Modulation method and system for improving test power supply efficiency of current transformer
By establishing a time-domain model and dynamically adjusting the phase shift angle, the efficiency degradation problem of LLC resonant converter under low-frequency and light-load conditions was solved, achieving higher overall conversion efficiency and power output capability.
Patent Information
- Application Number
- CN202511357239.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-22
- Publication Date
- 2025-12-12
AI Technical Summary
LLC resonant converters experience a significant decrease in efficiency under low-frequency, light-load conditions. Traditional modulation strategies cannot effectively regulate output power, leading to increased switching losses and core losses.
A time-domain model is established to determine the operating status of the LLC resonant converter by detecting its output load and operating frequency. The phase shift angle is dynamically adjusted under low-frequency light load conditions to avoid entering the low-frequency light load mode and reduce switching losses and core losses.
The overall conversion efficiency of the LLC resonant converter under low-frequency and light-load conditions has been improved, and the resonant characteristics and power output capability have been optimized.
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Figure CN121124571A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of power electronic converters, in particular to a modulation method and system for improving the efficiency of a current transformer test power supply. BACKGROUND
[0002] With the gradual maturity of high-voltage direct current transmission technology, the problems of line loss, voltage step drop, voltage fluctuation, and power grid harmonics of alternating current distribution network are gradually replaced by direct current distribution network. Direct current distribution network has the advantages of small line loss, high power supply reliability, no phase and frequency control, no reactive power and alternating current charging current, easy access to distributed power supply and energy storage devices, and environmental protection.
[0003] The current transformer is a sensor that can sense the measured voltage and convert it into a usable output signal, and is widely used in direct current distribution network. At present, a large number of power semiconductor devices are applied to the field of electric energy conversion. The switching power supply has the advantages of smaller size, smaller output current ripple, faster dynamic response speed, and can realize higher power density, and is suitable for high-voltage and high-power occasions. Therefore, power electronic technology can be applied to the current transformer test power supply. The resonant converter has the advantages of simple structure, high efficiency, current and voltage waveform close to sine wave, wide input voltage range, and easy magnetic integration, and has been widely used in the calibration power supply of high-voltage direct current transformer.
[0004] The working principle of LLC resonant converter is based on the resonance phenomenon. Zero voltage switching (ZVS) and zero current switching (ZCS) are realized through the resonant network (including resonant inductance and resonant capacitance), so as to reduce the switching loss and improve the overall efficiency of the converter. However, in practical application, the efficiency of LLC resonant converter often faces the problem of significant decline under low-frequency light load conditions. This is mainly due to the fact that under light load conditions, the resonant capacitor is not fully charged, the excitation current and resonant current peak value are large, resulting in increased switching loss and magnetic core iron loss. In addition, the traditional modulation strategy cannot effectively regulate the output power under light load conditions, resulting in large power loss of the converter under light load.
[0005] Therefore, it is particularly important to develop a new low-frequency light load modulation strategy. The ideal modulation strategy should not only be able to optimize the working efficiency of LLC resonant converter under light load conditions, but also have the characteristics of simplicity, practicality and easy implementation. Such a strategy should be able to reduce the switching frequency while improving the resonant characteristics and power output capability, thereby effectively improving the overall conversion efficiency under low-frequency light load conditions. SUMMARY
[0006] In order to solve the problems existing in the prior art, the present application proposes a modulation method for improving the efficiency of a current transformer test power supply.
[0007] The technical scheme of the present application is as follows: In one aspect, the present application provides a modulation method for improving the efficiency of a current transformer test power supply, and the specific steps include: Based on the primary side resonant capacitor of the LLC resonant converter u Cr1 , the primary side resonant inductance current i Lr1 , and the excitation inductance current i m A time domain model is established, and a time domain expression of the LLC resonant converter in a single phase-shift mode is derived using a time domain analysis method, and then the size of the phase-shift angle of the LLC resonant converter in a low-frequency light-load working mode is calculated by combining the modal time domain equation; When the LLC resonant converter is working, the output load and working frequency of the LLC resonant converter are detected, and the working state of the LLC resonant converter is judged; When the output load of the LLC resonant converter is lower than the light-load threshold, and the working frequency is less than the low-frequency threshold, the LLC resonant converter automatically enters a low-frequency light-load running mode; When the LLC resonant converter enters the low-frequency light-load running mode, the size of the phase-shift angle is adjusted according to the time domain model, so that the LLC resonant converter is out of the low-frequency light-load running mode.
[0008] As a preferred embodiment, the topology structure of the LLC resonant converter includes a switching tube S 1– S 8, an anti-parallel diode D S1 – D S8 , and a parasitic capacitor C oss1 – C oss8 ; a primary side resonant inductor L r1 , a primary side resonant capacitor C r1 , a transformer excitation inductor L m , a transformer with a turn ratio of n :1, an output capacitor C s , a direct current input voltage U in , a direct current output voltage U o , and an output resistance R ; a resonant inductor L r1 , a resonant capacitor C r1 , and a transformer with a turn ration The transformer of claim 1 constitutes a resonant cavity of an LLC resonant converter; Wherein, the positive pole of the direct current input voltage U in is connected with the source of the primary side switch tube S 1, S 3; the negative pole of the direct current input voltage U in is connected with the drain of the primary side switch tube S 2, S 4; the output capacitor C s is connected in parallel with the output resistor R .
[0009] As a preferred embodiment, the working parameters of the LLC resonant converter include the series resonant frequency L r1 and the characteristic impedance of the LLC resonant converter primary side resonant inductance C r1 and resonant capacitance f r , and the specific calculation method is as follows: ; In the formula, L r1 is the primary side resonant inductance, C r1 is the primary side resonant capacitance.
[0010] As a preferred embodiment, the time domain model is established based on the primary side resonant capacitance u Cr1 , the primary side resonant inductance current i Lr1 and the excitation inductance current i m of the LLC resonant converter, and the time domain expression of the LLC resonant converter single phase shift mode is derived by using the time domain analysis method, which is specifically: ; U 1= U in ; U 2= nU o ; i L1 = i Lr1 ; u C1 = u Cr1 ; In the formula, the light load working mode can be divided into P, O, and OO modes, t 0 is the initial time of the P mode; ω r is the angular frequency of the resonant converter, i m is the excitation current t 0) is the value of the resonant capacitor voltage i m at the time t 0. u C2 is the value of the resonant capacitor voltage t 0) is the secondary side resonant capacitor voltage u C2 at the time t 0.
[0011] As a preferred embodiment, the step of calculating the phase shift angle of the LLC resonant converter in the low-frequency light load working mode based on the modal time domain equation comprises the following steps:
[0012] wherein D is the phase shift angle, D set is the phase shift angle threshold of the LLC resonant converter in the low-frequency light load working mode.
[0013] On the other hand, the present application provides a modulation system for improving the efficiency of a current transformer test power supply, comprising: a phase shift angle range calculation module, which calculates the phase shift angle range of the LLC resonant converter based on the resonant capacitor voltage u Cr1 , the resonant inductor current i Lr1 , and the excitation inductor current i m establishes a time domain model, uses a time domain analysis method to derive the time domain expression of the LLC resonant converter in the single phase shift mode, and calculates the phase shift angle of the LLC resonant converter in the low-frequency light load working mode based on the modal time domain equation; a working state detection module, which detects the output load and working frequency of the LLC resonant converter when the LLC resonant converter is working, and judges the working state of the LLC resonant converter; a low-frequency load cut-in module, which automatically enters the low-frequency light load working mode when the output load of the LLC resonant converter is lower than the light load threshold and the working frequency is lower than the low-frequency threshold; a low-frequency load cut-out module, which adjusts the phase shift angle based on the time domain model when the LLC resonant converter enters the low-frequency light load working mode, so that the LLC resonant converter exits the low-frequency light load working mode.
[0014] In another aspect, the present application provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the modulation method for improving the efficiency of a current transformer test power supply according to any one of the embodiments of the present application when executing the program.
[0015] In another aspect, the present application provides a computer readable storage medium having a computer program stored thereon, wherein the program, when executed by a processor, implements the modulation method for improving the efficiency of a current transformer test power supply according to any one of the embodiments of the present application.
[0016] The present application has the following beneficial effects: 1. The present application creates a time domain model to judge the phase shift angle range of the LLC resonant converter in a low-frequency light load state, and dynamically adjusts the phase shift angle according to the range, so as to ensure that the working state of the LLC resonant converter does not enter the low-frequency light load mode, reduce the switching loss and magnetic core loss, and improve the efficiency of the LLC resonant converter. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 The circuit diagram of the LLC resonant converter; Figure 2 The working waveform diagram of the low-frequency traditional modulation method of the LLC resonant converter; Figure 3 The working waveform diagram of the low-frequency modulation method of the LLC resonant converter of the present application; Figure 4 The analysis and comparison diagram of the power loss of the LLC resonant converter of the present application and the power loss of the traditional method; Figure 5 The working framework schematic diagram of the load shedding process of the LLC resonant converter; Figure 6 The simulation working waveform diagram of the load shedding process of the LLC resonant converter. DETAILED DESCRIPTION
[0018] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0019] It should be understood that the step numbers used herein are only for the convenience of description, and are not limited to the execution sequence of the steps.
[0020] It is to be understood that the terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting thereof. As used in the description of the application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
[0021] The terms "including" and "comprising" as used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.
[0022] The term "and / or" means any combination of one or more of the associated listed items and all possible combinations thereof.
[0023] Embodiment One: A modulation method for improving the efficiency of a current transformer test power supply, the specific steps comprising: Based on the primary side resonant capacitor of the LLC resonant converter u Cr1 , the primary side resonant inductance current i Lr1 , and the excitation inductance current i m A time domain model is established, and the time domain expression of the LLC resonant converter in the single phase shift mode is derived using the time domain analysis method. Then, the size of the phase shift angle of the LLC resonant converter in the low-frequency light-load working mode is calculated by combining the modal time domain equation; When the LLC resonant converter is working, the output load and working frequency of the LLC resonant converter are detected, and the working state of the LLC resonant converter is judged; When the output load of the LLC resonant converter is lower than the light-load threshold value, and the working frequency is less than the low-frequency threshold value, the LLC resonant converter automatically enters the low-frequency light-load running mode; When the LLC resonant converter enters the low-frequency light-load running mode, the size of the phase shift angle is adjusted according to the time domain model, so that the LLC resonant converter is out of the low-frequency light-load running mode.
[0024] As a preferred embodiment of the present embodiment, the topology structure of the LLC resonant converter comprises a switch tube S 1– S 8, an anti-parallel diode D S1 – D S8 , and a parasitic capacitor C oss1 – C oss8 ; a primary side resonant inductance Lr1 Primary side resonant capacitor C r1 Transformer magnetizing inductance L m Turns ratio is n :1 transformer, output capacitor C s DC input voltage U in DC output voltage U o and output resistance R Resonant inductor L r1 resonant capacitor C r1 and turns ratio is n A 1-type transformer forms the resonant cavity of the LLC resonant converter; Among them, DC input voltage U in The positive terminal is simultaneously connected to the original side switch transistor. S 1. S The sources of 3 are connected; DC input voltage U in The negative terminal is simultaneously connected to the primary side switch transistor. S 2. S The drains of 4 are connected; the output capacitor C s With output resistance R in parallel.
[0025] In this embodiment, the circuit diagram of the LLC resonant converter is as follows: Figure 1 As shown.
[0026] In a preferred embodiment of this invention, the operating parameters of the LLC resonant converter include the primary-side resonant inductance of the LLC resonant converter. L r1 and resonant capacitor C r1 Series resonant frequency f r The characteristic impedance is calculated using the following method: ; In the formula, L r1 It is the primary side resonant inductor. C r1 This is the primary side resonant capacitor.
[0027] As a preferred embodiment of this example, the primary-side resonant capacitor of the LLC resonant converter... u Cr1 Primary side resonant inductor current iLr1 and excitation inductance current i m The time domain model is established, and the time domain expression of the LLC resonant converter in the single phase shift mode is derived by using the time domain analysis method. ; U 1= U in ; U 2= nU o ; i L1 = i Lr1 ; u C1 = u Cr1 ; In the formula, the light load working mode can be divided into P, O and OO modes, t 0 is the initial time of the P mode; ω r is the angular frequency of the resonant converter, i m ( t 0) is the value of the excitation current i m at the time t 0, u C2 ( t 0) is the value of the resonant capacitor voltage u C2 at the time t 0.
[0028] In this embodiment, in order to simplify the circuit and facilitate calculation, the resonant parameters of the LLC converter should meet the following conditions: L 1= L 2= L r1 = n 2 L r2 and C 1= C 2= C r1 = C r2 / n 2 . The resonant current and the resonant voltage should meet: i L1 = i Lr1 ,i L2 = i Lr1 / n 2 、 u C1 = u Cr1 and u C2 = n 2 u Cr1 . The input and output voltages should satisfy: U 1= U in and U 2= nU o . The light load modulation strategy modes can be defined as P, O, OO modes: When the LLC resonant converter works in P mode, the normalized expressions of i L1 , i L2 , u C1 , u C2 are as follows:
[0029] The excitation current in O mode under low frequency light load modulation strategy is assumed to be almost the same as that in P mode, as follows:
[0030] where, i m ( t 1) is the excitation current i m at t 1 moment.
[0031] The expression of OO mode under low frequency light load modulation strategy is as follows:
[0032] where, i m ( t 0) is the excitation current i m at t 0 moment, i m ( t 2) is the excitation current i m at t 2 moment,i m ( t 3) is the excitation current i m At t 3, the value of t 2 / t 3 is the time when the OO mode operates.
[0033] The working waveform of the LLC resonant converter low-frequency conventional modulation method is as shown in Figure 2 , and the working waveform of the LLC resonant converter low-frequency modulation method of the present scheme is as shown in Figure 3 ; As a preferred embodiment of the present embodiment, the step of calculating the phase-shifting angle size of the LLC resonant converter for the low-frequency light-load working mode based on the modal time-domain equation is specifically:
[0034] wherein D is the phase-shifting angle, D set is the phase-shifting angle threshold of the LLC resonant converter in the low-frequency light-load working mode.
[0035] In the present embodiment, the phase-shifting angle under low-frequency light load is related to the load and the frequency size, and the calculated phase-shifting angle D is usually less than 0.1.
[0036] In the actual test process, the analysis comparison of the power loss of the present scheme and the conventional method is as shown in Figure 4 , based on the working state of the real-time LLC resonant converter, the load and the frequency of the LLC resonant converter are adjusted, and then the frequency conversion and phase-shifting operation are realized, and the control process is as shown in Figure 5 , the load shedding process of the LLC resonant converter is simulated, and the simulation waveform diagram is as shown in Figure 6 .
[0037] Embodiment Two: A modulation system for improving the efficiency of a current transformer test power supply, comprising: a phase-shifting angle range calculation module, which is based on the resonant capacitance u Cr1 , the resonant inductance current i Lr1 and the excitation inductance current i m establishes a time-domain model, uses a time-domain analysis method to derive the time-domain expression of the LLC resonant converter in the single phase-shifting mode, and then calculates the phase-shifting angle size of the LLC resonant converter for the low-frequency light-load working mode based on the modal time-domain equation. The working state detection module detects the output load and working frequency of the LLC resonant converter when the LLC resonant converter works, and judges the working state of the LLC resonant converter; The low-frequency load cut-in module is used for automatically entering the LLC resonant converter into a low-frequency light-load operation mode when the output load of the LLC resonant converter is lower than a light-load threshold and the working frequency is less than a low-frequency threshold. The low-frequency load cut-out module is used for adjusting the phase shift angle according to a time domain model when the LLC resonant converter enters the low-frequency light-load operation mode, so that the LLC resonant converter is out of the low-frequency light-load operation mode.
[0038] The above-mentioned embodiments are only examples of the present application, and do not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation, or direct or indirect application in other related technical fields, which is made by using the content of the present application specification and drawings, is also included in the patent protection scope of the present application.
Claims
1. A modulation method for improving the efficiency of a current transformer test power supply, characterized in that, The specific steps include: Based on the primary-side resonant capacitor of the LLC resonant converter u Cr1 Primary side resonant inductor current i Lr1 and excitation inductor current i m A time-domain model is established, and the time-domain expression of the single-phase-shift mode of the LLC resonant converter is derived using time-domain analysis methods. Then, the phase-shift angle of the LLC resonant converter in low-frequency light-load operating mode is calculated by combining the modal time-domain equation. When the LLC resonant converter is working, the output load and operating frequency of the LLC resonant converter are detected, and the operating status of the LLC resonant converter is determined. When the output load of the LLC resonant converter is lower than the light load threshold and the operating frequency is lower than the low frequency threshold, the LLC resonant converter automatically enters the low frequency light load operation mode. When the LLC resonant converter enters the low-frequency light-load operation mode, the phase shift angle is adjusted according to the time-domain model, so that the LLC resonant converter can exit the low-frequency light-load operation mode.
2. The modulation method for improving the efficiency of a current transformer test power supply according to claim 1, characterized in that, The topology of the LLC resonant converter includes switching transistors. S 1 – S 8. Anti-parallel diode D S1 – D S8 and parasitic capacitance C oss1 – C oss8 Primary side resonant inductor L r1 Primary side resonant capacitor C r1 Transformer magnetizing inductance L m Turns ratio is n :1 transformer, output capacitor C s DC input voltage U in DC output voltage U o and output resistance R Resonant inductor L r1 resonant capacitor C r1 and turns ratio is n A 1-type transformer forms the resonant cavity of the LLC resonant converter; Among them, DC input voltage U in The positive terminal is simultaneously connected to the original side switch transistor. S 1. S The sources of 3 are connected; DC input voltage U in The negative terminal is simultaneously connected to the primary side switch transistor. S 2. S The drains of 4 are connected; the output capacitor C s With output resistance R in parallel.
3. The modulation method for improving the efficiency of a current transformer test power supply according to claim 2, characterized in that, The operating parameters of the LLC resonant converter include the primary-side resonant inductance of the LLC resonant converter. L r1 and resonant capacitor C r1 Series resonant frequency f r The characteristic impedance is calculated using the following method: ； In the formula, L r1 It is the primary side resonant inductor. C r1 This is the primary side resonant capacitor.
4. The modulation method for improving the efficiency of a current transformer test power supply according to claim 2, characterized in that, The primary-side resonant capacitor based on the LLC resonant converter u Cr1 Primary side resonant inductor current i Lr1 and excitation inductor current i m A time-domain model is established, and the time-domain expression of the single-phase-shift mode of the LLC resonant converter is derived using time-domain analysis methods as follows: ； U 1 = U in ； U 2 = nU o ； i L1 = i Lr1 ； u C1 = u Cr1 ； In the formula, the light-load operating mode can be divided into three modes: P, O, and OO. t 0 represents the initial moment of the P mode; ω r The angular frequency of the resonant converter. i m ( t 0) is the excitation current. i m exist t The value at time 0, u C2 ( t 0) is the voltage of the secondary side resonant capacitor. u C2 exist t The value at time 0.
5. A modulation method for improving the efficiency of a current transformer test power supply according to claim 1, characterized in that, The specific steps for calculating the phase shift angle of the LLC resonant converter in low-frequency, light-load operating mode using the modal time-domain equations are as follows: Where D is the phase shift angle, D set The phase shift angle threshold for the LLC resonant converter in low-frequency, light-load operating mode.
6. A modulation system for improving the efficiency of a current transformer test power supply, characterized in that, include: The phase shift angle range calculation module is based on the primary-side resonant capacitor of the LLC resonant converter. u Cr1 Primary side resonant inductor current i Lr1 and excitation inductor current i m A time-domain model is established, and the time-domain expression of the single-phase-shift mode of the LLC resonant converter is derived using time-domain analysis methods. Then, the phase-shift angle of the LLC resonant converter in low-frequency light-load operating mode is calculated by combining the modal time-domain equation. The operating status detection module detects the output load and operating frequency of the LLC resonant converter when it is working, and determines the operating status of the LLC resonant converter. The low-frequency load switching module automatically switches the LLC resonant converter into low-frequency light-load operation mode when the output load of the LLC resonant converter is lower than the light-load threshold and the operating frequency is lower than the low-frequency threshold. The low-frequency load cut-out module adjusts the phase shift angle according to the time-domain model when the LLC resonant converter enters the low-frequency light-load operation mode, so that the LLC resonant converter can exit the low-frequency light-load operation mode.
7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements a modulation method for improving the efficiency of a current transformer test power supply as described in any one of claims 1 to 5.
8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements a modulation method for improving the efficiency of a test power supply for a current transformer as described in any one of claims 1 to 5.