Grid connection device

Abstract

The invention provides a grid connection device. The grid-connected device comprises a switch transformer, the switch transformer comprises a full-bridge inversion module, the input end of the full-bridge inversion module is electrically connected with a power generation device, the output end of the full-bridge inversion module is electrically connected with a power grid, the full-bridge inversion module has a working state and a closed state, and when the full-bridge inversion module is in the working state, the full-bridge inversion module is in the closed state; the full-bridge inverter module boosts the power generation voltage and outputs the power generation voltage to a power grid; the input end of the diode is electrically connected with the power generation device, the output end of the diode is selectively conducted with the power grid, and the diode has a conduction state for directly conducting the power generation voltage to the power grid in a one-way mode and a disconnection state for cutting off the power generation device and the power grid; and when the power generation voltage of the power generation device is greater than a preset value, the diode is in a conducting state and the full-bridge inversion module is in a closed state. The problems of low efficiency and high cost caused by material redundancy and whole-course high-loss operation of a switch transformer in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a grid-connected device. Background Art

[0002] With the popularization of frequency conversion technology, switching transformers are mostly used in electronic display screens, computers, solar photovoltaic power generation, and high-power industrial equipment DC power, which need to increase or decrease voltage. In the process of solar power generation, when sunlight shines on the photovoltaic panels, the DC power generated is input into the switching transformer assembly through wires. The switching transformer assembly is used to convert the DC power output by the photovoltaic panels into voltage and enter the inverter. The inverter converts the DC power into AC power. Finally, the AC power output by the inverter is connected to the power grid to complete the conversion and transmission of solar power.

[0003] In the prior art, the switch transformer assembly has the following disadvantages during the power generation process: 1. There are two primary windings, which wastes a lot of materials; 2. The photovoltaic power is completely transmitted by the switch transformer, resulting in a high utilization rate of the switch transformer, and the resulting loss affects the photovoltaic power generation efficiency; 3. The current switch transformer is still traditional, and the loss is more obvious when used in large quantities.

[0004] There is no effective solution to the above problems yet. Summary of the invention

[0005] The main purpose of the present invention is to provide a grid-connected device to solve the problems of low efficiency and high cost caused by material redundancy and high loss operation throughout the switching transformer in the prior art.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a grid-connected device, comprising: a switching transformer, the switching transformer comprising a full-bridge inverter module, the input end of the full-bridge inverter module being electrically connected to the power generation device, the output end of the full-bridge inverter module being electrically connected to the power grid, the full-bridge inverter module having a working state and a closed state, wherein when the full-bridge inverter module is in the working state, the full-bridge inverter module boosts the power generation voltage of the power generation device and outputs it to the power grid; a diode, the input end of the diode being electrically connected to the power generation device, the output end of the diode being selectively conductive to the power grid, the diode having a conductive state for directly unidirectionally conductive ...

[0007] Furthermore, when the power generation voltage of the power generation device is less than or equal to a preset value, the diode is in an open circuit state and the full-bridge inverter module is in an operating state.

[0008] Furthermore, the full-bridge inverter module includes four switching tubes, which are diagonally connected in pairs to form a full-bridge topology structure. The full-bridge inverter module also includes a transformer, which includes a primary winding and a secondary winding, wherein the primary winding is electrically connected to the full-bridge topology structure so that the full-bridge inverter module can adjust the voltage and power density of the primary winding by adjusting the duty cycle and switching frequency of the switching tube, thereby controlling the output voltage and power density of the secondary winding, wherein the full-bridge inverter module is used to boost the direct current of the power generation device and convert it into alternating current for output to the power grid.

[0009] Furthermore, the full-bridge inverter module also includes a capacitor group, which includes at least one capacitor. The capacitor group is connected in series with the secondary winding, wherein the switching tube is adjusted to control the flow direction of the electromotive force of the secondary winding, thereby controlling the capacitor group to be in a charging state or a discharging state.

[0010] Furthermore, the capacitor bank includes a plurality of capacitors, and the plurality of capacitors are arranged in series or in parallel.

[0011] Furthermore, the full-bridge inverter module boosts the direct current of the power generation device and converts it into alternating current for output to the power grid.

[0012] Furthermore, the grid-connected device also includes: an inverter, the input end of the inverter is electrically connected to the output end of the full-bridge inverter module, the input end of the inverter is electrically connected to the output end of the diode, and the output end of the inverter is electrically connected to the power grid, wherein the inverter is used to match the output voltage of the full-bridge inverter module or the output voltage of the diode with the operating voltage of the power grid.

[0013] Further, the number of capacitors in the capacitor bank is set in proportion to the maximum power of the full-bridge inverter module.

[0014] Further, the number of turns of the primary winding is different from the number of turns of the secondary winding.

[0015] Furthermore, the capacitor is a low voltage large capacity capacitor below 1000V.

[0016] By applying the technical solution of the present invention, the intelligent management of the output voltage of the power generation device is realized by combining the characteristics of the full-bridge inverter module and the diode. When the power generation voltage is higher than the preset value, the diode directly conducts the voltage to the power grid, avoiding unnecessary power loss of the full-bridge inverter module; when the power generation voltage is lower than or equal to the preset value, the full-bridge inverter module works to ensure that the grid-connected voltage matches the grid voltage. This design not only improves the grid-connected efficiency, reduces the loss and material consumption in the energy conversion process, but also enhances the stability and reliability of the system. When the lighting conditions change, it can automatically adjust to ensure the optimal use of electric energy. This solution solves the problems of low efficiency and high cost of the switch transformer in the prior art due to material redundancy and high loss operation throughout the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0018] Figure 1 A schematic diagram of a power conversion system combining a solar panel and a switching transformer is shown;

[0019] Figure 2 A schematic structural diagram of a first embodiment of a grid-connected device according to the present invention is shown;

[0020] Figure 3 A schematic structural diagram of a second embodiment of a grid-connected device according to the present invention is shown;

[0021] Figure 4 A schematic structural diagram of a third embodiment of a grid-connected device according to the present invention is shown.

[0022] The above drawings include the following reference numerals:

[0023] 1. Switching transformer;

[0024] 2. Full-bridge inverter module;

[0025] 3. Diode;

[0026] 4. Switching tube;

[0027] 5. Transformer;

[0028] 6. Primary winding;

[0029] 7. Secondary winding;

[0030] 8. Capacitor bank;

[0031] 9. Inverter;

[0032] 201. Solar panels of photovoltaic power generation group; 202. Half-bridge rectifier module; 203. Inverter assembly; 204. Power grid. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0036] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art. In the accompanying drawings, for the sake of clarity, the thickness of the layers and regions may be enlarged, and the same reference numerals are used to represent the same devices, and thus their descriptions will be omitted.

[0037] In the prior art, a reactive power compensation device can be installed on the transformer side to stabilize the voltage and offset the inductive reactive power without affecting the transformer capacity.

[0038] The basic principle of the reactive power compensation device is to offset or compensate the reactive power demand in the power system by introducing capacitive reactive power that is opposite to the inductive reactive power in the system, thereby improving the power factor of the system, reducing losses during power transmission, and improving the efficiency and stability of the power system.

[0039] In the power system, many loads will generate inductive reactive power when running, which will cause a phase difference between current and voltage, so that part of the current in the power system is not directly used to generate actual useful power (active power), but is used to establish a magnetic field or electric field. The existence of this reactive power will increase the current on the power line, resulting in a decrease in the capacity utilization of power equipment such as lines and transformers, and will also increase the loss in the power transmission process.

[0040] Reactive power compensation devices can generate capacitive reactive power by using devices such as capacitors or synchronous condensers. This reactive power is opposite to inductive reactive power and can offset the reactive power demand in the system. When the capacitor is connected to the grid, it absorbs excess voltage changes and releases them when needed to keep the voltage stable.

[0041] Reactive power compensation devices can improve the operation efficiency indirectly by continuously optimizing the reactive power of the power system and reducing line losses. However, they may also introduce additional losses (such as self-loss of capacitors and energy consumption of control circuits).

[0042] Combination Figures 1 to 4 As shown, according to a specific embodiment of the present application, a grid-connected device is provided.

[0043] Specifically, the grid-connected device includes: a switching transformer 1 and a diode 3. The switching transformer 1 includes a full-bridge inverter module 2, the input end of the full-bridge inverter module 2 is electrically connected to the power generation device, and the output end of the full-bridge inverter module 2, such as a motor, a transformer, etc., is electrically connected to the power grid. The full-bridge inverter module 2 has a working state and a closed state, wherein when the full-bridge inverter module 2 is in the working state, the full-bridge inverter module 2 boosts the power generation voltage of the power generation device and outputs it to the power grid through the inverter; the input end of the diode 3 is electrically connected to the power generation device, and the output end of the diode 3 can be selectively connected to the power grid. The diode 3 has a conducting state in which the power generation voltage is directly unidirectionally conducted to the power grid through the inverter, and the diode 3 has a disconnecting state in which the power generation device is cut off from the power grid; wherein, when the power generation voltage of the power generation device is greater than a preset value, the diode 3 is in a conducting state and the full-bridge inverter module 2 is in a closed state.

[0044] By applying the technical solution of the present invention, by combining the characteristics of the full-bridge inverter module 2 and the diode 3, the intelligent management of the output voltage of the grid-connected device is realized. When the power generation voltage is higher than the preset value, the diode directly conducts the voltage to the grid through the inverter, avoiding unnecessary power loss of the full-bridge inverter module 2; when the power generation voltage is lower than or equal to the preset value, the full-bridge inverter module works to ensure that the grid-connected voltage matches the grid voltage. This design not only improves the grid-connected efficiency, reduces the loss and material consumption in the energy conversion process, but also enhances the stability and reliability of the system. When the lighting conditions change, it can automatically adjust to ensure the optimal use of electric energy. This solution solves the problems of low efficiency and high cost of the switch transformer in the prior art due to material redundancy and high loss operation throughout the process.

[0045] Optionally, when the power generation voltage of the power generation device is greater than a preset value, the diode 3 is in a conducting state and the full-bridge inverter module 2 is in a closed state. This design utilizes the unidirectional conductive property of the diode to ensure that the current can only flow from the low voltage side to the high voltage side, but not in the reverse direction.

[0046] It needs to be further explained that if Figure 1 The figure shows the working principle of a power conversion system combining solar panels and switching transformers in the prior art. The system is mainly used to convert direct current (DC) converted by solar energy into alternating current (AC) and increase the voltage, and finally connect the electric energy to the power grid or use it for other power needs. The following is a detailed explanation of the working principle of each part of the system:

[0047] Photovoltaic power generation group solar panel 201: The photovoltaic power generation group consists of multiple solar panels, which can convert sunlight energy into direct current electricity. When sunlight shines on the solar panel, the photovoltaic effect prompts the semiconductor material (such as silicon) in the panel to generate electron-hole pairs. These charge carriers move under the action of the internal electric field, thereby generating voltage and current at both ends of the panel.

[0048] The switching transformer and its variable frequency switching tube and half-bridge rectifier module 202 on the existing market: The switching transformer is the core component in the power conversion system, which is used to convert the direct current output by the photovoltaic panel into alternating current and perform voltage conversion. Figure 1In the switching transformer, a half-bridge rectifier circuit is used, which means that it has two switching tubes (frequency conversion switching tubes) working alternately to achieve current conversion. Frequency conversion switching tubes are key components in switching power supplies. They can switch quickly to convert DC power into high-frequency AC power, which is converted in the transformer to achieve voltage step-up or step-down. The half-bridge rectifier circuit converts the high-frequency AC power output by the switching tube into DC power, but it is different from the full-bridge circuit (it divides the primary winding into two, which wastes materials and increases costs. In this case, the primary winding uses a full-bridge circuit for this design, which saves half of the winding. The secondary winding is connected in series with a capacitor to increase the voltage by 2 times, and the step-up efficiency is high.

[0049] Inverter component 203: The inverter is responsible for converting the DC power output by the switching transformer into AC power again. Figure 1 In the inverter, the power is converted into 220V AC output, which is usually used to meet the power needs of households or industries, or the standard voltage for connecting power to the grid. The control circuit in the inverter adjusts the frequency and phase of the output AC according to the grid frequency and phase to synchronize it with the grid, so that it can be efficiently connected to the grid or supply power to the load.

[0050] Grid 204: The grid is a power transmission and distribution system. The AC power output by the inverter is connected to the grid through appropriate interfaces and control equipment, and the electrical energy is input into the larger power network for various purposes.

[0051] The working process of the whole system is as follows: when the sun shines on the solar panel 201 of the photovoltaic power generation group, the generated DC power is input into the primary winding of the switching transformer 1 through the wire. The variable frequency switch tube of the switching transformer converts the input DC power into high-frequency AC power, and steps up or down the voltage through the transformer to complete the voltage conversion. After the converted DC power is smoothed by the half-bridge rectifier circuit, it enters the inverter component 203, and the inverter converts the DC power into 220V AC power again. Finally, the AC power output by the inverter is connected to the power grid 204 to complete the conversion and transmission of solar power.

[0052] Specifically, in the present application, when the power generation voltage of the power generation device is less than or equal to a preset value, the diode 3 is in an open circuit state and the full-bridge inverter module 2 is in an operating state.

[0053] Optionally, when the power generation voltage of the power generation device is less than or equal to the preset value, the diode 3 will be in a reverse bias state, that is, an open circuit state, due to its working characteristics, to prevent current from passing. At this time, the full-bridge inverter module 2 is activated as the main voltage boosting device, and its function is to boost the DC power and convert it into AC power through the inverter, and increase the voltage in the process so that it can be output to the power grid. This control strategy can prevent the photovoltaic power from being unable to be sent to the power grid when the power generation voltage is too low (the direct conduction of the diode may cause the power grid voltage fluctuation). At the same time, through the regulation of the full-bridge inverter module, it is ensured that under low light or unstable power generation conditions, the system can continuously and efficiently supply power to the power grid.

[0054] Specifically, the full-bridge inverter module 2 includes four switch tubes 4, which are diagonally connected in pairs to form a full-bridge topology structure. The full-bridge inverter module 2 also includes a transformer 5, which includes a primary winding 6 and a secondary winding 7, wherein the primary winding 6 is electrically connected to the full-bridge topology structure so that the full-bridge inverter module 2 adjusts the voltage of the primary winding 6 by adjusting the duty cycle and switching frequency of the switch tube, thereby controlling the output voltage and power density of the secondary winding 7, wherein the full-bridge inverter module 2 is used to boost the DC power of the power generation device and convert it into AC power through an inverter and output it to the power grid.

[0055] Alternatively, if Figure 2 As shown, the four switch tubes are Q1, Q2, Q3, and Q4. Q1 and Q4 are connected diagonally, and Q2 and Q3 are connected diagonally to form a full-bridge topology. The working principle of the full-bridge topology is to convert the DC voltage into AC voltage by controlling the alternating conduction of the four switch devices. Since the full-bridge topology can conduct alternately in both directions, it can theoretically achieve a conversion efficiency close to 100%, and the actual efficiency is usually very high. By adjusting the conduction time and frequency of the switch devices, the output voltage and current, as well as the frequency of the output AC power, can be flexibly controlled to meet various needs.

[0056] Specifically, the working principle of the transformer 5 is that in each switching cycle, a pair of diagonal switch tubes will be turned on alternately. When the switch tube 4 is turned on, the current generates a magnetic field in the iron core through the primary winding 6, and the magnetic field energy is converted into an AC voltage through the secondary winding 7. This AC voltage (frequency and amplitude) can be adjusted by controlling the on and off time (duty cycle) and frequency of the switch tube 4. When the duty cycle increases and the frequency is increased, the average current passing through the primary winding increases, and the output voltage of the secondary winding also increases accordingly; conversely, when the duty cycle and frequency decrease, the output voltage of the secondary winding decreases, thereby achieving precise control of the output voltage. In addition to increasing or decreasing the voltage (boosting or bucking) as needed, the transformer also provides electrical isolation to protect the inverter and the power grid.

[0057] It needs to be further explained that if Figure 2 As shown, the grid-connected device in this embodiment includes a full-bridge inverter module 2, and Figure 1 The figure shows a half-bridge inverter module, which is usually composed of two switch tubes and a capacitor, and the capacitor is connected in parallel with the load. When working, the two switch tubes are alternately turned on and off, so that one end of the capacitor is connected to the power supply and the other end is connected to the ground, thereby generating alternating positive and negative voltages at the output end. However, in this structure, the primary winding of the transformer needs to bear half of the power supply voltage (in an ideal case), so Figure 1 Two windings are required to be connected to two switching tubes respectively to ensure the correct voltage conversion. Compared with the half-bridge inverter, the voltage obtained on the primary winding of the full-bridge inverter is the complete form of the input voltage. Therefore, in the design, only one primary winding is needed to bear the full voltage, which not only saves winding materials, but also simplifies the design of the transformer, helping to reduce the size and cost of the overall equipment.

[0058] Specifically, the full-bridge inverter module 2 also includes a capacitor group 8, which includes at least one capacitor. The capacitor group 8 is connected in series with the secondary winding 7, wherein the switching tube is adjusted to control the flow direction of the electromotive force of the secondary winding 7, thereby controlling the capacitor group 8 to be in a charging state or a discharging state.

[0059] like Figure 2 As shown, when the switch tube 4 of the full-bridge inverter module 2 controls the secondary winding 7 to generate a forward electromotive force, the current is charged through the capacitor bank 8. The microcontroller or digital signal processor (DSP) controls the on and off of the switch tube through a PWM (pulse width modulation) signal. Specifically, Q2 and Q3 are controlled to be turned on at the same time, while the other pair of switch tubes 4 are controlled to be turned off. When Q2 and Q3 are turned on, the positive pole of the DC power supply is connected to the primary winding through Q2, and the negative pole is connected to the other end of the primary winding through Q3, forming a forward current path. The forward current in the primary winding 6 generates a magnetic field in the magnetic core of the transformer 5, which in turn induces the secondary winding 7 to generate a forward electromotive force. The forward electromotive force generated by the secondary winding 7 is connected in series with the capacitor bank 8, so that the capacitor bank 8 starts to charge, and the current direction is consistent with the positive direction of the capacitor bank 8, flowing from the negative end of the capacitor bank 8 to the positive end (such as Figure 2 The charging process of the capacitor bank 8 will increase the output voltage of the secondary winding 7, and the voltage of the capacitor bank gradually rises until it reaches a set or limited safety threshold, at which point the charging process of the capacitor ends.

[0060] like Figure 3As shown, when the switch tube 4 of the full-bridge inverter module controls the secondary winding 7 to generate a reverse electromotive force, the capacitor group 8 begins to discharge. The electric energy stored in the capacitor group 8 is superimposed on the electromotive force of the secondary winding 7, and together they push the current to flow to the load or to the grid through the inverter, thereby achieving voltage boost and improving power generation efficiency. The microcontroller changes the conduction state of the switch tube 4. At this time, Q1 and Q4 are controlled to be on, while the previously on Q2 and Q3 are controlled to be off. Current path: When Q1 and Q4 are on, the negative pole of the DC power supply is connected to the primary winding through Q1, and the positive pole is connected to the other end of the primary winding 6 through Q4, forming a reverse current path. The current direction in the secondary winding 7 is reversed, generating a reverse electromotive force. Under the action of the reverse electromotive force, the capacitor group 8 begins to discharge, and the current direction is consistent with the reverse direction of the capacitor group 8. During the discharge process, the electric energy stored in the capacitor group 8 is superimposed on the electromotive force of the secondary winding 7, and together they push the current to the load or grid output (such as Figure 3 The voltage is increased as shown by the arrow.

[0061] This mechanism utilizes the characteristics of the capacitor bank 8, that is, storing energy when charging and releasing energy when discharging, and combines it with the voltage conversion function of the transformer. By controlling the operating frequency and duty cycle of the transformer, the charging and discharging of the capacitor bank can be accurately controlled, which can significantly improve the efficiency of voltage conversion. In order to prevent damage from overvoltage or overcurrent, the voltage and current of the capacitor bank 8 will be monitored. Once it approaches or reaches the set safety threshold, the conduction state of the switch tube will be adjusted immediately to avoid overcharging or overdischarging of the capacitor bank 8, while protecting the normal operation of the transformer.

[0062] Specifically, the capacitor bank 8 includes a plurality of capacitors, which are arranged in parallel. The capacitor bank connected in parallel increases or decreases the number of capacitors according to the voltage. When the load current is large, the number of capacitors connected in parallel is increased accordingly, and when the load current is small, the number of capacitors connected in parallel is reduced, which helps to improve the output voltage stability of the grid-connected device.

[0063] Optionally, the capacitor bank 8 can also be designed as a single capacitor, and the capacitance is matched with the switching transformer capacity to ensure stable and efficient voltage conversion under various operating conditions. A single large-capacity capacitor is applicable in a certain load range to meet specific transformer design requirements. The application of a single capacitor in the circuit can reduce the harmonic components caused by the difference in capacitance values ​​between multiple capacitors, thereby improving the purity and stability of the output signal.

[0064] Specifically, the capacity of a transformer usually refers to the maximum power or load capacity it can handle, which is an important parameter to measure the working performance and application range of a switching transformer. The capacity of a transformer is mainly affected by the turns ratio of the primary winding and the secondary winding, the core material and size, the coil material and construction of the winding, the operating frequency and other parameters. The capacity of a transformer is very important for its application. For example, in power electronic equipment, communication power supply, solar inverter system and industrial control, it is necessary to select the appropriate switching transformer capacity according to the load requirements and system design. If the capacity is not selected properly, it may cause problems such as transformer overheating, reduced efficiency or failure to meet load requirements.

[0065] Specifically, the full-bridge inverter module 2 boosts the DC power of the power generation device and converts it into AC power through the inverter for output to the power grid. The full-bridge inverter module 2 not only realizes the conversion from DC to AC, but also realizes the effective boost and stabilization of the voltage through the cooperation of the transformer and the capacitor bank, ensuring that the power generation device can efficiently and reliably provide clean electricity to the power grid.

[0066] Optionally, for example, when the sunlight is insufficient, the DC power output by the solar panel is input to the full-bridge inverter module 2, and the diode 3 is in the cut-off state. The PWM signal in the module controls the four MOSFET switches Q1, Q2, Q3, and Q4 to be turned on and off alternately, and the switching frequency changes from low frequency to medium frequency. During the boost process, the capacitor bank 8 is connected in series with the secondary winding of the transformer, and the charging and discharging characteristics of the capacitor are used to increase and stabilize the output voltage. When the current passes through the capacitor, the capacitor is charged and the voltage is increased; when the current direction is reversed, the capacitor is discharged and superimposed with the output voltage of the transformer to further increase the voltage. After the boost, it is output to the power grid through the inverter to supply power to household, commercial or industrial loads.

[0067] Specifically, the grid-connected device further includes: Figure 4 The inverter 9 in the power supply circuit has an input terminal electrically connected to the output terminal of the full-bridge inverter module 2, an input terminal electrically connected to the output terminal of the diode 3, and an output terminal electrically connected to the power grid, wherein the inverter 9 is used to match the output voltage of the full-bridge inverter module 2 or the output voltage of the diode 3 with the operating voltage of the power grid. The addition of the inverter further enhances the voltage matching capability of the grid-connected device, ensures the efficient transmission of electric power, and is suitable for environments with large fluctuations in power grid voltage.

[0068] Alternatively, if Figure 4As shown, the inverter 9 receives the DC voltage from the full-bridge inverter module 2 or the diode 3, and converts it into an AC voltage through an internal PWM (pulse width modulation) control circuit, while ensuring that the frequency of the output AC voltage is consistent with the frequency of the power grid. The inverter 9 needs to be synchronized with the phase of the power grid, which means that the phase of the output AC voltage must be consistent with the phase of the power grid voltage to avoid impact and energy waste when connected to the grid. The inverter 9 also has a protection function for the grid-connected device. Once overvoltage, overcurrent or short circuit is detected, the protection mechanism is immediately activated to cut off the connection with the power grid to prevent damage or safety hazards.

[0069] Specifically, the number of capacitors in parallel in the capacitor bank 8 is set in proportion to the maximum power of the full-bridge inverter module 2. The function of the capacitor bank 8 is to assist in boosting the voltage through its charge and discharge characteristics and to provide voltage stability under transient conditions. In high-power applications, the full-bridge inverter module 2 needs to handle high current and voltage levels, which requires the capacitor bank 8 to be able to withstand the corresponding voltage and have sufficient energy storage and rapid release capabilities to meet the instantaneous power requirements of the system. The number of parallel capacitors is proportional to the maximum power (and the accompanying voltage requirements) of the full-bridge inverter module 2. This configuration ensures that the capacitor bank can work effectively at different power levels, improving the adaptability and flexibility of the grid-connected device.

[0070] Specifically, the number of turns of the primary winding 6 is different from the number of turns of the secondary winding 7. By adjusting the turns ratio of the primary winding 6 and the secondary winding 7 of the transformer, the output voltage can be accurately controlled, which directly determines the increase or decrease of the output voltage relative to the input voltage. For example, if an input voltage of 18V is to be converted into an output voltage of 36V, the number of turns of the secondary winding will be twice the number of turns of the primary winding. In this way, even in the case of insufficient light, the charging and discharging of the capacitor and the boosting effect of the transformer can ensure that the system outputs a stable voltage.

[0071] Specifically, capacitors are divided into high-voltage small-capacity and low-voltage large-capacity. In this case, low-voltage large-capacity capacitors below 1000V are selected.

[0072] By selecting different types of capacitors, it can be optimized for different working environments and performance requirements, increasing the environmental adaptability and functional diversity of the grid-connected device, and is suitable for grid-connected applications under various extreme conditions, such as solar power stations in desert areas or wind power stations in extremely cold areas.

[0073] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0074] 1. By optimizing the combination of the full-bridge inverter module and the diode, such as directly transmitting power to the inverter through the diode when there is sufficient light, the frequency of use of the switching transformer is reduced and energy loss is reduced. When the light is weakened, the series design of the capacitor bank and the secondary winding of the transformer can respond quickly and increase the voltage to the level required by the power grid, ensuring the adaptability and flexibility of the system to different environmental conditions.

[0075] 2. The capacitor bank is connected in series with the secondary winding of the transformer, and the voltage is increased by charging and discharging the capacitor bank. By controlling the operating frequency and duty cycle of the transformer, the charging and discharging process of the capacitor bank can be accurately controlled, which significantly improves the efficiency of voltage conversion. The capacitor connected in series with the secondary winding of the transformer reduces the materials used in the transformer core and winding, reduces the overall volume of the switching transformer, and reduces the corresponding iron loss and copper loss.

[0076] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0077] In addition to the above, it should be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the present invention.

[0078] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A grid-connected device, characterized in that: include: A switching transformer (1), the switching transformer (1) comprising a full-bridge inverter module (2), the input end of the full-bridge inverter module (2) being electrically connected to a power generation device, the output end of the full-bridge inverter module (2) being electrically connected to a power grid, the full-bridge inverter module (2) having an operating state and an off state, wherein when the full-bridge inverter module (2) is in the operating state, the full-bridge inverter module (2) boosts the generated voltage of the power generation device and outputs the boosted voltage to the power grid; A diode (3), wherein an input end of the diode (3) is electrically connected to the power generation device, an output end of the diode (3) is selectively conductive to the power grid, the diode (3) has a conductive state for directly unidirectionally conducting the generated voltage to the power grid, and the diode (3) has an open state for disconnecting the power generation device from the power grid; Wherein, when the power generation voltage of the power generation device is greater than a preset value, the diode (3) is in the on state and the full-bridge inverter module (2) is in the off state.

2. The grid-connected device according to claim 1, characterized in that: When the power generation voltage of the power generation device is less than or equal to a preset value, the diode (3) is in the open circuit state and the full-bridge inverter module (2) is in the working state.

3. The grid-connected device according to claim 2, characterized in that: The full-bridge inverter module (2) comprises four switch tubes (4), wherein the four switch tubes (4) are diagonally connected in pairs to form a full-bridge topology structure. The full-bridge inverter module (2) also comprises a transformer (5), wherein the transformer (5) comprises a primary winding (6) and a secondary winding (7), wherein the primary winding (6) is electrically connected to the full-bridge topology structure, so that the full-bridge inverter module (2) adjusts the voltage and power density of the primary winding (6) by adjusting the duty cycle and switching frequency of the switch tubes, thereby controlling the output voltage and power density of the secondary winding (7), wherein the full-bridge inverter module (2) is used to boost the direct current of the power generation device and convert it into alternating current for output to a power grid.

4. The grid-connected device according to claim 3, characterized in that: The full-bridge inverter module (2) further comprises a capacitor group (8), the capacitor group (8) comprising at least one capacitor, the capacitor group (8) being connected in series with the secondary winding, wherein the switching tube is adjusted to control the flow direction of the electromotive force of the secondary winding, thereby controlling the capacitor group (8) to be in a charging state or a discharging state.

5. The grid-connected device according to claim 4, characterized in that: The capacitor group (8) comprises a plurality of capacitors, and the plurality of capacitors are arranged in series or in parallel.

6. The grid-connected device according to claim 1, characterized in that: The full-bridge inverter module (2) boosts the direct current of the power generation device and converts it into alternating current, which is then output to the power grid.

7. The grid-connected device according to claim 1, characterized in that: The grid-connected device further comprises: an inverter (9), wherein an input end of the inverter (9) is electrically connected to an output end of the full-bridge inverter module (2), an input end of the inverter (9) is electrically connected to an output end of the diode (3), and an output end of the inverter (9) is electrically connected to a power grid, wherein the inverter (9) is used to match an output voltage of the full-bridge inverter module (2) or an output voltage of the diode (3) with an operating voltage of the power grid.

8. The grid-connected device according to claim 4, characterized in that: The number of capacitors in the capacitor bank (8) is set in proportion to the maximum power of the full-bridge inverter module (2).

9. The grid-connected device according to claim 3, characterized in that: The number of turns of the primary winding (6) is different from the number of turns of the secondary winding (7).

10. The grid-connected device according to claim 5, characterized in that: The capacitor is a low-voltage large-capacity capacitor below 1000V.

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