Twist features

The TWIST board provides a fully integrated fast prototyping platform for anyone wishing to start learning and/or developing in power electronics. Its multiple features are explained in this page.

Board sub-systems Overview

There are 4 main sub systems inside the SPIN board.

• The Spin which you can know more about in its repository
• The Communication Block
• The Power Block
• The Measurement Blocks (High and Low Side)
• The Connectors (High and Low Side)
• The Feeder Block

The image below illustrates their interconnection.

flowchart TB
    subgraph TWIST
      direction TB
      B <--> |Data| A[Communication Block]    
      B[Spin] --> |PWM| C1[Power Block]
      D --> |Signals| B
      E --> |Signals| B
      C1 <-.-> |Power| D[High-Side Meas. Block]
      C1 <-.-> |Power| E[Low-Side Meas. Block]
      J[Feeder] 
      D <-.-> |Power| F[High-Side Connector]    
      E <-.-> |Power| G[Low-Side Connector]
end

These blocks can be seen on the photo of the TWIST below.

View of the twist board and its sub-blocks

The Communication Block

The communication block deploys an unique communication architecture currently under development at LAAS-CNRS. Combining multiple solutions for exchanging information between two power conveters, this block allows the user to deploy a daisy chain and coordinate multiple power converters.

Three TWIST boards connected in a Communication and Power Daisy Chain

The RJ45 connector deploys 4 different types of communication methods:

• A slow communication via CAN Bus
• A fast communication via RS485 and ModBus
• An ultra-fast analog communication
• A sync signal

Its schematic is shown in the image below.

Schematic of the RJ45 connector used in the communication block

The CAN bus implementation is based on a similar implementation done by LibreSolar in their power converters (a big thanks to Marin Jager).

The schematics of the CAN bus implementation done by LibreSolar

The RS485 communication allows the power converters to exchange data on a much faster pace, typically using it in their inner control loops.

The schematics of the RS485 implementation

For a much faster current sharing capabilities, an analog bus sharing bus is also available.

_Schematic of the analog current control (simulation available here)

This implementation allows the highest current to yielding block to control the bus and provide its current value to the others. This value can then, in turn be used by other blocks to control their own current/voltage.

The Power Block

Power conversion is the main feature of the twist board. To achieve a re-programmable and flexible power conversion, the twist board uses a special architecture called dual synchronous buck. The circuit below introduces its main components:

Circuit diagram of the power block

This architecture has a high voltage and a low voltage side. On the low side, the converter features two channels, which are then connected in parallel on the high side. This high-side connection allows four main conversion functions :

• Buck mode : Power goes from the low to the high side
• Boost mode : Power goes from the high to the low side
• Independent buck-boost mode : Power can go from leg 1 to leg 2 and vice-versa
• AC mode : Both legs are used together to create a sine wave

Buck mode

When connected in buck mode, the converter drives power from a high-voltage (up to 100V) source to a low-voltage sink. The image below gives the example of a PV battery charger in buck mode.

Twist board in buck mode

The source in the example above is a 40V PV panel which is connected to the high-side. Both legs are driven together, to maximize power transfer and minimize the current ripple. The load in the example is a 12V battery connected to the low-side.

Notice that to operate in DC mode, the converter has a special Neutral to Ground swich (TN_GND) which must be ON to allow the power to flow.

Boost mode

When connected in boost mode, the converter drives power from a low-voltage (up to 80V) source to a high-voltage sink (up to 100V). The image below gives the example of a PV battery charger in boost mode.

Twist board in boost mode

The source in the example above is a 40V PV panel which is connected to the low-side. Both legs are driven together, to maximize power transfer and minimize the current ripple. The load in the example is a 72V battery connected to the high-side.

Notice that to operate in DC mode, the converter has a special Neutral to Ground swich (TN_GND) which must be ON to allow the power to flow.

Independent buck-boost mode

Imagine you wish to connect two batteries in parallel. When connected in independent buck-boost mode, the converter drives power from a low-voltage (up to 80V) source to another low-voltage sink (up to 80V). The image below gives the example of a battery to battery connection.

Twist board in independent buck-boost mode

The battery connected to leg 1 in the example above is 24V and the battery connected to leg 2 is a 12V. Both legs are driven independently, to allow bi-directional power transfer.

Notice that to operate in DC mode, the converter has a special Neutral to Ground swich (TN_GND) which must be ON to allow the power to flow.

AC mode

Imagine you wish to drive a single phase AC motor. When connected in AC mode, the converter drives power from a high-voltage (up to 100V) source to both low-voltage legs (up to 80V_pk or 56V_RMS). The image below gives the example of a battery to battery connection.

Twist board in AC mode

The battery connected to leg 1 in the example above is 24V and the battery connected to leg 2 is a 12V. Both legs are driven independently, to allow bi-directional power transfer.

Notice that to operate in AC mode, the special Neutral to Ground swich (TN_GND) must be OFF to allow the neutral to float.

The Measurement Block

Power control requires accurate measurements. The TWIST board has 6 different measurements which allow full visibility of its power flow:

All measurements are conditioned and boosted by an operational amplifier that sends the raw signal from the sensor to the Spin board.

The Connectors

The Feeder Block