A Research On AC Electronic Load Based On DSP Control

The burn-in test has been regarded as a feasible approach for quality certification of new AC Source products.A passive load bank is generally used, and significant energy is wasted.From the viewpoint of energy conservation, a load consumption-free method is need.With the development of power electronic technology, a new AC Electronic Load by replacing the consumption load bank with a pulse width modulation (PWM) converter is present.Implementing this new idea, the testing power can be sent back to the utility system for reuse, and offers more flexibility, enhanced reliability, less space and lower cost than an assortment of passive loads.The architecture of AC Electronic Load studied in this thesis consists of two power stages.The input stage where a voltage source PWM rectifier is used to imitate the required load characteristic, such as R,RL and RC load characteristic.The output stage is a PWM inverter which sends back the recycling energy to the utility.Digitally controlled PWM converters have gained increasing attention because of a number of potential advantages.One of the major challenging issues in digital control is the undesired limit-cycle oscillations due to the lack of time resolution in the digital pulse-width modulator (DPWM) to satisfy specified output voltage regulation accuracy.The relationship between DPWM resolution and output voltage regulation accuracy is analyzed for several basic converters operating in continuous conduction mode (CCM).The minimum DPWM resolution required to prevent limit-cycle oscillation is derived.The conclusions are verified by simulation and experimental results based on a digitally controlled BUCK converter.A novel solution of consumptive AC Electronic Load suit for function test of AC Source products is proposed.The control strategy of the AC Electronic Load with energy recycle capability is analyzed and simulated with Saber.The design of passive components in the power stage is studied, especially the inductor in the input stage.A TMS320F2812 DSP based prototype of AC Electronic Load is designed and implemented.Simulation and experimental results confirm the validity and effectiveness of the presented solution.Since the islanding of the grid-connected systems can cause a loss of lives and damage to equipments, it has to be avoided by a reliable detection system.An anti-islanding method based on positive feedback concept is discussed and validated by simulation.