Abstarct: To improve the quality and address the unbalanced loads and fault of power distribution systems, various technologies have been invented and proposed. Among the most efficient and effective of these is the use of Static Synchronous Compensator (STATCOM). These devices are designed baxsed on the principles of Voltage Source Converter (VSC), which control active and reactive power flow by injecting current, thus stabilizing the bus voltage at the installation site.in industrial applications, such as electric arc furnaces, the converter seeks to exchange positive and negative currents. Since these types of loads are usually connected to relatively strong networks, the delta configuration seems to be the best choice for such applications. The Cascaded H-Bridge Multilevel Inverter with a delta configuration is suitable for STATCOM due to its simple control and high-quality output. When this converter is used as a STATCOM with a delta connection in this thesis, it can not only control positive sequence reactions but also negative sequence reactive power. Therefore, it will be demonstrated in this research that the star-connected converter has limited capability compared to the delta-connected converter for compensating unbalanced loads.For the control of this converter, proportional-integral (PI) control methods and Model Predictive Control (MPC) are comparatively presented. In this thesis, the proportional and integral (PI) control method was first investigated. Due to the nonlinearity of the system, this control method has a limited performance range compared to the predictive control (MPC) method. The results show that The predictive control method works well in different working points, but the proportional and integral (PI) control method works only in one working point. Finally, the results show that the synchronous static compensator with triangle configuration with the predictive control method performs better to compensate the unbalanced voltage. It has a star configuration and is also capable of harmonic load compensation.