Operational planning and optimisation in active distribution networks using modern intelligent power flow controllers

Abstract

In this paper, a centralised control framework is introduced for day-ahead operational planning of active distribution networks which accommodate high levels of distributed generation resources. The purpose of the framework is to plan network operation in order to minimise power curtailment from distributed generation and maintaining acceptable levels of voltage regulation throughout the network. For this purpose, both power flow control and rapid network reconfiguration have been considered as various acceptable levels of control available to the network operator to provide required levels of operational flexibility. The power flow control within the network is promised by the application of fully controlled back-back voltage source converters placed in key points (both normally-open and normally-close) in the network. Meanwhile, the network reconfiguration constraints guarantee that radial topology is always maintained in order to avoid tremendous changes in the protection system coordination. The operation of a modified 33-bus system exemplar is analysed in three case studies namely, passive network (base case), active network using remote-controlled switches and active network using intelligent power converters. Results show a significant saving in terms of operational costs as well as transmission losses in active cases despite the radial constraint condition in place.

A simplified algorithm to solve optimal power flows in hybrid VSC-based AC/DC systems

“…Type-2 steady-state models for hybrid VSC-based AC/DC systems were proposed in [3], [22], [24], [44] and have been used to incorporate models of STATCOMs [23], point-to-point [3], back-to-back [17] and multi-terminal [3] VSC-HVDC systems into OPF problems.…”

“…Converter losses are prepresented by a variable shunt conductance (see Fig. 3b) proportional to the square of the AC current of the VSC (G sw,i ) [17], [22], [23]:…”

“…The work in [3]- [5], [7], [9], [11] presented the guidelines for modelling VSC-HVDC multi-terminal systems (VSC-MTDC, for short) in OPF problems. Those algorithms have been used succesfully for a wide range of applications in VSC-based AC/DC systems, such as minimisation of generation costs [3], [4], [14], minimisation of system losses [5], [11], [15], analysis of different objective functions [9], cost-benefit analysis of VSC-MTDC installations with different topologies [7], optimal operation in multi-area systems with different TSOs [8], [10], [16], analysis of the impact of VSC losses on OPF solutions [13] and optimisation in active distribution grids [17], among others. Meanwhile, several security-constrained OPF models for hybrid AC/DC systems were proposed in [6], [12], [18]- [21].…”

“…Regarding the modelling approach used, OPF algorithms for hybrid AC/DC systems published so far can be classified into two types, that will be referred in this paper as type-1 [4]- [14] and type-2 [3], [17], [22]- [24] models. Both approaches differ in the way in which VSC stations and DC grids are modelled.…”

“…Although the formulation of OPF problems in hybrid AC/DC systems been reported in the literature [3]- [14], [17], [23], the implementation of either type 1 or type 2 models in only-AC OPF tools is often troublesome (or even impossible) due to lack of flexibility in those tools.…”