Power System Planning and Operation (Slides)

This panel session contains the following presentations:
1. Impact Assessment of Active Network Management Schemes on DG Capacity of Distribution Systems
The transition from fossil fuel-based generation toward renewable-based distributed generation (DG) has motivated system operators to determine the maximum DG capacity that can be safely accommodated in distribution systems. Active network management (ANM) schemes can mitigate the technical issues arising from high DG penetration and, therefore, increase DG capacity in a distribution network. This paper develops an optimal power flow (OPF)-based DG capacity assessment approach that respects the local standard ANM schemes, particularly to control the grid-connected inverters. First, we investigate the effectiveness of different standard local ANM schemes on improving the DG capacity of distribution systems. We then compare them with the central approach that assumes a live, two-way communication infrastructure as an upper limit benchmark for the DG capacity. We use the proposed model to obtain the DG capacity of the three-phase IEEE 37-node and IEEE 906-node networks in the presence of different local and central ANM schemes. Our simulations show that real power based local control strategies are more effective than their reactive power based counterparts in improving the DG capacity of both networks. Additionally, in the voltage-constrained test system IEEE 906-node, the central approach enhances the network's DG capacity at least 25% more than local approaches.
2. Power Network Strength Analysis from a Time-Variant Perspective
The penetration of renewable energy sources brings environmental and economic benefits to the power system operation but could adversely affect the power network strength. Due to the dynamic characteristics of the load and renewable power generation, the power network strength varies throughout the day. This paper analyzes the short-circuit ratio and inertia of the network and highlights that the power network strength should be analyzed from a time-variant perspective. Based on the dynamic power network performance, two measures are introduced to enhance the power network strength: distributing synchronous generation sources over a wide geographical area and operating synchronous generators in close proximity to busbars with low short-circuit strength. A case study with the South Australia network confirms the time-variant nature of the power network strength and the effectiveness of the two measures.
3. Extended Secondary Control with Grid-Forming Inverters for Communication-Free Island Operation
To ensure communication-free island grid operation, an approach is needed which has been proposed in literature, consisting of a secondary control with grid-forming inverters and state machines implemented within smart meters. However, further extensions were found to be necessary to address some drawbacks of the presented approach. This publication introduces these extensions and presents the advantages, compared to the originally presented secondary control with grid-forming inverters by showing different RMS simulation cases which are carried out in PowerFactory.
4. Operation of Grid Boosters in Highly Loaded Transmission Grids
In this paper, grid booster operation in highly loaded grid situations is analyzed with respect to power system dynamics. The grid booster consists of fast reacting flexible power units, such as battery energy storage systems and offshore wind parks. Two study cases are simulated representing two highly loaded grid scenarios in the German transmission grid. The paper shows the impact of corrective congestion management with grid boosters on the dynamic stability in a large power system and highlights the importance of additional system services, e.g. providing additional dynamic reactive power reserve. In order to successfully perform a corrective congestion management action in a highly loaded grid scenario, grid boosters should also be considered to provide additional system services. Especially battery energy storage systems proof to be a promising technology for grid booster operations as they can provide different system services depending on the grid situation.
5. Influence of DC Network Structure on the Optimal Power Flow of Hybrid AC-DC Transmission Grids
This paper investigates the influence of various DC network configurations on the optimal operation of a hybrid AC-DC transmission grid with DC overlay network. An optimal power flow algorithm focusing on minimizing the losses in the system is developed considering various configurations of the DC overlay grid, connected with the high voltage direct current (HVDC) converters. It is observed that different DC network constructions lead to major changes in the power flow of the existing grid and a more meshed configuration could be potentially utilized for reducing the transmission losses for the AC network. Using a MATLAB based interior point solver, the optimal power flow method is validated for a 66 bus hybrid AC-DC transmission test system for three different stages of the DC network development.