Optimization of PI coefficients in DSTATCOM nonlinear controller for regulating DC voltage using Genetic Algorithm

Abstract

Regarding nonlinear operation of DSTATCOM,nonlinear controller is preferred to linear controller. Regulating and fixing the capacitor DC voltage in DSTATCOM can improve the system dynamic. The nonlinear control is based on exact linearization via feedback. There is a PI controller in this control system to regulate DC voltage. In conventional scheme, the trial and error method is used to determine PI values. Exact calculation of optimized PI coefficients can be carried out to reduce disturbances in DC link voltage and thus, in this paper Genetic Algorithm is applied. As a result, capacitor voltage tracks the reference value in an era and vibration less than conventional status. Both trial and error method and GA are implemented. A set of corresponding diagrams achieved by these two methods are offered to demonstrate the effectiveness of new method. Optimizations and simulations are worked out in MATLAB environment.

Partial feedback linearizing controller design for a DSTATCOM to enhance voltage stability of distribution network with distributed generation

“…When 1j + r2 < n , we can do only partial linearization and this case, the transformed states z can be written as z=¢(x)=[z zy (15) where z represents the states obtained from the nonlinear coordinate transformation up to the order lj + r2 and Z represents the states related to the remaining n -lj + r2 order. The dynamics of z is called the internal dynamics and its stability needs to be ensured before designing the linear controller for the following partially linearized system (16).…”

“…'i = Az +Bv (16) where A is the system matrix for the partially linearized system, B is the input matrix for the partially linearized system, and v is the new control input for the partially linearized system.…”

“…Since feedback linearization cancels nonlinearities by introducing nonlinear tenns, the feedback linearized system is independent of operating points. The exact linearization approach is widely used as STATCOM controllers to regulate the voltage of transmission network as well as distribution networks [14] [16]. But DSTATCOMs can be partially linearized rather than fully linearized and in this case, exact linearization is no more applicable.…”

Implementation of Selective Harmonic Elimination PWM switching strategy on DSTATCOM

“…In this case, this model is used for simulation purpose, but not to choose and tune the controller. A Generalized Averaging method [20] is used to get a continuous time invariant model of the converter. The equations will be finally:…”

“…4) Mutation: this is performed by an operation determined by the installed mutation probability or mutation, and a new individual is generated. 5) End judging: if end conditions are fulfilled, the best individual thus obtained is the semi-optimal solution in question .Otherwise, return to 2) [20].…”