Pulse charging method and system for electric vehicle

Abstract

The invention provides a pulse charging method for an electric vehicle, which comprises the following steps of: acquiring control mode data and secondary side reference data of a DAB converter, and acquiring a phase-shift ratio and access data at the current k moment; wherein the control mode data comprises a voltage mode and a power mode; the input and output data comprises an input voltage, an output current and an output voltage; determining a phase shift ratio prediction set based on the control mode data, the secondary side reference data, the phase shift ratio and the access data; predicting the output voltage at the k + 2 moment according to randomly selected preset number of elements in the phase-shift ratio prediction set, and generating a data prediction set; determining an optimal phase shift ratio based on the control mode data and the data prediction set; according to the optimal phase-shift ratio, a pulse generation module is controlled to generate four paths of complementary square wave signals to control a switch tube of a DAB converter to be switched on, and charging control over the electric vehicle is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicle charging, and in particular to a pulse charging method and system for an electric vehicle. Background Art

[0002] There are potential safety risks in the charging process of electric vehicles, so it is necessary to conduct in-depth research on electric vehicle charging strategies to improve the comprehensive performance of the power supply.

[0003] In recent years, DAB converter topology has been widely used in emerging energy conversion systems such as energy storage and electric vehicles due to its many advantages such as high power density, bidirectional energy flow capability, electrical isolation and easy soft switching. DAB converters using advanced charging methods can provide electric vehicles with reliable power supply. However, the traditional constant current constant voltage (CC-CV) electric vehicle charging method lacks flexibility during the charging process, and its control parameters are limited, including only CC level current, CV level voltage and cut-off current. In addition, waveform-based charging methods, such as multi-stage constant current (MS-CC) and multi-stage charging based on SOC, although improving charging performance to a certain extent, still face problems such as extended charging time and increased ohmic loss. In order to solve the problems existing in the above charging methods, the charging method of the present invention is proposed as an effective strategy to solve the above problems. Pulse charging eliminates polarization through short-term relaxation, increases acceptable current, inhibits dendrite growth, slows down capacity decay, and accelerates ion diffusion, thereby improving charging performance. However, the above charging method of the present invention has poor anti-interference ability, that is, when there is an instantaneous change in load current and voltage fluctuation on the grid side, it may cause the output voltage of the pulse power supply to fluctuate, thereby affecting the normal charging process. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a pulse charging method and system for an electric vehicle, which solves the problems in the prior art.

[0005] According to an embodiment of the present invention, a pulse charging method for an electric vehicle includes:

[0006] Obtain the control mode data and secondary side reference data of the DAB converter, and collect the phase shift ratio D at the current time k old and input and output data; wherein the control mode data includes voltage mode and power mode; the input and output data includes: input voltage, output current and output voltage;

[0007] Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p ;

[0008] According to the phase shift ratio prediction set D of the preset number of randomly selected p The elements in predict the output voltage at time k+2 to generate a data prediction set;

[0009] Determine the optimal phase shift ratio D based on the control mode data and the data prediction set a ;

[0010] According to the optimal phase shift ratio D a The control pulse generation module generates 4 complementary square wave signals to control the switch tube of the DAB converter to conduct, thereby completing the charging control of the electric vehicle.

[0011] As an embodiment of the present invention, the secondary reference data includes: a secondary side output voltage reference value V LV_ref and the secondary output current reference value I LV_ref ;

[0012] Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p ,include:

[0013] Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p , phase shift ratio prediction set D p As shown below:

[0014] D p ={D old -nΔ adp , …, D old , …, D old +nΔ adp}

[0015] Among them, Δ adp is the adaptive step size, adaptive step size Δ adp The calculation formula is as follows:

[0016]

[0017] Wherein, S=0 indicates that the control mode data is voltage mode, S=1 indicates that the control mode data is power mode, λ 1 and λ 2 are coefficients related to dynamic performance, V Δ is the system output voltage deviation value, I Δ is the system output current deviation value, the system output voltage deviation value V Δ The calculation formula is as follows:

[0018]

[0019] Among them, V m Indicates the saturation voltage, V LV [k] represents the output voltage at the current time k;

[0020] System output current deviation value I Δ The calculation formula is as follows:

[0021]

[0022] Among them, I m Indicates the saturation current, I LV [k] represents the output current at the current moment k.

[0023] As an embodiment of the present invention, a preset number of phase shift ratio prediction sets D are randomly selected. p The elements in predict the output voltage at time k+2 and generate an output data prediction set, including:

[0024] Randomly obtain a phase shift ratio prediction set D p The elements in calculate the output current I at time k+1 LV [k+1], the calculation formula is as follows:

[0025]

[0026] Where D represents the randomly selected phase shift ratio prediction set D p The elements in the equation are: N represents the ratio of the transformer primary side to the secondary side, f s Indicates the system switching frequency, L p Indicates the inductance value, V HV represents the input voltage at the current time k;

[0027] Based on the output current I at time k+1 LV [k+1] Calculate the output voltage V at time k+1 LV [k+1], the calculation formula is as follows:

[0028]

[0029] Among them, I load [k] is the load current sampling value, C LV is the capacitance on the secondary side of the DAB converter;

[0030] Based on the output voltage V at time k+1 LV [k+1] Calculate the output voltage V at time k+2 LV [k+2], the calculation formula is as follows:

[0031]

[0032] Among them, I LV_comp [k] is the difference between the observed current at time k and the predicted value, calculated as follows:

[0033] I LV_comp [k] = I LV_r [k]-I LV [k]

[0034] Among them, i LV_r [k] is the observed current of the DAB converter, calculated as follows:

[0035] I LV_r [k] = 2I load [k]+C LV f s (V LV [k]-V LV [k-1])

[0036] Among them, V LV [k-1] is the output voltage at time k-1;

[0037] Repeat the above steps for a preset number of times to calculate the output voltage V at a certain k+2 time LV The output current I at [k+2] and k+1 LV [k+1], get the data prediction set.

[0038] As an embodiment of the present invention, the optimal phase shift ratio D is determined based on the control mode data and the data prediction set. a ,include:

[0039] If the control mode data is voltage mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset first cost function. a ;

[0040] If the control mode data is a power mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset second cost function. a .

[0041] As an embodiment of the present invention, if the control mode data is a voltage mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset first cost function. a ,include:

[0042] If the control mode data is voltage mode, obtain an element in the data prediction set and convert the output voltage V at time k+2 in the element LV [k+2] is substituted into the first preset cost function for calculation, and the first cost value ct is calculated. 1 , ct 1 The calculation formula is as follows:

[0043] ct 1 =α 1 G 1 +α 2 G 2

[0044] Among them, α 1 and α 2 The objective function G is 1 and G 2 The weight factor of the objective function G 1 and G 2 The calculation formula is as follows:

[0045]

[0046] Repeat the above steps until all elements in the data prediction set are traversed to obtain the first cost set;

[0047] Select the output voltage V at time k+2 with the smallest first cost value in the first cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a .

[0048] As an embodiment of the present invention, if the control mode data is a power mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset second cost function. a ,include:

[0049] If the control mode data is power mode, obtain an element in the data prediction set and convert the output voltage V at time k+2 in the element LV The output current I at [k+2] and k+1 LV [k+1] is substituted into the second preset cost function for calculation to obtain the second cost value ct 2 , ct 2 The calculation formula is as follows:

[0050] ct 2 =α 3 G 3

[0051] G 3 =(V LV_ref I LV_ref -V LV [k+2]·I LV [k+1]) 2

[0052] Among them, α 3 Denotes the objective function G 3 The weight factor of

[0053] Repeat the above steps until all elements in the data prediction set are traversed to obtain the second cost set;

[0054] Select the output voltage V at time k+2 with the smallest second cost value in the second cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a .

[0055] A pulse charging system for an electric vehicle, used to execute the pulse charging method for an electric vehicle, comprising: a DAB converter and a control module, wherein the input end of the DAB converter is connected to a power grid, and the output end of the DAB converter is connected to an energy storage battery, and is used to charge the energy storage battery;

[0056] The control module includes:

[0057] The voltage sampling module is used to collect the voltages at the input and output ends of the DAB converter to obtain the input voltage and output voltage;

[0058] The current sampling module is used to collect the output current and load current of the DAB converter to obtain the output current and load current sampling values;

[0059] The control unit is electrically connected to the voltage acquisition module and the current acquisition module respectively, and is used to determine the optimal phase shift ratio D according to the input voltage, output voltage and output current. a ;

[0060] The pulse generating module is electrically connected to the control unit and is used to generate a pulse according to the optimal phase shift ratio D a Generate 4 complementary square wave signals to control the switching tubes of the DAB converter.

[0061] Compared with the prior art, the present invention has the following beneficial effects: when there is an instantaneous change in load current and a voltage fluctuation on the grid side, four complementary square wave signals are generated by the detected input and output data to control the conduction of the switch tube of the DAB converter, adjust the conduction condition of the switch tube of the DAB converter, improve the anti-interference ability of the DAB converter, and avoid fluctuations in the output voltage of the pulse power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is a schematic flow chart of a charging method according to an embodiment of the present invention;

[0063] Figure 2 is a schematic diagram of a charging system according to another embodiment of the present invention;

[0064] Figure 3 A flow chart of weighting factor design based on artificial neural network according to another embodiment of the present invention;

[0065] Figure 4A weighted factor result diagram based on an artificial neural network according to another embodiment of the present invention;

[0066] Figure 5 A frequency domain comparison diagram of output impedance when a DAB converter adopts PI, VDPC, and the charging method of the present invention according to another embodiment of the present invention;

[0067] Figure 6 A time domain comparison diagram of load interference suppression performance when a DAB converter adopts PI, VDPC, and the charging method of the present invention according to another embodiment of the present invention;

[0068] Figure 7 A frequency domain comparison diagram of input voltage interference suppression performance when a DAB converter according to another embodiment of the present invention adopts PI, VDPC, and the charging method of the present invention;

[0069] Figure 8 A time domain diagram of input voltage interference suppression performance when a DAB converter according to another embodiment of the present invention adopts PI, VDPC, and the charging method of the present invention;

[0070] Fig. 9 A dynamic performance comparison diagram of a DAB converter according to another embodiment of the present invention when using PI;

[0071] Fig.10 This is a dynamic performance comparison diagram of another embodiment of the present invention when DAB conversion adopts the charging method of the present invention. DETAILED DESCRIPTION

[0072] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0073] like Figure 1 As shown, the embodiment of the present invention provides a pulse charging method and system for an electric vehicle, including:

[0074] S1: Obtain the control mode data and secondary side reference data of the DAB converter, and collect the phase shift ratio D at the current time k old and input and output data; wherein the control mode data includes voltage mode and power mode; the input and output data includes: input voltage, output current and output voltage;

[0075] S2: Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p ;

[0076] S3: randomly select a preset number of phase shift ratio prediction sets D p The elements in predict the output voltage at time k+2 to generate a data prediction set;

[0077] S4: Determine the optimal phase shift ratio D based on the control mode data and the data prediction set a ;

[0078] S5: According to the optimal phase shift ratio D a The control pulse generation module generates 4 complementary square wave signals to control the switch tube of the DAB converter to conduct, thus completing the charging control of the electric vehicle;

[0079] The working principle of the above technical solution is: during the charging process, the control mode data of the DAB converter and the secondary side reference data are obtained to collect the phase shift ratio D at the current time k. old and input and output data; wherein the control mode data includes voltage mode and power mode; the input and output data include: input voltage, output current and output voltage; then determine the phase shift ratio prediction set D according to the above acquired data p , and then predict the output voltage at time k+2 corresponding to the phase shift ratio element by selecting a preset number of elements in the phase shift ratio prediction set, and generate a data prediction set through multiple phase shift ratio elements; then determine the optimal phase shift ratio D based on the control mode data and the data prediction set a ; Finally, according to the optimal phase shift ratio D a The control pulse generation module generates 4 complementary square wave signals (the 4 complementary square wave signals are Figure 2 g in 1 , g 2 , g 3 and g 4 ) Control the switch tube of the DAB converter to conduct, and complete the charging control and regulation of the electric vehicle;

[0080] The beneficial effects of the above technical solution: Through the above technical solution, when there are instantaneous changes in load current and voltage fluctuations on the grid side, 4 complementary square wave signals are generated by the detected input and output data to control the conduction of the switch tube of the DAB converter, adjust the conduction of the switch tube of the DAB converter, improve the anti-interference ability of the DAB converter, and avoid fluctuations in the output voltage of the pulse power supply.

[0081] In one embodiment, the secondary reference data includes: a secondary side output voltage reference value V LV_ref and the secondary output current reference value I LV_ref ;

[0082] Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p ,include:

[0083] S2: Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output datap , phase shift ratio prediction set D p As shown below:

[0084] D p ={D old -nΔ adp , …, D old , …, D old +nΔ adp}

[0085] Among them, Δ adp is the adaptive step size, adaptive step size Δ adp The calculation formula is as follows:

[0086]

[0087] Wherein, S=0 indicates that the control mode data is voltage mode, S=1 indicates that the control mode data is power mode, λ 1 and λ 2 are coefficients related to dynamic performance, V Δ is the system output voltage deviation value, I Δ is the system output current deviation value, the system output voltage deviation value V Δ The calculation formula is as follows:

[0088]

[0089] Among them, V m Indicates the saturation voltage, V LV [k] represents the output voltage at the current time k;

[0090] System output current deviation value I Δ The calculation formula is as follows:

[0091]

[0092] Among them, I m Indicates the saturation current, I LV [k] represents the output current at the current moment k;

[0093] The working principle and beneficial effects of the above technical solution are as follows: V is calculated by obtaining the secondary side reference data and the input and output data. Δ and I Δ , and then calculate the adaptive step size Δ based on the control mode data adp , then based on the phase shift ratio D at the current k moment old Determine the phase shift ratio prediction set; wherein the secondary side reference data includes: the secondary side output voltage reference value V LV_ref and the secondary output current reference value I LV_ref , or the secondary side output voltage reference value VLV_ref And the secondary side output power reference value P LV_ref , when the staff sets the secondary side reference data to or the secondary side output voltage reference value V LV_ref And the secondary side output power reference value P LV_ref When I LV_ref .

[0094] In one embodiment, a preset number of phase shift ratio prediction sets D are randomly selected. p The elements in predict the output voltage at time k+2 and generate an output data prediction set, including:

[0095] S31: Randomly obtain a phase shift ratio prediction set D p The elements in calculate the output current I at time k+1 LV [k+1], the calculation formula is as follows:

[0096]

[0097] Where D represents the randomly selected phase shift ratio prediction set D p The elements in the equation are: N represents the ratio of the transformer primary side to the secondary side, f s Indicates the system switching frequency, L p Indicates the inductance value, V HV represents the input voltage at the current time k;

[0098] S32: Output current I based on time k+1 LV [k+1] Calculate the output voltage V at time k+1 LV [k+1], the calculation formula is as follows:

[0099]

[0100] Among them, I load [k] is the load current sampling value, C LV is the capacitance on the secondary side of the DAB converter;

[0101] S33: Based on the output voltage V at time k+1 LV [k+1] Calculate the output voltage V at time k+2 LV [k+2], the calculation formula is as follows:

[0102]

[0103] Among them, I LV_comp [k] is the difference between the observed current at time k and the predicted value, calculated as follows:

[0104] I LV_comp [k] = ILV_r [k]-I LV [k]

[0105] Among them, i LV_r [k] is the observed current of the DAB converter, calculated as follows:

[0106] I LV_r [k] = 2I load [k]+C LV f s (V LV [k]-V LV [k-1])

[0107] Among them, V LV [k-1] is the output voltage at time k-1;

[0108] S34: Repeat the above steps S31-S33 for a preset number of times to calculate the output voltage V at a certain k+2 time LV The output current I at [k+2] and k+1 LV [k+1], get the data prediction set;

[0109] The working principle and beneficial effects of the above technical solution are as follows: The output voltage V at time k+2 is predicted by calculating the elements in the phase shift ratio prediction set. LV The output current I at [k+2] and k+1 LV [k+1], and then continue to loop to obtain the data prediction set; among them, an element in the data prediction set includes the selected phase shift ratio and its corresponding calculated output voltage V at time k+2 LV The output current I at [k+2] and k+1 LV [k+1]; and V LV [k-1] is calculated by discretizing the capacitor voltage differential scheme. The discretized calculation formula is as follows:

[0110] C LV ·[V LV (k)-V LV (k-1)]=I LV (k)

[0111] Among them, C LV is the capacitance on the secondary side of the DAB converter.

[0112] In one embodiment, the optimal phase shift ratio D is determined based on the control mode data and the data prediction set. a ,include:

[0113] S41: If the control mode data is a voltage mode, determine the optimal phase shift ratio D based on the data prediction set and a preset first cost function a;

[0114] S42: If the control mode data is a power mode, determine the optimal phase shift ratio D based on the data prediction set and a preset second cost function a ;

[0115] The working principle and beneficial effects of the above technical solution are as follows: the preset cost function to be selected is determined by the control mode data, that is, if the control mode data is a voltage mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset first cost function. a If the control mode data is a power mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset second cost function a .

[0116] In one embodiment, if the control mode data is a voltage mode, the optimal phase shift ratio D is determined based on the data prediction set and a preset first cost function. a ,include:

[0117] S411: If the control mode data is a voltage mode, obtain an element in the data prediction set and convert the output voltage V at time k+2 in the element LV [k+2] is substituted into the first preset cost function for calculation, and the first cost value ct is calculated. 1 , ct 1 The calculation formula is as follows:

[0118] ct 1 =α 1 G 1 +α 2 G 2

[0119] Among them, α 1 and α 2 The objective function G is 1 and G 2 The weight factor of the objective function G 1 and G 2 The calculation formula is as follows:

[0120]

[0121] S412: repeat the above step S411 until all elements in the data prediction set are traversed to obtain a first cost set;

[0122] S413: Select the output voltage V at time k+2 with the smallest first cost value in the first cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a ;

[0123] The working principle and beneficial effects of the above technical solution are as follows: if the control mode data is a voltage mode, an element in the data prediction set is obtained, and the output voltage V at time k+2 in the element is LV [k+2] is substituted into the first preset cost function for calculation, and the first cost value ct is calculated. 1 ; Repeat the above calculation process until all elements in the data prediction set are traversed to obtain the first cost set; finally, select the output voltage V at time k+2 with the smallest first cost value in the first cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a , which is the phase shift ratio of the next cycle;

[0124] like Figure 3 and Figure 4 As shown in Figure 1, in order to optimize the MPC performance, an artificial neural network-based method is used to adjust the weight factor in MPC. Based on the ANN network model, the weight factor is preferably set to α 1 =1 and α 2 =4.

[0125] In one embodiment, if the control mode data is a power mode, the optimal phase shift ratio D is determined based on the data prediction set and a preset second cost function. a ,include:

[0126] S421: If the control mode data is the power mode, obtain an element in the data prediction set and convert the output voltage V at time k+2 in the element LV The output current I at [k+2] and k+1 LV [k+1] is substituted into the second preset cost function for calculation to obtain the second cost value ct 2 , ct 2 The calculation formula is as follows:

[0127] ct 2 =α 3 G 3

[0128] G 3 =(V LV_ref I LV_reff -V LV [k+2]·I LV [k+1]) 2

[0129] Among them, α 3 Denotes the objective function G 3 The weight factor of

[0130] S422: Repeat the above steps until all elements in the data prediction set are traversed to obtain a second cost set;

[0131] S423: Select the output voltage V at time k+2 with the smallest second cost value in the second cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a .

[0132] The working principle and beneficial effects of the above technical solution: If the control mode data is the power mode, obtain an element in the data prediction set, and convert the output voltage V at the k+2 moment in the element LV The output current I at [k+2] and k+1 LV [k+1] is substituted into the second preset cost function for calculation to obtain the second cost value ct 2 ; Repeat the above calculation process until all elements in the data prediction set are traversed to obtain the second cost set; finally select the output voltage V at time k+2 with the smallest second cost value in the second cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a , which is the phase shift ratio of the next cycle; among them, the weight factor α 3 The preferred setting is 1.

[0133] On the other hand, an embodiment of the present invention further provides a pulse charging system for an electric vehicle, comprising: a DAB converter and a control module, wherein the input end of the DAB converter is connected to a power grid, and the output end of the DAB converter is connected to an energy storage battery, for charging the energy storage battery;

[0134] The control module includes:

[0135] The voltage sampling module is used to collect the voltages at the input and output ends of the DAB converter to obtain the input voltage and output voltage;

[0136] The current sampling module is used to collect the output current and load current of the DAB converter to obtain the output current and load current sampling values;

[0137] The control unit is electrically connected to the voltage acquisition module and the current acquisition module respectively, and is used to determine the optimal phase shift ratio D according to the input voltage, output voltage and output current. a ;

[0138] The pulse generating module is electrically connected to the control unit and is used to generate a pulse according to the optimal phase shift ratio D a Generate 4 complementary square wave signals to control the conduction of the switch tube of the DAB converter;

[0139] In one embodiment, the present invention also provides verification experimental data of the above-mentioned pulse charging method and system for electric vehicles, as follows:

[0140] The proposed PPM-MPC controller was evaluated in time and frequency domains using the simulation software PLECS / Simulink.

[0141] The output impedance of the DAB converter is selected as an indicator for evaluating the load's ability to resist current interference. In the simulation, the output impedance of the DAB converter controlled by PI, VDCP, and the charging method of the present invention is scanned and simulated using the describing function method; Figure 5 , Figure 6 The output impedance frequency domain comparison and load interference suppression performance time domain comparison of the DAB converter when using PI, VDPC and the charging method of the present invention are shown respectively;

[0142] like Figure 5 As shown, the charging method of the present invention can maintain a low output impedance of the DAB converter in a wide frequency range until it reaches 0 dB at 1 kHz; on the contrary, when the PI controller and VDPC are used, the output impedance rises above 0 dB at 40 and 100 Hz respectively;

[0143] By observing the image, it can be found that compared with the PI and VDPC schemes, the output impedance of the charging method of the present invention is the smallest when the frequency is less than 500 Hz, which verifies that the power supply controlled by the charging method of the present invention has a stronger ability to resist load current interference.

[0144] It is also crucial to evaluate the power supply input voltage interference suppression capability, and the input voltage interference suppression performance of the DAB converter using PI, VDPC, and the charging method of the present invention is compared; Figure 7 and Figure 8 The comparison results are in frequency domain and time domain respectively.

[0145] like Figure 7 As shown in the figure, when the PI controller is used, the input voltage disturbance suppression function Gv rises from -48 to -8dB in the range of 10 to 200Hz; the Gv of the VDPC controller is significantly lower than the Gv of the PI controller; and in the low-frequency range, the Gv amplitude of the PPM-MPC control is the smallest; Figure 7 As shown, when the pulse voltage is connected in series with a 300V DC voltage, the pulse voltage is set to 15V and the duty cycle is 50%; when the PI controller is used, VLV will have large changes and oscillations; while when the charging method of the present invention and VDPC control are used, the maximum change of the output voltage VLV is 0.2V. The difference is that the voltage waveform oscillation of the charging method of the present invention is the smallest; it is verified that the power supply controlled by the charging method of the present invention has a stronger input voltage disturbance suppression capability;

[0146] The dynamic performance of the power supply when providing pulsed power; Fig. 9 and Fig.10A comparison diagram of the dynamic performance of the DAB converter when using the PI charging method and the charging method of the present invention respectively;

[0147] like Fig. 9 As shown in Figure 1, when the power supply using the PI controller provides pulse power, there are voltage drops and overshoot phenomena; Fig.10 As shown, when the power supply using the charging method of the present invention provides pulse power, it can provide a better output voltage, which verifies that the power supply controlled by the charging method of the present invention has stronger dynamic performance.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A pulse charging method for an electric vehicle, characterized in that: include: Obtain the control mode data and secondary side reference data of the DAB converter, and collect the phase shift ratio D at the current time k old and input and output data; wherein the control mode data includes voltage mode and power mode; the input and output data includes: input voltage, output current and output voltage; Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p ; According to the phase shift ratio prediction set D of the preset number of randomly selected p The elements in predict the output voltage at time k+2 to generate a data prediction set; Determine the optimal phase shift ratio D based on the control mode data and the data prediction set a ; According to the optimal phase shift ratio D a The control pulse generation module generates 4 complementary square wave signals to control the switch tube of the DAB converter to conduct, thereby completing the charging control of the electric vehicle.

2. A pulse charging method for an electric vehicle according to claim 1, characterized in that: Secondary reference data include: Secondary side output voltage reference value V LV_ref and the secondary output current reference value I LV_ref ; Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p ,include: Based on control mode data, secondary side reference data, phase shift ratio D old The phase shift ratio prediction set D is determined by the input and output data p , phase shift ratio prediction set D p As shown below: D p ={D old -nΔ adp ,…,D old ,…,D old +nΔ adp } Among them, Δ adp is the adaptive step size, adaptive step size Δ adp The calculation formula is as follows: Among them, S = 0 means that the control mode data is voltage mode, S = 1 means that the control mode data is power mode, λ1 and λ2 are coefficients related to dynamic performance, V Δ is the system output voltage deviation value, I Δ is the system output current deviation value, the system output voltage deviation value V Δ The calculation formula is as follows: Among them, V m Indicates the saturation voltage, V LV [k] represents the output voltage at the current time k; The calculation formula of the system output current deviation value IΔ is as follows: Wherein, Im represents the saturation current, and ILV[k] represents the output current at the current moment k.

3. The pulse charging method for an electric vehicle according to claim 1, characterized in that: According to the phase shift ratio prediction set D of the preset number of randomly selected p The elements in predict the output voltage at time k+2 and generate an output data prediction set, including: Randomly obtain a phase shift ratio prediction set D p The elements in calculate the output current I at time k+1 LV [k+1], the calculation formula is as follows: Where D represents the randomly selected phase shift ratio prediction set D p The elements in the equation are: N represents the ratio of the transformer primary side to the secondary side, f s Indicates the system switching frequency, L p Indicates the inductance value, V HV represents the input voltage at the current time k; Based on the output current I at time k+1 LV [k+1] Calculate the output voltage V at time k+1 LV [k+1], the calculation formula is as follows: Among them, I load [k] is the load current sampling value, C LV is the capacitance on the secondary side of the DAB converter; Based on the output voltage V at time k+1 LV [k+1] Calculate the output voltage V at time k+2 LV [k+2], the calculation formula is as follows: Among them, ILV comp [k] is the difference between the observed current at time k and the predicted value, calculated as follows: ILV comp [k]=ILVr[k]-ILV[k] Among them, i LV_r [k] is the observed current of the DAB converter, calculated as follows: I LV_r [k]=2I load [k]+C LV f s (In LV [k]-V LV [k-1]) Among them, V LV [k-1] is the output voltage at time k-1; Repeat the above steps for a preset number of times to calculate the output voltage V at a certain k+2 time LV The output current ILV[k+1] at time [k+2] and time k+1 is used to obtain the data prediction set.

4. The pulse charging method for an electric vehicle according to claim 1, characterized in that: Determine the optimal phase shift ratio D based on the control mode data and the data prediction set a ,include: If the control mode data is voltage mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset first cost function. a ; If the control mode data is a power mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset second cost function. a .

5. A pulse charging method for an electric vehicle according to claim 4, characterized in that: If the control mode data is voltage mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset first cost function. a ,include: If the control mode data is voltage mode, obtain an element in the data prediction set and convert the output voltage V at time k+2 in the element LV [k+2] is substituted into the first preset cost function for calculation to obtain the first cost value ct1. The calculation formula of ct1 is as follows: ct1=α1G1+α2G2 Among them, α1 and α2 are the weight factors of objective functions G1 and G2 respectively. The calculation formulas of objective functions G1 and G2 are as follows: Repeat the above steps until all elements in the data prediction set are traversed to obtain the first cost set; Select the output voltage V at time k+2 with the smallest first cost value in the first cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a .

6. A pulse charging method for an electric vehicle according to claim 4, characterized in that: If the control mode data is a power mode, the optimal phase shift ratio D is determined based on the data prediction set and the preset second cost function. a ,include: If the control mode data is power mode, obtain an element in the data prediction set and convert the output voltage V at time k+2 in the element LV The output current I at [k+2] and k+1 LV [k+1] is substituted into the second preset cost function for calculation to obtain the second cost value ct2. The calculation formula of ct2 is as follows: ct2=α3G3 G3=(V LV_ref ·I LV_ref -V LV [k+2] I LV [k+1]) 2 Among them, α3 represents the weight factor of the objective function G3; Repeat the above steps until all elements in the data prediction set are traversed to obtain the second cost set; Select the output voltage V at time k+2 with the smallest second cost value in the second cost set LV The phase shift ratio corresponding to [k+2] is taken as the optimal phase shift ratio D a .

7. A pulse charging system for an electric vehicle, characterized in that: include: A DAB converter and a control module, wherein the input end of the DAB converter is connected to the power grid, and the output end of the DAB converter is connected to the energy storage battery for charging the energy storage battery; The control module includes: The voltage sampling module is used to collect the voltages at the input and output ends of the DAB converter to obtain the input voltage and output voltage; The current sampling module is used to collect the output current and load current of the DAB converter to obtain the output current and load current sampling values; The control unit is electrically connected to the voltage acquisition module and the current acquisition module respectively, and is used to determine the optimal phase shift ratio D according to the input voltage, output voltage and output current. a ; The pulse generating module is electrically connected to the control unit and is used to generate a pulse according to the optimal phase shift ratio D a Generate 4 complementary square wave signals to control the switching tubes of the DAB converter.

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