Abstract
Two parallel grid-connected inverters can increase system capacitance effectively. In order to exert maximum efficiency of parallel grid-connected inverters, an optimal power allocation (OPA) method is proposed. Firstly, the power model of every inverter is established. Compared with the equal power allocation (EPA) method, theoretically, higher overall system efficiency can be achieved with the OPA method. Secondly, the overall system efficiency can be calculated with easily measurable electric parameters, and the online optimization realized by adopting an existing method, such as the hill-climbing method. Lastly, the feasibility of the OPA method is verified by simulation and experimentation.
Highlights
Parallel connection techniques for inverters have been gaining increasing attention in motor drive, PV inverter, and distributed generation systems[1,2,3,4,5,6,7,8], due to the economy of design and the flexibility of maintenance
Since the same numerator of system efficiency exists with optimal power allocation (OPA) and equal power allocation (EPA), the relationship of system efficiency can be obtained by comparing the denominator of ηOPA with that of ηEPA
The overall system efficiency under OPA is higher than its counterpart under EPA
Summary
Parallel connection techniques for inverters have been gaining increasing attention in motor drive, PV inverter, and distributed generation systems[1,2,3,4,5,6,7,8], due to the economy of design and the flexibility of maintenance. In the study of parallel inverters, most existing control schemes focus on the circulating current problem. Circulating currents will make grid-connected currents distortional, increase the losses and decrease the efficiency of the system On this basis, many control schemes have been proposed and have made great achievements. In reference[10], the circulating currents can be reduced by adjusting the SVPWM zero vectors of the controllers in each paralleled converter Few of the existing documents take improving overall system efficiency into account For this reason, it is important to propose a control method to realize maximum system efficiency point tracking, such as reported in [18]. W. Jiang et al.: Optimal Power Allocation for Parallel Grid-Connected Inverters Based on Lagrangian Function Method 69.
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