Continuous dynamic sliding mode control strategy of PWM based voltage source inverter under load variations

For closed-loop controlled DC-AC inverter system, the performance is highly influenced by load variations and online current measurement. Any variation in the load will introduce unwanted periodic error at the inverter output voltage. In addition, when the current sensor is in faulty condition, the current measurement will be imprecise and the designed feedback control law will be ineffective. In this paper, a sensorless continuous sliding mode control (SMC) scheme has been proposed to address these issues. The chattering effect due to the discontinuous switching nature of SMC has been attenuated by designing a novel boundary-based saturation function where the selection of the thickness of boundary is dependent to the PWM signal generation of the inverter. In order to remove the dependency on the current sensor, a particle swarm optimization(PSO) based modified observer is proposed to estimate the inductor current in which the observer gains are optimized using PSO by reducing the estimation errors cost function. The proposed dynamic smooth SMC algorithm has been simulated in MATLAB Simulink environment for 0.2-kVA DC-AC inverter and the results exhibit rapid dynamic response with a steady-state error of 0.4V peak-to-peak voltage under linear and nonlinear load perturbations. The total harmonic distortion (THD) is also reduced to 0.20% and 1.14% for linear and non-linear loads, respectively

Photo-electrochemically synthesized light emtting nanoporous silicon based UV photodetector: influence of current density

Nanoporous silicon (n-PSi) with diverse morphologies was prepared on silicon (Si) substrate via photo-electrochemical etching technique. The role of changing current density (15, 30 and 45 mA cm−2) on the structure, morphology and optical properties was determined. As-prepared samples were systematically characterized using XRD, FESEM, AFM and photoluminescence measurements. Furthermore, the achieved n-PSi sample was used to make metal–semiconductor–metal (MSM) UV photodetector. The performance of these photodetectors was evaluated upon exposing to visible light of wavelength 530 nm (power density 1.55 mW cm−2), which exhibited very high sensitivity of 150.26 with a low dark current. The achieved internal photoconductive gain was 2.50, the photoresponse peak was 1.23 A W−1 and the response time was 0.49 s and the recovery time was 0.47 s. Excellent attributes of the fabricated photodetectors suggest that the present approach may provide a cost effective and simple way to obtain n-PSi suitable for sundry applications

Photophysical performance of radio frequency sputtered Pt/n-PSi/ZnO NCs/Pt photovoltaic photodetectors

The effect of the annealing temperature on the photoelectrical properties of the nanoporous silicon/zinc oxide nanocrystallites-based (Pt/n-PSi/ZnO NCs/Pt) photodetector was investigated. Different morphologies of 3D ZnO were synthesized onto the n-PSi substrates via radio frequency (RF) sputtering in the absence of a catalyst. The synthesis of ZnO NCs was controlled by varying the growth temperature between 600–700 °C and 800–900 °C. The effect of the synthesis temperature on the structural, morphological, and optical properties of the n-PSi/ZnO NCs was systematically studied using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence spectroscopy (PL) techniques. The roughness was found to be dependent on the anodization current density. The optimal n-PSi/ZnO NCs-based metal-semiconductor-metal UV detector (MSM) was fabricated at 700 °C. The fabricated device showed a high sensitivity of 1007.14, an internal photoconductive gain of 11.07, and a responsivity of 5.99 A/W with a low dark current when illuminated with 380 nm light (1.55 mW/cm2) at +5 V bias voltage. In addition, the response and recovery times were determined to be 0.34 and 0.22 s, respectively. This approach offers a cost-effective substrate and simple synthesis method to improve the growth of the n-PSi/ZnO NCs and demonstrates the successful fabrication of nanoscale photodetectors with potential application in nano-optics devices

Modular approach to implement model predictive control on three phase voltage source inverter

A modular abstraction is presented to implement model predictive control (MPC) on a three phase two level voltage source inverter to control its output current. Traditional ways of coded implementation do not provide insights into the complex nature of MPC; hence a more intuitive, logical and flexible approach for hardware implementation is conceptualized in the form of signal flow graphs (SFGs) for estimation, prediction and optimization. Simulation results show good performance of the approach and easier code generation for real time implementation. RL load is assumed for the inverter and the importance of choosing load inductance and sampling time ratio is emphasized for better control performance

Modular Approach to Implement Model Predictive Control on Three Phase Voltage Source Inverter

A modular abstraction is presented to implement model predictive control (MPC) on a three phase two level voltage source inverter to control its output current. Traditional ways of coded implementation do not provide insights into the complex nature of MPC; hence a more intuitive, logical and flexible approach for hardware implementation is conceptualized in the form of signal flow graphs (SFGs) for estimation, prediction and optimization. Simulation results show good performance of the approach and easier code generation for real time implementation. RL load is assumed for the inverter and the importance of choosing load inductance and sampling time ratio is emphasized for better control performance

A sampling time study for model predictive control in induction motor using processor-in-loop verification

This paper examines the impact of sampling time variation on Model Predictive Control (MPC) when it is applied to Induction motors (IM). Sampling time is a vital element in digital controllers, and selecting the appropriate value can be challenging. MPC is a model-dependent digital controller, which is highly affected by sampling time as well as the discretization technique employed by the hardware implementation. Hardware typically uses a discrete controller, and the sampling time and the discretisation method are important factors in the performance. The study proposes utilizing PIL verification with a variety of discretisation methods and sampling times with MPFOC to monitor the performance of the microcontroller. The optimal sampling time is selected by using a numerical optimization method within several test results. The optimisation results found that using a 25 μ s sampling time with the proposed discretisation method will achieve an enhancement of 16% in total in terms of calculation time and accuracy as compared with conventional Euler’s method

Photophysical performance of Nd-YAG annealed Pt/n-PSi /Pt photovoltaic photodetectors at different laser energy

This study investigates the electrical and photoresponse properties of Nd-YAG annealed Pt/n-PSi/Pt photodetectors. A porous silicon (PSi) layer was deposited on a single crystalline n-type Si via photoelectrochemical etching in aqueous hydrofluoric acid at 45 mA cm−2 for 30 min. Annealing of the n-PSi layer was conducted using a Q-switching Nd:YAG laser at different fluence laser energies (20, 30, 40, 60 mJ cm−2) with a pulse duration of 10 ns. The effect of Nd:YAG laser irradiation on the morphological and structural properties of the deposited n-PSi layer was determined. The n-PSi sample synthesized at 40 mJ cm−2 showed the maximum average discrepancy. The photodetectors fabricated using such materials showed very high sensitivity (1527.9) and low dark current (2.58 × 10−4 A) with an internal photoconductive gain of 16.27, photoresponse of 3.1 A W−1, response time of 0.29 s, and recovery time of 0.45 s. These exceptional properties of the fabricated photodetectors indicate that the laser annealing approach is a viable tool for the synthesis of n-PSi that is suitable for various applications

Exploration of reaction mechanisms on the plastic waste polyethylene terephthalate (PET) dissolved in phenol steam reforming reaction to produce hydrogen and valuable liquid fuels

The recycling of plastic waste is a good idea for countries which concern air pollution, CO2 emission, and public health. In this research article, PET, as one of the significant plastic waste, was selected to dissolve in phenol for value‐added liquid fuels and hydrogen gas production. This research aims to provide insight into the mechanism of PET waste and phenol steam reforming reaction. The catalytic steam reforming of PET dissolved in phenol employing Ni-Pt/Al-Ti catalyst was conducted in a fixed bed reactor. The reaction test illustrated that Ni-Pt/Al-Ti catalyst possesses high activity and stability in a long time on stream experiment. It was found that valuable liquid fuels such as styrene, acetic acid, benzoic, benzene, and many other components successfully produced from the PET-phenol steam reforming reaction. It was found that during the catalytic reforming of PET, several types of reactions such as dehydrogenation reaction, thermal cracking, steam reforming, water gas shift reaction, carbenium ion reaction, free radical reaction, dihydroxylation reaction, and coke formation occurred

Ni–Pt/Al nano-sized catalyst supported on TNPs for hydrogen and valuable fuel production from the steam reforming of plastic waste dissolved in phenol

In this research, titanium nanoparticles (TNPs) for Ni–Pt/Al nano-sized catalysts were prepared via the hydrothermal technique, and their catalytic performance for the polyethylene terephthalate (PET) as plastic waste and phenol steam reforming reaction was examined. Complementary characterization methods, such as BET, ICP, TEM, XRD, FTIR, NH3-TPD, H2-TPR, CO2-TPD, TGA, and CHNS, were conducted to relate surface functionality and structure to the activity of catalysts. The catalytic activity and stability with ten days on stream at 700 °C were investigated. It was found that the catalyst properties such as surface area and the number of acid sites play a crucial role in catalyst activity. The feed conversion and hydrogen yield for the optimum catalyst that is Ni–Pt/Ti–Al were found to be 92% and 75%, respectively. This research has also emphasized the opportunities of this method to resolve the threat of PET plastic waste to the environment concerning the creation of valuable fuels such as benzene, toluene, styrene, methylindene, etc