H.J. Beukes

Maximum power point trackers for wind turbines

Maximum power point tracking methods are presented whereby the loading on the wind turbine is controlled to ensure that the maximum available energy from the wind is captured. The wind turbine system is modelled and used in simulations to evaluate two proposed maximum power point trackers, named anemometer control and calculation control for the purpose of this paper. An additional analog system is also created whereby the complete wind turbine system can be simulated. An inverter is used to replicate the generator and the loading is controlled using an active rectifier. The results from the simulations and analog system are presented whereby the two trackers are shown to be close to ideal. The appeal of the calculation method is in the redundancy of an anemometer making it attractive to less expensive, small-scale systems.

Finding an optimal PV panel maximum power point tracking method

The need for a maximum power point tracker in a photovoltaic system is explained. A variety of photovoltaic panel maximum power point tracking methods are then briefly compared. The optimal method from those compared, where the photovoltaic panel power-voltage curve is scanned periodically, and the maximum power point tracker is controlled by current, is discussed in detail. Problems with this implementation are highlighted, and the design of a voltage-controlled implementation using the same power-voltage curve scan is presented. Problems and advantages of this system are given.

Busbar design considerations for high power IGBT converters

This paper addresses an important issue in the design and synthesis of high power IGBT converters, i.e. the layout and design of connection busbars. Parasitic inductance, caused by the physical distance current has to flow from the storage capacitors to the static switches and back, is the major constraint in developing a bus structure. This leads to nonideal converter operation, namely voltage overshoot, voltage drop and resonance with snubber capacitors. By analyzing the currents and fields in and around busbars, parasitic inductance can be predicted and limited.

Performance of the auxiliary resonant commutated pole converter in converter based utility devices

In this paper the performance of the auxiliary resonant commutated pole converter is investigated experimentally for converter based utility devices. Converter performance is evaluated at high power and the results are compared with hard switched converter technology.

Integrated active snubber for high power IGBT modules

This paper presents an integrated active snubber (IASM) to be used with IGBT modules in power converters, applied in utility devices. The IASM is a compound component, consisting of all active and passive components necessary to change a hard switched converter into a soft switching converter, i.e. the auxiliary resonant commutated pole (ARCP) converter. The IASM mounts directly onto standard IGBT modules. Although the IASM does not provide perfect soft switching, the switching losses are reduced such that IGBTs can be used at their maximum current and voltage ratings and frequencies of up to 15 kHz, with reduced EMI.

Control complexities related to high power resonant inverters

Numerous resonant soft-switching inverter topologies have been introduced. This paper offers a clearly arranged survey of control and sensing complexity, application ranges and device requirements related to several promising topologies. By presenting implementation details and experimental results on two representative inverter types, typical control issues and problems of resonant link and resonant pole inverters are illustrated.

A distributed control strategy for multi-cell converters

Multi-cell and multi-level converters are receiving a lot of attention. These types of converters have a number of advantages (EMC, modularity, etc.), but are also more difficult to control and construct. An emerging trend in the control of power converters is the use of distributed control. This paper investigates the applicability of distributed control to multi-cell power converters.

A detailed analysis of the effect of dead time on harmonic distortion in a class D audio amplifier

This paper presents an analytical method for determining the effect of dead time on harmonic distortion in a class D audio amplifier. The analysis is based on the well established double Fourier series, providing accurate analytical solutions to the pulse width modulated spectra under natural sampling. The proposed analytical model differs from that of previous work in the sense that the precise contribution of each separate component can be determined, i.e. the fundamental component, baseband, carrier and sideband harmonics.

An AC-to-AC converter based voltage regulator

This paper presents an AC voltage regulator based on a pulse width modulated AC-to-AC converter and a step-down transformer. The regulator is aimed at electrification of small rural communities and compensates for the voltage variations ranging from +10% to 40% of the nominal. The fast dynamics associated with a pulse width modulated converter is a significant benefit when compared to more conventional techniques, for instance the use of tap changing, transformers.

Feasibility study of electricity theft detection using mobile remote check meters

Check metering is an effective method for measuring the losses and electricity theft in a low voltage (LV) reticulation network. Populating a LV reticulation network with permanent check meters is expensive. Electricity theft or tampering is a dynamic process. Current developments in the telecommunications industry make it possible to implement a mobile remote check meter. A data collection infrastructure and data mining software, combined with check metering, can provide valuable information regarding the network. Before devices are placed in the field, a study is conducted to determine the optimum stationary time period for detecting electricity theft in the area, based on available consumption data in the area. This paper discusses simulations and models based on data from pre-paid meters in order to determine the feasibility and method of operation of a remote check meter