TY - JOUR
T1 - Single-source multi-battery solar charger
T2 - Analysis and stability issues
AU - Kuperman, Alon
AU - Sitbon, Moshe
AU - Gadelovits, Shlomo
AU - Averbukh, Moshe
AU - Suntio, Teuvo
PY - 2015
Y1 - 2015
N2 - 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.
AB - 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.
KW - Battery charging
KW - Input voltage control
KW - Photovoltaic converters
KW - Small-signal modeling
KW - Stability assessment
UR - http://www.scopus.com/inward/record.url?scp=84939185867&partnerID=8YFLogxK
U2 - 10.3390/en8076427
DO - 10.3390/en8076427
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AN - SCOPUS:84939185867
SN - 1996-1073
VL - 8
SP - 6427
EP - 6450
JO - Energies
JF - Energies
IS - 7
ER -