| 1. |
- Matevosyan, Julija, 1978-
(författare)
-
Wind Power Integration in Power Systems with Transmission Bottlenecks
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- During the last two decades, the increase in electricity demand and environmental concern resulted in fast growth of power production from renewable sources. Wind power is one of the most efficient alternatives. Due to the rapid development of wind turbine technology and increasing size of wind farms, wind power plays a significant part in the power production mix of Germany, Spain, Denmark, and some other countries. The best conditions for the development of wind farms are in remote, open areas with low population density. The transmission system in such areas might not be dimensioned to accommodate additional large-scale power infeed. Furthermore a part of the existing transmission capacity might already be reserved for conventional power plants situated in the same area. In this thesis four alternatives for large-scale wind power integration in areas with transmission bottlenecks are considered. The first possibility is to revise the methods for calculation of available transmission capacity. The second solution for large-scale integration of wind power in such areas is to reinforce the network. This alternative, however, may be expensive and time consuming. As wind power production depends on the wind speed, the full load hours of wind turbine generator are only 2000-4000 hours per year. Therefore reinforcing a transmission network in order to remove a bottleneck completely is often not economically justified. Wind energy curtailments during congestion situations is then the third solution for large-scale wind power integration with less or no grid reinforcement. The fourth solution is to store excess wind energy. Pumped hydro storage or battery storage for the large-scale wind farms are still rather expensive options, but existing conventional power plants with fast production control capabilities and sufficient storage capacity, e.g., hydro power plants, could be used for this purpose. As there is a lot of research work on the first two alternatives, the thesis provides a review and summarizes the main conclusions from the existing work. The thesis is then directed towards the development of the methods for estimation of wind energy curtailments, evaluation of wind energy storage possibility in hydro reservoirs and development of short term hydro power production planning methods, considering coordination with wind power. Additionally in the thesis the strategy that minimizes imbalance costs of a wind power utility, trading wind power on the short term power market is elaborated and analyzed.
|
|
| 2. |
- Samaranayake, Lilantha, 1974-
(författare)
-
Distributed Control of Electric Drive Systems via Ethernet
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is on adapting standard Switched Ethernet for distributed control applications in electric drive systems. The critical issue of Ethernet here is to provide services to real-time applications. The architectural construction of Ethernet is described, where the objective is to summarize the state of the art and indicate the causes of delays. This results in a network configuration suitable for distributed control applications, with no modifications to the protocols, but introducing the correct placement for the Ethernet Switch. A timing analysis on the Switch itself results in useful conclusions on the causes of non-deterministic nature of delays. Further, the delay measurements are taken on a real Switched Ethernet network, which are used to characterize the network. The delays are addressed also in the control systems perspective, as they trigger unwanted performance issues. They set limitations on the performance that can be achieved, even with the best possible controller. The architectures for connecting the nodes of a distributed control system is also studied, which are categorized according to the triggering mechanism. Both the networking and control system perspectives are extended for the delay compensation, where standard delay compensation techniques are experimentally verified on a speed control of a Brushless DC motor drive setup. The Proportional Integral controller with robust tuning techniques and Smith Predictor delay compensation, modified with the algebraic design techniques as well as State Feedback controller deploying on-line delay compensation have been verified. The latter technique proved to be promising but at the cost of time stamped measurements, which require synchronization of clocks at the nodes. This is presently cumbersome with most of the cost effective sensor actuator modules with Ethernet connectivity. Therefore the state feedback method is further improved using a plant model based predictor, where it eliminates the need of time stamped measurements. The stability has been studied and the design methodology is derived, which is proved to be better in simulations. However, the methodology expects the control delay not to exceed the sampling period. The thesis introduces an adaptive sampling scheme to cope with this situation, in which the sampling period is varied on-line depending on the current control delay. Further this methodology is experimentally verified using distributed position control of an XY board via Ethernet. The network connectivity for the motors of the XY board are obtained through Ethernet Ready Sensor Actuator (ERSA) modules designed and manufactured in the course of studies. Finally the general aspects of design, simulation and applications of distributed control systems have been presented.
|
|
