Voltage Stability And Grid-Connection Control System Of Self-Excited Induction Generator

Self-excited induction generator (SEIG) has been widely used in renewable energy power generation system Because of its inherent advantages which are rugged construction, low cost and self-protection against faults, but it suffer from poor load capacity, and its terminal voltage is changed under different loads and various speed conditions when it operate in a standalone generation system, and a reactive power compensation technique is required to keep terminal voltage of SEIG constant. However, in grid-connection operate mode, to improve the anti-jam capability and control performance of grid-cnnection system, a coordination control strategy for generator-side PWM converter and grid-side PWM converter is needed to control the dual PWM converter. To deal with these problems, studies are carried out, the voltage stability system and grid-connection system of induction generator are designed as well in this paper.With SEIG mathematic model, a digital simulation method is used to analyze the dynamic performances of the terminal voltage of SEIG under variable speed, different capacity of excitation capacitor and different loads conditions. In order to keep voltage stability of SEIG, a voltage stability system based on static synchronous compensator (STATCOM) is used to compensate reactive power for SEIG, and a conventional PID controller and a nonlinear PID controller are proposed to control the voltage stability system of SEIG. Results show that terminal voltage of SEIG can be regulated continuously and smoothly with proposed the reactive power compensation method, and the generator terminal voltage can be kept constant under variable speed and different loads conditions, and the voltage regulation performances of SEIG can be improved as well.To realize grid-connected operation for SEIG, a control strategy based on instantaneous power theory is used to control the dual PWM converter. A coordinated control method is applied to regulate active power and reactive power of generator system; the generator-side converter is controlled with voltage orientation method which is not affected by generator parameters; the grid-side converter is controlled to keep dc-link voltage constant and ensure the system stability.An experiment platform is set up to test control performances of the voltage stability system and the grid-connected control system, and a floating-point DSP is adopted to design the algorithm of generation system. Finally, the experiments of voltage stability control and grid-connection control are carried out in experiment platform to varify the proposed approach.