Islanded Operation of Wind Turbine with Solar Power and Battery Storage - A Power-Balance-Oriented Energy Management Approach

Abstract

This thesis studies the monitoring and control of an islanded hybrid power system composed of a wind turbine, photovoltaic generation, a battery energy storage system, and local load demand. The motivation of the study is that when the system operates without the continuous support of the external power grid, it needs to coordinate local power generation and energy storage. Therefore, the research focuses on the analysis of active power balance, battery dispatch, wind-power curtailment, load shedding and wind turbine response under islanded operating conditions. A layered modelling strategy is used in MATLAB/Simulink. The inherited windturbine model is kept as the wind-side technical basis, and the main work of this thesis is to build and connect an Energy Management System (EMS) around it. The EMS takes the realised wind-turbine output, an equivalent AC-side photovoltaic active-power contribution, load demand, and battery state of charge as inputs. It then calculates the battery-power reference, the constrained battery response, the residual mismatch quantities, the wind-curtailment request, and the load-shedding request. In this work, the available wind-power estimate and the realised simulated wind-turbine output are not treated as the same signal. The available wind-power signal is used as a wind-side availability reference, while the realised wind-turbine output is the simulated power after the turbine dynamics and, when it is active, the wind-spill and blade-pitch action. An important implementation point is that the EMS curtailment request is sent to the inherited wind-spill input as a spilling-power command. Therefore, curtailment is represented through the turbine-side control path, rather than by directly subtracting power from the wind-power signal. In the short-term integrated simulation, the EMS response is analysed together with the simulated blade-pitch response, the wind-spill command, and the realised wind-turbine power. The results show a change from an initial deficit condition to a surplus condition. After this change, the battery charging becomes constrained, residual surplus is formed, the wind-spill request is activated, and the realised simulated wind-turbine output is reduced. A complementary long-term EMS/BESS simulation is performed over an 1800 s horizon using prescribed wind, PV, and load input profiles. The battery-power reference, constrained battery power, SOC evolution, original and residual mismatch quantities, and corrective-action requests are analysed as simulation outputs of the developed supervisory controller. The long-term results show that the battery first absorbs renewable surplus within its implemented charging and SOC constraints, while remaining residual surplus is assigned to wind-power curtailment. An additional deficit-dominated EMS-level case is included to verify the load-shedding branch of the supervisory controller. In this case, an imposed high-load interval produces a power deficit that exceeds the allowable battery discharge response. The battery first supplies power within its implemented limit, after which the remaining residual deficit is converted into a load-shedding request. This case complements the surplus-dominated long-term case and confirms the intended priority order of the EMS under both surplus and deficit conditions. This thesis shows that the developed supervisory structure provides a useful simulation framework for the operation of an islanded wind-solar-battery system. The study clarifies the difference between prescribed operating inputs, inherited windmodel quantities, and simulated EMS/BESS outputs; it also gives a basis for future work on more detailed converter-level implementation, improved battery modelling, and wider islanded microgrid studies.