A NEW APPROACH FOR SEMI-AUTOMATED MEASUREMENT OF PV INVERTERS, ESPECIALLY MPPTRACKING EFFICIENCY, USING A LINEAR PV ARRAY SIMULATOR WITH HIGH STABILITY

摘要

HTI Burgdorf's PV laboratory has carried out many tests with small grid-connected PV-inverters since 1988.At first the size of the available PV generator was 3 kWp, then since 1994 60kWp. A significant extension of the testing facilitieswas possible with the introduction of suitable PV array simulators. Several linear PV generator simulators up to 25kWwith high stability and fast transient response were developed in 1998 to 2000. In 2002 and 2003, a significant improvementof the measuring software was realised which makes possible semi-automated tests of PV inverters including the measurementof MPP-tracking efficiency. Only with such semi-automated tests it is possible to perform extended inverter testsunder many different operating conditions (e.g. for different DC voltages and on I-V-curves with different fill-factors andshapes) in a reasonable time. Measurement of MPP-tracking efficiency is quite difficult and requires a PV array simulator ofhigh stability and no interaction with the inverter to be tested. In this paper, a new method of extracting MPP-power directlyfrom the measured data points is presented. In many cases, this method allows automatic determination of static and dynamicMPPT-efficiency with no need for time-consuming separate MPP-measurements on each power level with external devices.