The Neutral Point Clamped (NPC) Multi-Level Inverters (MLI) have been ruling the power electronics industries for the past two decades. The Multi-Carrier Pulse Width Modulation (MCPWM) is common PWM techniques which are widely used in NPC-MLI applications. However, MCPWM is not having a good impact on the balancing of DC-link voltages, Common Mode Voltage (CMV) and limiting the Total Harmonics Distortion (THD). The Selective Harmonic Elimination (SHE) technique is introduced for reducing the THD, however all the switching angles should be maintained less than π/2 to keep the eliminated harmonics at constant level which narrows down the modulation index range. Hence, in recent days Space Vector Modulation (SVM) technique is widely used in NPC-MLI, which gives better DC-link voltage balancing, self-neutral point balancing, near-zero CMV reduction, better-quality harmonics profile and switching loss minimization. Hence, it is a preferred solution for the majority of electrical conversion applications such as electric traction, high power industrial drives, renewable power generation, and grid-connected inverters, etc. The paper gives a comprehensive review of the SVM for NPC-MLI. First, this paper deliberates the state of art for two-level SVM and extends it to three-level (3L) SVM. Also compares the 3L SVM performance with other MCPWM techniques. Followed by the various modified MLI SVM techniques in terms of their implementations, DC-link capacitor balancing, and reduction of CMV. Further, the review of MLI SVM is widened to open-end winding Inverters and multiphase MLIs. The final part of this paper discussed the future trends and research directions on MLI SVM techniques and its applications.

In industries, the demand for multi-phase Multi-Level Inverters (MLIs) increases as they have reduced switching loss, Common Mode Voltage (CMV) and voltage stress across switches. The Multi-Carrier PWM (MCPWM) and Space Vector Modulation (SVM) techniques are predominantly used for controlling the inverter. This paper discusses various PWM techniques like PD, POD, APOD, IC, PSC, VFC PWM and SVM (OFV and SVM with Zero CMV) for 5-phase NPC 3L Inverter. Each PWM techniques gives better results in voltage THD/ dc-link balancing/ CMV. The SVM is significant for obtaining better performances in all these aspects. The Optimized Five Vector (OFV) which has 113 vectors is preferred than normal SVM as it has inequality relationship between 5-phase voltages. Though, OFV gives better results in terms of higher output voltage and lower NPF, the CMV is not eliminated. To eliminate CMV, 51 vectors that generates Zero CMV is selected to drive the inverter where output voltage and NPF is also improved. However, due to the presence of x-y components the distortion is present. The vectors are further reduced to 31 where the x-y components are neglected to reduce the distortion is proposed in this paper. The performance of the inverter drive is enhanced by applying proposed SVM with 31 vectors. The NPF, CMV and losses are calculated for all PWM techniques, also the THD performances of an inverter is found for various techniques. The simulation is carried out for all PWM techniques and the results are verified by experimental results.

The inverter drives for controlling multiple loads will provide several advantages like lower power electronic components, costs, space, etc. In this paper, a new Three-Level (3L) Neutral Point Clamped (NPC) inverter topology for controlling the two independent Five-Phase Load (FPL) is proposed which is named as Twenty Five Switch Inverter (TFSI) topology. This TFSI topology has five switches and two diodes in each leg. The number of switches in the conventional two load inverter is 30 switches which is reduced to 25 switches in the proposed topology. The Space Vector Modulation (SVM) for the proposed TFSI topology has 1024 vectors which is the addition of two individual Five-Phase Three-Level (FPTL) SVM. The performance of two loads for the proposed topology is examined at different conditions like changing the fundamental frequency (f _o ), switching frequency (f _sw ) and modulation indices. The simulation is carried out with MATLAB/Simulink and the results are validated with hardware implementation.

A new inverter topology for driving two five-phase loads (FPL) independently is proposed in this paper. Driving two loads with a single inverter will provide good performance with reduced switches. A neutral point clamped (NPC) inverter is developed, which can provide three-level outputs. In this Twenty-Five Switch Inverter (TFSI) topology, two independent FPL can be driven with five switches and two diodes in each leg. On comparing the conventional topology for driving the two independent FPL, the number of switching devices is reduced in the proposed topology, which eventually reduces the cost and size of the inverter. The Space Vector Modulation (SVM) for this topology will combine the two individual five-phase three-level (FPTL) SVM. The resultant space vectors for the proposed TFSI topology will be 1024 vectors. The SVM is calculated for the proposed topology and investigated their performances are investigated with the help of simulation.