Two-level VSI Research Articles

A novel virtual vector-based direct power control strategy to reduce common mode voltage in transformer-less two-level grid-connected VSI

A novel virtual vector-based direct power control strategy to reduce common mode voltage in transformer-less two-level grid-connected VSI

MPPT efficiency enhancement of a grid connected solar PV system using Finite Control set model predictive controller

Maximum power point tracking (MPPT) is required to get the highest possible power generated from a photovoltaic (PV) cell. Numerous researchers have proposed different MPPT strategies to be able to collect maximum generated electricity from the photovoltaic cells.In this research paper, a MPPT model predictive control strategy for a grid-connected PV system is presented. Model predictive control (MPC) was used to develop and model the AC load energy tracking efficiency for the PV systems with a power rate of 20 kW at standard test conditions. For the purpose of obtaining the power tracking performance, a DC-DC boost converter, DC-AC two level three phase inverter, and control mechanism for a grid connected AC load system was examined and presented in this paper. To approximate the actual PV array properties, the PV model is used, and the MPPT approach is suggested as a way to regulate the DC-DC boost converter and get the most power possible from the PV array when compared to P&O and model predictive control system. A three-phase, two-level VSI is employed in this study that is controlled by a model predictive control system with SVPWM. The inverter's control structure is developed using a model predictive control system (inner loop current controller) with reference frame transformation (abc to dq) coordinates by utilizing PLL. The PLL is used to obtain critical information about the grid voltage. A RL filter is then used to lower the total harmonic distortion of the output and connect the inverter's output to the grid. The MATLAB R2019a environment is used to create the system model. The overall performance of the system for conventional perturb and observer is around 97.72%, while for Finite Control Set Model Predictive Controller is 99.80%, which is better than previous similar research with faster time response and less oscillation around maximum power point.

Prediction Window Selection in FCS-MPC for Two-Level VSI Applications

Prediction Window Selection in FCS-MPC for Two-Level VSI Applications

Review, Comprehensive Analysis and Derivation of Analytical Power Loss Calculation Equations for Two- to Three-Level Midpoint Clamped Inverter Topologies with Hybrid Switch Configurations

Increased performance requirements in new power electronics areas of application, such as electric aircraft, make innovations on different design levels necessary. In order to quickly compare different topologies, analytical loss equations provide a fast and straightforward way to narrow down the possible solution space. The approach widely used in the literature results in long and complex terms, which can only be compared between different literature sources with great effort. Moreover, the literature lacks a detailed summarizing description of these analytical equations and their derivation, starting from the standard two-level VSI up to three-level midpoint clamped inverter topologies, such as the ANPC topology in its different modulation schemes. The application of such higher-level inverter topologies allows hybrid device configurations to become performant solutions. This work aims to give a closed-form description of the analytical loss modeling and the theoretical background and provide an implementation approach for a wide span of inverter topologies and for different modulation methods.

Harmonic Voltage Amplitude Calculation and Fundamental Amplitude Correction Based on Synchronized SVPWM of Two-level VSI under Low Switching Frequency

The switching frequency of two-level VSI is usually limited to a very low level for high-power drives to minimize the switching losses. For the synchronized SVPWM under low switching frequency, there will be a relative deviation of fundamental amplitude between the output voltage and the reference voltage. To solve this problem, in this paper, a method to calculate the amplitude of output phase voltage harmonics under synchronized SVPWM is proposed, and an online fundamental amplitude correction method is proposed based on this calculation result.

Six-phase Two-level VSI Control based on Polar Voltage Space Vectors

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Hysteresis Model Predictive Current Control for PMSM With LC Filter Considering Different Error Shapes

This paper investigates three-phase two-level VSI hysteresis-based Model Predictive Control (MPC) for permanent magnet synchronous machines with different current error shapes. To limit the motor current harmonics and prevent overheating of the magnets, motor filters (mostly LC filters) are often used. The hysteresis-based MPC is investigated to provide high dynamic performance and limit the size of the filter. To compensate the resonance introduced by the LC filter and to improve system efficiency, a virtual resistor active damping strategy is implemented. To avoid additional sensors, the filter states are determined by a Luenberger Observer. However, up to now these strategies have never been investigated together with MPC and different current error shapes for motor applications. Simulation results for the different strategies prove the performance efficiency and experimental tests verify the results in a laboratory environment.

Generalized Chudnovsky Algorithm for Real-Time PWM Selective Harmonic Elimination/Modulation: Two-Level VSI Example

This article presents a novel approach to significantly reducing the mathematical complexity associated with the selective harmonic elimination (SHE), which allows for the real-time implementation of SHE with a reasonable utilization of the computational power of the digital controller. First, the transcendental equations of the optimization problem are converted to a set of algebraic equations using Chebyshev polynomials. Second, the set of algebraic equations is reduced to a single univalent polynomial using generalized Newton's identities. The roots of the polynomial hold a unique solution to the optimization problem. We show that the roots of the univalent polynomial can be solved in real time by direct substitution with no initial guess or iteration. The proposed method is a generalization of a Chudnovsky algorithm; it allows the modulation of the selected harmonics rather than eliminating them. Furthermore, the technique by which the roots of the polynomial are obtained enables one to implement the algorithm in real time with determinate execution time. This article lays the groundwork for presenting the generalized algorithm through a two-level voltage-source inverter drive. More application will follow in the near future.

Analysis of disturbing effect of 3 kV DC supplied traction vehicles equipped with two-level and three-level VSI on railway signalling track circuits

Abstract Electric traction vehicles cooperating with a 3kV DC traction system and equipped with drive systems based on voltage source inverters are the most significant sources of disturbances for a railway signalling system. Every traction vehicle to be authorised for operation on railway lines must fulfil the limits imposed on current harmonics magnitudes and those provided by railway operators. The solution introduced for prototypes of most modern traction drives is to replace the two-level inverters with three-level topology. Therefore, it is essential to establish the influence of the new solution on the railway signalling system. This paper presents a comparative analysis between simulation results delivered for two and three-level traction drive system regarding generation of disturbing current harmonics. Two types of VSI modulation techniques were taken under consideration: sinusoidal PWM (SPWM) and a new one, proposed by the authors, based on selective harmonic elimination (SHE). Furthermore, the authors presented application of one of the SHE based optimization techniques for shaping the EMU’s (electric multiple unit) DC side input current harmonics spectrum in order to meet the required limits. The described technique is based on off-line generation of a set of solutions for each of the VSI operating points and selection of the best solution for the assumed criteria. The applied simulation models and the concept of SHE control were verified in a laboratory by means of a low-power drive stand. Using the three-level inverter in traction drives system results in less current harmonics than using two-level topology without modification of the modulation technique. Thus, it does not guarantee fulfilling all limits assumed in this paper. The proposed modulation technique allows for fulfilling the limits, and the technical implementation of the proposed technique in a traction drive system will be considered in future studies.

Comparative Analysis of Two Level VSI and Three Level Neutral Point Clamped Inverter for Torque Ripple Reduction in Induction Drive

This paper presents the comparative analysis of various level of multilevel inverter for induction motor torque ripple minimization. The neutralpoint clamped (NPC) inverter is used an adequate solution in AC drives application. The Conventional inverters compared to multilevel inverters have many limitations in high-voltage and high-power applications like poor power quality, high voltage stress, EMI/EMC issue etc. Also proposed the Space Vector neutral point clamped inverter for Torque ripple reduction in induction drive. The Simple Space vector control scheme is applied to neutral point clamped inverter by reference torque estimation. In this proposed topology offer an improved performance in the form of torque ripple reduction scheme. The Classical direct torque control of two-level VSI scheme is compared with proposed three-level NPC scheme. The main aim of this paper to provide a significant method and control scheme to obtained torque ripple reduction in induction motor Drive. The result shows the performance of neutral point clamped inverter using CB-PWM on induction drive. In this paper three levels VSI based Neutral Point Clamped (NPC) multilevel inverter fed induction motor drive is simulated, analyzed and compared with two levels VSI based NPC inverter drives. Torque of the motor is controlled by using space vector based direct torque control (DTC) method. The simulation results are carried out by using MATLAB/SIMULAINK environment.

Simplified circuit and modulation scheme for five‐phase three‐level voltage source inverter

The simplified circuit and modulation scheme is presented for a five-phase three-level voltage source inverter (FPTL-VSI). The simplified FPTL-VSI is a concatenation of a dual-buck stage and a two-level VSI (TL-VSI), and the space vector pulse width modulation (SVPWM) is used as the modulation scheme. Owing to the merit of the dual-buck stage which uses only four controllable switching devices, the TL-VSI can produce a three-level voltage waveform. By simplification of the space voltage vectors, a simplified SVPWM scheme can be obtained. Thus, the simplified FPTL-VSI reduces the hardware costs and improves the quality of the output voltage waveforms. Furthermore, the hardware implementation of the simplified SVPWM scheme can be easily realised. The experimental results prove the feasibility and validity of the proposed inverter and the modulation scheme.

Direct Torque Control for Three-Level Neutral Point Clamped Inverter-Fed Induction Motor Drive

Direct torque control (DTC) is a control technique in AC drive systems to obtain high performance torque control. The classical DTC drive contains a pair of hysteresis comparators and suffers from variable switching frequency and high torque ripple. These problems can be solved by using space vector depending on the reference torque and flux. In this paper the space vector modulation technique is applied to the three-level Neutral Point Clamped (NPC) inverter control in the proposed DTC-based induction motor drive system, resulting to a significant reduce of torque ripple. Three-level neutral point clamped inverters have been widely used in medium voltage applications. This type of inverters have several advantages over standard two-level VSI, such as greater number of levels in the output voltage waveforms, less harmonic distortion in voltage and current waveforms and lower switching frequencies. This paper emphasizes the derivation of switching states using the Space Vector Pulse Width Modulation (SVPWM) technique. The control scheme is implemented using Matlab/Simulink. Experimental results using dSPACE validate the steady-state and the dynamic performance of the proposed control strategy.

Virtual-Flux Direct Power Control for Mains Connected Three-Level NPC Inverter Systems

This paper proposes a control strategy which extends the Virtual-Flux Direct Power Control traditionally employed for the conventional two-level VSI to a three-level NPC inverter. This topology generates a higher number of output voltage levels, increasing the flexibility for selecting an appropriate voltage vector. The mid-point potential is controlled according to the direction of the mid-point current and the sign of the mid-point voltage deviation. The method is adapted to be used with an LCL output filter, where some undesirable characteristics, such as filter resonance, have to be compensated. Further investigation concerning the dependency of the mid-point voltage with the current phase-shift is given. Theoretical analysis is presented and the performance of the proposed method is verified by simulation.