Control Device and Control Method for Reusing Differential Power Unit in Dual-Input Inverter

Abstract

The present invention discloses a control device and a control method for a multiplexed difference power unit in a dual-input inverter. The control device includes a control and drive unit and a dual-input inverter circuit. 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 signal output by the multiplexed difference power unit, and generate a first switching logic signal, a second switching logic signal, and a third switching logic signal according to the voltage feedback signals and current feedback signals, so as to perform drive control on the first switch, the second switch, and the multiplexed difference power unit respectively according to the first switching logic signal, the second switching logic signal, and the third 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 multiplexed difference 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 way of cascading a boost converter and an inverter, but this way 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. For this purpose, the first object of the present invention is to provide a control device for a multiplexed difference power unit in a dual-input inverter, which can solve the problem of insufficient bus voltage of the inverter 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 multiplexed difference 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 multiplexed difference 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 switch, a second switch, a multiplexed 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 second terminal of the first switch, one end of the first filter capacitor, the anode of the first diode, and the first terminal of the second switch. The negative electrode of the first photovoltaic cell module is respectively connected to the first terminal of the first switch, the sixth terminal of the first switch, 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 fifth terminal of the first switch, the sixth terminal of the second switch, 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 second terminal of the second switch and the positive input terminal of the dual-input inverter. The anode of the second diode is respectively connected to the fifth terminal of the second switch and the negative input terminal of the dual-input inverter. The positive output terminal of the dual-input inverter is connected to the positive terminal of the load / grid. The positive input terminal of the multiplexed difference power unit is connected to the fourth terminal of the first switch. The negative input terminal of the multiplexed difference power unit is connected to the third terminal of the first switch. The positive output terminal of the multiplexed difference power unit is connected to the fourth terminal of the second switch. The negative output terminal of the multiplexed difference power unit is connected to the third terminal of the second switch;

[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, and the multiplexed difference power unit. The output terminals of the control and drive unit are respectively connected to the multiplexed difference power unit, the first switch, and the second switch. 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 signal output by the multiplexed difference power unit, and generate a first switch logic signal, a second switch logic signal, and a third switch logic signal according to the voltage feedback signals and the current feedback signals, so as to respectively drive and control the first switch, the second switch, and the multiplexed difference power unit according to the first switch logic signal, the second switch logic signal, and the third switch logic signal.

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

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

[0011] A digital signal processor, whose input end is connected to the first output end of the sensor assembly. The digital signal processor is used 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 switching logic signal and a second switching logic signal;

[0012] A control circuit, whose first input end is connected to the output end of the digital signal processor, and whose second input end is connected to the second output end of the sensor assembly. The control circuit is used to sum the first voltage reference signal and the second voltage reference signal, and generate a third switching logic signal according to the signal after subtracting the third voltage feedback signal from the sum of the signals;

[0013] A drive circuit, whose input end is connected to the digital signal processor, and whose output ends are respectively connected to the first switch and the second switch. The drive circuit is used to generate a first drive signal and a second drive signal respectively according to the first switching logic signal and the second switching logic signal, so as to drive the first switch and the second switch to work in corresponding switching states through the first drive signal and the second drive signal.

[0014] Optionally, the sensor assembly includes:

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

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

[0017] 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 digital signal processor. The first current sensor is used to collect the first current feedback signal and transmit it to the digital signal processor;

[0018] 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 digital signal processor. The second current sensor is used to collect the second current feedback signal and transmit it to the digital signal processor;

[0019] A third voltage sensor, whose input end is connected to the output end of the multiplexing difference power unit, and the output end of the third voltage sensor is connected to the control circuit. The third voltage sensor is used to collect the third 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 used 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 used 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 used 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 used 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 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;

[0026] The differential power unit control module, whose input terminals are respectively connected to the first output terminal of the first analog-to-digital conversion module, the first output terminal of the second analog-to-digital conversion module, and the output terminal of the power calculation module. 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 switch logic digital signal, and a second switch logic digital signal;

[0027] The first digital-to-analog conversion module, whose input terminal is connected to the first output terminal of the differential power unit control module. 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 terminal is connected to the second output terminal of the differential power unit control module. 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 terminal is connected to the third output terminal of the differential power unit control module. The third digital-to-analog conversion module is used to perform digital-to-analog conversion on the first switch logic digital signal to obtain the first switch logic signal;

[0030] The fourth digital-to-analog conversion module, whose input terminal is connected to the fourth output terminal of the differential power unit control module. The fourth digital-to-analog conversion module is used to perform digital-to-analog conversion on the second switch logic digital signal to obtain the second switch logic signal.

[0031] Optionally, the control circuit includes:

[0032] The voltage regulator, whose first input terminals are respectively connected to the output terminal of the first digital-to-analog conversion module and the output terminal of the second digital-to-analog conversion module. The second input terminal of the voltage regulator is connected to the output terminal of the third voltage sensor. The voltage regulator is used to perform voltage regulation on the signal obtained by summing the first voltage reference signal and the second voltage reference signal and subtracting the third voltage feedback signal to obtain a third switch logic signal, and to perform switch control on the multiplexed differential power unit through the third switch logic signal.

[0033] Optionally, the drive circuit includes:

[0034] The first driving unit, whose input end is connected to the output end of the third digital-to-analog conversion module, and the output end of the first driving unit is connected to the first switch. The first driving unit is configured to generate the first driving signal according to the first switch logic signal, and drive the first switch to work in the corresponding switch state through the first driving signal;

[0035] The second driving unit, whose input end is connected to the output end of the fourth digital-to-analog conversion module, and the output end of the second driving unit is connected to the second switch. The second driving unit is configured to generate the second driving signal according to the second switch logic signal, and drive the second switch to work in the corresponding switch state through the second driving signal.

[0036] Optionally, when the fifth end of the first switch is connected to the third end of the first switch, the sixth end of the first switch is connected to the fourth end of the first switch, the third end of the second switch is connected to the first end of the second switch, and the fourth end of the second switch is connected to the second end of the second switch, the dual-input inverter circuit works in the first gating path; when the first end of the first switch is connected to the third end of the first switch, the second end of the first switch is connected to the fourth end of the first switch, the third end of the second switch is connected to the fifth end of the second switch, and the fourth end of the second switch is connected to the sixth end of the second switch, the dual-input inverter circuit works in the second gating path.

[0037] Optionally, the multiplexed difference power unit is an isolated converter, and 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, the first filter capacitor and the second filter capacitor are polarized capacitors or non-polarized capacitors, and the first switch and the second switch are double-pole double-throw relays.

[0039] To achieve the above object, a second aspect of the present invention provides a control method for a multiplexed difference power unit in a dual-input inverter, including:

[0040] Using a sensor assembly to collect the output voltages of the first photovoltaic cell module and the second photovoltaic cell module in real time, and comparing the output voltages with the peak value of the load / grid voltage at a preset ratio;

[0041] If the output voltages are both greater than the peak value of the load / grid voltage at a preset ratio, then obtain the output powers of the first photovoltaic cell module and the second photovoltaic cell module, and compare the absolute value of the difference between the two output powers with the rated power of the load / grid at a set ratio;

[0042] If the absolute value of the load / grid rated power is less than the set ratio, then control the multiplexed differential power unit not to work; if the absolute value of the load / grid rated power is greater than the set ratio, then compare the output powers of the first photovoltaic cell module and the second photovoltaic cell module;

[0043] If the output power of the first photovoltaic cell module is less than or greater than the output power of the second photovoltaic cell module, then start the multiplexed differential power unit, and control the first switch and the second switch to control the dual-input inverter circuit to work on the first selected path or the second selected path accordingly;

[0044] If only one of the output voltages is less than the preset ratio of the load / grid voltage peak value in the output voltage, then compare the output voltages of the first photovoltaic cell module and the second photovoltaic cell module;

[0045] If the output voltage of the first photovoltaic cell module is less than or greater than the output voltage of the second photovoltaic cell module, then start the multiplexed differential power unit, and control the first switch and the second switch to control the dual-input inverter circuit to work on the first selected path or the second selected path accordingly.

[0046] The present invention has at least the following technical effects:

[0047] The present invention is applicable to the occasion of a dual-input inverter, which can effectively solve the problem of insufficient inverter bus voltage under shadow conditions, can achieve the maximum power output of two photovoltaic cell modules, the power balance of the positive and negative half-cycles of the dual-input inverter, and high output voltage or current waveform quality. In addition, since the multiplexed differential power unit only undertakes half of the differential power of the two photovoltaic cell modules, the power is small and the cost is low, which improves the system conversion efficiency. And compared with the control of two sets of differential power units, replacing one set of differential power units with a double-pole double-throw relay effectively saves the device cost.

[0048] 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

[0049] Figure 1 It is a structural block diagram of a control device for a multiplexed differential power unit in a dual-input inverter provided by an embodiment of the present invention;

[0050] Figure 2 It is a circuit topology schematic diagram of a dual-input inverter provided by an embodiment of the present invention;

[0051] Figure 3Schematic diagram of the circuit structure of the control drive unit provided by an embodiment of the present invention;

[0052] Figure 4 Flowchart of the control method for the multiplexed difference power unit in a dual-input inverter provided by an embodiment of the present invention;

[0053] Figure 5 Flowchart of the control method for the multiplexed difference power unit in a dual-input inverter provided by a specific example of the present invention. Detailed implementation manners

[0054] The following details this embodiment. The examples of the embodiment are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0055] The following describes the control device and control method for the multiplexed difference power unit in the dual-input inverter of this embodiment with reference to the accompanying drawings.

[0056] Figure 1 Block diagram of the control device for the multiplexed difference power unit in a dual-input inverter provided by an embodiment of the present invention. As Figure 1 shown, the control device 100 for the multiplexed difference power unit in the dual-input inverter includes a control drive unit 10 and a dual-input inverter circuit 20.

[0057] As Figure 2 shown, the dual-input inverter circuit 20 includes a first photovoltaic cell module PV1, a second photovoltaic cell module PV2, a first filter capacitor C in1 , a second filter capacitor C in2 , a first diode D 1 , a second diode D 2 , a first switch S 1 , a second switch S 2 , a multiplexed difference power unit F, a dual-input inverter G, and a load / grid Z.

[0058] Among them, the multiplexed difference power unit F is an isolated converter such as a flyback converter, a forward converter, and a push-pull converter, etc., and 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., and specifically can be a double-grounded, dual-input, and highly reliable photovoltaic inverter. In this embodiment, the first diode D 1 and the second diode D 2 are silicon carbide diodes or fast recovery diodes, and the first filter capacitor C in1 and the second filter capacitor C in2is a polarized capacitor or a non-polarized capacitor, and the first switch S 1 and the second switch S 2 are double-pole double-throw relays. It should be noted that the above devices are not specifically limited in this embodiment.

[0059] In an embodiment of the present invention, the specific circuit topology of the dual-input inverter circuit 20 is as follows: The positive electrode of the first photovoltaic cell module PV1 is respectively connected to the second end of the first switch S 1 , one end of the first filter capacitor C in1 , the anode of the first diode D 1 and the first end of the second switch S 2 . The negative electrode of the first photovoltaic cell module PV1 is respectively connected to the first end of the first switch S 1 , the sixth end of the first switch S 1 , the other end of the first filter capacitor C in1 , the positive electrode of the second photovoltaic cell module PV2, one end of the second filter capacitor C in2 and the negative end of the load / grid Z. The negative electrode of the second photovoltaic cell module PV2 is respectively connected to the fifth end of the first switch S 1 , the sixth end of the second switch S 2 , the other end of the second filter capacitor C in2 and the cathode of the second diode D 2 . The cathode of the first diode D 1 is respectively connected to the second end of the second switch S 2 and the positive input end of the dual-input inverter G. The anode of the second diode D 2 is respectively connected to the fifth end of the second switch S 2 and the negative input end of the dual-input inverter G. The positive output end of the dual-input inverter G is connected to the positive end of the load / grid Z. The positive input end of the multiplexed difference power unit F is connected to the fourth end of the first switch S 1 . The negative input end of the multiplexed difference power unit F is connected to the third end of the first switch S 1 . The positive output end of the multiplexed difference power unit F is connected to the fourth end of the second switch S 2 . The negative output end of the multiplexed difference power unit F is connected to the third end of the second switch S 2 .

[0060] In this embodiment, the fifth end of the first switch S 1 is connected to its third end, the sixth end of the first switch S 1 is connected to its fourth end, the third end of the second switch S 2 is connected to its first end, and the third end of the second switch S 2When the fourth terminal is connected to its second terminal, the dual-input inverter circuit operates in the first gating path; the first switch S 1 's first terminal is connected to its third terminal, the first switch S 1 's second terminal is connected to its fourth terminal, the second switch S 2 's third terminal is connected to its fifth terminal and the second switch S 2 's fourth terminal is connected to its sixth terminal, the dual-input inverter circuit operates in the second gating path.

[0061] 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 multiplexed difference power unit F does not work, both diodes are conducting; when the multiplexed difference power unit F works, the corresponding diodes connected to its output side are reverse-biased and turned off, and the dual-input inverter circuit 20 operates in the first gating path or the second gating path, so that the device can achieve power balance in the positive and negative half-cycles of the dual-input inverter, and the multiplexed difference power unit F only bears half of the difference power between the two photovoltaic cell modules, thus facilitating the improvement of the system conversion efficiency.

[0062] 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, and the multiplexed difference power unit F. The output terminals of the control and drive unit 10 are respectively connected to the multiplexed difference power unit F, the first switch S 1 and the second switch S2. The control and drive unit 10 is used 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 signal output by the multiplexed difference power unit F, and generate a first switch logic signal, a second switch logic signal, and a third switch logic signal according to the voltage feedback signals and current feedback signals, so as to respectively drive and control the first switch, the second switch, and the multiplexed difference power unit F according to the first switch logic signal, the second switch logic signal, and the third switch logic signal.

[0063] As Figure 3 shown, the control and drive unit 10 includes a sensor component 1, a digital signal processor 2, a control circuit 3, and a drive circuit 4.

[0064] Among them, the input terminals of the sensor component 1 are respectively connected to the output terminals of the first photovoltaic cell module PV1, the second photovoltaic cell module PV2, and the multiplexed difference power unit F. The sensor component 1 is used 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 ipv2 and is used to collect a third voltage feedback signal u at the output end of the multiplexed difference power unit F C .

[0065] The input end of the digital signal processor 2 is connected to the first output end of the sensor assembly 1, and is used to process the first voltage feedback signal U of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2 pv1 , the second voltage feedback signal U pv2 , the first current feedback signal i pv1 and the second current feedback signal i pv2 , and generate a first voltage reference signal u ref1 , a second voltage reference signal u ref2 , a first switch logic signal O 1 and a second switch logic signal O 2 ;

[0066] 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 used to sum the first voltage reference signal u ref1 and the second voltage reference signal u ref2 , and perform voltage comparison control on the signal after subtracting the third voltage feedback signal u C from the summed signal, so as to generate a third switch logic signal O 3 ;

[0067] The input end of the drive circuit 4 is connected to the output end of the digital signal processor 2, and its output end is respectively connected to the first switch S 1 and the second switch S 2 . The drive circuit 4 respectively generates a first drive signal and a second drive signal according to the first switch logic signal O 1 and the second switch logic signal O 2 , so as to respectively drive the first switch S 1 and the second switch S 2 to work in the corresponding states.

[0068] Please continue to refer to Figure 3 , 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 and a third voltage sensor 105.

[0069] Among them, the input end of the first voltage sensor 101 is connected to the first photovoltaic cell module PV1, and its output end is connected to the input end of the digital signal processor 2. The first voltage sensor 101 is used to collect the first voltage feedback signal U pv1and 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 its output end is connected to the input end of the digital signal processor 2. The second voltage sensor 102 is used 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 its output end is connected to the input end of the digital signal processor 2. The first current sensor 103 is used 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 its output end is connected to the input end of the digital signal processor 2. The second current sensor 104 is used to collect the second current feedback signal i pv2 and 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 multiplexed difference power unit F, and the output end of the third voltage sensor 105 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 C and transmit it to the control circuit 3.

[0070] As Figure 3 shown, 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.

[0071] 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. The first analog-to-digital conversion module AD1 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. The second analog-to-digital conversion module AD2 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. The third analog-to-digital conversion module AD3 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. The fourth analog-to-digital conversion module AD4 is used to perform analog-to-digital conversion on the second current feedback signal i pv2 to obtain a fourth digital signal.

[0072] 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. The power calculation module 201 is configured 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 switch logic digital signal, and a second switch logic digital signal.

[0073] 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. The first digital-to-analog conversion module DA1 is configured 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):

[0074]

[0075] u ref1 =U pv2 -U pv1 (2)

[0076] u ref1 =mU om -U pv1 (3)

[0077] Among them, 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 pv1 is the output voltage of the first photovoltaic cell module PV1, U pv2 is the output voltage of the second photovoltaic cell module PV2, m is a preset ratio, and U om is the peak value of the load / grid voltage.

[0078] In this embodiment, 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. The second digital-to-analog conversion module DA2 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 ref2 satisfies the following formula (4) or formula (5) or formula (6):

[0079]

[0080] u ref2 = U pv1 - U pv2 (5)

[0081] u ref2 = mU om - U pv2 (6)

[0082] In this embodiment, the input end of the third digital-to-analog conversion module DA3 is connected to the third output end of the differential power unit control module 202. The third digital-to-analog conversion module DA3 is used to perform digital-to-analog conversion on the first switch logic digital signal to obtain a first switch logic signal O 1 ; the input end of the fourth digital-to-analog conversion module DA4 is connected to the fourth output end of the differential power unit control module 202. The fourth digital-to-analog conversion module DA4 is used to perform digital-to-analog conversion on the second switch logic digital signal to obtain a second switch logic signal O 2 .

[0083] Please continue to refer to Figure 3 , the control circuit 3 includes a voltage regulator 301. Its first input end is connected to the output end of the first digital-to-analog conversion module DA1 and the output end of the second digital-to-analog conversion module DA2. Its second input end is connected to the output end of the third voltage sensor 105. The voltage regulator 301 is used to sum the first voltage reference signal u ref1 and the second voltage reference signal u ref2 and perform voltage regulation on the signal after subtracting the third voltage feedback signal u C to obtain a third switch logic signal O 3 , and transmit it to the multiplexed differential power unit F to perform switch control on the switching tubes in the multiplexed differential power unit F.

[0084] It should be noted that the voltage regulator 301 in this embodiment adopts PI (Proportional Integral) control.

[0085] In an embodiment of the present invention, the driving circuit 4 includes: a first driving unit 401 and a second driving unit 402. Among them, the input end of the first driving unit 401 is connected to the output end of the third digital-to-analog conversion module DA3, the output end of the first driving unit 401 is connected to the first switch S1, and the first driving unit 401 is configured to generate a first driving signal according to the first switch logic signal, and drive the first switch S1 to work in a corresponding switch state through the first driving signal.

[0086] In this embodiment, the input end of the second driving unit 402 is connected to the output end of the fourth digital-to-analog conversion module DA4, the output end of the second driving unit 402 is connected to the second switch S2, and the second driving unit 402 is configured to generate a second driving signal according to the second switch logic signal, and drive the second switch S2 to work in a corresponding switch state through the second driving signal.

[0087] Figure 4 It is a flowchart of a control method for a multiplexed difference power unit in a dual-input inverter provided in an embodiment of the present invention. As Figure 4 shown, the control method includes:

[0088] Step S1: Use a sensor component to collect the output voltages of the first photovoltaic cell module and the second photovoltaic cell module in real time, and compare the output voltages with the peak value of the load / grid voltage at a preset ratio.

[0089] Step S2: If the output voltages are both greater than the peak value of the load / grid voltage at a preset ratio, obtain the output powers of the first photovoltaic cell module and the second photovoltaic cell module, and compare the absolute value of the difference between the two output powers with the rated power of the load / grid at a set ratio.

[0090] Step S3: If the absolute value is less than the rated power of the load / grid at a set ratio, control the multiplexed difference power unit not to work; if the absolute value is greater than the rated power of the load / grid at a set ratio, compare the output powers of the first photovoltaic cell module and the second photovoltaic cell module.

[0091] Step S4: If the output power of the first photovoltaic cell module is less than or greater than the output power of the second photovoltaic cell module, start the multiplexed difference power unit, and control the first switch and the second switch to control the dual-input inverter circuit to work in the first selected path or the second selected path accordingly.

[0092] Step S5: When only one of the output voltages is less than the peak value of the load / grid voltage at a preset ratio, compare the output voltages of the first photovoltaic cell module and the second photovoltaic cell module.

[0093] Step S6: If the output voltage of the first photovoltaic cell module is less than or greater than the output voltage of the second photovoltaic cell module, start the multiplexing difference power unit and control the first switch and the second switch to control the dual-input inverter circuit to operate on the first gating path or the second gating path accordingly.

[0094] As a specific example, such as Figure 5 shown, the control method may specifically include:

[0095] Step 1: The sensor assembly 1 continuously acquires the output voltages U pv1 and U pv2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2, and makes a first determination on the output voltages U pv1 and U pv2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2 and the peak value mU om of the load / grid voltage at a preset ratio, determining whether both U pv1 and U pv2 are greater than or only one voltage is less than mU om .

[0096] Step 2: The sensor assembly 1 also continuously acquires the output currents i pv1 and i pv2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2, and calculates the output powers p 1 and p 2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2 respectively in the digital signal processor 2.

[0097] Step 3: When the output voltages U pv1 and U pv2 of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2 are both greater than the peak value mU om of the load / grid voltage at a preset ratio, take the absolute value |p 1 -p 2 | of the difference between the output powers of the two modules, and make a second determination with the rated power nP o of the load / grid at a set ratio. If it is less, the multiplexing difference power unit F is not started.

[0098] Step 4: Take the absolute value |p 1 -p 2 | of the difference between the output powers of the two modules, and make a second determination with the rated power nP o of the load / grid at a set ratio. If it is greater, make a third determination on the magnitudes of the output powers of the two modules. If the output power p 1Greater than the output power p of the second photovoltaic cell module PV2 2 , then calculate its second voltage reference signal u ref2 and activate the multiplexed difference power unit F, and control the first switch S 1 and the second switch S 2 to selectively close, so that the dual-input inverter circuit 20 operates on the second gating path.

[0099] Wherein, when the second voltage reference signal u is calculated ref2 , if the superimposed value of the second voltage reference signal u ref2 and U pv2 is less than another preset ratio of the peak load / grid voltage kU om , then the multiplexed difference power unit F can be directly activated.

[0100] Step 5: Take the absolute value of the difference between the output powers of the two modules |p 1 - p 2 |, and perform a second determination with the rated power nP of the load / grid at a set ratio. If it is greater, perform a third determination on the magnitudes of the output powers of the two modules. If the output power p of the first photovoltaic cell module PV1 o is less than the output power p of the second photovoltaic cell module PV2 1 , then activate the multiplexed difference power unit and calculate its first voltage reference signal u 2 , and control the first switch S ref1 and the second switch S 1 to selectively close, so that the dual-input inverter circuit 20 operates on the first gating path. 2

[0101] Step 6: When only one of the output voltages Uof the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2 pv1 and U pv2 is less than a preset ratio of the peak load / grid voltage mU om , perform a fourth determination on the magnitudes of the output voltages of the two modules. If the output voltage U pv1 of the first photovoltaic cell module PV1 is greater than the output voltage U pv2 of the second photovoltaic cell module PV2 ref2 , then activate the multiplexed difference power unit and calculate its second voltage reference signal u 1 , and control the first switch S 2 to selectively close, so that the dual-input inverter circuit 20 operates on the second gating path.

[0102] Step 7: When the output voltages U of the first photovoltaic cell module PV1 and the second photovoltaic cell module PV2pv1 and U pv2 When there is only one load / grid voltage peak mV less than a certain ratio, a fourth determination is made on the output voltage magnitudes of the two modules. If the output voltage U of the first photovoltaic cell module PV1 om is less than the output voltage U of the second photovoltaic cell module PV2 pv1 ,the multiplexed difference power unit is started and its first voltage reference signal u is calculated pv2 ,and the first switch S ref1 and the second switch S 1 are selectively closed to make the dual-input inverter circuit 20 operate on the first gating path. 2 In the above steps, the voltage coefficient, i.e., the preset ratio m, generally takes a value of 1.05 - 1.1, the power coefficient, i.e., the set ratio n, generally takes a value of 0.05 - 0.1, and the voltage coefficient k, i.e., the other preset ratio above, generally takes a value of 1.2.

[0103] It should be noted that in this embodiment, the output voltages of the two photovoltaic cell modules are required to have one not less than mU

[0104] ,and since there is only one set of difference power units, except for the reference voltage signal started and calculated by the multiplexed difference power unit in the steps, the other reference voltage signal is synchronously set to zero. om Specifically, the present invention needs to collect the output voltage and power of the photovoltaic cell module in real time, set the voltage coefficient m, and set the power coefficient n. When the output voltages of the two detected photovoltaic cell modules are both greater than m times the output rated voltage peak, it can be compared whether the absolute value of the output power difference between the two photovoltaic modules is greater than n times the output rated power. If it is greater, by comparing the output power magnitudes of the two modules, the reference voltage of the difference power unit is calculated and determined, and the multiplexed difference power unit is started, and the switches are closed to select the corresponding input / output closed path to achieve the maximum power output of the two photovoltaic cell modules, the positive and negative half-cycle power balance of the dual-input inverter, and high output voltage or current waveform quality. If the output power difference between the two photovoltaic modules is less than n times the output rated power, the multiplexed difference power unit does not work to avoid the loss caused by the light load operation of the multiplexed difference power unit; when only one of the output voltages of the two detected photovoltaic cell modules is less than m times the output rated voltage peak, by comparing the output voltage magnitudes of the two modules, the reference voltage of the difference power unit is calculated and determined, and the multiplexed difference power unit is started, and the switches are closed to select the corresponding input / output closed path to compensate for the missing power and voltage. Since the multiplexed difference power unit in the present invention only undertakes half of the difference power of the two photovoltaic cell modules, the power is small, the cost is low, and the system conversion efficiency can be effectively improved.

[0105] Specifically, the present invention needs to collect the output voltage and power of the photovoltaic cell module in real time, set the voltage coefficient m, and set the power coefficient n. When the output voltages of the two detected photovoltaic cell modules are both greater than m times the output rated voltage peak, it can be compared whether the absolute value of the output power difference between the two photovoltaic modules is greater than n times the output rated power. If it is greater, by comparing the output power magnitudes of the two modules, the reference voltage of the difference power unit is calculated and determined, and the multiplexed difference power unit is started, and the switches are closed to select the corresponding input / output closed path to achieve the maximum power output of the two photovoltaic cell modules, the positive and negative half-cycle power balance of the dual-input inverter, and high output voltage or current waveform quality. If the output power difference between the two photovoltaic modules is less than n times the output rated power, the multiplexed difference power unit does not work to avoid the loss caused by the light load operation of the multiplexed difference power unit; when only one of the output voltages of the two detected photovoltaic cell modules is less than m times the output rated voltage peak, by comparing the output voltage magnitudes of the two modules, the reference voltage of the difference power unit is calculated and determined, and the multiplexed difference power unit is started, and the switches are closed to select the corresponding input / output closed path to compensate for the missing power and voltage. Since the multiplexed difference power unit in the present invention only undertakes half of the difference power of the two photovoltaic cell modules, the power is small, the cost is low, and the system conversion efficiency can be effectively improved.

[0106] In summary, the present invention is applicable to the occasion of a dual-input inverter, which can effectively solve the problem of insufficient bus voltage of the inverter under shadow conditions, and can achieve the maximum power output of two photovoltaic cell modules, the power balance of the positive and negative half-cycles of the dual-input inverter, and high output voltage or current waveform quality. In addition, since the redundant difference power unit only undertakes half of the difference power of the two photovoltaic cell modules, the power is small and the cost is low, which improves the system conversion efficiency. Moreover, compared with the control of two sets of difference power units, a double-pole double-throw relay is used to replace one set of difference power units, effectively saving the device cost.

[0107] It should be noted that in this article, 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 elements inherent to such process, method, article or device. Without further limitation, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0108] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered 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 multiplexed difference 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 switch, a second switch, a multiplexed difference 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 second end of the first switch, one end of the first filter capacitor, the anode of the first diode and the first end of the second switch. The negative pole of the first photovoltaic cell module is respectively connected to the first end of the first switch, the sixth end of the first switch, 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 fifth end of the first switch, the sixth end of the second switch, 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 second end of the second switch and the positive input end of the dual-input inverter. The anode of the second diode is respectively connected to the fifth end of the second switch and the negative input end of the dual-input inverter. The positive output end of the dual-input inverter is connected to the positive end of the load / grid. The positive input end of the multiplexed difference power unit is connected to the fourth end of the first switch. The negative input end of the multiplexed difference power unit is connected to the third end of the first switch. The positive output end of the multiplexed difference power unit is connected to the fourth end of the second switch. The negative output end of the multiplexed difference power unit is connected to the third end of the second switch; A control and drive unit, whose input ends are respectively connected to the first photovoltaic cell module, the second photovoltaic cell module and the output end of the multiplexed difference power unit. The output ends of the control and drive unit are respectively connected to the multiplexed difference power unit, the first switch and the second switch. 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 signal output by the multiplexed difference power unit, and generate a first switch logic signal, a second switch logic signal and a third switch logic signal according to the voltage feedback signal and the current feedback signal, so as to respectively drive and control the first switch, the second switch and the multiplexed difference power unit according to the first switch logic signal, the second switch logic signal and the third switch logic signal.

2. The control device for a multiplexed difference 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 ends are respectively connected to the first photovoltaic cell module, the second photovoltaic cell module and the output end of the multiplexed 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 output by the multiplexed difference 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 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 switching logic signal, and a second switching logic signal; A control circuit, whose first input end is connected to the output end of the digital signal processor, and whose second input end is connected to the second output end of the sensor assembly, and the control circuit is configured to sum the first voltage reference signal and the second voltage reference signal, and generate a third switching logic signal according to the signal after subtracting the third voltage feedback signal from the summed signal; A driving circuit, whose input end is connected to the digital signal processor, and whose output end is respectively connected to the first switch and the second switch, and the driving circuit is configured to respectively generate a first driving signal and a second driving signal according to the first switching logic signal and the second switching logic signal, so as to drive the first switch and the second switch to work in corresponding switching states through the first driving signal and the second driving signal.

3. The control device for a multiplexed difference power unit 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 whose output end is connected to the digital signal processor, and the first voltage sensor is configured to collect the first voltage feedback signal and transmit it to the digital signal processor; A second voltage sensor, whose input end is connected to the second photovoltaic cell module, and whose output end is connected to the digital signal processor, and the second voltage sensor is configured to collect the second voltage feedback signal and transmit it to the digital signal processor; A first current sensor, whose input end is connected to the first photovoltaic cell module, and whose output end is connected to the digital signal processor, and the first current sensor is configured to collect the first current feedback signal and transmit it to the digital signal processor; A second current sensor, whose input end is connected to the second photovoltaic cell module, and whose output end is connected to the digital signal processor, and the second current sensor is configured to collect the second current feedback signal and transmit it to the digital signal processor; A third voltage sensor, whose input end is connected to the output end of the multiplexed difference power unit, and whose output end is connected to the control circuit, and the third voltage sensor is configured to collect the third voltage feedback signal and transmit it to the control circuit.

4. The control device for a multiplexed difference power unit 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 terminal is connected to the output terminal 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 terminal is connected to the output terminal 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 terminal is connected to the output terminal 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 terminal is connected to the output terminal 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 terminals are respectively connected to the second output terminal of the first analog-to-digital conversion module, the second output terminal of the second analog-to-digital conversion module, the output terminal of the third analog-to-digital conversion module, and the output terminal 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 terminals are respectively connected to the first output terminal of the first analog-to-digital conversion module, the first output terminal of the second analog-to-digital conversion module, and the output terminal 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 switch logic digital signal, and a second switch logic digital signal; The first digital-to-analog conversion module, whose input terminal is connected to the first output terminal 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 terminal is connected to the second output terminal 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 terminal is connected to the third output terminal 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 switch logic digital signal to obtain the first switch logic signal; The fourth digital-to-analog conversion module, whose input terminal is connected to the fourth output terminal 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 switch logic digital signal to obtain the second switch logic signal.

5. The multiplexed differential power unit control device in the dual-input inverter as claimed in claim 4, characterized in that, the control circuit includes: A voltage regulator, whose first input terminal is respectively connected to the output terminals of the first digital-to-analog conversion module and the second digital-to-analog conversion module, and the second input terminal of the voltage regulator is connected to the output terminal of the third voltage sensor. The voltage regulator is used to perform voltage regulation on the signal obtained by summing the first voltage reference signal and the second voltage reference signal and subtracting the third voltage feedback signal, so as to obtain a third switching logic signal, and perform switching control on the multiplexed difference power unit through the third switching logic signal.

6. The control device for the multiplexed difference power unit in the dual-input inverter according to claim 5, characterized in that, the drive circuit includes: A first drive unit, whose input terminal is connected to the output terminal of the third digital-to-analog conversion module, and the output terminal of the first drive unit is connected to the first switch. The first drive unit is used to generate the first drive signal according to the first switching logic signal, and drive the first switch to work in the corresponding switching state through the first drive signal; A second drive unit, whose input terminal is connected to the output terminal of the fourth digital-to-analog conversion module, and the output terminal of the second drive unit is connected to the second switch. The second drive unit is used to generate the second drive signal according to the second switching logic signal, and drive the second switch to work in the corresponding switching state through the second drive signal.

7. The control device for the multiplexed difference power unit in the dual-input inverter according to claim 1, characterized in that, When the fifth terminal of the first switch is connected to the third terminal of the first switch, the sixth terminal of the first switch is connected to the fourth terminal of the first switch, the third terminal of the second switch is connected to the first terminal of the second switch, and the fourth terminal of the second switch is connected to the second terminal of the second switch, the dual-input inverter circuit works in the first selection path; when the first terminal of the first switch is connected to the third terminal of the first switch, the second terminal of the first switch is connected to the fourth terminal of the first switch, the third terminal of the second switch is connected to the fifth terminal of the second switch, and the fourth terminal of the second switch is connected to the sixth terminal of the second switch, the dual-input inverter circuit works in the second selection path.

8. The control device for the multiplexed difference power unit in the dual-input inverter according to claim 1, characterized in that, the multiplexed difference power unit is an isolated converter, and the dual-input inverter is a half-bridge inverter.

9. The control device for the multiplexed difference 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, the first filter capacitor and the second filter capacitor are polarized capacitors or non-polarized capacitors, and the first switch and the second switch are double-pole double-throw relays.

10. The control method for the control device of the multiplexed difference power unit in the dual-input inverter according to any one of claims 1-9, characterized in that, includes: The sensor component is adopted to collect the output voltages of the first photovoltaic cell module and the second photovoltaic cell module in real time, and compare the output voltages with the peak value of the load / grid voltage at a preset ratio; If both of the output voltages are greater than the peak value of the load / grid voltage at a preset ratio, the output powers of the first photovoltaic cell module and the second photovoltaic cell module are obtained, and the absolute value of the difference between the two output powers is compared with the rated power of the load / grid at a set ratio; If the absolute value is less than the rated power of the load / grid at a set ratio, the multiplexed difference power unit is controlled not to work; if the absolute value is greater than the rated power of the load / grid at a set ratio, the output powers of the first photovoltaic cell module and the second photovoltaic cell module are compared; If the output power of the first photovoltaic cell module is less than or greater than the output power of the second photovoltaic cell module, the multiplexed difference power unit is started, and the first switch and the second switch are controlled to control the dual-input inverter circuit to work on the first selection path or the second selection path accordingly; When only one of the output voltages is less than the peak value of the load / grid voltage at a preset ratio, the output voltages of the first photovoltaic cell module and the second photovoltaic cell module are compared; If the output voltage of the first photovoltaic cell module is less than or greater than the output voltage of the second photovoltaic cell module, the multiplexed difference power unit is started, and the first switch and the second switch are controlled to control the dual-input inverter circuit to work on the first selection path or the second selection path accordingly.

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