Converter for grid connection of new energy, control method and electronic equipment

Abstract

The application discloses a new energy grid-connected converter, a control method and electronic equipment. The converter comprises: a plurality of phase line conversion modules, the input ends of different phase line conversion modules are connected with different alternating current output phase lines of a new energy end, the output ends of different phase line conversion modules are connected with different alternating current input phase lines of a power grid, the phase line conversion module comprises a plurality of conversion sub-modules, the first input ends of different conversion sub-modules in the same phase line conversion module are connected with the same alternating current output phase line of different new energy ends, and the plurality of conversion sub-modules in the same phase line conversion module are connected in cascade; and a controller is used for superimposing voltage on initial alternating current output by the new energy end to obtain target alternating current, and integrating the target alternating current into the power grid. The application solves the technical problems of high complexity and cost of the converter for new energy grid connection in the related art, and high complexity of the control process for new energy grid connection.

Description

Technical Field

[0001] This invention relates to the fields of new energy technology and power systems, and more specifically, to a converter, control method, and electronic equipment for grid-connected new energy sources. Background Technology

[0002] With the rapid development of new energy power generation such as solar and wind power, the integration of a high proportion of new energy into the power grid is gradually becoming a development trend, posing technical challenges to the stability and reliability of traditional grid connection control. The intermittency and volatility of new energy power generation, such as the impact of varying sunlight on photovoltaic systems, can lead to unstable output power, making direct grid synchronization difficult and prone to voltage collapse and frequency instability. Current grid connection schemes often use multi-stage transformers to amplify and boost voltage, increasing the complexity, cost, and losses of converters. This makes it difficult to avoid the high cost and control complexity of power devices, resulting in high complexity and cost of converters used for new energy grid connection, as well as high complexity in the control process.

[0003] There is currently no effective solution to the above problems. Summary of the Invention

[0004] This invention provides a converter, control method, and electronic device for grid connection of new energy sources, which at least solves the technical problems of high complexity and cost of converters used for grid connection of new energy sources, and high complexity of the control process for grid connection of new energy sources in related technologies.

[0005] According to one aspect of the embodiments of this application, a converter for grid connection of new energy sources is provided, comprising: multiple phase-line converter modules, wherein the input terminals of different phase-line converter modules are connected to different AC output phase lines of the new energy source, the output terminals of different phase-line converter modules are connected to different AC input phase lines of the power grid, each phase-line converter module includes multiple converter sub-modules, the first input terminals of different converter sub-modules in the same phase-line converter module are connected to the same AC output phase line of different new energy sources, multiple converter sub-modules in the same phase-line converter module are cascaded, and the output terminal of the first converter sub-module in the same phase-line converter module is connected to the second input terminal of the next converter sub-module; the same phase-line converter module is connected to the first converter sub-module in the same phase-line converter module. The second input terminal of the intermediate converter submodule in the converter module is connected to the output terminal of the previous converter submodule, and the output terminal of the intermediate converter submodule is connected to the second input terminal of the next converter submodule; the second input terminal of the last converter submodule in the same phase line converter module is connected to the output terminal of the previous converter module, and the output terminal of the last converter submodule in different phase line converter modules is connected to the corresponding AC input phase line of the power grid; the controller is connected to the control terminal of the switching transistor in the converter submodule and is used to control the on / off state of the switching transistor in the converter submodule to superimpose the voltage of the initial AC power output from the new energy source to obtain the target AC power, and then connect the target AC power into the power grid.

[0006] In this embodiment of the invention, the converter submodule includes: a first bridge arm, a first end of which is connected to a first DC bus, a second end of which is connected to a second DC bus, and a third end of which is connected to a first input terminal of the converter submodule; a second bridge arm, a first end of which is connected to the first DC bus, a second end of which is connected to the second DC bus, and a third end of which is connected to a second input terminal of the converter submodule; and a third bridge arm, a first end of which is connected to the first DC bus, a second end of which is connected to the second DC bus, and a third end of which is connected to an output terminal of the converter submodule.

[0007] In this embodiment of the invention, any one of the first bridge arm, the second bridge arm, and the third bridge arm comprises: a first switch, the output of which is connected to a first end of the target bridge arm, and a reference ground of which is connected to a third end of the target bridge arm; a second switch, the output of which is connected to a third end of the target bridge arm, and a reference ground of which is connected to a second end of the target bridge arm; and a controller, connected to the control terminals of the first and second switches, for controlling the on / off states of the first and second switches.

[0008] In this embodiment of the invention, the converter submodule further includes: an energy storage unit, the positive terminal of which is connected to a first DC bus, and the negative terminal of which is connected to a second DC bus; and a filter capacitor, one end of which is connected to the first DC bus, and the other end of which is connected to the second DC bus.

[0009] According to another aspect of the embodiments of this application, a converter control method for grid-connected new energy is also provided, applied to the aforementioned grid-connected new energy converter, comprising: acquiring a first operating state parameter of the new energy terminal and a second operating state parameter of the power grid; based on the first operating state parameter and the second operating state parameter, controlling the on / off state of the switching transistors in a plurality of converter submodules in the converter to superimpose the voltages of the plurality of initial AC currents output from the new energy terminal to obtain a target AC current, and connecting the target AC current into the power grid.

[0010] In this embodiment of the invention, based on a first operating state parameter and a second operating state parameter, the on / off state of the switching transistors in multiple converter submodules in the converter is controlled to superimpose the voltages of multiple initial AC currents output from the new energy source to obtain a target AC current, and the target AC current is then connected to the power grid. This includes: generating a first pulse width modulation signal based on the first operating state parameter and generating a second pulse width modulation signal based on the second operating state parameter; controlling the on / off state of the switching transistors in the first and second bridge arms of the converter based on the first pulse width modulation signal to perform new energy-side inverter control and receive multiple initial AC currents; and controlling the on / off state of the switching transistors in the third and second bridge arms of the converter based on the second pulse width modulation signal to perform grid-side inverter control, superimposing the voltages of the multiple initial AC currents to obtain the target AC current, and then connecting the target AC current to the power grid.

[0011] In this embodiment of the invention, generating a first pulse width modulation signal based on a first operating state parameter includes: controlling the DC-to-AC converter at the new energy source end to be in power point tracking control mode; obtaining the converter output voltage in the first operating state parameter, wherein the converter output voltage is used to characterize the output voltage of the DC-to-AC converter; determining a voltage reference for performing inverter control on the new energy side based on the converter output voltage; and generating the first pulse width modulation signal based on the voltage reference using a new energy side modulation wave generation module of the converter.

[0012] In this embodiment of the invention, generating a second pulse width modulation signal based on a second operating state parameter includes: acquiring voltage and current parameters from the second operating state parameter, and active and reactive power references from the grid side of the converter; determining the active and reactive power demand of the grid based on the voltage and current parameters; and generating the second pulse width modulation signal based on the active power demand, reactive power demand, active power reference, and reactive power reference.

[0013] In this embodiment of the invention, the method further includes: controlling the switch in the third bridge arm to be in an off state within a first preset time period, and controlling the on / off state of the switches in the first bridge arm and the second bridge arm based on a first pulse width modulation signal; controlling the switch in the first bridge arm to be in an off state within a second preset time period, and controlling the on / off state of the switches in the third bridge arm and the second bridge arm based on a second pulse width modulation signal.

[0014] In this embodiment of the invention, the converter for grid-connected new energy sources includes: multiple phase-line converter modules, the input terminals of different phase-line converter modules are connected to different AC output phase lines of the new energy source, the output terminals of different phase-line converter modules are connected to different AC input phase lines of the power grid, each phase-line converter module includes multiple converter sub-modules, the first input terminals of different converter sub-modules in the same phase-line converter module are connected to the same AC output phase line of different new energy sources, multiple converter sub-modules in the same phase-line converter module are cascaded, and the output terminal of the first converter sub-module in the same phase-line converter module is connected to the second input terminal of the next converter sub-module; within the same phase-line converter module... The second input terminal of the intermediate converter submodule is connected to the output terminal of the previous converter submodule, and the output terminal of the intermediate converter submodule is connected to the second input terminal of the next converter submodule; the second input terminal of the last converter submodule in the same phase line converter module is connected to the output terminal of the previous converter module, and the output terminal of the last converter submodule in different phase line converter modules is connected to the corresponding AC input phase line of the power grid; the controller is connected to the control terminal of the switching transistor in the converter submodule, and is used to control the on / off state of the switching transistor in the converter submodule, so as to superimpose the voltage of the initial AC power output from the new energy terminal to obtain the target AC power, and then connect the target AC power into the power grid. The proposed topology of the renewable energy grid-connected converter includes multiple phase-line converter modules. Each phase-line converter module can contain multiple cascaded converter submodules, eliminating the need for multi-stage transformers, simplifying the grid connection topology, and reducing converter cost and footprint. This cascaded structure can effectively convert multiple lower-voltage renewable energy output AC power into higher-voltage AC power through superposition and cascading, enabling direct high-voltage grid connection to meet grid access standards. The controller in the renewable energy grid-connected converter can coordinate and control the on / off states of the switching transistors in each converter submodule, ensuring accurate superposition of the output voltage, improving the quality of grid-connected power, reducing energy loss and grid interference caused by voltage instability, enhancing the operational stability of the entire renewable energy grid-connected converter process, and ensuring continuity and safety during renewable energy grid connection. This solves the technical problems of high complexity and cost of converters used for renewable energy grid connection, as well as the high complexity of the control process for renewable energy grid connection in related technologies. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0016] Figure 1 This is a schematic diagram of a new energy grid-connected converter according to an embodiment of the present invention;

[0017] Figure 2 This is a schematic diagram of an optional new energy grid-connected converter according to an embodiment of the present invention;

[0018] Figure 3 This is a flowchart of a converter control method for grid connection of new energy sources according to an embodiment of the present invention;

[0019] Figure 4 This is a flowchart of an optional new energy inverter control process according to an embodiment of the present invention;

[0020] Figure 5 This is a flowchart of an optional grid-side inverter control process according to an embodiment of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of the present invention.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] According to an embodiment of this application, a converter for grid-connected new energy sources is provided. Figure 1 This is a schematic diagram of a grid-connected converter for new energy sources according to this application, as shown below. Figure 1As shown, the converter for grid connection of the new energy source includes: multiple phase line converter modules 102 and controller 104.

[0024] The system includes multiple phase-line converter modules 102. The input terminals of different phase-line converter modules are connected to different AC output phase lines of the new energy source 106, and the output terminals of different phase-line converter modules are connected to different AC input phase lines of the power grid 108. Each phase-line converter module includes multiple converter submodules 1022. The first input terminals of different converter submodules within the same phase-line converter module are connected to the same AC output phase line of different new energy sources. Multiple converter submodules within the same phase-line converter module are cascaded. The output terminal of the first converter submodule within the same phase-line converter module is connected to the second input terminal of the next converter submodule. The second input terminal of an intermediate converter submodule within the same phase-line converter module is connected to the output terminal of the previous converter submodule, and the output terminal of the intermediate converter submodule is connected to the second input terminal of the next converter submodule. The second input terminal of the last converter submodule within the same phase-line converter module is connected to the output terminal of the previous converter module. The output terminal of the last converter submodule among different phase-line converter modules is connected to the corresponding AC input phase line of the power grid.

[0025] The aforementioned phase line converter module can refer to a converter module that can superimpose the AC power output from multiple new energy sources and connect it to the AC power grid. For example, a three-phase AC power grid can be equipped with three phase line converter modules respectively.

[0026] The aforementioned new energy source can refer to various new energy power generation sources that can output alternating current, such as photovoltaic power generation sources.

[0027] The aforementioned power grid can refer to an AC power grid, or a three-phase AC power grid, etc.

[0028] The aforementioned converter submodules can refer to multiple converter units included in the phase line converter module. Multiple converter submodules in the phase line converter module can be connected one-to-one with multiple new energy terminals. Multiple converter submodules in the phase line converter module can be connected in a cascade manner to superimpose the voltage of the AC power output from multiple new energy sources and connect it to the AC power grid.

[0029] The first input terminal mentioned above can refer to the port where the converter module connects to the new energy source, and can receive the AC power output from the new energy source.

[0030] The aforementioned second input terminal can refer to the port where the converter submodule is connected to the previous converter submodule, and can receive the AC power superimposed on the previous converter submodule.

[0031] The first converter submodule mentioned above can refer to the starting converter submodule in the phase line converter module. The first converter submodule may not have a second input terminal.

[0032] The aforementioned intermediate converter submodules can refer to the other converter submodules in the phase line converter module besides the first and last converter submodules. The specific number of intermediate converter submodules can be determined according to actual needs.

[0033] The last converter submodule mentioned above can refer to the end converter submodule in the phase line converter module. The output terminal of the last converter submodule can be connected to the corresponding AC input phase line of the power grid.

[0034] In one optional embodiment, the topology of the renewable energy grid-connected converter may include multiple phase-line converter modules. The renewable energy grid-connected converter can adopt a three-phase or multi-phase design, with each phase containing a phase-line converter module composed of multiple cascaded converter submodules. The first input terminal of each converter submodule can be connected to the corresponding AC output phase line of the renewable energy source, and the output terminal of each converter submodule can be connected to the corresponding AC input phase line of the power grid. Within the same phase-line converter module, the output terminal of the first converter submodule is connected to the second input terminal of the next submodule, forming a cascaded connection, and so on until the last converter submodule. The output terminal of the last converter submodule can be connected to the AC input phase line of the power grid, achieving direct high-voltage grid connection. This cascaded structure can effectively convert multiple lower-voltage renewable energy output AC power into higher-voltage AC power through superposition and cascading to meet grid connection standards, while maintaining the quality and stability of grid-connected power.

[0035] In the above setup, the cascaded design of converter submodules enables the superposition of output voltages without the need for multiple transformer stages. This simplifies the grid connection topology, reduces converter costs and footprint, and also minimizes energy losses during power conversion, improving system efficiency. The number of cascaded converter submodules can be increased or decreased, allowing converters for renewable energy grid connection to flexibly adjust output voltage levels and power handling capabilities to adapt to the grid connection needs of renewable energy plants of different sizes, achieving direct high-voltage grid connection and providing technical support for the grid-connected operation of large-scale renewable energy power generation systems.

[0036] The controller 104 is connected to the control terminal of the switching transistor in the converter submodule. It is used to control the on / off state of the switching transistor in the converter submodule so as to superimpose the voltage of the initial AC power output from the new energy terminal to obtain the target AC power and then connect the target AC power into the power grid.

[0037] The aforementioned initial AC power can refer to the AC power output from the new energy source. Multiple new energy sources can each correspond to multiple initial AC power sources.

[0038] The aforementioned target AC power can refer to the AC power obtained by superimposing the initial AC power output from the new energy source through the phase line converter module, which can then be connected to the power grid.

[0039] In one optional embodiment, the controller in the renewable energy grid-connected converter can coordinate and control the on / off states of the switching transistors in each converter submodule. The controller's design and functionality can be used for power conversion and improvement at the renewable energy end, and can ensure stable grid connection. By connecting to the control terminals of the switching transistors in the converter submodule, the controller can dynamically adjust the on and off times of each transistor to precisely control the power conversion process. The controller's control mechanism can be based on real-time monitoring of the initial AC output from the renewable energy end, and can utilize pulse width modulation signals to control the switching actions of the transistors, enabling the converter submodule to invert AC power and perform voltage superposition.

[0040] In the above configuration, the controller precisely controls the on / off times of the switching transistors in each converter submodule to ensure accurate superposition of the output voltage of the converter for new energy grid connection, improving the quality of grid-connected power and reducing energy loss and grid interference caused by voltage instability. The controller supports grid-connected operation and can autonomously build and maintain stable voltage and frequency, ensuring efficient absorption of new energy and stable grid operation even under conditions of uneven sunlight or grid fluctuations. By coordinating the switching actions of the transistors in each converter submodule, the controller effectively prevents and suppresses converter oscillations, improving the operational stability of the entire new energy grid-connected power conversion process and ensuring continuity and safety during grid connection.

[0041] In this embodiment of the invention, the converter for grid-connected new energy sources includes: multiple phase-line converter modules, the input terminals of different phase-line converter modules are connected to different AC output phase lines of the new energy source, the output terminals of different phase-line converter modules are connected to different AC input phase lines of the power grid, each phase-line converter module includes multiple converter sub-modules, the first input terminals of different converter sub-modules in the same phase-line converter module are connected to the same AC output phase line of different new energy sources, multiple converter sub-modules in the same phase-line converter module are cascaded, and the output terminal of the first converter sub-module in the same phase-line converter module is connected to the second input terminal of the next converter sub-module; within the same phase-line converter module... The second input terminal of the intermediate converter submodule is connected to the output terminal of the previous converter submodule, and the output terminal of the intermediate converter submodule is connected to the second input terminal of the next converter submodule; the second input terminal of the last converter submodule in the same phase line converter module is connected to the output terminal of the previous converter module, and the output terminal of the last converter submodule in different phase line converter modules is connected to the corresponding AC input phase line of the power grid; the controller is connected to the control terminal of the switching transistor in the converter submodule, and is used to control the on / off state of the switching transistor in the converter submodule, so as to superimpose the voltage of the initial AC power output from the new energy terminal to obtain the target AC power, and then connect the target AC power into the power grid. The proposed topology of the renewable energy grid-connected converter includes multiple phase-line converter modules. Each phase-line converter module can contain multiple cascaded converter submodules, eliminating the need for multi-stage transformers, simplifying the grid connection topology, and reducing converter cost and footprint. This cascaded structure can effectively convert multiple lower-voltage renewable energy output AC power into higher-voltage AC power through superposition and cascading, enabling direct high-voltage grid connection to meet grid access standards. The controller in the renewable energy grid-connected converter can coordinate and control the on / off states of the switching transistors in each converter submodule, ensuring accurate superposition of the output voltage, improving the quality of grid-connected power, reducing energy loss and grid interference caused by voltage instability, enhancing the operational stability of the entire renewable energy grid-connected converter process, and ensuring continuity and safety during renewable energy grid connection. This solves the technical problems of high complexity and cost of converters used for renewable energy grid connection, as well as the high complexity of the control process for renewable energy grid connection in related technologies.

[0042] In this embodiment of the invention, the converter submodule includes: a first bridge arm, a first end of which is connected to a first DC bus, a second end of which is connected to a second DC bus, and a third end of which is connected to a first input terminal of the converter submodule; a second bridge arm, a first end of which is connected to the first DC bus, a second end of which is connected to the second DC bus, and a third end of which is connected to a second input terminal of the converter submodule; and a third bridge arm, a first end of which is connected to the first DC bus, a second end of which is connected to the second DC bus, and a third end of which is connected to an output terminal of the converter submodule.

[0043] The first bridge arm mentioned above can refer to the bridge arm in the converter submodule that is closer to the new energy source. The third end of the first bridge arm can be connected to the first input end of the converter submodule to realize the connection with the AC output phase line of the new energy source.

[0044] The aforementioned second bridge arm can refer to the bridge arm located between the first and third bridge arms in the converter submodule, and in this application, it can be used as a shared bridge arm for the inverter control on the new energy side and the inverter control on the grid side.

[0045] The aforementioned third bridge arm can refer to the bridge arm in the converter submodule that is closest to the grid end. The third end of the third bridge arm can be connected to the output end of the converter submodule to realize the connection with the AC input phase line corresponding to the grid.

[0046] In one optional embodiment, the converter submodule can consist of three bridge arms, including a first bridge arm, a second bridge arm, and a third bridge arm, to realize energy conversion and control for grid-connected renewable energy. Specifically, in each converter submodule, the first end of the first bridge arm can be connected to a first DC bus, the second end of the first bridge arm can be connected to a second DC bus, and the third end of the first bridge arm can be connected to the first input terminal of the converter submodule. The first bridge arm can directly act on the renewable energy side; by controlling the switching transistor within the first bridge arm, it can achieve inversion of the input AC power, facilitating subsequent voltage superposition and energy conversion. The first end of the second bridge arm can be connected to the first DC bus, the second end of the second bridge arm can be connected to the second DC bus, and the third end of the second bridge arm can be connected to the second input terminal of the converter submodule. In this application, the first and second bridge arms can jointly constitute an inverter unit on the renewable energy side, realizing the inversion of the input AC power from the renewable energy side and performing preliminary power regulation. The first end of the third bridge arm can be connected to the first DC bus, the second end of the third bridge arm can be connected to the second DC bus, and the third end of the third bridge arm can be connected to the output terminal of the converter submodule. In this application, the third bridge arm and the second bridge arm can jointly constitute the grid-side inverter unit, which can invert the processed electrical energy into the target AC power to meet grid connection requirements. By reusing the third bridge arm with the second bridge arm, efficient support for both the renewable energy-side inverter unit and the grid-connected inverter unit is achieved.

[0047] In the above configuration, the bridge arm design of the converter submodule utilizes the potential difference between the first and second DC buses. By controlling the on and off states of the switching transistors in the converter submodule, it achieves the inversion of the input AC power and the grid connection of the output AC power, providing a foundation for the efficient operation of the renewable energy grid-connected converter. Through this bridge arm design, the converter submodule can efficiently convert AC power from the renewable energy side into DC power, and then invert it into AC power that meets grid requirements, minimizing losses during the energy conversion process. The reuse mechanism of the second bridge arm reduces the number of switching transistors in the converter submodule, lowers costs, and enables independent control of the renewable energy side and the grid-connected side. This resolves control conflicts when the converter submodule is reused between the two inverters, enhancing the overall performance of the renewable energy grid-connected converter.

[0048] In this embodiment of the invention, any one of the first bridge arm, the second bridge arm, and the third bridge arm comprises: a first switch, the output of which is connected to a first end of the target bridge arm, and a reference ground of which is connected to a third end of the target bridge arm; a second switch, the output of which is connected to a third end of the target bridge arm, and a reference ground of which is connected to a second end of the target bridge arm; and a controller, connected to the control terminals of the first and second switches, for controlling the on / off states of the first and second switches.

[0049] The aforementioned reference ground can refer to the emitter or source of the switching transistor, which can be determined according to the specific type of the switching transistor. For example, the specific type of transistor can be a bipolar transistor, a field-effect transistor, or an insulated-gate bipolar transistor.

[0050] The aforementioned output terminal can refer to the collector or drain of the switching transistor, which can be determined based on the specific type of the switching transistor.

[0051] In one optional embodiment, the bridge arm structure in the converter submodule, through the combination of a first and a second switching transistor and the control of a controller, can realize the function of a new energy grid-connected converter. In any of the first, second, and third target bridge arms, the output terminal of the first switching transistor can be connected to the first end of the target bridge arm, and the reference ground terminal of the first switching transistor can be connected to the third end of the target bridge arm; the output terminal of the second switching transistor can be connected to the third end of the target bridge arm, and the reference ground terminal of the second switching transistor can be connected to the second end of the target bridge arm. This switching transistor configuration enables the target bridge arm to achieve bidirectional conversion between DC and AC, that is, it can realize the inversion process from DC to AC and the rectification process from AC to DC. The controller can be connected to the control terminals of the first and second switching transistors, and the controller can control the on / off state of the first and second switching transistors by sending control signals. The control strategy can be based on pulse width modulation and time-division multiplexing strategies, which can accurately adjust the conduction time of each switching transistor, thereby controlling the voltage and current waveforms output by the bridge arm to adapt to the power quality required for new energy grid connection.

[0052] In the above configuration, through the designed switching transistor connection method, the converter submodule can convert renewable energy into target AC power suitable for grid connection with minimal losses, improving the efficiency of power conversion. Precise control by the controller ensures that the target bridge arm maintains stable output voltage and current under various operating conditions, guaranteeing smooth grid connection of renewable energy and preventing grid connection failure or converter oscillation due to unstable power quality. The simplified design of the first and second switching transistors reduces the number of required power switching devices. Through the aforementioned bridge arm design, power processing on the renewable energy side and the grid connection side is decoupled, allowing each bridge arm to independently handle fluctuations on the renewable energy side or changes in demand on the grid connection side, increasing the response speed and adjustment flexibility of the conversion process.

[0053] In this embodiment of the invention, the converter submodule further includes: an energy storage unit, the positive terminal of which is connected to a first DC bus, and the negative terminal of which is connected to a second DC bus; and a filter capacitor, one end of which is connected to the first DC bus, and the other end of which is connected to the second DC bus.

[0054] The aforementioned energy storage unit can refer to an energy storage unit designed to smooth out power fluctuations at the renewable energy source and ensure relatively stable power output to the converter.

[0055] The aforementioned filter capacitors can refer to filter capacitors installed to improve the voltage quality of the first DC bus and the second DC bus, reduce voltage ripple and high-frequency noise, and ensure the voltage stability of the first DC bus and the second DC bus.

[0056] In an optional embodiment, the converter submodule may also include an energy storage unit and a filter capacitor. The integration of the energy storage unit and the filter capacitor enhances the adaptability to input power fluctuations and improves the quality of the DC bus voltage, providing favorable conditions for power conversion. Specifically, the positive terminal of the energy storage unit can be connected to the first DC bus, and the negative terminal can be connected to the second DC bus, allowing the energy storage unit to intervene in the DC bus stage of the converter submodule, acting as an energy buffer. When the power supply from the renewable energy source exceeds demand, the excess power can be charged into the energy storage unit for temporary storage; when the power supply is insufficient, the energy storage unit can discharge to fill the instantaneous power gap, achieving a dynamic balance between power supply and demand. One end of the filter capacitor can be connected to the first DC bus, and the other end can be connected to the second DC bus. The filter capacitor is positioned between the first and second DC buses of the converter submodule. The filter capacitor filters the DC bus, eliminating voltage ripple generated during current conversion and ensuring the stability of the DC bus voltage.

[0057] In the above configuration, the converter submodule integrates an energy storage unit and a filter capacitor. The energy storage unit can respond to power fluctuations, absorbing or releasing electrical energy, effectively smoothing the intermittency and volatility of new energy power generation, ensuring continuous and stable power delivery to the grid, and enhancing the grid-connected converter's grid-connection capability. The filter capacitor eliminates DC bus voltage ripple, ensuring DC bus voltage stability and helping to improve the converter's inverter efficiency and power quality. Through the integration of the energy storage unit and the filter capacitor, the converter submodule gains greater control flexibility, enabling more precise adjustment of grid voltage and power output to adapt to different grid connection conditions and operating states.

[0058] Figure 2 This is a schematic diagram of an optional new energy grid-connected converter according to an embodiment of the present invention, such as... Figure 2As shown, the converter for grid-connected new energy sources includes: three phase-line converter modules, namely phase A, phase B, and phase C. Each phase-line converter module includes multiple converter sub-modules. The first input terminals of different converter sub-modules within the same phase-line converter module are connected to the same AC output phase line of different new energy sources via a DC / AC converter. Multiple converter sub-modules within the same phase-line converter module are cascaded. The output terminal of the first converter sub-module within the same phase-line converter module is connected to the second input terminal of the next converter sub-module. The second input terminal of an intermediate converter sub-module within the same phase-line converter module is connected to the output terminal of the previous converter sub-module, and the output terminal of the intermediate converter sub-module is connected to the second input terminal of the next converter sub-module. The second input terminal of the last converter sub-module within the same phase-line converter module is connected to the output terminal of the previous converter module. The output terminal of the last converter sub-module in different phase-line converter modules is connected to the corresponding AC input phase line of the power grid. Figure 2 As shown, the converter submodule includes: a first bridge arm, which can be any one of A1a, A2a...Ana in the figure, with its first end connected to the first DC bus, its second end connected to the second DC bus, and its third end connected to the first input terminal of the converter submodule; a second bridge arm, which can be A1b, A2b...Anb in the figure and the second bridge arm of the corresponding first bridge arm in the same converter submodule, with its first end connected to the first DC bus, its second end connected to the second DC bus, and its third end connected to the second input terminal of the converter submodule; and a third bridge arm, which can be A1c, A2c...Anc in the figure and the third bridge arm of the corresponding first bridge arm in the same converter submodule, with its first end connected to the first DC bus, its second end connected to the second DC bus, and its third end connected to the output terminal of the converter submodule.

[0059] like Figure 2As shown, any one of the first, second, and third bridge arms includes: a first switch Q1, whose output is connected to the first end of the target bridge arm, and whose reference ground is connected to the third end of the target bridge arm; a second switch Q2, whose output is connected to the third end of the target bridge arm, and whose reference ground is connected to the second end of the target bridge arm. The converter submodule also includes: an energy storage unit B, whose positive terminal "+" is connected to the first DC bus, and whose negative terminal "-" is connected to the second DC bus; and a filter capacitor C1, one end of which is connected to the first DC bus, and the other end of which is connected to the second DC bus. The converter submodule also includes: an inductor L, one end of which is connected to the first input terminal of the converter submodule, and the other end of which is connected to the third end of the first bridge arm; and a capacitor C2, one end of which is connected to the first input terminal of the converter submodule, and the other end of which is connected to the third end of the second bridge arm.

[0060] Figure 3 This is a flowchart of a converter control method for grid-connected new energy sources according to an embodiment of this application, applied to the aforementioned grid-connected new energy converter, such as... Figure 3 As shown, the method includes the following steps:

[0061] Step S302: Obtain the first operating status parameters of the new energy source and the second operating status parameters of the power grid.

[0062] The aforementioned first operating status parameter can refer to the operating status parameters of the new energy source, which may include, but are not limited to, the voltage, current, power, temperature, and power point tracking status of the new energy source. The first operating status parameter can be used to guide the converter in improving the inverter operation on the new energy side, ensuring the efficiency and reliability of the current conversion process.

[0063] The aforementioned second operating status parameter can refer to the operating status parameters on the grid side, which may include, but are not limited to, grid voltage, grid current, frequency, and phase angle. The second operating status parameter can provide the controller with information about the grid's operating status, enabling adjustments to the converter's output to meet grid stability and quality requirements.

[0064] Step S304: Based on the first operating state parameters and the second operating state parameters, control the on / off state of the switching transistors in multiple converter submodules in the converter to superimpose the voltages of multiple initial AC power outputs from the new energy terminal to obtain the target AC power, and then connect the target AC power into the power grid.

[0065] In one optional embodiment, the switching states of multiple converter submodules in the converter can be dynamically adjusted based on real-time acquired first and second operating state parameters to achieve efficient conversion of renewable energy and stable grid connection. The real-time status of the renewable energy source is continuously read and analyzed, including, but not limited to, the output voltage and current of the photovoltaic array, and environmental conditions such as light intensity, to form the first operating state parameters and assess the availability and power output characteristics of the renewable energy source. Operating information from the grid side, such as grid voltage, current, frequency, and phase, as well as the grid's active and reactive power demands, can be collected to form the second operating state parameters, providing guidance for the converter's output regulation. Based on the first operating state parameters, the controller uses a power point tracking algorithm to determine the operating point suitable for the current light or wind speed conditions, generating a corresponding pulse width modulation signal to control the switching of the inverter unit on the renewable energy side, ensuring efficient utilization of the renewable energy source. Based on the second operating state parameters, a grid synchronization control strategy can be adopted to generate another set of pulse width modulation signals, adjusting the switching of the inverter units on the grid-connected side to match the voltage and frequency of the converter output with grid conditions, while simultaneously providing active and reactive power support to the grid. By controlling the switching states of each converter submodule, multiple initial AC currents from renewable energy sources can be collaboratively superimposed to generate the target AC current. The output voltages of multiple converter submodules are superimposed on the grid-connected side, ultimately matching the grid voltage to achieve stable grid connection.

[0066] In the above process, based on the real-time monitoring of the operating status of the new energy source and the grid, the converter can quickly respond to changes in the new energy source and the grid. The converter is connected in parallel with the grid through voltage superposition, which reduces the loss in the power conversion process and improves the overall efficiency of the conversion process.

[0067] In this embodiment of the invention, based on a first operating state parameter and a second operating state parameter, the on / off state of the switching transistors in multiple converter submodules in the converter is controlled to superimpose the voltages of multiple initial AC currents output from the new energy source to obtain a target AC current, and the target AC current is then connected to the power grid. This includes: generating a first pulse width modulation signal based on the first operating state parameter and generating a second pulse width modulation signal based on the second operating state parameter; controlling the on / off state of the switching transistors in the first and second bridge arms of the converter based on the first pulse width modulation signal to perform new energy-side inverter control and receive multiple initial AC currents; and controlling the on / off state of the switching transistors in the third and second bridge arms of the converter based on the second pulse width modulation signal to perform grid-side inverter control, superimposing the voltages of the multiple initial AC currents to obtain the target AC current, and then connecting the target AC current to the power grid.

[0068] The aforementioned inverter control on the new energy side can refer to the control operation of the converter at the new energy end to convert mismatched AC power into AC power suitable for grid connection or stable AC power output. It can include improved control on the input side of the converter to ensure that the AC power output from the new energy end can be efficiently converted and utilized.

[0069] The aforementioned grid-side inverter control refers to the control operation of the converter at the grid connection end, which shapes the inverted AC power to the voltage, frequency and phase required by the grid for grid connection, and can provide active power support and reactive power support to the grid to maintain the stable operation of the grid.

[0070] In one optional embodiment, the controller can generate a first pulse width modulation (PWM) signal based on a first operating state parameter. Subsequently, the controller can use the generated PWM signal to precisely control the on / off states of the switches of the first and second bridge arms in the renewable energy-side inverter unit, enabling the reception and inversion of multiple initial AC currents, ensuring the power quality after inversion and a large power output from the renewable energy source. The controller can also generate a second PWM signal based on a second operating state parameter. The generation of the second PWM signal can take into account the real-time operating state and power demand of the grid, thereby improving the switch control strategy of the grid-connected inverter unit. The controller can use the second PWM signal to control the on / off states of the switches of the third and second bridge arms in the grid-connected inverter unit, superimposing the voltages of multiple initial AC currents to form a target AC current matching the grid, achieving efficient grid connection of renewable energy.

[0071] In the above process, inverter control on the renewable energy side ensures that the renewable energy source operates at a higher power point, thereby maximizing energy capture efficiency. The grid-side inverter control strategy guarantees the matching of inverter power with grid conditions, reducing shocks and fluctuations during grid connection and enhancing grid stability and reliability. By independently controlling the inverter processes on the renewable energy and grid sides, power decoupling is achieved, effectively addressing the fluctuations in renewable energy output.

[0072] In this embodiment of the invention, generating a first pulse width modulation signal based on a first operating state parameter includes: controlling the DC-to-AC converter at the new energy source end to be in power point tracking control mode; obtaining the converter output voltage in the first operating state parameter, wherein the converter output voltage is used to characterize the output voltage of the DC-to-AC converter; determining a voltage reference for performing inverter control on the new energy side based on the converter output voltage; and generating the first pulse width modulation signal based on the voltage reference using a new energy side modulation wave generation module of the converter.

[0073] The aforementioned DC-to-AC converter refers to a converter used to convert DC power generated by new energy equipment such as photovoltaic arrays or wind turbines into initial AC power. The DC-to-AC converter can be located at the port connecting the new energy source and the converter submodule.

[0074] The aforementioned voltage reference can refer to the reference voltage setting value used for inverter control on the renewable energy side. The voltage reference can be obtained by calculation and adjustment based on the output voltage of the DC-to-AC converter, and is used to guide the voltage output of the renewable energy side inverter unit.

[0075] The aforementioned converter new energy side modulation wave generation module can refer to the modulation wave generation module responsible for generating the first pulse width modulation signal based on the voltage reference.

[0076] In one optional embodiment, the DC-to-AC converter at the renewable energy source can be controlled to operate in power point tracking mode to adapt to the fluctuations at the renewable energy source and ensure that more energy is captured. The controller can continuously monitor the output voltage of the DC-to-AC converter, which reflects the actual status of renewable energy generation. Then, based on the converter output voltage, a suitable voltage reference can be determined to guide the inverter control on the renewable energy side. The voltage reference can be dynamically adjusted according to the grid demand and the renewable energy generation status. Next, the converter's renewable energy side modulation wave generation module can generate a modulation wave based on the voltage reference. This modulation wave can be compared with a carrier signal to generate a first pulse width modulation signal, which can be used to control the switching transistors of the first and second arms in the renewable energy side inverter unit.

[0077] Figure 4 This is a flowchart of an optional renewable energy inverter control process according to an embodiment of the present invention, such as... Figure 4 As shown, the method includes the following steps:

[0078] Step S402: Control the DC-to-AC converter on the new energy side to be in power tracking control mode and obtain the converter output voltage from the first operating state parameters; Step S404: Based on the converter output voltage, determine the voltage reference for new energy side inverter control; Step S406: Use the new energy side modulation wave generation module of the converter to generate a first pulse width modulation signal based on the voltage reference; Step S408: Based on the first pulse width modulation signal, control the on / off state of the switching transistors in the first and second bridge arms of the converter to perform new energy side inverter control and receive multiple initial AC currents.

[0079] In the above process, by controlling the DC-to-AC converter at the new energy end to operate in power point tracking mode, the new energy end can capture solar or wind energy at a higher power. Based on real-time output voltage monitoring and dynamically adjusted voltage reference, the controller can flexibly cope with the volatility and uncertainty of new energy power generation and maintain the stability and efficiency of the inverter process.

[0080] In this embodiment of the invention, generating a second pulse width modulation signal based on a second operating state parameter includes: acquiring voltage and current parameters from the second operating state parameter, and active and reactive power references from the grid side of the converter; determining the active and reactive power demand of the grid based on the voltage and current parameters; and generating the second pulse width modulation signal based on the active power demand, reactive power demand, active power reference, and reactive power reference.

[0081] The voltage parameters mentioned above can refer to the instantaneous voltage values ​​on the grid side, which can reflect the real-time status of the grid voltage and can be used to evaluate grid quality, stability, and the output matching degree of grid-connected converters.

[0082] The aforementioned current parameters can refer to the instantaneous current value on the grid side, which can reflect the load condition of the grid and help determine whether the grid is at risk of overload.

[0083] The aforementioned active power reference can refer to the active power target value of the converter on the grid side, which can reflect the active power level output by the converter on the grid side and can be set based on grid dispatching requirements.

[0084] The aforementioned reactive power reference can refer to the target value of reactive power of the converter on the grid side. It can be used to control the reactive power output of the converter on the grid side in order to maintain the voltage level at the grid connection point and avoid voltage fluctuations caused by insufficient reactive power.

[0085] The aforementioned active power demand refers to the active power value that the grid side needs to receive. It reflects the grid's immediate demand for electricity and can be used to guide the output adjustment of converters to maintain the power balance of the grid.

[0086] The aforementioned reactive power demand refers to the grid's demand for reactive power, which can be used to compensate for reactive power losses in the grid and maintain grid voltage stability.

[0087] In one optional embodiment, voltage and current parameters from the grid side, as well as active and reactive power references from the converter's grid side, can be collected in real time to provide a data foundation for subsequent control strategy calculations. Based on the monitored voltage and current parameters, the controller can determine the current active and reactive power demands of the grid through real-time calculations, including assessments of grid power balance and voltage stability. Then, the active power demand can be compared with the active power reference to generate corresponding control signals, adjusting the active power output of the converter to ensure grid power balance. Furthermore, by comparing the reactive power demand with the reactive power reference, the controller generates control signals to adjust the reactive power output of the converter, maintaining the voltage level at the grid connection point and providing the reactive power support required by the grid. Based on the above demand analysis and control strategy, the controller can generate a second pulse-width modulation signal to control the switching transistors of the third and second arms of the converter, adjusting the converter's output characteristics to meet the active and reactive power demands of the grid.

[0088] Figure 5 This is a flowchart of an optional grid-side inverter control process according to an embodiment of the present invention, such as... Figure 5 As shown, the method includes the following steps:

[0089] Step S502: Obtain the voltage and current parameters from the second operating state parameters, and the active and reactive power references on the grid side of the converter; Step S504: Determine the active and reactive power demand of the grid based on the voltage and current parameters; Step S506: Generate a second pulse width modulation signal based on the active power demand, reactive power demand, active power reference, and reactive power reference; Step S508: Based on the second pulse width modulation signal, control the on / off state of the switching transistors in the third and second bridge arms of the converter to perform grid-side inverter control, superimpose the voltages of multiple initial AC currents to obtain the target AC current, and connect the target AC current to the grid.

[0090] In the above process, through real-time monitoring and demand analysis, the converter can quickly respond to changes in the power demand of the power grid, providing active and reactive power support, thereby enhancing the stability and reliability of the power grid. Reactive power compensation helps maintain grid voltage stability, avoids voltage fluctuations, improves power quality, and enhances the user's electricity experience. The above control strategy achieves precise matching between the converter's output power and grid demand, avoiding overload or power waste and improving energy conversion efficiency.

[0091] In this embodiment of the invention, the method further includes: controlling the switch in the third bridge arm to be in an off state within a first preset time period, and controlling the on / off state of the switches in the first bridge arm and the second bridge arm based on a first pulse width modulation signal; controlling the switch in the first bridge arm to be in an off state within a second preset time period, and controlling the on / off state of the switches in the third bridge arm and the second bridge arm based on a second pulse width modulation signal.

[0092] The aforementioned first and second preset time periods refer to the time windows set by the controller when executing the time-division multiplexing modulation strategy. These windows control the alternating operation of the renewable energy-side inverter unit and the grid-side inverter unit, ensuring independent operation without mutual interference. The setting of these first and second preset time periods allows the controller to focus on controlling the inverter outputs of the renewable energy side and the grid side separately during different time periods, avoiding signal conflicts caused by multiplexing bridge arms and achieving efficient and stable operation of the converter process.

[0093] In one optional embodiment, during a first preset time period, the controller can set the switch of the third bridge arm to the off state, and the third bridge arm will not participate in the control of the current stage. Based on the first pulse width modulation signal, the controller can precisely control the on / off state of the switches in the first and second bridge arms, focusing on grid connection control and high power point tracking on the renewable energy side to ensure efficient power conversion and provide stable voltage and frequency support. During a second preset time period, the controller can set the switch of the first bridge arm to the off state, no longer participating in the control of the current stage, and can control the on / off state of the switches in the third and second bridge arms based on the second pulse width modulation signal to achieve grid connection control on the grid side, ensuring that the inverter power matches the grid requirements, while providing active and reactive power support to the grid.

[0094] In the above process, by alternately using the first and second preset time periods, the control processes of the renewable energy side and the grid side can be effectively isolated, avoiding mutual interference between them. This ensures the independence and accuracy of grid control when multiplexing bridge arms. The use of time-division multiplexing of bridge arms reduces the number of power switches required, thereby lowering hardware costs. Simultaneously, improvements in the control strategy reduce the maintenance and operating costs of the converter.

[0095] The technical solution proposed in this application will be described below with reference to an optional embodiment. This application proposes a topology for a new energy high-voltage direct-connected grid-connected converter and a bidirectional grid construction control strategy.

[0096] This application utilizes a single-unit, high-capacity converter to collect and directly connect renewable energy to the grid, eliminating the need for intermediate transformers, reducing costs, and improving the efficiency of the renewable energy grid-connected system. The single-unit converter enables bidirectional grid control of both the renewable energy and grid-connected sides, ensuring stable grid voltage and frequency even under intermittent or fluctuating power output, preventing grid disconnection due to insufficient sunlight. Decoupling the renewable energy and grid-connected sides allows for flexible adjustment of grid voltage and power, enabling independent and flexible support for both sides during dynamic system fluctuations. Based on the proposed converter topology and an intermediate DC bus incorporating energy storage, grid support is provided to both the renewable energy and grid-connected sides, constructing a bidirectional and relatively independent support system. The buffering and supporting role of the intermediate DC bus prevents direct mutual interference between the two sides, enhancing the stability and anti-interference capability of the entire conversion process.

[0097] This application proposes an independent grid for each module on the renewable energy side and cascades them on the grid-connected side. While achieving direct high-voltage grid connection on the parallel side, each module on the renewable energy side is independently zoned for connection to renewable energy power plants. This ensures flexible adjustment of the collection voltage in each renewable energy area, avoiding the limitation of large-scale power plants to achieve maximum output due to renewable energy port collection voltage constraints under uneven sunlight conditions. This application significantly improves the flexibility of renewable energy collection voltage through zoning, enabling greater power output in each zone even under uneven sunlight. Each module is equipped with energy storage, which can significantly mitigate the impact of renewable energy. Since the total power of the renewable energy power plant is divided into renewable energy power capacities for each zone, the energy storage capacity can be divided proportionally, avoiding imbalance problems caused by large-scale parallel connection of energy storage. The converter modules on both the renewable energy and grid-connected sides share a common bridge arm, reducing the number of power switches used in the system and thus lowering costs. A time-division multiplexing modulation strategy is proposed to solve the problem of power device switching interference caused by dual-sided inverter units when multiplexing the middle bridge arm.

[0098] This application proposes a new energy high-voltage direct-connect grid-connected converter topology. The converter can consist of three phase-line converter modules, each of which can be composed of multiple converter sub-modules. Each converter sub-module consists of a DC bus, an energy storage unit, a DC bus filter capacitor, and three bridge arms: a first bridge arm, a second bridge arm, and a third bridge arm. The second bridge arm can be multiplexed from the new energy-side inverter unit and the grid-connected inverter unit. The first and second bridge arms can form the new energy-side inverter unit, and the third and second bridge arms can form the grid-connected inverter unit. The new energy-side inverter unit is connected to the photovoltaic port converter of the DC-to-AC converter in the new energy power station via an inductor-capacitor filter. The grid-connected inverter units of multiple converter sub-modules in each phase-line converter module are connected in series to achieve voltage boosting, thereby directly connecting to the high-voltage grid and realizing direct grid connection of new energy without a transformer on the grid-connected side.

[0099] The converter topology submodules, with their intermediate DC bus and energy storage, form a grid connecting both the renewable energy side and the grid-connected side. Each submodule on the renewable energy side is connected to the renewable energy port DC-to-AC converter. A voltage reference adapted to the renewable energy port voltage can be constructed based on the photovoltaic array's illumination conditions. This provides stable voltage and frequency support for renewable energy and, by adjusting the grid voltage reference, provides sufficient adjustment margin for the high-power point tracking of the renewable energy port DC-to-AC converter, enabling efficient absorption and application of renewable energy. Furthermore, the intermediate DC bus, equipped with energy storage units, can smooth out fluctuations in renewable energy output, decoupling renewable energy power from grid-connected power and preventing the intermittent and fluctuating renewable energy output from affecting the grid-connected side. It also provides energy to support the power demand of the bidirectional grid.

[0100] Each submodule of this converter operates independently on the renewable energy side, allowing for the construction of different voltage references based on the output of the connected renewable energy areas. This ensures maximum output from renewable energy sources in each region, significantly improving the overall output of the renewable energy power station. Furthermore, the independent operation of multiple modules on the renewable energy side enables the distribution of power generation across the entire power station, avoiding the need for parallel connection of multiple switching devices for high current demands and eliminating current imbalance issues at the source. Additionally, each submodule on the renewable energy side can be independently controlled, reducing the complexity of grid support control on the renewable energy side.

[0101] The converter's various submodules are cascaded on the grid side, enabling direct grid connection for renewable energy sources through individual unit operation. This eliminates the need for grid-connected transformers, reducing equipment costs while significantly improving conversion efficiency. Grid-side cascading boosts the voltage; with a fixed input power capacity, the output current is 1 / N of the overall current of the renewable energy power station, where N is the number of cascaded units. This output current matches the current on the renewable energy side of each submodule, preventing an increase in voltage and current stress on the converter's grid-connected power devices despite the elimination of grid-connected transformers.

[0102] The converter's grid-connected submodules are cascaded, with each submodule independently controlled by the grid. The output voltages are superimposed, achieving voltage boosting through cascading. The cascaded H-bridge topology outputs a stepped waveform through voltage superposition, generating a near-sine wave. The more units, the more output voltage levels, resulting in a smoother waveform and significantly reduced harmonic content. This reduces harmonic pollution to the grid and load, eliminating the need for additional large-capacity filters and lowering system cost and size. Each H-bridge unit can withstand only 1 / N of the total system voltage, where N is the number of cascaded units. Low-voltage power electronic devices, such as insulated-gate bipolar transistors (IGBTs), can be used to achieve high-voltage output, avoiding the use of expensive and technically complex high-voltage components. By increasing the number of cascaded units, the system's voltage level and power capacity can be flexibly expanded, easily meeting the needs of medium- and high-voltage, large-capacity applications, such as high-voltage motor drives and grid reactive power compensation. The converter can be composed of multiple H-bridge unit modules with identical structures; this modular design facilitates standardized production, installation, and maintenance. In the event of a single unit failure, redundancy design or fault-tolerant control, such as disconnecting the faulty unit and adjusting the output of the remaining units, ensures the converter continues to operate, significantly improving overall reliability. The number of units can be flexibly increased or decreased according to different power requirements, offering strong adaptability. Each H-bridge unit can be controlled independently, not only adjusting the amplitude and frequency of the output voltage but also achieving independent control of active and reactive power, suitable for active filtering, reactive power compensation, and other applications. It supports multiple modulation strategies, such as carrier phase-shift pulse width modulation, which can further reduce harmonics, improve switching frequency utilization, and reduce device switching losses. Cascaded H-bridges eliminate the need for clamping diodes or capacitors, reducing loss paths in the energy conversion process. Low-voltage devices have lower switching losses, and with appropriate modulation strategies, the switching frequency can be improved, further enhancing the efficiency of the conversion process.

[0103] The bidirectional grid control strategy of this application's topology allows both the power plant side and the grid-connected side of the converter to employ grid control. Each sub-module on the power plant side of the converter operates independently with no coupling, coordinating with its connected power plant to provide the necessary voltage reference. This ensures that all power plants in each region can operate at maximum output. The control strategy for each sub-module circuit on the power plant side of the converter ensures that the DC-to-AC converter of the photovoltaic interface operates in a high power point tracking (PPT) control state, guaranteeing the real-time maximum output of the photovoltaic array. The frequency and phase references of the DC-to-AC converter can be derived from the grid voltage established on the power plant side of the converter, transmitted to the DC-to-AC controller via a phase-locked loop. The reference voltage amplitude for grid control on the power plant side of the converter can be derived from the output voltage of the DC-to-AC converter in PPT control mode. The voltage and current references generated by the grid control on the new energy side of the converter are transmitted to the modulation wave generation module on the new energy side of the converter, which in turn generates the drive signals of each power switch on the new energy side of each module of the converter, thereby driving the converter to support the grid construction of the new energy power station.

[0104] The converter's grid-connected side consists of a cascaded H-bridge topology composed of interconnected module circuits, operating directly connected to the grid. The interconnected modules on the grid-connected side collectively form the grid-connected voltage source. The grid-connected side grid control strategy calculates the active and reactive power demands on the grid-connected side by collecting voltage and current data at the grid connection point. Based on the voltage and power composition of each module in the cascaded H-bridge on the grid-connected side, it calculates the active and reactive power references for each module and transmits them to the grid-connected module grid control units and the converter DC bus balancing control unit. The grid-connected module grid control units generate their respective grid voltages based on the active and reactive power references and transmit them to the modulation wave reference unit. Furthermore, the converter DC bus balancing control unit ensures balanced charging and discharging of the energy storage units in each module and transmits the DC bus voltage reference to the modulation wave reference unit. The modulation wave reference unit generates a modulation wave and compares it with the corresponding carrier wave of each module to obtain the drive signal of each module on the grid-connected side of the converter, thereby driving the switching devices on the grid-connected side of the converter to turn on and off, realizing grid-connected side grid control.

[0105] The proposed topology-based time-division multiplexing modulation strategy addresses the issue that the intermediate bridge arms of each module in the proposed converter topology are multiplexed by the renewable energy-side inverter unit and the grid-connected inverter unit. Since both the renewable energy-side and grid-connected inverters employ network control, the difference in control objectives leads to mutual interference when the intermediate bridge arms are multiplexed on both sides, thus affecting the achievement of the expected control goals. To address this problem, this application proposes a time-division multiplexing modulation strategy. Based on the original continuous carrier wave, the drive carriers of the renewable energy-side inverter and the grid-connected inverter are complementary and alternately compared with the modulation wave. This allows the renewable energy-side inverter and the grid-connected inverter to turn on and off alternately, enabling the intermediate bridge arms to satisfy the outputs of the renewable energy-side inverter and the grid-connected inverter at different times, thereby resolving the contradiction of needing to simultaneously satisfy the operating objectives of the renewable energy-side inverter and the grid-connected inverter. When the new energy side inverter is working, the two switches of the third bridge arm of the grid-connected side inverter are in the open state. Similarly, when the grid-connected side inverter is working, the two switches of the first bridge arm of the new energy side inverter are in the open state.

[0106] This application proposes a converter topology that enables bidirectional grid connection support between renewable energy power plants and the power grid. This converter topology consists of multiple identical modules. The renewable energy side is independently connected to the renewable energy port converter, while the modules on the grid-connected side are cascaded to form a cascaded H-bridge topology, achieving direct high-voltage grid connection. Based on this converter topology, the modules on the renewable energy side of the converter provide zoned grid connection support for renewable energy power plants. Each module on the renewable energy side is independently connected, and the grid voltage reference can be flexibly adjusted according to the renewable energy output, ensuring maximum output from the connected area. Based on this converter topology, the modules on the grid-connected side of the converter are cascaded to jointly construct the grid-connected voltage source, achieving grid connection support for the power grid. Furthermore, the cascading enables direct high-voltage grid connection, eliminating the need for a grid-connected transformer and improving the conversion efficiency of the renewable energy system. An energy storage unit is configured on the intermediate DC bus of the converter topology, achieving decoupled control between the renewable energy side and the grid-connected side. The presence of energy storage can also smooth out fluctuations on the renewable energy side, ensuring stable input on the grid-connected side. Furthermore, energy storage can be connected to the grid on the renewable energy side, providing a stable voltage reference and ensuring stable and reliable grid connection. In the converter topology, each module on both the renewable energy and grid-connected sides share a central bridge arm, enabling inverter grid output to both sides. Compared to back-to-back converter topologies, this eliminates one bridge arm, reducing the number of converter components and thus lowering costs.

[0107] The converter topology in this application adopts an independent renewable energy side and a cascaded grid-connected side. Each module unit is an AC-to-DC-to-AC architecture, with the central DC bus connecting to the energy storage unit. This overall architecture features a bidirectional grid connection from the central DC bus to both sides of the inverter network, connecting to both the renewable energy side and the grid-connected side. Furthermore, each module is independent on the renewable energy side, while the grid-connected side is cascaded and directly connected to the grid at high voltage. A time-division multiplexing modulation strategy can resolve the interference problem caused by the reuse of the central bridge arm power switch in the renewable energy side and the grid-connected side inverter units of each module. Independent grid control for each renewable energy side module allows for flexible adjustment of the grid voltage reference based on the collected renewable energy irradiance, enabling flexible grid support for each renewable energy collection area and thus promoting greater photovoltaic absorption. Sub-module reuse of the bridge arm reduces the number of power switches by a quarter, significantly reducing equipment hardware costs in scenarios with high-voltage direct-connected multi-module cascades. Grid control from the central DC bus to both sides divides the converter into relatively independent parts, each of which can be flexibly adjusted according to its own operating conditions. When disturbances occur on one side, such as grid voltage fluctuations or sudden load changes, the other side can maintain stable operation to a certain extent, reducing the impact of disturbances on the entire converter and improving the anti-interference capability and stability of the conversion process. Compared to unified control of the entire cascaded H-bridge system, controlling the system separately from the central DC bus to both sides decomposes a large-scale control problem into two relatively smaller control problems, which reduces the complexity of the control algorithm to a certain extent and makes the design and implementation of the control strategy easier.

[0108] This application has been verified through simulation and hardware-in-the-loop simulation. On the renewable energy side, it achieves stable support and high power point tracking for photovoltaic (PV) power plants under uneven dynamic illumination, enabling significant renewable energy absorption. Furthermore, on the grid-connected side, it achieves high-voltage direct grid connection and operation. Each module on both the renewable energy and grid-connected sides implements grid connection control with bidirectional control functionality. The renewable energy side provides stable support for PV, while the grid-connected side provides stable support for the power grid. Moreover, the grid connection voltage reference on the renewable energy side is independently adjustable for each module, and the power and signal of the renewable energy and grid-connected sides are decoupled. Based on a time-division multiplexing modulation strategy, the conflict between the renewable energy and grid-connected inverter units caused by the multiplexing of the intermediate bridge arms is effectively resolved, and the simulation waveforms are consistent with the design waveforms.

[0109] Embodiments of this application also provide an electronic device, including: a memory storing an executable program; and a processor for running the program, wherein the program executes the methods in various embodiments of this application when it runs.

[0110] The aforementioned memory can refer to devices inside a computer used to store data and programs, including RAM, hard disks, etc. RAM can be used to temporarily store running programs and data, while hard disks can be used to store programs and data long-term. Memory enables the computer to read and write data and execute programs. The aforementioned processor is responsible for executing instructions in computer programs and performing data processing. It can also be responsible for controlling and executing various operations, including arithmetic operations, logical operations, and data transmission.

[0111] Embodiments of this application also provide a computer-readable storage medium including a stored executable program, wherein, when the executable program is running, it controls the device where the computer-readable storage medium is located to perform the methods of various embodiments of this application.

[0112] The aforementioned computer storage media can refer to the media used in computer memory to store certain discontinuous physical quantities. Computer storage media mainly include semiconductors, magnetic cores, magnetic drums, magnetic tapes, laser discs, etc. Computer-readable storage media include stored programs, which can be a set of instructions that a computer can recognize and execute, running on an electronic computer to meet certain information needs.

[0113] Embodiments of this application also provide a computer program product, including a computer program that, when executed by a processor, implements the methods of various embodiments of this application.

[0114] The aforementioned computer program products can refer to software programs that have been written, tested, and released, and can run on computers or other devices. Computer program products can include application programs, operating systems, utility software, etc., used to achieve specific functions or solve specific problems.

[0115] Embodiments of this application also provide a computer program product, including a non-volatile computer-readable storage medium for storing a computer program that, when executed by a processor, implements the methods in various embodiments of this application.

[0116] The aforementioned non-volatile computer-readable storage medium can refer to a medium for storing data. Non-volatile computer-readable storage media can retain data without loss when power is off and can be used to store long-term data, such as operating systems, applications, and user files. Non-volatile storage media can include hard disk drives, solid-state drives, optical disks, and flash memory storage devices, etc.

[0117] Embodiments of this application also provide a computer program that, when executed by a processor, implements the methods described in the various embodiments of this application.

[0118] The aforementioned computer program can refer to a set of instructions used to tell the computer to perform specific tasks or operations. Computer programs can be written by programmers using specific programming languages ​​and can include algorithms, data structures, logic, and control flow. Computer programs can be used for a variety of purposes, including application software, operating systems, etc.

[0119] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0120] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of units can be a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling, direct coupling, or communication connection may be through some interfaces; the indirect coupling or communication connection between units or modules may be electrical or other forms.

[0121] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0122] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0123] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0124] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A grid-connected converter for new energy, characterized in that, The application relates to a multi-phase converter module, and a multi-phase converter module includes a plurality of converter sub-modules, the first input end of different converter sub-modules in the same multi-phase converter module is connected with the same alternating current output phase line of different new energy ends, the plurality of converter sub-modules in the same multi-phase converter module are connected in cascade, the output end of the first converter sub-module in the same multi-phase converter module is connected with the second input end of the next converter sub-module, the second input end of the intermediate converter sub-module in the same multi-phase converter module is connected with the output end of the previous converter sub-module, the output end of the intermediate converter sub-module is connected with the second input end of the next converter sub-module, the second input end of the last converter sub-module in the same multi-phase converter module is connected with the output end of the previous converter sub-module, and the output end of the last converter sub-module in different multi-phase converter modules is connected with the corresponding alternating current input phase line of the power grid. The converter sub-module includes a first bridge arm, a second bridge arm and a third bridge arm, the first end of the first bridge arm is connected with a first direct current bus, the second end of the first bridge arm is connected with a second direct current bus, the third end of the first bridge arm is connected with the first input end of the converter sub-module, the first end of the second bridge arm is connected with the first direct current bus, the second end of the second bridge arm is connected with the second direct current bus, the third end of the second bridge arm is connected with the second input end of the converter sub-module, the first end of the third bridge arm is connected with the first direct current bus, the second end of the third bridge arm is connected with the second direct current bus, and the third end of the third bridge arm is connected with the output end of the converter sub-module. The controller is connected with the control end of a switch tube in the converter sub-module, is used for acquiring a first running state parameter of a new energy end and a second running state parameter of a power grid, generates a first pulse width modulation signal based on the first running state parameter and generates a second pulse width modulation signal based on the second running state parameter, controls the on-off state of the switch tube in the first bridge arm and the second bridge arm in the converter based on the first pulse width modulation signal to perform new energy side inversion control, controls the on-off state of the switch tube in the third bridge arm and the second bridge arm in the converter based on the second pulse width modulation signal to perform power grid side inversion control, superimposes voltages on the plurality of initial alternating currents to obtain target alternating currents, and integrates the target alternating currents into the power grid. Any target bridge arm in the first bridge arm, the second bridge arm and the third bridge arm includes a first switch tube, the output pole of the first switch tube is connected with the first end of the target bridge arm, and the reference ground pole of the first switch tube is connected with the third end of the target bridge arm, a second switch tube, the output pole of the second switch tube is connected with the third end of the target bridge arm, and the reference ground pole of the second switch tube is connected with the second end of the target bridge arm.

2. The grid-connected converter of claim 1, wherein, ​ ​ ​ The controller is connected with control ends of the first switch tube and the second switch tube, and is used for controlling on-off states of the first switch tube and the second switch tube.

3. The grid-connected converter of claim 1, wherein, The current transformer further comprises: An energy storage unit, a positive electrode of the energy storage unit being connected with the first DC bus, and a negative electrode of the energy storage unit being connected with the second DC bus; A filter capacitor, one end of the filter capacitor being connected with the first DC bus, and the other end of the filter capacitor being connected with the second DC bus.

4. A method for grid-connected variable flow control of new energy, characterized in that, The method is applied to the current transformer in any one of claims 1 to 3, and the method comprises: obtaining first operating state parameters of a new energy end and second operating state parameters of a power grid; generating a first pulse width modulation signal based on the first operating state parameters, and generating a second pulse width modulation signal based on the second operating state parameters; based on the first pulse width modulation signal, receiving a plurality of initial alternating currents, controlling on-off states of switch tubes in a first bridge arm and a second bridge arm of the current transformer, to perform new energy side inversion control; based on the second pulse width modulation signal, controlling on-off states of switch tubes in a third bridge arm and the second bridge arm of the current transformer, to perform power grid side inversion control, performing voltage superposition on the plurality of initial alternating currents to obtain target alternating currents, and integrating the target alternating currents into the power grid.

5. The grid-connected variable current control method of new energy according to claim 4, characterized in that, The method further comprises: controlling the DC-to-AC current transformer of the new energy end to be in a power tracking control mode, and obtaining a current transformer output voltage in the first operating state parameters, wherein the current transformer output voltage is used to represent an output voltage of the DC-to-AC current transformer; determining a voltage reference for the new energy side inversion control based on the current transformer output voltage; generating the first pulse width modulation signal based on the voltage reference by using a current transformer new energy side modulation wave generation module.

6. The grid-connected variable current control method of new energy according to claim 4, characterized in that, The method further comprises: obtaining voltage parameters and current parameters in the second operating state parameters, and active power reference and reactive power reference of the power grid side of the current transformer; determining active power demand and reactive power demand of the power grid based on the voltage parameters and the current parameters; generating the second pulse width modulation signal based on the active power demand, the reactive power demand, the active power reference, and the reactive power reference.

7. The grid-connected variable current control method of new energy according to claim 4, characterized in that, The method further comprises: in a first preset time period, controlling switch tubes in the third bridge arm to be in an off state, and controlling on-off states of switch tubes in the first bridge arm and the second bridge arm based on the first pulse width modulation signal; in a second preset time period, controlling switch tubes in the first bridge arm to be in an off state, and controlling on-off states of switch tubes in the third bridge arm and the second bridge arm based on the second pulse width modulation signal.

8. An electronic device, comprising: The method further comprises: a memory storing an executable program; a processor configured to run the program, wherein the program, when running, performs the current control method for new energy grid connection in any one of claims 4 to 7.

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