Designing and Simulating Microgrids & Grid Connected Converters

Design and simulation of power converters in microgrids and grid connected systems

It is important to understand fully how the power converters in a microgrid or other grid-connected systems interact with the other components of that system. A microgrid can also be defined to mean almost any small-scale independent generation and load connected together, it doesn't have to be a PV panel with a battery charger. A microgrid could be used to model the power system of an EV, satellite, naval boat, mine site, renewable energy installation, etc. All of these examples contain interconnected generation, energy storage, and loads that need to work with each other.

Whatever you use the word microgrid to define, Altair has solutions that will help you model and control it to ensure stability, reliability, and efficiency.

System Level Simulation

Play nice!

Power converters typically do not play nicely with each other, like small children fighting over same toy you can expect power converters to act the same way. A steady and dependable control algorithm is required to keep these unruly systems working and sharing with each other properly.

A wide variety of systems contain multiple power converters, power sources, and loads. Power sources could be batteries, PV/Solar, Wind, diesel generator, the utility gird, etc, Power will need to flow from the sources to the loads, and will likely need to be bi-directional if batteries are involved. Modular and Multilevel converters are allowing for more power to be handled and the reliance on large magnetics for power transformation to be greatly reduced; however, there are more than a couple of different topologies and control techniques available. The complexities and combinations of what a “microgrid” can be are truly endless. PSIM is a tool that can allow you study these complexities and develop robust control strategies.

Transient Simulation

It is important to run simulations that include the active switching instance, this can be problematic for many simulation tools as it can cause convergence problems. A typical technique is to use simplified models, but these simplified models will hide some of the control challenges. A good example is droop control for parallel inverters, which means changing the voltage and frequency to change the real and reactive power-sharing. If you use simplified models for the inverters the control response complexity is greatly reduced.

Sacrificing Accuracy For Speed

Average models, reduced complexity, partial systems, reduced switching speeds etc. are compromises you should not make when simulating your microgrid.

Current techniques for the simulation of large systems like microgrids are about compromise or expensive dedicated real-time hardware simulators. Average models are swapped for the switches, switching speeds are reduced, the complexity of the system and number of components get reduced. These simplified systems aren’t actually the system you want to study so the results may or may not be very representative of what you need to study.

Trial licenses of PSIM and SmartCtrl can be setup through Altair Marketplace.

Other resources

Webinar comparing multi-level and 2 level inverters.

Attached is a demo system with 2x 3 phase converters with closed loop droop control implemented for reactive power. The converters are setup with dq control with an inner current and outer voltage loop after an LCL filter to produce a clean sine wave output.