Search

This paper presents the modelling and design steps of a digital proportional multi-resonant controller used in a grid-connected photovoltaic (PV) system. It is shown that the use of only one Proportional-Resonant (PR) compensator, tuned to the system fundamental frequency, may have its effectiveness compromised due to nonlinearities in the system components. To overcome this drawback and improve the system's output current waveform, a multi-resonant controller is introduced. The performance of the discrete-time designed controller is tested on a grid-connected photovoltaic power plant. Experimental results obtained with the operation of a 30 kWp PV system connected to a distribution network, using only the leakage inductances of a connection transformer as passive filter are presented and discussed to demonstrate the performance of the designed control strategy.

This paper presents the modelling and design steps of a digital proportional multi-resonant controller used in a grid-connected photovoltaic (PV) system. It is shown that the use of only one Proportional-Resonant (PR) compensator, tuned to the system fundamental frequency, may have its effectiveness compromised due to nonlinearities in the system components. To overcome this drawback and improve the system's output current waveform, a multi-resonant controller is introduced. The performance of the discrete-time designed controller is tested on a grid-connected photovoltaic power plant. Experimental results obtained with the operation of a 30 kWp PV system connected to a distribution network, using only the leakage inductances of a connection transformer as passive filter are presented and discussed to demonstrate the performance of the designed control strategy.

An expansion is planned for the underground operation at Caraiba copper mine to extend its life beyond 1998. Extension to 2003 is envisaged exploiting a mineable reserve of 6 000 000 tons of ore, or, with backfilling, extension to 2006 with a mineable reserve of 10 500 000 tons. Exploitation of reserves beneath the currently-worked panel will involve the use of drilling and blasting with large diameter holes and of vertical crater retreat methods, with access and extraction via a new ramp. The choice from amongst alternative expansion plans and mining methods, analysis of requirements for equipment, manpower and associated investment and operating costs, and analysis of cash flow, are presented., An expansion is planned for the underground operation at Caraiba copper mine to extend its life beyond 1998. Extension to 2003 is envisaged exploiting a mineable reserve of 6 000 000 tons of ore, or, with backfilling, extension to 2006 with a mineable reserve of 10 500 000 tons. Exploitation of reserves beneath the currently-worked panel will involve the use of drilling and blasting with large diameter holes and of vertical crater retreat methods, with access and extraction via a new ramp. The choice from amongst alternative expansion plans and mining methods, analysis of requirements for equipment, manpower and associated investment and operating costs, and analysis of cash flow, are presented.

The deposit is a Lower Proterozoic sill consisting of magnetite-bearing hypersthenites, melanorites and norites with disseminated chalcopyrite and bornite mineralisation, the largest of hundreds of mafic-ultramafic bodies in the Curaca Valley high-grade metamorphic terrane. It forms a N-S-trending, tightly isoclinal and asymmetric F3 synform, with 1 000 m amplitude and axial plane dipping W at 70-75 degrees, in the western limb of a normal regional antiform. The interference pattern of F3 with E-W-trending F2 folds gives the deposit a 5 km long and 800 m wide mushroom shape. Brittle fracturing and boudinage disrupted the orebody throughout its structural evolution, so mine planning and underground exploitation are difficult in parts of the mine. Because the orebody acted as a barrier to the intense, ductile and melt-assisted D3 event, it has preserved evidence for the earlier structural history of the terrane., The deposit is a Lower Proterozoic sill consisting of magnetite-bearing hypersthenites, melanorites and norites with disseminated chalcopyrite and bornite mineralisation, the largest of hundreds of mafic-ultramafic bodies in the Curaca Valley high-grade metamorphic terrane. It forms a N-S-trending, tightly isoclinal and asymmetric F3 synform, with 1 000 m amplitude and axial plane dipping W at 70-75 degrees, in the western limb of a normal regional antiform. The interference pattern of F3 with E-W-trending F2 folds gives the deposit a 5 km long and 800 m wide mushroom shape. Brittle fracturing and boudinage disrupted the orebody throughout its structural evolution, so mine planning and underground exploitation are difficult in parts of the mine. Because the orebody acted as a barrier to the intense, ductile and melt-assisted D3 event, it has preserved evidence for the earlier structural history of the terrane.