A method for phase-shifting control of an SSDAB converter for extending the power range of MBD-GaN

Abstract

The embodiment of the application provides an SSDAB converter frequency conversion phase shift control method for extending the application power range of MBD-GaN, relates to the technical field of converter control, and comprises the following steps: acquiring the alternating current side voltage, the alternating current side current and the direct current side voltage of a single-stage double active bridge (SSDAB) converter by setting an initial switching frequency; obtaining a voltage gain parameter and a normalized power parameter; obtaining a real-time operation interval according to a preset operation interval determination mechanism; taking the minimization of a switching stress factor as a target, obtaining a limited switching frequency, an inner phase shift amount, an outer phase shift amount and an outer phase shift angle, inputting a PWM module to generate a driving signal, and completing the frequency conversion phase shift control of the SSDAB converter. The problem that the application power range of MBD-GaN devices is limited under the high-power working condition of the SSDAB converter in the prior art is solved. The current stress and the current effective value are greatly reduced, the switching loss is reduced, and the power application range is extended.

Description

Technical Field

[0001] This invention relates to the field of converter control technology, and in particular to a frequency conversion and phase shift control method for SSDAB converters that extends the applicable power range of MBD-GaN. Background Technology

[0002] The Single-Stage Dual Active Bridge (SSDAB) converter is a key AC-DC topology used in residential photovoltaic energy storage, on-board chargers (OBCs) for electric vehicles, and other applications. It enables single-stage power conversion from grid AC to battery DC. Traditional two-stage converters consist of a front-end PFC and a rear-end isolated DC / DC converter, requiring two power conversion modules connected by a large-capacity electrolytic capacitor. In contrast, the single-stage converter offers advantages such as higher power density, system efficiency, reliability, and lifespan.

[0003] Compared to conventional single-stage topologies, including single-stage matrix converters and single-stage resonant converters (such as single-stage LLC converters), the SSDAB converter has a naturally symmetrical structure, enabling bidirectional energy flow without the need for additional auxiliary circuitry. Its more flexible control strategies allow for a wider range of battery voltage regulation. Furthermore, traditional AC-side switches (MOSFETs, IGBTs, etc.) can only achieve unidirectional blocking, requiring two devices to be connected back-to-back. In contrast, monolithic bidirectional gallium nitride (MDB-GaN) devices possess both bidirectional blocking and bidirectional conduction capabilities. A single chip can replace two traditional back-to-back silicon devices, significantly reducing the number of devices and the complexity of the drive circuitry, further improving the power density of the SSDAB converter.

[0004] However, due to limitations in device characteristics and existing control strategies, the combination of high-frequency switching and huge peak current will cause the device to suffer extremely high current stress and turn-off losses, making it difficult for SSDAB converters to expand their applicable power range while ensuring device safety. Their application range is limited to 0-3.3kW, which is challenging in high-power systems.

[0005] [Infineon Technologies. IGT65R055D2 - CoolGaN™ 650 V e-mode HEMT Datasheet, Rev. 1.0, Nov. 2024.] discloses the technical parameters of mainstream commercial gallium nitride (GaN) power switches. Although these devices perform well in high-frequency applications, their rated current capability is difficult to fully cover the double-frequency peak current required by a single-stage AC / DC converter in high-power applications of 6.6kW and above (e.g., the current corresponding to 13.2kW instantaneous power). This results in the device facing great overcurrent risk and thermal management challenges under high-frequency and high-current conditions, limiting the applicable power range of the system.

[0006] The literature [Q. Gu, L. Yuan, J. Nie, J. Sun and Z. Zhao, "Current Stress Minimization of Dual-Active-Bridge DC–DC Converter Within the Whole Operating Range," in IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 7, no. 1, pp. 129-142, March 2019.] proposes a minimum current stress (MCS+CF) control method based on constant frequency. By deeply exploring the relationship between current stress and phase shift angle, stress optimization is achieved at a fixed frequency. However, under heavy load or high power output conditions, in order to meet power transmission requirements, this type of pure phase-shift control strategy essentially converges to extended phase-shift (EPS) or single phase-shift (SPS) control, resulting in a significant reduction in control freedom. It is impossible to further reduce current stress under heavy load, and fixed-frequency operation limits the optimization of switching losses.

[0007] The literature [Z. Fan, H. Lu, J. Chai, Y. Li and X. Sun, "Partition Variable Frequency and EPS Hybrid Control to Achieve Full Load Range ZVS for Dual-Active Bridge Converters," in IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 12, no. 1, pp. 143-155, Feb. 2024.] discusses a phase-shifting frequency modulation (PFM) strategy, introducing the switching frequency as a control variable into the system. However, existing research in this area mainly focuses on extending the zero-voltage turn-on (ZVS) range of the converter to reduce turn-on losses, with little attention paid to how to jointly optimize current stress or turn-off losses through frequency conversion under heavy load or high load conditions, making it difficult to solve the problem of excessive device temperature rise under high power conditions.

[0008] It should be noted that the information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a frequency conversion and phase shift control method for SSDAB converters that extends the applicable power range of MBD-GaN devices. This method solves the problem of limited applicable power range of MBD-GaN devices under high-power conditions in existing SSDAB converters. The specific technical solution is as follows:

[0010] According to a first aspect of the present invention, a frequency conversion phase shift control method for an SSDAB converter that extends the applicable power range of MBD-GaN is provided, the method comprising:

[0011] Set the initial switching frequency and obtain the AC side voltage, AC side current and DC side voltage of the single-stage dual active bridge SSDAB converter;

[0012] Voltage gain and normalized power parameters are obtained by performing voltage gain and normalized power analysis based on the AC side voltage, AC side current and DC side voltage.

[0013] According to the preset operating range determination mechanism, the voltage gain parameter and the normalized power parameter are used to determine the operating range to obtain the real-time operating range.

[0014] The switching stress factor is obtained, and with the goal of minimizing the switching stress factor, the limited switching frequency and phase shift control quantity are determined based on the real-time operating range, voltage gain parameter and normalized power parameter. The limited switching frequency, inner phase shift quantity and outer phase shift quantity are obtained and input into the PWM module to generate drive signals to complete the frequency conversion and phase shift control of the SSDAB converter.

[0015] In one implementation, the method further performs the following processing:

[0016] The voltage gain analysis formula is obtained, and the AC side voltage and DC side voltage are analyzed using the voltage gain analysis formula to obtain the voltage gain parameters. The voltage gain analysis formula is as follows:

[0017] ;

[0018] in, For voltage gain parameters, For transformer turns ratio, This is the peak value of the AC side voltage. This is the DC side voltage.

[0019] In one implementation, the method further performs the following processing:

[0020] Obtain the normalized power analysis formula, and use the normalized power analysis formula to analyze the AC side voltage and AC side current to obtain the normalized power parameters. The normalized power analysis formula is as follows:

[0021] ;

[0022] in, For normalized power parameters, For transformer turns ratio, DC side voltage For switching frequency, This is the effective value of the AC side current. For transmitting inductance.

[0023] In one implementation, the preset operating range determination mechanism includes:

[0024] When M≥1 and 0≤p≤2(M-1) / M 2 When this time, it is determined to be the minimum current stress control range for fixed frequency;

[0025] When M≥1 and 1≥p>2(M-1) / M 2 When this occurs, it is determined to be an extended phase-shift frequency reduction control range;

[0026] When M<1 and 0≤p≤2M(1-M), it is determined to be the fixed-frequency minimum current stress control range;

[0027] When M < 1 and 1 ≥ p > 2M(1-M), it is determined to be an extended phase-shifting frequency reduction control interval.

[0028] In one implementation, the method further performs the following processing:

[0029] When the real-time operating range is the extended phase-shift frequency reduction control range, the peak current... The expression is:

[0030] ;

[0031] in, This is the peak value of the AC side voltage. For transformer turns ratio, To transmit inductance, For switching frequency, For outward shift phasors, For the central axis phase difference, This refers to the internal phase shifter.

[0032] In one implementation, the switching stress factor is: ;

[0033] in, For switching stress factor, For switching frequency, This is the peak value of the AC side voltage. This is the peak current. To transmit inductance, For voltage gain parameters, This is the normalized power parameter.

[0034] In one implementation, the method further performs the following processing:

[0035] The partial derivative function is obtained by taking the partial derivative of the switching stress factor with respect to the switching frequency.

[0036] When the partial derivative is greater than 0, the optimal switching frequency can be obtained analytically.

[0037] The optimal switching frequency is: ;

[0038] To achieve the optimal switching frequency, For AC side current, For voltage gain parameters;

[0039] The optimal switching frequency is determined by a limiting function to obtain a limited switching frequency.

[0040] In one implementation, the limiting function is:

[0041] ;

[0042] in, To limit the switching frequency, To achieve the optimal switching frequency, This is the initial switching frequency.

[0043] In one implementation, the partial derivative function is: .

[0044] In one embodiment, the AC side of the single-stage dual active bridge SSDAB converter includes four monolithic bidirectional gallium nitride devices, and the DC side includes four SiC devices. The full-bridge circuits on both sides are connected by a series inductor L and a transformer T with a transformer turns ratio of n:1.

[0045] Beneficial effects of the embodiments of the present invention:

[0046] In the solution provided by this invention, an initial switching frequency is set to obtain the AC side voltage, AC side current, and DC side voltage of a single-stage dual active bridge SSDAB converter. Voltage gain and normalized power analysis are performed based on the AC side voltage, AC side current, and DC side voltage to obtain voltage gain parameters and normalized power parameters. According to a preset operating range determination mechanism, the operating range of the voltage gain parameters and normalized power parameters is determined to obtain the real-time operating range. The switching stress factor is obtained, and with the goal of minimizing the switching stress factor, a limited switching frequency and phase shift control quantity are determined based on the real-time operating range, voltage gain parameters, and normalized power parameters to obtain the limited switching frequency, inner phase shift quantity, outer phase shift quantity, and outer phase shift angle. These are input into the PWM module to generate a drive signal, completing the frequency conversion and phase shift control of the SSDAB converter. This achieves the effects of significantly reducing current stress and RMS current, reducing switching losses, and expanding the applicable power range. Of course, implementing any product or method of this invention does not necessarily require achieving all the advantages described above simultaneously. Attached Figure Description

[0047] 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.

[0048] Figure 1 This invention provides a schematic flowchart of a frequency conversion phase shift control method for an SSDAB converter that extends the applicable power range of MBD-GaN.

[0049] Figure 2 The diagram shows a schematic topology of the SSDAB converter in a frequency conversion phase-shift control method for extending the applicable power range of MBD-GaN provided by the present invention, and a key waveform diagram when the average output power is 6.6kW.

[0050] Figure 3 The figure shows a key DAB waveform under TPS control in an SSDAB converter frequency conversion phase shift control method that extends the applicable power range of MBD-GaN provided by the present invention.

[0051] Figure 4 The diagram shows the current stress variation of MCS control at different switching frequencies in an SSDAB converter frequency conversion phase shift control method for extending the applicable power range of MBD-GaN provided by the present invention.

[0052] Figure 5 This invention illustrates the optimal current stress versus frequency curves versus power graphs in a frequency conversion phase-shift control method for SSDAB converters that extends the applicable power range of MBD-GaN, as provided by this invention.

[0053] Figure 6 The diagram shows the frequency-corrected characteristic of an SSDAB converter frequency conversion phase-shift control method that extends the applicable power range of MBD-GaN provided by the present invention.

[0054] Figure 7 The diagram shows the system control block diagram and waveform diagram of a frequency conversion phase shift control method for an SSDAB converter that extends the applicable power range of MBD-GaN provided by the present invention. Detailed Implementation

[0055] To facilitate understanding of the present invention, a more complete description of the invention will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein; rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the invention.

[0056] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0057] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0058] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0059] This invention provides a frequency conversion and phase shift control method for SSDAB converters that extends the applicable power range of MBD-GaN, thereby solving the problem that the applicable power range of MBD-GaN devices is limited under high-power conditions in the prior art.

[0060] See Figure 1 The present invention provides a flowchart of a frequency conversion phase shift control method for an SSDAB converter that extends the applicable power range of MBD-GaN, the method comprising:

[0061] Set the initial switching frequency and obtain the AC side voltage, AC side current and DC side voltage of the single-stage dual active bridge SSDAB converter;

[0062] Furthermore, the AC side of the single-stage dual active bridge SSDAB converter includes four monolithic bidirectional gallium nitride devices, and the DC side includes four SiC devices. The full-bridge circuits on both sides are connected by a series inductor L and a transformer T with a transformer turns ratio of n:1.

[0063] It should be noted that, as Figure 2 The schematic diagram of the topology of the single-stage dual active bridge SSDAB converter shown illustrates the converter's structure. On the AC side, there are four monolithic bidirectional gallium nitride devices, namely S1-S4, forming a full-bridge circuit directly connected to the 220V / 50Hz AC power grid. On the DC side, four SiC devices, namely Q1-Q4, form a full-bridge current connection connected to a 400V battery pack. The full-bridge circuits on both sides are connected through a series inductor L and a transformer T with a transformer turns ratio of n:1 to achieve energy transfer and electrical isolation.

[0064] Preferably, the typical operating waveform of a single-stage dual active bridge SSDAB converter is as follows: Figure 3As shown, D1 and D2 are the duty cycles of the midpoint voltages v1 and v2 of the primary and secondary bridge arms, respectively, D3 is the phase shift duty cycle of Q4 compared to S4, and T... hs This is a half-switching cycle. The mid-axis phase difference between voltages v1 and v2 is defined as Φ = D3 + (D2 – D1) / 2. When Φ > 0, power is transmitted in the forward direction; when Φ < 0, power is transmitted in the reverse direction. Phase shift angles D1 and D2, and Φ are selected as control variables, and the value range of each control variable is: D1, D2, Φ ∈ [0, 1].

[0065] Under phase-shift control, although the DAB converter has 12 modes, scholars have solved the optimal phase-shift expression for the DAB converter under full power and full voltage range, as summarized in Table 1. This MCS control has been fully verified theoretically and experimentally and is recognized as the best current stress control method under phase-shift control. Since the DAB converter operates with symmetry, this paper analyzes the operating characteristics of the DAB converter under boost conditions as an example.

[0066] Table 1 Key Expressions for MCS Control

[0067]

[0068] The controller uses an ADC module to cyclically read the voltage signal output from the AC-side voltage sensor, the current signal output from the AC-side current sensor, and the voltage signal output from the DC-side voltage sensor at a sampling rate of 20kHz. By clarifying the specific topology of the SSDAB converter, especially the feature of using MBD-GaN devices on the AC side, it is pointed out that the technical problem to be solved by this invention is the applicability problem of such devices under high power, thus establishing a clear correspondence between the subsequent control method and the hardware platform. Secondly, accurate data acquisition is the prerequisite for all subsequent calculations and determines the control accuracy. Thirdly, the initial switching frequency setting provides a reference for frequency conversion regulation.

[0069] Voltage gain and normalized power parameters are obtained by performing voltage gain and normalized power analysis based on the AC side voltage, AC side current and DC side voltage.

[0070] Furthermore, embodiments of the present invention also include:

[0071] The voltage gain analysis formula is obtained, and the AC side voltage and DC side voltage are analyzed using the voltage gain analysis formula to obtain the voltage gain parameters. The voltage gain analysis formula is as follows:

[0072] ;

[0073] in, For voltage gain parameters, For transformer turns ratio, This represents the peak value of the AC side voltage. This is the DC side voltage.

[0074] Furthermore, embodiments of the present invention also include:

[0075] Obtain the normalized power analysis formula, and use the normalized power analysis formula to analyze the AC side voltage and AC side current to obtain the normalized power parameters. The normalized power analysis formula is as follows:

[0076] ;

[0077] in, For normalized power parameters, For transformer turns ratio, DC side voltage For switching frequency, This is the effective value of the AC side current. For transmitting inductance.

[0078] It should be noted that voltage gain analysis refers to the process of establishing a mathematical relationship between the output voltage and the input voltage using the basic principles of a converter, and calculating the dimensionless parameter characterizing this relationship. The voltage gain parameter M is one of the core operating condition characterization quantities of this invention. Its physical meaning is the ratio of the output voltage (referred to the primary side of the transformer) to the input voltage, used to determine whether the converter is currently operating in boost or buck mode. The normalized power parameter p is another core operating condition characterization quantity of this invention, used to uniformly describe the load level under different voltages and frequencies, facilitating the establishment of a universal control law.

[0079] By calculating M and p, the actual physical operating state is converted into standardized parameters in the analytical model, enabling the control algorithm to perform interval division and optimization decisions based on a unified mathematical model. M determines the piecewise form of the phase-shifting control expression, and p determines whether the system enters the heavy-load region, thereby triggering the frequency reduction optimization mechanism.

[0080] According to the preset operating range determination mechanism, the voltage gain parameter and the normalized power parameter are used to determine the operating range to obtain the real-time operating range.

[0081] Furthermore, the preset operating range determination mechanism includes:

[0082] When M≥1 and 0≤p≤2(M-1) / M 2 When this time, it is determined to be the minimum current stress control range for fixed frequency;

[0083] When M≥1 and 1≥p>2(M-1) / M 2 When this occurs, it is determined to be an extended phase-shift frequency reduction control range;

[0084] When M<1 and 0≤p≤2M(1-M), it is determined to be the fixed-frequency minimum current stress control range;

[0085] When M < 1 and 1 ≥ p > 2M(1-M), it is determined to be an extended phase-shifting frequency reduction control interval.

[0086] It should be noted that, through analysis, the EPS-DF control expression shown in Table 2 can be determined, from which the operating range under different voltage gains and normalized power, as well as the corresponding control quantities, can be determined.

[0087] Table 2 EPS-DF Control Expressions

[0088]

[0089] It should be noted that the fixed-frequency minimum current stress control range refers to maintaining the switching frequency at the initial switching frequency within this range, and adjusting the current stress solely through phase-shift control to minimize the current peak value. The extended phase-shift frequency reduction control range refers to not only adjusting the phase-shift control but also optimizing and reducing the switching frequency within this range to further reduce the switching stress factor. In the judgment conditions, M≥1 represents the boost condition, M<1 represents the buck condition, and 0≤p≤2(M−1) / M 2 This indicates that the power is in the low to medium load range, and 1≥p>2(M−1) / M 2 This indicates that the system has entered a heavy load or high power range.

[0090] The system employs an automatic switching control strategy based on operating voltage mode and load intensity. This ensures constant-frequency operation in light or medium-load ranges to maintain high efficiency and power density, while a frequency reduction optimization mechanism is introduced in heavy-load ranges to prevent performance degradation across the entire power range from the limitations of a single control strategy. This segmented control mechanism guarantees the system operates in optimal control mode across different load ranges, representing a crucial transitional step in achieving joint optimization of current stress and turn-off losses.

[0091] The switching stress factor is obtained, and with the goal of minimizing the switching stress factor, the limited switching frequency and phase shift control quantity are determined based on the real-time operating range, voltage gain parameter and normalized power parameter. The limited switching frequency, inner phase shift quantity and outer phase shift quantity are obtained and input into the PWM module to generate drive signals to complete the frequency conversion and phase shift control of the SSDAB converter.

[0092] Furthermore, embodiments of the present invention also include:

[0093] When the real-time operating range is the extended phase-shift frequency reduction control range, the peak current... The expression is:

[0094] ;

[0095] in, This is the peak value of the AC side voltage. For transformer turns ratio, To transmit inductance, For switching frequency, For outward shift phasors, For the central axis phase difference, This refers to the internal phase shifter.

[0096] Furthermore, the switching stress factor is ;

[0097] in, For switching stress factor, For switching frequency, This is the peak value of the AC side voltage. This is the peak current. To transmit inductance, For voltage gain parameters, This is the normalized power parameter.

[0098] Furthermore, embodiments of the present invention also include:

[0099] The partial derivative function is obtained by taking the partial derivative of the switching stress factor with respect to the switching frequency.

[0100] When the partial derivative is greater than 0, the optimal switching frequency can be obtained analytically.

[0101] The optimal switching frequency is: ;

[0102] To achieve the optimal switching frequency, For AC side current, For voltage gain parameters;

[0103] The optimal switching frequency is determined by a limiting function to obtain a limited switching frequency.

[0104] Furthermore, the limiting function is:

[0105] ;

[0106] in, To limit the switching frequency, To achieve the optimal switching frequency, This is the initial switching frequency.

[0107] Furthermore, the partial derivative function is: .

[0108] It should be noted that the applicable power range of GaN switches is affected by both current stress and power losses and temperature rise. Although frequency increase can optimize current stress in certain power ranges, it may actually increase turn-off losses. Further clarification is needed regarding the frequency range where current stress can be optimized and turn-off losses reduced. The system power range is determined by the switch temperature rise at the point of maximum loss, and the switch turning off at the peak current always has the highest temperature. The turn-off loss of the switch turning off at the peak current can be calculated by considering the drain-source voltage V. DS Current I at turn-off time max Switching frequency f s The unified representation of the function: P off =f(V DS ,I max ,f s Here, switching stress is defined as an equivalent replacement for P. off This refers to the role of the turn-off loss of the switching transistor. The specific expression for the switching stress factor is obtained. The switching stress factor is used to comprehensively characterize the loss level of the switching transistor at the turn-off moment. Since the turn-off loss is approximately proportional to the current value and switching frequency at the turn-off moment, the switching stress factor can serve as an equivalent evaluation index for turn-off loss, without relying on the datasheet parameters of specific devices, and has universality.

[0109] Preferably, by taking the partial derivative of the switching stress factor with respect to the switching frequency, we can obtain... Since 0 ≤ p ≤ 1 and M ≥ 1, then This holds true indefinitely. Therefore, for the same output power, the lower the frequency fs, the smaller the S value. However, continuously decreasing the frequency may lead to a reverse increase in current stress. For example... Figure 4 As shown, when the frequency decreases to 0.6 fs*, the current stress will be greater than fs*. Therefore, in order to optimize the current stress while reducing the turn-off loss, the limited switching frequency is set to [value missing]. .

[0110] Preferably, as shown in Table 1, under high load conditions (p>2(M-1) / M2), the system will operate in EPS mode to generate high power output. In reality, the actual current I flowing through the switch... max It should be expressed as It can be used at different switching frequencies f s The current stress I under MCS control is plotted below. max ,like Figure 4 As shown, where P o This represents the system's output power. Observation shows that when 4200... <P o <5000W f s * The current stress at =1.2 is better than f s* =1.0, while when Po>6200W, f s * The current stress at =0.8 is better than f s * =1.0 and f s * =0.6. f s * =f s / 250kHz. Therefore, there must exist such as Figure 4 The optimal current stress frequency conversion curve is shown. Based on this, the optimal switching frequency can be determined in conjunction with Table 2. The expression is shown above.

[0111] Depend on Figure 5 It can be seen that the current stress of phase-shift modulation can be further optimized through frequency adjustment. Meanwhile, the optimal frequency gradually decreases with increasing power. Furthermore, from... Figure 6 It can be seen that, after limiting the function, the current stress after frequency conversion is still better than that of MCS control, with an optimization effect of 31% at the peak point. Benefiting from frequency reduction, the optimization effect of switching stress is even more significant, reaching 63% at the peak point.

[0112] The above describes the working condition where M ≥ 1. Similarly, the working condition where M < 1 can be obtained, as follows:

[0113] .

[0114] Where p1 = 2(2–2M) 0.5 / (1+(2(1–M)) 0.5 ),p2=2(2(M–1)) 0.5 / (M+(2(M–1)) 0.5 Furthermore, taking the OBC mode as an example, the control loop block diagram proposed in this invention and its closed-loop control effect under boost conditions are shown as follows. Figure 7 As shown. First, the system needs to sample I. g V g V dc Three electrical quantities, and V g Perform phase-locked loop (PLL), multiply by the set |Igref|, and then multiply by the actual I. g The difference is fed into the PI loop, and its output is set as the PI component of the outward phase shift angle Φ. To improve the system response speed, a feedforward element is used here to calculate p and the feedforward quantity Φ. F , and Φ PI The sums are then used to obtain Φ. Finally, according to Table 2, all control quantities are used to generate waves in the PWM circuit.

[0115] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0116] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A frequency conversion and phase shift control method for an SSDAB converter that extends the applicable power range of MBD-GaN, characterized in that, The method includes: Set the initial switching frequency and obtain the AC side voltage, AC side current and DC side voltage of the single-stage dual active bridge SSDAB converter; Voltage gain and normalized power parameters are obtained by performing voltage gain and normalized power analysis based on the AC side voltage, AC side current and DC side voltage. According to the preset operating range determination mechanism, the voltage gain parameter and the normalized power parameter are used to determine the operating range to obtain the real-time operating range. The switching stress factor is obtained, and with the goal of minimizing the switching stress factor, the limited switching frequency and phase shift control quantity are determined based on the real-time operating range, voltage gain parameter and normalized power parameter. The limited switching frequency, inner phase shift quantity and outer phase shift quantity are obtained and input into the PWM module to generate drive signals to complete the frequency conversion and phase shift control of the SSDAB converter.

2. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 1, characterized in that, include: The voltage gain analysis formula is obtained, and the AC side voltage and DC side voltage are analyzed using the voltage gain analysis formula to obtain the voltage gain parameters. The voltage gain analysis formula is as follows: ； in, For voltage gain parameters, For transformer turns ratio, This represents the peak value of the AC side voltage. This is the DC side voltage.

3. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 2, characterized in that, include: Obtain the normalized power analysis formula, and use the normalized power analysis formula to analyze the AC side voltage and AC side current to obtain the normalized power parameters. The normalized power analysis formula is as follows: ； in, For normalized power parameters, For transformer turns ratio, DC side voltage For switching frequency, This is the effective value of the AC side current. For transmitting inductance.

4. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 1, characterized in that, The preset operating range determination mechanism includes: When M≥1 and 0≤p≤2(M-1) / M 2 When this time, it is determined to be the minimum current stress control range for fixed frequency; When M≥1 and 1≥p>2(M-1) / M 2 When this occurs, it is determined to be an extended phase-shift frequency reduction control range; When M<1 and 0≤p≤2M(1-M), it is determined to be the fixed-frequency minimum current stress control range; When M < 1 and 1 ≥ p > 2M(1-M), it is determined to be an extended phase-shifting frequency reduction control interval.

5. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 4, characterized in that, include: When the real-time operating range is the extended phase-shift frequency reduction control range, the peak current... The expression is: ； in, This represents the peak value of the AC side voltage. For transformer turns ratio, To transmit inductance, For switching frequency, For outward shift phasors, For the central axis phase difference, This refers to the internal phase shifter.

6. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 1, characterized in that, Switching stress factor is ; in, For switching stress factor, For switching frequency, This represents the peak value of the AC side voltage. This is the peak current. To transmit inductance, For voltage gain parameters, This is the normalized power parameter.

7. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 6, characterized in that, include: The partial derivative function is obtained by taking the partial derivative of the switching stress factor with respect to the switching frequency. When the partial derivative is greater than 0, the optimal switching frequency can be obtained analytically. The optimal switching frequency is: ; To achieve the optimal switching frequency, For AC side current, For voltage gain parameters; The optimal switching frequency is determined by a limiting function to obtain a limited switching frequency.

8. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 7, characterized in that, The limiting function is: ； in, To limit the switching frequency, To achieve the optimal switching frequency, This is the initial switching frequency.

9. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 7, characterized in that, The partial derivative function is: .

10. The SSDAB converter frequency conversion and phase shift control method for extending the applicable power range of MBD-GaN as described in claim 1, characterized in that, The AC side of the single-stage dual active bridge SSDAB converter includes four monolithic bidirectional gallium nitride devices, and the DC side includes four SiC devices. The full-bridge circuits on both sides are connected by a series inductor L and a transformer T with a transformer turns ratio of n:1.

Images