Low power accurate output device and method based on phase-shift angle and target phase angle cooperation

Abstract

The application discloses a low-power accurate output device and method based on phase-shifting angle and target phase angle cooperation. The device comprises a ground end phase-shifting full-bridge inverter, a double-sided LCC resonant network, a power regulation loop, a frequency tracking loop and a controller; the ground end phase-shifting full-bridge inverter is used for outputting high-frequency alternating current, the power regulation loop calculates a ground end phase-shifting angle p , and the frequency tracking loop calculates a target phase angle θ according to resonant current phase information; the method is as follows: the power regulation loop calculates φ p in real time, judges whether the phase-shifting angle lower limit φ min based on ZVS condition is reached, adjusts φ p to regulate power if φ min ≥ φ p , fixes φ p as φ min if φ p < φ min , and the controller controls the frequency tracking loop to increase the target phase angle θ, so that the system actual phase angle θ c is offset to the inductive side, active power is reduced, and reactive power is increased; the target phase angle θ is cyclically regulated to realize low-power accurate control. The application belongs to the technical field of high-power wireless charging.

Description

Technical Field

[0001] This invention relates to the field of power electronic systems, and more particularly to a low-power precision output device and method based on the coordination of phase shift angle and target phase angle. Background Technology

[0002] Wireless charging systems are contactless power transfer devices based on the principle of magnetic coupling resonance. Due to their high efficiency and ease of use, they have been widely used in electric vehicles, consumer electronics, and other fields. A typical high-power wireless charging system mainly consists of a ground-side transmitter and an on-vehicle receiver, which achieve wireless energy transfer through magnetic coupling coils. The transmitter generates an alternating magnetic field driven by a high-frequency inverter, while the receiver coil receives energy through electromagnetic induction and, after rectification and filtering, provides stable DC power to the vehicle load or battery.

[0003] In high-power wireless charging systems, phase-shifted full-bridge (PSFB) inverters are commonly used as the main power conversion topology to achieve efficient high-frequency AC output. However, unlike traditional wired high-power converters (such as phase-shifted full-bridge LLC resonant converters), the operation of wireless charging systems is strictly constrained by soft-switching conditions and resonant network characteristics. To ensure that the system maintains soft-switching characteristics such as zero-voltage switching (ZVS) over a wide load range and meets the energy exchange requirements of the resonant circuit, its phase shift angle usually needs to be maintained above a relatively high minimum value and cannot be arbitrarily reduced to zero. In practical applications, the phase shift angle range during normal system operation is typically limited to between 90° and 180°.

[0004] This characteristic presents a significant challenge to the system when a lower target output power is required. For example, in a wireless charging system with a rated power of 10kW, when the target output power is below 3kW, the system's power regulation capability is limited because the phase shift angle cannot be further reduced (i.e., it is "stuck" at the minimum allowable value, such as 90°), making it difficult to achieve accurate and stable low power output.

[0005] To extend the output power range of a system, various solutions have been proposed in existing technologies. A common approach is to introduce an additional DC-DC converter (such as an LLC resonant converter) in the front-end stage of the transmitter, indirectly controlling the output power by adjusting the inverter input voltage. However, this approach significantly increases system cost, size, and complexity, and the introduction of an additional power stage may affect overall reliability and efficiency.

[0006] Another approach is to add a buck DC-DC converter (such as a Buck converter) after the receiving stage to achieve impedance matching and regulate the output voltage. However, in high-power applications (such as those ranging from several kW to 10 kW), such converters need to withstand high currents, resulting in bulky inductors and complex heat dissipation structures, which are difficult to meet the requirements of vehicle space and lightweight design. Furthermore, automakers and customers generally find it unacceptable to integrate such a bulky and aesthetically pleasing additional device inside a vehicle. At the same time, the efficiency losses caused by multi-stage power conversion further limit the practicality of this solution.

[0007] Therefore, existing high-power wireless charging systems have the following main drawbacks when achieving low-power output:

[0008] 1. Limited low-power regulation capability: Due to the requirements of soft switching and resonant operation, the minimum phase shift angle of the phase-shifted full-bridge inverter is usually not too small (e.g., not less than 90°), which causes the system to lose the freedom of power regulation under light load and makes it difficult to stably output low power.

[0009] 2. Reliance on additional DC-DC converters, resulting in high cost and size: To extend the power range, existing solutions often add a front-end LLC or a rear-end Buck converter, which significantly increases the system cost and complexity; especially when adding high-power Buck circuits at the vehicle end, the inductor is large and difficult to lay out, making it difficult to meet the vehicle integration requirements.

[0010] 3. Multi-stage conversion reduces system efficiency: Introducing an additional DC-DC stage lengthens the power link, and losses at each stage are superimposed, resulting in a significant decrease in efficiency, especially under low-power conditions, thus affecting overall energy efficiency performance. Moreover, the control strategy becomes more complex.

[0011] 4. Ineffective utilization of reactive power regulation capability: Existing frequency tracking technology is mostly used for impedance matching and fails to combine phase control to actively regulate reactive power. It cannot achieve fine low-power output by decoupling active and reactive power while maintaining a large phase shift angle.

[0012] The aforementioned problems restrict the system's flexible operation across the entire power range. Therefore, there is an urgent need for a technical solution that can achieve wide-range power regulation without relying on additional hardware, solely through optimized control. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a low-power precision output device and method based on the coordination of phase shift angle and target phase angle, which can achieve wide-range power regulation without adding additional hardware and only by optimizing the control strategy.

[0014] The technical solution adopted in this invention is a low-power precision output device based on the coordination of phase shift angle and target phase angle, which is applied to a high-power wireless charging system using phase-shift full-bridge modulation. The device includes a ground-terminal phase-shift full-bridge inverter, a bilateral LCC resonant network, a power regulation loop, a frequency tracking loop, and a controller.

[0015] The output terminal of the ground-terminal phase-shifting full-bridge inverter is connected to the input terminal of the bilateral LCC resonant network, which is used to convert DC voltage into high-frequency AC power and input it into the bilateral LCC resonant network.

[0016] The power regulation loop is used to calculate the ground phase shift angle φ of the ground-terminal phase-shifted full-bridge inverter based on the system output voltage and output current. p ;

[0017] The frequency tracking loop is used to acquire the phase information of the resonant current in the bilateral LCC resonant network and calculate the target phase angle θ for frequency tracking.

[0018] The controller is connected to the power regulation loop and the frequency tracking loop respectively, and is used to determine φ. p Is it less than the lower limit φ of the phase shift angle set based on ZVS conditions? min If φ p ≥φ min Adjust φ through the power regulating ring p Adjust the output power; if φ p <φ min , fixed φ p For φ min Simultaneously, the frequency tracking loop is adjusted upwards by θ to make the actual phase angle of the system θ c Shifting towards the inductive side reduces active power.

[0019] Furthermore, the lower limit of the phase shift angle φ min The value of is determined by the ZVS condition of the ground-side phase-shifted full-bridge inverter, with a preferred value of 90°.

[0020] Furthermore, the frequency tracking loop acquires resonant current phase information through methods including zero-crossing detection, peak phase detection, resonant current orthogonal algorithm, or state observer, and the phase information is used to calculate the target phase angle θ.

[0021] Furthermore, the actual phase angle θ of the system c The equivalent impedance from the bilateral LCC resonant network to the load is determined, and θ c The phase angle is indirectly controlled by the target phase angle θ, meaning that changes in θ are transmitted to θ through the impedance matching process of the frequency tracking loop. c To achieve θ c The offset.

[0022] Furthermore, the output power P of the ground-terminal phase-shifted full-bridge inverter satisfies the following relationship:

[0023] P=[U in •U out •(1+cosφ p )] / (ωL rp •L rs ),

[0024] Among them U in U is the input voltage. out Where L is the output voltage, ω is the angular frequency, and L is the output voltage. rp L is the ground resonant inductor. rs For the resonant inductance at the vehicle end; φ p When fixed, P changes with θ adjustment, resulting in θ c It decreases due to the offset.

[0025] A method for achieving low-power, precise output based on the coordination of phase shift angle and target phase angle using the above-mentioned device, the method comprising the following steps:

[0026] S1. System startup: The ground-terminal phase-shifted full-bridge inverter outputs high-frequency AC power. The dual-sided LCC resonant network realizes energy transfer. The power regulation loop collects the output voltage and output current in real time and calculates the ground-terminal phase-shift angle φ. p ;

[0027] S2, Controller determines φ p Is it less than the lower limit of the phase shift angle φ? min If φ p ≥φ min Return to step S1 and adjust φ p Continue adjusting the output power; if φ p <φ min Perform step S3;

[0028] S3, the controller controls the φ of the ground-side phase-shifting full-bridge inverter. p Fixed as φ min Maintain ZVS conditions;

[0029] S4. The frequency tracking loop collects the resonant current phase information of the bilateral LCC resonant network and calculates the current target phase angle θ.

[0030] S5. The controller adjusts the frequency tracking loop upwards by a unit step size of θ, so that the actual phase angle θ of the system is... c Shifting towards the inductive side increases reactive power and reduces active power output;

[0031] S6. Real-time detection of whether the output power has reached the target low power value. If not, repeat steps S4 to S5. If it has, maintain the current θ and enter a stable output state.

[0032] S7. If further power reduction is required, repeat steps S4 to S6 to achieve continuous and precise adjustment in the low power range.

[0033] Furthermore, in step S5, the unit step adjustment of the target phase angle θ is 1° to 5°, which is determined according to the low power adjustment accuracy requirements; after θ is adjusted upward, the increase in reactive power and the decrease in active power of the system satisfy the following: the increase in reactive power is positively correlated with the increase in θ, and the decrease in active power is positively correlated with the increase in θ.

[0034] Furthermore, the ground-end phase shift angle φ p The conduction angle α of the full-bridge controlled rectifier circuit satisfies the relationship φ p =π-2α, where the range of α is 0<α≤π / 2; φ p Fixed as φ min At the same time, α is kept constant to avoid a decrease in the efficiency of the rectifier circuit due to α being too small.

[0035] Further, in step S1, the vehicle-end rectification method of the bilateral LCC resonant network includes either diode passive rectification or synchronous rectification; under both rectification methods, φ p Both the synergistic control mechanism with θ are effective and do not affect the low-power regulation accuracy.

[0036] The beneficial effects of this invention are:

[0037] 1. Achieving precise low-power adjustment: In this invention, when φ p Reaching φ min (e.g., at 90°), the controller adjusts the target phase angle θ upwards through the frequency tracking loop, so that the actual phase angle of the system is θ. c Shifting towards the inductive side alters the equivalent impedance of the resonant network, increasing reactive power and decreasing active power output, without requiring a change in φ. p To maintain ZVS conditions, this invention can achieve continuous and precise adjustment of the low-power segment of a high-power wireless charging system based on the coordination of phase shift angle and target phase angle, while meeting soft switching requirements, thus solving the adjustment failure problem caused by phase shift angle jamming in the prior art.

[0038] 2. Reduced system cost and size: This invention eliminates the need for an LLC converter in the front stage of the transmitter and a Buck converter in the back stage of the receiver. It achieves low-power precise output of a high-power wireless charging system based on the coordination of phase shift angle and target phase angle by optimizing the control strategy. This saves on the cost and installation space of additional hardware, improves the integration feasibility of the vehicle end, and meets the requirements of lightweight vehicle design.

[0039] 3. Improve system operating efficiency: This invention has no additional power stage, and the power link only includes "phase-shifted full-bridge inverter - bilateral LCC resonant network - load", which reduces the superposition of losses caused by multi-stage conversion. Especially under low power conditions, it avoids the conduction loss and switching loss of additional DC-DC converters, which can effectively improve the overall efficiency of high-power wireless charging system.

[0040] 4. Expanding the degree of freedom in power adjustment: This invention utilizes the target phase angle θ of the frequency tracking loop to control the actual phase angle θ of the system. c This achieves decoupling of active and reactive power—φ p When fixed, the active power output can be continuously changed by continuously adjusting θ, breaking through the limitation of single phase angle adjustment, and enabling the high-power wireless charging system based on the coordination of phase angle and target phase angle to have flexible adjustment capability within the rated power range. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a ground-side inverter that uses phase-shifted full-bridge modulation;

[0042] Figure 2 This is a control flow diagram of the method of the present invention;

[0043] Figure 3 The waveform and data display diagram of the process of precisely operating the power while keeping the conduction angle constant by adjusting the value of the target phase angle;

[0044] Figure 4 The waveform and data display diagram of the second process is shown, which involves adjusting the target phase angle to achieve precise operation of power while keeping the conduction angle constant.

[0045] Figure 5 The waveform and data display diagram of the third process is shown, which involves adjusting the target phase angle to achieve precise operation of power while keeping the conduction angle constant.

[0046] Figure 6 The waveform and data display diagram of the fourth process is shown below, which shows how to precisely operate the power while keeping the conduction angle constant by adjusting the value of the target phase angle.

[0047] Figure 7 The waveform and data display diagram of the fifth process is to achieve precise operation of power while keeping the conduction angle constant by adjusting the value of the target phase angle;

[0048] Figure 8 The waveform and data display diagram of the process is shown in section six, which shows how to precisely operate the power while keeping the conduction angle constant by adjusting the value of the target phase angle.

[0049] Figure 9The waveform and data display diagram of the process is shown in section seven, which shows how to precisely operate the power while keeping the conduction angle constant by adjusting the value of the target phase angle.

[0050] Figure 10 The waveform and data display diagram of the process of precisely operating the power while keeping the conduction angle constant by adjusting the value of the target phase angle;

[0051] Figure 11 This is a waveform and data display diagram for medium to high power output. Detailed Implementation

[0052] like Figures 1 to 11 As shown, the present invention discloses a low-power precision output device based on the coordination of phase shift angle and target phase angle, which is applied to a high-power wireless charging system using phase-shifted full-bridge modulation. The device includes a ground-terminal phase-shifted full-bridge inverter, a bilateral LCC resonant network, a power conditioning loop, a frequency tracking loop, and a controller.

[0053] The output terminal of the ground-terminal phase-shifting full-bridge inverter is connected to the input terminal of the bilateral LCC resonant network, which is used to convert DC voltage into high-frequency AC power and input it into the bilateral LCC resonant network.

[0054] The power regulation loop is used to calculate the ground phase shift angle φ of the ground-terminal phase-shifted full-bridge inverter based on the system output voltage and output current. p ;

[0055] The frequency tracking loop is used to acquire the phase information of the resonant current in the bilateral LCC resonant network and calculate the target phase angle θ for frequency tracking.

[0056] The controller is connected to the power regulation loop and the frequency tracking loop respectively, and is used to determine φ. p Is it less than the lower limit φ of the phase shift angle set based on ZVS conditions? min If φ p ≥φ min Adjust φ through the power regulating ring p Adjust the output power; if φ p <φ min , fixed φ p For φ min Simultaneously, the frequency tracking loop is adjusted upwards by θ to make the actual phase angle of the system θ c Shifting towards the inductive side reduces active power.

[0057] Specifically, the lower limit of the phase shift angle φ minThe value of θ is determined by the ZVS condition of the ground-side phase-shifted full-bridge inverter, with a preferred value of 90°. The frequency tracking loop acquires resonant current phase information using methods including zero-crossing detection, peak phase detection, resonant current quadrature algorithm, or state observer. This phase information is used to calculate the target phase angle θ. The actual phase angle θ of the system... c The equivalent impedance from the bilateral LCC resonant network to the load is determined, and θ c The phase angle is indirectly controlled by the target phase angle θ, meaning that changes in θ are transmitted to θ through the impedance matching process of the frequency tracking loop. c To achieve θ c The offset. The output power P of the ground-terminal phase-shifted full-bridge inverter satisfies the following relationship:

[0058] P=[U in •U out •(1+cosφ p )] / (ωL rp •L rs ),

[0059] Among them U in U is the input voltage. out Where L is the output voltage, ω is the angular frequency, and L is the output voltage. rp L is the ground resonant inductor. rs For the resonant inductance at the vehicle end; φ p When fixed, P changes with θ adjustment, resulting in θ c It decreases due to the offset.

[0060] A method for achieving low-power, precise output based on the coordination of phase shift angle and target phase angle using the above-mentioned device, the method comprising the following steps:

[0061] S1. System startup: The ground-terminal phase-shifted full-bridge inverter outputs high-frequency AC power. The dual-sided LCC resonant network realizes energy transfer. The power regulation loop collects the output voltage and output current in real time and calculates the ground-terminal phase-shift angle φ. p ;

[0062] S2, Controller determines φ p Is it less than the lower limit of the phase shift angle φ? min If φ p ≥φ min Return to step S1 and adjust φ p Continue adjusting the output power; if φ p <φ min Perform step S3;

[0063] S3, the controller controls the φ of the ground-side phase-shifting full-bridge inverter. p Fixed as φ min Maintain ZVS conditions;

[0064] S4. The frequency tracking loop collects the resonant current phase information of the bilateral LCC resonant network and calculates the current target phase angle θ.

[0065] S5. The controller adjusts the frequency tracking loop upwards by a unit step size of θ, so that the actual phase angle θ of the system is... c Shifting towards the inductive side increases reactive power and reduces active power output;

[0066] S6. Real-time detection of whether the output power has reached the target low power value. If not, repeat steps S4 to S5. If it has, maintain the current θ and enter a stable output state.

[0067] S7. If further power reduction is required, repeat steps S4 to S6 to achieve continuous and precise adjustment in the low power range.

[0068] Specifically, in step S5, the unit step adjustment of the target phase angle θ is 1° to 5°, which is determined according to the low power adjustment accuracy requirements; after θ is adjusted upward, the increase in reactive power and the decrease in active power of the system satisfy the following: the increase in reactive power is positively correlated with the upward adjustment of θ, and the decrease in active power is positively correlated with the upward adjustment of θ.

[0069] The ground phase shift angle φ p The conduction angle α of the full-bridge controlled rectifier circuit satisfies the relationship φ p =π-2α, where the range of α is 0<α≤π / 2; φ p Fixed as φ min At the same time, α is kept constant to avoid a decrease in the efficiency of the rectifier circuit due to α being too small.

[0070] In step S1, the vehicle-end rectification method of the bilateral LCC resonant network includes either diode passive rectification or synchronous rectification; under both rectification methods, φ p Both the synergistic control mechanism with θ are effective and do not affect the low-power regulation accuracy.

[0071] The specific implementation principle of this invention is as follows.

[0072] The ground-side inverter using this solution must have both power regulation and frequency tracking capabilities. The power regulation loop calculates the required ground-side phase shift angle φ based on the output voltage and output current. p Frequency tracking calculates the target phase angle θ based on the phase information obtained from the ground resonant cavity.

[0073] This phase information is typically the zero-crossing point or peak position of the ground resonant current. In some applications, orthogonal algorithms or state observers are even used to analyze the resonant current. In short, there are many methods to obtain phase information. These methods are merely inputs to the process of calculating the phase angle θ in frequency tracking, and all can be applied to this invention.

[0074] The mathematical model of the phase-shifting full-bridge phase-shifting system in the form of Fourier trigonometric series can be expressed as:

[0075] Output voltage of the full-bridge ground terminal:

[0076] Voltage connected to the resonant cavity at the vehicle end:

[0077] like Figure 1 As shown, V in It is the input voltage, V out It is the output voltage, ω is the angular frequency, and φ is the output voltage. p It is the ground phase shift angle, φ s It is the phase shift angle at the vehicle end (phase shift angle φ) s (usually an angle close to π), θ c It is the system phase angle (determined by the equivalent impedance from the resonant cavity to the load, which can be indirectly controlled by the target phase angle θ of the frequency tracking operation, because impedance matching is performed in this process).

[0078] This expression can fully represent the properties of the input / output resonant voltage under this strategy, including the content of each component and the phase angle change, etc.

[0079] Under these reasonable resonance conditions, the power transferred by the system can be expressed as:

[0080]

[0081] This formula shows that the calculated φ for the power loop of the phase-shifted full-bridge modulation at the ground terminal is... p It is the ground phase shift angle and the standard phase angle θ calculated by the frequency loop of frequency tracking. The two can jointly affect the output power P and perform relatively accurate operation.

[0082] However, this formula only represents the effect of input parameters on the transferred power. To express the conduction angle and the correlation effect from the output to the load, we need to analyze the output current and output power of the system.

[0083] The time during which the output current does not pass through the load:

[0084] In the formula, α is the conduction angle, and T is the switching period. The conduction angle of the full-bridge controlled rectifier circuit in half a cycle is 2α (0 < α ≤ π / 2), that is, the time during which current flows through the load in half a cycle is α / (π*f). w According to the characteristics of a full-bridge rectifier circuit with capacitor filtering, the resonant current I at the vehicle terminal on the AC side is... rs With DC side current I L The following relationship exists:

[0085]

[0086] Charging power P L The expression is:

[0087]

[0088] The load charging power is positively correlated with the load's equivalent resistance. Without neglecting the internal resistance of the transmitting and receiving coils, the system transmission efficiency η can be derived. t The expression:

[0089]

[0090] When the equivalent impedance Z of the full-bridge rectifier circuit eq The system transmission efficiency reaches its maximum value η when the following equation is satisfied. m

[0091]

[0092] At this point, the maximum system transmission efficiency η m for:

[0093] η m = 1 2 [ R p 2 R s 2 L rs 2 C s 2 M 4 + R p R s L rs C s M 2 + R p R s L rs C s M 2 ] + 1

[0094] Therefore, system efficiency corresponds to impedance matching. The impedance matching process can be adjusted through frequency tracking.

[0095] By analyzing the equivalent resistance of the rectifier circuit at the vehicle end, the relationship between the system output characteristics and the conduction angle is derived.

[0096] As can be seen from the above analysis, the input of the full-bridge controllable rectifier circuit at the vehicle end can be regarded as a current source, as analyzed below.

[0097] The input current of the rectifier circuit is

[0098] Ignoring the voltage drop during capacitor discharge, capacitor C can be... f It can be equivalent to a first-order current source with current i. c The internal resistance is r c .

[0099] Let the power factor of the capacitor-filtered full-bridge controlled rectifier circuit be λ, then the following relationship exists:

[0100]

[0101] Furthermore, due to the internal resistance r in the equivalent circuit c R is relatively small, so it can be considered thatL >>r c It can be simplified to:

[0102]

[0103] And i c ·r c The voltage across the filter capacitor is constant in a steady state. Therefore, the input voltage waveform of the full-bridge controlled rectifier circuit can be considered as a portion near the peak of a sine wave. Thus, the expression for the input voltage of the full-bridge controlled rectifier circuit can be obtained as follows:

[0104]

[0105] From the above expression for the input voltage, we can further derive the effective value U of the input voltage of the full-bridge controlled rectifier circuit in half a cycle. s The expression:

[0106]

[0107] The effective value of the input voltage U of the full-bridge controlled rectifier circuit s From this, we can derive the expression for the power factor λ of a capacitor-filtered full-bridge controlled rectifier circuit:

[0108]

[0109]

[0110]

[0111] Finally, without considering the losses of the full-bridge controlled rectifier circuit, the active power on the AC side is equal to the output power on the DC side:

[0112]

[0113] The equivalent impedance Z of the capacitor-filtered full-bridge controllable rectifier circuit eq The expression is:

[0114]

[0115] in, Z eq ∈ [ 0 , 8 π 2 R L ] That is, the equivalent impedance of the full-bridge controllable rectifier circuit is less than the equivalent resistance of the load.

[0116] Then, the ground phase shift angle φ p The relationship with the conduction angle α is as follows:

[0117] ,

[0118] Ground phase shift angle φp With equivalent impedance Z eq The relation is:

[0119]

[0120] Load charging current I L Phase shift angle φ at ground end p The relation is:

[0121]

[0122] Therefore, when the local terminal phase shift angle φ p If the load charging current remains constant, it can remain unchanged.

[0123] The ground-end phase shift angle φ can be derived from the above formula. p With load charging current I L Relationship:

[0124] φ p = arccos [ πω L rp L rs I L 2 MU P − 1 ]

[0125] The ground phase shift angle φ can be obtained from the range of values ​​of the conduction angle α. p The range is 0 to 180°.

[0126] Ground phase shift angle φ p At lower angles, the decrease in output power is not significant, and the ZVS condition is easily not met. Therefore, in some high-power wireless charging systems, a lower limit φ for the phase shift angle is generally set. min (Usually around 90°, depending on the ZVS conditions of the system). During normal operation, its ground phase shift angle φ... p In practice, the value will not be lower than this to ensure that the ZVS condition is met.

[0127] When the power loop calculates φ p Less than φ min At that point, the system will be unable to reduce output power by further reducing the phase shift angle.

[0128] Based on the formula derivation above, at the ground-end phase shift angle φ p Reaching the lower limit of the phase shift angle φ min Subsequently, to further reduce the output power, the target phase angle θ of the frequency tracking operation can be increased, resulting in a change in the system phase angle θ. c The power is increased so that the power can be further reduced while the conduction angle remains unchanged.

[0129] Therefore, the method proposed in this invention can achieve a phase shift angle φ at the ground end under medium and low power conditions. p Reaching the lower limit of the phase shift angle φ minThen, the output power value can be freely controlled by the target phase angle θ of the frequency tracking operation.

[0130] The embodiments of the present invention possess both an experimental machine and simulation data based on the aforementioned mathematical model. Comparing the two provides a clearer representation of the phase shift angle φ at the ground end. p Reaching the lower limit of the phase shift angle φ min Next, we need to figure out how to precisely control the power while keeping the conduction angle constant by adjusting the value of the target phase angle θ.

[0131] like Figures 3 to 11 As shown, the left side displays the key waveforms of the testing machine, and the right side shows the simulation data based on the preceding mathematical model. To provide a more complete demonstration of the operation process, a relatively small mutual inductance M was specifically chosen for the experiment and simulation. Therefore, the ground phase shift angle φ can be maintained even at almost full power output. p Reaching the lower limit of the phase shift angle φ min The state.

[0132] in, Figure 3 In the middle, the output is 60V, 0A, and the ground phase shift angle is φ. p Reaching the lower limit of the phase shift angle φ min The value is 90° because the minimum output of this mathematical model is less than zero, only around 5A, with the lowest output fluctuating between 300 and 400W. The phase angle is set to 75°.

[0133] Figure 4 In the middle, the output is 60V, 10A, and the ground phase shift angle is φ. p Reaching the lower limit of the phase shift angle φ min The value is 90°, and the target phase angle is 62°.

[0134] Figure 5 In the middle, the output is 60V, 20A, and the ground phase shift angle is φ. p Reaching the lower limit of the phase shift angle φ min The value is 90°, and the target phase angle is 52°.

[0135] Figure 6 In the middle, the output is 60V, 30A, and the ground phase shift angle is φ. p Reaching the lower limit of the phase shift angle φ min The value is 90°, and the target phase angle is 35°.

[0136] Figure 7 In the middle, the output is 60V, 40A, and the ground phase shift angle is φ. p Reaching the lower limit of the phase shift angle φ min The value is 90°, and the target phase angle is 31°.

[0137] Figure 8 In the middle, the output is 60V, 50A, and the ground phase shift angle is φ. pReaching the lower limit of the phase shift angle φ min The value is 90°, and the target phase angle is 25°.

[0138] Figure 9 In the middle, the output is 60V, 55A, and the ground phase shift angle is φ. p Reaching the lower limit of the phase shift angle φ min The value is 90°, and the target phase angle is 20°.

[0139] Figure 10 In the middle, the output is 60V, 60A, and the ground phase shift angle is φ. p It's about 135°, and the target phase angle is tracked to 15°.

[0140] like Figure 11 As shown, the mid-to-high output can be controlled to cross the zero point through frequency tracking.

[0141] The technology of this invention can achieve a phase shift angle φ at the ground end. p Reaching the lower limit of the phase shift angle φ min After setting the value and locking it at 90°, the output power is then precisely controlled by using the target phase angle.

[0142] This invention is also applicable to charging scenarios such as ground AC and underground AC charging piles, as well as power transmission and distribution and control equipment.

[0143] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-power precision output device based on the coordination of phase shift angle and target phase angle, applied in a high-power wireless charging system employing phase-shifted full-bridge modulation, characterized in that, The device includes a ground-terminal phase-shifted full-bridge inverter, a bilateral LCC resonant network, a power regulation loop, a frequency tracking loop, and a controller. The output terminal of the ground-terminal phase-shifting full-bridge inverter is connected to the input terminal of the bilateral LCC resonant network, which is used to convert DC voltage into high-frequency AC power and input it into the bilateral LCC resonant network. The power regulation loop is used to calculate the ground phase shift angle φ of the ground-terminal phase-shifted full-bridge inverter based on the system output voltage and output current. p ; The frequency tracking loop is used to acquire the phase information of the resonant current in the bilateral LCC resonant network and calculate the target phase angle θ for frequency tracking. The controller is connected to the power regulation loop and the frequency tracking loop respectively, and is used to determine φ. p Is it less than the lower limit φ of the phase shift angle set based on ZVS conditions? min If φ p ≥φ min Adjust φ through the power regulating ring p Adjust the output power; if φ p <φ min , fixed φ p For φ min Simultaneously, the frequency tracking loop is adjusted upwards by θ to make the actual phase angle of the system θ c Shifting towards the inductive side reduces active power.

2. The low-power precision output device based on the coordination of phase shift angle and target phase angle according to claim 1, characterized in that, The lower limit of the phase shift angle φ min The value of is determined by the ZVS condition of the ground-side phase-shifted full-bridge inverter.

3. The low-power precision output device based on the coordination of phase shift angle and target phase angle according to claim 2, characterized in that, The lower limit of the phase shift angle φ min The value is 90°.

4. The low-power precision output device based on the coordination of phase shift angle and target phase angle according to claim 1, characterized in that, The frequency tracking loop acquires resonant current phase information through methods including zero-crossing detection, peak phase detection, resonant current orthogonal algorithm, or state observer. The phase information is used to calculate the target phase angle θ.

5. The low-power precision output device based on the coordination of phase shift angle and target phase angle according to claim 1, characterized in that, The actual phase angle θ of the system c The equivalent impedance from the bilateral LCC resonant network to the load is determined, and θ c The phase angle is indirectly controlled by the target phase angle θ, meaning that changes in θ are transmitted to θ through the impedance matching process of the frequency tracking loop. c To achieve θ c The offset.

6. The low-power precision output device based on the coordination of phase shift angle and target phase angle according to claim 1, characterized in that, The output power P of the ground-side phase-shifted full-bridge inverter satisfies the following relationship: P=[U in •U out •(1+cosφ p )] / (ω L rp • L rs ), Among them U in U is the input voltage. out Where ω is the output voltage and ω is the angular frequency. L rp For ground resonant inductance, L rs For the resonant inductance at the vehicle end; φ p When fixed, P changes with θ adjustment, resulting in θ c It decreases due to the offset.

7. A method for achieving low-power precise output based on the coordination of phase shift angle and target phase angle using the apparatus as described in any one of claims 1 to 6, characterized in that, The method includes the following steps: S1. System startup: The ground-terminal phase-shifted full-bridge inverter outputs high-frequency AC power. The dual-sided LCC resonant network realizes energy transfer. The power regulation loop collects the output voltage and output current in real time and calculates the ground-terminal phase-shift angle φ. p ; S2, Controller determines φ p Is it less than the lower limit of the phase shift angle φ? min If φ p ≥φ min Return to step S1 and adjust φ p Continue adjusting the output power; if φ p <φ min Perform step S3; S3, the controller controls the φ of the ground-side phase-shifting full-bridge inverter. p Fixed as φ min Maintain ZVS conditions; S4. The frequency tracking loop collects the resonant current phase information of the bilateral LCC resonant network and calculates the current target phase angle θ. S5. The controller adjusts the frequency tracking loop upwards by a unit step size of θ, so that the actual phase angle θ of the system is... c Shifting towards the inductive side increases reactive power and reduces active power output; S6. Real-time detection of whether the output power has reached the target low power value. If not, repeat steps S4 to S5. If it has, maintain the current θ and enter a stable output state. S7. If further power reduction is required, repeat steps S4 to S6 to achieve continuous and precise adjustment in the low power range.

8. The method according to claim 7, characterized in that: In step S5, the unit step adjustment of the target phase angle θ is 1° to 5°, which is determined according to the low power adjustment accuracy requirements. After θ is adjusted upward, the increase in reactive power and the decrease in active power of the system satisfy the following: the increase in reactive power is positively correlated with the upward adjustment of θ, and the decrease in active power is positively correlated with the upward adjustment of θ.

9. The method according to claim 7, characterized in that: The ground phase shift angle φ p The conduction angle α of the full-bridge controlled rectifier circuit satisfies the relationship φ p =π-2α, where the range of α is 0<α≤π / 2; φ p Fixed as φ min At the same time, α is kept constant to avoid a decrease in the efficiency of the rectifier circuit due to α being too small.

10. The method according to claim 7, characterized in that: In step S1, the vehicle-end rectification method of the bilateral LCC resonant network includes either diode passive rectification or synchronous rectification; under both rectification methods, φ p Both the synergistic control mechanism with θ are effective and do not affect the low-power regulation accuracy.

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