Application of an optimal coordinated control strategy to VSC HVDC

International Journal of Electrical Power & Energy Systems

2015

International audienceThe HVDC links are increasingly used not only to interconnect asynchronous AC systems but are also embedded into a same meshed AC power system. Thanks to its speed and flexibility, the HVDC technology is able to provide transmission system advantages as transfer capacity enhancement and power flow control. In addition, studies have shown that the way of controlling the HVDC converters impacts the stability of the AC system. This can be particularly exploited to enhance the dynamic power system performances during transients. In this paper a robust multivariable control design for HVDC link converters is proposed. It is based on the coordination of the control actions of the HVDC converters and the use of a control model which takes into account the dynamics that mostly impact stability of the neighbor zone of the HVDC link. This new methodology was used to synthesize the controller for an actual grid 1000 MW HVDC link reinforcement project called ''Midi-Provence'' in the southern part of the French grid. The synthesis , implementation and validation processes are presented in detail. The new controller is tested in comparison with the standard vector control. A large-scale dynamic model of the whole European power system, currently used and updated by the European TSO's for the interconnection studies has been used with Eurostag simulation software. Ó 2015 Elsevier Ltd. All rights reserved. Introduction The HVDC link is a mean of transmission of electric power based on high power electronics. Thanks to its speed and flexibility, the HVDC technology is able to provide the transmission system advantages as transfer capacity enhancement and power flow control [1]. Initially, it was used in power systems to interconnect asyn-chronous AC systems. The ends of the HVDC link are electrically independent one from each other and this reduces significantly the propagation of perturbations between the two AC grids as it is the case of the England–France interconnection [2]. Nowadays, HVDC links are increasingly embedded into a same meshed AC system in order to enhance the grid's transmission capability and flexibility of the power system. In this context, the HVDC link co-exists with other AC system elements as for instance AC lines and generators. Several projects of insertion of this type of device in a meshed AC system are underway in Europe, as for instance France–Spain HVDC project [3], France–Italy interconnection and Midi-Provence HVDC project [4]. This latter is our case of study. In fact, a 1000 MW HVDC link will be inserted in France between the two areas Fos and Gaudière, in order to enhance capacity of power transmission and the stability of the Midi-Provence region. The need of such HVDC link is due to the fact that only one single 400 kV AC line interconnects the two areas (see Fig. 1). It was shown that the strategy used to control the HVDC converters can impact the stability of the system in which the link is embedded [5–12]. This conducted us develop a methodology which takes into accou...

Section: Solution Of the H ∞ Control Problemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multivariable control with grid objectives of an HVDC link embedded in a large-scale AC grid

International Journal of Electrical Power & Energy Systems

2015

“…In other methods, the transient stability is considered as an a priori objective for the synthesis of coordinated controllers for HVDC. Thus, the whole AC system is considered in the control model [21,22] but the effectiveness of these methods had not yet been studied in the case of large-scale power systems.…”

Section: Introductionmentioning

confidence: 99%

Control of high voltage direct current links with overall large‐scale grid objectives

IET Generation, Transmission & Distribution

2014

When a high voltage direct current (HVDC) link connects two distinct power systems, the latter are usually modelled by two infinite buses. However, in some context of use, the HVDC links are no longer separating two systems but they are embedded into meshed AC systems in parallel with other AC lines and interact with other elements of the power system. This led us to enhance the control objectives by considering stability requirements. In this context, the previous modeling assumption presents serious limitations. Instead, a more efficient control model is used. It is developed such that the concerned dynamics of the system are taken into account during the synthesis. It is shown how the controllers of the HVDC converters can be synthesised using the control model mentioned above such that global grid performances are ensured, in addition to the local objectives like power and DC voltage control. In order to avoid remote measures, an output feedback control which uses only local measures is developed. The new controller is tested in comparison with the standard vector control and a non-linear feedback linearisation control via simulation tests. The tests showed that the controller synthesised using the new control model contributes to a better coordination of the control actions and thus improve grid performances. In particular, the transient stability of the neighbour zone is a priori taken into account at the synthesis level.

“…Several controller schemes have been proposed to enhance the dynamic performances of the neighbor zone of the HVDC link. In , for instance, the control of the HVDC converters is developed on the base of the model of the whole power system, but this approach is not possible for large‐scale power systems. Indeed, the major difficulty encountered during the control law synthesis is the way to take into account the rest of the power system.…”

Section: Introductionmentioning

confidence: 99%

Robust grid-oriented control of high voltage DC links embedded in an AC transmission system

Int. J. Robust. Nonlinear Control

2015

SUMMARYSeveral studies have shown that the way to design controllers for the high-voltage direct current (HVDC) links impacts the transient behavior of the electric system in which the latter are inserted. This can be exploited to improve the performances of the stability of the power system. In this paper, a robust multivariable control design for the converters of an HVDC link is proposed. It is based on the coordination of the control actions of the HVDC converters and the use of a control model. The latter takes into consideration, in addition to the dynamics that mostly impact the stability of the neighbor zone of the HVDC link, several cases of faulted situations modeled as uncertainties. An H 1 controller allowed us to achieve robustness against such uncertainties. The new controller is tested in comparison with the standard vector control and an optimal linear quadratic controller using the EUROSTAG simulation software (Tractebel Engineering, Brussels, Belgium and Réseau de Transport d'Electricité (RTE) -France) on both academic and realistic large-scale power systems.