Research On The Control Strategy Of The Chain STATCOM

The chain STATCOM has a good dynamic characteristic in high-power high-voltagereactive power compensation, has the advantage of modular, multi-level features, easyexpansion to achieve redundancy, etc. It has got a good attention from people. This paperstudies related technologies for the chain STATCOM, discusses the modeling and control ofSTATCOM reactive current and DC voltage control testing and other issues, including thefollowing specific research areas:Introduces the basic working principle of STATCOM, a mathematical model of chainSTATCOM in three-phase stationary coordinate system is described. To facilitate the designof the controller, established a low-frequency dynamic model of the chain STATCOM.Analysis the chain STATCOM in the frequency domain equivalent model, knows thatchain STATCOM is a strongly coupled nonlinear system. Uses the feed forward decoupling ofthe inner current control strategies to achieve effective separation of active current andreactive current, for the power of the outer ring, using the PI controller to get currentreference value chain of STATCOM.Briefly discusses two basic methods for detecting harmonic current and reactive current:p-q method and ip-iq method. Uses the sequence-decoupled resonant controller to improvethe typical phase-locked loop and get a new ip-iq detecting method based on the SDRphase-locked loop.To start analysis from the power balance, analysis the system from positive sequence andnegative sequence. The overall balance of positive sequence voltage draw current on thesystem, the negative impact of the various phases sequence current voltage balance. Improvedthe traditional three DC voltage control algorithm to obtain a new three DC capacitor voltagebalance control method: The first level is controlled by the positive sequence current controlvoltage balance the overall chain STATCOM; the second stage uses a chain of negativesequence current STATCOM voltage control to achieve a balance between the phases; thethird stage capacitor voltage balance for each phase within a single-phase inverter bridge(HBI) module to achieve its precise control by adjusting the H-bridge output voltage andcurrent of amplitude and phase. Using MATLAB/SIMULINK to build a number of links to10of the simulation model, simulation results show that this new control strategy caneffectively achieve three phase DC side voltage balanced.