Employing high frequency (HF) transformer in DC-DC converter is a popular strategy in power electronic industry. Equivalent circuit model of transformer in HF Dual Active Bridge (DAB) converters is investigated along with its impact on power transfer characteristic for Single Phase Shift (SPS) and Extended Phase Shift (EPS) modulation. Equivalent branches of magnetizing inductance allocated in primary and secondary side can inject the inductive current at switching instants to extend Zero Voltage Switching (ZVS) range. ZVS maps are proposed. Based on the power transfer characteristics and ZVS maps, an Advanced Extended Phase Shift (AEPS) modulation method with modified coupling relationship for phase shift is proposed to reduce the current stress and improve the voltage utilization. Finally, AEPS modulation is implemented in PLECS simulations to verify the analyzation presented.

One of the advantages of multiphase machine is the capability of fault tolerance. Variety of post-fault control methods based on hysteresis, proportional-integral (PI), proportional resonant (PR) and model predictive controller (MPC) have gradually been developed. Due to simple structure and decoupling of reduced-order matrix, it is used as an alternative to the Clarke matrix in the healthy mode when the fault happens. Although a lot of control methods adopted a reduced-order matrix as the basic derived technology, the performance of controllers is different, and they need to be compared in term of specific applications in fault tolerance. For this propose, the paper deals with the steady-state and dynamic performance of four current control methods, hysteresis control, PI control, PR control and model predictive control in open-circuit fault. The results shows that the PR control method has low torque ripple, copper loss and derating in healthy and post-fault stage, and the MPC control method has low torque ripple in fault stage and fast response capability after applying fault-tolerant methods.

Distributed energy resources and new loads such as fast charging stations for electric vehicles are often dc-based. By using low-voltage dc microgrids to connect such systems to the grid, conversion stages can be omitted and higher efficiencies can be achieved. Challenges exist with respect to the protection of dc microgrids, where dc fuses are a viable solution but selective tripping must be ensured. The grid-forming converter must be able to supply the fault current in the case of a line-to-line short-circuit in a feeder without tripping due to over-current. To avoid expensive over-sizing, this paper proposes to use a virtual resistance in the control of the grid-forming converter to limit its output current. The range of the virtual resistance is discussed for normal grid operation and the effect of the virtual resistance on limiting the bus current during a short-circuit fault is discussed. In addition, the impedance models of the source and load systems are presented. Based on this, the influence of the virtual resistance on the system stability is analyzed. To validate the theoretical part, a switching model is simulated and the results show a good agreement with the theoretical analysis.

The concept of multiport dc-dc converter was proposed to reduce the conversion stages of dc microgrid on more electric aircraft (MEA). The structure of multiport dc-dc converter is basically developed from the dual active bridge (DAB) converter because of its galvanic isolation and bidirectional power flow. A power electronics converter as a key element of the electrical power distribution system may cause stability issues. To address these challenges, the impedance characteristic of the multiport converter will be analyzed. In this paper, a transfer function based small signal model is developed and validated with a switching model, to figure out the characteristic of input impedance of triple active bridge (TAB) converter. Preliminary experimental results are presented to be as a support.

In the More Electric Aircraft framework, the objective is to increase the efficiency and the reliability of the aircraft by gradually substituting the existing subsystems with electrical ones. Newer aircrafts already incorporate a great share of electric power, making the on-board electrical power distribution system (EPDS) a complex structure composed of generators, actuators and storage. Because of the importance of power electronics in this scenario, the control system is critical to ensure the stability of the EPDS. This paper analyzes the sensitivity to the control parameters of the EPDS stabiltiy. A state-space model is derived and the root loci are used to show in a graphical way the effects of the design parameters.

In the framework of the More Electric Aircraft (MEA), weight reduction and energy efficiency constitute the key figures. In addition to these requirements, the safety and the continuity of operation is of critical importance. These sets of desired feature are in disagreement, because the redundancy needed to guarantee the safety of operation implies necessarily in additional weight. Several concepts of the electrical power distribution systems have been proposed, in this manuscript, an approach based on the widespread use of multi-port power converters both for the DC/DC and for the DC/AC stages is proposed. These two technologies allows for a ring distribution of the electrical power whereas the galvanic isolation is still kept. Simulation and experimental results show the feasibility of the concept in common and fault operation conditions.

Dual-active-bridge (DAB) DC-DC isolated converter is widely used in many applications e.g. power supplies, transportations and renewable power systems. In this paper, general modulation characterization and optimization of DAB converters have been analyzed and advanced modulation methods are proposed. Simulations and experiments are implemented to verify the effectiveness of the proposed modulation strategies.

The Modular multilevel matrix converter (M3C) is a promising topology for medium-voltage, high-power applications. Due to the modular structure, it is scalable, produces high quality output waveforms and can be fault tolerant. However, the M3C suffers from capacitor-voltage fluctuation if the output frequency is similar to the input frequency. This problem could limit the circuit's application in the adjustable speed drives (ASD). This paper introduces a theoretical analysis in the phasor-domain to find the branch energy equilibrium point of the M3C when operating with equal input and output frequencies. On the basis of this equilibrium point, a branch current reallocation based energy balancing control method is proposed to equalize the energy stored in the nine converter branches. With this novel control method, the M3C can effectively overcome the capacitor voltage fluctuation without using balancing techniques based on common mode voltage or applying reactive power at the input side.