Negative Sequence Current Control in Wind Power Plants With VSC-HVDC Connection

Abstract

Large offshore wind power plants may have multi-MW wind turbine generators (WTG) equipped with full-scale converters (FSC) and voltage source converter (VSC) based high voltaage direct-current (HVDC) transmission for grid connection. The power electronic converters in the WTG-FSC and the VSC-HVDC allow fast current control in the offshore grid. This paper presents a method of controlling the negative sequence current injection into the offshore grid from the VSC-HVDC as well as WTG-FSCs. This would minimize the power oscillations and hence reduce the dc voltage overshoots in the VSC-HVDC system as well as in the WTG-FSCs; especially when the offshore grid is unbalanced due to asymmetric faults. The formulation for negative sequence current injection is mathematically derived and then implemented in electromagnetic transients (EMT) simulation model. The simulated results show that the negative sequence current control mitigates the power oscillations and therefore limits the dc voltage excursions in the VSC-HVDC system during the asymmetric faults.Index Terms-Full-scale converter, high voltage direct-current (HVDC), second-order generalized integrator (SOGI), sequence components, voltage source converter (VSC), wind power plant, wind turbine generator.

Enhanced Instantaneous Power Theory for Control of Grid Connected Voltage Sourced Converters Under Unbalanced Conditions

“…Additionally, the VSC is also expected to deal with harmonic distortion, following network recommendations and standards [13][14][15][16][17][18][19][20].…”

“…Therefore, several solutions have been explored in the past, by appropriately injecting synthesized currents to attenuate power oscillations. These control strategies include rotating reference frames [86,87] with proportional-integral controllers [85,88], stationary frames [17] with proportional-resonant controllers [16,89], as well as nonlinear hysteresis and predictive deadbeat controllers, among others [90].…”

“…Many technical solutions have been proposed to deal with voltage sourced converters operating under unbalanced and distorted voltage conditions [15][16][17][18][19][20], for example by injecting appropriately synthesized unbalanced currents. Nevertheless, dealing with zero sequence transients is still complicated, as it will be explained in the thesis.…”

Information Gap Decision Theory Based OPF With HVDC Connected Wind Farms

“…• Advantages : Black start capability [19], no requirement for reactive power compensation, more compact and lighter compared to LCC, no need for harmonic filter, can be operated in both capacitive or inductive modes [20], [21], VSC valves are independent of the zero crossings of the current and balanced operation of the linked AC system, ability to control the negative sequence current injection in the offshore wind power plant [22], shorter design and installation times [15], using IGBT switches enables the VSC-HVDC scheme to be switched on and off at higher rate [23] and needs no external voltage source for commutation [24].…”

Handling of unbalanced faults in HVDC-connected wind power plants

“…seq. handling by WT converters is treated in [10,11,12,13,14,15,16,17,18] and in the light of VSC-HVDC-interfaced AC grids in [19,20,21,22]. Converter control regarding neg.…”