The proliferation of matrix converter interfaces coupled with traditional loads produces nonstandard and high-frequency harmonics in the range of (2 to 150) kHz in the power system. Although several research works have been conducted on passive and active filter solutions, most of these are low-frequency (below 2 kHz) solutions and are not effective under supraharmonic frequencies. An experimental study of a fuzzy-inference-system-controlled hybrid active power filter (HAPF) for the attenuation of higher frequency harmonics (above 8 kHz) is proposed. The compensational approach introduced is different from traditional approaches and the use of the fuzzy logic controller eliminates complexities involved in active filter designs. The proposed filter obtained a total harmonic distortion (THD) of 1.16% of the fundamental 50 Hz supply frequency. The performance of the proposed hybrid filter was compared with that of the proportional and integral (PI) controlled topology. The results obtained indicated superior performance of the fuzzy logic controller over the PI in terms of compensational speed, accuracy, the THD of the supply current and the overall integrity of the matrix converter. Illustrative design blocks and simulation in MATLAB/Simulink environment are provided to buttress these findings.

A numerical study on the creep damage in soldered interconnects in c-Si solar photovoltaic cells has been conducted using equivalent creep strain, accumulated creep strain and accumulated creep energy density methods. The study used data from outdoor weathering of photovoltaic (PV) modules over a three-year period (2012–2014) to produce temperature cycle profiles that served as thermal loads and boundary conditions for the investigation of the soldered interconnects’ thermo-mechanical response when exposed to real-world conditions. A test region average (TRA) temperature cycle determined in a previous study for the 2012–2014 data was also used. The appropriate constitutive models of constituent materials forming a typical solar cell were utilized to generate accurate material responses to evaluate the damage from the thermal cycles. This study modeled two forms of soldered interconnections: Sn60Pb40 (SnPb) and Sn3.8Ag0.7Cu (Pb-free). The results of the damage analysis of the interconnections generated from the thermal cycle loads using accumulated creep strain method showed that the Pb-free solder interconnection recorded greater damage than that of the SnPb-solder interconnection for the TRA, 2012, 2013 and 2014 temperature cycles. The percentage changes from SnPb to Pb-free were 57.96%, 43.61%, 44.87% and 45.43%, respectively. This shows significant damage to the Pb-free solder under the TRA conditions. Results from the accumulated creep energy density (ACED) method showed a percentage change of 71.4% (from 1.3573 × 10⁵ J/mm³ to 2.3275 × 10⁵ J/mm³) in accumulated creep energy density by replacing SnPb-solder with Pb-free solder interconnection during the TRA thermal cycle. At the KNUST test site in Kumasi, Ghana, the findings show that Sn60Pb40 solder interconnections are likely to be more reliable than Pb-free solder interconnections. The systematic technique employed in this study would be useful to the thermo-mechanical reliability research community. The study also provides useful information to PV design and manufacturing engineers for the design of robust PV modules.

Interconnecting power transmission systems provide reliability of electric power supply. The security of the system is however questioned when a disturbance in any part of the interconnected system causes instability in the entire network. Unified Power Flow Controller (UPFC), which is a member of the flexible alternating current transmission system (FACTS) family, has the capability of controlling active and reactive power flow in a transmission line thereby improving the voltage stability of the system especially at the 500 kV configuration level. The performance of a 161-kV UPFC modelled in SimPowerSystems is tested on Ghana’s power transmission network. The optimal placement of the UPFC is done using fast voltage stability index (FVSI) and maximum loadability assessment (MLA). The results show that the device improved the connecting bus voltage from 0.88 p.u. to 0.98 p.u. Active power loss in the network was also reduced from 13.40 MW to 10.39 MW when the UPFC was in circuit.Keywords: Ghana, Stability, Transmission system and Unified Power Flow Controller (UPFC)