Recent Developments of Electrical Drives - Part 20. The book stating the recent developments of electrical drives, can be useful for engineers and researchers investigating and designing electrical and electronic devices as well as for students and young researchers dealing with electrical and electronic engineering, computer sciences (advanced computer modelling, sophisticated control systems with artificial intelligence tools applied, optimal design bye use of classical and genetic algorithms employed), applied mathematics and all the topics where electromagnetic, thermal, mechanical phenomena occur | 182 Muntean et al. low speed have been recently reported 11 12 . The initial angular position of the stator flux-linkage vector fis may be obtained from a low-resolution encoder. Subsequently this encoder is not needed under the DTC scheme. Electromagnetic torque and stator flux-linkage magnitude errors generated by comparison between estimated and reference values are inputs to the respective flux and torque hysteresis regulators. The discretized outputs of these regulators are inputs to the optimum voltage switching selection table. It is used to properly choose the VSI-fed voltage vectors to regulate the stator flux and torque within their error bands. In the IPMSM DTC scheme of Fig. 3 the reference electromagnetic torque me ref is obtained as the output of the rotor-speed controller from the outer loop and is limited at a certain value which guarantees the stator current not to exceed its maximum admissible value. In its turn the reference value of the stator flux-linkage vector modulus fis ref is generated in the proposed IPMSM DTC scheme as a function of the electromagnetic torque reference . fis ref me ref by maximizing the IPMSM torque over the wide-speed operation range in the presence of current and voltage constraints. The stator-current limit Is lim is an IPMSM thermal rating or a VSI maximum available current. The stator-voltage limit Us lim is the VSI maximum available output voltage depending on the DC-link voltage. Hence the current and voltage constraints establish the following operating limits for the VSI-fed IPMSM 1 tfd i2q 1 2 Is lim 9 K 1 u2d u2q 1 2 UsMm 10 In the speed operation range I from standstill up to the base rotor speed a rb current constraint of equation 9 is dominant preventing the IPMSM overheating whereas voltage constraint of equation 10 can be met since the back-emf is rather low. Thus the required function fis ref 11 meref I for the reference value of the stator flux-linkage magnitude in the speed range I can be obtained .
