SSZT041 february 2023
Harald Parzhuber
With energy storage systems prices becoming more affordable and electricity prices going up, the demand for renewable energy sources is increasing. Many residences now use a combined solar energy generation and battery energy storage system to make energy available when solar power is not sufficient to support demand. Figure 1 illustrates a residential use case and Figure 2 shows how a typical solar inverter system can be integrated with an energy storage system.
In the best-case scenario, this type of system has highly efficient power management components for AC/DC and DC/DC conversion and high power density (with the smallest possible solution size) that are highly reliable (with the lowest losses) and enable fast time to market. Those requirements are not always achievable at the same time, however, and you will need to make trade-offs on the best power-conversion topologies for these subblocks.
What existing power topologies for AC/DC and DC/DC buck and boost power converters have in common are half bridges or converter branches that run interleaved, either to increase power levels in a DC/DC converter or to achieve three-phase operation in an AC/DC inverter or power factor correction stage by placing three branches running in 120-degree phase shifts. Figure 3 shows simplified schematics of five power topologies.
Three-level topologies allow the use of smaller passive components and have lower EMI compared to two-level converters. There are four three-level topologies:
Table 1 lists the benefits and challenges of the different topologies.
2L TIDA-01606 in 2L |
T-Type 3L TIDA-01606 |
ANPC TIDA-010210 |
NPC 3L derived from ANPC |
FC3L Flying capacitor 3L |
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Benefits |
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Challenges |
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All four three-level topologies have clear advantages on power density (with the smallest possible solution size), highly reliable operation, and fast time to market over traditional two-level converters. Using wide band-gap devices and high-performance MCUs increase these advantages even further, at a comparable cost.