Current space vector decoupling control method, system and device for dual-active bridge type single-stage AC-DC converter and medium

Abstract

The invention relates to the technical field of power supply control, and discloses a current space vector decoupling control method, system and device for a dual-active bridge type single-stage AC-DC converter and a medium, and the method comprises the steps: enabling the dual-active bridge type single-stage AC-DC converter to be equivalent to two independent dual-active bridge type DC-DC converters in a control period, an alternating current side three-phase current synthesis vector is decomposed to calculate an input average current, a duty ratio is determined in combination with parameters such as an input line voltage and an instantaneous voltage transformation ratio, a switch tube action logic is generated, and a current space vector decoupling modulation strategy is realized. According to the method, the problem of alternating current side transmission current distortion is solved, the actual alternating current side transmission current of the system approaches a given value more accurately, and grid side current distortion is reduced. And meanwhile, the action logic of a switching tube is accurately controlled, the internal circulation of the converter is reduced, the system efficiency is improved, the buck-boost characteristic of the dual-active bridge type single-stage AC-DC converter is exerted, and the actual requirement of an AC grid-connected energy storage system is better met.

Description

Technical Field

[0001] This invention relates to the field of power supply control technology, and in particular to a current space vector decoupling control method, system, device and medium for a dual active bridge type single-stage AC-DC converter. Background Technology

[0002] With the increasing depletion of traditional fossil fuels globally, green and renewable energy is leading a profound transformation of the global energy structure. The low-carbon development model of power systems based on new energy power generation technologies, such as wind and solar power, is being vigorously promoted and developed. Energy storage systems, represented by batteries and supercapacitors, are playing an increasingly crucial role in many areas of new energy. In energy storage systems, isolated AC-DC converters are typically required to achieve grid connection and bidirectional power control. Existing isolated AC-DC converters are mainly classified into power frequency isolated and high-frequency isolated types based on their isolation methods. The dual active bridge single-stage AC-DC converter is a novel topology proposed in recent years. It achieves bidirectional step-up / step-down AC-DC conversion through a single-stage structure and enables soft-switching operation of all power switching devices.

[0003] The dual active bridge three-phase single-stage AC-DC converter topology enables bidirectional AC-DC buck-boost conversion with a wider voltage conversion range, and the three-phase single-stage topology eliminates the need for resonant capacitors, resulting in a higher power transfer capacity. Compared to other isolated AC-DC converter topologies, the dual active bridge single-stage AC-DC converter topology is more suitable for the actual needs of AC grid-connected energy storage systems.

[0004] For dual active bridge three-phase single-stage AC-DC converters, the traditional SVPWM+SPS modulation strategy is commonly used for control. Under SPS modulation, the diagonally opposite switches of the primary and secondary bridge arms are simultaneously turned on and off, and the midpoint voltage of the primary and secondary bridge arms is at full duty cycle. The magnitude and direction of transmitted power are controlled by adjusting the phase shift angle between the midpoint voltages of the primary and secondary bridge arms. The SVPWM+SPS modulation strategy introduces voltage-type SPWM modulation to the DC-side bridge arm based on the SPS modulation strategy. By constraining the duty cycle of the output voltage at the midpoint of the DC-side bridge arm, it ensures that the transformer current is zero at the beginning and end of the switching cycle, thereby decoupling the transformer current between adjacent switching cycles and ensuring precise control of the average current transmitted within the switching cycle.

[0005] However, this modulation strategy based on voltage-type SPWM plus single-phase shift (SPWM+SPS) can only achieve AC-DC boost conversion. The series of approximate analysis methods it employs cause a deviation between the actual AC side transmission current and the given transmission current, resulting in grid-side current distortion. This causes the dual active bridge single-phase single-stage AC-DC converter to lose its excellent buck-boost conversion characteristics, greatly increasing the internal circulating current of the converter and reducing system efficiency. Summary of the Invention

[0006] In view of the aforementioned existing problems, the present invention is proposed.

[0007] Therefore, this invention provides a current space vector decoupling control method, system, device, and medium for a dual active bridge single-stage AC-DC converter, which can solve the problems of AC-side transmission current distortion and inaccurate relationship between the effective current vector action time and the given AC-side transmission current in the existing modulation strategy of the dual active bridge single-stage AC-DC converter, thus failing to achieve accurate control of the AC-side transmission current of the system.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a current space vector decoupling control method for a dual active bridge type single-stage AC-DC converter, comprising: The dual active bridge single-stage AC-DC converter is equivalent to two independent dual active bridge DC-DC converters within the control cycle. Based on the given composite vector of the three-phase currents on the AC side, calculate the average input current of each of the two equivalent dual active bridge DC-DC converters during the control cycle. Based on the current three-phase input phase voltage and DC side voltage, determine the sector where the AC side three-phase current synthesis vector is located, and calculate the input line voltage and instantaneous voltage ratio of the two equivalent dual active bridge DC-DC converters in that sector; Based on the instantaneous voltage transformation ratio and the corresponding average input current, the duty cycles of the two equivalent dual active bridge DC-DC converters are calculated respectively. Based on the preset switching transistor correspondence, and combined with the duty cycle, the action logic of each switching transistor within the control cycle is generated, thereby realizing the current space vector decoupling modulation strategy.

[0009] As a preferred embodiment of the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter described in this invention, the step of calculating the average input current corresponding to each of the two equivalent dual active bridge DC-DC converters within the control cycle based on the given composite vector of the three-phase currents on the AC side includes: The combined vector of the three-phase currents on the AC side is decomposed into two adjacent basic current space vectors; Calculate the equivalent dual active bridge DC-DC converter's average input current corresponding to the two basic current space vectors within the control cycle, such that the sum of the two average input currents equals the total average current corresponding to the composite vector of the three-phase currents on the AC side.

[0010] This preferred solution effectively decomposes the complex composite vector of three-phase AC currents, facilitating accurate calculation of the average input current of the two equivalent dual active bridge DC-DC converters. By decomposing it into adjacent basic current space vectors, the computational complexity is reduced, while the accuracy and efficiency are improved. This allows for a more precise understanding of the input current of each equivalent converter, providing a more reliable basis for subsequently determining parameters such as input line voltage, instantaneous voltage ratio, and duty cycle. Simultaneously, ensuring that the sum of the two average input currents equals the total average current guarantees the integrity and accuracy of current information during the decomposition process. This contributes to a more precise current space vector decoupling modulation strategy, thereby improving the overall performance of the dual active bridge single-stage AC-DC converter.

[0011] As a preferred embodiment of the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter described in this invention, wherein the two equivalent dual active bridge DC-DC converters set within the control cycle have equal switching cycle lengths.

[0012] As a preferred embodiment of the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter described in this invention, the input line voltage is the line voltage between any two phases of the three-phase input phase voltage on the AC side, and its specific value is determined according to the combination of switching states activated in the current sector.

[0013] As a preferred embodiment of the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter described in this invention, the instantaneous voltage transformation ratio is the ratio between the primary input line voltage of the equivalent dual active bridge DC-DC converter and the DC side voltage referred to the primary side.

[0014] As a preferred embodiment of the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter described in this invention, the duty cycle is calculated based on the positive / negative relationship between the instantaneous voltage transformation ratio and the average input current, and is handled in four separate cases: When the instantaneous voltage transformation ratio is greater than 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in one switching cycle is greater than or equal to zero and less than or equal to the maximum allowable value of the average current of the secondary side in that switching cycle, the first set of duty cycle calculation formulas shall be used. When the instantaneous voltage transformation ratio is greater than 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in one switching cycle is greater than or equal to a certain critical current value, and at the same time less than or equal to the maximum allowable value of the average current of the secondary side in that switching cycle, the second set of duty cycle calculation formulas shall be used. When the instantaneous voltage transformation ratio is less than or equal to 1, and the average current on the secondary side of the equivalent dual active bridge DC-DC converter is greater than or equal to zero and less than or equal to another specific critical current value in one switching cycle, the third set of duty cycle calculation formulas shall be used. When the instantaneous voltage transformation ratio is less than or equal to 1, and the average current on the secondary side of the equivalent dual active bridge DC-DC converter in one switching cycle is greater than the specific critical current value, while being less than or equal to the maximum allowable value of the average current on the secondary side, the fourth set of duty cycle calculation formulas shall be used.

[0015] As a preferred embodiment of the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter described in this invention, the switching transistor operation logic is generated in the following manner: Based on the equivalent dual active bridge DC-DC converter structure corresponding to the current sector, establish the correspondence between the bidirectional switches in the AC side matrix converter and the power switching transistors in the equivalent dual active bridge DC-DC converter. The calculated duty cycle is mapped to the turn-on and turn-off timing of the corresponding switching transistors in their respective switching cycles, thereby generating a complete switching drive signal.

[0016] Secondly, the present invention provides a current space vector decoupling control system for a dual active bridge single-stage AC-DC converter, comprising: Equivalent module, used to convert a dual active bridge single-stage AC-DC converter into two independent dual active bridge DC-DC converters within the control cycle; The first calculation module is used to calculate the average input current of each of the two equivalent dual active bridge DC-DC converters within the control cycle based on the given composite vector of the three-phase current on the AC side. The second calculation module is used to determine the sector where the AC side three-phase current synthesis vector is located based on the current three-phase input phase voltage and DC side voltage, and to calculate the input line voltage and instantaneous voltage ratio of the two equivalent dual active bridge DC-DC converters in the sector. The third calculation module is used to calculate the duty cycle of the two equivalent dual active bridge DC-DC converters based on the instantaneous voltage transformation ratio and the corresponding average input current. The decoupling modulation module is used to generate the action logic of each switch in the control cycle according to the preset switching transistor correspondence and the duty cycle, thereby realizing the current space vector decoupling modulation strategy.

[0017] Thirdly, the present invention provides an electronic device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the method described above.

[0018] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described above.

[0019] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention proposes a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter. By treating the dual active bridge single-stage AC-DC converter as two independent dual active bridge DC-DC converters within the control cycle, the method decomposes the composite vector of the three-phase current on the AC side to calculate the average input current. Combined with parameters such as input line voltage and instantaneous voltage transformation ratio, the duty cycle is determined, and the switching logic is generated, thus realizing the current space vector decoupling modulation strategy. This method avoids the limitation of traditional SVPWM+SPS modulation strategies, which can only achieve AC-DC boost conversion. It effectively solves the problem of AC side transmission current distortion, enabling the actual AC side transmission current to more accurately approach the given transmission current and reducing grid-side current distortion. Simultaneously, by precisely controlling the switching logic, this method reduces the circulating current within the converter, improves system efficiency, and fully utilizes the excellent buck-boost conversion characteristics of the dual active bridge single-stage AC-DC converter, better meeting the actual needs of AC grid-connected energy storage systems. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0021] Figure 1 The present invention provides a flowchart of a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter.

[0022] Figure 2 The flowchart illustrates the implementation of a DPD-SVPSM modulation strategy for a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter, as provided in one embodiment of the present invention.

[0023] Figure 3 This invention provides a simplified circuit diagram of a three-phase single-stage topology for a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter, under various switching state combinations, and its equivalent relationship with a DAB converter.

[0024] Figure 4 This invention provides an equivalent DAB converter topology for a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter, as provided in one embodiment of the present invention.

[0025] Figure 5 The diagram shows the overall structure of an experimental system for a three-phase single-stage AC-DC converter, which provides a current space vector decoupling control method for a dual active bridge type single-stage AC-DC converter according to an embodiment of the present invention.

[0026] Figure 6 The grid-side current THD curve is shown in an embodiment of the present invention for a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter.

[0027] Figure 7 This is an internal structure diagram of an electronic device for a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter, provided as an embodiment of the present invention. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0029] Example 1, referring to Figures 1-6 This is the first embodiment of the present invention, which provides a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter, comprising: In existing related technologies, there are some problems. For example, the traditional SVPWM+SPS modulation strategy can only achieve AC-DC boost conversion, and the approximate analysis method used causes the actual AC side transmission current of the system to deviate from the given transmission current, which causes grid-side current distortion, increases the internal circulating current of the converter, and reduces system efficiency.

[0030] This application provides a method that can effectively solve the problems mentioned above. The following will describe in detail how to implement the current space vector decoupling control method for a dual active bridge single-stage AC-DC converter with multiple embodiments. Figure 1 A flowchart of a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter is shown, including: S101 converts the dual active bridge single-stage AC-DC converter into two independent dual active bridge DC-DC converters within the control cycle. It should be noted that, in order to implement the current space vector decoupling control method for the dual active bridge single-stage AC-DC converter, the complex dual active bridge single-stage AC-DC converter is equivalent to two relatively simple independent dual active bridge DC-DC converters within the control cycle. This equivalent treatment is based on the working principle and characteristics of the dual active bridge single-stage AC-DC converter and is derived through reasonable circuit analysis and mathematical derivation. This equivalent approach can transform the originally complex AC-DC conversion problem into two relatively independent DC-DC conversion problems, thereby simplifying the subsequent calculation and control process.

[0031] In one optional implementation, the equivalent relationship between the three-phase single-stage topology and the DAB DC-DC converter is analyzed, and independent switching cycles are set for the two equivalent DAB converters within the control cycle. Based on the given AC side three-phase current synthesis vector, the average input current of the equivalent DAB_N within the switching cycle is calculated, and the given average input current corresponding to the two switching cycles within the control cycle CT is obtained. Based on the three-phase input phase voltage and DC side voltage, the input line voltage and instantaneous voltage transformation ratio corresponding to the two switching cycles within sector N are calculated. Based on the instantaneous voltage transformation ratio and the desired average input current, the duty cycle is calculated. Based on the defined switching transistor correspondence, the switching transistor operation logic in the switching cycle is obtained, and finally, the DPD-SVPSM modulation strategy is implemented.

[0032] In one alternative implementation, such as Figure 3 As shown, the dual active bridge three-phase single-stage AC-DC converter topology consists of a grid-side LC filter, an AC-side matrix converter, a high-frequency isolation transformer, a DC-side H-bridge, and DC energy storage elements. The AC-side matrix converter uses a bidirectional switch S... bi The high-frequency transformer can be attributed to the leakage inductance L on the primary side. leak It is equivalent to a combined model of an ideal transformer with a turns ratio of n:1. PV stands for photovoltaic array, which consists of multiple photovoltaic cells connected in series and parallel; C in The bus capacitor is used to connect the input and the inverter full bridge. It utilizes the energy storage function of the bus capacitor to buffer the power balance of the system.

[0033] In one alternative implementation, the three-phase single-stage topology employs an LC filter on the network side, exhibiting voltage source characteristics for the AC-side matrix converter; the DC side is a DC voltage source, exhibiting voltage source characteristics for the DC-side H-bridge. In contrast, the current-source PWM rectifier exhibits voltage source characteristics on the AC side and current source characteristics on the DC side. Therefore, the dual voltage source characteristics of the three-phase single-stage topology fundamentally differ from the principle of a current-source PWM rectifier, while sharing many similarities with a DAB converter.

[0034] It should be noted that, due to the use of an LC filter on the AC side, to avoid short-circuiting the filter capacitor and to provide a freewheeling path for the transformer current, only one bidirectional switch is turned on in each of the upper and lower arms of the AC side matrix converter at any given time. Based on this, all switching states of the AC side matrix converter can be obtained, as shown in Table 1. Here, 1 represents S... bi On, 0 represents S bi Turn off.

[0035] Table 1 All possible switching states of the AC-side matrix converter

[0036] In one alternative implementation, such as Figure 4 The diagram shows the equivalent DAB converter topology for a three-phase single-stage topology. In a three-phase single-stage topology, the AC side is always relative to the transformer primary input line voltage or zero voltage. For specific effective input line voltages, the circuit of a three-phase single-stage topology can be simplified when operating under specific switching state combinations. For example, when… Furthermore, when the converter operates in the four state combinations shown in Table 1 (1, 4, 7, and 8), the bidirectional switch S... b5 and S b6 It is always in the off state. At the switching cycle level, the AC input voltage can be considered as a positive polarity DC voltage; therefore, the three-phase single-stage topology can be equivalent to... Figure 4 The DAB converter shown is illustrated. Similarly, equivalent DAB converters corresponding to the switching state combinations in the remaining sectors can be obtained, with their primary-side input voltage, current, and switch transistor designations being the same as those shown. Figure 4 The correspondence of the equivalent DAB converters shown is shown in Table 2.

[0037] Table 2. Equivalent relationship between simplified circuit and DAB converter for various switching state combinations of three-phase single-stage topology.

[0038] In this embodiment of the invention, the topology of the dual active bridge single-phase quasi-single-stage AC-DC converter consists of a front-stage synchronous rectifier and a rear-stage DAB converter. In the rear-stage DAB converter, HB1 and HB2 represent two H-bridge converters, respectively. The sample parameters are then set... and These represent the DC-side input voltages of HB1 and HB2, respectively. The leakage inductance of the high-frequency transformer. and These represent the AC output voltages of HB1 and HB2, respectively. Indicates the turns ratio of a high-frequency transformer. This represents the primary current of the high-frequency transformer, and the desired average input current is... The average input current during the control cycle is , Switching cycle The outward phase angle.

[0039] S102, based on the given composite vector of the three-phase AC currents, calculate the average input current of each of the two equivalent dual-active-bridge DC-DC converters within the control cycle, where: It should be noted that after the dual active bridge single-stage AC-DC converter is equivalent to two independent dual active bridge DC-DC converters, the average input current of each of the two equivalent converters during the control cycle can be calculated based on the given composite vector of the three-phase currents on the AC side.

[0040] In this embodiment of the invention, based on a given composite vector of the three-phase AC currents, the average input current of each of the two equivalent dual-active-bridge DC-DC converters within the control cycle is calculated, including: The composite vector of the three-phase currents on the AC side is decomposed into two adjacent basic current space vectors; Calculate the equivalent average input current of the dual active bridge DC-DC converter corresponding to the two basic current space vectors during the control cycle, so that the sum of the two average input currents is equal to the total average current corresponding to the composite vector of the three-phase currents on the AC side.

[0041] In this embodiment of the invention, the two equivalent dual active bridge DC-DC converters configured within the control cycle have equal switching cycle lengths.

[0042] It should be noted that the AC side three-phase current composite vector refers to the combination of the three-phase currents into a spatial vector according to certain rules in a three-phase AC system. This vector can represent information such as the amplitude, phase, and frequency of the three-phase currents. In an alternative implementation, the three-phase current is converted into a vector form in a two-phase stationary or rotating coordinate system using the Clarke or Park transformation to describe the dynamic characteristics of the current.

[0043] It should be noted that the basic current space vector refers to two adjacent vectors with definite direction and amplitude obtained by decomposing the three-phase current composite vector. They are the basic units that constitute any three-phase current state. In an optional implementation, a hexagonal space vector modulation method is used to decompose the three-phase current composite vector into two adjacent vectors among the six basic vectors, and calculate the corresponding average input current based on their duration.

[0044] It should be noted that the average input current refers to the integral average value of the input current of the equivalent dual active bridge DC-DC converter within one switching cycle during the control cycle. It reflects the current characteristics of the converter under steady-state operating conditions. In an alternative implementation, the average input current of each converter can be obtained by measuring the input current waveform of the converter and calculating its average value, and it is ensured that the sum of the average input currents of the two converters is equal to the total average current.

[0045] It should be noted that the total average current refers to the average value of the total input current determined by the composite vector of the three-phase currents on the AC side during the control cycle. It is the algebraic sum of the average input currents of two equivalent dual active bridge DC-DC converters. In one alternative implementation, the specific value of the total average current can be determined by calculating the effective value of the three-phase current and its corresponding time weight, and this value can be used as the basis for allocating the input current of the two converters.

[0046] It should be noted that the switching cycle length refers to the time required for the power switching device in the equivalent dual active bridge DC-DC converter to complete one complete switching action, which determines the converter's operating frequency and dynamic response characteristics. In an alternative implementation, the switching cycle lengths of the two converters are set to be equal, for example, 100 microseconds each, to ensure that they work in coordination on the same time base.

[0047] S103, based on the current three-phase input phase voltage and DC side voltage, determine the sector where the AC side three-phase current synthesis vector is located, and calculate the input line voltage and instantaneous voltage ratio of the two equivalent dual active bridge DC-DC converters in that sector; In this embodiment of the invention, the input line voltage is the line voltage between any two phases of the three-phase input phase voltage on the AC side, and its specific value is determined according to the combination of switch states activated in the current sector.

[0048] It should be noted that the input line voltage refers to the voltage difference between any two phases of the three-phase input phase voltage on the AC side. Its magnitude and direction are determined by the combination of switch states activated in the current sector, and will be dynamically adjusted as the sector changes. In an optional implementation, when the three-phase input phase voltage is U a U b U c When, if the current active sector's switch state combination corresponds to U ab Then the input line voltage is U ab =U a -U b Similarly, other sectors may correspond to U bc or U ca .

[0049] It should be noted that the instantaneous voltage transformation ratio refers to the ratio between the input line voltage and the DC side voltage in two equivalent dual active bridge DC-DC converters within the current sector. The calculation result is used to guide the generation of subsequent control strategies. In an optional implementation, if the input line voltage of the current sector is U ab The DC side voltage is U dc Then the instantaneous voltage transformation ratio can be expressed as k=U ab / U dc This ratio will directly affect the modulation waveform and power transmission characteristics of the converter.

[0050] S104, based on the instantaneous voltage transformation ratio and the corresponding average input current, calculate the duty cycle of the two equivalent dual active bridge DC-DC converters respectively; In this embodiment of the invention, the instantaneous voltage transformation ratio is the ratio between the primary input line voltage of the equivalent dual active bridge DC-DC converter and the DC side voltage referred to the primary side.

[0051] It should be noted that the instantaneous voltage transformation ratio refers to the ratio between the primary input line voltage of an equivalent dual active bridge DC-DC converter and the DC-side voltage referred to the primary side. This parameter reflects the relative relationship between the input voltage and the DC-side voltage at a certain instant and is an important basis for calculating the duty cycle. In one optional implementation, when the primary input line voltage is 400V and the DC-side voltage referred to the primary side is 800V, the instantaneous voltage transformation ratio is 0.5; in another implementation, if the primary input line voltage is 600V and the DC-side voltage referred to the primary side is 1200V, the instantaneous voltage transformation ratio is also 0.5; for example, when the primary input line voltage is 300V and the DC-side voltage referred to the primary side is 900V, the instantaneous voltage transformation ratio is 0.33.

[0052] It should be noted that the average input current refers to the averaged value of the current flowing into the equivalent dual active bridge DC-DC converter within a certain time range. This value is used to characterize the overall level of the input current and is a key variable in the duty cycle calculation. In one alternative implementation, if the input current measured within 1 second is 10A, 12A, 8A, and 10A respectively, then the average input current is 10A; in another implementation, if the input current is 5A, 6A, and 4A respectively within 0.5 seconds, then the average input current is 5A; and for example, if the input current is 2A, 2.5A, and 1.5A respectively within 10 milliseconds, then the average input current is 2A.

[0053] It should be noted that the duty cycle refers to the ratio of the on-time of the switching device to the entire switching cycle in an equivalent dual active bridge DC-DC converter. It directly determines the working state and energy transfer efficiency of the converter and is a core parameter in the control strategy. In one alternative implementation, if the switching period is 10 microseconds and the switching device conduction time is 4 microseconds, the duty cycle is 0.4; in another implementation, if the switching period is 20 microseconds and the switching device conduction time is 10 microseconds, the duty cycle is 0.5; and for example, when the switching period is 50 microseconds and the switching device conduction time is 15 microseconds, the duty cycle is 0.3.

[0054] S105 generates the action logic of each switch within the control cycle based on the preset switching transistor correspondence and the duty cycle, thereby realizing the current space vector decoupling modulation strategy.

[0055] In this embodiment of the invention, the duty cycle is calculated based on the positive or negative relationship between the instantaneous voltage transformation ratio and the average input current, and is handled in four separate cases: When the instantaneous voltage transformation ratio is greater than 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in one switching cycle is greater than or equal to zero and less than or equal to the maximum allowable value of the average current of the secondary side in that switching cycle, the first set of duty cycle calculation formulas shall be used. When the instantaneous voltage transformation ratio is greater than 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in one switching cycle is greater than or equal to a certain critical current value, and at the same time less than or equal to the maximum allowable value of the average current of the secondary side in that switching cycle, the second set of duty cycle calculation formulas shall be used. When the instantaneous voltage transformation ratio is less than or equal to 1, and the average current on the secondary side of the equivalent dual active bridge DC-DC converter is greater than or equal to zero and less than or equal to another specific critical current value in one switching cycle, the third set of duty cycle calculation formulas shall be used. When the instantaneous voltage transformation ratio is less than or equal to 1, and the average current on the secondary side of the equivalent dual active bridge DC-DC converter in one switching cycle is greater than the specific critical current value, while being less than or equal to the maximum allowable value of the average current on the secondary side, the fourth set of duty cycle calculation formulas shall be used.

[0056] In this embodiment of the invention, the operating logic of the switching transistor is generated in the following manner: Based on the equivalent dual active bridge DC-DC converter structure corresponding to the current sector, establish the correspondence between the bidirectional switches in the AC side matrix converter and the power switching transistors in the equivalent dual active bridge DC-DC converter. The calculated duty cycle is mapped to the turn-on and turn-off timing of the corresponding switching transistors in their respective switching cycles, thereby generating a complete switching drive signal.

[0057] It should be noted that the preset switching transistor correspondence refers to establishing a mapping relationship between the bidirectional switches and power switching transistors in the AC side matrix converter in the equivalent dual active bridge DC-DC converter. This relationship provides the basis for subsequent duty cycle allocation and action logic generation. In one alternative implementation, by analyzing the circuit topology corresponding to the current sector, the functional positioning of each switch and its role in the modulation strategy can be clarified. For example, when in a specific sector, bidirectional switches S1 and S2 may correspond to the operating states of power switches Q1 and Q2, respectively, and the generation rules of subsequent control signals can be defined based on this.

[0058] It should be noted that the operation logic of each switch in the control cycle is generated by combining the duty cycle. This means that the duty cycle value calculated under four different conditions is converted into a specific time sequence signal to guide the conduction and turn-off behavior of each switch in each cycle. In one alternative implementation, regardless of which duty cycle calculation formula is used, the final calculated result will be verified to ensure that the converter can maintain input and output power balance during actual operation. For example, under certain set conditions, if the expected average current to be transmitted is 10A, the duty cycle can be adjusted to ensure that the actual transmitted current is close to or equal to the target value.

[0059] Specifically, Figure 2 This is a schematic diagram of the process of the present invention. The method designed based on the above embodiments can be used to design the following method for current space vector decoupling control of a dual active bridge single-stage AC-DC converter, including the following steps: Step 1: Calculate the average transmission phase current of the given three phases on the AC side. When power is transmitted from the AC side to the DC side with unity power factor, the formula for calculating the average transmission phase current of the given three phases on the AC side is:

[0060] in, Given the combined vector of the three-phase currents on the AC side, Given the average current space vector.

[0061] Step 2: Calculate the average current corresponding to the given input during the two switching cycles within the control cycle of the CT. and The calculation formula is as follows:

[0062] Step 3: Based on the given AC three-phase current synthesis vector We obtain the sector N where it is located. We calculate the average input current of the equivalent DAB converter during the switching cycle as follows:

[0063] In this case, DAB_N and DAB_N+1 are set to two equal switching cycles within the control cycle CT, i.e. .

[0064] Step 4: Based on the three-phase input phase voltage and DC side voltage, calculate the input line voltage corresponding to two switching cycles within sector N. and The formula for calculating the primary input line voltage of the equivalent DAB converter is:

[0065] Step 5: Calculate the instantaneous voltage transformation ratio corresponding to the two switching cycles within sector N. and Voltage ratio The calculation formula is:

[0066] Step 6: Based on the above instantaneous voltage transformation ratio ( and expected average input current *( *), the calculation formula for duty cycle D is divided into four cases and handled separately.

[0067] when and When using the first set of duty cycle calculation formulas;

[0068] when and When using the second set of duty cycle calculation formulas;

[0069] when and At that time, the third set of duty cycle calculation formulas shall be used;

[0070] when and At that time, the fourth set of duty cycle calculation formulas shall be used;

[0071] in,

[0072] in, The duty cycle of the original H-bridge. The duty cycle component is related to the phase shift angle. DC side voltage In one switching cycle Average DC-side current within the circuit. The expected average input current of the first equivalent DAB converter.

[0073] Step 7: By defining the correspondence between the switching transistors and the equivalent relationship between the simplified circuit and the DAB converter under various switching state combinations of the three-phase single-stage topology, the switching period is obtained. The switching logic ultimately implements the DPD-SVPSM modulation strategy.

[0074] In view of the problem that the traditional SVPWM+SPS modulation strategy cannot achieve precise control of the AC side transmission current of the converter, this invention proposes a current DPD-SVPSM modulation strategy based on a dual active bridge single-stage AC-DC converter.

[0075] In traditional SPWM+SPS modulation strategies, the average line current on the AC side of the converter during each switching cycle is determined by the duty cycles of the two current space vectors and the outward phase shift angle between the two high-frequency output voltages of the converter. This makes it difficult to accurately control the AC side transmission current of the system. Furthermore, the series of approximate analysis methods employed lead to deviations between the actual AC side transmission current and the given transmission current, resulting in grid-side current distortion. Therefore, to ensure the sinusoidal nature of the grid-side current, it is necessary to decouple the two adjacent current space vectors and avoid using approximate methods to analyze the AC side transmission current of the converter.

[0076] The DPD-SVPSM modulation strategy of this invention analyzes the equivalent relationship between a three-phase single-stage topology and a DAB DC-DC converter, and sets independent switching cycles for the two equivalent DAB converters within the control cycle. This leads to a modulation strategy that can achieve decoupling control of the current space vector, thereby ensuring accurate control of the AC transmission current of the system and solving the grid-side current distortion problem.

[0077] The three-phase single-stage topology can be equivalent to a series of DAB DC-DC converters. For a three-phase system, the three-phase current synthesis vector can be synthesized from two space current vectors. Since the average input current of each equivalent DAB converter corresponds to an average current space vector, this average current space vector can be used to synthesize the AC-side three-phase current synthesis vector, thereby achieving sinusoidal waveform control of the grid-side current. The DPD-SVPSM modulation strategy enables decoupling control of the two equivalent DAB converters, thus ensuring the decoupling of their corresponding two average current space vectors, and consequently guaranteeing precise control of the AC-side transmission current of the system.

[0078] In summary, this invention proposes a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter. By treating the dual active bridge single-stage AC-DC converter as two independent dual active bridge DC-DC converters within the control cycle, the method decomposes the composite vector of the three-phase AC currents to calculate the average input current. Combining parameters such as input line voltage and instantaneous voltage transformation ratio, the duty cycle is determined, and the switching logic is generated, thus realizing a current space vector decoupling modulation strategy. This method avoids the limitation of traditional SVPWM+SPS modulation strategies, which can only achieve AC-DC boost conversion. It effectively solves the problem of AC-side transmission current distortion, enabling the actual AC-side transmission current to more accurately approach the given transmission current and reducing grid-side current distortion. Simultaneously, by precisely controlling the switching logic, this method reduces the circulating current within the converter, improves system efficiency, and fully utilizes the excellent buck-boost conversion characteristics of the dual active bridge single-stage AC-DC converter, better meeting the actual needs of AC grid-connected energy storage systems.

[0079] Example 2, refer to Figures 5-6 This is the second embodiment of the present invention, which provides a current space vector decoupling control system for a dual active bridge single-stage AC-DC converter. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0080] like Figure 5 The diagram shows the overall structure of a three-phase single-stage converter experimental system. It comprises a programmable AC source, a programmable DC source, power resistors, a grid-side LC filter, a matrix converter, a high-frequency transformer, a full-bridge converter, voltage and current signal acquisition circuits, control circuits, and drive circuits. Power resistors are connected in parallel to the voltage output terminals of both the programmable DC and AC sources. The filter circuit includes an output inductor and an output capacitor. The full-bridge inverter circuit includes multiple fully controlled power switches and is connected to the AC grid via a high-frequency transformer. The high-frequency transformer is also connected to the AC grid via a filter circuit.

[0081] The control period CT of the proposed modulation strategy is set to 50μs. A programmable AC source outputs a three-phase sinusoidal voltage with an amplitude of 311V and a frequency of 50Hz to simulate the three-phase power grid voltage. A programmable AC source also outputs a sinusoidal voltage with an amplitude of 311V and a frequency of 50Hz to simulate the single-phase power grid voltage. Simultaneously, a programmable DC source is used to simulate DC-side energy storage elements. Furthermore, power resistors are connected in parallel at the voltage output terminals of both the programmable DC and AC sources to simulate bidirectional power transmission.

[0082] like Figure 6 As shown, the THD (Total Displacement of Current) curves of the grid-side current under various transmission current levels for the DPD-SVPSM modulation strategy and the SVPWM+SPS modulation strategy are presented. The THD value of the grid-side current for the SVPWM+SPS modulation strategy is higher than 12% at all current transmission levels, proving that the SVPWM+SPS modulation strategy cannot achieve accurate control of the grid-side current and leads to grid-side current distortion. The THD curve of the grid-side current for the DPD-SVPSM modulation strategy, as shown, is lower than 5% at all current transmission levels, effectively suppressing grid-side current distortion.

[0083] Example 3: This example also provides a current space vector decoupling control system for a dual active bridge single-stage AC-DC converter, comprising: Equivalent module, used to convert a dual active bridge single-stage AC-DC converter into two independent dual active bridge DC-DC converters within the control cycle; The first calculation module is used to calculate the average input current of each of the two equivalent dual active bridge DC-DC converters within the control cycle based on the given composite vector of the three-phase current on the AC side. The second calculation module is used to determine the sector where the AC side three-phase current synthesis vector is located based on the current three-phase input phase voltage and DC side voltage, and to calculate the input line voltage and instantaneous voltage ratio of the two equivalent dual active bridge DC-DC converters in that sector; The third calculation module is used to calculate the duty cycle of the two equivalent dual active bridge DC-DC converters based on the instantaneous voltage transformation ratio and the corresponding average input current. The decoupling modulation module is used to generate the action logic of each switch in the control cycle according to the preset switching transistor correspondence and the duty cycle, thereby realizing the current space vector decoupling modulation strategy.

[0084] The above-mentioned unit modules can be embedded in the processor of the electronic device in hardware form or independent of it, or they can be stored in the memory of the electronic device in software form, so that the processor can call and execute the corresponding operations of the above modules.

[0085] This embodiment also provides an electronic device, which can be a terminal, and its internal structure diagram can be as follows: Figure 7 As shown, the electronic device includes a processor, memory, communication interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a current space vector decoupling control method for a dual active bridge single-stage AC-DC converter. The display screen can be an LCD screen or an e-ink display screen. The input device can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the device's casing, or an external keyboard, touchpad, or mouse.

[0086] This embodiment also provides a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, it performs the following steps: The dual active bridge single-stage AC-DC converter is equivalent to two independent dual active bridge DC-DC converters within the control cycle. Based on the given composite vector of the three-phase currents on the AC side, calculate the average input current of each of the two equivalent dual active bridge DC-DC converters during the control cycle. Based on the current three-phase input phase voltage and DC side voltage, determine the sector where the AC side three-phase current synthesis vector is located, and calculate the input line voltage and instantaneous voltage ratio of the two equivalent dual active bridge DC-DC converters in that sector; Based on the instantaneous voltage transformation ratio and the corresponding average input current, the duty cycle of the two equivalent dual active bridge DC-DC converters is calculated respectively. Based on the preset switching transistor correspondence, and combined with the duty cycle, the action logic of each switching transistor within the control cycle is generated, thereby realizing the current space vector decoupling modulation strategy.

[0087] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0088] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented 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. The solutions in the embodiments of this application can be implemented using various computer languages.

[0089] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. 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... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0090] 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.

[0091] 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.

[0092] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0093] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A current space vector decoupled control method for a dual active bridge single-stage AC-DC converter, characterized in that, The application relates to a current space vector decoupling modulation strategy for a dual active bridge (DAB) single-stage AC-DC converter. The application comprises the following steps: The dual active bridge single-stage AC-DC converter is equivalent to two independent dual active bridge DC-DC converters in a control period; According to a given three-phase current synthesis vector of an AC side, the input average currents of the two equivalent dual active bridge DC-DC converters in the control period are calculated; According to the current three-phase input phase voltage and the DC side voltage, the sector in which the three-phase current synthesis vector of the AC side is located is determined, and the input line voltage and the instantaneous voltage transformation ratio of the two equivalent dual active bridge DC-DC converters in the sector are calculated; Based on the instantaneous voltage transformation ratio and the corresponding input average current, the duty cycles of the two equivalent dual active bridge DC-DC converters are calculated respectively; 2. The current space vector decoupled control method for a dual active bridge single-stage AC-DC converter of claim 1, wherein, According to a preset switch corresponding relationship, the action logic of each switch in the control period is generated in combination with the duty cycles, so that the current space vector decoupling modulation strategy is realized. The calculation of the input average currents of the two equivalent dual active bridge DC-DC converters in the control period according to the given three-phase current synthesis vector of the AC side comprises the following steps: The three-phase current synthesis vector of the AC side is decomposed into two adjacent basic current space vectors; 3. The current space vector decoupled control method for a dual active bridge single-stage AC-DC converter of claim 2, wherein, The input average currents of the two equivalent dual active bridge DC-DC converters corresponding to the two basic current space vectors in the control period are calculated respectively, so that the sum of the two input average currents is equal to the total average current corresponding to the three-phase current synthesis vector of the AC side.

4. The current space vector decoupled control method for a dual active bridge single-stage AC-DC converter of claim 3, wherein, The two equivalent dual active bridge DC-DC converters set in the control period have equal switch cycle lengths.

5. The current space vector decoupled control method for a dual active bridge single-stage AC-DC converter of claim 4, wherein, The input line voltage is the line voltage between any two phases of the three-phase input phase voltage of the AC side, and the specific value is determined according to the switch state combination activated in the current sector.

6. The current space vector decoupled control method for a dual active bridge single-stage AC-DC converter of claim 5, wherein, The instantaneous voltage transformation ratio is the ratio between the primary side input line voltage of the equivalent dual active bridge DC-DC converter and the DC side voltage reduced to the primary side. The calculation of the duty cycles is divided into four cases for processing according to the positive and negative relationship between the instantaneous voltage transformation ratio and the input average current: When the instantaneous voltage transformation ratio is greater than 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in a switch cycle is greater than or equal to zero and less than or equal to the maximum allowable value of the average current of the secondary side in the switch cycle, a first group of duty cycle calculation formulas is adopted; When the instantaneous voltage transformation ratio is greater than 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in a switch cycle is greater than or equal to a certain critical current value and less than or equal to the maximum allowable value of the average current of the secondary side in the switch cycle, a second group of duty cycle calculation formulas is adopted; When the instantaneous voltage transformation ratio is less than or equal to 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in a switch cycle is greater than or equal to zero and less than or equal to another specific critical current value, a third group of duty cycle calculation formulas is adopted; When the instantaneous voltage transformation ratio is less than or equal to 1, and the average current of the secondary side of the equivalent dual active bridge DC-DC converter in a switch cycle is greater than the specific critical current value and less than or equal to the maximum allowable value of the average current of the secondary side, a fourth group of duty cycle calculation formulas is adopted.

7. The current space vector decoupled control method for a dual active bridge single-stage AC-DC converter of claim 6, wherein, The action logic of the switch tube is generated by the following way: According to the equivalent dual active bridge type DC-DC converter structure corresponding to the current sector, the corresponding relationship between the bidirectional switch in the AC side matrix converter and the power switch tube in the equivalent dual active bridge type DC-DC converter is established; The calculated duty ratio is mapped to the conduction and turn-off timing of the corresponding switch tube in the respective switching period, so as to generate a complete switch driving signal.

8. A current space vector decoupled control system for a dual active bridge single stage AC-DC converter, applying the method of any one of claims 1 to 7, characterized in that, It comprises: An equivalent module for equivalent to two independent dual active bridge type DC-DC converters in a control period; A first calculation module for calculating the input average current corresponding to two equivalent dual active bridge type DC-DC converters respectively according to the given AC side three-phase current synthesis vector; A second calculation module for determining the sector in which the AC side three-phase current synthesis vector is located according to the current three-phase input phase voltage and the DC side voltage, and calculating the input line voltage and instantaneous voltage ratio corresponding to the two equivalent dual active bridge type DC-DC converters in the sector; A third calculation module for calculating the duty ratio of the two equivalent dual active bridge type DC-DC converters respectively based on the instantaneous voltage ratio and the corresponding input average current; A decoupling modulation module for generating the action logic of each switch tube in the control period according to the preset switch tube corresponding relationship and the duty ratio, so as to realize the current space vector decoupling modulation strategy. 9.An electronic device comprising a memory and a processor, the memory storing a computer program, wherein, The processor executes the computer program to realize the steps of the current space vector decoupling control method for the dual active bridge type single-stage AC-DC converter according to any one of claims 1-7.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the current space vector decoupling control method for the dual active bridge type single-stage AC-DC converter according to any one of claims 1-7.

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