MMC-DES integrated system control method, device, equipment, storage medium and product

Abstract

The application relates to a control method and device of an MMC-DES integrated system, equipment, a storage medium and a product. The method comprises the following steps: determining a direct-current input current reference value corresponding to a desired output power of the MMC-DES integrated system; determining a global balancing current reference, an inter-phase balancing current reference and an intra-phase balancing current reference in the MMC-DES integrated system based on a global, inter-phase and intra-phase three-level energy balancing management mechanism of the MMC-DES integrated system; determining a bridge arm voltage reference value based on the direct-current input current reference value, the global balancing current reference, the inter-phase balancing current reference and the intra-phase balancing current reference; and controlling the MMC-DES integrated system based on the bridge arm voltage reference value. The method can realize stable operation of the system and reasonable distribution of energy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage power supply, in particular to a control method and device of MMC-DES integrated system, equipment, storage medium and product. BACKGROUND

[0002] With the continuous rise of the proportion of renewable energy in the power grid, higher requirements are put forward for the flexibility, dynamic response capability and stability of energy storage systems. Modular multilevel converter (MMC) has become a key device in high-voltage and high-power scenarios due to its modular structure and high voltage adaptability; distributed energy storage (DES) effectively reduces power transmission loss and enhances the resilience of the power grid through local deployment. In the MMC-DES integrated system, energy storage units are configured in the MMC submodules, aiming to further optimize energy management.

[0003] However, the existing MMC-DES integrated system control technology still faces many challenges. Firstly, there is current fluctuation between MMC bridge arms, resulting in unbalanced energy distribution; secondly, the traditional control technology does not fully consider the impact of DES dynamic access on the harmonic characteristics of MMC, resulting in high total harmonic distortion (THD) of alternating current side current; thirdly, the existing control strategy relies on a single closed loop when adjusting power mutations, which is difficult to meet the real-time control requirements of high proportion of new energy grid connection. SUMMARY

[0004] Therefore, it is necessary to provide a control method, device, equipment, storage medium and product of MMC-DES integrated system which can guarantee balanced energy distribution between bridge arms, reduce total harmonic distortion of alternating current side current, and meet the real-time control requirements of high proportion of new energy grid connection.

[0005] In a first aspect, the present application provides a control method of MMC-DES integrated system, comprising:

[0006] determining a direct current input current reference value corresponding to the expected output power of the MMC-DES integrated system;

[0007] determining a global balance current reference, an inter-phase balance current reference and an intra-phase balance current reference in the MMC-DES integrated system based on a three-level energy balance management mechanism of the MMC-DES integrated system, including global, inter-phase and intra-phase;

[0008] determining a bridge arm voltage reference value based on the direct current input current reference value, the global balance current reference, the inter-phase balance current reference and the intra-phase balance current reference;

[0009] control the MMC-DES integrated system based on the bridge arm voltage reference value.

[0010] In one of the embodiments, the method for determining the global balancing current reference in the MMC-DES integrated system comprises:

[0011] obtaining a first energy deviation between the bridge arm total storage energy reference value and the actual bridge arm total storage energy;

[0012] obtaining a global energy power reference value through a PI controller based on the first energy deviation;

[0013] determining the global balancing current reference based on the global energy power reference value and the DC voltage of the MMC-DES integrated system.

[0014] In one of the embodiments, the method for determining the inter-phase balancing current reference in the MMC-DES integrated system comprises:

[0015] obtaining the storage energy of each bridge arm and the actual bridge arm total storage energy;

[0016] determining the storage energy in each phase based on the storage energy of each bridge arm;

[0017] obtaining an inter-phase balancing power reference value in each phase through a PI controller based on a second energy deviation between the storage energy in each phase and one third of the actual bridge arm total storage energy;

[0018] determining the inter-phase balancing current reference based on the inter-phase balancing power reference value in each phase and the DC voltage of the MMC-DES integrated system.

[0019] In one of the embodiments, the method for determining the intra-phase balancing current reference in the MMC-DES integrated system comprises:

[0020] determining the upper and lower bridge arm energy difference in each phase according to the storage energy of each bridge arm;

[0021] obtaining an intra-phase balancing power reference value in each phase through a PI controller based on the upper and lower bridge arm energy difference in each phase;

[0022] determining the intra-phase balancing current reference based on the intra-phase balancing power reference value in each phase and the DC voltage of the MMC-DES integrated system.

[0023] In one of the embodiments, the expected output power comprises an expected AC output power and an expected total energy storage unit output power, and the method for determining the DC input current reference value corresponding to the expected output power of the MMC-DES integrated system comprises:

[0024] The DC input current reference value is determined based on the expected AC output power and the expected total energy storage unit output power.

[0025] In one embodiment, the determination of the DC input current reference value based on the expected AC output power and the expected total energy storage unit output power comprises:

[0026] determining a power difference between the expected AC output power and the expected total energy storage unit output power;

[0027] determining the DC input current reference value based on the power difference and a DC voltage of the MMC-DES integrated system.

[0028] In one embodiment, the determination of the bridge arm voltage reference value based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference comprises:

[0029] determining a circulating current reference of each phase based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference;

[0030] determining a d-axis current reference in a dq coordinate system based on the expected AC output power and a d-axis voltage in the dq coordinate system;

[0031] obtaining an AC voltage component of each phase by a DQ controller based on the d-axis current reference;

[0032] obtaining a DC voltage component of each phase by a PI controller based on the circulating current reference of each phase;

[0033] determining the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase.

[0034] In one embodiment, the determination of the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase comprises:

[0035] determining the bridge arm voltage reference value based on a DC voltage of the MMC-DES integrated system and the AC voltage component and the DC voltage component of each phase.

[0036] In one embodiment, the method further comprises:

[0037] determining a reference value of a charging current of a capacitor of each sub-module of the energy storage unit based on the expected total energy storage unit output power, a number of the sub-modules in the energy storage unit of the MMC-DES integrated system, and a capacitor voltage of the sub-module;

[0038] controlling the MMC-DES integrated system based on the bridge arm voltage reference value, comprising:

[0039] The MMC-DES integrated system is controlled based on the bridge arm voltage reference value and a reference value of a charging current of each energy storage unit to the capacitor of the sub-module.

[0040] In a second aspect, the application further provides a control device of the MMC-DES integrated system, comprising:

[0041] A direct current input current reference determination module is configured to determine a direct current input current reference value corresponding to a desired output power of the MMC-DES integrated system.

[0042] A balanced current reference determination module is configured to determine a global balanced current reference, an inter-phase balanced current reference and an intra-phase balanced current reference in the MMC-DES integrated system based on a global, inter-phase and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system.

[0043] A bridge arm voltage reference value determination module is configured to determine the bridge arm voltage reference value based on the direct current input current reference value, the global balanced current reference, the inter-phase balanced current reference and the intra-phase balanced current reference.

[0044] A control module is configured to control the MMC-DES integrated system based on the bridge arm voltage reference value.

[0045] In a third aspect, the application further provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the following steps when executing the computer program:

[0046] determining a direct current input current reference value corresponding to a desired output power of the MMC-DES integrated system;

[0047] determining a global balanced current reference, an inter-phase balanced current reference and an intra-phase balanced current reference in the MMC-DES integrated system based on a global, inter-phase and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system.

[0048] determining the bridge arm voltage reference value based on the direct current input current reference value, the global balanced current reference, the inter-phase balanced current reference and the intra-phase balanced current reference.

[0049] controlling the MMC-DES integrated system based on the bridge arm voltage reference value.

[0050] In a fourth aspect, the application further provides a computer readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the following steps:

[0051] determining a direct current input current reference value corresponding to a desired output power of the MMC-DES integrated system;

[0052] determine the global balanced current reference, the inter-phase balanced current reference and the intra-phase balanced current reference in the MMC-DES integrated system based on the global, inter-phase and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system;

[0053] determine the bridge arm voltage reference value based on the DC input current reference value, the global balanced current reference, the inter-phase balanced current reference and the intra-phase balanced current reference;

[0054] control the MMC-DES integrated system based on the bridge arm voltage reference value.

[0055] In a fifth aspect, the present application also provides a computer program product comprising a computer program which, when executed by a processor, implements the following steps:

[0056] determine the DC input current reference value corresponding to the expected output power of the MMC-DES integrated system;

[0057] determine the global balanced current reference, the inter-phase balanced current reference and the intra-phase balanced current reference in the MMC-DES integrated system based on the global, inter-phase and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system;

[0058] determine the bridge arm voltage reference value based on the DC input current reference value, the global balanced current reference, the inter-phase balanced current reference and the intra-phase balanced current reference;

[0059] control the MMC-DES integrated system based on the bridge arm voltage reference value.

[0060] The control method, device, equipment, storage medium and product of the MMC-DES integrated system described above, by comprehensively considering the expected output power of the MMC-DES integrated system and the energy balance management at each level, determining the bridge arm voltage reference value to control the MMC-DES integrated system based on the energy-power-current three-level collaborative control method, helps to realize stable operation of the system and reasonable allocation of energy, so as to ensure balanced energy distribution between bridge arms, reduce total harmonic distortion of alternating current side current, and meet real-time control requirements of high proportion of new energy grid connection. BRIEF DESCRIPTION OF DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the drawings needed to be used in the embodiment or related art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0062] Figure 1Fig. 1 is a structural schematic diagram of an MMC-DES integrated system with a three-phase MMC architecture in one embodiment;

[0063] Figure 2 Fig. 2 is a structural schematic diagram of a bridge arm of the MMC-DES integrated system in one embodiment;

[0064] Figure 3 Fig. 3 is a structural schematic diagram of an SM with an energy storage unit of the MMC-DES integrated system in one embodiment;

[0065] Figure 4 Fig. 4 is an application environment diagram of a control method of the MMC-DES integrated system in one embodiment;

[0066] Figure 5 Fig. 5 is a flowchart of the control method of the MMC-DES integrated system in one embodiment;

[0067] Figure 6 Fig. 6 is a flowchart of the control method of the MMC-DES integrated system in another embodiment;

[0068] Figure 7 Fig. 7 is a global energy balance control block diagram in one embodiment;

[0069] Figure 8 Fig. 8 is a flowchart of the control method of the MMC-DES integrated system in another embodiment;

[0070] Figure 9 Fig. 9 is an A-phase inter-phase energy balance control block diagram in one embodiment;

[0071] Figure 10 Fig. 10 is a B-phase inter-phase energy balance control block diagram in one embodiment;

[0072] Figure 11 Fig. 11 is a C-phase inter-phase energy balance control block diagram in one embodiment;

[0073] Figure 12 Fig. 12 is a flowchart of the control method of the MMC-DES integrated system in another embodiment;

[0074] Figure 13 Fig. 13 is an A-phase intra-phase energy balance control block diagram in one embodiment;

[0075] Figure 14 Fig. 14 is a B-phase intra-phase energy balance control block diagram in one embodiment;

[0076] Figure 15 Fig. 15 is a C-phase intra-phase energy balance control block diagram in one embodiment;

[0077] Figure 16 Fig. 16 is a flowchart of the control method of the MMC-DES integrated system in another embodiment;

[0078] Figure 17 Control block diagram for obtaining the DC input current reference value in one embodiment;

[0079] Figure 18 Flowchart of the control method of the MMC-DES integrated system in another embodiment;

[0080] Figure 19 Control block diagram for obtaining the d-axis current reference value in the dq coordinate system in one embodiment;

[0081] Figure 20 Control block diagram of the AC voltage component of each phase in one embodiment;

[0082] Figure 21 Control block diagram of the DC voltage component of each phase in one embodiment;

[0083] Figure 22 Flowchart of the control method of the MMC-DES integrated system in another embodiment;

[0084] Figure 23 Control block diagram for obtaining the reference value of the charging current of the sub-module capacitor by each energy storage unit in one embodiment;

[0085] Flowchart of the control method of the MMC-DES integrated system in another embodiment; Figure 24

[0086] System waveform diagram in one embodiment Figure 25 System waveform diagram in one embodiment

[0087] Figure 26 System waveform diagram in one embodiment System waveform diagram in one embodiment

[0088] Figure 27 System waveform diagram in one embodiment

[0089] Figure 28 Structural block diagram of the control device of the MMC-DES integrated system in one embodiment. DETAILED DESCRIPTION

[0090] ​​​​​​​In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0091] With the continuous rise of renewable energy in the power grid, higher requirements are placed on the flexibility, dynamic response capability and stability of energy storage systems. Modular multilevel converter (MMC) has become a key device in high-voltage and high-power scenarios due to its modular structure and high voltage adaptability; distributed energy storage (DES) effectively reduces power transmission loss and enhances grid resilience through local deployment. In the MMC-DES integrated system, the energy storage unit is configured in the MMC sub-module, aiming to further optimize energy management.

[0092] Figure 1 It is shown that the MMC is a three-phase architecture, each phase including an upper bridge arm and a lower bridge arm, each bridge arm being composed of a series connection of multiple sub-modules (SMs) and a bridge arm reactor. The upper bridge arms of the three phases A, B and C are labeled as A1, B1 and C1, respectively, while the lower bridge arms are labeled as A2, B2 and C2. The voltages across the bridge arms A1, A2, B1, B2, C1 and C2 are denoted as , , , , and , respectively. Correspondingly, the bridge arm currents are denoted as , , , , and , respectively. The output currents of the three-phase AC system are denoted as , and . The DC voltage is denoted as , and the three-phase AC voltages are denoted as , and , respectively. Figure 1 The reference directions of the voltages and currents in the figure represent the power flowing from the DC side to the AC side, in which case the MMC is in inverter mode.

[0093] Figure 2 It is shown that the internal structure of each bridge arm is composed of Nsm SMs containing energy storage units connected in series. By controlling the state of the power switches in the SM, each SM uses its capacitor voltage to synthesize the bridge arm voltage.

[0094] Figure 3 The topology of SMs with energy storage units is shown. The energy storage units are connected to the capacitors of half-bridge SMs through PCSs. The energy storage units charge or discharge the SM capacitors through the PCSs, and the charge and discharge currents are represented as . Figure 3 In represent the bridge arm currents ( , , , , and ), represent the capacitor voltages.

[0095] Assuming that the capacitor voltage in a certain SM is , the energy stored in this SM is ; assuming that the rated value of the capacitor voltage is , the total energy reference value stored in the capacitor in each bridge arm is . Accordingly, the total energy stored in the six bridge arms , the total energy reference value stored in the six bridge arms , and the energy stored in each bridge arm are represented as , , , , and .

[0096] However, the existing MMC-DES integrated system control technology still faces many challenges. First, there is current fluctuation between MMC bridge arms, which causes unbalanced energy distribution; second, the traditional control technology does not fully consider the influence of DES dynamic access on the harmonic characteristics of MMC, resulting in high total harmonic distortion (THD) of alternating current side current; third, the existing control strategy relies on a single closed loop when adjusting power mutations, which is difficult to meet the real-time control demand of high proportion of new energy grid connection. The present application provides a control method for an MMC-DES integrated system, which aims to solve the above problems.

[0097] After the background technology of the control method for the MMC-DES integrated system provided by the embodiments of the present application is introduced above, the implementation environment related to the control method for the MMC-DES integrated system provided by the embodiments of the present application will be briefly described below. The control method for the MMC-DES integrated system provided by the embodiments of the present application can be applied to, for example Figure 4The computer device shown includes a processor, a memory, an input / output interface, a communication interface, a display unit and an input device. Among them, the processor, the memory and the input / output interface are connected through the system bus, and the communication interface, the display unit and the input device are connected to the system bus through the input / output interface. Among them, the processor of the computer device is used to provide computing and control capability. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operating system and the computer program in the non-volatile storage medium to run. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals in a wired or wireless manner. The wireless manner can be realized through WIFI, mobile cellular network, NFC (near field communication) or other technologies. The computer program is executed by the processor to realize a control method of an MMC-DES integrated system. The display unit of the computer device is used to form a visually visible picture, which can be a display screen, a projection device or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device can be a touch layer overlaid on the display screen, or a key, trackball or touchpad arranged on the shell of the computer device, or an external keyboard, touchpad or mouse, etc.

[0098] Those skilled in the art can understand that, Figure 4 The structure shown in the figure is only a block diagram of part of the structure related to the scheme of the present application, and does not constitute a limitation on the computer device to which the scheme of the present application is applied. A specific terminal can include more or fewer components than those shown in the figure, or combine certain components, or have a different component arrangement.

[0099] After the above describes the application scenario of the control method of the MMC-DES integrated system provided by the embodiments of the present application, the control method of the MMC-DES integrated system described in the present application is mainly introduced.

[0100] In one embodiment, as Figure 5 shown, a control method of an MMC-DES integrated system is provided. Taking the computer device in Figure 4 as an example, the method includes the following steps:

[0101] S201, determining a direct current input current reference value corresponding to the expected output power of the MMC-DES integrated system.

[0102] The expected output power of the MMC-DES integrated system refers to the power size that the MMC-DES integrated system is expected to stably output when the MMC-DES integrated system is designed. For example, the MMC-DES integrated system is designed to stably output 1000 kilowatts (1 megawatt) of electric energy under normal circumstances, and 1000 kilowatts is the expected output power thereof.

[0103] In this embodiment, the expected output power of the MMC-DES integrated system can be acquired first, and the direct current input current reference value corresponding to the expected output power can be determined according to the relationship between the expected output power and the direct current input current reference value.

[0104] It should be noted that when the relationship between the expected output power and the direct current input current reference value is determined, the efficiency, loss, and possible voltage fluctuation of the MMC-DES integrated system can also be considered to ensure the accuracy of the determined relationship between the expected output power and the direct current input current reference value.

[0105] S202, based on the global, inter-phase, and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system, determine the global balance current reference, the inter-phase balance current reference, and the intra-phase balance current reference in the MMC-DES integrated system.

[0106] The global energy balance management mechanism of the MMC-DES integrated system mainly focuses on the energy distribution and balance of the MMC-DES integrated system, and the core thereof is to realize the balance of the total energy of each phase by controlling the global balance current, that is, the global energy balance management mechanism dynamically adjusts the total power inflow or outflow of each phase according to the overall operating state and energy demand of the MMC-DES integrated system, ensures that the energy of the entire system is balanced, and avoids the situation that the total energy is overloaded or insufficient.

[0107] The inter-phase energy balance management mechanism of the MMC-DES integrated system mainly aims at the energy balance between each phase of the MMC, and the core thereof is to change the power distribution between each phase by controlling the inter-phase balance current, so as to realize the energy balance of the three phases, that is, the mechanism detects the power difference between each phase, and adjusts the power flow between each phase through appropriate control strategies (such as circulating current control), so as to ensure that the energy distribution between each phase is uniform, and avoid the instability of the system caused by the imbalance of the inter-phase power.

[0108] The in-phase energy balance management mechanism of the MMC-DES integrated system is mainly aimed at balancing the energy of each in-phase upper and lower bridge arm, and the core is to change the power distribution between the upper and lower bridge arms in each phase by controlling the in-phase balancing current, that is, the mechanism detects the power difference between the upper and lower bridge arms in each phase, and adjusts the power flow between the upper and lower bridge arms in each phase through appropriate control strategies (such as circulating current control), to ensure uniform energy distribution within each phase and avoid system instability caused by in-phase power imbalance.

[0109] It should be noted that through the above three-level energy balance management mechanism, the MMC-DES integrated system can achieve reasonable distribution and balance of energy at different levels, ensuring that the total energy stored in each bridge arm capacitor is stable around the rated value, thereby improving the overall performance and reliability of the system.

[0110] In this embodiment, the global balancing current reference in the MMC-DES integrated system can be determined based on the global energy balance management mechanism of the MMC-DES integrated system, the inter-phase balancing current reference in the MMC-DES integrated system can be determined based on the inter-phase energy balance management mechanism of the MMC-DES integrated system, and the in-phase balancing current reference in the MMC-DES integrated system can be determined based on the in-phase energy balance management mechanism of the MMC-DES integrated system.

[0111] S203, determining a bridge arm voltage reference value based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the in-phase balancing current reference.

[0112] The bridge arm voltage reference value refers to the target voltage value that each bridge arm (upper bridge arm or lower bridge arm) needs to output in the MMC-DES integrated system. By reasonably calculating and dynamically adjusting the bridge arm voltage reference value, stable operation, energy balance, and power quality optimization of the MMC-DES integrated system can be achieved.

[0113] In this embodiment, after the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the in-phase balancing current reference are determined as described above, the bridge arm voltage reference value can be determined based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the in-phase balancing current reference.

[0114] S204, controlling the MMC-DES integrated system based on the bridge arm voltage reference value.

[0115] In the embodiment, after the bridge arm voltage reference value is obtained, the MMC-DES integrated system can be controlled based on a circulating current control and energy balancing strategy, a fault response and current limiting control strategy, a modulation strategy and sub-module control strategy, or a thermal balancing and voltage adjustment strategy to realize stable operation of the MMC-DES integrated system.

[0116] Optionally, for the modulation strategy and sub-module control strategy, the bridge arm voltage reference value can be converted into a sub-module switching signal through the modulation strategy (such as the nearest level approximation modulation strategy), and the MMC-DES integrated system can be controlled based on the sub-module switching signal to realize stable operation of the MMC-DES integrated system.

[0117] In the embodiment, the bridge arm voltage reference value is determined by comprehensively considering the expected output power of the MMC-DES integrated system and the energy balancing management at each level, which helps to realize stable operation of the system and reasonable allocation of energy, so as to ensure balanced energy distribution between bridge arms, reduce total harmonic distortion of alternating current side current, and meet real-time control requirements of high proportion of new energy grid connection.

[0118] In one embodiment, in the process of determining the global balanced current reference in the MMC-DES integrated system, the following steps can be performed: Figure 5 Based on the embodiment shown in the foregoing description, the process of determining the global balanced current reference in the MMC-DES integrated system can be described as follows: Figure 6 The step S202 of determining the global balanced current reference in the MMC-DES integrated system includes the following steps:

[0119] S301, obtaining a first energy deviation between a bridge arm total storage energy reference value and an actual bridge arm total storage energy.

[0120] The bridge arm total storage energy reference value is used to describe the expected value of the total energy stored in all sub-modules (SMs) in the bridge arm, and the bridge arm total storage energy reference value is crucial for energy balancing, stable operation and optimized control strategy of the system.

[0121] The actual bridge arm total storage energy is the total energy actually stored in all sub-modules (SMs) in the bridge arm at a certain moment.

[0122] In the embodiment, the bridge arm total storage energy reference value and the actual bridge arm total storage energy can be obtained first, and the difference between the bridge arm total storage energy reference value and the actual bridge arm total storage energy is taken as the first energy deviation.

[0123] S302, obtaining a global energy power reference value by a PI controller based on the first energy deviation.

[0124] wherein the global energy power reference value refers to an energy power target value that the entire system (such as an MMC-DES integrated system) needs to achieve in a global range.

[0125] wherein the PI controller (proportional-integral controller) is a commonly used feedback controller, which is used to adjust the output of the system according to the deviation value to achieve the desired control target. The output of the PI controller consists of two parts: the proportional part (proportional to the first energy deviation) and the integral part (proportional to the integral of the first energy deviation).

[0126] In this embodiment, after obtaining the first energy deviation, the PI controller is used to process the first energy deviation, thereby obtaining the global energy power reference value .

[0127] S303, determining a global balancing current reference based on the global energy power reference value and the DC voltage of the MMC-DES integrated system.

[0128] wherein the DC voltage of the MMC-DES integrated system refers to the voltage of the DC bus in the MMC-DES integrated system, which plays a role in energy transmission and distribution in the system.

[0129] In this embodiment, after obtaining the global energy power reference value , the DC voltage of the MMC-DES integrated system may also be obtained, and the ratio of the global energy power reference value to the DC voltage of the MMC-DES integrated system is determined as the global balancing current reference .

[0130] It should be noted that the global energy balancing control block diagram for obtaining the global balancing current reference is shown in Figure 7 .

[0131] In this embodiment, by processing the deviation between the bridge arm total storage energy reference value and the actual bridge arm total storage energy, the global balancing current reference is determined, which can realize the global energy balancing management of the MMC-DES integrated system.

[0132] In one embodiment, based on the embodiment shown in Figure 5 , the process of determining the inter-phase balancing current reference in the MMC-DES integrated system can be described, as shown in Figure 8As shown, the above S202 "determining the inter-phase balanced current reference in the MMC-DES integrated system" comprises:

[0133] S401, obtaining the energy stored in each bridge arm and the total energy stored in the actual bridge arm.

[0134] Wherein, the energy stored in each bridge arm refers to the total energy actually stored by all SM capacitors in a single bridge arm at a certain moment. For example, please refer to Figure 1 As shown in the three-phase architecture, each phase includes an upper bridge arm and a lower bridge arm, and the A, B and C upper bridge arms are marked as A1, B1 and C1 respectively, while the lower bridge arms are marked as A2, B2 and C2. The energy stored in each bridge arm is represented as , , , , , .

[0135] Wherein, the total energy stored in the actual bridge arm refers to the total energy actually stored by all SM capacitors in the bridge arm at a certain moment.

[0136] In this embodiment, before determining the inter-phase balanced current reference in the MMC-DES integrated system, the energy stored in each bridge arm and the total energy stored in the actual bridge arm can be obtained.

[0137] S402, based on the energy stored in each bridge arm, determining the energy stored in each phase.

[0138] In this embodiment, after obtaining the energy stored in each bridge arm, the bridge arm energy of the upper bridge arm and the bridge arm energy of the lower bridge arm in each phase can be determined as the energy stored in each phase. For example, please continue to refer to Figure 1 According to the sum of the bridge arm energy of the upper bridge arm and the bridge arm energy of the lower bridge arm in the A phase, the energy stored in the A phase (i.e. + ) is determined, according to the sum of the bridge arm energy of the upper bridge arm and the bridge arm energy of the lower bridge arm in the B phase, the energy stored in the B phase (i.e. + ) is determined, and according to the sum of the bridge arm energy of the upper bridge arm and the bridge arm energy of the lower bridge arm in the C phase, the energy stored in the C phase (i.e. + ) is determined.

[0139] S403. Based on the second energy deviation between the energy stored in each phase and one-third of the total energy stored in the actual bridge arm, the inter-phase equalization power reference value in each phase is obtained through the PI controller.

[0140] The interphase equalization power reference value in each phase refers to the target power value set in a multiphase MMC-DES integrated system to achieve energy balance between phases. This reference value is usually used to guide the control strategy of the MMC-DES integrated system, ensuring that the power flow between phases reaches a balanced state and avoiding voltage fluctuations, current imbalances or other system instability caused by power imbalance.

[0141] In this embodiment, the actual total stored energy of the bridge arm is obtained. Next, the total stored energy of the actual bridge arm was determined. One-third of the energy, and after obtaining the stored energy in each phase, determining the stored energy in each phase and the actual total stored energy of the bridge arm. The second energy deviation is between 1 / 3 and the energy stored in each phase and the total energy stored in the actual bridge arm. The second energy deviation between 1 / 3 and the PI controller is input to obtain the interphase equalization power reference value in each phase.

[0142] For example, in obtaining energy stored in phase A (i.e. + After that, the energy stored in phase A (i.e.) and The deviation between (i.e.) + ), is determined as the second energy deviation corresponding to A, and the second energy deviation corresponding to A (i.e. + The input is sent to the PI controller to obtain the interphase equalization power reference value in phase A. ; to obtain energy stored in phase B (i.e. + After that, the energy stored in phase B (i.e. + )and The deviation between (i.e.) + ), is determined as the second energy deviation corresponding to B, and the second energy deviation corresponding to B (i.e. + The input is sent to the PI controller to obtain the interphase equalization power reference value in phase B. ; and the energy stored in the C phase (i.e. + After that, the energy stored in phase C (i.e. + )and the second energy deviation corresponding to phase C is determined, and the second energy deviation corresponding to phase C (i.e. + ) is input to the PI controller to obtain the inter-phase balanced power reference value in phase C . .

[0143] S404, based on the inter-phase balanced power reference value in each phase and the DC voltage of the MMC-DES integrated system, determine the inter-phase balanced current reference.

[0144] In this embodiment, after obtaining the inter-phase balanced power reference value in each phase , and , the ratio of the inter-phase balanced power reference value in each phase , and to the DC voltage of the MMC-DES integrated system is determined as the inter-phase balanced current reference , and .

[0145] For example, the ratio of the inter-phase balanced power reference value in phase A to the DC voltage of the MMC-DES integrated system is determined as the inter-phase balanced current reference , see Figure 9 for the inter-phase energy balancing control block diagram for obtaining the inter-phase balanced current reference in phase A; the ratio of the inter-phase balanced power reference value in phase B to the DC voltage of the MMC-DES integrated system is determined as the inter-phase balanced current reference , see Figure 10 for the inter-phase energy balancing control block diagram for obtaining the inter-phase balanced current reference in phase B; the ratio of the inter-phase balanced power reference value in phase C to the DC voltage of the MMC-DES integrated system is determined as the inter-phase balanced current reference , see Figure 11 for the inter-phase energy balancing control block diagram for obtaining the inter-phase balanced current reference in phase C.

[0146] In this embodiment, the inter-phase balanced current reference is determined according to the energy of each bridge arm and the total energy of the actual bridge arm, which can realize the inter-phase energy balancing management of the MMC-DES integrated system.​

[0147] In one embodiment, the process of determining the in-phase balancing current reference in the MMC-DES integrated system can be described based on the embodiment shown in Figure 5 Figure 12 As shown in the above S202, "determining the in-phase balancing current reference in the MMC-DES integrated system", comprises:

[0148] S501, determining the upper and lower arm energy difference in each phase according to the energy stored in each bridge arm.

[0149] In this embodiment, please continue to refer to Figure 1 Each phase includes an upper bridge arm and a lower bridge arm, and the upper bridge arms of the three phases A, B and C are marked as A1, B1 and C1 respectively, while the lower bridge arms are marked as A2, B2 and C2. The energy stored in each bridge arm is represented as , , , , , According to the energy stored in each bridge arm, the upper and lower arm energy difference in each phase is determined.

[0150] For example, according to the difference between the upper arm energy stored in phase A and the lower arm energy stored in phase A , the upper and lower arm energy difference in phase A (i.e. - ) is determined; according to the difference between the upper arm energy stored in phase B and the lower arm energy stored in phase B , the upper and lower arm energy difference in phase B (i.e. - ) is determined; according to the difference between the upper arm energy stored in phase C and the lower arm energy stored in phase C , the upper and lower arm energy difference in phase C (i.e. - ) is determined.

[0151] S502, obtaining the in-phase balancing power reference value in each phase through a PI controller based on the upper and lower arm energy difference in each phase.

[0152] The in-phase balancing power reference value in each phase refers to the target power value set in each phase of the MMC-DES integrated system in order to achieve balanced power distribution between the upper and lower arms.

[0153] In this embodiment, after determining the upper and lower arm energy difference in each phase, the PI controller is used to process the upper and lower arm energy difference in each phase to obtain the in-phase balancing power reference value ,​ and .

[0154] S503, determine the in-phase balancing current reference based on the in-phase balancing power reference value in each phase and the DC voltage of the MMC-DES integrated system.

[0155] In this embodiment, after obtaining the in-phase balancing power reference value in each phase , and , the ratio of the in-phase balancing power reference value in each phase , and to the DC voltage of the MMC-DES integrated system is determined as the in-phase balancing current reference , and .

[0156] For example, the ratio of the in-phase balancing power reference value in phase A to the DC voltage of the MMC-DES integrated system is determined as the in-phase balancing current reference , see Figure 13 for the in-phase energy balancing control block diagram for obtaining the in-phase balancing current reference of phase A; the ratio of the in-phase balancing power reference value in phase B to the DC voltage of the MMC-DES integrated system is determined as the in-phase balancing current reference , see Figure 14 for the in-phase energy balancing control block diagram for obtaining the in-phase balancing current reference of phase B; the ratio of the in-phase balancing power reference value in phase C to the DC voltage of the MMC-DES integrated system is determined as the in-phase balancing current reference , see Figure 15 for the in-phase energy balancing control block diagram for obtaining the in-phase balancing current reference of phase C.

[0157] In this embodiment, the in-phase balancing current reference is determined according to the energy difference between the upper and lower bridge arms in each phase, which can achieve energy balancing management in the MMC-DES integrated system.

[0158] In one embodiment, in Figure 5Based on the embodiment shown above, the expected output power includes: expected AC output power and expected total energy storage unit output power, and the process of determining the corresponding DC input current reference value can be described, and S201 "determining the DC input current reference value corresponding to the expected output power of the MMC-DES integrated system" includes:

[0159] Based on the expected AC output power and the expected total energy storage unit output power, the DC input current reference value is determined.

[0160] Wherein, the expected AC output power is the target power value that the system hopes to output on the AC side during design or operation. The expected total energy storage unit output power is the total power value that the energy storage system hopes to output or absorb at a certain moment.

[0161] In this embodiment, the expected AC output power and the expected total energy storage unit output power can be obtained first, and the DC input current reference value is determined according to the expected AC output power and the expected total energy storage unit output power .

[0162] Optionally, a specific implementation of determining the DC input current reference value is provided below, referring to Figure 16 , the "determining the DC input current reference value based on the expected AC output power and the expected total energy storage unit output power" includes:

[0163] S601, determining the power difference of the expected AC output power and the expected total energy storage unit output power.

[0164] In this embodiment, after obtaining the expected AC output power and the expected total energy storage unit output power , the difference between the expected AC output power and the expected total energy storage unit output power is determined, and the difference is determined as the power difference.

[0165] S602, determining the DC input current reference value based on the power difference and the DC voltage of the MMC-DES integrated system.

[0166] In this embodiment, after obtaining the power difference, the DC input power instruction is obtained according to the power difference, and the ratio between the DC input power instruction and the DC voltage Vdc of the MMC-DES integrated system is determined as the DC input current reference value . Referring to Figure 17 , a control block diagram for obtaining the DC input current reference value is provided.

[0167] In this embodiment, by calculating the power difference between the expected AC output power and the expected total energy storage unit output power and combining the DC voltage, the DC input current reference value can be accurately determined.

[0168] In one embodiment, based on the embodiment shown in Figure 5 , as shown in Figure 18 , the process of determining the bridge arm voltage reference value can be described, and the above S203 "determining the bridge arm voltage reference value based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference" includes:

[0169] S701, determining the circulating current reference of each phase based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference.

[0170] In this embodiment, after obtaining the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference, the circulating current reference of each phase can be determined according to the following formula (1) 、 、 .

[0171]

[0172] S702, determining the d-axis current reference value in the dq coordinate system based on the expected AC output power and the d-axis voltage in the dq coordinate system.

[0173] Wherein, the d-axis voltage in the dq coordinate system (i.e. the synchronous rotating coordinate system), in the dq coordinate system, the voltage, current and magnetic flux are decomposed into d-axis (direct axis) and q-axis (quadrature axis) components. The d-axis voltage is the projection of the voltage vector on the d-axis, which reflects the component of the voltage in the direct axis direction, and is usually used to control the excitation or DC bus voltage of the motor.

[0174] In this embodiment, after obtaining the expected AC output power, the d-axis voltage in the dq coordinate system can be obtained, and the ratio between the expected AC output power and the d-axis voltage in the dq coordinate system u d is determined as the d-axis current reference value in the dq coordinate system . Referring to Figure 19 , a control block diagram for obtaining the d-axis current reference value in the dq coordinate system is provided.

[0175] S703, obtaining an alternating voltage component of each phase based on the d-axis current reference value through a DQ controller.

[0176] The DQ controller is a control strategy based on a dq coordinate system (i.e., a synchronous rotating coordinate system) and is widely used in the fields of power electronics and motor control. It converts the voltage and current in a three-phase alternating current system to the dq coordinate system to achieve independent control of active power and reactive power. The core advantage of the DQ controller is that it can simplify complex alternating current system control problems and improve the dynamic response speed and control accuracy of the system.

[0177] In this embodiment, after obtaining the d-axis current reference value , the DQ controller is used to process the d-axis current reference value to obtain the alternating voltage component of each phase , and . Referring to Figure 20 , a control block diagram for obtaining the alternating voltage component of each phase , and is provided.

[0178] S704, obtaining a direct current voltage component of each phase based on the circulating current reference of each phase through a PI controller.

[0179] In this embodiment, after obtaining the circulating current reference of each phase, the PI controller is used to process the circulating current reference of each phase , , to obtain the direct current voltage component of each phase , and c. Referring to Figure 21 , a control block diagram for obtaining the direct current voltage component of each phase , and c is provided.

[0180] S705, determining a bridge arm voltage reference value based on the alternating voltage component of each phase and the direct current voltage component of each phase.

[0181] In this embodiment, after obtaining the alternating voltage component of each phase , and , and the direct current voltage component of each phase , and c, the alternating voltage component of each phase , and , and the direct current voltage component of each phase 、 and c, determining the bridge arm voltage reference value.

[0182] Optionally, the following provides a specific embodiment of determining the bridge arm voltage reference value, i.e., the above S705 "determining the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase", comprising: determining the bridge arm voltage reference value based on the DC voltage of the MMC-DES integrated system and the AC voltage component and the DC voltage component of each phase.

[0183] In this embodiment, after obtaining the AC voltage component of each phase 、 and and the DC voltage component of each phase 、 and c, the bridge arm voltage reference value of each bridge arm can be calculated according to formula (2) based on the AC voltage component of each phase 、 and , the DC voltage component of each phase 、 and c, and the DC side voltage .

[0184]

[0185] In this embodiment, the bridge arm voltage reference value is determined by combining the system DC voltage and the AC and DC voltage components, further improving the accuracy of the bridge arm voltage reference value. In addition, the bridge arm voltage reference value is used for the modulation of the MMC-DES integrated system bridge arm, which can realize the stable operation of the MMC-DES integrated system.

[0186] In one embodiment, based on the embodiment shown in Figure 5 , as shown in Figure 22 , the above method further comprises:

[0187] S205, determining the reference value of the charging current of each energy storage unit to the capacitor of the sub-module based on the expected total power output of the energy storage unit, the number of sub-modules in the energy storage unit of the MMC-DES integrated system, and the capacitor voltage of the sub-module.

[0188] In this embodiment, the number of sub-modules in the energy storage unit of the MMC-DES integrated system and the capacitor voltage of the sub-module can be obtained first, and the product of the number of sub-modules in the energy storage unit and the capacitor voltage of the sub-module is calculated to obtain the product value Nsm*Vc, see Figure 1In the three-phase system, the product value is calculated 6 times, 6*Nsm*Vc, and the expected total power output of the energy storage unit is obtained The ratio between the expected total power output of the energy storage unit and 6*Nsm*Vc is determined as the reference value of the charging current of each energy storage unit to the sub-module capacitor Referring to Figure 23 , a control block diagram for obtaining the reference value of the charging current of each energy storage unit to the sub-module capacitor is provided.

[0189] The above S204 "controlling the MMC-DES integrated system based on the bridge arm voltage reference value" includes:

[0190] S204, controlling the MMC-DES integrated system based on the bridge arm voltage reference value and the reference value of the charging current of each energy storage unit to the sub-module capacitor.

[0191] In this embodiment, after obtaining the bridge arm voltage reference value and the reference value of the charging current of each energy storage unit to the sub-module capacitor, the MMC-DES integrated system can be controlled based on the bridge arm voltage reference value and the reference value of the charging current of each energy storage unit to the sub-module capacitor.

[0192] In this embodiment, when controlling the MMC-DES integrated system, the bridge arm voltage reference value and the reference value of the charging current of each energy storage unit to the sub-module capacitor are combined, which can better achieve energy management and control of the system and avoid local overcharging or overdischarging of the energy storage unit.

[0193] In one embodiment, referring to Figure 24 , a control method of an MMC-DES integrated system is also provided, including:

[0194] T1, determining the power difference between the expected AC output power and the expected total power output of the energy storage unit;

[0195] T2, determining the DC input current reference value based on the power difference and the DC voltage of the MMC-DES integrated system;

[0196] T3, obtaining the first energy deviation between the bridge arm total storage energy reference value and the actual bridge arm total storage energy;

[0197] T4, obtaining the global energy power reference value through a PI controller based on the first energy deviation;

[0198] T5, determining the global balancing current reference based on the global energy power reference value and the DC voltage of the MMC-DES integrated system;

[0199] T6, obtaining the energy storage energy of each bridge arm and the actual bridge arm total storage energy; ​

[0200] T7, determining the stored energy in each phase based on the stored energy of each bridge arm;

[0201] T8, obtaining, by a PI controller, an inter-phase balancing power reference value in each phase based on a second energy deviation between the stored energy in each phase and one third of the total stored energy of the actual bridge arms;

[0202] T9, determining an inter-phase balancing current reference based on the inter-phase balancing power reference value in each phase and the DC voltage of the MMC-DES integrated system;

[0203] T10, determining the energy difference between upper and lower bridge arms in each phase based on the stored energy of each bridge arm;

[0204] T11, obtaining, by a PI controller, an intra-phase balancing power reference value in each phase based on the energy difference between upper and lower bridge arms in each phase;

[0205] T12, determining an intra-phase balancing current reference based on the intra-phase balancing power reference value in each phase and the DC voltage of the MMC-DES integrated system;

[0206] T13, determining a circulating current reference for each phase based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference;

[0207] T14, determining a d-axis current reference value in the dq coordinate system based on the expected AC output power and the d-axis voltage in the dq coordinate system;

[0208] T15, obtaining, by a DQ controller, an AC voltage component for each phase based on the d-axis current reference value;

[0209] T16, obtaining, by a PI controller, a DC voltage component for each phase based on the circulating current reference for each phase;

[0210] T17, determining a bridge arm voltage reference value based on the DC voltage of the MMC-DES integrated system, and the AC voltage component and the DC voltage component for each phase;

[0211] T18, determining a reference value for the charging current of the sub-module capacitor by each energy storage unit based on the expected total power output by the energy storage units, the number of sub-modules in the energy storage units in the MMC-DES integrated system, and the capacitor voltage of the sub-modules;

[0212] T19, controlling the MMC-DES integrated system based on the bridge arm voltage reference value and the reference value for the charging current of the sub-module capacitor by each energy storage unit.

[0213] It should be noted that the descriptions in T1-T19 above can refer to the related descriptions in the above embodiments, and have similar effects, which will not be repeated here.

[0214] In one embodiment, this application also simulates the operation of MMC-DES, and the simulation parameters are shown in Table 1 below.

[0215] AC output power under three different operating conditions All remain at 1 pu, total output power of energy storage unit The waveforms for 0 pu, 0.2 pu, and 0.5 pu are as follows: Figure 25 , Figure 26 and Figure 27 As shown in the figure, under all test conditions, the three-phase AC current maintains an ideal sinusoidal waveform, completely in phase with the corresponding AC voltage, and the total harmonic distortion is 1.04%, 1.08%, and 1.33%, respectively. In addition, energy balance among the six bridge arms can be achieved under all three operating conditions, and the energy fluctuation of the bridge arms changes controllably with the increase of energy storage power, verifying the synergistic effect of energy balance, power distribution, and current control.

[0216] Table 1 Simulation parameters of MMC-DES operation

[0217]

[0218] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0219] Based on the same inventive concept, this application also provides a control device for an MMC-DES integrated system for implementing the control method of the MMC-DES integrated system described above. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more control device embodiments of the MMC-DES integrated system provided below can be found in the limitations of the control method for the MMC-DES integrated system described above, and will not be repeated here.

[0220] In one exemplary embodiment, such as Figure 28As shown, a control device of an MMC-DES integrated system is provided, comprising: a DC input current reference determination module 10, a balanced current reference determination module 11, a bridge arm voltage reference value determination module 12, and a control module 13, wherein:

[0221] The DC input current reference determination module 10 is configured to determine a DC input current reference value corresponding to a desired output power of the MMC-DES integrated system.

[0222] The balanced current reference determination module 11 is configured to determine a global balanced current reference, an inter-phase balanced current reference, and an intra-phase balanced current reference in the MMC-DES integrated system based on a global, inter-phase, and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system.

[0223] The bridge arm voltage reference value determination module 12 is configured to determine a bridge arm voltage reference value based on the DC input current reference value, the global balanced current reference, the inter-phase balanced current reference, and the intra-phase balanced current reference.

[0224] The control module 13 is configured to control the MMC-DES integrated system based on the bridge arm voltage reference value.

[0225] In an exemplary embodiment, the balanced current reference determination module 11 comprises:

[0226] A first obtaining unit is specifically configured to obtain a first energy deviation between a bridge arm total storage energy reference value and an actual bridge arm total storage energy.

[0227] A second obtaining unit is specifically configured to obtain a global energy power reference value through a PI controller based on the first energy deviation.

[0228] A first determination unit is specifically configured to determine the global balanced current reference based on the global energy power reference value and a DC voltage of the MMC-DES integrated system.

[0229] In an exemplary embodiment, the balanced current reference determination module 11 comprises:

[0230] A third obtaining unit is specifically configured to obtain a bridge arm storage energy and an actual bridge arm total storage energy.

[0231] A second determination unit is specifically configured to determine a per-phase storage energy based on the bridge arm storage energy.

[0232] A fourth obtaining unit is specifically configured to obtain an inter-phase balanced power reference value in each phase through a PI controller based on a second energy deviation between the per-phase storage energy and one third of the actual bridge arm total storage energy.

[0233] The third determining unit is specifically configured to determine the inter-phase balancing current reference based on the inter-phase balancing power reference in each phase and the DC voltage of the MMC-DES integrated system.

[0234] In an exemplary embodiment, the balancing current reference determining module 11 comprises:

[0235] The fourth determining unit is specifically configured to determine the energy difference between the upper and lower bridge arms in each phase according to the energy stored in each bridge arm.

[0236] The fifth obtaining unit is specifically configured to obtain the intra-phase balancing power reference in each phase through a PI controller based on the energy difference between the upper and lower bridge arms in each phase.

[0237] The fifth determining unit is specifically configured to determine the intra-phase balancing current reference based on the intra-phase balancing power reference in each phase and the DC voltage of the MMC-DES integrated system.

[0238] In an exemplary embodiment, the expected output power comprises an expected AC output power and an expected total energy storage unit output power, and the DC input current reference determining module 10 is further configured to determine the DC input current reference value based on the expected AC output power and the expected total energy storage unit output power.

[0239] In an exemplary embodiment, the DC input current reference determining module 10 comprises:

[0240] The sixth determining unit is specifically configured to determine the power difference between the expected AC output power and the expected total energy storage unit output power.

[0241] The seventh determining unit is specifically configured to determine the DC input current reference value based on the power difference and the DC voltage of the MMC-DES integrated system.

[0242] In an exemplary embodiment, the bridge arm voltage reference value determining module 12 comprises:

[0243] The eighth determining unit is specifically configured to determine the circulating current reference of each phase based on the DC input current reference value, the global balancing current reference, the inter-phase balancing current reference, and the intra-phase balancing current reference.

[0244] The ninth determining unit is specifically configured to determine the d-axis current reference value in the dq coordinate system based on the expected AC output power and the d-axis voltage in the dq coordinate system.

[0245] The sixth obtaining unit is specifically configured to obtain the AC voltage component of each phase through a DQ controller based on the d-axis current reference value.

[0246] The seventh obtaining unit is specifically configured to obtain the DC voltage component of each phase through a PI controller based on the circulating current reference of each phase.

[0247] The tenth determining unit is specifically configured to determine the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase.

[0248] In an exemplary embodiment, the tenth determining unit is further specifically configured to determine the bridge arm voltage reference value based on the DC voltage of the MMC-DES integrated system and the AC voltage component and the DC voltage component of each phase.

[0249] In an exemplary embodiment, the device further includes a reference value module of the capacitor charging current, configured to determine the reference value of the capacitor charging current of each energy storage unit to the sub-module based on the expected total power output of the energy storage unit, the number of sub-modules in the energy storage unit of the MMC-DES integrated system, and the capacitor voltage of the sub-module.

[0250] The control module 13 is further configured to control the MMC-DES integrated system based on the bridge arm voltage reference value and the reference value of the capacitor charging current of each energy storage unit to the sub-module.

[0251] The modules in the control device of the MMC-DES integrated system can be realized by software, hardware, or a combination thereof, in whole or in part. The modules can be embedded in or independent of the processor in the computer device in hardware form, or stored in the memory of the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to the modules.

[0252] In an embodiment, a computer device is also provided, including a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps in the above method embodiments.

[0253] In an embodiment, a computer readable storage medium is provided, storing a computer program, and the computer program is executed by a processor to implement the steps in the above method embodiments.

[0254] In an embodiment, a computer program product is provided, including a computer program, and the computer program is executed by a processor to implement the steps in the above method embodiments.

[0255] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when the computer program is executed, the processes of the above-mentioned embodiments of the methods can be included. Any reference to memory, database or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical storage, high-density embedded non-volatile memory, resistive memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The database involved in the embodiments provided in the present application can include at least one of a relational database and a non-relational database. The non-relational database can include a distributed database based on a block chain, etc., without being limited thereto. The processor involved in the embodiments provided in the present application can be a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., without being limited thereto.

[0256] Any combination of the technical features of the above embodiments can be made. In order to make the description simple, all possible combinations of the technical features in the above embodiments are not described, however, as long as the combination of the technical features does not exist, it should be considered as the scope of the present application.

[0257] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A control method for an MMC-DES integrated system, characterized in that, include: Determine the reference value of the DC input current corresponding to the expected output power of the MMC-DES integrated system; Based on the global, inter-phase, and intra-phase three-level energy balance management mechanism of the MMC-DES integrated system, the global balance current reference, inter-phase balance current reference, and intra-phase balance current reference in the MMC-DES integrated system are determined. Based on the DC input current reference value, the global equalization current reference, the interphase equalization current reference, and the intraphase equalization current reference, the bridge arm voltage reference value is determined. The MMC-DES integrated system is controlled based on the bridge arm voltage reference value. The process of determining the bridge arm voltage reference value based on the DC input current reference value, the global equalization current reference, the inter-phase equalization current reference, and the intra-phase equalization current reference includes: determining the circulating current reference for each phase based on the DC input current reference value, the global equalization current reference, the inter-phase equalization current reference, and the intra-phase equalization current reference; determining the d-axis current reference value in the dq coordinate system based on the desired AC output power and the d-axis voltage in the dq coordinate system; acquiring the AC voltage component of each phase through a DQ controller based on the d-axis current reference value; acquiring the DC voltage component of each phase through a PI controller based on the circulating current reference for each phase; and determining the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase. The process of determining the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase includes: determining the bridge arm voltage reference value based on the DC voltage of the MMC-DES integrated system, and the AC voltage component and the DC voltage component of each phase.

2. The method according to claim 1, characterized in that, The methods for determining the global equalization current reference in the MMC-DES integrated system include: Obtain the first energy deviation between the reference value of the total stored energy of the bridge arm and the actual total stored energy of the bridge arm; Based on the first energy deviation, a global energy power reference value is obtained through a PI controller; Based on the global energy power reference value and the DC voltage of the MMC-DES integrated system, a global equalization current reference is determined.

3. The method according to claim 1, characterized in that, The methods for determining the interphase equalization current reference in the MMC-DES integrated system include: Obtain the stored energy of each bridge arm and the actual total stored energy of the bridge arms; Based on the energy stored in each bridge arm, the energy stored in each phase is determined; Based on the second energy deviation between the energy stored in each phase and one-third of the total energy stored in the actual bridge arm, the interphase equalization power reference value of each phase is obtained through the PI controller; The interphase equalization current reference is determined based on the interphase equalization power reference value in each phase and the DC voltage of the MMC-DES integrated system.

4. The method according to claim 1, characterized in that, The methods for determining the intra-phase equalization current reference in the MMC-DES integrated system include: The energy difference between the upper and lower arms in each phase is determined based on the energy stored in each arm. Based on the energy difference between the upper and lower bridge arms in each phase, the intra-phase equalization power reference value of each phase is obtained through a PI controller; The intra-phase equalization current reference is determined based on the intra-phase equalization power reference value in each phase and the DC voltage of the MMC-DES integrated system.

5. The method according to claim 1, characterized in that, The desired output power includes: the desired AC output power and the desired total output power of the energy storage unit. Determining the DC input current reference value corresponding to the desired output power of the MMC-DES integrated system includes: Based on the desired AC output power and the desired total output power of the energy storage unit, a reference value for the DC input current is determined.

6. The method according to claim 5, characterized in that, The determination of the DC input current reference value based on the desired AC output power and the desired total output power of the energy storage unit includes: Determine the power difference between the desired AC output power and the desired total output power of the energy storage unit; The reference value of the DC input current is determined based on the power difference and the DC voltage of the MMC-DES integrated system.

7. The method according to claim 1, characterized in that, The method further includes: Based on the expected total output power of the energy storage unit, the number of sub-modules in the energy storage unit of the MMC-DES integrated system, and the capacitor voltage of the sub-module, a reference value for the charging current of each energy storage unit to the capacitor of the sub-module is determined. The control of the MMC-DES integrated system based on the bridge arm voltage reference value includes: The MMC-DES integrated system is controlled based on the reference value of the bridge arm voltage and the reference value of the charging current of each energy storage unit to the submodule capacitor.

8. A control device for an MMC-DES integrated system, characterized in that, include: A DC input current reference determination module is used to determine a DC input current reference value corresponding to the expected output power of the MMC-DES integrated system. The equalization current reference determination module is used to determine the global equalization current reference, inter-phase equalization current reference and intra-phase equalization current reference in the MMC-DES integrated system based on the global, inter-phase and intra-phase three-level energy equalization management mechanism of the MMC-DES integrated system. The arm voltage reference value determination module is used to determine the arm voltage reference value based on the DC input current reference value, the global equalization current reference, the inter-phase equalization current reference, and the intra-phase equalization current reference. The control module is used to control the MMC-DES integrated system based on the bridge arm voltage reference value; The process of determining the bridge arm voltage reference value based on the DC input current reference value, the global equalization current reference, the inter-phase equalization current reference, and the intra-phase equalization current reference includes: determining the circulating current reference for each phase based on the DC input current reference value, the global equalization current reference, the inter-phase equalization current reference, and the intra-phase equalization current reference; determining the d-axis current reference value in the dq coordinate system based on the desired AC output power and the d-axis voltage in the dq coordinate system; acquiring the AC voltage component of each phase through a DQ controller based on the d-axis current reference value; acquiring the DC voltage component of each phase through a PI controller based on the circulating current reference for each phase; and determining the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase. The process of determining the bridge arm voltage reference value based on the AC voltage component and the DC voltage component of each phase includes: determining the bridge arm voltage reference value based on the DC voltage of the MMC-DES integrated system, and the AC voltage component and the DC voltage component of each phase.

9. A computer device, characterized in that, include: A memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the method as claimed in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores a computer program thereon, which, when executed by a processor, implements the method as described in any one of claims 1 to 7.

11. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements the method as described in any one of claims 1 to 7.

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