In this paper, an improved distributed dynamic event-triggered secondary control algorithm is proposed to restore frequency and voltage, as well as to achieve accurate active power sharing in islanded AC microgrids. Based on the sampled-data mechanism, the proposed design begins with the optimization of the event-triggering conditions by introducing internal dynamic variables. This approach not only reduces the triggering number but also inherently prevents Zeno behavior. Subsequently, a self-triggered scheme is introduced using an integral operator to predict estimation errors. This allows event checking to rely only on the states at triggering instants, thereby eliminating the need for unnecessary periodic sampling. Furthermore, a rigorous stability analysis is conducted using Lyapunov stability theory. Finally, the effectiveness is demonstrated through numerical simulations in MATLAB/Simulink. Compared to the traditional methods, the proposed scheme significantly reduces system overhead without compromising control performance.