Modeling and Control of Diode Rectifier Fed PMSG Based Wind Turbine Zhipeng QIU, Keliang ZHOU Department of Electrical Engineering Southeast University Nanjing, China
[email protected],
[email protected]
Yingtao LI Department of Electrical Engineering Shandong University Ji’nan, China
[email protected]
Abstract—This paper analyzes and models Permanent Magnet Synchronous Generator (PMSG) based wind turbine with diode rectifier + boost converter + PWM inverter based power electronic interface, and proposes corresponding control strategy that is capable of maximum power point tracking (MPPT), reactive power regulation and fault ride through (FRT) capability. Using DIgSILENT/Power Factory 14.0, simulations are carried out to show the superior features of such wind turbine and the validity of proposed control strategy. Keywords- diode rectifier; direct drive permanent synchronous generator; maximum power point tracking; fault ride through; reactive power regulation; voltage dip
I.
INTRODUCTION
Both the volume and the cost of PMSG based wind turbine are much higher that those of DFIG based wind turbine, since multi-pole PMSG and full power converter are employed. However, the elimination of the gearbox enable PMSG based wind turbine to operate with higher efficiency, more reliability and lower noise. Through AC-DC-AC interface, PMSG connects with the grid and the DC link decouples PMSG and the grid, which enhances the FRT capability of the wind turbine. PMSG based wind turbine currently becomes the mainstream wind turbine for offshore wind farms. At present, Ldc
there are mainly two kinds of power electronic interface for grid-connection of the wind turbine: back-to-back power converter and diode rectifier +boost circuit + inverter. Back-toback power converter with complicated control strategy enable PMSG based wind turbine to have superior operation performance at high cost. Whereas the latter one with diode rectifier and simple control strategy is less expensive and more reliable. Currently PMSG based wind turbine with back-toback power converter is widely investigated [1]-[7]. However, diode rectifier fed PMSG based wind turbine need further investigation. This paper establishes the mathematic model of the wind turbine in detail and proposes corresponding control strategy, which is capable of MPPT, reactive power regulation and FRT. Using DIgSILENT/Power Factory14.0, a diode rectifier fed PMSG based wind farm, which integrates with a small grid, is developed to validate the proposed strategy and evaluate its grid-integration performance. II.
PPMSG
PC Cdc1
WIND TURBINE MODELING
The Configuration of PMSG based wind turbine with diode rectifier interface is shown in Fig.1where the bypass chopper is provided to help the wind turbine enhance the fault ridethrough capability. Pgrid
L ac Qgrid
Ppass
Cdc2
Ldc R
Figure 1. Configuration of PMSG based wind turbine with a diode rectifier
This work was supported by the National Natural Science Foundation of China under Grant No. 50977013, the Research Fund for the Doctoral Program of Higher Education of China under Grant No. 20070286013，and the Outstanding Talents in Six Fields of Jiangsu Province under Grant No. 2008116.
978-1-4577-0365-2/11/$26.00 ©2011 IEEE
1384
uac
v8
A. The Turbine The wind power from the flowing air captured by wind turbine can be expressed as:
1 Pwt = ρSv w3 C p ( β , λ ) 2
v7 v6
(1)
Pwt ( p.u.)
v4
v3
where Pwt is the wind power, ρ is the air density, S is the effective rotor swept area, vw is the wind speed, Cp is the power coefficient, β is the pitch angle, and λ is the tip-speed ratio given by (2) ,in which, ω and R are rotational speed and radius of the rotor respectively.
λ=
ωR
v1
From (1), Cp depends on β and λ, representing the aerodynamic characteristic of the turbine. If λ is kept constant, Cp gets larger when β gets less. Similarly, given β constant, there is a value of λ making Cp maximum. The curve family of Cp versus β and λ is illustrated in Fig.2, where, 0=β0
