Wireless power transmission system efficiency optimization control method based on rectifier mode switching

Abstract

The invention provides a wireless power transmission system efficiency optimization control method based on rectifier mode switching, and the method can achieve the optimal efficiency in a wide load range, and achieves the constant current output at the same time. In the control strategy, by judging the size of the load, the rectifier bridge works in a diode bridge mode when the load is light, works in a semi-active bridge mode when the load is large, works in an H bridge mode when the load is heavy, and simultaneously works at the optimal load point corresponding to the maximum efficiency in the semi-active bridge mode and the H bridge mode. In this way, efficiency optimization in a wide load range is achieved, and meanwhile the output current is constant by adjusting the voltage of the direct-current input side of the inverter. Compared with the prior art, the method has the advantages that an additional DC-DC converter does not need to be used, the control complexity is reduced, and efficiency optimization can be achieved in a wide load range.

Description

Technical Field

[0001] The present invention relates to wireless power transmission technology, and in particular to a wireless power transmission system efficiency optimization control method based on rectifier mode switching. Background Art

[0002] Compared with traditional cable charging methods, wireless power transmission has the characteristics of safety, durability and flexibility, and is gradually becoming a way to replace wired charging. Two factors need to be considered when designing a wireless power transmission system. One is to have a constant output capability, and the other is to operate efficiently within a wide load variation range, which is especially important in high-power applications. There are four ways to improve its efficiency:

[0003] 1) High-quality passive component method: The efficiency of the wireless power transmission system is proportional to the quality factor, so high-quality coils and compensation circuit components can be used to improve the system efficiency.

[0004] 2) Passive impedance matching method: A capacitor array is used to maintain system resonance by switching capacitor connections to achieve high-efficiency operation. However, this method requires multiple capacitors and switches, which increases costs and cannot achieve stepless tuning.

[0005] 3) Active impedance matching method: The maximum efficiency tracking is achieved by controlling the duty cycle of the power electronic converter so that it works at the optimal load point corresponding to the maximum efficiency. For example, a DC-DC converter is connected to the front end of the inverter or the back end of the diode rectifier bridge, and the duty cycle is controlled to make it work at the optimal load point for maximum efficiency, or the minimum input current corresponding to the minimum input power is tracked to achieve maximum efficiency tracking. However, this method adds additional power electronic converters and costs, and the control is more complicated. In order to reduce the use of power electronic converters, the uncontrollable diode rectifier bridge can be replaced with a semi-active rectifier or H-bridge rectifier, and the duty cycle can be controlled to adjust the equivalent impedance seen from the AC side of the rectifier so that it works at the optimal equivalent load point corresponding to the maximum efficiency. However, when the optimal equivalent load point is greater than the equivalent resistance seen from the AC input side of the uncontrollable diode rectifier bridge, it is impossible to adjust the duty cycle to keep it running at maximum efficiency all the time.

[0006] 4) Mode switching method: In order to overcome the problem that the controlled rectifier bridge (semi-active bridge rectifier, H-bridge rectifier) ​​cannot be adjusted to work at the optimal load point by adjusting the duty cycle, the primary inverter and the secondary rectifier can be operated in different modes, and the modes can be combined and switched under different loads, such as full-bridge inverter-full-bridge rectifier mode, semi-active bridge inverter-semi-active bridge rectifier mode, full-bridge inverter-semi-active bridge rectifier mode and semi-active bridge inverter-full-bridge rectifier mode. This method does not require additional hardware circuits and complex control methods, and can achieve efficiency optimization in a wide range. However, this method does not always work at the optimal load point corresponding to the maximum efficiency, and requires the primary and secondary sides to switch at the same time to achieve the set output voltage. At the same time, the adjustable range of the ratio of the output voltage to the input voltage is limited due to the influence of the converter working mode. At the same time, it is necessary to give the switch tube on and off signals within the full load range, which increases the system switching loss and reduces the efficiency.

[0007] Therefore, how to design a control strategy to achieve maximum efficiency tracking and wide-range output only by switching the secondary rectifier mode while minimizing the number of times the switch is turned on and off is of great significance for the efficient and stable operation of the inductive wireless power transfer system when the load changes. Summary of the invention

[0008] To achieve the above objectives, the present invention provides an efficiency optimization control strategy for an inductive wireless power transmission system based on rectifier mode switching:

[0009] The efficiency optimization control strategy of the wireless power transmission system based on rectifier mode switching proposed in the present invention realizes maximum efficiency tracking within a wide range of load changes by switching the rectifier working mode, and realizes constant output current by adjusting the inverter input voltage. The topology used in the present invention includes a Q 1 , Q 2 , Q 3 and Q 4 The high-frequency full-bridge inverter circuit is composed of the primary compensation capacitor C p , coil L p and coil L s The loose coupling mechanism is formed and the mutual inductance between them is M, and the secondary side compensation capacitor C s The internal resistance of the primary coil and the secondary coil are r p and r s , by Q 5 , Q 6 , Q 7 and Q 8 The rectifier bridge and load R LThe rectifier bridge includes three operating modes, namely, diode bridge operating mode, semi-active bridge operating mode and full bridge operating mode. A wireless power transmission system efficiency optimization control method based on rectifier mode switching includes the following steps:

[0010] Step 1: Give the driving signal of the rectifier in different modes:

[0011] In diode bridge operation mode, the four switches do not require drive pulses;

[0012] In the semi-active bridge operation mode, the switch tube Q 5 and Q 7 No driving pulse is required, the switch tube Q 6 and Q 8 The driving pulse is a complementary PWM signal, and the switch tube Q 8 After the receiving side current crosses zero from negative to positive (1-D s_SA )π, where D s_SA is the duty cycle of the input side voltage in semi-active bridge mode.

[0013] In full-bridge operation mode, the switch tube Q 5 and Q 6 The driving pulse is a complementary PWM signal, and the switch tube Q 7 and Q 8 The driving pulse is a complementary PWM signal, the switch Q 5 After the current on the receiving side crosses zero from negative to positive, θ 1 Open at switch Q 8 After the current on the receiving side changes from negative to positive and crosses the zero point, θ 2 Opened, is the phase difference between the voltage and current on the rectifier input side in H-bridge mode, D s_H is the duty cycle of the input voltage in H-bridge mode, and the relationship between them is:

[0014]

[0015] Step 2: Calculate the AC side impedance of the rectifier in different modes:

[0016] The rectifier input voltage in diode bridge, semi-active bridge and H-bridge modes is V s_x (x=D,SA,H) is:

[0017]

[0018] Among them, x=D represents the diode bridge operation mode, x=SA represents the semi-active bridge operation mode, and x=H represents the H-bridge operation mode.

[0019] Rectifier input current I in diode bridge, semi-active bridge, H-bridge mode s_x (x=D,SA,H) is:

[0020]

[0021] Among them, I s_D ,I s_SA and I s_H They are the effective values ​​of the rectifier input current in diode bridge, semi-active bridge and H-bridge modes respectively.

[0022] According to the voltage and current waveforms of the rectifier bridge in the three modes, the current I after the DC output capacitor filtering in the diode bridge, semi-active bridge and H-bridge modes is obtained. o_x (x=D,SA,H) is:

[0023]

[0024] Input impedance Z of the rectifier in diode bridge, semi-active bridge, H-bridge mode eq_x (x=D,SA,H) is:

[0025]

[0026] Combining (2), (3), (4) and (5), we can get the equivalent impedance Z in diode bridge, semi-active bridge and H-bridge modes: eq_x_ (x=D,SA,H) are:

[0027]

[0028] Among them, R eq_D is the equivalent resistance of the AC side in diode bridge mode, R eq_SA and X eq_SA is the equivalent resistance and reactance of the AC side in the semi-active bridge mode, R eq_H and X eq_H is the equivalent resistance and reactance on the AC side in H-bridge mode.

[0029] Step 3: Calculate the efficiency from the inverter output side to the rectifier bridge input side:

[0030] I p_x and I s_x (x=D,SA,H) represent the current flowing through the primary side and the current flowing through the secondary side in the x mode respectively, R eq_x and X eq_x They represent the resistance and reactance seen by the rectifier AC input side in x mode respectively, and the KVL equations for the transmitting side and the receiving side are written as:

[0031]

[0032] Among them, X p , X s and X m are the transmitting side resonant reactance, receiving side resonant reactance and mutual inductance reactance, which are:

[0033]

[0034] Substituting (8) into (7), we can obtain the current I flowing through the emitter side p_x and the current I flowing through the receiving side s_x for:

[0035]

[0036] Efficiency η from the inverter output side to the rectifier bridge input side x (x=D,SA,H) is:

[0037]

[0038] Combining (6), (8), (9) and (10), the efficiency η in diode bridge, semi-active bridge and H-bridge modes is x (x=D,SA,H) are:

[0039]

[0040] From (11), it can be seen that the efficiency in the diode rectifier bridge mode is related to the load, the efficiency in the semi-active bridge mode is related to the load and the duty cycle, and the efficiency in the H-bridge mode is related to the load, the duty cycle and the phase shift angle. Therefore, the maximum efficiency tracking in the semi-active bridge mode and the H-bridge mode can be achieved by controlling the duty cycle.

[0041] Step 4: Calculate the maximum efficiency that can be achieved under different loads:

[0042] In semi-active bridge mode, the efficiency η from the inverter output side to the rectifier bridge SA Right D s_SA Find the partial derivative, the duty cycle corresponding to the optimal load point is D SA_opt ; In H-bridge mode, the efficiency η from the inverter output side to the rectifier bridge H Right D s_H Find the partial derivative, the duty cycle corresponding to the optimal load point is D H_opt , respectively expressed as:

[0043]

[0044] At this time, the efficiency η under different loads in semi-active bridge and H-bridge modes max_SA and η max_H Substituting (12) into (11) yields the maximum efficiency η under different loads in diode rectifier bridge mode:max_D Same as (11), at this time, the maximum efficiency of diode bridge, semi-active bridge and H-bridge modes under different loads is:

[0045]

[0046] Step 5: Calculate the switching conditions under the three modes:

[0047] Let η max_D =η max_SA , we get the load resistance R when the maximum efficiency is equal in diode bridge mode and semi-active bridge mode L_mc1 for:

[0048]

[0049] Let η max_SA =η max_H , we get the load resistance R when the maximum efficiency is equal in the semi-active bridge mode and the H-bridge mode L_mc2 for:

[0050]

[0051] When R L <R L_mc1 When η max_D >η max_SA , the system operates in diode bridge mode; when R L_mc1 ≤R L <R L_mc2 When η max_SA >η max_H The system operates in semi-active bridge mode; when R L ≤R L_mc2 When η max_H ≥η max_SA , the system operates in H-bridge mode, so R L_mc1 is the switching load from diode bridge mode to semi-active bridge mode, R L_mc2 It is the switching load from semi-active bridge mode to H-bridge mode.

[0052] From (15), it can be seen that the switching load in the semi-active bridge mode and H-bridge mode is related to the phase shift angle. Therefore, it is very necessary to determine the phase shift angle.

[0053] Step 5: Determine the phase shift angle in H-bridge mode:

[0054] When the minimum system efficiency is required to be η ref When the system efficiency η in semi-active bridge mode is ref_SA Equal to η ref When the load resistance R L _ ref for:

[0055]

[0056] Let R L_mc2 =R L _ ref , the phase shift angle in H-bridge mode is:

[0057]

[0058] From the above analysis, it can be seen that when the load is different, the rectifier works in different modes to achieve the optimal efficiency within the full load range. When the rectifier works in the diode rectifier bridge mode, although the load change will change the efficiency, the DC side output current will not change; however, when the rectifier works in the semi-active bridge mode and H-bridge mode, although the duty cycle is adjusted under different loads to achieve the optimal efficiency, the rectifier bridge output current will also change, which cannot meet the constant current charging of the battery. Therefore, it is necessary to provide a method to achieve constant charging.

[0059] Step 6: Realize constant current charging in diode rectifier bridge, semi-active bridge and H-bridge modes:

[0060] When the inverter operates in complementary conduction mode and the conduction angle is 180°, the effective value of the inverter output voltage V p_x (x=D,SA,H) is:

[0061]

[0062] Among them, V dc_x (x=D,SA,H) is the DC input side voltage of the inverter in x mode.

[0063] Transconductance gain G of the resonant compensation network in diode bridge, semi-active bridge and H-bridge modes ri_x (x=D,SA,H) is:

[0064]

[0065] Transconductance gain G from output current to input voltage in diode bridge, semi-active bridge and H-bridge modes iv_x (x=D,SA,H) is:

[0066]

[0067] In order to achieve constant current charging, the inverter input voltage can be adjusted to achieve constant transconductance gain. If the system constant output current is required to be I ref , from formula (20), the input voltage V in diode bridge mode is dc_D for:

[0068]

[0069] Input voltage V in semi-active bridge mode dc_SA for:

[0070]

[0071] Input voltage V in H-bridge mode dc_H for:

[0072]

[0073] Through the above steps, the wireless power transmission system efficiency optimization control strategy based on rectifier mode switching of the present invention can achieve the optimal efficiency of the wireless power transmission link within the full load range, while maintaining a constant output current.

[0074] The following is a detailed description with reference to the accompanying drawings in conjunction with embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 It is an inductive wireless power transfer system topology based on rectifier mode switching;

[0076] Figure 2 It is a diode bridge operation mode structure;

[0077] Figure 3 It is a semi-active bridge operation mode structure;

[0078] Figure 4 It is a full-bridge operation mode structure;

[0079] Figure 5 This is the system control strategy block diagram;

[0080] Figure 6 The voltage and current waveforms of the rectifier bridge in the diode bridge operation mode;

[0081] Figure 7 Driving signal and rectifier bridge voltage and current waveforms in semi-active bridge operation mode;

[0082] Figure 8 Driving signal and rectifier bridge voltage and current waveforms in H-bridge operation mode;

[0083] Fig. 9 The AC equivalent circuit of the inductive wireless power transfer system topology with rectifier mode switching;

[0084] Fig.10 Output voltage and current waveforms when the load changes from 5Ω to 10Ω in diode bridge mode;

[0085] Fig.11 Output voltage and current waveforms when the load changes from 20Ω to 60Ω in semi-active bridge mode;

[0086] Fig.12 Output voltage and current waveforms when the load changes from 80Ω to 130Ω in H-bridge mode;

[0087] Fig.13 Before adopting the proposed rectifier mode switching method, the system efficiency changes with load in diode rectifier bridge mode, semi-active bridge mode and H-bridge mode;

[0088] Fig.14 The system efficiency changes with load in the full load range after adopting the proposed rectifier mode switching method; DETAILED DESCRIPTION

[0089] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0090] The technical solution adopted by the present invention is as follows Figure 1 As shown, including Q 1 , Q 2 , Q 3 and Q 4 The high-frequency full-bridge inverter circuit is composed of the primary compensation capacitor C p , coil L p and coil L s The loose coupling mechanism is formed and the mutual inductance between them is M, and the secondary side compensation capacitor C s The internal resistance of the primary coil and the secondary coil are r p and r s , by Q 5 , Q 6 , Q 7 and Q 8 The rectifier bridge and load R L The rectifier bridge includes three operating modes, namely diode bridge operating mode, semi-active bridge operating mode and full bridge operating mode. Figure 2 to Figure 4 The control strategy block diagram is shown in Figure 5 As shown, a wireless power transmission system efficiency optimization control method based on rectifier mode switching includes the following steps:

[0091] Step 1: Give the driving signal of the rectifier in different modes:

[0092] The voltage and current waveforms of the rectifier bridge in diode bridge operation mode are as follows: Figure 6 As shown, the four switching tubes do not need driving pulses;

[0093] The driving signal and the voltage and current waveforms of the rectifier bridge in the semi-active bridge operation mode are as follows: Figure 7 As shown, the switch tube Q 5 and Q 7 No driving pulse is required, the switch tube Q6 and Q 8 The driving pulse is a complementary PWM signal, and the switch tube Q 8 After the receiving side current crosses zero from negative to positive (1-D s_SA )π, where D s_SA is the duty cycle of the input side voltage in semi-active bridge mode.

[0094] The driving signal and the voltage and current waveforms of the rectifier bridge in full-bridge operation mode are as follows: Figure 8 As shown, the switch tube Q 5 and Q 6 The driving pulse is a complementary PWM signal, and the switch tube Q 7 and Q 8 The driving pulse is a complementary PWM signal, the switch Q 5 After the current on the receiving side crosses zero from negative to positive, θ 1 Open at switch Q 8 After the current on the receiving side changes from negative to positive and crosses the zero point, θ 2 Opened, is the phase difference between the voltage and current on the rectifier input side in H-bridge mode, D s_H is the duty cycle of the input voltage in H-bridge mode, and the relationship between them is:

[0095]

[0096] Step 2: Calculate the AC side impedance of the rectifier in different modes:

[0097] The rectifier input voltage in diode bridge, semi-active bridge and H-bridge modes is V s_x (x=D,SA,H) is:

[0098]

[0099] Among them, x=D represents the diode bridge operation mode, x=SA represents the semi-active bridge operation mode, and x=H represents the H-bridge operation mode.

[0100] Rectifier input current I in diode bridge, semi-active bridge, H-bridge mode s_x (x=D,SA,H) is:

[0101]

[0102] Among them, I s_D ,I s_SA and I s_H They are the effective values ​​of the rectifier input current in diode bridge, semi-active bridge and H-bridge modes respectively.

[0103] According to the voltage and current waveforms of the rectifier bridge in the three modes, the current I after the DC output capacitor filtering in the diode bridge, semi-active bridge and H-bridge modes is obtained. o_x (x=D,SA,H) is:

[0104]

[0105] Input impedance Z of the rectifier in diode bridge, semi-active bridge, H-bridge mode eq_x (x=D,SA,H) is:

[0106]

[0107] Combining (2), (3), (4) and (5), we can get the equivalent impedance Z in diode bridge, semi-active bridge and H-bridge modes: eq_x_ (x=D,SA,H) are:

[0108]

[0109] Among them, R eq_D is the equivalent resistance of the AC side in diode bridge mode, R eq_SA and X eq_SA is the equivalent resistance and reactance of the AC side in the semi-active bridge mode, R eq_H and X eq_H is the equivalent resistance and reactance on the AC side in H-bridge mode.

[0110] Step 3: Calculate the efficiency from the inverter output side to the rectifier bridge input side:

[0111] The AC equivalent circuit of the topology used in the present invention is as follows: Fig. 9 As shown, I p_x and I s_x (x=D,SA,H) represent the current flowing through the primary side and the current flowing through the secondary side in the x mode respectively, R eq_x and X eq_x They represent the resistance and reactance seen by the rectifier AC input side in x mode respectively, and the KVL equations for the transmitting side and the receiving side are written as:

[0112]

[0113] Among them, X p , X s and X m are the transmitting side resonant reactance, receiving side resonant reactance and mutual inductance reactance, which are:

[0114]

[0115] Substituting (8) into (7), we can obtain the current I flowing through the emitter side p_xand the current I flowing through the receiving side s_x for:

[0116]

[0117] Efficiency η from the inverter output side to the rectifier bridge input side x (x=D,SA,H) is:

[0118]

[0119] Combining (6), (8), (9) and (10), the efficiency η in diode bridge, semi-active bridge and H-bridge modes is x (x=D,SA,H) are:

[0120]

[0121] From (11), it can be seen that the efficiency in the diode rectifier bridge mode is related to the load, the efficiency in the semi-active bridge mode is related to the load and the duty cycle, and the efficiency in the H-bridge mode is related to the load, the duty cycle and the phase shift angle. Therefore, the maximum efficiency tracking in the semi-active bridge mode and the H-bridge mode can be achieved by controlling the duty cycle.

[0122] Step 4: Calculate the maximum efficiency that can be achieved under different loads:

[0123] In semi-active bridge mode, the efficiency η from the inverter output side to the rectifier bridge SA Right D s_SA Find the partial derivative, the duty cycle corresponding to the optimal load point is D SA_opt ; In H-bridge mode, the efficiency η from the inverter output side to the rectifier bridge H Right D s_H Find the partial derivative, the duty cycle corresponding to the optimal load point is D H_opt , respectively expressed as:

[0124]

[0125] At this time, the efficiency η under different loads in semi-active bridge and H-bridge modes max_SA and η max_H Substituting (12) into (11) yields the maximum efficiency η under different loads in diode rectifier bridge mode: max_D Same as (11), at this time, the maximum efficiency of diode bridge, semi-active bridge and H-bridge modes under different loads is:

[0126]

[0127] Step 5: Calculate the switching conditions under the three modes:

[0128] Let η max_D=η max_SA , we get the load resistance R when the maximum efficiency is equal in diode bridge mode and semi-active bridge mode L_mc1 for:

[0129]

[0130] Let η max_SA =η max_H , we get the load resistance R when the maximum efficiency is equal in the semi-active bridge mode and the H-bridge mode L_mc2 for:

[0131]

[0132] When R L <R L_mc1 When η max_D >η max_SA , the system operates in diode bridge mode; when R L_mc1 ≤R L <R L_mc2 When η max_SA >η max_H The system operates in semi-active bridge mode; when R L ≤R L_mc2 When η max_H ≥η max_SA , the system operates in H-bridge mode, so R L_mc1 is the switching load from diode bridge mode to semi-active bridge mode, R L_mc2 It is the switching load from semi-active bridge mode to H-bridge mode.

[0133] From (15), it can be seen that the switching load in the semi-active bridge mode and H-bridge mode is related to the phase shift angle. Therefore, it is very necessary to determine the phase shift angle.

[0134] Step 5: Determine the phase shift angle in H-bridge mode:

[0135] When the minimum system efficiency is required to be η ref When the system efficiency η in semi-active bridge mode is ref_SA Equal to η ref When the load resistance R L _ ref for:

[0136]

[0137] Let R L_mc2 =R L _ ref , the phase shift angle in H-bridge mode is:

[0138]

[0139] From the above analysis, it can be seen that when the load is different, the rectifier works in different modes to achieve the optimal efficiency within the full load range. When the rectifier works in the diode rectifier bridge mode, although the load change will change the efficiency, the DC side output current will not change; however, when the rectifier works in the semi-active bridge mode and H-bridge mode, although the duty cycle is adjusted under different loads to achieve the optimal efficiency, the rectifier bridge output current will also change, which cannot meet the constant current charging of the battery. Therefore, it is necessary to provide a method to achieve constant charging.

[0140] Step 6: Realize constant current charging in diode rectifier bridge, semi-active bridge and H-bridge modes:

[0141] When the inverter operates in complementary conduction mode and the conduction angle is 180°, the effective value of the inverter output voltage V p_x (x=D,SA,H) is:

[0142]

[0143] Among them, V dc_x (x=D,SA,H) is the DC input side voltage of the inverter in x mode.

[0144] Transconductance gain G of the resonant compensation network in diode bridge, semi-active bridge and H-bridge modes ri_x (x=D,SA,H) is:

[0145]

[0146] Transconductance gain G from output current to input voltage in diode bridge, semi-active bridge and H-bridge modes iv_x (x=D,SA,H) is:

[0147]

[0148] In order to achieve constant current charging, the inverter input voltage can be adjusted to achieve constant transconductance gain. If the system constant output current is required to be I ref , from formula (20), the input voltage V in diode bridge mode is dc_D for:

[0149]

[0150] Input voltage V in semi-active bridge mode dc_SA for:

[0151]

[0152] Input voltage V in H-bridge mode dc_H for:

[0153]

[0154] Through the above steps, the wireless power transmission system efficiency optimization control strategy based on rectifier mode switching of the present invention can achieve the optimal efficiency of the wireless power transmission link within the full load range, while maintaining a constant output current.

[0155] Example: Analysis of simulation results.

[0156] The model was built in Matlab / Simulink. The simulation parameters are as follows: the switching frequency f is 50kHz, the self-inductance L of the coupling mechanism is p and L s is 118μH, the self-inductance M is 23.6μH, and the primary internal resistance r p The secondary internal resistance is 0.1235Ω. s It is 0.1235Ω. Fig.10 The output voltage and current waveforms when the load changes from 5Ω to 10Ω in diode bridge mode are shown below. Fig.11 The output voltage and current waveforms when the load changes from 20Ω to 60Ω in semi-active bridge mode are shown below. Fig.12 The output voltage and current waveforms when the load changes from 80Ω to 130Ω in H-bridge mode. It can be seen that when the load changes, all three modes achieve constant current output, and the load output current is about 2A. Fig.13 Before adopting the proposed rectifier mode switching method, the system efficiency changes with load in diode rectifier bridge mode, semi-active bridge mode and H-bridge mode. It can be seen that when R L <20Ω, the efficiency of the diode bridge mode is the highest. <R L <74Ω, the semi-active bridge mode has the highest efficiency. <R L When >74Ω, H-bridge mode has the highest efficiency. Fig.14 The figure shows the change of system efficiency with load in the full load range after adopting the proposed rectifier mode switching method. It can be seen that under the full range of load changes, the efficiency of the proposed control method can be above 94%.

[0157] It can be seen from the above embodiments that the efficiency optimization control method for a wireless power transmission system based on rectifier mode switching proposed by the present invention can achieve efficiency optimization within the full load range and realize constant current output at the same time.

[0158] The above embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention. The protection scope of the present invention is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present invention within the essence and protection scope of the present invention, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present invention.

Claims

1. A wireless power transmission system efficiency optimization control method based on rectifier mode switching, which switches the rectifier working mode to achieve maximum efficiency tracking within a wide range of load changes, and adjusts the inverter input voltage to achieve constant output current. The wireless power transmission system topology includes a high-frequency full-bridge inverter circuit composed of Q1, Q2, Q3 and Q4, and a primary compensation capacitor C p , coil L p and coil L s The loose coupling mechanism is formed and the mutual inductance between them is M, and the secondary side compensation capacitor C s The internal resistance of the primary coil and the secondary coil are r p and r s , the rectifier bridge composed of Q5, Q6, Q7 and Q8 and the load R L The rectifier bridge includes three operating modes, namely, diode bridge operating mode, semi-active bridge operating mode and full-bridge operating mode, which is characterized by: The following steps are involved: 1) Give the driving signal of the rectifier in different modes; 2) Calculate the AC side impedance of the rectifier in different modes; 3) Calculate the efficiency from the inverter output side to the rectifier bridge input side; 4) Calculate the maximum efficiency that can be achieved under different loads; 5) Calculate the switching conditions under the three modes; 6) Realize constant current charging in diode rectifier bridge, semi-active bridge and H-bridge modes.

2. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In the step 1), the driving signals of the rectifiers in different modes are given: In diode bridge operation mode, the four switches do not need drive pulses; in semi-active bridge operation mode, switch tubes Q5 and Q7 do not need drive pulses, and the drive pulses of switch tubes Q6 and Q8 are complementary PWM signals. After the current on the receiving side crosses zero from negative to positive (1-D s_SA )π, where D s_SA is the duty cycle of the input side voltage in the semi-active bridge mode; in the full-bridge operation mode, the driving pulses of the switch tubes Q5 and Q6 are complementary PWM signals, and the driving pulses of the switch tubes Q7 and Q8 are complementary PWM signals. The switch Q5 is turned on at θ1 after the receiving side current crosses the zero point from negative to positive, and the switch Q8 is turned on at θ2 after the receiving side current crosses the zero point from negative to positive. is the phase difference between the voltage and current on the rectifier input side in H-bridge mode, D s_H is the duty cycle of the input voltage in H-bridge mode, and the relationship between them is:

3. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In step 2), the AC side impedance of the rectifier under different modes is calculated: The rectifier input voltage in diode bridge, semi-active bridge and H-bridge modes is V s_x (x=D,SA,H) is: Wherein, x=D represents the diode bridge operation mode, x=SA represents the semi-active bridge operation mode, and x=H represents the H-bridge operation mode; Rectifier input current I in diode bridge, semi-active bridge, H-bridge mode s_x (x=D,SA,H) is: Among them, I s_D ,I s_SA and I s_H They are the effective values ​​of the rectifier input current in diode bridge, semi-active bridge and H-bridge modes respectively; According to the voltage and current waveforms of the rectifier bridge in the three modes, the current I after the DC output capacitor filtering in the diode bridge, semi-active bridge and H-bridge modes is obtained. o_x (x=D,SA,H) is: Input impedance Z of the rectifier in diode bridge, semi-active bridge, H-bridge mode eq_x (x=D,SA,H) is: Combining (2), (3), (4) and (5), we can get the equivalent impedance Z in diode bridge, semi-active bridge and H-bridge modes: eq_x_ (x=D,SA,H) are: Among them, R eq_D is the equivalent resistance of the AC side in diode bridge mode, R eq_SA and X eq_SA is the equivalent resistance and reactance of the AC side in the semi-active bridge mode, R eq_H and X eq_H is the equivalent resistance and reactance on the AC side in H-bridge mode.

4. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In step 3), the efficiency from the inverter output side to the rectifier bridge input side is calculated: I p_x and I s_x (x=D,SA,H) represent the current flowing through the primary side and the current flowing through the secondary side in the x mode respectively, R eq_x and X eq_x They represent the resistance and reactance seen by the rectifier AC input side in x mode respectively, and the KVL equations for the transmitting side and the receiving side are written as: Among them, X p , X s and X m are the transmitting side resonant reactance, receiving side resonant reactance and mutual inductance reactance, which are: Substituting (8) into (7), we can obtain the current I flowing through the emitter side p_x and the current I flowing through the receiving side s_x for: Efficiency η from the inverter output side to the rectifier bridge input side x (x=D,SA,H) is: Combining (6), (8), (9) and (10), the efficiency η in diode bridge, semi-active bridge and H-bridge modes is x (x=D,SA,H) are: From (11), it can be seen that the efficiency in the diode rectifier bridge mode is related to the load, the efficiency in the semi-active bridge mode is related to the load and the duty cycle, and the efficiency in the H-bridge mode is related to the load, the duty cycle and the phase shift angle. Therefore, the maximum efficiency tracking in the semi-active bridge mode and the H-bridge mode can be achieved by controlling the duty cycle.

5. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In step 4), the maximum efficiency that can be achieved under different loads is calculated: In semi-active bridge mode, the efficiency η from the inverter output side to the rectifier bridge SA Right D s_SA Find the partial derivative, the duty cycle corresponding to the optimal load point is D SA_opt ; In H-bridge mode, the efficiency η from the inverter output side to the rectifier bridge H Right D s_H Find the partial derivative, the duty cycle corresponding to the optimal load point is D H_opt , respectively expressed as: At this time, the efficiency η under different loads in semi-active bridge and H-bridge modes max_SA and η max_H Substituting (12) into (11) yields the maximum efficiency η under different loads in diode rectifier bridge mode: max_D Same as (11), at this time, the maximum efficiency of diode bridge, semi-active bridge and H-bridge modes under different loads is:

6. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In step 5), the switching conditions in the three modes are calculated: Let η max_D =η max_SA , we get the load resistance R when the maximum efficiency is equal in diode bridge mode and semi-active bridge mode L_mc1 for: Let η max_SA =η max_H , we get the load resistance R when the maximum efficiency is equal in the semi-active bridge mode and the H-bridge mode L_mc2 for: When R L <R L_mc1 When η max_D >η max_SA , the system operates in diode bridge mode; when R L_mc1 ≤R L <R L_mc2 When η max_SA >η max_H The system operates in semi-active bridge mode; when R L ≤R L_mc2 When η max_H ≥η max_SA , the system operates in H-bridge mode, so R L_mc1 is the switching load from diode bridge mode to semi-active bridge mode, R L_mc2 is the switching load from the semi-active bridge mode to the H-bridge mode; from (15), it can be seen that the switching load between the semi-active bridge mode and the H-bridge mode is related to the phase shift angle.

7. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In step 5), the phase shift angle in the H-bridge mode is determined: When the minimum system efficiency is required to be η ref When the system efficiency η in semi-active bridge mode is ref_SA Equal to η ref When the load resistance R L _ ref for: Let R L_mc2 =R L _ ref , the phase shift angle in H-bridge mode is:

8. The method for optimizing the efficiency of a wireless power transmission system based on rectifier mode switching according to claim 1, characterized in that: In step 6), constant current charging in diode rectifier bridge, semi-active bridge and H-bridge modes is realized: When the inverter operates in complementary conduction mode and the conduction angle is 180°, the effective value of the inverter output voltage V p_x (x=D,SA,H) is: Among them, V dc_x (x=D,SA,H) is the DC input voltage of the inverter in mode x; Transconductance gain G of the resonant compensation network in diode bridge, semi-active bridge and H-bridge modes ri_x (x=D,SA,H) is: Transconductance gain G from output current to input voltage in diode bridge, semi-active bridge and H-bridge modes iv_x (x=D,SA,H) is: In order to achieve constant current charging, the inverter input voltage can be adjusted to achieve constant transconductance gain. If the system requires a constant output current of I ref , from formula (20), the input voltage V in diode bridge mode is dc_D for: Input voltage V in semi-active bridge mode dc_SA for: Input voltage V in H-bridge mode dc_H for:

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