Fractional order proportional-integral-derivative(FOPID) controllers have attracted increasing attentions recently due to their better control performance than the traditional integer-order proportional-integral-derivative (PID) controllers. However, there are only few studies concerning the fractional order control of microgrids based on evolutionary algorithms. From the perspective of multi-objective optimization, this paper presents an effective FOPID based frequency controller design method called MOEO-FOPID for an islanded microgrid by using a Multi-objective extremal optimization (MOEO) algorithm to minimize frequency deviation and controller output signal simultaneously in order to improve finally the efficient operation of distributed generations and energy storage devices. Its superiority to nondominated sorting genetic algorithm-II (NSGA-II) based FOPID/PID controllers and other recently reported single-objective evolutionary algorithms such as Kriging-based surrogate modeling and real-coded population extremal optimization-based FOPID controllers is demonstrated by the simulation studies on a typical islanded microgrid in terms of the control performance including frequency deviation, deficit grid power, controller output signal and robustness.

A novel droop control with coupling compensation and inertia is proposed for a microgrid to achieve high dynamic performance and stability of distributed generation (DG) units. The coupling compensation scheme consists of angular frequency deviation compensation and voltage deviation compensation. They can reduce the influence of uncontrolled power coupling. The inertia scheme consists of angular frequency inertia and voltage inertia. They can slow down the change rates of the angular frequency and voltage and reduce their fluctuation magnitudes. The combination of this novel droop control method and virtual impedance can help achieve accurate power sharing. An improved particle swarm optimization (PSO) algorithm with multi-swarm and multi-velocity (MMPSO) is also proposed to optimize the parameters of the coupling compensation and inertia with high precision and high reliability. A simulated model and experiment platform of a microgrid are set up for testing, and the simulation and experimental results validate the excellent performance of the MMPSO and the effectiveness of the novel droop control method.

The optimal P-Q control issue of the active and reactive power for a microgrid in the grid-connected mode has attracted increasing interests recently. In this paper, an optimal active and reactive power control is developed for a three-phase grid-connected inverter in a microgrid by using an adaptive population-based extremal optimization algorithm (APEO). Firstly, the optimal P-Q control issue of grid-connected inverters in a microgrid is formulated as a constrained optimization problem, where six parameters of three decoupled PI controllers are real-coded as the decision variables, and the integral time absolute error (ITAE) between the output and referenced active power and the ITAE between the output and referenced reactive power are weighted as the objective function. Then, an effective and efficient APEO algorithm with an adaptive mutation operation is proposed for solving this constrained optimization problem. The simulation and experiments for a 3 kW three-phase grid-connected inverter under both nominal and variable reference active power values have shown that the proposed APEO-based P-Q control method outperforms the traditional Z-N empirical method, the adaptive genetic algorithm-based, and particle swarm optimization-based P-Q control methods.

Electro-aerodynamic unmanned aerial vehicles (EAD-UAV) have strict requirements for lightweight. Due to the heavy weight of magnetic components and insulation materials, the power source of the EAD-UAV, an L CC high voltage power supply (HVPS)'s specific power cannot meet the minimum requirements. To improve the specific power of L CC HVPS, this paper will optimize the magnetic core, insulation materials, and magnetic integrated transformer structure. Firstly, the weight-frequency relation of the high-voltage transformer core is derived, and it is shown that there is an optimal frequency to minimize the weight of the high-voltage transformer core. Then, for insulation material optimization, the existing method points out that the input parallel output series (IPOS) array structure can reduce the amount of insulation material. This paper uses the structure. But this paper combined with the optimal frequency proposed the number of array transformers and insulation design method. Next, for each transformer in the array, an asymmetric magnetic integrated transformer structure is proposed. Which realizes the resonant inductance integration. At the same time, the magnetic shunt can be adjusted according to the needs of the winding. So, this structure can improve the utilization rate of the transformer window, and reduce the weight of the magnetic core. Finally, a 619W-rated laboratory prototype is designed to convert 140 V input to 40kV output. The designed IPOS transformer array weighs is 213.5g, the total weight of the HVPS is 423.9g, and the specific power is 1.46kW/kg, working at the optimal frequency of 101.2kHz.

Fast and reliable protection against short-circuit (SC) faults is critically important for the reliable operation of power devices. In this letter, an ultrafast and universal short-circuit protection (SCP) method is proposed for silicon carbide metal–oxide–semiconductor field-effect transistors based on gate current detection. This method exploits the characteristic of the gate current to become negative during SC faults and constant positive during normal operation. The proposed gate current detection approach swiftly identifies faults during the SC process, ensuring rapid response time. In addition, this method boasts broad applicability, being effective for both hard switching faults (HSFs) and faults under loads (FULs), and no extra auxiliary design is required for the three-pin device. The efficacy of the proposed SCP technique is validated through the testing of the SCP circuit. Experimental results demonstrate that the proposed circuit is applicable to both HSFs and FULs, with response delays of 69 ns for HSFs and 50 ns for FULs, and total protection trigger time of 383 ns for HSFs and 352 ns for FULs.

In battery charging applications, the charger changes its output voltage in a wide range during the charging process. This makes the design of LLC converters difficult to be optimized between the efficiency and the gain range. In this paper, an improved resonant transformer is presented for LLC resonant converter charger to improve the gain adjustment and charger efficiency. The resonant inductance and magnetizing inductance are integrated in the designed LLC transformer, and the magnetizing inductance can be adjusted dynamically with the change of output voltage and load, which is realized by a switch-controlled inductor (SCI) parallel to the secondary winding of transformer. The proposed transformer has 22.4% reduction in losses under full load conditions compared to conventional solutions. Moreover, the conduction loss and switching loss of LLC resonant tank are reduced by dynamically adjusting the magnetizing inductance, which improves the comprehensive efficiency of the whole charging process. The proposed transformer design is verified on a 720 W prototype.