The proper operation of single-phase and three-phase grid-connected power converters depends on the synchronization with utility networks. The major challenge of the synchronization is how to quickly and precisely extract the ac signal and fundamental positive sequence in single- and three-phase power systems, respectively. This paper proposes a new detection technique based on a modified Kalman filter and the generalized averaging method. The method has an open-loop structure, and uses the orthogonal signals which are obtained directly from the Kalman filter. The resulted detection system is very simple and robust even in the presence of power quality disturbances, such as voltage imbalance, harmonics, and voltage fluctuations. The proposed technique can detect the fundamental and harmonics frequencies within or less than half a cycle in all situations, such as small and considerable frequency variations. Meanwhile, the method guarantees the zero steady-state error in complicated harmonic scenarios, including all typical single-phase and three-phase harmonics. Various case studies are assessed and the performance of the proposed detection method is verified by experiments.

A new non-isolated, high step-up DC-DC converter is proposed based on the current-fed Cockcroft-Walton Voltage Multiplier (CW-VM) that can be used as the boosting power stage of converter for low-voltage low power renewable energy sources such as photovoltaic and fuel cells. The proposed converter employs two low-voltage common-emitter switches. Utilizing the current-fed CW-VM eliminates some problems associated with the conventional voltage-fed type such as voltage ripple and load-dependent voltage droop. Other advantages of the proposed converter are continuous input current, high voltage gain, and high efficiency. Steady state operation principles, specifications, and design considerations of the proposed converter are illustrated. Furthermore, efficiency analysis of the converter is performed and discussed. Experimental tests for a 200 W prototype are carried out which confirm the theoretical analysis.

A new approach for minimization of total harmonic distortion (THD) of a multilevel flying capacitor inverter (MFCI) based on the selective harmonic elimination named stochastic THD (STHD) strategy is proposed. In the STHD strategy, the step voltage levels of multilevel inverter are considered to be varying due to unbalanced capacitor voltages. Moreover, this paper improves modeling of harmonic elimination by considering the effects of dissipative snubbers, blanking time, gate-drive circuits, and computation time in microcontrollers on the THD calculation. Switching instants are deviated from the desired moments by regarding the mentioned effects. In the proposed strategy, the switching angle variations and unbalancing of flying capacitor voltages are evaluated by 2 m + 1 point estimate strategy. Then, the formulation is combined with new modified cuckoo search algorithm and a self-adaptive mutation tactic for the establishment of new robust algorithm for minimization of the THD. The proposed STHD strategy is capable of determining the best switching angles pattern in low switching frequency without measuring current and capacitor voltages, as well as not using any controller. The proposed strategy is applied on three MFCIs and the results show that the proposed method effectively minimizes specific harmonics with low THD.

Stochastic security constrained unit commitment (SSCUC) based on a DC model could be problematic in AC networks because the DC model is potentially inaccurate. However, solving SSCUC problems using an AC model is still very challenging. Accordingly, an improved linearised AC optimal power flow (ILACOPF) model is provided in order to optimise the SSCUC problem. The proposed SSCUC model includes a linear representation of network losses and reactive power and bus voltage magnitudes. Moreover, in this study, transmission switching (TS), a powerful tool for grid side flexibility, is introduced and utilised to facilitate the mitigation of the uncertainty of wind power generation. Nevertheless, solving the SSCUC problem with TS in a full AC network is still one of the challenges in practical implementation, which is facilitated by the proposed ILACOPF model. Additionally, the aim of this study is to develop a more accurate power flow model to obtain a more realistic SSCUC solution using TS. The proposed ILAC‐SSCUC model using TS is formulated as a mixed‐integer linear programme, being solved by the proposed effective solution approach based on Benders’ decomposition. Numerical simulations on a 6‐bus and IEEE 118‐bus systems have been performed to evaluate the effectiveness of the method.

Consequent-pole permanent magnet (PM) synchronous machines (PMSMs) provide especial features by the use of alternate PM and ferromagnetic poles. The design of these types of electric machines requires an accurate model due to the asymmetrical flux distribution in the air gap under adjacent poles. The equivalent magnetic circuit technique can hardly offer an accurate model for consequent-pole PMSMs. To this end, a 2-D analytical model is presented for consequent-pole slotted stator PMSMs to accurately compute the magnetic field distribution due to PMs and armature reaction. The slotting effects and the tooth-tip effects are taken into consideration by using the subdomain technique. The proposed model is used to calculate the magnetic flux density distributions of three consequent-pole PMSMs: an 8-pole, 9-slot machine with a non-overlapping winding; a 4-pole, 15-slot machine with an overlapping winding; and a 10-pole, 12-slot machine with a non-overlapping winding, each with three different magnetization patterns, i.e., radial, parallel, and Halbach. Based on the magnetic flux distribution, the electromagnetic torque, the self- and mutual-inductances, and the unbalanced magnetic forces have been analytically calculated. The analytical results are compared with those obtained from the finite-element method to show the accuracy and efficacy of the proposed 2-D analytical model.

Brushless machines with interior permanent magnets (PMs) are mostly made with PM geometries inconsistent with the polar coordinates of the rotor cross-section. Therefore, without any sub-domain transformation, the analytical approaches cannot precisely model the interior PM machines in a single coordinate. This paper presents an accurate two-dimensional (2-D) analytical model for electromagnetic analysis of slotted brushless machines with rectangular spoke permanent magnets (PMs) assisted by hub magnets. The slotting effect is modeled via sub-domain technique. However, the spoke PM is not consistent enough with polar coordinates to be approximated by one sub-domain. In order to map the spoke PMs in polar coordinates, herein, the rectangular geometry is approximated by a combination of arc shaped sub-domains. On this basis, the 2-D analytic model is developed for M-fraction spoke PM. To verify the accuracy of the proposed 2-D approach, analytic results are compared with numeric results of finite elements method (FEM). It is revealed that by dividing the spoke PM into arc sub-domains, the 2-D model achieves higher accuracy in calculation of electromagnetic quantities such as PM and armature reaction (AR) fields, electromagnetic torque and Back Electromotive Force (BEMF).