Research Of Comprehensive Compensation System For Multiple Converters

With the development of the ACVV technology, AC-DC-AC variable frequencydevices are widely used in in various fields of industry. However this technology has thefollowing defects: a lot of harmonics and reactive power are injected to grid by the use ofthe diode rectifier. Besides, the motor braking energy is released in the form of heat,causing a huge waste of energy. In this context, this thesis studied in the following aspects:A new topological structure for multiple converters was designed in this thesis. Basedon analysis of the main circuit of grid-side converter, the mathematical model underdifferent coordinate system was established, and the principle of PWM rectifier in fourquadrant operation was analyzed. On the basis of dq coordinate system mathematicalmodel, the double closed loop control strategy was studied. In order to reduce thedisturbance of regenerating energy, feedback current feed-forward control was proposed.The detection of harmonic and reactive current was in ip-iqoperation way, and themoving average filter was put forward to improve the traditional low-pass filtercharacteristic. Multiple resonant controllers are adopted to independently control differentfrequency of harmonic loop without steady error. Aimed to get rid of disadvantages oftraditional hardware cross-zero PLL, the three-phase PLL based on dual dq coordinatetransformation was proposed, improving the system’s adaptability to complex workingenvironment. This thesis introduced the system’s starting and working process, and thesystem main parameters were also designed. The system test platform was built by usingSaber simulation software. The feasibility of the integrated system topology was verified.Active filter, reactive power compensation and energy feedback experiments forsingle-load and multi-load were made to verify the rationality of the integrated controlscheme.