Electric automobile two-way wireless charging system transmission power control method

Abstract

The invention belongs to the technical field of wireless charging and particularly relates to an electric automobile two-way wireless charging system transmission power control method. The method includes the following steps that the mutual inductance between a primary coil and an secondary coil of a system is calculated, and an inward-shifting phase angle of a primary convertor and a secondary convertor is obtained through calculation according to an output power command value; a primary controller and a secondary controller correspondingly adjust the phases of bridge arm switching signals inthe primary convertor and the secondary convertor with corresponding clock signals as standards, and control over the direction and the size of the transmission power is uncoupled; and the extreme value of the output current is tracked, so that the phases of control signals of the primary convertor and the secondary convertor are synchronous, and the direction of the system transmission power iscontrolled. The problem that an outward-shifting phase angle is unknowable and uncontrollable due to communication delay is solved, control over the direction and the size of the transmission power isuncoupled, phase information of the high-frequency current in the primary coil and the secondary coil is not needed, the circuit design difficulty and the requirement for the arithmetic speed are reduced, cost is reduced, and anti-interference performance and reliability are improved.

Description

technical field [0001] The invention belongs to the technical field of wireless charging, and in particular relates to a transmission power control method of a two-way wireless charging system for an electric vehicle. Background technique [0002] Wireless Power Transfer (WPT) technology has been widely used in smart phones, medical equipment, electric vehicles, industrial automation and other fields. Compared with traditional wired charging, the two-way wireless charging system is more suitable for the application of vehicle to grid (V2G) than wired charging because of its characteristics of no plug-in and unplugging, instant charging, and flexibility. The two-way flow of power between power grids has strong advantages in peak shaving and valley filling, no-load backup, peak power adjustment, and automatic power generation control. [0003] The control object is the bidirectional wireless charging system (Bidirectional Wireless Charging System, BWCS) of electric vehicles, ...

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Problems solved by technology

[0013] There are two control methods for the existing BWCS system: 1) The converter on one side operates in the high-frequency inverter mode, and the converter on the other side operates in the uncontrolled rectification mode. Only by adjusting α (adjusting β in discharge mode) , to control the transmission power of the system, the main problem is that it is impossible to ensure that the transmission power reaches the command value P ref While ensuring that the voltage gain satisfies the constraints 2) By adding an auxiliary coil in addition to the secondary coil, it is used to obtain the phase of the primary coil current after making a difference with the secondary coil current, and by tracking the primary current phase to ensure that the external phase angle γ is maintained at π / 2 (or 3π / 2), the main problem is that this method relies on the accurate sampling of the phase difference between the high-frequency current in the primary and secondary coils, which requires very high synchronization between the sampling circuit and the controller, and the control bandwidth is limited The parameters of the phase-locked loop have a great influence. At the same time, because the high-frequency signal is measured, it is greatly affected by high-frequency electromagnetic interference, and the system cost is high.

However, due to the millisecond-level communication delay in existing wireless communication technologies (such as Bluetooth, ZigBee, etc.), and the switching cycle of the system is mostly in the microsecond level, and there is a frequency deviation between the primary and secondary controller crystal oscillators, the above reasons will lead to The external phase angle γ is in an unknown and uncontrollable state

In addition, the external phase angle γ that controls the transmission power direction is coupled with α and β that control the transmission power, which also brings difficulties to the control of γ

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