smaller, lighter, more robust and more efficient higher-speed turbine. The suggested design is much simpler and eliminates all mechanical adjustments through a novel electronic power conditioning system for connection to the electric grid. In this way, it allows obtaining higher reliability and lower cost of the power plant. A full detailed model of the MHPP is derived and a new three-level control scheme is designed. The dynamic performance of the proposed MHPP is validated through digital simulations and employing a small-scale experimental set-up.
Keywords :Distributed generation (DG)，Micro-hydro power plant (MHPP)，
Dynamic modeling，AC/DC/AC power conditioning system，Control technique
1. Introduction
In the last decade, problems related to energy factors (oil crisis),ecological aspects (climatic change), electric demand
(significant growth) and financial/regulatory restrictions of wholesale markets have arisen worldwide.
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These difficulties, far from finding effective solutions, are continuously increasing, which suggests the need of technological alternatives to assure their solution. One of these technological alternatives is named distributed generation (DG), and consists on generating electricity as near as possible of the consumption site, in fact like it was made in the beginnings of the electric industry, but
now incorporating the advantages of the modern technology [1].Here it is consolidated the idea of using renewable energy sources (RESs) that do not cause environmental pollution, such as wind, photovoltaic, hydraulic, among others [2].
In recent years, a rising interest on grid integration of micro-hydro power plants (MHPPs) has emerged, mainly because they are a proven technology with a very good
performance and feasible with low investment costs, resulting in the technology based on RESs with smaller costs even when they are compared to wind generation [3]. This trend is expected to be increased even more due to the high potential of application of MHPPs in DG and to the large amount of benefits for the use of renewable energy sources, including favourable incentives in many countries and the retributions coming from trading carbon emission reduction (CER) credits.
A small-scale (from pico to mini) hydro power station is usually a run-of-river plant that uses a fixed speed drive with mechanical regulation of the turbine water flow rate through adjustable guide vanes and runner blades for controlling the active power generation. This design enables to reach high efficiency over a wide range of water flows but using a complex operating mechanism, which is in consequence expensive and tends to be more affordable for large-scale systems.
This paper proposes an advanced structure of a MHPP based on a smaller, 16
lighter, more robust and more efficient higher-speed turbine. The suggested design is much simpler and eliminates all mechanical adjustments through a novel electronic power conditioning system (PCS) to connect to the electric distribution grid, as depicted in Fig. 1. In this way, this topology allows
obtaining higher reliability and lower cost of the power plant. A full detailed model of the MHPP is derived and a new three-level control scheme is designed. The control consists of a multi-level hierarchical structure and incorporates a maximum power point tracker (MPPT) for better use of the hydro resource, in addition to reactive power compensation capabilities. The dynamic performance of the propose control schemes is validated through digital simulations in
MATLAB/Simulink. Moreover, a 350 W MHPP experimental set-up build at the Institute of Power Electronics and Electrical Drives of the University of Siegen (Germany) was implemented to demonstrate the accuracy of proposed models. 2. Modeling of the proposed micro-hydro power plant
The proposed hydropower station is a run-of-river plant which consequently does not have any significant water reservoir such as large dams. Only a fraction of the available stream flow at a given time is used, this leading to a good agreement with the environment and
permitting the utilization of low head water sources as DG. In order to allow extended control features when they are integrated into the electric power grid and also to provide the enough flexibility to adapt to the specific conditions of rivers with low water flow rate, a
variable-speed turbine is proposed to be used in this work. Thus, by optimizing the turbine working point in order to extract the maximum power of the water flowing per second, superior efficiencies respect to traditional hydro turbines can be obtained. Moreover, by replacing mechanical controls with advance technologies in power electronic devices, higher reliability stations with better efficiencies can be reached. The modeling approach of the proposed
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micro-hydro power plant is based on the structure of Fig. 1. The MHPS consists
of a variable speed micro-hydro turbine directly coupled to a permanent magnet synchronous generator (PMSG) and connected to the electric grid through an advanced power conditioning system (PCS). The proposed PCS is composed of a three-phase rectifier bridge, a DC/DC converter and a DC/AC power inverter.
Fig. 1–Layout of the implemented MHPP. 2.1. Hydraulic turbine characteristics
The proposed hydro power is a basic reaction turbo-machine well suited for low water heads and low water flow rates. This hydraulic turbine is a propeller type, modified from a Kaplan turbine with neither blade pitch control nor upstream guide vane one. In addition, the turbine does not implement a gear box for coupling to the generator which yields a simple and robust design. Fig. 2
shows a computer-aided design (CAD) of the implemented propeller hydraulic turbine. The turbine is a vertical axis machine with a spiral case and a radial guide vane configuration.
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Fig. 2 – CAD of the proposed propeller hydraulic turbine. The hydraulic turbine characterized in the laboratory is a 350 W rated power one designed for an average 1.5 m head and a water flow rate of 35 L/s , which is shown in the photograph of Fig. 1 (right side). The hydraulic turbine
外文翻译--一种先进的应用于分布式发电中的微型水电站的动态模型仿真和控制设计
