In order to improve power quality of electrical distribution networks, a lot of methods are used that their most efficient and effective is the usage of custom power equipment. This equipment has designed based on voltage source inverter and each of its equipment is suitable for compensation of some power quality phenomenon. Distribution Static Synchronous Compensator (D-STATCOM) is one of the custom power equipment that bus reactive power is controlled by current injection and is caused to fix bus voltage in installment location. D-STATCOM performance is simulated based on sinusoidal PULSE WIDTH MODULATION (SPWM) and SPACE VECTOR PULSE WIDTH MODULATION ((SVPWM)) using PSCAD/EMTDC software in improvement of voltage sag and swell, and these MODULATIONs are used to produce switching signals of voltage source inverter the equipment. D-STATCOM performance is compared with each other applying these MODULATIONs. D-STATCOM based on (SVPWM) restores voltages sag and swell effectively. In addition, it produces lower distribution harmonic.

Renewable energy sources, such as photovoltaic (PV) and fuel cells, have been given attention during the latest decades due to the limitations of non-renewable sources. Therefore, it is essential to improve the structure of voltage source inverters (VSIs) to increase their voltage gain in these applications. The split-source inverter (SSI) is a single-stage topology that uses the same number of power switches and switching states as VSI with boosting capability and the continuous input current. Three-phase switched-inductor SSI (SI-SSI) consists of two equal inductors, six diodes, one capacitor, and the bridge structure. This topology increases the voltage gain of conventional SSI. On the other hand, the MODULATION scheme impacts the inverters' performance. SPACE VECTOR PULSE WIDTH MODULATION ((SVPWM)) operates more efficiently than the third-harmonic injection PULSE WIDTH MODULATION (THIPWM) and sinusoidal PULSE WIDTH MODULATION (SPWM). However, varying the duty cycle of charging the inductors in each switching cycle increases the low-frequency ripples on the DC side of the inverter. To overcome the mentioned drawback in (SVPWM), the modified (SVPWM) has been proposed. In the modified (SVPWM), the interval corresponding to zero states is redistributed to charge both inductors of SI-SSI with similar constant duty cycles. Thus, the low-frequency components on the inductors' current and capacitor voltage are decreased without affecting the active states. The operation of three-phase SI-SSI with SPWM, THIPWM, traditional (SVPWM), and modified (SVPWM) is investigated and simulated by MATLAB/Simulink.

In this paper, a 7-level Diode Clamped Multilevel Inverter (DCMLI) is simulated with three different carrier PWM techniques. Here, Carrier based Sinusoidal PULSE WIDTH MODULATION (SPWM), Third Harmonic Injected PULSE WIDTH MODULATION (THIPWM) and Modified Carrier-Based SPACE VECTOR PULSE WIDTH MODULATION ((SVPWM)) are used as MODULATION strategies. These MODULATION strategies include Phase Disposition technique (PD), Phase Opposition Disposition technique (POD), and Alternate Phase Opposition Disposition technique (APOD). In all the MODULATION strategies, triangular carrier and trapezoidal triangular carrier signals are compared with reference signal, then control PULSEs are generated. The detailed analysis of the results has been presented and compared with experimental results in terms of fundamental component of output voltage and percent of THD.

The conventional SPACE VECTOR PULSE-WIDTH MODULATION ((SVPWM)) for cascaded H-bridge inverters (CHBIs) has problems of computational complexity and memory requirements. Operation in overMODULATION mode is the other reason for the complexity in (SVPWM). This paper proposes a novel MODULATION method, named as level VECTOR PULSE-WIDTH MODULATION (LVPWM), for voltage control of CHBIs. The concept of the proposed method is similar to the (SVPWM) but with different VECTOR diagram and dwell times calculations. Unlike the (SVPWM), the α and β axes and also their variables are considered separately without gathering in complex variables. The VECTOR diagram has two separated α and β axes each of which contains individual switching VECTORs and reference VECTORs. The selection of the VECTORs to synthesize the reference VECTORs depends only on the amplitudes of the reference VECTORs. The computational overhead and memory requirement are independent of the number of cascaded H-bridges. Lower computational overhead and easy and continuous extension to overMODULATION region are the advantages of the proposed method compared with the (SVPWM)-based methods. Moreover, the switching algorithm achieves improved efficiency for the inverter. Simulation and experimental results verify the effectiveness of the proposed algorithm.

Abstract- The SPACE VECTOR PULSE-WIDTH MODULATION ((SVPWM)) is a simple and suitable method for voltage control of three-phase two-level voltage source inverters (VSI)s. However, there are plenty of methods to improve the two-level VSIs performance by adding virtual VECTORs or sub-sectors to the (SVPWM) diagram which cause complexity in implementation of (SVPWM) for VSIs similar to multilevel inverters. Operation in overMODULATION mode is the other reason for complexity in conventional (SVPWM). This paper proposes a novel MODULATION method, named as level VECTOR PULSE-WIDTH MODULATION (LVPWM), for voltage control of VSIs. The concept of the proposed method is similar to (SVPWM) but with different VECTOR diagram and dwell times calculations. Unlike the (SVPWM), the α and β axes and also their variables are considered separately without gathering in complex variables. The VECTOR diagram has two separated α and β axes each of which contains individual switching VECTORs and reference VECTORs. The selection of the VECTORs to synthesize the reference VECTORs depends on only the amplitudes of the reference VECTORs. With lower computational overhead and easy and continuous extension to overMODULATION region, the proposed method is a simple solution to the mentioned problems. Simulation and experimental results and harmonics analysis verify the effectiveness of the proposed algorithm.

Common-mode voltage (CMV) generated by the inverter causes motor bearing failures in multiphase drives. On the other hand, presence of undesired z-component currents in six-phase induction machine (SPIM) leads to extra current losses and have to be considered in PULSE WIDTH MODULATION (PWM) techniques. In this paper, it is shown that the presence of z-component currents and CMV in six phase drive system are two major limiting factors in SPACE VECTOR selection. The calculated voltage SPACE VECTORs for both symmetrical and asymmetrical SPIM drive system with three-level inverter are illustrated in the decoupled subSPACEs and described in terms of undesirable voltage components and CMV value. Several SPACE VECTOR PULSE WIDTH MODULATION ((SVPWM)) techniques are investigated based on CMV and z-component currents generation. Then, a modified (SVPWM) technique with minimum current distortion, undesired current components and CMV with a modest torque ripple is proposed based on the simulation results.

This paper presents the low voltage Dynamic Voltage Restorer (DVR) based on application of SPACE VECTOR PULSE WIDTH MODULATION ((SVPWM)) for three phases Voltage Source Converter (VSC) and it is the standard PWM techniques to utilize the DC-AC power conversion. A control technique based on (SVPWM) is also proposed for dynamic voltage restorer. The DVR was a power electronics device that was able to compensate voltage sags on critical loads dynamically. By injecting an appropriate voltage, the DVR restores a voltage waveform and ensures constant load voltage. The compensating signals are determined dynamically based on the difference between desired and measured values. The DVR consists of VSC, injection transformers, passive filters and energy storage (lead acid battery). The efficiency of the DVR depends on the efficiency of the control technique involved in switching of the inverter. In this paper a novel structure for voltage sags mitigation and for power quality improvement are proposed. There was an increasing trend of using SPACE VECTOR PWM ((SVPWM)) because of their easier digital realization and better dc bus utilization. The proposed control algorithm is investigated through computer simulation by using PSCAD/EMTDC software and hardware implementation using DSP TMS320F2812. The results of the simulation and experimental show the performance of the proposed low voltage dynamic voltage restorer and prove the validity of the proposed topology. It was concluded that the proposed low voltage dynamic voltage restorer works well both in balance and unbalance conditions of voltages.