A single-stage high-frequency converter and control method

Abstract

The present invention discloses a single-stage high-frequency converter and control method, which relates to the technical field of power electronic conversion, and includes: an input uncontrolled rectifier bridge, an absorption capacitor and an isolated DC / DC resonant conversion circuit; the AC input end of the input uncontrolled rectifier bridge serves as the AC input end of the single-stage high-frequency converter, and the DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the isolated DC / DC resonant conversion circuit and is connected in parallel with the absorption capacitor; the DC output end of the isolated DC / DC resonant conversion circuit serves as the DC output end of the single-stage high-frequency converter and is connected to an external device. A single-stage high-frequency resonant converter is used to replace the machine-side Boost converter and the grid-side PWM converter, and no large-capacity capacitor is required. High power factor operation and isolated DC output of a direct-drive wind generator can be achieved, as well as converter soft switch control, to achieve efficient power conversion of direct-drive wind power generation.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic conversion, and in particular to a single-stage high-frequency converter and a control method thereof. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In direct-drive wind power generation systems, there are currently two main types of machine-side AC / DC converters. The first type is a fully controlled PWM (Pulse Width Modulation) converter, and the second type uses a diode uncontrolled rectifier + Boost converter. The grid side uses a DC / AC or DC / DC converter for AC or DC grid connection, or island operation.

[0004] The second type of converter mentioned above adopts uncontrolled rectification, which is relatively low in cost and relatively high in efficiency compared with the first type of converter. However, since the machine side still needs to be boosted by a Boost converter, that is, both the machine side and the grid side require high-frequency PWM conversion and control, and the machine side Boost converter is not easy to achieve soft switching, an additional auxiliary soft switching circuit is required, and the DC bus between the machine side converter and the grid side converter also requires a large-capacity electrolytic capacitor to maintain the DC bus voltage, which restricts the system life and reduces the power conversion efficiency. Summary of the invention

[0005] In order to solve the problems existing in the above-mentioned second type of direct-drive wind power generation system, the present invention proposes a single-stage high-frequency converter and a control method, which adopts a single-stage high-frequency conversion topology structure to replace the machine-side Boost converter and the grid-side PWM converter, does not require a large-capacity capacitor, improves the power conversion efficiency, realizes the unity power factor operation and isolated DC output of the direct-drive wind generator, and realizes the soft switching control of the converter, thereby realizing efficient power conversion of direct-drive wind power generation.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a single-stage high-frequency converter, comprising: an input uncontrolled rectifier bridge, an absorption capacitor, and an isolated DC / DC resonant conversion circuit;

[0008] The AC input end of the input uncontrolled rectifier bridge serves as the AC input end of the single-stage high-frequency converter, and the DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the isolated DC / DC resonant conversion circuit and is connected in parallel with the absorption capacitor; the DC output end of the isolated DC / DC resonant conversion circuit serves as the DC output end of the single-stage high-frequency converter and is connected to an external device.

[0009] As an optional implementation, the absorption capacitor is used to absorb high-frequency switching voltage spikes of the isolated DC / DC resonant conversion circuit.

[0010] As an optional implementation, the isolated DC / DC resonant conversion circuit includes a high-frequency DC / AC converter, a resonant network, a high-frequency isolation transformer and an output uncontrolled rectifier bridge;

[0011] The DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the high-frequency DC / AC converter, the AC output end of the high-frequency DC / AC converter is connected to the resonant network, the resonant network is connected to the primary side of the high-frequency isolation transformer, the secondary side of the high-frequency isolation transformer is connected to the AC input end of the output uncontrolled rectifier bridge, and the DC output end of the output uncontrolled rectifier bridge serves as the DC output end of the isolated DC / DC resonant conversion circuit.

[0012] As an optional implementation, the resonant network adopts an LLC resonant network.

[0013] As an optional implementation, the isolated DC / DC resonant conversion circuit includes a high-frequency DC / AC converter, a resonant network, a high-frequency isolation transformer and an output uncontrolled rectifier bridge;

[0014] The DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the high-frequency DC / AC converter, the AC output end of the high-frequency DC / AC converter is connected to the primary side of the high-frequency isolation transformer, the secondary side of the high-frequency isolation transformer is connected to the resonant network, the resonant network is connected to the AC input end of the output uncontrolled rectifier bridge, and the DC output end of the output uncontrolled rectifier bridge serves as the DC output end of the isolated DC / DC resonant conversion circuit.

[0015] As an optional implementation, the resonant network adopts an LC resonant network.

[0016] As an optional implementation, the high-frequency DC / AC converter adopts a half-bridge, full-bridge, three-level or multi-level structure.

[0017] In a second aspect, the present invention provides a control method for a single-stage high-frequency converter, using the single-stage high-frequency converter described in the first aspect, comprising:

[0018] Obtaining a DC input voltage, a DC input current and a DC output voltage of an isolated DC / DC resonant conversion circuit, and thereby obtaining a current control signal;

[0019] After the DC input voltage is normalized, it is combined with the current control signal to obtain a DC input current reference signal;

[0020] Obtaining a DC input current feedback signal according to a filtered signal of the DC input voltage and the DC input current;

[0021] A switch control signal for controlling the operation of an isolated DC / DC resonant conversion circuit is obtained according to a DC input current reference signal and a DC input current feedback signal.

[0022] As an optional implementation method, the filtered signal after the DC input voltage is filtered is: Subtract the filtered signal from the DC input current to obtain a DC input current feedback signal;

[0023] In the formula, is the transfer function of the high-pass filter, τ d is the differential time constant, T d is the inertia time constant, U dc is the DC input voltage.

[0024] As an optional implementation, the unitized signal u of the DC input voltage is uint With the current control signal I m The product of is used as the DC input current reference signal.

[0025] As an optional implementation, the process of obtaining the current control signal includes:

[0026] The DC input voltage and the DC input current are filtered to obtain an average DC input voltage and an average DC input current, and the average active power is obtained according to the product of the average DC input voltage and the average DC input current.

[0027] According to the average value of DC input voltage, average value of DC input current and average active power, the control quantity I is obtained through maximum power tracking control. m1 ;

[0028] According to the average value of DC input voltage, average active power and given value of active power, the control quantity I is obtained through constant power control. m2 ;

[0029] According to the average value of DC input voltage, DC output voltage and rated output voltage given value, as well as average active power and active power given value, the control quantity I is obtained through output voltage droop control. m3 ;

[0030] The control quantity I m1 ,I m2 and I m3 The current control signal is obtained after selection by the three-to-one switch.

[0031] As an optional implementation, frequency conversion or frequency conversion + width modulation control is performed according to the switch control signal, and soft switch control is implemented.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention adopts a single-stage high-frequency conversion topology structure, replacing Figure 1 The machine-side Boost converter and the grid-side PWM converter of the conventional typical direct-drive wind power system converter topology shown in the figure reduce one level of high-frequency conversion compared with the conventional two-level high-frequency conversion, thereby improving the power conversion efficiency.

[0034] (2) The present invention adopts an isolated resonant converter for power transmission, which can realize soft switching operation, and adopts a high-frequency transformer to realize electrical isolation and voltage boost, thereby reducing the volume and output current and improving the power conversion and transmission efficiency.

[0035] (3) The present invention uses a very small capacity capacitor to replace a large capacity electrolytic capacitor, which on the one hand eliminates the impact of the large capacity electrolytic capacitor on the system life and reduces the cost, and on the other hand improves the power factor on the machine side.

[0036] (4) The present invention utilizes the voltage step-up and voltage step-down characteristics of the resonant converter and controls the input current of the single-phase isolated DC / DC resonant conversion circuit to track its DC input voltage waveform through a current controller, thereby improving the power factor on the machine side.

[0037] (5) The present invention superimposes the DC input voltage differential feedback on the DC current feedback signal, which can effectively weaken the DC input voltage and current oscillation under light load.

[0038] (6) The present invention integrates the machine-side control and the grid-side control to realize the single-stage integrated control of direct-drive wind power generation. At the same time, only the input / output voltage and current of the converter need to be detected to realize the maximum power tracking control, constant power control and output voltage droop control, without the need to detect the rotor position or speed of the direct-drive wind turbine generator, thus simplifying the system design.

[0039] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0041] Figure 1 This is a topological diagram of the diode uncontrolled rectification + Boost converter of the existing direct-drive wind power system;

[0042] Figure 2 A topological structure diagram of a single-stage high-frequency converter provided in Example 1 of the present invention;

[0043] Figure 3 An embodiment of the isolated DC / DC resonant conversion circuit provided in Embodiment 1 of the present invention;

[0044] Figure 4 Another embodiment of the isolated DC / DC resonant conversion circuit provided in Embodiment 1 of the present invention;

[0045] Figure 5 A flow chart of a control method for a single-stage high-frequency converter provided in Embodiment 2 of the present invention;

[0046] Figure 6 for Figure 6 Flowchart of the integrated controller in;

[0047] Figure 7 for Figure 6 Flow chart of the constant power control method in;

[0048] Figure 8 for Figure 6 Flow chart of the output voltage droop control method in;

[0049] Fig. 9 for Figure 5 A flow chart of a current controller in;

[0050] Fig.10 for Fig. 9 Output voltage and current waveforms of high frequency DC / AC converter in control method;

[0051] Fig.11 for Figure 5 Flow chart of another current controller in;

[0052] Fig.12 for Fig.11 The control method is used in the high frequency DC / AC converter output voltage and current waveform diagram;

[0053] Among them, 1. input uncontrolled rectifier bridge, 2. isolated DC / DC resonant conversion circuit, 3. high-frequency DC / AC converter, 4. resonant network, 5. high-frequency isolation transformer, 6. output uncontrolled rectifier bridge, 7. integrated controller, 8. current controller, 9. maximum power tracking control, 10. constant power control, 11. output voltage droop control, 12. three-choice switch. DETAILED DESCRIPTION

[0054] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0055] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0056] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "include" and "comprise" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0057] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0058] Example 1

[0059] like Figure 1 The figure shows the topological structure of the diode uncontrolled rectification + Boost converter of the existing direct-drive wind power system. Figure 1 In the process, the machine side adopts diode uncontrolled rectification + Boost converter, the grid side adopts high-frequency fully controlled PWM converter, the intermediate DC bus adopts large-capacity electrolytic capacitors to maintain the DC voltage, the Boost converter realizes voltage boost and improves the power factor on the machine side to a certain extent. Figure 1 It adopts two-stage high-frequency conversion on the machine side and the grid side, with a large-capacity electrolytic capacitor C in the middle. dc .

[0060] Therefore, for Figure 1 The present embodiment provides a single-stage high-frequency converter for realizing efficient AC-DC power conversion of direct-drive wind power generation. Figure 2 As shown, it specifically includes: input uncontrolled rectifier bridge 1, absorption capacitor C s , isolated DC / DC resonant conversion circuit 2;

[0061] The AC input end of the input uncontrolled rectifier bridge 1 is used as the AC input end of the single-stage high-frequency converter, and the two DC output ends of the input uncontrolled rectifier bridge 1 are connected to the two DC input ends of the isolated DC / DC resonant conversion circuit 2 and connected to the absorption capacitor C s in parallel;

[0062] The two DC output terminals of the isolated DC / DC resonant conversion circuit 2 serve as DC output terminals of a single-stage high-frequency converter and are connected to a DC grid or a load.

[0063] As an optional implementation, the absorption capacitor C s Used to absorb the high-frequency switching voltage spike of the isolated DC / DC resonant conversion circuit 2, omitting the large-capacity electrolytic capacitor C dc .

[0064] The single-stage high-frequency converter proposed in this embodiment utilizes the step-up / step-down characteristics of the isolated DC / DC resonant conversion circuit to achieve input DC voltage step-up and current regulation, and replaces the single-stage high-frequency conversion circuit with Figure 2 The Boost converter and grid-side PWM converter in the system.

[0065] In this embodiment, if Figure 3 As shown, the isolated DC / DC resonant conversion circuit 2 includes a high-frequency DC / AC converter 3 , a resonant network 4 , a high-frequency isolation transformer 5 and an output uncontrolled rectifier bridge 6 .

[0066] Among them, the DC output end of the input uncontrolled rectifier bridge 2 is connected to the DC input end of the high-frequency DC / AC converter 3, the AC output end of the high-frequency DC / AC converter 3 is connected to the resonant network 4, the resonant network 4 is connected to the primary side of the high-frequency isolation transformer 5, the secondary side of the high-frequency isolation transformer 5 is connected to the AC input end of the output uncontrolled rectifier bridge 6, and the DC output end of the output uncontrolled rectifier bridge 6 serves as the DC output end of the isolated DC / DC resonant conversion circuit 2.

[0067] As an optional implementation, Figure 3 In the embodiment, the resonant network 4 adopts an LLC resonant network; wherein the inductor L m represents the excitation inductance of the high-frequency isolation transformer 5, and the inductance L r is the resonant inductor, which may be the leakage inductance of the high-frequency isolation transformer 5 .

[0068] As an optional implementation, Figure 3 In the embodiment, the high frequency DC / AC converter 3 adopts a half-bridge, full-bridge, three-level or multi-level structure.

[0069] In this embodiment, if Figure 4 As shown, the isolated DC / DC resonant conversion circuit 2 includes a high-frequency DC / AC converter 3 , a resonant network 4 , a high-frequency isolation transformer 5 and an output uncontrolled rectifier bridge 6 .

[0070] Among them, the DC output end of the input uncontrolled rectifier bridge 2 is connected to the DC input end of the high-frequency DC / AC converter 3, the AC output end of the high-frequency DC / AC converter 3 is connected to the primary side of the high-frequency isolation transformer 5, the secondary side of the high-frequency isolation transformer 5 is connected to the resonant network 4, the resonant network 4 is connected to the AC input end of the output uncontrolled rectifier bridge 6, and the DC output end of the output uncontrolled rectifier bridge 6 serves as the DC output end of the isolated DC / DC resonant conversion circuit 2.

[0071] As an optional implementation, Figure 4 In the embodiment, the resonant network 4 adopts an LC resonant network; wherein the inductor L m represents the excitation inductance of the high-frequency isolation transformer 5, and the inductance L r is the resonant inductor, which may be the leakage inductance of the high-frequency isolation transformer 5 .

[0072] As an optional implementation, Figure 4 In the embodiment, the high frequency DC / AC converter 3 adopts a half-bridge, full-bridge, three-level or multi-level structure.

[0073] It is understandable that the resonant network 4 is not limited to the above Figure 3 and Figure 4 The LLC resonant network and LC resonant network are given.

[0074] Example 2

[0075] This embodiment provides a control method for the single-stage high-frequency converter described in Embodiment 1, such as Figure 5 As shown, including:

[0076] Step 1): Detect the DC input voltage U of the isolated DC / DC resonant conversion circuit dc , DC input current i dc And DC output voltage U out .

[0077] Step 2): The detected DC input voltage U of the isolated DC / DC resonant conversion circuit is dc , DC input current i dc And DC output voltage U out , after being processed by the integrated controller 7, the current control signal I is obtained m .

[0078] Step 3): The DC input voltage U of the isolated DC / DC resonant conversion circuit is detected. dc Perform unitization processing to obtain the DC input voltage unitization signal u uint .

[0079] The unitization process is as follows: the DC input voltage U of the isolated DC / DC resonant conversion circuit obtained by detection is converted intodc Divide by its rated DC voltage U dcN , to perform unitization processing and obtain the input voltage unitization signal u uint ,Right now:

[0080] Step 4): The detected DC input current i of the isolated DC / DC resonant conversion circuit is dc Subtract the DC input voltage U dc After the signal is processed by the high-pass filter HF1, the DC input current feedback signal I is obtained. dc ,Right now:

[0081]

[0082] In the formula, represents the transfer function of the high-pass filter HF1, τ d is the differential time constant, T d is the inertia time constant.

[0083] Step 5): Convert the DC input voltage to a unit signal u uint With the current control signal I m The product of is used as the DC input current reference signal Right now:

[0084]

[0085] Step 6): The obtained DC input current feedback signal I dc and DC input current reference signal After being processed by the current controller 8, a switch control signal Ks of the isolated DC / DC resonant conversion circuit is obtained, thereby performing frequency conversion or frequency conversion + width modulation control and realizing soft switching control.

[0086] In this embodiment, if Figure 6 As shown, the implementation scheme of the integrated controller 7 specifically includes:

[0087] Step 2-1): The DC input voltage U of the isolated DC / DC resonant conversion circuit is detected. dc and the DC input current i dc The average values ​​of the DC input voltages are obtained by filtering through low-pass filters LF1 and LF2 respectively. and the average DC input current Then according to and The product of gets the average active power P, that is:

[0088] Step 2-2): Based on the average DC input voltage Average DC input current And the average active power P, after the maximum power tracking control 9, the control quantity I is obtained m1 ;

[0089] According to the average DC input voltage Average active power P and active power set value P * , after constant power control 10, the control quantity I is obtained m2 ;

[0090] According to the average DC input voltage DC output voltage U out and rated output voltage given value As well as the average active power P and the active power given value P * , after the output voltage droop control 11, the control quantity I is obtained m3 .

[0091] Step 2-3): The obtained control amount I m1 ,I m2 and I m3 After the three-to-one switch 12 selects, the current control signal I is obtained. m .

[0092] Among them, the total active power given value P * and rated output voltage given value Given by the upper system.

[0093] Among them, the maximum power point tracking (MPPT) control can adopt the existing MPPT algorithms, such as the conductance increment method, the interference observation method, etc.

[0094] In this embodiment, if Figure 7 As shown, the implementation scheme of the constant power control 10 specifically includes:

[0095] Step 1): Compare the calculated average active power P with the active power given value P * After being processed by the power regulator W1, the control quantity U W1 .

[0096] Step 2): Set the control quantity U W1 Divide by the rated DC voltage U dcN , then multiply by the average DC input voltage Get the control quantity I m2 ,Right now

[0097] Wherein, the power regulator W1 can be a PI regulator.

[0098] In this embodiment, if Figure 8 As shown, the implementation scheme of the output voltage droop control 11 can realize the output voltage droop control with droop characteristics and inertia, specifically including:

[0099] Step 1): Set the rated output voltage to a given value Subtract the total output voltage U out After and droop coefficient K u The product of the active power given value P * The difference between the average active power P (P * -P), and then the output reference voltage is obtained after passing through the integrator G1 Right now J u is the integration time constant.

[0100] Step 2): Calculate the output voltage U out With output reference voltage After being processed by the voltage regulator W2, the control quantity U W2 .

[0101] Step 3): Set the control quantity U W2 Divide by the rated DC voltage U dcN , then multiply by the average DC input voltage Get the control quantity I m3 ,Right now

[0102] Wherein, the voltage regulator W2 may be a PI regulator.

[0103] In this embodiment, if Fig. 9 As shown, the implementation scheme of the current controller 8 can realize the tracking control of the input DC current through frequency conversion control, which specifically includes:

[0104] Step 6-1): The obtained DC input current feedback signal I dc and DC input current reference signal After being processed by the current regulator W3, the switching cycle signal T of the high-frequency DC / AC converter 2 is obtained. s .

[0105] Step 6-2): Based on the switching cycle signal T s The switching cycle T is generated by the switch signal generating unit UT1. s The square wave pulse signal is output and the switch control signal Ks is output.

[0106] For Figure 3 In the embodiment shown, the switching period T s The maximum value of is limited to the LLC circuit output no-load resonant period, that is, To achieve soft switching operation of the converter;

[0107] For Figure 3 In the embodiment shown, the switching period T s The maximum value of is limited to the LC circuit output no-load resonant period, that is, To achieve soft switching operation of the converter.

[0108] Wherein, the current regulator W3 can be a PI regulator.

[0109] Fig.10 Given the corresponding Fig. 9 The high-frequency DC / AC converter output voltage and current waveform of the current controller. In the figure, U T is the output voltage, i T is the output current, T s is the switching cycle.

[0110] In this embodiment, if Fig.11 As shown, another implementation scheme of the current controller 8 is also provided, which can realize the tracking control of the input DC current through frequency conversion + width modulation control, specifically including:

[0111] Step 6-1): The obtained DC input current feedback signal I dc and DC input current reference signal After being processed by the current regulator W4, the high-frequency DC / AC converter output voltage pulse width signal T is obtained. pw .

[0112] Step 6-2): The high frequency DC / AC converter output voltage U T With the output current i T The phase difference time signal T q With its reference signal After being processed by the phase regulator W5, the switching cycle signal T of the high-frequency DC / AC converter is obtained. s , reference signal It is greater than the dead time of the switching signal and can be twice the dead time.

[0113] Step 6-3): Based on the switching cycle signal T s And the output voltage pulse width signal T pw The switch signal generating unit UT2 outputs the switch control signal Ks, which makes the high frequency DC / AC converter output voltage U T The switching period is T s and the pulse width is T pw The voltage pulse makes the output current i T Phase time lag T q .

[0114] For Figure 3 In the embodiment shown, the switching period T s The maximum value of is limited to the LLC circuit output no-load resonant period, that is, To achieve soft switching operation of the converter;

[0115] For Figure 4 In the embodiment shown, the switching period T s The maximum value of is limited to the LC circuit output no-load resonant period, that is, To achieve soft switching operation of the converter.

[0116] Wherein, the current regulator W4 and the phase regulator W5 can be PI regulators.

[0117] Fig.12 Given the corresponding Fig.11 The high-frequency DC / AC converter output voltage and current waveform of the current controller 8, in which U T is the output voltage, i T is the output current, T s is the switching period, T pw is the voltage pulse width, T q is the output voltage U T With the output current i T The phase difference time signal.

[0118] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A control method for a single-stage high-frequency converter, characterized in that: include: Obtaining a DC input voltage, a DC input current and a DC output voltage of an isolated DC / DC resonant conversion circuit, and thereby obtaining a current control signal; After the DC input voltage is normalized, it is combined with the current control signal to obtain a DC input current reference signal; Obtaining a DC input current feedback signal according to a filtered signal of the DC input voltage and the DC input current; According to the DC input current reference signal and the DC input current feedback signal, a switch control signal for controlling the operation of the isolated DC / DC resonant conversion circuit is obtained; The filtered signal of the DC input voltage after filtering is: Subtract the filtered signal from the DC input current to obtain a DC input current feedback signal; In the formula, is the transfer function of the high-pass filter, τ d is the differential time constant, T d is the inertia time constant, U dc is the DC input voltage; The unitized signal u of the DC input voltage uint With the current control signal I m The product of is used as the DC input current reference signal; The single-stage high-frequency converter comprises: an input uncontrolled rectifier bridge, an absorption capacitor and an isolated DC / DC resonant conversion circuit; The AC input end of the input uncontrolled rectifier bridge serves as the AC input end of the single-stage high-frequency converter, and the DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the isolated DC / DC resonant conversion circuit and is connected in parallel with the absorption capacitor; the DC output end of the isolated DC / DC resonant conversion circuit serves as the DC output end of the single-stage high-frequency converter and is connected to an external device.

2. A control method for a single-stage high-frequency converter as claimed in claim 1, characterized in that: The isolated DC / DC resonant conversion circuit includes a high-frequency DC / AC converter, a resonant network, a high-frequency isolation transformer and an output uncontrolled rectifier bridge; The DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the high-frequency DC / AC converter, the AC output end of the high-frequency DC / AC converter is connected to the resonant network, the resonant network is connected to the primary side of the high-frequency isolation transformer, the secondary side of the high-frequency isolation transformer is connected to the AC input end of the output uncontrolled rectifier bridge, and the DC output end of the output uncontrolled rectifier bridge serves as the DC output end of the isolated DC / DC resonant conversion circuit.

3. A control method for a single-stage high-frequency converter as claimed in claim 2, characterized in that: The resonant network adopts an LLC resonant network.

4. The control method of a single-stage high-frequency converter according to claim 1, characterized in that: The isolated DC / DC resonant conversion circuit includes a high-frequency DC / AC converter, a resonant network, a high-frequency isolation transformer and an output uncontrolled rectifier bridge; The DC output end of the input uncontrolled rectifier bridge is connected to the DC input end of the high-frequency DC / AC converter, the AC output end of the high-frequency DC / AC converter is connected to the primary side of the high-frequency isolation transformer, the secondary side of the high-frequency isolation transformer is connected to the resonant network, the resonant network is connected to the AC input end of the output uncontrolled rectifier bridge, and the DC output end of the output uncontrolled rectifier bridge serves as the DC output end of the isolated DC / DC resonant conversion circuit.

5. A control method for a single-stage high-frequency converter as claimed in claim 4, characterized in that: The resonant network adopts an LC resonant network.

6. A control method for a single-stage high-frequency converter as claimed in claim 2 or 4, characterized in that: The high frequency DC / AC converter adopts a half-bridge, full-bridge, three-level or multi-level structure.

7. The control method of a single-stage high-frequency converter according to claim 1, characterized in that: The process of obtaining the current control signal includes: The DC input voltage and the DC input current are filtered to obtain an average DC input voltage and an average DC input current, and the average active power is obtained according to the product of the average DC input voltage and the average DC input current. According to the average value of DC input voltage, average value of DC input current and average active power, the control quantity I is obtained through maximum power tracking control. m1 ; According to the average value of DC input voltage, average active power and given value of active power, the control quantity I is obtained through constant power control. m2 ; According to the average value of DC input voltage, DC output voltage and rated output voltage given value, as well as average active power and active power given value, the control quantity I is obtained through output voltage droop control. m3 ; The control quantity I m1 ,I m2 and I m3 The current control signal is obtained after selection by the three-to-one switch.

8. The control method of a single-stage high-frequency converter according to claim 1, characterized in that: Frequency conversion or frequency conversion + width modulation control is performed according to the switch control signal, and soft switching control is realized.

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