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Modern industrial customers, such as pulp and paper industries, have increased the vulnerability to power quality problems. A voltage source converter based high-voltage direct current (VSC-HVDC) transmission has the potential to offer high power quality when transmitting large amount of power. Therefore, in this paper, a VSC-HVDC transmission is proposed to supply such industrial plants in order to improve their power quality. The proposed VSC-HVDC together with an industrial plant is simulated in PSCAD/EMTDC to investigate the dynamic performance of the studied system during various operation conditions and after different events. Grid faults, different power production levels of the generator and trip of the generator are studied. Simulation results show that with a VSC-HVDC supply the power quality of industrial plants can be significantly improved. The extent of the improvement strongly depends on the VSC current limits, the generator power production levels and the generator ratings. Index Terms--Frequency controller, industrial plants with onsite generator, VSC-HVDC.

This paper studies three different frequency controllers and their effects on the voltage disturbance ride-through capability of a VSC-HVDC supplied industrial system. The idea of implementing frequency controller is to improve the power quality of industrial plants by slightly decreasing the VSC output voltage frequency since industrial processes are more sensitive to voltage drops than frequency deviations. The first two controllers, frequency controllers I and II, are fixed frequency controllers and the third one, frequency controller III, is a PI frequency controller. In order to compare three different controllers, a system with a simplified VSC-HVDC and different load types is simulated in PSCAD/EMTDC. Simulation results show that with frequency controller III, the VSC-HVDC supplied industrial plant can avoid a voltage collapse by decreasing frequency during or after disturbances. Furthermore, with an increase of the converter current limit, the possibility of mitigating voltage dips increases. For frequency controllers I and II, the extent of the disturbance ride-through capability depends on the current limit of the VSC-HVDC. A higher current limit results in a higher ride-through capability. The effect of the dc capacitor on improving the system voltage disturbance tolerance is also investigated during and after disturbances when the VSC-HVDC uses frequency controller I. The system voltage disturbance ride-through capability increases with an increase of the dc capacitance or the current limit. Index Terms--Current limit, frequency controllers, voltage dips, voltage disturbance ride-through capability, voltage source converters-high-voltage direct current (VSC-HVDC).

This paper presents a voltage-source-converter (VSC)-HVDC-supplied industrial system with onsite generation where the VSC-HVDC and generator are taking part in the voltage and frequency control. The reason for using a frequency controller in the converter is to increase the ridethrough capability of the VSC-HVDC-supplied industrial system by exploiting the inertia energy of rotating masses in case of voltage disturbances. The investigation is performed using the PSCAD/EMTDC program and the dynamic performance of the system is evaluated during grid faults and load changes. Three comparisons are done to analyze the system response when the inverter uses different frequency-control strategies, the impact on the system when the turbine operates in different modes, and the VSC-HVDC's ability to mitigate voltage dips from the grid. Simulation results show that the use of a VSC-HVDC for feeding industrial plants can mitigate voltage dips in the grid. Different frequency-control strategies have different responses on the system. The best frequency response is achieved when the turbine is also equipped with a frequency controller. Index Terms--Current limit, frequency controllers, onsite generation, voltage dips, voltage-source converter (VSC)-HVDC.

This paper proposes a control strategy for a VSC-HVDC for improving the quality of power supply to industrial plants. The new idea of this control strategy is to give high priority to keep up the ac voltage and slightly decrease the frequency during disturbances. The motivation for choosing this strategy is that the sensitive processing industries are much more sensitive to voltage drops as compared with frequency deviations. In order to test this control strategy, the dynamic performance of a VSC-HVDC supplied industrial plant is investigated during sudden load disturbances, balanced and unbalanced faults from the grid. Simulation results obtained using PSCAD/EMTDC show that with the use of the proposed control strategy, the system can ride through disturbances such as motor starting and faults by slightly decreasing the frequency. The current limit of the VSC-HVDC converters has a significant influence on the dynamics of the system. An increase of the current limit significantly improves the power quality of the system. The comparison of the behavior between a pure ac supplied industrial plant and a VSC-HVDC supplied industrial plant clearly shows the capability of the VSC-HVDC to mitigate voltage dips during faults. Index Terms--AC voltage control, dc voltage control, frequency control, power quality, voltage dips, VSC-HVDC.

This paper reports on the feasibility study performed to investigate the possibilities of connecting the 640-MW off-shore wind power farm, planned for Kriegers Flak 30 km south of Trelleborg, to the E.ON 130-kV subtransmission system. The Kriegers Flak commissioning is planned for 2010. The aim of this study is to answer the question if such a connection is possible, and under what conditions; it is not meant as a design project. Following a general connection design discussion, the study comprises of three major parts: fault current calculations, load flow calculations, and dynamic simulations. The study shows that it is possible to connect such a large off-shore wind power farm to the 130-kV subtransmission system, but reinforcement concerning load currents during normal operation and fault currents have to be made. Index Terms--Grid code, grid wind power connection, grid wind power interaction, off-shore, wind power.

This paper deals with the load behavior of pulp and paper industries after planned or forced outages. Real data of the power consumption following outages have been collected for most of the industries in Sweden. Based on these data load models have been proposed. The economical consequences of disturbances have been evaluated and a method of estimating the costs following a disturbance is presented. The possibility to disconnect parts of the load in a pulp and paper industry is discussed and can result in a reduction of the number of gas turbines necessary for the disturbance power reserve. Index Terms--Pulp and paper industry, outage, cold load pick up, load recovery.

Modern industrial customers, such as pulp and paper industries, have increased the vulnerability to power quality problems. A voltage source converter based high-voltage direct current (VSC-HVDC) transmission has the potential to offer high power quality when transmitting large amount of power. Therefore, in this paper, a VSC-HVDC transmission is proposed to supply such industrial plants in order to improve their power quality. The proposed VSC-HVDC together with an industrial plant is simulated in PSCAD/EMTDC to investigate the dynamic performance of the studied system during various operation conditions and after different events. Grid faults, different power production levels of the generator and trip of the generator are studied. Simulation results show that with a VSC-HVDC supply the power quality of industrial plants can be significantly improved. The extent of the improvement strongly depends on the VSC current limits, the generator power production levels and the generator ratings. [ABSTRACT FROM AUTHOR]

This paper proposes a control strategy for a VSC-HVDC for improving the quality of power supply to industrial plants. The new idea of this control strategy is to give high priority to keep up the ac voltage and slightly decrease the frequency during disturbances. The motivation for choosing this strategy is that the sensitive processing industries are much more sensitive to voltage drops as compared with frequency deviations. In order to test this control strategy, the dynamic performance of a VSC-HVDC supplied industrial plant is investigated during sudden load disturbances, balanced and unbalanced faults from the grid. Simulation results obtained using PSCAD/EMTDC show that with the use of the proposed control strategy, the system can ride through disturbances such as motor starting and faults by slightly decreasing the frequency. The current limit of the VSC-HVDC converters has a significant influence on the dynamics of the system. An increase of the current limit significantly improves the power quality of the system. The comparison of the behavior between a pure ac supplied industrial plant and a VSC-HVDC supplied industrial plant clearly shows the capability of the VSC-HVDC to mitigate voltage dips during faults. [ABSTRACT FROM AUTHOR]