AC / DC voltage coordination matching control method for modular commutation type converter

Abstract

The invention discloses an alternating current and direct current voltage coordination matching control method of a modular commutation type converter. The method comprises the following steps: generating three-phase sine reference signals corresponding to single-phase converters based on electrical data of an MCC alternating current side; on the basis of a delay commutation trigger mechanism, a commutation delay angle is introduced to modulate a three-phase sine reference signal, so that each cascade module chain is controlled to perform voltage synthesis, and a direct-current side output voltage of the modular commutation type converter is obtained; real-time current data of the MCC direct current side are collected, and when it is judged that the direct current side output voltage or the real-time current data meet the voltage reduction triggering preset condition, a commutation delay angle in a delay commutation triggering mechanism is dynamically adjusted according to the direct current side output voltage and the real-time current data; and a target delay angle is obtained to repeat the modulation process of the three-phase sine reference signal until the voltage reduction trigger preset condition is not satisfied any more, so that continuous and stable operation of the AC side voltage during the abnormal drop period of the DC side voltage is ensured.

Description

Technical Field

[0001] This invention relates to the field of DC power transmission technology in power systems, and in particular to a method for AC / DC voltage coordination and matching control of a modular commutator converter. Background Technology

[0002] The converter is the core component in DC power transmission, enabling bidirectional conversion between AC and DC energy. Its engineering applications have gone through two stages: line-commutated converter (LCC) and voltage-source converter (VSC). In VSC technology, the modular multilevel converter (MMC) has become the mainstream topology for flexible DC transmission, possessing advantages such as low harmonic content, independent power decoupling control, and no commutation failure. Meanwhile, with the continuous evolution of topologies and the development of new power devices, various new DC technology routes are gradually developing.

[0003] High-overload modular commutated converters (MCCs) based on IGCT devices offer advantages in terms of loss, size, and number of components compared to conventional and flexible DC technologies. However, the tight coupling between AC and DC voltages in MCC technology makes it difficult to independently adjust the DC voltage, resulting in inflexible configuration of DC energy storage capacity, higher costs, and significant challenges in matching AC and DC voltages during DC-side faults.

[0004] Therefore, there is an urgent need for a control technology that can flexibly adjust the DC side voltage of the MCC in order to achieve coordinated matching and stability of the AC and DC side voltages of the MCC. Summary of the Invention

[0005] This invention provides a method for coordinated AC / DC voltage matching control of a modular commutator converter, solving the problem of how to provide a precise control technology for flexibly adjusting the DC side voltage of the MCC to achieve coordinated matching and stability of the AC / DC side voltage of the MCC.

[0006] To address the aforementioned technical problems, the first aspect of this invention provides a method for coordinated AC / DC voltage matching control of a modular commutator, wherein the modular commutator includes three single-phase converters, each single-phase converter including an AC-side turn-off commutator bridge and a cascaded module chain on the DC side, and the DC sides of the three single-phase converters are connected in series to form a common DC bus; wherein the method includes: The electrical data of the AC side is acquired in real time, and a three-phase sinusoidal reference signal corresponding to each of the single-phase converters is generated based on the electrical data. Based on the delayed commutation triggering mechanism, the three-phase sinusoidal reference signal is modulated by introducing a commutation delay angle, and the voltage synthesis of each cascaded module chain is controlled according to the modulation result to obtain the DC-side output voltage of the modular commutator; the commutation delay angle is configured as the bridge arm switch triggering sequence of the turn-off commutator bridge in each single-phase converter. The real-time current data of the common DC bus is acquired, and when the DC side output voltage or the real-time current data is determined to meet the preset conditions for buck triggering, the commutation delay angle is dynamically adjusted according to the DC side output voltage or the real-time current data to obtain the target delay angle. The modulation process of the three-phase sinusoidal reference signal is repeated according to the target delay angle until the buck trigger preset condition is not met, so as to realize the AC / DC voltage coordination and matching control of the modular commutator.

[0007] As one preferred embodiment, the cascaded module chain is composed of several cascaded sub-modules, wherein the sub-modules are half-bridge sub-modules or full-bridge sub-modules; the shut-off commutation bridge includes four bridge arms using IGCT devices.

[0008] As one preferred embodiment, the step of generating a three-phase sinusoidal reference signal corresponding to each of the single-phase converters based on the electrical data includes: The power grid base frequency and real-time phase are extracted from the electrical data to generate a three-phase sinusoidal reference signal that is consistent with the power grid base frequency and corresponds to each of the single-phase converters; the three phases in the three-phase sinusoidal reference signal are determined based on the real-time phase. The three-phase sinusoidal reference signal is standardized to obtain the processed three-phase sinusoidal reference signal.

[0009] As one preferred embodiment, the method based on delayed commutation triggering, which modulates the three-phase sinusoidal reference signal by introducing a commutation delay angle, includes: The positive and negative half-cycles of the three-phase sinusoidal reference signal are determined by a comparator to generate an initial square wave modulation signal that is synchronized with the positive and negative half-cycles. The commutation delay angle is introduced into the initial square wave modulation signal to generate a delayed square wave modulation signal to control the execution of each of the shut-off commutation bridges, so as to flip the negative half-cycle of the three-phase sinusoidal reference signal to obtain a three-phase modulation wave.

[0010] As one preferred embodiment, the step of controlling each of the cascaded module chains to perform voltage synthesis based on the modulation result to obtain the DC-side output voltage of the modular commutator includes: Based on the three-phase modulation wave, the number of sub-modules in each cascaded module chain is controlled to obtain the three-phase phase-shifted voltage; The three-phase phase-shifted voltages are connected in series and superimposed on the DC side to synthesize a DC voltage as the DC-side output voltage of the modular commutator.

[0011] As one preferred embodiment, the step of determining that the DC-side output voltage or the real-time current data meets the preset conditions for buck triggering includes: When the DC-side output voltage is less than a preset voltage data, it is determined that the DC-side output voltage meets the preset condition for buck triggering; or when the real-time current data is greater than a preset current data, it is determined that the real-time current data meets the preset condition for buck triggering.

[0012] As one preferred embodiment, the step of dynamically adjusting the commutation delay angle based on the DC-side output voltage or the real-time current data to obtain the target delay angle includes: The voltage difference is determined based on the DC-side output voltage and the preset voltage data, and the current difference is determined based on the real-time current data and the preset current data. The voltage difference or the current difference is used as input, and a PI controller is used to perform proportional-integral calculations to obtain the dynamic compensation amount. The target delay angle is obtained by adjusting the commutation delay angle using the dynamic compensation amount.

[0013] A second aspect of the present invention provides an AC / DC voltage coordination and matching control system for a modular commutator, wherein the modular commutator includes three single-phase converters, each single-phase converter including an AC-side turn-off commutator bridge and a cascaded module chain on the DC side, and the DC sides of the three single-phase converters are connected in series to form a common DC bus; wherein the system includes: The signal generation module is used to acquire the electrical data of the AC side in real time and generate a three-phase sinusoidal reference signal corresponding to each of the single-phase converters based on the electrical data. A voltage synthesis module is used to modulate the three-phase sinusoidal reference signal by introducing a commutation delay angle based on a delayed commutation triggering mechanism, and to control each of the cascaded module chains to perform voltage synthesis according to the modulation result, so as to obtain the DC-side output voltage of the modular commutated converter; the commutation delay angle is configured as the bridge arm switch triggering sequence of the turn-off commutation bridge in each of the single-phase converters. The delay angle adjustment module is used to acquire the real-time current data of the common DC bus, and when it is determined that the DC side output voltage or the real-time current data meets the voltage reduction trigger preset condition, dynamically adjust the commutation delay angle according to the DC side output voltage or the real-time current data to obtain the target delay angle; The iterative buck module is used to repeatedly modulate the three-phase sinusoidal reference signal according to the target delay angle until the buck trigger preset condition is not met, so as to realize the AC / DC voltage coordinated matching control of the modular commutator.

[0014] A third aspect of the present invention provides an electronic device including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the AC / DC voltage coordination and matching control method for a modular commutated converter as described above.

[0015] A fourth aspect of the present invention provides a computer-readable storage medium comprising a stored computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the AC / DC voltage coordination and matching control method for a modular commutator as described above.

[0016] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows: By dynamically adjusting the commutation delay angle, the duty cycle of the positive and negative half-cycles of the three-phase modulation wave can be directly changed, thereby precisely controlling the amplitude of the DC component after the three phases are superimposed. This solves the problem that the DC voltage is difficult to adjust independently due to the voltage coupling between the AC and DC sides of the MCC. The control logic is based on a three-phase sinusoidal reference signal + square wave modulation architecture, which does not require additional complex controller configuration. It has a fast response and is easy to implement, achieving coordinated matching and stability of the AC and DC sides of the MCC. This improves the operational flexibility and economy of the modular commutator converter and has certain engineering application prospects. Attached Figure Description

[0017] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a structural diagram of a modular commutator provided in a certain embodiment of the present invention; Figure 2 This is a flowchart of an AC / DC voltage coordination and matching control method for a modular commutator provided in a certain embodiment of the present invention; Figure 3 This is a diagram illustrating the synthesis process of the DC-side output voltage according to a certain embodiment of the present invention; Figure 4 This is a waveform diagram of the commutation control modulation wave and DC voltage output of each phase of the MCC when the square wave is triggered without delay, according to a certain embodiment of the present invention. Figure 5 This is a waveform diagram of the commutation control modulation wave and DC voltage output of each phase of the MCC when the square wave is triggered by a 30° delay, according to a certain embodiment of the present invention. Figure 6 This is a waveform diagram of the commutation control modulation wave and DC voltage output of each phase of the MCC when the width of the positive and negative half-cycles of the square wave changes, according to a certain embodiment of the present invention. Figure 7 This is a structural diagram of an AC / DC voltage coordination and matching control system for a modular commutator provided in a certain embodiment of the present invention; Figure 8 This is a structural diagram of an electronic device provided in a certain embodiment of the present invention; Figure label: Among them, 10 is the signal generation module; 20 is the voltage synthesis module; 30 is the delay angle adjustment module; 40 is the iterative step-down module; 5000 is the electronic equipment; 5001 is the processor; 5002 is the bus; 5003 is the memory; and 5004 is the transceiver. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings and examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of this application, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art will be able to understand the specific meaning of the above terms in this application according to the specific circumstances.

[0021] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is merely for describing specific embodiments and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] In one embodiment, the first aspect of the present invention provides an AC / DC voltage coordination and matching control method for a modular commutator, wherein the structure of the modular commutator is as follows: Figure 1 As shown, the modular commutator includes three single-phase converters (valve groups A, B, and C). Each single-phase converter includes an AC-side shut-off commutator bridge (H-bridge) and a DC-side cascaded module chain. The DC side of the single-phase converter is connected in series via MCC single-phase converter valves to form a common DC bus, thereby supporting the DC-side high-voltage output. The AC side of the three single-phase converters is connected to the AC grid through a converter transformer.

[0023] Please see Figure 1 Taking valve group A of a single-phase converter as an example, the shut-off commutation bridge includes four H-bridge arms (H1, H2, H3, H4) composed of IGCT devices. The AC port of the H-bridge (the connection point between the midpoints of two bridge arms) is connected to the AC power grid through the converter transformer to receive single-phase AC voltage input. The DC port of the H-bridge is directly connected to the AC side port of the corresponding cascaded module chain to flip the negative half-cycle of the three-phase AC voltage to the positive half-cycle waveform during operation, thereby providing input voltage to the cascaded module chain port. The cascaded module chain is composed of several sub-modules consistent with conventional MMC cascaded together (SM). A1 SM A2 SM An The submodules are either half-bridge or full-bridge submodules (SM), or a hybrid structure of both. A half-bridge submodule contains two switching devices (such as IGBTs), one capacitor, and an anti-parallel diode. A full-bridge submodule contains four switching devices and a capacitor, allowing for more flexible voltage polarity adjustment. The cascaded module chain converts the input flipped voltage into the DC port voltage of the single-phase converter through the switching combination of submodules, thus constructing the DC port voltage of the single-phase converter in series at the bridge ports. The single-phase converter valve groups B and C have the same structure as single-phase converter valve group A, and the number of cascaded submodules in the cascaded module chain is also the same, which will not be elaborated further here.

[0024] The AC / DC voltage coordination and matching control method, such as Figure 2 As shown, it includes: S1. Real-time acquisition of electrical data on the AC side, and generation of three-phase sinusoidal reference signals corresponding to each single-phase converter based on the electrical data; Specifically, the present invention uses voltage, current and other sensors to collect in real-time electrical data of the distribution network on the AC side (connected via converter transformer) of each single-phase converter in the modular commutator, including the amplitude, frequency and phase information of AC voltage / current, etc.

[0025] In one embodiment, generating a three-phase sinusoidal reference signal corresponding to each of the single-phase converters based on the electrical data includes: The power grid base frequency and real-time phase are extracted from the electrical data to generate a three-phase sinusoidal reference signal that is consistent with the power grid base frequency and corresponds to each of the single-phase converters; the three phases in the three-phase sinusoidal reference signal are determined based on the real-time phase. The three-phase sinusoidal reference signal is standardized to obtain the processed three-phase sinusoidal reference signal.

[0026] Specifically, a digital phase-locked loop (DPLL) is used to extract the power grid fundamental frequency and real-time phase from the acquired electrical data to ensure that subsequent signals are strictly synchronized with the power grid. Based on the extracted fundamental frequency and phase, a sinusoidal reference signal with the same fundamental frequency as the power grid and a phase difference of 2π / 3 (120°) between its three phases is generated. The specific rules are as follows: Three single-phase converters correspond to the three phases respectively. Phase A generates a sine wave with the same fundamental frequency as the power grid, based on the real-time phase. The sine wave generated by phase B has a phase of θ + 2π / 3, which is 120° out of phase with phase A. The sine wave generated by phase C has a phase of θ + 4π / 3, which is 240° out of phase with phase A. This forms a three-phase sinusoidal reference signal, which is expressed by the following formula: In the formula, , , These are the sinusoidal reference signals for phases A, B, and C, respectively. It represents the amplitude of the three-phase sinusoidal voltage, which is determined by the amplitude of the three-phase voltage of the AC system. w Angular frequency; t For time; f For frequency.

[0027] Next, the generated three-phase sinusoidal reference signal is normalized to obtain the processed three-phase sinusoidal reference signal, which is adapted to the signal interface requirements of the subsequent square wave modulation stage.

[0028] This invention generates a three-phase sinusoidal reference signal by extracting the grid base frequency and real-time phase, which enables the output of the single-phase converter to be strictly synchronized with the grid, avoiding phase abrupt changes and power oscillations during grid connection and improving system stability; the sinusoidal signal with a phase difference of 120° can suppress harmonic pollution and reduce three-phase imbalance.

[0029] S2. Based on the delayed commutation triggering mechanism, the three-phase sinusoidal reference signal is modulated by introducing a commutation delay angle, and the voltage synthesis of each cascaded module chain is controlled according to the modulation result to obtain the DC-side output voltage of the modular commutation converter; the commutation delay angle is configured as the bridge arm switch triggering sequence of the turn-off commutation bridge in each single-phase converter. In one embodiment, the method of modulating the three-phase sinusoidal reference signal by introducing a commutation delay angle based on the delayed commutation triggering mechanism includes: The positive and negative half-cycles of the three-phase sinusoidal reference signal are determined by a comparator to generate an initial square wave modulation signal that is synchronized with the positive and negative half-cycles. The commutation delay angle is introduced into the initial square wave modulation signal to generate a delayed square wave modulation signal to control the execution of each of the shut-off commutation bridges, so as to flip the negative half-cycle of the three-phase sinusoidal reference signal to obtain a three-phase modulation wave.

[0030] Specifically, this invention modulates a three-phase sinusoidal reference signal based on a delayed commutation triggering mechanism. This delayed commutation triggering mechanism introduces an adjustable delay angle into the triggering sequence of the commutator bridge shutdown, changing the reversal time of the negative half-cycle of the AC voltage, thereby controlling the duty cycle of the positive and negative half-cycles of the cascaded module chain modulation wave, ultimately achieving the core control strategy of flexible DC-side voltage reduction. This modulation process includes: Each phase of the sinusoidal signal is input to a comparator and compared with the zero potential (0). When the sinusoidal signal is ≥0, the comparator outputs +1; when the sinusoidal signal is <0, the comparator outputs -1. This yields three initial square wave signals that are completely synchronized with the positive and negative half-cycles of the sine wave. At this time, the rising and falling edges of the square wave are aligned with the zero-crossing point of the sine wave.

[0031] Next, a time delay is added at each transition edge (including the rising and falling edges) of the generated initial square wave signal. The electrical angle corresponding to this delay time is the commutation delay angle α, which is initially zero, resulting in three delayed square wave modulated signals, which are expressed by the following formula: In the formula, The delayed square wave modulation signal of phase A is calculated in the same way as the delayed square wave modulation signals of the other two phases, only the value ranges are different, and the phase difference between the three phases is 2π / 3.

[0032] The standardized three-phase sinusoidal reference signal is multiplied point-by-point with the three corresponding delayed square wave signals (i.e., multiplied once per sampling period in the digital controller). In the +1 range of the square wave, the sine wave remains unchanged; in the -1 range, the polarity of the sine wave is reversed (i.e., the negative half-cycle becomes positive), resulting in the final three-phase modulated wave. Because the square wave is delayed, only the negative half-cycle portion of the sine wave exceeding angle α is reversed, thus forming an asymmetrical waveform with a wide positive half-cycle and a narrow (or vice versa) negative half-cycle. This waveform determines the final voltage shape of the cascaded module chain output. Furthermore, the generated delayed square wave signal itself directly serves as the trigger signal to drive the turn-off commutator bridge (H-bridge) of the corresponding modular commutator. Based on this signal, the H-bridge guides current to allow the positive half-cycle to pass at +1 level and performs commutation operation at -1 level, reversing the negative half-cycle to obtain the three-phase modulated wave. The duty cycle of the positive and negative half-cycles of the three-phase modulated wave varies with α.

[0033] This invention can continuously adjust the DC-side output voltage through a single control parameter—the commutation delay angle α—solving the inherent problem of tight coupling between the AC and DC sides of the MCC. It can maintain the stability of the AC-side voltage even when the DC-side voltage drops or even reaches zero. This control strategy does not require any additional power circuits or complex auxiliary equipment, making it low-cost and easy to implement in engineering. The control logic is essentially signal processing, with low computational load and short delay, enabling it to respond quickly to changes in system operating conditions.

[0034] In one embodiment, controlling each of the cascaded module chains to perform voltage synthesis based on the modulation result to obtain the DC-side output voltage of the modular commutator includes: Based on the three-phase modulation wave, the number of sub-modules in each cascaded module chain is controlled to obtain the three-phase phase-shifted voltage; The three-phase phase-shifted voltages are connected in series and superimposed on the DC side to synthesize a DC voltage as the DC-side output voltage of the modular commutator.

[0035] Specifically, for each phase of the three-phase modulated wave, based on the instantaneous amplitude of the current modulated wave and the rated voltage of the submodule capacitor, calculate the number N of submodules that need to be put into operation: N = round(V mod (t) / V sm ); where V mod (t) represents the instantaneous amplitude of the modulated wave; V smThe rated voltage of the submodule capacitor is denoted by 'round', which represents the round function and embodies the concept of nearest-level approximation modulation. From the pool of available submodules for this phase, several submodules with the lowest capacitor voltages are selected for activation (sending trigger pulses) according to a capacitor voltage balancing strategy, while the remaining submodules are bypassed. This ensures that the capacitor voltages of all submodules remain balanced during operation, preventing overvoltage in individual capacitors. The activated submodule capacitors are connected in series and summed, generating a stepped wave voltage at the output port of this phase. After multiple stages of series connection, this stepped wave closely approximates the ideal modulation wave, forming a multi-level three-phase phase-shifted voltage.

[0036] The DC outputs of three single-phase converters are directly connected in series in the circuit. According to Kirchhoff's voltage law, the total voltage in the series circuit is equal to the sum of the individual voltages. This allows for the synthesis of a total DC voltage, and the amplitude of the DC component of the summation waveform can be used as the DC-side output voltage of the modular commutator. Since the three-phase AC voltages are 120° out of phase, when they are connected in series on the DC side, specific harmonics (especially low-order harmonics) of each phase voltage will cancel each other out due to the phase difference. Ultimately, the main component of the DC bus voltage ripple is boosted to 6 times the power frequency, resulting in a significant reduction in ripple amplitude.

[0037] The process of synthesizing the DC-side output voltage is as follows: Figure 3 As shown, this invention introduces a flexible voltage reduction mechanism with a delayed commutation, so that energy storage devices directly connected to the DC side no longer need to be strictly bound to a fixed DC voltage. This can optimize energy storage capacity configuration and improve system economy and operational flexibility.

[0038] S3. Obtain the real-time current data of the common DC bus, and when it is determined that the DC side output voltage or the real-time current data meets the voltage reduction trigger preset condition, dynamically adjust the commutation delay angle according to the DC side output voltage or the real-time current data to obtain the target delay angle. In one embodiment, determining that the DC-side output voltage or the real-time current data meets the buck trigger preset condition includes: When the DC-side output voltage is less than a preset voltage data, it is determined that the DC-side output voltage meets the preset condition for buck triggering; or when the real-time current data is greater than a preset current data, it is determined that the real-time current data meets the preset condition for buck triggering.

[0039] Specifically, this invention uses current sensors to collect real-time current data of the common DC bus. When the real-time current data exceeds a preset current data, the circuit is determined to be overcurrent, thus meeting the preset conditions for voltage reduction triggering; or when the DC-side output voltage is less than a preset voltage data, the DC bus voltage is determined to be undervoltage, also meeting the preset conditions for voltage reduction triggering. The preset current data is the normal operating current that the system aims to maintain, and the preset voltage data is the normal operating voltage that the system aims to maintain, determined based on the actual circuit conditions or expert experience. The DC-side voltage of the MCC is generated by modulating the AC-side voltage, and the two are closely coupled. When the DC-side voltage drops or even reaches zero during system operation, the AC-side voltage is affected and drops synchronously. Therefore, this invention proposes a delayed commutation mechanism to achieve DC-side voltage reduction by adjusting the delayed trigger angle: when the DC-side voltage drops under certain scenarios (such as DC-side faults), the system actively adjusts the delayed trigger angle to ensure that the calculated DC-side output voltage actively matches the dropped DC voltage, preventing the AC-side voltage from dropping synchronously, thus maintaining the coordinated matching and stability of the MCC AC and DC-side voltages.

[0040] This invention proactively intervenes during system transient faults by monitoring key operating parameters in real time, thereby improving system stability and reliability. It introduces two independent criteria: undervoltage and overcurrent, ensuring reliable activation of protection mechanisms during transient faults. The judgment logic is simple to calculate and can be completed within microseconds in a digital controller. Once the conditions are met, it immediately sends instructions to subsequent step-down control circuits, achieving rapid response and effectively maintaining AC voltage stability to prevent system instability.

[0041] In one embodiment, the step of dynamically adjusting the commutation delay angle based on the DC-side output voltage or the real-time current data to obtain the target delay angle includes: The voltage difference is determined based on the DC-side output voltage and the preset voltage data, and the current difference is determined based on the real-time current data and the preset current data. The voltage difference or the current difference is used as input, and a PI controller is used to perform proportional-integral calculations to obtain the dynamic compensation amount. The target delay angle is obtained by adjusting the commutation delay angle using the dynamic compensation amount.

[0042] Specifically, under undervoltage conditions, the voltage difference between the DC-side output voltage and the preset voltage data is calculated. This voltage difference is then used as input, and a PI controller performs proportional-integral calculations to obtain the dynamic compensation amount. The PI controller calculates the compensation using the following formula: In the formula, This is a dynamic compensation amount; , These are the proportional coefficient and the integral coefficient, respectively. This is the voltage difference; For time.

[0043] Alternatively, under overcurrent conditions, the dynamic compensation amount can be obtained by calculating the current difference between real-time current data and preset current data, then using this current difference as input, and performing proportional-integral calculations through a PI controller. The PI controller calculates according to the following formula: In the formula, This represents the current difference.

[0044] The calculated dynamic compensation amount is added to the original commutation delay angle to obtain the target delay angle. Alternatively, the difference between the maximum DC voltage at α=0 and the target voltage can be divided by the rate of change of DC voltage with α determined by simulation or experimental data, and the quotient can be used as the dynamic compensation amount.

[0045] This invention uses a PI controller to calculate the adjustment amount of the commutation delay angle, achieving zero steady-state error control, which can improve dynamic response performance and stability, enhance system robustness, and the output of the PI controller is continuously changing, which makes the adjustment of the delay angle α smooth and gradual, avoiding current surges and harmonic problems caused by step changes, and ensuring the stability of power conversion.

[0046] S4. The modulation process of the three-phase sinusoidal reference signal is repeated according to the target delay angle until the voltage reduction trigger preset condition is not met, so as to realize the AC / DC voltage coordination and matching control of the modular commutator. Specifically, the present invention introduces the calculated target delay angle into the square wave modulation signal, and repeatedly executes the process of modulation of the three-phase sinusoidal reference signal, superposition of three-phase voltage and DC side voltage output, so as to adjust the positive and negative half-cycle duty cycles of the three-phase modulation wave (the larger α is, the smaller the positive half-cycle duty cycle is, and the lower the DC component of the three-phase superposition is), and monitors the calculated DC side output voltage and the real-time current data of the common DC bus in real time. When neither of them meets the voltage reduction trigger condition, the α adjustment is stopped, the system returns to the normal operation mode, and thus the AC / DC voltage coordination and matching control of the modular commutator is realized.

[0047] Furthermore, the modulated wave and DC voltage output waveform after adopting the AC / DC voltage coordinated matching control method described in the first aspect of the present invention are as follows: When the square wave is triggered without delay, the commutation control modulation wave and DC voltage output waveform of each phase of the MCC are as follows: Figure 4As shown, when the square wave is triggered without delay, the three-phase voltages on the AC grid side are sequentially input to each single-phase converter with a phase difference of 120°. The commutation switch flips the negative half-cycle of the AC voltage based on the square wave signal, turning it into a positive half-cycle waveform. The flipped voltage is sent to the cascaded module chain, and a multi-level sinusoidal half-wave is synthesized through phase shifting and series connection. Finally, a smooth DC voltage is formed at the DC port, thereby realizing the energy conversion from three-phase AC to DC.

[0048] When the square wave is triggered with a 30° delay, the commutation control modulation wave and DC voltage output waveform of each phase of the MCC are as follows: Figure 5 As shown, compared with no-delay triggering, the switching time of the port voltage is delayed due to the 30° delay of the square wave transition, thereby introducing a corresponding negative voltage component, which causes the transient voltage waveform at the DC end to change and reduces the final effective value of the DC voltage output.

[0049] When the widths of the positive and negative half-cycles of the square wave change, the commutation control modulation wave and DC voltage output waveforms of each phase of the MCC are as follows: Figure 6 As shown, compared with the case where α is zero or unmodulated, the transient waveform of the DC voltage at the port changes, and the effective value of the DC voltage after the three phases are superimposed and summed changes with the adjustment of α, thereby further realizing the flexible adjustment and control of the DC port voltage.

[0050] Therefore, it can be seen that when there is a DC side fault, the present invention can achieve matching with the DC voltage by adjusting the delayed firing angle, thereby avoiding AC voltage drop and achieving coordinated stability of the AC and DC side voltages of the MCC.

[0051] This application proposes a precise control technique for flexibly adjusting the DC-side voltage of the MCC to achieve coordinated matching and stability of the AC and DC-side voltages of the MCC. A method for coordinated matching control of the AC and DC voltages of a modular commutator is designed. First, a three-phase sinusoidal reference signal is constructed on the AC side, and its positive and negative half-cycles are determined by a comparator to obtain a time-delayed reference square wave signal. Then, a delayed trigger angle is introduced into this square wave to generate an H-bridge trigger signal for converter control. This trigger signal is multiplied by the three-phase sinusoidal reference signal to form a modulation wave of the cascaded module chain. Finally, the cascaded module chain switches sub-modules SM according to the modulation wave, and after phase shifting and series connection, the required voltage is output on the DC side. By dynamically adjusting the commutation delay angle, the duty cycle of the positive and negative half-cycles of the three-phase modulation wave can be directly changed, thereby precisely controlling the amplitude of the DC component after the three-phase superposition. This solves the problem of difficulty in independently adjusting the DC voltage caused by the coupling of the AC and DC-side voltages of the MCC, achieving coordinated matching and stability of the AC and DC-side voltages of the MCC.

[0052] It should be noted that although the steps in the flowchart above are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order requirement for the execution of these steps, and they can be executed in other orders.

[0053] In another embodiment, such as Figure 7 As shown, a second aspect of the present invention provides an AC / DC voltage coordination and matching control system for a modular commutator, wherein the modular commutator includes three single-phase converters, each single-phase converter including an AC-side turn-off commutator bridge and a cascaded module chain on the DC side, and the DC sides of the three single-phase converters are connected in series to form a common DC bus; wherein the system includes: The signal generation module 10 is used to acquire the electrical data of the AC side in real time, and generate a three-phase sinusoidal reference signal corresponding to each of the single-phase converters based on the electrical data. The voltage synthesis module 20 is used to modulate the three-phase sinusoidal reference signal by introducing a commutation delay angle based on the delayed commutation triggering mechanism, and to control each of the cascaded module chains to perform voltage synthesis according to the modulation result, so as to obtain the DC-side output voltage of the modular commutated converter; the commutation delay angle is configured as the bridge arm switch triggering sequence of the turn-off commutation bridge in each of the single-phase converters. The delay angle adjustment module 30 is used to acquire the real-time current data of the common DC bus, and when it is determined that the DC side output voltage or the real-time current data meets the voltage reduction trigger preset condition, dynamically adjust the commutation delay angle according to the DC side output voltage or the real-time current data to obtain the target delay angle. The iterative buck module 40 is used to repeatedly modulate the three-phase sinusoidal reference signal according to the target delay angle until the buck trigger preset condition is not met, so as to realize the AC / DC voltage coordinated matching control of the modular commutator.

[0054] It should be noted that each module in the AC / DC voltage coordination and matching control system of the aforementioned modular commutator can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module. For specific limitations regarding the AC / DC voltage coordination and matching control system of a modular commutator, please refer to the limitations of the AC / DC voltage coordination and matching control method of a modular commutator described above; both have the same function and role, and will not be repeated here.

[0055] A third aspect of the present invention provides an electronic device comprising: Processor, memory, and bus; The bus is used to connect the processor and the memory; The memory is used to store operation instructions; The processor is configured to execute instructions by calling the operation instructions, causing the processor to perform operations corresponding to the AC / DC voltage coordination and matching control method for a modular commutator as shown in the first aspect of this application.

[0056] In one alternative embodiment, an electronic device is provided, such as Figure 8 As shown, Figure 8 The illustrated electronic device 5000 includes a processor 5001 and a memory 5003. The processor 5001 and the memory 5003 are connected, for example, via a bus 5002. Optionally, the electronic device 5000 may also include a transceiver 5004. It should be noted that in practical applications, the transceiver 5004 is not limited to one type, and the structure of this electronic device 5000 does not constitute a limitation on the embodiments of this application.

[0057] Processor 5001 may be a CPU, a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, transistor logic device, hardware component, or any combination thereof. It may implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. Processor 5001 may also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc.

[0058] Bus 5002 may include a path for transmitting information between the aforementioned components. Bus 5002 may be a PCI bus or an EISA bus, etc. Bus 5002 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 8 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0059] The memory 5003 may be a ROM or other type of static storage device capable of storing static information and instructions, RAM or other type of dynamic storage device capable of storing information and instructions, or it may be an EEPROM, CD-ROM or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto.

[0060] The memory 5003 is used to store application code that executes the scheme of this application, and its execution is controlled by the processor 5001. The processor 5001 is used to execute the application code stored in the memory 5003 to implement the content shown in any of the foregoing method embodiments.

[0061] Among them, electronic devices include, but are not limited to: mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), and in-vehicle terminals (such as in-vehicle navigation terminals), as well as fixed terminals such as digital TVs and desktop computers.

[0062] The fourth aspect of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements an AC / DC voltage coordination and matching control method for a modular commutator as shown in the first aspect of the present application.

[0063] Another embodiment of this application provides a computer-readable storage medium storing a computer program that, when run on a computer, enables the computer to execute the corresponding content in the aforementioned method embodiments.

[0064] Furthermore, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0065] In summary, this invention relates to the field of DC transmission technology in power systems, and discloses a method for coordinated AC / DC voltage matching control of a modular commutator converter. This method generates a three-phase sinusoidal reference signal corresponding to each single-phase converter based on electrical data from the AC side of the MCC. Based on a delayed commutation triggering mechanism, a commutation delay angle is introduced to modulate the three-phase sinusoidal reference signal, and this is used to control the voltage synthesis of each cascaded module chain to obtain the DC-side output voltage of the modular commutator converter. Real-time current data from the DC side of the MCC is collected, and when the DC-side output voltage or real-time current data meets the preset conditions for buck triggering, the commutation delay angle in the delayed commutation triggering mechanism is dynamically adjusted according to the DC-side output voltage and real-time current data to obtain a target delay angle. This is used to repeat the modulation process of the three-phase sinusoidal reference signal until the preset conditions for buck triggering are no longer met, thus ensuring the continuous and stable operation of the AC-side voltage during periods of abnormal DC-side voltage drop.

[0066] The various embodiments in this specification are described in a progressive manner. For directly identical or similar parts of the embodiments, refer to each other. Each embodiment focuses on its differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0067] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A method for coordinated AC / DC voltage matching control of a modular commutator, characterized in that, The modular commutator includes three single-phase converters, each of which includes an AC-side turn-off commutator bridge and a cascaded module chain on the DC side. The DC sides of the three single-phase converters are connected in series to form a common DC bus; wherein, the method includes: The electrical data of the AC side is acquired in real time, and a three-phase sinusoidal reference signal corresponding to each of the single-phase converters is generated based on the electrical data. Based on the delayed commutation triggering mechanism, the three-phase sinusoidal reference signal is modulated by introducing a commutation delay angle, and the voltage synthesis of each cascaded module chain is controlled according to the modulation result to obtain the DC-side output voltage of the modular commutator; the commutation delay angle is configured as the bridge arm switch triggering sequence of the turn-off commutator bridge in each single-phase converter. The real-time current data of the common DC bus is acquired, and when the DC side output voltage or the real-time current data is determined to meet the preset conditions for buck triggering, the commutation delay angle is dynamically adjusted according to the DC side output voltage or the real-time current data to obtain the target delay angle. The modulation process of the three-phase sinusoidal reference signal is repeated according to the target delay angle until the buck trigger preset condition is not met, so as to realize the AC / DC voltage coordination and matching control of the modular commutator.

2. The AC / DC voltage coordination and matching control method for a modular commutator according to claim 1, characterized in that, The cascaded module chain is composed of several cascaded sub-modules, and the sub-modules are half-bridge sub-modules or full-bridge sub-modules; the shut-off commutation bridge includes four bridge arms using IGCT devices.

3. The AC / DC voltage coordination and matching control method for a modular commutator according to claim 1, characterized in that, The step of generating a three-phase sinusoidal reference signal corresponding to each of the single-phase converters based on the electrical data includes: The power grid base frequency and real-time phase are extracted from the electrical data to generate a three-phase sinusoidal reference signal that is consistent with the power grid base frequency and corresponds to each of the single-phase converters; the three phases in the three-phase sinusoidal reference signal are determined based on the real-time phase. The three-phase sinusoidal reference signal is standardized to obtain the processed three-phase sinusoidal reference signal.

4. The AC / DC voltage coordination and matching control method for a modular commutator according to claim 2, characterized in that, The delayed commutation triggering mechanism modulates the three-phase sinusoidal reference signal by introducing a commutation delay angle, including: The positive and negative half-cycles of the three-phase sinusoidal reference signal are determined by a comparator to generate an initial square wave modulation signal that is synchronized with the positive and negative half-cycles. The commutation delay angle is introduced into the initial square wave modulation signal to generate a delayed square wave modulation signal to control the execution of each of the shut-off commutation bridges, so as to flip the negative half-cycle of the three-phase sinusoidal reference signal to obtain a three-phase modulation wave.

5. The AC / DC voltage coordination and matching control method for a modular commutator according to claim 4, characterized in that, The step of controlling each of the cascaded module chains to perform voltage synthesis based on the modulation result to obtain the DC-side output voltage of the modular commutator includes: Based on the three-phase modulation wave, the number of sub-modules in each cascaded module chain is controlled to obtain the three-phase phase-shifted voltage; The three-phase phase-shifted voltages are connected in series and superimposed on the DC side to synthesize a DC voltage as the DC-side output voltage of the modular commutator.

6. The AC / DC voltage coordination and matching control method for a modular commutator according to claim 1, characterized in that, The step of determining whether the DC-side output voltage or the real-time current data meets the preset conditions for buck triggering includes: When the DC-side output voltage is less than a preset voltage data, it is determined that the DC-side output voltage meets the preset condition for buck triggering; or when the real-time current data is greater than a preset current data, it is determined that the real-time current data meets the preset condition for buck triggering.

7. The AC / DC voltage coordination and matching control method for a modular commutator according to claim 6, characterized in that, The step of dynamically adjusting the commutation delay angle based on the DC-side output voltage or the real-time current data to obtain the target delay angle includes: The voltage difference is determined based on the DC-side output voltage and the preset voltage data, and the current difference is determined based on the real-time current data and the preset current data. The voltage difference or the current difference is used as input, and a PI controller is used to perform proportional-integral calculations to obtain the dynamic compensation amount. The target delay angle is obtained by adjusting the commutation delay angle using the dynamic compensation amount.

8. A modular commutator AC / DC voltage coordination and matching control system, characterized in that, The modular commutator includes three single-phase converters, each of which includes an AC-side turn-off commutator bridge and a cascaded module chain on the DC side. The DC sides of the three single-phase converters are connected in series to form a common DC bus; wherein, the system includes: The signal generation module is used to acquire the electrical data of the AC side in real time and generate a three-phase sinusoidal reference signal corresponding to each of the single-phase converters based on the electrical data. A voltage synthesis module is used to modulate the three-phase sinusoidal reference signal by introducing a commutation delay angle based on a delayed commutation triggering mechanism, and to control each of the cascaded module chains to perform voltage synthesis according to the modulation result, so as to obtain the DC-side output voltage of the modular commutated converter; the commutation delay angle is configured as the bridge arm switch triggering sequence of the turn-off commutation bridge in each of the single-phase converters. The delay angle adjustment module is used to acquire the real-time current data of the common DC bus, and when it is determined that the DC side output voltage or the real-time current data meets the voltage reduction trigger preset condition, dynamically adjust the commutation delay angle according to the DC side output voltage or the real-time current data to obtain the target delay angle; The iterative buck module is used to repeatedly modulate the three-phase sinusoidal reference signal according to the target delay angle until the buck trigger preset condition is not met, so as to realize the AC / DC voltage coordinated matching control of the modular commutator.

9. An electronic device, characterized in that, The device includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor, when executing the computer program, implements the AC / DC voltage coordination and matching control method for a modular commutator as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the device containing the computer-readable storage medium executes the computer program, it implements the AC / DC voltage coordination and matching control method for a modular commutator as described in any one of claims 1 to 7.

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