Parameter estimation method of resonant converter, control method of resonant converter and resonant converter

Abstract

This invention discloses a parameter estimation method, a control method, and a resonant converter for a resonant converter. The resonant converter has a first port and a second port, and includes a resonant cavity containing an equivalent resonant capacitance and an equivalent resonant inductance. The parameter estimation method includes: estimating a second voltage, and / or an estimated equivalent resonant capacitance and an estimated equivalent resonant inductance at the second port of the resonant converter based on a first voltage at the first port and the values ​​of the equivalent resonant capacitance voltage and equivalent resonant inductance current at at least three effective points. The at least three effective points have different coordinates on the state plane of the equivalent resonant capacitance voltage and equivalent resonant inductance current, and lie on a state trajectory formed by the equivalent resonant capacitance voltage and equivalent resonant inductance current, and the at least three effective points are not symmetrical about the center of the state trajectory. This invention can realize parameter estimation of the resonant converter and achieve stable control of the output voltage.

Description

Technical Field

[0001] This invention relates to converter technology, and more particularly to a parameter estimation method for a resonant converter, a control method for a resonant converter, and a resonant converter. Background Technology

[0002] High-frequency resonant converters are applied to solid-state transformers (SSTs) and have broad application prospects in DC power consumption or power generation fields such as data centers, electric vehicle charging and swapping stations, photovoltaics, and energy storage.

[0003] In the aforementioned applications, the SST input is medium-voltage AC and the output is low-voltage DC, comprising a front-end AC-DC converter and a back-end DC-DC converter. In the SST's DC-DC converter, the primary side (medium voltage) and secondary side (low voltage) of the high-frequency transformer typically require isolation. Furthermore, the existing SST's primary and secondary fiber optic communication connections are complex, and primary-side frequency modulation control relies on fiber optic communication between the primary and secondary sides. When communication between the primary and secondary sides fails or is absent, the output voltage V is estimated... o This ensures stable system operation, thereby reducing the control's reliance on communication. Furthermore, the actual parameters of the resonant converter are affected by temperature, operating conditions, etc., and may deviate from the design values, impacting control performance. The equivalent resonant inductance L of the resonant converter... r Equivalent resonant capacitance C r Magnetizing inductance L m Estimating parameters such as these can promptly reflect circuit changes and adjust control parameters, which is beneficial for fault diagnosis and fault-tolerant operation of the resonant converter. Therefore, parameter estimation of the resonant converter is of great significance for improving the control performance and reliability of the SST.

[0004] Existing technologies also disclose some methods for parameter estimation in the frequency domain, but these methods all have some limitations. Summary of the Invention

[0005] The purpose of this invention is to provide a parameter estimation method, a control method, and a resonant converter for a resonant converter, which can effectively solve at least one defect of the prior art, improve the operational reliability of the resonant converter, and meet the requirement of efficient system operation when there is no communication between the primary and secondary sides.

[0006] To achieve the above objectives, the present invention provides a parameter estimation method for a resonant converter. The resonant converter has a first port and a second port, and includes a resonant cavity. The resonant cavity includes an equivalent resonant capacitance and an equivalent resonant inductance. The parameter estimation method includes: estimating a second voltage estimate, an equivalent resonant capacitance estimate, and / or an equivalent resonant inductance estimate for the second port of the resonant converter based on a first voltage at the first port and the values ​​of the equivalent resonant capacitance voltage and the equivalent resonant inductance current at at least three valid points. The at least three valid points have different coordinates on the state plane of the equivalent resonant capacitance voltage and the equivalent resonant inductance current, and lie on a state trajectory formed by the equivalent resonant capacitance voltage and the equivalent resonant inductance current. The at least three valid points are not symmetrical about the center of the state trajectory.

[0007] In one embodiment of the present invention, the at least three valid points can be obtained by sampling, that is, sampling the resonant capacitor voltage and resonant inductor current of at least three valid sampling points. The valid sampling points are defined as those where no two sampling points are spaced apart. Where m is a positive integer, T s The switching cycle of the resonant converter is defined as follows: at each effective sampling point, the resonant capacitor voltage and the resonant inductor current are sampled synchronously.

[0008] In one embodiment of the present invention, estimating the second voltage estimate includes: when the resonant converter is working or starting up, constructing a resonant cavity energy function based on the state equations of the resonant capacitor voltage and the resonant inductor current in the time domain, and obtaining the trajectory equations of the state trajectories of the resonant capacitor voltage and the resonant inductor current on the state plane; estimating the second voltage estimate based on the trajectory equations and the at least three effective points.

[0009] In one embodiment of the present invention, the parameter estimation method further includes: estimating the resonant impedance estimate of the resonant converter based on the trajectory equation.

[0010] In one embodiment of the present invention, the at least three valid sampling points are sampled during the positive or negative half-cycle of the same switching cycle.

[0011] In one embodiment of the present invention, when sampling is performed during the positive half-cycle, the sampling begins at the rising edge of the primary arm voltage of the resonant converter or after a first lag time, and the resonant capacitor voltage and the resonant inductor current are sampled synchronously after a first interval time, wherein the first interval time is the same or different each time; when sampling is performed during the negative half-cycle, the sampling begins at the falling edge of the primary arm voltage of the resonant converter or after a second lag time, and the resonant capacitor voltage and the resonant inductor current are sampled synchronously after a second interval time, wherein the second interval time is the same or different each time.

[0012] In one embodiment of the present invention, the at least three valid sampling points are sampled in both the positive and negative half-cycles within the same switching cycle.

[0013] In one embodiment of the present invention, when making an estimation, the sampling points of the positive half-cycle and the negative half-cycle are centrally symmetrical. The effective sampling points located in the negative half-cycle are converted to the positive half-cycle for estimation, or the effective sampling points located in the positive half-cycle are converted to the negative half-cycle for estimation.

[0014] In one embodiment of the present invention, the at least three valid sampling points are sampled within different multiple switching cycles, wherein the multiple switching cycles are continuous or discontinuous.

[0015] In one embodiment of the present invention, estimating the estimated value of the equivalent resonant capacitance and / or the estimated value of the equivalent resonant inductance includes: normalizing the state trajectory to obtain a normalized trajectory, and estimating the estimated value of the resonant angular frequency of the resonant converter based on the normalized trajectory; and estimating the estimated value of the equivalent resonant capacitance and / or the estimated value of the equivalent resonant inductance based on the estimated value of the resonant impedance and the estimated value of the resonant angular frequency.

[0016] In one embodiment of the present invention, the resonant cavity further includes a magnetizing inductor, and the parameter estimation method further includes: when the at least three effective points include a sampling point P0 corresponding to the rising edge or falling edge of the primary side bridge arm voltage of the resonant converter, estimating the magnetizing inductor of the resonant converter based on the estimated second voltage estimate and the per-unit value of the peak current of the magnetizing inductor.

[0017] In one embodiment of the present invention, the resonant cavity further includes a magnetizing inductor, and the parameter estimation method further includes: when the at least three effective points do not include a sampling point P0 corresponding to the rising edge or falling edge of the primary side bridge arm voltage of the resonant converter, adding a sampling point corresponding to the sampling point P0, using the sampled values ​​of the resonant capacitor voltage and the resonant inductor current corresponding to the sampling point P0 to estimate the second voltage estimate, and estimating the magnetizing inductor estimate of the resonant converter based on the second voltage estimate and the per-unit value of the peak current of the magnetizing inductor.

[0018] In one embodiment of the present invention, the parameter estimation method further includes: estimating the average value of the resonant current for half a switching cycle based on the resonant current values ​​corresponding to the two effective points.

[0019] In one embodiment of the present invention, when there are more than three valid points, the least squares method is used to fit and estimate the second voltage estimate, the equivalent resonant capacitance estimate, and / or the equivalent resonant inductance estimate of the second port of the resonant converter.

[0020] In one embodiment of the present invention, the resonant converter is an LLC resonant converter.

[0021] In one embodiment of the present invention, the resonant converter is a CLLC resonant converter. The equivalent value of the equivalent resonant capacitor voltage is calculated by sampling the primary resonant capacitor voltage, the secondary resonant capacitor voltage, and the primary resonant current of the CLLC resonant converter, and the equivalent value of the primary resonant capacitor voltage is calculated based on the sampled values ​​of the primary resonant capacitor voltage and the secondary resonant capacitor voltage, so as to estimate the equivalent value of the equivalent resonant capacitor voltage and the sampled value of the primary resonant current.

[0022] To achieve the above objectives, the present invention further provides a control method for a resonant converter, comprising:

[0023] A dual-loop controller is configured, having a voltage feedback terminal and a current feedback terminal. The voltage feedback terminal is located in the outer loop and is configured to receive a voltage signal reflecting the output voltage of the output port of the resonant converter, wherein the voltage value of the voltage signal is either a sampled output voltage value from the output port or a second voltage estimate obtained using the parameter estimation method described above. The current feedback terminal is located in the inner loop and is configured to receive an estimate of the average resonant current over half a switching cycle, obtained using the parameter estimation method described above.

[0024] When the output voltage sample value can be sampled and obtained, the dual closed-loop controller receives the output voltage sample value through the voltage feedback terminal and controls the primary-side switching frequency of the primary-side switch in the primary-side circuit of the resonant converter.

[0025] When the output voltage sample value cannot be obtained, the dual closed-loop controller receives the output voltage estimate through the voltage feedback terminal and controls the primary-side switching frequency of the primary-side switch.

[0026] In another embodiment of the present invention, the primary-side circuit includes a first primary-side bridge arm and a second primary-side bridge arm connected in parallel. The first primary-side bridge arm includes a first primary-side switch and a second primary-side switch connected in series. The second primary-side bridge arm includes a third primary-side switch and a fourth primary-side switch connected in series. The dual closed-loop controller controls the first primary-side switch and the fourth primary-side switch to be synchronized, and the second primary-side switch and the third primary-side switch to be synchronized. The first primary-side switch and the second primary-side switch, and the third primary-side switch and the fourth primary-side switch are complementaryly turned on with a 50% duty cycle.

[0027] To achieve the above objectives, the present invention provides a resonant converter having a first port and a second port, and including a resonant cavity, the resonant cavity including an equivalent resonant capacitance and an equivalent resonant inductance. The resonant converter further includes an estimation unit configured to perform the parameter estimation method described above to obtain a second voltage estimate, an equivalent resonant capacitance estimate, and / or an equivalent resonant inductance estimate for the second port of the resonant converter.

[0028] In another embodiment of the invention, the resonant cavity further includes a magnetizing inductor, and the estimation unit is further configured to perform the parameter estimation method described above to obtain an estimated value of the magnetizing inductor of the resonant converter.

[0029] In another embodiment of the invention, the estimation unit is further configured to perform the parameter estimation method as described above to obtain an estimate of the average value of the resonant current of the resonant converter over half a switching cycle.

[0030] In another embodiment of the present invention, the first port is the input port of the resonant converter and is used to receive an input voltage, and the second port is the output port of the resonant converter and is used to output an output voltage; the resonant converter further includes:

[0031] A dual-loop controller has a voltage feedback terminal and a current feedback terminal; the voltage feedback terminal is located in the outer loop and is configured to receive a voltage signal reflecting the output voltage, wherein the voltage value of the voltage signal is either a sampled output voltage value from the output port or a second voltage estimate obtained using the parameter estimation method described above; the current feedback terminal is located in the inner loop and is configured to receive an estimate of the average value of the resonant current over half a switching cycle;

[0032] When the output voltage sample value can be sampled and obtained, the dual closed-loop controller receives the output voltage sample value through the voltage feedback terminal and controls the primary-side switching frequency of multiple primary-side switches in the primary-side circuit of the resonant converter.

[0033] When the output voltage sample value cannot be obtained, the dual closed-loop controller receives the output voltage estimate through the voltage feedback terminal and controls the primary-side switching frequency of the primary-side switch.

[0034] In another embodiment of the present invention, the plurality of primary-side switches include a first controllable switch, a second controllable switch, a third controllable switch, and a fourth controllable switch. The first controllable switch and the second controllable switch are connected in series to form a first primary-side bridge arm, and the third controllable switch and the fourth controllable switch are connected in series to form a second primary-side bridge arm. The first primary-side bridge arm and the second primary-side bridge arm are connected in parallel. The midpoint of the first primary-side bridge arm and the midpoint of the second primary-side bridge arm are connected to the first end of the resonant cavity. The dual closed-loop controller controls the first controllable switch and the fourth controllable switch to be synchronized, and the second controllable switch and the third controllable switch to be synchronized. The first controllable switch and the second controllable switch, and the third controllable switch and the fourth controllable switch are complementary in conducting with a 50% duty cycle.

[0035] In another embodiment of the present invention, the secondary circuit of the resonant converter includes a first switch, a second switch, a third switch, and a fourth switch. The first switch and the second switch are connected in series to form a first secondary bridge arm, and the third switch and the fourth switch are connected in series to form a second secondary bridge arm. The first secondary bridge arm and the second secondary bridge arm are connected in parallel, and the midpoint of the first secondary bridge arm and the midpoint of the second secondary bridge arm are connected to the second end of the resonant cavity.

[0036] In another embodiment of the present invention, the dual closed-loop controller includes a voltage comparison module, a first regulator, a current comparison module, a second regulator, a frequency comparison module, a limiter, and a carrier generation module; the output terminal of the voltage comparison module is connected to the input terminal of the current comparison module via the first regulator, for comparing the voltage signal with an output voltage reference signal, and after being regulated by the first regulator, outputting a reference signal representing the average resonant current of half a switching cycle and transmitting it to the current comparison module; the output terminal of the current comparison module is connected to the input terminal of the frequency comparison module via the second ..., for comparing the voltage signal with an output voltage reference signal, and after being regulated by the The reference signal of the average resonant current for half a switching cycle is compared with the estimated value of the average resonant current for half a switching cycle, and after being adjusted by the second regulator, an adjustment signal is output and transmitted to the frequency comparison module; the output of the frequency comparison module is connected to the input of the carrier generation module via the limiter, so as to compare the frequency of the adjustment signal with an initial switching frequency of the resonant converter, and after being limited by the limiter, a limited signal is output and transmitted to the carrier generation module; the carrier generation module is used to generate multiple drive signals based on the limited signal to drive the multiple primary-side switches respectively.

[0037] In another embodiment of the present invention, the carrier generation module includes a carrier generation unit and a PWM generation unit, wherein the carrier generation unit is used to generate a triangular carrier based on the amplitude limiting signal, and the PWM generation unit is used to generate the plurality of driving signals based on the triangular carrier.

[0038] This invention utilizes the state trajectory in the time domain to achieve parameter estimation of the resonant converter.

[0039] Based on the estimated output voltage of the resonant converter and the estimated average value of the resonant current over half a switching cycle, this invention can design a dual closed-loop controller to achieve stable control of the output voltage. It is suitable for control without communication between the primary and secondary sides of the resonant converter.

[0040] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. Attached Figure Description

[0041] The above and other features and advantages of the present invention will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0042] Figure 1 This is a topology and control block diagram of the resonant converter of the present invention;

[0043] Figure 2 This is a flowchart illustrating the parameter estimation method for the resonant converter of the present invention.

[0044] Figure 3 For the switching frequency f s >Resonant frequency f r At that time, the equivalent resonant capacitor voltage v Cr and equivalent resonant inductor current i Lr A schematic diagram of the state trajectory;

[0045] Figures 4A to 4C They are the switching frequencies f s >Resonant frequency f r Switching frequency f s =Resonant frequency f r Switching frequency f s <Resonant frequency f r Schematic diagram of the state trajectory obtained by resonant cavity sampling at different switching frequencies;

[0046] Figure 5 The equivalent resonant capacitor voltage v of the resonant converter of this invention during startup. Cr and equivalent resonant inductor current i Lr A schematic diagram of the state trajectory;

[0047] Figure 6A and Figure 6B These are schematic diagrams of the state trajectories obtained by resonant cavity sampling at different sampling rates;

[0048] Figure 7A The switching frequency f is shown. s >Resonant frequency f r At that time, the equivalent resonant capacitor voltage v Cr and equivalent resonant inductor current i Lr The resulting elliptical trajectory;

[0049] Figure 7B It shows Figure 7A The normalized trajectory of the elliptical locus;

[0050] Figure 8 The switching frequency f is shown. s >Resonant frequency f r The waveform of the resonant cavity at that time;

[0051] Figure 9A This is a flowchart illustrating the control method of the resonant converter of the present invention;

[0052] Figure 9B This is a block diagram of the dual closed-loop controller of the resonant converter of the present invention;

[0053] Figure 10 It shows the use of Figure 1 The control block diagram shown illustrates the control effect during load addition and reduction.

[0054] Figure 11 This demonstrates the control effect when the output voltage reference increases, assuming no communication between the primary and secondary sides.

[0055] Figure 12 This demonstrates the control effect when there is no communication between the primary and secondary sides and the input voltage contains second-harmonic fluctuations.

[0056] Figure 13 This illustrates the equivalent resonant capacitor voltage v of the present invention when the resonant cavity parameters are consistent with the design values. Cr and equivalent resonant inductor current i Lr The sampling effect;

[0057] Figure 14 The control effect of the present invention is shown when the resonant cavity parameters are consistent with the design values;

[0058] Figure 15 It shows that when the actual L r The control effect of the present invention when the value is 10% larger and other parameters remain unchanged;

[0059] Figure 16 For the switching frequency f s >Resonant frequency f r At that time, the equivalent resonant capacitor voltage v is obtained by sampling 7 sampling points within half a switching cycle. Cr and equivalent resonant inductor current i Lr A schematic diagram of the state trajectory;

[0060] Figure 17 This is a schematic diagram of the CLLC resonant converter topology and resonant cavity equivalent of the present invention. Detailed Implementation

[0061] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0062] In describing the elements / components / etc. described and / or illustrated herein, the terms “a,” “an,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc. The terms “comprising,” “including,” and “having” are used to indicate an open-ended inclusion and to mean that additional elements / components / etc. may exist in addition to those listed. Furthermore, the terms “first,” “second,” etc., in the claims are used only as designations and are not intended to limit the number of objects to which they pertain.

[0063] Figure 1 The circuit topology and control block diagram of the resonant converter 100 of the present invention are shown. Figure 1 As shown, the resonant converter 100 of the present invention has a first port 101 and a second port 102, and may include a resonant cavity 10. The first port 101 may be the input port of the resonant converter for receiving an input voltage V. in The second port 102 can be the output port of the resonant converter, used to output an output voltage V. o The resonant cavity 10 may include an equivalent resonant capacitance C. r and equivalent resonant inductance L r The turns ratio of the primary and secondary sides of the transformer can be, for example, n:1. In this invention, the resonant converter 100 may further include an estimation unit 20, which can be configured to perform a parameter estimation method (described in further detail below) to obtain a second voltage estimate v at the second port 102 of the resonant converter. oEst (Hereinafter sometimes referred to as "output voltage estimate"), equivalent resonant capacitance estimate C rEst And / or the estimated value of the equivalent resonant inductance L rEst .

[0064] In this invention, the resonant converter 100 further includes a primary-side circuit OSC located on the primary side and a secondary-side circuit VSC located on the secondary side. The primary-side circuit OSC may be, for example, a fully controlled H-bridge or a series half-bridge (SHB) topology, and the secondary-side circuit VSC may be, for example, an uncontrolled rectifier circuit or a synchronous rectifier circuit. However, it is understood that in other embodiments, the primary-side circuit OSC and the secondary-side circuit VSC may also be other circuit topologies, and these are not intended to limit the invention.

[0065] exist Figure 1 In the illustrated embodiment, the primary-side circuit OSC may have multiple primary-side switches, such as a first controllable switch S1, a second controllable switch S2, a third controllable switch S3, and a fourth controllable switch S4. The first controllable switch S1 and the second controllable switch S2 are connected in series to form a first primary-side bridge arm, and the third controllable switch S3 and the fourth controllable switch S4 are connected in series to form a second primary-side bridge arm. The first primary-side bridge arm and the second primary-side bridge arm are connected in parallel. The midpoint N1 of the first primary-side bridge arm and the midpoint N2 of the second primary-side bridge arm are connected to the first end of the resonant cavity 10. A primary-side bridge arm voltage v exists between the midpoint N1 of the first primary-side bridge arm and the midpoint N2 of the second primary-side bridge arm. p .

[0066] exist Figure 1In the illustrated embodiment, the secondary-side circuit VSC may have multiple secondary-side switches, such as a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4. The first switch Q1 and the second switch Q2 are connected in series to form a first secondary-side bridge arm, and the third switch Q3 and the fourth switch Q4 are connected in series to form a second secondary-side bridge arm. The first secondary-side bridge arm and the second secondary-side bridge arm are connected in parallel. The midpoint N3 of the first secondary-side bridge arm and the midpoint N4 of the second secondary-side bridge arm are connected to the second end of the resonant cavity 10. A secondary-side bridge arm voltage v exists between the midpoint N3 of the first secondary-side bridge arm and the midpoint N4 of the second secondary-side bridge arm. s The resonant converter 100 also has an output capacitor C on its secondary side. o It is connected in parallel with the first secondary side arm and the second secondary side arm.

[0067] In some embodiments of the present invention, the resonant cavity 10 may further include a magnetizing inductor L. m That is, the resonant converter 100 may be, for example, an LLC resonant converter. The estimation unit 20 may further be configured to perform a parameter estimation method (described in detail below) to obtain an estimated value L of the magnetizing inductance of the resonant converter. mEst Furthermore, the estimation unit 20 can also be configured to execute the parameter estimation method to obtain an estimate i of the average resonant current value of the resonant converter over half a switching cycle. LrAvgEst .

[0068] In some embodiments of the present invention, the resonant converter 100 may further include a dual-loop controller 30. The dual-loop controller 30 has a voltage feedback terminal 301 and a current feedback terminal 302. The voltage feedback terminal 301 may be located in the outer loop and is configured to receive feedback reflecting the output voltage V. o The voltage signal, wherein the voltage value of the voltage signal is the output voltage sample value v sampled from the output port (i.e., the second port 102). o Alternatively, the second voltage estimate v obtained using the parameter estimation method described above. oEst As an output voltage estimate (for clarity, the term "output voltage estimate" and "second voltage estimate" may be referred to using the same notation "v" in the following text), oEst The current feedback terminal 302 may be located in the inner loop and configured to receive an estimate i of the average resonant current of the resonant converter 100 over half a switching cycle. LrAvgEst Among them, when the output voltage sample value v can be sampled and obtained. o At that time, the dual closed-loop controller 30 receives the output voltage sample value v through the voltage feedback terminal 301. oAnd control the primary-side switching frequency of multiple primary-side switches in the primary-side circuit OSC of the resonant converter 100. When it is not possible to sample and obtain the output voltage sampling value v o (Including but not limited to the case where there is no communication between the primary and secondary sides of the resonant converter), the dual closed-loop controller 30 receives the output voltage estimate v through the voltage feedback terminal 301. oEst And control the primary-side switching frequency of multiple primary-side switches in the primary-side circuit OSC of the resonant converter 100.

[0069] Preferably, the dual closed-loop controller 30 can, for example, synchronize the first controllable switch S1 with the fourth controllable switch S4, and the second controllable switch S2 with the third controllable switch S3, and the first controllable switch S1 and the second controllable switch S2, and the third controllable switch S3 and the fourth controllable switch S4 can be complementaryly turned on with a 50% duty cycle. Of course, it is understood that using other duty cycle ratios for control is also feasible, and this is not intended to limit the invention.

[0070] exist Figure 1 In the illustrated embodiment, the dual closed-loop controller 30 may include, for example, a voltage comparison module 31, a first regulator 32, a current comparison module 33, a second regulator 34, a frequency comparison module 35, a limiter 36, and a carrier generation module 37. The output of the voltage comparison module 31 is connected to the input of the current comparison module 33 via the first regulator 32, for converting the voltage signal (e.g., the output voltage sample value v) into a signal. o Or output voltage estimate v oEst ) and an output voltage reference signal v oref The values ​​are compared, and after being adjusted by the first regulator 32, a reference signal i representing the average resonant current of half a switching cycle is output. LrAvgref The signal is then transmitted to the current comparison module 33. The output of the current comparison module 33 is connected to the input of the frequency comparison module 35 via the second regulator 34, to convert the average value reference signal i of the resonant current over half a switching cycle. LrAvgref The estimated value i of the average resonant current over half a switching cycle LrAvgEst The frequency is compared and adjusted by the second regulator 34, then an adjustment signal is output and transmitted to the frequency comparison module 35. The output of the frequency comparison module 35 is connected to the input of the carrier generation module 37 via the limiter 36, so as to compare the frequency of the adjustment signal with an initial switching frequency f of the resonant converter. rThe resonant frequencies are compared, and after being limited by the limiter 36, a limited signal is output and transmitted to the carrier generation module 37. The carrier generation module 37 is used to generate multiple drive signals based on the limited signal to drive the multiple primary-side switches respectively. For example, drive signals CS can be generated respectively. S1 CS S2 CS S3 CS S4 To drive the first controllable switch S1, the second controllable switch S2, the third controllable switch S3, and the fourth controllable switch S4 respectively.

[0071] Preferably, the carrier generation module 37 may include, for example, a carrier generation unit 371 and a PWM generation unit 372. The carrier generation unit 371 can be used to generate a triangular carrier based on the amplitude limiting signal, and the PWM generation unit 372 can be used to generate the plurality of drive signals CS based on the triangular carrier. S1 CS S2 CS S3 CS S4 , used to drive multiple primary-side switches respectively.

[0072] like Figure 2 As shown, in conjunction with reference Figure 1 The resonant converter 100 shown in the present invention includes a parameter estimation method 200 for the resonant converter, comprising:

[0073] Step S201, based on the first voltage of the first port 101 (e.g. Figure 1 The input voltage V in and the equivalent resonant capacitor voltage v at at least three effective points. Cr and equivalent resonant inductor current i Lr The value of the second voltage estimate v at the second port 102 of the resonant converter is used to estimate the second voltage estimate v. oEst Estimated equivalent resonant capacitance C rEst And / or the estimated value of the equivalent resonant inductance L rEst The at least three effective points have different coordinates on the equivalent resonant capacitor voltage and equivalent resonant inductor current state plane, and lie on a state trajectory formed by the equivalent resonant capacitor voltage and the equivalent resonant inductor current, and the at least three effective points are not symmetrical about the center of the state trajectory.

[0074] In this invention, the at least three valid points can be obtained through sampling, specifically by sampling the resonant capacitor voltage and resonant inductor current at at least three valid sampling points. A valid sampling point can be defined as any pair of sampling points that cannot be spaced apart. Where m is a positive integer (i.e., m = 1, 2, 3...), T sThe switching period of the resonant converter is given. Preferably, the resonant capacitor voltage and resonant inductor current are simultaneously sampled at each effective sampling point.

[0075] Among them, in estimating the second voltage estimate v oEst When the resonant converter is operating or starting up, the resonant cavity energy function can be constructed based on the state equations of the resonant capacitor voltage and the resonant inductor current in the time domain, and the trajectory equations of the resonant capacitor voltage and the resonant inductor current on the state plane can be obtained; then, based on the trajectory equations and the at least three effective points, the second voltage estimate v can be estimated. oEst .

[0076] like Figure 3 As shown, it illustrates the equivalent resonant capacitor voltage v in the parameter estimation method of the present invention. Cr and equivalent resonant inductor current i Lr The state trajectory.

[0077] exist Figure 3 In the middle, at the primary side bridge arm voltage v p rising edge (corresponding to) Figure 3 The sampling point p0 can also be slightly delayed, for example, starting from the first lag time, and then successively delayed by an interval T. d Sampling resonant capacitor voltage (e.g.) Figure 1 Equivalent resonant capacitor C r The equivalent resonant capacitor voltage v Cr ) and resonant current (e.g. Figure 1 The equivalent resonant inductance L flows through the middle. r The equivalent resonant inductor current i Lr The resonant capacitor voltage and the resonant current are each sampled at least 3 valid sampling points (e.g., including sampling point p1, sampling point p2, and sampling point p3).

[0078] Furthermore, when the sampling rate is high, three samples can be taken simultaneously within half a switching cycle, such as... Figure 3 The illustrated embodiment performs sampling within the positive half-cycle. If the sampling rate cannot meet the requirements, sampling can be distributed across multiple switching cycles; however, this is not intended to limit the invention.

[0079] In this embodiment, it is assumed that the coordinates of the sampling point are p. i (x i ,y i ), i = 1 to 3, and each sampling point corresponds to the synchronous sampling of the resonant capacitor voltage and resonant current. Based on the elliptic arc The output voltage estimate can be obtained from the equation of the ellipse. in The detailed process of parameter estimation will be explained in more detail later.

[0080] The parameter estimation method of this invention can also be sampled during the negative half-cycle or during multiple switching cycles, which is consistent with... Figure 3 The example shown, which involves sampling during the positive half-cycle, is similar and will not be repeated here.

[0081] This invention estimates parameters using a time-domain elliptical trajectory, achieving higher accuracy than existing methods that utilize frequency-domain fundamental wave equivalence. Furthermore, this invention can estimate the output voltage, making it suitable for applications where there is no communication between the primary and secondary sides.

[0082] The parameter estimation method of the present invention will be further described in detail below.

[0083] (I) Sampling instructions and output voltage estimation method

[0084] (1) When the switching frequencies are different

[0085] Figures 4A to 4C Taking positive half-cycle sampling as an example, resonant cavity sampling methods at different switching frequencies are presented. Figures 4A to 4C The switching frequency f is shown respectively. s >Resonant frequency f r Switching frequency f s =Resonant frequency f r Switching frequency f s <Resonant frequency f r The state trajectory is obtained by sampling the resonant cavity at different switching frequencies. This invention can estimate the output voltage using at least three effective sampling points, i.e., by estimating the output voltage estimate v. oEst The following explanation will use three valid sampling points as an example.

[0086] exist Figures 4A to 4C In the diagram, sampling point p0 corresponds to the primary side bridge arm voltage v. p The rising edge of the primary side bridge arm voltage v is detected. p After the rising edge, there can be a time interval T. d Sampling is performed at sampling points p1, p2, and p3. Sampling during the negative half-cycle is similar and will not be elaborated further. At different switching frequencies f... s Below, sampling points p1, p2, and p3 are all located on the elliptical arc during power transfer from the primary side to the secondary side. Therefore, the output voltage estimate v oEst The calculation method is the same.

[0087] In this invention, such as Figure 1 The LLC resonant converter shown has the following voltage v in the time domain when it is in operation: Cr and resonant current iLr The state equation is:

[0088]

[0089] Constructing the energy function of the resonant cavity: It is easy to know: Then the resonant capacitor voltage v Cr and resonant current i Lr The waveform is an elliptical arc with its focus on the horizontal axis:

[0090]

[0091] Where: E(0) is the initial energy of the resonant cavity. Equation (2) can be rewritten as the standard elliptic equation:

[0092]

[0093] in, c = v p -nv s .

[0094] Since LLC control (frequency modulation / phase shifting) essentially changes the voltage applied across the resonant cavity, i.e., v... p -nv s , thereby changing v Cr i Lr This causes a change in the trajectory. Substituting the coordinates of sampling points p1, p2, and p3 into the ellipse equation (3), we get:

[0095]

[0096] Thus, the output voltage estimate can be obtained based on c. According to a 2 and b 2 The resonant impedance of the resonant converter can then be estimated.

[0097] Furthermore, when the resonant converter starts up, the resonant capacitor voltage v Cr and resonant current i Lr State trajectory (e.g.) Figure 5 The figure shown also satisfies the equation of an ellipse, and the corresponding parameters can be estimated using the parameter estimation method described above.

[0098] (2) When the sampling point distribution is different

[0099] by Figures 6A-6B The switching frequency f shown s >Resonant frequency f r Taking an example, at least three valid sampling points are required. s =fr f s <f r Similarly, this will not be elaborated upon here.

[0100] When the sampling points are distributed differently, sampling can be performed within the same switching cycle, including but not limited to continuous sampling only in the positive half-cycle or only in the negative half-cycle.

[0101] When the sampling rate is high enough, at least three valid sampling points can be continuously sampled only during the positive or negative half-cycle of the same switching cycle. For example... Figure 6A As shown, when sampling is performed only during the positive half-cycle (i.e., the effective sampling point is only located in the positive half-cycle), the primary side bridge arm voltage v p Starting from the rising edge (corresponding to sampling point p0) or a point after which, a delay of one interval T is sequentially applied. d Sampling is performed, with a delay interval T for each time. d They can be the same or different; for example, sampling can be performed at sampling points p1, p2, and p3. Figure 6A As shown, when sampling is performed only during the negative half-cycle (i.e., the effective sampling point is only located in the negative half-cycle), the primary side bridge arm voltage v p The falling edge (corresponding to sampling point p'0) starts or lags by one point, and is subsequently delayed by an interval T. d Sampling is performed, with a delay interval T for each time. d They can be the same or different, for example, sampling can be performed at sampling points p'1, ​​p'2, and p'3.

[0102] Alternatively, valid sampling points can also be located simultaneously in the positive and negative half-cycles. For example, at least three valid sampling points can be continuously sampled in the positive and negative half-cycles within the same switching cycle, including but not limited to... Figure 6B The scenario shown illustrates that sampling points p1 and p2 are sampled during the positive half-cycle, and sampling point p3 is sampled during the negative half-cycle. For example... Figure 6B In the situation shown, during estimation, the central symmetry of the sampling points in the positive and negative half-cycles can be utilized. Effective sampling points located in the negative half-cycle can be converted to the positive half-cycle for parameter estimation. For example, [the following is an example of this:] Figure 6B The sampling point p3 in the model is converted to the sampling point p'3. In other embodiments, effective sampling points located in the positive half-cycle can also be converted to the negative half-cycle for parameter estimation, which is not intended to limit the invention.

[0103] When the sampling points are distributed differently, sampling can be performed within multiple different switching cycles. That is, sampling can be performed within multiple different switching cycles (these multiple switching cycles can be continuous or discontinuous), and at least three valid sampling points need to be ensured when performing parameter estimation.

[0104] (II) Resonant cavity parameters (equivalent resonant inductance L) r Equivalent resonant capacitance C r Magnetizing inductance L m And the average value of the resonant current i over half a switching cycle LrAvg estimation method

[0105] (1) Estimate the equivalent resonant inductance L r Equivalent resonant capacitance C r

[0106] In this invention, when estimating the equivalent resonant capacitance estimate C... rEst and / or the estimated value of the equivalent resonant inductance L rEst First, the state trajectory is normalized to obtain the normalized trajectory, and then the resonant angular frequency ω of the resonant converter is estimated based on the normalized trajectory. rEst Then, based on the resonant impedance estimate Z... rEst And the estimated value of the resonant angular frequency ω rEst The equivalent resonant capacitance C can be estimated. rEst and / or the estimated value of the equivalent resonant inductance L rEst .

[0107] like Figure 7A , Figure 7B As shown, the switching frequencies f are respectively... s >Resonant frequency f r Equivalent resonant capacitor voltage v Cr and equivalent resonant inductor current i Lr The resulting elliptical trajectory, and the trajectory after normalization of the elliptical trajectory (e.g., a circular trajectory after normalization, but this invention is not limited thereto, when the switching frequency f... s =Resonant frequency f r When and when the switching frequency f s <Resonant frequency f r (The same applies at the same time). Figure 7B In the normalized trajectory shown, for the arc segment p0 to p, its center is (1+k,0) and its radius is r0; for the arc segment p to p3, its center is (1-k,0) and its radius is r1. Considering the triangle formed by sampling points p1, p2, and the center O1, we can obtain: The estimated value of the resonant angular frequency can then be approximated as: According to Z rEst and ω rEst The estimated value of the equivalent resonant capacitance C can be estimated. rEst and / or the estimated value of the equivalent resonant inductance L rEst :

[0108]

[0109] In summary, the output voltage estimate v can be obtained using three effective sampling points. oEst Estimated equivalent resonant capacitance C rEst Estimated equivalent resonant inductance L rEst The estimate.

[0110] (2) Estimate the excitation inductance L m

[0111] When three valid sampling points contain sampling point p0 (refer to...) Figure 6A That is, the corresponding primary side bridge arm voltage v p The sampling point at the rising edge (or sampling point p'0, which can be referenced) Figure 6A That is, the corresponding primary side bridge arm voltage v p When sampling at the falling edge of the curve (the sampling point), the excitation inductance L can be directly estimated. m .

[0112] When the three valid sampling points do not include sampling point p0 or sampling point p'0, additional sampling corresponding to sampling point p0 or sampling point p'0 is required. The estimated output voltage v is obtained by using the sampled values ​​of the resonant capacitor voltage and resonant current corresponding to sampling point p0 or sampling point p'0. oEst (i.e., the second voltage estimate). Then, based on the output voltage estimate v... oEst and the per-unit value i of the peak current of the magnetizing inductor. LmpkEst This allows for the estimation of the magnetizing inductance L of the resonant converter. mEst .

[0113] For example, in Figure 7B middle, arc segment and arc segment The intersection point p(ξ,η) satisfies: And the ordinate of the intersection point p is the per-unit value of the peak current of the magnetizing inductor, that is... but:

[0114]

[0115] The parameter estimation method of this invention utilizes an elliptical trajectory in the time domain to estimate the output voltage value v. oEst Estimated equivalent resonant capacitance C rEst Estimated equivalent resonant inductance L rEst Estimated value of excitation inductance L mEst It can achieve online estimation of resonant parameters without prior knowledge.

[0116] (3) Estimate the average value of the resonant current i during half a switching cycle. LrAvg

[0117] When the switching frequency f s>Resonant frequency f r At that time, the resonant cavity waveform is as follows Figure 8 As shown, the sampled value of the resonant current at time t0 is i. Lr1 (i.e., the resonant current i corresponding to sampling point p0) Lrp0 ), with an interval of time T d Afterwards, the resonant current sampling value is i Lr2 (i.e., the resonant current i corresponding to sampling point p1) Lrp1 ).

[0118] Assuming the resonant current is approximately sinusoidal, that is Based on the sampled value i of sampling point p0 Lr1 and the sampled value i of sampling point p1 Lr2 The resonant current i can be approximately estimated. Lr Fundamental waveform:

[0119]

[0120] Then half a switching cycle T h The estimated value of the average resonant current i LrAvgEst for:

[0121]

[0122] in

[0123] In this invention, based on the estimated output voltage v o and resonant current i Lr This can realize the v of the resonant converter. o Outer ring - i Lr The inner loop employs dual closed-loop control. For example, by controlling the resonant current i... Lr The fundamental frequency approximation can meet the control requirements of the inner current loop. Furthermore, when there is output voltage sampling, the outer loop can use the sampled output voltage value as feedback; when the output voltage cannot be obtained, the estimated output voltage value v can be used. oEst This feedback mechanism enables dual closed-loop control.

[0124] As shown in Figure 9, the present invention also provides a control method 900 for a resonant converter, which may include:

[0125] Step S901: Configure a dual closed-loop controller 30 (refer to the reference). Figure 1 As shown), it may have a voltage feedback terminal 301 and a current feedback terminal 302; the voltage feedback terminal 301 is located in the outer loop and is configured to receive a voltage signal reflecting the output voltage of the output port 102 of the resonant converter, wherein the voltage value of the voltage signal is the output voltage sample value v sampled from the output port. oAlternatively, the second voltage estimate v can be obtained using parameter estimation methods. oEst As the output voltage estimate v oEst The current feedback terminal 302 is located in the inner loop and is configured to receive the estimated value i of the average resonant current of half a switching cycle obtained by the parameter estimation method. LrAvgEst ;

[0126] Step S902, when the output voltage sample value v can be sampled and acquired o At that time, the dual closed-loop controller 30 receives the output voltage sample value v through the voltage feedback terminal 301. o And control the primary-side switching frequency of the primary-side switch in the primary-side circuit OSC of the resonant converter;

[0127] Step S903, when it is not possible to sample and obtain the output voltage sample value v o At that time, the dual closed-loop controller 30 receives the output voltage estimate v through the voltage feedback terminal 301. oEst And control the primary-side switching frequency of the primary-side switch.

[0128] In this invention, when there is no communication between the primary and secondary sides, the following can be used: Figure 9B The control block diagram shown controls the primary-side switch. Furthermore, the control effect during load addition and subtraction is as follows: Figure 10 As shown, where Figure 10 Part a shows the control effect under sudden loading of 40A-80A. Figure 10 Part b illustrates the control effect during a sudden load reduction of 80A-50A. Figure 10 It is evident that the control method provided by this invention is stable under dynamic conditions of sudden load increase and decrease, and the output voltage estimate v oEst The results are basically consistent with the actual values, which verifies the feasibility of the elliptical trajectory fitting algorithm used in this invention.

[0129] In this invention, when there is no communication between the primary and secondary sides, the output voltage reference value v oref The control effect during change is as follows Figure 11 As shown, the control effect when the input voltage contains second harmonic fluctuations is as follows: Figure 12 As shown. By Figure 11 and Figure 12 It can be seen that the control method proposed in this invention is adaptable to both the step value of the output voltage setpoint and the fluctuation of the input voltage.

[0130] In this invention, when the resonant cavity parameters are consistent with the design values, the resonant capacitor voltage v proposed in this invention... Cr Resonant current i Lr The sampling results are as follows: Figure 13 As shown in parts b and a, the control effect is as follows: Figure 14As shown in the figure. The simulation takes four sampling points during the positive half-cycle as an example. From the control effect, it can be seen that the estimated value of the average resonant current i during half a switching cycle is... LrAvgEst and output voltage estimate v oEst The results are basically consistent with the actual values, and the estimation error of the resonant cavity parameters is less than 1.2%. The simulation demonstrates the feasibility of the resonant cavity sampling and parameter estimation method proposed in this invention.

[0131] In this invention, when the actual L r When the value is 10% larger and other parameters remain unchanged, the control effect of the control method proposed in this invention is as follows: Figure 15 As shown. By Figure 15 It can be seen that before 0.02s, the resonant cavity parameter estimation was not initiated; only the output voltage and resonant current were estimated. Since the estimated output voltage value v... oEst The estimated value of i, the average value of the resonant current over half a switching cycle. LrAvgEst The estimation does not depend on the resonant cavity parameters; the estimated value follows the actual parameters. However, the estimated resonant capacitance C... rEst Estimated value of resonant inductance L rEst And the estimated value of magnetizing inductance L mEst The estimation depends on the normalization of the resonant impedance, when the resonant inductance L r When the calculated parameters do not match the design values, there is a significant error between the actual and calculated values. After initiating resonant cavity parameter estimation at 0.02s, the estimated resonant impedance Z... rEst The estimated results are close to the actual values, and the estimated values ​​of the resonant cavity parameters are even closer to the actual values.

[0132] The parameter estimation method for LLC resonant converters proposed in this invention can be applied in SST (Single-Stage Transformer) systems to fast charging stations, photovoltaic power plants, data centers, energy storage, and microgrids. The embodiments of this invention are not limited to the estimation of resonant cavity parameters for LLC resonant converters, nor are they limited to the embodiments listed below.

[0133] Example 1: Parameter estimation when there are more than 4 sampling points

[0134] like Figure 16 As shown, it illustrates the switching frequency f. s >Resonant frequency f r At that time, the equivalent resonant capacitor voltage v Cr and equivalent resonant inductor current i Lr The resulting trajectory. When the sampling rate meets the requirements, as many samples as possible should be taken to improve the accuracy of parameter estimation. Figure 16 A schematic diagram is given showing the sampling of 7 points within half a switching cycle, i.e., the sampling point is p. i (x i ,y i), where i = 0 to 6, and the sampling points p1 to p6 fall on the second elliptical arc. Substituting the data of the six sampling points p1 to p6 into the elliptical equation, we obtain an overdetermined system of six equations containing three unknowns a, b, and c:

[0135]

[0136] Subtracting each pair of equations in equation (9) and multiplying both sides by b2, we get:

[0137]

[0138] Equation (10) can be rewritten as A m×2 z = B, where: m is the number of sampling points on the elliptical arc; in this embodiment, m = 6. The least squares solution z = (A) can be obtained. T ·A) -1 A T B, and thus the output voltage estimate is obtained. and resonant impedance estimate

[0139] Example 2: Equivalent Parameter Estimation of CLLC Resonant Converter

[0140] Figure 17 The circuit topology and equivalent cavity diagram of the CLLC resonant converter are shown below, where C r1 and C r2 These are the primary-side resonant capacitor and the secondary-side resonant capacitor, respectively, L r1 and L r2 These are the primary resonant inductance and the secondary resonant inductance, respectively, C r For the equivalent resonant capacitance, L r Here, n is the equivalent resonant inductance, and n is the transformer turns ratio.

[0141] Based on the equivalent impedance relationship of the primary and secondary sides of the transformer, we can obtain L r =L r1 +n 2 L r2 , By sampling the primary resonant capacitor voltage v Cr1 and secondary resonant capacitor voltage v Cr2 and the primary resonant current i Lr1 Then the equivalent resonant capacitor voltage is v Cr =v Cr +nv Cr According to v Cr and i Lr1 The parameter estimation method proposed in this invention can be used for parameter estimation.

[0142] This invention proposes a parameter estimation method for a resonant converter. By sampling the resonant capacitor voltage and resonant inductor current, and utilizing the elliptical trajectory in the time domain, C can be estimated. r L r L m V o i LrAvg Estimation of parameters such as...

[0143] This invention is based on the output voltage estimate v oEst The estimated value of i, the average value of the resonant current over half a switching cycle. LrAvgEst It is also possible to design v oEst Outer ring - i LrAvgEst The inner loop dual closed-loop controller achieves stable control of the output voltage and is suitable for control without communication between the primary and secondary sides of a resonant converter.

[0144] Exemplary embodiments of the present invention have been specifically illustrated and described above. It should be understood that the present invention is not limited to the disclosed embodiments; rather, the present invention is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A parameter estimation method for a resonant converter, characterized in that, The resonant converter has a first port and a second port, and includes a resonant cavity, the resonant cavity including an equivalent resonant capacitance and an equivalent resonant inductance, and the parameter estimation method includes: Based on the first voltage at the first port and the values ​​of the equivalent resonant capacitor voltage and equivalent resonant inductor current at at least three valid points, estimate the second voltage, equivalent resonant capacitor, and / or equivalent resonant inductor of the second port of the resonant converter. The at least three valid points have different coordinates on the state plane of the equivalent resonant capacitor voltage and the equivalent resonant inductor current, lie on a state trajectory formed by the equivalent resonant capacitor voltage and the equivalent resonant inductor current, and are not symmetrical about the center of the state trajectory. The at least three valid points can be obtained through sampling, that is, sampling the resonant capacitor voltage and resonant inductor current of at least three valid sampling points. The valid sampling points are defined as those where no two sampling points are spaced apart. Where m is a positive integer, T s The switching period of the resonant converter is defined as follows: at each effective sampling point, the resonant capacitor voltage and the resonant inductor current are sampled synchronously. The at least three valid sampling points are sampled during the positive or negative half-cycle of the same switching cycle. When sampling is performed during the positive half-cycle, it starts from the rising edge of the primary side bridge arm voltage of the resonant converter or after the first lag time, and the resonant capacitor voltage and the resonant inductor current are sampled synchronously after being delayed by the first interval time in sequence, wherein the first interval time of each delay is the same or different. When sampling is performed during the negative half-cycle, it begins with the falling edge of the primary side bridge arm voltage of the resonant converter or after a second lag time, and the resonant capacitor voltage and the resonant inductor current are sampled synchronously with a second delay time in sequence, wherein the second delay time is the same or different each time.

2. The parameter estimation method according to claim 1, characterized in that, When estimating the second voltage estimate, the following are included: When the resonant converter is working or starting up, the resonant cavity energy function is constructed according to the state equations of the resonant capacitor voltage and the resonant inductor current in the time domain, and the trajectory equations of the state trajectories of the resonant capacitor voltage and the resonant inductor current on the state plane are obtained. The second voltage estimate is estimated based on the trajectory equation and the at least three valid points.

3. The parameter estimation method according to claim 2, characterized in that, Also includes: Based on the trajectory equation, estimate the resonant impedance of the resonant converter.

4. The parameter estimation method according to claim 1, characterized in that, The at least three valid sampling points are sampled in both the positive and negative half-cycles within the same switching cycle.

5. The parameter estimation method according to claim 4, characterized in that, When making the estimation, the sampling points of the positive half-cycle and the negative half-cycle are centrally symmetric. The effective sampling points located in the negative half-cycle are converted to the positive half-cycle for estimation, or the effective sampling points located in the positive half-cycle are converted to the negative half-cycle for estimation.

6. The parameter estimation method according to claim 1, characterized in that, The at least three valid sampling points are sampled within different multiple switching cycles, which may be continuous or discontinuous.

7. The parameter estimation method according to claim 3, characterized in that, When estimating the estimated values ​​of the equivalent resonant capacitance and / or equivalent resonant inductance, the following are included: The state trajectory is normalized to obtain a normalized trajectory, and the resonant angular frequency of the resonant converter is estimated based on the normalized trajectory. Based on the estimated resonant impedance and the estimated resonant angular frequency, estimate the estimated equivalent resonant capacitance and / or the estimated equivalent resonant inductance.

8. The parameter estimation method according to claim 1, characterized in that, The resonant cavity also includes a magnetizing inductor, and the parameter estimation method further includes: When the at least three valid points include a sampling point P0 corresponding to the rising or falling edge of the primary side bridge arm voltage of the resonant converter, the estimated value of the magnetizing inductance of the resonant converter is estimated based on the estimated value of the second voltage and the per-unit value of the peak current of the magnetizing inductance.

9. The parameter estimation method according to claim 1, characterized in that, The resonant cavity also includes a magnetizing inductor, and the parameter estimation method further includes: When the at least three valid points do not include a sampling point P0 corresponding to the rising or falling edge of the primary side bridge arm voltage of the resonant converter, an additional sampling point corresponding to P0 is added. The second voltage estimate is obtained by using the sampled values ​​of the resonant capacitor voltage and resonant inductor current corresponding to the sampling point P0. The magnetizing inductance estimate of the resonant converter is then estimated based on the second voltage estimate and the per-unit value of the peak current of the magnetizing inductor.

10. The parameter estimation method according to claim 1, characterized in that, Also includes: Based on the resonant current values ​​corresponding to the two effective points, estimate the average value of the resonant current for half a switching cycle.

11. The parameter estimation method according to claim 1, characterized in that, When there are more than three valid points, the least squares method is used to fit and estimate the second voltage estimate, the equivalent resonant capacitance estimate, and / or the equivalent resonant inductance estimate of the second port of the resonant converter.

12. The parameter estimation method according to any one of claims 1 to 11, characterized in that, The resonant converter is an LLC resonant converter.

13. The parameter estimation method according to any one of claims 1 to 11, characterized in that, The resonant converter is a CLLC resonant converter. It is calculated by sampling the primary resonant capacitor voltage, the secondary resonant capacitor voltage, and the primary resonant current of the CLLC resonant converter. The equivalent value of the equivalent resonant capacitor voltage is calculated based on the sampled values ​​of the primary resonant capacitor voltage and the secondary resonant capacitor voltage. The equivalent value of the equivalent resonant capacitor voltage and the sampled value of the primary resonant current are then used for estimation.

14. A control method for a resonant converter, characterized in that, include: Configure a dual closed-loop controller, which has a voltage feedback terminal and a current feedback terminal; The voltage feedback terminal is located in the outer loop and is configured to receive a voltage signal reflecting the output voltage of the output port of the resonant converter, wherein the voltage value of the voltage signal is the output voltage sample value sampled from the output port, or a second voltage estimate obtained by using the parameter estimation method as described in any one of claims 1 to 13 as the output voltage estimate. The current feedback terminal is located in the inner loop and is configured to receive an estimate of the average value of the resonant current for half a switching cycle obtained by the parameter estimation method as described in claim 10. When the output voltage sample value can be sampled and obtained, the dual closed-loop controller receives the output voltage sample value through the voltage feedback terminal and controls the primary-side switching frequency of the primary-side switch in the primary-side circuit of the resonant converter. When the output voltage sample value cannot be obtained, the dual closed-loop controller receives the output voltage estimate through the voltage feedback terminal and controls the primary-side switching frequency of the primary-side switch.

15. The control method for the resonant converter according to claim 14, characterized in that, The primary-side circuit includes a first primary-side bridge arm and a second primary-side bridge arm connected in parallel. The first primary-side bridge arm includes a first primary-side switch and a second primary-side switch connected in series. The second primary-side bridge arm includes a third primary-side switch and a fourth primary-side switch connected in series. The dual closed-loop controller controls the first primary-side switch and the fourth primary-side switch to be synchronized, the second primary-side switch and the third primary-side switch to be synchronized, and the first primary-side switch and the second primary-side switch, the third primary-side switch and the fourth primary-side switch are complementaryly turned on with a 50% duty cycle.

16. A resonant converter, characterized in that, The resonant converter has a first port and a second port, and includes a resonant cavity, the resonant cavity including an equivalent resonant capacitance and an equivalent resonant inductance, and the resonant converter further includes: The estimation unit is configured to perform the parameter estimation method as described in any one of claims 1 to 13 to obtain a second voltage estimate, an equivalent resonant capacitance estimate, and / or an equivalent resonant inductance estimate for the second port of the resonant converter.

17. The resonant converter according to claim 16, characterized in that, The resonant cavity further includes a magnetizing inductor, and the estimation unit is further configured to perform the parameter estimation method as described in claim 8 or 9 to obtain an estimated value of the magnetizing inductor of the resonant converter.

18. The resonant converter according to claim 16, characterized in that, The estimation unit is further configured to perform the parameter estimation method as described in claim 10 to obtain an estimate of the average resonant current of the resonant converter over half a switching cycle.

19. The resonant converter according to claim 18, characterized in that, The first port is the input port of the resonant converter and is used to receive an input voltage; the second port is the output port of the resonant converter and is used to output an output voltage. The resonant converter also includes: A dual-loop controller has a voltage feedback terminal and a current feedback terminal; the voltage feedback terminal is located in the outer loop and is configured to receive a voltage signal reflecting the output voltage, wherein the voltage value of the voltage signal is an output voltage sample value sampled from the output port, or a second voltage estimate obtained by using the parameter estimation method as described in any one of claims 1 to 13 as the output voltage estimate; the current feedback terminal is located in the inner loop and is configured to receive an estimate of the average value of the resonant current over half a switching cycle; When the output voltage sample value can be sampled and obtained, the dual closed-loop controller receives the output voltage sample value through the voltage feedback terminal and controls the primary-side switching frequency of multiple primary-side switches in the primary-side circuit of the resonant converter. When the output voltage sample value cannot be obtained, the dual closed-loop controller receives the output voltage estimate through the voltage feedback terminal and controls the primary-side switching frequency of the primary-side switch.

20. The resonant converter according to claim 19, characterized in that, The plurality of primary-side switches include a first controllable switch, a second controllable switch, a third controllable switch, and a fourth controllable switch. The first controllable switch and the second controllable switch are connected in series to form a first primary-side bridge arm, and the third controllable switch and the fourth controllable switch are connected in series to form a second primary-side bridge arm. The first primary-side bridge arm and the second primary-side bridge arm are connected in parallel, and the midpoint of the first primary-side bridge arm and the midpoint of the second primary-side bridge arm are connected to the first end of the resonant cavity. The dual closed-loop controller synchronizes the first controllable switch with the fourth controllable switch, and the second controllable switch with the third controllable switch. The first controllable switch and the second controllable switch, as well as the third controllable switch and the fourth controllable switch, are turned on complementaryly with a 50% duty cycle.

21. The resonant converter according to claim 20, characterized in that, The secondary circuit of the resonant converter includes a first switch, a second switch, a third switch, and a fourth switch. The first switch and the second switch are connected in series to form a first secondary bridge arm, and the third switch and the fourth switch are connected in series to form a second secondary bridge arm. The first secondary bridge arm and the second secondary bridge arm are connected in parallel, and the midpoint of the first secondary bridge arm and the midpoint of the second secondary bridge arm are connected to the second end of the resonant cavity.

22. The resonant converter according to claim 20, characterized in that, The dual closed-loop controller includes a voltage comparison module, a first regulator, a current comparison module, a second regulator, a frequency comparison module, a limiter, and a carrier generation module. The output of the voltage comparison module is connected to the input of the current comparison module via the first regulator to compare the voltage signal with an output voltage reference signal. After being regulated by the first regulator, the average value reference signal of the resonant current for half a switching cycle is output and transmitted to the current comparison module. The output of the current comparison module is connected to the input of the frequency comparison module via the second regulator to compare the reference signal of the average value of the resonant current of half a switching cycle with the estimated value of the average value of the resonant current of half a switching cycle, and after being adjusted by the second regulator, an adjustment signal is output and transmitted to the frequency comparison module. The output of the frequency comparison module is connected to the input of the carrier generation module via the limiter, so as to compare the frequency of the adjustment signal with an initial switching frequency of the resonant converter, and output a limited signal after being limited by the limiter and transmitted to the carrier generation module. The carrier generation module is used to generate multiple drive signals based on the amplitude limiting signal, so as to drive the multiple primary-side switches respectively.

23. The resonant converter according to claim 22, characterized in that, The carrier generation module includes a carrier generation unit and a PWM generation unit, wherein the carrier generation unit is used to generate a triangular carrier based on the amplitude limiting signal, and the PWM generation unit is used to generate the plurality of driving signals based on the triangular carrier.

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