Synchronization Strategy Based on Pulse Voltage Injection for Bidirectional Wireless Power Transfer Systems

Synchronization between the inverter and active rectifier is challenging in bidirectional wireless power transfer (BWPT) systems. This article proposes a novel pulse voltage injection method (PVIM) to achieve synchronization between converters on both sides without using any communication link. The synchronization principle of PVIM is to inject voltage pulses at the primary side and detect pulses at the secondary side to generate synchronization signals. By capturing the synchronization signals, the frequency and phase of the primary side can be locked. To realize the voltage pulse injection on the primary side, a novel nanosecond pulse generator with simple topology and control is proposed. In addition, two magnetic rings connected in series with resonant tanks are used for injection and detection of voltage pulses. Compared with the existing synchronization strategies, PVIM demonstrates significant advantages in six key aspects: high synchronization accuracy (<0.2°), fast dynamic response (within 1 switching cycle, <20 μs), low hardware requirements (no need for voltage/current sampling, auxiliary coils, or analog-to-digital converters), strong immunity to harmonic currents and system detuning, low computational complexity, and broad applicability to BWPT systems with various compensation topologies. Experimental results have validated the effectiveness of the proposed method.