A control method and related device of a phase-shifted full-bridge converter

Abstract

The present application provides a control method and related equipment for a phase-shifted full-bridge converter, the method comprising: obtaining an inductor current value at the start time of a current switching cycle of an output filter inductor, and a duty cycle at the start time of a previous switching cycle of a secondary side equivalent circuit on a secondary side rectifier side; based on a first lumped disturbance estimation model, obtaining a first inductor current estimation value and a first lumped disturbance estimation value according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, wherein the first lumped disturbance estimation model is constructed according to a linear extended state observer; based on a second lumped disturbance estimation model, obtaining a lumped disturbance total estimation value at the start time of the current switching cycle according to the first inductor current estimation value and the first lumped disturbance estimation value, wherein the second lumped disturbance estimation model is constructed according to an extended state observer; and controlling the conduction of a switch tube in a primary inverter side of a next switching cycle based on the lumped disturbance total estimation value.

Description

Technical Field

[0001] The present application relates to the field of power electronic control technology, and in particular to a control method and related equipment of a phase-shifted full-bridge converter. Background Art

[0002] Compared with the single-inductor dual-output buck-boost converter, the phase-shifted full-bridge (PSFB) converter has a transformer and can be used as the actuator of the current conversion device between the low-voltage DC side and the high-voltage DC side in equipment such as photovoltaic power supply systems, photovoltaic storage devices, uninterruptible power supplies (UPS) and vehicle-mounted DC converters.

[0003] At present, when phase-shifted full-bridge converters are used in industry, single phase shift control (SPS) is mostly adopted. The control system of single phase shift control only considers some ideal working conditions, and does not take into account most of the actual complex working conditions. Complex working conditions cause the external environment or internal changes of the phase-shifted full-bridge converter, resulting in lumped disturbances, which leads to the performance degradation of the phase-shifted full-bridge converter. At the same time, the phase-shifted full-bridge converter itself also has problems such as unstable dynamic response, poor anti-interference performance, and large sudden interference vibration.

[0004] In this way, based on the complexity and variability of actual complex working conditions and the inherent problems of the phase-shifted full-bridge converter, the phase-shifted full-bridge converter produces a lumped disturbance. When single-phase shift control is adopted, the control system efficiency is reduced, the output voltage quality is reduced, and the control performance is reduced.

[0005] In view of this, it is necessary to find a method to improve the control system working efficiency, output voltage quality and control performance of the phase-shifted full-bridge converter. Summary of the invention

[0006] The present application provides a control method and related equipment for a phase-shifted full-bridge converter, so as to improve the control system working efficiency, output voltage quality and control performance of the phase-shifted full-bridge converter.

[0007] The first aspect of the present application provides a control method for a phase-shifted full-bridge converter, wherein the phase-shifted full-bridge converter includes a primary inverter side and a secondary rectifier side, wherein the secondary rectifier side includes an output filter inductor, and the method includes: obtaining an inductor current value at the start time of a current switching cycle of the output filter inductor, and a duty cycle at the start time of a previous switching cycle of a secondary equivalent circuit of the secondary rectifier side; based on a first lumped disturbance estimation model, obtaining a first inductor current estimation value and a first lumped disturbance estimation value according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, wherein the first lumped disturbance estimation model is constructed according to a linear extended state observer; based on a second lumped disturbance estimation model, obtaining a lumped disturbance total estimation value at the start time of the current switching cycle according to the first inductor current estimation value and the first lumped disturbance estimation value, wherein the second lumped disturbance estimation model is constructed according to an extended state observer; and controlling the conduction of a switch tube in the primary inverter side of the next switching cycle based on the lumped disturbance total estimation value.

[0008] In some embodiments of the first aspect, a first inductor current estimate value and a first lumped disturbance estimate value are obtained according to the inductor current value at the start time of a current switching cycle and the duty cycle at the start time of a previous switching cycle, including: determining the first lumped disturbance estimate value based on the inductor current value at the start time of the current switching cycle; determining the first inductor current estimate value based on the first lumped disturbance estimate value.

[0009] In some embodiments of the first aspect, a total estimated value of the lumped disturbance at the start time of the current switching cycle is obtained based on the first inductor current estimate value and the first lumped disturbance estimate value, including: determining a second lumped disturbance estimate value based on the first inductor current estimate value; obtaining a total estimated value of the lumped disturbance at the start time of the current switching cycle based on the first lumped disturbance estimate value and the second lumped disturbance estimate value.

[0010] In some embodiments of the first aspect, the conduction of the switch tube in the primary inverter side of the next switching cycle is controlled based on the total estimated value of the lumped disturbance, including: determining the required duty cycle at the start time of the next switching cycle of the secondary equivalent circuit based on the total estimated value of the lumped disturbance; determining the duty cycle at the start time of the next switching cycle of the primary inverter side according to the required duty cycle and the compensation duty cycle at the start time of the next switching cycle of the secondary equivalent circuit; determining the phase shift angle at the start time of the next switching cycle of the primary inverter side according to the duty cycle at the start time of the next switching cycle of the primary inverter side; and controlling the conduction of the switch tube in the primary inverter side of the next switching cycle based on the phase shift angle at the start time of the next switching cycle.

[0011] In some embodiments of the first aspect, the method also includes: defining an equivalent mathematical model of an output filter inductor based on the principle of Kirchhoff's voltage law; constructing a first-order hyperlocal model of the secondary rectifier side based on the equivalent mathematical model of the output filter inductor; obtaining a duty cycle prediction model based on the cost function of the output filter inductor and the first-order hyperlocal model; the duty cycle prediction model is used to input a total estimated value of the lumped disturbance, and based on the total estimated value of the lumped disturbance, determine the duty cycle of the secondary equivalent circuit at the starting time of the next switching cycle; determine the duty cycle of the primary inverter side at the starting time of the next switching cycle according to the required duty cycle and the compensated duty cycle at the starting time of the next switching cycle of the secondary equivalent circuit.

[0012] In some embodiments of the first aspect, the switch tube in the primary inverter side of the next switching cycle is controlled to be turned on based on the phase shift angle at the starting moment of the next switching cycle, including: based on the phase shift angle at the starting moment of the next switching cycle, more than two switch tubes in the same voltage loop in the primary inverter side are controlled to be turned on at preset moments of the next switching cycle respectively.

[0013] The second aspect of the present application provides a current conversion device, including a control system and a phase-shifted full-bridge converter, the phase-shifted full-bridge converter including a primary inverter side and a secondary rectifier side, the secondary rectifier side including an output filter inductor, the control system is used to obtain the inductor current value of the output filter inductor at the start time of the current switching cycle, and the duty cycle of the secondary equivalent circuit of the secondary rectifier side at the start time of the previous switching cycle; based on a first lumped disturbance estimation model, according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, a first inductor current estimation value and a first lumped disturbance estimation value are obtained, wherein the first lumped disturbance estimation model is constructed according to a linear extended state observer; based on a second lumped disturbance estimation model, according to the first inductor current estimation value and the first lumped disturbance estimation value, a lumped disturbance total estimation value at the start time of the current switching cycle is obtained, wherein the second lumped disturbance estimation model is constructed according to an extended state observer; based on the lumped disturbance total estimation value, the switch tube in the primary inverter side of the next switching cycle is controlled to be turned on.

[0014] The third aspect of the present application also provides a control system for a phase-shifted full-bridge converter, comprising: a processor and a memory; the memory is coupled to the processor, the memory is used to store computer program code, and the processor calls the computer program code to enable the controlled system to execute the method of the first aspect.

[0015] The control method of the phase-shifted full-bridge converter, the current conversion device and the control system of the phase-shifted full-bridge converter provided by the present application are based on the first lumped disturbance estimation model constructed according to the linear extended state observer (mainly used to observe linear lumped disturbances). According to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, a first inductor current estimation value and a first lumped disturbance estimation value that are more accurate than the inductor current value at the start time of the current switching cycle can be obtained. Then, based on the second lumped disturbance estimation model constructed according to the extended state observer (mainly used to observe nonlinear lumped disturbances), according to the first inductor current estimation value and the first lumped disturbance estimation value, a lumped disturbance total estimation value (i.e., total lumped disturbance) is obtained, nonlinear lumped disturbances and linear lumped disturbances can be observed, and the lumped disturbance total estimation value is obtained by correcting the first lumped disturbance estimation model and the second lumped disturbance estimation model, thereby improving the tracking accuracy of the lumped disturbance of the current conversion device.

[0016] Finally, the switch tube in the primary inverter side is controlled to conduct based on the total estimated value of the lumped disturbance, which reduces the power supply loss from the primary inverter side to the secondary rectifier side, and can improve the power transmission efficiency between the power supply and the load. It also improves the working efficiency of the current conversion device, the quality of the output voltage and the control performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0018] Figure 1 A schematic diagram of a structure of a current conversion device provided in an embodiment of the present application;

[0019] Figure 2 A schematic diagram of a flow chart of a control method for a phase-shifted full-bridge converter provided in an embodiment of the present application;

[0020] Figure 3 An equivalent circuit diagram of the secondary rectification side of the phase-shifted full-bridge converter provided in an embodiment of the present application;

[0021] Figure 4 Another schematic diagram of a flow chart of a control method for a phase-shifted full-bridge converter provided in an embodiment of the present application;

[0022] Figure 5 A diagram of a scenario of a control method for a phase-shifted full-bridge converter provided in an embodiment of the present application;

[0023] Figure 6 Another scenario diagram of the control method of the phase-shifted full-bridge converter provided in the embodiment of the present application;

[0024] Figure 7A schematic diagram of the structure of a control system of a phase-shifted full-bridge converter provided in an embodiment of the present application.

[0025] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0026] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0027] The terms "first", "second", etc. involved in this application are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0028] See also Figure 1 , Figure 1 It is a structural schematic diagram of the current conversion device of the present application. The current conversion device 100 includes a control system 10 and a phase-shifted full-bridge (PSFB) converter 20. The control system 10 controls the current conversion device 100 to perform current conversion between the power supply and the load based on the control method of the phase-shifted full-bridge converter of the present application. The phase-shifted full-bridge converter 20 includes a primary inverter side 21 and a secondary rectifier side 22. The primary inverter side 21 is used to convert the direct current of the power supply into alternating current. The secondary rectifier side 22 is used to convert the alternating current into direct current (i.e., into output current) and supply the load. Both the power supply and the load can be a low-voltage DC side or a high-voltage DC side, depending on the specific application scenario. For example, in a photovoltaic power supply system, a photovoltaic storage integrated machine, and an uninterruptible power supply, the power supply is a low-voltage DC side and the load is a high-voltage DC side. When the current conversion device 100 is used as a vehicle-mounted DC converter, the load is a low-voltage DC side and the power supply is a high-voltage DC side.

[0029] The phase-shifted full-bridge converter 20 further includes a transformer 30, and both the primary inverter side 21 and the secondary rectifier side 22 include more than two switch tubes. The control system 10 controls the switch tube of the primary inverter side 21 to be turned on or off, so that the transformer 30 transforms the voltage between the primary inverter side 21 and the secondary rectifier side 22 to control the output voltage of the phase-shifted full-bridge converter 20.

[0030] The secondary rectifier side 22 also includes an output filter inductor L f And the switch tube Q 1 To Q 4 The primary inverter side 21 also includes a primary inductor Lr and a switch tube Q 5 To Q 8 .

[0031] In some embodiments, the current conversion device 100 further includes a primary ePWM drive unit 41, a secondary ePWM drive unit 42 and a voltage sampling unit 43. The control system 10 obtains the phase shift angle according to the control method. The primary ePWM drive unit 41 converts the phase shift angle into a first drive signal, and the first drive signal is used to drive the switch tube Q 1 To Q 4 The secondary side ePWM driving unit 42 converts the phase shift angle into a second driving signal, and the second driving signal is used to drive the switch tube Q 5 To Q 8 For other components not described, please refer to the introduction of the phase-shifted full-bridge converter in the related art.

[0032] It should be noted that Figure 1 This is only a schematic diagram of a structure provided in the embodiment of the present application. Figure 1 The actual form of the various devices included in the Figure 1 The interaction mode between devices is limited, and in the specific application of the solution, it can be set according to actual needs.

[0033] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0034] Please combine Figure 1 and Figure 2 , Figure 2 The control method of the phase-shifted full-bridge converter provided in the present application is a flow chart of a control method, and the execution subject of the control method may be a current conversion device 100, specifically, a control system 10. Figure 2 As shown, the control method may include the following steps:

[0035] Step S110: acquiring the inductor current value of the output filter inductor at the start time of the current switching cycle, and the duty cycle of the secondary side equivalent circuit at the start time of the previous switching cycle of the secondary side rectifier side.

[0036] First, construct the equivalent circuit of the secondary rectifier side, that is, construct the secondary equivalent circuit. The circuit diagram of the secondary equivalent circuit is as follows: Figure 3 As shown, R represents the load, D loss represents the duty cycle lost by the secondary equivalent circuit, D represents the duty cycle of the secondary equivalent circuit, V in Indicates the input voltage. It can be understood that the duty cycle of the primary inverter side = D loss +D.

[0037] See also Figure 1 and Figure 3 The current conversion device 100 also includes various sensing devices (not shown), including a current sensing device, which senses the output filter inductor L f The inductor current value is calculated and sent to the control system 10. The switching cycle refers to the time required for the switch tube to complete a complete process from the on state to the off state and then back to the on state. The duty cycle refers to the ratio of the on time of the switch tube to the entire cycle time in a switching cycle. The control system 10 can calculate the duty cycle of the secondary side equivalent circuit through the relevant sensing values ​​and the component parameters of the current conversion device 100, combined with the secondary side equivalent circuit.

[0038] Step S120: Based on the first lumped disturbance estimation model, according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle ， A first inductor current estimation value and a first lumped disturbance estimation value are obtained.

[0039] The linear extended state observer (LESO) (hereinafter referred to as the LESO observer) is mainly used to estimate the linear lumped disturbance of the current conversion device 100. The generation of linear lumped disturbances includes, in actual working conditions, the linear rise of the ambient temperature around the current conversion device 100, and the poor accuracy of the large signal reduced-order model of the phase-shifted full-bridge converter 20. Based on the linear extended state observer, mathematical transformation is performed to obtain the transformed linear extended state observer (that is, the first lumped disturbance estimation model). The inductor current value at the start of the current switching cycle and the duty cycle at the start of the previous switching cycle are input into the first lumped disturbance estimation model to obtain the first inductor current estimation value and the first lumped disturbance estimation value.

[0040] Exemplarily, the formula for determining the first lumped disturbance estimation value and the first inductor current estimation value (ie, the first lumped disturbance estimation model) is as follows:

[0041] (1)

[0042] The first formula of formula (1) is a formula for determining the first lumped disturbance estimated value, and the second formula of formula (1) is a formula for determining the first inductor current estimated value. By running formula (1), the first lumped disturbance estimated value and the first inductor current estimated value can be determined.

[0043] In formula (1), It represents the first lumped disturbance estimate, which mainly includes the linear lumped disturbance. express The derivative of . represents the bandwidth of the LESO observer, The value is preset based on relevant parameters of the current conversion device 100 . represents the first inductor current estimation value, express The derivative of . Indicates the inductor current at the start of the current switching cycle.

[0044] It can be understood that based on the inductor current value at the start of the current switching cycle , the first lumped disturbance estimate can be determined After running the formula, the first lumped disturbance estimate can be determined. That is, based on the inductor current value at the start of the current switching cycle , determine the first lumped disturbance estimate .

[0045] In the second formula of formula (1), represents the physical gain of the control system 10, The physical gain value is preset according to relevant parameters of the control system 10 . represents the duty cycle at the start of the previous switching cycle of the secondary rectifier side 22. It can be understood that the first lumped disturbance estimate To calculate the first inductor current estimate One of the variables, based on the first lumped disturbance estimate , the first inductor current estimate can be determined That is, based on the first aggregate disturbance estimate , determine the first inductor current estimate .

[0046] It can be understood that according to the actual inductor current value (that is, the inductor current value at the start of the current switching cycle ), determine the disturbance state generated by the current conversion device 100 (the first lumped disturbance estimate Then, the inductor current value at the start of the current switching cycle is corrected according to the disturbance state. For a more accurate estimate of the first inductor current , so as to improve the accuracy of determining the inductor current of the phase-shifted full-bridge converter 20.

[0047] Step S130: Based on the second lumped disturbance estimation model, a lumped disturbance total estimation value is obtained according to the first inductor current estimation value and the first lumped disturbance estimation value.

[0048] The Extended State Observer (ESO) (hereinafter referred to as the ESO observer) mainly observes nonlinear lumped disturbances. The generation of nonlinear lumped disturbances includes the transformer 30, the primary inductor Lr of the primary inverter side 21, the switch tube and other nonlinear element failures, and the sudden vibration of the current conversion device 100. After mathematical transformation, the extended state observer can obtain the second lumped disturbance estimation model.

[0049] The first inductor current estimation value and the first lumped disturbance estimation value are input into the second lumped disturbance estimation model to obtain the total lumped disturbance estimation value.

[0050] Exemplarily, the formula for determining the total estimated value of the lumped disturbance (the second lumped disturbance estimation model) is as follows:

[0051] (2)

[0052] Among them, the first formula of formula (2) is the formula for determining the second lumped disturbance estimate, and the second formula of formula (2) is the formula for determining the second inductor current estimate. By running the first and second formulas of formula (2) at the same time, the second lumped disturbance estimate and the second inductor current estimate can be obtained. The third formula of formula (2) is the formula for determining the total lumped disturbance estimate.

[0053] In formula (2), The second set of total disturbance estimates is It mainly includes nonlinear lumped perturbations. express The derivative of . represents the bandwidth of the ESO observer, and represents the proportionality coefficient, value, value, The value is preset based on relevant parameters of the current conversion device 100 . represents the second inductor current estimation value, express It can be understood that based on the first inductor current estimation value , we can get the second lumped disturbance estimate After running the formula, the estimated value of the second lumped disturbance can be determined That is, based on the first inductor current estimation value, the second lumped disturbance estimation value is determined. It is corrected based on the more accurate first inductor current estimate. Therefore, the second lumped disturbance estimate is It is also more accurate.

[0054] It is understood that the total estimated value of the lumped disturbance is is the first lumped disturbance estimate and the second ensemble disturbance estimate That is, the total estimated value of the aggregate disturbance is obtained according to the first estimated value of the aggregate disturbance and the second estimated value of the aggregate disturbance. Therefore, the total estimated value of the aggregate disturbance is It can reflect both nonlinear lumped disturbances and linear disturbances.

[0055] It is understandable that in the related technology, there is a technology that only uses the LESO observer to observe the lumped disturbance under small disturbance conditions, but its anti-disturbance performance will decrease as the disturbance amplitude increases. There is also a technology that only uses the ESO observer to observe the lumped disturbance under large disturbance conditions, but the ESO observer needs to deal with nonlinear lumped disturbances and expansion states, which requires more calculations and is more complicated. There is also a switching control technology that uses the LESO observer to observe under small disturbance conditions and switches to the ESO observer under large disturbance conditions. However, in actual operation, improper switching of switching control may cause the control system to oscillate more. It is necessary to focus on the smoothness of the switching process. When the control system has parameter mismatch after long-term operation, the oscillation of the switching process may intensify.

[0056] Compared with the related art, in the embodiment of the present application, based on the first lumped disturbance estimation model, according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle ， The first inductor current estimation value and the first lumped disturbance estimation value are obtained. Based on the first lumped disturbance estimation model, the lumped disturbance total estimation value is obtained according to the first inductor current estimation value and the first lumped disturbance estimation value. By using the linear extended state observer and the nonlinear extended state observer at the same time, the anti-disturbance performance will not decrease with the increase of the disturbance amplitude, and the calculation amount is smaller. In the actual operation process, the occurrence of system oscillation can be reduced.

[0057] Step S140: Controlling the conduction of the switch tube in the primary inverter side based on the total estimated value of the lumped disturbance.

[0058] In order to obtain the total estimated value of the lumped disturbance After that, the control system 10 is based on the total estimated value of the lumped disturbance , controls the switch tube in the primary inverter side 21 to conduct, thereby changing the way the primary inverter side 21 transmits power to the secondary rectifier side 22, taking into account the nonlinear lumped disturbance and linear lumped disturbance under different working conditions. Reduces the power supply loss from the primary inverter side 21 to the secondary rectifier side 22, improves the working efficiency of the current conversion device 100, and improves the quality and control performance of the output voltage.

[0059] In the above technical solution, based on the first lumped disturbance estimation model constructed according to the linear extended state observer (mainly used to observe linear lumped disturbances), according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, a first inductor current estimation value and a first lumped disturbance estimation value that are more accurate than the inductor current value at the start time of the current switching cycle can be obtained. Then, based on the second lumped disturbance estimation model constructed according to the extended state observer (mainly used to observe nonlinear lumped disturbances), according to the first inductor current estimation value and the first lumped disturbance estimation value, a lumped disturbance total estimation value (i.e., total lumped disturbance) is obtained, nonlinear lumped disturbances and linear lumped disturbances can be observed, and the lumped disturbance total estimation value is obtained by correcting the first lumped disturbance estimation model and the second lumped disturbance estimation model, thereby improving the tracking accuracy of the lumped disturbance of the current conversion device 100.

[0060] Finally, the switch tube in the primary inverter side 21 is controlled to be turned on based on the total estimated value of the lumped disturbance, which reduces the power supply loss from the primary inverter side 21 to the secondary rectifier side 22, improves the working efficiency of the current conversion device 100, and improves the quality and control performance of the output voltage. The power conversion efficiency between the power supply and the load can be improved.

[0061] In some embodiments, the method of the present application further includes a method for constructing a first lumped disturbance estimation model, and the method for constructing the first lumped disturbance estimation model includes the following steps:

[0062] Step S121: Based on the operating state of the phase-shifted full-bridge converter, a linear extended state observer is defined.

[0063] The formula of the linear extended state observer is as follows:

[0064]

[0065] in, represents the observation error of the linear extended state observer. , Represents the error feedback gain value, which is set based on experience or determined by the bandwidth method. represents the duty cycle observed by the linear extended state observer.

[0066] Step S122: determining a first lumped disturbance estimation model according to a first preset ratio between an error feedback gain value and a bandwidth in a linear extended state observer.

[0067] Among them, the first preset ratio between the error feedback gain value and the bandwidth is Substituting the first preset ratio back into the formula of the linear extended state observer, we can obtain formula (1), that is, we can obtain the first lumped disturbance estimation model.

[0068] It can be understood that the bandwidth of the linear extended state observer is determined by the preset ratio to improve the observation performance of the linear extended state observer.

[0069] So that the inductor current value at the start of the current switching cycle and the duty cycle at the start of the previous switching cycle ， A first lumped disturbance estimation model is input to obtain a first inductor current estimation value and a first lumped disturbance estimation value.

[0070] In some embodiments, the method of the present application further includes a method for constructing a second lumped disturbance estimation model, and the method for constructing the second lumped disturbance estimation model includes:

[0071] Step S131: Based on the operating state of the phase-shifted full-bridge converter, an extended state observer is defined.

[0072] The formula of the extended state observer is as follows:

[0073]

[0074] in, and Represents an exponential power, indicating two gains of different magnitudes. , It represents the error feedback gain value, which is set based on experience or determined by the bandwidth method. Represents the proportionality factor.

[0075] Step S132: transforming the nonlinear function of the extended state observer;

[0076] In order to facilitate the analysis of performance, the nonlinear function of the expanded state observer is fal Perform the following mathematical transformation:

[0077]

[0078] Understandable, Equivalent to , the nonlinear function fal Transformed into a linear time-varying variable. Through this mathematical change, the ESO observer can be approximated as a linear time-varying gain state expansion observer, that is, the formula is as follows:

[0079]

[0080] Step S133: changing the inductor current value variable at the start time of the current switching cycle in the transformed extended state observer into a first inductor current estimated value variable.

[0081] That is, change y to the first inductor current estimated value .

[0082] Step S134: In the modified extended state observer, a formula is added in which the total estimated value of the lumped disturbance is equal to the sum of the first estimated value of the lumped disturbance and the second estimated value of the lumped disturbance, that is, the third formula of formula (2) is added.

[0083] Step S135: determining a second lumped disturbance estimation model according to a second preset ratio between the error feedback gain value and the bandwidth in the added extended state observer.

[0084] The second preset ratio between the error feedback gain value and the bandwidth is: Bringing the second preset ratio back into the formula of the replaced extended state observer, we can get formula (2). It can be understood that the bandwidth of the nonlinear extended state observer is determined by the second preset ratio to improve the observation performance of the nonlinear extended state observer.

[0085] So that the first inductor current estimation value and the first lumped disturbance estimation value are input into the second lumped disturbance estimation model to obtain the total lumped disturbance estimation value.

[0086] In some embodiments, see Figure 3 , Figure 4 and Figure 5 Step S140: controlling the switch tube in the primary inverter side to conduct based on the total estimated value of the lumped disturbance, comprising the following steps:

[0087] Step S141: determining the required duty cycle at the start time of the next switching cycle of the secondary side equivalent circuit based on the total estimated value of the lumped disturbance.

[0088] Step S142: Determine the duty cycle at the start time of the next switching cycle of the primary inverter side according to the required duty cycle and the compensation duty cycle at the start time of the next switching cycle of the secondary equivalent circuit.

[0089] Specifically, see Figure 3 and 5,First, a duty cycle prediction model (also a duty cycle prediction module) is constructed. The steps of constructing the duty cycle prediction model are as follows a1 to a3.

[0090] a1: Based on Kirchhoff's voltage law, define the output filter inductor L f The equivalent mathematical model of .

[0091] Output filter inductor L f The formula of the equivalent mathematical model is as follows:

[0092] (3)

[0093] in, dy / dt represents the derivative of the inductor current changing with time, N represents the turns ratio of the transformer 30, V in Indicates the input voltage, V out Indicates the output voltage.

[0094] a2: Based on the equivalent mathematical model of the output filter inductor, a first-order super-local model of the secondary rectifier side is constructed (i.e., a mathematical model of the secondary equivalent circuit is constructed).

[0095] According to the turns ratio N , Input voltage V in And the output voltage V out With physical gain value , the total estimated value of the aggregate disturbance The mathematical conversion relationship of the secondary rectifier side 22 is constructed as follows:

[0096] (4)

[0097] Formula (4) is discretized to obtain the discretized first-order hyperlocal model, formula (5) is as follows:

[0098] (5)

[0099] in, Indicates the inductor current value at the start of the next switching cycle, Indicates the inductor current value at the start of the current switching cycle y Or the second inductor current estimate , Indicates the duty cycle of the secondary side equivalent circuit at the start of the current switching cycle. Indicates the duration of each switching cycle, which is preset. Represents the total estimated value of the lumped disturbance at the start of the current switching cycle .

[0100] It can be understood that the first-order hyperlocal model is the mathematical model of the secondary side equivalent circuit.

[0101] Understandable, The value of can be the sensed inductor current value , or the corrected estimated value of the second inductor current , using the second inductor current estimate More accurate.

[0102] a3: Cost function based on output filter inductor ( ) and the first-order hyperlocal model, the duty cycle prediction model is obtained. The formula of the duty cycle prediction model is shown as follows (6):

[0103] (6)

[0104] in, represents the required duty cycle at the start of the next switching cycle of the duty cycle prediction model, Indicates the duty cycle at the start of the next switching cycle on the primary inverter side. Indicates the compensation duty cycle, which is preset. Represents the reference inductor current, which can be preset.

[0105] So that the total estimated value of the lumped disturbance is A duty cycle prediction model is input, and the duty cycle prediction model determines the duty cycle at the start time of the next switching cycle of the primary inverter side according to the required duty cycle and the compensation duty cycle at the start time of the next switching cycle of the secondary equivalent circuit.

[0106] It can be understood that, since the secondary rectifier side 22 (i.e., the secondary equivalent circuit) of the phase-shifted full-bridge converter 20 has the defect of duty cycle loss, it is necessary to add a duty cycle compensation link (i.e., the second formula of formula (6)), and assign the duty cycle value obtained after compensation to both the primary inverter side 21 and the secondary rectifier side 22. The primary inverter side 21 performs phase shift modulation, and the secondary rectifier side 22 performs synchronous rectification. This link can enhance system stability, improve reliability, and reduce operating losses.

[0107] It can be understood that in the related technology, the proportional integral controller (PI) controller has been widely used in the current industrial control system 10. The principle is to minimize the error by adjusting the error between the output of the current converter and the given reference value so as to track the given reference value. There are complex parameter setting problems, and the same parameters cannot meet all working conditions in most cases. The actual working conditions of the phase-shifted full-bridge converter 20 are more complicated. Many application environments have strict requirements on the reliability of the phase-shifted full-bridge converter 20, such as extreme temperature, humidity, vibration, electromagnetic interference and other harsh conditions. This requires the control system 10 to have higher performance, and PI control is difficult to meet the rapidity and stability control of the system.

[0108] It can be understood that, compared with the PI controller, in this step, based on the principle of Kirchhoff's voltage law, an equivalent mathematical model of the output filter inductor Lf is defined. f The equivalent mathematical model of the phase-shifted full-bridge converter 20 is used to construct a first-order super-local model of the secondary rectifier side 22. The first-order super-local model is used to predict the behavior of the phase-shifted full-bridge converter 20 in the future. At the same time, various constraints of the phase-shifted full-bridge converter 20 can be added to it, including input constraints, state constraints and output constraints. When the phase-shifted full-bridge converter 20 performs current conversion, it helps to prevent overvoltage, overcurrent and other phenomena. The simple first-order super-local model can realize efficient control of the motion state of the complex phase-shifted full-bridge converter 20, improve the dynamic performance and robustness of the control system 10, and optimize the overall performance.

[0109] Finally, based on the output filter inductor L f The cost function and the first-order hyperlocal model are used to obtain the duty cycle prediction model. The combination of the first lumped disturbance estimation module, the first lumped disturbance estimation module and the duty cycle prediction model is a model-free controller, which essentially uses algebraic parameter identification technology to online estimate linear lumped disturbances including nonlinear lumped disturbances and internal and external uncertainties. It has the advantages of adapting to various control systems 10 and not relying on the parameters of the control system 10, and can improve the robustness of the control system 10.

[0110] Step S143: determining a phase shift angle at a start time of a next switching cycle of the primary inverter side according to a duty cycle at a start time of a next switching cycle of the primary inverter side.

[0111] Specifically, the duty cycle at the start of the next switching cycle is input into the mathematical model of the phase shift angle and the duty cycle, and the phase shift angle at the start of the next switching cycle is output. The formula of the mathematical model of the phase shift angle and the duty cycle is: , is the phase shift angle at the start of the next switching cycle.

[0112] Step S144: controlling the switch tube in the primary inverter side of the next switching cycle to be turned on based on the phase shift angle at the start time of the next switching cycle.

[0113] In one implementation, two or more switch tubes in the same voltage loop in the primary inverter side are controlled based on the phase shift angle at the start time of the next switching cycle, and are turned on at preset times of the next switching cycle respectively.

[0114] In one example, the switching period is from t0 to t5. Figure 5 As shown, when the switch tubes Q1 and Q4 are turned on, the primary inverter side 21 forms a voltage loop. Based on the phase shift angle at the start of the next switching cycle, the switch tube Q1 is turned on at time t2, and the switch tube Q4 is turned on at time t4. In another example, based on the phase shift angle at the start of the next switching cycle, the switch tube Q4 is turned on at time t2, and the switch tube Q1 is turned on at time t4. It can be understood that the phase shift angle is used to modulate the order and turn-on time of multiple switch tubes in a voltage loop within a switching cycle, so that multiple switch tubes in a voltage loop in a switching cycle are turned on at the same time for a longer time and transmit more power.

[0115] Combination Figure 5 and Figure 6 The following uses an application scenario to further illustrate some or all of the above embodiments. The control system 10 performs the following steps:

[0116] b1: Get the inductor current value of the output filter inductor Lf at the start of the current switching cycle , and the duty cycle of the secondary side equivalent circuit of the secondary rectifier side 22 at the start of the previous switching cycle , and input the lumped disturbance total estimation module 91, outputting the lumped disturbance total estimation value at the start time of the current switching cycle and the second inductor current estimate at the start of the current switching cycle ;

[0117] The lumped disturbance total estimation module 91 is used to estimate the inductor current value at the start time of the current switching cycle based on the first lumped disturbance estimation model. and the duty cycle at the start of the previous switching cycle , get the first inductor current estimate and the first lumped disturbance estimate . And the second lumped disturbance estimation model, according to the first inductor current estimation value and the first lumped disturbance estimate , get the total estimated value of the lumped disturbance at the start of the current switching cycle and the second inductor current estimate at the start of the current switching cycle .

[0118] b2: Get the output voltage of the load , and calculate the output voltage With preset reference voltage The difference is input into the voltage outer loop module 92, and the reference inductor current value at the start time of the next switching cycle is output. ;

[0119] The voltage outer loop module 92 is used to obtain the inductor current reference value at the start time of the next switching cycle according to the difference according to the Super Twisting Sliding Mode Control (SMC) algorithm. .

[0120] b3: Set the inductor current reference value at the start of the next switching cycle , the total estimated value of the lumped disturbance at the start of the current switching cycle and the second inductor current estimate at the start of the current switching cycle , input duty cycle prediction module 93 (the function of duty cycle prediction module 93 is consistent with the above-mentioned duty cycle prediction model) outputs the duty cycle of the next switching cycle of the primary inverter side 21 at the start time ;

[0121] b4: Set the duty cycle at the start of the next switching cycle Input duty cycle-phase shift angle conversion module 94 to obtain the phase shift angle at the start time of the next switching cycle , and based on the phase shift angle at the start of the next switching cycle The two or more switch tubes in the same voltage loop in the primary inverter side 21 are controlled to be turned on at preset moments of the next switching cycle.

[0122] The duty cycle-phase shift angle conversion module 94 is used to convert the phase shift angle and the duty cycle according to the mathematical model of the phase shift angle and the duty cycle and the duty cycle at the start time of the next switching cycle. , output the phase shift angle at the start of the next switching cycle .

[0123] b5: Phase shift angle The ePWM phase-shift modulation module 95 is input, and the ePWM phase-shift modulation module 95 outputs a first driving signal, and the first driving signal is used to drive the switch tubes Q1 to Q4 to turn on.

[0124] The secondary rectification side 22 uses a switch tube body diode to conduct rectification to achieve synchronous rectification.

[0125] The conduction conditions of the two or more switch tubes in the same voltage loop in the primary inverter side 21 at the preset time of the next switching cycle are as follows: Figure 6 As shown, Figure 6 The horizontal axis represents time, and the vertical axis represents changes in multiple parameters of the phase-shifted full-bridge converter 20. V si It represents the on-state voltage of the switch tube in the primary inverter side 21, and the on-state voltage indicates that the switch tube corresponding to the on-state voltage is on. V AB It represents the voltage on both sides of the transformer 30 close to the primary inverter side 21. V rec It represents the voltage on both sides of the transformer 30 close to the secondary rectifier side 22. i D i Indicates the current flowing through the two clamping diodes. The clamping diodes are two diodes added to the primary side transformer 30 to prevent excessive voltage stress on the secondary side switch tube.

[0126] Understandable, such as Figure 6 As shown, t0 to t18 is a switching cycle, the duration of the simultaneous conduction of Q1 and Q4 switches is t13 to t18, and power is generated on both sides of the transformer 30 close to the primary inverter side 21 ( Figure 6 V AB The power can be reflected in the change of power), so as to transmit the power to both sides of the transformer 30 of the secondary rectifier side 22 ( Figure 6 V rec It can reflect the change of power).

[0127] Figure 7 This is a schematic diagram of the control system of the phase-shifted full-bridge converter provided in this application. Figure 7 As shown, the control system 10 includes:

[0128] Processor 11, memory 12 and bus 13;

[0129] The memory 12 is used to store the computer program code of the processor 11;

[0130] The processor 11 is configured to execute the technical solution of the control method of the phase-shifted full-bridge converter in any of the aforementioned method embodiments by executing the computer program code.

[0131] Optionally, the memory 12 may be independent or integrated with the processor 11 .

[0132] The memory 12 is connected to the processor 11 via the bus 13 and completes the communication between them.

[0133] Optionally, the memory 12 may include a random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0134] The bus 13 may be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus.

[0135] The above-mentioned processor can be a general-purpose processor, including a central processing unit CPU, a network processor (NP), etc.; it can also be a digital signal processor DSP, an application-specific integrated circuit ASIC, a field programmable gate array FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0136] The control system 10 is used to execute the technical solution provided in any of the aforementioned method embodiments, and its implementation principle and technical effect are similar and will not be repeated here.

[0137] Those skilled in the art can understand that all or part of the steps of implementing the above-mentioned method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps of the above-mentioned method embodiments are executed; and the aforementioned storage medium includes: ROM, RAM, disk or optical disk and other media that can store program codes.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A control method for a phase-shifted full-bridge converter, characterized in that: The phase-shifted full-bridge converter includes a primary inverter side and a secondary rectifier side, the secondary rectifier side includes an output filter inductor, and the method includes: Acquire the inductor current value of the output filter inductor at the start time of the current switching cycle, and the duty cycle of the secondary side equivalent circuit of the secondary side rectifier at the start time of the previous switching cycle; Based on the first lumped disturbance estimation model, according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, a first inductor current estimation value and a first lumped disturbance estimation value are obtained, wherein the first lumped disturbance estimation model is constructed according to a linear extended state observer; Based on a second lumped disturbance estimation model, and according to the first inductor current estimation value and the first lumped disturbance estimation value, a lumped disturbance total estimation value at the start time of the current switching cycle is obtained, wherein the second lumped disturbance estimation model is constructed according to an extended state observer; The switch tube in the primary inverter side of the next switching cycle is controlled to be turned on based on the total estimated value of the lumped disturbance.

2. The method according to claim 1, characterized in that: The step of obtaining a first inductor current estimation value and a first lumped disturbance estimation value according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle includes: Determine a first lumped disturbance estimation value based on the inductor current value at the start time of the current switching cycle; The first inductor current estimate value is determined based on the first lumped disturbance estimate value.

3. The method according to claim 1, characterized in that The step of obtaining the total estimated value of the lumped disturbance at the start time of the current switching cycle according to the first estimated value of the inductor current and the first estimated value of the lumped disturbance comprises: Determining a second lumped disturbance estimate based on the first inductor current estimate; The total estimated value of the aggregate disturbance at the start time of the current switching cycle is obtained according to the first aggregated disturbance estimated value and the second aggregated disturbance estimated value.

4. The method according to claim 1, characterized in that The method of controlling the conduction of the switch tube in the primary inverter side in the next switching cycle based on the total estimated value of the lumped disturbance includes: Determining a required duty cycle at a start time of a next switching cycle of the secondary side equivalent circuit based on the total estimated value of the lumped disturbance; Determining the duty cycle at the start time of the next switching cycle of the primary inverter side according to the required duty cycle and the compensation duty cycle at the start time of the next switching cycle of the secondary equivalent circuit; Determining a phase shift angle at a start time of a next switching cycle of the primary inverter side according to a duty cycle at a start time of a next switching cycle of the primary inverter side; The switching tube in the primary inverter side of the next switching cycle is controlled to be turned on based on the phase shift angle at the start time of the next switching cycle.

5. The method according to claim 4, characterized in that The method further comprises: Based on the principle of Kirchhoff's voltage law, an equivalent mathematical model of the output filter inductor is defined; Based on the equivalent mathematical model of the output filter inductor, a first-order super-local model of the secondary rectification side is constructed; Defining a cost function of the output filter inductor according to a reference inductor current of the output filter inductor and an inductor current value at a start time of a next switching cycle; Obtaining a duty cycle prediction model based on the cost function of the output filter inductor and the first-order hyperlocal model; The duty cycle prediction model is used to input the total estimated value of the lumped disturbance, and determine the duty cycle of the secondary equivalent circuit at the start time of the next switching cycle based on the total estimated value of the lumped disturbance; and determine the duty cycle of the primary inverter side at the start time of the next switching cycle according to the required duty cycle and the compensated duty cycle at the start time of the next switching cycle of the secondary equivalent circuit.

6. The method according to claim 4, characterized in that The controlling the switching on of the switch tube in the primary inverter side of the next switching cycle based on the phase shift angle at the start time of the next switching cycle includes: Based on the phase shift angle at the start time of the next switching cycle, two or more switch tubes in the same voltage loop in the primary inverter side are controlled to be turned on at preset times of the next switching cycle respectively.

7. A current conversion device, characterized in that: The invention comprises a control system and a phase-shifted full-bridge converter, wherein the phase-shifted full-bridge converter comprises a primary inverter side and a secondary rectifier side, wherein the secondary rectifier side comprises an output filter inductor, and the control system is used to: Acquire the inductor current value of the output filter inductor at the start time of the current switching cycle, and the duty cycle of the secondary side equivalent circuit of the secondary side rectifier at the start time of the previous switching cycle; Based on the first lumped disturbance estimation model, according to the inductor current value at the start time of the current switching cycle and the duty cycle at the start time of the previous switching cycle, a first inductor current estimation value and a first lumped disturbance estimation value are obtained, wherein the first lumped disturbance estimation model is constructed according to a linear extended state observer; Based on a second lumped disturbance estimation model, and according to the first inductor current estimation value and the first lumped disturbance estimation value, a lumped disturbance total estimation value at the start time of the current switching cycle is obtained, wherein the second lumped disturbance estimation model is constructed according to an extended state observer; The switch tube in the primary inverter side of the next switching cycle is controlled to be turned on based on the total estimated value of the lumped disturbance.

8. A control system for a phase-shifted full-bridge converter, characterized in that: include: Processor and memory; The memory is coupled to the processor, and the memory is used to store computer program codes. The processor calls the computer program codes to enable the controlled system to execute the method according to any one of claims 1 to 6.

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