Model predictive control for current balancing in a four-phase buck converter

Multiphase buck topology offers smaller ripple current and lower component ratings. This, however, compromises unbalanced output current between each phase of an inductor which leads to over-current and inductor saturation issues. Often when discussing the linear control schemes, it involves the use of superposition theorem to understand the system’s response. However, the limitation of superposition theorem in this application is that it assumes the circuit to be completely linear. For components with nonlinear behaviour such as power switches and diodes, the analytical results may not be accurate resulting to unexpected behaviour as the algorithm is implemented on a real system. Hence, the use of a more advanced control scheme is necessary to improve a system with a non-linear characteristic. This paper proposes a current limit control (CLC) consists of MPC for inner loop control and PID for outer loop control for phase current balancing in a four-phase buck converter. The controller is designed to achieve balanced current for each phase with acceptable response time. The proposed system is designed using MATLAB/Simulink simulation software and verified by a laboratory prototype with a TMS320F28335 as the main controller. Simulation and experimental results are provided to validate the system performance

Improvement of speed response in four-phase DC–DC converter switching using two shunt voltage-source

This study proposes a technique that is able to improve the speed response of a four-phase DC–DC converter switching. The basic concept of the proposed technique is the inclusion of two shunt-connected voltage sources in series to the converter system. Using a higher input voltage to drive the load, a higher current per microsecond output system will be obtained and reverts to its nominal input upon obtaining desired references. Thus, the transient response observed when using this proposed technique is found to be much faster when compared to the conventional converter. Moreover, this technique is easily implemented as it requires only an additional voltage source, power switch, and power diode. The integrated model of the two shunt voltage-source in a four-phase DC–DC converter was simulated in MATLAB/Simulink and validated against the experimental results of a laboratory prototype, 600 W four-phase DC–DC converter. The novelty of this proposed technique is its ability to provide faster operations for critical loads applications, lower output capacitor and lower operating frequency

Analysis of Performance SCTP in Mobile-IP Network Environment

This research describes and makes an analysis of performance of Stream Control Transmission Protocol (SCTP) compared with User Datagram Protocol (UDP) using Network Simulator (NS-2). This new transport layer protocol has recently been accepted by Internet Engineering Task Force (IETF) as a proposed standard to address a number of Transport Control Protocol (TCP) limitations. Here, the interaction of these two transport protocols (SCTP & UDP) has been investigated through the examination of traffic flows through a number of network topologies. SCTP has many new features that could not be found in other transport protocol such as multi-streaming and multi-homing. This performance analysis was done over mobile-IP network environment that enables to measure the several performance metrics such as packet delay, packet loss and jitter. At the end of the study, results and analysis shows that the research objective was achieved as well as comparative studies between the three transport protocols that is SCTP, UDP and TCP

Vehicle Steering Dynamic Calculation and Simulation: Vehicle Steering Dynamic Calculation and Simulation

This paper presents fundamental mathematical estimations of vehicle sideslip in stationary conditions regarding the influences of the vehicle parameters such as the tire stiffness, the position of gravity centre, the vehicle speed and the turning radius. The vehicle dynamics on steady state and transient responses are also investigated to see the effects of the yaw natural frequency and yaw damping rate on the steering system. Results from this study can be used in designing an automatic control of tracking vehicle in the future

Design Of A Cathodic Protection Against Corrosion For Marine And Offshore Structure

Large marine structures and machineries such as oil platforms and ships use numerous ways to propagate or prevent corrosion, and one of the technique is Cathodic Protection (CP). For more than 50 years, CP has been employed to prevent corrosion on pipelines, storage tanks as well as buried and submerged metallic structures. It is the most effective and least expensive method for controlling corrosion. Large marine structures have probably the greatest application of cathodic protection, followed by marine machineries and equipments such as vessels and pipelines. As the technology progresses gradually, the application of CP increases as more structures being constructed or built around or even submerged in aggressive corrosion environment. Designs of CP were often based upon guesswork than the application of science. This condition serves as the basic of the project, with the aim of improving the performance of CP system by introducing new design of sacrificial anode CP block. This improvement is mainly achieved by increasing the protection area of the sacrificial CP anode block. The characteristic that will be improved is determined first, which acts as initial step of the project’s methodology. After the design has been completed, fabrication session commenced, followed by an experimental work and analysis of the corrosion protection effect on the new design. The experiments have been done using basic immersion technique, and the final results were obtained using FerroVer® method of the Powder Pillow Test. The result obtained from the analysis proved that the design modification upon the CP sacrificial block has a significant effect of improvement onto the corrosion protection performance

Switching speed improvements in multiphase buck converter via two-shunt voltage-sources

Multiphase Buck converters are well known for their smaller ripple current, smaller filter design and smaller component ratings. The converter operating responses however depend on the value of inductor and load resistance. Increasing the switching frequency can improve the transient responses. However, it reduces the system efficiency and controlling the current response can be complex. This paper proposes an improved multiphase buck converter for a lithium-ion battery charging applications. The proposed system is based on the ‘Bi-level drives’ concept, which requires two input voltage in which one is higher than the other input and is connected in series to the system. By driving the load with a higher input voltage, the transient response is observed to be much faster. Upon reaching the desired reference output, the system will revert to a lower input voltage, thus, the efficiency of the system will not be affected. This scheme requires additional two power switches and a power diode. The operation and the switching scheme will be discussed in this paper

Experimental implementation controlled SPWM inverter based harmony search algorithm

An optimum PI controller using harmony search optimization algorithm (HS) is utilized in this research for the single-phase bipolar SPWM inverter. The aim of this algorithm is to avoid the conventional trial and error procedure which is usually applied in finding the PI coefficients in order to obtain the desired performance. Then, the control algorithm of the inverter prototype is experimentally implemented using the eZdsp F28355 board along with the bipolar sinusoidal pulse width modulation (SPWM) to control the output voltage drop under different load conditions. The proposed overall inverter design and the control algorithm are modelled using MATLAB environment (Simulink/m-file Code). The mean absolute error (MAE) formula is used as an objective function with the HS algorithm in finding the adaptive values of  and  parameters to minimize the error of the inverter output voltage. Based on the output results, the proposed voltage controller using HS algorithm based PI (HS-PI) showed that the inverter output performance is improved in terms of voltage amplitude, robustness, and convergence rate speed as compared to PSO algorithm based PI (PSO-PI). This is to say that the proposed controller provides a good dynamic responses in both cases; transient and steady-state. Finally, the experimental setup result of the inverter controller is verified to validate the simulation results

Learners' attitude towards learning through CD-ROM courseware : a case study of an organization.

The paper seeks to explore two factors associated with learners’ attitude toward learning through CD-ROM courseware: (1) learners’ characteristic; and (2) characteristics of CD-ROM courseware. Data were administered using an instrument custom designed for the study. The respondents were 150 employees of the selected organisation who had used any CD-ROM courseware in any of the organisation’s learning centres during a specified one-month period. Results show that: (1) the majority of respondents surveyed found to have favourable attitude toward the last CD-ROM courseware they had used; (2) learners’ attitude towards computers was found to be highly correlated with learners’ attitude towards CD-ROM courseware; and (3) courseware characteristics of textology and immediate feedback were identified as two of the most highly correlated factors. In learning through CD-ROM courseware, learners’ characteristics such as learners’ attitude towards computers, their working experience and educational achievement need to be taken into consideration. In CD-ROM courseware development, characteristics such as textology and immediate feedback are important elements that facilitate positive attitude towards learning. This study is useful to CD-ROM courseware developers and training managers in developing a more appropriate training for learners

Digital current sensing in modular multilevel converter for HVDC applications

For long-distance transmission, HVDC (High-Voltage, Direct-Current) is proven to be less expensive and have lower electrical losses as compared to HVAC (High-Voltage, Alternating-Current). Now a days, the advancement of power electronic switches such as IGBT's and MOSFET enables the use of converters for HVDC applications. Among the well-known converters used for HVDC are Voltage Source Converter (VSC) Line Commutated Converter (LCC) and Modular Multilevel Converter (MMC). The MMC is still new and a promising technology for HVDC application. The MMC has many advantages such as controlling high amount of active/reactive power and possess lower losses as compared to other converters. To control the active/reactive power in a MMC, control scheme such as free-running hysteresis uses the reference voltage and the inductor current to produce the required switching pulses. This study proposed a technique in which a voltage sensor is use to measure the inductor current. Conventionally, the inductor current is sensed either with a resistor or Current Transformer (CT). This method is associated with some disadvantages; requires additional circuitry which introduces some power loss and requires higher bandwidth in order to sense accurately. This study instead, measures the current indirectly by using the information of the phase inductor voltage. As the voltage sensor is placed in parallel to the inductor, this measuring technique is immune to I2R loss. The proposed technique will be investigated using MATLAB simulation to determine its current sensing capability in a MMC for HVDC applications. To design an improved current-less sensing method using a digital RC network. To extract the inductor current values from the phase inductor voltage an RC filter is required and placed in parallel across the inductor. In this way, all the high frequency harmonics will be filtered out and only the low frequency inductor current can be seen across the capacitor. The selection of RC values, however is dependent on the inductor value and inductor DC-Resistance (RDCR). The main concern with this technique is that selection of DCR RC values sometimes can be unavailable for hardware implementation. To further improve the implementation of RC network and eliminate the problems of selecting suitable RC values for hardware implementation. This paper proposed the used of digital filter based on the RC network concept. Instead of using the actual components for filtering the high frequency harmonics, this technique uses only the DSP for filtering to remove the high frequency harmonics. The proposed technique is able to convert the high frequency voltage VL1 measured from the phase inductor L1 into the phase inductor current iL1without any delay or difficulty. By 1 L1 comparing the signals of proposed method to the series sensing method and the conventional RC filter method the waveforms of both signals are almost identical. However, the proposed method eliminates the need for RC components as compared to the conventional RC filter method. This technique improves the efficiency of the system in terms of improve signal noise ratio and eliminates the need for passive component on the system

Thermal degradation and kinetic analysis on stembark biomass of melaleuca cajuputi powell (gelam) / Muhamad Razimie Mansor

Melaleuca species (pokok Gelam) are a potential sources of renewable energy, melaleuca bark can produce the porous carbon materials for hydrogen storage, which is clean energy solution for future transportation. In this research, stembark of Melaleuca cajuput; Powell ware washed with distilled water to remove any contaminant and dirt before dry it at room temperature. After drying, it was shredded into smaller size for process crushed and grinded into powdered form. In pyrolysis process, powdered stembark of Melaleuca cajuput; Powell were investigate in a non-isothermal thermogravimetric analyser (TGA) in order to determine the degradation behavior of powdered stembark. There are two stage present, which first stage due to the elimination of moisture content and small amount of volatile matter compound and second stage is the place where plant biomass (hemicellulos, cellulose and lignin) degrade. The main decomposition of samples occurred between 230 - 387°C, at heating rate 10°C/min, corresponds to the degradation of 63.47% of volatile matter. Weight loss of sample, was strongly affected by heating rates. It was found that an increasing in heating rates results in a shift of thermograms to higher temperature. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR.) was performed to determine the possible chemical functional groups present in stembark of Melaleuca cajuputi Powell. From the ATR-FTIR. analysis, there were volatile components that found. such as CO, H20, O-H, and cyclic and C02. Results showed that. stem bark of Melaleuca cajuput Powell can be characterized as high volatile matter and low ash components compared to other biomasses. The activation energy of Melaleuca cajuputi Powell, was calculated by using model free FLYNN-WALL-OZAWA (FWO) and Kissinger-Akahira-Sunose (KAS) methods and ranges value were 17.15 - 32.6 kJ/mol and 17.35 - 30.04 kJ/mol, respectively