Decentralized Dynamic Compensation Control Strategy For Microgrid Parallel Converters Based On Robust Residual Generator

The microgrid can realize the active management of multiple types of distributed generators,and its flexible operation mode provides an effective solution for large-scale distributed generators to connect to new power systems.With the continuous expansion of the scale of the microgrid,the demand for power generation capacity of the load in the system is also increasing.Parallel technology of multiple converters can effectively compensate for the intermittency of distributed power sources while meeting system expansion,and realize the power output requirements of multiple parallel converters.It is a key technology to promote the development and application of microgrids.However,the microgrid parallel system contains a large number of power electronic converters,and the system has low inertia and is more susceptible to disturbances.In order to study and solve the disturbance problem of the parallel converter system,improve the reliability,stability,and improvement of the power quality of the microgrid,and facilitate the "plug and play" operation function of multiple converters This paper proposes a microgrid parallel converters decentralized dynamic disturbance compensation control strategy based on the robust residual generator.First,according to the topology of the parallel system,analyze and define the circulating current characteristics of the parallel inverters,establish a coupled statespace model of multiple inverters in parallel under quasi-stationary line conditions,its related power quality problems are analyzed and classified based on a mathematical model.Secondly,a process monitoring and control framework suitable for the "plugand-play" function of the control system is proved through theoretical derivation such as the left and right coprime decomposition and Yola parameterization.Combined with the residual signal of inverter in the parametric matrix controller specific compensation position analysis and comparison,aiming at the structure of the multiple loop control for inverter,put forward the dynamic disturbance compensation controller Qs,i(s)is designed from the angle of the disturbance cancellation,and the control signal applied to the input current loop.Realizing the superposition with the given current signal of the original system,to achieve the effect of the disturbance signal joint compensation,further simplify the current loop control structure.By adding a robust residual generator and dynamic compensation controller Qs,i(s)to each parallel inverter,the interaction between multiple inverters is further decoupled.Based on the robust model matching principle,the expression of the parameterized matrix controller of Qs,i(s)was deduced according to the local information of the inverter,and the simulation test was carried out by using PSCAD/EMTDC simulation software.Then,based on the structure of the decentralized dynamic disturbance compensation control strategy,the small-signal model of each controller loop is derived one by one.Combined with the small-signal model of the parallel inverters and its circuit,the complete small-signal model of the parallel inverters system is merged.Through parallel inverters parameter design and Matlab/Simulink software to get the initial static working point of parallel inverters,and the characteristic root distribution diagram of the parallel inverters under the decentralized dynamic disturbance compensation control is drawn to verify that the control strategy can meet the small-signal stability.Meanwhile,the root locus analysis provides a theoretical basis for the parameter selection under the control strategy.Finally,based on the digital controller TMS320F28335 and RTDS real-time digital simulation platform built three parallel inverters system of different capacity of the hardware-in-loop experiment,through the RTDS experiment shows that under the load change,inverter plug in and out,distributed generator power fluctuations,three-phase unbalance occurs,nonlinear device access and virtual impedance parameter design is not reasonable,the proposed control strategy can significantly improve dynamic characteristic of the parallel system,reduce the inverter and the bus voltage fluctuation,and make the output power of the parallel inverters rapidly and reasonably distributed according to capacity under disturbance,reduce the circulating current between the inverters.