Per Norrlund
Uppsala University
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Publication
Featured researches published by Per Norrlund.
IEEE Transactions on Energy Conversion | 2015
Linn Saarinen; Per Norrlund; Urban Lundin
The dynamic behavior of hydropower plants participating in primary frequency control is investigated in this paper through frequency response, step response, and setpoint change tests on three Swedish hydropower plants. Gray-box system identification is used to estimate the parameters of simple linear models suitable for power system analysis and the major shortcomings of the linear models are discussed. It is found that frequency response tests with sinusoidal input signals give more reliable information about the dynamics of the plants than step response tests. It is also shown that backlash in the runner and guide vane regulating mechanisms are of great importance for the dynamic behavior of the plants, and that the incremental gain from guide vane opening to power varies considerably with the operation point.
IEEE Transactions on Power Systems | 2017
Weijia Yang; Per Norrlund; Linn Saarinen; Jiandong Yang; Wei Zeng; Urban Lundin
Nowadays, the wear and tear of hydropower turbines is increasing, due to more regulation movements caused by the increasing integration of intermittent renewable energy sources. In this paper, a controller filter is proposed as a solution to the tradeoff between reducing the wear of turbines and maintaining the regulation performance and thereby the frequency quality of the power systems. The widely used dead zone is compared with a floating dead zone and a linear filter, by time-domain simulation and frequency-domain analysis. Simulink models are built and compared with onsite measurement. Then, the time-domain simulation is used to investigate the guide vane movement, the load disturbance and the power system frequency, based on a one-day grid frequency data measured in this study. In the theoretical analysis, the describing functions method and the Nyquist criterion are adopted to examine the stability of the system with different filters. The results show that the floating dead zone, especially the one after the controller, has a better performance than the dead zone on both the wear reduction and frequency quality. The linear filter has a relatively weak impact on both guide vane movements and the frequency quality. Other related conclusion and understandings are also obtained.
Electric Power Components and Systems | 2015
Weijia Yang; Jiandong Yang; Wencheng Guo; Per Norrlund
Abstract Currently, the Thoma criterion is often violated to diminish the cross-section of the surge tank; therefore, the surge fluctuation is aggravated and the frequency stability becomes more deteriorative. The focus of this article is on stabilizing the low-frequency oscillation of an isolated hydropower plant caused by surge fluctuation. From a new perspective of hydropower plant operation mode, frequency stability under power control is investigated and compared with frequency control by adopting the Hurwitz criterion and numerical simulation. In a theoretical derivation, the governor equations of frequency control and power control are introduced to the mathematical model. For numerical simulation, a governor model with a control mode switch-over function is built. The frequency oscillations under frequency control, power control, and control mode switch-over are simulated and investigated, respectively, with different governor parameters and operation cases. The result shows that the power control has a better performance on frequency stability at the expense of rapidity compared with the frequency control. Other recommendations regarding worst operation cases and choice of control modes are also developed.
power and energy society general meeting | 2016
Linn Saarinen; Per Norrlund; Urban Lundin; Evert Agneholm; Andreas Westberg
The grid frequency quality in the Nordic power system has been deteriorating during the last decade. To improve the situation, a better understanding of the system is needed. In this paper, a model of the Nordic power system dynamics with respect to normal operation frequency control is set up and compared with full-scale measurements on the system. The “60 s oscillation” of the grid frequency is measured and explained by the system model.
Nature Communications | 2018
Weijia Yang; Per Norrlund; Linn Saarinen; Adam M. Witt; Brennan T. Smith; Jiandong Yang; Urban Lundin
There is a general need to change hydropower operational regimes to balance the growing contribution of variable renewable energy sources in power systems. Quantifying the burden on generation equipment is increasingly uncertain and difficult. Here, we propose a framework combining technical and economic indicators to analyze primary frequency control (PFC) on a timescale of seconds. We develop a model integrating hydraulic, mechanical, and electrical subsystems to characterize efficiency loss, wear and fatigue, regulation mileage, and frequency quality. We evaluate burden relief strategies under three idealized remuneration schemes for PFC, inspired by those used in Sweden, the USA, and China, respectively. We show how burden and compensation vary under future scenarios of renewable power systems. Our framework can be used by producers to develop favorable operation strategies that reduce burden and increase economic value, and by transmission system operators to provide insights on the relation between incentive structures and regulating performance.Quantifying burden on hydropower units for balancing variable renewable energy sources has been uncertain and difficult. Herein Yang et al. propose a framework and characterize the burden, performance and compensation of hydropower regulation of renewable power systems.
IOP Conference Series: Earth and Environmental Science | 2016
Weijia Yang; Per Norrlund; Jiandong Yang
Since a few years, there has been a tendency that hydropower turbines experience fatigue to a greater extent, due to increasingly more regulation movements of governor actuators. The aim of this pa ...
Energies | 2015
Weijia Yang; Jiandong Yang; Wencheng Guo; Wei Zeng; Chao Wang; Linn Saarinen; Per Norrlund
International Journal of Electrical Power & Energy Systems | 2016
Weijia Yang; Jiandong Yang; Wencheng Guo; Per Norrlund
Renewable Energy | 2016
Weijia Yang; Per Norrlund; Linn Saarinen; Jiandong Yang; Wencheng Guo; Wei Zeng
Renewable Energy | 2018
Weijia Yang; Per Norrlund; Chi Yung Chung; Jiandong Yang; Urban Lundin