Method and device for controlling three-level energy storage converter

Abstract

The invention provides a control method and device for a three-level energy storage converter. The method comprises the following steps: acquiring a control parameter; determining a first sector to which the spatial reference voltage vector belongs according to the first orthogonal component, the second orthogonal component and a first sector determination rule, and determining a second sector to which the spatial reference voltage vector belongs according to the spatial reference voltage vector, the first sector to which the spatial reference voltage vector belongs and a corresponding second sector determination rule; if it is judged that the midpoint potential offset degree is larger than or equal to the reference threshold value, corresponding three vectors are obtained, and corresponding vector action time is calculated; querying to obtain a corresponding three-phase switch sequence; and generating a corresponding pulse width modulation signal according to the three-phase switch sequence. The device is used for executing the method. According to the control method and device of the three-level energy storage converter provided by the embodiment of the invention, the operation stability of the three-level energy storage converter is improved.

Description

Technical Field

[0001] This invention relates to the field of power technology, specifically to a control method and device for a three-level energy storage converter. Background Technology

[0002] With the large-scale grid connection of renewable energy generation (such as photovoltaic and wind power) and the increasing demand for flexible regulation in the power system, energy storage systems have become a key component of the modern energy system. The power conversion system (PCS), as the energy conversion interface between energy storage devices and the grid / load, directly affects system efficiency, power quality, and equipment lifespan due to its control performance.

[0003] To overcome the limitations of two-level topologies, three-level energy storage converters, with their advantages of halved device voltage stress, low harmonic content, and improved efficiency, are gradually becoming the preferred solution for medium- and high-voltage energy storage systems. Existing control methods for three-level energy storage converters often focus on single issues such as midpoint potential regulation or power point tracking, employing carrier-modulated voltage closed-loop control or finite-state model predictive control (FCS-MPC). While these methods partially improve dynamic performance, they still suffer from midpoint potential recovery lag, leading to uneven device voltage stress and threatening system reliability. Summary of the Invention

[0004] To address the problems in the prior art, embodiments of the present invention provide a control method and apparatus for a three-level energy storage converter, which can at least partially solve the problems existing in the prior art.

[0005] In a first aspect, the present invention proposes a control method for a three-level energy storage converter, comprising:

[0006] Acquire control parameters, which include the first and second orthogonal components of the space reference voltage vector in the two-phase stationary coordinate system, the adjustment factor, and the midpoint potential offset.

[0007] Based on the first orthogonal component, the second orthogonal component, and the first sector determination rule, the first sector to which the spatial reference voltage vector belongs is determined, and based on the spatial reference voltage vector, the first sector to which the spatial reference voltage vector belongs, and the corresponding second sector determination rule, the second sector to which the spatial reference voltage vector belongs is determined; wherein, the spatial vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors;

[0008] If it is determined that the midpoint potential offset is greater than or equal to the reference threshold, then based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor, the three vectors corresponding to the spatial reference voltage vector are obtained and the corresponding vector action time is calculated.

[0009] Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switch sequence is obtained by querying; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switch sequence is preset;

[0010] Based on the three-phase switch sequence, a corresponding pulse width modulation signal is generated.

[0011] In a second aspect, the present invention provides a control device for a three-level energy storage converter, comprising:

[0012] The acquisition module is used to acquire control parameters, which include the first and second orthogonal components of the space reference voltage vector in the two-phase stationary coordinate system, the adjustment factor, and the midpoint potential offset.

[0013] The determination module determines the first sector to which the spatial reference voltage vector belongs based on the first orthogonal component, the second orthogonal component, and the first sector determination rule, and determines the second sector to which the spatial reference voltage vector belongs based on the spatial reference voltage vector, the first sector to which the spatial reference voltage vector belongs, and the corresponding second sector determination rule; wherein, the spatial vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors;

[0014] The judgment module is used to determine the three vectors corresponding to the spatial reference voltage vector and calculate the vector action time based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor if it is determined that the midpoint potential offset is greater than or equal to the reference threshold.

[0015] The query module is used to query and obtain the corresponding three-phase switch sequence based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switch sequence is preset;

[0016] The generation module is used to generate a corresponding pulse width modulation signal based on the three-phase switch sequence.

[0017] Thirdly, the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the program to implement the control method of the three-level energy storage converter described in any of the above embodiments.

[0018] Fourthly, the present invention provides a computer-readable storage medium storing a computer program / instructions that, when executed by a processor, implement the control method for the three-level energy storage converter described in any of the above embodiments.

[0019] Fifthly, the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the control method of the three-level energy storage converter described in any of the above embodiments.

[0020] The control method and apparatus for a three-level energy storage converter provided in this invention can acquire control parameters, including the first and second orthogonal components of a space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor, and a midpoint potential offset. Based on the first and second orthogonal components and a first sector determination rule, the first sector to which the space reference voltage vector belongs is determined, and based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and the corresponding second sector determination rule, the second sector to which the space reference voltage vector belongs is determined. The space vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors. If it is determined that the midpoint potential offset is greater than or equal to a reference threshold, then based on the first sector to which the space reference voltage vector belongs, the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs, and the corresponding second sector determination rule, the second sector to which the space reference voltage vector belongs is determined. The system obtains the three-phase switching sequence corresponding to the spatial reference voltage vector by defining the second sector to which the spatial reference voltage vector belongs and the adjustment factor, and calculates the corresponding vector action time. Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switching sequence is obtained by querying. The correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switching sequence is preset. Based on the three-phase switching sequence, a corresponding pulse width modulation signal is generated. Through refined division of the second sector, the corresponding three-phase switching sequence is obtained, enabling dynamic adjustment of the vector action time while considering waveform optimization and midpoint potential balance, thus improving the operational stability of the three-level energy storage converter. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0022] Figure 1 This is a schematic diagram of the topology of the NPC-type three-level energy storage converter provided in the first embodiment of the present invention.

[0023] Figure 2 This is a vector space distribution diagram of the three-level energy storage converter provided in the second embodiment of the present invention.

[0024] Figure 3 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the third embodiment of the present invention.

[0025] Figure 4 This is a spatial vector plane schematic diagram of the three-level energy storage converter provided in the fourth embodiment of the present invention.

[0026] Figure 5 This is a schematic diagram of the second sector division of the first sector I provided in the fifth embodiment of the present invention.

[0027] Figure 6 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the sixth embodiment of the present invention.

[0028] Figure 7 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the seventh embodiment of the present invention.

[0029] Figure 8 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the eighth embodiment of the present invention.

[0030] Figure 9 This is a schematic diagram of the space vector plane of the standardized three-level energy storage converter provided in the ninth embodiment of the present invention.

[0031] Figure 10 This is a schematic diagram of the first sector I of the space vector plane of the standardized three-level energy storage converter provided in the tenth embodiment of the present invention.

[0032] Figure 11 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the ninth embodiment of the present invention.

[0033] Figure 12 This is a schematic diagram of coordinate transformation of the first sector provided in the tenth embodiment of the present invention.

[0034] Figure 13 This is a schematic diagram of the control device for a three-level energy storage converter provided in the eleventh embodiment of the present invention.

[0035] Figure 14 This is a schematic diagram of the physical structure of a computer device provided in the twelfth embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and their descriptions are used to explain the present invention, but are not intended to limit the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other. The acquisition, storage, use, and processing of data in the technical solutions of this application all comply with relevant laws and regulations. The user information in the embodiments of this application is obtained through legal and compliant means, and the acquisition, storage, use, and processing of user information have been authorized and agreed upon by the customer.

[0037] To facilitate understanding of the technical solution provided in this application, the relevant content of the technical solution in this application will be explained below.

[0038] like Figure 1 As shown, the topology of the NPC-type three-level energy storage converter includes three bridge arms. Each bridge arm has four power switches and four freewheeling diodes, with two diodes clamping the DC-side midpoint. The DC-side power supply voltage is evenly divided by two capacitors. By controlling the on (set to 1) and off (set to 0) states of the four power switches on each phase bridge arm, three different voltage levels are output, namely U... dc / 2 (1 or P), 0 (0 or O), -U dc / 2 (-1 or N). The phase voltages corresponding to the P, O, and N levels output by each phase arm (in a three-phase power system, the voltage between each phase and the neutral point (or ground)) are U dc / 2, 0, -U dc / 2. Line voltage (the voltage between any two phases in a three-phase power system) has five levels, namely U... dc U dc / 2, 0, -U dc / 2 and -U dcSince each phase has three switching states, there are a total of 27 possible switching state combinations for the three phases, corresponding to 19 voltage vectors. These vectors can be categorized into four types based on their length: large vector, medium vector, small vector, and zero vector. Each voltage vector can be represented by a combination of the letters P, O, and N, representing the switching states of phases A, B, and C, respectively. The vector space distribution of the three-level energy storage converter is shown below. Figure 2 As shown.

[0039] A large vector refers to a vector in which all three phases are connected to the same polarity (positive P or negative N) and do not pass through the neutral point (O). Therefore, a large vector has no effect on the neutral point current. A characteristic of a large vector is its maximum voltage amplitude; the line voltage amplitude is 2 / 3 of the DC bus voltage. If the total bus voltage is U... dc The amplitude of the line voltage of the large vector is 2 / 3U. dc A neutral vector is a vector where one phase is connected to the neutral point (O), and the other two phases are connected to the opposite polarity (P or N). The characteristics of a neutral vector are moderate voltage amplitude, with the line voltage amplitude being approximately [amount missing] times that of the DC bus voltage. The neutral vector affects the neutral point current. Since a single phase passes through the neutral point, a neutral point current is generated, which can be used for neutral point potential regulation. The small vector refers to a vector generated by connecting two phases to the neutral point (O) or through redundant switching states. It has two equivalent forms: positive small vector and negative small vector. The small vector is characterized by its minimum voltage amplitude, with the line voltage amplitude being 1 / 3 of the DC bus voltage. The small vector is redundant; the same output voltage can be generated by two switching states (such as POO and OON), but the neutral point current direction is opposite, which can be used for dynamic balancing of the neutral point potential. The zero vector is a vector where all three phases are connected to the neutral point (O) and the output voltage is zero. The zero vector is characterized by no output voltage, does not participate in vector synthesis, but is used to fill the remaining time of the switching cycle. The zero vector does not generate a neutral point current.

[0040] Midpoint potential adjustment targets two capacitors connected in series on the DC side. Figure 1 The potential adjustment of the midpoint of capacitors C1 and C2 is crucial. The midpoint of the capacitors serves as the reference point for the three-phase bridge arm. However, due to factors such as load imbalance, differences in switching device characteristics, and modulation strategies, the voltages of the two capacitors may become unequal, resulting in a midpoint potential shift. This midpoint potential shift can lead to a series of problems, such as increased harmonic content in the output voltage, reduced inverter efficiency, and even potential damage to the switching devices. Therefore, midpoint potential adjustment is necessary.

[0041] Traditional midpoint potential balancing methods have the following limitations: (1) Operating condition dependence: When the power factor is low (e.g., high reactive power ratio) or the modulation system is high (close to the modulation limit), the regulation capability of the positive and negative small vectors is saturated, and the midpoint potential deviation cannot be completely eliminated, resulting in third harmonic fluctuations; (2) Insufficient dynamic response: Under extreme operating conditions such as low voltage ride-through and load change, the system power factor is significantly reduced, the midpoint potential fluctuation is aggravated, and the output voltage waveform quality is further deteriorated (THD increases by 5%-10%); (3) Open-loop control defects: It relies on fixed regulation rules and lacks a closed-loop feedback mechanism, and cannot compensate for potential drift caused by parasitic parameters, device aging, etc. in real time.

[0042] Virtual Space Vector Pulse Width Modulation (VSVPWM) is developed based on traditional Space Vector Pulse Width Modulation (SVPWM). It introduces the concept of virtual space vectors into the modulation strategy, achieving precise control of the inverter's output voltage and current through the synthesis and control of virtual space vectors. However, it has the following drawbacks: (1) Passive regulation characteristics: It can only passively suppress midpoint potential fluctuations, lacking active control capabilities and unable to actively inject compensation current when the potential is severely unbalanced; (2) Switching frequency sensitivity: When the switching frequency decreases (e.g., to meet the requirements of high-frequency design), the midpoint potential suppression effect is significantly reduced, leading to an increase in low-frequency harmonic content; (3) Suboptimal vector synthesis: The virtual vector generation rule does not consider geometric optimality, causing the output voltage vector trajectory to deviate from the ideal circle, resulting in a decrease in waveform quality.

[0043] Existing methods for midpoint potential control generally fall into a trade-off between midpoint potential control and waveform quality optimization, specifically manifested as follows: (1) Conflict between control capability and waveform quality: Enhancing the midpoint potential regulation capability requires increasing the proportion of small vectors or changing the vector sequence, but this will introduce additional switching actions or deviate from the optimal vector path, resulting in increased harmonics; (2) Separation of static and dynamic performance: A single control mode cannot simultaneously meet the requirements of steady-state high precision and dynamic fast response, and the system stability decreases under extreme conditions; (3) Contradiction between algorithm complexity and real-time performance: Some improvement schemes improve performance through complex algorithms (such as multi-objective optimization), but the computational burden is too heavy and it is difficult to adapt to high switching frequency scenarios.

[0044] In existing technologies, midpoint potential control technology is limited by passive adjustment mechanisms, strong dependence on operating conditions, and insufficient multi-objective coordination capabilities. This leads to the following drawbacks for three-level energy storage converters under complex operating conditions: increased output voltage waveform distortion, affecting grid-connected power quality; uneven voltage stress on devices, reducing system reliability; slow dynamic response, posing a risk of runaway under extreme conditions; and limited overall efficiency, making it difficult to meet the demands of high power density applications. These drawbacks severely restrict the large-scale application of three-level energy storage converters in new energy power generation and energy storage systems.

[0045] Therefore, this invention proposes a control method for a three-level energy storage converter, constructs a dual-mode control architecture, and realizes dynamic switching of control strategies by real-time detection of the DC side midpoint voltage offset. Through hierarchical optimization architecture and dynamic weight allocation strategy, two different midpoint potential control modes are adopted for different degrees of midpoint potential offset.

[0046] (1) Under the condition of slight offset, by establishing a closed-loop feedback regulation mechanism for the midpoint potential, under the condition of ensuring that the minimum switching loss constraint is always met during the voltage vector synthesis process, the three vector combinations with the closest geometric distance are selected first for spatial vector synthesis, so that the total harmonic distortion rate of the output phase voltage is reduced by 12%-18%, while maintaining the midpoint potential fluctuation range within ±1%.

[0047] (2) When a significant offset condition is detected, the system automatically switches to dynamic compensation mode. By reconstructing the virtual vector sequence, a weighted combination of small vectors with bidirectional midpoint current adjustment capability is introduced, increasing the duty cycle utilization of the small vectors to over 85%. Combined with a feedforward potential compensation algorithm, real-time correction of the midpoint current injection is achieved, reducing the dynamic response time for the midpoint potential to return to equilibrium by 40%-60%.

[0048] While ensuring midpoint potential self-balancing, this method achieves rapid power response, minimizes switching losses, and allows for flexible switching of grid interaction functions. The control method for the three-level energy storage converter in this application effectively solves the problems of high computational complexity and difficulty in coordinating multi-objective coupling in existing technologies, significantly improving system efficiency and reliability. It is suitable for large-scale energy storage power stations, microgrids, and industrial and commercial energy storage scenarios.

[0049] This invention fundamentally solves the long-standing multi-objective coordination problem of midpoint potential control, waveform quality, and dynamic response in three-level energy storage converters. It overcomes the technical bottlenecks of traditional methods in terms of adaptability to all operating conditions, robustness under extreme conditions, and overall efficiency optimization, providing a high-performance energy storage converter control solution for scenarios such as new energy grid connection and energy storage systems. Under non-ideal operating conditions such as grid voltage dips and load step changes, this invention effectively balances midpoint potential control accuracy (steady-state error <0.5%) and output voltage waveform quality (THD <3%). Compared to traditional single-mode control methods, the overall system efficiency is improved by 4.5 percentage points, and the temperature rise of power devices is reduced by more than 15K.

[0050] Figure 3 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the third embodiment of the present invention, as shown below. Figure 3 As shown, the control method for a three-level energy storage converter provided in this embodiment of the invention includes:

[0051] S301. Obtain control parameters, the control parameters including the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system, the adjustment factor and the midpoint potential offset.

[0052] Specifically, the spatial reference voltage vector can be decomposed into two orthogonal components in a two-phase stationary coordinate system (α-β coordinate system): the component of the reference voltage on the α-axis and the component of the reference voltage on the β-axis. The first orthogonal component can be the component of the reference voltage on the α-axis, and the second orthogonal component can be the component of the reference voltage on the β-axis.

[0053] When the three-phase voltages of the three-level energy storage converter are respectively u a u b and u c At that time, the first orthogonal component u refα Second orthogonal component u refβ It can be calculated using the following formula.

[0054]

[0055] Convert to matrix representation:

[0056]

[0057] When the three phases are in equilibrium, i.e., u a +u b +u c When =0, u can be omitted. c calculate:

[0058] u c =-u a -u b

[0059] After substituting, the formula simplifies to:

[0060] u refα =u a

[0061]

[0062] In energy storage systems, converting three-phase AC signals to the α-β coordinate system can simplify control algorithm design, improve dynamic response capabilities, and achieve more efficient energy management.

[0063] The adjustment factor is used to adjust the working time distribution ratio of the positive and negative small vectors. By adjusting this ratio, the direction of the midpoint current is controlled, thereby compensating for the voltage difference between the two capacitors connected in series on the DC side. The adjustment factor can be determined based on the proportional adjustment coefficient, the voltage difference between the two capacitors connected in series on the DC side, and the current direction sign function. The proportional adjustment coefficient is a gain parameter in closed-loop control, determining the adjustment strength. A larger proportional adjustment coefficient results in faster adjustment but may cause oscillations; a smaller proportional adjustment coefficient results in a slow response. The value of the proportional adjustment coefficient is usually determined based on the system's dynamic characteristics or experimental optimization. The voltage difference between the two capacitors connected in series on the DC side reflects the degree of midpoint potential deviation; the larger the absolute value of this voltage difference, the stronger the adjustment is required. The current direction sign function returns +1 or -1 based on the polarity of the midpoint current, ensuring that the adjustment direction matches the midpoint current direction and avoiding miscompensation.

[0064] The midpoint potential deviation directly reflects the degree of deviation of the midpoint potential in a three-level energy storage converter and is a key basis for determining the balance state in the control algorithm. By combining amplitude limiting and threshold comparison, efficient closed-loop control of the midpoint potential is achieved, taking into account both waveform quality and dynamic response.

[0065] For example, the midpoint potential offset can be calculated using the formula... Calculated, u C1 This represents the voltage of the capacitor on the DC side, specifically the voltage value of the upper half of the capacitor in the DC bus of the three-level energy storage converter (unit: volts); u C2 This represents the voltage of the lower capacitor on the DC side, specifically the voltage value of the lower half of the capacitor in the DC bus of the three-level energy storage converter (unit: volts); k o The difference in normalized capacitor voltages represents the degree to which the midpoint potential deviates from equilibrium. (Molecular value - u) C1 -u C2 ): Directly reflects the voltage difference between the two capacitors; denominator (u) C1 -u C2): Total DC bus voltage (i.e., the sum of the voltages of the two capacitors); the ratio of the voltage difference between the two capacitors to the total DC bus voltage is used as the offset to eliminate the influence of the amplitude variation of the total DC bus voltage, making k o Reflects relative deviation. When u C1 >u C2 When the molecule is positive, the midpoint potential shifts upward; when u C1 C2 When the molecule is negative, the midpoint potential shifts downwards. When u C1 =u C2 k o The value is 0, and the midpoint potential is balanced.

[0066] S302. Based on the first orthogonal component, the second orthogonal component, and the first sector determination rule, determine the first sector to which the space reference voltage vector belongs, and based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and the corresponding second sector determination rule, determine the second sector to which the space reference voltage vector belongs; wherein, the space vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors;

[0067] Specifically, the space vector plane of the three-level energy storage converter can be divided into multiple first sectors, and each first sector can be further divided into multiple second sectors. Based on the first and second orthogonal components of the space reference voltage vector in the two-phase stationary coordinate system and the first sector determination rules, the first sector to which the space reference voltage vector belongs can be determined. The first sector determination rules are preset and used to determine the first sector to which the space reference voltage vector belongs.

[0068] After determining the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs can be determined based on the spatial reference voltage vector, the first sector to which the spatial reference voltage vector belongs, and the corresponding second sector determination rules. The second sector to which the spatial reference voltage vector belongs is the second sector within the first sector to which the spatial reference voltage vector belongs. The second sector determination rules are preset and can be set according to actual needs; this embodiment of the invention does not impose limitations.

[0069] ​The number of sectors in the first sector is set according to actual needs, and this embodiment of the invention does not limit it. For example, the space vector plane of the three-level energy storage converter is divided into six first sectors. The number of sectors in the second sector involves the trade-off between performance optimization and complexity. The selection of the number of sectors needs to take into account the following factors: (1) Control accuracy and harmonic performance. Accuracy requirements: The more small sectors there are, the higher the synthesis accuracy of the reference vector and the smaller the voltage harmonics. Harmonic distribution: More small sectors can optimize the switching sequence and disperse the harmonic energy at the switching frequency. Dividing 2 to 3 small sectors: suitable for low-cost systems with low harmonic requirements; dividing 5 to 8 small sectors: used for high-precision servo systems or new energy converters to suppress current ripple. (2) Switching loss and efficiency, number of switching: the number of switching state changes may increase with each additional small sector; zero vector allocation strategy: the division of small sectors affects the insertion method of zero vectors, and it is necessary to balance loss and harmonics; low loss scenario: divide into 2 to 3 small sectors and use centralized zero vector insertion; high precision scenario: divide into 5 to 8 small sectors and distribute zero vectors to amortize loss. (3) Algorithm complexity and real-time performance, computational load: the complexity of sector judgment, vector action time calculation and pulse width modulation signal generation increases with each doubling of the number of small sectors; hardware resources: low-end MCUs (such as STM32F103) may only support the division of 2 to 3 small sectors, while high-end DSPs (such as TI C2000) can handle more than 8; dividing into 2 to 3 small sectors: only simple threshold comparison is required; dividing into 5 to 8 small sectors: it is necessary to calculate the proportional coefficient and judge multiple intervals. (4) Dynamic response and overmodulation capability, dynamic performance: dividing too many small sectors can easily lead to algorithm delay and affect the current loop bandwidth; overmodulation region: when the DC bus voltage is insufficient, dividing more small sectors can expand the linear modulation range and avoid entering the six-beat mode. (5) Comprehensive design factors, performance index priority: if you want to pursue lower harmonics, choose 5 to 8 small sectors; if you want to pursue lower losses, choose 2 to 3; hardware platform limitations: DSP / FPGA resources determine the maximum feasible number of divisions. For example, FPGA can support real-time 8 small sector divisions (clock frequency > 100MHz); low-end MCUs are recommended to not exceed 5; experimental verification: compare the current THD and efficiency under different divisions through simulation (such as MATLAB / PLECS), and finally determine the optimal value through experiments. Start with 5 small sectors (a compromise solution) and gradually optimize; if the current THD does not meet the requirements, try to increase to 6 to 8; if the real-time performance is insufficient or the loss is too high, reduce to 3 to 4.

[0070] In the space vector modulation of a three-level energy storage converter, the first sector containing the space reference voltage vector is quickly located, providing direction for subsequent virtual vector synthesis, midpoint potential adjustment, and switching signal generation. The core principle lies in balancing computational complexity and real-time performance. This application, based on the first sector division, further divides the first sector into multiple second sectors. By refining the second sector based on parity, the dynamic adjustment capability of the midpoint potential is further improved.

[0071] S303. If it is determined that the midpoint potential offset is greater than or equal to the reference threshold, then according to the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor, the corresponding three vectors are obtained and the vector action time is calculated.

[0072] Specifically, the midpoint potential offset is compared with a reference threshold. If the midpoint potential offset is greater than or equal to the reference threshold, then the three vectors corresponding to the spatial reference voltage vector are obtained based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor, and the corresponding vector action time is calculated. The correspondence between each first sector, each second sector of each first sector, the adjustment factor, and the three vectors is predetermined.

[0073] For example, such as Figure 4 As shown, the space vector plane of the three-level energy storage converter is divided into six first sectors: Sector I, Sector II, Sector III, Sector IV, Sector V, and Sector VI, each covering an angular range of 60°. Each first sector is... Figure 4 The dashed line divides the area into eight second sectors. A virtual mid-vector V is constructed. M V M1 V M2 V M3 V M4 and V M5 and virtual small vector V S1 V S2 V S3 V S4 V S5 and V S6 .

[0074] The virtual neutral vector is constructed to achieve dynamic balance of the neutral point potential and waveform optimization of the output voltage by combining basic vectors. Neutral point potential balance: The direction of the neutral point current is dynamically adjusted by combining small positive and negative vectors. Waveform quality optimization: Equivalent vectors are smoothly switched to reduce harmonic content in the output voltage.

[0075] A virtual vector is formed by dynamically combining two adjacent redundant small vectors (positive and negative small vectors), and its mathematical expression is:

[0076]

[0077] V 正小矢量 Indicates the current flowing out at the midpoint; V 负小矢量 Indicates the current flowing into the midpoint; k s This indicates a regulatory factor.

[0078] For odd-numbered small sectors, the virtual center vector is generated by combining small vectors (such as POO / ONN) connected by the midpoints of a single phase; for even-numbered small sectors, the virtual center vector is generated by combining small vectors (such as PPO / OON) connected by the midpoints of two phases.

[0079] by Figure 5 V′ in the first sector I shown S1 and V′ S2 Taking this as an example, we can illustrate the construction of virtual small vectors. Figure 5 In this diagram, sector I comprises eight second sectors: sector 1, sector 2, sector 3, sector 4, sector 5, sector 6, sector 7, and sector 8. Sector 1, sector 3, sector 5, and sector 7 are odd-numbered sectors. Sector 2, sector 4, sector 6, and sector 8 are even-numbered sectors.

[0080] If the second sector to which the space reference voltage vector belongs is an odd-numbered small sector, the virtual small vector corresponding to the second sector to which the space reference voltage vector belongs is constructed using the following formula. The virtual small vector is synthesized from a positive small vector (such as a P-type small vector) and a zero vector, thereby enhancing the charging capability of the DC-side capacitor.

[0081]

[0082] V′ S1 A virtual small vector representing an odd-numbered small sector, dynamically weighted and synthesized from positive and negative small vectors, is used for midpoint potential adjustment; V′ S2 The virtual small vector representing an even-numbered small sector is composed of positive and negative small vectors in a fixed proportion to maintain midpoint balance.

[0083] If the second sector to which the space reference voltage vector belongs is an even-numbered small sector, the virtual small vector corresponding to the second sector to which the virtual space reference voltage vector belongs is constructed using the following formula. The virtual small vector is synthesized from the negative small vector (such as the N-type small vector) and the zero vector, thereby enhancing the charging capability of the capacitor on the DC side.

[0084]

[0085] V′S1 The virtual small vector representing an odd-numbered small sector is synthesized from positive and negative small vectors in a fixed proportion to maintain the midpoint potential balance; V′ S2 The virtual small vector representing an even-numbered small sector is dynamically weighted and synthesized from positive and negative small vectors, and is used for midpoint potential adjustment.

[0086] Table 1. Replaced Three Vectors

[0087]

[0088] for Figure 5 In the first sector I shown, in the second sector 1-6: the selected small vector (POO or ONN) replaces the corresponding virtual small vector and participates in vector synthesis; in the second sector 7-8: a small vector is forcibly introduced to participate in vector synthesis, and the results are shown in Table 1. For example, based on the first sector I and the second sector 1, the corresponding virtual small vector and / or the three vectors after the virtual medium vector has been replaced can be obtained by querying, and the k in the above three vectors can be replaced with an adjustment factor. S This yields the three vectors corresponding to the first sector I, the second sector 1, and the adjustment factor.

[0089] Midpoint potential imbalance causes changes in the amplitude of the small vector voltage, and the calculation of the vector's duration must consider the effect of changes in the small vector's length. The voltage amplitude of the small vector directly depends on the DC-side capacitor voltage u. C1 and u C2 Under conditions of midpoint potential imbalance, the actual voltage amplitude of the small vector deviates from the nominal value. If u C1 >u C2 The voltage amplitude of a positive small vector (such as POO) will increase, while the voltage amplitude of a negative small vector (such as ONN) will decrease. The vector action time originally designed based on equilibrium is no longer accurate and needs to be recalculated according to the actual voltage amplitude; otherwise, it will lead to errors in the space reference voltage vector V. ref Synthesis error.

[0090] When the midpoint potential offset is greater than or equal to the reference threshold and k s <0, the DC side capacitor voltage u needs to be increased. C1 When using this formula, the following method is employed:

[0091] V ref ·T s =V ONN ·T ONN +V S2 ·T S2 +V0·T0

[0092]

[0093] V ONN ∝sin(60°-θ′),VS2 ∝sinθ′

[0094]

[0095] Among them, V ref T represents the space reference voltage vector. s V represents the switching period. ONN T represents the negative small vector. ONN V represents ONN The corresponding vector action time, V S2 T represents a virtual small vector. S2 V represents S2 The corresponding vector action time, V0 represents the zero vector, T0 represents the vector action time corresponding to V0, and m represents the normalized reference voltage amplitude: m=|V ref | / (U dc / 2), U dc Represents the bus voltage, k o θ′ represents the midpoint potential offset, and θ′ represents the equivalent angle within the sector, θ′=θ ref -(N-1)·60° converts the global angle to the local angle of the current sector. It converts the reference voltage amplitude to a ratio relative to the DC bus voltage, simplifying calculations. The normalization parameter m allows the algorithm to adapt to different DC bus voltages, improving versatility. It uniformly maps the reference vector at any location to a standard sector (0°~60°), simplifying cross-sector calculation logic. N represents the sector number: the spatial vector plane of the three-level energy storage converter is divided into 6 large sectors (N=1~6), each sector covering 60°.

[0096] Angle conversion rule: If the reference vector is located in the Nth sector, then its global angle range is:

[0097] By subtracting (N-1)·60°, the global angle is mapped to the local angle θ′ within the current sector, that is:

[0098] Sector I (N=1): θ ref ∈[0°,60°)→θ′=θ ref ;

[0099] Sector II (N=2): θ ref ∈[60°,120°)→θ′=θ ref -60°;

[0100] Sector III (N=3): θ ref ∈[120°,180°)→θ′=θ ref -120°;

[0101] And so on.

[0102] The time allocation for virtual vector 2: Time is allocated according to the direction of the reference vector to ensure volt-second balance. Time is also allocated directly using a sine function based on the local angle θ′ of the reference vector within the sector to ensure volt-second balance.

[0103] The duration of the zero vector (OOO) at time T0: fills the remaining time to ensure the total period T. s Complete. Fill in the remaining time to ensure the total time percentage is 1. If the result is negative, time overflow handling is required (forced zeroing and reallocation). Zero vector characteristic: The voltage of a zero vector (such as OOO) is zero (V0 = 0), used only to fill the remaining time not occupied by non-zero vectors, and does not participate in the synthesis of the reference vector. Time conservation constraint: The sum of the action times of all vectors must be equal to the switching period T. s ,Right now Therefore, the proportion of zero vector time is: Time percentages of non-zero vectors V1 and V2 and The direction and magnitude of the composite reference vector are determined, while the zero vector is only used to make up for the remaining time to ensure the integrity of the total period.

[0104] When the midpoint potential is unbalanced, the non-zero vector time may be affected by the adjustment factor k. s The corrections are beyond a reasonable range (e.g.) ),lead to At this point, time overflow handling is required:

[0105] Forced zeroing: Set

[0106] Time reallocation: Adjustment or The value ensures Zero vector fills the remaining time to avoid waveform distortion (such as pulse loss) caused by incomplete switching cycles. When the midpoint potential is unbalanced, forced correction ensures the validity of the time and maintains system stability.

[0107] Midpoint potential offset is greater than or equal to the reference threshold and k s When the value is greater than 0, the voltage u of the DC-side capacitor needs to be reduced. C1 Only the duration of positive small vectors (such as POO) needs to be adjusted, while the duration of other vectors (such as medium vectors or redundant small vectors) and zero vectors remains unchanged.

[0108]

[0109] This indicates the duration of the positive small vector (POO): it flows out through the midpoint current, reducing u... C1Compensation for midpoint potential under-bias (u) C1 C2 sin(60°-θ′) represents the projection component of the space reference voltage vector in the transverse direction (perpendicular to the current sector's principal direction). Correction for small vector voltage magnitude: when k o <0(u C1 C2 ), denominator 1+k o Decrease or increase the duration of the positive small vector (POO) to accelerate u. C1 Charging. When k s >0: u needs to be reduced C1 Select the positive smallest vector (POO).

[0110] The moderating effect of the positive small vector (POO): k s >0 indicates that the DC-side capacitor voltage u needs to be reduced. C1 At this point, the duration of the positive small vector (POO) needs to be increased to increase the outflow of the midpoint current and accelerate u. C1 The discharge. By replacing k o →-k o The effective voltage magnitude of the positive small vector is corrected, thereby adjusting its time proportion. Medium vector / redundant small vector (VS2): Its duration is determined by the geometric projection of the reference vector (dependent only on θ′ and m), and is independent of the midpoint potential offset. Zero vector (OOO): It only fills the remaining time; its time proportion is determined by the time allocation of other vectors and requires no additional correction.

[0111] Voltage of the positive small vector (POO):

[0112]

[0113] Voltage of the negative small vector (ONN):

[0114]

[0115] V ref ·T s =V POO ·T POO +V S2 ·T S2 +V0·T0

[0116]

[0117] When the adjustment direction is from lifting U c1 (ks<0) becomes a decrease in U c1 When (ks>0): When the goal becomes reducing U c1 Positive small vector (POO) must be used, and its voltage denominator is 1+k. o (corresponding to U)​​c1 c2 When the adjustment target changes from increasing U c1 (Using negative small vectors) to reduce U c1 When using positive small vectors, k needs to be... o Replace with -k o This is to reflect the reversal of the capacitor-voltage relationship and ensure accurate matching of the volt-second product.

[0118] A midpoint potential deviation greater than or equal to the reference threshold indicates that the midpoint potential is in equilibrium (u C1 =u C2 At this time, the midpoint potential offset When the midpoint is balanced, the voltage amplitudes of the positive small vector (such as POO) and the negative small vector (such as ONN) return to their nominal values ​​without needing to be corrected due to the midpoint potential shift.

[0119]

[0120] When k o When = 0, the correction term 1+k o Degenerates to 1. No need to consider k. o The correction time allocation is determined solely by the geometric projection of the reference vector.

[0121] Because the midpoint potential is in an unbalanced state, this imbalance causes a change in the amplitude of the small vector voltage. The calculation of the vector's duration must consider the effect of changes in the small vector's length. The voltage amplitude of the small vector depends on the voltage U of the DC-side capacitor. c1 and U c2 Imbalance: U c1 ≠U c2 The actual voltage amplitude of the small vector deviates from the nominal value. If U c1 >U c2 The voltage amplitude of a positive small vector (such as POO) will increase, while the voltage amplitude of a negative small vector (such as ONN) will decrease. The vector action time originally designed based on equilibrium is no longer accurate and needs to be recalculated according to the actual voltage amplitude; otherwise, it will affect the reference voltage V. ref Synthesis error.

[0122] The small vector adjusts the capacitor voltage by controlling the direction of the current (inflow or outflow) at its midpoint.

[0123] Positive small vector (e.g., POO): Midpoint current flows out, reducing U. c1 ;

[0124] Negative small vector (e.g., ONN): Midpoint current flows in, boosting U c1 .

[0125] ​An adjustment factor is introduced to dynamically adjust the action time ratio of the positive / negative small vectors, quickly restoring midpoint balance. The effective length of the small vectors is corrected by the midpoint potential offset to ensure that the time allocation matches the actual voltage amplitude.

[0126] Midpoint potential imbalance causes the actual voltage amplitude of the small vector to deviate from the nominal value, directly affecting the accuracy of the volt-second balance. To correct voltage amplitude errors, ensure accurate synthesis of the reference vector, dynamically adjust the midpoint current direction to quickly restore capacitor voltage balance, and avoid time allocation failures to prevent control anomalies caused by negative time, it is necessary to introduce a midpoint potential offset k when calculating the vector's action time. o Or the adjustment factor k s The effective length of the small vector is dynamically adjusted to improve the stability of the three-level energy storage converter under high dynamic conditions.

[0127] According to the volt-second balance principle, in one switching cycle T s Within this context, the volt-second product of the composite vector must be equal to the volt-second product of the space reference voltage vector:

[0128] V ref ·T s =V1·t1+v2·t2+v3·t3

[0129] Among them, V ref T represents the space reference voltage vector. s Let T represent the switching period, V1, V2, and V3 represent the three fundamental vectors corresponding to the space reference voltage vector, t1 represent the vector action time corresponding to V1, t2 represent the vector action time corresponding to V2, and t3 represent the vector action time corresponding to V3, and t1 + t2 + t3 ≤ T. s .

[0130] If the midpoint potential is unbalanced, the redundancy selection of the small vector needs to be adjusted:

[0131] Positive small vector (e.g., POO): Midpoint current flows out, reducing U. c1 ;

[0132] Negative small vector (e.g., OON): Midpoint current flows in, increasing U. c1 ;

[0133] The time ratio of positive and negative small vectors is dynamically adjusted by regulating the adjustment factor. Time allocation is corrected.

[0134] Increase the time of the positive small vector (if U needs to be reduced) c1 ):t POO =t POo ·(1+k s )

[0135] Increase the time of the negative small vector (if U needs to be increased)c1 ):t PoO =t Poo ·(1-k s )

[0136] The DC-side capacitor voltage (U) of the three-level energy storage converter c1 and U c2 Imbalance in the voltage distribution can cause midpoint potential shift, affecting the output waveform quality. This application addresses this by using finely divided small sectors and dynamically adjusting the duration of the virtual vector to balance waveform optimization and midpoint potential balance.

[0137] S304. Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switch sequence is obtained by querying; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switch sequence is preset;

[0138] Specifically, if the midpoint potential deviation is greater than or equal to the reference threshold, it indicates that the midpoint potential is unbalanced, and dynamic adjustment of the midpoint potential is required. The three-phase switch sequence corresponding to the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential deviation, and the adjustment factor can be obtained by querying these parameters. The correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential deviation, and the adjustment factor and the three-phase switch sequence is preset. The reference threshold is set according to actual needs, and this embodiment of the invention does not impose limitations. For example, if the design requires triggering midpoint potential adjustment when the midpoint potential deviation exceeds 5%, then the reference threshold is set to 0.05.

[0139] S305. Generate a corresponding pulse width modulation signal according to the three-phase switch sequence.

[0140] Specifically, after obtaining the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the three-phase switch sequence corresponding to the adjustment factor, a corresponding pulse width modulation signal can be generated based on the above three-phase switch sequence. The pulse width modulation signal is used to drive the operation of the power switching transistors on the bridge arm of the three-level energy storage converter.

[0141] The control method for a three-level energy storage converter provided in this embodiment of the invention can acquire control parameters, which include the first and second orthogonal components of the space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor, and a midpoint potential offset. Based on the first and second orthogonal components and a first sector determination rule, the first sector to which the space reference voltage vector belongs is determined, and based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and the corresponding second sector determination rule, the second sector to which the space reference voltage vector belongs is determined. The space vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors. If it is determined that the midpoint potential offset is greater than or equal to a reference threshold, then based on the first sector to which the space reference voltage vector belongs, the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs, and the corresponding second sector determination rule, the second sector to which the space reference voltage vector belongs is determined. The system obtains the three-phase switching sequence corresponding to the spatial reference voltage vector by considering the second sector to which the spatial reference voltage vector belongs and the adjustment factor, and calculates the corresponding vector action time. Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switching sequence is obtained by querying. The correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switching sequence is preset. Based on the three-phase switching sequence, a corresponding pulse width modulation signal is generated. Through refined division of the second sector, the corresponding three-phase switching sequence is obtained, enabling dynamic adjustment of the vector action time while considering waveform optimization and midpoint potential balance, thus improving the operational stability of the three-level energy storage converter.

[0142] Figure 6 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the sixth embodiment of the present invention, as shown below. Figure 6 As shown, based on the above embodiments, the control method for the three-level energy storage converter provided in this embodiment further includes:

[0143] S601. If it is determined that the midpoint potential offset is less than the reference threshold, then the corresponding three vectors and the corresponding vector action time are obtained according to the first sector to which the spatial reference voltage vector belongs.

[0144] Specifically, the midpoint potential offset is compared with a reference threshold. If the midpoint potential offset is less than the reference threshold, then three basic vectors corresponding to the first sector to which the spatial reference voltage vector belongs are selected in the spatial vector plane of the three-level energy storage converter, based on the first sector to which the spatial reference voltage vector belongs. These three vectors are obtained as the corresponding first sector to which the spatial reference voltage vector belongs. The three basic vectors corresponding to the first sector can be selected based on the nearest neighbor three-vector optimization modulation method. The duration of action of the three basic vectors can be calculated based on the volt-second balance principle.

[0145] When the midpoint potential offset is less than the reference threshold, the midpoint potential is in a balanced state. Since the action time of the vectors corresponding to the three basic vectors of each first sector can be pre-calculated when the midpoint potential is in a balanced state, after obtaining the three basic vectors corresponding to the first sector to which the spatial reference voltage vector belongs, the action time of the vectors corresponding to the three basic vectors of the first sector to which the spatial reference voltage vector belongs can be obtained by querying the three basic vectors of the first sector to which the spatial reference voltage vector belongs.

[0146] Table 2 Basic Vectors of Three-Level Energy Storage Converter

[0147]

[0148] Based on the spatial vector plane of the three-level energy storage converter, the three basic vectors corresponding to the first sector to which the spatial reference voltage vector belongs can be selected. This selection can be based on the nearest-neighbor three-vector optimization modulation method. The basic vectors include a large vector, a medium vector, a small vector, and a zero vector. The basic vector of the three-level energy storage converter is 0.5.

[0149] S602. Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the midpoint potential offset, the corresponding three-phase switch sequence is obtained by querying; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the three-phase switch sequence is preset.

[0150] Specifically, the midpoint potential offset is compared with a reference threshold. If the midpoint potential offset is less than the reference threshold, it indicates that the midpoint potential is balanced, and no adjustment is needed. Waveform quality can be optimized using Nearest Tri-Vector Modulation (NTVM). The corresponding three-phase switching sequence can be obtained by querying the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the midpoint potential offset. The correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the three-phase switching sequence is preset.

[0151] Figure 7 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the seventh embodiment of the present invention, as shown below. Figure 7 As shown, based on the above embodiments, further, the determination rules for the first orthogonal component, the second orthogonal component, and the first sector, to determine the first sector to which the spatial reference voltage vector belongs, include:

[0152] S701. Calculate and obtain intermediate variables based on the first orthogonal component and the second orthogonal component;

[0153] Specifically, the determination of the first sector to which the space reference voltage vector belongs can be achieved by calculating the angle of the space reference voltage vector, mapping the angle of the space reference voltage vector to the range of 0° to 360°, and then comparing it with the angle range corresponding to each first sector, thereby determining the first sector to which the space reference voltage vector belongs.

[0154] Calculating the angle of the space reference voltage vector requires the use of the arctangent function. To avoid this calculation and simplify the process, an intermediate variable can be calculated based on the first and second orthogonal components. Then, based on the first and second orthogonal components and the intermediate variable, the first sector to which the space reference voltage vector belongs can be determined.

[0155] For example, the first orthogonal component u refα Second orthogonal component u refβ It can be done through formula The intermediate variable k is calculated.

[0156] S702. Based on the first orthogonal component, the second orthogonal component, the intermediate variable, and the determination conditions corresponding to each first sector included in the first sector determination rule, obtain the first sector to which the space reference voltage vector belongs.

[0157] Specifically, the first sector determination rule includes determination conditions corresponding to each first sector. Based on the first orthogonal component, the second orthogonal component, and the intermediate variable, it is determined which first sector's determination conditions the first orthogonal component, the second orthogonal component, and the intermediate variable meet, thereby determining the first sector to which the space reference voltage vector belongs.

[0158] For example, such as Figure 4 As shown, the space vector plane of the three-level energy storage converter is divided into six first sectors: sector I, sector II, sector III, sector IV, sector V, and sector VI, each covering an angular range of 60°. The determining condition for sector I is: the first orthogonal component u refα >0, the second orthogonal component u refβ ≥0 and k is an intermediate variable. The determination condition for the second sector II is: u refα >0,u refβ >0 and Or, u refα <0,u refβα >0 and The determination condition for the third sector III is: u refα <0,u refβ >0 and The determination condition for the fourth sector IV is: u refα <0,u refβ ≤0 and The condition for determining the fifth sector V is: u refα <0,u refβ <0 and Or, u refα >0,u refβ <0 The condition for determining the sixth sector VI is: u refα >0,u refβ <0 and The first orthogonal direction is the horizontal direction, and the second orthogonal direction is the vertical direction.

[0159] Figure 8 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the sixth embodiment of the present invention, as shown below. Figure 8 As shown, based on the above embodiments, further, determining the second sector to which the space reference voltage vector belongs, according to the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and the corresponding second sector determination rules, includes:

[0160] S801. Transform the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system to the 60-degree coordinate system to obtain the coordinates of the space reference voltage vector in the 60-degree coordinate system.

[0161] Specifically, the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system are the coordinates of the space reference voltage vector in the two-phase stationary coordinate system. By transforming the coordinates of the space reference voltage vector in the two-phase stationary coordinate system to the 60-degree coordinate system, the coordinates of the space reference voltage vector in the 60-degree coordinate system can be obtained.

[0162] S802. Based on the coordinates of the space reference voltage vector in the 60-degree coordinate system and the intermediate parameter formula of the second sector corresponding to the first sector to which the space reference voltage vector belongs, obtain the intermediate parameter of the second sector corresponding to the space reference voltage vector.

[0163] Specifically, based on the coordinates of the spatial reference voltage vector in a 60-degree coordinate system and the intermediate parameter formula of the second sector corresponding to the first sector to which the spatial reference voltage vector belongs, the intermediate parameters of the second sector corresponding to the spatial reference voltage vector can be calculated. The intermediate parameter formula of the second sector corresponding to the first sector is preset. There may be multiple second sectors corresponding to the first sector, and each second sector has its own corresponding intermediate parameter formula; wherein, the intermediate parameter formula of the second sector corresponding to the first sector is preset.

[0164] S803. Determine the second sector to which the space reference voltage vector belongs based on the intermediate parameters of the second sector corresponding to the space reference voltage vector, the phase angle of the space reference voltage vector, and the second sector judgment rule corresponding to the first sector to which the space reference voltage vector belongs.

[0165] Specifically, each first sector has a corresponding second sector determination rule, and there can be multiple second sectors corresponding to the first sector. Each second sector has a corresponding second sector determination condition. By determining the intermediate parameters of the second sector corresponding to the spatial reference voltage vector and the angle of the spatial reference voltage vector, and satisfying the second sector determination condition of which second sector of the first sector to which the spatial reference voltage vector belongs, the second sector of the first sector to which the spatial reference voltage vector belongs can be determined.

[0166] The phase angle of the space reference voltage vector can be determined according to the formula. θ is calculated. ref U represents the phase angle of the space reference voltage vector. refα U represents the coordinates of the space reference voltage vector on the α-axis. refβThis represents the coordinates of the space reference voltage vector on the β axis.

[0167] For example, the space vector plane of a three-level energy storage converter is divided into six first sectors, each covering an angular range of 60°, such as... Figure 4 As shown. Each first sector is divided into eight second sectors. The division method for the second sectors of each first sector is the same. The following explanation uses the first sector I as an example. Figure 5 As shown, sector I is divided into eight second sectors: sector 1, sector 2, sector 3, sector 4, sector 5, sector 6, sector 7, and sector 8. The second sector judgment rules corresponding to each sector I include the second sector judgment conditions corresponding to each sector, for a total of eight second sector judgment conditions.

[0168] Space reference voltage vector V ref Located in the first sector, its coordinates in the α-β coordinate system are (V α V β A 60° coordinate system (gh coordinate system) is established, with the g-axis coinciding with the α-axis and the h-axis forming a 60° angle with the g-axis. The spatial reference voltage vector V is then used. ref In the gh coordinate system, the coordinates are labeled as (V). g V h ).

[0169] The coordinate transformation relationship between the α-β coordinate system and the gh coordinate system is as follows:

[0170]

[0171] The coordinates of the spatial reference voltage vector in the two-phase stationary coordinate system can be transformed to the gh coordinate system by using the coordinate transformation relationship between the α-β coordinate system and the gh coordinate system.

[0172] Through Park transformation, the relationship between the three-phase coordinate system and the rectangular coordinate system can be obtained as follows:

[0173]

[0174] By understanding the coordinate transformation relationship between the α-β coordinate system and the gh coordinate system, and the relationship between the three-phase coordinate system and the rectangular coordinate system, the relationship between the three-phase coordinate system and the gh coordinate system can be obtained as follows:

[0175]

[0176] To simplify the calculation, the length of the small vector is used as the standard to standardize all vectors in the space vector plane of the three-level energy storage converter. The lengths corresponding to the zero vector, small vector, and large vector are then 0, 12, and 12 respectively. The standardized space vector plane of the three-level energy storage converter is as follows: Figure 9 As shown.

[0177] The first sector I of the space vector plane of the standardized three-level energy storage converter, such as Figure 10 As shown. The first sector I is V g +V h -1 = 0, V g +2V h -2 = 0, 2V g +V h -2 = 0 and θ = π / 6 are used to divide the system into eight second sectors. The intermediate parameters of the second sector corresponding to the space reference voltage vector are divided into p1, p2, and p3, where p1 = V g +V h -1, p2 = V g +2V h -2, p3 = 2V g +V h -2. The judgment conditions for the eight second sectors corresponding to the first sector I are shown in Table 3. The judgment condition for the second sector corresponding to the second sector 1 is p1<0 and 0<θ. ref The condition for determining the second sector corresponding to sector 2 is p1<0 and π / 6≤θ. ref <π / 3, the judgment conditions for the other second sectors are detailed in Table 3, and will not be repeated here.

[0178] Table 3. Judgment conditions for the second sector

[0179] <![CDATA[p1]]> <![CDATA[p2]]> <![CDATA[p3]]> <![CDATA[θ ref <!-- 16 -->]]> Second sector 1 <![CDATA[p1<0]]> - - <![CDATA[0<θ ref <π / 6]]> Second sector 2 <![CDATA[p1<0]]> - - <![CDATA[π / 6≤θ ref <π / 3]]> Second sector 3 <![CDATA[p1>0]]> <![CDATA[p2<0]]> <![CDATA[p3<0]]> <![CDATA[θ ref <π / 6]]> Second sector 4 <![CDATA[p1>0]]> <![CDATA[p2<0]]> <![CDATA[p3<0]]> <![CDATA[π / 6≤θ ref <π / 3]]> Second sector 5 - <![CDATA[p2<0]]> <![CDATA[p3>0]]> - Second sector 6 - <![CDATA[p2>0]]> <![CDATA[p3<0]]> - Second sector 7 - <![CDATA[p2>0]]> <![CDATA[p3>0]]> <![CDATA[0<θ ref <π / 6]]> Second sector 8 - <![CDATA[p2>0]]> <![CDATA[p3>0]]> <![CDATA[π / 6≤θ ref <π / 3]]>

[0180] Figure 11 This is a flowchart illustrating the control method for a three-level energy storage converter provided in the eleventh embodiment of the present invention, as shown below. Figure 11 As shown, based on the above embodiments, further, determining the second sector to which the space reference voltage vector belongs, according to the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and the corresponding second sector determination rules, includes:

[0181] S1101. Transform the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system to the 60-degree coordinate system to obtain the coordinates of the space reference voltage vector in the 60-degree coordinate system.

[0182] Specifically, the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system are the coordinates of the space reference voltage vector in the two-phase stationary coordinate system. By transforming the coordinates of the space reference voltage vector in the two-phase stationary coordinate system to the 60-degree coordinate system, the coordinates of the space reference voltage vector in the 60-degree coordinate system can be obtained.

[0183] S1102. If the first sector to which the spatial reference voltage vector belongs is not the target sector, then the coordinates of the spatial reference voltage vector in the 60-degree coordinate system are transformed to the target sector to obtain the transformed coordinates of the spatial reference voltage vector in the target sector.

[0184] Specifically, each first sector is divided into multiple second sectors, and each second sector within each first sector has a corresponding second sector determination rule. This requires significant memory to store these rules, causing inconvenience in practical applications. To reduce the amount of data stored for the second sector determination rules, a rule corresponding to the first sector can be stored, with the first sector serving as the target sector. When the first sector to which the spatial reference voltage vector to be determined belongs is not the target sector, coordinate transformation can be used to convert the coordinates of the spatial reference voltage vector to the target sector. Then, based on the stored second sector determination rule corresponding to the target sector, the second sector to which the spatial reference voltage vector belongs can be determined.

[0185] It is determined whether the first sector to which the spatial reference voltage vector belongs is the target sector. If it is not the target sector, the coordinates of the spatial reference voltage vector in the 60-degree coordinate system are transformed to the target sector to obtain the transformed coordinates of the spatial reference voltage vector in the target sector. The target sector is pre-selected and can be arbitrarily chosen from multiple first sectors.

[0186] S1103. Based on the transformation coordinates of the space reference voltage vector in the target sector and the intermediate parameter formula of the second sector corresponding to the target sector, obtain the intermediate parameter of the second sector corresponding to the space reference voltage vector.

[0187] Specifically, based on the transformed coordinates of the space reference voltage vector in the target sector and the intermediate parameter formula of the second sector corresponding to the target sector, the intermediate parameter of the second sector corresponding to the space reference voltage vector can be calculated.

[0188] S1104. Determine the second sector to which the space reference voltage vector belongs based on the intermediate parameters of the second sector corresponding to the space reference voltage vector, the phase angle of the space reference voltage vector, and the second sector judgment rule corresponding to the target sector.

[0189] Specifically, the second sector determination rule corresponding to the target sector includes multiple second sector determination conditions corresponding to the target sector, with each second sector of the target sector having its own second sector determination condition. Based on the intermediate parameters of the second sector corresponding to the space reference voltage vector and the phase pin of the space reference voltage vector, it is determined which second sector of the target sector the space reference voltage vector satisfies, thereby determining the second sector to which the space reference voltage vector belongs. Since the division method of the second sectors of each first sector is the same, determining the second sector of the target sector to which the space reference voltage vector belongs also determines the second sector of the first sector to which the space reference voltage vector belongs.

[0190] For example, the space vector plane of a three-level energy storage converter is divided into six first sectors, each covering an angular range of 60°, such as... Figure 4 As shown. Taking the first sector I as the target sector, the following uses the space reference voltage vector in the first sector II as an example to illustrate the process of transforming the coordinates of the space reference voltage vector in the gh coordinate system to the target sector.

[0191] like Figure 12 As shown, the space reference voltage vector V ref Located in sector II, its coordinates in the gh coordinate system are (V g V h ), will (V g V h Rotating it 60° clockwise can convert it into a space reference voltage vector V. ref The vector V corresponding to the first sector I ref * Vector V ref * The coordinates are (V g * V h * ).

[0192] Based on geometric mathematics, it can be known Figure 12 middle Each first sector is an equilateral triangle, from which the following relationship can be obtained:

[0193]

[0194] Space reference voltage vector V ref The coordinate transformation relationship from the gh coordinate system to the target sector can be expressed as:

[0195]

[0196] Similarly, the coordinate transformation relationship between the reference vector of other first sectors and the target sector can be derived, and can be uniformly expressed as:

[0197]

[0198] Where M represents the ratio of the rotation angle of the first sector to which the space reference voltage vector belongs to coinciding with the target sector to 60°.

[0199] After rotating the space reference voltage vector to the target sector, the second sector to which the space reference voltage vector belongs is determined based on the second sector determination rules corresponding to the target sector.

[0200] Based on the above embodiments, further, obtaining the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system includes:

[0201] According to the formula The first orthogonal component u is calculated. refα And according to the formula The second orthogonal component u is calculated. refβ , where u a u b and u c This represents the three-phase voltage signal of a three-level energy storage converter.

[0202] Specifically, the three-phase voltage signal u of the three-level energy storage converter can be acquired. a u b and u c Then u a u b and u c Substitute into the formula In this process, the first orthogonal component u can be calculated. eefα . will u b and u c Substitute into the formula In this process, the second orthogonal component u can be calculated. refβ .

[0203] Based on the above embodiments, obtaining the adjustment factor further includes:

[0204] According to formula k s =k p ·sgn(i x )·Δu C Calculate and obtain the adjustment factor k s , where k p This represents the proportional adjustment coefficient, Δu. C sgn(i) represents the voltage difference between the DC-side capacitors. x) represents the sign function of current direction, i x This represents the midpoint current of a three-level energy storage converter.

[0205] Specifically, the adjustment factor k s This algorithm dynamically adjusts the action time ratio of the positive and negative small vectors to achieve precise control of the midpoint potential. Combining real-time current direction and the voltage difference between the DC-side capacitors, it dynamically corrects the action time of the small vectors using proportional adjustment, which is one of the core algorithms for achieving midpoint potential balance. It balances dynamic response speed and stability, making it suitable for the control system of high-precision three-level energy storage converters.

[0206] Formula k s =k p ·sgn(i x )·Δu C Through the current direction (sgn(i) x and voltage difference (Δu) C Real-time feedback automatically adjusts the adjustment factor k. s It adapts to different power factors or load conditions, dynamically adjusting to changes in operating conditions. The current direction sign function ensures that the adjustment direction always matches the current direction, preventing incorrect compensation direction due to current polarity reversal, thus avoiding miscompensation. This is achieved through a proportional adjustment coefficient k. p With proper design, a balance can be achieved between rapid convergence of the midpoint potential and system stability.

[0207] Regulation factor k s The working time allocation ratio between the positive and negative small vectors is determined. By adjusting this ratio, the direction of the midpoint current is controlled, thereby compensating for the voltage difference Δu of the DC-side capacitor. C Proportional adjustment coefficient k p , is the gain parameter in closed-loop control, which determines the adjustment intensity, k p The larger the value, the faster the adjustment speed, k p A value that is too small will result in a slow response. k p The specific value can be determined based on the system's dynamic characteristics or experimental optimization. Current direction sign function sgn(i x The polarity of the current signal synthesized by the three-level energy storage converter (also known as the midpoint current) returns +1 or -1 when i x When >0, sgn(i x )=1, when i x When <0, sgn(i) x = -1. Introducing a current direction sign function ensures that the adjustment direction matches the current direction, avoiding miscompensation. Δu C =u C1 -u C2 Δu reflects the degree of shift in the midpoint potential. CThe larger the absolute value, the stronger the adjustment required. C1 and u C2 It is the voltage of the two capacitors on the DC side of the three-level energy storage converter, which can be directly measured.

[0208] i x According to formula i x =(J a ·i la +J b ·i lb +J c ·i lc The result is obtained by calculating ) / 2, where:

[0209]

[0210] Where, θ ref i represents the phase angle of the space reference voltage vector. la i lb and i lc This represents the three-phase current of a three-level energy storage converter.

[0211] Based on the above embodiments, further, obtaining the midpoint potential offset includes:

[0212] According to the formula Calculate the midpoint potential offset k o , where u C1 u represents the voltage of the first capacitor on the DC side of the three-level energy storage converter. C2 This indicates the voltage of the second capacitor on the DC side of the three-level energy storage converter.

[0213] Specifically, k o This represents the midpoint potential deviation, a normalized difference in capacitor voltage, indicating the degree to which the midpoint potential deviates from the equilibrium state. (Molecular value - u) C1 -u C2 ): Directly reflects the voltage difference between the two capacitors; denominator (u) C1 -u C2 ): Total DC bus voltage (i.e., the sum of the voltages of the two capacitors); the ratio of the voltage difference between the two capacitors to the total DC bus voltage is used as the offset to eliminate the influence of the amplitude variation of the total DC bus voltage, making k o Reflects relative deviation. When u C1 >u C2 When the molecule is positive, the midpoint potential shifts towards the first capacitor; when u C1 C2 When the numerator is negative, the midpoint potential shifts towards the second capacitor. C1 =u C2 k o The value is 0, and the midpoint potential is balanced.​

[0214] Based on the above embodiments, the control method for the three-level energy storage converter provided in this embodiment of the invention further includes:

[0215] If it is determined that the midpoint potential offset is greater than 0.99, then the midpoint potential offset is set to 0.99; if it is determined that the midpoint potential offset is less than -0.99, then the midpoint potential offset is set to -0.99.

[0216] Specifically, the theoretical range of the midpoint potential offset is [-1, 1]. However, when the voltage of one capacitor on the DC side is close to 0 and the other capacitor on the DC side bears the entire bus voltage, the midpoint potential will be in an extremely unbalanced state. This will lead to instability in calculations and may also cause overvoltage damage to devices, which needs to be avoided in practical applications. Therefore, the range of the midpoint potential offset is limited to [-0.99, 0.99].

[0217] The following specific embodiment illustrates the detailed implementation process of the control method for the three-level energy storage converter provided in this invention.

[0218] like Figure 4 As shown, the space vector plane of the three-level energy storage converter is divided into six first sectors: Sector I, Sector II, Sector III, Sector IV, Sector V, and Sector VI, each covering an angular range of 60°. Each first sector is... Figure 4 The dashed lines divide the area into eight second sectors. Pre-defined rules for determining the first sector and the corresponding second sector for each first sector are established. The target sector is first sector I, and the second sector determination conditions corresponding to each second sector of the target sector are shown in Figure 2.

[0219] Assuming the DC bus voltage U of the three-level energy storage converter dc =600V, the voltages of the two capacitors on the DC side are expressed as U. c1 and U c2 Obtain the space reference voltage vector V. ref The first orthogonal component U in the two-phase stationary coordinate system α The voltage is 150V, and the second orthogonal component U β 50V. Switching cycle T s =100 microseconds. The adjustment factor k for the midpoint potential. s =0.1, Δuc=U c1 -U c2 .

[0220] According to the formula Calculate and obtain intermediate variables According to the first orthogonal component Uα The second orthogonal component U β The determination conditions corresponding to the intermediate variable k and the first sector II: u refα >0,u refβ >0 and Determine the space reference voltage vector V ref It belongs to sector II of the first sector. According to the formula... The phase angle of the inter-reference voltage vector was calculated to be 0.32 rad.

[0221] The space reference voltage vector V ref Coordinates in the α-β coordinate system (U α U β Transform to the gh coordinate system, the space reference voltage vector V ref In the gh coordinate system, the coordinates are... According to the formula p1=V g +V h -1, p2 = V g +2V h -2, p3 = 2V g +V h -2, calculated to obtain p3 = 298. Based on the judgment conditions for each second sector in Table 2, the space reference voltage vector V can be determined. ref It belongs to sector 7 of the second sector.

[0222] Assuming the midpoint potential offset is greater than the reference threshold, according to the spatial reference voltage vector V ref The first sector II and the space reference voltage vector V belong to ref The vector can be obtained from the second sector 7, which belongs to the same sector. (See Table 1 for the vector.) V7, V8, k s Replace V with 0.1 正小矢量 V 1(POO) V 负小矢量 V 2(PPO) The space reference voltage vector V is obtained. ref The corresponding three vectors.

[0223] Midpoint potential offset is greater than or equal to the reference threshold and k s When the value is greater than 0, the voltage Uc1 on the DC side capacitor needs to be reduced. The positive small vector V needs to be adjusted. 1(POO) The duration of action of the vectors remains constant, while the durations of action of other vectors remain unchanged. According to the formula... Obtain the positive small vector V 1(POO) Adjusted vector action time.

[0224] According to the space reference voltage vector V refBelonging to the first sector II, space reference voltage vector V ref The space reference voltage vector V can be obtained by referring to Table 4, which lists the second sector 7, midpoint potential offset, and adjustment factor. ref The corresponding three-phase switch sequence is then used to generate the corresponding pulse width modulation signal.

[0225] Table 4 Three-phase switch sequence table

[0226]

[0227] (1) When the midpoint potential is unbalanced (i.e., k M When = 1), if the adjustment factor k s An excessively large amplitude may cause some vector action time to be calculated as negative. Negative time will prevent the modulation algorithm from generating a valid PWM signal, leading to distortion of the energy storage converter's output voltage, overcurrent, or overheating of the switching devices. The vector action time represents the conduction duration of the power device and must physically be a non-negative value. If the calculated time is negative, it cannot be actually executed, causing the control logic to fail.

[0228] When the vector action time is negative: Reference vector V ref The vector synthesis capability of the current small sector is exceeded, and it is impossible to synthesize the selected three vectors.

[0229] Total time conservation: The sum of the action times of all vectors must equal the switching period T. s If the duration of some vectors is negative, the remaining time needs to be reallocated to ensure that the sum of the durations of all vectors is valid.

[0230] Time overflow handling is a key fault-tolerance mechanism for CFSVM when there is a severe imbalance in the midpoint potential. Its core lies in:

[0231] Negative time zeroing: Forces the negative time to be set to 0 to avoid invalid or reverse operations;

[0232] Dynamic reallocation: Maintaining the total switching period T by adjusting the remaining time. s whole;

[0233] Sector differentiation strategy: Select the optimal correction logic based on the location and vector type of the small sector.

[0234] This mechanism ensures the stable operation of the three-level energy storage converter under extreme conditions and is an essential design element of high-performance power electronic systems.

[0235] (2) I.1 Small sector (parameter: k) o =0.4, m=0.5, θ′=15°, k s <0)

[0236] Calculated Zero vector time It is negative.

[0237] Processing steps:

[0238] Forced zeroing: Set

[0239] Adjust to other times: Keep reallocation

[0240] Result: Effective time allocation is Total time T s =1.

[0241] (3) I.3 small sector (virtual mid-vector time detected) )

[0242] Processing steps:

[0243] Forced zeroing: Set

[0244] Divide the remaining time equally: Let (The remaining time is divided equally.)

[0245] result: Total time T s =1.

[0246] (4) I.5 small sector (large vector time detected) )

[0247] Processing steps:

[0248] Forced zeroing: Set

[0249] Adjust to other times: Keep Original value; reallocation

[0250] result: The total time T remains unchanged. s =1.

[0251] (5) I.7 Small sector (large vector detected, time T7*<0)

[0252] Processing steps:

[0253] Forced zeroing: Set

[0254] Adjust other times: Keep the time of the medium vector V8 reallocation

[0255] result: The total time T remains unchanged. s =1.

[0256] (6) Correction logic

[0257]

[0258] Taking I.1 sector as an example

[0259] Original calculation:

[0260] Revised version: Synthesis effect: By forcibly assigning, ensure V ref Synthesize within a feasible area to avoid getting out of control.

[0261] It should be noted that the space vector plane of the three-level energy storage converter has hexagonal symmetry, and each large sector (such as sector I) is further divided into several smaller sectors. Sectors I.1 and I.2 are mirror-symmetric within sector I.

[0262] I.1 Small sector: Coverage angle range 0°≤θ′<30°;

[0263] Ⅰ.2 Small sector: Coverage angle range 30°≤θ′<60°.

[0264] By replacing θ′ with 60°-θ′, the geometric relationship of sector I.2 can be mapped to the symmetrical position of sector I.1.

[0265] If θ′ = 15° in I.1, then the corresponding θ′ = 45° in I.2, which, after substitution, becomes 60° - 45° = 15°, thus reusing the formula in I.1. Other small sectors are handled similarly.

[0266] Figure 13 This is a schematic diagram of the control device for the three-level energy storage converter provided in the thirteenth embodiment of the present invention, as shown below. Figure 13 As shown, the control device for the three-level energy storage converter provided in this embodiment of the invention includes an acquisition module 1301, a determination module 1302, a judgment module 1303, a query module 1304, and a generation module 1305, wherein:

[0267] The acquisition module 1301 is used to acquire control parameters, including the first and second orthogonal components of the space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor, and a midpoint potential offset. The determination module 1302 determines the first sector to which the space reference voltage vector belongs based on the first and second orthogonal components and the first sector determination rule, and determines the second sector to which the space reference voltage vector belongs based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and the corresponding second sector determination rule. The space vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors. The judgment module 1303 is used to determine if the midpoint potential offset is known. If the shift is greater than or equal to the reference threshold, then the corresponding three vectors are obtained and the vector action time is calculated based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor; the query module 1304 is used to query and obtain the corresponding three-phase switch sequence based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential shift, and the adjustment factor; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential shift, and the adjustment factor and the three-phase switch sequence is preset; the generation module 1305 is used to generate the corresponding pulse width modulation signal based on the three-phase switch sequence.

[0268] Based on the above embodiments, the control device for the three-level energy storage converter provided in this embodiment further includes an acquisition module and a switch sequence query module, wherein:

[0269] The acquisition module is used to obtain the corresponding three-phase vector and the corresponding vector action time according to the first sector to which the spatial reference voltage vector belongs if it is determined that the midpoint potential offset is less than the reference threshold; the switch sequence query module is used to query the corresponding three-phase switch sequence according to the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the midpoint potential offset; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the three-phase switch sequence is preset.

[0270] Based on the above embodiments, the determination module 1302 is further specifically used for:

[0271] Based on the first orthogonal component and the second orthogonal component, an intermediate variable is calculated; based on the first orthogonal component, the second orthogonal component, the intermediate variable, and the determination conditions corresponding to each first sector included in the first sector determination rule, the first sector to which the space reference voltage vector belongs is obtained.

[0272] Based on the above embodiments, the determination module 1302 is further specifically used for:

[0273] The first and second orthogonal components of the space reference voltage vector in the two-phase stationary coordinate system are transformed to the 60-degree coordinate system to obtain the coordinates of the space reference voltage vector in the 60-degree coordinate system. Based on the coordinates of the space reference voltage vector in the 60-degree coordinate system and the intermediate parameter formula for the second sector corresponding to the first sector to which the space reference voltage vector belongs, the intermediate parameters of the second sector corresponding to the space reference voltage vector are obtained. Based on the intermediate parameters of the second sector corresponding to the space reference voltage vector, the phase angle of the space reference voltage vector, and the determination rule for the second sector corresponding to the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs is determined.

[0274] Based on the above embodiments, the determination module 1302 is further specifically used for:

[0275] The first and second orthogonal components of the space reference voltage vector in the two-phase stationary coordinate system are transformed to the 60-degree coordinate system to obtain the coordinates of the space reference voltage vector in the 60-degree coordinate system. If the first sector to which the space reference voltage vector belongs is not the target sector, the coordinates of the space reference voltage vector in the 60-degree coordinate system are transformed to the target sector to obtain the transformed coordinates of the space reference voltage vector in the target sector. According to the transformed coordinates of the space reference voltage vector in the target sector and the intermediate parameter formula of the second sector corresponding to the target sector, the intermediate parameters of the second sector corresponding to the space reference voltage vector are obtained. According to the intermediate parameters of the second sector corresponding to the space reference voltage vector, the phase angle of the space reference voltage vector, and the second sector judgment rule corresponding to the target sector, the second sector to which the space reference voltage vector belongs is determined.

[0276] Based on the above embodiments, the acquisition module 1301 is further specifically used for:

[0277] According to the formula The first orthogonal component u is calculated. refα And according to the formula The second orthogonal component u is calculated. refβ , where u a u b and uc This represents the three-phase voltage signal of a three-level energy storage converter.

[0278] Based on the above embodiments, the acquisition module 1101 is further specifically used for:

[0279] According to formula k s =k p ·sgn(i x )·Δu C Calculate and obtain the adjustment factor k s , where k p This represents the proportional adjustment coefficient, Δu. C sgn(i) represents the voltage difference between the DC-side capacitors. x ) represents the sign function of current direction, i x This represents the midpoint current of a three-level energy storage converter.

[0280] Based on the above embodiments, the acquisition module 1301 is further specifically used for:

[0281] According to the formula Calculate the midpoint potential offset k o , where u C1 u represents the voltage of the first capacitor on the DC side of the three-level energy storage converter. C2 This indicates the voltage of the second capacitor on the DC side of the three-level energy storage converter.

[0282] Based on the above embodiments, the acquisition module 1301 is further configured to:

[0283] If it is determined that the midpoint potential offset is greater than 0.99, then the midpoint potential offset is set to 0.99; if it is determined that the midpoint potential offset is less than -0.99, then the midpoint potential offset is set to -0.99.

[0284] The embodiments of the device provided in this invention can be used to execute the processing flow of the above-described method embodiments. Its functions will not be repeated here, but can be referred to the detailed description of the above-described method embodiments.

[0285] Figure 14 This is a schematic diagram of the physical structure of the computer device provided in the fourteenth embodiment of the present invention, as shown below. Figure 14As shown, the computer device may include: a processor 1401, a communication interface 1402, a memory 1403, and a communication bus 1404, wherein the processor 1401, the communication interface 1402, and the memory 1403 communicate with each other through the communication bus 1404. The processor 1401 can call logical instructions in the memory 1403 to execute the methods provided in the above-described method embodiments, such as: acquiring control parameters, the control parameters including a first orthogonal component and a second orthogonal component of the space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor, and a midpoint potential offset; determining the first sector to which the space reference voltage vector belongs based on the first orthogonal component, the second orthogonal component, and a first sector determination rule, and determining the second sector to which the space reference voltage vector belongs based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and a corresponding second sector determination rule; wherein the space vector plane of the three-level energy storage converter is pre-divided into multiple first sectors, and each first sector corresponds to multiple second sectors. If it is determined that the midpoint potential offset is greater than or equal to the reference threshold, then based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor, the three vectors corresponding to the spatial reference voltage vector are obtained, and the corresponding vector action time is calculated; based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switch sequence is obtained by querying; wherein, the correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switch sequence is preset; based on the three-phase switch sequence, the corresponding pulse width modulation signal is generated.

[0286] Furthermore, the logical instructions in the aforementioned memory 1203 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a 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 several 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 described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0287] This embodiment discloses a computer program product, which includes a computer program / instructions stored on a computer-readable storage medium. When the computer program / instructions are executed by a computer, the computer can execute the methods provided in the above-described method embodiments, including, for example,: acquiring control parameters, the control parameters including a first orthogonal component and a second orthogonal component of a space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor, and a midpoint potential offset; determining the first sector to which the space reference voltage vector belongs based on the first orthogonal component, the second orthogonal component, and a first sector determination rule, and determining the second sector to which the space reference voltage vector belongs based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and a corresponding second sector determination rule; wherein, the space vector plane of the three-level energy storage converter is pre-defined. First, the system is divided into multiple first sectors, each corresponding to multiple second sectors. If the midpoint potential offset is determined to be greater than or equal to a reference threshold, then based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor, the three vectors corresponding to the spatial reference voltage vector are obtained, and the corresponding vector action time is calculated. Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switch sequence is obtained. The correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, the adjustment factor, and the three-phase switch sequence is preset. Based on the three-phase switch sequence, a corresponding pulse width modulation signal is generated.

[0288] This embodiment provides a computer-readable storage medium storing a computer program / instruction. When the computer program / instruction is executed by a processor, it causes the computer to perform the methods provided in the above-described method embodiments. For example, the methods include: acquiring control parameters, which include a first orthogonal component and a second orthogonal component of a space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor, and a midpoint potential offset; determining the first sector to which the space reference voltage vector belongs based on the first orthogonal component, the second orthogonal component, and a first sector determination rule; and determining the second sector to which the space reference voltage vector belongs based on the space reference voltage vector, the first sector to which the space reference voltage vector belongs, and a corresponding second sector determination rule; wherein the space vector plane of the three-level energy storage converter is pre-divided into multiple... There are three first sectors, each corresponding to multiple second sectors. If it is determined that the midpoint potential offset is greater than or equal to a reference threshold, then based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, and the adjustment factor, the three vectors corresponding to the spatial reference voltage vector are obtained, and the corresponding vector action time is calculated. Based on the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor, the corresponding three-phase switch sequence is obtained by querying. The correspondence between the first sector to which the spatial reference voltage vector belongs, the second sector to which the spatial reference voltage vector belongs, the midpoint potential offset, and the adjustment factor and the three-phase switch sequence is preset. Based on the three-phase switch sequence, a corresponding pulse width modulation signal is generated.

[0289] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0290] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0291] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0292] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0293] In the description of this specification, the references to terms such as "an embodiment," "a specific embodiment," "some embodiments," "for example," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0294] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method of a three-level energy storage converter, characterized by, The method comprises the following steps: obtaining a control parameter, the control parameter comprising a first orthogonal component and a second orthogonal component of a space reference voltage vector in a two-phase stationary coordinate system, an adjustment factor and a midpoint potential offset degree; determining a first sector to which the space reference voltage vector belongs according to the first orthogonal component and the second orthogonal component and a first sector determination rule, and determining a second sector to which the space reference voltage vector belongs according to the space reference voltage vector, the first sector to which the space reference voltage vector belongs and a corresponding second sector determination rule; wherein the space vector plane of the three-level energy storage converter is divided into a plurality of first sectors in advance, and each first sector corresponds to a plurality of second sectors; if it is judged that the midpoint potential offset degree is greater than or equal to a reference threshold, obtaining a three-vector corresponding to the space reference voltage vector and calculating a corresponding vector action time according to the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs and the adjustment factor; obtaining a corresponding three-phase switch sequence according to the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs, the midpoint potential offset degree and the adjustment factor; wherein the corresponding relationship between the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs, the midpoint potential offset degree, the adjustment factor and the three-phase switch sequence is preset; generating a corresponding pulse width modulation signal according to the three-phase switch sequence.

2. The method of claim 1, wherein, The method further comprises the following steps: if it is judged that the midpoint potential offset degree is less than the reference threshold, obtaining a corresponding three-vector and a corresponding vector action time according to the first sector to which the space reference voltage vector belongs; obtaining a corresponding three-phase switch sequence according to the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs and the midpoint potential offset degree; wherein the corresponding relationship between the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs and the three-phase switch sequence is preset.

3. The method of claim 1, wherein, The first orthogonal component and the second orthogonal component and the first sector determination rule for determining the first sector to which the space reference voltage vector belongs comprise the following steps: obtaining an intermediate variable according to the first orthogonal component and the second orthogonal component; obtaining the first sector to which the space reference voltage vector belongs according to the first orthogonal component, the second orthogonal component, the intermediate variable and the determination conditions of each first sector included in the first sector determination rule.

4. The method of claim 1, wherein, The determination of the second sector to which the space reference voltage vector belongs according to the space reference voltage vector, the first sector to which the space reference voltage vector belongs and the corresponding second sector determination rule comprises the following steps: converting the first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase stationary coordinate system to a 60-degree coordinate system to obtain the coordinates of the space reference voltage vector in the 60-degree coordinate system; According to the coordinate of the space reference voltage vector in the 60-degree coordinate system and a second sector intermediate parameter formula corresponding to the first sector to which the space reference voltage vector belongs, a second sector intermediate parameter corresponding to the space reference voltage vector is obtained; According to the second sector intermediate parameter corresponding to the space reference voltage vector, a phase angle of the space reference voltage vector and a second sector judgment rule corresponding to the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs is determined.

5. The method of claim 1, wherein, The determination of the second sector to which the space reference voltage vector belongs according to the space reference voltage vector, the first sector to which the space reference voltage vector belongs and the corresponding second sector determination rule comprises: The first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase static coordinate system are converted into the 60-degree coordinate system to obtain the coordinate of the space reference voltage vector in the 60-degree coordinate system; If the first sector to which the space reference voltage vector belongs is not a target sector, the coordinate of the space reference voltage vector in the 60-degree coordinate system is converted into the target sector to obtain the converted coordinate of the space reference voltage vector in the target sector; According to the converted coordinate of the space reference voltage vector in the target sector and a second sector intermediate parameter formula corresponding to the target sector, a second sector intermediate parameter corresponding to the space reference voltage vector is obtained; According to the second sector intermediate parameter corresponding to the space reference voltage vector, a phase angle of the space reference voltage vector and a second sector judgment rule corresponding to the target sector, the second sector to which the space reference voltage vector belongs is determined.

6. The method according to any one of claims 1 to 5, characterized in that, The first orthogonal component and the second orthogonal component of the space reference voltage vector in the two-phase static coordinate system are obtained by: According to the formula The first orthogonal component u refα is calculated and obtained according to the formula The second orthogonal component u refβ is calculated and obtained according to the formula a , u b , and u c represent three-phase voltage signals of the three-level energy storage converter.

7. The method according to any one of claims 1 to 5, characterized in that, The adjustment factor is obtained by: According to the formula k s = k p · sgn(i x ) · Δu C The adjustment factor k s is calculated, where k p represents the proportional adjustment coefficient, Δu C represents the voltage difference of the DC side capacitor, sgn(i x ) represents the current direction sign function, and i x represents the midpoint current of the three-level energy storage converter.

8. The method according to any one of claims 1 to 5, characterized in that, The midpoint potential offset degree is obtained by: According to the formula The midpoint potential offset degree k is obtained by calculation o wherein u C1 represents the voltage of the first capacitor of the direct current side of the three-level energy storage converter, u C2 represents the voltage of the second capacitor of the direct current side of the three-level energy storage converter.

9. The method of claim 8, wherein, Further comprising: If it is determined that the midpoint potential offset degree is greater than 0.99, the midpoint potential offset degree is set to 0.99; if it is determined that the midpoint potential offset degree is less than -0.99, the midpoint potential offset degree is set to -0.

99.

10. A control device for a three-level energy storage converter, characterized by Comprising: The acquisition module is configured to acquire a control parameter, the control parameter comprising a first orthogonal component and a second orthogonal component of a space reference voltage vector in a two-phase static coordinate system, an adjustment factor and a midpoint potential offset degree; The determination module is configured to determine the first sector to which the space reference voltage vector belongs according to the first orthogonal component and the second orthogonal component and a first sector determination rule, and determine the second sector to which the space reference voltage vector belongs according to the space reference voltage vector, the first sector to which the space reference voltage vector belongs and a corresponding second sector determination rule; wherein the space vector plane of the three-level energy storage converter is divided into a plurality of first sectors in advance, and each first sector corresponds to a plurality of second sectors; The judging module is configured to, if it is judged that the midpoint potential offset degree is greater than or equal to a reference threshold, obtain a three-vector corresponding to the space reference voltage vector and calculate a vector action time according to a first sector to which the space reference voltage vector belongs, a second sector to which the space reference voltage vector belongs, and an adjustment factor. The querying module is configured to query a corresponding three-phase switch sequence according to the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs, the midpoint potential offset degree, and the adjustment factor, wherein a corresponding relationship between the first sector to which the space reference voltage vector belongs, the second sector to which the space reference voltage vector belongs, the midpoint potential offset degree, the adjustment factor, and the three-phase switch sequence is preset. The generating module is configured to generate a corresponding pulse width modulation signal according to the three-phase switch sequence.

11. A computer device comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program comprises instructions that, when executed by the processor, cause the processor to perform the method of any one of claims 1-10. The processor executes the computer program to implement the method in any one of claims 1 to 9.

12. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer programs / instructions, which are executed by the processor to implement the method in any one of claims 1 to 9.

13. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to implement the method in any one of claims 1 to 9.

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