Vol.:(0123456789) Energy Systems https://doi.org/10.1007/s12667-020-00378-9 1 3 ORIGINAL PAPER Static optimal load fow of combined heat and power system with valve point efect and prohibited operating zones using Krill Herd algorithm Pradosh Kumar Adhvaryyu 1  · Shreya Adhvaryyu 2 Received: 30 September 2019 / Accepted: 10 January 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Cogeneration of heat as well as electrical energy is an efcient and matured method which consumes less primary energy and reduces emission level signifcantly. In this process, heat production is reliant on power production and is restricted by the feasible operation region (FOR). This paper considered prohibited operating zones and valve point efect in its maiden formulation of static load fow problem of power system involving cogeneration units for maintaining voltage level of buses within specifed limits while satisfying other linear and non-linear constraints in order to make the production cost efective. Cost of production and transmission loss is opti- mized using Krill Herd algorithm. This algorithm is based on the foraging activities of individual Krill. The distance of Krill individual from food and the denser swarm constitutes the objective function. The efcacy of the algorithm is showed through results of two test systems. Both test systems have been adapted from IEEE 30 bus 6 generators standard test system. Keywords Optimal load fow · Valve point efect (VPE) · Prohibited operating zone (POZ) · Krill · Krill Herd algorithm (KHA) · Feasible operation region (FOR) Abbreviations CHP Combined heat and power (Power-MW; Heat-MWTh) TCT Tap changing transformer VPE Valve point efect POZ Prohibited operating zone KH Krill Herd POU Power only unit * Pradosh Kumar Adhvaryyu pka_03@yahoo.com 1 Siliguri Institute of Technology, Siliguri 734009, India 2 Electrical Engineering Department, NSHM Faculty of Engineering and Technology, Durgapur 713212, India