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The circuit parameters involving stray load loss and harmonic torques of high speed induction motors fed by inverters are determined by both finite element method and experiments, respectively. In the finite element method, the parameters are directly determined from the electromagnetic field distribution of the motors under load conditions. On the other hand, in the experiment, the parameters are...
This paper presents a direct power control strategy for a doubly fed induction generator by using an artificial neural network controller with the multilayer perceptron structure. This controller generates the direct- and quadrature-axis rotor voltage signals from both the stator current and voltage that are measured by the Hall sensors. The input variables of the control system are the rotor speed,...
This paper proposes a new method for the probabilistic risk assessment of rotor angle instability in power systems using fuzzy inference systems (FISs). The novel two-step approach first models the stochastic uncertainties present within the power system to produced probability density functions (pdfs) for stability indicators. These stability indicators are established for both small and large disturbance...
This paper proposes a novel recurrent neural network (RNN) based vector control method for a doubly fed induction generator (DFIG) and especially focuses on how to train the neural network controller for the current-loop control of DFIG. The proposed RNN vector control utilizes the stator voltage oriented frame and the role of the RNN is to substitute the two decoupled current-loop PI controllers...
Untransposed transmission lines, unbalanced tap changer operations, and unbalanced loading in weak distribution lines can cause unbalanced-voltage conditions. The resulting unbalanced voltage at the point of interconnection affects proper gird integration and reduces the lifetime of wind turbines due to power oscillations, torque pulsations, mechanical stresses, energy losses, and uneven and overheating...
Modern wind turbines operate with variable speed and most of them are based on doubly fed induction generators (DFIG), with a back-to-back power converter. During voltage dips, the stator terminals can cause overcurrents in the rotor windings, which could threaten the converter integrity. The use of crowbar systems is the most common technique to avoid this situation. The crowbar activation disables...
Hydropower is the largest producer of renewable energy in the U.S. More than 60% of the total renewable generation comes from hydropower. There is also approximately 22 GW of pumped storage hydropower (PSH). Conventional PSH uses a synchronous generator, and thus the rotational speed is constant at synchronous speed. This work details a hydrodynamic model and generator/power converter dynamic model...
Modeling renewable energy generation systems with electrical machines has been an active area of research, wherein interfacing the machine models with power electronic converters is a known challenge area. As an alternative to traditional qd models, the coupled-circuit phase-domain (CCPD) and voltage-behind-reactance (VBR) models have been recently proposed. The permanent magnet (PM) generator has...
With the planning and constructing of UHV grid in China, some huge thermal plant bases are going to be connected to the receiving grid via UHV transmission lines. Therefore, it is significant and urgent to study the ATC (available transfer capability) of the point-to-grid transmission system quickly for each connection scheme in planning stage. In the paper, firstly, the physical mechanism of ATC...
This paper proposes a novel rotor position estimation algorithm used for reference frame transformation in the direct power control (DPC) of a doubly-fed induction generator (DFIG) in wind power applications. The proposed algorithm can be used as a primary rotor position information provider to replace the rotor position sensor or a backup rotor position information provider during the malfunction...
This paper proposes a decoupling based direct method to analyze the post-contingency transient stability for a general multi-machine power system. A linear decoupling transformation is used to construct the same number of independent single machine infinite bus (SMIB) power systems as oscillation modes. Each SMIB system carries stability information regarding one oscillation mode of the original system...
This paper investigates the application of sweeping method in initializing the state variables of an unbalanced radial distribution system for small signal analysis. The unbalance is caused by a single-phase PV system. The system is composed of a three-phase induction machine (IM), a single-phase PV, a load, and a power factor correction (PFC) unit. The IM is modeled in positive-, negative-, and zero-...
The rotor angle and rotor speed estimation of synchronous generators is a key for developing practical local or wide-area control of power system. The critical information in this context is the input signals such as field voltage and mechanical torque which are not available from easily available terminal phasor measurement unit (PMU) signals. To overcome these issues, the Extended Kalman Filter...
A common approach to deal with transient stability constraints in optimization problems is the combination of a numerical discretization method with interior point methods (IPMs) for solving large-scale nonlinear programming (NLP). The numerical discretization is adopted to convert the differential equations that describe the electromechanical transients in power systems in a set of algebraic equations...
This paper presents an innovative DFIG which has autonomous frequency control for stand-alone operation. When the wind farm is islanded, such DFIGs synchronize to form a reliable wind farm frequency source which does not collapse when member DFIGs fail. The frequency enables frequency droop control to be implemented for load sharing. The wind farm can provide fast reserve, ready to support a weakened...
As the wind power penetration level increases, the inertial response of a wind power plant (WPP) is important to the grid under load and generation imbalance. In this paper, we present coordinated WPP control for frequency support under wake effects. By de-loading the power from a WPP, the inertial response can be obtained from the kinetic energy of wind turbine rotors. The coordinated WPP control...
Initialization to the brushless doubly-fed induction machines (BDFMs) is necessary for grid integration, while not investigated. Based on the equivalent circuit, power and torque constraints during steady state are defined. Due to dependency of active power loss on stator voltage and power flow, BDFM under the maximum power point tracking (MPPT) mode is initialized by simultaneous solution to BDFM...
Wind turbines play an important role in producing clean energy and reducing pollution, but they can fail during the operation due to various types of faults and environment uncertainties. Therefore, one of the key problems in wind energy systems is the resilient control to achieve their high reliability. To reach this goal, we first design a resilient controller by incorporating faults into the wind...
This paper presents a time-based methodology to identify short circuits among coils in field windings of round rotor synchronous machines by analyzing their induced voltage harmonic content. The procedure is applied to two cylindrical rotor synchronous machines. Results show the effect of rotor inter-turn faults on the armature voltage profile, enabling its detection without the need of acquiring...
This paper analyzes the response of conventional protection schemes (Line current Differential and Mho Distance elements) and the supervisory elements associated with those protective elements in commercial relays for Type 3 (Doubly Fed Induction Generator based) grid integrated wind farms. The response of line protection elements and their supervisory elements are analyzed using real time by hardware-in-the-loop...
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