Method and device for improving dynamic characteristics of two-stage resonant converter based on virtual resistance

Abstract

The present invention discloses a method and device for improving the dynamic characteristics of a two-stage resonant converter based on virtual resistance. In the converter, a front-stage Buck converter and a rear-stage LLC resonant converter are connected via a common DC bus. The dynamic characteristics improvement method includes: inputting the bus capacitor voltage on the common DC bus into an active damping inner loop controller, simulating the virtual resistance connected to the converter through the output; inputting the difference between the resonant converter output voltage and a reference voltage into a voltage outer loop proportional-integral controller; and subtracting the output signals of the active damping controller and the voltage outer loop controller to obtain an improved duty cycle of the front-stage Buck converter, which is used to control the switching device. Using the above technical solution, a control method combining voltage outer loop control and active damping inner loop control is used to suppress dual resonance spikes in the voltage loop, effectively expanding the voltage loop bandwidth.

Description

Technical Field

[0001] The present invention relates to the field of power electronic converter control, and in particular to a method and device for improving the dynamic characteristics of a two-stage resonant converter based on virtual resistance. Background Art

[0002] Although single-stage resonant converters offer advantages such as simple structure, high efficiency, and high energy density, they have significant limitations. First, they have a narrow voltage gain range, making them difficult to adapt to wide input voltages or large load transitions. Second, they typically employ pulse-width frequency modulation, making resonant component parameter optimization difficult and requiring high magnetic integration complexity, limiting their application. In contrast, two-stage resonant converters, with their wide voltage gain and easily optimized resonant parameters, are attracting increasing attention.

[0003] The two-stage resonant converter consists of a front-stage PWM (Pulse Width Modulation, PWM) converter and a rear-stage DCX-LLC (DC Transformer, DCX) resonant converter. The front-stage PWM converter is used to regulate the voltage and give full play to the advantages of wide voltage gain; the rear-stage DCX-LLC resonant converter plays a role in electrical isolation.

[0004] However, there are double resonance spikes in the voltage loop of the two-stage resonant converter, that is, the gain curve of the control loop has multiple peaks near the resonant frequency, which reduces the gain margin and phase margin of the system, resulting in insufficient bandwidth of the traditional single-loop voltage control and reduced dynamic characteristics of the converter.

[0005] Although the virtual resistor active damping technology provided by the existing technology can suppress the resonant spike, these technologies are mainly aimed at systems with single resonant spikes, such as LCL-type grid-connected converters or LC-type uninterruptible power supplies, and cannot solve the problem of double resonant spikes in two-stage resonant converters. Summary of the Invention

[0006] Purpose of the invention: The present invention provides a method and device for improving the dynamic characteristics of a two-stage resonant converter based on virtual resistance, aiming to solve the technical problem of double resonance peaks in the voltage loop of a two-stage resonant converter in the prior art.

[0007] Technical solution: The present invention provides a method for improving the dynamic characteristics of a two-stage resonant converter based on virtual resistance, comprising: the two-stage resonant converter comprises a front-stage Buck converter and a rear-stage LLC resonant converter, wherein the positive and negative terminals on the output side of the front-stage Buck converter are respectively connected to the two ends of a common DC bus, and the positive and negative terminals on the input side of the rear-stage LLC resonant converter are respectively connected to the two ends of the common DC bus; the output side of the two-stage resonant converter is connected to the load; a bus capacitor is provided on the common DC bus; the method for improving the dynamic characteristics comprises: The capacitor voltage is used as an input signal and input into an active damping inner-loop controller, and the active damping inner-loop controller simulates a virtual resistance connected to the converter through an output; the difference between the output voltage loaded on the load on the output side of the converter and a reference voltage is used as an input signal and input into a voltage outer-loop proportional-integral controller; the output signal of the active damping inner-loop controller is subtracted from the output signal of the voltage outer-loop proportional-integral controller to calculate the improved duty cycle of the preceding-stage Buck converter, and the control signal obtained according to the improved duty cycle controls the closing and closing of the switching device of the preceding-stage Buck converter.

[0008] Specifically, the switching frequency of the switching device of the subsequent LLC resonant converter is controlled to be fixed and equal to the resonant frequency of the subsequent LLC resonant converter.

[0009] Specifically, the active damping inner loop controller simulates a virtual resistor connected in parallel with the bus capacitor.

[0010] Specifically, the active damping inner loop characteristic polynomial corresponding to the virtual resistor in parallel with the bus capacitor is as follows:

[0011] det(sI 4×4 -A m )=0,

[0012] Among them, det represents the matrix determinant, s represents the complex frequency variable, I 4×4 represents the 4×4 identity matrix, A m Represents the state matrix of the two-stage resonant converter.

[0013] Specifically, the characteristic polynomial of the active damping inner loop is converted into a root locus formula of the active damping inner loop with respect to the virtual resistor; based on the root locus formula of the active damping inner loop with respect to the virtual resistor and combined with the poles of the root locus function of the active damping inner loop, the corresponding virtual resistor value is obtained.

[0014] Specifically, obtaining the virtual resistance value includes: taking the virtual resistance value corresponding to the maximum damping of the two-stage resonant converter as the applied virtual resistance value in the extreme point of the active damping inner loop root locus function.

[0015] Specifically, the root locus formula of the active damping inner loop with respect to the virtual resistance is as follows:

[0016] 1+R v T Rv (s)=0,

[0017] Among them, R v Represents virtual resistance, T Rv (s) represents the root locus function of the active damping inner loop,

[0018] ,

[0019] Among them, C dc1 Represents bus capacitance, C dc2 Represents the output capacitor connected in parallel on the output side of the two-stage resonant converter, L e Indicates the equivalent inductance of the front-stage Buck converter, L eq Represents the equivalent inductance of the subsequent LLC resonant converter, R L represents the load, and N represents the transformer ratio of the subsequent LLC resonant converter.

[0020] Specifically, the closed-loop transfer function G of the active damping inner loop is pm (s), as follows:

[0021] G pm (s)=C(sI 4×4 -A m )B u ,

[0022] Among them, C=[0,0,0,1], B u =[M(D)e(s) / L b ,0,0,0] T , M(D) represents the voltage gain of the front-stage Buck converter, e(s) represents the controlled voltage source coefficient of the front-stage Buck converter, L b Indicates the filter inductance of the front-stage Buck converter.

[0023] Specifically, the voltage outer loop gain function under active damping inner loop control is as follows:

[0024] T pm (s) = G PI (s)G pm (s),

[0025] Among them, T pm (s) represents the voltage outer loop gain, G PI (s) represents the voltage outer loop proportional integral controller function, G PI (s)=k p +k i / s,k p represents the proportional gain, k i represents the integral gain;

[0026] When the voltage outer loop gain satisfies the conditions that the gain margin is greater than 4 dB and the phase margin is greater than 45°, the corresponding proportional gain and integral gain of the voltage outer loop are used as the proportional gain and integral gain of the application.

[0027] The present invention also provides a two-stage resonant converter dynamic characteristic improvement device based on virtual resistance, comprising: a signal acquisition unit and a signal processing unit, wherein: the two-stage resonant converter comprises a front-stage Buck converter and a rear-stage LLC resonant converter, wherein the positive and negative terminals on the output side of the front-stage Buck converter are respectively connected to the two ends of a common DC bus, the positive and negative terminals on the input side of the rear-stage LLC resonant converter are respectively connected to the two ends of a common DC bus, and the output side of the rear-stage LLC resonant converter is connected to a load; a bus capacitor is provided on the common DC bus; the signal acquisition unit is used to connect the bus capacitor to the bus The capacitor voltage is used as an input signal and input into an active damping inner-loop controller, and the active damping inner-loop controller simulates a virtual resistor connected to the converter through an output; the difference between the output voltage loaded on the load on the output side of the converter and a reference voltage is used as an input signal and input into a voltage outer-loop proportional-integral controller; the signal processing unit is used to perform a calculation to obtain an improved duty cycle of the preceding Buck converter by taking the difference between the output signal of the active damping inner-loop controller and the output signal of the voltage outer-loop proportional-integral controller, and to control the closing and closing of the switching device of the preceding Buck converter according to a control signal obtained from the improved duty cycle.

[0028] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: through the control method that combines voltage outer loop control and active damping inner loop control, it can suppress the double resonance peaks in the voltage loop, effectively expand the voltage loop bandwidth, improve the dynamic response capability, and significantly shorten the control time of the output voltage, making it applicable to various working conditions such as load mutation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the two-stage resonant converter topology and active damping control provided by the present invention;

[0030] Figure 2 Schematic diagram of the equivalent circuit of the two-stage resonant converter topology provided by the present invention;

[0031] Figure 3 A schematic diagram of a virtual resistor connection method provided by the present invention;

[0032] Figure 4 A schematic diagram of the derivation process of the virtual resistance of the active damping controller provided by the present invention;

[0033] Figure 5 A schematic diagram of the derivation process of the virtual resistor and filter inductor of the active damping controller provided by the present invention;

[0034] Figure 6 A schematic diagram of the derivation process of the active damping controller provided by the present invention;

[0035] Figure 7 A schematic diagram of the active damping inner loop poles provided by the present invention with respect to the virtual resistance root locus;

[0036] Figure 8 A Bode diagram of the voltage loop gain provided by the present invention;

[0037] Figure 9 The voltage and current waveforms of a two-stage resonant converter when applying the voltage single-loop control in the prior art are shown;

[0038] Figure 10 The voltage and current waveform diagram of the virtual resistance active damping control provided by the present invention is shown. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0040] See Figure 1 , which is a schematic diagram of the two-stage resonant converter topology and active damping control provided by the present invention.

[0041] like Figure 1 As shown in FIG, the two-stage resonant converter includes a front-stage Buck converter and a rear-stage LLC resonant converter. The front-stage Buck converter includes a filter inductor L b , diode D b And the switch tube S b , input voltage v in The subsequent LLC resonant converter includes a resonant capacitor C r , resonant inductor L r , excitation inductance L m , a high-frequency transformer with a transformation ratio of N, switches S1 to S4, and diode D R1 to D R4 The front and rear converters are connected through a common DC bus (intermediate DC bus), and a bus capacitor is provided on the common DC bus; the output side (rectifier side) of the rear LLC resonant converter is connected to the load R L Connection; the front-stage Buck converter controls the switching device S b Duty cycle d y To regulate the output voltage v of the two-stage resonant converter topology dc2, that is, loaded on the load R L The voltage on.

[0042] In the embodiment of the present invention, the switching frequency f of the switching device of the subsequent LLC resonant converter is controlled s Fixed and equal to the resonant frequency f of the subsequent LLC resonant converter r .

[0043] In a specific implementation, the switching frequency of the switching device of the subsequent LLC resonant converter is controlled to be equal to its resonant frequency, so that it operates in DCX (DC Transformer) mode, which can achieve a fixed voltage conversion ratio between input and output, ensure that the LLC resonant converter operates at the optimal efficiency operating point, and provide electrical isolation.

[0044] The method for improving the dynamic characteristics provided by the present invention comprises: dc1 As the input signal, it is input to the active damping inner loop controller G ad (s), the active damping inner loop controller simulates the virtual resistance of the converter through the output; the output voltage v loaded on the load at the output side of the converter is dc2 With reference voltage v dc2_ref The difference between them is used as the input signal and input to the voltage outer loop proportional integral controller G PI (s); the output signal of the active damping inner loop controller is subtracted from the output signal of the voltage outer loop proportional integral controller to calculate the improved duty cycle of the front-stage Buck converter, and the control signal obtained according to the improved duty cycle (obtained by inputting the duty cycle into the PWM module) controls the front-stage Buck converter switching device S b closing and closing.

[0045] See Figure 2 , which is a schematic diagram of an equivalent circuit of a two-stage resonant converter topology provided by the present invention.

[0046] Figure 2 It can be seen that the two-stage resonant converter contains four state variables, namely, the Buck converter inductor current i Lb , intermediate DC bus capacitor voltage v dc1 , the rectifier side current i of the subsequent LLC resonant converter rect And the output voltage v dc2 The subsequent LLC resonant converter includes a resonant capacitor C r and resonant inductor L r The equivalent inductance L in series eq The expression is:

[0047] L eq =L r π2 / 4N 2 , formula (1). L e Indicates the equivalent inductance of the front-stage Buck converter.

[0048] The expression of the controlled voltage source coefficient e(s) of the front-stage Buck converter is:

[0049] e(s) = V dc1 / D y 2 , formula (2),

[0050] Among them, V dc1 Indicates the steady-state value of the intermediate DC bus capacitor voltage, D y Indicates the steady-state value of the duty cycle of the preceding Buck converter.

[0051] The voltage gain M(D) of the front-stage Buck converter is:

[0052] M(D)= D y , formula (3).

[0053] Based on the selected state variables and calculated parameters, the state space model of the two-stage resonant converter is as follows:

[0054] x'=A0x+B u d y +B v +B io i o , formula (4).

[0055] In formula (4), x' represents the calculated state vector, i o Represents the output current of the two-stage resonant converter. Other symbols are as follows:

[0056] x=[i Le ,v dc1 ,i rect ,v dc2 ] T , B u =[M(D)e(s) / L b ,0,0,0] T , B v =[M(D) / L b ,0,0,0] T , B io =[0,0,0,-1 / C dc2 ] T , formula (5), where i Le Represents the output current of the front-stage Buck converter, C dc2represents the output capacitor connected in parallel on the output side of the two-stage resonant converter, and T represents matrix transpose.

[0057] , formula (6),

[0058] Among them, C dc1 Indicates the bus capacitance set on the common DC bus.

[0059] See Figure 3 , which is a schematic diagram of the virtual resistor connection method provided by the present invention.

[0060] In the embodiment of the present invention, the active damping inner loop controller simulates the bus capacitor C dc1 Parallel virtual resistor R v .

[0061] See Figures 4 to 6 , which are respectively the derivation process of the virtual resistance of the active damping controller provided by the present invention, the derivation process of the virtual resistance and filter inductance of the active damping controller, and a schematic diagram of the derivation process of the active damping controller.

[0062] In the specific implementation, when using R v Parallel C dc1 , and the intermediate DC bus capacitor voltage v dc1 When used as the active damping feedback variable, the active damping inner loop controller G ad (s) is expressed as:

[0063] G ad (s)=(L b / M(D)e(s)R v )(ω ad s / (ω ad +s)), formula (7),

[0064] Among them, ω ad Represents the first-order high-pass filter corner frequency, which usually needs to be much larger than the high-frequency resonant frequency of the two-stage resonant converter, and s represents the complex frequency variable. Figure 6 It can be seen that the derived active damping controller contains a differential operator, which will amplify the high-frequency interference in the feedback signal. Therefore, in actual engineering, a first-order high-pass filter is used to replace it, as shown in formula (7).

[0065] Using R v Parallel C dc1 After the virtual resistor connection mode, the system state matrix A of the two-stage resonant converter m for:

[0066] , formula (8).

[0067] Furthermore, after adopting the connection mode of virtual resistor in parallel with bus capacitor, the characteristic polynomial of active damping inner loop is:

[0068] det(sI 4×4 -A m )=0, formula (9),

[0069] Among them, det represents the matrix determinant, s represents the complex frequency variable, I 4×4 represents the 4×4 identity matrix, A m Represents the state matrix of the two-stage resonant converter.

[0070] In specific implementation, formula (9) can be converted into the active damping inner loop about the virtual resistance R v The formula for the root locus is as follows:

[0071] 1+R v T Rv (s)=0, formula (10),

[0072] Among them, T Rv (s) represents the root locus function of the active damping inner loop.

[0073] , formula (11),

[0074] Among them, C dc1 Represents bus capacitance, C dc2 Represents the output capacitor connected in parallel on the output side of the two-stage resonant converter, L e Indicates the equivalent inductance of the front-stage Buck converter, L eq Represents the equivalent inductance of the subsequent LLC resonant converter, R L represents the load, and N represents the transformer ratio of the subsequent LLC resonant converter.

[0075] In the embodiment of the present invention, based on the root locus formula of the active damping inner loop with respect to the virtual resistor and in combination with the poles of the root locus function of the active damping inner loop, the corresponding virtual resistor value is obtained.

[0076] In the embodiment of the present invention, at the pole of the active damping inner loop root locus function, the virtual resistance value corresponding to the maximum damping of the two-stage resonant converter is used as the applied virtual resistance value.

[0077] See Figure 7 , which is a schematic diagram of the active damping inner loop pole provided by the present invention with respect to the virtual resistance root locus.

[0078] like Figure 7 As shown, according to T Rv (s) Draw the inner loop of the active damping about R v Root locus. Figure 7It can be seen that the damping of the inner loop pole of the active damping ζ increases with R v First increases and then decreases, when R v =R v,op The active damping inner loop pole damping reaches its maximum value when . Therefore, choose R v,op As the final R v The value of .

[0079] In the embodiment of the present invention, the closed-loop transfer function G of the active damping inner loop is pm (s), as follows:

[0080] G pm (s)=C(sI 4×4 -A m )B u , formula (12),

[0081] Among them, C=[0,0,0,1], B u =[M(D)e(s) / L b ,0,0,0] T , M(D) represents the voltage gain of the front-stage Buck converter, e(s) represents the controlled voltage source coefficient of the front-stage Buck converter, L b Indicates the filter inductance of the front-stage Buck converter.

[0082] In the embodiment of the present invention, the voltage outer loop gain function under the active damping inner loop control is as follows:

[0083] T pm (s) = G PI (s)G pm (s),

[0084] Among them, T pm (s) represents the voltage outer loop gain, G PI (s) represents the voltage outer loop proportional integral controller function, G PI (s)=k p +k i / s,k p represents the proportional gain, k i Indicates the integral gain.

[0085] See Figure 8 , which is the voltage loop gain T provided by the present invention pm Bode plot of (s).

[0086] In a specific implementation, the proportional gain k is adjusted p and integral gain k iThe voltage outer loop gain should satisfy a gain margin greater than 4dB (preferably greater than 4.5dB) to ensure the control system maintains sufficient stability under factors such as model errors, nonlinearities, and disturbances. A phase margin greater than 45° ensures good dynamic response and sufficient robustness to avoid excessive oscillation or instability. The corresponding proportional and integral gains of the voltage outer loop are used as the proportional and integral gains of the application.

[0087] At this point, the design of all control parameters is completed.

[0088] In a specific implementation, the method for improving the dynamic characteristics of the two-stage resonant converter provided by the present invention is experimentally verified, wherein the system parameters of the two-stage resonant converter are as follows: L b =1mH, C dc1 =800μF, N=1:1, L m =100μH,L r =24μH, C r =0.42μF, C dc2 = 800μF. The system's rated input and output voltages are both 200V, and the rated output power is 2kW. When the output power of the two-stage resonant converter is stepped from 1kW to 2kW, the voltage fluctuation range and stabilization time under different control schemes are compared.

[0089] like Figure 9 As shown in the voltage and current waveforms of the two-stage resonant converter when the voltage single-loop control in the prior art is adopted, the output power undergoes a step change. It can be seen that the output voltage fluctuation range is 195.5V to 204.3V, and there are also double resonant peaks. The stabilization time is 170ms.

[0090] like Figure 10 As shown in the figure, under the same experimental conditions, the voltage and current waveforms corresponding to the active damping control based on virtual resistance provided by the present invention are applied. It can be seen that the output voltage fluctuation range is 198.1V to 200.3V. It should be noted that while suppressing the double resonance peak, the stabilization time is only 1.12ms. Therefore, the control scheme provided by the present invention has better dynamic characteristics than the traditional voltage single-loop control scheme.

[0091] The present invention also provides a two-stage resonant converter dynamic characteristic improvement device based on virtual resistance, comprising: a signal acquisition unit and a signal processing unit, wherein: the two-stage resonant converter comprises a front-stage Buck converter and a rear-stage LLC resonant converter, wherein the positive and negative terminals on the output side of the front-stage Buck converter are respectively connected to the two ends of a common DC bus, the positive and negative terminals on the input side of the rear-stage LLC resonant converter are respectively connected to the two ends of a common DC bus, and the output side of the rear-stage LLC resonant converter is connected to a load; a bus capacitor is provided on the common DC bus; the signal acquisition unit is used to connect the bus capacitor to the bus The capacitor voltage is used as an input signal and input into an active damping inner-loop controller, and the active damping inner-loop controller simulates a virtual resistor connected to the converter through an output; the difference between the output voltage loaded on the load on the output side of the converter and a reference voltage is used as an input signal and input into a voltage outer-loop proportional-integral controller; the signal processing unit is used to perform a calculation to obtain an improved duty cycle of the preceding Buck converter by taking the difference between the output signal of the active damping inner-loop controller and the output signal of the voltage outer-loop proportional-integral controller, and to control the closing and closing of the switching device of the preceding Buck converter according to a control signal obtained from the improved duty cycle.

[0092] The present invention provides a two-stage resonant converter dynamic characteristics improvement device based on virtual resistance, wherein the unit for executing methods, steps or functions, and the methods, steps or functions executed by them can refer to the two-stage resonant converter dynamic characteristics improvement method based on virtual resistance provided by the present invention.

Claims

1. A method for improving the dynamic characteristics of a two-stage resonant converter based on virtual resistance, characterized in that: include: The two-stage resonant converter includes a front-stage Buck converter and a rear-stage LLC resonant converter, wherein the positive and negative terminals on the output side of the front-stage Buck converter are respectively connected to the two ends of a common DC bus, and the positive and negative terminals on the input side of the rear-stage LLC resonant converter are respectively connected to the two ends of the common DC bus; the output side of the two-stage resonant converter is connected to the load; and a bus capacitor is provided on the common DC bus; The dynamic characteristics improvement method comprises: The bus capacitor voltage of the bus capacitor is used as an input signal and inputted into an active damping inner loop controller, and the active damping inner loop controller simulates a virtual resistance connected to the converter through an output; the difference between the output voltage loaded on the load at the output side of the converter and a reference voltage is used as an input signal and inputted into a voltage outer loop proportional integral controller; The output signal of the active damping inner loop controller is subtracted from the output signal of the voltage outer loop proportional-integral controller to calculate the improved duty cycle of the front-stage Buck converter. The control signal obtained according to the improved duty cycle controls the closing and closing of the switching device of the front-stage Buck converter.

2. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 1, wherein: The switching frequency of the switching device of the subsequent LLC resonant converter is controlled to be fixed and equal to the resonant frequency of the subsequent LLC resonant converter.

3. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 1, wherein: The active damping inner loop controller simulates a virtual resistor connected in parallel with the bus capacitor.

4. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 3, characterized in that: The active damping inner loop characteristic polynomial corresponding to the virtual resistor in parallel with the bus capacitor is as follows: it(sI 4×4 -A m )=0, Among them, det represents the matrix determinant, s represents the complex frequency variable, I 4×4 represents the 4×4 identity matrix, A m Represents the state matrix of the two-stage resonant converter.

5. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 4, wherein: Converting the active damping inner loop characteristic polynomial into a root locus formula of the active damping inner loop with respect to a virtual resistor; Based on the root locus formula of the active damping inner loop with respect to the virtual resistor and the poles of the root locus function of the active damping inner loop, the corresponding virtual resistor value is obtained.

6. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 5, characterized in that: The obtaining of the virtual resistance value includes: In the pole of the active damping inner loop root locus function, the virtual resistance value corresponding to the maximum damping of the two-stage resonant converter is used as the applied virtual resistance value.

7. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 5, wherein: The root locus formula of the active damping inner loop with respect to the virtual resistance is as follows: 1+R v T Rv (s)=0, Among them, R v Represents virtual resistance, T Rv (s) represents the root locus function of the active damping inner loop, ， Among them, C dc1 Represents bus capacitance, C dc2 Represents the output capacitor connected in parallel on the output side of the two-stage resonant converter, L e Represents the equivalent inductance of the front-stage Buck converter, L eq Represents the equivalent inductance of the subsequent LLC resonant converter, R L represents the load, and N represents the transformer ratio of the subsequent LLC resonant converter.

8. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 7, characterized in that: The closed-loop transfer function G of the active damping inner loop is pm (s), as follows: G pm (s)=C(sI 4×4 -A m )B u , Among them, C=[0,0,0,1], B u =[M(D)e(s) / L b ,0,0,0] T , M(D) represents the voltage gain of the front-stage Buck converter, e(s) represents the controlled voltage source coefficient of the front-stage Buck converter, L b Indicates the filter inductance of the front-stage Buck converter.

9. The method for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance according to claim 8, characterized in that: The voltage outer loop gain function under active damping inner loop control is as follows: T pm (s)= G PI (s)G pm (s), Among them, T pm (s) represents the voltage outer loop gain, G PI (s) represents the voltage outer loop proportional integral controller function, G PI (s)=k p +k i / s,k p represents the proportional gain, k i represents the integral gain; When the voltage outer loop gain satisfies the conditions that the gain margin is greater than 4 dB and the phase margin is greater than 45°, the corresponding proportional gain and integral gain of the voltage outer loop are used as the proportional gain and integral gain of the application.

10. A device for improving dynamic characteristics of a two-stage resonant converter based on virtual resistance, characterized in that: include: Signal acquisition unit and signal processing unit, wherein: The two-stage resonant converter includes a front-stage Buck converter and a rear-stage LLC resonant converter, wherein the positive and negative terminals on the output side of the front-stage Buck converter are respectively connected to the two ends of a common DC bus, the positive and negative terminals on the input side of the rear-stage LLC resonant converter are respectively connected to the two ends of the common DC bus, and the output side of the rear-stage LLC resonant converter is connected to a load; a bus capacitor is provided on the common DC bus; The signal acquisition unit is configured to use the bus capacitor voltage of the bus capacitor as an input signal to input into an active damping inner loop controller, wherein the active damping inner loop controller simulates a virtual resistor connected to the converter through an output; and use the difference between the output voltage loaded on the load at the output side of the converter and a reference voltage as an input signal to input into a voltage outer loop proportional integral controller; The signal processing unit is used to calculate the improved duty cycle of the front-stage Buck converter by subtracting the output signal of the active damping inner-loop controller from the output signal of the voltage outer-loop proportional-integral controller, and control the closing and closing of the switching device of the front-stage Buck converter according to the control signal obtained from the improved duty cycle.

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