Capability chart for distributed reactive power resources

Abstract

Abstract-The ubiquity of synchronous generation should not be assumed in highly renewable power systems. Various problems may consequently arise: not least, the difficulties entailed in maintaining regional reactive power balance. Offering a potential solution to such problems, modern renewable generator technologies offer controllable reactive power resources. As many of these generators will be embedded in distribution networks, their incorporation into transmission system operational and planning activities appears challenging. An extension of the capability chart concept offers insight here: for a given active power exchange between the transmission system and a distribution network section, the range of controllable reactive power typically available is of interest. This aggregate capability depends on the innate machine capabilities of the distributed generators and on the prevailing conditions within the distribution network. Novel optimisation techniques are useful in addressing the latter point, offering a means to identify the combination of power flow profiles within the distribution system most restrictive to reactive power provision. The capability chart thus derived gives the dependable range of reactive power available, under the assumption that each generator is operated to locally maximise its own reactive power contribution. Such a description can be applied in transmission system planning, or to quantify the effects of modifications to the distribution system.

Voltage Responsive Distribution Networks: Comparing Autonomous and Centralized Solutions

“…Both methodologies draw on the ac optimal power flow tool first described in [17], in addition to previous enhancements given in [13] and [18]; taken together, these references elucidate the detailed model whose treatment here is somewhat abbreviated for brevity. Central to the tool are the power flow equations for π-equivalent medium length lines, supplemented by the essential bounding constraints on such variables as node voltages.…”

“…This approach builds on previous work by the authors; [13,14] quantified how voltage-controlling distributed generators can deliver reactive power to the transmission system, a capability demonstrated to be tangibly useful for system-wide voltage security in [7,15]; [16] shows how optimally-selected static power factor settings for distributed generators can substantially reduce draw-down of reactive power from the transmission network. This last reference concludes that enhanced static power factor settings can offer performance comparable to that available with a full smart grid scheme.…”

Information Gap Decision Theory-Based Congestion and Voltage Management in the Presence of Uncertain Wind Power

“…IGDT has been used in many fields of research, in [18] to assess the management of timber production and in [19] for the planning of water resources. This approach is also applicable to power system analysis [20][21][22][23] especially under severe uncertainty.…”

“…The reactive power capability chart of the DG units, illustrated in Fig. 1, closely mapping that of modern variable speed wind turbines is modeled with two symmetric sigmoid functions (23) and (24) for the lower and upper limits respectively. For active power generation, P G i,t , above 15% of the maximum capability, an inductive and capacitive limit for reactive power of 0.5 times the maximum active power generation is enforced.…”

Optimal allocation of wind generation subject to voltage stability constraints

“…Generator status matrix, ω s G , was built based on unit commitment carried for a range of loading conditions representing the study scenarios using the FAST unit commitment and dispatch tool [12]. Conventional generators were set to regulate voltage at their connection bus to 1 pu [13]. For the purpose of this study, wind farms allocated are required to inject power at unity power factor in all operating points.…”