Lech Grzesiak

Novel hybrid load-adaptive variable-speed generating system

Light loading of generator sets has long been the cause of accelerated aging and premature engine failure. This problem is exacerbated by impact and nonlinear loads because generator sets are oversized to cope with this condition whilst maintaining the voltage within the specified limits. A new hybrid engine-friendly load-adaptive variable speed generating system has been developed which decouples the engine from the load by means of a decoupling converter. The engine load torque can be precisely controlled independently of the load so that optimal engine operation is achieved for a wide range of load power demands. Test results show outstanding performance under the worst load conditions, superior to that of comparable systems.

Application of a permanent magnet machine in the novel Hygen adjustable-speed load-adaptive electricity generating system

Hygen is an adjustable-speed load-adaptive electricity generating system comprising one or more energy sources, e.g. an engine-generator unit, an energy storage means and a power electronic converter system with microprocessor control. A medium frequency permanent magnet alternator is integrated into a diesel engine to form a compact generator unit. A variable-ratio boost rectifier converts the variable voltage/frequency of the generator unit and regulates the output as required by the converter system. This combination provides a compact and efficient energy delivery sub-system with many benefits.

Power quality of the Hygen autonomous load-adaptive adjustable-speed generating system

The Hygen off-grid adjustable-speed load-adaptive generating system produces standard AC 50 Hz, 230 V RMS voltage for common applications- and for very sensitive loads. A permanent magnet generator generates a variable voltage and variable frequency which is converted by an AC/DC/AC power electronic system. The system provides an uninterruptible high quality output voltage under the most adverse load conditions-large step/impact loads, nonlinear loads and arc welding machines. Experimental results produced by Volt Ampere confirm the high quality of the output voltage.

AC machine torque and stator flux estimation using a neural network based on the steady-state 2D field model

This paper presents a neural estimator of torque and stator flux, based on knowledge of stator current and speed. The suggested estimator is constructed from a multilayer feedforward neural network. Training sets are based on calculations using an FEM model of an induction machine. The steady-state performance of an AC motor has been assumed and the nonlinearity of the laminated core has been taken into consideration while modelling the problem. The end-regions impedance has been considered by means of modification of the rotor cage conductivity.

Particle swarm optimization of the multioscillatory LQR for a three-phase grid-tie converter

This paper presents an evolutionary optimization of the linear-quadratic (LQ) current controller for a three-phase grid-tie voltage source converter with an L-type input filter. The current control system is equipped with multi-oscillatory terms, which enable the converter to obtain nearly sinusoidal shape and balanced input currents under unbalanced and distorted grid voltage conditions. The augmentation of the state vector to include additional states which describe dynamics of disturbances increases the number of weights to be selected for a cost function in the LQR procedure design. Therefore, it is proposed that optimal weighting factors are sought using particle-swarm-based method. Finally, the simulational tuning based on the linear model and the numerical verification based on a non-linear model of the system with a pulse width modulator are addressed. Streszczenie. Artykuł prezentuje optymalizację ewolucyjną liniowo-kwadratowego regulatora prądu dla trójfazowego przekształtnika sieciowego z filtrem wejściowym typu L. Układ regulacji prądu jest wypozażony w człony oscylacyjne co pozwala na kształtowanie niemal sinusoidalnych i symetrycznych prądów wejściowych w warunkach występowania wyższych harmonicznych i asymetrii napięć sieci. Rozszerzenie wektora stanu o dodatkowe stany opisujące dynamikę zakłóceń zwiększa liczbę wag, które należy dobrać dla funkcji celu ujętej w procedurze projektowania LQR. Dlatego zaproponowano dobór optymalnych wsółczynników wagowych przy użyciu optymalizacji metodą roju cząstek. Finalnie zostały omówione strojenie symulacyjne na modelu liniowym oraz weryfikacja numeryczna na modelu nieliniowym z modulatorem szerokości impulsów. (Optymalizacja rojem cząstek regulatora liniowo-kwadratowego z członami oscylacyjnymi dla trójfazowego przekształtnika sieciowego)