Resonant circuit starting method, resonant converter and energy storage system

Abstract

The application relates to a resonant circuit starting method, a resonant converter and an energy storage system. The resonant circuit comprises a primary side and a secondary side. The method comprises the following steps: in a first soft starting stage, a primary side switch tube is controlled to continuously operate at an initial duty ratio until a capacitor voltage value of a bus capacitor on the secondary side rises to a first preset voltage value; in a second soft starting stage, the primary side switch tube is controlled to continuously operate at the initial duty ratio as a starting point and linearly increase at a first slope value until the capacitor voltage value rises to a second preset voltage value; and in a third soft starting stage, the primary side switch tube is controlled to continuously operate at a primary side duty ratio at the end of the second soft starting stage as a starting point and linearly increase at a second slope value until the capacitor voltage value rises to a third preset voltage value. The resonant circuit starting method can inhibit current stress of the primary side switch tube and shorten the duration of the early soft starting stage.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a resonant circuit startup method, a resonant converter, and an energy storage system. Background Technology

[0002] Resonant circuits (LLCs) are widely used in power electronic systems due to their high efficiency, high power density, and ease of implementing zero voltage switching (ZVS) and zero current switching (ZCS).

[0003] However, during the startup process of the resonant circuit, the resonant inductor and resonant capacitor in the resonant circuit will generate a large inrush current and resonant voltage due to the instability of the initial state of the resonant circuit. This will lead to a sudden increase in the voltage stress and current value of the switching transistor in the resonant circuit, making the switching transistor prone to damage.

[0004] Therefore, resonant circuits suffer from high stress on the switching transistors during startup. Summary of the Invention

[0005] Based on this, this application provides a resonant circuit startup method, a resonant converter, and an energy storage system, which can suppress the current stress of the primary-side switching transistor while shortening the duration of the early soft-start phase.

[0006] In a first aspect, this application provides a method for starting up a resonant circuit, the resonant circuit including a primary side and a secondary side, the method comprising:

[0007] The initial duty cycle of the primary-side switch is determined based on the rated current value of the primary-side switch.

[0008] During the first soft start phase, the primary-side switching transistor is controlled to run continuously at the initial duty cycle until the capacitor voltage of the secondary-side bus capacitor rises to the first preset voltage value.

[0009] In the second soft-start phase, based on the bus capacitor charging current value at the first moment, the bus capacitor charging current value at the second moment, the first output voltage value on the secondary side at the second moment, and the first preset voltage value, the first slope value of the primary side duty cycle is determined; the primary side switch is controlled to operate linearly with the initial duty cycle as the starting point and the first slope value, until the capacitor voltage value rises to the second preset voltage value.

[0010] In the third soft-start phase, based on the bus capacitor charging current value at the first moment, the bus capacitor charging current value at the third moment, the second output voltage value and the second preset voltage value on the secondary side at the third moment, the second slope value of the primary side duty cycle is determined; the primary side switch is controlled to operate linearly with the primary side duty cycle at the end of the second soft-start phase as the starting point and with the second slope value, until the capacitor voltage value rises to the third preset voltage value.

[0011] The first time, the second time, and the third time are the start time of the first soft boot phase, the end time of the first soft boot phase, and the end time of the second soft boot phase, respectively.

[0012] In some embodiments, the first preset voltage value is the product of a first preset multiple and the rated voltage value of the bus capacitor, the second preset voltage value is the product of a second preset multiple and the rated voltage value of the bus capacitor, and the third preset voltage value is the rated voltage value of the bus capacitor.

[0013] Both the first preset multiple and the second preset multiple are positive numbers less than 1, and the first preset multiple is less than the second preset multiple.

[0014] In some embodiments, determining the initial duty cycle of the primary-side switch based on its rated current value includes:

[0015] When the voltage of the bus capacitor is 0, the primary-side switching transistors are controlled to operate at each preset duty cycle, and the peak current of each primary-side switching transistor corresponding to each preset duty cycle is monitored.

[0016] The duty cycle of the primary-side switch corresponding to the target time is determined as the initial duty cycle. The target time is the time when the peak current of the primary-side switch is the product of the rated current of the primary-side switch and the third preset multiple. The third preset multiple is a positive number less than 1.

[0017] In some embodiments, determining a first slope value of the primary side duty cycle based on the bus capacitor charging current value at a first time moment, the bus capacitor charging current value at a second time moment, the first output voltage value on the secondary side at the second time moment, and a first preset voltage value includes:

[0018] The first voltage difference is determined based on the first output voltage value and the first preset voltage value;

[0019] The product of the voltage coefficient and the first voltage difference is determined as the first product value;

[0020] The ratio of the bus capacitor charging current value at the second moment to the bus capacitor charging current value at the first moment is determined as the first ratio.

[0021] The ratio of the first ratio to the first product value is determined as the second ratio.

[0022] The ratio of the second ratio to the duty cycle coefficient is then divided by the turns ratio of the transformer in the resonant circuit to determine the third ratio.

[0023] The first slope value is determined based on the difference between the third ratio and the initial duty cycle.

[0024] In some embodiments, determining a second slope value of the primary side duty cycle based on the bus capacitor charging current value at a first time moment, the bus capacitor charging current value at a third time moment, the second output voltage value on the secondary side at the third time moment, and the second preset voltage value includes:

[0025] The second voltage difference is determined based on the second output voltage value and the second preset voltage value;

[0026] The product of the voltage coefficient and the second voltage difference is determined as the second product value;

[0027] The ratio of the bus capacitor charging current value at the third moment to the bus capacitor charging current value at the first moment is determined as the fourth ratio.

[0028] The ratio of the fourth ratio to the ratio of the second product is determined as the fifth ratio;

[0029] The ratio of the fifth ratio to the duty cycle coefficient is then divided by the turns ratio of the transformer in the resonant circuit to determine the sixth ratio.

[0030] The second slope value is determined based on the difference between the sixth ratio and the duty cycle of the primary-side switch at the third time.

[0031] In some embodiments, the method further includes: determining a duty cycle factor; determining the duty cycle factor includes:

[0032] Determine the expression for the current variable of the primary-side switch; the current variable is directly proportional to the duty cycle variable, duty cycle coefficient, and voltage difference variable of the primary-side switch, respectively; the voltage difference variable is the difference between the output voltage value of the secondary side and the capacitance voltage value of the bus capacitor.

[0033] Within a preset time period, the input voltage on the primary side of the fixed resonant circuit is used to obtain a first data set during the linear increase of the duty cycle of the primary-side switch. The first data set includes the instantaneous duty cycle value and instantaneous current value of the primary-side switch at each moment.

[0034] Based on the expression of the current variable of the primary-side switch, a straight line is fitted to the first data set to obtain the first straight line of the instantaneous current value of the primary-side switch with respect to the instantaneous duty cycle value. The slope of the first straight line is determined as the duty cycle coefficient.

[0035] In some embodiments, the method further includes: determining a voltage coefficient; determining the voltage coefficient includes:

[0036] Determine the expression for the current variable of the primary-side switch; the current variable is directly proportional to the voltage coefficient, the duty cycle variable of the primary-side switch, and the voltage difference variable, respectively. The voltage difference variable is the difference between the output voltage value of the secondary side and the capacitance voltage value of the bus capacitor.

[0037] Within a preset time period, the duty cycle of the primary-side switch is fixed, and a second data set is obtained during the linear increase of the input voltage value on the primary side. The second data set includes the instantaneous voltage difference and the instantaneous current value of the primary-side switch at each moment.

[0038] Based on the expression for the current variable of the primary-side switch, a straight line is fitted to the second data set to obtain a second straight line with respect to the instantaneous difference in voltage between the instantaneous current value of the primary-side switch and the instantaneous voltage value. The slope of the second straight line is then determined as the voltage coefficient.

[0039] In some embodiments, the expression for the current variable of the primary-side switch is: the product of the turns ratio of the transformer in the resonant circuit, the bus capacitor charging current value at the first moment, the duty cycle variable of the primary-side switch, the duty cycle coefficient, the voltage difference variable, and the voltage coefficient.

[0040] In a second aspect, this application provides a resonant converter, which includes a controller and a resonant circuit connected to the controller; the controller is used to perform the method of any one of the first aspects.

[0041] Thirdly, this application provides an energy storage system, which includes the resonant converter of the second aspect.

[0042] In the technical solution provided in this application embodiment, during the first soft-start stage, the primary-side switch does not operate with a gradually increasing duty cycle starting from zero, but rather operates continuously with a fixed duty cycle determined based on its rated current value. Since the initial duty cycle of the primary-side switch is determined based on the rated current value, the current stress of the primary-side switch can be suppressed. Furthermore, by avoiding the process of the duty cycle slowly climbing from an extremely low value, this stage allows the secondary-side bus capacitor voltage to rise rapidly to the first preset voltage value, thereby significantly shortening the duration of the early soft-start phase. In each soft-start stage of the second and third soft-start stages, the slope of the duty cycle increase can be determined based on the bus capacitor charging current value at the start of the start, the bus capacitor charging current value at the end of the previous soft-start stage, and the remaining charging voltage value of the bus capacitor. This allows for adjustment of the duty cycle increase slope in this stage based on the charging status of the bus capacitor in the resonant circuit, thereby suppressing the current stress of the primary-side switch while shortening the duration of the early soft-start phase. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 Schematic diagrams of the resonant circuit provided for some embodiments;

[0045] Figure 2 A flowchart illustrating a resonant circuit startup method provided in some embodiments;

[0046] Figure 3 A schematic diagram illustrating the relationship between the charging current and capacitor voltage of a bus capacitor provided in some embodiments;

[0047] Figure 4 A flowchart illustrating a method for determining a first slope value of the primary side duty cycle provided in some embodiments;

[0048] Figure 5 A flowchart illustrating a method for determining a second slope value of the primary edge duty cycle provided in some embodiments;

[0049] Figure 6 A schematic diagram illustrating the relationship between time and duty cycle in various resonant circuit startup methods provided in some embodiments;

[0050] Figure 7 A schematic diagram showing the relationship between the startup time and the current value of the primary-side switch in a segmented variable duty cycle resonant circuit startup method provided in some embodiments;

[0051] Figure 8 A schematic diagram showing the relationship between the startup time and the current value of the primary-side switch in a linear variable duty cycle resonant circuit startup method provided in some embodiments;

[0052] Figure 9 A schematic diagram showing the relationship between the startup time and the current value of the primary-side switch in the startup method of the exponentially variable duty cycle resonant circuit provided in some embodiments;

[0053] Figure 10 Schematic diagrams of the resonant converter provided for some embodiments;

[0054] Figure 11 A schematic diagram of the structure of an energy storage system provided for some embodiments. Detailed Implementation

[0055] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0057] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined. In the description of the embodiments of this application, "each" means each of the multiple options, unless otherwise explicitly defined.

[0058] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0059] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0060] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0061] Figure 1A schematic diagram of the resonant circuit provided for some embodiments, such as Figure 1 As shown, the resonant circuit includes a primary side and a secondary side. In some embodiments, the primary side can be connected to a battery, and the secondary side can be connected to an inverter circuit.

[0062] On the secondary side of the resonant circuit, the first terminal of the transformer secondary winding is connected to the first terminal of the magnetizing inductor Lm1, which is also connected to the first terminal of the resonant inductor Lr1. The second terminal of the magnetizing inductor Lm1 is connected to the second terminal of the transformer secondary winding. The second terminal of the resonant inductor Lr1 is connected to the first terminal of the resonant capacitor Cr1, which is connected to the source of the first switching transistor T1. The source of the first switching transistor T1 is also connected to the source of the second switching transistor T2. The drain of the first switching transistor T1 is connected to the drain of the third switching transistor T3, which is also connected to V. out The positive terminal of the second switch T2 is connected to the source of the fourth switch T4, and the source of the fourth switch T4 is also connected to V. out The negative terminal of the third switch T3 is connected to the source of the fourth switch T4, and the source of the third switch T3 is also connected to the second terminal of the magnetizing inductor Lm1. The first terminal of the bus capacitor Cs is connected to V. out The positive terminal of the bus capacitor Cs is connected to V. out The negative electrode.

[0063] On the primary side of the resonant circuit, V in The positive terminal is connected to the drain of the fifth switching transistor T5, V in The negative terminal of the transistor is connected to the source of the sixth switch transistor T6. The drain of the fifth switch transistor T5 is also connected to the drain of the seventh switch transistor T7. The source of the sixth switch transistor T6 is also connected to the source of the eighth switch transistor T8. The source of the fifth switch transistor T5 is connected to the drain of the sixth switch transistor T6. The source of the fifth switch transistor T5 is also connected to the first end of the primary winding of the transformer. The source of the seventh switch transistor T7 is connected to the drain of the eighth switch transistor T8. The source of the seventh switch transistor T7 is also connected to the second end of the primary winding of the transformer.

[0064] The fifth switch T5, the sixth switch T6, the seventh switch T7, and the eighth switch T8 on the primary side of the resonant circuit are the primary-side switches of the resonant circuit. The drive signals for the fifth switch T5, the sixth switch T6, the seventh switch T7, and the eighth switch T8 are PWM3A, PWM3B, PWM4A, and PWM4B, respectively. inThe input voltage on the primary side is given. The first switch T1, second switch T2, third switch T3, and fourth switch T4 on the secondary side of the resonant circuit are the secondary switching transistors of the resonant circuit. The drive signals for the first switch T1, second switch T2, third switch T3, and fourth switch T4 are PWM1A, PWM1B, PWM2A, and PWM2B, respectively. Lm1 is the magnetizing inductor, Lr1 is the resonant inductor, and Cr1 is the resonant capacitor. For example, the resonant frequency can be 80kHz, and the drive frequency for each switch can be 80kHz. Cs is the bus capacitor, V... out This is the output voltage on the secondary side.

[0065] It should be noted that, Figure 1 The embodiment shown is an exemplary implementation of a resonant circuit. In other embodiments, the resonant circuit may have other implementations, and the embodiments of this application do not limit this.

[0066] The methods in any embodiment of this application can be applied to a controller, processor, or computer device. Exemplarily, a computer device may include one or a combination of at least two of the following: a server, a mobile phone, a tablet computer, a computer with transceiver capabilities, a handheld computer, a desktop computer, a virtual reality (VR) device, an augmented reality (AR) device, and so on.

[0067] The resonant circuit in the embodiments of this application can be Figure 1 The resonant circuit shown can be used as a... Figure 1 Other resonant circuits obtained by modifying the resonant circuit shown are not limited in this respect.

[0068] Figure 2 This is a flowchart illustrating a resonant circuit startup method provided in some embodiments. The resonant circuit includes a primary side and a secondary side, such as... Figure 2 As shown, the method includes the following steps:

[0069] S201. Determine the initial duty cycle of the primary-side switch based on the rated current value of the primary-side switch.

[0070] The primary-side switch can be any primary-side switch. The rated current value of the primary-side switch can be obtained from the device datasheet. The rated current value of the primary-side switch refers to the maximum drain current that the primary-side switch can continuously and safely pass under specified heat dissipation conditions and rated operating temperature.

[0071] The initial duty cycle of the primary-side switch can be the duty cycle of the primary-side switch at the first moment. Here, the first moment is the start time of the first soft-start phase.

[0072] In some embodiments, when the voltage of the bus capacitor is 0, the primary-side switching transistors are controlled to operate at each preset duty cycle, and the peak current of each primary-side switching transistor corresponding to each preset duty cycle is detected. The preset duty cycle corresponding to the peak current that is less than or equal to the rated current value and is closest to the rated current value is determined as the initial duty cycle.

[0073] The resonant circuit startup method in this application includes three stages: a first soft-start stage, a second soft-start stage, and a third soft-start stage. The startup process of these three stages is described below.

[0074] In this embodiment, the startup process of the resonant circuit includes: the capacitor voltage value of the bus capacitor on the secondary side gradually increases from an initial zero value until it reaches a preset output voltage value on the secondary side. In some embodiments, the preset output voltage value on the secondary side can be the product of the input voltage value on the primary side and the turns ratio of the transformer.

[0075] S202. In the first soft start phase, the primary-side switching transistor is controlled to run continuously at the initial duty cycle until the capacitor voltage of the secondary-side bus capacitor rises to the first preset voltage value.

[0076] The first soft-start phase is the phase in which the primary-side switching transistors operate continuously with a fixed initial duty cycle.

[0077] The primary-side switch operates continuously with a duty cycle, which can include the primary-side switch continuously generating waves with a duty cycle. Here, primary-side switch wave generation refers to the primary-side switch in the resonant circuit performing high-frequency, periodic turn-on and turn-off actions according to a set duty cycle and operating frequency.

[0078] In this embodiment, during the startup process of the resonant circuit, the operating frequency of the primary-side switching transistor is the resonant frequency of the resonant circuit. In this embodiment, the turns ratio of the transformer represents the ratio between the number of turns in the secondary winding and the number of turns in the primary winding of the transformer.

[0079] The first preset voltage value is less than the preset output voltage value on the secondary side.

[0080] In some embodiments, the first preset voltage value may be a pre-set fixed voltage value. In other embodiments, the first preset voltage value may be determined based on the rated current of the primary-side switching transistor.

[0081] For example, the first preset voltage value is the product of a first preset multiple and the rated voltage value of the bus capacitor. The first preset multiple is a positive number less than 1.

[0082] For example, the value range of the first preset multiple can be 0.1-0.3. For instance, the first preset multiple can be 0.1, 0.2, or 0.3.

[0083] For example, the maximum allowable current value of the primary-side switch is determined based on the product of the rated current value of the primary-side switch and a third preset multiple; the difference between the maximum allowable current value and the preset redundant current value is determined as the stage end current value; in the first soft-start stage, when the peak current of the primary-side switch reaches the stage end current value, the first soft-start stage ends, and the capacitor voltage value of the bus capacitor when the peak current of the primary-side switch reaches the stage end current value is determined as the first preset voltage value. For example, the third preset multiple is a positive number less than 1. For example, the value range of the third preset multiple can be 0.8-0.95. For example, the third preset multiple can be 0.8, 0.85, 0.9, or 0.95, etc.

[0084] S203. In the second soft-start stage, based on the bus capacitor charging current value at the first moment, the bus capacitor charging current value at the second moment, the first output voltage value on the secondary side at the second moment, and the first preset voltage value, the first slope value of the primary side duty cycle is determined; the primary side switch is controlled to operate linearly with the initial duty cycle as the starting point and the first slope value, until the capacitor voltage value rises to the second preset voltage value.

[0085] In this embodiment, the charging current value of the bus capacitor is the current value flowing through the bus capacitor Cs. The current flowing through the bus capacitor Cs can be obtained by sampling. The capacitor voltage value of the bus capacitor and the output voltage of the secondary side of the resonant circuit can also be obtained by sampling.

[0086] Wherein, the bus capacitor charging current value I0 at the first moment is the current flowing through the bus capacitor Cs during the first soft-start phase when running at the initial duty cycle; the second moment is the termination time of the first soft-start phase. The second soft-start phase is a phase in which the primary-side switch operates continuously with the initial duty cycle as the starting point and a linear increase at a first slope value. The bus capacitor voltage value at the first moment is 0, and the bus capacitor voltage value at the second moment is a first preset voltage value.

[0087] In some embodiments, the first output voltage value on the secondary side at the second moment can be obtained by measurement. In other embodiments, the first output voltage value on the secondary side at the second moment can be the product of the input voltage value on the primary side and the turns ratio of the transformer.

[0088] Figure 3 A schematic diagram illustrating the relationship between the charging current and capacitor voltage of the bus capacitor provided in some embodiments, such as... Figure 3As shown, the vertical axis represents the charging current (I) of the bus capacitor, and the horizontal axis represents the capacitor voltage (U). There is a negative correlation between the charging current and the capacitor voltage. The charging current is at its maximum when the capacitor voltage is 0. , ; This indicates the preset output voltage value on the secondary side. This represents the equivalent internal resistance of the bus capacitor (i.e., the equivalent series resistance of the bus capacitor). When the charging current of the bus capacitor is 0, the capacitor voltage is at its maximum, and the capacitor voltage is [value missing]. .

[0089] In some embodiments, the second preset voltage value may be a pre-set fixed voltage value. In other embodiments, the second preset voltage value may be determined based on the rated current of the primary-side switch.

[0090] For example, the second preset voltage value is the product of a second preset multiple and the rated voltage value of the bus capacitor. The second preset multiple is a positive number less than 1, and the first preset multiple is less than the second preset multiple.

[0091] For example, the value range of the second preset multiple can be 0.5-0.7. For instance, the second preset multiple can be 0.5, 0.6, or 0.7.

[0092] For example, the maximum allowable current value of the primary-side switch is determined based on the product of the rated current value of the primary-side switch and the third preset multiple; the difference between the maximum allowable current value and the preset redundant current value is determined as the stage end current value; in the second soft-start stage, when the peak current of the primary-side switch reaches the stage end current value, it indicates that the second soft-start stage ends, and the capacitor voltage value of the bus capacitor when the peak current of the primary-side switch reaches the stage end current value is determined as the second preset voltage value.

[0093] S204. In the third soft-start stage, based on the bus capacitor charging current value at the first moment, the bus capacitor charging current value at the third moment, the second output voltage value and the second preset voltage value on the secondary side at the third moment, determine the second slope value of the primary side duty cycle; control the primary side switch to operate linearly with the primary side duty cycle at the end of the second soft-start stage as the starting point and with the second slope value until the capacitor voltage value rises to the third preset voltage value.

[0094] The third time point is the end time of the second soft start phase. The third soft start phase is a phase that starts with the original edge duty cycle at the end time of the second soft start phase and continues to operate linearly with the second slope value.

[0095] In this embodiment, the third preset voltage value is the rated voltage value of the bus capacitor. In another embodiment, the third preset voltage value is the difference between the rated voltage value of the bus capacitor and the preset offset voltage value.

[0096] In some embodiments, the second output voltage value on the secondary side at the third time can be obtained by measurement. In other embodiments, the second output voltage value on the secondary side at the third time can be the product of the input voltage value on the primary side and the turns ratio of the transformer. In this embodiment, the second output voltage value on the secondary side at the third time is the same as the first output voltage value on the secondary side at the second time.

[0097] In the technical solution provided in this application embodiment, during the first soft-start stage, the primary-side switch does not operate with a gradually increasing duty cycle starting from zero, but rather operates continuously with a fixed duty cycle determined based on its rated current value. Since the initial duty cycle of the primary-side switch is determined based on the rated current value, the current stress of the primary-side switch can be suppressed. Furthermore, by avoiding the process of the duty cycle slowly climbing from an extremely low value, this stage allows the secondary-side bus capacitor voltage to rise rapidly to the first preset voltage value, thereby significantly shortening the duration of the early soft-start phase. In each soft-start stage of the second and third soft-start stages, the slope of the duty cycle increase can be determined based on the bus capacitor charging current value at the start of the start, the bus capacitor charging current value at the end of the previous soft-start stage, and the remaining charging voltage value of the bus capacitor. This allows for adjustment of the duty cycle increase slope in this stage based on the charging status of the bus capacitor in the resonant circuit, thereby suppressing the current stress of the primary-side switch while shortening the duration of the early soft-start phase.

[0098] In this embodiment, the current stress of the primary-side switch refers to the current load borne by the primary-side switch.

[0099] The implementation of S201 is described below. In some embodiments, the initial duty cycle of the primary-side switch is determined based on the rated current value of the primary-side switch, including: when the voltage of the bus capacitor is 0, controlling the primary-side switch to operate at each preset duty cycle, and monitoring the current peak value of each primary-side switch corresponding to each preset duty cycle; determining the duty cycle of the primary-side switch corresponding to the target time as the initial duty cycle, wherein the target time is the time when the current peak value of the primary-side switch is the product of the rated current value of the primary-side switch and a third preset multiple; the third preset multiple is a positive number less than 1.

[0100] In some embodiments, the duty cycle of the primary-side switch corresponding to the target current peak is determined as the initial duty cycle, and the target current peak is the product of the rated current value of the primary-side switch and a third preset multiple. Alternatively, each preset duty cycle increases sequentially, and the target current peak is the current peak that is first greater than or equal to the product of the rated current value of the primary-side switch and the third preset multiple.

[0101] In some embodiments, the product of the rated current value of the primary-side switch and a third preset multiple can be determined as the maximum allowable current value of the primary-side switch. The target time is the time corresponding to when the peak current of the primary-side switch is the maximum allowable current value.

[0102] The voltage across the bus capacitor is 0, indicating that the voltage across the bus capacitor has been discharged to its initial zero state before the resonant circuit is powered on and started.

[0103] For example, the multiple preset duty cycles include multiple discrete duty cycle values ​​that are evenly distributed in the range of 0% to 50%, and the step size between adjacent preset duty cycles is a preset step size, which can be in the range of 1% to 5%.

[0104] As the voltage across the bus capacitor gradually increases, the peak current of the primary-side switch gradually decreases when operating at a fixed duty cycle. Therefore, in this embodiment, the primary-side switch is controlled to operate at a preset duty cycle each time, with the voltage across the bus capacitor at 0. This allows the detection of the maximum peak current of the primary-side switch during each operation at the preset duty cycle.

[0105] For example, when the voltage of the bus capacitor is 0, the primary-side switch is controlled to operate at each preset duty cycle. For instance, the primary-side switch is controlled to operate at the first preset duty cycle when the voltage of the bus capacitor is 0, and then controlled to operate at the second preset duty cycle when the voltage of the bus capacitor is 0. The preset duty cycles are gradually increased. The current value of the primary-side switch (i.e., the peak current) is observed at the moment when the waveform starts to be generated. When the peak current of the primary-side switch is the maximum allowable current value of the primary-side switch, the duty cycle of the primary-side switch at this time is recorded as the initial duty cycle.

[0106] In the technical solution provided in this application embodiment, under the most stringent initial startup condition of 0 bus capacitor voltage, the switching transistors are driven to run sequentially with each preset duty cycle, and the peak current of the switching transistors corresponding to each duty cycle is detected. Since the peak current is the largest when the bus capacitor voltage is 0, the peak current measured at this time is the highest value of the duty cycle in the entire startup process. Then, the duty cycle of the primary-side switching transistor corresponding to the target time is determined as the initial duty cycle. The initial duty cycle determined in this way is the maximum duty cycle under the premise that the peak current of the primary-side switching transistor does not exceed the maximum allowable current value, thereby suppressing the current stress of the primary-side switching transistor and shortening the duration of the early stage of soft start.

[0107] Figure 4 A flowchart illustrating a method for determining the first slope value of the primary side duty cycle provided in some embodiments, such as... Figure 4 As shown, this method is an exemplary interpretation of step S203, which includes the following steps S2031 to S2036.

[0108] Step S2031: Determine the first voltage difference based on the first output voltage value and the first preset voltage value.

[0109] The first voltage difference represents the voltage difference at the second moment. The first output voltage value is the first output voltage value on the secondary side at the second moment, and the first preset voltage value is the capacitor voltage value of the bus capacitor at the second moment.

[0110] The first voltage difference is the difference between the first output voltage value and the first preset voltage value. The first voltage difference (i.e., the voltage difference at the second time t1) It can be determined by the following formula ;in, This represents the first output voltage value on the secondary side at the second moment. This represents the first preset voltage value (i.e., the capacitor voltage value of the bus capacitor at the second moment).

[0111] Step S2032: Determine the first product value by multiplying the voltage coefficient and the first voltage difference.

[0112] The voltage coefficient represents the degree to which the residual charging voltage of the bus capacitor affects the current value of the primary-side switch. For example, the residual charging voltage of the bus capacitor at the second moment is the first voltage difference value.

[0113] For example, the voltage coefficient can be a preset coefficient, used... The first product value can be represented as... .

[0114] Step S2033: Determine the ratio of the bus capacitor charging current value at the second moment to the bus capacitor charging current value at the first moment as the first ratio.

[0115] The bus capacitor charging current value at the second moment can be expressed as: The bus capacitor charging current value at the first moment can be expressed as: The first ratio can be expressed as .

[0116] Step S2034: Determine the ratio of the first ratio to the first product value as the second ratio.

[0117] The first ratio is expressed as The first product value is expressed as The second ratio is the first ratio. and the first product value The ratio of the two ratios, the second ratio can be expressed as .

[0118] Step S2035: The ratio of the second ratio to the duty cycle coefficient is then compared with the turns ratio of the transformer in the resonant circuit to determine the third ratio.

[0119] The duty cycle factor represents the degree to which the duty cycle of the primary-side switch affects the current value of the primary-side switch.

[0120] For example, the duty cycle factor can be a pre-set factor, used... The turns ratio of the transformer in a resonant circuit is expressed as... This indicates that the second ratio is... and duty cycle coefficient The ratio can be expressed as The second ratio and duty cycle coefficient ratio Then compare the turns ratio of the transformer in the resonant circuit. The resulting third ratio can be expressed as .

[0121] Step S2036: Determine the first slope value based on the difference between the third ratio and the initial duty cycle.

[0122] For example, the difference between the third ratio and the initial duty cycle is determined as the first slope value. The initial duty cycle is the duty cycle of the primary-side switch at the second time step, which can be expressed as... Therefore, the first slope value It can be the third ratio and initial duty cycle The difference. Therefore, the first slope value. The calculation formula is as follows:

[0123] (1).

[0124] Figure 5 A flowchart illustrating a method for determining a second slope value of the primary side duty cycle provided in some embodiments, such as... Figure 5 As shown, this method is an exemplary interpretation of step S204, which includes the steps S2041 to S2046.

[0125] S2041: Determine the second voltage difference based on the second output voltage value and the second preset voltage value.

[0126] The second voltage difference represents the voltage difference at the third moment. The second output voltage value is the second output voltage value on the secondary side at the third moment, and the second preset voltage value is the capacitor voltage value of the bus capacitor at the third moment.

[0127] The second voltage difference is the difference between the second output voltage value and the second preset voltage value. That is, the second voltage difference (i.e., the voltage difference at the third time t2). It can be determined by the following formula ;in, This represents the second output voltage value on the secondary side at the third moment. This represents the second preset voltage value (i.e., the capacitor voltage value of the bus capacitor at the third moment).

[0128] S2042: The product of the voltage coefficient and the second voltage difference is determined as the second product value.

[0129] The voltage coefficient represents the degree to which the residual charging voltage of the bus capacitor affects the current value of the primary-side switch. For example, the residual charging voltage of the bus capacitor at the third moment is the second voltage difference.

[0130] For example, the voltage coefficient can be a preset coefficient, used... The second product value can be expressed as... .

[0131] S2043: The ratio of the bus capacitor charging current value at the third moment to the bus capacitor charging current value at the first moment is determined as the fourth ratio.

[0132] The bus capacitor charging current value at the third moment can be expressed as: The bus capacitor charging current value at the first moment can be expressed as: The fourth ratio can be expressed as .

[0133] S2044: The ratio of the fourth ratio to the second product value is determined as the fifth ratio.

[0134] The fourth ratio is expressed as The second product value is expressed as The fifth ratio is the fourth ratio. Second product value The ratio of the fifth ratio can be expressed as .

[0135] S2045: The ratio of the fifth ratio to the duty cycle coefficient is then divided by the turns ratio of the transformer in the resonant circuit to determine the sixth ratio.

[0136] For example, the duty cycle factor can be a pre-set factor, used... The turns ratio of the transformer in a resonant circuit is expressed as... This indicates that the fifth ratio is... and duty cycle coefficient The ratio can be expressed as The fifth ratio and duty cycle coefficient ratio Then compare the turns ratio of the transformer in the resonant circuit. The sixth ratio obtained can be expressed as .

[0137] S2046: Determine the second slope value based on the difference between the sixth ratio and the duty cycle of the primary-side switch at the third time.

[0138] For example, the difference between the sixth ratio and the duty cycle of the primary-side switch at the third time step is determined as the second slope value. The duty cycle of the primary-side switch at the third time step can be expressed as... Therefore, the second slope value It can be the sixth ratio. Duty cycle of the primary-side switch at the third time step The difference, therefore, the second slope value The calculation formula is as follows:

[0139] (2).

[0140] In some embodiments, the first slope value Second slope value It can be based on the expression of the current variable of the primary-side switch. The expression for the current variable of the primary-side switch is: the turns ratio of the transformer in the resonant circuit. The bus capacitor charging current value at the first moment Duty cycle variable of primary-side switching transistor Duty cycle coefficient Voltage difference variable and voltage coefficient The product between them. Where t represents any time, This represents the current variable of the primary-side switching transistor.

[0141] Specifically, (3).

[0142] The following explanation The derivation process:

[0143] In this embodiment, during the startup process of the resonant circuit, the operating frequency of the primary-side switch is the resonant frequency of the resonant circuit, and the gain is 1. That is, under ideal conditions, the primary-side current of the transformer is... With the secondary current of the transformer The ratio is the turns ratio of the transformer. ,Right now .

[0144] When the duty cycle of the primary-side switch of the LLC is The formula for calculating the energy transferred to the resonant cavity is: ;in, To transfer energy to the resonant cavity, the cavity is composed of a resonant inductor, a resonant capacitor, and the magnetizing inductance of a transformer. These components form a current resonant path, enabling high-frequency energy transfer and conversion. The switching cycle of the primary-side switching transistor. This is the input voltage value on the primary side. This is the value of the resonant current flowing through the resonant inductor.

[0145] The average output current after secondary-side rectification is positively correlated with the energy E; that is, the more energy transferred by the resonant cavity per unit time, the greater the average output current after secondary-side rectification. Therefore, by controlling the duty cycle of the primary-side switch... The charging current of the secondary high-voltage side bus capacitor can be limited, which in turn controls the current of the primary side switching transistor.

[0146] Due to the integral-type rise characteristic of the secondary capacitor voltage, the secondary capacitor voltage The rate of ascent satisfies the differential equation ;in, This represents the charging current value of the bus capacitor. This refers to the bus capacitor capacity. The turns ratio of the transformer. This is the input voltage value on the primary side. This is the equivalent load impedance on the secondary side.

[0147] In this way, the duty cycle of the primary-side switching transistor is constrained. It can effectively control the rate of change of bus capacitor voltage, realize quasi-static voltage ramp-up, make the output voltage build-up stable, and suppress the inrush current when the primary-side switch of the resonant circuit starts up.

[0148] Through formula It can be deduced that .in addition, ,thereby . , , All are fixed values, including the current value of the primary-side switching transistor. Duty cycle of the primary-side switch They are positively correlated.

[0149] and, , This indicates the voltage difference between the output voltage on the secondary side and the voltage across the bus capacitor. Additionally, This represents the equivalent internal resistance of the bus capacitor (i.e., the equivalent series resistance of the bus capacitor). ,thereby Then the current value of the primary-side switch transistor With voltage difference They are positively correlated.

[0150] The duty cycle of the primary-side switching transistor Fixed, and voltage difference Under fixed conditions, the duty cycle of the primary-side switch and voltage difference It will not affect the current value of the primary-side switching transistor. This will have an impact, at this time The duty cycle of the primary-side switching transistor. Under fixed conditions, the duty cycle of the primary-side switch It will not affect the current value of the primary-side switching transistor. This will have an impact, at this time At voltage difference Under fixed conditions, voltage difference It will not affect the current value of the primary-side switching transistor. To have an impact The duty cycle of the primary-side switching transistor. Changes, and voltage difference Under changing conditions, the duty cycle of the primary-side switch and voltage difference Both will affect the current value of the primary-side switching transistor. This has an impact, thus leading to the above formula (3), that is... The duty cycle of the primary-side switching transistor. Fixed, and voltage difference Under fixed conditions, and Both are 1. The duty cycle of the primary-side switch is 1. Changes, and voltage difference Under changing circumstances, according to , , Influence coefficient (using) express), as well as Influence coefficient (using) (This indicates) that they jointly determine it.

[0151] The following explains how to derive the first slope value based on the above formula (3). The process:

[0152] For step S203, in the second soft-start stage, the duty cycle of the primary-side switch is determined according to the first slope value. Linear change, therefore, ,in, Indicates the second moment. Indicates the unit of time. This indicates the time interval of the second time step, which is a unit of time. Substitute into formula (3): ,get ,and for ,thereby Solving within one control cycle , For one control cycle, due to one control cycle It is very small, thus within a very short control cycle. It can be approximated as unchanged. It can be approximated as unchanged. It can be seen as , It can be seen as , The unit duration is set to 1, thus yielding the first slope value. The calculation method is as follows: .

[0153] For step S204, in the third soft-start stage, the duty cycle of the primary-side switch is determined according to the second slope value. Linear change, therefore, ,in, Indicates the third moment. Indicates the unit of time. This indicates the time interval of a unit of time at the third time point. Substitute into formula (3): ,get ,and for ,thereby Solving within one control cycle , For one control cycle, due to one control cycle It is very small, thus within a very short control cycle. It can be approximated as unchanged. It can be approximated as unchanged. It can be seen as , It can be seen as , The unit duration is set to 1, thus ultimately yielding the second slope value. The calculation method is as follows: .

[0154] In the above embodiment, the first slope value Second slope value The process utilizes voltage coefficients. and duty cycle coefficient In some embodiments, the voltage coefficient It can be a preset coefficient, duty cycle coefficient This can be a pre-set coefficient. In other embodiments, the voltage coefficient... and duty cycle coefficient It can be based on the expression for the current variable of the primary-side switching transistor. The following sections will explain the expressions for the current variables based on the primary-side switching transistor. Determine the voltage coefficient and duty cycle coefficient In this way.

[0155] In some embodiments, the duty cycle coefficient is determined. The process includes:

[0156] Determine the expression for the current variable of the primary-side switch. Current variation of the primary-side switch The duty cycle variables of the primary-side switching transistors are respectively Duty cycle coefficient Voltage difference variable The voltage difference variable is directly proportional to the voltage difference variable. This is the difference between the output voltage value on the secondary side and the capacitance voltage value on the bus capacitor.

[0157] Within a preset time period, the input voltage on the primary side of the fixed resonant circuit is used to obtain a first data set during the linear increase of the duty cycle of the primary-side switch. The first data set includes the instantaneous duty cycle value and instantaneous current value of the primary-side switch at each moment.

[0158] Expression based on the current variable of the primary-side switch A linear fit is performed on the first dataset to obtain the first straight line of the instantaneous current value of the primary-side switch transistor with respect to the instantaneous duty cycle value. The slope of the first straight line is determined as the duty cycle coefficient. .

[0159] For example, the instantaneous duty cycle of the primary-side switch at each moment can be the duty cycle of each primary-side switch that increases linearly, and the instantaneous current of the primary-side switch at each moment can be the maximum peak current of the primary-side switch corresponding to the duty cycle of each primary-side switch.

[0160] In some embodiments, the voltage coefficient is determined. ,include:

[0161] Determine the expression for the current variable of the primary-side switch. Current variation of the primary-side switching transistor With voltage coefficient respectively Duty cycle variable of primary-side switching transistor Voltage difference variable The voltage difference variable is directly proportional to the voltage difference variable. This is the difference between the output voltage value on the secondary side and the capacitance voltage value on the bus capacitor.

[0162] Within a preset time period, the duty cycle of the primary-side switch is fixed, and a second data set is obtained during the linear increase of the input voltage value on the primary side. The second data set includes the instantaneous voltage difference and the instantaneous current value of the primary-side switch at each moment.

[0163] Expression based on the current variable of the primary-side switch A linear fit is performed on the second dataset to obtain a second straight line representing the instantaneous current value of the primary-side switch transistor with respect to the instantaneous voltage difference. The slope of this second straight line is then determined as the voltage coefficient. .

[0164] For example, the instantaneous voltage difference at each moment can be the product of each linearly increasing input voltage value and the turns ratio of the transformer, and the instantaneous current value of the primary-side switch at each moment can be the maximum peak current value of the primary-side switch corresponding to the instantaneous voltage difference at each moment.

[0165] For example, the expression for the current variable of the primary-side switch. For: the turns ratio of the transformer in the resonant circuit The bus capacitor charging current value at the first moment Duty cycle variable of primary-side switching transistor Duty cycle coefficient Voltage difference variable and voltage coefficient The product of the two. That is... .

[0166] From the formula It can be seen that, Under fixed conditions, and They are positively correlated.

[0167] Therefore, with the input voltage on the primary side of the resonant circuit fixed, the duty cycle of the primary-side switch varies. Current variation of the primary-side switching transistor They are positively correlated. Therefore, the expression based on the current variable of the primary-side switch is... By performing linear fitting on the first dataset, a first straight line is obtained, representing the instantaneous current value of the primary-side switch transistor with respect to the instantaneous duty cycle value. The slope of this first straight line is determined as the duty cycle coefficient, thus accurately obtaining the duty cycle coefficient. .

[0168] From the formula It can be seen that, Under fixed conditions, and They are positively correlated.

[0169] Therefore, with the duty cycle of the primary-side switch fixed, the voltage difference variable Current variation of the primary-side switching transistor They are positively correlated. Therefore, the expression based on the current variable of the primary-side switch is... By performing linear fitting on the second dataset, a second straight line is obtained, representing the instantaneous current value of the primary-side switch transistor with respect to the instantaneous voltage difference. The slope of this second straight line is then determined as the voltage coefficient, allowing for accurate determination of the voltage coefficient. .

[0170] Figure 6 A schematic diagram illustrating the relationship between time and duty cycle in various resonant circuit startup methods provided in some embodiments, such as... Figure 6 As shown, the segmented variable duty cycle resonant circuit startup method is the resonant circuit startup method in the embodiments of this application, while the linear variable duty cycle resonant circuit startup method and the exponential variable duty cycle resonant circuit startup method are comparative startup methods.

[0171] Figure 7This diagram illustrates the relationship between the startup time and the current value of the primary-side switch in a segmented variable duty cycle resonant circuit startup method provided in some embodiments. Figure 8 This diagram illustrates the relationship between the startup time and the current value of the primary-side switch in a linear variable duty cycle resonant circuit startup method provided in some embodiments. Figure 9 This diagram illustrates the relationship between the startup time and the current value of the primary-side switch in the startup method of the exponentially variable duty cycle resonant circuit provided in some embodiments.

[0172] exist Figures 7-9 In the diagram, the horizontal axis represents the start-up time t of the resonant circuit, in milliseconds, and the vertical axis represents the current i of the primary-side switching transistor, in amperes (A).

[0173] from Figures 7-9 It can be seen that the peak current of the primary-side switch is the smallest in the segmented variable duty cycle resonant circuit startup method.

[0174] Figure 10 The diagram illustrates the structure of a resonant converter provided in some embodiments. The resonant converter includes a controller and a resonant circuit connected to the controller; the controller is used to execute the method in any embodiment of this application.

[0175] Figure 11 Schematic diagrams of the energy storage system provided for some embodiments, such as Figure 11 As shown, the energy storage system includes a resonant converter. The resonant converter includes a controller and a resonant circuit connected to the controller; the controller is used to perform the method in any embodiment of this application.

[0176] The energy storage system also includes a battery and an inverter circuit. The battery is connected to the primary side of the resonant circuit, and the inverter circuit is connected to the secondary side of the resonant circuit.

[0177] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0178] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method of starting a resonant circuit, characterized by, The resonant circuit includes a primary side and a secondary side, and the method includes: The initial duty cycle of the primary-side switch is determined based on the rated current value of the primary-side switch. During the first soft start phase, the primary-side switching transistor is controlled to run continuously at the initial duty cycle until the capacitor voltage value of the secondary-side bus capacitor rises to the first preset voltage value. In the second soft-start phase, based on the bus capacitor charging current value at the first moment, the bus capacitor charging current value at the second moment, the first output voltage value on the secondary side at the second moment, and the first preset voltage value, a first slope value of the primary side duty cycle is determined; the primary side switch is controlled to operate linearly with the initial duty cycle as the starting point and with the first slope value until the capacitor voltage value rises to the second preset voltage value. In the third soft-start phase, based on the bus capacitor charging current value at the first moment, the bus capacitor charging current value at the third moment, the second output voltage value on the secondary side at the third moment, and the second preset voltage value, a second slope value of the primary side duty cycle is determined; the primary side switch is controlled to operate linearly with the primary side duty cycle at the end of the second soft-start phase as the starting point and with the second slope value, until the capacitor voltage value rises to the third preset voltage value; Wherein, the first time, the second time, and the third time are the start time of the first soft boot phase, the end time of the first soft boot phase, and the end time of the second soft boot phase, respectively.

2. The method of claim 1, wherein, The first preset voltage value is the product of a first preset multiple and the rated voltage value of the bus capacitor; the second preset voltage value is the product of a second preset multiple and the rated voltage value of the bus capacitor; and the third preset voltage value is the rated voltage value of the bus capacitor. Both the first preset multiple and the second preset multiple are positive numbers less than 1, and the first preset multiple is less than the second preset multiple.

3. The method of claim 1, wherein, Determining the initial duty cycle of the primary-side switch based on its rated current value includes: When the voltage of the bus capacitor is 0, the primary-side switching transistors are controlled to operate at each preset duty cycle, and the peak current of each primary-side switching transistor corresponding to each preset duty cycle is monitored. The duty cycle of the primary-side switch corresponding to the target time is determined as the initial duty cycle. The target time is the time when the peak current of the primary-side switch is the product of the rated current value of the primary-side switch and a third preset multiple. The third preset multiple is a positive number less than 1.

4. The method of claim 1, wherein, The determination of the first slope value of the primary side duty cycle based on the bus capacitor charging current value at a first moment, the bus capacitor charging current value at a second moment, the first output voltage value on the secondary side at the second moment, and the first preset voltage value includes: Based on the first output voltage value and the first preset voltage value, a first voltage difference is determined; The product of the voltage coefficient and the first voltage difference is determined as the first product value; The ratio of the bus capacitor charging current value at the second time point to the bus capacitor charging current value at the first time point is determined as the first ratio. The ratio of the first ratio to the first product value is determined as the second ratio. The ratio of the second ratio to the duty cycle coefficient is then compared with the turns ratio of the transformer in the resonant circuit to determine the third ratio. The first slope value is determined based on the difference between the third ratio and the initial duty cycle.

5. The method of claim 1, wherein, The determination of the second slope value of the primary side duty cycle based on the bus capacitor charging current value at the first time moment, the bus capacitor charging current value at the third time moment, the second output voltage value on the secondary side at the third time moment, and the second preset voltage value includes: The second voltage difference is determined based on the second output voltage value and the second preset voltage value; The product of the voltage coefficient and the second voltage difference is determined as the second product value; The ratio of the bus capacitor charging current value at the third time point to the bus capacitor charging current value at the first time point is determined as the fourth ratio. The ratio of the fourth ratio to the second product value is determined as the fifth ratio; The ratio of the fifth ratio to the duty cycle coefficient is then compared with the turns ratio of the transformer in the resonant circuit to determine the sixth ratio. The second slope value is determined based on the difference between the sixth ratio and the duty cycle of the primary-side switch at the third time.

6. The method according to claim 4 or 5, characterized in that, The method further includes: determining the duty cycle coefficient; the determination of the duty cycle coefficient includes: Determine the expression for the current variable of the primary-side switch; the current variable is proportional to the duty cycle variable, the duty cycle coefficient, and the voltage difference variable of the primary-side switch, respectively; the voltage difference variable is the difference between the output voltage value of the secondary side and the capacitance voltage value of the bus capacitor. Within a preset time period, the input voltage on the primary side of the resonant circuit is fixed, and a first data set is obtained during the linear increase of the duty cycle of the primary-side switch. The first data set includes the instantaneous duty cycle value and instantaneous current value of the primary-side switch at each moment. Based on the expression of the current variable of the primary-side switch, a straight line is fitted to the first data set to obtain a first straight line of the instantaneous current value of the primary-side switch with respect to the instantaneous duty cycle value, and the slope of the first straight line is determined as the duty cycle coefficient.

7. The method according to claim 4 or 5, characterized in that, The method further includes: determining the voltage coefficient; the determination of the voltage coefficient includes: Determine the expression for the current variable of the primary-side switch; the current variable is proportional to the voltage coefficient, the duty cycle variable of the primary-side switch, and the voltage difference variable, respectively, and the voltage difference variable is the difference between the output voltage value of the secondary side and the capacitance voltage value of the bus capacitor; Within a preset time period, the duty cycle of the primary-side switch is fixed, and a second data set is obtained during the linear increase of the input voltage value on the primary side. The second data set includes the instantaneous voltage difference at each moment and the instantaneous current value of the primary-side switch. Based on the expression for the current variable of the primary-side switch, a straight line is fitted to the second data set to obtain a second straight line with respect to the instantaneous current value of the primary-side switch and the instantaneous voltage difference. The slope of the second straight line is determined as the voltage coefficient.

8. The method of claim 7, wherein, The expression for the current variable of the primary-side switch is: the product of the turns ratio of the transformer in the resonant circuit, the bus capacitor charging current value at the first moment, the duty cycle variable of the primary-side switch, the duty cycle coefficient, the voltage difference variable, and the voltage coefficient.

9. A resonant converter characterized by, The resonant converter includes a controller and a resonant circuit connected to the controller; the controller is used to perform the method according to any one of claims 1-8.

10. An energy storage system characterized by, The energy storage system includes the resonant converter as described in claim 9.

Images