Francisco Beltrán Carbajal

84 Pulse Converter, Design and Simulations with Matlab

Flexible Alternating Current Transmission System (FACTS) devices have been proposed for fast dynamic control of voltage, impedance, and phase angle in high-voltage AC lines. The application of this technology has opened new and better opportunities for an appropriate transmission and distribution control. The efforts performed all over the world to improve the power quality have originated several power conditioners, which by themselves contribute to power degradation due to switching of the semiconductor devices, and harmonic effects generated in the converters. Thus, big elements have been used as filters, pursuing to have appropriate power quality with low extra noise. Because of that, this technology has not been probed in stringent applications such as hospitals or airports, which are two of the environments to consider. The series and shunt power systems compensation are used with the purpose of improving the operating conditions; respect to the voltage, the compensation has the purpose of handling reactive power to maintain bus voltages close to their nominal values, reduce line currents, and reduce system losses. The voltage magnitude in some buses may be controlled through sophisticated and versatile devices such as the StatCom, which is the smaller and most cost effective FACTS device in many applications (Hingorani, 2007), and is a power reactive source (Acha et al., 2004; Song & Johns, 1999). By regulation of the StatCom’s output voltage magnitude, the reactive power exchanged between the StatCom and the transmission system can be controlled (CIGRE, 1998; Davalos, 2003; El-Moursi & Sharaf, 2005; Hingorani & Gyugyi, 2000;Wang, 2000). This Chapter describes how the assembling of a Voltage Source Converter (VSC) that meets the IEEE Std. 519-1992 (IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems) is performed, and emphasizes its development through Matlab simulations. The low Total Harmonic Distortion (THD) that this VSC produces allows this power conditioner to be considered for its use on stringent applications or in the reactive power compensation and the power quality improvement. The reinjection principle used, makes this proposal to be considered as an affordable solution to the sinusoidal synthesization due to the reduced number of switches needed. The reinjection transformer is one of the most important elements in this configuration, and it can have a wide turn ratio’s variation without leading out the special application standards.

Robust Control of Active Vehicle Suspension Systems Using Sliding Modes and Differential Flatness with MATLAB

The main control objectives of active vehicle suspension systems are to improve the ride comfort and handling performance of the vehicle by adding degrees of freedom to the system and/or controlling actuator forces depending on feedback and feedforward information of the system obtained from sensors. Passenger comfort is provided by isolating the passengers from undesirable vibrations induced from irregular road disturbances, and its performance is evaluated by the level of acceleration which vehicle passengers are exposed. Handling performance is achieved by maintaining a good contact between the tire and the road to provide guidance along the track. The topic of active vehicle suspension control system, for linear and nonlinear models, in general, has been quite challenging over the years and we refer the reader to some of the fundamental work in the area which has been helpful in the preparation of this chapter. Control strategies like Linear Quadratic Regulator (LQR) in combination with nonlinear backstepping control techniques are proposed in (Liu et al., 2006). This strategy requires information about the state vector (vertical positions and speeds of the tire and car body). A reduced order controller is proposed in (Yousefi et al., 2006) to decrease the implementation costs without sacrificing the security and the comfort by using accelerometers for measurements of the vertical movement of the tire and car body. In (Tahboub, 2005) a controller of variable gain that considers the nonlinear dynamics of the suspension system is proposed. It requires measurements of the vertical positions of the car body and the tire, and the estimation of other states and of the road profile. On the other hand, many dynamical systems exhibit a structural property called differential flatness. This property is equivalent to the existence of a set of independent outputs, called flat outputs and equal in number to the control inputs, which completely parameterizes every state variable and control input (Fliess et al., 1995). By means of differential flatness