Proper operation of the grid-tie transformerless converters under unbalanced and distorted conditions entails a precise detection of the frequency and fundamental component of the grid voltage. One ...of the main problems that could arise during the estimation of grid parameters is the existence of a DC offset generated from measurement and A/D conversion. This undesirable induced DC offset could appear as a part of the reference sinusoidal current of grid-tie converters. Although literature has proposed the use of an extended complex Kalman filter (ECKF) for the estimation of positive and negative sequence voltage components as a promising competitor to phase locked loops, mitigating the effect of possible DC offsets when a Kalman filter is employed remains scarce. This paper proposes a new extended complex Kalman filter to improve the filter stability for estimating the frequency and the fundamental positive and negative symmetrical components of the grid voltages, where DC offset, scaling error, and noise can successfully be rejected. The theoretical findings are experimentally validated.
Extensive efforts have been made to develop reliable and efficient onboard generation systems for electric aircraft. Due to the inherited robustness, Switched Reluctance Machines (SRMs) have ...attracted attention as a promising candidate for an integrated starter/generator in aerospace applications. This paper presents two modes of operation: Constant Current (CC) and Constant Voltage (CV). A Particle Swarm Optimization (PSO)-based tuning approach is employed to optimize the controller of a Switched Reluctance Generator (SRG). The presented controller is evaluated using a three-phase 6/4 SRG. The Control-Hardware-in-the-loop (CHiL) has been used to elucidate the viability of the explored control concept practically.
Multiphase machines are commonly analyzed using vector space decomposition modeling technique, where the original phase variables are decomposed into multiple orthogonal subspaces. The machine torque ...production and, therefore, its dynamic response are mainly decided from the <inline-formula> <tex-math notation="LaTeX">\alpha </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">\beta </tex-math></inline-formula> fundamental subspace. In the available literature, other non-fundamental subspaces are commonly regarded as the non-flux/torque producing subspaces while mainly contributing to the extra winding joule losses. Although the primitive harmonic-free models are usually assumed for these secondary subspaces in the asymmetrical six-phase induction machines, a clear evidence to include or discard the effect of the low-order space harmonics of the air gap flux distribution under different neutral configurations has not been established so far. To this end, this paper investigates the effect of the induced air gap harmonics mapped to the <inline-formula> <tex-math notation="LaTeX">x </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">y </tex-math></inline-formula> and zero subspaces on the dynamic modeling and, hence, the dynamic response of an asymmetrical six-phase induction machine. An improved space harmonic model is, then, proposed to better explore/simulate their effect under both healthy as well as fault conditions. The proposed model is experimentally validated using a 1.5-kW prototype induction machine.
Despite the increased interest in multiphase induction machines for safety-critical applications, machine parameter identification for the different sequence planes is still a challenging research ...point. In most available literature, the effect of nonfundamental sequence planes is overlooked due to the assumption of sinusoidal winding distribution and healthy operation. However, in a single layer or concentric winding layout with an odd number of phases, the effect of flux produced by nonfundamental sequence planes cannot be ignored for the open-phase case. This paper proposes a simple offline method to estimate the parameters of a five-phase induction machine corresponding to different sequence planes. The proposed technique can estimate the stator leakage inductance as well as the magnetizing inductance of both fundamental and third sequences by applying a quasi-square voltage to the stator winding while the machine is running at no-load. Consequently, the rotor circuit parameters of the fundamental sequence plane can be simply obtained by deducting the stator impedance from the blocked rotor machine impedance. For the third sequence plane, an approximate relation to estimate these parameters based on the measured fundamental sequence rotor parameters is also given. An experimental 1.5 Hp prototype machine is used to verify the proposed technique.
Multiphase machines have attracted significant attention in both academic and industrial sectors as candidates for high-power safety-critical applications as well as wind energy conversion systems. ...Undoubtedly, this interest has been fueled by the rapid development in semiconductor devices. Due to the lack of available standard stator frames suitable for constructing multiphase machines of any phase order, machines with multiple three-phase winding sets seem to be the standard topology in many industrial applications. Recent literature has demonstrated a simple generalized technique to rewind a standard three-phase stator frame with a generic prime-phase order stator winding. However, based on the selected slot/pole combination, this technique yields a small unbalance component in the stator phase currents due to the stator leakage inductance mismatch among different phases. This paper further investigates the optimal slot/pole choices, for a given phase-order, that minimize the unbalance in the stator leakage components between phases to ensure comparable performance to standard symmetrical <inline-formula> <tex-math notation="LaTeX">n </tex-math></inline-formula>-phase machines. The analysis is presented for the well-known phase orders employed in literature, namely, 5-phase, 7-phase, and 11-phase windings. The effect of winding asymmetry on mathematical modeling and, hence, the dynamic response is also investigated. A 1kW prototype machine equipped with a five-phase winding is used to experimentally verify the theoretical findings.
The combined star/pentagon connection of five-phase induction machines was recently demonstrated as a promising compromise between conventional star and pentagon connections. It combines the ...advantages of both star and pentagon connections without any additional hardware for winding changeover. This connection is based on two five-phase single layer concentrated winding sets shifted in space by π/10 and connected in a combined star/pentagon configuration to provide five-phase terminals. Since the combined star/pentagon connected induction machine is fundamentally an asymmetrical ten-phase machine, the machine mathematical model possesses additional subspaces, which affect the behavior of the machine especially under open line conditions. Starting from the conventional five-phase and m -bar squirrel cage induction machine model, the phase-variable model of the combined star/pentagon connection is introduced in this paper. The corresponding equivalent dq model with five decoupled subspaces, which can account for air gap harmonics up to ninth order, is then derived. Finally, it was shown that the machine model could be simply approximated with only two subspaces similar to a conventional five-phase induction machine with sinusoidally distributed winding, where the flux produced by the nonfundamental subspace could be neglected. The model is verified using a 1 kW prototype five-phase induction machine.
In rural and remote areas, solar photovoltaic energy (PV) water pumping systems (SPWPSs) are being favored over diesel-powered water pumping due to environmental and economic considerations. PV is a ...clean source of electric energy offering low operational and maintenance cost. However, the direct-coupled SPWPS requires inventive solutions to improve the system’s efficiency under solar power variations while producing the required amount of pumped water concurrently. This paper introduces a new quadratic V/f (Q V/f) control method to drive an induction motor powered directly from a solar PV source using a two-stage power converter without storage batteries. Conventional controllers usually employ linear V/f control, where the reference motor speed is derived from the PV input power and the dc-link voltage error using a simple proportional–integral (PI) controller. The proposed Q V/f-based system is compared with the conventional linear V/f control using a simulation case study under different operating conditions. The proposed controller expectedly enhances the system output power and efficiency, particularly under low levels of solar irradiance. Some alternative controllers rather than the simple PI controller are also investigated in an attempt to improve the system dynamics as well as the water flow output. An experimental prototype system is used to validate the proposed Q V/f under diverse operating conditions.
This paper proposes a data-driven approach strategy for enhancing the performance of grid forming converters (GFCs) in microgrids by leveraging the capabilities of dynamic mode decomposition (DMD) in ...combination with finite-control-set model predictive control (FCS-MPC). Conventional FCS-MPC, based on static models, have encountered numerous challenges in addressing parametric uncertainties in microgrid applications. To address this, the proposed strategy introduces an adaptive model based on DMD, integrated into the FCS-MPC framework to yield a more robust and reliable control technique in the presence of parametric uncertainties. The proposed data-driven approach utilizes the DMD-based model in combination with FCS-MPC to effectively share power through primary control and maintain voltage and frequency stability through secondary control, thus achieving improved reference tracking, load power variation robustness, and power quality. The effectiveness and efficiency of this proposed data-driven approach were validated through a comparative study with conventional static model FCS-MPC and double loop PI control, utilizing the MATLAB/Simulink platform.
The transition to electric vehicles (EVs) has received global support as initiatives and legislation are introduced in support of a zero-emissions future envisaged for transportation. Integrated ...on-board battery chargers (OBCs), which exploit the EV drivetrain elements into the charging process, are considered an elegant solution to achieve this widespread adoption of EVs. Surface-mounted permanent-magnet (SPM) machines have emerged as plausible candidates for EV traction due to their nonsalient characteristics and ease of manufacturing. From an electric machine design perspective, parasitic torque ripple and core losses need to be minimized in integrated OBCs during both propulsion and charging modes. The optimal design of EV propulsion motors has been extensively presented in the literature; however, the performance of the optimal traction machine under the charging mode of operation for integrated OBCs has not received much attention in the literature thus far. This paper investigates the optimal design of a six-phase SPM machine employed in an integrated OBC with two possible winding layouts, namely, dual three-phase or asymmetrical six-phase winding arrangements. First, the sizing equation and optimized geometrical parameters of a six-phase 12-slot/10-pole fractional slot concentrated winding (FSCW)-based SPM machine are introduced. Then, variations in the output average torque, parasitic torque ripple, and parasitic core losses with the slot opening width and the PM width-to-pole pitch ratio are further investigated for the two proposed winding layouts under various operation modes. Eventually, the optimally designed machine is simulated using analytical magnetic equivalent circuit (MEC) models. The obtained results are validated using 2D finite element (FE) analysis.
Research on common-mode-voltage (CMV) reduction in multiphase drive systems has recently met an intensified interest in the available literature. This paper first explores two existing ...space-vector-based CMV reduction (CMVR) schemes for five-phase voltage source inverters, represented as CMVR1 and CMVR2, which reduce the CMV by 40% and 80%, respectively. Moreover, a new space-vector-based CMVR scheme, termed as CMVR3, is proposed that not only minimizes the CMV but also reduces the overall switching losses when compared with the other schemes. The optimal duty cycles and the switching sequence of all schemes are introduced. Since the implementation of space-vector-based schemes using look-up tables is a relatively complex and time-consuming process, this paper proposes a simpler scalar PWM approach. This approach can easily be implemented using embedded PWM modules of most commercial digital signal processors. To evaluate the performance of the presented CMVR schemes, a detailed evaluation study is presented. The optimal CMVR scheme over the full modulation index range is also highlighted. The theoretical findings are verified using a prototype five-phase induction machine through simulations and experimentally.
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