Single-Source Multi-Battery Solar Charger: Analysis and Stability Issues

Alon Kuperman, Moshe Sitbon, Shlomo Gadelovits, Moshe Averbukh and Teuvo Suntio
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Alon Kuperman: Department of Electrical Engineering and Electronics, Ariel University, Ariel 40700, Israel
Moshe Sitbon: Department of Electrical Engineering and Electronics, Ariel University, Ariel 40700, Israel
Shlomo Gadelovits: Department of Electrical Engineering and Electronics, Ariel University, Ariel 40700, Israel
Moshe Averbukh: Department of Electrical Engineering and Electronics, Ariel University, Ariel 40700, Israel
Teuvo Suntio: Department of Electrical Engineering, Tampere University of Technology, Tampere FI-33101, Finland

Energies, 2015, vol. 8, issue 7, 1-24

Abstract: In this paper, dynamic analysis of a multi-battery dual mode charger, powered by a single solar array and suitable for lead-acid and lithium-ion cell-based batteries is presented. Each battery is interfaced to the solar array by means of a current-controlled buck power stage, operating either in constant power or constant voltage mode. Operation in former/latter charging mode implies regulating input/output voltage of the converter, which is a non-trivial situation since while feeding different batteries, all the converters share the same input terminals, connected to the solar array. It is revealed that when at least one of the batteries operates in constant power charging mode, open-loop instability occurs whenever converter input voltage is lower than maximum power point voltage of the solar array. Consequently, input voltage regulating controller must be designed to stabilize closed-loop dynamics for the worst case of instability, which is also derived. Moreover, it is shown that the dynamics of the converters operating under output voltage control are perceived as disturbances by input voltage control loop and must be properly rejected. Simple loop shaping design is proposed based on a PI controller, allowing stabilizing the system in case of worst case instability and rejecting output voltage control induced disturbances at the expense of non-constant, operating-point dependent closed-loop damping.

Keywords: battery charging; photovoltaic converters; small-signal modeling; input voltage control; stability assessment (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2015
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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