Communication-Less Frequency Support From Offshore Wind Farms Connected to HVdc via Diode Rectifiers

Abstract

Before diode rectifier (DR) technology for connecting offshore wind farms (OWFs) to HVdc is deployed, indepth studies are needed to assess the actual capabilities of DRconnected OWFs to contribute to the secure operation of the networks linked to them. This study assesses the capability of such an OWF to provide communication-less frequency support (CLFS) to an onshore ac network. It is shown that the HVdc link's offshore terminal direct voltage can be estimated from measurements at the OWF's point of connection with the DR platform. Two different methods are proposed for implementing CLFS in the OWF active power controls. In Method 1, the estimated offshore terminal direct voltage is used for estimating the onshore frequency deviation. In Method 2, the actual offshore terminal direct voltage measurement is used instead. Unique features of the provision of CLFS from OWFs connected to HVdc via DRs are highlighted, and the dynamic and static performance of the CLFS control scheme is compared to that of the communication-based frequency support scheme. To assess the impact of parameter estimation errors on the provision of CLFS, a parametric sensitivity study is presented as well, and recommendations are given to increase accuracy.

Primary Frequency Support from Offshore Wind Power Plants Connected to HVDC Grids

“…where R g3 and D 3 are respectively the frequency droop of the governor and damping factor of ac system B. The relation between power and frequency of onshore A considering (14) cab be express as…”

An Improved Adaptive Coordination Control of Wind Integrated Multi-Terminal HVdc System

“…As a result, traditional droop control is incapable of coordinating dc voltage regulation, frequency support, and power dispatch. When it comes to frequency support, numerous studies have found that control schemes that provide frequency support have a very positive impact [13][14][15][16]. Paper [17] uses pilot voltage droop (PVD) control to enhance the dc voltage regulation and frequency deviation sharing.…”

Frequency Dynamics of the Northern European AC/DC Power System: A Look-Ahead Study

“…The literature proposes various ways to support the frequency of AC systems such as wind power-HVDC systems [16]- [18], multi-terminal HVDC grids [19]- [21], and fast frequency reserve sources [22], [23]. Furthermore, assuming advanced communication infrastructure and adaptive control capabilities, interesting control methods were assessed in [24]- [27].…”