*1.2. Proposed Solution*

To remedy the issue of higher flexibility requirements of modern and future power networks, more sustainable methods of renewable integration are required. This paper proposes a hybrid PV and ternary PSH (TPSH) combination and designs controls for the same to ensure that the PV system and the TPSH system work in a coordinated manner to cater to the network requirements and to suppress internal disturbances. The proposed system controls can be decomposed into three parts: (a) hybrid plant control, (b) PV plant control, and (c) TPSH plant control. These are detailed in this paper.

Resilience is enhanced by fast responses of the PV converter systems and flexibility of the pump mode with hydraulic short-circuit (HSC) of the TPSH. Reliability is provided through the firming capability of TPSH in pump mode using the HSC. Using the HSC, the TPSH firms the irradiance-based PV disturbances within operational constraints.

**Citation:** Nag, S.; Lee, K.Y. Neural Network-Based Control for Hybrid PV and Ternary Pumped-Storage Hydro Plants. *Energies* **2021**, *14*, 4397. https://doi.org/10.3390/en14154397

Academic Editors: John M. Cimbala and Bryan J. Lewis

Received: 25 June 2021 Accepted: 15 July 2021 Published: 21 July 2021

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When used in a collocated manner with the PV plant, the TPSH aids in firming and shifting PV generation. To firm PV generation is to make constant the power generated from the PV plant by absorbing the excess and supplying the deficit. Shifting PV generation is to absorb the excess and supply the absorbed during peak hours. The key strategy is to utilize the HSC of the TPSH to firm the PV system during the entire day while also storing energy. This stored energy is then used during the peak hours of the day using generation mode of TPSH. This provides an option for avoiding curtailment. Since both PV and TPSH are collocated, the transmission losses while pumping are negligible. The controls for the PV plant enable it to compensate for the nonlinearities of the hydro plant and enhance its response.
