魏金成(1966),男,硕士,教授,研究方向为大功率智能型电源、智能控制技术及应用、电力电子技术与电气传动控制(E-mail:
廖师师(1995),女,硕士在读,研究方向为无线电能传输
邱晓初(1964),男,博士,副教授,研究方向为电力电子与电力传动、电能质量控制、人工智能及模式识别
在无线充电过程中,电池阻值的变化会引起输出功率的波动,从而减短电池寿命,影响充电安全。针对磁耦合谐振式无线电能传输变负载系统,通常是在接收端加入控制电路使输出功率稳定,但这增加了用电设备的体积。因此,文中提出了基于反射阻抗原理的2种恒功率控制策略:Sepic电路恒功率输出控制策略和移相控制恒功率输出控制策略。首先分析了负载电阻对输出功率的影响;然后分别推导了Sepic电路驱动信号的占空比、移相控制中驱动信号的移相角与输出功率的关系,给出了恒功率控制策略的原理;最后通过Matlab/Simulink搭建仿真模型,验证了文中理论分析及所提控制策略的正确性。仿真结果表明,2种控制策略均能有效实现恒功率输出。
In the process of wireless charging, the fluctuation of output power is caused by the change of battery resistance, which shortens the battery life and affects the safety of charging. For the magnetic coupling resonance type wireless power transmission variable load system, the control circuit is usually added at the receiving end to stabilize the output power, but it expands the volume of the electrical equipment. Therefore, two constant power control strategies based on the principle of reflected impedance are proposed in the article, namely Sepic circuit constant power output control strategy and phase shift control constant power output control strategy. Firstly, the influence of load resistance on the output power is analyzed. Secondly, the relationship between the duty cycle of the Sepic circuit drive signal and the output power, and the relationship between the phase shift angle of the drive signal and the output power in the phase shift control are deduced respectively. The principle of the constant power control strategy in the article is given. Finally, a simulation model is built through Matlab/Simulink to verify the correctness of the theoretical analysis and the proposed control strategies. The simulation results show that both control strategies can effectively achieve constant power output.
相对于传统有线电能传输,无线电能传输不存在磨损老化的问题,更加安全、便捷[
目前针对MCRWPT的研究主要集中在线圈结构[
因此,文中提出基于反射阻抗原理的2种恒功率控制策略:Sepic电路恒功率输出控制策略和移相控制恒功率输出控制策略。2种控制策略均不必外加通信回路,减小了用电设备体积,节约了成本。首先,对系统模型进行理论分析,说明了负载电阻、发射端电压对输出功率的影响,给出了通过反射阻抗识别输出功率的方法。然后,分别推导了Sepic电路驱动信号的占空比、移相控制中驱动信号的移相角与输出功率的关系,通过调节占空比或移相角来实现对输出功率的调节。最后通过Matlab/Simulink搭建仿真模型进行验证,结果表明,当负载阻值变化时,2种控制方法均能有效地将输出功率稳定在规定范围内。
文中采用两线圈MCRWPT系统S/S模型,如
两线圈MCRWPT系统S/S模型结构
S/S model structure of two-coil MCRWPT system
为便于分析,可将
根据
式中:
其中,
当系统谐振时:
此时,发射端和接收端阻抗为:
此时系统输出功率达到最大值。根据式(1)-式(5)得到谐振状态下系统输出功率
根据式(6)得到
输出功率与负载电阻及发射端电压的三维关系
The relationship between output power and load resistance and transmitter voltage
控制输出功率稳定,首先要识别输出功率并判断其是否稳定在规定值。若在接收端加入电路识别输出功率,并通过无线通信的方式将识别结果传输到发射端,再对其进行控制,则不仅增加了用电设备的体积和系统成本,还存在通信延时的问题。因此,文中利用反射阻抗原理,可直接在发射端检测识别输出功率。引入反射阻抗之后,可将
引入反射阻抗之后的等效电路
Equivalent circuit after introducing reflected impedance
接收端等效到发射端的反射阻抗
式中:
由第1章分析可知,根据当前输出功率值调节发射端电压即可使输出功率稳定。调压方式有多种,在实际应用中可根据不同应用场景选择不同的方式,文中重点研究Sepic电路调压和移相控制调压。
Sepic电路作为DC-DC变换电路之一,可以实现对输入电压增大或减小的调节[
因此:
式中:
The relationship between
基于Sepic电路恒功率输出控制的原理如
Sepic电路恒功率输出控制原理示意
Schematic diagram of constant power output control based on Sepic circuit
移相控制调压可以实现零电压开通(zero voltage switch, ZVS),不必外接DC-DC变换电路,不仅减小了系统体积,还减小了开关管带来的高频损耗。因此, 移相控制适用于对系统体积要求严格的应用场景。
移相控制开关管工作模态如
开关管工作模态
Switch tube working mode
The relationship between
移相控制恒功率输出控制原理如
移相控制的恒功率输出控制原理示意
Schematic diagram of constant power output control based on phase shift control
为验证所提出的2种恒功率控制策略的可行性,按照
恒功率控制系统结构
Structure of constant power control system
按照电动汽车通用充电频率,设定系统频率为85 kHz,输出功率要求稳定在1 kW左右,且误差不超过5%。在电能传输过程中,调节
系统仿真参数
System simulation parameters
参数 | 数值 | 参数 | 数值 | |
70.1 | 85 | |||
50 | 7 | |||
50 | 0.2 | |||
100 |
Sepic电路能够调节电压增大或减小,而移相控制只能减小电压,因此设定Sepic电路输入直流电压
Sepic电路恒功率输出控制仿真结果
Simulation results of constant power output control based on Sepic circuit
移相控制恒功率输出控制仿真结果
Simulation results of constant power output control based on phase shift control
从仿真结果来看,输出功率对于负载电阻的变化较为敏感,当负载发生变化时,若不加入有效的控制方法,输出功率将会产生较大的波动。文中所提2种恒功率控制策略均能有效稳定输出功率。
文中对MCRWPT系统S/S模型进行理论分析,给出了输出功率与发射端电压、负载电阻的关系。针对无线充电过程中负载阻值变化引起的功率波动,提出Sepic电路和移相控制2种恒功率输出控制策略。仿真结果表明,所提出的控制方法能使输出功率稳定在规定值。此外,基于文中研究基础,可在今后的研究中结合其他系统参数对输出功率的影响,提出能够适应更多应用场景的恒功率控制策略。
本文得到四川省电力电子节能技术与装备重点实验室资助项目(SZJJ2016-049),西华大学自然科学重点基金资助项目(z1620906)资助,谨此致谢!
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