Wireless charging method and system based on disturbance detection-golden section

Abstract

The present invention provides a wireless charging method and system based on disturbance detection-golden section, which solves the shortcomings of the existing maximum efficiency tracking control method, such as high time complexity, slow solution speed and low maximum tracking speed. The present invention adopts an improved disturbance detection-golden section method to achieve fast maximum efficiency tracking. First, the current solution should be compared not only with the previous solution, but also with the next solution. If the current solution is better than both the previous solution and the next solution, the interval where the optimal solution is located can be determined; secondly, the maximum efficiency tracking is performed through the golden section search algorithm. The time complexity of the golden section search algorithm is usually O(log n), where n is the dimension of the solution space. Therefore, the use of the disturbance detection-golden section method can improve the speed of maximum efficiency tracking to a certain extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater wireless charging, and in particular relates to a wireless charging method and system based on disturbance detection-golden section. Background Art

[0002] Wireless charging technology is a contactless charging technology. The system consists of two parts: the transmitter and the receiver. It is currently widely used in the fields of smartphones, smart home appliances and electric vehicles. In wireless charging technology, pursuing maximum charging efficiency is an important direction. If the maximum efficiency of the system is to be achieved, maximum efficiency tracking and control is required. Most of the current technical solutions are to send the operating parameters (such as voltage and current) of the receiver to the transmitter through a wireless communication network. The transmitter can calculate the optimal DC / DC voltage value through a series of derived formulas to achieve maximum efficiency. This calculation method can obtain accurate maximum efficiency, but it requires wireless communication, which is prone to interference in a strong magnetic field environment such as wireless charging, resulting in problems such as packet loss and connection interruption.

[0003] Chinese patent CN111509865B provides a maximum efficiency tracking control method and system for a wireless charging system, and Chinese patent application CN110571899A provides a constant current output control and efficiency improvement method for a wireless power transmission system based on a variable step size disturbance observation method. The above schemes can perform maximum efficiency tracking without the need for wireless communication. However, the above maximum efficiency tracking control methods are all based on the disturbance observation method, which is a greedy algorithm, that is, starting from a point in the solution space, moving to adjacent points until a local optimal solution that cannot be moved is reached. The time complexity of a typical greedy algorithm is usually linear or nearly linear, that is, O(n), where n is the dimension of the solution space. It has a high time complexity, a slow solution speed, and a low maximum tracking speed. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the existing maximum efficiency tracking control method, such as high time complexity, slow solution speed and low maximum tracking speed, and to provide a wireless charging method and system based on disturbance detection-golden section.

[0005] To achieve the above purpose, the technical solution provided by the present invention is:

[0006] The wireless charging method based on disturbance detection-golden section is special in that it includes the following steps:

[0007] 1) Optimal solution existence judgment stage

[0008] According to the stable output voltage range of the primary side DC-DC converter, from the maximum output voltage Vinmax Start by decreasing it twice with its minimum resolution, taking V(1)=V inmax 、V(2)=V inmax -ΔV, V(3)=V(2)-ΔV as input voltage, and calculate the corresponding input power P respectively in (1) P in (2) and P in (3); where ΔV is the minimum resolution of the primary-side DC-DC converter output voltage;

[0009] If P in (1) <P in (2) <P in (3), the maximum output voltage V of the primary side DC-DC converter is inmax The optimal output voltage value for system efficiency is selected, the maximum efficiency tracking is completed, and the process goes to step 4);

[0010] Otherwise, go to step 2);

[0011] 2) Improve the disturbance observation phase

[0012] In the stable output voltage range of the primary side DC-DC converter, the output voltage is in descending order (V inmax -V inmin ) / 10 as the step size ΔV' is gradually reduced (therefore, the optimal solution interval can be determined in 10 times at most), and V(k-1)=V(k-2)-ΔV', V(k)=V(k-1)-ΔV', V(k+1)=V(k)-ΔV' are used as input voltages in turn, and the corresponding input power P is calculated respectively. in (k-1), P in (k) and P in (k+1); where k ranges from 2 to 9; during the iteration process:

[0013] If P in (k+1)>P in (k) <P in (k-1), then the optimal output voltage selection range for system efficiency is [V(k+1), V(k-1)], and go to step 3);

[0014] If P in (k+1)>P in (k)≥P in (k-1), then the optimal output voltage selection range for system efficiency is [V(k), V(k-1)], and go to step 3);

[0015] If there is always P in (k+1) <P in (k) <Pin (k-1), until V(k+1)≤V inmin (In actual situations, the minimum output voltage of the primary-side DC-DC converter is V inmin , but in the judgment, it is also possible to perform the next iteration to obtain the calculated value. Therefore, in the judgment process, V(k+1) can be less than V inmin ), then the minimum output voltage V inmin The optimal output voltage value for system efficiency is selected, the maximum efficiency tracking is completed, and the process goes to step 4);

[0016] In the method of the present invention, in order to avoid more judgments, P is not considered. in (k+1)=P in (k) In this way, the judgment logic and process can be simplified;

[0017] 3) Golden section search phase

[0018] Use the golden section search algorithm to select the best output voltage selection value within the best output voltage selection range selected in step 2), and proceed to step 4);

[0019] 4) Use the selected optimal output voltage value as the input voltage for wireless charging to achieve maximum efficiency control of the wireless charging system.

[0020] Meanwhile, the present invention provides a wireless charging system, which is special in that it includes a transmitting end and a receiving end;

[0021] The transmitting end includes a power supply battery, a primary side controller, a primary side DC-DC converter, an inverter, a primary side compensation network and a primary side coupler;

[0022] The positive and negative electrodes of the power supply battery are connected to the positive and negative input ports of the primary-side DC-DC converter, the output port of the primary-side DC-DC converter is connected to the input port of the inverter, the output port of the inverter is connected to the input port of the primary-side compensation network, and the output port of the primary-side compensation network is connected to the primary-side coupler; wherein the primary-side controller controls the output voltage of the primary-side DC-DC converter through the PWM duty cycle, that is, the maximum efficiency tracking is performed through the input voltage of the wireless charging system inverter;

[0023] The receiving end includes a rechargeable battery, a secondary side controller, a secondary side DC-DC converter, a rectifier, a secondary side compensation network and a secondary side coupler;

[0024] The secondary side coupler is connected to the input port of the secondary side compensation network, the output port of the secondary side compensation network is connected to the input port of the rectifier, the high frequency alternating current is converted into direct current after passing through the rectifier, the output port of the rectifier is connected to the input port of the secondary side DC-DC converter, and the output positive and negative ports of the secondary side DC-DC converter are connected to the positive and negative electrodes of the rechargeable battery;

[0025] The primary side coupler and the secondary side coupler are coupled after the transmitting end and the receiving end are connected, and the two wirelessly transmit electric energy through electromagnetic induction generated by high-frequency alternating current;

[0026] The secondary-side DC-DC converter controls the output current and voltage according to the load requirements of the rechargeable battery, that is, the secondary-side DC-DC converter generates the voltage or current required by the rechargeable battery to supply energy to the rechargeable battery under the control of the secondary-side controller;

[0027] The primary side DC-DC converter adopts the above-mentioned wireless charging method based on disturbance detection-golden section to achieve maximum efficiency tracking of the wireless charging system, and finds the optimal output voltage selection value of the primary side DC-DC converter, that is, the input voltage of the inverter.

[0028] Furthermore, the driving signal of the inverter is constant, the duty cycle is 50%, and the phase shift angle is 180°.

[0029] Concept and principle of the present invention:

[0030] In view of the problems existing in the prior art, the research team of the present invention conducted an in-depth analysis and found that the current perturbation observation method has a high time complexity of the algorithm when executing, which is O(n), the calculation time is long, the maximum efficiency tracking speed is slow, and there will be a three-point oscillation link in the final stage, which is not conducive to the rapid tracking of the maximum efficiency point. At the same time, the theoretical optimal point finally found by the perturbation observation method is in the three-point oscillation area near the actual optimal point. Therefore, the selection of the perturbation step size ΔV needs to be balanced between the convergence speed and the oscillation, such as Figure 2 As shown in the figure, although increasing the perturbation step size ΔV can increase the maximum efficiency tracking speed, the final three-point oscillation area will be very large; although reducing the perturbation step size ΔV can reduce the three-point oscillation area, it will significantly increase the maximum efficiency tracking time; the operating mechanism of using the existing perturbation observation method for maximum efficiency tracking in the wireless charging system is as follows:

[0031] First, the receiving end maintains the current value or voltage value required by the load under the control of the primary side DC-DC converter (i.e., buck-boost converter). At this time, the output power P of the receiving end is outThen, the output voltage of the primary-side DC-DC converter is adjusted based on the disturbance observation method. When the output power of the power supply battery (which is also the input power P of the wireless charging system) is detected, in ) reaches the minimum, the efficiency of the entire system reaches the maximum. When the system is in range A and range C, the inverter input voltage value can be increased or decreased by the disturbance step ΔV, thereby continuously reducing the input power P in When the system enters range B, V in The state changes to P2, P min The three-point oscillation stage between P1 and P4 points, that is, the optimal inverter input voltage for maximum efficiency is found. During operation, the change of the inverter input voltage is controlled by the duty cycle of the primary-side DC-DC converter, and the control method is the fixed-step perturbation observation method described in CN111509865B. It can be seen that if the amplitude of the final three-point oscillation stage is to be avoided, the perturbation step size needs to be reduced; if the speed of maximum efficiency tracking is to be increased, the perturbation step size needs to be increased. Therefore, the selection of the perturbation step size requires a trade-off between the oscillation amplitude and the tracking speed, which is obviously not conducive to the stability of the system.

[0032] Therefore, in order to improve the speed of tracking the maximum efficiency point, the present invention adopts an improved disturbance detection-golden section method (also known as disturbance observation-golden section method) to achieve fast maximum efficiency tracking. First, the current solution should be compared not only with the previous solution, but also with the next solution. If the current solution is better than both the previous solution and the next solution, the interval where the optimal solution is located can be determined; secondly, the maximum efficiency tracking is performed through the golden section search algorithm. The time complexity of the golden section search algorithm is usually O(log n), where n is the dimension of the solution space. Since the dimension of the solution space is usually greater than 1, O(log n) < O(n), so the use of the disturbance detection-golden section method can improve the speed of maximum efficiency tracking to a certain extent.

[0033] In the wireless charging method provided by the present invention, the secondary side DC-DC converter is used to adjust the output to maintain a constant output voltage V required by the load. out Or the constant output current I required by the load out The input voltage of the primary side coupler V in Only the primary-side DC-DC converter performs iterative adjustment (reduction or increase), and the control method is to improve the disturbance detection-golden section method until the output power of the power supply battery (i.e., the input power P of the wireless power transmission system) reaches in ) reaches the minimum point. For a given output voltage or output current, reaching the minimum input power operating point is equivalent to reaching the maximum energy efficiency operating point (system efficiency η=P out / P in , then when Pout unchanged, P in During the whole operation, the driving signal of the inverter is constant, with a duty cycle of 50% and a phase shift angle of 180°, so as to better ensure that the system is in a soft switching state.

[0034] The advantages of the present invention are:

[0035] 1. The transmitting end of the wireless charging system of the present invention includes a power supply battery, a primary side controller, a primary side DC-DC converter, an inverter, a primary side compensation network and a primary side coupler, and the receiving end includes a rechargeable battery, a secondary side controller, a secondary side DC-DC converter, a rectifier, a secondary side compensation network and a secondary side coupler; and the secondary side DC-DC converter controls the output current and voltage according to the rechargeable battery load requirements, and the primary side DC-DC converter uses the improved disturbance detection-golden section method proposed in the present invention to quickly achieve the maximum efficiency tracking of the wireless charging system. In the conventional disturbance observation method, the current solution only needs to be compared with the previous solution, so there will be Figure 2 The three-point oscillation in the final stage shown in range B; in the improved disturbance detection of the present invention, the current solution needs to be compared not only with the previous solution, but also with the next solution. After judging the preferred interval, the golden section method is used to optimize the interval; since the golden section method is unique and has low time complexity and fast solution speed, it can quickly achieve maximum efficiency tracking and avoid three-point oscillation.

[0036] 2. Compared with the simple disturbance observation method, the disturbance detection-golden section wireless charging method proposed in the present invention can realize the rapid maximum efficiency tracking of the system without communication conditions and avoid the three-point oscillation existing in the disturbance observation method. At the same time, because no communication is required, it also avoids the different degrees of attenuation of electromagnetic waves caused by different underwater environmental temperatures, salinity and conductivity, resulting in long delays and poor stability of the communication system, reducing the cost, volume and complexity of the underwater wireless charging system, and improving its stability. In addition, since the proposed method does not involve mutual inductance, it can be unaffected by the docking situation on the system power transmission to a certain extent, and achieves the maximum efficiency transmission in this docking state, so it is still effective when the coupler is misaligned. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of a non-communication LCC-S compensation wireless charging system provided by the present invention;

[0038] Figure 2 The operating mechanism of the fixed-step maximum efficiency tracking disturbance observation method in the current wireless charging system;

[0039] Figure 3This is a flow chart of the disturbance detection-golden section method of the present invention;

[0040] Figure 4 : is the relationship between the efficiency of the system of the present invention and the output voltage range of the primary side DC-DC converter; (a) is case A, (b) is case B, and (c) is case C;

[0041] Figure 5 To improve the optimal solution interval iteration process in the disturbance observation phase of the wireless charging method of the present invention;

[0042] Figure 6 It is an iterative calculation process of the golden section search phase of the wireless charging method of the present invention;

[0043] Figure 7 Comparison of system efficiency when using the disturbance detection-golden section method of the present invention and when not using the method of the present invention;

[0044] Figure 8 Comparison between the disturbance detection-golden section method of the present invention and the traditional disturbance observation method; wherein (a) is a load resistance R=5Ω; (b) is a load resistance R=10Ω; and (c) is a load resistance R=15Ω. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0046] In order to improve the speed of maximum efficiency tracking, the flow chart of the disturbance detection-golden section method proposed in the present invention is as follows: Figure 3 As shown in the figure, it includes the optimal solution existence judgment stage, the improved disturbance observation stage and the golden section search stage. The specific steps are as follows:

[0047] 1) Optimal solution existence judgment stage

[0048] Since the stable output voltage range of the primary-side DC-DC converter is a finite interval, this interval may be on the left side of the best efficiency point, on the right side of the best efficiency point, or include the best efficiency point, such as Figure 4 Therefore, it is necessary to determine whether the interval of the primary-side DC-DC converter output voltage contains the optimal solution before performing maximum efficiency tracking.

[0049] In the optimal solution existence judgment stage, the minimum resolution of the primary side DC-DC converter output voltage is used as the disturbance step ΔV, and the primary side DC-DC converter is adjusted from the maximum output voltage V(1)=V inmax Start by decreasing twice with the minimum resolution, that is, V(2)=V inmax -ΔV and V(3)=V(2)-ΔV, and calculate the corresponding input power P respectively in(1) P in (2) and P in (3). If P in (1) <P in (2) <P in (3), that is, Figure 4 In case (a) A, the maximum output voltage of the primary side DC-DC converter is V inmax The optimal output voltage value for system efficiency is selected, the maximum efficiency tracking is completed, and the process goes to step 4); otherwise, the process goes to step 2).

[0050] 2) Improve the disturbance observation phase

[0051] In the improved disturbance observation stage, the present invention improves the disturbance observation method so that the current solution P in (k) Not only must it be consistent with the previous solution P in (k-1) and compare it with the next solution P in (k+1) comparison. In order to increase the speed of maximum efficiency tracking, the step size of voltage change can be larger, that is, V (k) =V (k-1) -n ΔV, where ΔV is the minimum resolution of the primary-side DC-DC converter output voltage, n ΔV is the new step length ΔV', ΔV'=(V inmax -V inmin ) / 10, then, n=[(V inmax -V inmin ) / 10] / ΔV.

[0052] In the improved disturbance observation stage, if the relationship between the system efficiency and the output voltage range of the primary side DC-DC converter belongs to Figure 4 (b) Case B. In this case, if P in (k+1)>P in (k) <P in (k-1), the optimal output voltage selection range for system efficiency is [V(k+1), V(k-1)], and go to step 3).

[0053] If P in (k+1)>P in (k)≥P in (k-1), the optimal output voltage selection range for system efficiency is [V(k), V(k-1)], and go to step 3).

[0054] Figure 5 The iterative process of improving the optimal solution interval in the disturbance observation phase is shown. During the search process, if there is always P in (k+1) <Pin (k) <P in (k-1), until V(k+1)≤V inmin , that is, belongs to Figure 4 In case (c) C, the minimum output voltage V of the primary side DC-DC converter is inmin The optimal output voltage value for system efficiency is selected, the maximum efficiency tracking is completed, and the process goes to step 4).

[0055] 3) Golden section search phase

[0056] After improving the disturbance observation stage, it is found that there is an optimal solution interval (i.e., the optimal output voltage selection range for system efficiency). The next step is to use the golden section search algorithm to find the optimal solution (i.e., the optimal output voltage selection value for system efficiency).

[0057] The golden section search algorithm is an accurate line search algorithm. When using the golden section search algorithm, the second point and the third point constitute the golden section point of the initial interval, such as Figure 6 As shown in the figure, when the optimal solution interval is from the first point to the third point, the second point is exactly the golden section point of the new interval; when the optimal solution interval is from the second point to the fourth point, the third point is exactly the golden section point of the new interval. Therefore, the golden section point of the initial interval can be reused in the next iteration, greatly reducing the number of experiments.

[0058] The proposed disturbance detection-golden section method can achieve faster maximum efficiency tracking. This is because in the improved disturbance observation stage, the step size of the voltage change can take a larger value, and the time complexity of the golden section search algorithm is lower than that of the disturbance observation method. In addition, the proposed disturbance detection-golden section method for maximum efficiency tracking can also effectively avoid the three-point oscillation existing in the disturbance observation method.

[0059] Figure 7 The curves showing the system efficiency as a function of load resistance, coupling coefficient, and whether the perturbation detection-golden section method is used are shown. It can be seen that the system efficiency decreases as the load resistance increases, because the efficiency of the wireless charging system is related to the load resistance. When the coupling coefficient k is 0.45 or 0.50, the system efficiency using the perturbation detection-golden section method is higher than that when it is not used. Therefore, it can be verified that the perturbation detection-golden section method improves the system efficiency. In addition, it can be proved that the proposed method is still effective when the coupling coefficient changes (i.e., coupler offset).

[0060] In the disturbance detection-golden section method, in the optimal solution existence judgment stage, the voltage V in The step size of the change is the same as that of the traditional disturbance observation method, that is, ΔV, where ΔV is the minimum output resolution of the primary-side DC-DC converter; in the improved ramp stage, the voltage Vin The step size of the change is (V inmax -V inmin ) / 10 to speed up the maximum efficiency tracking.

[0061] Figure 8 The input power P of the disturbance detection-golden section method and the traditional disturbance observation method is shown under the conditions of coupling coefficient k=0.45, 0.50 and load resistance R=5Ω, 10Ω, and 15Ω. in The relationship curve between . Figure 8 It can be clearly seen from (a), (b), and (c) that the traditional perturbation observation method will have three-point oscillation in the final stage, while the perturbation detection-golden section method of the present invention can effectively avoid oscillation. Figure 8 Under the same number of iterations, the P of the disturbance detection-golden section method in The value is smaller than that of the traditional perturbation observation method, which means it is more efficient.

[0062] In summary, the perturbation observation-golden section method proposed in the present invention can reduce time complexity, improve the solution speed and the speed of maximum efficiency tracking.

[0063] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A wireless charging method based on disturbance detection-golden section, characterized in that: The following steps are involved: 1) Optimal solution existence judgment stage According to the stable output voltage range of the primary side DC-DC converter, from the maximum output voltage V inmax Start by decreasing it twice with its minimum resolution, taking V(1)=V inmax 、V(2)=V inmax -ΔV, V(3)=V(2)-ΔV as input voltage, and calculate the corresponding input power P respectively in (1) P in (2) and P in (3); where ΔV is the minimum resolution of the primary-side DC-DC converter output voltage; If P in (1) <P in (2) <P in (3), the maximum output voltage V of the primary side DC-DC converter is inmax The optimal output voltage value for system efficiency is selected, the maximum efficiency tracking is completed, and the process goes to step 4); Otherwise, go to step 2); 2) Improve the disturbance observation phase In the stable output voltage range of the primary side DC-DC converter, the output voltage is in descending order (V inmax -V inmin ) / 10 as the step size ΔV' is gradually reduced, and V(k-1)=V(k-2)-ΔV', V(k)=V(k-1)-ΔV', V(k+1)=V(k)-ΔV' are used as the input voltages in turn, and the corresponding input powers P are calculated respectively. in (k-1), P in (k) and P in (k+1); where k ranges from 2 to 9; during the iteration process: If P in (k+1)>P in (k) <P in (k-1), then the optimal output voltage selection range for system efficiency is [V(k+1), V(k-1)], and go to step 3); If P in (k+1)>P in (k)≥P in (k-1), then the optimal output voltage selection range for system efficiency is [V(k), V(k-1)], and go to step 3); If there is always P in (k+1) <P in (k) <P in (k-1), until V(k+1)≤V inmin , then the minimum output voltage V of the primary side DC-DC converter inmin The optimal output voltage value for system efficiency is selected, the maximum efficiency tracking is completed, and the process goes to step 4); 3) Golden section search phase Use the golden section search algorithm to select the best output voltage selection value within the best output voltage selection range selected in step 2), and proceed to step 4); 4) Use the selected optimal output voltage value as the input voltage for wireless charging to achieve maximum efficiency control of the wireless charging system.

2. A wireless charging system, characterized in that: Includes a transmitter and a receiver; The transmitting end includes a power supply battery, a primary side controller, a primary side DC-DC converter, an inverter, a primary side compensation network and a primary side coupler; The positive and negative electrodes of the power supply battery are connected to the positive and negative input ports of the primary side DC-DC converter, the output port of the primary side DC-DC converter is connected to the input port of the inverter, the output port of the inverter is connected to the input port of the primary side compensation network, and the output port of the primary side compensation network is connected to the primary side coupler; wherein the primary side controller controls the output voltage of the primary side DC-DC converter through the PWM duty cycle; The receiving end includes a rechargeable battery, a secondary side controller, a secondary side DC-DC converter, a rectifier, a secondary side compensation network and a secondary side coupler; The secondary side coupler is connected to the input port of the secondary side compensation network, the output port of the secondary side compensation network is connected to the input port of the rectifier, the output port of the rectifier is connected to the input port of the secondary side DC-DC converter, and the output positive and negative ports of the secondary side DC-DC converter are connected to the positive and negative electrodes of the rechargeable battery; The primary side coupler and the secondary side coupler are coupled after the transmitting end and the receiving end are connected, and the two wirelessly transmit electric energy through electromagnetic induction generated by high-frequency alternating current; The secondary-side DC-DC converter controls the output current and voltage according to the rechargeable battery load requirements; The primary side DC-DC converter adopts the wireless charging method based on disturbance detection-golden section described in claim 1 to achieve maximum efficiency tracking of the wireless charging system and find the optimal output voltage selection value of the primary side DC-DC converter.

3. A wireless charging system according to claim 2, characterized in that: The drive signal of the inverter is constant, the duty cycle is 50%, and the phase shift angle is 180°.

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