Modular multilevel matrix converter grid-connected starting system and method

Abstract

The application belongs to the technical field of power electronic control, and discloses a modular multilevel matrix converter grid-connected starting system and method, which comprises a power module control module, a soft bypass module and a voltage boosting module are arranged in the power module control module; the soft bypass module is used for acquiring the module voltage of each power module, and according to the module voltage of each power module, the deviation between the DC voltage value of the power module on each bridge arm in the modular multilevel matrix converter and the preset DC voltage instruction value is less than the preset unlocking deviation threshold; the voltage boosting module is used for acquiring the current module voltage of each power module, generating a pulse sequence according to the current module voltage and the rated module voltage of each power module, and sending the pulse sequence to each power module, so that the current module voltage of each power module is boosted to the rated module voltage, the module voltage can be balanced, and the impact current in the whole starting process can be effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of power electronic control technology and relates to a modular multilevel matrix converter grid-connected startup system and method. Background Technology

[0002] Due to the large available space and potential of offshore wind power, many well-developed wind power projects are located offshore. With the development of offshore wind power, the next generation of offshore wind farms is expected to be located 300km offshore, making the solutions for wind power grid connection and long-distance, large-capacity transmission extremely important. Fractional Frequency Transmission System (FFTS) technology, as a novel transmission method, improves power frequency AC transmission by reducing the transmission frequency to decrease transmission reactance, thereby increasing transmission capacity. This significantly extends the transmission distance of high-voltage AC transmission and has been increasingly recognized by researchers as one of the most promising solutions for offshore wind power transmission and grid connection. The AC / AC converter is the core device of FFTS, and the Modular Multilevel Matrix Converters (M3C) within the AC / AC converter features low output harmonics, low switching frequency, direct AC-AC conversion, good scalability and redundancy, and has also received widespread attention in fields such as variable frequency speed control.

[0003] Currently, research on modular multilevel matrix converters mainly focuses on outer loop control, inner current loop control, capacitor voltage equalization control, circulating current control, carrier phase shift modulation, and space vector pulse width modulation. However, research on startup methods for modular multilevel matrix converters is relatively limited.

[0004] Chinese patent application CN110661410A discloses a protective startup method for a modular multilevel matrix converter (M3C) system. This method involves pre-charging the uncontrolled rectifier submodule capacitors before performing controlled charging of the submodule capacitor voltage. Specifically, the submodule capacitor voltage after uncontrolled charging is used as the initial reference value for closed-loop control, with the reference value linearly increasing over time to the rated voltage of the submodule capacitor. However, this method has the following drawback: in practical engineering, the differences in components constituting the power module and the different positions of the power modules lead to inconsistent submodule voltages after uncontrolled charging, making it difficult to determine a suitable initial reference value for the submodule capacitor voltage. Another Chinese patent application, CN102983735A, discloses a modular multilevel matrix converter capacitor pre-charging system and method, which divides the submodules on each bridge arm into two groups for uncontrolled charging. However, this method is only suitable for systems with high input-side charging power supply voltage and low rated voltage of the module capacitors; otherwise, the module capacitor voltage can only be charged to a relatively low level, causing a significant impact during unlocking. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing M3C system startup method, which has a small applicable range and causes a relatively large impact when unlocking, and to provide a modular multilevel matrix converter grid-connected startup system and method.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a grid-connected startup system for a modular multilevel matrix converter, comprising a power module control module; the power module control module includes a soft bypass module and a boost module; both the soft bypass module and the boost module are connected to each power module of the modular multilevel matrix converter.

[0008] The soft bypass module is used to obtain the module voltage of each power module, and based on the module voltage of each power module, the deviation between the DC voltage value of each power module on each bridge arm in the soft bypass modular multilevel matrix converter and the preset DC voltage command value is less than the preset unlocking deviation threshold.

[0009] The boost module is used to obtain the current module voltage of each power module, and generate a pulse sequence based on the current module voltage and the rated module voltage of each power module and send it to each power module; the pulse sequence is used to trigger the current module voltage of each power module to boost to the rated module voltage.

[0010] Optionally, it also includes a soft-start resistor, a soft-start resistor bypass switch, and a switch control module; one end of the soft-start resistor is used to connect to the AC power supply, and the other end is connected to the modular multilevel matrix converter; the soft-start resistor bypass switch is connected in parallel with the soft-start resistor; the switch control module is connected to the soft-start resistor bypass switch.

[0011] The switch control module is used to obtain the DC voltage value of each bridge arm in the modular multilevel matrix converter, and close the soft-start resistor bypass switch when the DC voltage value of each bridge arm in the modular multilevel matrix converter is greater than the preset soft-start resistor cut-off voltage threshold.

[0012] Optionally, it may also include a first AC circuit breaker and a second AC circuit breaker;

[0013] The soft-start resistor is connected to the AC power supply through the first AC circuit breaker, and the second AC circuit breaker is connected to the low-frequency side of the modular multilevel matrix converter. Both the first and second AC circuit breakers are connected to the switch control module, which is also used to control the opening and closing of the first and second AC circuit breakers.

[0014] Optionally, the soft-start resistor cut-off voltage threshold is 0.9 times the peak phase voltage of the grid to be connected, and the unlocking deviation threshold is 10% of the DC voltage command value.

[0015] Optionally, the power modules on each bridge arm of the soft-side modular multilevel matrix converter include:

[0016] During each interrupt cycle of the power module control module, the following steps are performed:

[0017] For each bridge arm within the modular multilevel matrix converter, the following steps are performed for each bridge arm:

[0018] The number of power modules in the soft bypass is increased one by one according to the order of the module voltage of each power module on the current bridge arm from large to small, until the number of power modules in the soft bypass on the current bridge arm reaches the preset number.

[0019] Optionally, the preset quantity N bypass We obtain it from the following formula:

[0020]

[0021] Where, N sm_all U represents the number of power modules on the current bridge arm, and round(.) is the floor function. grid_line U is the effective value of the phase voltage on the AC side. dc_ref This is the DC voltage command value.

[0022] Optionally, the boost module is specifically used for:

[0023] The current module voltage of each power module is obtained. Based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module using the ramp linear boost method. The pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage in the ramp linear boost method.

[0024] In a second aspect, the present invention provides a grid-connected startup method for a modular multilevel matrix converter, applicable to a grid-connected startup system for a modular multilevel matrix converter, wherein the grid-connected startup system for the modular multilevel matrix converter includes a power module control module; the power module control module includes a soft bypass module and a boost module.

[0025] The grid-connected startup method for the modular multilevel matrix converter includes:

[0026] The module voltage of each power module is obtained through the soft bypass module, and based on the module voltage of each power module, the deviation between the DC voltage value of each power module on each bridge arm in the soft bypass modular multilevel matrix converter and the preset DC voltage command value is less than the preset unlocking deviation threshold.

[0027] The current module voltage of each power module is obtained through the boost module. Based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module. The pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage.

[0028] Optionally, the modular multilevel matrix converter grid-connected startup system further includes a soft-start resistor, a soft-start resistor bypass switch, and a switch control module; one end of the soft-start resistor is used to connect to the AC power supply, and the other end is connected to the modular multilevel matrix converter; the soft-start resistor bypass switch is connected in parallel with the soft-start resistor; the switch control module is connected to the soft-start resistor bypass switch.

[0029] The grid-connected startup method for the modular multilevel matrix converter also includes:

[0030] The DC voltage values ​​of each bridge arm in the modular multilevel matrix converter are obtained through the switch control module, and when the DC voltage value of each bridge arm in the modular multilevel matrix converter is greater than the preset soft-start resistor cut-off voltage threshold, the soft-start resistor bypass switch is closed.

[0031] Optionally, the power modules on each bridge arm of the soft-side modular multilevel matrix converter include:

[0032] During each interrupt cycle of the power module control module, the following steps are performed:

[0033] For each bridge arm within the modular multilevel matrix converter, the following steps are performed for each bridge arm:

[0034] According to the order of the module voltage of each power module on the current bridge arm from large to small, increase the number of soft bypass power modules one by one until the number of soft bypass power modules on the current bridge arm reaches the preset number.

[0035] The step of generating a pulse sequence and sending it to each power module based on the current module voltage and the rated module voltage of each power module includes:

[0036] Based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module using the ramp linear boost method; the pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage in a ramp linear boost manner.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] This invention relates to a modular multilevel matrix converter grid-connected startup system. The soft bypass module can bypass the power modules on each bridge arm within the modular multilevel matrix converter. Through a self-equalizing voltage strategy of bypassing a certain number of power modules, it ensures that the module voltages of each power module are balanced, even if the components constituting the power modules differ or the power modules are located differently. Simultaneously, based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module, causing the current module voltage of each power module to gradually rise to its rated module voltage. This suppresses the inrush current during the process of the module voltage rising to the rated value, effectively reducing the inrush current when the modular multilevel matrix converter is unlocked and connected to the grid.

[0039] Furthermore, a soft-start resistor is set to limit the current and then charge the power modules on each bridge arm of the modular multilevel matrix converter uncontrolled. This is suitable not only for systems with high input power supply voltage and low rated voltage of module capacitors, but also for systems with low input power supply voltage and high rated voltage of module capacitors. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the grid-connected startup system structure of a modular multilevel matrix converter according to an embodiment of the present invention.

[0041] Figure 2 This is a topology diagram of a modular multilevel matrix converter according to an embodiment of the present invention.

[0042] Figure 3 Embodiments of the present invention Figure 2 Detailed topology diagram at point A in the middle.

[0043] Figure 4 This is a flowchart of the grid-connected startup method for a modular multilevel matrix converter according to an embodiment of the present invention.

[0044] Wherein: 1-AC power supply; 2-first AC circuit breaker; 3-soft start resistor bypass switch; 4-modular multilevel matrix converter; 5-second AC circuit breaker; 6-soft start resistor. Detailed Implementation

[0045] 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 protection of the present invention.

[0046] 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.

[0047] The present invention will now be described in further detail with reference to the accompanying drawings:

[0048] See Figures 1 to 3 In one embodiment of the present invention, a grid-connected startup system for a modular multilevel matrix converter is provided, including a power module control module; the power module control module is provided with a soft bypass module and a boost module; both the soft bypass module and the boost module are connected to each power module of the modular multilevel matrix converter 4.

[0049] The soft bypass module is used to acquire the module voltage of each power module, and based on the module voltage of each power module, the deviation between the DC voltage value of each power module on each bridge arm of the soft bypass modular multilevel matrix converter 4 and the preset DC voltage command value is less than a preset unlocking deviation threshold. The boost module is used to acquire the current module voltage of each power module, and based on the current module voltage and the rated module voltage of each power module, generate a pulse sequence and send it to each power module. The pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage.

[0050] This invention relates to a modular multilevel matrix converter grid-connected startup system. The soft bypass module can bypass the power modules on each bridge arm within the modular multilevel matrix converter 4. Through a self-equalizing voltage strategy of bypassing a certain number of power modules, it ensures that the module voltages of each power module are balanced, even if the components constituting the power modules differ or their positions are different. Simultaneously, based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module, causing the current module voltage of each power module to gradually rise to its rated module voltage. This suppresses the inrush current during the process of the module voltage rising to its rated value, effectively reducing the inrush current when the modular multilevel matrix converter 4 is unlocked and connected to the grid.

[0051] In one possible implementation, the modular multilevel matrix converter grid-connected startup system further includes a soft-start resistor, a soft-start resistor bypass switch 3, and a switch control module; one end of the soft-start resistor is connected to the AC power supply 1, and the other end is connected to the modular multilevel matrix converter 4; the soft-start resistor bypass switch 3 is connected in parallel with the soft-start resistor; and the switch control module is connected to the soft-start resistor bypass switch 3.

[0052] The switch control module is used to obtain the DC voltage value of each bridge arm in the modular multilevel matrix converter 4, and close the soft start resistor bypass switch 3 when the DC voltage value of each bridge arm in the modular multilevel matrix converter 4 is greater than the preset soft start resistor cut-off voltage threshold.

[0053] Specifically, by limiting the current through the soft-start resistor 6, uncontrolled charging is performed on the power modules on each bridge arm of the modular multilevel matrix converter 4. This method is suitable not only for systems with high input-side charging power supply voltage and low rated voltage of module capacitors, but also for systems with low input-side charging power supply voltage and high rated voltage of module capacitors.

[0054] In one possible implementation, the modular multilevel matrix converter grid-connected start-up system further includes a first AC circuit breaker 2 and a second AC circuit breaker 5; a soft-start resistor is connected to the AC power supply 1 through the first AC circuit breaker 2, and the second AC circuit breaker 5 is connected to the output side of the modular multilevel matrix converter 4; both the first AC circuit breaker 2 and the second AC circuit breaker 5 are connected to a switch control module, which is also used to control the opening and closing of the first AC circuit breaker 2 and the second AC circuit breaker 5.

[0055] By setting up the first AC circuit breaker 2 and the second AC circuit breaker 5, convenient control of the connection and disconnection between the modular multilevel matrix converter 4 and the AC source and the low-frequency side power grid can be achieved.

[0056] In one possible implementation, the soft-start resistor cut-off voltage threshold is 0.9 times the peak phase voltage of the grid to be connected, and the unlocking deviation threshold is 10% of the DC voltage command value.

[0057] Specifically, by considering the characteristics of the grid voltage after rectification by the power module diodes, the soft-start resistor cut-off voltage threshold is set to 0.9 times the peak phase voltage of the grid to be connected. By considering grid voltage fluctuations and sampling circuit errors, the unlocking deviation threshold is set to 10% of the DC voltage command value.

[0058] In one possible implementation, the power modules on each bridge arm of the soft-side modular multilevel matrix converter 4 include: in each interrupt cycle of the power module control module, the following steps are performed: for each bridge arm of the modular multilevel matrix converter 4, the following steps are performed for each bridge arm: according to the order of the module voltage of each power module on the current bridge arm from large to small, the number of soft-side power modules is increased one by one until the number of soft-side power modules on the current bridge arm reaches a preset number.

[0059] Wherein, the preset quantity N bypass We obtain it from the following formula:

[0060]

[0061] Where, N sm_all U represents the number of power modules on the current bridge arm, and round(.) is the floor function. grid_line U is the effective value of the phase voltage on the AC side. dc_ref This represents the DC voltage command value. The effective value of the AC phase voltage is the effective value of the phase voltage of the grid to be connected, obtained through sampling.

[0062] Specifically, to reduce the current surge during power module disconnection, soft bypass is performed on each bridge arm individually. The number of power modules in the soft bypass gradually increases from 1 to N when the soft bypass begins. bypass Soft bypass Nbypass After each power module, execute the soft bypass N. bypass Self-voltage balancing strategy for high-voltage power modules. Soft bypass N bypass The self-voltage equalization strategy for power modules with high module voltages involves detecting and sorting the module voltages of the power modules on each bridge arm during each processor interrupt cycle, and then... bypass A high-voltage power module is soft-swapped to balance the voltage of the power modules.

[0063] In one possible implementation, generating a pulse sequence based on the current module voltage and the rated module voltage of each power module and sending it to each power module includes: generating a pulse sequence based on a ramp linear boost method and sending it to each power module based on the current module voltage and the rated module voltage of each power module; the pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage in a ramp linear boost manner.

[0064] In summary, the modular multilevel matrix converter grid-connected startup system of this invention, during operation, performs uncontrolled charging of the power modules on each bridge arm of the modular multilevel matrix converter 4 after current limiting by the soft-start resistor. The soft-start resistor 6 is disconnected after the module voltage of the power module reaches the soft-start resistor disconnection threshold. Then, the module voltage of the power modules in each bridge arm is sampled and sorted. A certain number of high-voltage power modules are soft-bypassed to raise the module voltage of the low-voltage power modules and bring them close to their rated values. This soft-bypass is completed for each bridge arm. Finally, the pulse and module voltage controller of the modular multilevel matrix converter 4 is enabled, and the corresponding pulse sequence is sent to each power module of the modular multilevel matrix converter 4, linearly raising the current module voltage of each power module to its rated value via a ramp, thus completing the grid-connected startup.

[0065] See you again Figure 2 and 3 This paper illustrates a modular multilevel matrix converter (MLMC) topology 4, which consists of nine bridge arms. Each bridge arm comprises N H-bridges (power modules) connected in series with an arm inductor Lm, and its two ends are connected to the input three-phase system and the output three-phase system, respectively. The i-th power module on each bridge arm uses an SM-type multilevel matrix converter (MLMC). i In this context, i = 1 to N represents the AC voltage on the low-frequency side (output side), Ulu, Ulv, and Ulw represent the AC voltage on the power frequency side (input side), and Usa, Usb, and Usc represent the AC voltage on the mains frequency side (input side). The power module employs an H-bridge structure, including capacitors, four switching transistors T1 to T4, and four diodes D1 to D4.

[0066] In one possible implementation, a grid-connected startup method for a modular multilevel matrix converter (MMC) is provided, applied to a MMC grid-connected startup system. The MMC grid-connected startup system includes a power module control module; the power module control module contains a soft bypass module and a boost module; the MMC grid-connected startup method includes: acquiring the module voltage of each power module through the soft bypass module, and based on the module voltage of each power module, ensuring that the deviation between the DC voltage value of each power module on each bridge arm of the MMC 4 and a preset DC voltage command value is less than a preset unlocking deviation threshold; acquiring the current module voltage of each power module through the boost module, and generating a pulse sequence based on the current module voltage and the rated module voltage of each power module, sending it to each power module; the pulse sequence is used to trigger the current module voltage of each power module to boost to the rated module voltage.

[0067] In one possible implementation, the modular multilevel matrix converter grid-connected startup system further includes a soft-start resistor, a soft-start resistor bypass switch 3, and a switch control module; one end of the soft-start resistor is connected to the AC power supply 1, and the other end is connected to the modular multilevel matrix converter 4; the soft-start resistor bypass switch 3 is connected in parallel with the soft-start resistor; the switch control module is connected to the soft-start resistor bypass switch 3; the modular multilevel matrix converter grid-connected startup method further includes: obtaining the DC voltage value of each bridge arm in the modular multilevel matrix converter 4 through the switch control module, and closing the soft-start resistor bypass switch 3 when the DC voltage value of each bridge arm in the modular multilevel matrix converter 4 is greater than a preset soft-start resistor cut-off voltage threshold.

[0068] In one possible implementation, the power modules on each bridge arm of the soft-side modular multilevel matrix converter 4 include: in each interrupt cycle of the power module control module, the following steps are performed: for each bridge arm of the modular multilevel matrix converter 4, the following steps are performed for each bridge arm: according to the order of the module voltage of each power module on the current bridge arm from large to small, the number of soft-side power modules is increased one by one until the number of soft-side power modules on the current bridge arm reaches a preset number.

[0069] In one possible implementation, the preset quantity N bypass We obtain it from the following formula:

[0070]

[0071] Where, N sm_all U represents the number of power modules on the current bridge arm, and round(.) is the floor function. grid_line U is the effective value of the phase voltage on the AC side. dc_refThis is the DC voltage command value.

[0072] In one possible implementation, generating a pulse sequence based on the current module voltage and the rated module voltage of each power module and sending it to each power module includes: generating a pulse sequence based on a ramp linear boost method and sending it to each power module based on the current module voltage and the rated module voltage of each power module; the pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage in a ramp linear boost manner.

[0073] In one possible implementation, the soft-start resistor cut-off voltage threshold is 0.9 times the peak phase voltage of the grid to be connected, and the unlocking deviation threshold is 10% of the DC voltage command value.

[0074] In one possible implementation, the modular multilevel matrix converter grid-connected startup method can be based on the above-described modular multilevel matrix converter grid-connected startup method. For details, see [link to relevant documentation]. Figure 4 The modular multilevel matrix converter grid-connected startup method specifically includes the following steps:

[0075] S1: Keep both the first AC circuit breaker 2 on the input side and the second AC circuit breaker 5 on the output side of the modular multilevel matrix converter 4 in the open state.

[0076] S2: A DC voltage sensor is used to detect the module voltage Uci of each power module in each arm of the modular multilevel matrix converter 4. An AC voltage sensor is used to detect the three-phase AC voltages Ulu, Ulv and Ulw on the low-frequency side and the three-phase AC voltages Usa, Usb and Usc on the power frequency side of the modular multilevel matrix converter 4.

[0077] S3: Start the controller, close the first AC circuit breaker 2, keep the second AC circuit breaker 5 open, and perform uncontrolled charging of the power modules in each bridge arm after current limiting by the soft start resistor.

[0078] S4: Calculate the DC voltage value Udci of each bridge arm by detecting the module voltage Uci. When the DC voltage value Udci of the bridge arm is greater than the soft start resistor cut-off voltage threshold Udc_th, close the soft start resistor bypass switch 3 to cut off the soft start resistor 6.

[0079] S5: Controlled charging of the modular multilevel matrix converter 4 is performed one bridge arm at a time. The module voltage of the power module in each bridge arm is sampled and sorted. The T2 and T4 transistors of the power module are turned on, thereby soft-shortening a certain number of power modules with higher voltage to raise the module voltage of the power modules with lower voltage, until the DC voltage value Udci of the bridge arm matches the DC voltage command value U. dc_ref The deviation is less than the unlocking deviation threshold ΔUdc.

[0080] S6: Enables the pulse and boost modules of the modular multilevel matrix converter 4, that is, sends the corresponding pulse sequence to each power module of the modular multilevel matrix converter 4, and finally linearly boosts the module voltage of each power module from the current module voltage to the module voltage rating value through a ramp.

[0081] S7: Close the second AC circuit breaker 5.

[0082] In summary, the grid-connected startup method for the modular multilevel matrix converter of this invention is applicable not only to systems with high input-side charging power supply voltage and low rated module capacitor voltage, but also to systems with low input-side charging power supply voltage and high rated module capacitor voltage. By controlling the self-equalizing voltage strategy of bypassing a certain number of high-voltage modules during the charging phase, it can balance the module voltage even when there are differences in power module components and power module locations. By enabling the pulse and boost modules of the modular multilevel matrix converter 4, the corresponding pulse sequence is sent to each power module of the modular multilevel matrix converter 4, ultimately linearly raising the module voltage of each power module from its current voltage to its rated value via a ramp. This allows the voltage of each power module to rise slowly to its rated value, suppressing the inrush current during the voltage rise process and effectively reducing the inrush current when the modular multilevel matrix converter is unlocked and connected to the grid.

[0083] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0084] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0085] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0086] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable apparatus for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A modular multilevel matrix converter grid-connected startup system, characterized in that, Includes a power module control module; the power module control module is equipped with a soft bypass module and a boost module; both the soft bypass module and the boost module are connected to each power module of the modular multilevel matrix converter (4); The soft bypass module is used to obtain the module voltage of each power module, and according to the module voltage of each power module, the deviation between the DC voltage value of each bridge arm of the power module in the soft bypass modular multilevel matrix converter (4) and the preset DC voltage command value is less than the preset unlocking deviation threshold. The boost module is used to obtain the current module voltage of each power module, and generate a pulse sequence based on the current module voltage and the rated module voltage of each power module, and send it to each power module; the pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage; The power modules on each bridge arm of the soft-side modular multilevel matrix converter (4) include: During each interrupt cycle of the power module control module, the following steps are performed: For each bridge arm within the modular multilevel matrix converter (4), the following steps are performed for each bridge arm: According to the order of the module voltage of each power module on the current bridge arm from large to small, increase the number of soft bypass power modules one by one until the number of soft bypass power modules on the current bridge arm reaches the preset number. The preset quantity We obtain it from the following formula: in, This represents the current number of power modules on the bridge arm. For the floor function, This is the effective value of the phase voltage on the AC side. This is the DC voltage command value; The boost module is specifically used for: The current module voltage of each power module is obtained. Based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module using the ramp linear boost method. The pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage in the ramp linear boost method.

2. The modular multilevel matrix converter grid-connected startup system according to claim 1, characterized in that, It also includes a soft-start resistor, a soft-start resistor bypass switch (3) and a switch control module; one end of the soft-start resistor is used to connect to the AC power supply (1), and the other end is connected to the modular multilevel matrix converter (4); the soft-start resistor bypass switch (3) is connected in parallel with the soft-start resistor; the switch control module is connected to the soft-start resistor bypass switch (3). The switch control module is used to obtain the DC voltage value of each bridge arm in the modular multilevel matrix converter (4), and close the soft start resistor bypass switch (3) when the DC voltage value of each bridge arm in the modular multilevel matrix converter (4) is greater than the preset soft start resistor cut-off voltage threshold.

3. The modular multilevel matrix converter grid-connected startup system according to claim 2, characterized in that, It also includes a first AC circuit breaker (2) and a second AC circuit breaker (5); The soft-start resistor is connected to the AC power supply (1) through the first AC circuit breaker (2), and the second AC circuit breaker (5) is connected to the low-frequency side of the modular multilevel matrix converter (4). The first AC circuit breaker (2) and the second AC circuit breaker (5) are both connected to the switch control module, which is also used to control the opening and closing of the first AC circuit breaker (2) and the second AC circuit breaker (5).

4. The modular multilevel matrix converter grid-connected startup system according to claim 2, characterized in that, The soft-start resistor cut-off voltage threshold is 0.9 times the peak phase voltage of the grid to be connected, and the unlocking deviation threshold is 10% of the DC voltage command value.

5. A method for grid-connected startup of a modular multilevel matrix converter, characterized in that, This invention relates to a grid-connected startup system for modular multilevel matrix converters, wherein the system includes a power module control module; the power module control module contains a soft bypass module and a boost module. Both the soft bypass module and the boost module are connected to the power modules of the modular multilevel matrix converter (4); The grid-connected startup method for the modular multilevel matrix converter includes: The module voltage of each power module is obtained through the soft bypass module, and according to the module voltage of each power module, the deviation between the DC voltage value of each power module on each bridge arm of the soft bypass modular multilevel matrix converter (4) and the preset DC voltage command value is less than the preset unlocking deviation threshold. The current module voltage of each power module is obtained through the boost module. Based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module. The pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage. The power modules on each bridge arm of the soft-side modular multilevel matrix converter (4) include: During each interrupt cycle of the power module control module, the following steps are performed: For each bridge arm within the modular multilevel matrix converter (4), the following steps are performed for each bridge arm: According to the order of the module voltage of each power module on the current bridge arm from large to small, increase the number of soft bypass power modules one by one until the number of soft bypass power modules on the current bridge arm reaches the preset number. The preset quantity We obtain it from the following formula: in, This represents the current number of power modules on the bridge arm. For the floor function, This is the effective value of the phase voltage on the AC side. This is the DC voltage command value; The step of generating a pulse sequence and sending it to each power module based on the current module voltage and the rated module voltage of each power module includes: Based on the current module voltage and the rated module voltage of each power module, a pulse sequence is generated and sent to each power module using the ramp linear boost method; the pulse sequence is used to trigger the current module voltage of each power module to be boosted to the rated module voltage in a ramp linear boost manner.

6. The modular multilevel matrix converter grid-connected startup method according to claim 5, characterized in that, The modular multilevel matrix converter grid-connected start-up system also includes a soft-start resistor, a soft-start resistor bypass switch (3), and a switch control module; one end of the soft-start resistor is used to connect to the AC power supply (1), and the other end is connected to the modular multilevel matrix converter (4); the soft-start resistor bypass switch (3) is connected in parallel with the soft-start resistor; The switch control module is connected to the soft-start resistor bypass switch (3); The grid-connected startup method for the modular multilevel matrix converter also includes: The DC voltage values ​​of each bridge arm in the modular multilevel matrix converter (4) are obtained through the switch control module, and when the DC voltage values ​​of each bridge arm in the modular multilevel matrix converter (4) are greater than the preset soft-start resistor cut-off voltage threshold, the soft-start resistor bypass switch (3) is closed.

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