A comprehensive modeling framework for dynamic and steady-state analysis of voltage droop control strategies in HVDC grids

Abstract

a b s t r a c tThis paper presents a comprehensive modeling framework to analyze and compare the performance of different voltage droop control characteristics in an HVDC grid. All models are fully derived mathematically, both for dynamic simulations and for steady-state power flow analysis. The main contribution lies in the development of a common modeling and control approach for the different droop-based control schemes that have been presented in the literature. The discussion includes power-and current-based droop control, either in their standard form or combined with a deadband, a constant voltage control or consisting of different slopes. Dynamic simulations show that, when applying a comparable underlying dynamic converter control framework, similar dynamic responses can be expected from the different droop control schemes, while the steady-state voltage deviations and power sharing after a contingency are different. A comparison with results from a full-detailed power flow implementation shows that these voltage deviations and power sharing can accurately be predicted by the derived steady-state power flow models, thereby avoiding the need for time-consuming dynamic simulations.

Control of multi-terminal HVDC networks towards wind power integration: A review

“…This high reliability has made the droop scheme the most promising control in MT-HVDC networks. The evaluation of this scheme can be found in [16,22,25 among other references. In particular, an experimental implementation in a scale multi-terminal grid is presented in [26].…”

A categorization of converter station controllers within multi-terminal DC transmission systems

“…voltage deviation will result in an equivalent current deviation [11], [17]. On the other hand, power-based droop control is analogous to frequency control of synchronous generator in AC systems [12], [18], i.e. power deviation will result in changes of AC frequency in AC systems or similarly DC voltage in DC grids.…”

“…As mentioned in [12], it is common to assume a lossless system in the design of DC voltage droop control so that (3) can be rewritten as:…”

“…It should be noted that k DC P might include conversion factor from DC to AC value. The conversion factor can be avoided by dividing P AC in (4) with AC terminal voltage [12]. 2) indirect link: As an alternative, the droop control can be integrated with another d-axis outer controller loop, i.e.…”

“…power and current-based, basic and advanced droop control, while the droop control based on common measurement was not fully covered. Similar attempt was done in [12] to include how the droop control is implemented but the same limitation was present. In [13] and improved in [14], basic and advanced droop control were generalized as piece-wise function and the control implementation was proposed.…”