Inverter Switching Research Articles

DC-Link voltage control of a multifunctional PV-GCVSI to reduce VSI switching losses

ABSTRACT The reference input dc voltage of grid connected voltage source inverter (GCVSI) is altered in this article based on power (both active and reactive) injection from GCVSI for minimising inverter switching losses, and total harmonic distortion (THD) of grid current. If the GCVSI is exclusively used for actual power injection from the photo-voltaic (PV) system to the utility grid, the needed input dc voltage of GCVSI is twice the utility grid phase peak voltage. According to the literature, GCVSI is also used to compensate for power quality issues, and in these circumstances, the dc-link voltage value is determined by the maximum power injection of GCVSI. Under reduced load, and reduced power generation from the PV system, keeping maximum GCVSI input dc voltage reference causes extra voltage stress at GCVSI switches, and the grid current THD is worse due to high ripple current in filter inductance. Therefore, to reduce the inverter switching losses and to improve the grid current THD, the relationship between the GCVSI input dc voltage reference and the power flow from GCVSI has been formulated. The proposed work is verified using simulation studies, as well as hardware studies, and the results are compared with existing methods for validation.

ANFIS based Direct Torque Control of PMSM Motor for Speed and Torque Regulation

Nowadays, the Permanent Magnet Synchronous Motors (PMSM) are gaining popularity among electric motors due to their high efficiency, high-speed operation, ruggedness, and small size. PMSM motors comprise a trapezoidal electromotive force which is also called synchronous motors. Direct Torque Control (DTC) has been extensively applied in speed regulation systems due to its better dynamic behavior. The controller manages the amplitude of torque and stator flux directly using the direct axis current. To manage the motor speed, the torque error, flux error, and projected location of flux linkage are employed to adjust the inverter switching sequence via Space Vector Pulse Width Modulation (SVPWM). One of the most common problems encountered in a PMSM motor is Torque ripple, which is recreated by power electronic commutation and a better controller reduces the ripples to increase the drive's performance. Conventional controllers such as PI, PID and SVPWM-DTC were compared with the proposed Adaptive Neuro-Fuzzy Inference System (ANFIS) in terms of performance measures such as speed and torque ripple. In this work, the Two-Gaussian membership function of the ANFIS controller is used in conjunction with a PMSM motor to reduce torque ripple up to 0.53 Nm and maintain the speed with a distortion error of 2.33 %.

Diagnosis and localization of fault for a neutral point clamped inverter in wind energy conversion system using artificial neural network technique

Introduction. To attain high efficiency and reliability in the field of clean energy conversion, power electronics play a significant role in a wide range of applications. More effort is being made to increase the dependability of power electronics systems. Purpose. In order to avoid any undesirable effects or disturbances that negatively affect the continuity of service in the field of energy production, this research provides a fault detection technique for insulated-gate bipolar transistor open-circuit faults in a three-level diode-clamped inverter of a wind energy conversion system predicated on a doubly-fed induction generator. The novelty of the suggested work ensures the regulation of power exchanged between the system and the grid without faults, advanced intelligence approaches based on a multilayer artificial neural network are used to discover and locate this type of defect; the database is based on the module and phase angle of three-phase stator currents of induction generators. The proposed methods are designed for the detection of one or two open-circuit faults in the power switches of the side converter of a doubly-fed induction generator in a wind energy conversion system. Methods. In the proposed detection method, only the three-phase stator current module and phase angle are used to identify the faulty switch. The primary goal of this fault diagnosis system is to effectively detect and locate failures in one or even more neutral point clamped inverter switches. Practical value. The performance of the controllers is evaluated under different operating conditions of the power system, and the reliability, feasibility, and effectiveness of the proposed fault detection have been verified under various open-switch fault conditions. The diagnostic approach is also robust to transient conditions posed by changes in load and speed. The proposed diagnostic technique's performance and effectiveness are both proven by simulation in the SimPower /Simulink® MATLAB environment.

Harmonic Compensation via Grid-Tied Three-Phase Inverter with Variable Structure I&I Observer-Based Control Scheme

The power inverter topologies are indispensable devices to incorporate distributed generation schemes, like photovoltaic energy sources into the AC main. The nonlinear behavior of the power inverter draws a challenge when it comes to their control policy, rendering linear control methods often inadequate for the application. The control complexity can be further increased by the LCL filters, which are the preferred way to mitigate the current ripple caused by the inverter switching. This paper presents a robust variable structure control for a three-phase grid-tied inverter with an LCL filter. As well to the benefits of the sliding mode control (SMC), which is one of the control methods applied by power converters founded in literature, the proposed control scheme features a novel partial state observer based on the immersion and invariance technique, which thanks to its inherent robustness and speed of convergence is adequate for this application. This observer eliminates the need for physical current sensors, decreasing the overall cost and size, as well as probable sources of noise. The proposed controller is meant for a three-phase grid-tied inverter to inject active power to the grid while harmonics generated by nonlinear loads are compensated. The simulation results prove the effectiveness of the proposed method by compensating for current harmonics produced by the nonlinear loads and maintaining a low total harmonic distortion as recommended by the STD-IEEE519-2014, regardless of whether the system provides active power or not.

Hall sensor-based speed control of a 3-phase permanent-magnet synchronous motor using a field-oriented algorithm

To achieve optimum torque per amp, we retain the angle of the stator-current-vector with respect to the rotor-flux at 90 degrees, rather than controlling the amplitude of the stator-current-vector. Without or with the load torque, the proportional integral (PI) controller produced better results in the speed control loop. A controller is required to maintain a consistent speed and improve system performance as the load changes. This work develops an auto-tuning PI speed controller for 3-phase permanent-magn et synchronous motors using field oriented algorithm. The 3-phase voltage from the grid is converted to DC through a transformer and a grid-side rectifier. The DC voltage is converted back into AC through a machine-side inverter, which drives the motor with time-varying loud. The objective of field oriented control (FOC) in this work is to control the semiconductor switches in the machine-side power inverter to achieve the desired torque and flux. The stator-currents are measured and fed into the flux observer to obtain the direct-quadrature-zero (DQ-axis) current, the rotor magn etizing current, and the angle of the synchronously rotating reference frame. The results show that the motor's speed response has an earlier transient response and a less steady-state inaccuracy after tuning the controllers during acceleration and torque load adjustments.

PMSM Torque Ripple Minimization Based on Novel Low Carrier Ratio PWM Technique

Harmonic injection is commonly used in permanent magnet synchronous motor torque ripple minimization (TRM) of electric vehicle. Traditional inverter switching frequency limits TRM application at high speed due to harmonic modulation accuracy and inverter loss. To achieve TRM in the whole speed range and reduce inverter loss, a novel online calculated low carrier ratio pulsewidth modulation (LCRPWM) is proposed in this article. The carrier ratio determining regular according to the injected harmonics is established first. The relationship between injected harmonics and LCRPWM switching angle is revealed and a set of nonlinear equations is established. Thus, the problem is transformed from solving nonlinear equations into optimization by establishing a cost function. The analytical solutions of nonlinear equations are obtained, which avoids iterative operation and plunging into local minimum. Therefore, the switch angle solution method is suitable for online calculation. The LCRPWM is verified in simulation compared with the traditional regularly sampled space vector PWM, which achieves better results in voltage harmonic injection and flux tracking at a much lower switching frequency. At last, the LCRPWM is used in a test bench experiment that shows good TRM effects. The influence of sideband harmonics on torque ripple is analyzed.

An Improved Sliding Mode Control Method to Increase the Speed Stability of Permanent Magnet Synchronous Motors

A permanent magnet synchronous motor (PMSM) plays an important role in the operation performance of an electric vehicle. In order to increase the speed stability of PMSMs, an improved sliding mode control (SMC) method is proposed in this paper. Firstly, the control process of a PMSM is divided into parts, which are the torque closed-loop control and speed closed-loop control. Secondly, an integrated control method with proportional integral (PI) and inverter switching frequency is adopted in order to increase the torque performance of the PMSM. Lastly, compared with the traditional SMC method, an improved SMC method with saturation function is proposed in order to decrease the speed fluctuation of the PMSM from 7.7% to 5.9%, thereby increasing the speed stability of the PMSM. The results of the experimental test indicate that both the speed stability and starting performance of the PMSM are increased by the improved SMC method.

Current behavior-based open-switch fault on-line diagnosis of inverters in PMSM drive systems

The power switches of inverters in permanent magnet synchronous motor (PMSM) drive systems are prone to breaking down and may cause open-circuit fault (OC) due to high electrical and thermal stresses. This paper presents an OC fault diagnostic method of inverters in closed-loop controlled PMSM drive systems based on current behavior. A new detection scheme indicating the relationship between the OC fault and the current behavior variation are constructed. This scheme has the ability to detect the fault within one eighth of a current cycle. Meanwhile, a key transition model including 2 faulty states and 1 recovery state for the location of single-switch and double-switch OC faults are proposed for the first time. A total of 21 kinds of OC faults can be rapidly located. Experimental results validate that the proposed method has the advantage of fast fault diagnosis, accurate fault switch location and good robustness.

Enhanced Harmonics Reactive Power Control Strategy Based on Multilevel Inverter Using ML-FFNN for Dynamic Power Load Management in Microgrid.

The shift of the world in the past two decades towards renewable energy (RES), due to the continuously decreasing fossil fuel reserves and their bad impact on the environment, has attracted researchers all around the world to improve the efficiency of RES and eliminate problems that arise at the point of common coupling (PCC). Harmonics and un-balance in 3-phase voltages because of dynamic and nonlinear loads cause a lagging power factor due to inductive load, active power losses, and instability at the point of common coupling. This also happens due to a lack of system inertia in micro-grids. Passive filters are used to eliminate harmonics at both the electrical converter’s input and output sides and improve the system’s power factor. A Synchronous Reference Frame (SRF) control method is used to overcome the problem related to grid synchronization. The sine pulse width modulation (SPWM) technique provides gating signals to the switches of the multilevel inverter. A multi-layer feed forward neural network (ML-FFNN) is employed at the output of a system to minimize mean square error (MSE) by removing the errors between target voltages and reference voltages produced at the output of a trained model. Simulations were performed using MATLAB Simulink to highlight the significance of the proposed research study. The simulation results show that our proposed intelligent control scheme used for the suppression of harmonics compensated for reactive power more effectively than the SRF-based control methods. The simulation-based results confirm that the proposed ML-FFNN-based harmonic and reactive power control technique performs better in terms of MAE, for the case of MSE, and when evaluating based on the RMSE.

An optimized reduced switch load dependent 9-level VSI for high performance vector controlled PMSM drive

This paper presents the vector control of permanent magnet synchronous motor with load dependent voltage source multi-level inverter. The proposed voltage source multi-level inverter produces 9-level three phase balanced output voltage. The inverter switches are triggered in such a way that it can produce 5-level, 7-level, 9-level output voltage. The level of generated output voltage depends on the loading condition of inverter. The proposed inverter is connected to the permanent magnet synchronous motor for improved performance of drive. The concept of vector control has been used for decoupled control of torque and flux components of current; hence the permanent magnet synchronous motor is controlled like separately excited DC motor. The proposed work had been developed in MATLAB/SIMULINK environment and the performance had been investigated with change in load and speed. To show the effectiveness of proposed inverter FFT analysis of stator current, develop output voltage is done and THD is less than 5%. The ripple in electromagnetic torque had been reduced compared to existing methods. Hence it has been observed that overall performance of drive is enhanced.

Design of a Modified Single-Stage and Multistage EMI Filter to Attenuate Common-Mode and Differential-Mode Noises in SiC Inverter

The SiC inverter switching at high frequencies introduces increased common-mode (CM) and differential-mode (DM) electromagnetic interference (EMI) issues, such as shaft voltage, bearing currents, insulation degradation, and poor current quality in the motor. These EMI issues are commonly addressed with EMI filters employing CM and DM inductors. The increased volume and poor performance of a CM inductor designed for SiC inverter switching at high frequency require a modified EMI filter design procedure for enhanced performance and volume minimization. In this work, three EMI filters are presented with modified design procedures. A single-stage EMI filter is designed by incorporating a DM filter offering an equal attenuation to DM and CM noise at switching frequency. Here, the additional CM attenuation demand is fulfilled by a marginal value of the CM inductor, while, in multistage EMI filters, the required CM attenuation is split between the two stages. The multistage EMI filter 1 is designed using an additional CM inductor and existing load capacitance as the second stage, whereas the multistage EMI filter 2 is designed with a lesser value of CM inductance to provide CM attenuation over the entire conducted EMI frequency range. The modified EMI filters are tested on an SiC inverter operating at 200 kHz.

PV FED Interleaved Boost Converter for BLDC Motor

Abstract: The generation of solar energy and its conversion techniques gained greater importance due to increase use of electricity. The power generation scheme is more striking due to its advantages among all the Renewable Energy Sources. This project introduces a PV fed interleaved boost converter for BLDC motor, which is a simple, cost effective and efficient brushless DC (BLDC) motor drive for solar photovoltaic (SPV) array system. A interleaved boost converter is used in order to extract the maximum available power from the SPV array. This control algorithm eliminates phase current sensors and adapts a fundamental frequency switching of the voltage source inverter (VSI) hence avoids the power losses due to high frequency switching. In speed control of BLDC motor no additional circuitry or control is used. An appropriate control of interleaved boost converter is done by the incremental conductance maximum power point tracking (INC-MPPT) algorithm which offers soft starting of the BLDC motor. The proposed system is designed and modelled at steady state conditions of practical operating conditions is demonstrated through simulation results using MATLAB/ Simulink.

Investigation of the Effects of Fuel Cells on V-Q & V-P Characteristics

In this paper, the use of a FC system connected to the network is proposed as a source of DG with high reliability, and for this purpose, the dynamic model of the fuel cell has been simulated. A hybrid system of fuel cell distributed generation (FCDG) is presented to provide electrical energy for a small isolated area. Boost converter (DC/DC), in order to increase the voltage level of the system and stabilize the DC link voltage has been used, which provides the possibility of connecting several different scattered production sources in parallel. Voltage stability is concerned with the ability of a power system to maintain acceptable bus voltages under normal conditions and after being subjected to a disturbance. The use of DG sources has many advantages, including meeting peak load needs, reducing network losses, providing reactive power locally, and regulating network voltage. Among all sources of distributed production, fuel cells are of special importance due to their high efficiency, high energy density, the ability to simultaneously produce heat and electric power, and low emission of pollutants. Using fuel cells (FCs) have several advantages and in this paper we investigate the effects of FCs on power systems via simulation a single machine (DG as small gas turbine coupled with a FC) in the Dig Silent area for different PF of FC. Different PF for FC obtained with control the DC to AC inverter. We found that by control the PF of FCs, we can increase the limitation of reactive generation of overall system and improve the V-P V-Q characteristics of overall system. With the grid-connected inverter's switching control, the active and reactive power injected into the grid is controlled independently.

Instantaneous Reactive Power Control Based on Five-Level Inverter for Grid Connected PV System Improvement

Grid-connected photovoltaic systems have become the most important and popular use of the solar energy. In this paper, a photovoltaic system connected to a three-phase network is presented. The system is connected in a single step using a five-stage voltage source inverter to improve the quality of the power in the distribution system. The control strategy applied for the optimal operation of the photovoltaic system is based on the theory of instantaneous reactive power. This strategy is simple and has the advantage of running the system all day without using Phase-Locked Loop (PLL). The multilevel inverter switching signals are derived from the Pulse Width Modulated Current Controller, which provides good dynamic performance in both steady state and transient conditions. The voltage of the continuous bus capacitors is controlled using the PI controller. The validation of this proposed system is carried out through simulation with different levels of irradiations and by a comparison with the performance of a two-level inverter used in the original configuration. This specific configuration shows good results regarding the waveforms of the voltages and the output currents as well as the level of the quality of the energy represented in this paper by the THD parameter that has been studied in comparison with the two-level converter.

Analysis of torque ripples and switching losses of a diode clamped inverter fed permanent magnet synchronous motor drive

The modern-day electric vehicles use brush less DC motors (BLDC) and Permanent Magnet Synchronous Motors (PMSM) as the main driving units. The traction systems also have tried PMSM machine as the driving unit. The variable frequency power source is required to control the speed and torque of the motor to meet the load requirements. The Inverter – power modulator is causing the production of ripples in source current and flux components, hence the torque. This paper presents the effect of inverter on the flux and torque ripples. Also, the simulation results of inverter switching losses are discussed.

Design and Simulation of a Power System Composed of Grid-tied Five-level Inverter with LCL Filter

This paper presents the analysis, design, and simulation of a power system composed of a grid-tied single-phase five-level inverter with an LCL filter. First, the analysis of the proposed system has been carried out in the decoupled Direct-Quadrature frame, where the Phase-Lock-Loop technique has been used for synchronizing the LCL-filter-connected-grid with the five-level inverter. Next, the design of the LCL filter has been discussed. In this paper, we focused on the active power control based on grid current adjustment using a proportional-integral regulator and a high-frequency modulation technique for the switching of a five-level inverter, where the Sinusoidal-Pulse-Width-Modulation technique is selected. All circuit design and control schemes are discussed step by step to provide the effectiveness of the system analysis. The theoretical analysis is verified through simulation results in MATLAB/Simulink environments. An important finding when using the five-level inverter in a grid-connect system is improving the system output voltage; the total standing voltage and the total harmonic distortion are decreased compared to a conventional H-bridge inverter. The results indicate that the total harmonic distortion of grid-current is less than 0.2%, which is according to the international standards.

Modified full bridge dual inductive coupling resonant converter for electric vehicle battery charging applications

In this paper, a modified full bridge dual inductive coupling (LCL) resonant converter for electric vehicles (EVs) battery charging applications is proposed. The main objective of the proposed topology is to operate the converter in constant voltage (CV) and constant current (CC) mode during battery charging. The presented topology's uniqueness comprises the following: i) isolated charging and power factor correction (PFC), ii) to achieve zero-voltage switching (ZVS) and zero-current switching (ZCS) for inverter switches, iii) reduction of number of rectifier diodes to reduce the conduction and switching losses, and iv) reducing the magnetizing current. The output voltage dependence of resonant converter is reduced using a PFC converter against the variations of the alternating current (AC) grid input voltage. The variations of the wide range output voltage and load is compensated by a small variation in switching frequency. The proposed topology's detailed operation is simulated using the MATLAB/Simulink tool.

Finite Control Set–Model Predictive Control of H8 Inverter Considering Dead-Time Effect for PMSM Drive Systems With Reduced Conducted Common-Mode EMI and Current Distortions

To reduce the conducted common-mode (CM) electromagnetic interference (EMI) and current total harmonic distortion (THD) in permanent magnet synchronous motor drive systems, this article proposes a finite control set–model predictive control (FCS–MPC) method for an H8 inverter considering the dead-time (DT) effect. In a real system, the DT causes unexpected peak common-mode voltages (CMVs) and distortion of the inverter output voltage, which deteriorates both the CM EMI and current THD. The conventional double active voltage vector (VV) based MPC methods with an H6 inverter may not be a good solution because of the numerous CMV variations and the limit of the VV transitions. In contrast, the proposed FCS–MPC method allows all VV transitions possible without the peak CMVs by instantly operating the series-connected switch of the H8 inverter based on the previous VV, predicted current sector, and next optimal VV. Furthermore, the nonlinearity of the inverter output voltage due to the DT is compensated in a discrete-time model used for the current prediction, considering the calculation delay of the digital controller. Consequently, the current THD as well as the CM EMI can be improved. The simulation and experimental results are presented to verify the effectiveness of the proposed method.

Leveraging a Dynamic Differential Annealed Optimization and Recalling Enhanced Recurrent Neural Network for Maximum Power Point Tracking in Wind Energy Conversion System

In this article, a hybrid strategy is proposed to track that maximum power of Wind Energy Conversion System (WECS). The proposed technique is the joint execution of Dynamic Differential Annealed Optimization (DDAO) and Recalling Enhanced Recurrent Neural Network (RERNN) hence, it is called D2AORERN2 approach. In the proposed work, DDAO has input parameters, like rectifier outputs that means rectifier dc voltage, dc current, time. Based on input parameters, Dynamic Differential Annealed Optimization optimizes and minimizes the error in rectifier power and makes training dataset based on maximal power point tracking conditions. Based on accomplished dataset, the RERNN finds the optimal solution. The rectifier’s reference dc voltage is transformed for controlling the inverter switch pulses. Finally, the proposed method is activated in MATLAB/Simulink, its superiority is analyzed with various existing methods, like genetic algorithm (GA), particle swarm optimization (PSO), Hill Climb Search (HCS).The efficiency of proposed system is likened to several existing technique as GA, PSO and HCS. The efficiency of GA, PSO, HCS and proposed technique is 81%, 85%, 89% and99%. Thus the proposed technique achieves best result than the other techniques.

Induction Motor DTC Performance Improvement by Inserting Fuzzy Logic Controllers and Twelve-Sector Neural Network Switching Table

Human civilization has changed forever since induction motors were invented. Induction motors are widely used and have become the most prevalent electrical componentsdue to their beneficial characteristics. Many control strategies have been developed for their performance improvement, starting from scalar to vector to direct torque control. The latter, which is a class of vector control, was proposed as an alternative to ensure separate flux and torque control while remaining completely in a stationary reference frame. This technique allows direct inverter switching and reasonable simplicity compared to other vector control techniques, and it is less sensitive to parameter variation. Yet, the use of hysteresis controllers in conventional DTC involves undesired ripples in the stator current, flux, and torque, which lead to bad performances. This paper aims to minimize the ripple level and ensure the system’s performance in terms of robustness and stability. To generate the appropriate reference control voltages, the proposed method is an improved version of DTC, which combines the power of fuzzy logic, neural networks, and an increased number of sectors. Satisfactory results were obtained by numerical simulation in MATLAB/Simulink. The proposed method was proven to be a fast dynamic decoupled control that robustly responds to external disturbance and system uncertainties.