ABSTRACT The control of DC microgrids is a growing area of research. DC distribution networks present an effective solution to the integration of stochastic energy sources as renewable energy and renewable storages. A communication layer is required to exchange measured and estimated values for the secondary control loop. Faults and failures within the communication layer lead to malfunctions and divergence in system values. The control structure is presented using adaptive droop based secondary control for detection of communication islanding and stabilize the operation of the system. Recent years, more robust techniques and methodologies have been suggested to increase system resilience, but the communication islanding detection has not been addressed in DC microgrid at the multi-level control. This work, therefore, modifies the secondary level control to include a communication failure detection scheme that identifies communication islands within this network. Adaptive droop is employed to mitigate the effect of communication islands and regulate current sharing. The proposed scheme is verified using system-level simulations and analytical studies.

ABSTRACT Current harmonics are introduced in a distribution system due to the increasing utilization of nonlinear loads. Therefore, elimination of harmonics from supply current is an inevitable task to do. In this paper, an adaptive control technique called I-cos-theta (Icosθ) control algorithm along with a Kernel-based training method is proposed in a fuel cell-based Distributed STATic COMpensator (DSTATCOM) simulation for harmonic compensation. Specifically, the direct and quadrature components of the load current are extracted and retrained using the Kernel-based Icosθ control algorithm. The control algorithm is implemented to generate reference currents, and then the appropriate switching pulses for the Voltage Source Inverter (VSI) of the DSTATCOM. The fuel cell is intended to maintain the DC-link voltage of the DSTATCOM during different loading conditions for power quality improvement. Further, the DC-link voltage is maintained constant at 530 V with an acceptable voltage regulation of <±16%, even under load transients and temporary supply failure conditions. Moreover, the simulation of the fuel cell-based DSTATCOM has been performed in Sim Power System (SPS)/MATLAB Simulink software. Also, a low power rated prototype is developed to verify the proposed simulation model, incorporating with the dSPACE1104 real-time environment.

ABSTRACT This paper presents a comparison of prospective design concepts of DC/DC isolated converters for auxiliary drives of DC catenary fed light traction vehicles. Auxiliary drives are mostly dedicated to generate standard power grid supplying various on-board equipment and to charge on-board batteries. The DC/DC isolated converter consists of full-bridge (FB) converter feeding a high frequency transformer (HFT) and SiC diode rectifier which produces a DC voltage bus line for 3-phase voltage-source inverter. The input FB converter is in our case designed using 1200 V devices in discrete (Si IGBTs) and module (SiC JFETs) version. The comparison deals both the hard switching and soft switching topologies of the converters. The investigated design concepts are experimentally tested up to the switching frequency of 200 kHz. The main aim of this paper is to compare efficiencies of SiC JFET and Si IGBT LLC full bridge converters operated under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The introduced theoretical results and analyses are validated by the experiments made on developed prototype 8 kW, 400 V/600 V DC/DC isolated converter using SiC JFET and Si IGBTs

ABSTRACT This paper presents a study on the influence of different rectifiers on a super-high-speed permanent magnet generator (SHSPMG), which is used in a micro-gas turbine distributed generation system. Taking a 117 kW, 60,000 r/min SHSPMG as an example, the influence of PWM and uncontrolled rectifiers on the generator performances were studied comparatively. The current harmonics and its total harmonic distortion were analysed firstly, and the variation characteristics of voltage and current harmonics were obtained. Based on the 2-D electromagnetic analysis model, the losses of the generator with different rectifier load were studied, especially for the rotor losses, and the mechanisms of the losses variation were determined. By using the method of the 3-D coupling field between fluid and temperature, the temperature distributions of the SHSPMG connected with the PWM and uncontrolled rectifiers were calculated, respectively, and the influences of the different rectifiers on the generator temperature field were studied. It could be found that the PWM rectifier has the advantages of reducing generator losses and optimizing temperature distribution.

ABSTRACT With growing decentralized power generation, medium-voltage (MV) dc-dc converters are becoming increasingly important. A three-phase dual-active bridge (DAB3) is a promising topology for high-power MV applications. The semiconductor devices used in such converters at multi-megawatt level tend to be slow in switching. Hence, a considerable dead time between switching instants is required to avoid shoot-through in phase legs. This dead time forces the current to commutate to the freewheeling diodes and introduces a current dependence of the phase voltages. In this work, the effects of dead time on the operation of DAB3 are analysed in detail. The derived analytical expressions are used in the control development to compensate for the effects of dead time and hence achieve superior control performance. Measurements are carried out on a small-scale laboratory prototype to validate the derived operational modes and the effectiveness of the proposed dead time compensation.

ABSTRACT In this research paper, an Advanced Harmonic Filter (AHF) is designed and implemented for variable frequency drives of 55 kW rating. The AHF consists of a line reactor (Lo) and a Double Tuned Filter (DTF) to mitigate the 5th and 11th order harmonics of the drive current. The performance of AHF is verified using the MATLAB/Simulink platform. The complete design has been validated with experimental results and reasonable reduction of Total Harmonic Distortion (THD) is observed. The prototype is in good agreement with the IEEE 519–2014 standard limits. Also, the electrical and thermal test results of the AHF are showed.

ABSTRACT This paper presents the modelling of the DC–DC multilevel modular converter (DC–DC MMC) with half-bridge sub-modules and the control based on the inversion of its model. The DC–DC MMC presents many advantages such as its modularity, the absence of capacitors on the DC-bus voltage and a low switching frequency. This topology also preserves the intrinsic disadvantages of the MMC as the complexity controlling due to the large number of semiconductors and state variables to control. The control of this converter cannot be symmetrical due to the interconnection of the two parts by an internal AC grid. The control strategy of one part of the DC–DC MMC uses the conventional control scheme with current controls and stored energy control. The second one uses the energy control and produces the waveform of the three-phase internal AC bus voltage linking the two parts of the converter. The explicit control for the generation of internal AC voltages guarantees the correct operation of the converter even in a critical DC-voltage dip on DC buses. Thus, it avoids the need of a DC circuit breaker or the use of full-bridge MMC sub-modules. The validity of the proposed control is verified by simulation.

ABSTRACT This paper presents a power balance technique for high power welding machines with a modular design using a common-mode-coupled inductor (CMCI). The voltage applied across the CMCI can automatically adjust current slopes of transformer primary currents to be equalized so that the power transfer between power modules can be balanced even in the structure in which both the primary side and secondary side are parallel. To show the operation of the proposed method, an analysis has been performed with a welding machine with two transformers and design equations for CMCI has been derived based in the analysis. The feasibility of the proposed method is verified using a 20 kW welding machine consisting of two 10 kW modules.

ABSTRACT This paper proposes an efficient LED lamp converter circuit incorporating dimming feature and multiple lamp independent control. The converter consists of a half-bridge resonant converter in series with a DC source. This converter operates at 200 kHz. Soft switching is employed with resonant power conversion. With modulation of the low frequency pulse width, the dimming feature is incorporated. The proposed configuration provides lower voltage stress for switching devices as well as lower switching losses resulting in increased efficiency. It is possible to independently control the current of each lamp. For two lamps operating in parallel with a total power of 25 W, a laboratory prototype has been designed. It can be used in residential applications. The proposed circuit is presented with detailed operation of the circuit, simulation and experimental results.

ABSTRACT In this article, predictive torque control (PTC) of multi-level inversion (MLI) fed open-end winding induction motor (OEWIM) drive has been developed with predictive angle control technique. The classical PTC of induction motor drive involves direct control of torque and flux. The combination of direct torque control (DTC) with model predictive control (MPC) offers all the features of classical DTC and in addition it is easily implementable for MLI fed induction motor drives. This article introduces predictive angle control strategy for MLI fed OEWIM drive to reduce torque ripple, where as the classical PTC algorithm uses magnitudes of torque and flux. The proposed algorithm is developed by controlling the angle between stator flux and stator current, the voltage space vectors of MLI fed OEWIM drive are classified according to operating frequency range. The proposed PTC algorithm requires same computational time as that of classical PTC. The proposed algorithms are verified through simulation and experimental studies.