Alternative Hybrid-Electric Vehicle

An Alternative Hybrid-Electric Vehicle

Sunday, October 12, 2014

Light TECH

This is a concept of a one-way drive that can be modified to enable more than one shaft to drive only one sheave, or gear as the case maybe.

This the Motherboard of the Variable Frequency, Variable Voltage Inverter of the Prototype HEV. It uses TTL components that are readily available even in developing markets. With the concept having been demonstrated by this prototype, the next design would be using micro-controllers and micro-computers.

The control program for the prototype resides in a small laptop computer, running on MSDOS, to limit the amount of resources on-board the HEV.

The design of the prototype's control system follows a Decentralized philosophy. The participating modules are able to operate independently, and are able to protect themselves from damage.

The system's brain, which is the laptop PC receives data from all the modules. It analyses them and sends Control SETPOINTS back to the modules.

For example, the charger will operate independently of the PC, while it is plugged into the electric power grid. It will protect itself and the individual batteries as a decentralized stand-alone unit. 

Similarly, the VFI performs its functions by itself. The PC provides it with SETPOINTS for frequency, voltage, and current. The charger will send a signal to the VFI to shut down when notices that the charge on ANY cell of the battery bank is now low. It does this by pulling down the voltage set-point. This protects this cell from an irreparable deep discharge.

The charging system follows this control graph. The reference of the design is based on the "DOE HANDBOOK - PRIMER ON LEAD-ACID STORAGE BATTERIES" found in the link below. 

This is the charger system of the prototype HEV. The range of the input voltage is 80 to 120 volts AC. 
This is the voltage and current feedback system. This makes sure that the output voltage and output current are in accordance with the design.
This is the control board to interface the computer control software with the rest of the system. It sends control commands to the engine, the inverter, and the charger. It also receives feedback signals that are relevant to the operation of the system.

All signals going of the computer to the system pass through an optical isolation system. This prevents transients from entering and damaging the computer. Likewise, signals coming from the system are also opto-isolated from the computer.
Charger 01
Charger 02

The system generates voltage transients all the time. These transients will damage the PC, if it gets there by chance. The design incorporates opto-isolators to provide the required electrical isolation, while providing path for the flow of data.

The control system monitors many points in the Prototype

  • Human Safety. 
    • The working source voltage 84 volts DC is selected for safety reasons. 
    • The WYE configuration of the primary of the transformer is also selected so that a lower voltage is generated. The transformer will be removed and the DC voltage will be raised when the system is released for commercialization.
  • Over-Current, and Over-Voltage.
    • Currents and voltages are monitored.
    • Controls are in place to assure that all operating parameters are within their safe operating limits.
  • Battery Condition.
    • Since the battery bank is composed of "series-connected" cells, each cell is monitored for over-charging, for deep discharge, and for high charging or discharging currents.
    • Cell voltages are monitored with the cell charge.
    • A cell voltage during discharging (for this sulfuric acid battery bank) of 1.8 volts triggers a warning signal, and 1.75 volts triggers a shutdown.
    • The charging circuit does two things, simultaneously, for the shut down
      • It sends a signal to the controller, which sends a signal to the inverter to shut down.
      • It immediately removes the the voltage set point on the inverter forcing it to shut down in the absence of a signal in a "fail-safe" design.