Journal of Power Sources 129 (2004) 170–179 Effect of a SOFC plant on distribution system stability Francisco Jurado ∗ , Manuel Valverde, Antonio Cano Department of Electrical Engineering, University of Jaén, 23700 EUP Linares, Jaén, Spain Received 21 February 2003; accepted 3 November 2003 Abstract When connected in small amounts, the impact of distributed generation (DG) on distribution system stability will be negligible. However, if its penetration level becomes higher, distributed generation may start to influence the dynamic behavior of the system as a whole. This paper presents a mathematical representation of a solid oxide fuel cell plant that is suitable for use in distribution system stability studies. The model is applied to a distributed utility grid that uses a solid oxide fuel cell plant as distributed resource. Examinations include transient stability and voltage stability of the system. © 2003 Elsevier B.V. All rights reserved. Keywords: Distributed generation; Power system dynamic stability; Solid oxide fuel cell (SOFC); Transient stability 1. Introduction Distributed generation (DG) is electricity generation sited close to the load it serves, typically in the same building or complex. The DG embraces a palette of technologies in varying stages of availability, from entrenched to pilot. It is sometimes called a “disruptive” technology because of its potential to upset the utility industry’s apple cart. Most likely, fuel cells will be a dominant DGs [1,2]. These DGs are dynamic devices and when connected to the distri- bution system they will affect its dynamic behavior. Hence, several researchers are working to develop dynamic models for these components [3–10]. This paper develops a generic dynamic model for a grid-connected SOFC plant. The model is defined by a small number of parameters and is suitable for planning studies. The steady-state power generation characteristics of the plant are derived and analyzed. Understanding the transient behavior of SOFC is important for control of stationary util- ity generators during power system faults, surges and switch- ings. Voltage regulation is one of the main problems in the dis- tribution systems, especially at the much far-end load and in the rural areas. Voltage regulation and maintaining the voltage level are well-known problems in the radial distri- bution network. Several techniques have been applied by implementing many devices in the distribution network to ∗ Corresponding author. Tel.: +34-953-026518; fax: +34-953-026508. E-mail address: fjurado@ujaen.es (F. Jurado). solve these problems. The most common devices and tech- niques used are transformer equipped by load tap changer, supplementary line regulators installed on distribution feed- ers, shunt capacitor switched on distribution feeders [11] and shifting transformers towards the load center [12]. A multi- ple line drop compensation voltage regulation method that determines tap positions of under-load tap changer trans- formers is proposed in [13] to maintain the customers’ volt- ages within the permissible limits. The model derived is based on the main equations. It is developed in the Laplace domain and transient simulation is done using a software developed based on the MATLAB package. The paper is structured as follows. Section 2 presents a review of transient stability. Some basic concepts of voltage stability are introduced in Section 3. Section 4 de- scribes the SOFC model. Section 5 briefly discusses the utility-connected inverter control. Section 6 depicts some simulation results. Finally, conclusions are presented in Section 7. 2. Transient stability Transient stability is a term applied to alternating current (ac) electric power systems, denoting a condition in which the various synchronous machines of the system remain in synchronism, or in step each other. Conversely, instability denotes a condition involving loss of synchronism, or falling out of step [14]. 0378-7753/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2003.11.001