This paper analyses, the effect of the phase locked loop (PLL) controller in the stability of the voltage source converter(VSC) in a microgrid or when connected to a weak AC grid. While designing the controller for PLL, it may not be possible to consider the effect of the load and line impedance as they are not readily known. In a microgrid or in a weak grid, the dynamics of the PLL are affected due to the high impedance nature of the network. A small signal model is built to show how the PLL controller affects the stability of the VSC. A comparison is made between proportional (P) and proportionalintegral (PI) controller, using detailed time domain simulation in PSCAD/EMTDC to demonstrate this problem.
This paper proposes a simple indicator based phase lock loop (PLL) which is capable of producing distortionless reference waveforms in case of the presence of unbalance and harmonics in the grid. The proposed configuration also has a faster dynamic response thus catering to phase jumps as well. Unlike the existing research works, this proposal doesnt make use of filtering, signal modifications or advanced algorithms. The simplest form of synchronous reference frame (SRF) PLL is retained and effectively made use of in the simplest way to achieve the objectives. The proposed concept makes use of the idea of controlling the instantaneous acceleration between the point of common coupling (PCC) space vector and the existing d−q frame by adding the error to the PLL. This addition is activated or disabled depending on the conditions like phase jump, unbalance and harmonics leading to the acceleration. Separate algorithms indicate the condition. The proposed concept is validated with sufficient simulation results.
This paper presents the concept of electronic battery (e-Battery) for energy storage systems. The proposed e-Battery is a combination of ultra capacitor bank and power electronic converters. This paper looks at issues related to chemical batteries and proposes the concept of an e-Battery. The proposed e-Battery overcomes many of the drawbacks of a conventional chemical battery. The control strategy developed for the closed loop operation of the proposed e-Battery is also presented in this paper. The performance of the proposed e-Battery is verified through detailed time domain simulation in PSCAD/EMTDC. A hardware prototype is built to validate the performance of the proposed e-Battery experimentally.
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