In this paper, a brief review is presented of common electrical generation schemes for wind turbines (WTs) and photovoltaics (PVs). Attention is mainly focused on the power converter interfaces used for the grid connected operation of the renewable generators. The WT soft starting arrangements are described and the most common variable speed operation configurations are presented and discussed. The fundamental characteristics and requirements of the power conditioning equipment used in PVs are outlined and the power converters of certain PV generators are briefly presented.

Use of power electronic converters in wind turbines and photovoltaic generators

The most complex and most vulnerable component in a photovoltaic system is the inverter. Its quality influences the efficiency and reliability and thus the economy of the total PV system in a high degree. For optimal system design, it is therefore important to know exactly the inverters attributes of which the most important is efficiency in the whole power range a PV system operates. For precise efficiency measurements the specific conditions around the inverter have to be taken into consideration which are mainly: input ripple in current resp. voltage, non-sinusoidal inverter output and variable power factor. It is therefore important to use only instrumentation which is able to cope with these boundary conditions. The basic measurement scheme is given in Figure 1. The most critical aspect is that current and voltage may not be in phase at the inverters inand output. Power measurements are therefore only valid, if current and voltage are multiplied instantaneously (multiplication of mean effective-values may lead to substantial faults). This can be done by using fast electronic equipment working with sample(and multiplying) rates above 10 KHz or with analogous instruments. Integrating instruments of this type are the well-known

Recommendations for Measurements on Inverters for Photovoltaic Applications

A classification system is presented for stand-alone and utility-interactive dc-to-ac inverters used in photovoltaic systems in the 1-to-100-kVA power range. Additional inverter topologies, noted during the classification process, are introduced. To provide background, generally used dc-to-ac inversion technology is reviewed. Relative merits and liabilities of available power devices are discussed and device protective techniques are reviewed. Maximum power point tracking can enhance system value in utility-interactive no-battery photovoltaic power systems. This general theory is reviewed and an improved implementation is described.

E.E. Landsman

Papers

Classification and technical review of dc-ac inverters for use in photovoltaic power systems