22-12-2012, 01:17 PM
ADVANCED HYBRID ELECTRIC VEHICLE
1ADVANCED HYBRID.doc (Size: 578.5 KB / Downloads: 69)
ABSTRACT:
Development of power electronics and real time control technology for HEV is presented. These include AC drives with real time torque control, compact an drugged induction motors, auxiliary electric circuits etc. We have developed a set of DSP based circuits for AC Induction Motor Drives for EVs. It provides torque control for propulsion and power control for generation and battery charging. The propulsion motor is controlled by a fixed point DSP based controller, which provides torque control based on driver commands. The IC engine is coupled to a Generator, whose output is rectified to get the DC voltage. Another DSP based controller controls the DC bus voltage and the power flow. A dashboard, with microcontroller based circuits, provides the driver interface. For charging the battery during night time an in-built battery charger is developed. The battery charger and the cooling pump controllers etc. are also based on DSP circuits. The various controllers are inter linked through a serial network.
Introduction:
Due to environmental and fuel resource concerns, there is a growing demand for Electric Vehicles (EVs). The EV, when powered solely from the onboard battery pack, can run only in a limited range on a single charge. This limitation is overcome in a Hybrid Electric Vehicle (HEV) by the introduction of a down sized IC engine, coupled to a generator, which supplements the battery. Since the IC engine is operated at a constant speed, the pollution level is considerably reduced.
Development of power electronics technology for EVs assumes importance in this context. These include AC drives with real time torque control for propulsion and power control for generation, compact and rugged induction motors, low maintenance battery and it monitoring systems etc. Digital Signal processor based real time AC drive controllers play the key role in the effective system operation. It provides efficient torque control for the propulsion motor based on driver commands and implements added features like regenerative braking etc.
HEV Control Modules:
Dedicated DSP based controllers are developed for different HEV systems. His distributed control strategy allows better controllability and reduced hardware. The supervisory control and system monitoring is implemented through a Dash board controller. To reduce inter module control wiring and reliable data transfer between controllers RS485 Serial networking is implemented. The main control modules developed are discussed in the following section.
Generator Controller (GC):-
Here Induction generator is used to generate the demanding power in 3 phase AC with the down sized IC engine as the prime mover. The tasks performed by the controller are, operation of the machine in motoring mode till base speed and maintain constant power From base speed to maximum speed of operation maintaining constant DC bus. The IC
Engine is loaded accordingly to meet the power requirement.
Propulsion Motor Controller (PMC):
The motor used for the propulsion is chosen to be Induction motor. AC Induction Motor
offer better choice in terms of size, ruggedness, efficiency and maintainability when compared to the present DC motors. Moreover implementation of water-cooling for reduction in size and weight is simple. The various tasks to be performed by the controller are operation of the machine in all four quadrants with constant torque operation till the base speed and constant power operation from base speed to maximum speed of operation.
Dash Board Controller:
The dashboard houses the Speedo-meter, Odometer, Bar-graph display for battery parameters, LED indications for various status and fault indications of the system. LCD display is used to facilitate the display of quantitative values of the required monitoring parameter on selection. The information is passed from all the Drive Controller PCB’S to the dashboard through RS485 link. RS232C interface is provided for debugging. A local microprocessor PCB processes the data and gives output to the display, meters and LED indications.
Data acquisition module:
The data acquisition module is used for sensor interface, like motor winding and bearing
temperature, generator winding and bearing temperature, PMC, GC temperature etc. This
information is passed to the main controllers for supervisory operation and safe shutdown
under abnormal conditions. This 8-channel data acquisition module is based on AT89C2051 micro-controller.
AC drive Control:
The main power converter in PMC, GC, PMPC etc., is a high performance AC drive, which supplies a 3-phase induction motor/ generator. Intelligent Power Module (IPM) is used as the power-switching element, which offers higher reliability and requires lesser interface circuitry compared to other power switching devices. The real time control algorithm is based on Space Vector PWM, realized using digital controller based on TMS320F206 Digital Signal Processor (DSP).
Control Implementation with DSP:
The control can be realized through software by appropriately cascading the basic software building blocks integral, delay element, algebraic and table functions etc. on a common hardware platform. All these functions are implemented in a 16-bit fixed point DSP processor. In order to obtain reasonable accuracy the inputs and outputs are scaled for Q14 format. i.e. the per unit value corresponds to 14 bits. This is easily realizable in a
sixteen-bit DSP. Computations inside the functions are with 32-bit accuracy. Some of the
important functional modules are discussed below.
Controller implementation:
The steps involve modeling of the system and applying control for current/torque control
field/flux control. In addition the direct system performance is obtained through voltage/speed/position controller. The vector control of induction motor is realized as shown in Fig 9. This has two current control loops one for isd (field) control and one for isq (torque) control. The two outer loops namely speed control loop and flux control loop
generate reference values respectively.
HEV System Operation:
The power flow control starts with the switch ON of the master control on the dashboard.
This process ensures the energizing of all the controllers for operational stability. The vital auxiliary systems are started and their actions are communicated simultaneously to the dashboard to assist the driver to start the engine. Now the engine is started through the induction generator operating as motor powered from the Battery, thus eliminating the usual starter for the ICE. The engine is set to operate at two speeds i.e. idle and normal speeds. Once engine rises to normal speed the vehicle is ready for moving and wait for drivers pedal response. The power from the engine is supplemented by the battery during starting till it reaches steady speed and its responses are programmed to match the normal vehicle performance. The IC engine supplies steady average power while the batteries supplement it during starting, acceleration and gradient requirements. Regeneration mode starts when the driver removes the pedal and it is limited with the system specifications.
Conclusion:
The scheme is implemented for M/s Ashok Leyland and M/s BHEL. The system has successfully completed 8000 kms of road trials, performance evaluation etc. and the results so far are very encouraging. HEVs are the best choice as the environment friendly
and driver comfort vehicle for the metros.