RLC passive damped LCL single-phase voltage source inverter with capability to operate in grid-connected and islanded mo
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ORIGINAL PAPER
RLC passive damped LCL single‑phase voltage source inverter with capability to operate in grid‑connected and islanded modes: design and control strategy José Carlos Ugaz Peña1 · Leonardo Poltronieri Sampaio2 · Moacyr Aureliano Gomes de Brito3 · Carlos Alberto Canesin1 Received: 19 February 2020 / Accepted: 15 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A design procedure for an RLC damping branch applied at a voltage source inverter followed by an LCL output filter is carried out in this paper. The main purpose of the proposed methodology is to allow the system to operate properly in both grid-connected (GC) and islanded (IS) modes with smooth transitions between them. The usage of passive damping methods to smooth the resonating filters effects is well known. However, the design procedure of the damping branch is specific for either the GC or IS mode, and usually, the parameters tuned for an operation mode are unsuitable for the other one. Thereby, this paper contributes to presenting a methodology design of an RLC branch aimed to achieve damping effect for both operation modes, thus allowing the continuous operation with no hazardous transients during transitions. By means of the proposed approach, the passive elements are adequately designed in order to provide easy controller synthesis. Therefore, a two-loop control strategy is adopted where the inner loop controls the capacitor voltage and ensures the system stability for both operation modes; meanwhile, an additional outer loop controls the grid current for GC mode allowing active and reactive power flows. Experimental results for a 2-kW prototype are presented in order to validate the proposed design methodology and control strategy. Keywords Power electronics · RLC damping branch · Grid-connected system · Islanded system · Single-phase voltage source inverter
1 Introduction Voltage source inverter (VSI) is the most common topology for the DC–AC conversion in a wide power range of electrical distributed generation (DG) system [1, 2]. In order to attenuate the harmonic content in the injected currents, filters are used between the converter and the grid. A simple first-order L filter gives only minus 20 dB/dec; thus, high * Moacyr Aureliano Gomes de Brito [email protected] 1
Power Electronics Laboratory, São Paulo State UniversityUNESP, Ilha Solteira, SP, Brazil
2
Federal University of Technology-Paraná-UTFPR, Cornélio Procópio, PR, Brazil
3
Department of Electrical Engineering – DEL, Federal University of Mato Grosso do Sul-UFMS, Cidade Universitária, Caixa Postal 549, s/n, Campo Grande, MS CEP 79070‑900, Brazil
inductance and/or high switching frequency are mandatory; moreover, this configuration is not suitable to regulate an intermediate output voltage for intentional islanding. On the other hand, an LCL filter gives 60 dB/dec of attenuation; thus, the overall reactive component size could be significantly reduced; however, the third-order system has a resonant behavior leading to fu
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