Difference Power Unit Control Device and Control Method in Dual-Input Inverter

Abstract

The present invention discloses a control device and a control method for a differential power unit in a dual-input inverter. The control device includes: a dual-input inverter circuit and a control and drive unit. Among them, the control and drive unit is connected to the dual-input inverter circuit, and is used to collect the voltage feedback signals and current feedback signals of the first photovoltaic cell module and the second photovoltaic cell module in the dual-input inverter circuit, as well as the voltage feedback signals output by the first differential power unit and the second differential power unit, and generate a first switching logic signal and a second switching logic signal according to the voltage feedback signals and current feedback signals, so as to respectively drive and control the first differential power unit and the second differential power unit according to the first switching logic signal and the second switching logic signal. The present invention can solve the problem of insufficient inverter bus voltage under shadow conditions and can improve the system conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of inverter control, and in particular, to a control device and a control method for a differential power unit in a dual-input inverter. Background Art

[0002] A photovoltaic inverter is a core component of a photovoltaic power generation system. However, under the conditions of partial shadow occlusion or high temperature of photovoltaic modules, the voltage at the maximum power point of the photovoltaic cell array drops, and the input voltage may be less than the peak value of the grid voltage, resulting in the shutdown of the photovoltaic inverter due to undervoltage. The traditional method uses two-stage conversion to achieve step-up and step-down, that is, the cascaded mode of a boost converter and a photovoltaic inverter, but this method reduces the system conversion efficiency. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, the first object of the present invention is to provide a control device for a differential power unit in a dual-input inverter, which can solve the problem of insufficient inverter bus voltage under shadow conditions and can improve the system conversion efficiency.

[0004] The second object of the present invention is to provide a control method for a differential power unit in a dual-input inverter.

[0005] To achieve the above object, the present invention is realized by the following technical solutions:

[0006] A control device for a differential power unit in a dual-input inverter, comprising:

[0007] Dual-input inverter circuit, the dual-input inverter circuit includes a first photovoltaic cell module, a second photovoltaic cell module, a first filter capacitor, a second filter capacitor, a first diode, a second diode, a first difference power unit, a second difference power unit, a dual-input inverter, and a load / grid. Wherein, the positive electrode of the first photovoltaic cell module is respectively connected to the positive input terminal of the second difference power unit, one end of the first filter capacitor, the anode of the first diode, and the negative output terminal of the first difference power unit; the negative electrode of the first photovoltaic cell module is respectively connected to the positive input terminal of the first difference power unit, the negative input terminal of the second difference power unit, the other end of the first filter capacitor, the positive electrode of the second photovoltaic cell module, one end of the second filter capacitor, and the negative terminal of the load / grid; the negative electrode of the second photovoltaic cell module is respectively connected to the negative input terminal of the first difference power unit, the positive output terminal of the second difference power unit, the other end of the second filter capacitor, and the cathode of the second diode; the cathode of the first diode is respectively connected to the positive output terminal of the first difference power unit and the positive input terminal of the dual-input inverter; the anode of the second diode is respectively connected to the negative output terminal of the second difference power unit and the negative input terminal of the dual-input inverter, and the positive output terminal of the dual-input inverter is connected to the positive terminal of the load / grid;

[0008] A control and drive unit, whose input terminals are respectively connected to the output terminals of the first photovoltaic cell module, the second photovoltaic cell module, the first difference power unit, and the second difference power unit in the dual-input inverter circuit. The output terminals of the control and drive unit are respectively connected to the control terminals of the first difference power unit and the second difference power unit. The control and drive unit is used to collect the voltage feedback signals and current feedback signals of the first photovoltaic cell module and the second photovoltaic cell module, as well as the voltage feedback signals output by the first difference power unit and the second difference power unit, and generate a first switching logic signal and a second switching logic signal according to the voltage feedback signals and the current feedback signals, so as to respectively drive and control the first difference power unit and the second difference power unit according to the first switching logic signal and the second switching logic signal.

[0009] Optionally, the control and drive unit includes:

[0010] A sensor assembly, whose input terminals are respectively connected to the output terminals of the first photovoltaic cell module, the second photovoltaic cell module, the first difference power unit, and the second difference power unit. The sensor assembly is used to respectively collect the first voltage feedback signal, the second voltage feedback signal, the first current feedback signal, and the second current feedback signal of the first photovoltaic cell module and the second photovoltaic cell module, as well as the third voltage feedback signal and the fourth voltage feedback signal respectively output by the first difference power unit and the second difference power unit;

[0011] A digital signal processor, whose input end is connected to the first output end of the sensor assembly, and the digital signal processor is configured to perform signal processing on the first voltage feedback signal, the second voltage feedback signal, the first current feedback signal, and the second current feedback signal, and generate a first voltage reference signal, a second voltage reference signal, a first working selection signal, and a second working selection signal;

[0012] A control circuit, whose first input end is connected to the output end of the digital signal processor, and the second input end of the control circuit is connected to the second output end of the sensor assembly. The control circuit is configured to generate the first switching logic signal according to the signal obtained by subtracting the third voltage feedback signal from the first voltage reference signal, and generate the second switching logic signal according to the signal obtained by subtracting the fourth voltage feedback signal from the second voltage reference signal.

[0013] Optionally, the sensor assembly includes:

[0014] A first voltage sensor, whose input end is connected to the first photovoltaic cell module, and the output end of the first voltage sensor is connected to the input end of the digital signal processor. The first voltage sensor is configured to collect the first voltage feedback signal and transmit it to the digital signal processor;

[0015] A second voltage sensor, whose input end is connected to the second photovoltaic cell module, and the output end of the second voltage sensor is connected to the input end of the digital signal processor. The second voltage sensor is configured to collect the second voltage feedback signal and transmit it to the digital signal processor;

[0016] A first current sensor, whose input end is connected to the first photovoltaic cell module, and the output end of the first current sensor is connected to the input end of the digital signal processor. The first current sensor is configured to collect the first current feedback signal and transmit it to the digital signal processor;

[0017] A second current sensor, whose input end is connected to the second photovoltaic cell module, and the output end of the second current sensor is connected to the input end of the digital signal processor. The second current sensor is configured to collect the second current feedback signal and transmit it to the digital signal processor;

[0018] A third voltage sensor, whose input end is connected to the output end of the first difference power unit, and the output end of the third voltage sensor is connected to the input end of the control circuit. The third voltage sensor is configured to collect the third voltage feedback signal and transmit it to the control circuit;

[0019] A fourth voltage sensor, whose input end is connected to the output end of the second differential power unit, and whose output end is connected to the input end of the control circuit. The fourth voltage sensor is configured to collect the fourth voltage feedback signal and transmit it to the control circuit.

[0020] Optionally, the digital signal processor includes:

[0021] A first analog-to-digital conversion module, whose input end is connected to the output end of the first voltage sensor. The first analog-to-digital conversion module is configured to perform analog-to-digital conversion on the first voltage feedback signal to obtain a first digital signal;

[0022] A second analog-to-digital conversion module, whose input end is connected to the output end of the second voltage sensor. The second analog-to-digital conversion module is configured to perform analog-to-digital conversion on the second voltage feedback signal to obtain a second digital signal;

[0023] A third analog-to-digital conversion module, whose input end is connected to the output end of the first current sensor. The third analog-to-digital conversion module is configured to perform analog-to-digital conversion on the first current feedback signal to obtain a third digital signal;

[0024] A fourth analog-to-digital conversion module, whose input end is connected to the output end of the second current sensor. The fourth analog-to-digital conversion module is configured to perform analog-to-digital conversion on the second current feedback signal to obtain a fourth digital signal;

[0025] A power calculation module, whose input end is respectively connected to the second output end of the first analog-to-digital conversion module, the second output end of the second analog-to-digital conversion module, the output end of the third analog-to-digital conversion module, and the output end of the fourth analog-to-digital conversion module. The power calculation module is configured to perform power calculation on the first digital signal, the second digital signal, the third digital signal, and the fourth digital signal to obtain a fifth digital signal;

[0026] A differential power unit control module, whose input end is respectively connected to the first output end of the first analog-to-digital conversion module, the first output end of the second analog-to-digital conversion module, and the output end of the power calculation module. The differential power unit control module is configured to perform digital processing on the first digital signal, the second digital signal, and the fifth digital signal to obtain a first voltage reference digital signal, a second voltage reference digital signal, a first working selection digital signal, and a second working selection digital signal;

[0027] The first digital-to-analog conversion module, whose input end is connected to the first output end of the difference power unit control module, and the first digital-to-analog conversion module is used to perform digital-to-analog conversion on the first voltage reference digital signal to obtain the first voltage reference signal;

[0028] The second digital-to-analog conversion module, whose input end is connected to the second output end of the difference power unit control module, and the second digital-to-analog conversion module is used to perform digital-to-analog conversion on the second voltage reference digital signal to obtain the second voltage reference signal;

[0029] The third digital-to-analog conversion module, whose input end is connected to the third output end of the difference power unit control module, and the third digital-to-analog conversion module is used to perform digital-to-analog conversion on the first working selection digital signal to obtain the first working selection signal;

[0030] The fourth digital-to-analog conversion module, whose input end is connected to the fourth output end of the difference power unit control module, and the fourth digital-to-analog conversion module is used to perform digital-to-analog conversion on the second working selection digital signal to obtain the second working selection signal.

[0031] Optionally, the control circuit includes:

[0032] The first voltage regulator, whose first input end is connected to the output end of the first digital-to-analog conversion module, and the second input end of the first voltage regulator is connected to the output end of the third voltage sensor. The first voltage regulator is used to perform voltage regulation on the signal after subtracting the first voltage reference signal and the third voltage feedback signal to obtain the first high-frequency switching signal;

[0033] The second voltage regulator, whose first input end is connected to the output end of the second digital-to-analog conversion module, and the second input end of the second voltage regulator is connected to the output end of the fourth voltage sensor. The second voltage regulator is used to perform voltage regulation on the signal after subtracting the second voltage reference signal and the fourth voltage feedback signal to obtain the second high-frequency switching signal;

[0034] The first AND gate, whose first input end is connected to the output end of the first voltage regulator, and the second input end of the first AND gate is connected to the output end of the third digital-to-analog conversion module. The first AND gate is used to generate the first switching logic signal according to the first high-frequency switching signal and the first working selection signal and transmit it to the control end of the first difference power unit;

[0035] A second AND gate, whose first input terminal is connected to the output terminal of the second voltage regulator, and whose second input terminal is connected to the output terminal of the fourth digital-to-analog conversion module. The second AND gate is configured to generate a second switching logic signal according to the second high-frequency switching signal and the second operation selection signal, and transmit it to the control terminal of the second differential power unit.

[0036] Optionally, the first differential power unit and the second differential power unit are isolated transformers.

[0037] Optionally, the dual-input inverter is a half-bridge inverter.

[0038] Optionally, the first diode and the second diode are silicon carbide diodes or fast-recovery diodes.

[0039] Optionally, the first filter capacitor and the second filter capacitor are polarized capacitors or non-polarized capacitors.

[0040] To achieve the above object, a second aspect of the present invention provides a method for controlling a differential power unit in a dual-input inverter, including:

[0041] Using a sensor assembly to collect the input voltages of the first differential power unit and the second differential power unit in real time, and comparing the input voltages with the peak value of the load / grid voltage at a preset ratio;

[0042] If the input voltages of the first differential power unit and the second differential power unit are both greater than the peak value of the load / grid voltage, obtain the output powers of the first photovoltaic cell module and the second photovoltaic cell module, and perform corresponding control on the first differential power unit and the second differential power unit respectively according to the output powers;

[0043] If the input voltages of the first differential power unit and the second differential power unit are both less than the peak value of the load / grid voltage, directly start the first differential power unit and the second differential power unit;

[0044] If the input voltage of any one of the first differential power unit and the second differential power unit is less than the peak value of the load / grid voltage, compare the input voltage of the first differential power unit with the input voltage of the second differential power unit, and perform corresponding control on the first differential power unit and the second differential power unit respectively according to the comparison result.

[0045] The present invention has at least the following technical effects:

[0046] The present invention is applicable to the occasion of a dual-input inverter, which can achieve the maximum power output of two photovoltaic cell modules, thereby solving the problem of insufficient bus voltage of the inverter under shadow conditions. Moreover, it can also achieve power balance between the positive and negative half-cycles of the dual-input inverter and ensure high-quality output voltage or current waveforms. In addition, since the difference power unit of the present invention only bears half of the difference power between the two photovoltaic cell modules, the system power is small and the cost is low, improving the system conversion efficiency.

[0047] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a structural block diagram of a difference power unit control device in a dual-input inverter provided by an embodiment of the present invention;

[0049] Figure 2 It is a schematic diagram of the circuit topology of a dual-input inverter provided by an embodiment of the present invention;

[0050] Figure 3 It is a schematic diagram of the circuit structure of a control and drive unit provided by an embodiment of the present invention;

[0051] Figure 4 It is a flowchart of a difference power unit control method in a dual-input inverter provided by an embodiment of the present invention;

[0052] Figure 5 It is a flowchart of a difference power unit control method in a dual-input inverter provided by a specific example of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] The following details this embodiment, and the examples of the embodiment are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0054] The following describes the difference power unit control device and control method in the dual-input inverter of this embodiment with reference to the drawings.

[0055] Figure 1 It is a structural block diagram of a difference power unit control device in a dual-input inverter provided by an embodiment of the present invention. As Figure 1 shown, the difference power unit control device 100 in the dual-input inverter includes: a control and drive unit 10 and a dual-input inverter circuit 20.

[0056] As Figure 2As shown, the dual-input inverter circuit 20 includes: a first photovoltaic cell module PV1, a second photovoltaic cell module PV2, a first filter capacitor Cin1, a second filter capacitor Cin2, a first diode D1, a second diode D2, a first differential power unit F1, a second differential power unit F2, a dual-input inverter G, and a load / grid Z.

[0057] Among them, the differential power unit is an isolated converter such as a flyback converter, a forward converter, and a push-pull converter, etc. The dual-input inverter G is a half-bridge inverter such as a traditional half-bridge inverter and a dual buck half-bridge inverter, etc. Specifically, it can be a dual-grounded, dual-input, highly reliable photovoltaic inverter. The first diode D 1 and the second diode D 2 are silicon carbide diodes or fast-recovery diodes. The first filter capacitor C in1 and the second filter capacitor C in2 are polarized capacitors or non-polarized capacitors. It should be noted that the above devices are not specifically limited in this embodiment.

[0058] In an embodiment of the present invention, the specific circuit topology of the dual-input inverter circuit 20 is as follows: The positive pole of the first photovoltaic cell module PV1 is respectively connected to the positive input terminal of the second differential power unit F2, one end of the first filter capacitor Cin1, the anode of the first diode D1, and the negative output terminal of the first differential power unit F1; the negative pole of the first photovoltaic cell module PV1 is respectively connected to the positive input terminal of the first differential power unit F1, the negative input terminal of the second differential power unit F2, the other end of the first filter capacitor Cin1, the positive pole of the second photovoltaic cell module PV2, one end of the second filter capacitor Cin2, and the negative terminal of the load / grid Z; the negative pole of the second photovoltaic cell module PV2 is respectively connected to the negative input terminal of the first differential power unit F1, the positive output terminal of the second differential power unit F2, the other end of the second filter capacitor Cin2, and the cathode of the second diode D2; the cathode of the first diode D1 is respectively connected to the positive output terminal of the first differential power unit F1 and the positive input terminal of the dual-input inverter G, and the anode of the second diode D2 is respectively connected to the negative output terminal of the second differential power unit F2 and the negative input terminal of the dual-input inverter G. The positive output terminal of the dual-input inverter G is connected to the positive terminal of the load / grid Z.

[0059] In this embodiment, the input terminals of the control and drive unit 10 are respectively connected to the output terminals of the first photovoltaic cell module PV1, the second photovoltaic cell module PV2, the first differential power unit F1, and the second differential power unit F2 in the dual-input inverter circuit 20. The output terminals of the control and drive unit 10 are respectively connected to the control terminals of the first differential power unit F1 and the second differential power unit F2. The control and drive unit 10 is configured to collect the voltage feedback signals and current feedback signals of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2, as well as the voltage feedback signals output by the first differential power unit F1 and the second differential power unit F2, and generate a first switching logic signal and a second switching logic signal based on the above voltage feedback signals and current feedback signals, so as to respectively drive and control the first differential power unit and the second differential power unit according to the first switching logic signal and the second switching logic signal.

[0060] Specifically, the input voltage of the dual-input inverter G can be selected through the first diode D1 and the second diode D2. When the differential power unit is not working, the diodes in series with the corresponding photovoltaic modules on the output side are turned on; when the differential power unit is working, the diodes in series with the corresponding photovoltaic modules on the output side are reverse-biased and turned off. Thus, the device can achieve power balance in the positive and negative half-cycles of the dual-input inverter. And since the differential power unit only bears half of the difference power between the two photovoltaic cell modules, the power is small, the cost is low, and the system conversion efficiency is improved.

[0061] Furthermore, as Figure 3 shown, the control and drive unit 10 includes: a sensor assembly 1, a digital signal processor 2, and a control circuit 3.

[0062] Among them, the input terminals of the sensor assembly 1 are respectively connected to the output terminals of the first photovoltaic cell module PV1, the second photovoltaic cell module PV2, the first differential power unit F1, and the second differential power unit F2. The sensor assembly 1 is configured to respectively collect the first voltage feedback signal U pv1 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2, the second voltage feedback signal U pv2 , the first current feedback signal i pv1 and the second current feedback signal i pv2 , and is configured to collect the third voltage feedback signal u C1 and the fourth voltage feedback signal u C2 at the output terminals of the first differential power unit F1 and the second differential power unit F2;

[0063] The input terminal of the digital signal processor 2 is connected to the first output terminal of the sensor assembly 1, and is configured to process the first voltage feedback signal U pv1, the second voltage feedback signal U pv2 , the first current feedback signal i pv1 and the second current feedback signal i pv2 are subjected to signal processing and generate the first voltage reference signal u ref1 , the second voltage reference signal u ref2 , the first operation selection signal u wc1 and the second operation selection signal u wc2 ;

[0064] The first input end of the control circuit 3 is connected to the output end of the digital signal processor 2, and its second input end is connected to the second output end of the sensor assembly 1. The control circuit 3 is configured to, according to the first voltage reference signal u ref1 and the second voltage reference signal u ref2 , subtract the third voltage feedback signal u C1 and the fourth voltage feedback signal u C2 from the signal, perform voltage comparison control, and respectively generate the first switch logic signal O 1 and the second switch logic signal O 2 .

[0065] Please continue to refer to Figure 3 , in this embodiment, the sensor assembly 1 includes: a first voltage sensor 101, a second voltage sensor 102, a first current sensor 103, a second current sensor 104, a third voltage sensor 105, and a fourth voltage sensor 106.

[0066] Among them, the input end of the first voltage sensor 101 is connected to the first photovoltaic cell module PV1, and the output end is connected to the input end of the digital signal processor 2. The first voltage sensor 101 is configured to collect the first voltage feedback signal U pv1 and transmit it to the digital signal processor 2; the input end of the second voltage sensor 102 is connected to the second photovoltaic cell module PV2, and the output end is connected to the input end of the digital signal processor 2. The second voltage sensor 102 is configured to collect the second voltage feedback signal U pv2 and transmit it to the digital signal processor 2; the input end of the first current sensor 103 is connected to the first photovoltaic cell module PV1, and the output end is connected to the input end of the digital signal processor 2. The first current sensor 103 is configured to collect the first current feedback signal i pv1 and transmit it to the digital signal processor 2; the input end of the second current sensor 104 is connected to the second photovoltaic cell module PV2, and the output end is connected to the input end of the digital signal processor 2. The second current sensor 104 is configured to collect the second current feedback signal i pv2and transmit it to the digital signal processor 2; the input end of the third voltage sensor 105 is connected to the output end of the first difference power unit F1, and the output end is connected to the input end of the control circuit 3. The third voltage sensor 105 is used to collect the third voltage feedback signal u C1 and transmit it to the control circuit 3; the input end of the fourth voltage sensor 106 is connected to the output end of the second difference power unit F2, and the output end is connected to the input end of the control circuit 3. The fourth voltage sensor 106 is used to collect the fourth voltage feedback signal u C2 and transmit it to the control circuit 3.

[0067] Please continue to refer to Figure 3 , the digital signal processor 2 includes: a first analog-to-digital conversion module AD1, a second analog-to-digital conversion module AD2, a third analog-to-digital conversion module AD3, a fourth analog-to-digital conversion module AD4, a power calculation module 201, a difference power unit control module 202, a first digital-to-analog conversion module DA1, a second digital-to-analog conversion module DA2, a third digital-to-analog conversion module DA3, and a fourth digital-to-analog conversion module DA4.

[0068] Among them, the input end of the first analog-to-digital conversion module AD1 is connected to the output end of the first voltage sensor 101, and is used to perform analog-to-digital conversion on the first voltage feedback signal U pv1 to obtain a first digital signal; the input end of the second analog-to-digital conversion module AD2 is connected to the output end of the second voltage sensor 102, and is used to perform analog-to-digital conversion on the second voltage feedback signal U pv2 to obtain a second digital signal; the input end of the third analog-to-digital conversion module AD3 is connected to the output end of the first current sensor 103, and is used to perform analog-to-digital conversion on the first current feedback signal i pv1 to obtain a third digital signal; the input end of the fourth analog-to-digital conversion module AD4 is connected to the output end of the second current sensor 104, and is used to perform analog-to-digital conversion on the second current feedback signal i pv2 to obtain a fourth digital signal.

[0069] In this embodiment, the input end of the power calculation module 201 is respectively connected to the second output end of the first analog-to-digital conversion module AD1, the second output end of the second analog-to-digital conversion module AD2, the output end of the third analog-to-digital conversion module AD3, and the output end of the fourth analog-to-digital conversion module AD4, and is used to calculate the power of the first digital signal, the second digital signal, the third digital signal, and the fourth digital signal to obtain a fifth digital signal; the input end of the differential power unit control module 202 is respectively connected to the first output end of the first analog-to-digital conversion module AD1, the first output end of the second analog-to-digital conversion module AD2, and the output end of the power calculation module 201, and performs digital processing on the first digital signal, the second digital signal, and the fifth digital signal to obtain a first voltage reference digital signal, a second voltage reference digital signal, a first working selection digital signal, and a second working selection digital signal.

[0070] In this embodiment, the input end of the first digital-to-analog conversion module DA1 is connected to the first output end of the differential power unit control module 202, and is used to perform digital-to-analog conversion on the first voltage reference digital signal to obtain a first voltage reference signal u ref1 , where the first voltage reference signal u ref1 satisfies the following formula (1) or formula (2) or formula (3):

[0071]

[0072] u ref1 =U in2 -U in1 (2)

[0073] u ref1 =mU om -U in1 (3)

[0074] where u ref1 is the first voltage reference signal, p 1 is the output power of the first photovoltaic cell module PV1, p 2 is the output power of the second photovoltaic cell module PV2, U in1 is the input voltage of the first differential power unit F1, U in2 is the input voltage of the second differential power unit F2, m is a preset ratio, and U om is the peak value of the load / grid voltage.

[0075] Similarly, the input end of the second digital-to-analog conversion module DA2 is connected to the second output end of the differential power unit control module 202, and is used to perform digital-to-analog conversion on the second voltage reference digital signal to obtain a second voltage reference signal u ref2 , where the second voltage reference signal u ref2Satisfy the following formula (4) or formula (5) or formula (6):

[0076]

[0077] u ref2 = U in1 -U in2 (5)

[0078] u ref2 = mU om -U in2 (6)

[0079] In this embodiment, the input end of the third digital-to-analog conversion module DA3 is connected to the third output end of the difference power unit control module 202, and is used for performing digital-to-analog conversion on the first working selection digital signal to obtain the first working selection signal u wc1 ; the input end of the fourth digital-to-analog conversion module DA4 is connected to the fourth output end of the difference power unit control module 202, and is used for performing digital-to-analog conversion on the second working selection digital signal to obtain the second working selection signal u wc2 .

[0080] Please continue to refer to Figure 3 , the control circuit 3 includes: a first voltage regulator 301, a second voltage regulator 302, a first AND gate 303 and a second AND gate 304.

[0081] Among them, the first input end of the first voltage regulator 301 is connected to the output end of the first digital-to-analog conversion module DA1, and its second input end is connected to the output end of the third voltage sensor 105. The first voltage regulator 301 is used for performing voltage regulation on the signal after subtracting the first voltage reference signal u ref1 and the third voltage feedback signal u C1 to obtain the first high-frequency switching signal; the first input end of the second voltage regulator 302 is connected to the output end of the second digital-to-analog conversion module DA2, and its second input end is connected to the output end of the fourth voltage sensor 106. The second voltage regulator 302 is used for performing voltage regulation on the signal after subtracting the second voltage reference signal u ref2 and the fourth voltage feedback signal u C2 to obtain the second high-frequency switching signal; the first input end of the first AND gate 303 is connected to the output end of the first voltage regulator 301, and its second input end is connected to the output end of the third digital-to-analog conversion module DA3. The first AND gate 303 can obtain the first switching logic signal O wc1 according to the first high-frequency switching signal and the first working selection signal u 1, and transmit it to the control terminal of the first differential power unit F1; the first input terminal of the second AND gate 304 is connected to the output terminal of the second voltage regulator 302, and its second input terminal is connected to the output terminal of the fourth digital-to-analog conversion module DA4. The second AND gate 304 can obtain the second switching logic signal O according to the second high-frequency switching signal and the second operation selection signal u wc2 Obtain the second switching logic signal O 2 , and transmit it to the control terminal of the second differential power unit F2.

[0082] In this example, both the first voltage regulator 301 and the second voltage regulator 302 adopt PI (Proportional Integral) control.

[0083] Figure 4 is a flowchart of the control method for the differential power unit in the dual-input inverter provided by an embodiment of the present invention. As Figure 4 shown, the control method includes:

[0084] Step S1: Use the sensor component to collect the input voltages of the first differential power unit and the second differential power unit in real time, and compare the input voltages with the peak value of the load / grid voltage at a preset ratio;

[0085] Step S2: If the input voltages of both the first differential power unit and the second differential power unit are greater than the peak value of the load / grid voltage, obtain the output powers of the first photovoltaic cell module and the second photovoltaic cell module, and perform corresponding control on the first differential power unit and the second differential power unit respectively according to the output powers;

[0086] Step S3: If the input voltages of both the first differential power unit and the second differential power unit are less than the peak value of the load / grid voltage, directly start the first differential power unit and the second differential power unit;

[0087] Step S4: If the input voltage of any one of the first differential power unit and the second differential power unit is less than the peak value of the load / grid voltage, compare the input voltage of the first differential power unit with the input voltage of the second differential power unit, and perform corresponding control on the first differential power unit and the second differential power unit respectively according to the comparison result.

[0088] As a specific example, as Figure 5 shown, the control method may specifically include:

[0089] Step 1: Use the sensor component to collect the input voltages U in1 and U in2 of the first differential power unit F1 and the second differential power unit F2 in real time, and the input voltages Uin1 and U in2 with the load / grid voltage peak mU of a preset ratio om perform the first determination to determine U in1 and U in2 both greater than, both less than, or only one voltage less than mU om ;

[0090] Step 2: The sensor assembly continuously acquires the output voltages U pv1 and U pv2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2, as well as the output currents i pv1 and i pv2 , and respectively calculate the output powers p 1 and p 2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2 in the digital signal processor 2;

[0091] Step 3: When the input voltages U in1 and U in2 of the first difference power unit F1 and the second difference power unit F2 are both greater than the load / grid voltage peak mU of a preset ratio om , take the absolute value |p 1 -p 2 | of the difference between the output powers of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2, and perform the second determination with the rated power nP of the load / grid of a set ratio o . If |p 1 -p 2 | is less than nP o , then neither the first difference power unit, i.e., difference power unit 1, nor the second difference power unit, i.e., difference power unit 2, is started;

[0092] Step 4: If |p 1 -p 2 | is greater than nP o , then perform the third determination on the magnitudes of the output powers of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2. If the output power p 1 of the first photovoltaic cell module PV1 is greater than the output power p 2 of the second photovoltaic cell module PV2, then calculate its second voltage reference signal u ref2 , and superimpose the second voltage reference signal u ref2 with the input voltage U in2 of the second difference power unit F2. Then, when the superimposed value is less than another preset ratio of the load / grid voltage peak kU om , only start difference power unit 2;

[0093] Step 5: If the output power p of the first photovoltaic cell module PV1 1 is less than the output power p of the second photovoltaic cell module PV2 2 , then calculate its first voltage reference signal u ref1 , and only activate the differential power unit 1;

[0094] Step 6: When the input voltages U in1 and U in2 of the first differential power unit F1 and the second differential power unit F2 are both less than the peak value mU of the load / grid voltage at a preset ratio om , then calculate the first voltage reference signal u ref1 and the second voltage reference signal u ref2 , and directly activate the differential power unit 1 and the differential power unit 2;

[0095] Step 7: When only one of the input voltages U in1 and U in2 of the first differential power unit F1 and the second differential power unit F2 is less than the peak value mU of the load / grid voltage at a preset ratio om , then make a fourth determination on the magnitudes of the input voltages U in1 and U in2 . If the input voltage U in1 is greater than the input voltage U in2 , then calculate the second voltage reference signal u ref2 , and only activate the differential power unit 2;

[0096] Step 8: If the input voltage U in1 is less than the input voltage U in2 , then calculate the first voltage reference signal u ref1 , and only activate the differential power unit 1.

[0097] Specifically, the present invention requires real-time acquisition of the input voltages of two differential power units, the output voltages and powers of photovoltaic cell modules, setting the voltage coefficient as m, and setting the power coefficient as n. When it is detected that the input voltages of both differential power units are less than m times the peak value of the rated output voltage, the reference voltages of the respective differential power units can be calculated and determined, and the differential power units are all started to compensate for the bus voltage and power, thereby solving the problem of insufficient bus voltage of the inverter under shadow conditions; when it is detected that the input voltages of both differential power units are greater than m times the peak value of the rated output voltage, then compare whether the absolute value of the difference in the output powers of the two photovoltaic modules is greater than n times the rated output power. If it is greater, then by comparing the magnitudes of the output powers of the two modules, calculate and determine the reference voltage of the differential power unit, and start differential power unit 1 or differential power unit 2 to achieve maximum power output of the two photovoltaic cell modules, power balance between the positive and negative half-cycles of the dual-input inverter, and high output voltage or current waveform quality; if the difference in the output powers of the two photovoltaic modules is less than n times the rated output power, then the differential power units do not work to avoid the losses caused by the light-load operation of the differential power units; when only one of the input voltages of the two detected differential power units is less than m times the peak value of the rated output voltage, by comparing the magnitudes of the input voltages of the two differential power units, calculate and determine the reference voltage of the differential power unit, and start differential power unit 1 or differential power unit 2 to compensate for the missing power and voltage; since the differential power unit only undertakes half of the differential power of the two photovoltaic cell modules, therefore, the power is small, the cost is low, and the system conversion efficiency is improved.

[0098] In this embodiment, the voltage coefficient, i.e., the above-mentioned preset proportional value m, generally takes a value of 1.05 to 1.1, and the power coefficient, i.e., the above-mentioned set proportional value n, generally takes a value of 0.05 to 0.1.

[0099] It should be noted that in this embodiment, the sum of the input voltage of the differential power unit and the reference voltage generated by the other differential power unit does not exceed kU om , where the voltage coefficient k, i.e., the above-mentioned other preset proportional value, generally takes a value of 1.2.

[0100] In summary, the present invention is applicable to the occasion of a dual-input inverter. It can achieve maximum power output of two photovoltaic cell modules, thereby solving the problem of insufficient bus voltage of the inverter under shadow conditions, and it can also achieve power balance between the positive and negative half-cycles of the dual-input inverter, and can ensure high output voltage or current waveform quality. In addition, since the differential power unit only undertakes half of the differential power of the two photovoltaic cell modules in the present invention, the system power is small and the cost is low, and the system conversion efficiency is improved.

[0101] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising said element.

[0102] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be construed as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A control device for a differential power unit in a dual-input inverter, characterized in that, it includes: A dual-input inverter circuit, which includes a first photovoltaic cell module, a second photovoltaic cell module, a first filter capacitor, a second filter capacitor, a first diode, a second diode, a first differential power unit, a second differential power unit, a dual-input inverter and a load / grid. Among them, the positive pole of the first photovoltaic cell module is respectively connected to the positive input terminal of the second differential power unit, one end of the first filter capacitor, the anode of the first diode and the negative output terminal of the first differential power unit; the negative pole of the first photovoltaic cell module is respectively connected to the positive input terminal of the first differential power unit, the negative input terminal of the second differential power unit, the other end of the first filter capacitor, the positive pole of the second photovoltaic cell module, one end of the second filter capacitor and the negative end of the load / grid; the negative pole of the second photovoltaic cell module is respectively connected to the negative input terminal of the first differential power unit, the positive output terminal of the second differential power unit, the other end of the second filter capacitor and the cathode of the second diode; the cathode of the first diode is respectively connected to the positive output terminal of the first differential power unit and the positive input terminal of the dual-input inverter; the anode of the second diode is respectively connected to the negative output terminal of the second differential power unit and the negative input terminal of the dual-input inverter, and the positive output terminal of the dual-input inverter is connected to the positive end of the load / grid; A control and drive unit, whose input terminals are respectively connected to the output terminals of the first photovoltaic cell module, the second photovoltaic cell module, the first differential power unit and the second differential power unit in the dual-input inverter circuit. The output terminals of the control and drive unit are respectively connected to the control terminals of the first differential power unit and the second differential power unit. The control and drive unit is used to collect the voltage feedback signals and current feedback signals of the first photovoltaic cell module and the second photovoltaic cell module, as well as the voltage feedback signals output by the first differential power unit and the second differential power unit, and generate a first switching logic signal and a second switching logic signal according to the voltage feedback signals and the current feedback signals, so as to respectively drive and control the first differential power unit and the second differential power unit according to the first switching logic signal and the second switching logic signal.

2. The control device for a differential power unit in a dual-input inverter according to claim 1, characterized in that, the control and drive unit includes: A sensor assembly, whose input terminals are respectively connected to the output terminals of the first photovoltaic cell module, the second photovoltaic cell module, the first differential power unit and the second differential power unit. The sensor assembly is used to respectively collect the first voltage feedback signal, the second voltage feedback signal, the first current feedback signal and the second current feedback signal of the first photovoltaic cell module and the second photovoltaic cell module, as well as the third voltage feedback signal and the fourth voltage feedback signal respectively output by the first differential power unit and the second differential power unit; A digital signal processor, whose input end is connected to the first output end of the sensor assembly, and the digital signal processor is used for signal processing of the first voltage feedback signal, the second voltage feedback signal, the first current feedback signal and the second current feedback signal, and generating a first voltage reference signal, a second voltage reference signal, a first working selection signal and a second working selection signal; A control circuit, whose first input end is connected to the output end of the digital signal processor, and the second input end of the control circuit is connected to the second output end of the sensor assembly. The control circuit is used for generating the first switching logic signal according to the signal after subtracting the third voltage feedback signal from the first voltage reference signal, and generating the second switching logic signal according to the signal after subtracting the fourth voltage feedback signal from the second voltage reference signal.

3. The differential power unit control device in the dual-input inverter according to claim 2, characterized in that the sensor assembly includes: A first voltage sensor, whose input end is connected to the first photovoltaic cell module, and the output end of the first voltage sensor is connected to the input end of the digital signal processor. The first voltage sensor is used for collecting the first voltage feedback signal and transmitting it to the digital signal processor; A second voltage sensor, whose input end is connected to the second photovoltaic cell module, and the output end of the second voltage sensor is connected to the input end of the digital signal processor. The second voltage sensor is used for collecting the second voltage feedback signal and transmitting it to the digital signal processor; A first current sensor, whose input end is connected to the first photovoltaic cell module, and the output end of the first current sensor is connected to the input end of the digital signal processor. The first current sensor is used for collecting the first current feedback signal and transmitting it to the digital signal processor; A second current sensor, whose input end is connected to the second photovoltaic cell module, and the output end of the second current sensor is connected to the input end of the digital signal processor. The second current sensor is used for collecting the second current feedback signal and transmitting it to the digital signal processor; A third voltage sensor, whose input end is connected to the output end of the first differential power unit, and the output end of the third voltage sensor is connected to the input end of the control circuit. The third voltage sensor is used for collecting the third voltage feedback signal and transmitting it to the control circuit; A fourth voltage sensor, whose input end is connected to the output end of the second differential power unit, and the output end of the fourth voltage sensor is connected to the input end of the control circuit. The fourth voltage sensor is used for collecting the fourth voltage feedback signal and transmitting it to the control circuit.

4. The differential power unit control device in the dual-input inverter according to claim 3, characterized in that the digital signal processor includes: The first analog-to-digital conversion module, whose input end is connected to the output end of the first voltage sensor, and the first analog-to-digital conversion module is used to perform analog-to-digital conversion on the first voltage feedback signal to obtain a first digital signal; The second analog-to-digital conversion module, whose input end is connected to the output end of the second voltage sensor, and the second analog-to-digital conversion module is used to perform analog-to-digital conversion on the second voltage feedback signal to obtain a second digital signal; The third analog-to-digital conversion module, whose input end is connected to the output end of the first current sensor, and the third analog-to-digital conversion module is used to perform analog-to-digital conversion on the first current feedback signal to obtain a third digital signal; The fourth analog-to-digital conversion module, whose input end is connected to the output end of the second current sensor, and the fourth analog-to-digital conversion module is used to perform analog-to-digital conversion on the second current feedback signal to obtain a fourth digital signal; The power calculation module, whose input end is respectively connected to the second output end of the first analog-to-digital conversion module, the second output end of the second analog-to-digital conversion module, the output end of the third analog-to-digital conversion module and the output end of the fourth analog-to-digital conversion module, and the power calculation module is used to perform power calculation on the first digital signal, the second digital signal, the third digital signal and the fourth digital signal to obtain a fifth digital signal; The differential power unit control module, whose input end is respectively connected to the first output end of the first analog-to-digital conversion module, the first output end of the second analog-to-digital conversion module and the output end of the power calculation module, and the differential power unit control module is used to perform digital processing on the first digital signal, the second digital signal and the fifth digital signal to obtain a first voltage reference digital signal, a second voltage reference digital signal, a first working selection digital signal and a second working selection digital signal; The first digital-to-analog conversion module, whose input end is connected to the first output end of the differential power unit control module, and the first digital-to-analog conversion module is used to perform digital-to-analog conversion on the first voltage reference digital signal to obtain the first voltage reference signal; The second digital-to-analog conversion module, whose input end is connected to the second output end of the differential power unit control module, and the second digital-to-analog conversion module is used to perform digital-to-analog conversion on the second voltage reference digital signal to obtain the second voltage reference signal; The third digital-to-analog conversion module, whose input end is connected to the third output end of the differential power unit control module, and the third digital-to-analog conversion module is used to perform digital-to-analog conversion on the first working selection digital signal to obtain the first working selection signal; The fourth digital-to-analog conversion module, whose input end is connected to the fourth output end of the differential power unit control module, and the fourth digital-to-analog conversion module is used to perform digital-to-analog conversion on the second working selection digital signal to obtain the second working selection signal.

5. The differential power unit control device in the dual-input inverter according to claim 4, characterized in that, the control circuit includes: A first voltage regulator, whose first input terminal is connected to the output terminal of the first digital-to-analog conversion module, and whose second input terminal is connected to the output terminal of the third voltage sensor. The first voltage regulator is used to regulate the voltage of the signal obtained by subtracting the first voltage reference signal from the third voltage feedback signal to obtain a first high-frequency switching signal; A second voltage regulator, whose first input terminal is connected to the output terminal of the second digital-to-analog conversion module, and whose second input terminal is connected to the output terminal of the fourth voltage sensor. The second voltage regulator is used to regulate the voltage of the signal obtained by subtracting the second voltage reference signal from the fourth voltage feedback signal to obtain a second high-frequency switching signal; A first AND gate, whose first input terminal is connected to the output terminal of the first voltage regulator, and whose second input terminal is connected to the output terminal of the third digital-to-analog conversion module. The first AND gate is used to generate the first switching logic signal according to the first high-frequency switching signal and the first operating selection signal, and transmit it to the control terminal of the first differential power unit; A second AND gate, whose first input terminal is connected to the output terminal of the second voltage regulator, and whose second input terminal is connected to the output terminal of the fourth digital-to-analog conversion module. The second AND gate is used to generate the second switching logic signal according to the second high-frequency switching signal and the second operating selection signal, and transmit it to the control terminal of the second differential power unit.

6. The control device for the differential power unit in the dual-input inverter according to claim 1, characterized in that, the first differential power unit and the second differential power unit are isolated converters.

7. The control device for the differential power unit in the dual-input inverter according to claim 1, characterized in that, the dual-input inverter is a half-bridge inverter.

8. The control device for the differential power unit in the dual-input inverter according to claim 1, characterized in that, the first diode and the second diode are silicon carbide diodes or fast recovery diodes.

9. The control device for the differential power unit in the dual-input inverter according to claim 1, characterized in that, the first filter capacitor and the second filter capacitor are polarized capacitors or non-polarized capacitors.

10. The control method for the control device of the differential power unit in the dual-input inverter according to any one of claims 1-9, characterized in that, it includes: using a sensor assembly to collect the input voltages of the first differential power unit and the second differential power unit in real time, and comparing the input voltages with the peak value of the load / grid voltage at a preset ratio; if the input voltages of the first differential power unit and the second differential power unit are both greater than the peak value of the load / grid voltage, then obtain the output powers of the first photovoltaic cell module and the second photovoltaic cell module, and perform corresponding control on the first differential power unit and the second differential power unit respectively according to the output powers; If the input voltages of both the first differential power unit and the second differential power unit are less than the peak load / grid voltage, directly start the first differential power unit and the second differential power unit; If the input voltage of any one of the first differential power unit and the second differential power unit is less than the peak load / grid voltage, compare the input voltage of the first differential power unit with the input voltage of the second differential power unit, and perform corresponding control on the first differential power unit and the second differential power unit respectively according to the comparison result.

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