Nonlinear H2/H∞ Mixed Control and Modular Embeded Digital System Research of STATCOM
|Course||Agricultural Electrification and Automation|
|Keywords||STATCOM multi-level main circuit mixed-cascade switching angle robust coefficient parameter perturbations H2/H∞mixed control distributed control system embedded real-time multi-tasking operating system|
As one of the important members of FACTS,Static Synchronous Compensator（STATCOM） has widely applied all over the world.Because STATCOM has advanced control performance,it has become the direction of development research in the world’s SVC.As the important components of STATCOM,controller and control system directly impact on the operation performance of STATCOM.Aiming at the mixed-cascade multi-level main circuit and with the design and research of its controller and control system,this paper carries out and achieves system analysis in relation to controller and the control system hardware and software design.At first,the principle and performance of STATCOM are introduced in this thesis.Control system of STATCOM is a two-layer model,the system layer and the equipment layer.Its advantage is that a complex system can be divided into two designed relative easy subsystems, and each subsystem has not only its own control object but also a certain relationship between the various subsystems.In the control system model of STATCOM,parameter uncertainty not only brings uncertainty and perturbation of the STATCOM model but also impacts on the accuracy of the model.As equipment capacity becomes bigger and bigger,and then requirements of output waveform harmonic spectrum become higher,main circuit of the multi-level STATCOM becomes the direction of development in the future.Based on the main circuit structure and principle of STATCOM,the structure and principle of unit cascade multi-level main circuit are studied,and mixed-cascade multi-level main circuit compared with multi-level main circuit of other types of output same level has a advantage of the least needed power devices.Using SHE PWM technology lowers the low harmonic content of the main circuit output injection system current,analyzes the relationship between Switch angle error and harmonic and gives a method reducing its influence through the select switch angle robust coefficient.Secondly,based on nonlinear,parameter perturbation and external disturbance,STATCOM establishes two models existing parameter perturbation and external disturbance,system-level mathematical model and device-level mathematical model of the single infinite system.Using H2/H∞Mixed Control theory and direct feedback linear method,the two models are designed for the non-linear controller.Using LMI（LMI）for Solving the controller,through Matlab simulation,it shows the H2/H∞Mixed Control both robust performance and optimal performance, rapidly subsides oscillation of the system,effectively improves transient stability of the system, improves dynamic performance of the system,increases transmission capacity of the system and can satisfy the requirement of voltage precision after failure removal.The designed controller based on control performance has robust on uncertain parameters and has asymptotic stability within the perturbation range of all parameters.Then,analyzing the limitations of the traditional centralized control,according to the established mathematical model in this thesis,with the characteristics of the mixed-cascade multi-level main circuit,the distributed control system structure of modular embedded is presented in the control system design of STATCOM,namely,the basic control unit implementation layer,the coordination layer and the organizing layer.In this control system,the system has a good adaptability,when the external environment change or failure,through information exchange in the same level subsystems,as well as between subsystem and higher level subsystem,and the adjustment of the structure and function between the relevant level subsystems,thus the dynamic balance of the whole system is realized,so the whole system has response flexible,good flexibility and high reliability.At the same time,using standardized components and standardized communication interface specifications and interaction between the layers through the clear interface,there is no need of concern within the internal layer structure details.Generally,various components achieve different functional areas to function relatively independent,and the coupling of various components is loosely coupled.This realizes the so-called "plug-and-play" feature,and makes the control software debugging,maintaining and upgrading simplify.Subsequently,in hardware design,the basic control unit implementation layer and coordination layer are designed in detail.According to the functional requirements of the basic control unit implementation layer,the modular embedded single-phase control unit is introduced. Based on the ARM core of the 32 bits LPC2129 local controller and the CPLD design scheme, this unit completes the circuit unit design of the basic control unit implementation layer,such as trigger circuit,drive unit,communication unit,synchronization circuit and protection,and so on. According to the functional requirements of the coordination layer,using a dual-DSP project,the modular embedded main controller unit is designed.DSP56FS07（1）completes some functions, such as,acquisition,estimation and control strategy,and so on,while DSP56FS07（2）is responsible for the operation of the whole system,coordination and human-computer interaction.At the same time,the protection of STATCOM is discussed preliminarily.The main circuit fault detection schemes are presented.The controlled protection is a special and effective protection in STATCOM devices.The implementation method of the controlled protection is explained concretely in STATCOM.Finally,combining the hardware platform with two operation modes of STATCOM,the software of the STATCOM control system is designed.Using uC/OS-Ⅱembedded real-time multi-tasking operating system improves the transplantation,maintainability and scalability of the system software.