University of South Wales Master of Sciences Thesis
Standalone hybrid generation system for the remote area of Thar, Pakistan
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Standalone hybrid generation system for the remote area of Thar, Pakistan Figure 2.23 General block diagram of typical DE power electronic systems The design of the input converter module depends on the specific energy source or storage application. The DE systems that generate AC output, often with variable frequencies, such as wind, micro-turbine, IC engine, or flywheel storage needs an AC-DC converter. For DC output systems like PV, fuel cells, or batteries, a DC-DC converter is typically needed to change the DC voltage level. The DC-AC inverter module is the most generic of the modules and converts a DC source to grid- compatible AC power. The output interface module filters the AC output from the inverter and the monitoring and control module operates the interface, containing protection for the DE and utility point-of-common-coupling (PCC). The monitoring and control module also contains protective functions for the DE system and the local electric power system that permit paralleling and disconnection from the electric power system. Monitoring functions typically include real-power, reactive power, and voltage monitoring at the point of the DE connection with the utility at the PCC. These functions are necessary because, in order to synchronize the DE system, its output must have the same voltage magnitude, frequency, phase rotation, and phase angle as the utility. Synchronization is the act of checking that these four variables are within an acceptable range before paralleling two energy sources. In general, the term “power electronics” refers to the device switches (e.g., IGBT and SCR), and the various modules that they comprise. In power applications, these devices are most often used to convert electrical energy from one form to a more usable form. Benefits of power electronic devices include increased efficiency, lower cost, and reduced packaging size. A rectifier is a power electronics topology that converts AC to DC. Rectifier circuits are generally used to generate a controlled DC voltage from either an uncontrolled AC source (i.e., micro-turbine, wind turbine) or a controlled AC source (i.e., utility supply) (Kroposki et al. 2006). When converting from a utility supply, a rectifier application is usually for linking DC systems or providing DC voltage for specific load applications such as battery regulators and variable frequency drive (VFD) inputs. Some DE systems like photovoltaic and fuel cells produce DC power. In order to make this power useful for other applications, it must be converted to AC; therefore, inverters are used to convert DC to AC. Inverter circuits generate a regulated AC supply from a DC input. They are commonly found in systems providing standalone AC power, utility-connected DE systems, and on the motor side of a VFD. There are a number of applications for DC-to-DC systems. These systems are used to convert the DC voltage magnitude from one level to another with or without galvanic isolation. They take an uncontrolled, unregulated input DC voltage and condition it for the specific load application. An |