1.1 Applications of Power Converters and Drives
Power converters and drives are used in diverse sectors, ranging from industrial to residential applications [1, 2]. Several application examples for different sectors are shown in Figure 1.1, where a diagram of the system configuration is shown as an example for each group, marked with *.
Figure 1.1 Power converter applications
From the drive applications used in industry, pumps and fans are those that account for most of the energy consumption, with power ratings up to several megawatts. The use of adjustable speed drives can bring important benefits to these kinds of systems in terms of performance and efficiency. Many interesting applications of high-power drives can be found in the mining industry, for example, in downhill belt conveyors. A block diagram of one of these systems is shown in Figure 1.1, where three-level converters with active front-end rectifiers are used for regenerative operation, that is, power flowing from the motors to the grid [3, 4].
Common applications of drives can be found in transportation, where electric motors are used for traction and propulsion. In electric trains, the power is transferred from the overhead lines to the motors using a power converter like the one shown in the figure. This converter generates the required voltages for controlling the torque and speed of the electric motor. High-power drives can be found in ships, where diesel engines are used as generators and the propulsion is generated by electric motors. Newer applications in transportation can be found in electric and hybrid vehicles, and in aircraft.
The use of power converters in renewable energy conversion systems has been constantly increasing in recent years, mainly due to growing energy demands and environmental concerns. Among the different renewable energy sources, photovoltaic (PV) generation systems are a very interesting example of power converter applications because it is not possible to deliver power from the PV panel to the grid without a converter. An example of a power converter for a PV system is shown in Figure 1.1, composed of a DC–DC converter for optimal operation of the panel and an inverter for injection of sinusoidal currents to the grid. The use of power converters and drives in wind generation systems allows optimization of the amount of energy extracted from the wind and compliance with the new grid regulations that impose restrictions on the power quality and performance of the system [5].
The use of power converters can help to improve the quality and stability of the grid. Some examples of power converters with applications in power systems are active filters, converters for distributed generation, energy storage systems, static VAR compensators (STATCOM), and others. A diagram of an active filter application is also shown in Figure 1.1, where the power converter generates the required currents for compensating the distorted currents generated by a nonlinear load. In this way, distortion of the grid voltage is avoided.
Low-power drives and converters offer many possibilities in residential applications. The use of adjustable speed drives can increase the efficiency of systems like air conditioners and other home appliances [1, 6].