Power electronic equipment, power electronic equipment switching frequency optimization method and device and storage medium

Abstract

The invention belongs to the technical field of power electronic equipment, and particularly relates to power electronic equipment, a power electronic equipment switching frequency optimization method and device and a storage medium. The core optimization thought of switching frequency optimization is that in the sub-module voltage sorting process, the continuous input probability of a sub-module in an input state at a previous moment at a subsequent moment is improved. The novel switching frequency optimization method comprises two operation logics of charging and discharging, and different strategies are adopted under different logics, so that the energy loss of the flexible DC converter valve can be effectively reduced, and the transmission efficiency of the system is improved. The method has accuracy and high efficiency, and can be widely applied to novel power electronic equipment related to sub-module sorting, such as a flexible direct current converter valve, a direct current side direct hanging energy storage valve, a static var generator (SVG) and the like.

Description

Technical Field

[0001] This invention belongs to the field of power electronic equipment technology, specifically relating to a power electronic device, a method for optimizing the switching frequency of a power electronic device, an apparatus, and a storage medium. Background Technology

[0002] With the development of fully controllable power electronic devices and the application of power electronics technology in power systems, high-voltage direct current (VDC) transmission technology based on voltage-source converters (VSCs) has received increasing attention. Modular multilevel converters (MMCs), as an important form of voltage-source converter in flexible DC transmission systems, have been widely used in flexible DC transmission and renewable energy integration systems due to their significant advantages.

[0003] Each arm of the MMC-HVDC bridge consists of several sub-modules connected in series with the arm reactor. By controlling the number of sub-modules connected and disconnected in each arm, the AC output voltage can be made to approximate a sinusoidal AC voltage, and the DC output voltage can be made to approximate a DC voltage, thereby ensuring stable system operation.

[0004] As the voltage level of flexible DC transmission in China continues to increase, the number of submodules within the MMC (Multi-Module Control) arms in engineering projects is also constantly rising. Submodule voltage balancing has thus become a core issue in MMC control. The current approach selects which submodules to conduct based on their voltage ranking; however, excessively high switching frequencies can lead to increased converter losses and decreased transmission efficiency. Therefore, MMC voltage balancing control needs to incorporate switching frequency optimization to achieve a balance between system voltage balancing and loss control.

[0005] Chinese invention patent CN107528488B discloses a method for optimizing the switching frequency of submodules in a flexible DC transmission converter valve. This method first collects the voltage of all submodules within each arm of the converter valve; then it determines whether the voltage of each submodule within the arm is within a set range. If all are within the set range, the state of the k submodules with the lowest switching frequency in that arm is changed, where k is the number of submodules required for that arm. If not all are within the set range, the state of the submodules is controlled according to the voltage order and current direction within the arm, and an equal number of submodules with the lowest switching frequency are selected from those remaining unchanged for either shutdown or activation. This scheme significantly reduces the switching frequency of submodules while maintaining voltage imbalance in the flexible DC transmission converter valve submodules, thereby reducing converter valve losses and improving the efficiency of flexible DC transmission. However, in order to average out the number of switching operations, this scheme forcibly changes the states of the k sub-modules with the lowest switching frequencies, regardless of their current voltage levels. This could result in a sub-module with a lower voltage but fewer switching operations being put into charging, while a sub-module with an even lower voltage is disconnected. This comes at the cost of sacrificing the optimal instantaneous voltage balance, leading to voltage imbalance among the sub-modules. Furthermore, this scheme relies on historical switching frequencies, impacting the system's responsiveness to the current instantaneous state. Summary of the Invention

[0006] The purpose of this invention is to provide a power electronic device, a method, apparatus, and storage medium for optimizing the switching frequency of the power electronic device, in order to solve the problems of sub-module voltage imbalance and slow system response speed caused by existing solutions.

[0007] To address the aforementioned technical problems, this invention provides a technical solution for optimizing the switching frequency of power electronic equipment, as detailed below: The present invention provides a method for optimizing the switching frequency of power electronic equipment, comprising: When the bridge arm current direction is the charging direction, if the voltage of the submodule in the energized state is less than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's maximum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage minus the charging voltage gain; the charging voltage gain is half of the difference between the submodule's maximum voltage and the voltage standard value. When the bridge arm current direction is the discharge direction, if the voltage of the submodule in the energized state is greater than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's minimum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage plus the discharge voltage gain; the discharge voltage gain is half of the difference between the voltage standard value and the submodule's minimum voltage.

[0008] The beneficial effects of the above technical solution are as follows: The core idea of ​​the switching frequency optimization method of the present invention is to increase the probability that a submodule that was in the working state at the previous moment will remain in the working state at a subsequent moment when sorting the submodule voltages. Based on this idea, the following different strategies are designed for charging and discharging. During charging, for submodules with lower voltages, the sorted voltage is increased by adding the difference between its own voltage and the maximum voltage of the submodule to its own voltage; for submodules with higher voltages, the sorted voltage is decreased by a charging voltage gain. During discharging, for submodules with higher voltages, the sorted voltage is increased by adding the difference between its own voltage and the minimum voltage of the submodule to its own voltage; for submodules with lower voltages, the sorted voltage is increased by adding a discharging voltage gain to its own voltage. This method can make the relative positions of the two submodules in the sorting sequence more stable, increasing the probability that a single module maintains its relative position (i.e., remains in the working state) internally. The overall sorting is still based on the submodule voltage, avoiding the submodule voltage imbalance problem in the prior art. Moreover, the system response speed is faster, thereby reducing the switching frequency, effectively reducing the energy loss of the flexible DC converter valve, and improving the system transmission efficiency.

[0009] Furthermore, the voltage standard value is the average voltage of a single bridge arm submodule.

[0010] Furthermore, the method of controlling the entry and exit of sub-modules based on the sorting voltage of each sub-module is as follows: for a certain bridge arm, the sub-modules on the bridge arm are sorted according to the sorting voltage of each sub-module on the bridge arm, and the sub-modules are entered or exited accordingly based on the number of sub-modules to be entered in the bridge arm and the sorting result.

[0011] Furthermore, the method of correspondingly deploying or deploying sub-modules based on the number and sorting results of the sub-modules to be deployed in the bridge arm is as follows: if the current direction of the bridge arm is the charging direction, then deploy the N sub-modules with lower voltage on the bridge arm and deploy the remaining sub-modules; if the current direction of the bridge arm is the discharging direction, then deploy the N sub-modules with higher voltage on the bridge arm and deploy the remaining sub-modules; where N is the number of sub-modules to be deployed in the bridge arm.

[0012] To address the aforementioned technical problems, the present invention also provides a technical solution for a power electronic equipment switching frequency optimization device, as detailed below: A power electronic device switching frequency optimization apparatus includes a processor that executes a computer program to implement the steps of the following method: When the bridge arm current direction is the charging direction, if the voltage of the submodule in the energized state is less than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's maximum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage minus the charging voltage gain; the charging voltage gain is half of the difference between the submodule's maximum voltage and the voltage standard value. When the bridge arm current direction is the discharge direction, if the voltage of the submodule in the energized state is greater than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's minimum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage plus the discharge voltage gain; the discharge voltage gain is half of the difference between the voltage standard value and the submodule's minimum voltage.

[0013] The beneficial effects of the above technical solution are as follows: The device of the present invention provides basic hardware support for realizing the power electronic device switching frequency optimization method of the present invention, ensuring the reliable implementation of the method. The core idea of ​​the entire switching frequency optimization method is to increase the probability that a submodule that was in the working state at the previous moment will still be in the working state at a subsequent moment when sorting the submodule voltages. Based on this idea, the following different strategies are designed for charging and discharging. During charging, for submodules with smaller voltages, the sorted voltage is made by adding the difference between its own voltage and the maximum voltage of the submodule to its own voltage; for submodules with larger voltages, the sorted voltage is made by subtracting a charging voltage gain from its own voltage. During discharging, for submodules with larger voltages, the sorted voltage is made by adding the difference between its own voltage and the minimum voltage of the submodule to its own voltage; for submodules with smaller voltages, the sorted voltage is made by adding a discharging voltage gain to its own voltage. This method ensures that the relative positions of the two sub-modules in the sorting sequence are relatively stable, increasing the probability that a single module can maintain its relative position (i.e., remain in the working state) internally. The overall sorting is still based on the sub-module voltage, avoiding the problem of sub-module voltage imbalance in existing technologies. Furthermore, the system response speed is faster, thereby reducing the switching frequency, effectively reducing the energy loss of the flexible DC converter valve, and improving the system transmission efficiency.

[0014] Furthermore, the voltage standard value is the average voltage of a single bridge arm submodule.

[0015] Furthermore, the method of controlling the entry and exit of sub-modules based on the sorting voltage of each sub-module is as follows: for a certain bridge arm, the sub-modules on the bridge arm are sorted according to the sorting voltage of each sub-module on the bridge arm, and the sub-modules are entered or exited accordingly based on the number of sub-modules to be entered in the bridge arm and the sorting result.

[0016] Furthermore, the method of correspondingly deploying or deploying sub-modules based on the number and sorting results of the sub-modules to be deployed in the bridge arm is as follows: if the current direction of the bridge arm is the charging direction, then deploy the N sub-modules with lower voltage on the bridge arm and deploy the remaining sub-modules; if the current direction of the bridge arm is the discharging direction, then deploy the N sub-modules with higher voltage on the bridge arm and deploy the remaining sub-modules; where N is the number of sub-modules to be deployed in the bridge arm.

[0017] To address the aforementioned technical problems, the present invention also provides a technical solution for a computer-readable storage medium, as detailed below: A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the following method: When the bridge arm current direction is the charging direction, if the voltage of the submodule in the energized state is less than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's maximum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage minus the charging voltage gain; the charging voltage gain is half of the difference between the submodule's maximum voltage and the voltage standard value. When the bridge arm current direction is the discharge direction, if the voltage of the submodule in the energized state is greater than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's minimum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage plus the discharge voltage gain; the discharge voltage gain is half of the difference between the voltage standard value and the submodule's minimum voltage.

[0018] The beneficial effects of the above technical solution are as follows: the storage medium of this invention stores software code implementing the method of this invention, ensuring the reliable execution of the method. The core idea of ​​the entire switching frequency optimization method is to increase the probability that a submodule that was in the active state at the previous moment will still be active at a subsequent moment when sorting the submodule voltages. Based on this idea, the following different strategies for charging and discharging are designed. During charging, for submodules with smaller voltages, the sorted voltage is made by adding the difference between its own voltage and the maximum voltage of the submodule to its own voltage; for submodules with larger voltages, the sorted voltage is made by subtracting a charging voltage gain from its own voltage. During discharging, for submodules with larger voltages, the sorted voltage is made by adding the difference between its own voltage and the minimum voltage of the submodule to its own voltage; for submodules with smaller voltages, the sorted voltage is made by adding a discharging voltage gain to its own voltage. This method ensures that the relative positions of the two sub-modules in the sorting sequence are relatively stable, increasing the probability that a single module can maintain its relative position (i.e., remain in the working state) internally. The overall sorting is still based on the sub-module voltage, avoiding the problem of sub-module voltage imbalance in existing technologies. Furthermore, the system response speed is faster, thereby reducing the switching frequency, effectively reducing the energy loss of the flexible DC converter valve, and improving the system transmission efficiency.

[0019] Furthermore, the voltage standard value is the average voltage of a single bridge arm submodule.

[0020] Furthermore, the method of controlling the entry and exit of sub-modules based on the sorting voltage of each sub-module is as follows: for a certain bridge arm, the sub-modules on the bridge arm are sorted according to the sorting voltage of each sub-module on the bridge arm, and the sub-modules are entered or exited accordingly based on the number of sub-modules to be entered in the bridge arm and the sorting result.

[0021] Furthermore, the method of correspondingly deploying or deploying sub-modules based on the number and sorting results of the sub-modules to be deployed in the bridge arm is as follows: if the current direction of the bridge arm is the charging direction, then deploy the N sub-modules with lower voltage on the bridge arm and deploy the remaining sub-modules; if the current direction of the bridge arm is the discharging direction, then deploy the N sub-modules with higher voltage on the bridge arm and deploy the remaining sub-modules; where N is the number of sub-modules to be deployed in the bridge arm.

[0022] To address the aforementioned technical problems, the present invention also provides a technical solution for a power electronic device, as detailed below: A power electronic device includes six arms and an arm controller. Each arm has multiple sub-modules. The arm controller includes a processor that executes a computer program to implement the steps of the following method: When the bridge arm current direction is the charging direction, if the voltage of the submodule in the energized state is less than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's maximum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage minus the charging voltage gain; the charging voltage gain is half of the difference between the submodule's maximum voltage and the voltage standard value. When the bridge arm current direction is the discharge direction, if the voltage of the submodule in the energized state is greater than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's minimum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage plus the discharge voltage gain; the discharge voltage gain is half of the difference between the voltage standard value and the submodule's minimum voltage.

[0023] The beneficial effects of the above technical solution are as follows: The power electronic device of the present invention uses the switching frequency optimization method of the present invention to control the input and output states of submodules. The core idea of ​​the entire switching frequency optimization method is to increase the probability that a submodule that was in the input state at the previous moment will still be in the input state at a subsequent moment when sorting the submodule voltages. Based on this idea, the following different strategies are designed for charging and discharging. During charging, for submodules with lower voltages, the sorted voltage is made by adding the difference between its own voltage and the maximum voltage of the submodule to its own voltage; for submodules with higher voltages, the sorted voltage is made by subtracting a charging voltage gain from its own voltage. During discharging, for submodules with higher voltages, the sorted voltage is made by adding the difference between its own voltage and the minimum voltage of the submodule to its own voltage; for submodules with lower voltages, the sorted voltage is made by adding a discharging voltage gain to its own voltage. This method ensures a more stable relative position of the two submodules in the sorting sequence, increasing the probability that a single module maintains its relative position (i.e., remains in the active state). The overall sorting is still based on submodule voltage, avoiding the voltage imbalance problem found in existing technologies. Furthermore, the system response is faster, reducing the switching frequency, effectively lowering the energy loss of the flexible DC converter valve, and improving system transmission efficiency. This method is accurate and efficient, and can be widely applied to various new power electronic devices involving submodule sorting.

[0024] Furthermore, the power electronic device is an MMC, a DC-side direct-connected energy storage valve, or an SVG.

[0025] Furthermore, the submodule is a half-bridge submodule.

[0026] Furthermore, the voltage standard value is the average voltage of a single bridge arm submodule.

[0027] Furthermore, the method of controlling the entry and exit of sub-modules based on the sorting voltage of each sub-module is as follows: for a certain bridge arm, the sub-modules on the bridge arm are sorted according to the sorting voltage of each sub-module on the bridge arm, and the sub-modules are entered or exited accordingly based on the number of sub-modules to be entered in the bridge arm and the sorting result.

[0028] Furthermore, the method of correspondingly deploying or deploying sub-modules based on the number and sorting results of the sub-modules to be deployed in the bridge arm is as follows: if the current direction of the bridge arm is the charging direction, then deploy the N sub-modules with lower voltage on the bridge arm and deploy the remaining sub-modules; if the current direction of the bridge arm is the discharging direction, then deploy the N sub-modules with higher voltage on the bridge arm and deploy the remaining sub-modules; where N is the number of sub-modules to be deployed in the bridge arm. Attached Figure Description

[0029] Figure 1 This is a flowchart of the power electronic equipment switching frequency optimization method of the present invention; Figure 2a This is a schematic diagram showing the relationship between the bridge arm current direction and the submodule capacitor charging in this invention; Figure 2b This is a schematic diagram showing the relationship between the bridge arm current direction and the submodule capacitor discharge of the present invention; Figure 3 This is a submodule topology diagram of the present invention. Detailed Implementation

[0030] The core idea of ​​the switching frequency optimization method of this invention is to increase the probability that a submodule that was in the active state at a previous moment will remain active in a subsequent moment when sorting the submodule voltages. The switching frequency optimization method of this invention includes two operating logics: charging and discharging. Both charging and discharging states can effectively reduce the energy loss of the flexible DC converter valve and improve the system transmission efficiency. To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings.

[0031] An implementation method for optimizing the switching frequency of power electronic equipment: This invention provides a method for optimizing the switching frequency of power electronic equipment. This method is not only applicable to MMCs (Multi-Module Control Systems), but also to novel power electronic equipment involving submodule sequencing, such as DC-side direct-connected energy storage valves and SVG (Static Var Generator). The core optimization idea is to increase the probability of a submodule that was in operation at a previous time step remaining in operation at subsequent time steps during the submodule voltage sequencing process.

[0032] Based on this idea, the switching frequency optimization method of the present invention includes two operating logics: electrical and discharging. The entire process is as follows: Figure 1 As shown: When the bridge arm current direction is the charging direction, for each submodule in the energized state, if its submodule voltage V SM Less than or equal to the standard voltage value V0, i.e., V SM If the voltage is ≤V0, then the sorting voltage of the submodule is set to the submodule's own voltage V. SM The submodule's own voltage V is superimposed. SM The difference U between the maximum voltage of the submodule MAX That is, sorting voltage = V SM ×2-U MAX Submodule voltage V SM Greater than the standard voltage value V0, i.e., V SM If the value is greater than V0, set the sorting voltage of the submodule to its own voltage V. SM Subtract the charging voltage gain Δ1, where Δ1 is the maximum voltage U of the submodule. MAX Half the difference between the voltage standard value V0 and the sorted voltage = V SM -△1=V SM -(U MAX -V0) / 2. After determining the sorting voltage of each submodule in the input state, the submodules are sorted according to the sorting voltage. For each bridge arm, the N submodules with the lower voltage in that bridge arm are input, and the remaining submodules are cut off.

[0033] When the bridge arm current direction is the discharge direction, for each submodule in the energized state, if its submodule voltage V SM Greater than or equal to the standard voltage value V0, i.e., V SM If V0 ≥ 0, then the sorting voltage of the submodule is set to the submodule's own voltage V. SM The submodule's own voltage V is superimposed. SM The difference U between the minimum voltage of the submodule MIN That is, sorting voltage = V SM ×2-U MIN Submodule voltage V SM Less than the standard voltage value V0, i.e., V SM <V0, set the sorting voltage of this submodule to the submodule's own voltage V. SM Subtract the discharge voltage gain Δ2, where Δ2 is the voltage standard value V0 and the submodule minimum voltage U. MIN Half of the difference, i.e., sorting voltage = V SM -△2=V SM +(V0-U MIN ) / 2. After determining the sorting voltage of each submodule in the input state, sort the submodules according to the sorting voltage. For each bridge arm, input the N submodules with the higher voltage in that bridge arm and cut off the remaining submodules.

[0034] Regardless of whether it is charging or discharging, the standard voltage value V0 for voltage comparison can typically be set to the average voltage U of a single bridge arm submodule. AVE Accordingly, the entire plan is as follows: During charging, if V SM ≤U AVE Then the sorting voltage = V SM ×2-U MAX If V SM >U AVE Then the sorting voltage = V SM -△1=V SM -(U MAX -V0) / 2; During discharge, if V SM ≥U AVE Then the sorting voltage = V SM ×2-U MIN If V SM <U AVE Then the sorting voltage = V SM +△2=V SM +(V0-U MIN ) / 2.

[0035] Moreover, the number N of sub-modules that need to be deployed in the above process is generally calculated by the upper-level control unit. The calculated number of sub-modules to be deployed for each bridge arm is sent to the bridge arm controller, which sorts the sub-module voltages of each bridge arm.

[0036] In the above scheme, each submodule is not simply sorted according to its actual voltage, but rather clearly divided into two groups through calculation of the sorted voltage. For example, during charging, they are divided into a low-voltage group (V... SM ≤U AVE ) and high voltage group (V SM >U AVE In the low-voltage group, the sorting voltage is V. SM ×2-U MAX The characteristic of this formula is that when V SM Approaching U AVE At that time, due to the subtraction of U MAX This results in a lower sorting voltage, with the sorting voltages of all such submodules clustered closely at the bottom of the entire sorting sequence. In the high-voltage group, the sorting voltage is V. SM -△1, where △1 is V SM -(U MAX-V0) / 2 is a relatively large positive number, which shifts the overall sorting voltage of this type of submodule upwards, placing it in the upper-middle part of the sorting sequence. For a submodule to switch from the low-voltage group to the high-voltage group, its actual voltage must increase from below the average to above the average. This prevents the submodule's sorting position from repeatedly jumping around the input / output boundary when the submodule voltage fluctuates slightly near the average value, thus greatly stabilizing the state. Furthermore, in the low-voltage group, its sorting voltage is V... SM ×2-U MAX This amplifies the differences, making the relative positions of the two sub-modules in the sorting sequence more stable, thus increasing the probability that a single module will maintain its relative position (i.e., remain in the activated state) within the low-voltage group. The same applies to the discharge situation.

[0037] Taking the optimization of the switching frequency of a flexible DC converter valve in a certain project as an example, the specific implementation of the present invention is illustrated. The MMC submodule topology used in this project is as follows: Figure 3 As shown, this is the structure of a half-bridge submodule, with its charging and discharging directions as follows: Figure 2a , Figure 2b As shown, the system includes components such as bypass thyristors, bypass switches, upper IGBTs, lower IGBTs, capacitors, voltage equalizing resistors, secondary control boards, and power supplies. The system design parameters are as follows: active power 2000MW, DC voltage ±500kV, submodule rated voltage 2.1kV, and 500 bridge arm submodules.

[0038] To optimize the switching frequency of the flexible DC converter valve, it is necessary to distinguish between the charging and discharging states.

[0039] Switching frequency optimization during charging: For submodules in the active state, voltage V... SM Sort the data and monitor the average voltage U of the bridge arm submodules. AVE and the maximum voltage U of the sub-module MAX For example, the average voltage U of the submodule AVE It is 2150V. When V SM When the voltage is >2150V, the sorting voltage of each submodule in the energized state is determined according to "V". SM -(2350-2150) / 2=V SM -100” is calculated; when V SM When the voltage is ≤2150V, the sorting voltage is in “V” order. SM The result calculated using ×2-2350” is (i.e., the superimposed submodule's own voltage and U) MAX (the difference).

[0040] Switching frequency optimization under discharge conditions: Monitor the average voltage of the bridge arm submodules, such as the average submodule voltage U. AVEThe voltage V of the submodule in the energized state is set to 2000V, with 2000V as the threshold. SM Sort the submodules by their minimum voltage U. MIN When V SM When the voltage is <2000V, the sorting voltage of each submodule in the input state is determined according to "V". SM +(2150-1850) / 2=V SM +100” is calculated; when V SM When the voltage is ≥2000V, the sorting voltage is in “V” order. SM ×2-1850” calculation (i.e., superimposing the submodule's own voltage and U) MIN (the difference).

[0041] The above-mentioned switching frequency optimization strategy was substituted into the system design parameters for simulation verification. The results show that the optimized average switching frequency is 100Hz, while the switching frequency under the traditional strategy is 121Hz. This demonstrates that the novel switching frequency optimization strategy can effectively reduce the switching frequency of the MMC submodule, reduce the loss of the flexible DC converter valve, and improve the system transmission efficiency.

[0042] An implementation method for a power electronic equipment switching frequency optimization device: This invention discloses a power electronic device switching frequency optimization device. The device includes a memory, a processor, an internal bus, and a computer program stored in the memory. The processor and memory communicate and exchange data via the internal bus. The processor executes the computer program to implement the steps of the power electronic device switching frequency optimization method of this invention. The processor can be a microprocessor (MCU), a programmable logic device (FPGA), or other processing devices. The memory can be various types of memory that store information using electrical energy, such as RAM or ROM, or other types of memory.

[0043] Specifically, the device can ultimately exist in the form of a bridge arm controller for power electronic devices.

[0044] The core content of this method is: During charging, if V SM ≤U AVE Then the sorting voltage = V SM ×2-U MAX If V SM >U AVE Then the sorting voltage = V SM -△1=V SM -(U MAX -V0) / 2; During discharge, if V SM ≥U AVE Then the sorting voltage = V SM ×2-UMIN If V SM <U AVE Then the sorting voltage = V SM +△2=V SM +(V0-U MIN ) / 2.

[0045] For more detailed information on this method, please refer to the description of the method in an implementation plan of a method for optimizing the switching frequency of power electronic equipment.

[0046] One embodiment of a computer-readable storage medium: This invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the power electronic device switching frequency optimization method of this invention as described above. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory, electrically erasable programmable read-only memory, erasable programmable read-only memory, programmable read-only memory, read-only memory, etc.

[0047] The storage medium can be the memory in the arm controller of a power electronic device (such as an MMC).

[0048] The core content of this method is: During charging, if V SM ≤U AVE Then the sorting voltage = V SM ×2-U MAX If V SM >U AVE Then the sorting voltage = V SM -△1=V SM -(U MAX -V0) / 2; During discharge, if V SM ≥U AVE Then the sorting voltage = V SM ×2-U MIN If V SM <U AVE Then the sorting voltage = V SM +△2=V SM +(V0-U MIN ) / 2.

[0049] For more detailed information on this method, please refer to the description of the method in an implementation plan of a method for optimizing the switching frequency of power electronic equipment.

[0050] An embodiment of a power electronic device: The present invention provides a power electronic device, which can be an MMC, or a novel power electronic device involving the sequencing of submodules, such as a DC-side direct-connected energy storage valve or an SVG.

[0051] This embodiment targets an MMC-type power electronic device, which includes six bridge arms and a bridge arm controller to control the on / off switching of sub-modules on each bridge arm. The multiple sub-modules on each bridge arm can be as follows: Figure 3 The submodule of the topology shown is a half-bridge submodule structure, including components such as bypass thyristors, bypass switches, upper IGBT, lower IGBT, capacitors, voltage equalizing resistors, secondary control boards, and power supplies. The bridge arm controller includes a processor, which executes a computer program to implement the steps of the power electronic equipment switching frequency optimization method of the present invention.

[0052] The core content of this method is: During charging, if V SM ≤U AVE Then the sorting voltage = V SM ×2-U MAX If V SM >U AVE Then the sorting voltage = V SM -△1=V SM -(U MAX -V0) / 2; During discharge, if V SM ≥U AVE Then the sorting voltage = V SM ×2-U MIN If V SM <U AVE Then the sorting voltage = V SM +△2=V SM +(V0-U MIN ) / 2.

[0053] For more detailed information on this method, please refer to the description of the method in an implementation plan of a method for optimizing the switching frequency of power electronic equipment.

[0054] In summary, this invention proposes a novel switching frequency strategy optimization method for flexible DC-DC converter valves, which effectively reduces energy loss and improves system transmission efficiency. This method is accurate and efficient, and can be widely applied to novel power electronic devices involving submodule sequencing, such as flexible DC-DC converter valves, DC-side direct-connected energy storage valves, and static var generators (SVG).

Claims

1. A method for optimizing the switching frequency of power electronic equipment, characterized in that, include: When the bridge arm current direction is the charging direction, if the voltage of the submodule in the energized state is less than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's maximum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage minus the charging voltage gain; the charging voltage gain is half of the difference between the submodule's maximum voltage and the voltage standard value. When the bridge arm current direction is the discharge direction, if the voltage of the submodule in the energized state is greater than or equal to the voltage standard value, the sorting voltage of the submodule is set to the submodule's own voltage plus the difference between the submodule's own voltage and the submodule's minimum voltage; otherwise, the sorting voltage of the submodule is set to the submodule's own voltage plus the discharge voltage gain; the discharge voltage gain is half of the difference between the voltage standard value and the submodule's minimum voltage.

2. The method for optimizing the switching frequency of power electronic equipment according to claim 1, characterized in that, The standard voltage value is the average voltage of a single bridge arm submodule.

3. The method for optimizing the switching frequency of power electronic equipment according to claim 1 or 2, characterized in that, The method of controlling the entry and exit of submodules based on the sorting voltage of each submodule is as follows: For a certain bridge arm, the submodules on the bridge arm are sorted according to the sorting voltage of each submodule on the bridge arm, and the submodules are entered or exited accordingly based on the number of submodules to be entered in the bridge arm and the sorting result.

4. The method for optimizing the switching frequency of power electronic equipment according to claim 3, characterized in that, The method of deploying or deploying submodules according to the number and sorting results of the submodules to be deployed in the bridge arm is as follows: if the current direction of the bridge arm is the charging direction, then deploy the N submodules with lower voltage on the bridge arm and deploy the remaining submodules; if the current direction of the bridge arm is the discharging direction, then deploy the N submodules with higher voltage on the bridge arm and deploy the remaining submodules; where N is the number of submodules to be deployed in the bridge arm.

5. A power electronic equipment switching frequency optimization device, comprising a processor, characterized in that, The processor executes a computer program to implement the steps of the method described in any one of claims 1 to 4.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 4.

7. A power electronic device comprising six arms and an arm controller, each arm having multiple sub-modules, the arm controller including a processor, characterized in that, The processor executes a computer program to implement the steps of the method described in any one of claims 1 to 4.

8. The power electronic device according to claim 7, characterized in that, The power electronic equipment is an MMC, a DC-side direct-connected energy storage valve, or an SVG.

9. The power electronic device according to claim 7, characterized in that, The submodule is a half-bridge submodule.

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