Control method of LLC resonant converter, power module and charging system

Abstract

The invention provides a control method of an LLC resonant converter, a power module and a charging system, and relates to the technical field of power electronics. The method comprises the following steps: acquiring a bus voltage and an output voltage of the LLC resonant converter; determining a first disturbance state parameter corresponding to the bus voltage, and determining a second disturbance state parameter corresponding to the output voltage; obtaining a resonance current of the LLC resonant converter, and obtaining a first frequency regulation quantity according to the resonance current and the first disturbance state parameter; obtaining an output current of the LLC resonant converter, and obtaining a second frequency regulation quantity according to the output current and the second disturbance state parameter; and determining a target switching frequency according to the first frequency regulating variable, the second frequency regulating variable and a basic switching frequency corresponding to the LLC resonant converter, and controlling the LLC resonant converter based on the target switching frequency, so that efficient and dynamic suppression of low-frequency disturbance is realized, and rapid, stable and adaptive suppression of low-frequency ripples under all working conditions is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power electronics, in particular to a control method of an LLC resonant converter, a power module and a charging system. BACKGROUND

[0002] The dual-port DC-DC converter is widely researched and deployed in energy storage systems, charging modules, on-board chargers (OBC), vehicle-to-grid (V2G) and other applications. The "dual-port" can be bidirectional or unidirectional. Regardless of working in unidirectional or bidirectional mode, the typical application scenario is that the voltages on both sides are controlled by other converters, that is, the DCDC works in constant current mode (unidirectional or bidirectional). If there is low-frequency fluctuation in the constant current mode, the stability of the current control will be disturbed, resulting in superimposed low-frequency ripple in the output current. This not only increases the effective value of the current, but also may trigger overcurrent protection in severe cases.

[0003] In related technologies, the disturbance problem of the dual-port is solved by real-time acquisition of the voltage signal of the output port, extraction of the alternating fluctuation component, and superposition of the alternating fluctuation component as a feedforward or feedback signal to the reference value of the voltage loop or current loop to generate a cancellation inhibition component.

[0004] However, in the case of insufficient bandwidth of the current loop itself, the inhibition effect of superposition is relatively limited, and a phase difference is generated, which is not conducive to the suppression of fluctuation. SUMMARY

[0005] The present application aims to solve the technical problems in the prior art by providing a control method of an LLC resonant converter, a power module and a charging system.

[0006] To achieve the above-mentioned purpose, the technical solutions adopted by the embodiments of the present application are as follows: In a first aspect, the embodiments of the present application provide a control method of an LLC resonant converter, which comprises: obtaining a bus voltage of a DC bus port in the LLC resonant converter and an output voltage of an output port in the LLC resonant converter; determining a first disturbance state parameter corresponding to the bus voltage and a second disturbance state parameter corresponding to the output voltage; obtaining a resonant current of the LLC resonant converter, and obtaining a first frequency adjustment amount according to the resonant current and the first disturbance state parameter; obtaining an output current of the LLC resonant converter, and obtaining a second frequency adjustment amount according to the output current and the second disturbance state parameter; According to the first frequency adjustment amount, the second frequency adjustment amount, and a basic switching frequency corresponding to the LLC resonant converter, a target switching frequency is determined, and the LLC resonant converter is controlled based on the target switching frequency.

[0007] Optionally, the determining the first disturbance state parameter corresponding to the bus voltage comprises: The bus voltage is input to an SOGI phase-locked loop module, and the SOGI phase-locked loop module detects an alternating current component of the bus voltage to obtain a first voltage fundamental component and a second voltage fundamental component contained in the bus voltage, the first voltage fundamental component and the second voltage fundamental component being orthogonal components of each other. According to the first voltage fundamental component and the bus voltage, a direct current voltage component contained in the bus voltage is obtained. According to the first voltage fundamental component, the second voltage fundamental component, and the direct current voltage component, the first disturbance state parameter is obtained.

[0008] Optionally, the obtaining the first disturbance state parameter according to the first voltage fundamental component, the second voltage fundamental component, and the direct current voltage component comprises: The negated result of the direct current voltage component is superimposed on the second voltage fundamental component to obtain a filtered voltage fundamental component. The first voltage fundamental component and the filtered alternating current voltage component are subjected to matrix transformation to obtain a d-axis alternating current voltage component corresponding to the bus voltage. The d-axis alternating current voltage component is sequentially input to a low-pass filter and a PI controller to obtain the first disturbance state parameter.

[0009] Optionally, the first disturbance state parameter comprises a phase and an angular frequency. The obtaining the first frequency adjustment amount according to the resonant current and the first disturbance state parameter comprises: The resonant current is subjected to low-pass filtering processing to obtain a low-frequency current component contained in the resonant current. The low-frequency current component and the angular frequency are input to an SOGI phase-locked loop module to obtain a first alternating current component and a second alternating current component contained in the resonant current. According to the phase, the first alternating current component, and the second alternating current component, a first adjustment coefficient is obtained. According to the first adjustment coefficient and a pre-determined feedforward amount, the first frequency adjustment amount is obtained.

[0010] Optionally, the obtaining the first adjustment coefficient according to the phase, the first alternating current component and the second alternating current component comprises: performing matrix transformation according to the phase, the first alternating current component and the second alternating current component to obtain a q-axis alternating current component and a d-axis alternating current component; calculating an alternating current effective value according to the q-axis alternating current component and the d-axis alternating current component; inputting the alternating current effective value into a proportional-integral controller and a limiting module in sequence to obtain the first adjustment coefficient.

[0011] Optionally, the feedforward quantity comprises a bus voltage feedforward quantity and an output voltage feedforward quantity. the obtaining the first frequency adjustment quantity according to the first adjustment coefficient and a predetermined feedforward quantity comprises: taking a sum result of the bus voltage feedforward quantity and the output voltage feedforward quantity as the feedforward quantity; determining a first product result of the first adjustment coefficient and the feedforward quantity, and taking the first product result as the first frequency adjustment quantity.

[0012] Optionally, the determining process of the bus voltage feedforward quantity and the output voltage feedforward quantity comprises: obtaining a first gain corresponding to a bus voltage and a second gain corresponding to an output voltage; taking a product result of a first voltage fundamental component contained in the bus voltage and the first gain as the bus voltage feedforward quantity, and taking a product result of a first voltage fundamental component contained in the output voltage and the second gain as the output voltage feedforward quantity.

[0013] Optionally, the determining a target switching frequency according to the first frequency adjustment quantity, the second frequency adjustment quantity and a basic switching frequency corresponding to the LLC resonant converter comprises: superimposing the first frequency adjustment quantity and the second frequency adjustment quantity on the basic switching frequency to obtain a target switching frequency.

[0014] Optionally, the superimposing the first frequency adjustment quantity and the second frequency adjustment quantity on the basic switching frequency to obtain a target switching frequency comprises: determining a first frequency corresponding to a low-frequency alternating voltage component contained in the bus voltage, and determining a second frequency corresponding to a low-frequency alternating voltage component contained in the output voltage; determining whether the first frequency and the second frequency are the same; If yes, the first frequency adjustment amount is superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency. If no, both the first frequency adjustment amount and the second frequency adjustment amount are superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency.

[0015] In a second aspect, the embodiments of the present application further provide a power module, comprising: an LLC resonant converter and a controller, wherein the LLC resonant converter at least comprises: a primary side switching network; The input end of the controller is connected with the DC bus port and the output port of the LLC resonant converter respectively, and the output end of the controller is connected with the control end of the power switch tube in the primary side switching network. The controller is used for executing the control method of the LLC resonant converter provided in any one of the second aspect.

[0016] In a third aspect, the embodiments of the present application provide a charging system, comprising at least one power module provided in the second aspect, a controller, a power distribution device and at least one charging interface. The power distribution device is connected with the controller, each power module and each charging interface respectively. The power module is used for converting AC power of a power grid into DC power and providing the DC power to the charging interface. The controller is further used for acquiring the required power of each charging interface, and generating a scheduling instruction according to the connection relationship of the controllable switches in the power distribution device and the required power. The power distribution device is used for controlling the opening or closing of the controllable switches according to the scheduling instruction, so as to distribute the output power of each power module to each charging interface.

[0017] The present application has the following beneficial effects: The application provides a control method of an LLC resonant converter, a power module and a charging system. In the operation process of the LLC resonant converter, the bus voltage and the output voltage of a double port in the LLC resonant converter are acquired, and a first disturbance state parameter corresponding to the bus voltage and a second disturbance state parameter corresponding to the output voltage are extracted, that is, low-frequency disturbance information existing in the double port voltage is detected. Then, a first frequency adjustment amount is obtained based on the monitored resonant current and the first disturbance state parameter, and a second frequency adjustment amount is obtained based on the output current and the second disturbance state parameter, that is, an adjustment amount to be suppressed is obtained, and the frequency adjustment amount is superimposed on the basic switching frequency to obtain a dynamically adjusted target switching frequency, so that the LLC resonant converter is controlled based on the target switching frequency, that is, the power switch tube in the LLC resonant converter is driven to work at a new frequency. The problem that the resonant current and the output current of the LLC resonant converter are disturbed by low-frequency voltage ripples existing at the input and / or output side is solved, efficient and dynamic suppression of low-frequency disturbance is realized, and rapid, stable and self-adaptive suppression of low-frequency ripples under all working conditions is realized.

[0018] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0020] Figure 1 A schematic diagram of a front and rear cascaded topology structure of an LLC resonant converter provided by the prior art is shown in the figure. Figure 2 A schematic diagram of a specific topology structure of an LLC resonant converter provided by the prior art is shown in the figure. Figure 3 A schematic diagram of a power module provided by the application is shown in the figure. Figure 4 A flowchart of a control method of an LLC resonant converter provided by the application is shown in the figure. Figure 5 A flowchart of another control method of an LLC resonant converter provided by the application is shown in the figure. Figure 6 A flowchart of still another control method of an LLC resonant converter provided by the application is shown in the figure. Figure 7A bus voltage phase-locked detection and control loop schematic diagram provided for the present application; Figure 8 A flowchart schematic diagram of another control method of an LLC resonant converter provided for the present application; Figure 9 A flowchart schematic diagram of another control method of an LLC resonant converter provided for the present application; Figure 10 A schematic diagram of another SOGI control and feedforward control strategy based on resonant current detection provided for the present application; Figure 11 A flowchart schematic diagram of another control method of an LLC resonant converter provided for the present application; Figure 12 A flowchart schematic diagram of another control method of an LLC resonant converter provided for the present application; Figure 13 A flowchart schematic diagram of another control method of an LLC resonant converter provided for the present application; Figure 14 A schematic diagram of another SOGI control and feedforward control strategy based on resonant current detection provided for the present application; Figure 15 A structural schematic diagram of a charging system provided for the present application.

[0021] Icon: 100-power module; 1-controller; 200-charging system; 2-power distribution device; 3-charging interface. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts, fall within the scope of protection of the present application.

[0024] It should be noted that similar reference numerals and letters refer to similar items throughout the accompanying drawings, and once an item is defined in one drawing, that item does not need to be further defined and explained in subsequent drawings. Also, in the description of the present application, the terms "first", "second", and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily indicate or imply a relative importance.

[0025] It should be noted that, in this document, the terms "first", "second", and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily indicate or imply a relative importance.

[0026] In the description of the present application, it should be noted that the terms "upper", "lower", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the application is used, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0027] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "provided" and "connected" should be understood broadly, for example, can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be internal communication 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.

[0028] First, the professional terms involved in the present application are explained.

[0029] 1. LLC resonant converter is a high-efficiency DC / DC conversion topology widely used in high-power power electronic systems, and is widely used in new energy, electric vehicle chargers, communication power supplies, server power supplies and other fields due to its high efficiency, high power density and soft switching characteristics. For example, refer to Figures 1-2As shown, the LLC resonant converter topology includes an LLC primary network, a high-frequency transformer, and an LLC secondary network, which are cascaded as follows: The bus voltage Vdc of the front port: can be powered by an AC / DC converter (such as a three-phase rectifier PCS) or a DC power supply. When there is an unbalanced or nonlinear load from the power grid, a low-frequency AC ripple such as 100Hz is often superimposed on the bus voltage Vdc.

[0030] The output voltage Vo of the rear port: connected to a battery, an aging device, or other bidirectional PCS system, and may also introduce low-frequency voltage fluctuations due to the PCS.

[0031] Among them, the LLC primary network is composed of multiple power switches (such as a full-bridge LLC composed of 4 power switches, a half-bridge LLC composed of 2 power switches, a three-phase half-bridge LLC composed of 6 power switches, etc.), and the output current Io of the LLC resonant converter is controlled by adjusting the switching frequency of each power switch.

[0032] 2. The disturbance of the double port is that the bus voltage Vdc of the DC bus port and the output voltage Vo of the output port of the LLC resonant converter may have low-frequency AC ripples (for example, 100Hz, caused by unbalanced three-phase power grid or rectifier PCS), and these low-frequency AC ripples will be transmitted to the resonant current Ir and the output current Io through the LLC resonant converter, causing current fluctuations, affecting efficiency, temperature rise, EMI, and protection reliability.

[0033] Therefore, it is necessary to suppress the existing double-port disturbance, so that the LLC resonant converter has the advantages of fast response, good stability, and strong adaptability, and is particularly suitable for new energy storage PCS, electric vehicle chargers, and other application scenarios with significant low-frequency ripples.

[0034] Secondly, the background technology involved in the present application is introduced.

[0035] For one-way or bidirectional charging modules, the mainstream topology of DC / DC is LLC converter, LLC converter is a resonant converter, and the resonant network impedance is usually low, which is easily affected and disturbed by input and output voltage ripples, and has a great impact on resonant current or output current.

[0036] Generally, the front stage is an AC / DC non-isolation converter, which is used in cascade with the rear stage LLC, and is generally integrated in a shell for unified control or independent control, or can be split into two independent converters for cascade use, for example, PCS+DC / DC two-stage independent configuration. Regardless of integration or independence, if three-phase imbalance and other factors cause low-frequency ripple at the output of the PCS, generally 100Hz, the LLC resonant current and the output current are disturbed at low frequency, affecting the current protection, heat, and output indicators. For the same reason, if the output side is connected to a stable battery load, there is generally no output disturbance, and if the load is connected to a PCS bidirectional converter, there is also a disturbance of the output voltage, causing a disturbance of the resonant current and the output current.

[0037] In the related art, for the disturbance problem of the double-port, the voltage signal of the output port is collected in real time, and the alternating fluctuation component is extracted, and the alternating fluctuation component is used as a feedforward or feedback signal, which is superimposed on the reference value of the voltage loop or the current loop to generate a suppression component for cancellation.

[0038] However, the closed-loop bandwidth of the current loop is generally low (limited by factors such as sampling delay, compensation network, switching frequency, etc.), and when the superimposed "suppression component" is quickly responded by the current loop, due to its slow response speed (long rise time, low cutoff frequency), it cannot track the high-frequency or rapidly changing disturbance signal in time.

[0039] Therefore, the application provides a control method of an LLC resonant converter. In the operation process of the LLC resonant converter, the bus voltage of the DC bus port and the output voltage of the output port in the LLC resonant converter are collected, and a first disturbance state parameter corresponding to the bus voltage is extracted, and a second disturbance state parameter corresponding to the output voltage is extracted, that is, the low-frequency disturbance information existing in the double-port voltage is detected; then, a first frequency adjustment amount is obtained based on the resonant current and the first disturbance state parameter, and a second frequency adjustment amount is obtained based on the output current and the second disturbance state parameter, that is, a feedforward amount to be suppressed is obtained, and the frequency adjustment amount is superimposed on the basic switching frequency to obtain a dynamically adjusted target switching frequency, so that the LLC resonant converter is controlled based on the target switching frequency, that is, the power switch in the LLC resonant converter is driven to work at a new frequency, dynamic disturbance suppression is realized, and rapid, stable, and adaptive suppression of low-frequency ripple under all working conditions is realized.

[0040] The control method of the LLC resonant converter provided by the embodiments of the application will be explained in detail below with reference to the accompanying drawings.

[0041] Figure 3 The structural schematic diagram of the power module provided by the application is as follows, Figure 3As shown, the power module 100 comprises an LLC resonant converter and a controller 1. Exemplarily, the controller 1 can be a digital processing chip with data processing function, such as a DSP chip.

[0042] The controller 1 is configured to execute the control method of the LLC resonant converter provided in the embodiments below, so as to suppress the double-port disturbance existing in the LLC resonant converter, and better suppress the low-frequency disturbance of the double-port and adapt to more working conditions.

[0043] Figure 4 As shown, the flowchart of the control method of the LLC resonant converter provided in the embodiments of the present application is shown in FIG. 1. Figure 4 As shown, the method comprises: S101, obtaining a bus voltage of a DC bus port in the LLC resonant converter and an output voltage of an output port in the LLC resonant converter.

[0044] The bus voltage Vdc and the output voltage Vo can both have low-frequency AC ripple. The bus voltage Vdc can come from a grid-connected converter, and is affected by the three-phase imbalance of the power grid, and superimposes a 100Hz ripple; if the output port is connected with a dynamic load (such as a battery aging device), the output voltage Vo can also have low-frequency disturbance (for example, 100Hz).

[0045] In an implementable manner, the bus voltage Vdc and the output voltage Vo in the LLC resonant converter can be obtained in real time or periodically, so as to extract the disturbance component.

[0046] S102, determining a first disturbance state parameter corresponding to the bus voltage, and determining a second disturbance state parameter corresponding to the output voltage.

[0047] Exemplarily, the disturbance state parameter can comprise a phase θ, a frequency f or an amplitude A.

[0048] The first disturbance state parameter is used to represent the disturbance characteristics in the bus voltage Vdc; similarly, the second disturbance state parameter is used to represent the disturbance characteristics in the output voltage Vo.

[0049] In an implementable manner, the bus voltage Vdc can be signal-decomposed by a second-order generalized integrator and a phase-locked loop, so as to obtain the low-frequency AC component contained in the bus voltage Vdc, and obtain the phase, frequency and amplitude of the low-frequency AC component, and take the phase, frequency and amplitude of the low-frequency AC component as the first disturbance state parameter.

[0050] Similarly, the second disturbance state parameter corresponding to the output voltage Vo can also be obtained by using the same manner as above.

[0051] S103, obtain the resonant current of the LLC resonant converter, and obtain a first frequency adjustment amount according to the resonant current and a first disturbance state parameter.

[0052] S104, obtain the output current of the LLC resonant converter, and obtain a second frequency adjustment amount according to the output current and a second disturbance state parameter.

[0053] Optionally, when the relevant AC component and frequency phase information are obtained by phase locking the bus voltage Vdc and the output voltage Vo, the feedforward amount can be superimposed on the voltage loop or current loop output for feedforward suppression, which is usually f (switching frequency), or 1 / f.

[0054] In the embodiment, in order to further adjust to make the resonant current or the output current be completely suppressed, the detection and control of the resonant current Ir and / or the output current Io are added. Specifically, the resonant current Ir can reflect the low-frequency disturbance of the bus port, and therefore, the first frequency adjustment amount can be obtained based on the resonant current Ir and the first disturbance state parameter; similarly, the second frequency adjustment amount can also be obtained based on the output current Io and the second disturbance state parameter, and the first frequency adjustment amount and the second frequency adjustment amount can be used as the disturbance compensation amount to be compensated.

[0055] S105, determine a target switching frequency according to the first frequency adjustment amount, the second frequency adjustment amount, and a basic switching frequency corresponding to the LLC resonant converter, and control the LLC resonant converter based on the target switching frequency.

[0056] In an implementable manner, the first frequency adjustment amount and the second frequency adjustment amount can be superimposed on the basic switching frequency corresponding to the LLC resonant converter to obtain a new target switching frequency f, so as to adjust the switching frequency of the power switch tube in the LLC resonant converter through the target switching frequency f, to dynamically suppress the low-frequency disturbance of the double-port, and to realize fast, stable, and self-adaptive suppression of the low-frequency ripple in all working conditions.

[0057] In summary, the embodiment of the present application provides a control method of an LLC resonant converter. In the operation process of the LLC resonant converter, the bus voltage and the output voltage of the double port in the LLC resonant converter are obtained, and the first disturbance state parameter corresponding to the bus voltage and the second disturbance state parameter corresponding to the output voltage are extracted, that is, the low-frequency disturbance information existing in the double port voltage is detected; then, the first frequency adjustment amount is obtained based on the monitored resonant current and the first disturbance state parameter, and the second frequency adjustment amount is obtained based on the output current and the second disturbance state parameter, that is, the adjustment amount to be suppressed is obtained, and the frequency adjustment amount is superimposed on the basic switching frequency to obtain the dynamically adjusted target switching frequency, so that the LLC resonant converter is controlled based on the target switching frequency, that is, the power switch tube in the LLC resonant converter is driven to work at a new frequency, thereby solving the problem that the resonant current and the output current of the LLC resonant converter are disturbed at low frequency when low-frequency voltage ripples exist at the input and / or output side, and realizing efficient and dynamic suppression of low-frequency disturbance and rapid, stable and self-adaptive suppression of low-frequency ripples in all working conditions.

[0058] Optionally, referring to Figure 5 As shown in the above step S102, the first disturbance state parameter corresponding to the bus voltage is determined, including: S201, input the bus voltage to the SOGI phase-locked loop module, and detect the alternating current component of the bus voltage by the SOGI phase-locked loop module to obtain the first voltage fundamental component and the second voltage fundamental component contained in the line voltage.

[0059] Wherein, wherein, the first voltage fundamental component Vdc_ac and the second voltage fundamental component Vdc_β are orthogonal components, that is, the phase of the first voltage fundamental component Vdc_ac and the second voltage fundamental component Vdc_β is 90°.

[0060] It should be noted that the bus voltage Vdc is not a pure direct current, but contains a direct current component and an alternating current component, therefore, the alternating current disturbance component (such as 100Hz ripple) and its phase information need to be accurately extracted from the mixed signal of the bus voltage Vdc for subsequent feedforward suppression.

[0061] Optionally, in the embodiment, considering that the SOGI phase-locked loop module can accurately obtain the fundamental component corresponding to the grid voltage of each phase by extracting the fundamental component of the grid voltage, it is proposed that the bus voltage Vdc can be input to the SOGI phase-locked loop module, and the SOGI phase-locked loop module can detect the alternating current component of the bus voltage Vdc to obtain the first voltage fundamental component Vdc_ac and the second voltage fundamental component Vdc_β contained in the bus voltage Vdc.

[0062] S202, obtaining a direct current voltage component contained in the bus voltage according to the first voltage fundamental component and the bus voltage.

[0063] In an implementable manner, a first voltage difference value between the bus voltage Vdc and the first voltage fundamental component Vdc_ac is calculated, and the first voltage difference value is input to a low-pass filter. The first voltage difference value is low-pass filtered by the low-pass filter to obtain the direct current voltage component Vdc_dc contained in the bus voltage Vdc, so as to realize separation of the direct current voltage component of the bus voltage Vdc.

[0064] S203, obtaining a first disturbance state parameter according to the first voltage fundamental component, the second voltage fundamental component and the direct current voltage component.

[0065] In an implementable manner, the first voltage fundamental component, the second voltage fundamental component and the direct current voltage component can be further signal-decomposed to calculate the phase, the frequency or the amplitude of the low-frequency alternating current disturbance signal contained in the bus voltage Vdc as the first disturbance state parameter.

[0066] Optionally, referring to FIG. 3, the step S203 comprises: Figure 6 S301, superimposing the negated result of the direct current voltage component and the second voltage fundamental component to obtain a filtered alternating current voltage component.

[0067] S302, performing matrix transformation on the first voltage fundamental component and the filtered alternating current voltage component to obtain a d-axis alternating current voltage component corresponding to the bus voltage.

[0068] S303, sequentially inputting the d-axis alternating current voltage component to a low-pass filter and a PI controller to obtain the first disturbance state parameter.

[0069] In an implementable manner, as shown in FIG. 3, the step S203 comprises: Figure 7 ​As shown, the 0-degree in-phase component of the SOGI phase-locked loop module is essentially a band-pass filter, which can effectively suppress DC and high-frequency noise, and the output first voltage fundamental component Vdc_ac is a pure low-frequency fundamental component, without additional processing. The 90-degree quadrature component of the SOGI phase-locked loop module does not have DC suppression capability, that is, the output second voltage fundamental component Vdc_β retains the DC component in the bus voltage Vdc. Therefore, in order to obtain a pure quadrature signal, the DC component in the second voltage fundamental component Vdc_β must be offset to achieve accurate DC compensation. Therefore, in this embodiment, the DC voltage component Vdc_dc can be processed based on a preset coefficient k, and the DC filtered second voltage fundamental component Vβ can be obtained by performing DC filtering on the second voltage fundamental component Vdc_β based on the processed DC voltage component k x Vdc_dc. Then, the first voltage fundamental component Vdc_ac and the filtered voltage fundamental component Vβ are input into the matrix converter to perform dq matrix conversion, to obtain the d-axis alternating current voltage component Vd and the q-axis alternating current voltage component Vq corresponding to the bus voltage Vdc.

[0070] The d-axis alternating current voltage component Vd can also be referred to as a reactive voltage component, and the q-axis alternating current voltage component Vq can also be referred to as an active voltage component, which refers to the portion of the bus voltage that does work.

[0071] With reference to Figure 7 As shown, the d-axis alternating current voltage component Vd is sequentially input into the low-pass filter LPF and the PI controller, the d-axis alternating current voltage component Vd is filtered and processed by the low-pass filter LPF to obtain a filtered reactive voltage component, and the filtered reactive voltage component is input into the PI controller to obtain an angular frequency adjustment amount. Finally, the angular frequency adjustment amount is superimposed on the preset angular frequency ω0 to obtain the angular frequency ω corresponding to the d-axis alternating current voltage component Vd, and the angular frequency ω is integrated to obtain the phase θ corresponding to the d-axis alternating current voltage component Vd. Thus, the first disturbance state parameter contained in the bus voltage Vdc is obtained.

[0072] Similarly, the second disturbance state parameter corresponding to the output voltage Vo can also be extracted by using the above processing process, which will not be described in detail here.

[0073] Optionally, the first disturbance state parameter includes a phase and an angular frequency. With reference to Figure 8 As shown, the first frequency adjustment amount obtained in the step S103 according to the resonant current and the first disturbance state parameter includes: S401, low-pass filtering the resonant current to obtain a low-frequency current component contained in the resonant current.

[0074] Optionally, to further adjust so that the resonant current is completely suppressed, the "resonant current detection and control" is added. First, the resonant current Ir can reflect the low-frequency disturbance of the two-port, and is basically the "voltage difference" equivalent on the resonant network to adjust. Therefore, the resonant current Ir is detected to obtain the basic current, and the component of the basic current is the low-frequency component and the switching frequency.

[0075] In an implementable manner, the resonant current Ir is input to a low-pass filter, and the switching frequency up to about 100 kHz is filtered out by the "low-pass filter". The low-frequency current component Ir1 contained in the resonant current Ir can be obtained by effective filtering through a second-order low-pass filter and the like.

[0076] S402, input the low-frequency current component and the angular frequency to the SOGI phase-locked loop module to obtain the first alternating current component and the second alternating current component contained in the resonant current.

[0077] In an implementable manner, the low-frequency current component Ir and the angular frequency ω are simultaneously input to the SOGI phase-locked loop module, and the fundamental wave extraction of the low-frequency current component Ir and the angular frequency ω is performed by the SOGI phase-locked loop module to obtain the first alternating current component and the second alternating current component contained in the resonant current Ir, wherein the first alternating current component and the second alternating current component are mutually orthogonal signals.

[0078] S403, obtaining a first adjustment coefficient according to the phase, the first alternating current component and the second alternating current component.

[0079] The first adjustment coefficient is used to compensate for steady-state error or accelerate dynamic response and improve multi-working-condition adaptability.

[0080] In the embodiment, the first adjustment coefficient is calculated based on the phase, the first alternating current component and the second alternating current component, that is, the first adjustment coefficient not only depends on the current component but also introduces phase information to form a more accurate dynamic response mechanism.

[0081] S404, obtaining a first frequency adjustment amount according to the first adjustment coefficient and a predetermined feedforward amount.

[0082] The feedforward amount includes: an output voltage feedforward amount, a bus voltage feedforward amount.

[0083] In an implementable manner, the first frequency adjustment amount can be obtained based on the first adjustment coefficient and the predetermined feedforward amount, that is, the first frequency adjustment amount not only contains the feedback adjustment coefficient but also introduces the feedforward amount to improve the system response speed and the anti-disturbance ability.

[0084] Optionally, referring to Figure 9 the above step S403 includes: S501. Perform matrix transformation based on the phase, the first AC current component, and the second AC current component to obtain the q-axis AC current component and the d-axis AC current component.

[0085] S502. The effective value of the AC current is calculated based on the q-axis AC current component and the d-axis AC current component.

[0086] S503. The effective value of the AC current is sequentially input to the proportional-integral controller and the limiting module to obtain the first adjustment coefficient.

[0087] In one feasible approach, refer to Figure 10 As shown, the phase θ, the first AC current component, and the second AC current component are input to the matrix transformer Cdq. The matrix transformer Cdq, in conjunction with the phase θ, performs a matrix transformation on the first and second AC current components to obtain the q-axis AC current component Irq and the d-axis AC current component Ird. These two components are then input to an amplifier to calculate the effective value of the AC current. ,Right now ; and the effective value of alternating current The inputs are sequentially fed to the proportional-integral controller and the limiting module to obtain the first adjustment coefficient, wherein the limiting module adjusts the first adjustment coefficient, and the first adjustment coefficient ∈ (0, A), A>1.

[0088] Similarly, the second adjustment coefficient can be calculated using the above processing method, which will not be elaborated further here.

[0089] Optionally, the feedforward includes: bus voltage feedforward and output voltage feedforward; refer to Figure 11 As shown, step S404 above includes: S601. The sum of the bus voltage feedforward and the output voltage feedforward is taken as the feedforward quantity.

[0090] S602. Determine the first product of the first adjustment coefficient and the feedforward quantity, and use the first product as the first frequency adjustment quantity.

[0091] Among them, the bus voltage feedforward is used to reflect the energy status of the DC side. If the bus voltage fluctuates greatly, it indicates that the input power is unstable (such as the change of photovoltaic power generation with the amount of sunlight), and the frequency needs to be adjusted in advance to maintain balance.

[0092] Output voltage feedforward is used to reflect AC side operating conditions. For example, the output voltage is prone to distortion under weak power grid conditions. Feedforward can improve the immunity to disturbances.

[0093] Optionally, the bus voltage feedforward quantity and the output voltage feedforward quantity are superimposed together to form a comprehensive feedforward control signal, which has faster dynamic response speed and stronger robustness compared with single feedforward mode, realizes AC-DC collaborative perception, and enhances the adaptability of the system to multiple disturbances.

[0094] It should be noted that the bus voltage feedforward quantity is not the bus voltage value directly collected, but a compensation item after processing, which can be normalization, proportional scaling, error extraction, etc. For example, the bus voltage feedforward quantity is a compensation signal generated based on the difference between the bus voltage and a reference value.

[0095] In an implementable manner, the sum of the bus voltage feedforward quantity and the output voltage feedforward quantity is calculated, and the sum is taken as the total feedforward quantity, i.e., the bus voltage state and the output voltage state are jointly constructed into a unified feedforward quantity. Then, the product of the first adjustment coefficient, the feedforward quantity and the preset base frequency fr is calculated, and the calculated product is taken as the first frequency adjustment quantity, so as to realize adaptive adjustment of the feedforward gain.

[0096] Optionally, the bus voltage feedforward quantity and the output voltage feedforward quantity are superimposed together to form a comprehensive feedforward control signal, which has faster dynamic response speed and stronger robustness compared with single feedforward mode, realizes AC-DC collaborative perception, and enhances the adaptability of the system to multiple disturbances. Figure 12 As shown in the figure, the determination process of the bus voltage feedforward quantity and the output voltage feedforward quantity includes: S701, a first gain corresponding to the bus voltage and a second gain corresponding to the output voltage are acquired.

[0097] S702, the product of the first voltage fundamental component contained in the bus voltage and the first gain is taken as the bus voltage feedforward quantity, and the product of the first voltage fundamental component contained in the output voltage and the second gain is taken as the output voltage feedforward quantity.

[0098] In an implementable manner, the DC gain of the LLC resonant converter can be represented as: wherein, is the turns ratio of the transformer. When only the bus voltage Vdc contains a low-frequency component, if the gain is offset, it can be represented as: (Vdc+Vdc_ac)(M+m)=Vo+0; ignoring the high-frequency component, M*Vdc_ac+m* Vdc=0, then m=-M*Vdc_ac / Vdc=M1*Vdc_ac, the first gain M1 corresponding to the bus voltage can be calculated as -(nVo) / Vdc / Vdc.

[0099] If only the low-frequency component is contained in the output voltage Vo, and the gain is offset, it can be expressed as: Vdc(M+m)=Vo+Vo_ac; ignoring the high-frequency component, Vdc*m=Vo_ac, then m=Vo_ac / Vdc=M2*Vo_ac, the second gain M2 corresponding to the output voltage can be calculated as 1 / Vdc. Therefore, in this embodiment, the "independent gain allocation according to signal source" is proposed to realize fine control.

[0100] With reference to Figure 10 The product of the first voltage fundamental component Vdc_ac contained in the bus voltage and the first gain M1 is taken as the bus voltage feedforward, and the product of the first voltage fundamental component Vo_ac contained in the output voltage and the second gain M2 is taken as the output voltage feedforward.

[0101] Optionally, the step S105 comprises: The first frequency adjustment and the second frequency adjustment are superimposed on the basic switching frequency to obtain the target switching frequency.

[0102] With reference to Figure 10 The basic switching frequency f0 is output by the voltage loop or the current loop.

[0103] In an implementable manner, to further adjust so that the resonant current or the output current is completely suppressed, the embodiment proposes that the first frequency adjustment and the second frequency adjustment can be superimposed on the basic switching frequency to obtain the target switching frequency, so that the low-frequency disturbance of the double-port is better suppressed, and more working conditions are adapted.

[0104] Optionally, with reference to Figure 13 The step of superimposing the first frequency adjustment and the second frequency adjustment on the basic switching frequency to obtain the target switching frequency comprises: S801, determining a first frequency corresponding to a low-frequency alternating voltage component contained in a bus voltage, and determining a second frequency corresponding to a low-frequency alternating voltage component contained in an output voltage.

[0105] S802, determining whether the first frequency is the same as the second frequency.

[0106] S803, if yes, superimposing the first frequency adjustment on the basic switching frequency output by the current loop to obtain the target switching frequency.

[0107] It should be noted that it is necessary to first determine the first frequency corresponding to the low-frequency alternating voltage component contained in the bus voltage, and determine whether the second frequency corresponding to the low-frequency alternating voltage component contained in the output voltage is the same, if the same frequency low-frequency fluctuation component is detected in both ports, it indicates that the two ports are caused by the same disturbance source (such as synchronization with the power grid) Common mode disturbance; if low-frequency fluctuation components of different frequencies are detected in two ports, they cannot be directly superimposed and need to be processed separately.

[0108] In an implementable manner, as shown in FIG. 6, if the same frequency low-frequency fluctuation component is detected in two ports, the first frequency adjustment amount f1_ac is superimposed on the basic switching frequency f0 output by the current loop to obtain the target switching frequency f. Figure 10

[0109] Optionally, as shown in FIG. 7, the LLC topology gain frequency curve is in the form of a parabola, when the target switching frequency is equal to the basic frequency, that is, f=fr, the gain is approximately 1, and the gain decreases when it is greater than fr, and sharply increases when it is less than fr. Figure 10

[0110] S804, if not, the first frequency adjustment amount and the second frequency adjustment amount are superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency.

[0111] In another implementable manner, as shown in FIG. 8, if low-frequency fluctuation components of different frequencies are detected in two ports, the first frequency adjustment amount f1_ac and the second frequency adjustment amount f2_ac are superimposed on the basic switching frequency f0 output by the current loop to obtain the target switching frequency f. Figure 14 ω1 in the formula is the angular frequency corresponding to the d-axis alternating voltage component Vd contained in the bus voltage, and the phase θ1 is obtained by integrating the angular frequency ω1; and ω2 is the angular frequency corresponding to the d-axis alternating voltage component Vo contained in the output voltage, and the phase θ2 is obtained by integrating the angular frequency ω2.

[0112] Figure 14 Therefore, in the present application, whether the bus voltage disturbance on the input side or the output voltage disturbance on the output side can be detected in time and preliminarily suppressed through the loop; and by detecting the low-frequency component in the resonant current, accurate compensation is realized, and the suppression effect is fully exerted.

[0113] Optionally, the present application can detect low-frequency disturbance components of a single frequency, if there is a composite disturbance with multiple frequency components superimposed, multiple groups of independent phase-locked loops for different frequencies can be set to track the amplitude and phase of each frequency component, thereby realizing multi-band collaborative suppression and improving the anti-disturbance ability and output power quality of the system.

[0114] Optionally, the present application can detect low-frequency disturbance components of a single frequency, if there is a composite disturbance with multiple frequency components superimposed, multiple groups of independent phase-locked loops for different frequencies can be set to track the amplitude and phase of each frequency component, thereby realizing multi-band collaborative suppression and improving the anti-disturbance ability and output power quality of the system. ​​​

[0115] Optionally, referring to Figure 15 As shown in the figure, the charging system provided by the embodiment of the present application includes at least one power module 100, a controller 1, a power distribution device 2 and at least one charging interface 3 provided by the above embodiment; The power distribution device 2 is connected with the controller 1, each power module 100 and each charging interface 3 respectively; The power module 100 is configured to convert alternating current of a power grid into direct current and provide the direct current to the charging interface 3; The controller 1 is further configured to acquire demand power of each charging interface 3, and generate a scheduling instruction according to a connection relationship of controllable switches in the power distribution device 2 and the demand power; The power distribution device 2 is configured to control the controllable switches to be opened or closed according to the scheduling instruction, so as to distribute output power of each power module to each charging interface 3.

[0116] In an optional embodiment, the charging system provided by the embodiment of the present application is a one-piece direct-current charging pile, and the charging interface 3 is configured to connect a charging gun, and the charging gun is hung on a host of the charging system through a gun seat on a main body of the charging system.

[0117] In an optional embodiment, the charging system provided by the embodiment of the present application is a split-type direct-current charging pile, and the charging system further includes a plurality of charging terminals, the charging interface 3 is configured to connect the charging terminals, and the charging terminals are arranged separately from the main body of the charging system, and the charging terminals are configured with a single charging gun or a double charging gun, and are configured to output power to an electric vehicle.

[0118] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0119] It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims.

Claims

1. A control method of an LLC resonant converter, characterized by, The method comprises: acquiring a bus voltage of a DC bus port in an LLC resonant converter and an output voltage of an output port in the LLC resonant converter; determining a first perturbation state parameter corresponding to the bus voltage and a second perturbation state parameter corresponding to the output voltage; acquiring a resonant current of the LLC resonant converter and obtaining a first frequency adjustment amount according to the resonant current and the first perturbation state parameter; acquiring an output current of the LLC resonant converter and obtaining a second frequency adjustment amount according to the output current and the second perturbation state parameter; determining a target switching frequency according to the first frequency adjustment amount, the second frequency adjustment amount and a basic switching frequency corresponding to the LLC resonant converter, and controlling the LLC resonant converter based on the target switching frequency.

2. The method of claim 1, wherein, The determination of the first perturbation state parameter corresponding to the bus voltage comprises: inputting the bus voltage into an SOGI phase-locked loop module, detecting an alternating current component of the bus voltage by the SOGI phase-locked loop module, obtaining a first voltage fundamental component and a second voltage fundamental component contained in the bus voltage, the first voltage fundamental component and the second voltage fundamental component being orthogonal components; obtaining a direct current voltage component contained in the bus voltage according to the first voltage fundamental component and the bus voltage; obtaining the first perturbation state parameter according to the first voltage fundamental component, the second voltage fundamental component and the direct current voltage component.

3. The method of claim 2, wherein, The obtaining of the first perturbation state parameter according to the first voltage fundamental component, the second voltage fundamental component and the direct current voltage component comprises: superimposing a negated result of the direct current voltage component and the second voltage fundamental component to obtain a filtered voltage fundamental component; performing matrix transformation on the first voltage fundamental component and the filtered alternating current voltage component to obtain a d-axis alternating current voltage component corresponding to the bus voltage; inputting the d-axis alternating current voltage component into a low-pass filter and a PI controller in sequence to obtain the first perturbation state parameter.

4. The method of claim 1, wherein, The first perturbation state parameter comprises a phase and an angular frequency. The obtaining of the first frequency adjustment amount according to the resonant current and the first perturbation state parameter comprises: performing low-pass filtering on the resonant current to obtain a low-frequency current component contained in the resonant current; inputting the low-frequency current component and the angular frequency into an SOGI phase-locked loop module to obtain a first alternating current component and a second alternating current component contained in the resonant current; obtaining a first adjustment coefficient according to the phase, the first alternating current component and the second alternating current component; obtaining the first frequency adjustment amount according to the first adjustment coefficient and a pre-determined feedforward amount.

5. The method of claim 4, wherein, The obtaining of the first adjustment coefficient according to the phase, the first alternating current component and the second alternating current component comprises: performing matrix transformation on the phase, the first alternating current component and the second alternating current component to obtain a q-axis alternating current component and a d-axis alternating current component; According to the q-axis alternating current component and the d-axis alternating current component, an alternating current effective value is calculated; The alternating current effective value is sequentially input to a proportional-integral controller and a limiting module to obtain the first adjustment coefficient.

6. The method of claim 4, wherein, The feedforward quantity comprises a bus voltage feedforward quantity and an output voltage feedforward quantity; The first frequency adjustment quantity is obtained according to the first adjustment coefficient and a predetermined feedforward quantity. The sum of the bus voltage feedforward quantity and the output voltage feedforward quantity is taken as the feedforward quantity. A first product of the first adjustment coefficient and the feedforward quantity is determined, and the first product is taken as the first frequency adjustment quantity.

7. The method of claim 6, wherein, The determination process of the bus voltage feedforward quantity and the output voltage feedforward quantity comprises: A first gain corresponding to the bus voltage and a second gain corresponding to the output voltage are obtained; A first voltage fundamental component contained in the bus voltage and the first gain are multiplied to obtain the bus voltage feedforward quantity, and a first voltage fundamental component contained in the output voltage and the second gain are multiplied to obtain the output voltage feedforward quantity.

8. The method of claim 1, wherein, The target switching frequency is determined according to the first frequency adjustment quantity, the second frequency adjustment quantity and a basic switching frequency corresponding to the LLC resonant converter. The first frequency adjustment quantity and the second frequency adjustment quantity are superimposed on the basic switching frequency to obtain the target switching frequency.

9. The method of claim 8, wherein, The first frequency adjustment quantity and the second frequency adjustment quantity are superimposed on the basic switching frequency to obtain the target switching frequency, which comprises: A first frequency corresponding to a low-frequency alternating voltage component contained in the bus voltage is determined, and a second frequency corresponding to a low-frequency alternating voltage component contained in the output voltage is determined; It is determined whether the first frequency and the second frequency are the same; If yes, the first frequency adjustment quantity is superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency; If no, the first frequency adjustment quantity and the second frequency adjustment quantity are both superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency.

10. A power module, characterized by The power module comprises an LLC resonant converter and a controller, and the LLC resonant converter at least comprises a primary side switching network. The input end of the controller is connected with the DC bus port and the output port of the LLC resonant converter respectively, and the output end of the controller is connected with the control end of the power switch tube in the primary side switching network. The controller is used to execute the control method of the LLC resonant converter in any one of the preceding claims 1-9.

11. A charging system, characterized by The charging system comprises at least one power module, a controller, a power distribution device and at least one charging interface according to claim 10; The power distribution device is connected with the controller, each power module and each charging interface respectively; The power module is used to convert alternating current of a power grid into direct current and provide the direct current to the charging interface; The charging system comprises at least one power module, a controller, a power distribution device and at least one charging interface according to claim 10; The power distribution device is connected with the controller, each power module and each charging interface respectively; The power module is used to convert alternating current of a power grid into direct current and provide the direct current to the charging interface; The controller is further configured to acquire the required power of each charging interface, and generate a scheduling instruction according to the connection relationship of the controllable switches in the power distribution device and the required power. The power distribution device is configured to control the opening or closing of the controllable switches according to the scheduling instruction, so as to distribute the output power of each power module to each charging interface.

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