Parallel converter, current equalization control method, system, storage medium and electronic device

Abstract

This application relates to the field of power electronics technology, and more particularly to a parallel converter, a current sharing control method, a system, a storage medium, and an electronic device. The parallel converter includes at least two converter branches arranged in parallel. Each converter branch includes: a converter, equivalent to a voltage source; a first impedance connected in series with the converter, forming the inherent loop impedance of the converter branch; a second impedance connected in series with the first impedance; a first switching branch connected in parallel with the first impedance, wherein the first switching branch is composed of a first switch and a second switch connected in antiparallel; and a second switching branch connected in parallel with the second impedance, wherein the second switching branch is composed of a third switch and a fourth switch connected in antiparallel. This application changes the equivalent impedance path of each branch in the parallel system by adding a controllable impedance bypass (i.e., a switching branch), thereby achieving efficient current sharing through simple control logic.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a parallel converter, current sharing control method, system, storage medium and electronic equipment. Background Technology

[0002] The statements in this section are merely background information related to this application and do not necessarily constitute prior art.

[0003] In new energy systems such as photovoltaic power generation, wind power generation, and energy storage, multiple converters are often connected in parallel to improve the total power capacity and reliability of the system. However, due to the inevitable differences in manufacturing parameters, line impedance, and component characteristics among the parallel converters, unbalanced circulating currents can occur in the parallel circuit, resulting in uneven output current and unbalanced power distribution among the converters. This uneven current phenomenon can cause some converters to operate under overload for extended periods, reducing system efficiency, accelerating component aging, and in severe cases, even causing failures, threatening the safe and stable operation of the entire parallel system.

[0004] To address the current sharing problem in parallel circuits, existing technologies commonly employ multi-loop control strategies. For example, a dedicated current sharing loop is added outside the voltage outer loop and current inner loop, forming a three-loop control structure; or complex mathematical models based on passive theory are used for control. While these solutions can achieve current sharing to some extent, they have significant drawbacks: First, the control algorithms are complex, requiring multi-channel signal sampling, complex coordinate transformations (such as dq transformation), and proportional-integral (PI) calculations. Each control operation involves numerous calculation instructions, placing high demands on the controller's processing power and computational speed, resulting in high costs. Second, the dynamic response speed is limited by the bandwidth and communication latency of the control loop, making it difficult to quickly suppress instantaneous circulating current surges under conditions such as sudden load changes. Finally, the complex control algorithms require precise parameter tuning, leading to complex software implementation and challenges to system reliability and anti-interference capabilities.

[0005] With the increasingly widespread application of wide-bandgap semiconductor devices, represented by silicon carbide (SiC), in converters, their high-frequency and high-efficiency characteristics place higher demands on the dynamic performance and reliability of parallel current sharing control. Therefore, there is an urgent need for a parallel converter current sharing scheme that is simple in structure, has clear control logic, fast dynamic response, and high reliability. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this application provides a parallel converter, current sharing control method, system, storage medium and electronic device. By adding a controllable impedance bypass (i.e., a switching branch), the equivalent impedance path of each branch in the parallel system is changed, thereby achieving efficient current sharing through simple control logic.

[0007] To achieve the above objectives, this application provides the following technical solution: In a first aspect, a parallel converter is provided, comprising at least two converter branches arranged in parallel, each of the converter branches comprising: Converter; The first impedance is connected in series with the converter to form the inherent loop impedance of the converter branch. The second impedance is connected in series with the first impedance; The first switch branch is connected in parallel with the first impedance, and the first switch branch is composed of the first switch transistor and the second switch transistor connected in anti-parallel. The second switch branch is connected in parallel with the second impedance, and the second switch branch is composed of the third switch and the fourth switch connected in anti-parallel.

[0008] Furthermore, the first switch, the second switch, the third switch, and the fourth switch are all fully controllable switching devices.

[0009] Furthermore, the impedance value of the second impedance is equal to the impedance value of the first impedance.

[0010] Furthermore, the converter is a silicon carbide converter.

[0011] Secondly, a current sharing control method for a parallel converter is also provided, applied to the parallel converter as described above, the method comprising: The instantaneous value of the output current of each of the converter branches is obtained respectively; From all the instantaneous values ​​of the output current, determine the maximum instantaneous current value and the minimum instantaneous current value; Calculate the difference between the maximum instantaneous current value and the minimum instantaneous current value; The difference is compared with a preset current deviation threshold. Based on the comparison results, the on / off states of the first and second switch branches in each converter branch are controlled to achieve current sharing control among each converter branch.

[0012] Further, controlling the on / off state of the first and second switching branches in each of the converter branches based on the comparison results includes: When the difference is less than the current deviation threshold, for each converter branch, its first switch branch and second switch branch are controlled to alternately conduct in adjacent switching cycles.

[0013] Further, controlling the on / off state of the first and second switching branches in each of the converter branches based on the comparison results includes: When the difference is greater than or equal to the current deviation threshold, the first and second switch branches of the converter branch whose instantaneous value of the output current is the maximum instantaneous current value are shut off. For the remaining converter branches, control the first and second switching branches to alternately conduct in adjacent switching cycles.

[0014] Furthermore, the control of the first switch branch and the second switch branch to alternately conduct in adjacent switching cycles is specifically as follows: in the k-th switching cycle, the first switch branch of the converter branch is turned on and its second switch branch is turned off; in the (k+1)-th switching cycle, the first switch branch of the converter branch is turned off and its second switch branch is turned on, where k is a natural number.

[0015] Furthermore, the current deviation threshold is set based on the rated operating current of the converter.

[0016] Based on the same inventive concept, this application also provides a power electronic system, including the parallel converter as described above.

[0017] Based on the same inventive concept, this application also provides a computer-readable storage medium storing one or more programs, which, when executed, implement the current sharing control method for parallel converters as described above.

[0018] Based on the same inventive concept, this application also provides an electronic device, including a processor, a communication interface, a computer-readable storage medium as described above, and a communication bus; wherein the processor, the communication interface, and the computer-readable storage medium communicate with each other through the communication bus; the processor is used to execute a program stored in the computer-readable storage medium.

[0019] Compared with the prior art, the beneficial effects of this application are as follows: A novel parallel converter hardware architecture capable of achieving current sharing control is provided. By connecting a first impedance and a second impedance in series after the converter in each converter branch, and then connecting these two impedances in parallel with a first switching branch and a second switching branch composed of anti-parallel switching transistors, this converter structure provides the hardware foundation for implementing subsequent current sharing control methods. This structural scheme creatively adds a controllable impedance bypass (i.e., a switching branch), changing the equivalent impedance path of each branch in the parallel system. Thus, the impedance of each branch can be dynamically adjusted through simple switching control logic, thereby achieving efficient current sharing.

[0020] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings.

[0021] The present application will be further described below with reference to the accompanying drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a converter branch in a parallel converter according to an embodiment of this application; Figure 2 This is a basic flowchart illustrating a current sharing control method for a parallel converter according to an embodiment of this application; Figure 3 This is a schematic diagram of the overall flow of a current sharing control method for a parallel converter according to an embodiment of this application; Figure 4 This is a schematic diagram of the structure of an electronic device according to an embodiment of this application. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] like Figure 1 As shown (the branch structures of each converter are the same, therefore...) Figure 1 (Only one converter branch is shown). One embodiment of this application provides a parallel converter, including at least two converter branches arranged in parallel, each of the converter branches including: A converter is equivalent to a voltage source; The first impedance is connected in series with the converter to form the inherent loop impedance of the converter branch. The second impedance is connected in series with the first impedance; The first switch branch is connected in parallel with the first impedance, and the first switch branch is composed of the first switch transistor and the second switch transistor connected in anti-parallel. The second switch branch is connected in parallel with the second impedance, and the second switch branch is composed of the third switch and the fourth switch connected in anti-parallel.

[0026] The above technical solution provides a novel parallel converter hardware architecture capable of achieving current sharing control, laying the hardware foundation for achieving efficient current sharing through simple control logic.

[0027] The main technical advantages of this solution are: 1. Simplified structure, laying the foundation for simplified control: The structure itself does not contain complex control chips or multi-channel signal processing circuits. Its core is the addition of a switching branch in parallel with the impedance. This relatively simple topology allows for the use of an equally simple logic control method based on current difference threshold comparison (see the current sharing control method below) to replace the complex multi-loop control algorithm in traditional schemes. This provides a key hardware prerequisite for ultimately achieving the overall beneficial effect of "simple structure and control, high reliability".

[0028] 2. Controllable impedance path is achieved: By controlling the on / off states of the first and second switching branches, it can be determined whether the current flows through the first and second impedances, or through the switching branches connected in parallel with them (the impedance of the switching branches is extremely low when they are on, approximating a short circuit). This makes the total equivalent impedance of each parallel branch a controllable variable that can be quickly and discretely switched. When current imbalance is detected between parallel branches, the equivalent impedance can be instantly changed by switching the switching state of a specific branch, forcing a redistribution of current. This is the core physical mechanism for achieving rapid dynamic current sharing.

[0029] This scheme provides a novel, hardware-reconfigurable circuit topology that introduces parallel switching branches, enabling the equivalent impedance of each parallel branch to be easily and quickly externally controlled. This provides an essential and structurally simple physical carrier for achieving efficient, fast, and reliable parallel current sharing through extremely simplified control logic (as described in the current sharing control method below).

[0030] As a preferred technical solution, the first switch, the second switch, the third switch, and the fourth switch are all fully controllable switching devices.

[0031] This embodiment clarifies the key actuator type for implementing the controllable impedance path (switching branch), ensuring the effectiveness and speed of control. Specifically, this embodiment specifies that the switching transistor is a "fully controlled switching device," which is a necessary requirement for the implementation of the technical solution. Only a fully controlled switching device can accurately and quickly control the on / off state of the main circuit through the base / gate voltage, thereby achieving the timely "on" and "off" state switching required by the control logic in the aforementioned switching branch. This limitation ensures that the hardware architecture can respond to the control commands in the subsequent current sharing control method, which is the physical basis for achieving rapid dynamic current sharing.

[0032] In some preferred embodiments, the fully controllable switching device is an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET). This embodiment provides specific and preferred embodiments of switching devices for implementing the switching branch function, ensuring the practicality and feasibility of the solution. Specifically, the fully controllable switching device is an insulated-gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET). Among them, IGBTs and MOSFETs are the two most commonly used and mature types of fully controllable switching devices in the field of power electronics, and their driving, protection, and application technologies are very mature. Clearly defining these two types of devices provides a clear, reliable, and cost-controllable component selection for the actual product realization of this application, enhancing the feasibility of the solution.

[0033] As a preferred technical solution, the impedance value of the second impedance is equal to the impedance value of the first impedance.

[0034] This embodiment simplifies the analysis and design of the control strategy and enhances the symmetry and predictability of the current sharing effect by setting the impedance to be equal. Specifically, setting the impedance value of the "second impedance" to be equal to the "first impedance" (i.e., the inherent loop impedance) is a clever design of this scheme. This ensures that each parallel branch has twice the inherent impedance when all switching branches are off; when any switching branch is on, the equivalent impedance is the parallel value of the extremely low impedance of the on-circuit branch and the other impedance, which is approximately equal to the other impedance (i.e., the inherent impedance). This "equality" setting makes adjusting the change law of the equivalent impedance by switching the switch state simple and symmetrical, facilitating mathematical modeling and analysis, and providing theoretical convenience for setting a uniform current deviation threshold, thereby ultimately simplifying the control logic.

[0035] In some preferred embodiments, the number of converter branches is 2 to 10. This embodiment defines the typical and preferred parallel application scale of this application, which is more in line with actual engineering application scenarios. This embodiment specifically limits the number of parallel converter branches, on the one hand focusing the applicable scope from the theoretical "at least two" to the most common engineering application scenarios (small-scale parallel arrays), making the solution more practical and market-oriented; on the other hand, it also avoids the technical uncertainties that may arise in extreme cases due to an unlimited expansion of the number, making the solution itself more stable and clear.

[0036] As a preferred technical solution, the converter is a silicon carbide converter.

[0037] This section combines the hardware architecture of this application with the specific and advanced application scenario of silicon carbide (SiC) converters, emphasizing the applicability and advantages of this solution in addressing the unique parallel connection problems of SiC converters. It should be noted that the circuit structure and control method of this application are, in principle, applicable to various types of converters, especially silicon carbide converters. SiC devices offer advantages such as high frequency, high temperature, and high voltage, but their parallel operation requires higher dynamic performance in suppressing circulating current. This section emphasizes that the hardware architecture of this application is a preferred embodiment particularly suitable for SiC converters. Applying the hardware architecture of this application to a specific and significantly advanced technical field (SiC power electronics) enhances the commercial value and technical relevance of this application.

[0038] like Figure 2 As shown, one embodiment of this application also provides a current sharing control method for a parallel converter, applied to the parallel converter described above. The method includes the following steps: S1. Obtain the instantaneous value of the output current of each of the converter branches; S2. From all the instantaneous values ​​of the acquired output current, determine the maximum instantaneous current value and the minimum instantaneous current value; S3. Calculate the difference between the maximum instantaneous current value and the minimum instantaneous current value; S4. Compare the difference with a preset current deviation threshold; S5. Based on the comparison results, control the on / off state of the first switch branch and the second switch branch in each of the converter branches to achieve current sharing control among the converter branches.

[0039] The above technical solution presents an extremely simplified core flow of parallel current sharing control logic, transforming the complex multi-loop control problem into a logic judgment problem based on a current difference threshold. This solution completely changes the complex paradigm of traditional current sharing control (such as voltage loop, current loop plus current sharing loop), achieving current sharing control through a simple flow of "detecting current → finding maximum / minimum value → calculating difference → comparing with threshold → controlling switch according to result". This avoids the complex multi-channel signal sampling, coordinate transformation, PI calculation, etc. in traditional solutions, and is expected to reduce the controller's computational load by more than 70%. Furthermore, due to the simple and direct control logic, its theoretical response speed can reach a single switching cycle, quickly suppressing circulating current impacts caused by sudden load changes. The core effect of this method is "simple control and high reliability".

[0040] As a preferred technical solution, controlling the on / off state of the first and second switch branches in each of the converter branches according to the comparison results includes: When the difference is less than the current deviation threshold, for each converter branch, its first switch branch and second switch branch are controlled to alternately conduct in adjacent switching cycles.

[0041] This embodiment presents an optimized operating mode for situations with minimal current imbalance (difference less than a threshold), enabling the system to maintain dynamic regulation capabilities and balance switching losses even under basic current-sharing conditions. Specifically, when the current deviation in each branch is within an acceptable threshold range, the two switching branches of all branches are controlled to "alternately conduct within adjacent switching cycles." This alternating conduction mode causes the current path to periodically switch between a "first impedance" and a "second impedance." On one hand, this keeps the control loop constantly active, enabling it to adjust for minor deviations; on the other hand, the periodic flow of current along the two impedance paths helps to balance the current stress and heat loss in the two switching branches, improving the long-term operational reliability of the system.

[0042] As a preferred technical solution, controlling the on / off state of the first and second switch branches in each of the converter branches according to the comparison results includes: When the difference is greater than or equal to the current deviation threshold, the first and second switch branches of the converter branch whose instantaneous value of the output current is the maximum instantaneous current value are shut off. For the remaining converter branches, control the first and second switching branches to alternately conduct in adjacent switching cycles.

[0043] This embodiment presents a rapid error correction control strategy when a significant current imbalance (difference greater than or equal to a threshold) is detected, which can quickly suppress circulating current and protect overloaded branches. Specifically, when the current (maximum value) of a certain branch is detected to be significantly higher than that of other branches, an imbalance state is immediately determined. At this time, all switches of the branch with the largest current are directly "shut down," forcing its current to flow through the first and second impedances in series, thereby instantly increasing the equivalent impedance of that branch and suppressing its output current. At the same time, other branches still adopt the alternating conduction mode. This strategy can correct the imbalance state most quickly and directly, reduce the current of the overloaded branch, protect it from damage, and quickly restore the overall current sharing state of the system.

[0044] As a preferred technical solution, the control of the first switch branch and the second switch branch to alternately conduct in adjacent switching cycles specifically means: in the k-th switching cycle, the first switch branch of the converter branch is turned on and its second switch branch is turned off; in the k+1-th switching cycle, the first switch branch of the converter branch is turned off and its second switch branch is turned on, where k is a natural number.

[0045] This embodiment clarifies the specific timing implementation of "alternating conduction," eliminating ambiguity in the control logic and ensuring the accuracy and repeatability of the control. This scheme is a concretization of the aforementioned "alternating conduction," precisely defining the timing sequence of alternating conduction: in the "k-th switching cycle," the first switching branch is turned on, and the second switching branch is turned off; the opposite occurs in the immediately following "k+1-th switching cycle." This clear time base and switch state definition make the control logic extremely clear, deterministic, and unambiguous, easily implemented in digital controllers (such as DSPs and MCUs) through precise programming via timer interrupts, significantly improving the reliability and anti-interference capability of software execution.

[0046] As a preferred technical solution, the current deviation threshold is set based on the rated operating current of the converter.

[0047] This embodiment provides a scientific and reasonable basis for setting the key parameter "current deviation threshold" in the control logic, ensuring that the control criteria match the actual system capacity. Threshold (I th The threshold is the core of the control logic, and its setting directly affects the system's sensitivity, stability, and dynamic performance. This embodiment explicitly states that the threshold should be "set based on the rated operating current of the converter." This is a reasonable engineering principle, meaning that the threshold value is directly related to the system's power rating and current carrying capacity. For example, for systems with high rated current, the allowable absolute current deviation can be slightly larger; for low-current systems, the threshold should be set smaller. This ensures the universality and engineering applicability of the control strategy.

[0048] In some preferred embodiments, the current deviation threshold is 5% of the rated operating current. This embodiment provides a specific, preferred, and effective threshold setting ratio, offering a clear and quantifiable reference value for implementation. This embodiment explicitly sets the threshold to "5% of the rated operating current." This numerical ratio is a preferred value after a trade-off: too small a ratio may cause the system to frequently trigger error correction mode (i.e., the aforementioned fast error correction control strategy) under normal, minor fluctuations, affecting stability; too large a ratio may cause the system to fail to intervene in adjustment even when the imbalance is already severe. 5% is an empirical value that balances sensitivity, stability, and dynamic performance in practice, providing direct guidance for specific product implementation.

[0049] The rated current of each converter is a fixed value determined by the manufacturer, representing the maximum current that the equipment can safely operate for a long period under rated conditions. Converters with equal rated currents are typically selected and connected in parallel. When the instantaneous output current values ​​of each converter are i1, i2, ..., i... n Current sharing is required when the difference between the maximum and minimum values ​​is greater than or equal to a threshold (e.g., 5% of the rated current of each converter); otherwise, it is not required.

[0050] Based on the same inventive concept, this application also provides a power electronic system, including the parallel converter as described above. This embodiment no longer provides a single "converter" module, but rather a "system" using that module, such as a complete photovoltaic inverter, a wind turbine converter, or an energy storage converter system.

[0051] In some preferred embodiments, the power electronic system is a photovoltaic inverter system, and the parallel converter is used to convert direct current to alternating current; or the power electronic system is a wind turbine converter system, and the parallel converter is used to convert unstable alternating current to alternating current that meets grid connection requirements; or the power electronic system is an energy storage converter system. This embodiment specifically clarifies the three major mainstream new energy power electronic application areas to which this application applies. Specifically, this embodiment explicitly lists three types of power electronic systems: "photovoltaic inverter system," "wind turbine converter system," and "energy storage converter system." These three types of power electronic systems belong to the core application scenarios.

[0052] Photovoltaic inverters (corresponding to the aforementioned photovoltaic inverter system) play a core role in photovoltaic power generation systems. Their main function is to convert the direct current (DC) generated by photovoltaic modules into alternating current (AC) for compatibility with the power grid and household appliances. Photovoltaic inverters are not only key equipment for power conversion but also bear the important responsibility of monitoring, protecting, and optimizing the operation of photovoltaic systems. With the rapid development of the photovoltaic industry, improving inverter efficiency is of great significance to the overall efficiency and economy of photovoltaic power generation systems.

[0053] The main function of the wind turbine converter (corresponding to the aforementioned wind turbine converter system) is to convert the unstable AC power generated by the wind turbine generator into stable AC or DC power output that meets the grid requirements. This resolves the contradiction between the unstable and low-quality energy characteristics of wind power and the high stability and high-quality standards required by the power grid. The wind turbine converter is an indispensable energy conversion unit for wind turbine units, directly affecting electrical parameters and functions such as power generation efficiency and low-voltage ride-through. It resolves the contradiction between the unstable and low-quality energy characteristics of wind power and the high stability and high-quality standards required by the power grid, ensuring the stable grid-connected operation of the wind power generation system.

[0054] To make the above parallel converters and current sharing control methods clearer, the following explanation will take a silicon carbide converter as an example to illustrate the above preferred technical solutions.

[0055] Currently, the performance of traditional silicon-based power devices is approaching the theoretical limits of the materials, resulting not only in a sharp increase in cost but also in high energy loss. In recent years, wide-bandgap semiconductor devices, represented by silicon carbide (SiC), have received widespread attention. Silicon carbide materials possess several outstanding performance advantages, including high breakdown field strength, excellent thermal conductivity, high electron saturation drift velocity, and strong radiation resistance. Compared to silicon-based devices, the theoretical blocking voltage of SiC-based power devices can reach 10 times that of silicon-based devices, and the operating junction temperature can be increased to 4 times that of silicon devices. In addition, silicon carbide power devices have the great potential to achieve tens of thousands of volts and thousands of amperes in a single device in the future. Compared to silicon-based devices, silicon carbide power devices have unique requirements in terms of packaging, mainly due to their high temperature, high voltage, and high frequency performance. Compared with traditional silicon-based devices, SiC devices require packaging materials with higher heat resistance and thermal stability to withstand higher operating temperatures (typically above 200°C), and the packaging design needs to optimize heat dissipation performance to adapt to high power density applications. Furthermore, SiC devices are typically used in high-frequency switching applications, requiring packaging that minimizes parasitic inductance and reduces high-frequency losses. To ensure long-term reliable operation in harsh environments, the packaging must also possess stronger mechanical strength and electrical insulation properties to meet the challenges of high-voltage, high-frequency power electronic equipment. Therefore, research on the application of silicon carbide power devices and modules in wind turbines and photovoltaic converters has become a core issue in the field of power electronics, holding significant practical importance for promoting the construction of new energy systems and the transformation of power systems.

[0056] When silicon carbide converters (silicon-based device converters) are operated in parallel, differences in impedance characteristics can cause circulating currents between the parallel converters, resulting in an imbalance in output power among them. Therefore, this application proposes a current sharing scheme for parallel silicon carbide converters (i.e., the aforementioned parallel converters and current sharing control method), such as... Figure 1As shown in the figure (using U1 as an example, this diagram represents a parallel branch, where U1 is the equivalent voltage source of the converter), U g (This refers to the mains voltage; T1-T4 are switching transistors).

[0057] Each parallel converter is equivalent to a voltage source (i.e., U1, U2, ... U...). n (n is the number of parallel converters, usually less than 10).

[0058] Based on the circuit impedance of each converter (i.e., the aforementioned first impedance, which is illustrated in this embodiment using the parallel branch where U1 is located as an example, and the circuit impedance is represented as R1+jX1), an impedance of equal magnitude to the circuit impedance (i.e., the aforementioned second impedance, which is represented as R2+jX2) is connected in series. Each of the two impedances is connected in parallel with a switch branch (i.e., the first switch branch is connected in parallel with the first impedance R1+jX1, and the second switch branch is connected in parallel with the second impedance R2+jX2). Each switch branch is composed of two switches connected in antiparallel (i.e., the first switch branch is composed of the first switch T1 and the second switch T2 connected in antiparallel, and the second switch branch is composed of the third switch T3 and the fourth switch T4 connected in antiparallel).

[0059] Among them, the switching transistor is a fully controllable switching device, meaning that the connection between the collector and emitter (or drain and source) can be controlled by controlling the base voltage (or gate voltage). Commonly used switching transistors include IGBTs and MOSFETs.

[0060] like Figure 3 As shown, it presents a specific method for threshold judgment and switching control (i.e., a current sharing control method for parallel converters), including: Real-time monitoring of the instantaneous values ​​of the output current i1, i2, ..., i of each converter n (n is the number of parallel converters, usually less than 10).

[0061] Compare n current values ​​to obtain the maximum value i max and minimum value i min .

[0062] when i max i min The difference is less than the threshold I th At that time, the two switching branches of each parallel branch are alternately turned on (i.e., in one switching cycle, T1 and T2 are turned on, and T3 and T4 are turned off. In the next switching cycle, T3 and T4 are turned on, and T1 and T2 are turned off). When i max i min The difference is greater than the threshold I th When the turn-off current value is i max All the switch branches of the branch where the converter is located, and the other branches still alternately conduct two switch branches.

[0063] In simple terms, the current sharing control method for parallel converters in this embodiment first compares the maximum and minimum values, then compares the difference between the maximum and minimum values ​​with a threshold, and finally performs different switching controls based on the comparison result. The above scheme effectively achieves the current sharing function through parallel branch design and current sharing control method, with a simple structure and control, and high reliability. By adding parallel branches, converters with different impedance characteristics can operate in parallel, which can improve the reliability of converters in large-scale new energy bases.

[0064] Wherein, threshold I th The threshold value in this embodiment is determined based on actual needs and includes, but is not limited to, 5% of the rated current (i.e., the rated operating current of the converter).

[0065] Current current sharing schemes generally employ multi-loop control (such as a three-loop structure consisting of a voltage loop, a current loop, and a current sharing loop) or complex passive control models. This necessitates the algorithm to perform multi-channel signal sampling, PI calculations, and complex coordinate transformations. The computational load for a single control operation often exceeds tens to hundreds of instructions, and the dynamic response is limited by the loop bandwidth and communication latency. In contrast, this application simplifies current sharing control to a single logical judgment of the difference between the instantaneous values ​​of the currents in the two branches. This simplification brings significant quantifiable advantages. First, in terms of computational complexity, the algorithm requires only 10 comparison operations and one subtraction operation to complete the decision within one switching cycle (usually in the microsecond range), avoiding all integration, differentiation and modeling operations. It is expected to reduce the computing load of the controller by more than 70%, or make it possible to use a lower cost and lower frequency microprocessor.

[0066] Secondly, in terms of dynamic performance, since it directly responds to instantaneous current deviations and corrects them only by switching the state, its theoretical response speed can reach a single switching cycle, which is much faster than the traditional scheme that relies on the average value of the cycle and the slow PI regulator. It can more effectively suppress the circulating current impact caused by load changes.

[0067] Third, in terms of implementation cost and reliability, this solution does not require the addition of an independent current sampling channel or communication module for current sharing, nor does it require complex parameter tuning. This not only reduces hardware costs, but also significantly improves the determinism and anti-interference capability of the software due to its extremely simple logic, reducing potential failure points.

[0068] The circuit structure of this application (i.e., the aforementioned parallel converter) can be applied to photovoltaic inverters, wind turbine converters, or energy storage converter systems, etc.

[0069] Based on the same inventive concept, this application also provides a computer-readable storage medium storing one or more programs, which, when executed, implement the current sharing control method for parallel converters as described above.

[0070] Based on the same inventive concept, such as Figure 4 As shown, this application also provides an electronic device, including a processor, a communication interface, a computer-readable storage medium as described above, and a communication bus; wherein the processor, the communication interface, and the computer-readable storage medium communicate with each other through the communication bus; the processor is used to execute a program stored in the computer-readable storage medium.

[0071] In the above embodiments, 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.

[0072] The parts not mentioned in the above embodiments are the same as or can be implemented using existing technologies, and will not be further described here.

[0073] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A parallel converter, characterized in that, It includes at least two converter branches connected in parallel, each of the converter branches including: Converter; The first impedance is connected in series with the converter to form the inherent loop impedance of the converter branch. The second impedance is connected in series with the first impedance; The first switch branch is connected in parallel with the first impedance, and the first switch branch is composed of the first switch transistor and the second switch transistor connected in anti-parallel. The second switch branch is connected in parallel with the second impedance, and the second switch branch is composed of the third switch and the fourth switch connected in anti-parallel.

2. The parallel converter according to claim 1, characterized in that, The first switch, the second switch, the third switch, and the fourth switch are all fully controllable switching devices.

3. The parallel converter according to claim 1, characterized in that, The impedance value of the second impedance is equal to the impedance value of the first impedance.

4. The parallel converter according to any one of claims 1-3, characterized in that, The converter is a silicon carbide converter.

5. A current sharing control method for a parallel converter, applied to the parallel converter according to any one of claims 1-4, characterized in that, The method includes: The instantaneous value of the output current of each of the converter branches is obtained respectively; From all the instantaneous values ​​of the output current, determine the maximum instantaneous current value and the minimum instantaneous current value; Calculate the difference between the maximum instantaneous current value and the minimum instantaneous current value; The difference is compared with a preset current deviation threshold. Based on the comparison results, the on / off states of the first and second switch branches in each converter branch are controlled to achieve current sharing control among each converter branch.

6. The flow sharing control method according to claim 5, characterized in that, The step of controlling the on / off state of the first and second switch branches in each converter branch according to the comparison result includes: When the difference is less than the current deviation threshold, for each converter branch, its first switch branch and second switch branch are controlled to alternately conduct in adjacent switching cycles.

7. The flow sharing control method according to claim 5, characterized in that, The step of controlling the on / off state of the first and second switch branches in each converter branch according to the comparison result includes: When the difference is greater than or equal to the current deviation threshold, the first and second switch branches of the converter branch whose instantaneous value of the output current is the maximum instantaneous current value are shut off. For the remaining converter branches, control the first and second switching branches to alternately conduct in adjacent switching cycles.

8. The flow sharing control method according to claim 6 or 7, characterized in that, The control of alternating conduction of the first and second switch branches in adjacent switching cycles is specifically as follows: in the k-th switching cycle, the first switch branch of the converter branch is turned on and its second switch branch is turned off; in the (k+1)-th switching cycle, the first switch branch of the converter branch is turned off and its second switch branch is turned on, where k is a natural number.

9. The flow sharing control method according to claim 5, characterized in that, The current deviation threshold is set based on the rated operating current of the converter.

10. A power electronic system, characterized in that, Includes the parallel converter as described in any one of claims 1-4.

11. A computer-readable storage medium storing one or more programs, characterized in that, When one or more programs are executed, the current sharing control method for the parallel converter as described in any one of claims 5-9 is implemented.

12. An electronic device comprising a processor, a communication interface, a computer-readable storage medium as described in claim 11, and a communication bus; wherein, The processor, communication interface, and computer-readable storage medium communicate with each other via a communication bus; Its features are, The processor is used to execute programs stored in a computer-readable storage medium.

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