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.
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
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.
We propose a resource efficient precision transient circuit simulator approach without time step for solving the systems of differential equations. The method is notably suitable for optimization and worst-case dimensioning of small-scale electronic circuits. A closed-form analytic solution is computed for each of the electronic circuit states. Numerical integration is not required, and therefore, convergence problems are eliminated. An electronic circuit with only linear elements, for example, R, C, L and independent current, and voltage sources (LTI), is described with a system of differential (state) equations. Nonlinear elements, such as L(i), C(u), Diodes, MOSFETs, BJTs and/or PWM controllers are described with piecewise-linear models. Connecting linear and linearized nonlinear elements, results in a linear system of differential equations.
Controlled Diode Bridge Clamped (CDBC) three level inverter configuration is the optimized version of T-type voltage source inverter in terms of power switches and their associated gate driver components. After a brief introduction of CDBC VSI, this paper implements the concept of Z-source inverter into this configuration. The three level SVPWM technique has been used for the generation of gating pulses. It has been pointed out that, in contrast to three level VSI, the switching frequency of three level ZSI depends on the modulation index for any particular carrier frequency. Also, a new switching state pattern has been suggested for optimizing the switching frequency of the power switches using max constant boost (MCB) and simple boost control (SBC) approach of voltage boosting. Comparing the same category of MCB or SBC control, the proposed switching pattern offers minimum switching frequency of power switches without affecting total harmonic distortion of line voltage/current as compared to the existing PWM switching patterns of three level ZSI. The condition of nearest three vector switching has been followed to ensure better output waveform quality. Simulation and experimental results verify the proposed inverter configuration and its PWM technique.
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 5(th) and 11(th) 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.
Nowadays there are vast enlargements in the grid applications; the control strategy of power electronics systems has also spread their locality extensively. Single processor of complex hardware is used in the conventional method, to generate the control strategy for microgrid. To avoid this issue, we cultivate a low-power microgrid with the help of NoC. Reconfigurable Double Tailed Sense Amplifier (RDTSA) based on the NoC is selected for the reduction of power. History based Dynamic Frequency Scaling (HDFS) is implemented in RDTSA for further power reduction. The combination of this is named as a Mixture of Algorithm with NoC (MAN) architecture, which has been refined from the ALPIN architecture. Cultivation of the entire design results in delay and power reduction compared to the conventional method. The performance of delay, data rate static power and energy are evaluated compared to conventional method and the RDTSA. The overall performance of Heuristic Asynchronous NoC for Universal power electronics application (HANU) is superior to that of the conventional approaches.
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.
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.
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.
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.
This paper presents a modified topology for asymmetric modular multilevel inverter as a fundamental block. It consists of eight switches (including six bidirectional-conducting unidirectional-blocking switches and two bidirectional-conducting bidirectional-blocking switches) and four DC sources with unequal magnitudes, which generates 13-level output voltage. The proposed topology offers special features such as reduced number of switches, isolated DC sources, economical and less complexity with modular structure as compared to other contemporary topologies. Moreover, significant reduction in switch voltage can be achieved. The comparative study of proposed topologies with the conventional and recent topologies have been presented in terms of power switches, gate drivers, isolated DC voltage sources and total standing voltage on the switches. A multicarrier-based sinusoidal pulse width modulation scheme is adopted for generating the gate pulses using real-time simulation with dSPACE DS 1104. The proposed topology offers a fewer number of ON-state switches which lead to the reduction in power loss. The feasibility of proposed multilevel inverter, the simulation and experimental results are analysed under steady state and dynamic states.
The proposed light-controlled cascode is a power electronic device (or circuitry) which can be turned-on and -off by optical excitation. In contrast to the light-triggered thyristor, which can optically be turned-on but not -off, the proposed device allows optical turn-on and -off. Also, it allows a scalability of the blocking voltage by the extension to a light-controlled supercascode [1] which is also shown. After a brief theoretical consideration experimental set-ups will be presented and measurements are shown. Due to the difficulty to buy appropriate devices required for the experimental set-ups some compromises were necessary. Therefore, these first experiments show a very slow switching behaviour. However, this could become speeded up by an optimized photodiode made from wide band gap semiconductor material. In spite of these compromises pulses with a power of 1 kW were turned-on and - off by the experimental set-up. However, this device is far away from being ready for series production but the feasibility is demonstrated and the potentials are shown.
In this paper, two new structures are proposed for diode-assisted extended-boost continuous-current quasi-Z-source inverter (qZS). In the proposed structures to reduce the capacitors and diodes voltage stresses, a new switched inductor structure is used. Voltage gains of inverters in the proposed and conventional topologies have the same magnitude. Moreover, the startup inrush current in the proposed topologies is decreased. In this article, at first, the proposed Z-source inventers are investigated to find out their governing relations. Then, the proposed Z-source inverters are compared with the conventional ones by simulating them to assess their performance efficiency. Next, applying the simple boost pulse width modulation the simulation is carried out in PSCAD/EMTDC software. To evaluate the obtained results, the prototypes of the proposed inverters with 48Vdc input voltage are used.
Switched reluctance motors operate at very high-speed ranges. At high speed, the switched reluctance motor drives are losing the capability of high torque production. In this paper, a novel method is proposed for controlling high speed switched reluctance motor using both continuous and discontinuous conduction modes. The proposed method controls the machine torque in continuous-conduction mode using four control parameters. Simulation test-beds are constructed using three-dimensional finite element, and co-simulation to demonstrate the effectiveness of the proposed method.
This paper presents a new control scheme for the ac-dc-ac nine-switch converter (NSC) with induction motor operated at constant frequency. The NSC at constant frequency operates optimally and its application for induction motor drive with re-active power compensation is proposed. In industries for various applications, induction motors are operated at constant frequency but at different loading conditions. These motors are operated at lagging power factor. The power distribution company demands high power factor operation and it gives benefits to consumer on operating a system closer to unity. In this paper, a control scheme is proposed to operate NSC drive at unity as well as at leading power factor with sinusoidal input current. The independent active-reactive power control technique is developed. The input-output active power relation is developed such that with the change in load, output active power matches input active power without affecting dc-link voltage. This results in faster dynamic response as compared to conventional dc-link balancing control techniques. With the proposed control scheme, the NSC is operated at desired leading power factor to compensate reactive power at point of common coupling. The simulation and experimental results show the feasibility of the proposed control scheme.
The non-linearity of photovoltaic systems and the change in maximum power point with a level of insolation and temperature complicates the tracking of the maximum power point. Several maximum power point tracker methods have been proposed and implemented in literature. The paper studies a modified perturb and observe (P&O) approach for a photovoltaic system in order to extract the maximum power point with more precision, fast speed and avoid the problems caused by the classic P&O method under the change of climatic conditions. This work is tested with a resistive load powered by a photovoltaic generator via a DC/DC converter. These methods are implemented with STM32F4 microcontroller running environment MATLAB/SIMULINK, using a computer incorporating a card DS1104 for visualization. The simulations and experimental results show that the proposed algorithm offers a fast response with smaller stationary oscillations compared to conventional methods.
This paper presents a low-rated midpoint DC-link capacitor hybrid shunt active power filter (HSAPF) embedded with sliding window (SW) based harmonic detection method for power quality enhancement in a medium-voltage distribution network. The novel composite current control technique utilizes SW based high pass filtering for determining the reference voltages, SW based low pass filtering for absorbing the negative sequence currents of 5th order harmonic. In this study, an additional effort has been made to evaluate the compensation effect of the HSAPF system by using a combinational adaptive linear neural network and dynamic forgetting factor recursive least squares (RLS) (ADALINE-DFFRLS) algorithm. Due to the utilization of dynamic forgetting factor (DFF) mechanism, the DFFRLS based weight updating rule shows faster and accurate estimation results in noisy environments compared to the conventional RLS. The performance of the proposed ADALINE-DFFRLS estimation algorithm is compared with the ADALINE-RLS to exemplify its faster-tracking capability. Extensive simulation is carried out to show the compensating performance of the HSAPF system employing SW based proposed controller under different critical conditions. Additionally, an experimental setup is developed for validation of the proposed control strategy in the real-time using a Spartan 3A DSP processor.
