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The pulse frequency modulation with a constant on-time can be adopted for the series resonant converter operating in discontinuous conduction mode to regulate the output voltage. It is found for the first time that there are two different operation cases with different magnetic flux density (MFD) values. The boundary condition for the two cases is found out and the exact MFD expression of each case is derived. The MFD has smallest value under lowest switching frequency and increases with the increase of switching frequency for both cases, indicating the high-power transformer can be designed at highest switching frequency. A transformer turns ratio design guideline can be easily obtained to avoid the higher maximum MFD case. The theoretical analysis is verified by the simulation and experimental results.

The existing power electronic transformer (PET) topologies based on modular multilevel converter (MMC) can provide multiple voltage ports. However, these PET topologies need four power conversion stages, which leads to complex circuit structure and large size. A multiport PET topology based on MMC with resonant circuit for DC distribution has been proposed in this paper. A mixed-frequency modulation strategy is adopted and a group of LC resonant circuit is connected in parallel with each MMC arm, to realize power decoupling between MVDC and LVDC ports. The proposed PET topology can provide the required four ports with only three power conversion stages, which has the advantages of simplified circuit structure and smaller size. Finally, the simulation results verify that the proposed PET is feasible and effective.

This paper presents a design scheme of distributed energy storage system (ESS) which is used to improve the automatic generation control. Based on the constraints of ESS and the manual of supercapacitor, the selection of supercapacitor methods are described in detail, and the common product combinations are listed. Because of the large number of energy storage units and output levels, half-bridge topology is advised which enables to save switching devices. Due to the high loss, insufficient advantages of carrier phase-shifting PWM and output distortion of nearest level modulation in ESS application, carrier disposition modulation is recommended and convenient to realize power-sharing under low switching loss. Based on carrier disposition modulation, voltage balance algorithm and grid-connected algorithm are designed, and detailed trigger block diagrams of each switch device are presented. Finally, the feasibility of the proposed design method is verified by Simulink simulation.

With the integration of renewable energy resources and variable loads into power grid, power oscillations caused by persistent external fluctuating forces are becoming more prevalent. Termed as “forced oscillations (FO)”, such phenomena could happen even when the grid is with good damping characteristics. Therefore, conventional mitigation methods based on improving damping are rendered less effective. By leveraging the new control capability offered by static synchronous compensator with energy storage (E-STATCOM), a novel approach to mitigate FOs is proposed in this paper. A control strategy based on resonant controllers is adopted to modulate active and reactive power supplied by E-STATCOM. It is theoretically shown that FOs propagating from the disturbed area to other areas can be effectively eliminated by this method. Besides, we derived the analytical relationship among the location, the capacity of E-STATCOM and the suppression performance. Case studies demonstrate the effectiveness of the proposed method.

Due to the flexibility and programmability, software defined networking (SDN) has aroused wide public concern of academia and industrial circles, especially, the civil aviation information network with extremely sensitive information. Simultaneously, the separation of control plane and data plane in SDN provides a chance for the remote attacker to attack. The attacker uses the SDN detection technology to obtain some information such as the flow table rule and so on, and then they can make the attack strategy according to these information. Next, SDN also promote the development of anti-detection technology, thus further improving its security. The advantages and disadvantages of different schemes are summarized by deeply discussing the existing detection technologies of civil aviation information network, including network type detection and flow table capacity detection. Finally, the development of SDN detection technology in civil aviation information network in future is prospected, which has a certain reference significance for the researchers.

This paper presents two novel hybrid-magnetic-circuit variable flux memory machines (HMC-VFMMs) with different permanent magnet (PM) configurations. The proposed HMC-VFMMs are both characterized by a combination of series and parallel circuit topologies, but with different positions of series and parallel PM branches. The proposed HMC design can combine the merits of wide flux adjustment range in parallel structure and excellent unintentional demagnetization (UD) withstand capability in series structure. The topologies, features and working principles of the proposed HMC-VFMMs with different magnet arrangements are introduced, respectively. The magnetic circuit model is utilized to reveal the underlying working mechanism and performance metrics of the proposed HMC-VFMMs having different PM types. The electromagnetic characteristics of the HMC-VFMMs having radially-magnetized (RM) and circumferentially-magnetized (CM) LCF PM types are evaluated and compared by the finite-element (FE) method. The experiments on a 21-slot/4-pole prototype with RM-structure are carried out to validate the FE analyses.

In this paper, an active damping control strategy based on modifying third-harmonic injection reference current and output reference current is proposed for hybrid active third-harmonic injection matrix converter (H3IMC) to improve system instability. First, the system stability when H3IMC adopts no damping methods and passive damping method is analyzed through small-signal modeling and root locus analysis. Then, the active damping method based on virtual damping branch is applied to H3IMC. A specific implementation method based on the modification of reference third harmonic injection current is proposed, which can realize active damping control strategy directly and effectively by injecting the damping signal into the reference third harmonic injection current, and avoid the problem of reducing the control freedom of the output side. Finally, simulation results illustrate that, under the condition of the same parameters, the proposed active damping control strategy performs the same as passive damping control in damping at source side and better in filtering.

This paper proposes an optimized topology of hybrid active third-harmonic injection matrix converter (H3IMC), which mitigates input current distortions at sector boundaries. First, the research background and working principles of H3IMC are introduced. Then, the origin of the distortions is analyzed from the angle of commutation. To solve this problem, a modification of the original topology is proposed, which has a dc-link filter to bypass the switching frequency component of IVS output currents and then reduce the mutation in input currents. Moreover, the concept is verified by simulation results taken on a H3IMC Simulink model. Finally, the mains current quality and the number of passive elements used in the original optimized topology and are compared.

Finite States Model Predictive Control (MPC) has been recently applied to several converters topologies for the many advantages it can provide such as fast dynamics, multi-target control capabilities, easy implementation on digital control board and capability of including constraints in the control law. However, its variable switching frequency and lower steady state waveform quality, with respect to standard control plus modulator systems, represents a limitation to its applicability. Modulated Model Predictive Control (M²PC) combines all the advantages of the simple concept of MPC together with the fixed switching frequency characteristic of PWM algorithms. In particular this work focuses on the Indirect Matrix Converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M²PC design. This paper proposes an M²PC solution, suitable for IMC, with an optimal switching pattern to emulate the desired waveform quality features of Space Vector Modulation (SVM). In the optimal pattern, the switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying its commutation strategy. In addition, the optimal pattern enables M²PC to produce sinusoidal source current, sinusoidal output current and maintain all desirable characteristics of MPC.

As a new kind of compact-sized, bi-directional power flow AC/AC converter, indirect matrix converter draws wide attention in the field of aircraft power system, distributed generation and other industry application. This paper applies indirect matrix converter to permanent magnet synchronous generator system. The generator is connected with voltage source converter, control strategy of d-q axis closed loop control of load voltage and generator current of boost generation is discussed. The feasibility of the control schemes is verified by simulation results.

Indirect matrix converter (IMC) is studied for aircraft starter/generator(S/G) application in this paper. Careful consideration of two S/G system structures is presented. In the two structures, S/G is located at the voltage source side and the current source side of IMC respectively. The former is mentioned in existing literature and the latter is proposed by this paper. It is shown that the former has a high chance to suffer an overcurrent problem in starting mode, while the latter is more practical with achievable control strategies and thus is the main topic of this paper. In addition, it is easier to design and damp the LC filter in the latter. Typical starting control strategy and novel voltage-boost generating control strategy are presented. The feasibility of the proposed IMC-S/G system and its control strategies are verified by experimental results.

Low voltage transfer ratio is a main drawback of indirect matrix converter (IMC) for PMSM drive applications. This situation can be improved by unit power factor control of PMSM. According to the circuit equations of PMSM, this paper analysis the relationship between the amplitude of terminal voltage, so the terminal reactive power, and d-axis stator current. Based on the rotor field oriented vector control strategy of PMSM and space vector modulation algorithm of IMC, a novel unit power factor control method is proposed. In this method, a controller is employed to regulate the terminal reactive power and generate the reference value of d-axis current. Hence, the actual d-axis current is automatically adjusted to realize unit power factor operation of PMSM. The proposed method doesn't need accurate motor parameters and thus is robust. The validity and feasibility of the proposed strategy is verified by experiments carried out on a 2.4 kW IMC-PMSM prototype.