Build your own Microgrid: Parts List and Control Code

[BMac]

At the National Instruments office in Austin, Texas, we have a Low Voltage Microgrid Systems Engineering Lab that is used to validate and tune power electronics control code and simulation models.

Each of the mini-scale power converters on the microgrid uses power converter boards that have identical pin mapping as the full scale Semikron SKiiP3 interface PCB, so the actual control code for full size power converters (typical 50 kVA and larger) is tested and validated in the microgrid lab before it's used at the full power level. (The only thing that changes when running on the full scale converter is the FPGA RAM memory addresses for sensor scaling gains, offsets and fault trip limits.)

We have found the following workflow to result in extremely high productivity for developing power conversion control algorithms:

1. Rapid development of power electronics control system code using Multisim-LabVIEW FPGA co-simulation. Development of automated test code.

2. Testing, validation and tuning of control system code using mini-scale power converters in the microgrid lab. Reuse/development of automated test code. This includes simulation model validation and parameter identification.

3. Commissioning of the full scale power converter cabinet and full-power testing, validation and tuning of the control system code. Reuse/development of automated test code. This includes simulation model validation and parameter identification.

4. Real-time hardware-in-the-loop (HIL) simulation testing and validation of the control system code- we recommend the OpalRT eHS solvers which now support Multisim models and can be run on NI PXI or CompactRIO hardware. HIL simulation enables complete test coverage including test case conditions that would be impossible to create using physical hardware. NI Veristand and NI TestStand can be used to fully automate the testing.

Here's a photo of the low voltage microgrid configuration we currently have running for code development and testing at NI headquarters in Austin, with each microgrid control node numbered, a list of parts for each node, and links to download the code for each node.

Node/Item #	Description	Parts List	Code Download*, What to Run	Wiring, Settings, Notes
1	PMSG Genset Dyno	1. MotorSolver Dyno-kit with PMDC Motor, connection couplings, 8-pole PM AC Synchronous Motor, 1000 lin...		Wiring: Brushed PMDC motor is connected to inverter B. Encoder signals A,B,Z are connected to GPIC LVTTL lines, along with +5VDC power for the quadrature encoder. Only one of the two encoders on the dyno needs to be connected.
2	NI GPIC PMDC Dyno Motor Drive DC-DC Converter	1. sbRIO GPIC Control System Stack 2. Mini-Scale 3-Phase Back-to-Back Power Converter Development Board	GPIC Reference Design FPGA: [FPGA] GPIC 3-Phase DC-to-DC Converter Control.vi RT: [RT] GPIC 3-Phase DC-to-DC Converter Control.vi Desktop: [Desktop] Graphical User Interface - GPIC 3-Phase DC-to-DC Converter Control.vi	Wiring: All three Inverter B half-bridge outputs are wired in parallel to the PMDC brushed DC motor. Encoder feedback is connected to LVTTL signal and +5 VDC encoder power is provided via the same connector. Settings:  Inverter Type = "Power Converter RCP: Inverter B" Control Mode = "Speed>V>C>Vout Cascade" Speed Setpoint [RPM] = 900 (to produce 60 Hz 3-phase power on the PMAC Synchronous Motor) Notes: To simulate a stiffer or weaker grid, use the Desktop application to adjust the speed control gains (Speed>V>C>Vout Cascade PI Config). Very easy to demonstrate sub-synchronous oscillations between the 3-phase genset and bidirectional active front end (AFE) control systems. Replace the genset speed regulator PI controller with PID control to add damping.
3	NI GPIC Bidirectional AFE Inverter with 1547 Anti-Islanding and Back-to-Back Induction Motor VFD	1. sbRIO GPIC Control System Stack 2. Mini-Scale 3-Phase Back-to-Back Power Converter Development Board 3. MotorSolver AC induction motor (4-pole) on bracket, 1000 CPR encoder 4. Voltage divider resistors	Starsim NI GPIC GridAFE FPGA: [FPGA] Grid Tied AFE Control.vi RT: [RT] NI GPIC Grid Active Front End.vi Desktop: [Testbench] StarSim Grid Tied Inverter Control.vi	Wiring: The grid tied bidirectional active front end uses inverter B. The 3-phase induction motor VFD uses inverter A. On the bottom of the development board, the jumpers are removed for AI5+ / Vu_B, AI6+ / Vv_B, AI7+ / Vw_B to disconnect the internal voltage sensors, and external voltage divider resistors connected at the output of the line reactor filter (item # 4) are used to measure the voltage at the point of common coupling (PCC) to the grid. Settings: Regulate DC Link? = True Enable PWM = True Notes: Demonstrates the ability to measure loop gain Bode plots (amplitude and phase margins) for the 1547 anti-islanding algorithm while running. Adjust the grid stiffness using Node # 2 speed control tuning and observe that the 1547 frequency feedforward control algorithm is stable for stiff grid conditions and unstable for weak grid conditions.
4	AFE Inverter Line Reactor	1. FN 5040-8-82 3-Phase Line Reactor		Wiring: Connected at the output of the bidirectional active front end inverter (node #3).
5	NI CompactRIO Power Quality Analyzer (PQA)	1. CompactRIO cRIO-9068 Integrated Controller and Chassis System, Zynq-7020 FPGA 782663-01 2. Slot 7: NI 9225 3-Phase, 300 V (rms) Voltage Input Module 780159-01 3. Slot 8: NI 9227 3-Phase +N, 5 A (rms) Current Input Module 781099-01	PQA for Power Electronics FPGA: FPGA_PQ_25_27_60HZ.vi RT: Main_RT.vi	Wiring: Measurements are made at the point of common coupling (PCC) between nodes # 2 and 3, after the AFE inverter line reactor filter (item 4). Voltages are measured line-to-line using the NI 9225 module (differential connections). Phase currents are measured by series connection through the NI 9227 module. Notes: The PQA software configuration settings have not been evaluated, validated, tested. Changes to settings are likely required.
6	NI GPIC Buck-Boost Energy Storage DC-DC Converter with Digital Twin and Active Junction Temperature Regulation	1. sbRIO GPIC Control System Stack 2. Mini-Scale 3-Phase Back-to-Back Power Converter Development Board 3. NI PS-17 24 VDC, 20 Amp Regulated DC Power Supply 7. Power resistors to provide ~5 Amps current draw on PS-17 supply terminals 8. 24 VDC fan to cool inverters	GPIC Half-Bridge Buck-Boost FPGA: [FPGA] NI GPIC Buck-Boost Energy Storage Converter.vi RT: [RT] Operate Half-Bridge Buck-Boost Converter.vi Desktop: [TestBench] Bidirectional Half-Bridge Energy Storage Converter.vi	Wiring: Inverter A, Phase u half-bridge only is connected to the buck-boost series inductor (item # 9). Resistor divider is used to measure energy storage battery (item 😎 positive terminal voltage. PS-17 power supply is connected to Vdc_B and can be optionally connected to the DC link for Inverter A by closing the ConnectDCLink contactor on the development board to enable higher current testing. Since the PS-17 is a uni-directional (sourcing only) power supply and the buck-boost converter is bidirectional, properly sized power resistors are connected to the PS-17 terminals to provide ~5 Amps of current sinking ability. A 24 VDC fan is also connected to the PS-17 supply terminals and used to cool the inverters. Notes: The internal current sensor(s) on the power converter development board are being used for sensing the buck-boost current, rather than the shunt current sensor (item #10). See the RT applications for online parameter identification learning using differential evolution (DE) global optimizer.
7	DC Link Bus Connection			Notes: Use wires sized to handle 10-20 amps of current.
8	Lead-Acid Energy Storage Battery			Notes: Any automotive battery works well.
9	Buck-Boost Series Inductor	1. 5.6 mH, 0.7 Ohm ESR power inductor (or similar)
10	Shunt Current Sensor	1. 0.1 Ohm power resistor		Notes: Not currently being used for current sensing.
11	Semikron SKiiP3 IPM NI GPIC Bidirectional AFE Inverter	1. sbRIO GPIC Control System Stack 2. SKiiP3 GPIC Interface Board PCB Template 3. NI PS-17 24 VDC, 20 Amp Regulated DC Power Supply	Starsim NI GPIC GridAFE FPGA: [FPGA] Grid Tied AFE Control.vi RT: [RT] NI GPIC Grid Active Front End.vi Desktop: [Testbench] StarSim Grid Tied Inverter Control.vi	Notes: Can be used to simulate a high stiffness power grid source, with proper line reactor filters connected in series.

* Unzip to a short path (not desktop) using 7-Zip or WinZip (not Windows default ZIP utility)

I can post demonstration videos for any or all of the microgrid control systems if that would be useful.

Please reply to this thread directly with any questions or comments.

[MACLab]

Hi BMac,

Thank you for sharing with us. I wonder where I could find the demonstration videos of these parts, and also, do you have a overall schematic diagram for the whole system?

Thank you.

Jack