OBC working frequency control method based on LcBoost topology and OBC

Abstract

The invention relates to an OBC working frequency control method based on LcBoost topology and an OBC, and relates to the field of vehicle-mounted power equipment.The control method comprises the steps that S10, ideal frequencies and ideal phase shifting angles of the topology at different working frequencies, different phase shifting angles and different output voltages are obtained; s20, constructing a voltage correspondence table of the ideal frequency and the ideal phase-shifting angle corresponding to the output voltage, and a gain phase-shifting function of the ideal phase-shifting angle relative to the gain; s30, acquiring critical control frequencies of the switching tube at different output voltages, and constructing a critical frequency function; s40, setting a target output voltage, and collecting an input voltage; and S50, calculating the current gain, setting the current reference voltage, obtaining the current control frequency according to the current output voltage and the current reference voltage, obtaining the current phase shift angle according to the current gain, and controlling the on-off of each switch tube of the topology according to the current control frequency and the current phase shift angle. The electric energy conversion efficiency of the OBC can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of vehicle-mounted power equipment, in particular to an OBC operating frequency control method based on an LcBoost topology. In addition, the present application also relates to an OBC based on an LcBoost topology. BACKGROUND

[0002] OBC is the abbreviation of On-Board Charger, which means vehicle-mounted charger. It is a power conversion device set on a vehicle to obtain power from an external power grid to charge the automobile power battery. It has the characteristics of high operating power, wide voltage adaptation range, wide temperature adaptation range, and high critical requirements. It is one of the core devices of electric vehicle energy management. With the promotion of global double carbon target and the electric transformation of automobiles, the application prospect of OBC is becoming more and more extensive.

[0003] As a core device of electric vehicles, OBC can convert 220V alternating current into direct current through a household socket or a wall-mounted charging pile (AC pile) to charge the power battery; it can also charge the power battery through an AC charging pile equipped in public places such as shopping malls, parking lots, and communities, and connect the charging gun to the vehicle for 6.6kW-11kW power high-power charging; it can also convert the power of the power battery in the vehicle into alternating current when necessary, and output power for use by electrical appliances. OBC usually includes a PFC circuit and a DC-DC converter, where the PFC circuit is used to correct the power factor of alternating current and convert alternating current into direct current with a set voltage; the DC-DC converter is used to convert direct current with a set voltage into direct current with a set size of output voltage and ensure that it has sufficient output power. LcBoost topology is a commonly used DC-DC converter structure type, which can conveniently adjust the direct current output voltage and output power by adjusting the operating frequency and phase shift angle of the topology, and has the advantages of high output voltage adjustment capability and convenient adjustment.

[0004] The existing OBC based on LcBoost topology needs to adjust the operating frequency of the topology circuit in a large range when adjusting the output voltage in a large range, which significantly increases the loss of full-bridge switching elements and magnetic elements, reducing the efficiency of electric energy conversion. SUMMARY

[0005] In order to improve the efficiency of electric energy conversion of OBC, the present application provides an OBC operating frequency control method based on LcBoost topology and an OBC.

[0006] The OBC operating frequency control method based on LcBoost topology provided by the present application adopts the following technical scheme: The application discloses an OBC working frequency control method based on an LcBoost topology, and comprises the following steps: S10, in an open loop state, acquiring the electric energy conversion efficiency of the LcBoost topology in a full load state at a specific output voltage point under different working frequencies f and different phase shift angles θ, obtaining an ideal frequency f m and an ideal phase shift angle θ m when the electric energy conversion efficiency is maximum; S20, constructing a voltage corresponding table comprising different output voltages and corresponding ideal frequencies f m and ideal phase shift angles θ m , and calculating the gain M at different output voltages, and constructing a gain phase shift function of the ideal phase shift angle θ m about the gain M; S30, in a closed loop state, acquiring the working frequency of a switch tube in a ZVS critical state at different output voltages and different ideal phase shift angles θ m , taking the critical control frequency as a critical limit frequency function, and calculating the gain M at different output voltages, and constructing a critical limit frequency function taking the gain M as an independent variable and the critical control frequency as a dependent variable; S40, setting a target output voltage, and collecting an input voltage U bus ; S50, acquiring a current output voltage U bat in the working process of the LcBoost topology, and calculating a current gain M t ; setting a current reference voltage U bat between the current output voltage U ref and the target voltage, obtaining a current control frequency FSW according to the current output voltage U bat and the current reference voltage U ref , limiting the range of the current control frequency FSW by the critical control frequency, acquiring a current phase shift angle according to the current gain M t and the gain phase shift function, and controlling the on-off state of each switch tube of the LcBoost topology according to the current control frequency FSW and the current phase shift angle.

[0007] By adopting the technical scheme, the voltage corresponding table and the gain phase shift curve acquired in the open loop state and the critical limit frequency function acquired in the closed loop state are utilized, the working frequency of the LcBoost topology is adjusted based on the ideal output frequency f m , the working frequency is controlled to be above the critical control frequency, the turn-off current loss of the switch tube is reduced, and the electric energy conversion efficiency of the LcBoost topology is improved. The current reference voltage U bat between the current output voltage U ref and the target voltage is utilized, and the current output voltage U batCompared with the prior art, the current control frequency FSW is obtained by calculation, the adjustment range of the current control frequency FSW is reduced, the deviation of the current control frequency FSW from the ideal frequency f m is reduced, and the electric energy conversion efficiency of the system is improved.

[0008] In a specific embodiment, in step S10, an electronic load is connected to the output of the LcBoost topology, the output voltage of the LcBoost topology is adjusted to a set output voltage, the electronic load is adjusted so that the output power of the LcBoost topology is a full-load output power, and the electric energy conversion efficiency of the LcBoost topology under the current state is obtained by using a power analyzer; different operating frequencies f and different phase shift angles θ are adjusted respectively, the output voltage is ensured to be unchanged, the electric energy conversion efficiency under different operating frequencies f and phase shift angles θ combination states is recorded, and the operating frequency f and the phase shift angle θ when the electric energy conversion efficiency is maximum are selected as the ideal frequency f m and the ideal phase shift angle θ m under the corresponding output voltage respectively.

[0009] By using the above technical scheme, the ideal frequency f m and the ideal phase shift angle θ m under the full-load output power of different output voltages are determined, the current output voltage U bat is adjusted based on the ideal frequency f m and the ideal phase shift angle θ m with the highest electric energy conversion efficiency, and the electric energy conversion efficiency of the system under different output voltages is improved.

[0010] In a specific embodiment, step S20 includes the following steps: S21, gradually increasing the output voltage of the LcBoost topology from the minimum set output voltage to the maximum set output voltage at a set adjustment range, and obtaining the ideal frequency f m and the ideal phase shift angle θ m under different output voltages respectively; S22, establishing a correspondence table of different output voltages and corresponding ideal frequencies f m and ideal phase shift angles θ m , to obtain a voltage correspondence table; S23, calculating the gain M under different output voltage states according to the formula M = U bat * n / U bus , wherein U bat is the current output voltage, and n is the transformation ratio of the transformer T in the LcBoost topology; S24, fitting a gain phase shift function of the ideal phase shift angle θ m about the gain M according to the corresponding relationship curve, and constructing the gain phase shift function of the ideal phase shift angle θ m about the gain M.

[0011] By adopting the above technical solution, and by gradually increasing the output voltage from the minimum set output voltage to the maximum set output voltage according to a set adjustment range, the ideal frequency f under different output voltages can be easily obtained. m and the ideal phase shift angle θ m Quickly construct voltage correspondence tables and gain phase shift functions.

[0012] In one specific implementation, in step S30, the output voltage is fixed to a set value, and the phase shift angle θ is fixed to the ideal phase shift angle θ corresponding to the output voltage. m Gradually increase the output load of the LcBoost topology until the turn-off current of the switching transistor reaches the set value, and use the operating frequency of the switching transistor at this point as the critical control frequency; iterate the output voltage of the LcBoost topology through the entire output voltage range from the minimum set output voltage to the maximum set output voltage in set steps to obtain different output voltages and their corresponding ideal phase shift angles θ. m The critical control frequency below.

[0013] By adopting the above technical solution, and by fixing the output voltage and the corresponding ideal phase shift angle, the switching frequency of the full-bridge switching transistor can be gradually reduced as the load increases, and the turn-off current of the switching transistor can also gradually decrease. The switching frequency of the switching transistor when the turn-off current of the switching transistor decreases to a set value is used as the critical control frequency. The operating frequency of the LcBoost topology can be controlled above the critical control frequency, thereby reducing the operating loss of the switching transistor and ensuring the power conversion efficiency of the system.

[0014] In one specific implementation, in S40, the initial output voltage of the LcBoost topology is also acquired, and several reference voltages are set between the initial output voltage and the target output voltage with a set step size. In step S50, the current reference voltage U is set among the reference voltages. ref .

[0015] By adopting the above technical solution, and utilizing several reference voltages set with a set step size between the initial output voltage and the target output voltage, it can be ensured that the reference voltages are within the current output voltage U according to the set step size. bat The current output voltage U is uniformly arranged with respect to the target output voltage, so that the current output voltage U bat The real-time adjustment amplitude is more uniform, limiting the adjustment amplitude of the operating frequency at any moment during voltage regulation, which in turn limits the deviation of the current control frequency FSW from the ideal frequency f. m The magnitude of this amplitude is beneficial to improving the system's power conversion efficiency.

[0016] In one specific implementation, in step S50, the nearest current output voltage U is taken between the target output voltage and the current output voltage Ubat. bata reference voltage as the current reference voltage U ref , if there is no reference voltage between the target output voltage and the current output voltage U bat , the target output voltage is taken as the current reference voltage U ref , according to the deviation between the current output voltage U bat and the current reference voltage U ref , PI operation is performed based on the voltage correspondence table to obtain the current control frequency FSW.

[0017] By adopting the technical scheme, the PI control loop is used to perform PI operation according to the deviation between the current output voltage U m and the current reference voltage U bat based on the correspondence between the output voltage and the ideal frequency f ref in the voltage correspondence table, to obtain the current control frequency FSW, and the working of the LcBoost topology is controlled by the current control frequency FSW, so that the current output voltage U bat can more quickly approach the current reference voltage U ref .

[0018] In a specific implementation, the step S40 includes the following steps: S41, a correspondence curve of the gain M and the ideal frequency f m is fitted according to the voltage correspondence table, to obtain a gain full-load frequency curve, and a gain full-load frequency function is constructed according to the gain full-load frequency curve; S42, each ideal frequency f m in the voltage correspondence table is reduced by a set value to obtain a corresponding limited frequency, a correspondence curve of the gain M and the limited frequency is fitted according to the voltage correspondence table, to obtain a gain limited frequency curve, and a gain limited frequency function is constructed according to the gain limited frequency curve; S43, a target output voltage and a reference voltage adjustment amplitude are set, and an input voltage U bus and a starting output voltage are collected; S44, a current reference voltage U ref is set between the starting output voltage and the target output voltage, so that the difference between the current reference voltage U ref and the starting output voltage is the reference voltage adjustment amplitude; the step S50 includes the following steps: S51, the current output voltage U bat in the working process of the LcBoost topology is obtained, and the current gain M t is calculated; S52, the current phase shift angle is obtained according to the current gain M t and the gain phase shift function; S53, according to the difference between the current output voltage U bat and the current reference voltage U ref , PI operation is performed based on the voltage correspondence table to obtain the current control frequency FSW, and the current control frequency FSW is obtained according to the current gain M tand the gain limiting frequency function obtains a current limiting frequency, if the current control frequency FSW is less than the current limiting frequency, the current limiting frequency is taken as the current control frequency FSW; S54, according to the current control frequency FSW and the current phase shift angle, the on-off state of each switch tube of the LcBoost topology is controlled; S55, the current reference voltage U ref The reference voltage is adjusted in the direction of the target output voltage, and the adjustment amplitude is adjusted. ref If the current reference voltage U ref reaches or exceeds the target output voltage, the target output voltage is taken as the current reference voltage U m

[0019] By adopting the technical scheme, the ideal frequency f m is obtained under different gains M, the gain limiting frequency curve obtained by reducing the set value can limit the current control frequency FSW in the voltage adjustment process between the current limiting frequency and the set highest frequency, further reduces the variation range of the current control frequency FSW in the voltage adjustment process, and makes the current control frequency FSW more close to the ideal frequency f m .

[0020] In a specific embodiment, in the current output voltage U bat rising process, when the current gain M t is less than the set starting phase shift gain, the phase shift angle θ of the LcBoost topology is kept unchanged, and only the current control frequency FSW is adjusted; in the current output voltage U bat falling process, when the current gain M t is less than the set stop phase shift gain, the phase shift angle θ of the LcBoost topology is no longer adjusted, and only the current control frequency FSW is adjusted.

[0021] By adopting the technical scheme, when the current gain M t is less than the set size, the phase shift angle θ is kept unchanged, only the current control frequency FSW is adjusted, and the output voltage is adjusted, which can simplify the control process of the LcBoost topology when the output voltage is low, and is beneficial to improve the adjustment speed and efficiency of the output voltage.

[0022] In a specific embodiment, the resonant frequency of the LcBoost topology plus a set value is taken as the lowest limiting frequency, and the lowest limiting frequency is taken as the current limiting frequency in the state that the phase shift angle θ of the LcBoost topology is kept unchanged and only the current control frequency FSW is adjusted.

[0023] By adopting the technical scheme, the adjustment range of the current control frequency FSW is expanded in the case that the output voltage is low and only the current control frequency FSW is adjusted to adjust the output voltage, and it is ensured that the current output voltage Ubat Adjust to the current reference voltage U ref This ensures the smooth operation of the output voltage regulation process.

[0024] The OBC based on LcBoost topology provided in this application controls the operating frequency using the OBC operating frequency control method based on LcBoost topology provided in this application.

[0025] In summary, this application includes at least one of the following beneficial technical effects: The ideal frequency f, which maximizes the energy conversion efficiency under full load at different output voltages, is obtained in the open-loop state. m and the ideal phase shift angle θ m The voltage correspondence table and gain phase shift curve can be used to achieve the ideal frequency f. m The current control frequency FSW of the LcBoost topology is used as a reference to control the current control frequency FSW around the ideal frequency f. m The frequency is adjusted up and down, and the lower limit of the current control frequency FSW is limited by the critical frequency limiting function obtained in the closed loop state, so as to ensure that the full bridge switching transistors are always kept above the critical switching frequency, reduce the turn-off current loss of the switching transistors, and improve the power conversion efficiency of the LcBoost topology.

[0026] The current reference voltage U is determined within a set range. ref As the current output voltage U bat The phased adjustment target, based on the difference between the two, adjusts the magnitude of the current control frequency FSW, which can reduce the adjustment amplitude of the current control frequency FSW and reduce the deviation of the current control frequency FSW from the ideal frequency f during real-time adjustment. m The amplitude ensures the power conversion efficiency of the LcBoost topology.

[0027] Through the ideal frequency f m Reducing the setpoint yields the frequency limiting frequency, and using this frequency limiting frequency as the lower limit for adjusting the current control frequency FSW further reduces the deviation of the current control frequency FSW from the ideal frequency f. m The amplitude of the increase increases the minimum frequency of the current control frequency FSW, reduces the turn-off current of the full-bridge switch, and improves the power conversion efficiency of the LcBoost topology. Attached Figure Description

[0028] Figure 1 This is a flowchart of an embodiment of the OBC operating frequency control method based on LcBoost topology of this application.

[0029] Figure 2 This is an LcBoost topology diagram in one embodiment of the OBC operating frequency control method based on LcBoost topology of this application.

[0030] Figure 3 Gain phase function diagram for an embodiment of the OBC operating frequency control method based on LcBoost topology of the present application.

[0031] Figure 4 Flow chart diagram for step S20 in an embodiment of the OBC operating frequency control method based on LcBoost topology of the present application.

[0032] Figure 5 Gain limit frequency curve diagram for an embodiment of the OBC operating frequency control method based on LcBoost topology of the present application.

[0033] Figure 6 Flow chart diagram for step S40 in an embodiment of the OBC operating frequency control method based on LcBoost topology of the present application.

[0034] Figure 7 Flow chart diagram for step S50 in an embodiment of the OBC operating frequency control method based on LcBoost topology of the present application.

[0035] Figure 8 Control flow diagram for an embodiment of the OBC operating frequency control method based on LcBoost topology of the present application.

[0036] Figure 9 Control flow diagram for another embodiment of the OBC operating frequency control method based on LcBoost topology of the present application. DETAILED DESCRIPTION

[0037] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely intended to explain and illustrate the present application, and are not intended to limit the present application.

[0038] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "set", "connected" should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium; can be internal communication of two elements or mutual interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] An embodiment of the OBC operating frequency control method based on LcBoost topology of the present application, as shown in FIG. 1, includes the following steps: Figure 1 ​S10, obtain the power conversion efficiency of the LcBoost topology at different frequencies f and different phase shift angles θ in a fixed output voltage and full load state, and obtain the ideal frequency f at which the power conversion efficiency is maximum m and the ideal phase shift angle θ m。

[0040] As shown in the LcBoost topology as shown in Figure 2 The input end of the LcBoost topology is connected to a DC power supply with U bus =400V, the output is connected to an electronic load CR mode, in an open loop state, the host computer is used to control the operating frequency f and the phase shift angle θ of the LcBoost topology, so that the output voltage of the LcBoost topology is a set value. Adjust the electronic load CR mode so that the output power of the LcBoost topology reaches the full load power state. The output current can be measured by the ammeter arranged in the output circuit of the LcBoost topology, and the output power can be measured by the power analyzer arranged in the output circuit of the LcBoost topology, or by measuring the output voltage by the ammeter arranged in the output circuit of the LcBoost topology, and calculating the output power by the output current.

[0041] A power analyzer is arranged at the input and output ends of the LcBoost topology, and the power analyzer is used to measure the input power P bus and the output power P out , and the power conversion efficiency η of the LcBoost topology is calculated by the formula η=P out / P bus . Record the operating frequency f, the phase shift angle θ and the power conversion efficiency η in this state.

[0042] Adjust different operating frequencies f and different phase shift angles θ so that the output voltage remains unchanged, and obtain the power conversion efficiency η of the LcBoost topology under different operating frequencies f and phase shift angles θ combinations. Record the operating frequency f, the phase shift angle θ and the corresponding power conversion efficiency η in different states. Adjust multiple different operating frequency f and phase shift angle θ combinations to obtain multiple operating frequency f, phase shift angle θ and power conversion efficiency η data.

[0043] Select the group with the highest power conversion efficiency η from the multiple operating frequency f, phase shift angle θ and power conversion efficiency η data, and record the operating frequency f and the phase shift angle θ at which the power conversion efficiency η is maximum in the full load state of the output voltage as the ideal frequency f m and the ideal phase shift angle θ m .

[0044] In the set output voltage range, gradually change the set value of the output voltage with a set amplitude value, and obtain the ideal frequency f m and ideal phase shift angle θ m . Specifically, starting from the set lowest output voltage 200V, gradually increase the set value of the output voltage with an amplitude value of 10V until the set highest output voltage 500V, and obtain the ideal frequency f m and ideal phase shift angle θ m .

[0045] S20, use different output voltages and their corresponding ideal frequencies f m and ideal phase shift angles θ m to construct an output voltage and ideal frequency f m and ideal phase shift angle θ m correspondence table to obtain a voltage correspondence table.

[0046] Use the formula M=U bat *n / U bus to calculate the gain M corresponding to different output voltages, where U bat is the current output voltage, and n is the turns ratio of the magnetic transformer T in the LcBoost topology. According to the ideal phase shift angle θ m in the voltage correspondence table, calculate the gain M corresponding to different ideal phase shift angles θ m relative to the phase shift unit value of the circle, fit the relationship curve between the gain M and the phase shift unit value, and thus construct a gain phase shift function with the gain M as the independent variable and the phase shift unit value as the dependent variable, as shown in Figure 3 .

[0047] S30, in a closed loop state, adjust the output voltage of the LcBoost topology to different values, and at the same time adjust the phase shift angle θ of the LcBoost topology to the ideal phase shift angle θ m corresponding to the output voltage, adjust the electronic load CR mode to gradually increase the output load of the LcBoost topology, until the full-bridge switch tube enters the ZVS critical state. At this time, the working frequency f of the LcBoost topology is taken as the critical control frequency.

[0048] According to these different output voltages, calculate the corresponding gain M, and according to the correspondence between the gain M and the critical control frequency, fit the relationship curve between the gain M and the critical control frequency, and construct a critical limit frequency function with the gain M as the independent variable and the critical control frequency as the dependent variable.

[0049] S40, setting the target output voltage of the OBC in the host computer, and collecting the input voltage U of the LcBoost topology during the operation of the OBC by the voltage collection circuit arranged on the input circuit and the output circuit of the LcBoost topology bus .

[0050] S50, collecting the current output voltage U of the LcBoost topology by the voltage collection circuit during the operation of the OBC bat , the current output voltage U bat generally represents the battery voltage of the OBC when charging the automotive power battery. The collected current output voltage U bat is usually subjected to digital sliding mean filtering to reduce signal interference and improve the accuracy of the collected data. According to the current output voltage U bat , the current Lc gain M bat is calculated by the formula M=U bus *n / U t .

[0051] A set voltage value of the adjacent output voltage U bat is determined between the current output voltage U bat and the target output voltage as the current reference voltage U ref , and the current output voltage Ubat and the current reference voltage U ref are calculated according to a certain algorithm, and the current control frequency FSW is obtained based on the voltage corresponding table according to the calculation result; the current critical control frequency is calculated according to the current gain M t and the critical limit frequency function, and if the obtained current control frequency FSW is lower than the current critical control frequency, the current critical control frequency is taken as the current control frequency FSW.

[0052] The current phase shift reference value is calculated according to the current gain Mt and the gain phase shift function, and the current phase shift angle is calculated according to the current phase shift reference value.

[0053] The PWM pulse signal for controlling the on-off of each switch tube in the LcBoost topology is generated according to the current control frequency FSW and the current phase shift angle, and is sent to the control end of each switch tube to control the on-off of each switch tube at a set time sequence, forming a new current output voltage U bat .

[0054] After the voltage collection circuit collects the new current output voltage U bat , the current reference voltage U bat is determined according to the new current output voltage U ref , and the target output voltage and the current output voltage U batthe difference between them is small enough, the target output voltage is taken as the current reference voltage U ref . According to the new current output voltage U bat and the new current reference voltage U ref , a new current control frequency FSWis obtained; according to the new current output voltage U bat , the current gain M t is calculated and a new current phase shift angle is obtained. Then, the PWM pulse signal is updated according to the new current control frequency FSWand the new current phase shift angle, so that the current output voltage U bat continuously approaches the target output voltage until it reaches and stably maintains at the target output voltage level.

[0055] Since the ideal frequency f m and the ideal phase shift angle θ m in the full load state at different output voltages are determined, and the working frequency f and the phase shift angle θ of the LcBoost topology are controlled based on them, the LcBoost topology can work in a state with higher power conversion efficiency. By limiting the lower limit of the current control frequency FSWwith the critical control frequency, it can be ensured that the full-bridge switch works in a soft switching state, reducing the power consumption when the switch works. By setting several reference voltages U ref between the initial output voltage and the target output voltage, and taking the adjacent reference voltage U ref as the current voltage regulation target, the large change of the current control frequency FSWin the voltage regulation process can be reduced, the amplitude of the current control frequency FSWdeviating from the ideal frequency f m can be reduced, and the LcBoost topology can work in a state with higher power conversion efficiency, improving the power conversion efficiency of the LcBoost topology.

[0056] In some embodiments of the LcBoost topology-based OBC working frequency control method of the present application, in step S10, an electronic load CR mode is connected to the output circuit of the LcBoost topology in the OBC, and the working frequency f and / or the phase shift angle θ of the LcBoost topology are adjusted by the upper computer, so that the output voltage of the LcBoost topology, that is, the output voltage of the OBC, is the set output voltage. The electronic load CR mode is gradually adjusted to increase the current and output power of the OBC.

[0057] When the output voltage deviates during the adjustment process, the working frequency f or the phase shift angle θ can be fine-tuned to maintain the output voltage at the set value.

[0058] In the OBC of the present embodiment, the LcBoost topology is used as Figure 2The LcBoost topology shown has an input voltage of 400VDC, a rated output voltage of 500VDC, a rated output current of 24A, and a rated output power of 6.6kW. Continue adjusting the electronic load CRmode until the LcBoost topology's output current reaches the maximum output current of 24A, or the output power reaches the full-load output power of 6.6kW.

[0059] The input power P of the LcBoost topology is obtained using a power analyzer connected to the input and output circuits of the LcBoost topology. bus and output power P out According to the formula η=P out / P bus *Calculate the power conversion efficiency η of the LcBoost topology under the current state using 100% calculation. Record the current output voltage, operating frequency f, phase shift angle θ, and power conversion efficiency η.

[0060] The operating frequency f and phase shift angle θ of the LcBoost topology were varied to keep the output voltage constant under different combinations of operating frequency f and phase shift angle θ. The input power P of the LcBoost topology was obtained using a power analyzer. bus and output power P out And calculate the energy conversion efficiency η under the current state.

[0061] Record the energy conversion efficiency η for multiple combinations of different operating frequencies f and phase shift angles θ under full load conditions of the output voltage. Select the operating frequency f and phase shift angle θ combination with the highest energy conversion efficiency η, and use the operating frequency f as the ideal frequency f for the corresponding output voltage. m The phase shift angle θ is the ideal phase shift angle θ under the corresponding output voltage. m .

[0062] In a preferred embodiment of the OBC operating frequency control method based on LcBoost topology in this application, such as Figure 4 As shown, step S20 includes the following steps: S21. OBC typically has a normal operating output voltage setting range. First, adjust the output voltage of the LcBoost topology to the minimum value of the normal operating output voltage, which is usually the minimum voltage state when the power battery must be charged. Then, obtain the ideal frequency f under this state through step S10. m and the ideal phase shift angle θ m Then, the output voltage is gradually increased according to the set adjustment range, such as 10V, until the maximum value of the output voltage range, which is the maximum set output voltage state. In each state, the ideal frequency f of the current state is obtained through step S10. mand the ideal phase shift angle θ m The ideal frequency f under multiple output voltage states was obtained respectively. m and the ideal phase shift angle θ m .

[0063] S22, Establish a system that includes output voltage and ideal frequency f. m and the ideal phase shift angle θ m The table shows the relationship between each output voltage and its corresponding ideal frequency f. m and the ideal phase shift angle θ m The correspondence between them is used to obtain a voltage correspondence table.

[0064] S23. According to the formula M=U bat *n / U bus Calculate the gain M under different output voltage conditions in the voltage correspondence table, where U bat Let n be the current output voltage and n be the turns ratio of the magnetic transformer T in the LcBoost topology. The gain M under different output voltage conditions is also filled into the voltage correspondence table at the position corresponding to the corresponding output voltage. The ideal phase shift angle θ corresponding to different output voltages in the voltage correspondence table is then used. m Using the formula PHASE_pu=θ m Calculate the corresponding per-unit value PHASE_pu for each of the 360° phase shifts, and fill in each per-unit value PHASE_pu in the voltage correspondence table at the position corresponding to the corresponding output voltage.

[0065] S24, such as Figure 3 As shown, a curve relating gain M and phase shift per-unit value PHASE_pu is fitted in a coordinate system with gain M on the x-axis and phase shift per-unit value PHASE_pu on the y-axis. Based on this curve, a function is constructed with gain M as the independent variable and phase shift per-unit value PHASE_pu as the dependent variable, where phase shift per-unit value PHASE_pu is the ideal phase shift angle θ. m Another representation of this is, therefore, the function is also the ideal phase shift angle θ. m The function relating to the gain M is called the gain phase shift function.

[0066] In some embodiments of the OBC operating frequency control method based on LcBoost topology in this application, in step S30, the operating frequency f and phase shift angle θ of the LcBoost topology are adjusted by the host computer to adjust the output voltage of the LcBoost topology to different set values. Typically, the phase shift angle θ of the LcBoost topology is adjusted to the ideal phase shift angle θ corresponding to different output voltages in the voltage correspondence table. m Adjust the output voltage to the corresponding output voltage value in the voltage correspondence table.

[0067] The regulating electronic load CR mode gradually increases the output load of the LcBoost topology, and the phase shift angle θ and the output voltage of the LcBoost topology are kept unchanged during the regulation. As the output load increases, the operating frequency f of the LcBoost topology gradually decreases, and the turn-off current of the switch gradually decreases. When the turn-off current of the switch reaches a set value, such as a certain set value in the range of 2-3 A, it is considered that the switch is in the ZVS critical state. It is considered that the operating frequency of the switch at this time is the critical control frequency of the switch ZVS critical state, and the frequency is also used as the critical control frequency of the LcBoost topology.

[0068] According to the output voltage value in the voltage corresponding table, the output voltage value in the entire voltage corresponding table from the minimum set output voltage to the maximum set output voltage is traversed by the corresponding step size, and the different output voltages and the corresponding ideal phase shift angle θ m The critical control frequency is obtained. Different critical control frequencies are filled into the voltage corresponding table corresponding to the corresponding output voltage.

[0069] As Figure 5 shown, a gain-critical control frequency curve is made in a coordinate system with gain as the horizontal coordinate and frequency as the vertical coordinate, and a critical limit frequency function is fitted with gain M as the independent variable and critical control frequency as the dependent variable according to the gain-critical control frequency curve.

[0070] In some embodiments of the LcBoost topology-based OBC operating frequency control method of the present application, in S40, not only the input voltage U bus is collected, but also the initial output voltage when the LcBoost topology is working is collected.

[0071] On the basis of the initial output voltage, the reference voltage is continuously set in the direction of the target output voltage according to the set step size, until the difference between the set reference voltage and the target output voltage is less than or equal to the set step size.

[0072] Specifically, if the target output voltage is 500 V and the current output voltage is 298 V, the reference voltage is set with 0.5 V as the set step size, the value of the first reference voltage is 298.5 V, the value of the second reference voltage is 299 V, and so on. The value of the i-th reference voltage is 298+0.5iV, until the 403rd reference voltage 499.5V. At this time, since the difference between the reference voltage and the target output voltage is 0.5V, which is equal to the set step size, no new reference voltage value is set.

[0073] In step S50, when setting the current reference voltage Uref between the current output voltage Ubat and the target voltage, a reference voltage that conforms to a set rule is selected from multiple reference voltages as the current reference voltage. For example, in the aforementioned example, when the current output voltage Ubat and the current reference voltage Uref are... ref When the difference between them is less than 1V, select a voltage greater than the current output voltage U. bat The minimum reference voltage of 3V is used as the current output voltage. This allows for a certain adjustment range of the current output voltage while also controlling the voltage adjustment reference relative to the current output voltage U. bat The deviation between the values ​​reduces the voltage adjustment amplitude at any time during OBC operation, controls the adjustment amplitude of the current control frequency FSW and / or the current phase shift angle during the regulation process, and improves the power conversion efficiency of OBC while ensuring the output voltage regulation effect.

[0074] In a preferred embodiment of the OBC operating frequency control method based on LcBoost topology in this application, in step S50, a value greater than the current output voltage U is taken. bat The minimum reference voltage is used as the current reference voltage U. ref In the aforementioned example, if the current output voltage U bat If the current voltage is 298V, then 298.5V will be used as the current reference voltage; if the current output voltage U bat If the voltage rises to 298.5V, then 299V will be used as the current reference voltage, and so on. Ensure the current output voltage U... bat Slight and steady adjustments to reduce the deviation of the current control frequency FSW from the ideal frequency f. m And the current phase shift angle deviates from the ideal phase shift angle θ m This will further improve the power conversion efficiency of the OBC.

[0075] When the current output voltage U bat When there is no longer a reference voltage between the current output voltage and the target output voltage, as in the previous example, the current output voltage U... bat Once the voltage has been adjusted to 499.5V, the target output voltage, such as 500V, will be used as the current reference voltage U. ref To ensure the final current output voltage U bat It reaches and stabilizes at the target output voltage.

[0076] Based on the current output voltage U bat With the current reference voltage U refThe deviation between the voltage and the input voltage is calculated using a PI control loop based on a voltage correspondence table to obtain the current control frequency FSW. PI calculation is a well-known algorithm, and the PI control loop is also a well-known control loop. Dedicated PI control loop integrated circuit chips are also available for sale; their principles and specific implementation schemes will not be elaborated upon here. The current control frequency FSW obtained through PI calculation makes the current output voltage U... bat To the current reference voltage U ref Approaching, while the current control frequency FSW is directed towards the current reference voltage U. ref The corresponding ideal frequency f m Approaching.

[0077] In some embodiments of the OBC operating frequency control method based on LcBoost topology in this application, such as Figure 6 As shown, step S40 includes the following steps: S41, such as Figure 5 As shown, in a coordinate system with gain on the x-axis and frequency on the y-axis, plot the gain M and the corresponding ideal frequency f for different output voltages in the voltage correspondence table. m The curves corresponding to these relationships are used to obtain the full-load gain frequency curve. Then, based on the full-load gain frequency curve, a curve is constructed with gain M as the independent variable and the ideal frequency f. m The gain of the dependent variable is the full-load frequency function.

[0078] S42. Match the ideal frequencies f in the voltage correspondence table. m The value minus the set value, such as the ideal frequency f. m Subtract 5kHz from each value to obtain the frequency limiting frequency corresponding to each gain M, and fill it into the corresponding position in the voltage correspondence table. For example... Figure 5 As shown, curves depicting the correspondence between different gains M and their corresponding frequency limiting frequencies are plotted in a coordinate system with gain as the abscissa and frequency as the ordinate, thus obtaining the gain-frequency limiting curves. Then, a gain-frequency limiting function is constructed by fitting the gain-frequency limiting curves, with gain M as the independent variable and the frequency limiting frequency as the dependent variable. S43. In the host computer, set the target output voltage for the current operation of OBC and the reference voltage adjustment value used to determine the reference voltage amplitude; and set the voltage acquisition circuit to acquire the input voltage U of the LcBoost topology. bus And the initial output voltage of OBC at the beginning of startup.

[0079] S44. Set the current reference voltage U between the starting output voltage and the target output voltage. ref This makes the current reference voltage U ref The difference between the voltage and the initial output voltage is equal to the reference voltage adjustment amplitude.

[0080] If the target output voltage is set to 500V, the reference voltage adjustment amplitude is 0.5V, and the initial output voltage acquired when the OBC starts is 285V, then the current reference voltage U is 285.5V obtained by adding the reference voltage adjustment amplitude of 0.5V to the initial output voltage of 285V. ref .

[0081] like Figure 7 As shown, step S50 includes the following steps: S51. Utilize a voltage acquisition circuit to acquire the current output voltage U during the operation of the LcBoost topology in real time. bat And according to formula M t =U bat *n / U bus The current output voltage U is calculated. bat Current gain M in the state t .

[0082] S52, based on the current gain M t The current output voltage U is obtained by calculating the gain and phase shift function. bat The current phase shift angle in the current state.

[0083] S53, based on the current output voltage U bat With the current reference voltage U ref The difference between them is used to perform PI calculation based on the voltage correspondence table to obtain the current control frequency FSW; then, based on the current gain M... t The current output voltage U is obtained by calculating the gain-limiting function. bat The current frequency limiting frequency under the current state. If the current control frequency FSW obtained from the PI calculation is less than the current frequency limiting frequency, then the current frequency limiting frequency is used as the current control frequency FSW.

[0084] S54. Generate PWM pulse signals to control the on / off state of each switch in the LcBoost topology based on the current control frequency FSW and the current phase shift angle. Specifically, an ePWM controller chip can be used to generate the PWM pulse signals to control the on / off state of each switch in the LcBoost topology. Send the PWM pulse signals to the control terminals of each switch to control the on / off state of each switch according to the set timing, thus forming the current operating frequency and current phase shift angle of the LcBoost topology, causing the output voltage of the LcBoost topology to shift towards the current reference voltage U. ref Approaching, forming a new current output voltage U bat .

[0085] If, under the current control frequency FSW and current phase shift angle, the output voltage of the LcBoost topology cannot reach the current reference voltage U... ref First, reduce the current control frequency FSW to a level lower than the current output voltage U.bat The corresponding ideal frequency f m Furthermore, the frequency is higher than the limiting frequency corresponding to the current output voltage, causing the output voltage to rise; then, the current phase shift angle is adjusted at a set speed, so that the output voltage of the LcBoost topology is further shifted towards the current reference voltage U. ref near.

[0086] Specifically, if the current output voltage U bat The current reference voltage is 400V. ref The ideal frequency f corresponding to an output voltage of 400V is 400.5V. m The frequency is 78.8 kHz, the corresponding limiting frequency is 71.8 kHz, and the corresponding ideal phase shift angle θ is... m It is 57 degrees. Based on the current output voltage U... bat With the current reference voltage U ref The current control frequency FSW and the current output voltage U are obtained by performing PI calculations and then limiting them to the current frequency. bat The corresponding ideal phase shift angle θ m The new current output voltage U formed at 57 degrees bat The current reference voltage U is not reached. ref 400.5V. At this point, first, control the current control frequency FSW to decrease while maintaining a frequency no lower than 71.8kHz, so that the current output voltage U... bat Increase to the current reference voltage U ref 400.5V. If the current control frequency FSW is adjusted to 71.8kHz, the current output voltage U bat It has not yet risen to the current reference voltage U. ref Then, in the current actual output voltage U bat Further adjustments will be made based on this.

[0087] Based on the increased current output voltage U bat And the phase shift function, calculate the new current output voltage U. bat The corresponding ideal phase shift angle θ m Then, the current phase shift angle is adjusted at a rate of 0.36 degrees / 20 μs towards the newly calculated ideal phase shift angle θ. m adjust.

[0088] After each adjustment of the current phase shift angle, the current output voltage U is compared with the new current phase shift angle. bat With the current reference voltage U ref The magnitude of the new current output voltage U bat Higher than the current reference voltage U ref If the amplitude is set, the current control frequency FSW will increase through program control; if the new current output voltage Ubat Below the current reference voltage U ref Set the amplitude, then through the program control the current control frequency FSW down. Keep the new current output voltage U bat Stable at the current reference voltage U ref Level until the current phase shift angle equal to the current output voltage U bat The corresponding ideal phase shift angle θ m .

[0089] S55, the current reference voltage U ref Adjust the reference voltage adjustment amplitude in the direction of the target output voltage. This movement can be carried out when the output voltage of the LcBoost topology has been adjusted to equal the current reference voltage U ref , or automatically according to the set speed, such as when the reference voltage adjustment amplitude is 0.2V, at a speed of 0.2V / ms. When automatically according to the set speed, a reference voltage deviation amplitude is usually set, such as 5V, once the current reference voltage U ref Deviation from the current output voltage U bat The amplitude reaches the reference voltage deviation amplitude, the automatic adjustment of the current reference voltage U ref Is suspended.

[0090] On the basis of the new current output voltage U bat And the current reference voltage U ref The adjustment of the current control frequency FSW and the current phase shift angle is continued, so that the current output voltage U bat Gradually close to the target output voltage.

[0091] If the adjustment of the current reference voltage U ref The current reference voltage U ref Cross the target output voltage, or exactly equal to the target output voltage, then take the target output voltage as the current reference voltage U ref , No longer adjust the current reference voltage U ref , So that the current output voltage U bat Arrive and stably maintain at the target output voltage level.

[0092] With the change of the phase shift angle θ of the LcBoost topology, the current control frequency FSW will appear to a certain extent. After re-acquiring the current output voltage U bat , Adjust the current control frequency FSW again after the current phase shift angle is calibrated by the gain phase shift function. Through the closed loop of "frequency adjustment-voltage matching-phase calibration-frequency callback" repeated, the current output voltage U batThe voltage is smoothly adjusted to the target output voltage, and the current control frequency FSW during the adjustment process is close to the current ideal frequency, and the current phase shift angle is also close to the current ideal phase shift angle.

[0093] In a further preferred embodiment of the OBC operating frequency control method based on LcBoost topology in this application, such as Figure 8 As shown, at the current output voltage U bat During the rise, at the current output voltage U bat The smaller the value, the better the current gain M becomes. t When the initial phase shift gain is less than the set value (e.g., less than 0.87), the phase shift angle θ of the LcBoost topology remains unchanged, typically kept at zero. The output voltage of the LcBoost topology is then adjusted by regulating the current control frequency (FSW).

[0094] At the current output voltage U bat During the descent, as the current output voltage U... bat The decrease in M ​​makes the current gain M t When the phase shift gain is less than the set stop phase shift gain, such as less than 0.85, the phase shift angle θ of the LcBoost topology drops to zero. At this time, the phase shift angle θ of the LcBoost topology is no longer adjusted, and the output voltage of the LcBoost topology is adjusted only by adjusting the current control frequency FSW.

[0095] As a specific implementation of the OBC operating frequency control method based on LcBoost topology in this application, the resonant frequency of LcBoost topology is based on the inherent resonant frequency of LcBoost topology, and a set value is added to the resonant frequency of LcBoost topology, such as adding 10kHz as the minimum frequency limit.

[0096] like Figure 9 As shown, with the phase shift angle θ of the LcBoost topology remaining constant at zero, the current output voltage U is adjusted only by regulating the current control frequency FSW. bat At that time, the adjustment range of the current control frequency FSW is limited by the minimum limiting frequency. In other words, in order to ensure the current output voltage U... bat Reaching the current reference voltage U ref This allows you to adjust the current control frequency FSW to the lowest frequency limit.

[0097] If the current control frequency FSW is lowered to the current minimum limit frequency, the current output voltage U bat Still below the current reference voltage U ref, the down-regulation of the current control frequency FSW is no longer performed to prevent the full-bridge switch from working in a hard switching state and ensure the power conversion efficiency of the LcBoost topology. At this time, the output voltage of the LcBoost topology is adjusted by temporarily adjusting the current phase shift angle.

[0098] The OBC operating frequency control method based on the LcBoost topology of the present application is based on the real-time gain M t The dynamic frequency limitation of the LcBoost topology overcomes the defects of insufficient frequency limitation in some sections and excessive frequency limitation in other sections in a wide output voltage range when the operating frequency of the LcBoost topology is limited according to a fixed lower limit of the frequency. An optimal operating frequency can be formed for each output voltage point through the "gain-frequency" mapping relationship. This not only accurately and timely prevents the switch from entering the hard switching state with huge loss, but also avoids the output overcurrent risk from the root, thereby ensuring the system dynamic performance and reliability while significantly improving the overall efficiency and safety, significantly reducing the switching loss of the LcBoost topology, and enabling the power conversion efficiency of the OBC in a stable operating state to reach 95%, effectively improving the power conversion efficiency of the OBC.

[0099] One embodiment of the OBC based on the LcBoost topology of the present application includes an LcBoost topology as shown in Figure 2 The LcBoost topology is controlled in terms of the operating frequency f and the phase shift angle θ by using the OBC operating frequency control method based on the LcBoost topology of any embodiment of the present application.

[0100] In the description of the present application, the description of the terms "one embodiment", "a specific embodiment", "a preferred embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0101] The above are the preferred embodiments of the present application, which do not limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application shall be covered within the protection scope of the present application.

Claims

1. An OBC operating frequency control method based on LcBoost topology, characterized in that: The method comprises the following steps: S10, in the open loop state, the LcBoost topology is obtained in different working frequency f and different phase shift angle θ state, in different output voltage point when full load state of the electric energy conversion efficiency, get the ideal frequency f when the electric energy conversion efficiency is maximum m and the ideal phase shift angle θ m ; S20, constructing a table of voltage corresponding relationship including different output voltages and corresponding ideal frequencies f m and ideal phase shift angle θ m corresponding relationship, and calculating gain M at different output voltages, constructing ideal phase shift angle θ m gain phase shift function about gain M; S30、In the closed-loop state, the LcBoost topology is obtained at different output voltages and corresponding ideal phase shift angles θ m The working frequency when the switch tube is in the ZVS critical state is taken as the critical control frequency, and the gain M at different output voltages is calculated, and a critical limit frequency function with the gain M as the independent variable and the critical control frequency as the dependent variable is constructed. S40, set target output voltage, and collect input voltage U bus ; S50. Obtain the current output voltage U during the operation of the LcBoost topology. bat And calculate the current gain M t At the current output voltage U bat Set the current reference voltage U between the target voltage and the target voltage. ref According to the current output voltage U bat and the current reference voltage U ref The current control frequency FSW is obtained, and its range is limited by a critical control frequency, based on the current gain M. t The current phase shift angle is obtained by the gain phase shift function, and the on / off state of each switch in the LcBoost topology is controlled according to the current control frequency FSW and the current phase shift angle.

2. The OBC operating frequency control method based on the LcBoost topology according to claim 1, characterized in that: In step S10, the output voltage of the LcBoost topology is adjusted to the set output voltage when the electronic load is connected to the LcBoost topology, the electronic load is adjusted so that the output power of the LcBoost topology is the full-load output power, and the power analyzer is used to obtain the electrical energy conversion efficiency of the LcBoost topology in the current state; different operating frequencies f and different phase shift angles θ are adjusted respectively, the output voltage is ensured to be unchanged, the electrical energy conversion efficiency in different operating frequency f and phase shift angle θ combination states is recorded, and the operating frequency f and the phase shift angle θ when the electrical energy conversion efficiency is maximum are selected as the ideal frequency f m and the ideal phase shift angle θ m corresponding to the output voltage, respectively.

3. The OBC operating frequency control method based on LcBoost topology according to claim 2, characterized in that: The step S20 comprises the following steps: S21, gradually increase the output voltage of the LcBoost topology from the minimum set output voltage to the maximum set output voltage by the set adjustment amplitude, and obtain the ideal frequency f under different output voltages respectively m and the ideal phase shift angle θ m ; S22, establish different output voltage and corresponding ideal frequency f m and ideal phase shift angle θ m correspondence table, get voltage correspondence table; S23, according to the formula M = U bat n / U bus The gain M in different output voltage states is calculated, where U bat is the current output voltage, and n is the turns ratio of the transformer T in the LcBoost topology. S24, fitting the gain M with the ideal phase shift angle θ m correspondence curve, and constructing the ideal phase shift angle θ m gain phase shift function with respect to the gain M.

4. The OBC operating frequency control method based on LcBoost topology according to claim 1, characterized in that: In step S30, the output voltage is fixed to a set size, and the phase shift angle θ is fixed to the ideal phase shift angle θ corresponding to the output voltage m , the output load of the LcBoost topology is gradually increased until the off current of the switch tube reaches a set value, and the operating frequency of the switch tube at this time is taken as the critical control frequency; the output voltage of the LcBoost topology is traversed by a set step size throughout the entire output voltage range from the minimum set output voltage to the maximum set output voltage, and different output voltages and the corresponding ideal phase shift angle θ m critical control frequency are obtained.

5. The OBC operating frequency control method based on LcBoost topology according to claim 1, characterized in that: In step S40, also the starting output voltage of the LcBoost topology is acquired, between the starting output voltage and the target output voltage a number of reference voltages is set with a set step size, in step S50, in the reference voltages a current reference voltage U ref is set.

6. The OBC operating frequency control method based on the LcBoost topology according to claim 5, characterized in that: In step S50, a reference voltage adjacent to the current output voltage U bat between the target output voltage and the current output voltage U bat is taken as the current reference voltage U ref . If there is no reference voltage between the target output voltage and the current output voltage U bat , the target output voltage is taken as the current reference voltage U ref . Based on the deviation between the current output voltage U bat and the current reference voltage U ref , a PI operation is performed based on the voltage correspondence table to obtain the current control frequency FSW.

7. The OBC operating frequency control method based on LcBoost topology according to claim 1, characterized in that: The step S40 comprises the following steps: S41. Fit the gain M to the ideal frequency f according to the voltage correspondence table. m The corresponding relationship curve is used to obtain the gain full-load frequency curve, and the gain full-load frequency function is constructed based on the gain full-load frequency curve. S42. Match the ideal frequencies f in the voltage correspondence table. m Decrease the set value to obtain the corresponding frequency limiting frequency. Fit the curve of the relationship between gain M and frequency limiting frequency according to the voltage correspondence table to obtain the gain frequency limiting curve. Construct the gain frequency limiting function based on the gain frequency limiting curve. S43, set target output voltage and reference voltage regulation amplitude, collect input voltage U bus and the initial output voltage; S44, setting a current reference voltage U between the starting output voltage and the target output voltage ref such that the difference between the current reference voltage U and the starting output voltage is a reference voltage adjustment amplitude; ref such that the difference between the current reference voltage U and the starting output voltage is a reference voltage adjustment amplitude; The step S50 comprises the following steps: S51, obtain the current output voltage U in the working process of the LcBoost topology bat and calculate the current gain M t ; S52, according to the current gain M t and the gain phase shift function to obtain the current phase shift angle; S53、according to the current output voltage U bat the difference between the current reference voltage U ref , based on the voltage correspondence table, PI operation is performed to obtain the current control frequency FSW, and according to the current gain M t and the gain limiting frequency function to obtain the current limiting frequency, if the current control frequency FSW is less than the current limiting frequency, the current limiting frequency is taken as the current control frequency FSW; S54, controlling the on-off state of each switch tube of the LcBoost topology according to the current control frequency FSW and the current phase-shift angle LcBoost; S55, adjusting the reference voltage U ref the target output voltage, the reference voltage is adjusted in the direction of the target output voltage by an adjustment value, and if the current reference voltage U ref reaches or exceeds the target output voltage, the target output voltage is taken as the current reference voltage U ref .

8. The LcBoost topology based OBC operating frequency control method according to claim 7, characterized in that: At the current output voltage U bat During the rise, when the current gain Mt is less than the set initial phase shift gain, the phase shift angle θ of the LcBoost topology remains unchanged, and only the current control frequency FSW is adjusted; when the current output voltage U... bat During the descent process, when the current gain Mt is less than the set stop phase shift gain, the phase shift angle θ of the LcBoost topology will no longer be adjusted, and only the current control frequency FSW will be adjusted.

9. The OBC operating frequency control method based on LcBoost topology according to claim 8, characterized in that: In the state of keeping the phase-shift angle θ of the LcBoost topology unchanged and only adjusting the current control frequency FSW, taking the lowest limit frequency as the current limit frequency.

10. An LcBoost topology based OBC characterized in that: The LcBoost topology-based OBC operating frequency control method according to any one of claims 1-9 is used for operating frequency control.

Images