Development of a comprehensive MPPT for grid‐connected wind turbine driven PMSG

Abstract

This paper proposes a comprehensive MPPT method by which extraction of maximum power from wind turbine and its subsequent transfer through various power stages and final delivery to the connected grid are realized. In the proposed system, the operation of the wind turbine at its maximum efficiency point is maintained by control of grid-tied inverter such that the shaft speed of the generator is set to result the desired optimum tip speed ratio of the turbine. The proposed comprehensive MPPT estimates the required DC link voltage for each wind speed using a unified system model, uses a loss factor to account for the system losses, and then controls the inverter to push the WT extracted maximum power into the grid. The comprehensive MPPT is developed and is validated in MATLAB/Simulink platform in a wide range of operating wind speed. The results ascertain that the wind turbine is made to operate at its maximum efficiency point for all wind speeds below the rated one. KEYWORDS maximum power point tracking, turbine generator matching, unified system model, wind turbine generator 1 | INTRODUCTIONThe combined power conversion efficiency of a grid-connected fixed speed wind turbine generator (WTG), which essentially involves a squirrel cage induction generator coupled to a wind turbine (WT), varies with wind speed variation and thus yields poor average efficiency meaning suboptimal aggregate energy extraction for an installed WTG capacity. 1,2 On the other hand, the variable speed WTG, which employ either doubly fed induction generator (DFIG) or permanent magnet synchronous generator (PMSG), claim not only higher energy output owing to increased overall efficiency, but also longer plant life as the stress on tower, blades, gear, shaft etc. gets much reduced when compared with the fixed speed WTG. [1][2][3][4] The generic WT characteristics shown in Figure 1 is the plot of its power coefficient C p against the tip-speed ratio (TSR) λ, and the latter can be expressed aswhere, ω is the shaft speed, R is the length of the blade, and V w is the wind speed. 1-7 λ opt is the unique value of λ at which the WT operates at its maximum efficiency of C pmax . For any other value of λ, for example at λ 1 (that is less than λ opt ) and at λ 2 (that is higher than λ opt ), C p is less than C pmax . It therefore suggests the WT to have a varying ω in order to counteract the variation of V w in Equation 1.1 and thus to retain both λ and C p at the optimum point. In other words, if the turbine speed is allowed to vary proportional to the wind speed variation, then it is possible to maximize the wind electricity generation at any site and in turn maximize the profitability. Operation of WT at C pmax is termed as maximum power point tracking (MPPT) in a WT powered system.

Wind Power Extraction Optimization by Dynamic Gain Scheduling Approximation Based on Non-Linear Functions for a WECS Based on a PMSG

“…One of the advantages of using a generator of low speed type is that the WECS avoid problems related to the use of a gearbox [51][52][53][54], becoming less expensive. In addition, because of the extensive length of its operating speed in the asynchronous mode, PMSG is preferred over other electrical generators [42]. Table 2 shows the parameters associated with the PMSG, while Figure 4 shows a photo of the experimental setup which includes the speed variator as well as the direct drive connection between the three-phase induction motor and the PMSG.…”

“…The system is very complex because of its different components, so a complete model would probably be represented by a set of many non-linear differential equations. In order to represent a less complex mathematical model maintaining the system dynamic richness, some methods have been developed to set a unified system [41,42].…”

Comparative Study of P&O and Fuzzy MPPT Controllers and Their Optimization Using PSO and GA to Improve Wind Energy System

“…Furthermore, permanent magnet synchronous generators (PMSGs) were utilized with WECS because of their compact size, self-excitation, high reliability, minimal maintenance, lack of a gearbox system, and low noise. [4,5].…”

Maximum Power Extraction and Pitch Angle Control for Offshore Wind Turbine with Open-Loop Hydraulic Transmission

“…Another crucial factor affecting the output power is the control system in the variable speed and pitch wind turbine [9,10]. Considering the strong nonlinear nature of the wind turbine dynamics, some advanced intelligent controllers have been designed in the conventional mechanical wind energy transmission [11,12]. In [13], authors have employed fuzzy logic controller to regulate the rotational speed of the wind turbine rotor through controlling the electromagnetic torque.…”