Power droop flux linkage grid-forming modular multilevel converter control method and related device

Abstract

The application provides a power droop flux linkage network configuration type modular multilevel converter control method and related equipment. The method comprises the following steps: acquiring a network side three-phase voltage, three-phase current and DC capacitor voltage; calculating active power and reactive power measurement values according to the three-phase voltage and current; generating a reference voltage phase unit value by using active power-frequency droop control and generating a reference voltage amplitude unit value by using reactive power-voltage droop control; obtaining a three-phase output voltage reference value unit value through polar coordinate-three-phase coordinate conversion; integrating the three-phase voltage unit value and subtracting a DC component to obtain a three-phase flux linkage unit value; and inputting the difference between the three-phase voltage reference value and the three-phase flux linkage unit value into a modulation pulse generation module. The application combines power droop control and flux linkage feedback, can stably operate under strong and weak power grids, realizes autonomous power distribution, effectively suppresses excitation inrush current and low-frequency oscillation, does not require communication, has fast response, is simple to realize, and has strong compatibility.

Description

Technical Field

[0001] This application relates to the field of power system automation technology, and in particular to a control method and related equipment for a power droop flux grid-type modular multilevel converter. Background Technology

[0002] With the accelerated construction of new power systems, modular multilevel converters (MMCs), due to their modular topology, low harmonics, and low power loss, play a crucial role in maintaining the reliability and stability of power systems and are increasingly being widely used in AC-DC or DC-AC conversion fields. Simultaneously, as the proportion of new energy sources in power systems continues to increase, the large-scale integration of power electronic equipment into the grid has led to a decrease in grid stability. Voltage and current fluctuations are more likely to cause wideband oscillations in converters, and the large number of distribution transformers at the moment of distribution circuit closure can generate significant inrush current.

[0003] Grid-based control technology features voltage support and active inertia support, enabling it to replace synchronous machines for grid support and providing the ability to operate under load without an external grid, thus maintaining power system stability. However, traditional grid-based control utilizes self-synchronization to build voltage, resulting in stable operation in weak grids but prone to instability in strong grids. To address the challenges posed by large-scale renewable energy grid integration, modular multilevel converters are required to operate stably in both strong and weak grids.

[0004] Existing technologies have proposed using flux linkage feedback control in grid-based control to improve the stability of strong power grids. However, existing flux linkage feedback schemes typically use DC capacitor voltage PI control and AC voltage PI control as the outer loop to generate reference phase and amplitude. This approach still suffers from drawbacks in scenarios involving renewable energy grid integration with large power fluctuations, such as slow response speed, the need for multi-parameter tuning, and the inability to autonomously respond to power changes.

[0005] Therefore, there is an urgent need for a network-based MMC control method that can leverage the advantages of magnetic flux feedback, achieve autonomous power allocation, eliminate the need for communication, and provide a fast response. Summary of the Invention

[0006] The main objective of this application is to propose a control method, device, electronic device, storage medium, and program product for a power droop flux grid-type modular multilevel converter, aiming to solve the technical problems of poor stability of existing grid-type modular multilevel converters under strong power grid conditions, slow outer loop response of traditional flux feedback schemes, and reliance on PI parameter tuning.

[0007] To achieve the above objectives, one aspect of this application proposes a control method for a power droop flux mesh-type modular multilevel converter, the method comprising: Acquire the three-phase voltage measurement value, three-phase current measurement value, and DC side capacitor voltage measurement value of the modular multilevel converter grid side; Calculate the active power measurement value and reactive power measurement value based on the three-phase voltage measurement value and the three-phase current measurement value; The active power-frequency droop control is adopted. The difference between the measured active power value and the active power reference value is adjusted by the droop coefficient and integrated with the rated angular frequency of the system to generate the per-unit value of the reference voltage phase. The reactive power-voltage droop control is adopted, and the difference between the measured reactive power value and the reference reactive power value is adjusted by the droop coefficient to generate the per-unit value of the reference voltage amplitude. The per-unit values ​​of the reference voltage phase and the reference voltage amplitude are transformed from polar coordinates to three-phase coordinates to obtain the per-unit values ​​of the three-phase output voltage reference values. The three-phase voltage measurements are normalized, integrated, and their DC components are subtracted to obtain the three-phase flux per unit value. The modulation signal is obtained by subtracting the per-unit value of the three-phase output voltage reference value from the per-unit value of the three-phase flux linkage, and then input to the modulation pulse generation module of the modular multilevel converter to generate the drive pulse for each phase arm.

[0008] In some embodiments, the active power measurement value and the reactive power measurement value are calculated based on the dq-axis components of the three-phase flux linkage per unit value and the d-axis and q-axis components of the three-phase current measurement value; wherein, the dq-axis components of the three-phase flux linkage per unit value are obtained by Parker transformation of the three-phase flux linkage per unit value.

[0009] In some embodiments, the per-unit value of the reference voltage phase is generated by the following governing equation:

[0010] in, The per-unit value of the reference voltage phase. The system's rated angular frequency, This is the active power droop coefficient. This is a reference value for active power. This is the measured value of active power.

[0011] In some embodiments, the per-unit value of the reference voltage amplitude is generated by the following governing equation:

[0012] in, This is the per-unit value of the reference voltage amplitude. This is the per-unit value of the rated voltage amplitude. This is the reactive power droop factor. This is a reference value for reactive power. This is the measured value of reactive power.

[0013] In some embodiments, the active power measurement value is calculated using the following formula:

[0014] in, and These represent the d-axis and q-axis components of the per-unit flux linkage measurement at the grid-side outlet of the modular multilevel converter. and These are the d-axis and q-axis components of the grid-side output current of the modular multilevel converter, respectively.

[0015] In some embodiments, the reactive power measurement value is calculated using the following formula:

[0016] in, and These represent the d-axis and q-axis components of the per-unit flux linkage measurement at the grid-side outlet of the modular multilevel converter. and These are the d-axis and q-axis components of the grid-side output current of the modular multilevel converter, respectively.

[0017] In some embodiments, the per-unit value of the three-phase flux linkage is obtained through the following steps: The per-unit values ​​of the three-phase voltage measurements are integrated and multiplied by the system's rated angular frequency to obtain the preliminary per-unit values ​​of the flux linkage. The three-phase flux per unit value is obtained by subtracting its average value over one power frequency cycle from the initial flux per unit value to eliminate the DC component in the flux.

[0018] To achieve the above objectives, another aspect of this application proposes a control device for a power droop flux mesh-type modular multilevel converter, the device comprising: The per-unit module is used to standardize the three-phase voltage measurement values, three-phase current measurement values, and DC-side capacitor voltage measurement values ​​on the grid side of the modular multilevel converter. The power calculation module is used to calculate the active power measurement value and reactive power measurement value based on the per-unit three-phase voltage measurement value and three-phase current measurement value; The active power-frequency droop control module is used to integrate the difference between the measured active power value and the reference active power value with the rated angular frequency of the system after adjusting for droop coefficient, and generate a per-unit value for the reference voltage phase. The reactive power-voltage droop control module is used to generate a per-unit value of the reference voltage amplitude after adjusting the difference between the measured reactive power value and the reference reactive power value through a droop coefficient. The coordinate transformation module is used to transform the per-unit values ​​of the reference voltage phase and the reference voltage amplitude into per-unit values ​​of the three-phase output voltage reference value; The flux linkage observation module is used to integrate the standardized three-phase voltage measurement values ​​and subtract their DC components to obtain the three-phase flux linkage per unit value. The subtractor is used to calculate the difference between the per-unit value of the three-phase output voltage reference value and the per-unit value of the three-phase flux linkage, and output a modulation signal. The modulation pulse generation module is used to generate drive pulses for each phase arm of the modular multilevel converter based on the modulation signal.

[0019] To achieve the above objectives, another aspect of this application provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the method described above.

[0020] To achieve the above objectives, another aspect of the embodiments of this application proposes a computer-readable storage medium storing a computer program that, when executed by a processor, implements the method described above.

[0021] To achieve the above objectives, another aspect of the embodiments of this application proposes a computer program product, including a computer program that, when executed by a processor, implements the method described above.

[0022] Compared with the prior art, this application has the following beneficial effects: 1) Significantly improved stability of strong power grids: By combining power droop control with flux feedback, this application retains the synchronous stability advantage of flux feedback in strong power grids (short-circuit ratio can be increased to over 20), and introduces the autonomous power distribution characteristics of droop control, avoiding the dependence of traditional voltage PI control on multi-parameter tuning.

[0023] 2) Fast response speed and no communication required: Power droop control can achieve power distribution using local measurement information, without the need for inter-station communication. It has a fast response speed and is suitable for large-scale new energy grid connection scenarios.

[0024] 3) Effectively suppress inrush current and low-frequency oscillation: Through precise control of the magnetic flux at the grid connection point and elimination of DC components, flux feedback can effectively suppress inrush current and low-frequency oscillation caused by DC components when the transformer is closed.

[0025] 4) Simple to implement and highly compatible: This application only adds flux observation and differential links to the existing network control system without changing the modulation structure. It is applicable to various existing MMC tracking and network control systems.

[0026] 5) Adaptive operation between strong and weak power grids: Unlike traditional grid control which is prone to instability under strong power grids, the method proposed in this application can maintain stable operation over a wide range of short-circuit ratios from 1 to 20, thus achieving adaptive operation between strong and weak power grids. Attached Figure Description

[0027] Figure 1 This is a block diagram of the control strategy for a grid-type modular multilevel converter based on flux feedback and power droop control in the embodiments of this application.

[0028] Figure 2 This is an example diagram of the DC voltage waveform based on the flux linkage feedback control strategy when the short-circuit ratio changes, as shown in the embodiments of this application.

[0029] Figure 3 This is an example diagram of the three-phase voltage waveform based on the flux linkage feedback control strategy in the embodiments of this application.

[0030] Figure 4 This is an example diagram of the active power waveform based on the flux feedback control strategy when the short-circuit ratio changes, as shown in the embodiments of this application.

[0031] Figure 5 This is an example of a DC voltage waveform without a flux feedback control strategy when the short-circuit ratio changes, as shown in the embodiments of this application.

[0032] Figure 6 This is an example diagram of the three-phase voltage waveform without flux feedback control strategy when the short-circuit ratio changes, as shown in the embodiments of this application.

[0033] Figure 7 This is an example diagram of the active power waveform in an embodiment of this application without a flux feedback control strategy when the short-circuit ratio changes.

[0034] Figure 8 This is a diagram illustrating the implementation of the per-unit value of the three-phase flux linkage at the outlet of the modular multilevel converter filter in this embodiment.

[0035] Figure 9 This is a schematic diagram of the hardware structure of the electronic device provided in the embodiments of this application.

[0036] Figure 10 This is a flowchart of a control method for a power drooping flux mesh modular multilevel converter provided in an embodiment of this application.

[0037] Figure 1 The characters in the text are represented as follows: : Measured value of phase A current at the grid-side outlet of the modular multilevel converter; : Measurement value of phase B current at the grid-side outlet of the modular multilevel converter; : Measurement value of C-phase current at the grid-side outlet of the modular multilevel converter; : Measured value of phase A voltage at the grid-side outlet of the modular multilevel converter; : Measured value of phase B voltage at the grid-side outlet of the modular multilevel converter; : Measured value of phase C voltage at the grid-side outlet of the modular multilevel converter; Inductance of the filter at the grid-side outlet of the modular multilevel converter; : Capacitor of the filter at the grid-side outlet of the modular multilevel converter; The equivalent impedance value on the power grid side; The rated value of the equivalent impedance on the power grid side; : Rated voltage at the grid-side outlet of the modular multilevel converter; : Measurement value of DC capacitor voltage on the DC side of the modular multilevel converter; : Per-unit value of the A-phase voltage measurement at the grid-side outlet of the modular multilevel converter; : Per-unit value of the B-phase voltage measurement at the grid-side outlet of the modular multilevel converter; : Per-unit value of the C-phase voltage measurement at the grid-side outlet of the modular multilevel converter; : The per-unit value of the equivalent impedance on the power grid side; Reference value for DC capacitor voltage on the DC side of a modular multilevel converter; : Per-unit value of the reference value for DC capacitor voltage on the DC side of the modular multilevel converter; Per-unit value of DC capacitor voltage measurement on the DC side of a modular multilevel converter; Per-unit value of the A-phase flux linkage at the outlet of the modular multilevel converter filter; Per-unit value of B-phase flux linkage at the outlet of the modular multilevel converter filter; Per-unit value of C-phase flux linkage at the outlet of the modular multilevel converter filter; System rated frequency; The per-unit value of the reference phase of a modular multilevel converter; : Per-unit value of the amplitude of the reference voltage of the modular multilevel converter; : Per-unit value of the A-phase output voltage reference value of the modular multilevel converter; : Per-unit value of the B-phase output voltage reference value of the modular multilevel converter; : Per-unit value of the B-phase output voltage reference value of the modular multilevel converter; : Active power output measurement value of modular multilevel converter; Active power reference value; Power droop coefficient; Frequency deviation; : System rated angular frequency; Phase of the output voltage of a modular multilevel converter; : Reactive power measurement value of the modular multilevel converter output; Reactive power reference value; Voltage droop coefficient; Voltage amplitude deviation; Rated voltage amplitude; : Per-unit value of reference voltage amplitude; : Modular multilevel converter A-phase upper bridge arm submodule trigger pulse signal; : Modular multilevel converter A-phase lower bridge arm submodule trigger pulse signal; : Modular multilevel converter B-phase upper bridge arm submodule trigger pulse signal; : Modular multilevel converter B-phase lower bridge arm submodule trigger pulse signal; : Modular multilevel converter C-phase upper bridge arm submodule trigger pulse signal; : Modular multilevel converter C-phase lower bridge arm submodule trigger pulse signal. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0040] This invention provides a control method for a power droop flux-modulated modular multilevel converter (MMBPD) with a grid-type structure. The method employs a control strategy based on power droop control and flux modulation. Power droop control generates a per-unit value for the reference phase, and voltage droop control generates a per-unit value for the reference voltage amplitude. These two values ​​are then converted into per-unit values ​​of the three-phase output voltage reference values ​​of the MMBPD using a zero-pole coordinate system. The difference between the per-unit value of the three-phase output voltage reference values ​​and the per-unit value of the three-phase flux at the grid connection point filter output is used as the modulation pulse signal generation module for the MMBPD, significantly improving the converter's synchronization stability. As one implementation method, this control strategy is ultimately implemented on the PSCAD / EMTDC simulation platform.

[0041] like Figure 1 and Figure 10 As shown, this application provides a control method for a power droop flux mesh-type modular multilevel converter, including the following steps: Step S1: Data Acquisition and Standardization Obtain the three-phase voltage measurement value at the MMC grid-side outlet. Three-phase current measurement value and DC side capacitor voltage measurement value .

[0042] Based on the rated voltage at the MMC grid-side outlet Using the reference value, generate per-unit values ​​for the three-phase voltage measurements:

[0043] Reference value of DC side capacitor voltage Using the reference value, generate the per-unit value of the DC capacitor voltage measurement:

[0044] Step S2: Power Calculation Calculate the active power measurement value based on the per-unit values ​​of three-phase voltage and current. and reactive power measurement values Unlike traditional methods, the power calculation in this embodiment uses the dq-axis components of magnetic flux linkage and current: First, a Parker transform is performed on the per-unit values ​​of the three-phase flux linkage (obtained in step 5) to obtain the dq-axis components. and .Then:

[0045]

[0046] in and These are the d-axis and q-axis components of the grid-side current.

[0047] Step S3: Active-frequency droop control generates reference phase Active power-frequency droop control is employed, with reference voltage phase per unit value. It is generated by the following equation:

[0048] in, This refers to the power droop factor; The measured value of the active power output of the modular multilevel converter; This is a reference value for active power. This is the system's rated angular frequency. (The obtained value is missing from the original text.) The phase per-unit input serves as the reference voltage for the Polar2ABC transformation.

[0049] Step S4: Reactive power-voltage droop control generates reference amplitude. Reactive power-voltage droop control is adopted, with reference voltage amplitude per unit value. It is generated by the following equation:

[0050] in, This is the per-unit value of the reference voltage amplitude. This is the per-unit value of the rated voltage amplitude (usually set to 1). This is the reactive power droop factor. This is a reference value for reactive power. This is the measured value of reactive power.

[0051] Step S5: Polar coordinate to three-phase coordinate transformation The results obtained in steps 3 and 4 and The per-unit values ​​of the three-phase output voltage reference are generated through polar-to-three-phase coordinate transformation (Polar2ABC). .

[0052] Step S6: Magnetic flux observation The three-phase flux linkage per unit value is obtained using the voltage integration method. First, the preliminary flux linkage per unit value is calculated:

[0053] Then, the average value within one power frequency cycle is subtracted from each value to eliminate the DC component, thus obtaining the per-unit value of the three-phase flux linkage.

[0054] Specifically, the DC component of the flux linkage is obtained through the averaging module. The per-unit value of the three-phase voltage measurement is integrated with the grid's rated angular velocity, and then the average value is subtracted to eliminate the DC component of the flux linkage, thus obtaining the per-unit value of the three-phase flux linkage at the outlet of the modular multilevel converter filter. The implementation process is as follows: Figure 8 As shown. Figure 8 middle, These are the per-unit values ​​of the flux linkage for phases A, B, and C of the input average module, respectively. These are the per-unit flux linkage values ​​for phases A, B, and C at the outlet of the modular multilevel converter filter.

[0055] Step S7: Modulation signal generation The modulation signal is obtained by subtracting the per-unit value of the three-phase output voltage reference value from the per-unit value of the three-phase flux linkage.

[0056] in, This is the input signal for the modulation module; The per-unit value of the three-phase voltage reference value generated by the controller. This represents the per-unit value of the three-phase flux linkage measurement. The modulation signal is input to the modulation pulse generation module of the MMC to generate trigger pulse signals for the upper and lower bridge arms of phases A, B, and C.

[0057] Figure 2This is an example of a DC voltage waveform based on a flux linkage feedback control strategy when the short-circuit ratio changes. This application provides a grid reference phase through a power droop control strategy, which can effectively track the reference value of the DC-side capacitor voltage. Furthermore, by introducing the flux linkage feedback control strategy, it can maintain a constant DC voltage when the short-circuit ratio changes from 1 to 20.

[0058] Figure 3 This is an example of a three-phase voltage waveform based on a flux linkage feedback control strategy. The three-phase voltage waveform quality is intact. Flux linkage feedback control is an advantage of single-loop control, as it does not contain high-frequency components. Therefore, the introduction of flux linkage feedback does not affect the waveform quality.

[0059] Figure 4 This is an example of the active power waveform based on a flux linkage feedback control strategy when the short-circuit ratio changes. Under the action of flux linkage feedback, the DC voltage remains at its rated value as the short-circuit ratio changes, thus allowing the active power to be transmitted normally.

[0060] Figure 5 This is an example of a DC voltage waveform without a flux feedback control strategy when the short-circuit ratio changes. When the short-circuit ratio changes, the grid strength changes from a weak grid to a strong grid. Without introducing a flux feedback loop, the grid-controlled converter cannot maintain synchronous stability in a strong grid. When the short-circuit ratio increases, the DC voltage synchronization control loop cannot maintain DC voltage stability, resulting in oscillation and instability.

[0061] Figure 6 This is an example of a three-phase voltage waveform without flux feedback control strategy when the short-circuit ratio changes. Since grid-connected control is not suitable for strong grids, when the grid short-circuit ratio increases, the control instability of the DC voltage loop and the lack of flux feedback for precise control of the flux at the grid connection point cause continuous oscillations in the three-phase voltage waveform on the grid side.

[0062] Figure 7 This is an example of the active power waveform without flux feedback control strategy when the short-circuit ratio changes. Figure 4 The active waveform with flux feedback is compared. When the system short-circuit ratio changes, the lack of flux feedback causes the DC voltage control loop to be unable to stabilize the DC voltage, resulting in continuous oscillation of active power transmission.

[0063] In summary, the method of this application, compared with the prior art, has at least the following advantages and beneficial effects: (1) The grid-type modular multilevel converter control strategy proposed in this application based on flux feedback and power droop control can significantly improve the synchronization stability of the grid-type modular multilevel converter in a strong power grid. The effectiveness of this control strategy has been verified in the simulation platform PSCAD / EMTDC.

[0064] (2) The proposed control strategy for a grid-connected modular multilevel converter based on flux linkage feedback creatively uses the deviation between the per-unit value of the three-phase output voltage reference value and the per-unit value of the three-phase flux linkage at the output of the grid-connected filter as the modulation pulse signal generation module of the modular multilevel converter. Specifically, through power-voltage droop control, the per-unit value of the reference phase is generated, which, together with the per-unit value of the reference voltage amplitude, constitutes the per-unit value of the three-phase reference voltage. This enables stable operation of the converter under various operating conditions using simple single-loop control, while also solving the problem of inrush current during grid connection and low-frequency oscillation caused by the DC component, greatly improving the stability and robustness of the power system.

[0065] (3) The grid-type modular multilevel converter control strategy based on flux feedback proposed in this application uses the power droop link to construct the reference phase, which can be compatible with strong and weak power grids and operate stably; the flux modulation uses the voltage integral method to obtain the per-unit value of the three-phase flux and accurately controls it, which can effectively control the flux at the transformer outlet and effectively suppress the generation of excitation inrush current.

[0066] (4) The grid-type modular multilevel converter control strategy based on magnetic flux feedback proposed in this application can be applied to long-distance power transmission scenarios in various scenarios such as doubly fed wind power generation, direct-drive wind power generation, and photovoltaic power generation, and has broad application prospects.

[0067] This application embodiment also provides a power droop flux mesh modular multilevel converter control device that can implement the above method. The device includes: The per-unit module is used to standardize the three-phase voltage measurement values, three-phase current measurement values, and DC-side capacitor voltage measurement values ​​on the grid side of the modular multilevel converter. The power calculation module is used to calculate the active power measurement value and reactive power measurement value based on the per-unit three-phase voltage measurement value and three-phase current measurement value; The active power-frequency droop control module is used to integrate the difference between the measured active power value and the reference active power value with the rated angular frequency of the system after adjusting for droop coefficient, and generate a per-unit value for the reference voltage phase. The reactive power-voltage droop control module is used to generate a per-unit value of the reference voltage amplitude after adjusting the difference between the measured reactive power value and the reference reactive power value through a droop coefficient. The coordinate transformation module is used to transform the per-unit values ​​of the reference voltage phase and the reference voltage amplitude into per-unit values ​​of the three-phase output voltage reference value; The flux linkage observation module is used to integrate the standardized three-phase voltage measurement values ​​and subtract their DC components to obtain the three-phase flux linkage per unit value. The subtractor is used to calculate the difference between the per-unit value of the three-phase output voltage reference value and the per-unit value of the three-phase flux linkage, and output a modulation signal. The modulation pulse generation module is used to generate drive pulses for each phase arm of the modular multilevel converter based on the modulation signal.

[0068] It is understood that the content of the above method embodiments is applicable to the present device embodiments. The specific functions implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0069] This application also provides an electronic device, which includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described method. This electronic device can be any smart terminal, including tablet computers, in-vehicle computers, etc.

[0070] It is understood that the content of the above method embodiments is applicable to this device embodiment. The specific functions implemented by this device embodiment are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0071] Please see Figure 9 , Figure 9 The hardware structure of an electronic device according to another embodiment is illustrated. The electronic device includes: The processor 901 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this application. The memory 902 can be implemented as a read-only memory (ROM), static storage device, dynamic storage device, or random access memory (RAM). The memory 902 can store the operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented through software or firmware, the relevant program code is stored in the memory 902 and is called and executed by the processor 901 using the methods described in the embodiments of this application. The input / output interface 903 is used to implement information input and output; The communication interface 904 is used to enable communication and interaction between this device and other devices. Communication can be achieved through wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.). Bus 905 transmits information between various components of the device (e.g., processor 901, memory 902, input / output interface 903, and communication interface 904); The processor 901, memory 902, input / output interface 903, and communication interface 904 are connected to each other within the device via bus 905.

[0072] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method.

[0073] It is understood that the content of the above method embodiments is applicable to this storage medium embodiment. The specific functions implemented in this storage medium embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments.

[0074] Memory, as a non-transitory computer-readable storage medium, can be used to store non-transitory software programs and non-transitory computer-executable programs. Furthermore, memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some embodiments, memory may optionally include memory remotely located relative to the processor, and these remote memories can be connected to the processor via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0075] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0076] It is understood that the content of the above method embodiments is applicable to the embodiments of this program product. The specific functions implemented in the embodiments of this program product are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those achieved in the above method embodiments. The executable computer program code or "code" used to perform the various embodiments can be written in high-level programming languages ​​such as C, C++, Python, Smalltalk, Java, JavaScript, Visual Basic, Structured Query Language (e.g., Transact-SQL), Perl, or in various other programming languages.

[0077] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0078] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0079] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0080] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0081] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application 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 this application 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 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.

[0082] It should be understood that in this application, "at least one (item)" means one or more, and "more than" means two or more. "And / or" is used to describe the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: only A exists, only B exists, and both A and B exist simultaneously, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one (item) of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one (item) of a, b, or c can represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0083] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0084] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0085] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0086] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes multiple instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing programs, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0087] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A control method for a modular multilevel converter with a power droop flux linkage network, characterized in that, The method includes the following steps: Acquire the three-phase voltage measurement value, three-phase current measurement value, and DC side capacitor voltage measurement value of the modular multilevel converter grid side; Calculate the active power measurement value and reactive power measurement value based on the three-phase voltage measurement value and the three-phase current measurement value; The active power-frequency droop control is adopted. The difference between the measured active power value and the active power reference value is adjusted by the droop coefficient and integrated with the rated angular frequency of the system to generate the per-unit value of the reference voltage phase. The reactive power-voltage droop control is adopted, and the difference between the measured reactive power value and the reference reactive power value is adjusted by the droop coefficient to generate the per-unit value of the reference voltage amplitude. The per-unit values ​​of the reference voltage phase and the reference voltage amplitude are transformed from polar coordinates to three-phase coordinates to obtain the per-unit values ​​of the three-phase output voltage reference values. The three-phase voltage measurements are normalized, integrated, and their DC components are subtracted to obtain the three-phase flux per unit value. The modulation signal is obtained by subtracting the per-unit value of the three-phase output voltage reference value from the per-unit value of the three-phase flux linkage, and then input to the modulation pulse generation module of the modular multilevel converter to generate the drive pulse for each phase arm.

2. The method according to claim 1, characterized in that, The active power measurement value and the reactive power measurement value are calculated based on the dq axis components of the three-phase flux linkage per unit value and the d-axis and q-axis components of the three-phase current measurement value; wherein, the dq axis components of the three-phase flux linkage per unit value are obtained by Parker transformation of the three-phase flux linkage per unit value.

3. The method according to claim 1, characterized in that, The per-unit value of the reference voltage phase is generated by the following governing equation: in, The per-unit value of the reference voltage phase. The system's rated angular frequency, This is the active power droop coefficient. This is a reference value for active power. This is the measured value of active power.

4. The method according to claim 1, characterized in that, The per-unit value of the reference voltage amplitude is generated by the following governing equation: in, This is the per-unit value of the reference voltage amplitude. This is the per-unit value of the rated voltage amplitude. This is the reactive power droop factor. This is a reference value for reactive power. This is the measured value of reactive power.

5. The method according to claim 1, characterized in that, The formula for calculating the active power measurement value is as follows: in, and These represent the d-axis and q-axis components of the per-unit flux linkage measurement at the grid-side outlet of the modular multilevel converter. and These are the d-axis and q-axis components of the grid-side output current of the modular multilevel converter, respectively.

6. The method according to claim 1, characterized in that, The formula for calculating the reactive power measurement value is as follows: in, and These represent the d-axis and q-axis components of the per-unit flux linkage measurement at the grid-side outlet of the modular multilevel converter. and These are the d-axis and q-axis components of the grid-side output current of the modular multilevel converter, respectively.

7. The method according to claim 1, characterized in that, The per-unit value of the three-phase flux linkage is obtained through the following steps: Integrate the per-unit values ​​of the three-phase voltage measurements and multiply them by the system's rated angular frequency to obtain the preliminary per-unit values ​​of the flux linkage; The three-phase flux per unit value is obtained by subtracting its average value over one power frequency cycle from the initial flux per unit value to eliminate the DC component in the flux.

8. A control device for a modular multilevel converter with a power drooping flux linkage network, characterized in that, The device includes: The per-unit module is used to standardize the three-phase voltage measurement values, three-phase current measurement values, and DC-side capacitor voltage measurement values ​​on the grid side of the modular multilevel converter. The power calculation module is used to calculate the active power measurement value and reactive power measurement value based on the per-unit three-phase voltage measurement value and three-phase current measurement value; The active power-frequency droop control module is used to integrate the difference between the measured active power value and the reference active power value with the rated angular frequency of the system after adjusting for droop coefficient, and generate a per-unit value for the reference voltage phase. The reactive power-voltage droop control module is used to generate a per-unit value of the reference voltage amplitude after adjusting the difference between the measured reactive power value and the reference reactive power value through a droop coefficient. The coordinate transformation module is used to transform the per-unit values ​​of the reference voltage phase and the reference voltage amplitude into per-unit values ​​of the three-phase output voltage reference value; The flux linkage observation module is used to integrate the standardized three-phase voltage measurement values ​​and subtract their DC components to obtain the three-phase flux linkage per unit value. The subtractor is used to calculate the difference between the per-unit value of the three-phase output voltage reference value and the per-unit value of the three-phase flux linkage, and output a modulation signal. The modulation pulse generation module is used to generate drive pulses for each phase arm of the modular multilevel converter based on the modulation signal.

9. An electronic device, characterized in that, The electronic device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method of any one of claims 1 to 7.

Images