Experimental Identification of the Optimal Current Vectors for a Permanent-Magnet Synchronous Machine in Wave Energy Converters

Abstract

This paper investigates efficiency enhancements in Permanent-Magnet Synchronous Machines (PMSMs) used as generators in wave energy converters. A method is presented, which allows experimental identification of the optimal current vectors leading to minimal losses and maximum efficiency. Iron and inverter losses are considered. The proposed identification method is generic and is applicable to any PMSM used as a generator. The obtained results are compared to the well-known Maximum Torque per Current (MTPC) strategy. Two MTPC strategies are investigated: (i) MTPC using linearised flux linkages; and (ii) MTPC using measured, nonlinear flux linkages. For both MTPC strategies, the influence of the Voltage Source Inverter (VSI) is taken into account. All measurements are performed on a simple and cheap industrial-like test bench. All three presented methods lead to increased efficiency. The best efficiency is obtained by the proposed maximum efficiency strategy, where iron and inverter losses are taken into account by proper measurement of the optimal current vectors.

The Influence of Stator Winding Turns on the Steady-State Performances of Line-Start Permanent Magnet Synchronous Motors

“…The maximum is reached near 100 • , and the result is consistent with the above analysis. The other factor when using this method is the torque angle under different load powers, which can be estimated by the torque angle characteristic and the equation for the torque (neglecting the stator resistance), stated below as [3] 2 0…”

“…Line-start permanent magnet synchronous motors (LSPMSMs) have the advantage of a high power factor, high efficiency, wide economic operation range, and high power density by using a permanent magnet (PM) to generate a strong magnetic field [1][2][3][4][5]. At the time, brake torque occurs and causes a major drawback for the starting period by decreasing the start torque [6][7][8].…”

Sensorless PMSM Drive Implementation by Introduction of Maximum Efficiency Characteristics in Reference Current Generation

“…The power losses in a power inverter consist of conduction or Ohm's losses and switching losses. In this work they are minimized by proper selection of the DC-bus voltage, where the impact of dead times is minimized [5,8,9] and by proper selection of the switching frequency [7,24,36,37] as well. The proper values were determined experimentally by measurements performed on the tested PMSM drive.…”

“…By rearranging Equation (18) we obtain Equation (19) and consequently Equation (20) which provides the necessary current I d for every corresponding combination of I q and ω e . Figure 5 presents the obtained MTPA characteristic by Equation (8), and the obtained ME characteristics by Equation (20) at different values of rotor speed and different values of the iron core resistance R c . Although, this may not be evident from Figure 5 and similarly to the MTPA characteristics, the ME characteristics are nonlinear.…”

“…Besides designing a new machine, the efficiency of the drive can be improved by minimizing losses of the power inverter by proper selection of the DC-bus voltage and the switching frequency [7][8][9], and a proper control of the PMSM as well. Sensorless PMSM drive control algorithms vary in complexity and computational performance demanded by different target applications.…”