• Energy Research

Capítulos en libros This paper presents a general method to convert State feedback controllers to damp power system electromechanical oscillations to the standard structure formed by an Automatic Voltage Regulator (AVR) and a Power System Stabilizer (PSS). The proposed conversion method is based on least squares fitting in the frequency domain. info:eu-repo/semantics/publishedVersion

Artículos en revistas Units within a control area, participating in the secondary frequency control, are usually spinning generating units already connected to the network and operating outside their range of optimal performance. This paper deals with an alternative method of providing secondary frequency control called rapid-start (RS). It consists in assigning a regulation band to several offline units (RS units) which are capable of being started and connected rapidly, therefore allowing the online units to function more closely to their nominal power. RS units have commonly been used for peaking generation and for tertiary control reserve, and have been rarely used for secondary control reserve. As RS operation may have economic benefits, since it allows for better dispatch of the other units in the control area, an appropriate algorithm to start up an RS unit needs to be developed. This paper proposes a machine learning based system (MLBS) to be employed in the decision to start up an RS unit while being used to provide secondary frequency control. The decision-making procedure is carried out by a decision tree. The building and implementation of the RS machine learning based system is illustrated for a secondary frequency control zone within the Spanish power system. info:eu-repo/semantics/publishedVersion

Artículos en revistas Multi-terminal High Voltage Direct Current (HVDC) using Voltage Source Converters (VSC-HVDC) is a promising technology which provides flexible control of active and reactive power and facilitates remote renewable energy integration, above all using long cables. This paper analyses an active power control strategy for multi-terminal VSC-HVDC systems tailored to enhance transient stability of hybrid AC/DC grids. The proposed strategy controls each VSC using frequency measurements of all terminals. Its performance is compared to a strategy in which each VSC is controlled using only local frequency measurements of the AC side, proving that the proposed strategy shows better performance, even taking into account reasonable communication delays. The paper also shows that the proposed strategy generally gives similar results to those obtained when each VSC is controlled using the speed of the centre of inertia (COI). The speed of the COI is a more comprehensive and richer figure than the one proposed in this paper but it is also much more complex to obtain. Simulation results with PSS/E of a test system have been used to illustrate the comparisons and the main contributions of the proposal. info:eu-repo/semantics/publishedVersion

This paper investigates the dynamic patterns that arise in the small-signal models of multipole synchronous generators for wind power applications. Dynamic patterns are associations between state variables of linear dynamic systems and the eigenvalues of the corresponding state matrix. Dynamic patterns are identified using participation factors. Models for power system stability simulation and analysis are proposed based on the dynamic pattern analysis.

Capítulos en libros This paper studies the damping of electromechanical oscillations making use of both the ratio and phase modulation capabilities of static synchronous series sources. The design of the static synchronous series source damping controllers is addressed using eigenvalue sensitivities. The eigenvalue sensitivity with respect to a parameter of a feedback controller estimates the eigenvalue shift when such parameter is changed. The controller design comprises two steps: the design of the phase compensation network and the calculation of the controller gain. A combined method is developed to take advantage of both ratio and phase modulating capabilities of static synchronous series sources. Once the phase controller has been designed and incorporated into the system model, the ratio controller has to be designed taking into account the effect of the phase controller due to the direct relationship between the input of the ratio controller and the phase itself. The suggested approach is illustrated in a simple test system. info:eu-repo/semantics/publishedVersion

Artículos en revistas This paper presents a continuation and optimization based algorithm to detect power flow unsolvability. In addition, the algorithm obtains the power flow solution, if it exists, no matter how ill-conditioned the power system is. The proposed algorithm is based on the parameterization of the distance from the starting point to the real power flow to be solved, using a convergence margin. The performance of the algorithm is illustrated considering an highly loaded scenario of the operation of the Spanish power system. info:eu-repo/semantics/publishedVersion

Artículos en revistas Large frequency deviations due to a number of disturbances are frequent in small isolated power systems. The maximum frequency deviation in the system is limited to prevent other generator tripping. It is important to have an accurate model to calculate it, both for system planning and operation. A new simplified model to calculate the maximum frequency deviation when either a generator or load-related disturbance occurs in these systems is presented. This model takes into account the response of governor- prime mover even when different technologies are present in the power system. Model parameters can be easily obtained from either more complex models or from test records. Simulation results for an actual power system aimed at checking the model accuracy are presented. High accuracy is obtained while computation time is reduced due to the simplicity of the model. info:eu-repo/semantics/publishedVersion

Artículos en revistas Frequency control is a key ancillary service for the secure and reliable operation of power systems, and especially in isolated power systems such as Turkey which is not yet synchronously connected to the UCTE European system. Frequency control has been defined in the Turkish Power System as a mandatory remunerable ancillary service that is provided by generating units and managed by the system operator. This paper develops a centralized monitoring system of frequency that informs the System Operator if the generating units comply with the technical requirements of the Turkish grid code. The system consists of a reference model that validates the real operation of the primary and secondary regulation of the generating units comparing it with the desired behavior established by the technical requirements of the Turkish grid code. A number of quantitative measures, based on the deviation between the real and the desired response are proposed to evaluate the adequacy of each unit behavior. Application examples of the proposed monitoring system of frequency control are provided using real data of different Turkish power plants. info:eu-repo/semantics/publishedVersion

Artículos en revistas The authors present an efficient methodology for the analysis of small signal stability in large electric power systems. It is based on the selective modal analysis approach and assumes a multi-area structure of the small signal behavior in large power systems. In the proposed procedure, the system modes are separated into two categories (the inter-area and the intra-area modes) and are independently determined. Results of the application to a realistic large power system with 266 generators and 1472 buses are discussed. info:eu-repo/semantics/publishedVersion