The production and consumption of electricity on the power grid has to balance at all times. Slow balancing, over days and weeks, is governed by the electricity market and carried out through production planning.  Fast balancing, within the operational hour, is carried out by hydropower plants operating in frequency control mode. The need of balancing power is expected to increase as more varying renewable energy production is connected to the grid, and the deregulated electricity market presents a challenge to the frequency control of the grid. The first part of this thesis suggests a method to quantify the need for balancing or energy storage induced by varying renewable energy sources. It is found that for high shares of wind and solar power in the system, the energy storage need over a two-week horizon is almost 20% of the production. The second and third part of the thesis focus on frequency control. In the second part, measurements from three Swedish hydropower plants are compared with the behaviour expected from commonly used power system analysis hydropower models. It is found that backlash in the guide vane and runner regulating mechanisms has a large impact on the frequency control performance of the plants. In the third part of the thesis, the parameters of the primary frequency control in the Nordic grid are optimised with respect to performance, robustness and actuator work. It is found that retuning of the controller parameters can improve the performance and robustness, with a reasonable increase of the actuator work. A floating deadband in the controller is also discussed as a means to improve performance without increasing the actuator work.

As the awareness of energy security and global warming is increasing, alternative technologies are being developed such as electric vehicles. In addition, the integration of a more sustainable energy system with renewable resources put a lot of pressure on the electricity system in terms of regulation power. This thesis has investigated and developed proposals of business models with electric vehicles, which by their construction can raise value for both customers and electricity companies. The development of the business models have been done using a model, which was based on the complexity of the frequency control market, the charging of vehicles and the behavior of the drivers. The proposed models address two types of customer segments; business and private customers. In addition, applying a perspective that includes active and non-active customers has segmented these further. Based on the assumptions in the thesis, the most promising area of interest is the non-active business customer, in this case, a car pool. This proposal was based on the simulation results together with an analysis of advantages and disadvantages with active and non-active customers. This proposal assumed that customers preferred to be non-active in order to maintain flexibility and freedom, which could be studied further by customer surveys.

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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / In this paper, we develop a method for achieving high precision of time and frequency synchronization among multiple base stations in GPS system. We first describe the basic theory of timing and frequency checking, and then analyze several error sources which influence the precision of time and frequency synchronization. Furthermore, we derive explicit formula for calculating the precision of time and frequency. Tested results have indicated that our method can indeed achieve very high time and frequency precision.

The frequency control in the Nordic grid is to a large extent delivered by hydropower plants. The hydropower plants deliver frequency control of varying quality, meaning that a remuneration method based on more than just the static gain of the power plant is called for. This thesis has examined how three remuneration methods based on the hydropower plant output and the grid frequency deviation affects the grid stability. Using frequency data, the remunerated work along with the bandwidth and phase-crossover frequency was plotted and compared for varying governor settings. The results show that all three remuneration methods examined need constructive technical specifications (for example based on the frequency response) to not decrease the grid stability. The first remuneration method, where the power plant is remunerated for being on the right side of the power set point value as the grid frequency deviates, gave incentives for increased bandwidth, but no particular incentives regarding the phase-crossover frequency. The second remuneration method, where the power plant is remunerated for how well it matches the output power from a plant with no dynamics using a proportional controller, gave incentives for moderately high bandwidth and phase-crossover frequency. The third remuneration method, which remunerates how well the plant power output matches the load disturbance that gave rise to the grid frequency deviation, needs to be investigated further, but the initial analysis show that it did neither give incentives for increased bandwidth nor phase-crossover frequency.

The thesis describes the development of a generic nonlinear computer model of a pumped storage hydroelectric scheme. The model combines the hydraulic, electrical and control systems. In particular, this model includes the water hammer effects, the hydraulic coupling in the common water supply tunnel, the power system stiffness and the electrical coupling between the generator and the power system. The benefit of the simulation is that it gives insight into the plant characteristics and improves understanding of the physical phenomena involved. A specific case of the model for Dinorwig power station is tested against the plant responses and establishes a good degree of confidence in the simulation. The model is used to evaluate governor performance and establish stability boundaries for various operating conditions. The model is also used to design a new black-start regime which allows Dinorwig to energise the power system after blackout, with individual units picking up incremental loads up to 15% of machine rating while ensuring that frequency deviations remains within limits. Another application of the model is to explain why a period of sustained power oscillation occurred at Dinorwig and to identify under what circumstances this can take place. Linearised system models are used for governor tuning and root locus and Bode plot methods applied to establish the optimum governor settings for different operation conditions. The results demonstrate the significance of hydraulic coupling and the power system (grid) size on governor tuning. The final part of the work addresses conversion of the model to run in real-time and interfacing it with an actual unit governor. The results demonstrate the practicality of the hardware-in-the-loop simulation as a technique for safely implementing and testing new controllers or enhancements to the current controller.

The ongoing change towards completely renewable power production in Sweden entails new challenges in maintaining a stable power system and puts greater demands on the frequency control. Hydropower caters for all frequency control in the Swedish grid today. However, the new challenges make it necessary to explore other technologies that potentially could provide frequency control. The aim of this master thesis is thus to map different technologies that potentially could deliver the reserves FCR and aFRR, with the main focus of investigating the economic potential of these technologies and their competitiveness during different seasons. The technologies investigated were lithium-ion batteries, flywheels, demand response and wind power plants. Different applications for these technologies were also investigated. The different investment alternatives were evaluated by calculating the net present value and the net present value ratio. The results show that the economic potential is greatest in cases where existing infrastructure could be used. Investments in stand-alone energy storage systems are not profitable today but might be so in the future as the prices continue to decrease. The results also show that many of the technologies and applications are competitive alternatives to hydropower during different seasons, which shows that there is potential in participating in the balancing markets with these technologies. However, it seems relevant to investigate further if, and if so how, the regulations on endurance can be adapted to actual conditions to further opening up the markets to more actors while maintaining a stable power system.

This research focuses on frequency control ancillary services in large interconnected systems. It analyses and assesses possible alternatives for optimal and innovative solutions of major frequency control issues in large interconnected systems within liberalised electricity markets. Possible improvements in the performance of frequency control are identified. A framework of frequency control ancillary services in large interconnected systems by including loads and wind generation is also proposed.The research has been motivated by the paucity of research in power system dynamics focusing on large interconnected systems such as the European synchronous system and the Eastern interconnection which experience important frequency control challenges. These challenges include:- Decline in frequency response in the Eastern interconnection - Deterministic frequency deviations observed at the top of the hours in the European synchronous systemFrequency control issues became critical when electricity markets were deregulated and frequency control became an ancillary service with a decidedly commercial focus. This commercial focus has spawned a lot of work on frequency control markets and economics whereas not much research has been devoted to dynamic simulation of large interconnected systems. Apart from this commercial focus, frequency control in large interconnected systems is still based on historical practices mainly because changes suggested in the literature can be barely applied in large interconnected systems. This is essentially because dynamic simulation studies are uncorrelated with frequency control markets and economics. More specifically, dynamic studies do not take into account the characteristics of each reserve activated and also the way the reserve is activated. With the deregulation of the electricity market, reserve is considered as a product and not necessarily a response provided by a unit. The main objectives of this research therefore are to solve critical frequency control issues in large interconnected deregulated electricity systems, which may present potential economic benefits. To achieve these objectives, frequency control in large interconnected systems is studied by considering on one hand frequency control theory and on the other hand its implementation in practice taking account of frequency control ancillary service markets as well as the economics and practical consequences of frequency control. This approach is necessary to accommodate the future evolution of frequency control in large interconnected systems. The proposed approach is illustrated through a model of frequency control in the European synchronous system, where practices are better known, are clearly standardised and also where frequency data has been obtained.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / A new class of precision timing and frequency reference is introduced that indirectly receives GPS timing and frequency information via TIA/EIA Standard IS-95 Code Division Multiple Access (CDMA) mobile telecommunications base station transmissions. Like cell phones, these products operate indoors without external antennas and provide accuracy, low cost and ease of installation. The technology fits particularly well in IP network synchronization and quality-of-service monitoring applications where rooftop antenna installation is often impossible. The salient characteristics of the IS-95 CDMA signals that make them suitable for this purpose and a general CDMA timing receiver architecture are described. Performance data versus similar references that use conventional GPS reception are also presented.

Power system frequency is one of the key performance indices of system operation. Abnormal frequency deviations would incur negative impacts to power equipments and service quality. Thus, it is important to operate and regulate the system frequency within an acceptable range. North American Electric Reliability Corporation (NERC) has been using a Control Performance Standard (CPS) for frequency control performance assessment since 1997 which uses system frequency and inter--area power flow to evaluate the power system control performance. This thesis presents a design of CPS for isolated system and the results of Taiwan Power Company frequency control performance based on the proposed CPS1 formulation.