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.

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.

With the steady expansion of renewable energy sources (RES), the provision of ancillary services is becoming an increasingly challenging task within system operation. In order to add regulation capacity, battery energy storage systems (BESS) have been recognized as an efficient tool in recent literature. In this context, this paper proposes a novel BESS control strategy to improve dynamic performance of automatic generation control (AGC). Such control strategy is applicable to power systems which evaluate AGC performance utilizing regulation response accuracy margins, which typically define the slowest and fastest permitted power response to a regulation signal. The primary goal consists in enhancing the regulation service by minimizing the rate of non-compliance with respect to the corresponding dynamic performance criteria and its defined accuracy margins. Additionally a comprehensive State-of-Charge-control (SoC-control) is included in the strategy. By utilizing the BESS only during designated regulation assistance periods, preventing extreme levels of charge and furthermore identifying and avoiding futile regulation efforts, BESS degradation is kept to a minimum. To verify effectiveness a case study is conducted with 400 hours of real AGC operation of various BESS sizes. The obtained results show that a BESS is able to minimize the rate of non-compliance considerably, whilst preserving low BESS usage and degradation.

This paper presents tools and methods to study the application of controllable series capacitors for damping power system electromechanical oscillations. Two problems are discussed-location and controller design. The location of a controllable series capacitor consists of determining the series capacitor of the power system where the modulation of its series reactance will be more effective to damp out the modes of interest. It also involves the selection of the input variable to the controller. The basic design of the controller requires the design of the phase compensation network and the calculation of the controller gain. Small signal models of the power system and the corresponding eigenvalue sensitivities are used to address both problems.