Datta, Ujjwal (2020) Battery Energy Storage System for Renewable Energy Integrated Power System Stability Enhancement. PhD thesis, Victoria University.

Abstract

With growing environmental concerns and sustainability movements, renewable energy source (RES) penetration is increasing and expected to have a steady growth in the coming years. Power systems have encountered several inherent technical challenges, resulting from either low inertia contribution by the increased RES or the displacement of fossil fuel generation systems within the network. The decreased system inertia and the decline in power reserve capacity are affecting the dynamic and transient stability performance of the power system adversely and this adverse impact will continue to increase due to further RES penetration in electric power systems. In this context, this thesis contributes new knowledge to the modelling of droop controlled BESS for enhancing damping capability and transient stability of large-scale power networks with different level of RES penetration. The BESS with conventional Proportional Integral (PI), and two new PI-lead and lead-lag controlled BESS with coordinated charge control are given wider attention. In the initial stage, a wind farm is designed to perform frequency control in a microgrid. A sectional droop gain method is adopted for regulating doubly fed induction generation (DFIG) power output. It is observed that the proposed multi-gain droop control method demonstrates superior performance than the conventional approach. However, DFIG has a certain limit of providing under-frequency support as a result of inherent incapability of regulating incoming wind speed. Hence, a more reliable energy source is required to secure the stability of the system. Realizing these facts, comprehensive simulation studies have been carried out to explore various RES penetration level and dynamic response capability of the system undergoing multiple contingencies. Simulation results demonstrate that generator control and system loading conditions have significant impact on damping capability in primary frequency control. However, results with active power regulated BESS exhibit its effectiveness in enhancing primary frequency controllability of the system regardless of generator control and system loading conditions in power grid as RES penetration increases. Furthermore, a new state of charge (SOC) adaptive charging strategy is proposed for recovering battery SOC to ensure BESS reliability against future contingencies. The new adaptive SOC strategy defines separate levels of SOC charging limit than that of the maximum SOC limit to ensure sufficient SOC excursion for over-frequency events. In the next stage, a droop controlled BESS is modelled and investigated to control simultaneous voltage and frequency responses of the system by regulating its active and reactive power independently. The performance of BESS is compared with the state- of-the-art technology Static Compensator (STATCOM), while the system is exporting a large amount of power across the network under various contingency studies. It is shown via simulation studies that STATCOM fails to secure voltage and frequency stability of the system in the occurrence of a single or multiple adjacent faults. On the contrary, the incorporated BESS with active and reactive regulating capability remains successful in maintaining the stability of the power system. Also, lead-lag controlled BESS has demonstrated improved performance than PI and PI-lead controlled BESS. In the final stage of research, the effectiveness of BESS in a charging station is explored to avoid transformer overloading, provide PV smoothing and to increase the charging capacity of the station. Simulation studies showed that BESS can effectively reduce transformer overloading and as a result it prolongs its lifespan and provide grid services when charging station has no load demand.

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