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For <tex>$dq$</tex> control strategies in single-phase pulse width modulation (PWM) converters, the <tex>$\beta-\mathbf{axis}$</tex> current must be created by imaginary axis current estimation (IACE) methods. The estimated error of the <tex>$\beta-\mathbf{axis}$</tex> current during the transient process causes <tex>$d-q$</tex> axis current loops to be incompletely decoupled, thereby affecting the dynamic performance of the current loop. The second-order generalized integrator (SOGI) method suffers from slow dynamic response. The fictive-axis emulation (FAE) method provides fast dynamic response but it is sensitive to circuit parameters. A reference-input (RI)-based IACE method is proposed to overcome the above shortcomings. According to the characteristic that the <tex>$\beta-\mathbf{axis}$</tex> current loop has no transient process, the <tex>$\beta-\mathbf{axis}$</tex> current is estimated by the <tex>$d-q$</tex> axis reference inputs. This is equivalent to introducing the <tex>$\beta-\mathbf{axis}$</tex> reference input as a feedforward term into the <tex>$d-q$</tex> axis current loop, so the parameter sensitivity problem is solved, and the parameter tuning is not needed. The proposed method can maintain good steady-state performance and significantly improve the dynamic performance of the current loop. Furthermore, it is straightforward and can be easily implemented in digital controllers. Comprehensive hardware-in-the-loop (HIL) experimental comparisons with the SOGI and FAE methods have been conducted to verify the correctness and effectiveness of the proposed RI-based IACE method.