampling circuit. The input terminal of the first voltage sampling circuit is connected to the photovoltaic string, and the output terminal of the first voltage sampling circuit is connected to the second signal input terminal of the digital controller.

[0021] Further, the inverter boost-side circuit structure further includes a second voltage sampling circuit. The input end of the second voltage sampling circuit is connected to the first end of the first capacitor, and the output end of the second voltage sampling circuit is connected to the third signal input end of the digital controller.

[0022] Further, the inverter boost-side circuit structure further includes a first CT sampling circuit and a second CT sampling circuit. The input end of the first CT sampling circuit is connected to the second end of the first switching tube, and the input end of the second CT sampling circuit is connected to the second end of the second switching tube. The output ends of the first CT sampling circuit and the second CT sampling circuit are both connected to the superimposing module.

[0023] Further, the superimposing module includes a first superimposer and a second superimposer;

[0024] The first input end of the first superimposer is connected to the output end of the first CT sampling circuit, the second input end of the first superimposer is connected to the first output end of the slope compensation module, and the output end of the first superimposer is connected to the comparison module;

[0025] The first input end of the second superimposer is connected to the output end of the second CT sampling circuit, the second input end of the second superimposer is connected to the second output end of the slope compensation module, and the output end of the second superimposer is connected to the comparison module.

[0026] Further, the comparison module includes a first comparator and a second comparator;

[0027] The non-inverting input end of the first comparator is connected to the output end of the first superimposer, and the inverting input end of the first comparator is connected to the output end of the digital-to-analog conversion module;

[0028] The non-inverting input end of the second comparator is connected to the output end of the second superimposer, and the inverting input end of the second comparator is connected to the output end of the digital-to-analog conversion module;

[0029] The output ends of the first comparator and the second comparator are both connected to the triggering module.

[0030] Further, the first switching tube and the second switching tube are MOS tubes or IGBTs.

[0031] In a second aspect, the present application further provides a photovoltaic system, including the inverter boost-side circuit structure as described above.

[0032] The beneficial effects of the present application are as follows. The inverter boost-side circuit structure of the present application includes a digital controller and an external peak current control circuit. The external peak current control circuit includes a slope compensation module, a superimposition module, a digital-to-analog conversion module, a comparison module, and a trigger module. The digital controller is connected to the photovoltaic power circuit and is used to obtain the current and voltage information of the photovoltaic power circuit. The slope compensation module is connected to the first output terminal of the digital controller and is used to convert the pulse signal output by the digital controller into a slope voltage signal with a preset slope and then output it. The superimposition module is connected to the slope compensation module and the photovoltaic power circuit and is used to superimpose the slope voltage signal and the switch tube current signal of the photovoltaic power circuit and then output it. The digital-to-analog conversion module is connected to the second output terminal of the digital controller and is used to convert the digital signal output by the digital controller into a reference voltage signal and then output it. The input terminal of the comparison module is connected to the superimposition module and the digital-to-analog conversion module and is used to receive the signals output by the slope compensation module and the digital-to-analog conversion module, compare them, and then output. The trigger module is connected to the output terminal of the comparison module and the first output terminal of the digital controller and is used to receive the pulse signal and the signal output by the comparison module to output a drive signal to the switch tube of the photovoltaic power circuit. By setting an external peak current control circuit in the inverter, the limitation of chip resources is eliminated, better current peak control is achieved, and the circuit can be flexibly placed on different single boards to optimize the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 FIG. is a schematic diagram of the module structure of an embodiment of the inverter boost-side circuit structure provided by the present application;

[0034] Figure 2 FIG. is a schematic diagram of the circuit structure of an embodiment of the inverter boost-side circuit structure provided by the present application;

[0035] Figure 3 FIG. is a schematic diagram of the slope compensation logic waveform of an embodiment of the inverter boost-side circuit structure provided by the present application;

[0036] Figure 4 FIG. is a schematic diagram of the peak current control logic waveform of an embodiment of the inverter boost-side circuit structure provided by the present application;

[0037] Figure 5 FIG. is a schematic diagram of the peak current control to achieve interleaved parallel BOOST in an embodiment of the inverter boost-side circuit structure provided by the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] In order to make the objectives, technical solutions and advantages of the present utility model more clear and understandable, the present utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. The examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present utility model and should not be construed as a limitation to the present utility model. In addition, it should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0039] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "left", "right", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present utility model.

[0040] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the present utility model, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0041] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection, an electrical connection or a connection capable of mutual communication; it may be directly connected or indirectly connected through an intermediate medium, and may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0042] In the present utility model, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0043] The following disclosure provides many different embodiments or examples for implementing different structures of the present utility model. To simplify the disclosure of the present utility model, the components and settings of specific examples are described hereinafter. Of course, they are only examples and are not intended to limit the present utility model. In addition, the present utility model may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present utility model provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0044] The inverter boost-side circuit structure of the present application includes a digital controller and an external peak current control circuit. The external peak current control circuit includes a slope compensation module, a superposition module, a digital-to-analog conversion module, a comparison module, and a trigger module. The digital controller is connected to the photovoltaic power circuit for obtaining the current and voltage information of the photovoltaic power circuit. The slope compensation module is connected to the first output terminal of the digital controller and is used for converting the pulse signal output by the digital controller into a slope voltage signal with a preset slope and then outputting it. The superposition module is connected to the slope compensation module and the photovoltaic power circuit and is used for superposing the slope voltage signal and the switch tube current signal of the photovoltaic power circuit and then outputting the result. The digital-to-analog conversion module is connected to the second output terminal of the digital controller and is used for converting the digital signal output by the digital controller into a reference voltage signal and then outputting it. The input terminal of the comparison module is connected to the superposition module and the digital-to-analog conversion module and is used for receiving the signals output by the slope compensation module and the digital-to-analog conversion module, comparing them, and then outputting the result. The trigger module is connected to the output terminal of the comparison module and the first output terminal of the digital controller and is used for receiving the pulse signal and the signal output by the comparison module to output a driving signal to the switch tube of the photovoltaic power circuit. By arranging an external peak current control circuit in the inverter, the limitation of chip resources is eliminated, better current peak control can be achieved, and the circuit can be flexibly placed on different single boards to realize the optimization of the design.

[0045] Embodiment 1

[0046] AsFigures 1 to 5 As shown in Figures 1 to 5 , an embodiment of the present application provides an inverter boost-side circuit structure, including a digital controller 100 and an external peak current control circuit 200. The external peak current control circuit 200 includes a slope compensation module 210, a superposition module 220, a digital-to-analog conversion module 230, a comparison module 240, and a trigger module 250:

[0047] The digital controller 100 is connected to the photovoltaic power circuit 300 for obtaining the current and voltage information of the photovoltaic power circuit 300:

[0048] The slope compensation module 210 is connected to the first output terminal of the digital controller 100, and is configured to convert the pulse signal output by the digital controller 100 into a slope voltage signal with a preset slope and then output it;

[0049] The superposition module 220 is connected to the slope compensation module 210 and the photovoltaic power circuit 300, and is configured to superpose the slope voltage signal and the switch tube current signal of the photovoltaic power circuit 300 and then output it;

[0050] The digital-to-analog conversion module 230 is connected to the second output terminal of the digital controller 100, and is configured to convert the digital signal output by the digital controller 100 into a reference voltage signal and then output it;

[0051] The input terminal of the comparison module 240 is connected to the superposition module 220 and the digital-to-analog conversion module 230, and is configured to receive the signals output by the slope compensation module 210 and the digital-to-analog conversion module 230, compare them, and then output;

[0052] The trigger module 250 is connected to the output terminal of the comparison module 240 and the first output terminal of the digital controller 100, and is configured to receive the pulse signal and the signal output by the comparison module 240 and then output a drive signal to the switch tube of the photovoltaic power circuit 300.

[0053] During implementation, the photovoltaic power circuit 300 refers to the photovoltaic string V p The circuit connecting the inverter boost side, where the photovoltaic power circuit 300 includes the photovoltaic string V p , a first inductor L1, a second inductor L2, a first diode D1, a second diode D2, a first capacitor C, a first switch tube Q1, and a second switch tube Q2;

[0054] The first signal input terminal and the second signal input terminal of the digital controller 100 are connected to the photovoltaic string V p for obtaining the photovoltaic current signal i p of the photovoltaic string V L and the photovoltaic voltage signal V pv ;

[0055] The photovoltaic string V pThe first end of is connected to the positive electrode of the first diode D1 and the second end of the first switching tube Q1 through the first inductor L1, and the photovoltaic string V p The first end of is also connected to the positive electrode of the second diode D2 and the second end of the second switching tube Q2 through the second inductor L2;

[0056] The negative electrodes of the first diode D1 and the second diode D2 are both connected to the first end of the first capacitor C:

[0057] The first end of the first switching tube Q1, the first end of the second switching tube Q2, and the second end of the first capacitor C are all connected to the photovoltaic string V p The second end of is connected;

[0058] The control ends of the first switching tube Q1 and the second switching tube Q2 are both connected to the output end of the trigger module 250:

[0059] The third signal input end of the digital controller 100 is connected to the first end of the first capacitor C for obtaining the output voltage signal V of the photovoltaic power circuit 300 o .

[0060] The photovoltaic current signal i L Refers to the current output by the photovoltaic string V p And can be obtained by collecting the current at the output end of the photovoltaic string V p Exemplarily, the inverter boost side circuit structure provided in this application further includes a Hall sampling circuit (not shown in the figure). The input end of the Hall sampling circuit is connected to the photovoltaic string V p To collect the photovoltaic current signal i L , and the output end of the Hall sampling circuit is connected to the first signal input end of the digital controller 100 to output the collected photovoltaic current signal i L To the digital controller 100.

[0061] In some embodiments, since the first inductor L1 and the second inductor L2 are connected in parallel to the photovoltaic string V p , the current flowing through the first inductor L1 is i L1 , and the current flowing through the second inductor L2 is i L2 , i L =i L1 +i L2 .

[0062] The photovoltaic voltage signal V pv Refers to the voltage output by the photovoltaic string V p And can be obtained by collecting the voltage of the photovoltaic string V pThe output voltage is obtained by voltage sampling at the output terminal. Exemplarily, the inverter boost-side circuit structure provided in this application further includes a first voltage sampling circuit (not shown in the figure). The input terminal of the first voltage sampling circuit is connected to the photovoltaic string V p to collect the photovoltaic voltage signal V pv . The output terminal of the first voltage sampling circuit is connected to the second signal input terminal of the digital controller 100 to output the collected photovoltaic voltage signal V pv to the digital controller 100.

[0063] The output voltage signal V o of the photovoltaic power circuit 300, that is, the terminal voltage of the first capacitor C, can be obtained by voltage sampling of the first capacitor C. Exemplarily, the inverter boost-side circuit structure provided in this application further includes a second voltage sampling circuit (not shown in the figure). The input terminal of the second voltage sampling circuit is connected to the first terminal of the first capacitor C to collect the output voltage signal V o . The output terminal of the second voltage sampling circuit is connected to the third signal input terminal of the digital controller 100 to output the collected output voltage signal V o to the digital controller 100.

[0064] The first switching tube Q1 and the second switching tube Q2 can be MOS tubes or IGBTs (Insulate-Gate Bipolar Transistor), preferably, the first switching tube Q1 and the second switching tube Q2 are SiC MOS tubes, which is not limited.

[0065] During implementation, the superimposing module 220 needs to obtain the switching tube current signals of the photovoltaic power circuit 300, and the currents of the first switching tube Q1 and the second switching tube Q2 can be collected. Optionally, the inverter boost-side circuit structure of this application further includes a first CT sampling circuit (not shown in the figure) and a second CT sampling circuit (not shown in the figure). The input terminal of the first CT sampling circuit is connected to the second terminal of the first switching tube Q1, the input terminal of the second CT sampling circuit is connected to the second terminal of the second switching tube Q2, and the output terminals of the first CT sampling circuit and the second CT sampling circuit are both connected to the superimposing module 220.

[0066] During implementation, both the first CT sampling circuit and the second CT sampling circuit are CT sampling. CT sampling means sampling the currents of the first switching tube Q1 and the second switching tube Q2 through a current transformer (CT). Its working principle is based on the electromagnetic induction principle, and the current transformation and measurement are realized through the electromagnetic coupling between the primary winding and the secondary winding, which will not be elaborated. During implementation, the current sampled by the first CT sampling circuit for the first switching tube Q1 is i Q1 , and the current sampled by the second CT sampling circuit for the second switching tube is iQ2 .

[0067] In implementation, the superimposition module 220 includes a first superimposer M1 and a second superimposer M2;

[0068] The first input end of the first adder M1 is connected to the output end of the first CT sampling circuit, the second input end of the first adder M1 is connected to the first output end of the slope compensation module 210, and the output end of the first adder M1 is connected to the comparison module 240:

[0069] A first input end of the second adder M2 is connected to the output end of the second CT sampling circuit, a second input end of the second adder M2 is connected to the second output end of the slope compensation module 210 , and an output end of the second adder M2 is connected to the comparison module 240 .

[0070] During implementation, the digital controller 100 outputs the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 to the slope compensation module 210 , and the slope compensation module 210 generates a voltage signal with a certain slope and gives it to the first adder M1 and the second adder M2 .

[0071] Further, the comparison module 240 includes a first comparator QT1 and a second comparator QT2;

[0072] The non-inverting input terminal of the first comparator QT1 is connected to the output terminal of the first adder M1, and the inverting input terminal of the first comparator QT1 is connected to the output terminal of the digital-to-analog conversion module 230:

[0073] The non-inverting input terminal of the second comparator QT2 is connected to the output terminal of the second adder M2, and the inverting input terminal of the second comparator QT2 is connected to the output terminal of the digital-to-analog conversion module 230:

[0074] The output terminal of the first comparator QT1 and the output terminal of the second comparator QT2 are both connected to the trigger module 250 .

[0075] The boost side circuit structure of the inverter provided in the present application is composed of a Hall sampling circuit (such as a Hall sensor) sampling the photovoltaic string V p The photovoltaic current signal i L , and the first voltage sampling circuit samples the photovoltaic string V p The photovoltaic voltage signal V pv At the same time, the DC bus voltage (the output voltage signal V of the photovoltaic power circuit 300) is sampled by the second voltage sampling circuit o ) and input to the digital controller 100.

[0076] The digital controller 100 generates a photovoltaic current signal i L , Photovoltaic voltage signal V pv And the output voltage signal Vo , perform maximum power point tracking and generate the DC bus reference voltage V ref , and this reference voltage is converted into a PWM_DA signal by means of pulse width chopping. The digital controller 100 also outputs a first pulse signal PWM_CLK1 and a second pulse signal PWM_CLK2 according to the maximum duty cycle, and the phase difference between the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 is 180°. The PWM_DA signal is input to the digital-to-analog conversion module 230, and the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 are input to the slope compensation module 210.

[0077] The slope compensation module 210 generates a voltage value with a certain slope according to the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 of the digital controller 100. The first adder M1 adds the voltage value output by the slope compensation module 210 and the CT sampling signal sampled from the first switch Q1 and then outputs it to the non-inverting input terminal of the first comparator QT1; similarly, the second adder M2 adds the voltage value output by the slope compensation module 210 and the CT sampling signal sampled from the second switch Q2 and then outputs it to the non-inverting input terminal of the second comparator QT2; the digital-to-analog conversion module 230 converts the digital pulse width signal PWM_DA into the DC bus reference value V ref and then outputs it to the inverting input terminals of the first comparator QT1 and the second comparator QT2.

[0078] The first comparator QT1 compares the superimposed signal (corresponding to the first switch Q1) with the DC bus reference value V ref , and the level signal after comparison is input to the RESET1 bit of the trigger module 250 (such as a flip-flop). The second comparator QT2 compares the superimposed signal (corresponding to the second switch Q2) with the DC bus reference value V ref , and the level signal after comparison is input to the RESET2 bit of the trigger module 250. The trigger module 250 generates a driving signal for the power device with a certain logic to drive the first switch Q1 and the second switch Q2.

[0079] In some possible embodiments, the digital-to-analog conversion module 230 is composed of an inverter and a high-order filter. The PWM_DA signal with a higher modulation frequency is input to the inverter, and then the DC component is extracted through the high-order filter as the output, that is, the V ref signal. To reduce the ripple of the output DC output voltage, a reverse ripple signal can be added before the high-order low-pass filter to cancel each other out. The conversion relationship between its output and input depends on the duty cycle of the pulse width signal, V ref = D * PWM_DA.

[0080] In some embodiments, the slope compensation module 210 is composed of an analog circuit. According to the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 output by the digital controller 100, it controls a current source to discharge a slope capacitor, generating a voltage signal with a certain slope. When the actual duty cycle is greater than 50%, this slope signal is superimposed by the first adder M1 and the second adder M2 on the current signals of the switching tubes (the first switching tube Q1 and the second switching tube Q2) sampled by the DC pulse current transformer (CT), suppressing sub-harmonic oscillation. The calculation formulas for the slope capacitor and its voltage are as follows:

[0081]

[0082] In formulas ① and ②, N s is the number of turns of the primary coil of the DC pulse current transformer, N p is the number of turns of the secondary coil of the DC pulse current transformer, R is the CT current detection resistor, V omax is the upper limit of the output DC bus voltage, V pvmin is the minimum value of the output voltage of the photovoltaic module, and L is the boost inductor.

[0083] The waveform of the slope compensation superimposed on the CT sampled current is as Figure 3 shown. Among them, the signal output from the first output terminal of the slope compensation module 210 is V c1 , and the signal output from the second output terminal of the slope compensation module 210 is V c2 . When PWM_CLK1 and PWM_CLK2 are at a high level, a constant current source charges the slope capacitor, and the voltage across the capacitor rises linearly. When PWM_CLK1 and PWM_CLK2 become low level, the voltage across the slope capacitor is quickly discharged to zero. During the low level time period of PWM_CLK1 and PWM_CLK2, the voltage across the slope capacitor is maintained at zero until the next time PWM_CLK1 and PWM_CLK2 become high level.

[0084] In the above peak current controller, the results after comparing the peak currents i Q1 , i Q2 with the reference voltage V ref are output to the RESET1 terminal and the RESET2 terminal of the flip-flop. The other input terminal of the flip-flop is connected to the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2. At the same time, these two pulse signals are respectively AND-logiced with the Q terminal of the flip-flop output, and the output of the AND gate is finally given to the drive circuit of the switching tube to achieve peak current control of the switching device.

[0085] The flip-flop can use a D flip-flop to implement this logic. For the specific logic control waveform, see Figure 4, when the rising edges of the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 arrive, the outputs of PWM1 and PWM2 are high and the switching transistors are turned on; when the sampled currents i Q1 and i Q2 reach the reference voltage V ref threshold, RESET1 and RESET2 are set to zero, the outputs of PWM1 and PWM2 are low, and the switching transistors are immediately turned off. Since the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2 are ANDed with the Q output of the flip-flop, if the sampled currents i Q1 and i Q2 do not reach the reference voltage V ref threshold, the turn-off of the switching transistors is determined by the falling edges of the first pulse signal PWM_CLK1 and the second pulse signal PWM_CLK2.

[0086] The interleaved parallel Boost implemented by the external peak current control method in this application has a Boost waveform as Figure 5 shown, which are waveform diagrams under duty cycles less than 0.5 and greater than 0.5 respectively. The waveforms of the inductor current and the output voltage demonstrate the effectiveness of the control method in this application.

[0087] This application uses an external peak current control circuit 200 to get rid of the limitation of chip resources, and can flexibly place the circuit on different single boards to achieve design optimization.

[0088] Since the application scenario is a high-power boost topology and real-time response to the current signal of the power transistor is required, a DC pulse current transformer is selected to sample the current of the power transistor. The advantage of using a DC pulse current transformer to detect the current for current peak control is small delay and no need to send it back to the control board for current sampling. The inductor current sampling can still use a Hall current transformer.

[0089] In addition, compared with the traditional implementation method using an SR flip-flop, this application uses the output of a D flip-flop ANDed with the carrier signal. The advantage of doing this is that when the peak current is far from reaching the reference value, the actual duty cycle is determined by the carrier signal. The maximum duty cycle is limited to the duty cycle of the PWM signal and can be set by the host computer.

[0090] The circuit structure of the boost side of the inverter in this application includes a digital controller 100 and an external peak current control circuit 200. The external peak current control circuit 200 includes a slope compensation module 210, a superposition module 220, a digital-to-analog conversion module 230, a comparison module 240, and a trigger module 250. The digital controller 100 is connected to the photovoltaic power circuit 300 for obtaining the current and voltage information of the photovoltaic power circuit 300. The slope compensation module 210 is connected to the first output terminal of the digital controller 100 and is used for converting the pulse signal output by the digital controller 100 into a slope voltage signal with a preset slope and then outputting it. The superposition module 220 is connected to the slope compensation module 210 and the photovoltaic power circuit 300 and is used for superposing the slope voltage signal and the switch tube current signal of the photovoltaic power circuit 300 and then outputting. The digital-to-analog conversion module 230 is connected to the second output terminal of the digital controller 100 and is used for converting the digital signal output by the digital controller 100 into a reference voltage signal and then outputting. The input terminal of the comparison module 240 is connected to the superposition module 220 and the digital-to-analog conversion module 230 and is used for receiving the signals output by the slope compensation module 210 and the digital-to-analog conversion module 230, comparing them, and then outputting. The trigger module 250 is connected to the output terminal of the comparison module 240 and the first output terminal of the digital controller 100 and is used for receiving the pulse signal and the signal output by the comparison module 240 to output a drive signal to the switch tube of the photovoltaic power circuit 300. By setting the external peak current control circuit 200 in the inverter, the limitation of chip resources is overcome, better current peak control is achieved, and the circuit can be flexibly placed on different single boards to realize the optimization of the design.

[0091] Embodiment 2

[0092] In some alternative embodiments, this application also provides a photovoltaic system including the circuit structure of the boost side of the inverter as described above.

[0093] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the structure and implementation principle of the photovoltaic system described above can refer to the corresponding structure and implementation principle in the first embodiment described above, and will not be elaborated here.

[0094] The boost-side circuit structure of the inverter in this application includes a digital controller 100 and an external peak current control circuit 200. The external peak current control circuit 200 includes a slope compensation module 210, a superposition module 220, a digital-to-analog conversion module 230, a comparison module 240, and a trigger module 250. The digital controller 100 is connected to the photovoltaic power circuit 300 and is used to obtain the current and voltage information of the photovoltaic power circuit 300. The slope compensation module 210 is connected to the first output terminal of the digital controller 100 and is used to convert the pulse signal output by the digital controller 100 into a slope voltage signal with a preset slope and then output it. The superposition module 220 is connected to the slope compensation module 210 and the photovoltaic power circuit 300 and is used to superpose the slope voltage signal and the switch tube current signal of the photovoltaic power circuit 300 and then output it. The digital-to-analog conversion module 230 is connected to the second output terminal of the digital controller 100 and is used to convert the digital signal output by the digital controller 100 into a reference voltage signal and then output it. The input terminal of the comparison module 240 is connected to the superposition module 220 and the digital-to-analog conversion module 230 and is used to receive the signals output by the slope compensation module 210 and the digital-to-analog conversion module 230, compare them, and then output. The trigger module 250 is connected to the output terminal of the comparison module 240 and the first output terminal of the digital controller 100 and is used to receive the pulse signal and the signal output by the comparison module 240 to output a drive signal to the switch tube of the photovoltaic power circuit 300. By setting the external peak current control circuit 200 in the inverter, the limitation of chip resources is eliminated, better current peak control is achieved, and the circuit can be flexibly placed on different single boards to optimize the design.

[0095] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An inverter boost side circuit structure, characterized in that: It includes a digital controller and an external peak current control circuit, wherein the external peak current control circuit includes a slope compensation module, a superposition module, a digital-to-analog conversion module, a comparison module and a trigger module; The digital controller is connected to the photovoltaic power circuit and is used to obtain current and voltage information of the photovoltaic power circuit; The slope compensation module is connected to the first output terminal of the digital controller, and is used for converting the pulse signal output by the digital controller into a slope voltage signal with a preset slope and then outputting it; The superposition module is connected to the slope compensation module and the photovoltaic power circuit, and is used for superimposing the slope voltage signal and the switch tube current signal of the photovoltaic power circuit and then outputting the superposition signal; The digital-to-analog conversion module is connected to the second output terminal of the digital controller, and is used to convert the digital signal output by the digital controller into a reference voltage signal and then output it; The input end of the comparison module is connected to the superposition module and the digital-to-analog conversion module, and is used to receive the signals output by the slope compensation module and the digital-to-analog conversion module, and then output them after comparison; The trigger module is connected to the output end of the comparison module and the first output end of the digital controller, and is used to receive the pulse signal and the signal output by the comparison module to output a driving signal to the switch tube of the photovoltaic power circuit.

2. The inverter boost side circuit structure according to claim 1, characterized in that: The photovoltaic power circuit includes a photovoltaic string, a first inductor, a second inductor, a first diode, a second diode, a first capacitor, a first switch tube and a second switch tube; The first signal input terminal and the second signal input terminal of the digital controller are connected to the photovoltaic string, and are used to obtain the photovoltaic current signal and the photovoltaic voltage signal of the photovoltaic string; The first end of the photovoltaic string is connected to the positive electrode of the first diode and the second end of the first switch tube through the first inductor, and the first end of the photovoltaic string is also connected to the positive electrode of the second diode and the second end of the second switch tube through the second inductor; The cathode of the first diode and the cathode of the second diode are both connected to the first end of the first capacitor; The first end of the first switch tube, the first end of the second switch tube and the second end of the first capacitor are all connected to the second end of the photovoltaic string; The control end of the first switch tube and the control end of the second switch tube are both connected to the output end of the trigger module; The third signal input terminal of the digital controller is connected to the first terminal of the first capacitor for obtaining an output voltage signal of the photovoltaic power circuit.

3. The inverter boost side circuit structure according to claim 2, characterized in that: The inverter boost side circuit structure further includes a Hall sampling circuit, an input end of the Hall sampling circuit is connected to the photovoltaic string, and an output end of the Hall sampling circuit is connected to the first signal input end of the digital controller.

4. The inverter boost side circuit structure according to claim 2, characterized in that: The inverter boost side circuit structure also includes a first voltage sampling circuit, an input end of the first voltage sampling circuit is connected to the photovoltaic string, and an output end of the first voltage sampling circuit is connected to the second signal input end of the digital controller.

5. The inverter boost side circuit structure according to claim 2, characterized in that: The inverter boost side circuit structure also includes a second voltage sampling circuit, an input end of the second voltage sampling circuit is connected to the first end of the first capacitor, and an output end of the second voltage sampling circuit is connected to the third signal input end of the digital controller.

6. The inverter boost side circuit structure according to claim 2, characterized in that: The inverter boost side circuit structure also includes a first CT sampling circuit and a second CT sampling circuit, the input end of the first CT sampling circuit is connected to the second end of the first switch tube, the input end of the second CT sampling circuit is connected to the second end of the second switch tube, and the output end of the first CT sampling circuit and the output end of the second CT sampling circuit are both connected to the superposition module.

7. The inverter boost side circuit structure according to claim 6, characterized in that: The superposition module includes a first superimposer and a second superimposer; The first input end of the first adder is connected to the output end of the first CT sampling circuit, the second input end of the first adder is connected to the first output end of the slope compensation module, and the output end of the first adder is connected to the comparison module; The first input end of the second adder is connected to the output end of the second CT sampling circuit, the second input end of the second adder is connected to the second output end of the slope compensation module, and the output end of the second adder is connected to the comparison module.

8. The inverter boost side circuit structure according to claim 7, characterized in that: The comparison module includes a first comparator and a second comparator; The non-inverting input terminal of the first comparator is connected to the output terminal of the first adder, and the inverting input terminal of the first comparator is connected to the output terminal of the digital-to-analog conversion module; The non-inverting input terminal of the second comparator is connected to the output terminal of the second adder, and the inverting input terminal of the second comparator is connected to the output terminal of the digital-to-analog conversion module; An output terminal of the first comparator and an output terminal of the second comparator are both connected to the trigger module.

9. The inverter boost side circuit structure according to claim 2, characterized in that: The first switch tube and the second switch tube are MOS tubes or IGBTs.

10. A photovoltaic system, characterized in that: The invention comprises the inverter boost side circuit structure as claimed in any one of claims 1 to 9.

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