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Due to the rapid advancement of power semiconductor devices, the use of voltage source inverters (VSIs) has gained widespread acceptance. As a consequence, the performance of the voltage source inverter has emerged as a critical aspect that is highly reliant on the modulation strategy. The pulse width modulation (PWM) technique is the most widely utilized method of controlling power semiconductor switches of VSI. Power quality is always considered as an industrial concern for VSI-based power system such as grid-connected renewable energy systems and industrial motor drives which largely depends on the PWM technique used for switching. However, the existing PWM schemes for VSIs suffer from high total harmonic distortion (THD) and power loss problems. To mitigate the THD and power loss of VSI, a hybrid PWM technique has been proposed in this paper. The proposed hybrid PWM technique introduces a modified modulating signal along with newly shaped carrier signal. A two-level VSI is used to evaluate the performance of the proposed hybrid PWM technique both for with and without filter conditions against RL load. The proposed hybrid PWM technique offers 0.89% filtered voltage THD and 0.69% filtered current THD which are lower than that of existing PWM techniques. On the contrary, at without filter condition, the proposed hybrid PWM technique shows THDs of 45.77% and 12.50% for inverter output voltage and current, respectively which are also lower than those of existing PWM techniques. Apart from these, the proposed hybrid PWM technique reduces the switching and conduction power losses of the VSI as compared to existing PWM techniques. The simulation works are carried out in MATLAB/Simulink environment and a reduced scale experiment is conducted in laboratory to evaluate the performance of the proposed hybrid PWM technique. 2013 IEEE. Open Access funding provided by the Qatar National Library. Scopus

Recent developments in multilevel inverters have provided impetus for their applications in the medium voltage renewable energy generation processes. This paper proposes an advanced pulse width modulation technique for a modular multilevel cascaded (MMC) inverter based grid integrated solar photovoltaic (PV) system. It offers lower total harmonic distortion (THD) and power losses compared to the existing modulation techniques. This paper shows the design and performance evaluation of the proposed technique using a 3-phase 5-level MMC inverter-based grid connected PV system. The proposed PWM technique offers 12.49% (without filter) and 0.96% (with filter) output line voltage THDs. It also offers 4.64% output current THD, which complies with the IEEE-519 standard for grid integration. Besides THD reduction, it also reduces the switching and conduction power losses of the MMC inverter. Lower losses may help to keep device temperature low, which is essential for power converters used in superconducting magnetic energy storage (SMES) systems. The simulation is performed in MATLAB/Simulink and the proposed technique is experimentally validated with a laboratory test platform.

Nowadays, the use of superconductive magnetic energy storage (SMES) devices in grid integration are highly escalated with the technological amelioration of magnetic components. The power quality and energy conversion efficiency of the power conditioning system of the SMES and renewable energy systems depend on the control algorithms of the voltage source inverter (VSI). However, the traditional control schemes cause inferior response and conversion efficiency. In this paper, an advanced control technique named PI+LLC controller is proposed, which is based on the proportional integral (PI) controller and lead-lag compensator (LLC). The proposed control technique offers significant reduction in the total harmonic distortion (THD), superior dynamic response, smooth response against fault, excellent reference tracking capability of grid current and improved power quality performance at both inverter side and grid side for a 5-level neutral point clamped inverter based grid-tied photovoltaic system. It is expected that, the proposed control scheme can also be used to mitigate the excessive heat of the VSI based SMES system by improving the performance of the power conditioning system. The performance of the proposed control technique is evaluated in MATLAB/Simulink environment to validate the excellent features of the proposed control scheme.

Mitigation of excessive heat due to high frequency switching of voltage source converter (VSC) is always an industrial concern for superconducting magnetic energy storage (SMES) or high temperature superconducting (HTS) material based power conditioning system with grid-tied renewable energy interface. The pulse width modulation (PWM) technique employed for the switching of the VSC has a significant impact on joules heating, switching and conduction power losses, total harmonic distortion (THD) profile of the VSC output, and conversion efficiency in the SMES/HTS based grid-tied power system. In this paper, a modified reference saturated third harmonic injected equal loading PWM technique is proposed for a VSC-based grid-tied photovoltaic (PV) system, which offers lower THD and reduced power conversion losses. The proposed PWM technique employed in the VSC can be used in a PV-based SMES/HTS integrated power system to improve the performance of the power conditioner. To prove the superiority of the proposed PWM technique, a simulation in MATLAB/Simulink was carried out and the simulation results were validated by laboratory tests.

This paper presents a generalized structure of a new three-phase multilevel inverter (MLI) which ensures better performance with the minimum number of components for different applications including DC power supply-based renewable energy sources. The proposed MLI topology is developed in the form of several basic blocks which are individually made of a DC voltage source and a semiconductor switch. All the balanced DC sources required for the proposed inverter are made through a high-frequency magnetic link. The single–phase and three-phase five level (5-L) inverters with the rating of 3.5 and 100 kVA, respectively, are simulated, while a five level (5-L) single-phase inverter is implemented for demonstrating the switching strategy and different operational modes. The rigorous calculations are presented to determine switching losses and conduction losses which are minimum because only three conducting switches are responsible for generating each voltage level during every operating mode. The structure of the aforementioned inverter provides optimized value of total standing voltage (TSV = 5.5Vdc with 5-L single-phase leg) of the system. The proposed inverter offers energy conversion efficiency of 94.84% for 5-L single-phase leg which is significantly enhanced and it also minimizes the equipment ratings as well as overall costs of the entire system.

A new three phase multilevel inverter with reduced number of components count is proposed in this paper. This inverter is designed using a single DC source per phase to generate multiple level output voltage which makes it suitable for low and medium voltage applications, including ac-coupled renewables or energy storages. A generalized circuit configuration is shown in this paper following which the number of output voltage level can be increased as per expectation. Although, each element endures the voltage stress equivalent to the input DC voltage, the value of total standing voltage (TSV) is reduced by the utilization of minimized number of components with respect to the number of series connected capacitors. Further, staircase modulation scheme is used to generate the switching signals. Hence, the proposed inverter can be operated at low switching frequency with optimal output current harmonic distortion which decreases switching losses and suppresses power factor falling. In order to validate the theoretical explanations and practical performances of the proposed inverter, the hypothesis is simulated for 9, 13 and 39 output voltage level inverters for three phase with a line voltage total harmonic distortion (THD) of 6.06%, 4.16% and 2.10% respectively in MATLAB/Simulink and a 5-level single phase laboratory prototype is implemented in the laboratory.

The traditional DC-link indirect AC/AC power converters (AC/DC/AC converters) employ two-stage power conversion, which increases the circuit complexity along with gate driving challenges, placing an excessive burden on the processor while implementing complex switching modulation techniques and leads to power conversion losses due to the use of a large amount of controlled power semiconductor switches. On the contrary, the traditional direct AC/AC voltage controllers, as well as frequency changers, suffer from high total harmonic distortion (THD) problems. In this paper, a new single-phase to three-phase AC/AC step-down power converter is proposed, which utilizes a multi-linking transformer and bilateral triode thyristors (TRIACs) as power semiconductor switches. The proposed direct AC/AC power converter employs single-stage power conversion, which mitigates the complexity of two-stage DC-link indirect AC/AC converters and traditional single-stage AC/AC frequency changers. Instead of using high-frequency pulse width modulated gate driving signals, line frequency gate pulses are used to trigger the TRIACs of the proposed AC/AC converter, which not only aids in reducing the power loss of the converter but also mitigates the cost and complexity of gate driver circuits. The proposed AC/AC converter reduces the THD of the output voltage significantly as compared to traditional direct AC/AC frequency changers. The performance of the proposed AC/AC converter is validated against RL and induction motor load in terms of overall THD and individual harmonic components through MATLAB/Simulink environment. A reduced-scale laboratory prototype is built and tested to evaluate the performance of the proposed AC/AC power converter. The experimental and simulation outcomes reveal the feasibility and excellent features of the proposed single-phase to three-phase AC/AC converter topology.

A simple traditional inverter which generates a square wave is not satisfactory for grid integration. A pure sinusoidal wave is highly desired for grid tied inverter. Multilevel inverter (MLI) has emerged a key technological development in the field of energy control for high-power medium-voltage (6–36 kV) by generating sinusoidal output waveform without using large and bulky line filter. The cascaded H-bridge (CHB) inverters produce more output voltage levels (e.g., more sinusoidal) in the medium-voltage range, hence minimize the harmonic components. In this paper, a fifty-five level (55L) CHB converter is designed, simulated, and analyzed for 11kV system using a new modified third harmonic injected pulse width modulation-based (MTHPWM) switching technique. Performance of existing switching techniques and proposed switching technique with a 55L, 3- $\phi$ , 11kV CHB inverter is evaluated in terms of total harmonic distortion (THD) and inverter loss. The proposed modulation scheme results very promising THD profile (3.41%) and reduces switching losses over other conventional modulation techniques. All the simulated results are carried out in the MATLAB/Simulink environment.

In this paper, a new single-phase single-ended primary-inductor converter (SEPIC) topology-based ac-dc converter is proposed pursuing only a singular switch for power conversion. The proposed converter exhibits higher input power factor, moderated total harmonic distortion (THD) in the input line current complying with IEEE-519 standards and high voltage gain compared to its traditional counterpart. In addition, the proposed topology displays promising performance under unexpected load introduction and load variations. Furthermore, the proposed converter causes a very low power loss comparing to its conventional topologies for the utilization of only a single switch to signal control. All the simulations have been performed in MATLAB/Simulink environment which upholds the performance of the topology and validates the philosophy of proposed converter.

Distorted line current is always a common issue of induction motor drive (IMD) driven by an 18-pulse rectifier fed multilevel inverter (MLI). The basic 18-pulse diode bridge rectifier (DBR) used in IMD does not comply with the IEEE-519 standard. A 3-level neutral point clamped (NPC) MLI operating at low switching frequency is utilized on the motor side to provide compactness and good performance. Inverter switching uses pulse width modulation (PWM) technique which is largely affected by the total harmonic distortion (THD) produced by the DBR. A new PWM scheme is proposed which utilizes the injection of different odd harmonics into the multi-carrier based sixty-degree PWM (SDPWM) modulating signal to reduce harmonic contents of the line current. The proposed modulation technique reduces line current THD to 1.85%, which satisfies the requirement of IEEE-519 standard. The performance of the proposed PWM technique with 18-pulse 3-level NPC MLI fed IMD is analyzed by simulating it in MATLAB/Simulink environment under large load varying conditions. According to the simulation results, the system features a reduced line current THD and enhanced power quality performances.

The use of control algorithms in inverter topologies is becoming more attractive for integration of wind and photovoltaic (PV) energy with a grid. Among the various inverters, the non-isolated inverter topology has gotten a huge attention for fixing the problem of leakage current issue with other inverters. In this paper, a linear control strategy is offered for the grid connected non-isolated PV inverter. The proposed scheme consists of a proportional resonance (PR) controller with lag compensator (LC). This controller offers lower oscillation in output grid current and better steady state performance for the grid-tied PV inverter systems. The analytical comparison of proposed control scheme and the other control strategies are mentioned in this work. The simulation results indicate the improvements of the performance for the proposed controller in terms of reference tracking ability, total harmonic distortion (THD), and the supplied dc bus voltages of the grid-injected PV inverter systems. This proposed controller can enhance the performance of the PV systems by reducing energy consumption during load change and faulty condition.

Now-a-days, transformer-less grid connected solar photovoltaic (PV) inverters have attracted significant attention due to their special benefits such as higher efficiency, lower cost, and easy set up mechanism. A new transformer-less inverter topology with reduced leakage current and improved performances has been presented in this paper. This inverter circuit has been fabricated with eight semiconductor devices and an LCL filter at the output side. Three switches are used in the common mode voltage (CMV) clamping brunch to enhance inverter efficiency. In the freewheeling brunch, one switch is used so that the leakage current spikes get avoided. In the freewheeling mode common mode voltage is kept constant. While zero voltage state, CMV is clamped to half of the input voltage. The proposed inverter provides only a total of 10.18 mA leakage current. The grid current THD and grid voltage THD are found to be 1.42% and 0.37%, respectively. Unipolar SPWM method has been used to control the power switches. The behavior of the proposed TLPV inverter is verified via simulation analysis performed at MATLAB/Simulink environment.

Renewables such as solar, wind, tide energies are the new route for alternative power sources in spite of fossil fuels or other nonrenewable energies. From the last decade, converting the variable solar dc power to constant ac power has become a challenge. This paper underpins a novel three phase transformer-less grid connected photovoltaic inverter with the control blocks applicable for all types of grid voltage ranges. This novel three-phase inverter topology not only contains very lower reduced leakage current as well as less total harmonic distortion (THD) but also improved power quality. Filter clamping approach has been owned to eliminate extra leakage current through the ground path. Besides unipolar sinusoidal pulse width modulation (SPWM) method has been used to control the power switches. As a result, the common mode voltage has been held to constant, which is also responsible for reducing leakage current to 25.42 mA. The leakage current suppression has been analyzed in details with simulation results. The switches did not affect the efficiency of this inverter so much but reduced the leakage current. Switching losses and conduction losses are very low. The THD of Grid voltage of this proposed topology is recorded 0.94% likewise, grid current THD is measured as 0.42%. To check the performance of this proposed inverter more accurately, input voltage as well as load amount of this inverter have been changed instantly in the middle of simulation. This topology has been implemented and tested via MATLAB/Simulink platform.

Now-a-days, renewable energy has considered a potential source of energy to ensure the sustainable developments. Solar energy plays a vital role not only as a renewable energy source but also an environment friendly energy source. Power electronic inverter is commonly used to interconnect solar photovoltaic (PV) systems to power grids or ac loads. From last decades' industries have been developing solar PV inverters to make it transformer-less compact and lightweight, efficient, and grid friendly. This paper underpins a new single phase TLPV inverter topology, reducing extra leakage current, decreasing total harmonic distortion (THD) and improving power quality. Midpoint clamping method is applied to suppress leakage current. Unipolar sinusoidal pulse width modulation technique with zero dead time have been obtained to control the power switches that also helps to reduce the leakage current plus decreases THD by creating lower ripple on the output voltage. Seven super junction insulated gate bipolar transistors are used as the power switches. 10.28 mA leakage current has been recorded for the proposed inverter. The grid voltage and grid current THD have been recorded 0.42% and 1.62%, respectively. Besides 97.28% European efficiency has been found for this proposed H7 topology. The performance of the proposed inverter has been studied via MATLAB/Simulink simulation.

The neutral point clamped (NPC) inverter is the most prevalent topology among all the multilevel converter topologies because of its good power quality and high efficiency. For past few decades, NPC inverter is popularly being used in industrial motor drive applications. The modulation strategies have a significant impact on the power efficiency of inverter fed motor drive systems. This paper presents a comparative study on the performances of a three phase 11-level NPC fed induction motor for several common pulse width modulation (PWM) based multilevel converter modulation schemes using MATLAB/ Simulink. This study includes the results of line voltage and current profiles of an inverter, total harmonic distortion characteristics, power loss performance of NPC as well as induction motor’s torque and speed profiles. The main aim of this paper is to explore different recently developed modulation strategies to determine a suitable one to ensure high efficiency of an NPC converter fed induction motor drive system.

This paper presents a neutral point clamped (NPC) multilevel inverter (MLI) with an advanced controller for a three-phase grid-tied photovoltaic (PV) system. NPC inverter is the promising candidate among all MLI to mitigate total harmonic distortion (THD) of inverter current for grid-tied PV system. Controller is another crucial part for designing grid-tied power system. In this paper, a PI+HC controller is proposed to improve the control performance of a fifteen-level (15L)-NPC inverter fed grid tied PV system. The proposed controller is based on the linear PI controller which is connected with a feedback of harmonic compensator (HC) to show excellent performance in terms of injected grid current THD, steady state error, sudden load change response, and the capability of handling different fault conditions than existing controllers. The designed controller is simulated in MATLAB/Simulink environment. The simulated results present the excellent performance of the proposed controller.