A sliding mode control method and system for a dual active bridge DC-DC converter

Abstract

A sliding mode control method for a dual active bridge DC-DC converter includes: constructing a state-space model of the DAB using its transmitted power as the control variable; constructing a sliding mode surface function using the difference between the desired output voltage and the actual output voltage of the DAB as the system error variable; constructing a sliding mode control law based on the state-space model and sliding mode surface function of the DAB; tracking the output voltage of the DAB using the sliding mode control law to obtain the transmitted power of the DAB, and normalizing the transmitted power of the DAB; and solving for the shift ratio of the DAB based on the normalized transmitted power and the voltage conversion ratio K of the DAB. This design not only significantly improves the dynamic response of the system and suppresses the chattering phenomenon of traditional sliding mode, but also has low computational complexity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronic converters, in particular to a sliding mode control method and system of a dual active bridge DC-DC converter. BACKGROUND

[0002] To cope with the disturbance and stability problems of the DC micro-grid caused by the random fluctuation of distributed power and the frequent switching of the load, the energy storage unit and the bidirectional DC-DC converter become the core equipment of the DC micro-grid system. It can effectively suppress power fluctuation, stabilize the DC bus voltage, improve power quality and system performance. The dual active bridge DC-DC converter (DAB, hereinafter DAB) has the characteristics of bidirectional energy transfer, symmetrical topology, high power density, easy realization of zero voltage conduction, electrical isolation, etc., and has been widely concerned by domestic and foreign scholars. It has gradually become the mainstream converter of the DC micro-grid system.

[0003] However, high proportion of new energy access may cause large-scale fluctuation of the DC bus voltage of the DC micro-grid, resulting in mismatch between the input and output voltages of the DAB, increasing the backflow power and current stress, and making it difficult for some switching tubes to realize ZVS, etc. This in turn causes increased loss and reduced system efficiency, which affects the dynamic response performance of the system. Therefore, it is necessary to optimize the dynamic response performance of the DAB, and consider using sliding mode control to optimize the response speed of the DAB. However, the traditional sliding mode control strategy is prone to chattering phenomenon, which affects the control accuracy of the system and damages the performance of the system. At the same time, the existing sliding mode control and model predictive control methods have complex parameter design and large calculation amount, which affects the dynamic response performance of the system. Therefore, an improved control strategy of the dual active bridge DC-DC converter is needed, which can significantly improve the dynamic response of the system and significantly suppress the chattering phenomenon of the traditional sliding mode, so as to improve the overall performance of the DC micro-grid. SUMMARY

[0004] The purpose of the present application is to overcome the problems of PI control of the dual active bridge DC-DC converter in the prior art, such as insufficient control accuracy, poor tracking effect, chattering phenomenon of sliding mode control, affecting system stability, and high calculation complexity, and to provide a sliding mode control method and system of a dual active bridge DC-DC converter with small calculation amount, which can significantly improve the dynamic response of the system and suppress the chattering phenomenon of the traditional sliding mode.

[0005] To achieve the above purpose, the technical solution of the present application is as follows:

[0006] A sliding mode control method of a dual active bridge DC-DC converter, the control method comprising the following steps:

[0007] S1, taking the transmission power of the DAB as a control variable, constructing a state space model of the DAB;

[0008] S2, taking the difference between the expected output voltage of the DAB and the actual output voltage of the DAB as a system error variable, constructing a sliding surface function;

[0009] S3, constructing a sliding mode control law according to the state space model of the DAB and the sliding surface function;

[0010] S4, tracking the output voltage of the DAB using the sliding mode control law, obtaining the transmission power of the DAB, and normalizing the transmission power of the DAB;

[0011] S5, according to the normalized transmission power and the voltage conversion ratio K of the DAB, solving the phase shift ratio of the DAB.

[0012] In the step S1, the state space model of the DAB is:

[0013] ;

[0014] ;

[0015] ;

[0016] In the above formula, is the control variable; is the transmission power of the DAB; is the capacity of the secondary side capacitor; is the output voltage of the DAB; is the rate of change of the output voltage; is the output current of the DAB.

[0017] In the step S2, the sliding surface function is:

[0018] ;

[0019] In the above formula, is the system error variable, ; is the expected value of the output voltage of the DAB; is the output voltage of the DAB; and is the sliding surface control gain, and are both greater than zero.

[0020] In the step S3, the sliding mode control law is set according to the state space model of the DAB and the sliding surface function, including the following steps:

[0021] According to the state space model of the DAB, a model equivalent part of the sliding mode control law is obtained ;

[0022] According to the super-spiral algorithm, a switching control part of the sliding mode control law is obtained ;

[0023] According to the model equivalent part of the sliding mode control law , the switching control part of the sliding mode control law The sliding mode control law is obtained :

[0024] .

[0025] In the step S3, according to the state space model of the DAB, a model equivalent part of the sliding mode control law is obtained , comprising the following steps:

[0026] Substitute the state space model of the DAB into the sliding surface expression, and derive the sliding surface function to obtain the first derivative of the sliding surface function:

[0027] ;

[0028] Let the first derivative of the sliding surface function be , and the model equivalent part of the control law is obtained by solving :

[0029] ;

[0030] In the above formula, is the output current of the DAB; is the output voltage of the DAB, is the capacity of the secondary capacitor, ; is the system error variable, , is the expected value of the output voltage of the DAB; is the input voltage of the DAB; and are the sliding surface control gains; and are both greater than zero.

[0031] In the step S3, according to the super-spiral algorithm, a switching control part of the sliding mode control law is obtained comprising the following steps:

[0032] According to the super-spiral algorithm, the general form of the switching control part of the control law is obtained :

[0033] ;

[0034] In the above formula, , is a super-spiral control gain, , ; is a sliding mode surface function.

[0035] In the step S5, the voltage conversion ratio of the DAB is According to the following formula:

[0036] ;

[0037] In the formula, is an input voltage of the DAB; is an output voltage of the DAB; is a ratio of the number of turns of the primary coil to the number of turns of the secondary coil of the DAB.

[0038] A sliding mode control system of a dual active bridge DC-DC converter, the control system comprising:

[0039] A first construction module for constructing a state space model of the DAB by taking the transmission power of the DAB as a control variable;

[0040] The state space model of the DAB is:

[0041] ;

[0042] ;

[0043] ;

[0044] In the above formula, is a control variable; is a transmission power of the DAB; is a capacity of the secondary capacitor; is an output voltage of the DAB; is a rate of change of the output voltage; is an output current of the DAB;

[0045] A second construction module for constructing a sliding mode surface function by taking a difference between the expected output voltage of the DAB and the actual output voltage of the DAB as a system error variable;

[0046] The sliding mode surface function is:

[0047] ;

[0048] In the above formula, is a system error variable, ; is an output voltage expectation of the DAB; is an output voltage of the DAB; is a system error variable, is a sliding mode surface control gain, is a system error variable, are both greater than zero;

[0049] a third construction module, configured to construct a sliding mode control law according to a state space model of the DAB and a sliding mode surface function;

[0050] the setting of the sliding mode control law according to the state space model of the DAB and the sliding mode surface function comprises:

[0051] a model equivalent part of the sliding mode control law is obtained according to the state space model of the DAB and the sliding mode surface function :

[0052] ;

[0053] in the above formula, is an output current of the DAB; is an output voltage of the DAB, is a capacity of the secondary side capacitor, ; is a system error variable, , is an output voltage expectation of the DAB; is an input voltage of the DAB; is a system error variable, is a sliding mode surface control gain, is a system error variable, are both greater than zero;

[0054] a switching control part of the sliding mode control law is obtained according to the supercoil algorithm :

[0055] ;

[0056] in the above formula, , is a supercoil control gain, , ; is a sliding mode surface function;

[0057] the sliding mode control law is obtained according to the model equivalent part of the sliding mode control law , the switching control part of the sliding mode control law :

[0058] ;​

[0059] In the above formula, is a sliding mode control law, is a current of a load of the DAB, is a capacity of a secondary capacitor, is an output voltage of the DAB, , is a system error variable, and is a sliding mode surface control gain, and are both greater than zero, , is a super-spiral control gain, , , is a sliding mode surface function.

[0060] an output module configured to track the output voltage of the DAB by using the sliding mode control law, to obtain a transmission power of the DAB, and to normalize the transmission power of the DAB;

[0061] a solving module configured to solve a phase-shifting ratio of the DAB according to the normalized transmission power and a voltage conversion ratio K of the DAB;

[0062] the voltage conversion ratio K of the DAB is calculated by the following formula:

[0063] ;

[0064] In the formula, is an input voltage of the DAB, is an output voltage of the DAB, is a ratio of the number of turns of a primary coil to the number of turns of a secondary coil of the DAB.

[0065] Compared with the prior art, the present application has the following beneficial effects:

[0066] 1. In the double active bridge DC-DC converter sliding mode control method, the transmission power of the DAB is used as the control quantity, the state space model of the DAB is constructed, the difference between the expected output voltage of the DAB and the actual output voltage of the DAB is used as the system error variable, and the sliding mode surface function is constructed; the model equivalent part of the sliding mode control law is obtained according to the state space model of the DAB, the sliding mode surface function, the switching control part of the control law is obtained according to the super-helix algorithm, and then the sliding mode control law is obtained; the super-helix sliding mode control in the design is an improved sliding mode control method, the high-frequency switching term of the system switching control part in the traditional sliding mode control is replaced by an integral form by introducing a continuous control law, so that the control signal has continuity, and the chattering phenomenon of the traditional sliding mode control is effectively suppressed; at the same time, the design retains the advantages of fast response speed and strong robustness to parameter changes and external disturbances of the sliding mode control, significantly improves the dynamic response speed and regulation accuracy of the system, and can effectively cope with complex working conditions such as input voltage mutation, load change and reference voltage adjustment, and can significantly improve the dynamic performance of the DAB when the voltage fluctuates in the direct current microgrid. Therefore, in the design, the traditional sliding mode control is improved by the super-helix algorithm, the chattering phenomenon is effectively suppressed, the advantages of fast response speed and strong robustness to parameter changes and external disturbances of the sliding mode control are retained, and the dynamic performance of the DAB when the voltage fluctuates in the direct current microgrid is significantly improved.

[0067] 2. In the double active bridge DC-DC converter sliding mode control method, the control quantity of the sliding mode control system is the transmission power of the DAB, the input voltage and the output voltage of the DAB are tracked by using the sliding mode control law, and the transmission power of the DAB can be output, and then the transmission power of the DAB is converted into a normalized value; and the multiple target optimization control combined with the backflow power optimization under double phase shift is adopted, and the optimization control mathematical model of the backflow power is used, that is, the voltage conversion ratio k and the transmission power normalized value are used, and the output quantity is the inner and outer phase shift ratio of the extended phase shift, and the calculation amount is small. Therefore, the transmission power of the DAB is used as the control quantity, the input voltage and the output voltage of the DAB are tracked by using the sliding mode control law, the transmission power of the DAB is output, and then the transmission power is simply normalized into a normalized value, so that the optimal phase shift ratio can be directly output, and the calculation amount is small.

[0068] 3. In the double active bridge DC-DC converter sliding mode control method, the transmission power of the DAB is used as the control quantity, which is suitable for various phase shift modes of the DAB, such as single phase shift, extended phase shift, double phase shift, etc., which can be changed according to different phase shift modes, and has strong adaptability. Therefore, the transmission power of the DAB is used as the control quantity, which is suitable for various phase shift modes of the DAB, and has strong adaptability. BRIEF DESCRIPTION OF DRAWINGS

[0069] Figure 1 is a flowchart of a sliding mode control method of a dual active bridge DC-DC converter provided by an embodiment of the present application.

[0070] Figure 2 is a topological structure diagram of a dual active bridge DC-DC converter provided by an embodiment of the present application.

[0071] Figure 3 is a simplified topological diagram of a dual active bridge DC-DC converter provided by an embodiment of the present application.

[0072] Figure 4 is a control flowchart of a dual active bridge DC-DC converter provided by an embodiment of the present application.

[0073] Figure 5 is a simulation waveform comparison diagram of super-spiral sliding mode control (STSMC) and traditional sliding mode control (SMC) provided by an embodiment of the present application.

[0074] Figure 6 is an output voltage experimental waveform comparison diagram of super-spiral sliding mode control (STSMC) and PI control, traditional sliding mode control (SMC) when an output voltage reference value changes provided by an embodiment of the present application.

[0075] Figure 7 is an output voltage experimental waveform comparison diagram of super-spiral sliding mode control (STSMC) and PI control, traditional sliding mode control (SMC) when a load mutates provided by an embodiment of the present application.

[0076] Figure 8 is an output voltage experimental waveform comparison diagram of super-spiral sliding mode control (STSMC) and PI control, traditional sliding mode control (SMC) when an input voltage mutates provided by an embodiment of the present application.

[0077] Figure 9 is a structural diagram of a sliding mode control system of a dual active bridge DC-DC converter provided by an embodiment of the present application.

[0078] Figure 10 is a structural diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0079] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0080] The dual active bridge DC-DC converter, i.e., Dual Active Bridge (DAB), can realize a wide voltage range, high power density, electrical isolation and bidirectional power transmission, and is a key device for connecting DC bus lines of different voltage levels or realizing energy exchange between energy storage units and DC bus lines.

[0081] A sliding mode control method of a dual active bridge DC-DC converter, please see Figure 1 , Figure 1 is a flowchart of the sliding mode control method of the dual active bridge DC-DC converter provided by the embodiment of the present application, and the sliding mode control method comprises steps S1 to S5;

[0082] S1, the transmission power of the DAB is As a control quantity, according to the simplified topology diagram of the dual active bridge DC-DC converter (DAB, hereinafter referred to as DAB), the state space model of the DAB is constructed.

[0083] In this embodiment, the topology structure diagram of the dual active bridge DC-DC converter is as shown in Figure 2 The dual active bridge DC-DC converter is composed of primary and secondary side H1 full bridge and H2 full bridge, high frequency transformer T, inductance L (the value L is the sum of all leakage inductances of the transformer), input side DC power supply V1 and output side load R (the voltage on both sides of the load R is the output voltage V2), and buffer capacitor C1 and C2. The switch tubes S1-S4 constitute the primary side H1 bridge of the transformer, and the switch tubes S5-S8 constitute the secondary side H2 bridge; the transformer ratio of the dual active bridge DC-DC converter is n:1 (i.e. the ratio of the number of turns of the primary side coil to the number of turns of the secondary side coil of the DAB), 、 are the AC side voltages of H1 and H2 bridges respectively, is the leakage inductance voltage, is the inductance current.

[0084] As shown in Figure 3 , the topology structure diagram of the dual active bridge DC-DC converter is simplified to obtain the simplified topology diagram of the dual active bridge DC-DC converter. Figure 3 In this embodiment, is the average current of the secondary side of the DAB, is the current of the capacitor of the secondary side of the DAB, is the output voltage of the DAB, is the output current of the DAB.

[0085] In this embodiment, according to the simplified topology diagram of the DAB, the following can be obtained:

[0086] ;

[0087] ;

[0088] ;

[0089] In the above formula, ​the average current of the secondary side of the DAB; the output current of the DAB; the output voltage of the DAB; the output current of the DAB; the output voltage of the DAB; the transmission power of the DAB;

[0090] the transmission power of the DAB; As a control variable, the state space model of the above DAB can be simplified as:

[0091] ;

[0092] ;

[0093] ;

[0094] In the above formula, is a control variable; is the transmission power of the DAB; is the capacity of the output voltage of the DAB; is the output voltage of the DAB; is the rate of change of the output voltage of the DAB; is the output current of the DAB;

[0095] is represented as a whole to reduce the complexity and computational amount of the controller.

[0096] S2, the difference between the expected output voltage of the DAB and the actual output voltage of the DAB is taken as a system error variable, and a sliding mode surface function is constructed.

[0097] Specifically, the system error variable is defined first, and the difference between the expected output voltage of the DAB and the actual output voltage of the DAB is taken as the system error variable:

[0098] ;

[0099] In the above formula, is a system error variable; is the expected value of the output voltage of the DAB; is the output voltage of the secondary side of the DAB;

[0100] The sliding mode surface of the sliding mode control is constructed as follows:

[0101] ;

[0102] In the above formula, is a sliding mode surface function; ​is a system error variable; is a desired value of the output voltage of the DAB; is the output voltage of the DAB; is a sliding mode control gain, and is a sliding mode control gain, and is a sliding mode control gain, and are all greater than zero.

[0103] In the present embodiment, the sliding mode control gain is used to control the error convergence speed, and an integral term is introduced into the sliding mode surface to eliminate the output voltage steady-state error.

[0104] Let the sliding mode surface function be , and the expression of the error be obtained:

[0105] ;

[0106] In the above formula, is the initial value of the error of the output voltage at steady state, is the base of the natural logarithm.

[0107] When , it is necessary to make , that is, the error . According to the above formula, and are both greater than 0, which can make the error converge to 0 within a finite time, and the convergence speed depends on the values of and . Therefore, it is necessary to set the sliding mode control gain and to be greater than zero.

[0108] S3. Constructing a sliding mode control law according to the state space model of the DAB and the sliding mode surface function.

[0109] Deriving the sliding mode surface function, we obtain:

[0110] ;

[0111] Since the output voltage reference value is a constant, its derivative is 0, and the state space model of the DAB is substituted into the above formula, the first-order derivative of the sliding mode surface function is obtained:

[0112] ;

[0113] ;

[0114] Since the sliding mode control generally adopts the equivalent sliding mode method, the control law The control law is composed of two parts, i.e., a model equivalent part and a switching control part.

[0115] ;

[0116] In the above formulae, is the model equivalent part, which brings the system state to the sliding surface; is the switching control part, which ensures that the system state does not leave the sliding surface.

[0117] For the model equivalent part of the sliding mode control law , it can be obtained according to the state space model of the DAB and the sliding surface function:

[0118] When the system state does not reach the sliding surface, the influence of the switching control amount is ignored, and at this time the model equivalent control amount is the controller input, and the first-order derivative of the sliding surface function is used to solve the control amount, and the model equivalent control amount is obtained:

[0119] ;

[0120] ;

[0121] In the above formulae, is the output current of the DAB; is the output voltage of the DAB; is the capacity of the secondary side capacitor, ; is the system error variable; is the expected value of the output voltage of the DAB; is the input voltage of the DAB; and are the sliding surface control gains, and are both greater than zero.

[0122] For the switching control part of the sliding mode control law , it can be obtained by improving the switching control part of the traditional sliding mode control law through the super-spiral algorithm.

[0123] The traditional switching control part is generally:

[0124] ;

[0125] Among them, is the switching control part gain; is the sign function.

[0126] Because the switching control part of the traditional sliding mode control is a sign function, and directly acts on the control variable, when the system state reaches the sliding mode surface, the control signal will begin to have discontinuity, thus leading to the generation of chattering phenomenon. This phenomenon will affect the control accuracy of the system, increase the energy consumption, and destroy the performance of the system.

[0127] To eliminate the discontinuous term of the traditional sliding mode control, a higher order sliding mode control can be used, such as super-spiral sliding mode control. Replacing the switching control part in the sliding mode control with the super-spiral algorithm can eliminate the discontinuous term. For the system, the general form of the super-spiral algorithm is:

[0128] ;

[0129] From the above formula, the super-spiral algorithm makes the control signal continuous, thus suppressing the generation of chattering phenomenon.

[0130] From the above process, the switching control part of the control law is:

[0131] ;

[0132] In the formula, 、 is the super-spiral control gain, , ; is the sliding mode surface function; is a sign function.

[0133] According to the model equivalent part of the sliding mode control law , the switching control part of the sliding mode control law , the sliding mode control law is obtained:

[0134] Based on , it can be obtained that:

[0135] ;

[0136] Among them, ;

[0137] In the above formula, is the sliding mode control rate; is the current of the load of the DAB; is the capacity of the secondary side capacitor, is the output voltage of the DAB, ; is the system error variable; is the expected value of the output voltage of the DAB; and is the sliding mode surface control gain, and are all greater than zero; , is the super-spiral control gain, , ; is the sliding surface function.

[0138] In this embodiment, in order to prove the stability of the above sliding mode control law, the Lyapunov function method is used for stability analysis:

[0139] Substitute the general form of the super-spiral algorithm expression into the derivative formula of the sliding surface function , and obtain:

[0140] ;

[0141] In order to facilitate analysis, the above formula is rewritten as:

[0142] ;

[0143] In the above formula, , , , is the super-spiral control gain.

[0144] The Lyapunov function is constructed as:

[0145] ;

[0146] When the Lyapunov function satisfies the following three conditions a, b, and c, the sliding mode control law has stability:

[0147] a, , ;

[0148] b, , ;

[0149] c, , .

[0150] According to the Lyapunov function formula, the Lyapunov function clearly satisfies conditions a and b, so it is necessary to prove that the Lyapunov function satisfies condition c.

[0151] Proving that the Lyapunov function satisfies condition c includes the following steps:

[0152] Define the system state variables as follows:

[0153] ;

[0154] because The system is differentiable everywhere before it converges to a steady point (s=0), utilizing... For state variables Differentiate:

[0155] ;

[0156] Simplifying the above system state variables, we obtain the simplified system state variable equations:

[0157] ;

[0158] In the above formula, ;

[0159] This leads to the Lyapunov function. quadratic matrix :

[0160] ;

[0161] In the above formula, It is a real symmetric matrix. ;

[0162] For simplified system state variable equations Taking the derivative, we get:

[0163] ;

[0164] In the above formula, ;

[0165] use To determine the Lyapunov function Does condition c meet?

[0166] when When it is a negative definite matrix, quadratic matrix It is also negatively definite at this time. The system is asymptotically stable;

[0167] like For a matrix to be negative definite, it must satisfy:

[0168] ;

[0169] It can be seen that if For a negative definite matrix, it must satisfy the following conditions: , ;

[0170] because , , so when , At that time, the Lyapunov function If condition c is satisfied, the system is asymptotically stable; therefore... , Constraints on sliding mode control law parameters.

[0171] S4. Obtain the input voltage and output voltage of the DAB, track the input voltage and output voltage of the DAB using the sliding mode control law, obtain the transmission power of the DAB, and normalize the transmission power of the DAB.

[0172] Specifically, in step S4, the transmission power of the DAB is normalized according to the following formula:

[0173] ;

[0174] ;

[0175] In the formula, For DAB's transmission power, The reference power is the maximum transmission power of the dual active bridge DC-DC converter when using single-phase shift. For per-unit transmission power, For frequency.

[0176] S5. Based on the standardized transmission power and the voltage conversion ratio K of the DAB, calculate the shift ratio of the DAB, and then control the DAB.

[0177] In this embodiment, when the DAB employs dual phase-shift control, the step of determining the DAB's phase shift ratio based on the per-unit transmission power and the DAB's voltage conversion ratio K includes the following steps:

[0178] Using the table below, along with the per-unit transmission power and the voltage conversion ratio K of DAB, and with the goal of optimizing return power, the corresponding inward shift ratio is calculated. Compared to relocation And based on the inward shift compared Compared to relocation Regulate the DAB.

[0179]

[0180] The sliding mode control method for dual active bridge DC-DC converters in this invention is applicable to various phase shifting modes of DABs, such as single phase shifting, extended phase shifting, and dual phase shifting. It can adapt to different phase shifting modes, exhibiting strong adaptability. Furthermore, it can be combined with optimization schemes for various objectives to evolve into a multi-objective optimization control strategy.

[0181] Taking dual phase-shift control as an example, the control flowchart for controlling a dual active bridge DC-DC converter using the super-spiral sliding mode control method described in this invention, combined with return power optimization control, is as follows: Figure 4 As shown, the control method in this invention is verified using a simulation platform:

[0182] First, set the circuit simulation parameters and the return power optimization controller parameters.

[0183] The simulation parameters of the dual active bridge DC-DC converter circuit are shown in Table 1 below:

[0184]

[0185] Table 1: Simulation Circuit Parameters

[0186] A dual-phase-shifting return power optimization scheme is adopted, which optimizes the system return power through a return power optimization controller: the inputs are the voltage conversion ratio K and the per-unit value of the transmission power. The output consists of dual phase shifts, inner and outer phase shifts, D1 and D2. By sampling and calculating circuit parameters, the power range is determined, and the optimal phase shift is calculated to control the circuit.

[0187] The specific parameters of the return power optimization controller are shown in Table 2 below:

[0188]

[0189] Table 2: Parameters of the Return Power Optimization Controller

[0190] In Table 2, and Compared to the calculated optimal shift, This is the minimum return power at this time.

[0191] When DAB employs dual phase-shift control, it transmits power per unit value. Compared to the optimal inward and outward shifts calculated in Table 2 above. and .

[0192] For the super-spiral sliding mode control method for a dual active bridge DC-DC converter described in this invention, the control quantity is the transmission power P. The transmission power P is normalized to obtain the normalized transmission power. Using super-helical sliding mode control as the output voltage loop, the output is standardized transmission power. The per-unit transmission power The voltage conversion ratio K of the sampled DAB is input to the return power optimization controller to obtain the optimal inner and outer shift ratios, thereby controlling the dual active bridge DC-DC converter circuit.

[0193] After setting the circuit simulation parameters and the return current power optimization controller parameters, a simulation test was conducted. The test results are as follows:

[0194] Figure 5 This is a comparison of simulation waveforms between the super spiral sliding mode control (STSMC) and the traditional sliding mode control (SMC) provided in this embodiment of the invention. Figure 5 (Left) is the simulation waveform of traditional sliding mode control (SMC), such as... Figure 5 As shown on the left, when the output voltage V2 is not close to the reference value of 30V, that is, when the system is not close to the stable point, the switching control section of the SMC... It remains continuous, but as it approaches a stable point, the switching control part of the traditional sliding mode control... Generally , because The presence of this signal begins to exhibit discontinuity, causing the control quantity to chatter, resulting in a large V2 ripple (0.18V). Figure 5 (Right) is a simulation waveform diagram of the Superspiral Sliding Mode Control (STSMC) described in this invention. Figure 5 As shown on the right, since STSMC eliminates the discontinuity of SMC, the system exhibits continuity whether it is close to the steady point or not, which effectively solves the chattering phenomenon and also significantly reduces the V2 ripple (0.035V).

[0195] Figure 6 This is a comparison chart of the output voltage experimental waveforms of Super Spiral Sliding Mode Control (STSMC), PI control, and conventional Sliding Mode Control (SMC) provided in this embodiment of the invention when the output voltage reference value changes (the given value changes abruptly from 30V to 40V). Figure 7 This is a comparison diagram of the output voltage experimental waveforms of super spiral sliding mode control (STSMC), PI control, and conventional sliding mode control (SMC) provided by embodiments of the present invention when the load changes abruptly (the output load changes abruptly from 10Ω to 20Ω). Figure 8 This is a comparison chart of the output voltage experimental waveforms of Superhelical Sliding Mode Control (STSMC), PI control, and conventional Sliding Mode Control (SMC) provided in this embodiment of the invention when the input voltage changes abruptly (from 50V to 60V).

[0196] As can be seen from the simulation results above, the dynamic response time of both traditional sliding mode control and the super spiral control described in this invention is within 20ms and the overshoot is within 1V, which are much smaller than PI control. Moreover, the super spiral sliding mode control described in this invention can achieve zero overshoot.

[0197] In summary, this invention provides a sliding mode control method for a dual active bridge DC-DC converter. This sliding mode control method can achieve fast and smooth switching of the DAB converter under various system operating conditions, and its output voltage overshoot and response time are significantly less than those of PI control. In addition, this sliding mode control method adopts a super-spiral algorithm, which, compared with traditional PI control and traditional sliding mode control, can significantly improve the dynamic performance of the system under sudden input voltage changes, load changes, and reference voltage changes. At the same time, it can significantly suppress the chattering phenomenon of traditional sliding mode control, solving the dynamic response problem of dual active bridge DC-DC converters (DAB) in DC microgrids under system disturbances. Furthermore, this sliding mode control method is applicable to DABs using single phase shift, extended phase shift, and dual phase shift modes, and can be combined with various objective optimization schemes to evolve into a multi-objective optimization control strategy.

[0198] Based on the above method, this embodiment will further describe the sliding mode control system of the dual active bridge DC-DC converter from the perspective of the sliding mode control system of the dual active bridge DC-DC converter. The sliding mode control system of the dual active bridge DC-DC converter can be implemented as an independent entity or integrated into an electronic device, such as a terminal.

[0199] like Figure 9 As shown, a sliding mode control system for a dual active bridge DC-DC converter is disclosed. The system is used to execute the sliding mode control method for the dual active bridge DC-DC converter described in the above embodiments. The system includes:

[0200] The first building module is used to construct the state-space model of DAB using the transmission power of DAB as the control variable.

[0201] The state-space model of the DAB is as follows:

[0202] ;

[0203] ;

[0204] ;

[0205] In the above formula, To control the quantity, For DAB's transmission power, This refers to the capacitance of the secondary capacitor. The load voltage of DAB, For the output voltage of DAB, This is the output current of the DAB.

[0206] The second building module is used to construct the sliding surface function using the difference between the expected output voltage of the DAB and the actual output voltage of the DAB as the system error variable.

[0207] The sliding surface function is:

[0208] ;

[0209] In the above formula, For systematic error variables, The expected output voltage of the DAB is... The output voltage of the DAB. and To control the gain of the sliding surface, and All are greater than zero.

[0210] The third construction module is used to construct the sliding mode control law based on the state space model and sliding surface function of the DAB.

[0211] Setting the sliding mode control law based on the state-space model of DAB and the sliding mode surface function includes the following steps:

[0212] Based on the state-space model of DAB and the sliding surface function, the equivalent part of the sliding mode control law is obtained. ;

[0213] The switching control part of the sliding mode control law is obtained based on the superspiral algorithm. ;

[0214] Based on the model equivalent part of the sliding mode control law Switching control section of sliding mode control law Obtain the sliding mode control law :

[0215] .

[0216] Specifically, the equivalent part of the sliding mode control law is obtained based on the state-space model and sliding surface function of the DAB. This includes the following steps:

[0217] Substituting the state-space model of DAB into the sliding surface expression and differentiating the sliding surface function, we obtain the first derivative of the sliding surface function:

[0218] ;

[0219] Let the first derivative of the sliding surface function Solving for the equivalent part of the control law model yields the solution. :

[0220] ;

[0221] ;

[0222] In the above formula, The output current of the DAB, The output voltage of the DAB. This refers to the capacitance of the secondary capacitor. , For systematic error variables, The expected output voltage of the DAB is... The input voltage of DAB, For systematic error variables, and To control the gain of the sliding surface, and All are greater than zero.

[0223] The switching control part of the sliding mode control law is obtained based on the superspiral algorithm. Includes the following steps:

[0224] The switching control part of the control law is obtained by combining the superspiral algorithm and the general form of the switching control part of the control law. :

[0225] ;

[0226] In the formula, , To control the gain of the superspiral control, , , For sliding surface functions.

[0227] The output module uses the sliding mode control law to track the output voltage of the DAB, obtains the transmission power of the DAB, and normalizes the transmission power of the DAB.

[0228] The return power optimization control module is used to solve the shift ratio of DAB based on the per-unit transmission power and the voltage conversion ratio K of DAB.

[0229] The voltage conversion ratio of the DAB The following formula is used to calculate:

[0230] ;

[0231] In the formula, The input voltage of DAB, The output voltage of the DAB. This is the ratio of the number of turns in the primary coil to the number of turns in the secondary coil of the DAB.

[0232] Additionally, please see Figure 10 , Figure 10 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. For example... Figure 10 As shown, the electronic device includes a memory and a processor. The memory is used to store computer program code and transmit the computer program code to the processor. The processor is used to execute the sliding mode control method of the dual active bridge DC-DC converter as described in Embodiment 1 according to the instructions in the computer program code.

[0233] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be performed by instructions, or by instructions controlling related hardware. These instructions can be stored in a computer-readable storage medium and loaded and executed by a processor.

[0234] This invention also provides a storage medium storing multiple instructions that, when executed by a processor, implement the steps of the sliding mode control method for the dual active bridge DC-DC converter provided in the above embodiments. Since the instructions stored in this storage medium can execute the steps of the sliding mode control method for the dual active bridge DC-DC converter provided in this invention, the beneficial effects achievable by any of the sliding mode control methods for the dual active bridge DC-DC converter provided in this invention can be realized, as detailed in the foregoing embodiments, and will not be repeated here.

Claims

1.A method for controlling a dual active bridge (DAB) DC-DC converter, comprising the following steps: S1, constructing a state space model of the DAB by taking a transmission power of the DAB as a control variable; S2, constructing a sliding mode surface function by taking a difference between a desired output voltage of the DAB and an actual output voltage of the DAB as a system error variable; S3, constructing a sliding mode control law according to the state space model of the DAB and the sliding mode surface function; S4, tracking the output voltage of the DAB by using the sliding mode control law to obtain the transmission power of the DAB, and normalizing the transmission power of the DAB; S5, solving a phase shift ratio of the DAB according to the normalized transmission power and a voltage conversion ratio K of the DAB. In the step S3, the sliding mode control law is constructed according to the state space model of the DAB and the sliding mode surface function, and the step includes the following steps: 2.The method according to claim 1, wherein the state space model of the DAB is According to the state space model of the DAB, a model equivalent part of a sliding mode control law is obtained by a sliding mode surface function ; Switching control part of sliding mode control law acquired according to super-spiral algorithm ; a model equivalent part of the sliding mode control law a switching control part of the sliding mode control law obtaining the sliding mode control law : ； In the step S3, the switching control part of the sliding mode control law is obtained according to the super-twisting algorithm comprising the steps of: The switching control part of the control law is obtained in combination with the supercoiling algorithm and the general form of the switching control part of the control law : ； In the above equation, , is the super-twisting control gain, , ; is the sliding surface function. 3.The method according to claim 2, wherein the sliding mode surface function is 4.The method according to claim 3, wherein the state space model of the DAB is substituted into a sliding mode surface expression, and a first derivative of the sliding mode surface function is obtained by differentiating the sliding mode surface function. ； ； ； In the above equation, is a control quantity; is a transmission power of the DAB; is a capacity of the secondary capacitor; is an output voltage of the DAB; is a rate of change of the output voltage; is an output current of the DAB. 5.The method according to claim 1, wherein the phase shift ratio of the DAB is solved according to the normalized transmission power and the voltage conversion ratio K of the DAB. 6.A sliding mode control system for a dual active bridge (DAB) DC-DC converter, comprising: ； In the above equations, is a system error variable, ; is the desired output voltage of the DAB; is the output voltage of the DAB; and is a sliding mode surface control gain, and are both greater than zero. a first constructing module, configured to construct a state space model of the DAB by taking a transmission power of the DAB as a control variable; In the step S3, a model equivalent part of the sliding mode control law is obtained according to the state space model of the DAB, a sliding mode surface function, etc. comprising the steps of: a second constructing module, configured to construct a sliding mode surface function by taking a difference between a desired output voltage of the DAB and an actual output voltage of the DAB as a system error variable; ； Let the first derivative of the sliding surface function , the model equivalent part of the control law is obtained by solving : ； In the above equations, is the output current of the DAB; is the output voltage of the DAB, is the capacitance of the secondary side capacitor, is the system error variable, is the expected value of the output voltage of the DAB; is the input voltage of the DAB; is the sliding mode surface control gain; are all greater than zero.​​​​ a third constructing module, configured to construct a sliding mode control law according to the state space model of the DAB and the sliding mode surface function; In the step S5, the voltage conversion ratio of the DAB The calculation is made according to the following formula: ； In the formula, is the input voltage of the DAB; is the output voltage of the DAB; is the turns ratio of the primary coil to the secondary coil of the DAB. an output module, configured to track the output voltage of the DAB by using the sliding mode control law to obtain the transmission power of the DAB, and to normalize the transmission power of the DAB; a solving module, configured to solve a phase shift ratio of the DAB according to the normalized transmission power and a voltage conversion ratio K of the DAB. In the step of constructing the sliding mode control law according to the state space model of the DAB and the sliding mode surface function, the step includes the following steps: 7.The system according to claim 6, wherein the state space model of the DAB is the sliding mode surface function is the step of constructing the sliding mode control law according to the state space model of the DAB and the sliding mode surface function includes the following steps: 8.The system according to claim 7, wherein the state space model of the DAB is ​ According to the state space model of the DAB, a model equivalent part of a sliding mode control law is obtained according to a sliding mode surface function ; Switching control part of sliding mode control law acquired according to super-spiral algorithm ; a model equivalent part of the sliding mode control law a switching control part of the sliding mode control law obtaining the sliding mode control law : ； The switching control part of the sliding mode control law is obtained according to the super-spiral algorithm comprising the steps of: The switching control part of the control law is obtained in combination with the supercoiling algorithm and the general form of the switching control part of the control law : ； In the above equation, , is the super-twisting control gain, , ; is the sliding surface function. ​ ​ ； ； ； In the above equation, is a control amount; is a transmission power of the DAB; is a capacity of the secondary capacitor; is an output voltage of the DAB; is a rate of change of the output voltage; is an output current of the DAB; ​ ； In the above equation, is a system error variable, ; is the desired output voltage of the DAB; is the output voltage of the DAB; and is a sliding mode surface control gain, and are both greater than zero; ​ According to the state space model of the DAB, a model equivalent part of a sliding mode control law is obtained according to a sliding mode surface function : ； In the above equation, is the output current of the DAB; is the output voltage of the DAB, is the capacitance of the secondary capacitor, ; is the system error variable, , is the expected value of the output voltage of the DAB; is the input voltage of the DAB; and is the sliding mode surface control gain; and are both greater than zero; a model equivalent part of the sliding mode control law a switching control part of the sliding mode control law obtaining the sliding mode control law : ； In the above equation, is the sliding mode control law; is the current of the load of the DAB; is the capacitance of the secondary capacitor, is the output voltage of the DAB, ; is the system error variable; and is the sliding mode surface control gain; and are both greater than zero; , is the super-spiral control gain, , ; is the sliding mode surface function. ​ The voltage conversion ratio of the DAB The calculation formula is: ； In the formula, is the input voltage of the DAB, is the output voltage of the DAB, is the ratio of the number of turns of the primary coil to the number of turns of the secondary coil of the DAB.

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