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

Abstract

The application 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 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, so that efficient and dynamic suppression of low-frequency perturbation is realized, and fast, stable and self-adaptive suppression of low-frequency ripples under all working conditions is realized.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and more specifically, to a control method, power module, and charging system for an LLC resonant converter. Background Technology

[0002] Two-port DC-DC converters have been widely researched and deployed in applications such as energy storage systems, charging modules, on-board chargers (OBC), and vehicle-to-grid (V2G). The term "two-port" can refer to either bidirectional or unidirectional operation. Regardless of whether it operates unidirectionally or bidirectionally, its typical application scenario involves the voltages on both sides being controlled by other converters, i.e., the DC-DC converter operates in constant current mode (unidirectional or bidirectional). If low-frequency fluctuations exist in the voltages on both sides in constant current mode, it will interfere with the stability of current control, causing low-frequency ripple to be superimposed on the output current. This not only increases the effective value of the current but may also trigger overcurrent protection in severe cases.

[0003] In related technologies, the problem of disturbance in two-port circuits is addressed by real-time acquisition of the voltage signal at the output port, extraction of the AC fluctuation component, and then using the AC fluctuation component as a feedforward or feedback signal, which is superimposed on the reference value of the voltage loop or current loop to generate a suppressive component that cancels out the disturbance.

[0004] However, when the bandwidth of the current loop itself is insufficient, the superimposed suppression effect is relatively limited, and it will produce a phase difference, which is not conducive to suppressing fluctuations. Summary of the Invention

[0005] The purpose of this application is to provide a control method, power module, and charging system for an LLC resonant converter, in order to address the shortcomings of the prior art and solve the technical problems existing in the prior art.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0007] In a first aspect, embodiments of this application provide a control method for an LLC resonant converter. The method includes:

[0008] Obtain the bus voltage at the DC bus port and the output voltage at the output port of the LLC resonant converter;

[0009] Determine the first disturbance state parameter corresponding to the bus voltage, and determine the second disturbance state parameter corresponding to the output voltage;

[0010] Obtain the resonant current of the LLC resonant converter, and obtain the first frequency adjustment amount based on the resonant current and the first disturbance state parameter;

[0011] The output current of the LLC resonant converter is obtained, and the second frequency adjustment amount is obtained based on the output current and the second disturbance state parameter.

[0012] Based on the first frequency adjustment amount, the second frequency adjustment amount, and the base 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.

[0013] Optionally, determining the first disturbance state parameter corresponding to the bus voltage includes:

[0014] The bus voltage is input to the SOGI phase-locked loop module, and the SOGI phase-locked loop module performs AC component detection on the bus voltage to obtain the first voltage fundamental component and the second voltage fundamental component contained in the bus voltage. The first voltage fundamental component and the second voltage fundamental component are orthogonal to each other.

[0015] Based on the fundamental component of the first voltage and the bus voltage, the DC voltage component contained in the bus voltage is obtained;

[0016] The first disturbance state parameter is obtained based on the first fundamental voltage component, the second fundamental voltage component, and the DC voltage component.

[0017] Optionally, obtaining the first disturbance state parameter based on the first fundamental voltage component, the second fundamental voltage component, and the DC voltage component includes:

[0018] The inverted DC voltage component is superimposed on the second fundamental voltage component to obtain the filtered fundamental voltage component.

[0019] Perform matrix transformation on the fundamental component of the first voltage and the filtered AC voltage component to obtain the d-axis AC voltage component corresponding to the bus voltage.

[0020] The d-axis AC voltage component is sequentially input to a low-pass filter and a PI controller to obtain the first disturbance state parameter.

[0021] Optionally, the first disturbance state parameters include: phase and angular frequency;

[0022] The step of obtaining the first frequency adjustment amount based on the resonant current and the first disturbance state parameters includes:

[0023] The resonant current is subjected to low-pass filtering to obtain the low-frequency current component contained in the resonant current.

[0024] The low-frequency current component and the angular frequency are input to the SOGI phase-locked loop module to obtain the first AC current component and the second AC current component contained in the resonant current.

[0025] The first adjustment coefficient is obtained based on the phase, the first AC current component, and the second AC current component;

[0026] The first frequency adjustment amount is obtained based on the first adjustment coefficient and the predetermined feedforward amount.

[0027] Optionally, obtaining the first adjustment coefficient based on the phase, the first alternating current component, and the second alternating current component includes:

[0028] Based on the phase, the first AC current component and the second AC current component, a matrix transformation is performed to obtain the q-axis AC current component and the d-axis AC current component.

[0029] The effective value of the AC current is calculated based on the q-axis AC current component and the d-axis AC current component.

[0030] The effective value of the alternating current is sequentially input to the proportional-integral controller and the limiting module to obtain the first adjustment coefficient.

[0031] Optionally, the feedforward amount includes: bus voltage feedforward amount and output voltage feedforward amount;

[0032] The step of obtaining the first frequency adjustment amount based on the first adjustment coefficient and a predetermined feedforward amount includes:

[0033] The sum of the bus voltage feedforward and the output voltage feedforward is taken as the feedforward quantity;

[0034] Determine the first product result of the first adjustment coefficient and the feedforward amount, and use the first product result as the first frequency adjustment amount.

[0035] Optionally, the process of determining the bus voltage feedforward and the output voltage feedforward includes:

[0036] Obtain a first gain corresponding to a predetermined bus voltage and a second gain corresponding to the output voltage;

[0037] The product of the first fundamental voltage component contained in the bus voltage and the first gain is used as the bus voltage feedforward, and the product of the first fundamental voltage component contained in the output voltage and the second gain is used as the output voltage feedforward.

[0038] Optionally, determining the target switching frequency based on the first frequency adjustment amount, the second frequency adjustment amount, and the fundamental switching frequency corresponding to the LLC resonant converter includes:

[0039] The first frequency adjustment and the second frequency adjustment are superimposed on the base switching frequency to obtain the target switching frequency.

[0040] Optionally, the step of superimposing the first frequency adjustment amount and the second frequency adjustment amount onto the base switching frequency to obtain the target switching frequency includes:

[0041] Determine the first frequency corresponding to the low-frequency AC voltage component contained in the bus voltage, and determine the second frequency corresponding to the low-frequency AC voltage component contained in the output voltage.

[0042] Determine whether the first frequency and the second frequency are the same;

[0043] If so, the first frequency adjustment amount is superimposed on the base switching frequency output by the current loop to obtain the target switching frequency;

[0044] If not, the first frequency adjustment amount and the second frequency adjustment amount are both superimposed on the base switching frequency output by the current loop to obtain the target switching frequency.

[0045] Secondly, this application embodiment also provides a power module, the power module including: an LLC resonant converter and a controller, the LLC resonant converter including at least: a primary-side switching network;

[0046] The input terminal of the controller is connected to the DC bus port and the output port of the LLC resonant converter, respectively, and the output terminal of the controller is connected to the control terminal of the power switch in the primary-side switching network.

[0047] The controller is used to execute the control method for the LLC resonant converter provided in any of the second aspects above.

[0048] Thirdly, embodiments of this application provide a charging system, which includes at least one power module, controller, power distribution device and at least one charging interface as described in the second aspect above.

[0049] The power distribution device is connected to the controller, each of the power modules, and each charging interface, respectively.

[0050] The power module is used to convert AC power from the power grid into DC power and supply it to the charging interface;

[0051] The controller is also used to obtain the required power of each of the charging interfaces and generate scheduling instructions based on the connection relationship of the controllable switches in the power distribution device and the required power.

[0052] The power distribution device is used to control the opening or closing of the controllable switch according to the scheduling command, so as to distribute the output power of each power module to each charging interface.

[0053] The beneficial effects of this application are:

[0054] This application provides a control method, power module, and charging system for an LLC resonant converter. During the operation of the LLC resonant converter, the bus voltage and output voltage of the two-port circuit are acquired, and the first disturbance state parameter corresponding to the bus voltage and the second disturbance state parameter corresponding to the output voltage are extracted, i.e., low-frequency disturbance information is detected from the two-port voltage. Then, based on the monitored resonant current and the first disturbance state parameter, a first frequency adjustment amount is obtained, and based on the output current and the second disturbance state parameter, a second frequency adjustment amount is obtained, i.e., the adjustment amount to be suppressed is obtained. The frequency adjustment amount is superimposed on the base switching frequency to obtain the dynamically adjusted target switching frequency, so that the LLC resonant converter can be controlled based on the target switching frequency, i.e., the power switching transistors in the LLC resonant converter are driven to operate at the new frequency. This solves the problem that low-frequency disturbances are generated in the resonant current and output current of the LLC resonant converter when there are low-frequency voltage ripples on the input and / or output sides, achieving efficient and dynamic suppression of low-frequency disturbances, and realizing fast, stable, and adaptive suppression of low-frequency ripples under all operating conditions.

[0055] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0056] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 A schematic diagram of a cascaded topology of an LLC resonant converter, provided as an example of existing technology;

[0058] Figure 2 A schematic diagram of a specific topology of an LLC resonant converter is provided as an example of the prior art.

[0059] Figure 3 A schematic diagram of the structure of a power module provided in this application;

[0060] Figure 4 A flowchart illustrating a control method for an LLC resonant converter provided in this application;

[0061] Figure 5 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0062] Figure 6 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0063] Figure 7 This is a schematic diagram of the bus voltage phase-locked loop detection and control provided in this application;

[0064] Figure 8 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0065] Figure 9 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0066] Figure 10 A schematic diagram of an SOGI control and feedforward control strategy based on resonant current detection provided in this application;

[0067] Figure 11 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0068] Figure 12 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0069] Figure 13 A flowchart illustrating another control method for an LLC resonant converter provided in this application;

[0070] Figure 14 A schematic diagram of another SOGI control and feedforward control strategy based on resonant current detection provided in this application;

[0071] Figure 15 This is a schematic diagram of a charging system provided in this application.

[0072] Icons: 100-Power module; 1-Controller; 200-Charging system; 2-Power distribution device; 3-Charging interface. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0074] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0075] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of this application is usually placed in. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0078] In the description of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" 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 or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0079] First, the technical terms used in this application will be explained.

[0080] 1. LLC resonant converters are highly efficient DC / DC conversion topologies widely used in medium- and high-power power electronic systems. Due to their high efficiency, high power density, and soft-switching characteristics, they are commonly used in new energy, electric vehicle chargers, communication power supplies, server power supplies, and other fields. (See reference...) Figures 1-2 The diagram shows a typical LLC resonant converter topology. An LLC resonant converter consists of an LLC primary network, a high-frequency transformer, and an LLC secondary network, cascaded as follows:

[0081] The bus voltage Vdc at the front-end port can be powered by an AC / DC converter (such as a three-phase rectifier PCS) or a DC power supply. When the load comes from an unbalanced or nonlinear grid load, the bus voltage Vdc is often superimposed with a low-frequency AC ripple such as 100Hz.

[0082] The output voltage Vo at the downstream port: when connected to a battery, aging device, or other bidirectional PCS system, it may also introduce low-frequency voltage fluctuations due to the PCS.

[0083] The primary network of the LLC 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.). The output current Io of the LLC resonant converter is controlled by adjusting the switching frequency of each power switch.

[0084] 2. Two-port disturbances refer to the possibility that low-frequency AC ripples (e.g., 100Hz, caused by three-phase grid imbalance or rectifier PCS) may exist in both the DC bus voltage Vdc of the LLC resonant converter and the output voltage Vo of the output port. 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 and affecting efficiency, temperature rise, EMI and protection reliability.

[0085] Therefore, it is necessary to suppress the existing two-port disturbances so that the LLC resonant converter can have the advantages of fast response, good stability and strong adaptability, and is particularly suitable for application scenarios with significant low-frequency ripple, such as new energy storage PCS and electric vehicle chargers.

[0086] Secondly, the background technology involved in this application will be introduced.

[0087] For unidirectional or bidirectional charging modules, the mainstream DC / DC topology is generally an LLC converter. The LLC converter is a resonant converter. Usually, the resonant network impedance is relatively low, making it susceptible to input and output voltage ripple and interference, which has a significant impact on the resonant current or output current.

[0088] Typically, the front-end is an AC / DC non-isolated converter, cascaded with the downstream LLC. They are usually integrated into a single chassis for unified or independent control, or they can be separated into two independent converters cascaded, such as a PCS + DC / DC two-stage independent configuration. Regardless of whether they are independent or integrated, if factors such as three-phase imbalance cause low-frequency ripple in the PCS output (typically 100Hz), this will cause low-frequency disturbances in the LLC resonant current and output current, affecting current protection, thermal performance, and output specifications. Similarly, if a stable battery load is connected to the output side, there is generally no output disturbance. However, if an aging load or other bidirectional load is also connected to a PCS or other converter, there will be disturbances in the output voltage, leading to disturbances in the resonant current and output current.

[0089] In related technologies, the problem of disturbance in two-port circuits is addressed by real-time acquisition of the voltage signal at the output port, extraction of the AC fluctuation component, and then using the AC fluctuation component as a feedforward or feedback signal, which is superimposed on the reference value of the voltage loop or current loop to generate a suppressive component that cancels out the disturbance.

[0090] However, the closed-loop bandwidth of the current loop is usually low (limited by factors such as sampling delay, compensation network, and switching frequency). When the "suppression component" superimposed by the current loop is fast-responding, it cannot track high-frequency or rapidly changing disturbance signals in time due to its slow response speed (long rise time and low cutoff frequency).

[0091] To address this, this application proposes a control method for an LLC resonant converter. During the operation of the LLC resonant converter, the bus voltage at the DC bus port and the output voltage at the output port are collected. A first disturbance state parameter corresponding to the bus voltage and a second disturbance state parameter corresponding to the output voltage are extracted, i.e., low-frequency disturbance information is detected from the dual-port voltage. Then, based on the resonant current and the first disturbance state parameter, a first frequency adjustment amount is obtained, and based on the output current and the second disturbance state parameter, a second frequency adjustment amount is obtained, i.e., the feedforward amount to be suppressed is obtained. The frequency adjustment amount is superimposed on the base switching frequency to obtain the dynamically adjusted target switching frequency, so that the LLC resonant converter can be controlled based on the target switching frequency, i.e., the power switching transistors in the LLC resonant converter are driven to operate at the new frequency, realizing dynamic disturbance suppression and achieving fast, stable, and adaptive suppression of low-frequency ripple under all operating conditions.

[0092] The control method of the LLC resonant converter provided in the embodiments of this application will be explained in detail below with reference to the accompanying drawings.

[0093] Figure 3 The structural schematic diagram of the power module provided in this application is as follows: Figure 3 As shown, the power module 100 includes an LLC resonant converter and a controller 1. For example, the controller 1 can be a digital processing chip with data processing capabilities, such as a DSP chip.

[0094] The controller 1 is used to execute the control method of the LLC resonant converter provided in the following embodiment to suppress the two-port disturbance problem in the LLC resonant converter, so that the low-frequency disturbance of the two ports is better suppressed and adapted to a variety of operating conditions.

[0095] Figure 4 The diagram shown is a flowchart illustrating a control method for an LLC resonant converter according to an embodiment of this application. Figure 4 As shown, the method includes:

[0096] S101. Obtain the bus voltage at the DC bus port and the output voltage at the output port of the LLC resonant converter.

[0097] Both the bus voltage Vdc and the output voltage Vo may contain low-frequency AC ripple. The bus voltage Vdc may originate from the grid-connected converter and be affected by the three-phase imbalance of the power grid, resulting in a 100Hz ripple. If the output port is connected to a dynamic load (such as a battery aging device), the output voltage Vo may also contain low-frequency disturbances (e.g., 100Hz).

[0098] In one feasible approach, the bus voltage Vdc and output voltage Vo in the LLC resonant converter can be acquired in real time or periodically to facilitate the extraction of disturbance components.

[0099] S102. Determine the first disturbance state parameter corresponding to the bus voltage, and determine the second disturbance state parameter corresponding to the output voltage.

[0100] For example, the disturbance state parameters may include: phase θ, frequency f, or amplitude A.

[0101] 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.

[0102] In one feasible approach, the bus voltage Vdc can be decomposed using a second-order generalized integrator and a phase-locked loop to obtain the low-frequency AC component contained in the bus voltage Vdc, and to obtain the phase, frequency, and amplitude of the low-frequency AC component, and to use the phase, frequency, and amplitude of the low-frequency AC component as the first disturbance state parameter.

[0103] Similarly, the same method described above can be used to obtain the second disturbance state parameter corresponding to the output voltage Vo.

[0104] S103. Obtain the resonant current of the LLC resonant converter, and obtain the first frequency adjustment amount based on the resonant current and the first disturbance state parameter.

[0105] S104. Obtain the output current of the LLC resonant converter, and obtain the second frequency adjustment amount based on the output current and the second disturbance state parameter.

[0106] Optionally, after obtaining the relevant AC components and frequency phase information through phase-locked loop of bus voltage Vdc and output voltage Vo, feedforward suppression can be performed by superimposing the feedforward quantity onto the voltage loop or current loop output, which is usually f (switching frequency) or 1 / f.

[0107] In this embodiment, to further adjust and completely suppress the resonant current or output current, "detection and control of resonant current Ir and / or output current Io" is added. Specifically, the resonant current Ir can reflect low-frequency disturbances at the bus port. Therefore, a first frequency adjustment amount can be obtained based on the resonant current Ir and the first disturbance state parameter; similarly, a second frequency adjustment amount can be obtained based on the output current Io and the second disturbance state parameter. The first and second frequency adjustment amounts can be used as disturbance compensation amounts to be compensated.

[0108] S105. Determine the target switching frequency based on the first frequency adjustment amount, the second frequency adjustment amount, and the basic switching frequency corresponding to the LLC resonant converter, and control the LLC resonant converter based on the target switching frequency.

[0109] In one feasible manner, the first frequency adjustment and the second frequency adjustment can be superimposed on the base switching frequency corresponding to the LLC resonant converter to obtain a new target switching frequency f. The switching frequency of the power switch in the LLC resonant converter can be adjusted by the target switching frequency f to dynamically suppress the low-frequency disturbances of the two-port converter, thereby achieving fast, stable, and adaptive suppression of low-frequency ripples under all operating conditions.

[0110] In summary, this application provides a control method for an LLC resonant converter. During the operation of the LLC resonant converter, the bus voltage and output voltage of the two-port circuit are acquired, and the first disturbance state parameter corresponding to the bus voltage and the second disturbance state parameter corresponding to the output voltage are extracted, i.e., low-frequency disturbance information is detected from the two-port voltage. Then, based on the monitored resonant current and the first disturbance state parameter, a first frequency adjustment amount is obtained, and based on the output current and the second disturbance state parameter, a second frequency adjustment amount is obtained, i.e., the adjustment amount to be suppressed is obtained. The frequency adjustment amount is superimposed on the base switching frequency to obtain the dynamically adjusted target switching frequency, so that the LLC resonant converter can be controlled based on the target switching frequency, i.e., the power switching transistors in the LLC resonant converter are driven to work at the new frequency. This solves the problem that low-frequency disturbances are generated in the resonant current and output current of the LLC resonant converter when there are low-frequency voltage ripples on the input and / or output sides, achieving efficient and dynamic suppression of low-frequency disturbances, and realizing fast, stable, and adaptive suppression of low-frequency ripples under all operating conditions.

[0111] Optionally, refer to Figure 5 As shown, determining the first disturbance state parameter corresponding to the bus voltage in step S102 above includes:

[0112] S201. Input the bus voltage to the SOGI phase-locked loop module. The SOGI phase-locked loop module performs AC component detection on the bus voltage to obtain the first fundamental voltage component and the second fundamental voltage component contained in the line voltage.

[0113] Among them, the first voltage fundamental component Vdc_ac and the second voltage fundamental component Vdc_β are orthogonal components, that is, the first voltage fundamental component Vdc_ac and the second voltage fundamental component Vdc_β are 90° out of phase.

[0114] It should be noted that the bus voltage Vdc is not a pure DC signal, but contains both DC and AC components. Therefore, it is necessary to accurately extract the AC disturbance components (such as 100Hz ripple) and their phase information from the mixed signal of "bus voltage Vdc" for subsequent feedforward suppression.

[0115] Optionally, in this embodiment, considering that the SOGI phase-locked loop module can extract the fundamental frequency of the grid voltage and accurately obtain the fundamental frequency component corresponding to each phase of the grid voltage, it is proposed that the bus voltage Vdc be input to the SOGI phase-locked loop module, and the SOGI phase-locked loop module performs AC component detection on the bus voltage Vdc to obtain the first fundamental frequency component Vdc_ac and the second fundamental frequency component Vdc_β contained in the bus voltage Vdc.

[0116] S202. Based on the fundamental component of the first voltage and the bus voltage, obtain the DC voltage component contained in the bus voltage.

[0117] In one feasible approach, the first voltage difference between the bus voltage Vdc and the first fundamental voltage component Vdc_ac is calculated, and the first voltage difference is input to a low-pass filter. The low-pass filter performs low-pass filtering on the first voltage difference to obtain the DC voltage component Vdc_dc contained in the bus voltage Vdc, thereby achieving the separation of the DC voltage component of the bus voltage Vdc.

[0118] S203. Based on the first fundamental voltage component, the second fundamental voltage component, and the DC voltage component, the first disturbance state parameters are obtained.

[0119] In one feasible approach, the first voltage fundamental component, the second voltage fundamental component, and the DC voltage component can be further decomposed to calculate the first disturbance state parameters, such as the phase, frequency, or amplitude of the low-frequency AC disturbance signal contained in the bus voltage Vdc.

[0120] Optionally, refer to Figure 6 As shown, step S203 above includes:

[0121] S301. The inverted DC voltage component is superimposed with the fundamental voltage component to obtain the filtered AC voltage component.

[0122] S302. Perform matrix transformation on the fundamental component of the first voltage and the filtered AC voltage component to obtain the d-axis AC voltage component corresponding to the bus voltage.

[0123] S303. The d-axis AC voltage component is sequentially input to the low-pass filter and the PI controller to obtain the first disturbance state parameter.

[0124] In one feasible approach, as referenced Figure 7 As shown, the 0-degree in-phase component of the SOGI phase-locked loop module is essentially a bandpass filter, effectively suppressing DC and high-frequency noise. The output first fundamental voltage component, Vdc_ac, is a pure fundamental low-frequency component, requiring no additional processing. However, the 90-degree quadrature component of the SOGI phase-locked loop module lacks DC suppression capability, meaning the output second fundamental voltage component, Vdc_β, retains the DC component in the bus voltage Vdc. Therefore, to obtain a pure quadrature signal, the DC component in the second fundamental voltage component, Vdc_β, must be canceled out 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 second voltage fundamental component Vdc_β can be DC filtered based on the processed DC voltage component k×Vdc_dc to obtain the DC filtered second voltage fundamental component Vβ. Then, the first voltage fundamental component Vdc_ac and the filtered voltage fundamental component Vβ are simultaneously input into a matrix converter for dq matrix transformation to obtain the d-axis AC voltage component Vd and the q-axis AC voltage component Vq corresponding to the bus voltage Vdc.

[0125] Among them, the d-axis AC voltage component Vd can also be called the reactive voltage component; the q-axis AC voltage component Vq can also be called the active voltage component. The active voltage component refers to the voltage component that does work in the bus voltage.

[0126] Continue to refer to Figure 7 As shown, the d-axis AC voltage component Vd is sequentially input to a low-pass filter LPF and a PI controller. The low-pass filter LPF filters the d-axis AC voltage component Vd to obtain the filtered reactive voltage component. The filtered reactive voltage component is then input to the PI controller to obtain the angular frequency adjustment. Finally, the angular frequency adjustment is superimposed with the preset angular frequency ω0 to obtain the angular frequency ω corresponding to the d-axis AC voltage component Vd. The angular frequency ω is then integrated to obtain the phase θ corresponding to the d-axis AC voltage component Vd. Thus, the first disturbance state parameter contained in the bus voltage Vdc is obtained.

[0127] Similarly, the above processing procedure can be used to extract the second disturbance state parameter corresponding to the output voltage Vo, which will not be elaborated further here.

[0128] Optionally, the first disturbance state parameters include: phase and angular frequency;

[0129] refer to Figure 8 As shown, in step S103 above, the first frequency adjustment amount is obtained based on the resonant current and the first disturbance state parameters, including:

[0130] S401. Perform low-pass filtering on the resonant current to obtain the low-frequency current component contained in the resonant current.

[0131] Optionally, to further adjust and completely suppress the resonant current, "resonant current detection and control" is added. First, the resonant current Ir can react to low-frequency disturbances at the two-port network and is essentially adjusted by the equivalent "voltage difference" on the resonant network. Therefore, the resonant current Ir is detected to obtain the base current, which consists of low-frequency components and the switching frequency.

[0132] In one feasible approach, the resonant current Ir is input to a low-pass filter, which filters out the switching frequency up to around 100kHz. This can be achieved through effective filtering methods such as a second-order low-pass filter, to obtain the low-frequency current component Ir1 contained in the resonant current Ir.

[0133] S402. Input the low-frequency current component and angular frequency to the SOGI phase-locked loop module to obtain the first AC current component and the second AC current component contained in the resonant current.

[0134] In one feasible approach, the low-frequency current component Ir and the angular frequency ω are simultaneously input to the SOGI phase-locked loop module. The SOGI phase-locked loop module extracts the fundamental frequency from the low-frequency current component Ir and the angular frequency ω to obtain the first AC current component and the second AC current component contained in the resonant current Ir, wherein the first AC current component and the second AC current component are orthogonal signals.

[0135] S403. Based on the phase, the first AC current component, and the second AC current component, the first adjustment coefficient is obtained.

[0136] The first adjustment coefficient is used to compensate for steady-state errors or accelerate dynamic response, thereby improving adaptability to multiple operating conditions.

[0137] In this embodiment, a first adjustment coefficient is calculated based on the phase, the first AC current component, and the second AC current component. That is, the first adjustment coefficient not only depends on the current component but also incorporates phase information, forming a more accurate dynamic response mechanism.

[0138] S404. The first frequency adjustment amount is obtained based on the first adjustment coefficient and the predetermined feedforward amount.

[0139] Among them, the feedforward quantities include: output voltage feedforward quantity and bus voltage feedforward quantity.

[0140] In one feasible approach, the first frequency adjustment amount can be obtained based on the first adjustment coefficient and a predetermined feedforward amount. That is, the first frequency adjustment amount not only includes the feedback adjustment coefficient but also introduces the feedforward amount, so as to improve the system response speed and disturbance rejection capability.

[0141] Optionally, refer to Figure 9 As shown, step S403 above includes:

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] Similarly, the second adjustment coefficient can be calculated using the above processing method, which will not be elaborated further here.

[0147] Optionally, the feedforward includes: bus voltage feedforward and output voltage feedforward;

[0148] refer to Figure 11 As shown, step S404 above includes:

[0149] S601. The sum of the bus voltage feedforward and the output voltage feedforward is taken as the feedforward quantity.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] Optionally, the bus voltage feedforward and the output voltage feedforward can be superimposed to form a comprehensive feedforward control signal. Compared with a single feedforward method, it has a faster dynamic response speed and stronger robustness, realizes AC / DC collaborative sensing, and enhances the system's adaptability to multi-terminal disturbances.

[0154] It should be noted that the bus voltage feedforward does not refer to the directly acquired bus voltage value itself, but rather to a processed compensation term, which may involve normalization, scaling, error extraction, or other processing. For example, the bus voltage feedforward is a compensation signal generated based on the difference between the bus voltage and the reference value.

[0155] In one feasible approach, the sum of the bus voltage feedforward and the output voltage feedforward is calculated, and the sum is used as the total feedforward. That is, the bus voltage state and the output voltage state are jointly constructed into a unified feedforward. Then, the product of the first adjustment coefficient, the feedforward, and the preset fundamental frequency fr is calculated, and the calculated product is used as the first frequency adjustment, thereby realizing adaptive adjustment of the feedforward gain.

[0156] Optionally, refer to Figure 12 As shown, the process of determining the bus voltage feedforward and the output voltage feedforward includes:

[0157] S701. Obtain the first gain corresponding to the predetermined bus voltage and the second gain corresponding to the output voltage.

[0158] S702. The product of the first voltage fundamental component contained in the bus voltage and the first gain is used as the bus voltage feedforward, and the product of the first voltage fundamental component contained in the output voltage and the second gain is used as the output voltage feedforward.

[0159] In one feasible manner, the DC gain of the LLC resonant converter can be expressed as: ,in, Let V be the transformer turns ratio. If only the bus voltage Vdc contains low-frequency components, and the gain cancels them out, it can be expressed as: (Vdc + Vdc_ac)(M + m) = Vo + 0. Ignoring high-frequency components, M * Vdc_ac + m * Vdc = 0, then m = -M * Vdc_ac / Vdc = M1 * Vdc_ac. The first gain corresponding to the bus voltage can be calculated as M1 = -(nVo) / Vdc / Vdc.

[0160] If only the output voltage Vo contains low-frequency components, and the gain cancels them out, it can be expressed as: Vdc(M+m)=Vo+Vo_ac; ignoring high-frequency components, Vdc*m=Vo_ac, then m=Vo_ac / Vdc=M2*Vo_ac, and the second gain corresponding to the output voltage M2=1 / Vdc can be calculated. Therefore, in this embodiment, "independent gain allocation according to signal source" is proposed to achieve fine-grained control.

[0161] Continue to refer to Figure 10 The product of the first fundamental voltage component Vdc_ac contained in the bus voltage and the first gain M1 is used as the bus voltage feedforward, and the product of the first fundamental voltage component Vo_ac contained in the output voltage and the second gain M2 is used as the output voltage feedforward.

[0162] Optionally, step S105 above includes:

[0163] The first frequency adjustment and the second frequency adjustment are superimposed on the base switching frequency to obtain the target switching frequency.

[0164] Among them, continue to refer to Figure 10 As shown, the basic switching frequency f0 is output by the voltage loop or the current loop.

[0165] In one feasible approach, to further adjust and completely suppress the resonant current or output current, this embodiment proposes to superimpose the first frequency adjustment amount and the second frequency adjustment amount onto the base switching frequency to obtain the target switching frequency, so that the low-frequency disturbance of the two-port is better suppressed and adapted to a variety of operating conditions.

[0166] Optionally, refer to Figure 13 As shown, the above steps superimpose the first frequency adjustment and the second frequency adjustment onto the base switching frequency to obtain the target switching frequency, including:

[0167] S801. Determine the first frequency corresponding to the low-frequency AC voltage component contained in the bus voltage, and determine the second frequency corresponding to the low-frequency AC voltage component contained in the output voltage.

[0168] S802. Determine whether the first frequency and the second frequency are the same.

[0169] S803 If so, the first frequency adjustment amount is superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency.

[0170] It should be noted that it is necessary to first determine the first frequency corresponding to the low-frequency AC voltage component contained in the bus voltage, and determine whether the second frequency corresponding to the low-frequency AC voltage component contained in the output voltage is the same. If the same frequency of 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). If different frequency of low-frequency fluctuation component is detected in the two ports, they cannot be directly superimposed and need to be processed separately.

[0171] In one feasible approach, see further reference. Figure 10 As shown, if two ports detect low-frequency fluctuation components of the same frequency, 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.

[0172] Optionally, such as Figure 10 As shown, the LLC topology gain-frequency curve is parabolic. When the target switching frequency is equal to the fundamental frequency, i.e., f=fr, the gain is approximately 1. When the frequency is greater than fr, the gain decreases, and when the frequency is less than fr, the gain increases sharply.

[0173] S804. If not, then the first frequency adjustment amount and the second frequency adjustment amount are both superimposed on the basic switching frequency output by the current loop to obtain the target switching frequency.

[0174] In another possible approach, see further reference. Figure 14 As shown, if low-frequency fluctuation components of different frequencies are detected at the 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.

[0175] in, Figure 14 In this context, ω1 is the angular frequency corresponding to the d-axis AC 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 AC voltage component Vo contained in the output voltage, and the phase θ2 is obtained by integrating the angular frequency ω2.

[0176] Therefore, in this application, both the bus voltage disturbance on the input side and the output voltage disturbance on the output side can be detected in a timely manner and initially suppressed through the loop; and by detecting the low-frequency component in the resonant current, precise compensation can be achieved, thus fully leveraging the suppression effect.

[0177] Optionally, this application can detect low-frequency disturbance components of a single frequency. If there are composite disturbances with multiple frequency components superimposed, multiple independent phase-locked loops for different frequencies can be set to track the amplitude and phase of each frequency component, thereby achieving multi-band coordinated suppression and improving the system's anti-interference capability and output power quality.

[0178] Optionally, refer to Figure 15 As shown, a charging system provided in this application embodiment is provided. The charging system 200 includes: at least one power module 100, a controller 1, a power distribution device 2 and at least one charging interface 3 provided in the above embodiment.

[0179] The power distribution device 2 is connected to the controller 1, each power module 100 and each charging interface 3 respectively;

[0180] Power module 100 is used to convert AC power from the power grid into DC power to supply the charging interface 3;

[0181] The controller 1 is also used to obtain the power demand of each charging port 3, and generate scheduling instructions according to the connection relationship of the controllable switches in the power distribution device 2 and the power demand.

[0182] The power distribution device 2 is used to control the opening or closing of the controllable switch according to the scheduling command, so as to distribute the output power of each power module to each charging interface 3.

[0183] In one optional implementation, the charging system provided in this application is an integrated DC charging pile, and the charging interface 3 is used to connect the charging gun. The charging gun is hung on the host of the charging system through the gun holder on the main body of the charging system.

[0184] In one optional implementation, the charging system provided in this application is a split-type DC charging pile. The charging system also includes multiple charging terminals. The charging interface 3 is used to connect the charging terminals. The charging terminals are set separately from the main body of the charging system. The charging terminals are equipped with a single charging gun or dual charging guns for outputting power to electric vehicles.

[0185] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0186] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A control method for an LLC resonant converter, characterized in that, The method includes: Obtain the bus voltage at the DC bus port and the output voltage at the output port of the LLC resonant converter; Determine the first disturbance state parameter corresponding to the bus voltage, and determine the second disturbance state parameter corresponding to the output voltage; Obtain the resonant current of the LLC resonant converter, and obtain the first frequency adjustment amount based on the resonant current and the first disturbance state parameter; The output current of the LLC resonant converter is obtained, and the second frequency adjustment amount is obtained based on the output current and the second disturbance state parameter. Based on the first frequency adjustment amount, the second frequency adjustment amount, and the base 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. The first disturbance state parameters include: phase and angular frequency; The step of obtaining the first frequency adjustment amount based on the resonant current and the first disturbance state parameters includes: The resonant current is subjected to low-pass filtering to obtain the low-frequency current component contained in the resonant current. The low-frequency current component and the angular frequency are input to the SOGI phase-locked loop module to obtain the first AC current component and the second AC current component contained in the resonant current. The first adjustment coefficient is obtained based on the phase, the first AC current component, and the second AC current component; The first frequency adjustment amount is obtained based on the first adjustment coefficient and the predetermined feedforward amount; The step of obtaining the first adjustment coefficient based on the phase, the first alternating current component, and the second alternating current component includes: Based on the phase, the first AC current component and the second AC current component, a matrix transformation is performed to obtain the q-axis AC current component and the d-axis AC current component. The effective value of the AC current is calculated based on the q-axis AC current component and the d-axis AC current component. The effective value of the alternating current is sequentially input to the proportional-integral controller and the limiting module to obtain the first adjustment coefficient.

2. The method according to claim 1, characterized in that, Determining the first disturbance state parameter corresponding to the bus voltage includes: The bus voltage is input to the SOGI phase-locked loop module, and the SOGI phase-locked loop module performs AC component detection on the bus voltage to obtain the first voltage fundamental component and the second voltage fundamental component contained in the bus voltage. The first voltage fundamental component and the second voltage fundamental component are orthogonal to each other. Based on the fundamental component of the first voltage and the bus voltage, the DC voltage component contained in the bus voltage is obtained; The first disturbance state parameter is obtained based on the first fundamental voltage component, the second fundamental voltage component, and the DC voltage component.

3. The method according to claim 2, characterized in that, The step of obtaining the first disturbance state parameter based on the first fundamental voltage component, the second fundamental voltage component, and the DC voltage component includes: The inverted DC voltage component is superimposed on the second fundamental voltage component to obtain the filtered fundamental voltage component. Perform matrix transformation on the fundamental component of the first voltage and the filtered AC voltage component to obtain the d-axis AC voltage component corresponding to the bus voltage. The d-axis AC voltage component is sequentially input to a low-pass filter and a PI controller to obtain the first disturbance state parameter.

4. The method according to claim 1, characterized in that, The feedforward includes: bus voltage feedforward and output voltage feedforward; The step of obtaining the first frequency adjustment amount based on the first adjustment coefficient and a predetermined feedforward amount includes: The sum of the bus voltage feedforward and the output voltage feedforward is taken as the feedforward quantity; Determine the first product result of the first adjustment coefficient and the feedforward amount, and use the first product result as the first frequency adjustment amount.

5. The method according to claim 4, characterized in that, The process of determining the bus voltage feedforward and the output voltage feedforward includes: Obtain a first gain corresponding to a predetermined bus voltage and a second gain corresponding to the output voltage; The product of the first fundamental voltage component contained in the bus voltage and the first gain is used as the bus voltage feedforward, and the product of the first fundamental voltage component contained in the output voltage and the second gain is used as the output voltage feedforward.

6. The method according to claim 1, characterized in that, Determining the target switching frequency based on the first frequency adjustment amount, the second frequency adjustment amount, and the fundamental switching frequency corresponding to the LLC resonant converter includes: The first frequency adjustment and the second frequency adjustment are superimposed on the base switching frequency to obtain the target switching frequency.

7. The method according to claim 6, characterized in that, The step of superimposing the first frequency adjustment amount and the second frequency adjustment amount onto the base switching frequency to obtain the target switching frequency includes: Determine the first frequency corresponding to the low-frequency AC voltage component contained in the bus voltage, and determine the second frequency corresponding to the low-frequency AC voltage component contained in the output voltage. Determine whether the first frequency and the second frequency are the same; If so, the first frequency adjustment amount is superimposed on the base switching frequency output by the current loop to obtain the target switching frequency; If not, the first frequency adjustment amount and the second frequency adjustment amount are both superimposed on the base switching frequency output by the current loop to obtain the target switching frequency.

8. A power module, characterized in that, The power module includes: an LLC resonant converter and a controller, wherein the LLC resonant converter includes at least: a primary-side switching network; The input terminal of the controller is connected to the DC bus port and the output port of the LLC resonant converter, respectively, and the output terminal of the controller is connected to the control terminal of the power switch in the primary-side switching network. The controller is used to execute the control method of the LLC resonant converter according to any one of claims 1-7.

9. A charging system, characterized in that, The charging system includes at least one power module, controller, power distribution device as described in claim 8, and at least one charging interface; The power distribution device is connected to the controller, each of the power modules, and each charging interface, respectively. The power module is used to convert AC power from the power grid into DC power and supply it to the charging interface; The controller is also used to obtain the required power of each of the charging interfaces and generate scheduling instructions based on the connection relationship of the controllable switches in the power distribution device and the required power. The power distribution device is used to control the opening or closing of the controllable switch according to the scheduling command, so as to distribute the output power of each power module to each charging interface.

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