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Estimation of amplitude, instantaneous phase, and frequency of a single-phase grid voltage signal are studied in this letter. The proposed approach uses a novel circular limit cycle oscillator (CLO) coupled with a frequency-locked loop. Due to the nonlinear structure of the CLO, the proposed frequency adaptive CLO technique is robust against various perturbations faced in the practical settings, e.g., the discontinuous jump of phase, frequency, and amplitude. The global stability analysis of the CLO and local stability analysis of the frequency adaptive CLO are performed. Experimental results demonstrate the effectiveness of the proposed technique over a very recent technique proposed in the literature. [ABSTRACT FROM AUTHOR]

Accurate and fast estimation of single-phase grid voltage phase and frequency has the potential to improve the performances of various control and monitoring techniques used in electric power systems. This letter applies an adaptive sliding mode observer for frequency and phase estimation. The observer is simple, easy to tune, and suitable for real-time implementation. The proposed adaptive observer can be considered as an alternative to a phase-locked loop (PLL) with better performance. dSPACE-based experimental results are given to show the effectiveness and performance improvement of the proposed approach with respect to two other advanced PLL techniques, namely, pseudolinear enhanced PLL and second-order generalized integrator-frequency locked loop. [ABSTRACT FROM AUTHOR]

This paper presents the design, development, control, and supervision of a hardware-based laboratory multiterminal-direct-current (MTDC) testbed. This work is a part of the TWENTIES (transmission system operation with large penetration of wind and other renewable electricity sources in networks by means of innovative tools and integrated energy solutions) DEMO 3 European project, which aims to demonstrate the feasibility of a dc grid through experimental tests. This is a hardware-in-the-loop dc system testbed with simulated ac systems in real-time simulation; the dc cables and some converters are actual, at laboratory scale. The laboratory-scale testbed is homothetic to a full-scale high-voltage direct-current (HVDC) system: electrical elements are the same in per unit. The testbed is supervised by a supervisory control and data acquisition system based on PcVue. A primary control-based droop control method to provide dc grid power balance and coordinated control methods to dispatch power as scheduled by a transmission system operator are implemented. Since primary control acts as converter level by using local measurements, a coordinated control is proposed to manage the dc grid power flow. The implemented system is innovative and achievable for real-time real-world MTDC-HVDC grid applications. [ABSTRACT FROM PUBLISHER]

Various topologies of the Direct Current (DC) microgrid have been proposed in the literature by considering practical requirements. One of the important criteria in topology selection is the availability of a well-functioning protection scheme. A significant part of the DC microgrid protection system literature considers differential protection schemes for various topologies. However this scheme doesn’t work satisfactorily with noisy measurements. Noisy measurements are a reality and can not be avoided for any real engineering system. This article proposes a robust protection scheme to alleviate some problems associated with topology selection. The proposed scheme considers noisy current measurements and works by estimating the time derivative of line currents. The proposed approach uses continuous finite-time convergent differentiator to estimate the derivative. The gains of the differentiator were tuned through Firefly algorithm-based optimization technique. Matlab/Simulink ®-based simulations verified the effectiveness of the proposed approach over the existing differential current scheme. [ABSTRACT FROM AUTHOR]

This paper deals with harmonics cancellation using pulse height modulation (PHM). This technique allows simultaneous optimization of the total harmonic distortion (THD) rate and the number of power switches. This leads to substantial reduction of the power switching losses as compared with PWM. A novel six-level inverter model is presented with three-phase output voltages having similar symmetry properties to a pure three-phase sinusoidal system. The proposed method allows canceling all even-order harmonics and integer multiples of the third-order harmonic. Switching angles and input dc voltage levels are determined so as to cancel most of the successive low-order harmonics (the most harmful to the network) starting from rank 2, allowing to shift the first nonzero harmonic far away from the fundamental. For 12 switching states per period, PHM allows to cancel harmonics from rank 2 to 10 with lower THD. A comparative study of the obtained output voltage and current shows their compliance with IEEE 519-1992 and IEC 61000-3-12 standards. [ABSTRACT FROM AUTHOR]

This paper describes a novel inverse fuzzy model based rotor flux oriented vector control approach of the induction motor. In order to obtain high performance speed response, rotor flux oriented vector control techniques are usually used to control the torque and flux separately as in direct current machines. The application of fuzzy logic in modeling of uncertainly dynamical systems is in progress'; however fuzzy modeling is one of the major topics in the field of modeling of dynamical systems. The authors has made an effort to develop an inverse fuzzy model of the vector control block applied to the induction motor to successfully improve the classical approach of the vector control. For the simulations results, it is shown that the proposed algorithm can successfully find the inverse fuzzy model that approximate the rotor flux oriented vector control block, with a compact number of fuzzy rules and membership's functions. [ABSTRACT FROM AUTHOR]

Electric vehicle (EV) powertrains consist of power electronic components as well as electric machines to manage the energy flow between different powertrain subsystems and to deliver the necessary torque and power requirements at the wheels. These power subsystems can generate undesired electrical harmonics on the direct current (DC) bus of the powertrain. This may lead to the on-board battery being subjected to DC current superposed with undesirable high- and low- frequency current oscillations, known as ripples. From real-world measurements, significant current harmonics perturbations within the range of 50 Hz to 4 kHz have been observed on the high voltage DC bus of the EV. In the limited literature, investigations into the impact of these harmonics on the degradation of battery systems have been conducted. In these studies, the battery systems were supplied by superposed current signals i.e., DC superposed by a single frequency alternating current (AC). None of these studies considered applying the entire spectrum of the ripple current measured in the real-world scenario, which is focused on in this research. The preliminary results indicate that there is no difference concerning capacity fade or impedance rise between the cells subjected to just DC current and those subjected additionally to a superposed AC ripple current. [ABSTRACT FROM AUTHOR]