Wind-solar integrated power system and photovoltaic grid-connected circuit
By connecting the Boost mirror circuit to the neutral connection of the grid-side inverter, the problem of common-mode grounding current in the common DC collection mode is solved, thereby improving power quality and reducing safety hazards, avoiding the use of high-frequency transformers, and reducing the difficulty and cost of power system deployment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2026-03-17
AI Technical Summary
In the common DC collection method, stray capacitance between the new energy device and the grid grounding causes common mode grounding current, generating harmonics that are injected into the grid, reducing power quality and causing safety hazards. In addition, existing high-frequency transformer solutions have problems such as large size, high power consumption, and high cost.
By employing a Boost mirror circuit and a neutral connection with the grid-side inverter, voltage balance is achieved through synchronous control of the switching devices in the Boost branch, eliminating common-mode voltage and current and avoiding the use of transformers.
Without adding equipment, common-mode voltage and current are reduced, power quality is improved, the difficulty of power system layout and safety hazards are reduced, and costs are saved.
Smart Images
Figure CN224006505U_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of power technology, and in particular relates to a wind-solar integrated power system and a photovoltaic grid-connected circuit. Background Technology
[0002] With the continuous development of new energy technologies, the forms of new energy power generation are becoming increasingly diversified. New energy devices of the same or different types can be aggregated and connected to the power grid to provide electricity. The aggregation of new energy devices can include common DC aggregation and common AC aggregation. Among these, due to the reduction in the number of inverters and transformers, common DC aggregation has become a key technology of interest.
[0003] In a common-mode DC-DC power supply system, the DC-output renewable energy device is connected to the grid via an inverter, and the grid is connected to ground. Stray capacitance exists between the renewable energy device and the grid ground. Due to the lack of electrical isolation, a DC grounding current path is formed between the renewable energy device (as a power source) and the grid. Under the influence of stray capacitance and the inverter's filter inductance, a common-mode grounding current is generated. This common-mode grounding current contains low-frequency line components and high-frequency switching components. These components inject harmonics into the grid, thereby reducing power quality and potentially causing safety hazards.
[0004] To avoid common-mode grounding current, a high-frequency transformer can be added between the inverter and the power grid to achieve electrical isolation between the new energy device and the grid. However, high-frequency transformers have problems such as large size, high power consumption, and high cost, which increases the difficulty of power system deployment. Utility Model Content
[0005] This application provides a wind-solar integrated power system and a photovoltaic grid-connected circuit, which can reduce the difficulty of power system deployment and reduce power system safety hazards.
[0006] In a first aspect, embodiments of this application provide a wind-solar integrated power system, comprising: a photovoltaic DC system, the photovoltaic DC system including photovoltaic devices; a Boost mirror circuit, the DC input terminal of the Boost mirror circuit being connected to the DC output terminal of the photovoltaic DC system, the Boost mirror circuit also having a DC output terminal and a first neutral connection terminal, the Boost mirror circuit being configured to boost the output power of the photovoltaic DC system; and a wind turbine generator, including a grid-side inverter, the DC input terminal of the grid-side inverter being connected to the DC output terminal of the Boost mirror circuit, the grid-side inverter also having a second neutral connection terminal, the second neutral connection terminal being connected to the first neutral connection terminal, the voltage on the second neutral connection terminal being the ground balance voltage, and the AC output terminal of the grid-side inverter being configured to be connected to the power grid.
[0007] In some possible embodiments, the photovoltaic device includes a photovoltaic power generation unit and a DC / DC converter; the photovoltaic power generation unit is connected to the DC input terminal of the DC / DC converter, the DC output terminal of the DC / DC converter is connected to the DC input terminal of the Boost mirror circuit, and the DC output terminal of the Boost mirror circuit is connected to the DC input terminal of the grid-side inverter through the DC bus of the grid-side inverter.
[0008] In some possible embodiments, the photovoltaic DC system includes multiple photovoltaic devices connected to a DC collector line, which is connected to the DC input of a Boost mirror circuit.
[0009] In some possible embodiments, the Boost mirror circuit includes two Boost branches; each Boost branch includes a capacitor, an inductor, a switching device, and a diode, the capacitors in the two Boost branches are connected together, and one end of the connection is connected to a first neutral connection terminal, the switching devices in the two Boost branches are connected together, and one end of the connection is connected to the first neutral connection terminal.
[0010] In some possible embodiments, in one Boost branch, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the first terminal of the switching device and the anode of the diode, respectively. The cathode of the diode is connected to the DC output terminal of the Boost mirror circuit. In another Boost branch, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the second terminal of the switching device and the cathode of the diode, respectively. The anode of the diode is connected to the DC output terminal of the Boost mirror circuit. The other end of the capacitor in one Boost branch is connected to the other end of the capacitor in another Boost branch, and the second terminal of the switching device in one Boost branch is connected to the first terminal of the switching device in another Boost branch.
[0011] In some possible embodiments, the switching devices in one Boost branch are switched on and off synchronously with the switching devices in another Boost branch.
[0012] Secondly, embodiments of this application provide a photovoltaic grid-connected circuit, including: a Boost mirror circuit, the DC input terminal of which is configured to connect to a photovoltaic DC system, the Boost mirror circuit also having a DC output terminal and a first neutral connection terminal, the Boost mirror circuit being configured to boost the output power of the photovoltaic DC system; a grid-side inverter, the DC input terminal of which is connected to the DC output terminal of the Boost mirror circuit, the grid-side inverter also having a second neutral connection terminal, the second neutral connection terminal being connected to the first neutral connection terminal, the voltage on the second neutral connection terminal being the ground balance voltage, and the AC output terminal of the grid-side inverter being configured to connect to the power grid.
[0013] In some possible embodiments, the Boost mirror circuit includes two Boost branches; each Boost branch includes a capacitor, an inductor, a switching device, and a diode, the capacitors in the two Boost branches are connected together, and one end of the connection is connected to a first neutral connection terminal, the switching devices in the two Boost branches are connected together, and one end of the connection is connected to the first neutral connection terminal.
[0014] In some possible embodiments, in one Boost branch, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the first terminal of the switching device and the anode of the diode, respectively. The cathode of the diode is connected to the DC output terminal of the Boost mirror circuit. In another Boost branch, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the second terminal of the switching device and the cathode of the diode, respectively. The anode of the diode is connected to the DC output terminal of the Boost mirror circuit. The other end of the capacitor in one Boost branch is connected to the other end of the capacitor in another Boost branch, and the second terminal of the switching device in one Boost branch is connected to the first terminal of the switching device in another Boost branch.
[0015] In some possible embodiments, the switching devices in one Boost branch are switched on and off synchronously with the switching devices in another Boost branch.
[0016] This application provides a wind-solar integrated power system and a photovoltaic grid-connected circuit. The DC output terminal of the photovoltaic DC system is connected to the DC input terminal of a Boost mirror circuit. The DC output terminal of the Boost mirror circuit is connected to the DC input terminal of the grid-side inverter of the wind turbine. The AC output terminal of the grid-side inverter is configured to be connected to the power grid. The Boost mirror circuit has a first neutral connection terminal, and the grid-side inverter has a second neutral connection terminal. The voltage at the second neutral connection terminal is the ground balance voltage. The Boost mirror circuit can boost the output power of the photovoltaic DC system, realizing a voltage boosting function. The connection between the first and second neutral connection terminals allows the voltage at the first neutral connection terminal to follow the voltage at the second neutral connection terminal, pulling the voltage at the first neutral connection terminal to the ground balance voltage. Therefore, without setting up a transformer for the photovoltaic DC system, common-mode voltage and common-mode current can be reduced or even eliminated, improving the power quality supplied to the grid, reducing power system safety hazards, and reducing the difficulty of power system deployment. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram illustrating an example of using a high-frequency transformer to isolate an inverter from the power grid in related technologies.
[0019] Figure 2 A schematic diagram of the structure of a wind-solar integrated power system provided in an embodiment of this application;
[0020] Figure 3 A schematic diagram of the structure of a wind-solar integrated power system provided in another embodiment of this application;
[0021] Figure 4 A schematic diagram of the structure of a wind-solar integrated power system provided in another embodiment of this application;
[0022] Figure 5 A schematic diagram of the structure of a wind-solar integrated power system provided in another embodiment of this application;
[0023] Figure 6 This is a schematic diagram of the structure of a photovoltaic grid-connected circuit provided in one embodiment of this application;
[0024] Figure 7 This is a schematic diagram of a photovoltaic grid-connected circuit provided in another embodiment of this application. Detailed Implementation
[0025] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.
[0026] With the continuous development of new energy technologies, new energy power generation forms are becoming increasingly diversified. New energy devices of the same or different types can be aggregated and connected to the grid to provide power. New energy device aggregation can include common DC aggregation and common AC aggregation. Among these, due to the reduction in the number of inverters and transformers, common DC aggregation has become a key technology of interest. In common DC aggregation, the DC-output new energy device is connected to the grid via an inverter, and the grid is connected to ground. Stray capacitance exists between the new energy device and the grid ground. Due to the lack of electrical isolation, a DC ground current path will form between the DC-output new energy device and the grid. Under the influence of stray capacitance and the inverter's filter inductance, a common-mode ground current will be generated. The common-mode ground current contains low-frequency components of the line and high-frequency components of the switch. These components will inject harmonics into the grid, thereby reducing the power quality of the grid and potentially causing safety hazards. To avoid common-mode ground current, a high-frequency transformer can be added between the inverter and the grid. The high-frequency transformer achieves electrical isolation between the new energy device and the grid, making the new energy device and inverter a floating ground system. For example, Figure 1 This is a schematic diagram illustrating an example of using a high-frequency transformer to isolate an inverter from the power grid in related technologies, such as... Figure 1 As shown, the new energy device 11 is connected to the inverter 12, and the inverter 12 is connected to the power grid 14 through the transformer 13. However, high-frequency transformers have problems such as large size, high power consumption, and high cost, which increases the difficulty of power system deployment.
[0027] This application provides a wind-solar integrated power system and a photovoltaic grid-connected circuit. In the wind-solar integrated power system, the photovoltaic DC system of the photovoltaic device is connected to the DC input terminal of a Boost mirror circuit. The DC output terminal of the Boost mirror circuit is connected to the DC input terminal of the grid-side inverter of the wind turbine. The AC output terminal of the grid-side inverter is connected to the power grid. The Boost mirror circuit has a first neutral connection terminal, which is connected to the second neutral connection terminal of the grid-side inverter of the wind turbine. The voltage at the second neutral connection terminal is the ground balance voltage. The voltage at the first neutral connection terminal follows the voltage at the second neutral connection terminal to achieve ground balance, thereby reducing or even avoiding the generation of common-mode voltage and common-mode current. Furthermore, it eliminates the need for a transformer in the photovoltaic DC system, thereby improving power quality and eliminating safety hazards while reducing the difficulty of power system deployment.
[0028] The wind-solar integrated power system and photovoltaic grid-connected circuit provided in this application will be described below.
[0029] The first aspect of this application provides a wind-solar integrated power system. Figure 2 This is a schematic diagram of the structure of a wind-solar integrated power system provided in an embodiment of this application, as shown below. Figure 2As shown, the integrated wind and solar power system may include a photovoltaic DC system 20, a Boost mirror circuit 30, and a wind turbine 40.
[0030] The photovoltaic DC system 20 includes photovoltaic devices 21, and the number of photovoltaic devices 21 in the photovoltaic DC system 20 is not limited herein. The photovoltaic devices 21 are capable of converting light energy into electrical energy and outputting DC power.
[0031] The Boost mirror circuit 30 has a DC input terminal, a DC output terminal, and a first neutral connection terminal A1. The DC input terminal of the Boost mirror circuit 30 is connected to the DC output terminal of the photovoltaic DC system 20. The Boost mirror circuit 30 itself has a mirror structure characteristic, which enables it to have a first neutral connection terminal A1. The Boost mirror circuit 30 is configured to boost the electrical energy output from the photovoltaic DC system. In some examples, the Boost mirror circuit 30 can be a bidirectional boost-buck circuit, that is, in addition to boosting the electrical energy output from the photovoltaic DC system 20 and outputting it through the DC output terminal of the Boost mirror circuit 30, it can also step down the electrical energy obtained at the DC output terminal and transmit it to the photovoltaic DC system 20 through the DC input terminal.
[0032] Wind turbine 40 can convert wind energy into electrical energy. Wind turbine 40 may include a grid-side inverter 41. If wind turbine 40 is an AC wind turbine, then as follows... Figure 2 As shown, the wind turbine 40 may also include an AC wind power generation structure 42 and a machine-side rectifier 43; the AC wind power generation structure 42 may include blades, drive shafts, gearboxes, AC generators, etc., which are not limited here; the output terminal of the AC generator in the AC wind power generation structure 42 is connected to the AC input terminal of the machine-side rectifier 43, and the DC output terminal of the machine-side rectifier 43 is connected to the DC input terminal of the grid-side inverter 41. Figure 3 A schematic diagram of the structure of a wind-solar integrated power system provided in another embodiment of this application is shown below. Figure 3As shown, if the wind turbine 40 is a DC wind turbine, it may also include a DC wind power generation structure 44. The DC wind power generation structure 44 may include blades, a drive shaft, a gearbox, a DC generator, etc., which are not limited here. The output terminal of the DC generator in the DC wind power generation structure 44 is connected to the DC input terminal of the grid-side inverter 41. The DC input terminal of the grid-side inverter 41 is connected to the DC output terminal of the Boost mirror circuit 30. The AC output terminal of the grid-side inverter 41 is configured to be connected to the power grid 51. In some examples, the grid-side inverter 41 can be connected to the power grid 51 through the main transformer 52. The grid-side inverter 41 can convert DC power into AC power. The grid-side inverter 41 also has a second neutral connection terminal A2, and the voltage on the second neutral connection terminal A2 is the earth balance voltage. The earth balance voltage on the second neutral connection terminal A2 is naturally generated by the grid-side inverter 41 of the wind turbine 40 itself. For example, the grid-side inverter 41 includes a three-level converter, and the second neutral connection terminal A2 may include the neutral point of the three-level converter. The voltage of the neutral point of the three-level converter is naturally generated by the control of the three-level converter and generally fluctuates around the ground voltage, which is the earth balance voltage. As another example, the grid-side inverter 41 includes a two-level converter, and the second neutral connection terminal A2 may include the neutral point of the two-level converter. The voltage of the neutral point of the two-level converter is the average of the positive and negative voltages of the DC output terminals of the two-level converter, which is generally the ground voltage and can be considered as the earth balance voltage. The second neutral connection terminal A2 of the grid-side inverter 41 is connected to the first neutral connection terminal A1 of the Boost mirror circuit 30. The voltage of the first neutral connection terminal A1 will follow the voltage of the second neutral connection terminal A2, that is, the voltage of the first neutral connection terminal A1 is pulled to be consistent with the voltage of the second neutral connection terminal A2, thereby reducing or even eliminating common-mode voltage and common-mode current.
[0033] In this embodiment of the application, in the integrated wind and solar power system, the DC output terminal of the photovoltaic DC system 20 is connected to the DC input terminal of the Boost mirror circuit 30, and the DC output terminal of the Boost mirror circuit 30 is connected to the DC input terminal of the grid-side inverter 41 of the wind turbine 40. The AC output terminal of the grid-side inverter 41 is configured to be connected to the power grid 51. The Boost mirror circuit 30 has a first neutral connection terminal A1, and the grid-side inverter 41 has a second neutral connection terminal A2, the voltage on the second neutral connection terminal A2 being the earth balance voltage. The Boost mirror circuit 30 can boost the output power of the photovoltaic DC system 20, realizing the boost function. The first neutral connection terminal A1 is connected to the second neutral connection terminal A2, causing the voltage on the first neutral connection terminal A1 to follow the voltage on the second neutral connection terminal A2. This pulls the voltage on the first neutral connection terminal A1 to the ground equilibrium voltage, thereby reducing or even eliminating common-mode voltage and common-mode current without requiring a transformer for the photovoltaic DC system 20. This improves the power quality supplied to the grid, reduces power system safety hazards, simplifies power system deployment, and makes access to diversified DC power sources more user-friendly. It offers higher cost-effectiveness, especially for DC access to renewable energy systems with floating power supply voltages. In renewable energy wind-solar hybrid power systems, the photovoltaic DC system 20 can be connected to the wind turbine 40 nearby, sharing the grid-side inverter 41 of the wind turbine 40 to generate electricity and connect to the grid, saving costs and enabling rapid deployment.
[0034] In some embodiments, the photovoltaic device in the photovoltaic DC system 20 may include a photovoltaic power generation unit and a DC / DC converter. Figure 4 A schematic diagram of the structure of a wind-solar integrated power system provided in another embodiment of this application is shown below. Figure 4As shown, the photovoltaic DC system 20 may include multiple photovoltaic devices 21, each of which may include multiple photovoltaic power generation units 211 forming a photovoltaic array, and a DC / DC converter 212. The photovoltaic power generation units 211 are connected to the DC input terminal of the DC / DC converter 212. When the photovoltaic device 21 includes multiple photovoltaic power generation units 211, these units can be combined and connected to the DC input terminal of the DC / DC converter 212. The DC output terminal of the DC / DC converter 212 is connected to the DC input terminal of the Boost mirror circuit 30. The DC output terminal of the Boost mirror circuit 30 is connected to the DC input terminal of the grid-side inverter 41 via the DC bus. In the case where the wind turbine 40 is an AC wind turbine, the grid-side inverter 41 and the turbine-side rectifier 43 are connected via a DC bus, and the DC output terminal of the Boost mirror circuit 30 can be connected to this DC bus. When the wind turbine 40 is a DC wind turbine, the grid-side inverter 41 and the DC wind power generation structure 44 are connected through a DC bus, and the DC output terminal of the Boost mirror circuit 30 can be connected to the DC bus.
[0035] In some examples, where the photovoltaic DC system 20 includes multiple photovoltaic devices 21, the multiple photovoltaic devices 21 can share a single boost mirror circuit. For example... Figure 4 As shown, multiple photovoltaic devices 21 can be connected to a DC collector line 22, which is connected to the DC input terminal of a Boost mirror circuit 30. The electrical energy generated by the photovoltaic devices 21 is transmitted to the Boost mirror circuit for voltage boosting via the DC collector line 22, and then transmitted to the grid-side inverter 41 for output to the power grid 51.
[0036] In other examples, where the photovoltaic DC system 20 includes multiple photovoltaic devices 21, each photovoltaic device may correspond to a Boost mirror circuit 30, or the photovoltaic devices 21 may be grouped, with each group of photovoltaic devices 21 sharing a Boost mirror circuit 30, which is not limited here.
[0037] In some embodiments, the Boost mirror circuit may include two Boost branches forming a mirror structure. Each Boost branch includes a capacitor, an inductor, a switching device, and a diode. The capacitors in the two Boost branches are connected together, and one end of the capacitors in the two Boost branches is connected to a first neutral connection. The switching devices in the two Boost branches are connected together, and one end of the switching devices in the two Boost branches is connected to the first neutral connection. The inductor may be implemented as a reactor, and is not limited thereto. The switching device may be a fully controlled power switching device, such as an Insulated-Gate Bipolar Transistor (IGBT), a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), etc., and is not limited thereto.
[0038] Specifically, in one Boost branch, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the first terminal of the switching device and the anode of the diode, respectively. The cathode of the diode is connected to the DC output terminal of the Boost mirror circuit. In another Boost branch, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the second terminal of the switching device and the cathode of the diode, respectively. The anode of the diode is connected to the DC output terminal of the Boost mirror circuit. The other end of the capacitor in one Boost branch is connected to the other end of the capacitor in the other Boost branch, and the second terminal of the switching device in one Boost branch is connected to the first terminal of the switching device in the other Boost branch. The switching devices in one Boost branch and the other Boost branch are switched on and off synchronously; that is, at a certain moment, if the switching device in one Boost branch is in the on state, the switching device in the other Boost branch is also in the on state; at a certain moment, if the switching device in one Boost branch is in the off state, the switching device in the other Boost branch is also in the off state. The switching devices in the two Boost branches can be controlled by pulse signals to ensure that the pulse signals of the switching devices in the two Boost branches are synchronous and consistent.
[0039] For example, Figure 5 This is a schematic diagram of the structure of a wind-solar integrated power system provided in another embodiment of this application, as shown below. Figure 5As shown, the Boost mirror circuit includes two Boost branches 31. One Boost branch 31 includes a capacitor C1, an inductor L1, a switching device S1, and a diode D1. The other Boost branch 31 includes a capacitor C2, an inductor L2, a switching device S2, and a diode D2. One end of the capacitor C1 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the first terminal of the switching device S1 and the anode of the diode D1. The cathode of the diode D1 is connected to the DC output terminal of the Boost mirror circuit. In other words, the DC output terminal of the Boost mirror circuit includes the cathode of the diode D1, and the cathode of the diode D1 can be connected to the positive terminal of the DC input terminal of the grid-side inverter 41. One end of capacitor C2 is connected to one end of inductor L2. The other end of inductor L2 is connected to the second terminal of switching device S2 and the cathode of diode D2. The anode of diode D2 is connected to the DC output terminal of Boost mirror circuit 30. Alternatively, the DC output terminal of Boost mirror circuit 30 includes the anode of diode D1. The anode of diode D2 can be connected to the negative terminal of the DC input terminal of grid-side inverter 41. The other end of capacitor C1 is connected to the other end of capacitor C2, forming a neutral point. The other ends of capacitors C1 and C2 are connected to the first neutral connection terminal A1. The second terminal of switching device S1 is connected to the first terminal of switching device S2, forming a neutral point. The second terminal of switching device S1 and the first terminal of switching device S2 are connected to the first neutral connection terminal A1. The control terminals of switching devices S1 and S2 can receive control signals, thereby controlling the on / off state of switching devices S1 and S2 according to the control signals.
[0040] When switching devices S1 and S2 are both in the ON state, inductors L1 and L2 charge. When switching devices S1 and S2 are both in the OFF state, inductors L1 and L2 discharge. Diodes D1 and D2 provide a path for the discharge of inductors L1 and L2 and prevent current backflow. The periodic switching of switching devices S1 and S2 enables current flow from the low-voltage side to the high-voltage side. Therefore, the duty cycle of the pulse signal used to control switching devices S1 and S2 is related to the magnitude of the current output by the Boost mirror circuit 30. The magnitude of the current output by the Boost mirror circuit 30 can be adjusted by regulating the duty cycle of the pulse signal controlling the switching of switching devices S1 and S2.
[0041] In some examples, the first neutral connection terminal A1 is connected to the second neutral connection terminal A2, and the connection point of the first neutral connection terminal A1 and the second neutral connection terminal A2 can also be grounded, but this is not a limitation.
[0042] The second aspect of this application provides a photovoltaic grid-connected circuit. Figure 6This is a schematic diagram of the structure of a photovoltaic grid-connected circuit provided in an embodiment of this application, as shown below. Figure 6 As shown, the photovoltaic grid-connected circuit includes a Boost mirror circuit 30 and a grid-side inverter 41.
[0043] The DC input terminal of the Boost mirror circuit 30 is configured to connect to the photovoltaic DC system 20. The Boost mirror circuit 30 also has a DC output terminal and a first neutral connection terminal A1. The Boost mirror circuit 30 is configured to boost the electrical energy output from the photovoltaic DC system 20.
[0044] The DC input terminal of the grid-side inverter 41 is connected to the DC output terminal of the Boost mirror circuit 30. The grid-side inverter 41 also has a second neutral connection terminal A2, which is connected to the first neutral connection terminal A1. The voltage on the second neutral connection terminal A2 is the earth balance voltage. The AC output terminal of the grid-side inverter 41 is configured to be connected to the power grid 51.
[0045] In some embodiments, the Boost mirror circuit 30 includes two Boost branches 31. Each Boost branch 31 includes a capacitor, an inductor, a switching device, and a diode. The capacitors in the two Boost branches 31 are connected together, and one end of the capacitors in the two Boost branches 31 is connected to a first neutral connection terminal A1. The switching devices in the two Boost branches 31 are connected, and one end of the switching devices in the two Boost branches 31 is connected to the first neutral connection terminal. In one Boost branch 31, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the first terminal of the switching device and the anode of the diode, respectively. The cathode of the diode is connected to the DC output terminal of the Boost mirror circuit 30. In the other Boost branch 31, one end of the capacitor is connected to one end of the inductor, and the other end of the inductor is connected to the second terminal of the switching device and the cathode of the diode, respectively. The anode of the diode is connected to the DC output terminal of the Boost mirror circuit 30. One end of the capacitor in one Boost branch 31 is connected to the other end of the capacitor in another Boost branch 31, and the second end of the switching device in one Boost branch 31 is connected to the first end of the switching device in another Boost branch 31. The switching devices in one Boost branch 31 and the switching devices in the other Boost branch 31 are switched on and off synchronously.
[0046] For example, Figure 7 This is a schematic diagram of the structure of a photovoltaic grid-connected circuit provided in another embodiment of this application, as shown below. Figure 7 As shown, the structure of the Boost mirror circuit 30 can be found in [reference needed]. Figure 5The structure and related descriptions of the intermediate mirror circuit 30 will not be repeated here. The grid-side inverter 41 may include capacitor C3, capacitor C4, diode D3, diode D4, and multiple switching devices.
[0047] Multiple switching devices can be connected in series. Diodes D3 and D4 are connected in series, with the anode of diode D3 connected to the cathode of diode D4. The series-connected diodes D3 and D4 are then connected in parallel with several intermediate switching devices. One end of capacitor C3 is connected to the cathode of diode D1 in the Boost mirror circuit 30, the positive terminal of the DC input of the grid-side inverter 41, and the first terminal of one switching device in the grid-side inverter 41. The first terminal of the switching device in the grid-side inverter 41 connected to capacitor C3 is connected to the positive terminal of the DC input of the grid-side inverter 41. One end of capacitor C4 is connected to the anode of diode D2 in the Boost mirror circuit 30, the negative terminal of the DC input of the grid-side inverter 41, and the second terminal of another switching device in the grid-side inverter 41. The second terminal of the switching device in the grid-side inverter 41 connected to capacitor C4 is connected to the negative terminal of the DC input of the grid-side inverter 41. The other end of capacitor C3 is connected to the other end of capacitor C4, and the anode of diode D3 is connected to the cathode of diode D4. The other ends of capacitor C3, capacitor C4, the anode of diode D3, and the cathode of diode D4 are connected to the second neutral terminal A2. The other ends of capacitors C1, C2, C3, and C4 are interconnected.
[0048] The specific details of the Boost mirror circuit 30, the grid-side inverter 41, and the photovoltaic DC system 20 in the photovoltaic grid-connected circuit can be found in the relevant descriptions in the above embodiments, and will not be repeated here. All implementation methods in the above embodiments of the integrated wind and solar power system are applicable to the above embodiments of the photovoltaic grid-connected circuit and can achieve the same technical effects.
[0049] It should be clarified that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. This application is not limited to the specific structures described above and shown in the figures. Those skilled in the art can make various changes, modifications, and additions after understanding the spirit of this application. Furthermore, for the sake of brevity, detailed descriptions of known technologies are omitted here.
[0050] Those skilled in the art will understand that the above embodiments are exemplary and not restrictive. Different technical features appearing in different embodiments can be combined to achieve beneficial effects. Based on a study of the drawings, specification, and claims, those skilled in the art should be able to understand and implement other variations of the disclosed embodiments. In the claims, the term "comprising" does not exclude other devices; the quantifier "a" does not exclude a plurality; the terms "first" and "second" are used to identify names and not to indicate any specific order. Any reference numerals in the claims should not be construed as limiting the scope of protection. The appearance of certain technical features in different dependent claims does not mean that these technical features cannot be combined to achieve beneficial effects.
Claims
1. A wind-solar hybrid power system, characterized in that, The wind-solar integrated power system comprises: a photovoltaic direct-current system comprising a photovoltaic device; a Boost mirror circuit, a direct-current input end of the Boost mirror circuit being connected with a direct-current output end of the photovoltaic direct-current system, the Boost mirror circuit further having a direct-current output end and a first neutral connection end, the Boost mirror circuit being configured to boost the electrical energy output by the photovoltaic direct-current system; wherein the Boost mirror circuit comprises two Boost branches, the two Boost branches forming a mirror structure; each of the Boost branches comprises a capacitor, an inductor, a switching device and a diode, the capacitors in the two Boost branches being connected together, one end of the connected capacitors being connected with the first neutral connection end, the switching devices in the two Boost branches being connected together, one end of the connected switching devices being connected with the first neutral connection end; a wind turbine comprising a grid-side inverter, a direct-current input end of the grid-side inverter being connected with a direct-current output end of the Boost mirror circuit, the grid-side inverter further having a second neutral connection end, the second neutral connection end being connected with the first neutral connection end, a voltage on the second neutral connection end being a ground balance voltage, an alternating-current output end of the grid-side inverter being configured to be connected with a power grid.
2. The wind-solar hybrid power system according to claim 1, wherein, The photovoltaic device comprises a photovoltaic power generation unit and a direct-current / direct-current converter. The photovoltaic power generation unit is connected with a direct-current input end of the direct-current / direct-current converter, a direct-current output end of the direct-current / direct-current converter is connected with a direct-current input end of the Boost mirror circuit, and a direct-current output end of the Boost mirror circuit is connected with a direct-current input end of the grid-side inverter through a direct-current bus of the grid-side inverter.
3. The wind-solar hybrid power system according to claim 1, wherein, The photovoltaic direct-current system comprises a plurality of photovoltaic devices, the plurality of photovoltaic devices being connected with a direct-current collection line, and the direct-current collection line being connected with a direct-current input end of the Boost mirror circuit.
4. The wind-solar integrated power system according to claim 1, wherein in one of the Boost branches, one end of the capacitor is connected with one end of the inductor, the other end of the inductor is connected with a first end of the switching device and an anode of the diode respectively, and a cathode of the diode is connected with the direct-current output end of the Boost mirror circuit; in the other of the Boost branches, one end of the capacitor is connected with one end of the inductor, the other end of the inductor is connected with a second end of the switching device and a cathode of the diode respectively, and an anode of the diode is connected with the direct-current output end of the Boost mirror circuit; the other end of the capacitor in one of the Boost branches is connected with the other end of the capacitor in the other of the Boost branches, and the second end of the switching device in one of the Boost branches is connected with the first end of the switching device in the other of the Boost branches.
5. The wind-solar integrated power system according to claim 1 or 4, characterized in that, The switching devices in one of the Boost branches and the switching devices in the other of the Boost branches are synchronously turned on and turned off.
6. A photovoltaic grid-tie circuit, characterized by The wind-solar integrated power system comprises: The Boost mirror circuit has a direct current input end configured to be connected with a photovoltaic direct current system, and has a direct current output end and a first neutral connection end, and is configured to boost and output the electric energy output by the photovoltaic direct current system; wherein the Boost mirror circuit comprises two Boost branches, and the two Boost branches form a mirror structure; each Boost branch comprises a capacitor, an inductor, a switching device and a diode, the capacitors in the two Boost branches are connected together, and one end of the connection is connected with the first neutral connection end, the switching devices in the two Boost branches are connected together, and one end of the connection is connected with the first neutral connection end; a grid-side inverter, a direct current input end of the grid-side inverter is connected with the direct current output end of the Boost mirror circuit, the grid-side inverter further has a second neutral connection end, the second neutral connection end is connected with the first neutral connection end, the voltage on the second neutral connection end is a ground balance voltage, and an alternating current output end of the grid-side inverter is configured to be connected with a power grid.
7. The photovoltaic grid-connected circuit according to claim 6, characterized in that, in one of the Boost branches, one end of the capacitor is connected with one end of the inductor, the other end of the inductor is connected with the first end of the switching device and the anode of the diode respectively, the cathode of the diode is connected with the direct current output end of the Boost mirror circuit; in the other Boost branch, one end of the capacitor is connected with one end of the inductor, the other end of the inductor is connected with the second end of the switching device and the cathode of the diode respectively, and the anode of the diode is connected with the direct current output end of the Boost mirror circuit; the other end of the capacitor in one Boost branch is connected with the other end of the capacitor in the other Boost branch, and the second end of the switching device in one Boost branch is connected with the first end of the switching device in the other Boost branch.
8. Photovoltaic grid-connected circuit according to claim 6 or 7, characterized in that, the switching device in one Boost branch is synchronously turned on and turned off with the switching device in the other Boost branch.