A large-power dynamic wireless charging control method based on three-phase parallel BUCK

Abstract

A kind of high-power dynamic wireless charging control method based on three-phase parallel BUCK, including the following processes, S1: the parallel double receiving coil resonance angular frequency is set to 85kHz;S2: the power output end of rectifier circuit is electrically connected with the power input end of three-phase parallel BUCK current control circuit, and the power output end is electrically connected with the load on vehicle;S3: impedance mismatch compensation is carried out using current sharing control method;S4: the state average model of single-phase BUCK current control circuit is calculated;S5: the current data of first-phase BUCK circuit is calculated;S6: the duty cycle d1 of three-phase BUCK first phase, the duty cycle d2 and d3 data of second phase and third phase are calculated;S7: the data obtained in steps S3-S6 are input into the control system of three-phase parallel BUCK current control circuit, to control the charging mode of load.The present application ensures the balance of three-phase current, can improve the charging power, and improve the control response speed of system and the stability of output current, and plays a strong technical support for the development of wireless dynamic charging technology.

Description

Technical Field

[0001] This invention relates to the field of wireless charging technology, and in particular to a high-power dynamic wireless charging control method based on a three-phase parallel BUCK. Background Technology

[0002] Wireless charging technology (WPT) has seen rapid development in recent years due to its advantages such as convenience, safety, reliability, and the ability to bring innovative designs to electric products. Magnetic coupling-based wireless charging is considered an ideal charging method for devices such as mobile phones, smart home appliances, and electric vehicles. Dynamic wireless charging technology, building upon basic wireless charging, can replenish power to moving devices, such as in electric vehicles. Furthermore, using dynamic wireless charging technology for pure electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) is considered an effective and practical option, as it can not only extend the driving range of electric vehicles but also reduce the capacity of the onboard battery pack.

[0003] However, due to technological limitations, there are still many problems to be solved in the use of dynamic wireless charging for electric vehicles. Specifically, the coupling coefficient between the receiving coil installed on the electric vehicle and the transmitting coil laid on the ground fluctuates due to the movement of the electric vehicle, which reduces the dynamic wireless charging power and charging performance. Furthermore, the fluctuating charging current of the lithium-ion battery in the electric vehicle can affect battery life and even pose safety hazards. In reality, electric vehicles need high-power dynamic wireless charging capabilities to meet actual charging needs. To achieve this high-power wireless charging, current wireless charging receiver BUCK circuits generally use high-power components, which places higher demands on hardware components and increases production and usage costs. With technological advancements, a technical solution has emerged in the wireless charging field that uses a three-phase parallel interleaved BUCK control circuit at the receiver to power the load. This solution uses multiple BUCK converters (BUCK control circuits) connected in parallel to distribute the output current to each parallel branch, enabling safe output of high current and reducing current stress on components in each branch. Since it does not require high-power components, it reduces production and usage costs. Although the three-phase parallel interleaved BUCK control circuit has many advantages, the current technology only applies it to the field of static wireless charging. That is to say, its internal control logic is only applicable to static wireless charging. If it is directly used for dynamic wireless charging, it will still have the disadvantage of reducing the power and charging performance of electric vehicles in dynamic wireless charging. Summary of the Invention

[0004] To overcome the shortcomings of existing dynamic wireless charging technologies, as described in the background, this invention provides a high-power dynamic wireless charging control method based on a three-phase parallel BUCK control circuit. This method distributes the output current to each parallel branch, safely outputting large currents and reducing the current stress on each branch device. The parallel BUCK circuit reduces the requirements for individual switching devices and energy storage devices, lowering hardware costs. Furthermore, by combining the PI passive control algorithm and the BUCK three-phase current sharing algorithm, this method effectively improves the dynamic charging power, efficiency, stability, and reliability.

[0005] The technical solution adopted by this invention to solve the technical problem is:

[0006] A high-power dynamic wireless charging control method based on a three-phase parallel BUCK circuit, characterized by the following steps: S1: Setting the resonant angular frequency of the parallel dual receiving coils of the dynamic wireless charging receiver to 85kHz; S2: Electrically connecting the power output terminal of the rectifier circuit of the dynamic wireless charging receiver to the power input terminal of the three-phase parallel BUCK current control circuit, and electrically connecting the power output terminal of the three-phase parallel BUCK current control circuit to the battery load on the vehicle; S3: Compensating for impedance mismatch by using a current sharing control method for inductance and current imbalance in the three-phase parallel BUCK current control circuit, specifically including the following sub-steps: S31, using the formula... Calculate the inductor current value for each phase of each BUCK circuit, S32, using the formula. Calculate the equivalent impedance ratio, S33, using the formula... Calculate the compensation duty cycle data of the control system for a three-phase parallel BUCK current control circuit; S4: using the formula Calculate the differential equations of the state-averaged model of a single-phase BUCK current control circuit; S5: using the formula Calculate the current data of the outer loop of the three-phase parallel BUCK current control circuit using a PI controller to control the first phase BUCK circuit; S6: through the formula Calculate the duty cycle d1 of the first phase of the three-phase BUCK current control circuit obtained from the inner loop of the three-phase parallel BUCK current control circuit, and then calculate the compensated duty cycles d2 and d2 data of the second and third phases through the three-phase BUCK inductor current sharing control; S7; The data obtained in steps S3-S6 are input into the control system of the three-phase parallel BUCK current control circuit, thereby controlling the charging mode of the load.

[0007] Preferably, in step S33, the input voltage V iThe output voltage V0 is obtained by sampling through ADC, the equivalent impedance is measured in advance, M2 and M3 are fixed constants, the second and third phase compensation duty cycles are calculated based on the value of the first phase duty cycle d11 to maintain the current balance of each phase, and d1 needs to be calculated based on the requirements of the output to the load current.

[0008] Preferably, in step S4, it is necessary to first use a formula Calculate the current data for controlling the first phase.

[0009] Preferably, in step S4, i in i out i1 and i1 are the input current value, output current value, and inductor current of the first phase of the three-phase BUCK, where i in and i out Data obtained through Hall effect sensors at the wireless charging receiver.

[0010] Preferably, in step S4, the inner loop is calculated using a passive control algorithm.

[0011] The beneficial effects of this invention are as follows: Based on the dual-receiving coil structure of the wireless dynamic charging receiver, this invention ensures the stability of the mutual inductance values ​​between the transmitting and receiving coils of the electric vehicle, improves charging power, and provides the possibility for stabilizing the current output to the battery load. The use of a three-phase parallel BUCK current control circuit in the receiver circuit improves the charging power level and reduces component costs. By using a pulse capture module and a current-sharing control algorithm to calculate the three-phase duty cycle of the three-phase BUCK circuit, the balance of the three-phase current is ensured. By using a PI passive control algorithm to control the current output to the load battery of the dynamic wireless charging system, the system's control response speed and output current stability can be improved while increasing charging power, providing strong technical support for the development of wireless dynamic charging technology. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the overall structure of the improved high-power dynamic wireless charging system for electric vehicles according to the present invention.

[0013] Figure 2 This is a structural diagram of the transmitting and receiving coils of the present invention.

[0014] Figure 3 This is a topology diagram of the dynamic wireless charging for electric vehicles according to the present invention.

[0015] Figure 4 This is a block diagram of the three-phase BUCK circuit control strategy of the present invention.

[0016] Figure 5 This is the control principle diagram of the three-phase parallel BUCK current control circuit of the present invention. Detailed Implementation

[0017] Figure 1 This invention presents an improved overall structure for a high-power dynamic wireless charging system for electric vehicles. The system consists of two main parts: an electric vehicle energy receiver and a ground-based energy transmitter. The electric vehicle energy receiver comprises a resonant compensation circuit, a rectifier circuit, a three-phase parallel BUCK current control circuit, an electric vehicle battery load, and parallel double-D-type receiving coils mounted on the electric vehicle chassis. The ground-based energy transmitter comprises an AC / DC converter, a DC bus, a high-frequency full-bridge inverter circuit, a transmitter resonant compensation circuit, and multiple double-D-type transmitting coils embedded in the lane. The structures of the transmitter and receiver coils are as follows... Figure 2 As shown, both the transmitting and receiving coils employ a double D-type coil structure. This coil structure offers better resistance to offset, allowing the transmitting and receiving coils to maintain a relatively high mutual inductance value during the dynamic wireless charging process of an electric vehicle. Figure 1 As can be seen from the placement of the transmitting and receiving coils, the distance between the two transmitting coils is exactly the width of one receiving coil, and the distance between the two receiving coils is the width of one transmitting coil plus a gap. In this way, as the electric vehicle moves, the two parallel receiving coils are equivalent to always having one complete receiving coil facing the transmitting coil. This parallel receiving coil structure is equivalent to the superposition of the energy of the two receiving coils. Therefore, during vehicle movement and overcharging, energy close to that of one receiving coil will always be transmitted to the receiving end. Of course, this structural design alone cannot guarantee the stability of the energy at the receiving end, and there will still be an energy fluctuation of about 10%. This requires the control of the three-phase parallel BUCK current control circuit at the receiving end to improve the stability of the output current to the battery load.

[0018] Figure 3 This is a topology diagram of dynamic wireless charging for electric vehicles. The expression for the output power P of the resonant network with two parallel receiving coils is:

[0019]

[0020] Where k1 and k2 are the coupling factors of the two receiving coils and the transmitting coil, respectively, U AB U is the amplitude of the fundamental frequency component at the input terminal. ab L is the fundamental frequency component amplitude at the output of the resonant circuit, and L1 and L2 are the self-inductances of the transmitting and receiving coils, respectively. f1 and L f2 ω is the resonant inductance of the transmitter and receiver, and ω is a fixed resonant angular frequency. In this invention, the resonant angular frequency is 85kHz. As can be seen from formula (1), once the parameters of the coil and circuit are determined, if it is desired to increase the output power P, the input voltage U can be increased. ABThe output voltage U of the resonant circuit ab Input voltage U AB This can be increased directly through power supply. Since the voltage of the load battery is fixed, increasing the output voltage U of the resonant circuit will improve this. ab This requires adding a BUCK circuit at the front end of the load battery. By adjusting the duty cycle of the BUCK circuit, the output voltage U of the resonant circuit can be increased in reverse. ab Electric vehicles now require increasingly higher charging power. Without a BUCK control circuit, increasing the input voltage U... AB Increasing output power requires a sufficiently high voltage from the load battery to ensure the stability of the transmitting and receiving resonant circuits, which is clearly impractical. Furthermore, using a single-phase BUCK circuit necessitates increasing the size of the switching and energy storage devices to ensure effective and safe high-current output. This significantly increases the hardware cost and the difficulty of heat dissipation in the BUCK circuit, potentially leading to a substantial decrease in the stability of the BUCK converter and making it difficult to provide a stable and safe power supply environment for electrical equipment. Using multiple BUCK converters in parallel distributes the output current across the parallel branches, providing an effective way to safely output high current. This effectively reduces the current stress on the components in each branch. Simultaneously, the requirements for individual switching and energy storage devices are reduced in parallel BUCK circuits, thus lowering hardware costs and improving the efficiency and reliability of the BUCK circuit.

[0021] Figure 1 , 2 As shown in Figures 3 and 4, during the charging process of an electric vehicle on a dynamic wireless charging road, the mutual inductance between the transmitting coil and the parallel dual receiving coils will fluctuate to some extent. This means that the value of (k1+k2) in Formula 1 will fluctuate by about 10% at its highest point. The specific fluctuation value depends on factors such as the design of the transmitting and receiving coil structures. During the movement, this fluctuation needs to be stabilized to the current value of the load battery by adjusting the duty cycle of the BUCK circuit. The three-phase parallel BUCK current control circuit has the advantages of high output current and low ripple; however, ensuring the current balance of each phase is a crucial issue to guarantee the reliable operation of the three-phase BUCK circuit. If current imbalance occurs in each phase for a long period, it will reduce the lifespan of the three-phase BUCK converter and may even lead to converter failure, causing system paralysis. Simultaneously, the three-phase BUCK circuit must be controlled to ensure the stability of the output current and reduce current fluctuations to the battery load.

[0022] Figure 1 , 2As shown in Figures 3 and 4, the reason for the unbalanced inductor current in the three-phase parallel BUCK current control circuit is the inconsistency of the equivalent impedance of each phase circuit. This invention uses a current sharing control method to solve the above technical problem. It is known that the unbalanced current in the three-phase branches is due to the equivalent impedance mismatch, so impedance mismatch compensation is performed first. The inductor current value of each phase is shown in the following formula (2):

[0023]

[0024] Among them, V i V0 represents the input voltage of the three-phase BUCK, V1, R2, and R3 represent the equivalent impedance of each phase branch, d1, d2, and d3 are the duty cycles of each phase IGBT, and I1, I2, and I3 are the inductor currents of each phase (the formulas for calculating the inductance of each branch are given above). It is necessary to balance the currents in each phase, i.e., ensure that I1 = I2 = I3. Define the equivalent impedance ratios M2 = R2 / R1 and M3 = R3 / R1. This leads to the following formula:

[0025]

[0026] Here, the duty cycle is defined as d2 = d1 + Δd2, d3 = d1 + Δd3, where Δd2 and Δd3 are the compensation duty cycles. Substituting them into the formula, we can obtain the compensation duty cycle as:

[0027] (This step, through the above derivation, determines the required duty cycle compensation for the second and third paths; subsequent calculations will then directly compensate for the duty cycle.) In a three-phase BUCK circuit, the input voltage V... i The output voltage V0 is obtained by sampling through the ADC, and the equivalent impedance is measured in advance. Therefore, M2 and M3 are fixed constants. Thus, the compensation duty cycles of the second and third phases can be calculated based on the value of the first phase duty cycle d1 to maintain the current balance of each phase. 1 needs to be calculated based on the requirements of the output to the load current (this step explains how the parameters in the duty cycle compensation formula are obtained and calculated).

[0028] Figure 1 , 2 As shown in Figures 3 and 4, the most important control objective of the three-phase BUCK circuit is to meet the given value I of the charging current of the load battery. ref This also reduces fluctuations in charging current. The method for balancing three-phase current has already been given; therefore, here we only need to control the stability of the single-phase inductor current, that is, control the current of the first phase. Ignoring parasitic parameters, the differential equation of the state-averaged model of a single-phase BUCK can be calculated as follows (this step illustrates the objective and control algorithm of three-phase BUCK control, thus connecting to the following text):

[0029]

[0030] like Figure 4 As shown, C1 and C2 are the front-end and rear-end capacitor values ​​of the BUCK circuit, respectively, and L is the inductance value in the BUCK circuit. in i out i1 and i1 are the input current value, output current value, and inductor current of the first phase of the three-phase BUCK, where i in and i out The results are obtained through measurements using a Hall sensor (this step provides the calculation process for the differential equations of BUCK's state-averaged model).

[0031] Figure 5 This describes the control principle of a three-phase parallel BUCK current control circuit. The outer loop of the three-phase parallel BUCK current control circuit (the outer loop of the dual-loop control, which is the final control target loop, the loop that controls the buck output current) uses its PI controller to control the current of the first phase BUCK circuit. The control algorithm is as follows (this step serves as a connection to the following text, explaining the process of the control algorithm):

[0032]

[0033]

[0034] Among them, I ref It is the given output current control quantity, i out This is the actual measured value, e(t) is the single-phase deviation value, and K... p and K i These are the proportional-integral parameters of the outer-loop PI controller (the outer loop of a dual-loop control system, which is the final control target loop, the PI control loop that controls the buck output current), and the output quantity of the outer-loop PI controller. These are the input reference values ​​for the inner loop passive control algorithm. The inner loop (the inner loop of the dual-loop control, controlling the front-end voltage of the buck circuit, a fast-response loop) uses the passive control algorithm (PBC) because of its advantages of fast dynamic response and low steady-state error. The control algorithm formula is as follows (this step provides the inner and outer loop control methods and objectives of the dual-loop control, and explains...). Figure 5 ):

[0035]

[0036] like Figure 5As shown, the duty cycle d1 of the first phase of the three-phase BUCK is obtained through the passive control inner loop. Then, the compensated duty cycles d2 and d3 of the second and third phases are calculated through the three-phase BUCK inductor current sharing control (this step illustrates the relationship and calculation steps between the BUCK current control circuit and the current sharing control). Finally, the data obtained from all the above steps are input into the control system of the three-phase parallel BUCK current control circuit, thereby controlling the charging mode of the load (battery of electric vehicles, etc.). In this invention, since the voltage of the load battery in dynamic wireless charging is fixed, the power required to provide dynamic wireless charging needs to be increased. However, the battery voltage cannot be adjusted. Adding a BUCK circuit between the rectifier and the load battery effectively increases the voltage at the front end of the BUCK circuit, i.e., the voltage of the wireless charging secondary side. This results in an increased charging current to the load battery. This invention is applied to high-power dynamic wireless charging technology. To reduce the pressure on the single-phase BUCK circuit, a three-phase BUCK is used, adding a BUCK circuit to ensure increased power. (The safe and stable operation of the load battery and its extended lifespan require a stable charging current; improving the lifespan and reliability of the three-phase BUCK requires ensuring current sharing across all three phases). Therefore, a reliable and effective control algorithm is also needed to ensure stable current output to the load battery and current sharing operation of the three-phase BUCK. This ensures the safe operation of the three-phase BUCK and improves the lifespan and safety of the load battery. Therefore, the control technology in this invention serves these objectives.

[0037] Figure 1 , 2 As shown in Figures 3, 4, and 5, through the above technical solution, this invention adopts a dual-receiving coil structure, ensuring the stability of the mutual inductance values ​​of the transmitting and receiving coils of the electric vehicle, improving charging power, and providing the possibility for stabilizing the current output to the battery load. The use of a three-phase parallel BUCK current controller in the receiving circuit improves the charging power level and reduces component costs. By using a pulse capture module and a sensorless current sharing control algorithm to calculate the three-phase duty cycle of the three-phase BUCK, the balance of the three-phase current is ensured. By using a PI passive control algorithm to control the current output of the dynamic wireless charging system to the load battery, the charging power can be improved while also increasing the system's control response speed and output current stability.

[0038] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. It will be apparent to those skilled in the art that the present invention is limited to the details of the exemplary embodiments described above. This method of description is merely for clarity and does not imply that the implementation methods encompass only one independent technical solution. Furthermore, the present invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0039] The scope of this invention is defined by the appended claims rather than the foregoing description, and therefore it is intended to encompass all variations falling within the meaning and scope of equivalents of the claims.

Claims

1. A high-power dynamic wireless charging control method based on a three-phase parallel BUCK, characterized in that, The process includes the following steps: S1: Set the resonant angular frequency of the parallel dual receiving coils of the dynamic wireless charging receiver to 85kHz; S2: Electrically connect the power output terminal of the rectifier circuit of the dynamic wireless charging receiver to the power input terminal of the three-phase parallel BUCK current control circuit, and electrically connect the power output terminal of the three-phase parallel BUCK current control circuit to the battery load on the vehicle; S3: For the inductance and current imbalance of the three-phase parallel BUCK current control circuit, impedance mismatch compensation is performed using a current sharing control method, specifically including the following sub-steps: S31, using the formula... Calculate the inductor current value for each phase of each BUCK circuit, where, This indicates the input voltage of the three-phase BUCK. This indicates the output voltage of the three-phase BUCK, i.e., the battery load voltage. , and Indicates the equivalent impedance of each phase branch. , and It is the duty cycle of each phase of the IGBT. , and It is the inductor current of each phase; S32, through the formula Calculate the equivalent impedance ratio, where, It is the defined equivalent impedance ratio, S33, obtained through the formula. Calculate the compensation duty cycle data of the control system of the three-phase parallel BUCK current control circuit, where, and To compensate for the duty cycle; S4: through the formula Calculate the differential equation of the state-averaged model of a single-phase BUCK current control circuit, where, and These are the values ​​of the front-end and rear-end capacitors of the BUCK circuit, respectively. It is the duty cycle of the first phase IGBT. It is the inductance value in the BUCK circuit. , and These are the input current value, output current value, and inductor current of the first phase of the three-phase BUCK; S5: via formula , Calculate the current data of the first phase BUCK circuit controlled by the PI controller in the outer loop of the three-phase parallel BUCK current control circuit. In the formula, It is the given output current control quantity. These are actual measured values. This is the single-phase deviation value. and These are the proportional-integral parameters of the outer-loop PI controller, and the output of the outer-loop PI controller. It is the input reference value of the inner loop passive control algorithm; S6: Through formula The duty cycle of the first phase of the three-phase BUCK obtained from the inner loop of the three-phase parallel BUCK current control circuit is calculated. Then, the duty cycles of the compensated second and third phases are calculated using the three-phase BUCK inductor current sharing control. and data, in , These are the input and output current values ​​of the three-phase BUCK. This indicates the input voltage of the three-phase BUCK. It is the input reference value of the inner-loop passive control algorithm. The equivalent impedance of the first phase branch is represented; S7; The data obtained in steps S3-S6 are input into the control system of the three-phase parallel BUCK current control circuit, thereby controlling the charging mode of the load.

2. The high-power dynamic wireless charging control method based on a three-phase parallel BUCK as described in claim 1, characterized in that, In step S33, the input voltage and output voltage It is obtained through sampling by an ADC, and the equivalent impedance is measured in advance. and It is a fixed constant, based on the duty cycle of the first phase. The values ​​are used to calculate the compensation duty cycles of the second and third phases, thereby maintaining current balance in each phase. It needs to be calculated based on the required output current to the load.

3. The high-power dynamic wireless charging control method based on a three-phase parallel BUCK as described in claim 1, characterized in that, In step S4, it is necessary to first use the formula Calculate the current data for controlling the first phase, where, It is the given output current control quantity. It is the inductor current of the first phase.

4. The high-power dynamic wireless charging control method based on a three-phase parallel BUCK as described in claim 1, characterized in that, In step S4, , and These are the input current value, output current value, and inductor current of the first phase of the three-phase BUCK. and Data obtained through Hall effect sensors at the wireless charging receiver.

5. A high-power dynamic wireless charging control method based on a three-phase parallel BUCK as described in claim 1, characterized in that, In step S4, a passive control algorithm is used to calculate the inner loop.

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