Solid State Transformer | Details,Working And Advantages

Solid State Transformer

A solid-state transformer (SST), a power electronic transformer, or electronic power transformer is actually AC-AC converter, a type of electric power converter that replaces a conventional transformer used in AC electric power distribution. It is more complex than a conventional transformer operating at utility frequency, but it can be smaller and more efficient than a conventional transformer because it operates at high frequency.

The solid state transformer (SSTs) are designed with different topologies based on its application:

AC to AC buck converter: 

1.  Transformation of the voltage level directly without any isolation transformer
2. Switches must be capable of blocking full primary volatge during OFF state and conducting full secondary current during ON state.
3. Difficult to control series-connected devices
4. Lack of magnetic isolation
5. Inability to correct load power factor

SST without a DC link:

1.  Transformer weight and size reduced
2. Provides isolation
3. No power factor improvement is possible

SST with a DC link:

1. Reduced size due to a high-frequency transformer
2. Power factor improvement is possible
3. Multilevel converter topologies can be applied to achieve high voltage levels (e.g., 11 kV, 22 kV)
4. High cost and low efficiency
5. It is a three-stage topology: most popular now

SSTs that can be widely used in microgrid applications are relatively advantageous with respect to power quality.

Advantages

1. An excellent utilization of distributed renewable energy resources and distributed energy storage devices
2. Power factor control
3. Fast isolation under fault conditions due to a controlled SST
4. Control of both AC and DC loads can be done using the SST scheme
5. Improved power quality
6. DC and alternative frequency AC service options
7. Integration with system monitoring and advanced distribution
8. Reduced weight and size
9. Elimination of hazardous liquid dielectrics

Limitations

1. Multiple power conversion stages can lower the overall efficiency
2. DC-link capacitors are required
3. The transformer lifetime can be shorter due to storage devices