Optimization-based reactive power control in HVDC-connected wind power plants

Abstract

One application of high–voltage dc (HVdc) systems is the connection of remotely located offshore wind power plants (WPPs). In these systems, the offshore WPP grid and the synchronous main grid operate in decoupled mode, and the onshore HVdc converter fulfills the grid code requirements of the main grid. Thus, the offshore grid can be operated independently during normal conditions by the offshore HVdc converter and the connected wind turbines. In general, it is well known that optimized reactive power allocation might lower the component loading and power losses. This paper aims to propose and assess a reactive power allocation optimization within HVdc–connected WPPs. For these systems, the offshore converter operates the adjoining grid by imposing frequency and voltage. The reference voltage magnitude is used as additional control variable for the optimization algorithm. The loss function incorporates both the collection grid and the converter losses. The use of the proposed strategy results in an effective reduction of losses compared to conventional reactive power dispatch strategies alongside with improvements of the voltage profile. A case study for a 500 MW–sized WPP demonstrates an additional annual energy production of 6819 MWh or an economical benefit of 886 k€yr-1 when using the proposed strategy.Postprint (author's final draft

Enhanced Voltage Control of VSC-HVDC-Connected Offshore Wind Farms Based on Model Predictive Control

“…The converter loss can be approximated by a quadratic function depending on the converter current (in p.u.) [21],…”

“…In [20], the voltage reference of the pilot bus was determined by the offline optimal power flow calculation and the total reactive power reference was obtained using a PI controller and then dispatched to each WTG. In [21]- [23], the objectives of the OPF were the power loss of the OWF collector system, grid side converter (GSC) of WTGs and HVDC converters. Since the VSC-HVDC transmission system decouples the OWFs from the onshore AC grid, the main control aim for OWFs is to maintain the terminal voltage of each WTG within the feasible range [16], which was not considered in these OPF-based strategies.…”

Reactive power dispatch of DFIGs in wind farm based on multi‐object optimization

“…Compared with the DFIGs, the modeling and control to the shunt capacitors and the SVCs are easier, since they do not have the wind turbine (WT) and the generator. The PMSG is also easier than the DFIG due to the var decoupling by the B2B converters . There are already papers about var control and optimization to them, although using the simplified description of the WT without the generator and B2B converters .…”

“…The PMSG is also easier than the DFIG due to the var decoupling by the B2B converters. [9][10][11][12] There are already papers about var control and optimization to them, although using the simplified description of the WT without the generator and B2B converters. [13][14][15] For the DFIG-basedfarm, there are papers dispatching its total reactive power from system level.…”

Optimal Placement and Sizing of PV-STATCOM in Power Systems Using Empirical Data and Adaptive Particle Swarm Optimization

“…Reactive power is required due to loaded generators and transmission lines [2]. The technique of reactive power generation at loadside is called compensation.…”