http://hdl.handle.net/2117/3865 2013-05-26T02:56:14Z http://hdl.handle.net/2117/18728 Title: Control of Full-Scale Converter based Wind Power Plants for damping of low frequency system oscillations Authors: Rodríguez Cortés, Pedro; Teodorescu, Remus; Adamczyk, Andrzej Grzegorz Abstract: Damping of low frequency power oscillations is one of essential aspects of maintaining power system stability. In literature can be found publications on damping capability of Doubly Fed Induction Generator based wind turbines. This paper extends discussion on Wind Power Plant damping capability to Full-Scale Converter based type. Moreover resemblance of such Wind Power Plant to modern FACTS devices is recognized and exploited. Paper discusses many aspect of damping controller design, including feedback signal selection and control effectiveness with respect to wind farm location. Analysis and design is based on modal analysis, therefore matching modeling approach for wind power plant is proposed. Finally, performance of Wind Power Plant damping control is compared to a regular power system stabilizer installed on a synchronous generator. 2013-04-09T10:56:01Z http://hdl.handle.net/2117/18713 Title: Var reserve concept applied to a wind power plant Authors: Martinez, J.; Kjaer, Philip Carne; Rodríguez Cortés, Pedro; Teodorescu, Remus Abstract: wind power plants. This paper proposes two different VAr reserve control strategies for a wind power plant. The amount of dynamic VAr available most of the operation time, makes the wind power plant (WPP) a good candidate to include a VAr reserve management system. Two different ways of implementing a VAr management system are proposed and analyzed. 2013-04-09T07:36:56Z http://hdl.handle.net/2117/18500 Title: Storage possibilities for enabling higher wind energy penetration Authors: Swierczynski, M.; Teodorescu, Remus; Rasmunssen, C. N.; Rodríguez Cortés, Pedro; Vikelgaard, H. Abstract: As the installed worldwide wind energy capacity increases about 30% annually and Kyoto protocol that came in force in 2005, wind penetration level in power system is considered to significantly increase in near future. Due to increased penetration and nature of the wind, especially its intermittency, partly unpredictability and variability, wind power can put the operation of power system into risk. One of the possible solutions can be an addition of energy storage into wind power plant. This paper deals with state of the art of the Energy Storage (ES) technologies and their possibility of accommodation for wind turbines. Overview of ES technologies is done in respect to its suitability for Wind Power Plant (WPP). Services that energy storage can offer both to WPP and power system are discussed. Moreover examples of already existing installations are shown 2013-03-22T13:22:43Z http://hdl.handle.net/2117/18400 Title: Smart - STATCOM control strategy implementation in wind power plants Authors: Sintamarean, Craiun; Cantarellas, A.; Miranda, Hernan; Rodríguez Cortés, Pedro; Teodorescu, Remus Abstract: High penetration of wind energy into the grid may introduce stability and power quality problems due to the fluctuating nature of the wind and the increasing complexity of the power system. By implementing advanced functionalities in power converters, it is possible to improve the performance of the wind farm and also to provide grid support, as it is required by the grid codes. One of the main compliance difficulties that can be found in such power plants are related to reactive power compensation and to keep the harmonics content between the allowed limits, even if the power of the WPP converters is increasing. This paper deals with an advanced control strategy design of a three-level converter performing STATCOM and Active Filter functionalities. The proposed system is called Smart-STATCOM since it has the capability of self-controlling reactive power and harmonic voltages at the same time. Therefore, deciding the amount of non-active currents (fundamental, 5th and 7th harmonics) to be injected depending on the PCC voltage quality. Experimental results of the proposed control strategy are analyzed in order to validate the performance of the entire system. Keywords- STATCOM, Active Filter, Power Quality 2013-03-19T12:40:33Z http://hdl.handle.net/2117/18351 Title: Study on harmonic resonances and damping in wind power plant Authors: Md. Hasan, Khairul Nisak; Rauma, Kalle; Luna Alloza, Álvaro; Candela García, José Ignacio; Rodríguez Cortés, Pedro Abstract: Harmonic resonance is among imperative aspect need to be analyzed in a wind power plant (WPP). It becomes complex since it involves a large network with high operating power. This paper presents a study on harmonic resonances in a WPP, particularly on parallel resonance. Important factors including length of cable, number of operating wind turbine and usage of output grid-side filter are analyzed. The damping of resonance by using common passive filter and an alternative hybrid filter is also explored. An aggregated WPP model of 400 MW with 40 wind turbines of 10 MW each are used as a study case 2013-03-15T13:01:03Z http://hdl.handle.net/2117/18347 Title: PSO based optimal output feedback controller for two-area LFC system Authors: Rakhshani, Elyas; Luna Alloza, Álvaro; Sadeh, J.; Rodríguez Cortés, Pedro Abstract: A new combined method based on optimal control is proposed to enhance load frequency control dynamics. This method include of PSO and optimal output feedback controller. In the output feedback method only the measurable state variables within each control area is required to use for feedback. The optimal control law is determined by minimizing a performance index under the output feedback conditions leading to a coupled matrix equation. But for more accuracy and better design for this controller, PSO algorithm is applied to find the gain matrix of the controller. The results of the simulation are shown that with using this method, the load frequency control requirements in a practical environment are satisfied and also better dynamic responses are accessible 2013-03-15T11:51:51Z http://hdl.handle.net/2117/18281 Title: Enhanced average current-mode control for DC-DC converters based on an optimized fuzzy logic controller Authors: Rouzbehi, Kumars; Miranian, Arash; Citro, Costantino; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro Abstract: This paper proposes a novel optimized fuzzy logic controller (OFLC) for current-mode control (CMC)-based voltage regulation in DC-DC converters. The implementation of the proposed fuzzy logic controller (FLC) does not depend on the mathematical model of the converter and only requires knowledge about its operation modes. The fast and efficient algorithm of particle swarm optimization (PSO) has been employed to enhance the performance of the FLC by fine tuning its membership functions. The reference current for the current control loop has been obtained in the outer voltage loop by measuring load current and output voltage and calculating the load resistive impedance. The proposed OFLC has been used in four different case studies for evaluating its performance under different conditions of input voltage and load variations as well as variations in the system parameters, e.g. inductance and capacitance of the converter circuit. The results of simulations and comparison to a proportional-integral (PI) controller demonstrates the fast and robust performance of the proposed controller, able to effectively regulate the output voltage in presence of high perturbations in the input voltage and high variation of the converter components nominal values 2013-03-13T16:43:23Z http://hdl.handle.net/2117/17502 Title: Wind power plant control: an overview Authors: Altin, Müfit; Teodorescu, Remus; Bak-Jensen, Birgitte; Rodríguez Cortés, Pedro; Iov, Florin; Kjaer, Philip Carne Abstract: Recent developments in wind turbine technology go towards installation of larger Wind Power Plants (WPPs). Therefore, power system operators have been challenged by the WPP penetration impacts in order to maintain reliabillity and stability of the power system. The revised grid codes have concentrated on the WPP connection point and as a result a WPP is considered as a single power plant. Nevertheless, compared to conventional power plants, WPPs have different inherent features such as converter-based grid interface technology, internal electrical layout, and asynchronous operation of turbines. Talking these into account, a WPP controller is the key factor in order to satisfy the grid code requirements. This paper presents a comprehensive overview of various WPP controller strategies comprising active power, reactive power, voltage, frequency, and emulated inertia control. The WPP control architecture composed of WPP control level and wind turbine control level is also discussed considering the hierearchy and coordination of these levels. 2013-01-23T14:47:55Z http://hdl.handle.net/2117/17437 Title: FACTS Devices for large wind power plants Authors: Adamczyk, A.; Teodorescu, Remus; Mukerjee, R. N.; Rodríguez Cortés, Pedro Abstract: Growing number of wind turbines is changing electricity generation profile all over the world. However, high wind energy penetration affects power system safety and stability. For this reason transmission system operators (TSO) impose more stringent connection requirements on the wind power plant (WPP) owners. On the other hand flexible AC transmission systems (FACTS) devices offer enhancement of grid stability and can facilitate grid code compliance for WPP. In this paper state-of-the-art in FACTS for large WPPs with AC connection is given. FACTS devices (excluding HVDC) with their properties are described. Academic and industrial research in FACTS applicability for WPPs is summarized 2013-01-21T13:35:06Z http://hdl.handle.net/2117/17418 Title: Application of over-current relay in offshore wind power plant grid with VSC-HVDC connection Authors: Chaudhary, S. K.; Teodorescu, Remus; Rodríguez Cortés, Pedro; Kjaer, Philip Carne Abstract: This paper presents the setting and coordination of over-current relays in an offshore wind power plant (WPP) grid connected only to the power electronic converters with limited fault current capability. The limited fault current injection capability of the converters has been considered as a hindrance for the relay setting. This characteristic can be utilized to develop a deterministic picture of the radial grid network and then the relays settings could be applied. The relay coordination has been demonstrated through an implementation in the Real Time Digital Simulator (RTDS) platform. The setting of relay parameters based upon maximum nominal currents is explained and the consequences are investigated. 2013-01-18T10:41:07Z http://hdl.handle.net/2117/17279 Title: Effect of VSC-HVDC on load frequency control in multi-area power system Authors: Rakhshani, Elyas; Luna Alloza, Álvaro; Rouzbehi, Kumars; Rodríguez Cortés, Pedro; Etxeberria Otadui, Ion Abstract: This study presents a solution for reducing the frequency oscillations in multi-area interconnected power system by means of using an VSC-HVDC interconnection transmission line. The upcoming power-electronics based HVDC transmission system offers new features that can be advantageous for improving the frequency control and thus for enhancing the stability in transmission networks. This paper is structured in two main parts; the first one is be devoted to introduce the basic elements of HVDC links and the second part will be focused on the effects of the HVDC links in the frequency control of interconnected power systems. In order to show the positive effects of HVDC links under random load disturbance, a model with parallel AC-DC interconnected power system, including a new power modulation controller of bi-directional VSC-HVDC link, is proposed and simulated. Comparisons between HVAC and HVDC transmissions are presented and its performance is evaluated using Matlab/Simulink 2013-01-11T13:01:54Z http://hdl.handle.net/2117/17278 Title: Harmonic resonance damping in Wind Power Plant Authors: Nisak, Khairul; Rauma, Kalle; Luna Alloza, Álvaro; Candela García, José Ignacio; Rodríguez Cortés, Pedro Abstract: Harmonic is one of main concern in Wind Power Plant (WPP) as growing usage of power electronic converter is observed. Besides the injection of harmonic by individual wind turbine (WT) as source of harmonic, its propagation in network and problem of resonance is also an issue. By implementing passive filter for harmonic mitigation, additional resonance peak is observed due to its interaction with system side impedance. This paper explores the solution for harmonic mitigation with capability of damping resonance in WPP. An aggregated model of 400-MW WPP network is analyzed in correlating resonance and amplification. A passive filter and hybrid filter is designed to mitigate harmonic accordingly. It is shown that hybrid filter able to provide damping capability and improve the performance 2013-01-11T12:44:16Z http://hdl.handle.net/2117/17277 Title: Advanced structures for grid synchronization of power converters in distributed generation applications Authors: Luna Alloza, Álvaro; Rocabert Delgado, Joan; Candela García, José Ignacio; Rodríguez Cortés, Pedro; Teodorescu, Remus; Blaabjerg, Frede Abstract: The Transmission System Operators are specially concerned about the Low Voltage Ride Through requirements of distributed generation power plants. Solutions based on the installation of STATCOMs and DVRs, as well as on advanced control functionalities for the existing power converters have contributed to enhance their response under faulty and distorted scenarios, and hence to fulfill these requirements. In order to achieve satisfactory results it is necessary to count on accurate and fast grid voltage synchronization algorithms, which are able to work under unbalanced and distorted conditions. This paper analyzes and compares the synchronization capability of three advanced synchronization systems: the Decoupled Double Synchronous Reference Frame-Phase-Locked Loop, the Dual Second Order Generalized Integgrator- Phase-Locked Loop and the Three-Phase Enhanced Phase-Locked Loop, designed to work under such conditions. Its response will be analyzed with respect the synchronization needs that can be extracted from the standards 2013-01-11T12:31:17Z http://hdl.handle.net/2117/17264 Title: Identification and maximum power point tracking of photovoltaic generation by a local neuro-fuzzy model Authors: Rouzbehi, Kumars; Miranian, Arash; Luna Alloza, Álvaro; Rodríguez Cortés, Pedro Abstract: With the rapid proliferation of the DC distribution systems, special attentions are paid to the photovoltaic (PV) generations. This paper addresses the problem of maximum power point tracking (MPPT) for PV systems using a local neuro fuzzy (LNF) network and steepest descent (SD) optimization algorithm. The proposed approach, termed LNF + SD, first identifies a valid an accurate model for the PV system using the LNF network and through measurement data. Then the identified PV model is used for MPPT by SD optimization algorithm. The salient modeling abilities of the proposed LNF network results in a reliable and dependable PV model which takes voltage, temperature and insolation variations into account. The proposed approach is evaluated using several identification and MPPT simulations. The simulation results showed the accuracy of the LNF network in modeling of PV systems. Furthermore, simulations carried out for assessment of the MPPT performance during insolation transients demonstrated the high efficiency of the proposed LNF + SD approach for MPPT applications. Performance of the proposed method MPPT, while the PV array was supplying loads through DC-DC converters was also analyzed. Comparisons to the perturb-and-observe (P&O) and fuzzy logic methods revealed the superiority of the proposed approach 2013-01-10T14:26:42Z http://hdl.handle.net/2117/17254 Title: Application of imperialist competitive algorithm to design an optimal controller for LFC problem Authors: Rakhshani, Elyas; Luna Alloza, Álvaro; Rouzbehi, Kumars; Rodríguez Cortés, Pedro Abstract: A novel optimization algorithm is presented to improve the design of optimal controllers for load frequency control problem. This algorithm is applied for two area LFC system with using an output feedback controller. In the practical power system, access to some of the state variables in LFC system is limited and measuring is also impossible. So an optimal output feedback controller with a practical viewpoint is proposed. The optimal control law is determined by minimizing a performance index under the output feedback conditions leading to a coupled matrix equation. In order to solve these equations traditional methods may be used. But for more accuracy and better design for this controller, ICA algorithm is applied to find the global optimal gain matrix of the controller. Simulation results of ICA are compared with the conventional design. Comparison shows the success of ICA for design of optimal controller 2013-01-10T12:41:45Z