A smart grid is an automated system that monitors and manages the generation, transmission, and distribution of electricity to achieve maximum efficiency. It is regarded as one of the key technological advances of the last decade. In the future, the smart grid will considerably transform the electrical networks we use today. As power conversion plays a crucial role in implementing this technology, power electronics have become a vital part.
Integration of Renewable Energy Sources
The evolution of power electronics and the efficiency of these devices in managing power flows in recent years has made it possible to advance the use of renewable energy sources. Smooth integration of green energy is based on flexible AC transmission systems (FACTS) and automation technologies.
Full-scale converters are used to connect wind farms with the grind. These power electronic interfacing devices are placed between the turbine generator and the main power grind and adjust the speed of the turbine, maximizing power generation. These converters also control voltage, frequency, and active and reactive power on the grid side.
Double-fed induction generators in the turbines use partial scale converters that have 30% capacity of the turbine and work at optimum operating points of the machine to generate electricity at 50/60Hz. This reliable and cost-effective structure demonstrates full power controllability.
Turbines with permanent magnet synchronous machines require full-scale converters. They react to the frequency changes on both sides of the DC link. Their power output can be adjusted to keep the system frequency at the same level. Compared to two-level converters, these generate more output voltage and less dV/dt stress. Also, their small size allows them to be installed inside wind turbine towers.
Power electronic converters are widely used in photovoltaic systems. As their output power is direct current, it needs to be converted into alternating current for the grid. Hence the need for DC-AC inverters. Also, DC-DC converters are used to manage the terminal conditions of photovoltaic modules. Tracking the maximum power points allows for maximizing the energy capture.
Power Electronics in Microgrid
A microgrid can provide a reliable energy supply while making grid extension cheaper and cutting carbon emissions. Here, an important role is played by power electronic converters.
These converters control the output power coming from distributed generators, as well as active loads in stand-alone and grid-connected modes. Also, conversion systems based on power electronics are required to connect the grid with various energy sources: biogas, hydro-storage pumps, fuel cells, CHP, and CCHP systems.
Power Electronics in Electric Vehicles
Many power electronic devices are used in EVs. Voltage regulators are used to produce constant voltage at the battery terminals. Choppers are required for soft-switching. As EVs use AC motors (which are more efficient than DC motors), one needs traction inverters to power them. On-board chargers convert AC to DC to charge the EV’s batteries.
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LED lighting systems require DC power. A low-voltage DC grid is more efficient than the conventional AC power grid and overcomes the disadvantages of AC-DC and DC-AC conversion. LED lighting systems, as well as cell phones, computers, chargers, printers, and other devices working on 3-24V, can benefit from a low-voltage DC grid of 24C/48C. A power electronic conversion system between the AC source and the low-voltage DC grid can reduce conversion losses and make the system more cost-efficient.
As you can see, every system that controls power flow or uses AC-DC or DC-AC power conversion cannot do without power electronic interfacing devices. Thus, power electronics are the key to the evolution of smart grid technology.