DC Load Research Articles

Electric Traction System Technology as a Solution to African Transportation Industries

The electric traction system in the case of Africa is highly advantageous in terms of transportation. The electric traction system is designed to provide a DC output source from an AC source of 33kV/230V for suitable mobility of tract devices without minimum frequency change. In this work, electric traction system analysis was obtained using mathematical models and simulation of tracts system components using MATLAB. Due to the application of FACTs devices, a 12-pulse thyristor rectifier is used for rectification. The system components are an energy source, harmonic filter, step-down transformer, rectifier substation, and DC load. The maximum current of total harmonic distortion obtained is certified with the IEEE standard 5% total harmonic distortion. the output voltage is purely stable, and the power factor quality is improved.

Vibration analysis of a permanent magnet synchronous generator considering electromagnetic vibration sources under AC and DC load conditions

As the performance of permanent-magnet synchronous generators improves, research on device noise is also becoming important. This study analyzes the causes of electromagnetic noise, such as the back electromotive force, cogging torque, torque ripple, unbalanced magnetic force, and harmonics that occur during operation for each DC and AC load. In particular, it shows that the influence of the waterfall diagram changes depending on the harmonic order of the torque ripple. By combining 2D finite element analysis and 3D mechanical analysis, electromagnetic analysis can be used to analyze the noise-generating relationship. Based on the analysis results, the electromagnetic noise generation results depending on the load are presented. The electromagnetic performance and mechanical reliability of the designed model were verified by comparing the finite element method and experimental results.

Automatic transfer switch for DC system application

Automatic transfer switches (ATS) have the potential to be important in ensuring uninterruptible power supply across a wide range of sectors, enabling smooth transitions between utility and emergency RES power sources, generators, and more. Utilizing DC electricity provides a cost advantage and is suitable for short-distance transmission. The author proposes a 12-volt DC backup system that corresponds to a minimum input voltage of more than 10 Vdc and can be applied in various DC load applications. The ATS design incorporates multiple inputs and uses algorithms to prevent simultaneous operation of all sources and reduce feedback. These developments in backup system technology, coupled with the shift to renewable energy, are contributing to the creation of a sustainable and resilient electricity grid. In experiments, the ATS system demonstrated its ability to provide 24 hours of backup power with a specified load (lighting bulbs, light-emitting diodes (LEDs), motors, and fans) discharging 0.27–2.25 Amperes. Using the millis programming language, it supports the performance of a constant switch transition speed of around 0.6453 seconds for a switch from buck to SCC. 0.658 seconds for solar charge controller (SCC) to power supply (PSU), 0.656 seconds for PSU to CC PSU, and 0.61 seconds for PSU to OFF.

Kinerja Inverter 500 W untuk PLTS Skala Kecil

At Electrical Engineering Department of Politeknik Negeri Malang, there is an EBT learning module in the form of solar panel with small capacity, namely 80 Watts. The only load that can be supplied is DC load because there isn’t installed inverter. Therefore, it is necessary to determine the inverter specifications to be installed in small-scale solar system. This research aims to determine the specifications and test the performance of a 500 W inverter integrated with a 50 Wp solar system. Also analyze power quality parameters and efficiency when connected to various load. The test method is no-load and load testing with the parameters measured including current, voltage, power, frequency and THD. Analysis was also carried out on the correlation between efficiency and loading and inverter pins with THDV and THDI. In the no-load test, the inverter output voltage waveform was obtained as a pure sine wave with a frequency of 50.10 Hz. In testing the LED and LHE loads, it was found that the inverter was good for use when the load was 50-80% of its capacity. The lowest THDV value is at a Pin value of 26 W, namely a THDV value of 0.009%. The highest THDV on the Pin is 130 W with THDV value of 1.9%. The lowest THDI value is at Pin 9.75 W, namely 27.6%. The highest THDI value on the 130 W Pin is 80.9%. The THD limit is still within the IEEE standard limit, namely 5% - 10%.

Comparative Analysis of Various Topologies for AC and DC Power Distribution Systems on Efficiency Grounds

Efficiency is the factor that once wiped DC out of the power system at the birth of electricity, in nineteenth century. The battle of currents between AC and DC has reignited with the aggravating employment of DC in the sectors of generation, transmission, and utilization. This calls for cutting edge research in the field of comparative efficiency analysis of AC and DC, on distribution scale. The current research effort compares AC and DC distribution systems on efficiency grounds, for various topologies. The two systems are compared employing normal distribution technique for residential load profile. The varying efficiency of power electronic converters (PECs) with stochastic load profiles is modeled using MATLAB/SIMULINK, for each topology. DC takes the lead against AC with efficiency advantage for energy efficient load-based architectures. The architectures with variable speed drive-based loads, the efficiency advantage in favor of DC is between 1% and 2%, however, the efficiency advantage reaches to 12% with inherent DC loads. In contrast, AC takes the lead with conventional distribution, with an efficiency advantage between 4% and 5%. The findings of current research work can prove to be beneficial in making policy decisions for the adoption of DC at distribution scale.

Development of modified P&O algorithm based simple controller for constant voltage and frequency operation of three-phase IIG for micro-hydro application

This paper introduces Modified Perturb and Observe (MP&O) based MPPT algorithm for constant frequency and voltage operation of a three-phase Isolated Induction Generator (IIG) coupled to an ungoverned hydro turbine. The generator is operated at maximum output power point corresponding to the excitation capacitance connected across the Point of Common Coupling (PCC) of the IIG. The output power of the generator is always maintained constant. With a fixed capacitor bank connected across the stator terminals, the IIG simultaneously supplies power to both ac load (main load) and controlled dc load (dump load). This modified MPPT algorithm not only tracks the maximum output power point, but also diverts power from main load to dump load and vice-versa as per requirement to maintain the voltage and frequency at constant value. The electronic circuit is realized using an uncontrolled rectifier-chopper (diode-IGBT) combination connected across the IIG terminals supplying the controlled dc load. The IIG has been modeled based on stationary reference frame d-q axes theory. The proposed control algorithm has been experimentally implemented on a three-phase, 415 V, 2.2 kW induction machine using dSPACE 1104 platform and the effectiveness of the algorithm has been tested for various transient conditions, such as, sudden ac load application as well as removal.

EXPERIMENTAL DEMONSTRATION OF ELECTRICAL POWER GENERATION USING STATIONARY EXERCISE BICYCLE COUPLED WITH WIND TURBINE REGULATOR

The small power generation using exercise bicycle is one of the current areas patronized by researchers. This is due to the two major benefits obtainable from the exercise machine, the benefit of exercising one’s body and the utilization of electrical power generated. Wind turbine regulator is specifically designed to regulate the output voltage of a wind turbine generator, which is characterized by varying speed and hence varying output power. The exercise bicycle driven alternator has a similarity with wind turbine generator in terms of variable speed, especially when ridden by different personalities. This paper demonstrates how small power can be generated using exercise bicycle. Further, the paper analyzes the performance of the by regulating its output using small wind turbine regulator. The result shows that, a regulated output within the range of 12V is obtained for all the tested loads, which makes the system more compatible with all types of 12V DC loads. Also the excitation voltage of the machine is improved from 4.5V (1.22A) using the diodes rectifier to 2.5V (0.81A) when the wind turbine regulator is used. With the improved power generation in this work the exercise bicycle will be a better alternative source for small power generation which can be used in DC lightings, DC fans, charging batteries and laboratory experiments.

Medium Voltage Drives (MVD) – Design and Configuration of Eighteen-Pulse Phase Shifting Autotransformer Rectifier for Cascaded H-Bridge Motor Driver Application

Efficiency, dependability, and Simplicity make the eighteen-pulse phase shifting autotransformer rectifier (18PSATR) one of the best solutions to enhancement the power quality of electrical systems. The popular structures utilized in the market of 18PASTR were compared to achieve the best, lowest cost, highest quality, and optimized design. The 18PSATR is a competitive selection to reduce system general harmonics and insulate the grid from hormones produced by the cascaded H-bridge motor driver (CHBMD). A deep check of industrial demands and producer goods, the work considers four configurations contributing to harmonics accepted by IEEE-519 requirements. A comparison is done to exhaustive the best 18PSTAR topology with the minimum use of copper, lowest weight, best dimensions, power quality, and best output voltage waveform. All proposed 18PSATRs are tested, simulated, studied, shown, and produced with low rate of power, voltage and current. The output current, output voltage waveform, and total THD simulation results shown using Simulink analysis show considerable assimilation of each structure. The design of Symmetric Delta differential (18PSTAR-SDD) theoretical, and experimental results show the minimum power-losing rate which improved the quality of power and output voltage waveform. Delta differential configuration has an intelligible arrangement, painless assembly, minimum copper use, easy terminal connection, harmonic cancellation, and higher power quality. The THD of 18PSTAR-SDD from simulation results is less than 2.9%. Compared to other structures, the proposed 18PSTAR diagram reduces total cost and production by a considerable margin. Also, test results approved that the output power of DC load equals 85% of the rectifier rate.

Power quality interval grading evaluation method of AC/DC distribution network considering source-load weighting and voltage coupling

In the context of the ‘dual carbon’ goal, the integration of renewable energy sources has a significant impact on distribution systems, while the substantial integration of DC loads and photovoltaic power has led to a progressive transition of conventional distribution networks towards hybrid AC-DC distribution networks in the field of electrical engineering. However, this shift has brought about more formidable power quality challenges within the power industry. To address these emerging power quality issues, we propose a novel power quality interval grading evaluation method for AC/DC distribution networks considering source-load weighting and voltage coupling. Firstly, the voltage acquisition data is meticulously decoupled to disentangle the interdependencies. Secondly, the power quality evaluation system of the AC/DC distribution network is established. Considering the influence of different access source-load types on each node, the subjective weight is determined by source load weighted two-tuple linguistic analytic hierarchy process (AHP), the objective weight is determined by the entropy weight method, and the idea of using game equilibrium algorithm to obtain comprehensive weight to balance the error of single weight on evaluation result is put forward. Then, the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) of interval number improvement is used to classify and evaluate the power quality index to make up for the shortcomings of the single-point sampling method. Finally, a more accurate and comprehensive power quality evaluation result is obtained based on a practical example.

Topology and Control Optimization of Bidirectional DC/DC Converter for Electric Vehicles

With the rapid development of intelligent electric vehicles, the number of electrical equipment increases, and the interconnection and energy transmission between on-board DC buses has become urgent. This paper proposes a partial isolated bidirectional converter based on dual active bridge converter. By partial switch sharing, the converter has a simplified structure and can supply energy to DC loads of different voltage levels. The system adopts a hybrid control strategy of pulse width modulation and triple phase shift modulation, and introduces a fundamental phase shift to reduce coupling between variables. The operation process is analyzed, and the models of transmitted power, current stress and soft-switching range under two typical operation modes, corresponding to the full load and light load, are established respectively. Under wide gain and different power distribution conditions, the multi-objective optimization is realized. Finally, the correctness of theoretical analysis is verified by experiments.

Test rig for stand-alone small power wind turbine emulation for variable wind and load

This paper presents futures from experimental investigation of an autonomous small power wind system. The envisaged wind system is based on a PMSG (Permanent Magnet Synchronous Generator) directly connected to the wind turbine shaft, while the DC output load is supplied by a rectifier and a chopper. The DC load is considered as a resistive load with wide values range. Experimental investigations are provided in partial load regime. The power optimization is performed through a power loop in two ways: by controlling the electrical power or by controlling the electromechanical power. For the above two situations it is shown how the optimization power loop reference and power loop feedbacks can be set, in order to obtain maximum electrical power, for each wind speed value corresponding to the partial load regime. It was also highlighted that for a wide range of DC load values the mechanical and electrical powers are not constant as it should be corresponding to the mathematical model of the optimal conversion. This is due to mechanic-electrical subsystem processes. The electrical power variation range with the load should be provided by the manufacturer in the low-power wind system data sheet.

Modeling, Control and Simulation of a High-Current DC-DC Converter for Fuel Cell Applications

In this paper, a high-current two-stage DC-DC converter fed by a Proton Exchange Membrane Fuel Cell (PEMFC) is studied. The converter consists of two three-phase full-bridge inverters connected through three AC coupled inductors. The mathematical models of both converter and PEMFC are first presented, and a control scheme that ensures a high power factor at the AC stage and a regulated voltage at the DC load is then implemented. The performance of the proposed control system is verified through digital simulations.

Designing a High-Order Sliding Mode Controller for Photovoltaic- and Battery Energy Storage System-Based DC Microgrids with ANN-MPPT

This paper introduces a robust proportional integral derivative higher-order sliding mode controller (PID-HOSMC) based on a double power reaching law (DPRL) to enhance large-signal stability in DC microgrids. The microgrid integrates a solar photovoltaic (SPV) system, an energy storage system (ESS), and DC loads. Efficient DC-DC converters, including bidirectional and boost converters, are employed to maintain a constant voltage level despite the lower SPV output power. An artificial neural network (ANN) generates the optimal reference voltage for the SPV system. The dynamical model, which incorporates external disturbances, is initially developed and based on this model, and the PID-HOSMC is designed to control output power by generating switching gate pulses. Afterwards, Lyapunov stability theory is used to demonstrate the model’s closed-loop stability, and theoretical analysis indicates that the controller can converge tracking errors to zero within a finite time frame. Finally, a comparative numerical simulation result is presented, demonstrating that the proposed controller exhibits a 58% improvement in settling time and an 82% improvement in overshoot compared to the existing controller. Experimental validation using processor-in-the-loop (PIL) confirms the proposed controller’s performance on a real-time platform.

A new approach for reliability assessment of the smart microgrids using k-shortest path algorithms

The reliability of cyber-physical microgrids (MGs) is crucial in the development of smart grids. The reliability of MGs can be affected by cyber network failures, which have a significant impact on the physical components. Since MGs have interdependent cyber and physical elements, a smart MG can be viewed as a system of n dependent two-mode components. This paper proposes an approach to finding the k most likely configurations of the system. The method involves three phases. Firstly, the multi-mode model is obtained for physical components, considering the operation and topology of the cyber network. Then, the problem is transformed to finding the k most likely state of a system consisting of n independent multi-mode components. In the second phase, a transformation using new transformed metrics is applied. This results in the problem being converted to finding the k shortest path, which can be solved using efficient algorithms. Finally, the states are evaluated using a DC load flow, and reliability indices such as loss of load probability (LOLP) and expected energy not supplied (EENS) are calculated. Moreover, we have incorporated the dynamic thermal rating (DTR) system into our proposed model, addressing the safe enhancement of system component ratings. The results indicate that the most probable states of the system are related to the failure of distribution generators. The most severe events occur due to failure in the cyber network, and cyber network malfunction has a higher effect on EENS compared to LOLP. Additionally, we observe a significant enhancement in reliability indices when considering the DTR system over the static thermal rating (STR) system. This approach is efficient in reliability calculation using fewer system states.

Thermo-electro-mechanical effects on nonlinear dynamics of smart dielectric elastomer minimum energy structures

Minimum energy structures made up of smart electro-active polymers (SEAPs) have attracted significant attention in the field of soft robotics and actuators due to their exceptional property of undergoing large deformations when subjected to electric fields. In general, temperature also plays a crucial role in modeling of SEAPs because it affects the mechanical, electrical, and thermal properties of the polymer. These properties, in turn, determine the performance of smart polymer-based devices. Motivated by these ongoing advancements, this study investigates the effects of temperature on the nonlinear dynamic behavior of a smart dielectric elastomer-based minimum energy structure (SDEMES) actuator. The governing dynamic equation of the actuator is derived using the standard Euler–Lagrange’s equation. Through the utilization of time-evolution diagrams, Poincaré plots, and phase portraits, the study comprehensively evaluates the effects of temperature on the stability, periodicity, and resonant behavior of the actuator. The results highlight the significant influence of temperature on the stiffness of the elastomer within the SDEMES actuator, directly impacting its actuation performance. The frequency response of the actuator demonstrates a distinct increase in resonant frequency as the temperature rises. These findings shed light on the crucial role of temperature in shaping the stiffness and nonlinear dynamic behavior of smart dielectric elastomer minimum energy structures.

Efficiency Optimization and Power Flow Control in a Wind Energy Conversion System with Storage via Vienna rectifier

The study addresses efficiency enhancement and power flow control in a wind energy conversion system. This system comprises a Permanant Magnet Synchronous Generator (PMSM) driven by a wind turbine, Vienna rectifier, Li-ion battery, and DC load. Fluctuations in wind and energy demand impact battery life and state of health (SOH). To mitigate this, a nonlinear controller regulates current for optimal battery charging. Three operating modes, including MPPT, Constant Current (CC) charging, and Constant Voltage (CV) charging, are considered. An energy management algorithm facilitates smooth switching between controllers. The perfomances are evaluated using MATLAB/SIMULINK environment.

New single‐stage bidirectional three‐phase ac‐dc solid‐state transformer

AbstractHigh‐power applications with low‐voltage (LV) dc loads, for example, fast charging stations for electric vehicles (EVs), are typically supplied from the medium‐voltage (MV) grid. Aiming for low volume, MVac‐LVdc solid‐state transformers (SSTs) that provide galvanic separation with medium‐frequency transformers (MFTs) are thus considered, which are conventionally realized as two‐stage systems that consist of an ac‐dc power‐factor‐correction (PFC) rectifier and an isolated dc‐dc converter. This letter extends a new single‐stage isolated bidirectional PFC rectifier concept to MV levels, resulting in an SST that performs MVac‐LVdc conversion in a single converter stage and, unlike many modular SST concepts, employs only a single MFT. The SST's primary side operates modular‐multilevel‐converter (MMC) bridge legs, whose input voltages contain large ac components, in the quasi‐two‐level mode to minimize the cell capacitors. The secondary side employs a standard LV three‐phase rectifier, and a dual‐active‐bridge‐(DAB)‐like modulation strategy allows power flow regulation and ensures sinusoidal grid currents. The concept is explained and validated using detailed circuit simulations of an exemplary 1‐MW system operating between a 10‐kV three‐phase grid and an 800‐V dc output. The component stresses are evaluated, and an efficiency of 98.1% and a power density of up to 0.6 kW/dm3 are estimated.

A Tri-port DC-DC Converter for Bifacial PV Panels Coupled with Energy Storage

Abstract The power output of photovoltaic (PV) systems, especially bifacial modules, varies due to daily fluctuations in irradiance and temperature. Maximising the efficiency and power extraction are considered crucial. Hybrid DC off-grid topologies are highly promising for rural electrification with solar energy and battery backup. These systems, tailored for household appliance use, feature low semiconductor count, continuous current ports for PV, battery and DC loads, low-voltage levels for PV and battery, voltage regulation for DC loads, maximum power point tracking (MPPT), proper battery charging and discharging, high-voltage boosting without low-frequency transformers and reduced power converter stages. However, the existing schemes often lack the above-mentioned critical features. Hence, this paper proposes a novel three-switch tri-port converter with integrated energy storage for stand-alone bifacial PV applications, with modelling and experimental validation. The battery serves as an energy storage component, regulating the DC link voltage for consistency. This paper underscores PV system power optimisation and introduces a novel tri-port converter for stand-alone bifacial PV setups, emphasising energy storage’s role in voltage regulation.

Design and simulation of bidirectional DC-DC converter topology for battery applications

Recently, energy storage has become a significant topic for renewable energy based power system applications. Batteries are one of the most popular energy storage devices adopted by renewable energy sources, electrical vehicles and grid connected systems. In this context, the bidirectional DC-DC converter (BDC) enables bidirectional power flow by controlling the charging and discharging stage of the battery in battery applications. Accordingly, the battery current is regulated through the duty cycle of the BDC considering the state of charge of the battery and current direction. In this study, a non-isolated BDC, has a buck and boost principle of operation, is designed, analysed and simulated under various case studies. In the designed system, BDC controls the bidirectional power flow between the battery and DC link. Specifically, in the charging stage of battery operating in buck mode, DC-link supplies the power to the battery and BDC regulates the battery current using proportional-integral (PI) controller. On the other hand, in the discharging stage of the battery operating in boost mode, when DC source is disconnected, the battery supplies the power to DC load and DC-link voltage is controlled by the BDC via PI controller. The simulation results are presented to show the operation and control of the BDC under different scenarios.

ETAP software based power flow analysis of 225/60/11KV substation in Tinghir

Through technological advances, such as computer-based software, it is now possible to study and analyze complex electrical system problems and identify potential solutions. This analysis typically includes Load flow analysis (LFA), or power flow analysis (PFA). LFA is a crucial tool in power system engineering used for modeling and designing electrical power networks. It aims to determine the steady-state operating conditions of a power system to ensure a stable and efficient power balance between generation and load demands. LFA helps design robust power networks, maintains system stability, plans maintenance activities, and assists in the economic dispatch of power generation. This study focuses on modelling the 225/60/11 kV substation in Tinghir, a predominantly rural subdivision of the Drâa-Tafilalet region of Morocco. The model used data obtained from SPIE Maroc, specialists in industrial and tertiary electricity. AC and DC load flow analysis is performed on the Tinghir substation auxiliary services under two scenarios: one where the service equipment is powered by the auxiliary service transformer (AST) as the primary source, and another where the equipment supplied by a generator set due to a failure in the main power supply. ETAP software is selected for the simulation due to its advanced real-time power management capabilities and is widely used in power generation, transmission, and distribution systems. The Newton-Raphson method, known for its fast convergence and accuracy, is used for power flow analysis, making it ideal for complex systems. The results evaluate system performance under both normal and backup conditions, ensuring reliable operation of the auxiliary service installation at Tinghir’s substation.