PR controller designed for NPC three-level STATCOM in rural grid

Proportion resonant (PR) control is presented for neutral point clamped (NPC) three-level static synchronous compensator (STATCOM). Compared with proportional and integral (PI) controller, PR controller overcomes the drawbacks such as steady-state error for ac signal and poor disturbance rejection capability. Meanwhile, the proposed strategy has a less complexity of the control structure and a better capability to compensate low order harmonics than voltage oriented vector control (VOC) which needs coordinate transformation and decoupling network. A dual loop control is designed to stabilize the DC voltage and compensate reactive power. Furthermore, the voltage value difference between the upper and lower capacitors is fed back to achieve neutral point balance. Simulations are done in MATLAB/SIMULINK. And the results are satisfactory.