Abstract
The increasing penetration of PhotoVoltaic (PV) generation has a significant impact on the transient stability of power systems. Power electronics interface, control strategies and lack of inherent rotational element are the main factors that distinguish PV generation from conventional synchronous machine-based generation. In addition, the time constants of the PV control loops and Phase Locked Loop (PLL) are of the same order unlike the synchronous generators. The conventional equal area criterion based stability analysis is not applicable for PV generators with DC-link voltage and reactive power control. The transient stability analysis of power system with PV generation is not well explored in the literature. This paper proposes a criterion to assess the transient stability of a grid connected VSC-based PV generator with DC-link voltage and reactive power control. The PV generator is equipped with Low Voltage Ride Through (LVRT) capability, voltage and frequency support functionalities. The grid is modelled as a Synchronous Machine (SM) with finite inertia. The transient stability is assessed considering the dc link capacitor, outer and inner PV controls, PLL and grid dynamics. The proposed criterion is derived using two nonlinear functions and the Voltage Support (VS) signal of PV generator. The proposed criterion is applicable to all types of short-circuit faults with/without fault resistance. The criterion is validated through time-domain simulations. The Critical Clearing Time (CCT) calculated using the proposed criterion matches with the CCT obtained from time-domain simulations.
Highlights
The goal to generate electricity by harnessing Renewable Energy (RE) sources has led to a new paradigm in power systems [1]
The SP-Synchronous Machine (SM) system shown in Fig. 1 is considered to verify the proposed transient stability assessment criterion
The result of the criterion is verified through time-domain simulations carried out using PSCAD software
Summary
The goal to generate electricity by harnessing Renewable Energy (RE) sources has led to a new paradigm in power systems [1]. The energy conversion technology (solar/ wind to electrical) and the power electronic interface are the main factors that differentiate RE generators from Synchronous Generators (SG). Even though the power electronics offer a better control over the generated electrical energy, they bring new challenges to power system stability [2]–[4]. The RE generators’ dynamics have to be analyzed in detail to ensure a reliable operation of power grid. In this aspect, steady-state, small-signal and transient stability analysis are important. This paper focuses on the transient stability analysis of power systems with PV generator
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