Abstract
Models of reality (objects, processes, phenomena, etc.) are usually an element of the process presented in Fig. 5.1.
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For a properly designed WTGS, within the wind turbine operating speed range, the curves showing eigenfrequencies as a function of the rotor speed should not cross. This prevents resonance self-excitation.
Therefore, these two values cannot be subtracted directly. When computing rotor-shaft twist, it is necessary to divide or multiply the relevant torsion angle.
The mean value of wind velocity at partial load is usually assumed as equal to the value which on the WTGS power characteristic p=f(v) gives the highest slope, e.g. v0=9 m/s.
In general, in WTGS modeling, the drive-train model described in sect.5.2 should be used.
In general, in WTGS modeling, the drive-train model described in sect.5.2 should be used.
Other types of transformation are also utilized.
The subscript on defines the on-state of the swich, e.g. thyristor, while the subscript off defines the off-state of the switch.
The network consists of conductance-type branches only (except for current and voltage sources).
In some types of control systems the WTGS characteristic between points 2 and 3 in Fig. 5.44 is defined by the function P = K•w with high slope (high value of coefficient K).
When a non-realistic step change of the wind velocity is assumed.
In fact, energy storage is not utilized for this purpose today.
Various types of WTGS utilize supervisory algorithms that can differ from that presented here. Those algorithms should be considered as examples only.
Taking into account the number of conditions being checked.
The controller reaction to a given input signal depends, of course, on the controller structure. Here, a controller with integration block is considered.
The control system can determine the turbine power-speed characteristics.
Whether the real power is proportional to the d-axis rotor current and the reactive power is proportional to the q-axis rotor current, or whether the opposite state takes place depends on the dq-reference frame definition.
Insuch a case, the maximum point power tracking (MPPT) scheme, based on the dp/dw=0 rule, is not utilized.
The generator stator winding can be (and is) switched between delta and star connection. The area of operation of the generator with the given connection is marked in Fig.5.61. The generator operation with the star connection reduces losses when the wind speed is lower, A t higher winds, when the rated power is achieved, the generator operates with delta-connected stator windings.
Because the power flows here in one direction only, converters with non-controlled rectifiers can be (and usually are) utilized.
The rated voltage of the network depends on the power system.
Usually, in such a type of WTGS, the power factor cos is controlled, which means that present wind turbines are not utilized for voltage control.
The power network is modeled by a set of algebraic equations, while the generating units (and sometime loads), FACTS and AC/DC systems are modeled by a set of differential and algebraic equations.
Its multi-modality is the positive feature of the multi-machine produce many more complex and difficult operating conditions (characteristic of the real system) for turbine and generator controllers than those obtainable in the single-machine system.
The presented controlled rectifier model described by (5.237) is a simplified model of the one defined by (5.243).
This assumed that s=3v I, which causes the inductive power to be positive (Q 0). When equation s=3VI is used, the inductive power becomes negative (Q 0).Coefficient 3 results from utilizing the phase-to-neutral rms voltageV.
That is 10kv,15kv, 20kv or 60kv, depending on the country grid type (voltage level and the WTGS location).
It is usually possible to make these networks closed.
When the feeding bus voltage value is imposed, the WTGES voltage and current can be computed iteratively by using the WTGS f(P,Q,V) characteristics.
Terminal voltage (and mechanical torque) is the generator model input and the current is the output. Inverse models of generator.
A power system model in which the dynamic elements (e.g. generators) are modeled with current as outpur and voltage as input is considered.
All quantities are per unit quantities.
For load flow computation purposes (especially for computing bulk power systems), the methods using sparse matrix techniques are widely utilized.
The problem can be solved also in rectangular coordinates a,b (V=Va+jvb)
There are set as initial in the computing procedure.
When the loads are modeled as constant admittances then the power P.
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© 2003 Springer-Verlag Berlin Heidelberg
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Lubosny, Z. (2003). Mathematical Modeling of WTGS Components. In: Wind Turbine Operation in Electric Power Systems. Power Systems. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-10944-1_5
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DOI: https://doi.org/10.1007/978-3-662-10944-1_5
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