Sensorless control technique is regarded as the enabler of the reliability improvements for interior permanent magnet synchronous motor(IPMSM) drives. However, the con- ventional estimation schemes by using the phase-locked loop(PLL) and the frequency-locked loop(FLL) may experience undesired accuracy under acceleration and deceleration cases(ADCs). To ad-dress this, a speed estimation scheme by combining a closed-loop active flux observer(CLAFO) with a tracking differentiator-based frequency-locked loop(TD-FLL) was proposed in this paper. Starting from a brief introduction of the conventional PLL perfor-mance analysis with- and FLLADCs based estimation schemes, a detailed is provided. Accordingly, an estimation scheme based on the TD-FLL is elaborated. Considering the performance of the proposed TD-FLL scheme is adversely affected by various distur- bances, a CLAFO is carefully designed to improve the disturbance immunity of the proposed TD-FLL scheme. Extensive experimen-tal tests are conducted to verify the effectiveness of the proposed TD-FLL scheme under different test cases.