Electrical upgrades for a 1909 vintage hydro station

Information is provided on the electrical upgrade approach taken by Duke Power Company on one of its older hydroelectric stations, the Ninety-Nine Islands Hydro Station constructed in 1909. Equipment replaced, reasons for replacement, and the design of new equipment are discussed. Electrically, most of the original power and control equipment was still in service after nearly 80 years. Engineering studies were undertaken to evaluate not only what electrical equipment should be upgraded, but also what fundamental design changes should be made. The equipment upgrades outlined should result in improved unit reliability. Reductions in operating and maintenance costs are expected over what the costs would have been with the old equipment     

Modelling and stability of a hydro plant with two surge tanks

This paper deals with the modelling and the stability analysis of a hydroelectric power plant with two surge tanks placed upstream and downstream of the turbine. The interaction of the two surge tanks is investigated and the system is simulated for the case of sudden opening or closure of the turbine gates. The stability of the frequency control loop is assessed by using small signal analysis based on linearization. The above procedures have been applied to a real situation and proved to be extremely useful for preliminary control design purposes     

Online optimal power distribution between units of a hydro power plant

The paper presents a novel methodology for the operation of those hydro power plants provided with a single penstock by the optimal distribution of the dispatched power among its available generating units, aiming at the maximum efficiency of the whole power plant energy conversion. While previous optimization methods made use of off-line static curve and parameters or expensive flow meters, the proposed method is on-line in nature and uses a single pressure meter at the end of the power plant penstock. The method was applied to a power plant and has resulted in a higher efficiency operation under several conditions.     

Autonomous micro hydro power plant with induction generator

Autonomous micro hydro power plants (MHPP) are a reliable solution for supplying small power consumers in areas located far from the distribution grid. When an induction generator (IG) is used in such a power plant, voltage and frequency need to be stabilized. This paper presents a single control structure that ensures both the voltage and frequency regulation of an isolated induction generator (IG). The control structure consists in a voltage source inverter (VSI) with a dump load (DL) circuit on its DC side. The VSI operates at constant frequency, thus stabilizing the IG frequency also. For voltage regulation two cascaded regulators are used, which have as reference the line voltage and the VSI DC voltage, respectively. Simulations and experiments are carried out in order to investigate the reliability of such configuration when supplying static and dynamic loads.     

Techno-economic review of existing and new pumped hydro energy storage plant

There has been a renewed commercial and technical interest in pumped hydro energy storage (PHES) recently with the advent of increased variable renewable energy generation and the development of liberalized electricity markets. During the next 8 years over 7 GW of PHES capacity will be added to the European network while projects are also planned in the USA and Japan. This paper provides a review of existing and proposed PHES plant and discusses the technical and economic drivers for these developments. Current trends for new PHES development generally show that developers operating in liberalized markets are tending to repower, enhance projects or build ‘pump-back’ PHES rather than traditional ‘pure pumped storage’. Capital costs per kW for proposed PHES in the review region range between €470/kW and €2170/kW, however these costs are highly site and project specific. An emergence has also been observed in recent PHES developments of the use of variable speed technology. This technology, while incurring slightly higher capital costs, offers a greater range of operational flexibility and efficiency over conventional PHES. This paper has primarily been prompted by a lack of detailed information on PHES facilities worldwide and reviews current developments in the context of market and generation mix changes. The most recent large scale review of PHES faculties was undertaken by the American Society of Civil Engineers Hydro Power Task Committee on Pumped Storage in 1996. In the absence of data in the literature on new PHES plant development, this review draws primarily on publicly available information from utilities, government bodies and electricity regulators. In the same context this study is limited to a review region of the European Union, Japan and the United States as information on developments outside these areas is difficult to procure. This paper also gives a review of locations and proposed timelines for new PHES development and provides a thorough up-to-date overview of the development trends of this technology.     

The role of energy limited hydro equipment in an optimal plant mix

The main purpose of this paper is to highlight the influence of the main characteristics of hydropower on the choice of an optimal generating plant mix. Marginal conditions for a cost minimizing approach are developed while incorporating the effects of the rising costs of hydraulic forces, the cost of added hydroturbines (energy limited), and the costs of developing different hydro sites. It is seen that the main difference between the marginal conditions for a hydro system and for a thermal one comes from the limited availability of water power. This framework is then applied to data drawn from the current expansion programme of Quebec Hydro. Although the analytical framework relies on simplifying assumptions, the results are rather close to those provided by Quebec Hydro. The results are then used to evaluate the marginal costs of providing additional power for every hour of the year. These marginal generation costs range from a high of 6.0¢ during the peak period to a low of 1.6 ¢ for the base period, both being measured in 1980 dollars.     

A review on islanding operation and control for distribution network connected with small hydro power plant

Hydro power generation is the oldest generation and provides the largest contribution among the renewable energy types of generation. In distribution system, most of the distributed generation (DG) is small scale hydro generation of which utilizes the natural flowing water of the river. This generation requires governor and excitation control unit to control and sustain the power generation when subjected to any changes of load behavior. More advanced control strategy is critically expected when considering the recent interest in distribution system to perform islanding operation of DG. Many of the literature have clearly highlighted this issue, but only a few have discussed on the islanding operation of small hydro generation. This paper therefore reviews this topic and relates the discussion with the controller designed for other type of turbines interfaced with synchronous generator. To strengthen the knowledge on islanding operation, the background of islanding is also presented in this paper.     

小水电开发与生态环境保护

小水电的开发利用对我国农村经济社会的发展和生态环境的改善具有巨大的作用，但同时也存在些负面影响。文章结合开发实践，对小水电开发和生态环境保护问题作了扼要分析，并提出了减少或消除小水电开发对生态环境负面影响的对策。     

The application potential of hydro power

Water is the only renewable energy source that has been exploited by man on a large scale and that has a well-developed technological base to support its continued exploitation. At present about 23% of the world's electricity supply is from hydro plants. Since all the new energy sources under development are mainly exploitable through electricity generation, it seems likely that the world will have to move increasingly to an electricity-based energy regime.To make an effective contribution to new energy supply patterns. hydro power could be exploited by the development of small generating units to meet local community needs, by the use of pumped storage to optimize operation of other energy sources, and by the development of the many remaining sites in remote areas and third world countries with high power potential including perhaps glacier-derived power. This last development could spawn a new energy trade which would require a transfer of manufacturing resources to the countries with hydro power.Political decisions and economic considerations will influence these developments. An effective electric power trade between countries requires an acceptable international code of practice. Ultimately the speed of development of these resources will depend upon the cost of energy delivered to the consumer compared with the cost of other energy sources closer to the load centre.     

Retrofit of Trangslet hydro power station

An accident in Trangslet Power Station in the fall of 1982 resulted in, among other things, flooding of the control equipment. Despite the effective cleaning up after the flooding, the reliability was not adequate and new equipment was needed. When assessing various options, Stora Power came to the conclusion that a computerized control system would be the best solution because of its ability to optimize the power production of the station. The authors describe the utility requirements for the distributed control system and experiences from implementation and operation. They also cover the control system philosophy and implemented functions. During the installed system's first four years of operation, the requirements set by Stora Power have been achieved     

Low head pico hydro turbine selection using a multi-criteria analysis

Turbine types suit specific ranges of head, flow rate and shaft speed and are usually categorised by specific speed. In the pico range, under 5 kW, the requirements are often different to that of larger scale turbines and qualitative requirements become more influential in selection. Pico hydro turbines can be applied beyond these conventional application domains, for example at reduced heads, by using non-traditional components such as low speed generators. This paper describes a method to select which turbine architecture is most appropriate for a low-head pico hydro specification using quantitative and qualitative analyses of 13 turbine system architectures found in the literature. Quantitative and qualitative selection criteria are determined from the particular requirements of the end user. The individual scores from this analysis are weighted based on the perceived relative importance of each of the criteria against the original specification and selects a turbine variant based on the total weighted score. This methodology is applied to an example of a remote site, low head and variable flow requirement, leading to the selection of a propeller turbine variant or single-jet Turgo turbine for this specification.     

Case study of upgrading potential for a small hydro power station

Schemes for upgrading hydro power are formed in many parts of the world. Small hydro power (<15 MW) constitutes a fraction of all hydro power, but upgrading can still be worthwhile. In this article, a small generating station in Sweden, with two generators, is simulated with new generators. The voltage is increased by introducing a cable wound stator, thereby the transformers can be excluded, and more efficient generators are introduced with a higher power factor. These improvements lead to an active power increase from 8.9 to 9.4 MW per generator, which means an increased total annual production by 4.2 GW h.     

A combined wind and hydro power system

A high degree of coverage of electricity demand by wind energy conversion is possible only with access to energy storage. For regions with both hydro and wind resources, the hydro power system and the wind power system may complement each other and alleviate the need for any other energy storage. Scandinavia is such a region, and this article uses a simulation model to assess the conditions under which all the electricity needs of Norway and Denmark could be satisfied by a combination of the existing Norwegian hydro power system with a hypothetical all wind-based Danish power system.     

Investment planning for electricity generation expansion in a hydro dominated environment

This paper presents the investment planning model, which has been developed to rigorously valorize the large hydroelectric potential resources of Cameroon. Based on Benders technique, the decomposition approach proposed allows each component of the problem (investment and operation) to be conveniently modelled and solved by adapted methods. Furthermore, the relative small size of the actual system, the long experience of the manual generation management in use over a long time by the national electricity company (Sonel), and the fundamental data of the problem are exploited as the basis of the approach, to define a more detailed and adapted model. Formulated as a multistage mixed linear programming problem, the decomposition procedure of the Benders technique is applied to isolate from the problem so modelled its two main subproblems (investment and operation). The investment subproblem is modelled as a multistage mixed linear programming problem and solved by a branch and bound technique. The operation subproblem is represented as a multistage stochastic linear problem and solved by a revised simplex‐based method. Subsequently, a solution algorithm for the whole problem, defined by a finite iterative process where the subproblems are alternatively solved, is derived from the co‐ordination procedure of Benders technique. Case studies with the southern interconnected network of the Sonel system are presented and analysed. Copyright © 2001 John Wiley & Sons, Ltd.     

Speed and active power control of hydro turbine unit

In the paper, the procedure is given for designing speed and active power controller of hydro turbine units. The procedure is based on mathematical models of the controlled system. The controller parameters are obtained from closed-loop poles and hydro turbine parameters by derived analytical formulas over a wide range of the hydro turbine operating points. The described procedure allows the fast and direct determination of the controller parameters. There is no need for heuristic controller parameters tuning. Results from two hydro turbine units with the controllers designed using the described procedure are given as an illustration.     

Technical and economic characteristics of small hydro power plants

The cost indices of small hydro power plant capacity and mass are considered by analogy with solar radiation density as a function of water flow energy density. The variations of these indices as the water flow energy changes are determined.     

Small hydro power: technology and current status

Hydropower, large and small, remains by far the most important of the “renewables” for electrical power production worldwide, providing 19% of the planet’s electricity. Small-scale hydro is in most cases “run-of-river”, with no dam or water storage, and is one of the most cost-effective and environmentally benign energy technologies to be considered both for rural electrification in less developed countries and further hydro developments in Europe. The European Commission have a target to increase small hydro capacity by 4500MW (50%) by the year 2010. The UK has 100MW of existing small hydro capacity (under 5MW) operating from approximately 120 sites, and at least 400MW of unexploited potential. With positive environmental policies now being backed by favourable tariffs for ‘green’ electricity, the industry believes that small hydro will have a strong resurgence in Europe in the next 10 years, after 20 years of decline. This paper summarises the different small hydro technologies, new innovations being developed, and the barriers to further development.     

Feasibility study of a hybrid wind/hydro power-system for low-cost electricity production

This paper deals with the operation of a hybrid wind/hydro power system aiming at producing low cost electricity. A specific application on the island of Ikaria in Greece is analysed and typical results are presented and compared to the results produced from a simulation program. The simulation program, which is based on the stochastic behaviour of the weather conditions, uses as input data the monthly wind-speed distribution and, to a smaller extent, which is determined from the use of an appropriate weighting factor, the rate of rain water which is stored in the hydro reservoir. Useful conclusions were drawn regarding the feasibility of these applications in Greek islands and the expected electric energy saving.     

Private and social benefits of a pumped hydro energy storage with increasing amount of wind power

In this paper, we calculate the long-term profitability of a pumped hydro energy storage (PHES) plant that is planned to be built in an old mine. We model the optimal PHES operation for several scenarios with different wind power penetration levels. Our modelling approach first involves estimating wholesale electricity prices for the day-ahead, intraday and balancing market as a function of wind power penetration. The estimated price profiles are implemented in a dynamic programming model, where the PHES plant maximises its balancing market revenue given the optimal commitment in the day-ahead market. We show that increasing the wind penetration changes the optimal PHES operation and increases the PHES profits. Additionally, we quantify how the costs of wind power balancing are affected by the PHES investment. Policy implications are drawn based on the estimated private and social benefits from the investment.