A simple control strategy to increase the total efficiency of multi-converter systems

Abstract

Abstract-This paper presents a simple control strategy that is employed together with an optimization methodology to achieve optimal efficiency in systems composed by multiple parallel converters. An external loop is responsible for regulating the dc bus voltage and providing a current reference that is weighted in function of the power processed by the system, and then generating optimal current references for each converter. This enable the system to operate with optimal efficiency for all its load range. Experimental results demonstrate the superior performance of the proposed strategy, improving the efficiency of the system in almost 10 % under light load operation in comparison with the conventional strategy of equal power sharing among converters.

A Method to Enhance the Global Efficiency of High-Power Photovoltaic Inverters Connected in Parallel

“…Dupont [20] indicates that the efficiency of power inverters can be approximated by the second order function (2), being α 1 , α 0 , β 1 , and β 0 coefficients that can be obtained by applying curve fitting algorithms over experimental measurements and c is the load factor of the inverter.…”

“…The algorithm is initially based on the calculation of the local maxima by applying the second derivative test to the function that predicts the efficiency of the whole system, eff (c i , v in ). This function (20) computes the efficiency of the whole system starting from the efficiency of each one of the modules, η(c i , v in ) that can be obtained by means of one of the functional models that were described in the previous section. In (20), c i (i = 1, 2, .…”

“…This function (20) computes the efficiency of the whole system starting from the efficiency of each one of the modules, η(c i , v in ) that can be obtained by means of one of the functional models that were described in the previous section. In (20), c i (i = 1, 2, . .…”

“…Finally, if H in a critical point is negative definite, that critical point is a local maximum. Therefore, the optimal load factor for each one of the modules on stream that maximizes the global efficiency can be obtained by solving (20) and ( 21) for a certain operating point described by both the DC voltage and the supplied power. It is worth pointing out that the second derivative test does not calculate the maxima points when some of c i = 0.…”

“…These models can be classified as unidimensional and bidimensional, depending on whether they only take into account the generated power, or if they consider both the power generation and the DC voltage at the input of the inverter. Some unidimensional and bidimensional models were studied in [17][18][19][20][21][22][23][24][25].…”