Carrier shifting algorithms for the mitigation of circulating current in diode clamped MLI fed induction motor drive

Abstract: Reduction of circulating current is one of the major considerations in inverter fed electrical drives. Diode clamped MLI enables higher output current per phase, thereby rating of the drive gets increased effectively. Various methods of triggering in the inverter legs creates better voltage profile and leads to the enabling of circulating current in the drive system. The induced circulating current flows through the apparatus neutral (N) and supply ground (G) is caused by the existence of parasitic capacitance. This circulating current may cause potential danger especially when parasitic capacitance poses large. In the past, different modulation techniques and conversion topologies have been introduced to minimize the flow of circulating current. However, these techniques lead to complexity, high cost, low voltage profile and efficiency due to lower modulation parameters. This paper proposes PS, POD, PD carrier shifting PWM algorithms for diode clamped MLI to tumbling the circulating current within the each phase of inverter legs. The performances of proposed algorithm, in terms of circulating current, THD, losses and efficiencies are analyzed theoreticallyand are validated via simulation and experimental results

Synchronous PWM control of triple transformer-connected inverters for photovoltaic system

Abstract: This paper presents results of research of modulation processes in power conversion system with triple voltage source inverters, supplied by photovoltaic (PV) strings, and connected to a four-winding transformer. The transformer has in this case specific connections between the secondary windings and inverters, allowing providing of multilevel voltages at secondary windings of the transformer. Specialized space-vector-based strategy of pulsewidth modulation (PWM) has been used for control of inverters, insuring quarter-wave symmetry of winding voltages for any modulation indices and switching frequency of inverters. Analysis and comparison of harmonic composition of winding voltages and output voltages of inverters has been done. The validity of the analyzed processes has been verified by simulations: three basic variants of the scheme of modulation have been applied for control of inverters

Investigation of slim type BLDC motor drive with torque ripple minimization using abridged space-vector PWM control method

Abstract: Brushless DC (BLDC) motors are becoming an increasingly popular motor of choice for its unique characteristics. The BLDC motor drive is assumed to have trapezoidal back-electromotive force (EMF), rectangular phase currents and together produces the desired torque. However, practical back-EMF waveform might not be exactly trapezoidal because of current ripple, design considerations and manufacturing limitations. The adverse effect is the torque ripple generated due to the current ripple that causes mechanical vibration, acoustic noise and affects the accuracy of speed and position control which is not desirable in motor operation. In this paper an algorithm is developed to control and minimize the generated torque ripple using Space Vector Pulse Width Modulation (SVPWM) scheme. The efficiency improvement of slim type BLDC motor is confirmed using MATLAB environment and low cost TI Piccolo F28035 microcontroller (MC)

Enhancement of security and handling the inconspicuousness in IoT using a simple size extensible blockchain

Blockchain technology is increasingly used worldwide to enhance the performance and profit of any environment through its defining characteristics, such as security, auditability, immutability, and inconspicuousness. Owing to these characteristics, the blockchain can be used in various non-financial operations of some domains, such as the Internet of Things (IoT) and distributed computing. However, implementing blockchain technology in IoT is not always a feasible solution because blockchain deployment is costly, it has limited extensibility and provides irregular bandwidth and latency. In this regard, a simple size extensible (SSE) blockchain has been proposed to provide an optimal solution for IoT environments by satisfying the needs of the IoT environment as well as ensuring end-to-end security. The implementation of the proposed blockchain develops an overlay network to obtain a distributed environment where the blockchain is handled by the resources present therein. Two novel algorithms were introduced into the proposed system to minimize the irregularity and latency on one hand, and to maximize the throughput of the system on the other. The shared-time depending agreement algorithm (STD) minimizes the irregularity in the extraction operation and latency. The other, the shared throughput administration algorithm (STA) justifies the overall collection of the transmission load in the network and maintains the performance of the blockchain. The proposed system was applied to smart home IoT appliances to test the performance of the proposed system. The experimental results show that the proposed blockchain system minimizes nearly 70% of the data irregularity, latency, and furthermore, 30% of the blockchain extensibility is maximized as compared to the existing systems

Multiphase quad-inverter system with feedforward synchronous PWM and nonlinear voltage regulation

Abstract: This manuscript presents modified scheme of synchronous space-vector modulation allowing providing nonlinear dependences between the fundamental voltage and fundamental frequency of dual three-phase open-winding ac drive with four modulated inverters. Behavior of the system with six control modes (characterized by different dc-voltages and switching frequencies of inverters) and two nonlinear Voltage/Frequency ratios has been analyzed and simulated by the means of MATLAB-software

Periodic perturbation method for controlling chaos for a positive output DC-DC luo converter

Abstract: A simple, non-feedback method of controlling chaos is implemented for a DC-DC converter. The weak periodic perturbation (WPP) is the control technique applied to stabilize an unstable orbit in a current-mode controlled Positive Output Luo (POL) DC-DC converter operating in a chaotic regime. With WPP, the operation of the converter is limited to stable period-1 orbit that exists in the original chaotic attractor. The proposed control strategy is implemented using simulations and the results are verified with hardware setup. The experimental results of the converter with WPP control are presented which shows the effectiveness of the control strategy

Variable fractional power‐least mean square based control algorithm with optimized PI gains for the operation of dynamic voltage restorer

Abstract The operation of Dynamic Voltage Restorer has been studied for the mitigation of supply voltage disturbances like sag, swell, distortions, and unbalances. A Dynamic Voltage Restorer with three single‐phase Voltage Source Converters has been implemented for this purpose. Dynamic Voltage Restorer's compensation capability has been evaluated while introducing the above‐said voltage related disturbances in the supply by different means. A control algorithm named Variable Fractional Power‐Least Mean Square has been proposed for generating the load reference voltage for Dynamic Voltage Restorer. Variable Fractional Power‐Least Mean Square extracts the fundamental active and reactive component out of non‐ideal supply voltage and is thus, used in generating reference load voltage. This algorithm is more robust with respect to disturbance due to variable step size and is computationally less expensive. In addition, an optimization‐based approach has been proposed to estimate the approximate values of PI control gains. For this reason, a population‐based optimization method known as Sine Cosine Optimization has been used. The added feature of the optimization method is the reduction of computational time as compared to conventional PI controller tuning. A model of Dynamic Voltage Restorer using Variable Fractional Power‐Least Mean Square control algorithm with Sine Cosine Optimization tuned PI gains has been built in MATLAB Simulink as well as a reduced scale experimental prototype and their results have been presented with discussion

Authentication Protocol for Cloud Databases Using Blockchain Mechanism

Cloud computing has made the software development process fast and flexible but on the other hand it has contributed to increasing security attacks. Employees who manage the data in cloud companies may face insider attack, affecting their reputation. They have the advantage of accessing the user data by interacting with the authentication mechanism. The primary aim of this research paper is to provide a novel secure authentication mechanism by using Blockchain technology for cloud databases. Blockchain makes it difficult to change user login credentials details in the user authentication process by an insider. The insider is not able to access the user authentication data due to the distributed ledger-based authentication scheme. Activity of insider can be traced and cannot be changed. Both insider and outsider user’s are authenticated using individual IDs and signatures. Furthermore, the user access control on the cloud database is also authenticated. The algorithm and theorem of the proposed mechanism have been given to demonstrate the applicability and correctness.The proposed mechanism is tested on the Scyther formal system tool against denial of service, impersonation, offline guessing, and no replay attacks. Scyther results show that the proposed methodology is secure cum robust

Comparative analysis of modulation techniques in frequency converter

Abstract: A generalized frequency converter has been realized which makes use of a cyclo-converter in newer form AC-AC converter. An attempt has been made to operate this converter both in a conventional low frequency AC-AC converter and a new high frequency AC-AC converter. The ability to directly affect the frequency conversion of power without any intermediate stage involving DC power is a huge advantage of the system. The output of this converter has a frequency either fo = fi × Nr or fo = fi / Nr. where Nr is an integer and fi is the source frequency. A methodology is developed to generate the required trigger signal for any integer multiple/sub multiple of the output frequency. The undesirable harmonic components in the output of the frequency converter have been minimized using four modulation techniques namely; sinusoidal pulse width modulation (SPWM), delta modulation (DM), trapezoidal modulation (TM) and space vector modulation (SVM) technique. The converter is simulated using well known software package MATLAB. Comparative simulation analysis is presented for a single phase frequency converter (SPFC) topology with all these modulation techniques when the converter is operating both step up as well as for step down mode