Grid-forming control strategies for black start by offshore wind power plants

Abstract

Abstract. Large-scale integration of renewable energy sources with power-electronic converters is pushing the power system closer to its dynamic stability limit. This has increased the risk of wide-area blackouts. Thus, the changing generation profile in the power system necessitates the use of alternate sources of energy such as wind power plants, to provide black-start services in the future. However, this requires grid-forming and not the traditionally prevalent grid-following wind turbines. This paper introduces the general working principle of grid-forming control and examines four of such control schemes. To compare their performance, a simulation study has been carried out for the different stages of energization of onshore load by a high-voltage direct-current (HVDC)-connected wind power plant. Their transient behaviour during transformer inrush, converter pre-charging and de-blocking, and onshore block-load pickup has been compared and analysed qualitatively to highlight the advantages and disadvantages of each control strategy.

Wind farm flow control oriented to electricity markets and grid integration: Initial perspective analysis

“…Black start support from WPPs can be essential for power systems with high share of wind power following a blackout of the power system. Converters of modern wind turbines can have grid forming capabilities to support black start 95,96 . However, in order to provide black start support to the grid, the WPP needs to produce way less than the available wind energy, which may impact the structural loading of the wind turbines 97 .…”

Virtual Resistance Control for Sequential Green-start of Offshore Wind Power Plants

“…12 in Appendix A. The values of all the circuit parameters are based on [8], [18] and tabulated in Table I in the Appendix A.…”

“…The GSC is a 2-level voltage-sourced-converter (VSC) switching at 2 kHz with GFM strategy based on improved direct power control [21] as shown in Fig. 4a and similar to the implementation in [8]. The controller is tuned according to criteria as described in detail in [8] equivalent to a slow current controller with natural frequency of 4 Hz and damping ratio of (a) Direct Power GFM control for GSC based on [8].…”

“…4a and similar to the implementation in [8]. The controller is tuned according to criteria as described in detail in [8] equivalent to a slow current controller with natural frequency of 4 Hz and damping ratio of (a) Direct Power GFM control for GSC based on [8]. It consists of real and reactive power controllers for load sharing.…”

“…Many studies have been done on power system restoration with WPPs -a comprehensive review is presented in [8], where it has been highlighted that a change in control philosophy from conventional grid-following to grid-forming (GFM) is essential to facilitate early stage participation of WPPs in bottom-up network energization. Such GFM wind turbines (WT) can operate -albeit with changes to the turbine and converter control [9]- [11] -as a controlled AC voltage source without relying on an external grid and supply load in a power island [8], [12]. This also enables them to provide short term defense against imminent instabilities preceding a blackout by switching to trip-to-houseload and ensuring stable controlled islanded operation (CIO) -potential strategies for restoration procedures in the future decentralized converterrich power system [13].…”