Photovoltaic and commercial power synchronous power supply direct current system and control method thereof

Abstract

The invention belongs to the technical field of new energy power supply, and discloses a photovoltaic and commercial power synchronous power supply direct current system and a control method thereof.The photovoltaic and commercial power synchronous power supply direct current system comprises a photovoltaic power supply module, a commercial power supply module and a power supply control module, the photovoltaic power supply module comprises a photovoltaic panel, a BUCK / BOOST circuit and a first diode isolation circuit, and solar energy is converted into direct current; voltage is supplied to a load after being adjusted by a circuit; the commercial power supply module comprises an AC-DC rectification circuit, a BUCK circuit and a second diode isolation circuit, and converts commercial power into adaptive direct current. The power supply control module monitors load power, photovoltaic power and commercial power in real time based on a DSP control panel and a voltage and current sampling circuit, and dynamically controls power distribution of two power supplies through PWM signals. Through photovoltaic and commercial power intelligent cooperative power supply, a traditional energy storage battery is omitted, the maintenance difficulty is reduced, a dynamic power distribution algorithm is adopted to preferentially use photovoltaic energy, and the utilization rate of clean energy is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy power supply, and more specifically, relates to a photovoltaic and city power synchronous power supply direct current system and a control method thereof. Background Art

[0002] As the global energy structure transformation accelerates, photovoltaic power generation, as an important component of clean energy, has been widely used in distributed power supply systems. Traditional photovoltaic power supply systems generally adopt the "photovoltaic + energy storage battery + mains" architecture mode, using energy storage batteries to smooth the intermittent fluctuations of photovoltaic power generation and switch to mains power supply when the light is insufficient. However, this mode has exposed significant defects in actual applications: First, lead-acid or lithium battery energy storage units not only increase the system purchase cost (accounting for about 35%-45% of the total system cost), but also bring derivative problems such as regular maintenance, capacity decay monitoring and environmental recycling; second, the battery cycle life is usually 3-5 years, and frequent replacement in long-term operation scenarios will further increase operating costs; third, the existing dual power switching control system mostly uses relay mechanical switching or simple electronic switch control, which is easy to cause load-end voltage flicker or even short-term power outages when the photovoltaic power suddenly changes.

[0003] In recent years, the industry has tried to optimize energy efficiency by improving control strategies. Some have proposed a photovoltaic and mains parallel power supply architecture, but a buffer battery pack is still required to maintain bus voltage stability, and it has not been able to completely get rid of the reliance on energy storage; some have adopted bidirectional DC / AC converters to achieve AC / DC hybrid power supply, but the system topology is complex and there is a risk of mains backflow causing photovoltaic inverter overload. More importantly, existing technologies generally lack a dynamic matching mechanism for photovoltaic power and load demand. When there is sufficient sunlight, photovoltaic power generation capacity is still not fully utilized, resulting in a waste of clean energy.

[0004] To this end, the present invention provides a photovoltaic and mains synchronous power supply DC system and a control method thereof. Summary of the invention

[0005] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a photovoltaic and mains synchronous power supply DC system and a control method thereof, which can save traditional energy storage batteries, reduce costs and maintenance difficulties, and adopt a dynamic power allocation algorithm to give priority to the use of photovoltaic energy and improve the utilization rate of clean energy.

[0006] The purpose of the present invention can be achieved by the following technical solutions: A photovoltaic and city power synchronous power supply DC system, comprising: A photovoltaic power supply module for receiving solar energy and converting it into direct current, the photovoltaic power supply module comprising a photovoltaic panel, a BUCK / BOOST circuit and a first diode isolation circuit, the photovoltaic panel is electrically connected to the BUCK / BOOST circuit, the BUCK / BOOST circuit is electrically connected to the first diode isolation circuit, and the first diode isolation circuit is electrically connected to a DC load; A mains power supply module for converting mains power into direct current power, the mains power supply module comprising an AC-DC rectifier circuit, a BUCK circuit and a second diode isolation circuit, the AC-DC rectifier circuit is connected to the mains power, the AC-DC rectifier circuit is electrically connected to the BUCK circuit, the BUCK circuit is electrically connected to the second diode isolation circuit, and the second diode isolation circuit is electrically connected to the DC load; A power supply control module for power distribution and measuring the power of a DC load, the photovoltaic power of a photovoltaic power supply module, and the mains power of a mains power supply module, wherein the power supply control module comprises a DSP control board and a voltage and current sampling circuit, wherein the DSP control board is electrically connected to the voltage and current sampling circuit, and the DSP control board is also electrically connected to the photovoltaic power supply module and the mains power supply module; The DC system outputs PWM signals through the DSP controller to control the photovoltaic power supply module and the mains power supply module to achieve the following working modes: A. When the DC load power is less than or equal to the photovoltaic power, the photovoltaic power supply module supplies power independently and the mains power supply module is shut down; B. When the DC load power is greater than the photovoltaic power, the photovoltaic power supply module outputs the maximum power, and the mains power supply module supplements the remaining power; C. When the photovoltaic power is ≤0, the mains power supply module supplies power independently.

[0007] As a further preferred technical solution of the present invention, the BUCK / BOOST circuit of the photovoltaic power supply module includes an inductor L1, one end of the inductor L1 is electrically connected to the terminal PV+ of the photovoltaic panel, the other end of the inductor L1 is electrically connected to the Schottky barrier diode D1 and the MOS tube Q2, the cut-off end of the Schottky barrier diode D1 is electrically connected to the MOS tube Q1, the terminal S of the MOS tube Q1 is electrically connected to one end of the inductor L2 and the cut-off end of the Schottky barrier diode D5, and the other end of the inductor L2 is electrically connected to the capacitor C1 and one end of the capacitor C2.

[0008] As a further preferred technical solution of the present invention, the terminal G of the MOS tube Q2 is electrically connected to the resistor R3, the switching diode D3 and one end of the resistor R4, the other end of the resistor R3 and the cut-off end of the switching diode D3 are electrically connected to the terminal PWM1, the terminal G of the MOS tube Q1 is electrically connected to the resistor R1, the switching diode D2 and one end of the resistor R2, the other end of the resistor R1 and the cut-off end of the switching diode D2 are electrically connected to the terminal PWM2, and the photovoltaic power supply module is electrically connected to the DSP control board through the terminal PWM1 and the terminal PWM2; The other end of the resistor R4, the terminal S of the MOS tube Q2, the conduction end of the Schottky barrier diode D5, the other end of the capacitor C1 and the other end of the capacitor C2 are all electrically connected to the terminal PV+ of the photovoltaic panel and the terminal DC- of the DC load.

[0009] As a further preferred technical solution of the present invention, the first diode isolation circuit of the photovoltaic power supply module is a diode D4, the conduction end of the diode D4 is electrically connected to the BUCK / BOOST circuit, and the cut-off end of the diode D4 is electrically connected to the terminal DC+ of the DC load.

[0010] As a further preferred technical solution of the present invention, the AC-DC rectifier circuit of the AC power supply module includes a rectifier REC1, a second terminal of the rectifier REC1 is electrically connected to the AC terminal AC-L, a third terminal of the rectifier REC1 is electrically connected to the AC terminal AC-N, a first terminal of the rectifier REC1 is electrically connected to a capacitor C3 and one end of a capacitor C4, and a fourth terminal of the rectifier REC1, the other end of the capacitor C3 and the other end of the capacitor C4 are all electrically connected to the terminal DC- of the DC load.

[0011] As a further preferred technical solution of the present invention, the BUCK circuit of the AC power supply module includes a MOS tube Q3, a terminal D of the MOS tube Q3 is electrically connected to the AC-DC rectifier circuit, an S terminal of the MOS tube Q3 is electrically connected to a Schottky barrier diode D8 and one end of an inductor L3, and the other end of the inductor L3 is electrically connected to a capacitor C5 and one end of a capacitor C6; The terminal G of the MOS tube Q3 is electrically connected to the resistor R5, the switching diode D6 and one end of the resistor R2, the other end of the resistor R5 and the cut-off end of the switching diode D6 are electrically connected to the terminal PWM3, and the mains power supply module is electrically connected to the DSP control board through the terminal PWM3; The other end of the resistor R2 is electrically connected to the cut-off end of the Schottky barrier diode D8, and the conduction end of the Schottky barrier diode D8, the conduction end of the Schottky barrier diode D8, the other end of the capacitor C5 and the other end of the capacitor C6 are all electrically connected to the AC-DC rectifier circuit and the terminal DC- of the DC load; The second diode isolation circuit of the AC power supply module is a diode D7, one end of the diode D7 is electrically connected to the BUCK circuit, and the other end of the diode D7 is electrically connected to the terminal DC+ of the DC load.

[0012] As a further preferred technical solution of the present invention, the DSP control board of the power supply control module is provided with terminals PWM1, terminal PWM2, terminal PWM3, terminal PV-V, terminal AC-V, terminal PV-I and terminal AC-I, the DSP control board is electrically connected to the photovoltaic power supply module through terminals PWM1 and terminal PWM2, the DSP control board is electrically connected to the AC power supply module through terminal PWM3, and the DSP control board is electrically connected to the voltage and current sampling circuit through terminals PV-V, terminal AC-V, terminal PV-I and terminal AC-I.

[0013] As a further preferred technical solution of the present invention, the voltage and current sampling circuit of the power supply control module includes a current transformer CT1, a current transformer CT2, a photovoltaic voltage sampling circuit, a photovoltaic current sampling circuit, a mains voltage sampling circuit and a mains current sampling circuit, the current transformer CT1 is arranged between the BUCK / BOOST circuit and the first diode isolation circuit, the current transformer CT2 is arranged between the BUCK circuit and the second diode isolation circuit, the current transformer CT1 is provided with a terminal CT1+ and a terminal CT1-, the current transformer CT1 is electrically connected to the DSP control board through the terminal CT1+ and the terminal CT1-, the current transformer CT2 is provided with a terminal CT2+ and a terminal CT2-, the current transformer CT1 is electrically connected to the DSP control board through the terminal CT2+ and the terminal CT2-; The photovoltaic voltage sampling circuit is provided with an operational amplifier U1A, and the photovoltaic voltage sampling circuit is electrically connected to the DSP control board through the terminal PV-V. The mains voltage sampling circuit is provided with an operational amplifier U2A, and the mains voltage sampling circuit is electrically connected to the DSP control board through the terminal AC-V. The photovoltaic current sampling circuit is provided with an operational amplifier U3A, and the photovoltaic current sampling circuit is electrically connected to the DSP control board through the terminal PV-I. The mains current sampling circuit is provided with an operational amplifier U4A, and the mains current sampling circuit is electrically connected to the DSP control board through the terminal AC-I.

[0014] A control method for a photovoltaic and mains synchronous power supply DC system, based on the above DC system, comprises the following steps: S1: The DSP control board measures the load power of the DC load, the photovoltaic power of the photovoltaic power supply module, and the mains power of the mains power supply module through real-time sampling; S2: The DSP control board dynamically adjusts the duty cycle of the PWM signals of the terminals PWM1, PWM2 and PWM3 based on the power algorithm and in combination with the PID algorithm to control the power distribution of the photovoltaic power of the photovoltaic power supply module and the mains power of the mains power supply module; S3: Under the regulation of the DSP control board, the DC load uses the photovoltaic power supply module as a priority, and is supplemented by the mains power supply module when the photovoltaic power supply module is insufficient.

[0015] As a further preferred technical solution of the present invention, the power algorithm includes: A. Calculate the difference ΔP between the load power of the DC load and the photovoltaic power of the photovoltaic power supply module; B. If ΔP>0, start the AC power supply module and output the duty cycle of the terminal PWM3 corresponding to the AC power of ΔP; C. If ΔP≤0, turn off the AC power supply module.

[0016] As described above, the photovoltaic and mains synchronous power supply DC system and control method thereof provided by the present invention have the following beneficial effects: The present invention utilizes the above-mentioned photovoltaic and mains synchronous power supply DC system and its control method. Compared with the prior art, the present invention completely eliminates the traditional energy storage battery configuration through the intelligent coordinated power supply of photovoltaic and mains, avoids the battery purchase, maintenance and replacement costs, and solves the problems of short battery life and difficult environmental recycling. It is particularly suitable for long-term DC load scenarios; and, adopts DSP real-time dynamic power allocation algorithm, accurately monitors the load and photovoltaic power through voltage and current sampling circuits, and gives priority to calling photovoltaic energy to power the load. When the photovoltaic power is sufficient (load power ≤ photovoltaic power), the system is completely powered by photovoltaic power independently, and the mains power module is automatically shut down, thereby improving the utilization rate of clean energy.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 A framework diagram of a photovoltaic and mains synchronous power supply DC system and a control method thereof applied for by the present invention; Figure 2 A circuit structure diagram of a photovoltaic and mains synchronous power supply DC system applied for by the present invention; Figure 3 A circuit structure diagram of a BUCK / BOOST circuit of a photovoltaic and mains synchronous power supply DC system applied for by the present invention; Figure 4 A circuit structure diagram of an AC-DC rectifier circuit of a photovoltaic and mains synchronous power supply DC system applied for by the present invention; Figure 5 This is a circuit structure diagram of a BUCK circuit of a photovoltaic and mains synchronous power supply DC system applied for by the present invention.

[0020] Summary of reference numerals and their descriptions: 100. BUCK / BOOST circuit; 200. AC-DC rectifier circuit; 300. BUCK circuit. DETAILED DESCRIPTION

[0021] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0022] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions that the present invention can be implemented, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects that the present invention can produce and the purposes that can be achieved. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of the relative relationship should also be regarded as the scope of the implementation of the present invention without substantial changes in the technical content. The specific structure can be described with reference to the drawings of the patent application.

[0023] The present invention provides a photovoltaic and mains synchronous power supply DC system and a control method thereof, please refer to Figures 1 to 5 As shown, a photovoltaic and mains synchronous power supply DC system comprises: A photovoltaic power supply module for receiving solar energy and converting it into direct current, the photovoltaic power supply module comprising a photovoltaic panel, a BUCK / BOOST circuit 100 and a first diode isolation circuit, the photovoltaic panel being electrically connected to the BUCK / BOOST circuit 100, the BUCK / BOOST circuit 100 being electrically connected to the first diode isolation circuit, and the first diode isolation circuit being electrically connected to a DC load; A mains power supply module for converting mains power into direct current power, the mains power supply module comprising an AC-DC rectifier circuit 200, a BUCK circuit 300 and a second diode isolation circuit, the AC-DC rectifier circuit 200 is connected to the mains power, the AC-DC rectifier circuit 200 is electrically connected to the BUCK circuit 300, the BUCK circuit 300 is electrically connected to the second diode isolation circuit, and the second diode isolation circuit is electrically connected to a DC load; A power supply control module for power distribution and measuring the power of a DC load, the photovoltaic power of a photovoltaic power supply module, and the mains power of a mains power supply module, wherein the power supply control module comprises a DSP control board and a voltage and current sampling circuit, wherein the DSP control board is electrically connected to the voltage and current sampling circuit, and the DSP control board is also electrically connected to the photovoltaic power supply module and the mains power supply module; The DC system outputs PWM signals through the DSP controller to control the photovoltaic power supply module and the mains power supply module to achieve the following working modes: A. When the DC load power is less than or equal to the photovoltaic power, the photovoltaic power supply module supplies power independently and the mains power supply module is shut down; B. When the DC load power is greater than the photovoltaic power, the photovoltaic power supply module outputs the maximum power, and the mains power supply module supplements the remaining power; C. When the photovoltaic power is ≤0, the mains power supply module supplies power independently.

[0024] The BUCK / BOOST circuit 100 of the photovoltaic power supply module includes an inductor L1, one end of the inductor L1 is electrically connected to the terminal PV+ of the photovoltaic panel, the other end of the inductor L1 is electrically connected to the Schottky barrier diode D1 and the MOS transistor Q2, the cut-off end of the Schottky barrier diode D1 is electrically connected to the MOS transistor Q1, the terminal S of the MOS transistor Q1 is electrically connected to one end of the inductor L2 and the cut-off end of the Schottky barrier diode D5, and the other end of the inductor L2 is electrically connected to the capacitor C1 and one end of the capacitor C2; The terminal G of the MOS tube Q2 is electrically connected to the resistor R3, the switching diode D3 and one end of the resistor R4, the other end of the resistor R3 and the cut-off end of the switching diode D3 are electrically connected to the terminal PWM1, the terminal G of the MOS tube Q1 is electrically connected to the resistor R1, the switching diode D2 and one end of the resistor R2, the other end of the resistor R1 and the cut-off end of the switching diode D2 are electrically connected to the terminal PWM2, and the photovoltaic power supply module is electrically connected to the DSP control board through the terminal PWM1 and the terminal PWM2; The other end of the resistor R4, the terminal S of the MOS tube Q2, the conducting end of the Schottky barrier diode D5, the other end of the capacitor C1 and the other end of the capacitor C2 are all electrically connected to the terminal PV+ of the photovoltaic panel and the terminal DC- of the DC load; Specifically, the BUCK / BOOST circuit 100 includes two working states: boost and buck. The DSP control board switches and controls the PWM signals received by the MOS tubes Q1 and Q2 according to the photovoltaic input voltage range. The boost mode is enabled when the photovoltaic panel input voltage is lower than the DC load requirement, and the buck mode is enabled when it is higher than the DC load requirement.

[0025] It should be noted that: when the load power exceeds the photovoltaic output, the system uses the BUCK / BOOST circuit 100 to make the photovoltaic power supply module output the maximum power, and the BUCK circuit 300 of the mains power supply module dynamically supplements the difference power (ΔP). This mode adjusts the PWM duty cycle in real time through the PID algorithm to achieve smooth power superposition of photovoltaic and mains power, avoiding the risk of voltage fluctuation or interruption when the traditional system switches the power supply source; and the photovoltaic power supply module adopts the BUCK / BOOST bidirectional circuit structure, and the DSP control board automatically switches the boost / buck mode according to the input voltage range to ensure that the photovoltaic panel always works at the maximum power point, so that the power conversion efficiency is improved compared with the single-mode circuit.

[0026] The first diode isolation circuit of the photovoltaic power supply module is a diode D4, the conducting end of the diode D4 is electrically connected to the BUCK / BOOST circuit 100, and the cut-off end of the diode D4 is electrically connected to the terminal DC+ of the DC load.

[0027] The AC-DC rectifier circuit 200 of the AC power supply module includes a rectifier REC1, a second terminal of the rectifier REC1 is electrically connected to the AC terminal AC-L, a third terminal of the rectifier REC1 is electrically connected to the AC terminal AC-N, a first terminal of the rectifier REC1 is electrically connected to a capacitor C3 and one end of a capacitor C4, and a fourth terminal of the rectifier REC1, the other end of the capacitor C3 and the other end of the capacitor C4 are all electrically connected to the terminal DC- of the DC load.

[0028] The BUCK circuit 300 of the AC power supply module includes a MOS tube Q3, a terminal D of the MOS tube Q3 is electrically connected to the AC-DC rectifier circuit 200, an S terminal of the MOS tube Q3 is electrically connected to a Schottky barrier diode D8 and one end of an inductor L3, and the other end of the inductor L3 is electrically connected to a capacitor C5 and one end of a capacitor C6; The terminal G of the MOS tube Q3 is electrically connected to the resistor R5, the switching diode D6 and one end of the resistor R2, the other end of the resistor R5 and the cut-off end of the switching diode D6 are electrically connected to the terminal PWM3, and the mains power supply module is electrically connected to the DSP control board through the terminal PWM3; The other end of the resistor R2 is electrically connected to the cut-off end of the Schottky barrier diode D8, and the conduction end of the Schottky barrier diode D8, the conduction end of the Schottky barrier diode D8, the other end of the capacitor C5 and the other end of the capacitor C6 are all electrically connected to the AC-DC rectifier circuit 200 and the terminal DC- of the DC load; the DSP control board controls the MOS tube Q3 through the terminal PWM3 to achieve the buck output of the BUCK circuit 300, which is only enabled when the photovoltaic power is insufficient, and the mains supplementary power is the difference between the load power and the photovoltaic power.

[0029] The second diode isolation circuit of the AC power supply module is a diode D7, one end of the diode D7 is electrically connected to the BUCK circuit 300, and the other end of the diode D7 is electrically connected to the terminal DC+ of the DC load.

[0030] It should be noted that: the electrical isolation between the photovoltaic and mains modules is achieved by using the Schottky diodes D4 and D7 to prevent reverse current interference; and the cascade design of the AC-DC rectifier circuit 200 and the BUCK circuit 300 effectively suppresses mains harmonics.

[0031] The DSP control board of the power supply control module is provided with terminals PWM1, PWM2, PWM3, PV-V, AC-V, PV-I and AC-I. The DSP control board is electrically connected to the photovoltaic power supply module through terminals PWM1 and PWM2. The DSP control board is electrically connected to the mains power supply module through terminal PWM3. The DSP control board is electrically connected to the voltage and current sampling circuit through terminals PV-V, AC-V, PV-I and AC-I. The voltage and current sampling circuit of the power supply control module includes a current transformer CT1, a current transformer CT2, a photovoltaic voltage sampling circuit, a photovoltaic current sampling circuit, a mains voltage sampling circuit and a mains current sampling circuit. The current transformer CT1 is arranged between the BUCK / BOOST circuit 100 and the first diode isolation circuit, and the current transformer CT2 is arranged between the BUCK circuit 300 and the second diode isolation circuit. The current transformer CT1 is provided with a terminal CT1+ and a terminal CT1-, and the current transformer CT1 is electrically connected to the DSP control board through the terminal CT1+ and the terminal CT1-. The current transformer CT2 is provided with a terminal CT2+ and a terminal CT2-, and the current transformer CT1 is electrically connected to the DSP control board through the terminal CT2+ and the terminal CT2-. The photovoltaic voltage sampling circuit is provided with an operational amplifier U1A, and the photovoltaic voltage sampling circuit is electrically connected to the DSP control board through the terminal PV-V. The mains voltage sampling circuit is provided with an operational amplifier U2A, and the mains voltage sampling circuit is electrically connected to the DSP control board through the terminal AC-V. The photovoltaic current sampling circuit is provided with an operational amplifier U3A, and the photovoltaic current sampling circuit is electrically connected to the DSP control board through the terminal PV-I. The mains current sampling circuit is provided with an operational amplifier U4A, and the mains current sampling circuit is electrically connected to the DSP control board through the terminal AC-I. Current transformer CT1, current transformer CT2, photovoltaic voltage sampling circuit, photovoltaic current sampling circuit, mains voltage sampling circuit and mains current sampling circuit constitute a high-precision sampling network, which provides overload protection judgment basis for DSP and ensures safe operation of the system under complex working conditions.

[0032] A control method for a photovoltaic and mains synchronous power supply DC system, based on the above DC system, comprises the following steps: S1: The DSP control board measures the load power of the DC load, the photovoltaic power of the photovoltaic power supply module, and the mains power of the mains power supply module through real-time sampling; S2: The DSP control board dynamically adjusts the duty cycle of the PWM signals of the terminals PWM1, PWM2 and PWM3 based on the power algorithm and in combination with the PID algorithm to control the power distribution of the photovoltaic power of the photovoltaic power supply module and the mains power of the mains power supply module; S3: Under the regulation of the DSP control board, the DC load uses the photovoltaic power supply module as a priority, and is supplemented by the mains power supply module when the photovoltaic power supply module is insufficient.

[0033] The power algorithm includes: A. Calculate the difference ΔP between the load power of the DC load and the photovoltaic power of the photovoltaic power supply module; B. If ΔP>0, start the AC power supply module and output the duty cycle of the terminal PWM3 corresponding to the AC power of ΔP; C. If ΔP≤0, turn off the AC power supply module.

[0034] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A photovoltaic and mains synchronous power supply DC system, characterized in that: include: A photovoltaic power supply module for receiving solar energy and converting it into direct current, the photovoltaic power supply module comprising a photovoltaic panel, a BUCK / BOOST circuit and a first diode isolation circuit, the photovoltaic panel is electrically connected to the BUCK / BOOST circuit, the BUCK / BOOST circuit is electrically connected to the first diode isolation circuit, and the first diode isolation circuit is electrically connected to a DC load; A mains power supply module for converting mains power into direct current power, the mains power supply module comprising an AC-DC rectifier circuit, a BUCK circuit and a second diode isolation circuit, the AC-DC rectifier circuit is connected to the mains power, the AC-DC rectifier circuit is electrically connected to the BUCK circuit, the BUCK circuit is electrically connected to the second diode isolation circuit, and the second diode isolation circuit is electrically connected to the DC load; A power supply control module for power distribution and measuring the power of a DC load, the photovoltaic power of a photovoltaic power supply module, and the mains power of a mains power supply module, wherein the power supply control module comprises a DSP control board and a voltage and current sampling circuit, wherein the DSP control board is electrically connected to the voltage and current sampling circuit, and the DSP control board is also electrically connected to the photovoltaic power supply module and the mains power supply module; The DC system outputs PWM signals through the DSP controller to control the photovoltaic power supply module and the mains power supply module to achieve the following working modes: A. When the DC load power is less than or equal to the photovoltaic power, the photovoltaic power supply module supplies power independently and the mains power supply module is shut down; B. When the DC load power is greater than the photovoltaic power, the photovoltaic power supply module outputs the maximum power, and the mains power supply module supplements the remaining power; C. When the photovoltaic power is ≤0, the mains power supply module supplies power independently.

2. A photovoltaic and mains synchronous power supply DC system according to claim 1, characterized in that: The BUCK / BOOST circuit of the photovoltaic power supply module includes an inductor L1, one end of the inductor L1 is electrically connected to the terminal PV+ of the photovoltaic panel, the other end of the inductor L1 is electrically connected to the Schottky barrier diode D1 and the MOS tube Q2, the cut-off end of the Schottky barrier diode D1 is electrically connected to the MOS tube Q1, the terminal S of the MOS tube Q1 is electrically connected to one end of the inductor L2 and the cut-off end of the Schottky barrier diode D5, and the other end of the inductor L2 is electrically connected to the capacitor C1 and one end of the capacitor C2.

3. A photovoltaic and mains synchronous power supply DC system according to claim 2, characterized in that: The terminal G of the MOS tube Q2 is electrically connected to the resistor R3, the switching diode D3 and one end of the resistor R4, the other end of the resistor R3 and the cut-off end of the switching diode D3 are electrically connected to the terminal PWM1, the terminal G of the MOS tube Q1 is electrically connected to the resistor R1, the switching diode D2 and one end of the resistor R2, the other end of the resistor R1 and the cut-off end of the switching diode D2 are electrically connected to the terminal PWM2, and the photovoltaic power supply module is electrically connected to the DSP control board through the terminal PWM1 and the terminal PWM2; The other end of the resistor R4, the terminal S of the MOS tube Q2, the conduction end of the Schottky barrier diode D5, the other end of the capacitor C1 and the other end of the capacitor C2 are all electrically connected to the terminal PV+ of the photovoltaic panel and the terminal DC- of the DC load.

4. A photovoltaic and mains synchronous power supply DC system according to claim 3, characterized in that: The first diode isolation circuit of the photovoltaic power supply module is a diode D4, the conducting end of the diode D4 is electrically connected to the BUCK / BOOST circuit, and the cut-off end of the diode D4 is electrically connected to the terminal DC+ of the DC load.

5. A photovoltaic and mains synchronous power supply DC system according to claim 1, characterized in that: The AC-DC rectifier circuit of the AC power supply module includes a rectifier REC1, a second terminal of the rectifier REC1 is electrically connected to the AC power terminal AC-L, a third terminal of the rectifier REC1 is electrically connected to the AC power terminal AC-N, a first terminal of the rectifier REC1 is electrically connected to a capacitor C3 and one end of a capacitor C4, and a fourth terminal of the rectifier REC1, the other end of the capacitor C3 and the other end of the capacitor C4 are all electrically connected to the terminal DC- of the DC load.

6. A photovoltaic and mains synchronous power supply DC system according to claim 5, characterized in that: The BUCK circuit of the mains power supply module includes a MOS tube Q3, a terminal D of the MOS tube Q3 is electrically connected to the AC-DC rectifier circuit, an S terminal of the MOS tube Q3 is electrically connected to a Schottky barrier diode D8 and one end of an inductor L3, and the other end of the inductor L3 is electrically connected to a capacitor C5 and one end of a capacitor C6; The terminal G of the MOS tube Q3 is electrically connected to the resistor R5, the switching diode D6 and one end of the resistor R2, the other end of the resistor R5 and the cut-off end of the switching diode D6 are electrically connected to the terminal PWM3, and the mains power supply module is electrically connected to the DSP control board through the terminal PWM3; The other end of the resistor R2 is electrically connected to the cut-off end of the Schottky barrier diode D8, and the conduction end of the Schottky barrier diode D8, the conduction end of the Schottky barrier diode D8, the other end of the capacitor C5 and the other end of the capacitor C6 are all electrically connected to the AC-DC rectifier circuit and the terminal DC- of the DC load; The second diode isolation circuit of the AC power supply module is a diode D7, one end of the diode D7 is electrically connected to the BUCK circuit, and the other end of the diode D7 is electrically connected to the terminal DC+ of the DC load.

7. A photovoltaic and mains synchronous power supply DC system according to claim 4 or 6, characterized in that: The DSP control board of the power supply control module is provided with terminals PWM1, terminal PWM2, terminal PWM3, terminal PV-V, terminal AC-V, terminal PV-I and terminal AC-I. The DSP control board is electrically connected to the photovoltaic power supply module through terminals PWM1 and PWM2, the DSP control board is electrically connected to the AC power supply module through terminal PWM3, and the DSP control board is electrically connected to the voltage and current sampling circuit through terminals PV-V, terminal AC-V, terminal PV-I and terminal AC-I.

8. A photovoltaic and mains synchronous power supply DC system according to claim 7, characterized in that: The voltage and current sampling circuit of the power supply control module includes a current transformer CT1, a current transformer CT2, a photovoltaic voltage sampling circuit, a photovoltaic current sampling circuit, a mains voltage sampling circuit and a mains current sampling circuit. The current transformer CT1 is arranged between the BUCK / BOOST circuit and the first diode isolation circuit, and the current transformer CT2 is arranged between the BUCK circuit and the second diode isolation circuit. The current transformer CT1 is provided with a terminal CT1+ and a terminal CT1-, and the current transformer CT1 is electrically connected to the DSP control board through the terminal CT1+ and the terminal CT1-. The current transformer CT2 is provided with a terminal CT2+ and a terminal CT2-, and the current transformer CT1 is electrically connected to the DSP control board through the terminal CT2+ and the terminal CT2-. The photovoltaic voltage sampling circuit is provided with an operational amplifier U1A, and the photovoltaic voltage sampling circuit is electrically connected to the DSP control board through the terminal PV-V. The mains voltage sampling circuit is provided with an operational amplifier U2A, and the mains voltage sampling circuit is electrically connected to the DSP control board through the terminal AC-V. The photovoltaic current sampling circuit is provided with an operational amplifier U3A, and the photovoltaic current sampling circuit is electrically connected to the DSP control board through the terminal PV-I. The mains current sampling circuit is provided with an operational amplifier U4A, and the mains current sampling circuit is electrically connected to the DSP control board through the terminal AC-I.

9. A control method for a photovoltaic and mains synchronous power supply DC system, based on the DC system of claims 1-8, characterized in that: The following steps are involved: S1: The DSP control board measures the load power of the DC load, the photovoltaic power of the photovoltaic power supply module, and the mains power of the mains power supply module through real-time sampling; S2: The DSP control board dynamically adjusts the duty cycle of the PWM signals of the terminals PWM1, PWM2 and PWM3 based on the power algorithm and in combination with the PID algorithm to control the power distribution of the photovoltaic power of the photovoltaic power supply module and the mains power of the mains power supply module; S3: Under the control of the DSP control board, the DC load uses the photovoltaic power supply module as a priority, and is supplemented by the mains power supply module when the photovoltaic power supply module is insufficient.

10. A control method for a photovoltaic and mains synchronous power supply DC system according to claim 9, characterized in that: The power algorithm includes: A. Calculate the difference ΔP between the load power of the DC load and the photovoltaic power of the photovoltaic power supply module; B. If ΔP>0, start the AC power supply module and output the duty cycle of the terminal PWM3 corresponding to the AC power of ΔP; C. If ΔP≤0, turn off the AC power supply module.

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