Murata engineers used Model-Based Design to design and implement the EMS embedded control software.
Before starting the project, Dr. Ma attended a three-day MathWorks training course on the fundamentals of Model-Based Design and code generation.
Dr. Ma and his team created some plant models of the major system components, including the solar converter, battery DC-DC converter, and three-phase grid-tied inverter using Simscape Electrical™. The model was adjustable so that they could test different hardware topologies.
After adding measurement blocks to compute the total harmonic distortion (THD) and root-mean-square (RMS) of key signals, the team ran simulations to check that these metrics were within acceptable ranges and to compare the performance of different control strategies and hardware topologies.
Working in Simulink, the team modeled the system’s PI controller and then ran closed-loop simulations with the controller and the transfer function counterpart of the plant, using Simulink Control Design™ to tune control parameters.
Additional closed-loop simulations were performed to assess the design’s response to abnormal situations, including blackouts and phase unbalance of the grid, as well as some grid-tied requirements, including fault ride through (FRT) and maximum power point tracking (MPPT) for solar.
Using Stateflow®, they created state transition diagrams to model EMS startup, shutdown, and abnormal sequences as well as state transitions for the system’s various operating modes.
To implement the control logic on the micro-controller, they converted the floating-point design to fixed point using auto-scaling and other time-saving tools in Fixed-Point Designer.
Next, they generated C code and Code Composer Studio™ projects from the controller model with Embedded Coder®. Finally, they deployed it to Piccolo™ and Delfino™ 32-bit microcontrollers made by TI.
The team tested the microcontroller and EMS circuitry together to verify the code with the production hardware, by running open-loop tests to perform basic checks and by verifying system closed-loop controller and state transitions.
Murata has completed both the EMS project and a photovoltaic inverter project using Model-Based Design. The company is applying for JET certification for the grid connectivity, and the engineering team is preparing for long-term reliability testing.