Total Harmonic Distribution Research Articles

Unipolar sinusoidal current excited switched reluctance motor control based on a 3D space vector modulation

This paper reports on a novel unipolar current excited control scheme for the asymmetric bridge converter (ABC)-based switched reluctance drive (SRD), where the 3D space vector modulation under three modes is developed to reduce the total harmonic distribution (THD) and torque ripple. Firstly, two different 3D vector distributions, namely, the small voltage amplitude mode and large mode are presented based on the asymmetric converter. For both distributions, the zero-sequence voltages generated by the effective vectors are considered. Additionally, zero-sequence vectors (1,1,1) and (−1,−1,−1) are no longer treated as null vectors and involved in the control of zero-sequence current. Then, the duty cycles of both two modes are obtained by the combination of the zero-sequence and two adjacent active vectors. Moreover, based on the large modulation mode, a novel method combined with the small mode is proposed to further optimise the switching costs and torque ripples. The effectiveness of the proposed modes is verified through the simulation in MATLAB and the experiment on a dSPACE-1103-based prototype. Compared with the conventional switched reluctance motor vector control, the proposed scheme delivers better performances of THD, efficiency and torque ripple reduction.

Optimized CUK Converter Based 1Φ Grid Tied Photovoltaic System

Renewable energy-based power generation, particularly photovoltaic (PV)-connected grid systems, has gained popularity in recent years due to its widespread adoption for residential and commercial customers of all sizes, from kilowatt (KW) to megawatt (MW). The purpose of this work is to demonstrate how an efficient CUK-integrated boost converter with continuous current flow may be used to maximise the output of solar arrays. The constant voltage at the converter output is maintained with increased dynamic performance using a Proportional Integral (PI) controller based on a hybrid optimization technique GWO-PSO (Grey Wolf Optimization-Particle Swarm Optimization). This hybrid solution permits accurate and speedy monitoring of the PI controller, which reduces voltage ripples successfully. This system is connected to the 1 grid via a voltage source inverter (VSI). To ensure grid synchronisation, the inverter’s command pulses are generated by a PI controller depending on the grid’s actual power. The Total Harmonic Distribution (THD) of grid current is used to characterize the overall system. The THD is determined to be 1.8 percent with the suggested PI controller and 3.41 percent with the PI controller, and the tracking performance of the GWO-PSO algorithm is 99.8 percent.

Control of Buck-Type Dynamic Capacitor (DCAP) Using Model Predictive Control Method with PSO optimization algorithm for Dynamic Var and Harmonic Compensation

This paper presents a control method based on model predictive control (MPC) to control the buck-type dynamic capacitor (DCAP) to improve power quality. In this method, the reference current consists of two distinct parts, i.e., reactive power compensator (RPC), and harmonic current eliminator (HCE) and based on the load current and dynamically, it adapts itself to load changes. The proposed prediction model (PM) was extracted from the linearized differential equations of the DCAP. In the proposed method, vector decision variables in each cycle converter switching are updated only once during the prediction horizon, and the optimization problem related to predictive control is solved based on the particle swarm optimization (PSO) algorithm. This reduces the volume of calculations significantly. By considering the total harmonic distribution (THD) value and the power factor (PF) value, the prediction horizon is proposed. The proposed method, unlike the EHM method, has fewer control parameters and can be implemented more easily. The simulation results in MATLAB software showed the superiority of the proposed method in comparison with the EHM method on a single phase DCAP.

Comparative study of a new structure of HTS-bulk axial flux-switching machine

A high-temperature superconducting (HTS) axial flux permanent magnet (AFPM) machine was designed, using superconducting bulks over the rotor surface and rare-earth magnets in the middle of the stator teeth. Because of diamagnetic behavior of the HTS bulks and zero field cooling, leakage flux significantly reduces in the proposed machine compared to the existing machine with mounting rare-earth magnets. Three-dimensional finite element (FE) modelling was used to validate the design performance. The magnetic flux distribution, induced electromotive force (EMF), inductance, PM flux, losses, total harmonic distribution and cogging torque are computed and compared in two structures. The results show that the proposed machine structure is more efficient than the existing one.

Comparative Study Between a Novel Multi-Tooth and a V-Shaped Flux-Switching Permanent Magnet Machines

In this paper, on the basis of a conventional 12-stator-coils/17-rotor-teeth (12/17) flux-switching permanent magnet (PM) (FSPM) machine and a 6/17 V-shaped FSPM machine, a novel 6/17 multi-tooth FSPM machine with a pair of magnets located in the upper apex of stator tooth is proposed. Then, four multi-tooth topologies sharing the same 6-stator-coils but with different rotor teeth combinations, namely, 6/17, 6/10, 6/11, and 6/13, are compared by the 2-D finite element analysis (2-D-FEA). The FEA-predicted results reveal the optimal combinations of stator coils and rotor teeth should be 6/17 for high-performance multi-tooth machines. Thereafter, an optimal design criterion of multi-tooth FSPM machines for the combinations of stator coils and rotor teeth is proposed. Afterward, electromagnetic performance evaluation between the 6/17 V-shaped and 6/17 multi-tooth machines is conducted, in terms of back electromotive force (back EMF), electromagnetic torque, cogging torque, phase inductance, unbalanced magnetic force (UMF), torque/magnet ratio, and efficiency. The comparative results indicate that the proposed 6/17 multi-tooth machine is superior to the V-shaped one, since it exhibits much higher torque/magnet ratio, larger torque, lower inductance, and much lower UMF, though the cogging torque and total harmonic distribution of phase back EMF are unfavorably larger.

Asymmetrical SVPWM Fault-Tolerant Control of Five-Phase PM Brushless Motors

In this paper, an asymmetrical space vector pulse-width modulation (SVPWM) fault-tolerant control is proposed for the five-phase permanent-magnet motor under the open-circuit condition of a single phase. The key of this method comes from two parts. First, the voltage vector diagram is rebuilt in the event of an open-circuit fault. Second, the switching signals constructing an asymmetry waveform are selected in one sector. Then, this asymmetrical SVPWM control can reduce the amplitude and total harmonic distribution of currents in healthy phases, though it has limitation for the open-circuit condition of two phases. Additionally, both simulated and experimental results are provided to validate the good performances of the proposed fault-tolerant drive, maintaining average torque, and low torque ripple during fault. Finally, the dynamic responses of open-loop and close-loop condition are measured. The results show that the proposed method can offer comparable dynamic performance of normal SVPWM control that is widely used in healthy five-phase motor drive.

A novel flux-switching permanent magnet machine with v-shaped magnets

In this paper, firstly a novel 6-stator-coil/17-rotor-pole (6/17) flux-switching permanent magnet (FSPM) machine with V-shaped magnets, deduced from conventional 12/17 FSPM machines is proposed to achieve more symmetrical phase back-electromotive force (back-EMF), and smaller torque ripple by comparing with an existing 6/10 V-shaped FSPM machine. Then, to obtain larger electromagnetic torque, less torque ripple, and easier mechanical processing, two improved variants based on the original 6/17 V-shaped topology are proposed. For the first variant, the separate stator-core segments located on the stator yoke are connected into a united stator yoke, while for the second variant the stator core is a whole entity by adding magnetic bridges at the ends of permanent magnets (PMs). Consequently, the performances of the three 6/17 V-shaped FSPM machines, namely, the original one and the two variants, are conducted by finite element analysis (FEA). The results reveal that the first variant exhibits significantly larger torque and considerably improved torque per magnet volume, i.e., the magnet utilization ratio than the original one, and the second variant exhibits the smallest torque ripple, least total harmonic distribution (THD) of phase back-EMF, and easiest mechanical processing for manufacturing.

Multiobjective Optimization Design of Small-Scale Wind Power Generator With Outer Rotor Based on Box–Behnken Design

In this paper, the finite-element method (FEM) based on 2-D numerical analysis was used for the basic design and characteristics analysis of a small-scale 3-kW wind power generator to which a permanent-magnet generator was applied. A prototype was manufactured, and a characteristics experiment was performed to verify the designed generator. In addition, the optimization design in order to satisfy required power of a generator while minimizing the cogging torque and the back electromotive force (EMF) total harmonic distribution (THD) on the basis of the designed initial model generator was conducted using the Box-Behnken design (BBD), which is a response surface method (RSM). The cogging torque, the back EMF THD, and the output power for each level of the design factors selected by the BBD were derived by the FEM based on 2-D numerical analysis. As a result, the optimal design model was derived in consideration of the RSA among each factor and the main effect and the interaction effects of each factor. This demonstrated the validity of the optimized design of the urban small-scale wind power generator design using the BBD.

A New Fault-Tolerant Strategy Based on a Modified Selective Harmonic Technique for Three-Phase Multilevel Converters With a Single Faulty Cell

This paper proposes a new fault-tolerant strategy to revamp performance of three-phase multilevel converters with a single faulty switch. The proposed fault-tolerant strategy is based on the application of a modified selective harmonic elimination (SHE) technique in conjunction with the fundamental phase-shift compensation method. The proposed fault-tolerant strategy makes the most use of the converter capacity in the faulty condition, generates balanced line voltages, and eliminates a wide range of lower order harmonics to limit the total harmonic distribution of the converter voltages in the faulty condition. In this paper, first, a brief background about cascaded H-bridge multilevel converters and SHE technique is provided. Then, the proposed fault-tolerant strategy and the modified SHE technique are presented. Finally, several experimental results are provided to validate the operation of the proposed strategy.

Research of Compensated AC Regulated Power Supply in Electric Power Systems Based on a High-Frequency Isolated Transformer

In this paper, a new topology of compensated AC regulated power supply (ACRPS) in electric power systems based on a high-frequency isolated transformer (HFIT) is proposed. In order to overcome the slow response and low accuracy of the existing ACRPS, the phase shift regulating control (PSRC) based on instantaneous value of voltage single closed loop is applied as well as the software phase locked loop (SPLL). The proposed ACRPS has been simulated in the case of the voltage fluctuation, harmonics and frequency shift with Matlab. The simulation results show that output voltage precision is controlled within 0.5% and total harmonic distribution (THD) can be limited to less than 1%. In a word, the feasibility of the proposed ACRPS is effectively verified.