Improved voltage regulation for current-source inverters

Voltage regulation schemes for current-source inverters (CSIs) commonly use a simple proportional-integral (PI) stationary frame controller, but this approach is known to suffer from significant steady-state error. In contrast, the more advanced schemes that are routinely used for current regulation of voltage-source inverters (VSIs) avoid these problems. This paper presents an approach to directly utilize VSI current regulation strategies to control the voltage for a CSI, without requiring significant modification or development. The approach uses a space-vector mapping technique to convert VSI modulation signals to CSI gate drive signals, which allows VSI closed-loop current control strategies to be directly applied to CSI voltage regulation. Three new voltage regulation CSI controllers based on hysteresis, synchronous frame PI, and stationary frame P+Resonant control principles are presented based on this concept     

Prototype feedback-controlled bidirectional actuation system forMEMS applications

We have successfully developed a one degree-of-freedom microsuspension system, with active position control, as a paradigm of a micromagnetic bearing. This system integrates an electromagnetic actuator, a position sensor, and a feedback control system that provides active position control. This paper discusses the design and fabrication details of the microelectromechanical system (MEMS) components: the beam mass structure integrated with a drive coil and metallized targets, spacer plate, and sensor coils. It also discusses their integration with millimagnets and electronics. Noncontact magnetic bearings based on this principle have the potential of overcoming the tribo-physical issues associated with active MEMS devices     

Stationary frame harmonic reference generation for active filter systems

Harmonic reference generators for active filter systems are commonly implemented in the synchronous reference frame, so that simple low- or high-pass filter functions can be used depending on the requirements of a particular application. High-pass filters in particular are used when the reference generator is required to produce an "everything but the fundamental" target waveform. This paper presents a stationary frame notch filter equivalent to a high-pass synchronous frame harmonic reference generator for such systems. The use of the stationary frame allows for quicker calculation of the reference generation in a discrete digital implementation, and also allows classical control techniques to be used to analyze the active filter system without requiring synchronous frame transformations of the outside system model. Both simulation (continuous and discrete) and experimental results showing the equivalency of the stationary and synchronous frame reference generation process are presented using both shift and delta-operator-based infinite-impulse response digital filters.     

Structural and compositional studies of magnetron-sputtered Nd–Fe–B thin films on Si(100)

The structure and composition of the Nd–Fe–B thin films deposited on Si(100) have been investigated. Films have been prepared by direct-current magnetron sputtering in pure argon and xenon sputter media separately. Deposition has been carried out keeping the substrates at room temperature and 360°C. These films were subjected to the post-deposition annealing to a temperature of 60O°C in a vacuum of 5×10–7 Torr. The stoichiometry and structure of these films were analysed and correlated to the deposition and annealing conditions. Films deposited in xenon sputter medium showed better crystalline properties than those sputtered in pure argon. This difference was attributed to the presence of reflected high-energy neutral gas particles in the argon medium. Films deposited in xenon were found to be relatively rich in boron compared with argon-sputtered films. Post-deposition annealing resulted in the interdiffusion at the interface between the film and substrate. The use of a SiO2 film as a barrier layer between the silicon substrate and the Nd–Fe–B film has been explored. Thermally grown SiO2 was found to be an effective diffusion barrier. © 1998 Chapman & Hall     

Stationary frame current regulation of PWM inverters with zero steady-state error

Current regulators for AC inverters are commonly categorized as hysteresis, linear PI, or deadbeat predictive regulators, with a further sub-classification into stationary ABC frame and synchronous d-q frame implementations. Synchronous frame regulators are generally accepted to have a better performance than stationary frame regulators, as they operate on DC quantities and hence can eliminate steady-state errors. This paper establishes a theoretical connection between these two classes of regulators and proposes a new type of stationary frame regulator, the P+Resonant regulator, which achieves the same transient and steady-state performance as a synchronous frame PI regulator. The new regulator is applicable to both single-phase and three phase inverters.     

A comparative analysis of multiloop voltage regulation strategies for single and three-phase UPS systems

Most of the many reported control algorithms for uninterruptible power supplies (UPSs) use either filter inductor or filter capacitor currents as feedback variables to regulate the output voltage. This paper explores the fundamental performance issues associated with the use of these quantities as feedback variables, with a view to determining their contribution to the transient system response and output harmonic compensation in any particular situation. A proportional plus resonant (P+resonant) compensator is then added into the outer voltage regulation loop to achieve zero steady error, to develop a high performance UPS control algorithm, which is applicable to both single-phase and three-phase systems. Theory, simulation, and experimental results are presented in the paper.