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This paper presents a shunt active filter for non-linear loads designed to minimise the harmonics presented in the three-phase three-wire system. Due to the large proliferation of power electronic control systems in our day to day life, the switching of these power electronic circuits induces harmonics in the sources which cause undesirable effects on the electrical components. Shunt active filter is a harmonic mitigating device comprising of voltage source inverter fed through a DC capacitor. The control strategy is based on extraction of harmonics using synchronous reference frame theory. The extracted harmonics are used to generate pulse-width modulation (PWM) signals using the space vector PWM (SVPWM) for the voltage source inverter which has reduced losses. The proposed method is modelled and simulated using Matlab/Simulink and the output shows that the total harmonic distortion of the supply can be reduced at the point of common coupling. [ABSTRACT FROM AUTHOR]

The article presents abstracts on electric power topics which include a five-level diode-clamped active power filter, a new approach to harmonic allocation, and the design and implementation of a radial magnetic bearing.

Shunt active power filter (SAPF) is a well-established and widely accepted power electronic device for cancelling harmonic currents from electrical networks. The common configuration of SAPF utilises a proportional-plus-integral (PI) controller. However, the conventional approaches for determining the Picoefficients may not provide satisfactory results for a wide range of operating points (loads). This paper proposes to use the particle swarm optimisation (PSO) algorithm to determine the optimal coefficients of Picontroller for SAPF applications. The DC control approach is used to generate the reference harmonic signals from the non-sinusoidal load current while a hysteresis-based Picontroller is selected to control the compensating currents. Simulation results for a power network connected to a non-linear load are generated to investigate the dynamic performances of SAPF with the conventional-PI and enhanced PSO-Picontrollers. [ABSTRACT FROM AUTHOR]

Management of harmonic voltage levels can impose significant economic impacts for both electricity suppliers and customers. For the case where harmonic voltage levels are high, economic costs include damage to equipment and associated loss of production due to high voltage harmonic levels as well as the costs associated with mitigation of harmonic currents, for example, harmonic filters. In the alternate scenario, ie. the case where harmonic voltage levels are acceptable, considerable expense may be incurred mitigating harmonic currents unnecessarily due to lack of knowledge of harmonic levels and/or network capabilities. As such, there is considerable potential for industry to make large economic gains if harmonic voltage levels can be better understood. Using data collected as part of an ongoing long-term power quality monitoring project, this paper details the characteristics of voltage harmonic behaviour on Australia electricity distribution networks [ABSTRACT FROM AUTHOR]

This paper presents the loss analysis of a dual-air-gap axial flux permanent magnet machine for a flywheel energy storage system. Losses in iron-core and permanent magnets caused by both space harmonics and time harmonics are respectively analysed using a three-dimensional finite element method. The effect of skew of magnets on machine losses is also taken into account. The analysis is validated by comparisons of calculated losses and measured values on a prototype. A solution to reduce eddy-current losses in the magnets for this machine is also presented. The eddy-current losses in the permanent magnets can be significantly lessened by both circumferential and radial segmentations. [ABSTRACT FROM AUTHOR]

In traditional Z-source inverter (ZSI) fed induction motor drives, the Z-source capacitor voltage and the motor terminal voltage are controlled by the shoot-through duty ratio and the modulation index, respectively. Modified voltage space vector has been proposed to improve motor terminal voltage control with effective DC boost in the DC link. For the same shootthrough duty ratio, modified voltage space vector provides better voltage boost in the DC link with reduced harmonics in the load side than the traditional voltage space vector. This paper presents an integrated control technique to minimise the electromagnetic torque ripples in the rotor of the ZSI-fed induction motor drives using modified voltage space vector. To improve the stability of the overall drive system, the motor terminal voltage alone is sensed instead of sensing the Z-source capacitor voltage and motor terminal voltage independently. This provides a single-stage controller for motor drive systems. The proposed induction motor drive system provides a better ride-through capability during voltage sags, better line harmonic profile, and minimisation of the torque ripples in the rotor. The proposed control technique is simulated using MATLAB/Simulink software, and analysis and experimental results have been presented to validate them. [ABSTRACT FROM AUTHOR]

This paper presents the hybrid phase-shifted carrier (PSC) modulation for cascaded voltage source inverters, investigates their performance characteristics, and provides a comparison with the standard pulse-width modulation (PWM) methods. The proposed PWM combines the features of fundamental frequency PWM and high-frequency PSC-PWM in power conversion, and resolves the contradiction between high frequency and accuracy in a digital control scheme. The proposed PWM is developed based on PWM base generator and hybrid PWM control algorithm, and it is implemented using TMS320 F2407 DSP processor and Xilinx XC95108 CPLD controller, respectively. The main characteristic of this hybrid modulation is the reduction in switching losses, effectively improving harmonic performance, and solving the problem of unequal voltage stress and current stress of power devices. The performance of this hybrid modulation is analysed and compared with the original strategies. Power losses, total harmonic distortion (THD), weighted THD and the normalised weighted THD are evaluated. Simulation and experimental results verify that the proposed PWM technique is superior to standard techniques. Finally, it is concluded that the proposed strategy is highly suited to inverters with high number of voltage levels. [ABSTRACT FROM AUTHOR]

In traditional Z-source inverter (ZSI) fed induction motor drives, the Z-source capacitor voltage and the motor terminal voltage are controlled by the shoot-through duty ratio and the modulation index, respectively. Modified voltage space vector has been proposed to improve motor terminal voltage control with effective DC boost in the DC link. For the same shootthrough duty ratio, modified voltage space vector provides better voltage boost in the DC link with reduced harmonics in the load side than the traditional voltage space vector. This paper presents an integrated control technique to minimise the electromagnetic torque ripples in the rotor of the ZSI-fed induction motor drives using modified voltage space vector. To improve the stability of the overall drive system, the motor terminal voltage alone is sensed instead of sensing the Z-source capacitor voltage and motor terminal voltage independently. This provides a single-stage controller for motor drive systems. The proposed induction motor drive system provides a better ride-through capability during voltage sags, better line harmonic profile, and minimisation of the torque ripples in the rotor. The proposed control technique is simulated using MATLAB/Simulink software, and analysis and experimental results have been presented to validate them. [ABSTRACT FROM AUTHOR]

Distributors need to allocate a maximum allowed level of harmonic current to medium-voltage customers to keep voltage distortion acceptable. The paper describes a new approach, based on the concept of voltage droop, requiring much less calculation and data than required by the present approach based on an IEC technical report. The discrepancy between the new method and the present is studied by comparing some carefully selected scenarios. It is shown that the proposed method gives results within 20% of the standards-based approach which makes it a very attractive alternative for harmonic allocation. [ABSTRACT FROM AUTHOR]

This paper proposes an online algorithm to calculate the switching angles of the selective harmonic elimination pulse-width modulation (SHE-PWM) scheme for voltage source inverters (VSIs). It is based on the quadratic curve fitting of the trajectories of the exact SHEPWM angles. The result is a generalised quadratic equation that requires only the addition and multiplication processes, allowing its implementation using a low-cost microprocessor. Changes to the number of harmonics to be eliminated and the fundamental amplitude of the pole switching waveform (NP1) can be calculated independently. This feature is particularly suitable for motor drive applications. An extensive analysis to determine the accuracy of the algorithm is carried out. It is found that the maximum difference between the exact angle and the one calculated using this scheme (defined as angle error) is less than 1° for 0 < NP1 < 0.8. For higher values of NP1 (including over-modulation), the angle error is about 8°. However, by incorporating an error correction scheme, the angle error is reduced to between 3-6 times. To verify the workability of the technique, an experimental single-phase VSI is constructed. The SHE-PWM algorithm is implemented using a fixed-point, 16-bit microprocessor. For comparison, a MATLAB simulation of the same inverter system is carried out. The result obtained from the test rig is in very close agreement with the theoretical prediction and simulation. [ABSTRACT FROM AUTHOR]

This paper presents a new control scheme for shunt hybrid power filters that provides the capability of harmonics mitigation and reactive power compensation. The control system includes two main loops. The first control loop, which is responsible for harmonic mitigation, generates harmonic component of the active power filter reference voltage. In this control scheme no harmonic extracting circuit is used and, hence, it offers better filtering performances as compared with conventional control schemes of hybrid power filters. The second control loop is designed for reactive power compensation of non-linear loads. The magnitude of the fundamental injected voltage is controlled to adjust the reactive current of passive filter according to the reactive demand of loads, thereby making the line current in-phase with the system voltage. Frequency response of the shunt hybrid power filter is investigated by mathematical analysis and it is shown that the reduction of controller time delay improves filtering characteristic at high order harmonic frequencies. Computer simulations results, carried out for a typical distribution system with two non-linear loads, are presented to show fine steady-state and dynamic performances of the proposed controller . [ABSTRACT FROM AUTHOR]

This paper proposes an online algorithm to calculate the switching angles of the selective harmonic elimination pulse-width modulation (SHE-PWM) scheme for voltage source inverters (VSIs). It is based on the quadratic curve fitting of the trajectories of the exact SHEPWM angles. The result is a generalised quadratic equation that requires only the addition and multiplication processes, allowing its implementation using a low-cost microprocessor. Changes to the number of harmonics to be eliminated and the fundamental amplitude of the pole switching waveform (NP1) can be calculated independently. This feature is particularly suitable for motor drive applications. An extensive analysis to determine the accuracy of the algorithm is carried out. It is found that the maximum difference between the exact angle and the one calculated using this scheme (defined as angle error) is less than 1° for 0 < NP1 < 0.8. For higher values of NP1 (including over-modulation), the angle error is about 8°. However, by incorporating an error correction scheme, the angle error is reduced to between 3-6 times. To verify the workability of the technique, an experimental single-phase VSI is constructed. The SHE-PWM algorithm is implemented using a fixed-point, 16-bit microprocessor. For comparison, a MATLAB simulation of the same inverter system is carried out. The result obtained from the test rig is in very close agreement with the theoretical prediction and simulation. [ABSTRACT FROM AUTHOR]

This paper presents an isolated cycloconverter-type high-frequency (HF) link inverter that consists of three arms of bidirectional switches at the transformer secondary. This topology has the advantages of light weight and reduced switch count, when compared to other types of HF link inverters. However, like all HF link inverter topologies, this topology suffers from a high-voltage surge problem and power device switching loss. In order to overcome these problems, the natural commutation method that enables soft-switching operation is applied. To verify the viability of the scheme, a low-power laboratory prototype based on the Siemens 80C167 fixed-point microcontroller is constructed. In addition, the simulation of the inverter is also carried out. The prototype inverter is able to supply output voltage at 120 Vrms, with a total harmonics distortion of less than 1%. The total power conversion efficiency reaches 86% when the output power is over 300 W. [ABSTRACT FROM AUTHOR]

This paper presents a new control scheme for shunt hybrid power filters that provides the capability of harmonics mitigation and reactive power compensation. The control system includes two main loops. The first control loop, which is responsible for harmonic mitigation, generates harmonic component of the active power filter reference voltage. In this control scheme no harmonic extracting circuit is used and, hence, it offers better filtering performances as compared with conventional control schemes of hybrid power filters. The second control loop is designed for reactive power compensation of non-linear loads. The magnitude of the fundamental injected voltage is controlled to adjust the reactive current of passive filter according to the reactive demand of loads, thereby making the line current in-phase with the system voltage. Frequency response of the shunt hybrid power filter is investigated by mathematical analysis and it is shown that the reduction of controller time delay improves filtering characteristic at high order harmonic frequencies. Computer simulations results, carried out for a typical distribution system with two non-linear loads, are presented to show fine steady-state and dynamic performances of the proposed controller. [ABSTRACT FROM AUTHOR]