Lars Gertmar

Torque-maximizing field-weakening control: design, analysis, and parameter selection

The torque-maximizing field-weakening control scheme proposed by Kim and Sul is developed further. The performance under imperfect field orientation conditions is investigated, and it is shown that an overestimated-rather than an underestimated-model leakage inductance should be used. A slightly modified algorithm, which offers better robustness and reduced computational complexity, is presented. The importance, for good performance, of combining the scheme with current and speed controllers featuring antiwindup and improved disturbance rejection is emphasized. The dynamics of the resulting closed-loop system are analyzed. Obtained in the process, are rules for selection of all controller parameters, allowing tuning without trial-and error steps. Good performance of the resulting system is verified experimentally.

On DC injection to AC grids from distributed generation

Distributed generation, DG, introduces multi-generator grids and new modes of operation. DG will likely introduce power electronic, PE, converters on a large scale at the low- and medium-voltage levels. DC injection into the AC grid is a threat from grid-connected PE converters that are badly structured. Low DC currents in AC current are difficult to measure at those low levels decided in IEEEtrade 1547 and discussed in other international working groups. Transformers and PE can be co-designed to eliminate DC injection. Modern adjustable-speed drives, ASDs, especially, those with active rectifiers, form a basis to discuss and solve issues of DC injection to AC grids from DG also named distributed energy resources, DER or even DR. DC components from power electronics, embedded in solar power, wind power, energy storage, smart houses, smart-office buildings, own generators, etc. give rise to grid-aspects like AC components give frequencies around the fundamental one. FMEA, failure mode and effects analysis, is judged to be a tool for further synthesis

Are DC currents in an AC power distribution the root cause for some abnormalities in AU

Abnormalities within a limited number of small and medium enterprises (SMEs) in Australia are reported. A set of interrelated industrial issues are brought out in order to advance the state of knowledge and avoid similar abnormalities/irregularities and to bring back some ideas for the mitigations. Impacts on new automated systems and on industrial as well as safety standards are expected in the long run.

Control of a split pole pair induction machine

There are advantages with dividing a multi pole pair AC machine stator into two pole segments. Modularity, serviceability, lower component rating and improved control around the zero stator frequency region are feasible with a modular approach. This paper examines the impact of modularisation on the control capabilities. A control strategy is proposed whereby the stator frequencies of the stator segments is altered around the zero frequency region of the conventional motor. Experimental results confirm that modularisation provides excellent control capabilities around this region.