Voltage Source Inverter System Research Articles

Voltage-Modulated Direct Power Control for a Weak Grid-Connected Voltage Source Inverters

In this paper, we design a voltage-modulated direct power control (VM-DPC) for a three-phase voltage source inverter (VSI) connected to a weak grid, where the phase-locked loop (PLL) system may make the system unstable if the conventional vector current control (VCC) method is applied. Compared with the conventional VCC method, the main advantage of the proposed VM-DPC method is that the PLL system is eliminated. Moreover, in order to inject the rated real power to the weak grid, the VSI system should generate some certain amount of reactive power as well. An eigenvalues-based analysis shows that the system with the proposed method tracks its desired dynamics in the certain operating range. Both simulation and experimental results match the theoretical expectations closely.

Design and Development of Grid-connected Quasi-Z-Source PV Inverter

<span>An inverter system applied with the PV source typically has a problem of lower input voltage due to constraint in the PV strings connection. As a countermeasure a DC-DC boost converter is placed in between to achieve a higher voltage at the inverter DC link for connection to the grid and to realize the MPPT operation. This additional stage contributes to losses and complexity in control thus reducing the overall system efficiency. This work discussed on the design and development of a grid-connected quasi-Z-source PV inverter which has different topology and control method compared to the conventional voltage source inverter and able to overcome the above disadvantages. Modelling and performance analysis of the voltage and current controller to achieve a good power transfer from the PV source, as well sycnchronization with the grid are presented in detail. Results from both simulation and experimental verification demonstrate the designed and developed grid-connected qZSI PV inverter works successfully equivalent to the conventional voltage source inverter system.</span>

Harmonic Analysis and Mitigation of Low-Frequency Switching Voltage Source Inverter With Auxiliary VSI

The output currents of high-power voltage source inverters (VSIs) are distorted by the switching harmonics and the background harmonics in the grid voltage. This paper presents an active harmonic filtering scheme for high-power, low-frequency switching VSIs with an additional auxiliary VSI. In the approach, the auxiliary low-power, high-frequency switching VSI is used to compensate both the switching harmonics of the high-power VSI and the low-order harmonics introduced by the distorted grid voltage. Impedance modeling and analysis are implemented for the hybrid VSI system, where the impacts of the grid impedance are analyzed. Different control targets are then formulated based on the analysis, and the corresponding control strategies are proposed. Last, simulations and experimental results are provided to validate the theoretical analysis and the performance of the proposed control strategy.

HIL Co-Simulation of Finite Set-Model Predictive Control Using FPGA for a Three-Phase VSI System

The conversion and control for the utilization of power generated from energy sources can be performed using a power electronic converter system. The voltage source inverter (VSI) is one of the commonly used converter topologies, being controlled by a switching control algorithm for power conversion. Finite set-model predictive control (FS-MPC) is a modern switching control algorithm and has received significant attention due to its predictive nature. In this paper, the implementation of FS-MPC is presented for the load-side current control of a three-phase VSI system using an integrated platform of MATLAB/Simulink and Xilinx system generator (XSG). The XSG provides the functionality of digital design and intuitive implementation of field-programmable gate array (FPGA) controlled systems. The additional functionality of hardware-in-the-loop (HIL) co-simulation using FPGA is used for the testing and validation of controller performance. The controller performance is validated through three platforms: MATLAB/Simulink, XSG and HIL co-simulation using ZedBoard Zynq evaluation and development FPGA kit.

Simulation and Study of Multilevel Inverter System Fed By Photovoltaic Source

This paper proposes a simulation of Photovoltaic energy used to supply an induction motor with acomparison of two types of inverters.In general, the greater number of motorswhich"are used incommercial and industrial applicationsare"induction motors. To use PV source to run the induction motor, an interface circuits are used which are a dc-dc"converter and an inverter, the PV cell has nonlinear behavior,"adc-dc converter is used along with Maximum Power Point Tracker controllerto improve theefficiency by boosting the output voltage of the PV module and to match the load demand."The dc output voltage of PV modulethen"converted to AC, two types of inverter are presented, A conventional Voltage Source Inverter system and multilevel inverter system which employselective harmonic eliminationmethod fed three phase induction motor, these two types of inverters are simulated using Matlab/Simulink and their results are presented. The FFT spectrum is presented of the output currents to analyze the harmonics reduction, which shows that the"multilevel inverter is better than VSI system"according to harmonics reduction and increment in output voltage and power.

Power flow control model of energy storage connected to smart grid in unbalanced conditions: a GSA-technique-based assessment

ABSTRACTA gravitational search algorithm (GSA)-based power flow control (PFC) model for energy storage related to smart grid under unbalance conditions is proposed in this paper. Source side and load side power transfer capability is considered to be increased by this proposed algorithm and it offers several conveniences such as the improved predicting capability, degradation in complexity as well as the randomization and so on. The smart grid incorporates the combination of the microgrid (MG) such as renewable energy sources, energy storage devices, grid and load. Here, a renewable energy source of the photovoltaic (PV) system and energy storage of fuel cell (FC) is considered and AC load is utilized. In the proposed method, the controller parameters of the power controller are optimized by the GSA technique based on the variation of active and reactive power of the system. The better power flow under unbalanced load conditions with subject to the minimum power variation is ensured by the optimization process. The proper control signals to the voltage source inverter (VSI) system are generated by this proposed method. Then, the proposed method is implemented using the MATLAB/Simulink platform and a comparison analysis with the existing techniques presents the performance of the proposed method.

Current-Controller Effectiveness for Grid-Connected Converters: Comparative Case Studies

AbstractThis paper describes the implementation and comparison of two current-control strategies for a three-phase voltage source inverter (VSI) system grid connected via a LCL filter and used in d...

Analysis and controller design for stand‐alone VSIs in synchronous reference frame

The common practice for controlling the stand-alone voltage source inverters (VSIs) is to transform abc voltage and current signals to DC signals using the dq transformation, which makes it possible to control the new DC voltage and current signals just using simple proportional-integral controllers with a zero steady-state tracking error. However, the transformation causes coupling terms between d- and q-axis components in both current control loops and voltage control loops, which deteriorate the dynamic and steady-state performance of the control system. This study presents a step-by-step graphical analysis and design approach for a three-phase stand-alone VSI system in the dq reference frame, which provides a clear systematic decoupling process to design the inner- and outer-loop current and voltage controllers, respectively. The closed-loop d- and q-axis output impedances of the stand-alone VSI system by considering the coupling effects between axes are also formulated, modelled, and evaluated. The study investigates how the decoupling and compensating terms added in the current and voltage controllers affect the dynamic performance and output dq impedances of the VSI system. Simulation and hardware results verify the effectiveness of the graphic design and analysis strategy.

Sliding ModeControl of Dc/Dc Switching Converters for Photovoltaic Applications P

Maintaining good voltage regulation at output and having fast dynamic response under sudden load fluctuation are extremely important in distributed generation (DG) as well as uninterrupted power supply (UPS) systems. This paper presents a fixed frequency hysteresis current (FFHC) controller, which is implemented on the basis of sliding mode control (SMC) technique and fixed frequency current controller with a hysteresis band. The controller has the benefit of hysteretic current control having fast dynamic responses and reduces the disadvantages of the variable switching frequency. To overcome elliptical sliding surface was taken. These has been verified and compared with the carrier based pulse width modulated (PWM) voltage controller under the same load fluctuation. The proposed method is then applied to islanded single phase voltage source inverter (VSI) system. The results show that the dynamic response is quite faster than that of widely used PWM-controlled inverter systems. The DC voltage that is required for the inverter input is supposed to be given from the output of PV panel with buck converter. In PV system ,sliding mode control is used to track the maximum power point .Here inverter and buck converter connected to PV array are taken separately.

Predictive Direct Flux Control—A New Control Method of Voltage Source Inverters in Distributed Generation Applications

Voltage source inverters (VSIs) have been widely utilized in electric drives and distributed generations (DGs), where electromagnetic torque, currents and voltages are usually the control objectives. The inverter flux, defined as the integral of the inverter voltage, however, is seldom studied. Although a conventional flux control approach has been developed, it presents major drawbacks of large flux ripples, leading to distorted inverter output currents and large power ripples. This paper proposes a new control strategy of VSIs by controlling the inverter flux. To improve the system’s steady-state and transient performance, a predictive control scheme is adopted. The flux amplitude and flux angle can be well regulated by choosing the optimum inverter control action according to formulated selection criteria. Hence, the inverter flux can be controlled to have a specified magnitude and a specified position relative to the grid flux with less ripples. This results in a satisfactory line current performance with a fast transient response. The proposed predictive direct flux control (PDFC) method is tested in a 3 MW high-power grid-connected VSI system in the MATLAB/Simulink environment, and the results demonstrate its effectiveness.

An Evaluation of Linear Time Frequency Distribution Analysis for VSI Switch Faults Identification

This paper present an evaluation of linear time frequency distribution analysis for voltage source inverter system (VSI). Power electronic now are highly demand in industrial such as manufacturing, industrial process and semiconductor because of the reliability and sustainability. However, the phenomenon that happened in switch fault has become a critical issue in the development of advanced. This causes problems that occur study on fault switch at voltage source inverter (VSI) must be identified more closely so that problems like this can be prevented. The TFD which is STFT and S-transform method are analyzed the switch fault of VSI. To identify the VSI switches fault, the parameter of fault signal such as instantaneous of average current, RMS current, RMS fundamental current, total waveform distortion, total harmonic distortion and total non-harmonic distortion can be estimated from TFD. The analysis information are useful especially for industrial application in the process for identify the switch fault detection. Then the accuracy of both method, which mean STFT and S-transform are identified by the lowest value of mean absolute percentage error (MAPE). In addition, the S-transform gives a better accuracy compare with STFT and it can be implement for fault detection system.

Border Collision of Three-Phase Voltage-Source Inverter System with Interacting Loads

As a commercial interface, three-phase voltage-source inverters (VSI) are commonly equipped for energy conversion to export DC power from most distributed generation (DG) to the AC utility. Not only do voltage-source converters take charge of converting the power to the loads but support the grid voltage at the point of common connection (PCC) as well, which is dependent on the condition of the grid-connected loads. This paper explores the border collision and its interacting mechanism among the VSI, resistive interacting loads and grids, which manifests as the alternating emergence of the inverting and rectifying operations, where the normal operation is terminated and a new one is assumed. Their mutual effect on the power quality under investigation will cause the circuital stability issue and further deteriorate the voltage regulation capability of VSI by dramatically raising the grid voltage harmonics. It is found in a design-oriented view that the border collision operation will be induced within the unsuitable parameter space with respect to transmission lines of AC grid, resistive loads and internal resistance of VSI. The physical phenomenon is also identified by the theoretical analysis. With numerical simulations for various circuit conditions, the corresponding bifurcation boundaries are collected, where the stability of the system is lost via border collision.

New enhanced performance robust control design scheme for grid-connected VSI

In this paper, a new method for intelligent robust control design is presented that achieves the best possible convergence rate of the system, utilizing the knowledge on the range of uncertain parameter. Thus resulting in enhanced stability and performance. The proposed method is applied to the grid-connected voltage source inverter (VSI) system with uncertainties in grid-impedance. Simulation and experimental results illustrate the efficacy of the proposed scheme. Comparison with existing methods shows that the proposed scheme can provide better reference tracking, stability for a wider uncertainty range, and improved transient and steady-state performance with low implementation cost.

Accuracy Enhancement of Parameter Estimation and Sensorless Algorithms Based on Current Shaping

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

English

Parallel operation of number of Voltage Source Inverters (VSIs) composed of Microgrids (MGs). The steps towards the standardization of these MGs have been fulfilled in this paper. In this sagacity, a hierarchical control scheme for the parallel operated VSI system is urbanized self-possessed of two control levels. The primary control encloses the droop method pursued by the virtual impedance loops. The secondary control renovates the frequency and amplitude deviations twisted by the above method. In order to connect the MG to the main grid, a synchronization algorithm is obtainable. Simulation results are provided to accomplish the good frequency and voltage amplitude and also augment the consistency of the MG control system.

A Novel Finite-Time Settling Control Algorithm Designed for Grid-Connected Three-Phase Inverter With an LCL-Type Filter

In this paper, a cost-effective finite-time settling current control system for a utility-interactive three-phase voltage source inverter system with an inductor–capacitor–inductor (LCL)-type filter is originally designed and developed. The discrete-time system equation of the LCL-type filter is first simply derived in the $\alpha{-}\beta$ stationary reference frame. Then, the finite time of a three-sampling-period settling control algorithm is derived in the form of state feedback, whereas the required numbers of sensors are reduced by introducing an identification algorithm. Moreover, the implementation of the novel control scheme achieves the time-optimum response of a 3-D controlled variable in the LCL-type filter when damping the LC resonance strongly. The effectiveness of the proposed finite-time settling control algorithm is substantially confirmed by the simulation and experimental results of inverter, static synchronous compensator, and rectifier modes of operation.

Z Source Inverter Using Renewable Energy System

This paper presents a high performance, low cost inverter for Photo voltaic systems based on Z-source concept. Traditional Voltage-source inverter and Current Source Inverter has improved to the new Z-Source Inverter. This impedance source inverter can provide a single stage power conversion concept where as the traditional inverter requires two stage power conversion. A new low cost solar cell powered Z-source inverter system is simulated and the results are compared with the traditional Voltage Source Inverter system. Performance analysis confirms that Z source inverter system is more appropriate for photo voltaic applications. The Z-source concept can be applied to all dc-to-ac, ac-to-dc, ac-to-ac, and dc-to-dc power conversion.

IMPLEMENTATION OF IMPEDANCE SOURCE INVERTER SYSTEM FOR PHOTOVOLTAIC APPLICATIONS

This paper presents a high performance, low cost inverter for photovoltaic systems based on Impedance-source concept. Traditional Voltage-source inverter and Current-source inverter has improved to the new Z-source inverter, with a unique X-shaped network in it. This Impedance-source inverter can provide a single stage power conversion concept where as the traditional inverter requires two stage power conversion for renewable energy applications. A new low cost solar cell powered Z-source inverter system is simulated and the results are compared with the traditional Voltage-source inverter system. Performance analysis, simulation and comparison have been confirmed that the Z-source inverter system is more appropriate for photovoltaic application than their counterparts. Hardware implementation is done to validate the proposed system.

Analysis of PWM Strategy for Reduction of Conducted Electromagnetic Interference in an Adjustable-Speed AC Motor Drive

This paper presents various pulse width modulation (PWM) strategies capable of reducing conducted electromagnetic interference (EMI) generated in PWM voltage-source inverter systems. EMI problems caused by both conducted and radiated noise emissions have become a great concern in electrical/electronic systems. Thus, their effects are currently considerably taken into account in circuit design phase in order to restrict or reduce these severe problems. The proposed PWM strategy, which is one of different traditional and/or novel reduction techniques to solve such a problem, is chosen as an EMI reduction method and studied herein. The simulated results show that active vector PWM strategy seems to be a good alternative for inverter system. The impact of dead time of PWM signals is also investigated and discussed.

Modeling, Analysis, and Design of Stationary-Reference-Frame Droop-Controlled Parallel Three-Phase Voltage Source Inverters

Power-electronics-based microgrids (MGs) consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of parallel-connected three-phase VSIs are derived. The proposed voltage and current inner control loops and the mathematical models of the VSIs are based on the stationary reference frame. A hierarchical control scheme for the paralleled VSI system is developed comprising two levels. The primary control includes the droop method and the virtual impedance loops, in order to share active and reactive powers. The secondary control restores the frequency and amplitude deviations produced by the primary control. Also, a synchronization algorithm is presented in order to connect the MG to the grid. Experimental results are provided to validate the performance and robustness of the parallel VSI system control architecture.