Investigating the stability of phase-locked loop in network-connected applications affected by microgrid-side and network-side parameters

Abstract

In most today's power systems, microgrids are connected to the network through a grid-interface converter. In these converters, the phase-locked loop (PLL) is the most popular technique for network synchronization. This paper investigates the dynamic performance and the stability of synchronous reference frame PLL influenced by various factors. These factors include the network-side and microgrid-side parameters. Similar to the effect of networkside factors, the effect of microgrid components also plays an important role in the stability of the PLL. Given that the stability of PLL affected by microgrid-side parameters have not been studied yet, so in this article, after a detailed analytical modeling of microgrid components (including the production power fluctuations, energy storage system, microgrid-side loads, and controller parameters), the stability of PLL affected by different microgrid-side parameters has been evaluated. In addition, with the aim of achieving a criterion for the assessment of PLL stability, also, based on the proposed criterion, the rate of exchanged output power is determined for the grid-interface converter with the aim of guaranteeing the stability of PLL. KEYWORDS analytical modeling, grid-interface converter, microgrid, network-side and microgrid-side parameters, phase-locked loop stability, proposed PLL stability criteria List of symbols and abbreviations: R L1 , The equivalent resistance of power losses related to the switches of supercapacitor converter; R L2 , The equivalent resistance of power losses related to the switches of battery converter; φ net , The phase created by the existence of the network and load impedances in network frequency; φ P , The phase created by the existence of the network and load impedances in output Frequency of PLL; C eq , The equivalent capacitance of DC bus; C sc , The equivalent capacity of supercapacitor; R p , The equivalent parallel resistance of supercapacitor; R s , The equivalent series resistance of supercapacitors; u sc , The supercapacitor voltage; u b , The battery voltage; i sc , The supercapacitor current; i b , The battery current; L 22 , The inductance of output filter of supercapacitor converter; L 11 , The inductance of output filter of battery converter; d 2 , The duty cycle of supercapacitor converter; d 1 , The duty cycle of battery converter; Z LL , The local load impedance; Z net , The network impedance; u net , The network voltage; i Gl , Differences between the current of consumable load and the current produced by distributed generation sources; τ 1 , The time constant of low-pass filter; τ 2 , The time constant of band-pass filter; I * l1d , d-component reference current of grid-interface converter; i l1d , dcomponent instantaneous current of grid-interface converter; I * l1q , The component reference current of grid-interface converter; i l1q , The component instantaneous current of grid-interface converter; d d , The d-component duty cycle of grid-interface converter; d q , The q-component duty cycle of grid-interface co...

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