Synchronous machines that are optimally designed using finite-element (FE) software, and control of such machines using powerful digital signal processors (DSPs), are commonplace today. With field-orientated control, the maximum-torqueper-ampere control strategy for unsaturated voltage conditions (below the base speed) is well known; the field-weakening strategy, however, could be rather complicated. In this paper, a straightforward torque control strategy for the entire speed range is proposed and demonstrated. Practical implementation of the method is very simple since the calculations are done offline in an automated process and are therefore removed from the load of the DSP. The process relies on machine-specific data from FE analysis and therefore includes nonlinear effects such as saturation and cross coupling. Simulation and practical results for a permanentmagnet and a reluctance synchronous machine show that the torque is controlled effectively in the entire speed range using this generic method.
Index Terms-Finite-element (FE) analysis, synchronous machines, torque control. NOMENCLATURE u r Stator-voltage vector in the rotating dq reference frame. α r Stator-voltage angle in the rotating dq reference frame. i r Stator-current vector in the rotating dq reference frame. φ r Stator-current angle in the rotating dq reference frame. ψ r Stator-flux-linkage vector in the rotating dq reference frame. δ r Stator-flux-linkage angle in the rotating dq reference frame. ω r Electrical rotational speed. R s Stator resistance. T m Machine torque. p Number of pole pairs. PMSM Permanent-magnet synchronous machine. IPMSM Interior permanent-magnet synchronous machine. RSM Reluctance synchronous machine. 2-D Two-dimensional.
An emerging area of interest within photovoltaic (PV) centred research is the simulation of the propagation of electromagnetic interference (EMI) and surges within PV installations. An overarching constraint in all simulation-based research is the accuracy of the models employed. In general, for PV-focussed simulations, nonlinear models are utilised for direct current (DC) analyses, whilst linearised models are employed for analyses involving surges or conducted electromagnetic interference. For large-signal electromagnetic interference and surges, the following two problems arise: (1) the aforementioned linearisation is only valid for the small-signal case, and (2) as they are constructed using only DC measurements, traditional large-signal PV models are generally only valid for DC conditions. Therefore, neither of these approaches can properly represent real-world PV behaviour under dynamic conditions. To overcome this limitation, this article proposes a more suitable model, compatible with Simulation Program with Integrated Circuit Emphasis (SPICE), and which results from the combination of two sub-models: one for large-signal DC cases, and one for small-signal alternating current (AC) cases. Consequently, the combined model enables improved modelling of the effects of large-signal transient perturbations to be performed, as well as cases involving small-signal AC and large-signal DC perturbations. The model parameters are extracted using data from two different classes of measurement setups: the first utilised a vector network analyser (VNA) to produce small-signal AC impedance results (covering a frequency range between 1Hz and 50MHz), and the second produces DC current-voltage curves. Both classes of measurement setup consider the device under test at multiple operating points. Key results include: (1) an improved SPICE-compatible PV model which caters for large-signal transient simulations, as well as for small-signal AC and large-signal DC cases, (2) improvements in the modelling of reverse bias behaviour when compared to the standard SPICE diode implementation, (3) the correct implementation of a voltage-dependent total capacitance (suitable for large-signal simulations), (4) modelling parameters for both a small (10 W) and a large (310 W) PV module, (5) measurement results which de-embedded the parasitic effects of the test setups employed, and (6) above 1 MHz, the physical layouts of the cells within the PV modules begin to influence the observed impedances.
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