Finland: Efficient Grid Interconnection and Power Conditioning for CHP Systems

Combined heat and power (CHP) systems are very popular in high-rise buildings as well as industrial sites and other facilities where they produce heat and power at a reasonable cost. CHP systems can save as much as 40% energy compared with traditional ways of producing electricity and heat separately.

How can you save even more? And simultaneously increase the reliability and safety of onsite energy production and grid interconnection? There are a couple of rather easy ways to improve overall efficiency.

The answer is to start with a variable speed genset (VSG) drive train, VSG converter and permanent magnet generator (PMG) for grid interconnection and power conditioning. Beyond the savings, a VSG provides tools for power conditioning and fast grid disconnection when needed. The Switch converters fulfill the stringiest grid codes and utility demands for grid interconnection and power conditioning.

Using the VSG converter, CHP system fuel consumption can be optimized to match building loads. Better part-load efficiency enables better thermal load following and higher overall efficiencies.

The next step is to replace the traditional externally excited synchronous generator with a PMG, which has much higher efficiency at partial loads and about the same at the nominal point. PMG construction is simpler. And a PMG is almost maintenance-free and has a smaller physical size than traditional synchronous generators.

The technology transfer in wind turbines from externally excited synchronous generators to synchronous PMGs began several years ago. Now, all major wind turbine manufacturers are using the highly efficient permanent magnet technology.

The reasons are obvious: better overall efficiency, almost maintenance-free generator technology – and ultimately lower levelized cost of energy (LCOE). And these very same arguments are valid for onsite cogeneration systems too.

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Press release, July 1, 2013; Image: The Switch