Search

The voltage at the point of common coupling (PCC) in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage (voltage at the PCC), whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (StatCom), it is possible to compensate for the active power change as well as providing reactive power support. In this paper effective active power compensation schemes are proposed. Simulation and experimental results verify the compensation schemes by showing that a StatCom with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage under load disturbances. Index Terms--Active power compensation, energy storage, phase jump, StatCom, voltage dip, voltage source converter (VSC), weak network.

A transformer might be driven into saturation by faults in the connected system. In a transmission system with a Static synchronous Compensator and transformers connected at the point of common coupling, different modulation schemes utilized by the voltage source converter influence the transformer saturation in different ways. This paper compares the saturation effect during fault recovery when two alternative modulation schemes are utilized: voltage modulation and flux modulation. The comparison shows that utilization of flux modulation scheme tends to soften the saturation problem during fault recovery. However, this is achieved at a higher converter transient peak current. Index Terms--Converters, fault recovery, pulse width modulated power converters, StatCom, static synchronous compensator, transformer saturation, transformers, voltage source converter (VSC).

Voltage source converters (VSC) have been widely utilized to provide instantaneous reactive power support to power systems, an application referred to as static synchronous compensator (StatCom). Integration of energy storage (ES) into a StatCom makes it possible for the StatCom to provide a certain amount of active power as well as reactive power support. The possible benefit of the additional active power support of a StatCom can be power oscillation damping capability, mitigation of phase-jump related disturbances, etc. Direct connection of an ES device to the dc link of the VSC incurs unnecessarily high voltage rating of the VSC due to the considerable voltage swing associated with the ES device. In order to reduce the total cost, a dual thyristor converter topology has been proposed as the interface between the ES and the dc link of the VSC. In this paper, dynamics of the proposed system are investigated. Control strategies are proposed and verified by simulations with PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

In this paper, a novel control method of grid-connected voltage-source converters (VSCs) is proposed. The method can be generally applied for all grid-connected VSCs but may be of most importance in high-voltage dc (HVDC) applications. Different from the previous control methods, the proposed method utilizes the internal synchronization mechanism in ac systems, in principle, similar to the operation of a synchronous machine. By using this type of power-synchronization control, the VSC avoids the instability caused by a standard phase-locked loop in a weak ac-system connection. Moreover, a VSC terminal can give the weak ac system strong voltage support, just like a normal synchronous machine does. The control method is verified by both analytical models and time simulations. [ABSTRACT FROM AUTHOR]

The voltage at the point of common coupling (PCC) in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage (voltage at the PCC), whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (StatCom), it is possible to compensate for the active power change as well as providing reactive power support. In this paper effective active power compensation schemes are proposed. Simulation and experimental results verify the compensation schemes by showing that a StatCom with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage under load disturbances. [ABSTRACT FROM AUTHOR]

A transformer might be driven into saturation by faults in the connected system. In a transmission system with a Static synchronous Compensator and transformers connected at the point of common coupling, different modulation schemes utilized by the voltage source converter influence the transformer saturation in different ways. This paper compares the saturation effect during fault recovery when two alternative modulation schemes are utilized: voltage modulation and flux modulation. The comparison shows that utilization of flux modulation scheme tends to soften the saturation problem during fault recovery. However, this is achieved at a higher converter transient peak current. [ABSTRACT FROM AUTHOR]