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In order to solve the problem that the sparrow search algorithm is easy to fall into local optimum and lack of search ability in the process of optimization, a chaos improved sparrow search algorithm (SMSSA) is proposed, which combines the improved slime mold algorithm. Firstly, the Bernoulli chaotic map is used to improve the initial population quality of the algorithm; then the following optimization strategy of the spiral slime mold algorithm is combined in the follower position update to improve the global search ability of the sparrow algorithm in the iterative process; finally, the t-distribution opposition-based-learning strategy is used to perturb the position of the sparrow search algorithm to improve the algorithm's ability to jump out of the local optimum. In the simulation experiment, the algorithm is compared with other four basic algorithms based on 13 benchmark functions. The results show that the algorithm has good convergence and accuracy, and the global exploration ability is greatly improved compared with the original algorithm. Finally, SMSSA is applied to the Kapur entropy multi-threshold image segmentation task, and the results show that SMSSA has higher segmentation accuracy than the other four basic algorithms. [ABSTRACT FROM AUTHOR]

Due to line impedance mismatches, nonlinear loads and other reasons, the traditional droop control algorithms have great limitations on the control of reactive power sharing. Distributed control algorithms based on hierarchical structure have become an effective approach for reactive power sharing compared with traditional centralized control methods. In this paper, an event-triggered control algorithm based on stability analysis of Lyapunov method is put forward in order to satisfy the demand of low-bandwidth communication for distributed generator in islanded microgrid. Subsequently, a distributed hierarchical control scheme adopting proposed event-triggered strategy is designed to achieve proportional reactive power sharing in an islanded microgrid. Finally, the feasibility and validity of the proposed algorithm are further verified in MATLAB/Simulink environment. [ABSTRACT FROM AUTHOR]

THD and the amplitude balance of three-phase input current are an important index for the performance of three-phase power factor correction (PFC). In general, when the hardware and the load of three-phase PFC are confirmed, the THD and amplitude balance of three-phase input current mainly depend on voltage and current feedback loop of PFC. Firstly, this paper designs the traditional voltage and current feedback loop for three-phase PFC according to traditional small signal theory. Secondly, this paper studies the designing difficulty of large dc voltage ripple for PFC voltage controller and puts forward a new dc voltage ripple filter which can eliminate the ac component of sampling dc bus voltage. Finally, this paper proposes a novel filter with dc voltage ripple frequency adaption function to copy with the frequency variety of the voltage ripple caused by the change of the output inverter frequency. With the help of the proposed algorithm the distortion of three-phase 3 input current reference decreases rapidly, therefore, the low THD and good amplitude balance of three phase input current will be achieved. [ABSTRACT FROM AUTHOR]

In the conventional output voltage feedback loop design of an active power factor corrector (PFC), the bandwidth of the loop is limited to a frequency significantly lower than the input line voltage frequency. This is due to the fact that the compensator placed in the outputvoltage feedback loop is usually designed to have a narrow bandwidth in order to filter the voltage ripple of twice the line frequency coming from the PFC output dc voltage. This feedback loop is designed with this filtering effect because a relatively high ripple voltage would cause considerable distortion in the reference of the line current feedback loop. However, a low bandwidth voltage feedback loop would bring poor dynamic response which usually causes large overshoots and dips during load transient change. Therefore, a compromise is generally made for the traditional design of the output voltage feedback loop, which leads to an issue that both the steady and the dynamic behaviours of the PFC are not optimal. In this paper, mathematic model of the steady behaviour of a PFC with voltage ripple in the output-voltage feedback loop is studied using two parameters: the amplitude of the relative voltage ripple on the control output signal and its phase lag angle of the voltage feedback loop. On the basis of the analysis, a second-order voltage harmonic injection to the output-voltage feedback loop is used to eliminate the voltage harmonic components from the voltage feedback loop. Finally, the feasibility of the proposed second-order harmonic injection method was verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]