Current Controlled Voltage Source Inverter Research Articles

Implementation of Shunt Active Power Filter Using DSP Controller Based on Synchronous Reference Frame for Harmonic Mitigation

This research paper introduces the concept of a shunt active power filter (SAPF) that leverages synchronous-reference-frame (SRF) theory to mitigate harmonics in the power system. The SAPF works by injecting a compensating current at the point of common coupling (PCC) to counteract the harmonics in the line and restore sinusoidal current waveforms. It employs a three-phase current-controlled voltage source inverter (VSI) with a DC link capacitor for active filtering. An SRF algorithm is designed for a low-voltage laboratory prototype utilizing the TMS320F28335 Digital Signal Processor (DSP). The experimental findings affirm that the control strategy effectively aligns with the recommended harmonic standard limits of IEEE 519-1992.

Voltage and Current Control Strategy for Grid Connected WECS Employing Two and Three Level Voltage Source Converters

This paper presents voltage and current control strategy for grid connected variable speed wind turbine induction generator employing two and three level voltage source inverters. Induction generators are widely used because of its low cost, robust construction and capability of feeding active power to load without getting reactive power from separate source. The mechanical energy required to drive the generator is obtained from a variable speed wind turbine. Three phase induction machine is excited from a three phase voltage source converter. The DC voltage of the capacitor is inverted and fed to the three phase grid using a current controlled voltage source inverter. Control strategy has been developed for maintaining the DC link voltage constant and also to feed the power at unity power factor to the grid, even though there is variation in wind speed. It is also shown that the harmonics are considerably reduced when a two level inverter is replaced by a three level inverter. The simulation study has been carried out using MATLAB/Simulink. Simulation results indicate the feasibility of control strategy.

Comprehensive Analysis for DC-Link Capacitor Sizing for a Three-Phase Current-Controlled Voltage-Source Inverter

An analytical approach to size a dc-link capacitor for a three-phase current-controlled voltage-source inverter used for a permanent magnet synchronous motor is presented in this article considering the dc-link ripple voltage and capacitor ripple current. The analytical method derived in this article shows the variation of the dc-link voltage ripple with the change of the power factor and the modulation index. This analysis can be applied to determine the maximum possible ripple voltage for a given capacitor or the minimum capacitance needed to keep the voltage ripple under a limit. Then, current ripple analysis is used to determine the root-mean-square capacitor ripple current taking account of the thermal duty cycles of the application. Finally, capacitor life estimation analysis is used using the operating condition, thermal duty cycle, and ripple current to determine the capacitor end life for a given application. The research presents a sequential process to select a dc-link capacitor accounting for the electrical and thermal requirement of the system. The analysis is verified by simulation and experimental results, where the effect of components’ parasitic on the voltage and current ripple is presented.

Novel Self-Excited Brush-Less Wound Field Vernier Machine Topology

To realize the brush-less operation for wound field vernier machines (WFVMs), a novel self-excited topology is proposed in this paper which involves a four-pole main armature winding and a two-pole excitation winding connected in series using an uncontrolled rectifier. Upon supplying current from a single current-controlled voltage source inverter (VSI), this procedure results in four-pole and two-pole magnetomotive force (MMF) components in the airgap. The four-pole MMF produces the main stator field while the two-pole MMF component develops a sub-harmonic field in the airgap. The rotor is altered to house a forty-four-pole rotor field and two-pole harmonic windings. The two-pole harmonic field is employed to induce a current in the harmonic winding, which is rectified by means of a full-bridge diode rectifier to energize the rotor field winding and realize brush-less operation for WFVM. Two-dimensional finite element analysis (2-D FEA) is implemented in JMAG-Designer to confirm the operation of the proposed WFVM topology and attain the electromagnetic performance for a four-pole, twenty-four-slot outer-rotor vernier machine.

An Online Parameter Estimation Using Current Injection with Intelligent Current-Loop Control for IPMSM Drives

An online parameter estimation methodology using the d-axis current injection, which can estimate the distorted voltage of the current-controlled voltage source inverter (CCVSI), the varying dq-axis inductances, and the rotor flux, is proposed in this study for interior permanent magnet synchronous motor (IPMSM) drives in the constant torque region. First, a d-axis current injection-based parameter estimation methodology considering the nonlinearity of a CCVSI is proposed. Then, during current injection, a simple linear model is developed to model the cross- and self-saturation of the dq-axis inductances. Since the d-axis unsaturated inductance is difficult to obtain by merely using the recursive least square (RLS) method, a novel tuning method for the d-axis unsaturated inductance is proposed by using the theory of the maximum torque per ampere (MTPA) with the combination of the RLS method. Moreover, to improve the bandwidth of the current loop, an intelligent proportional-integral-derivative (PID) neural network controller with improved online learning algorithm is adopted to replace the traditional PI controller. The estimated the dq-axis inductances and the rotor flux are adopted in the decoupled control of the current loops. Finally, the experimental results at various operating conditions of the IPMSM in the constant torque region are given.

A Comparison of Instantaneous and Extension p-q Methods for Current Controlled Voltage Source Inverter in Microgrid

ABSTRACT With the advancement in technology and population growth, the motivation of integrating utility grid with the microgrid through power electronic converters increases. This paper presents the control of power electronic converter connected at the grid side. This converter regulates the power flow between renewable energy system (RES), load and grid in addition to the compensation of harmonic and reactive power. The reference currents are generated to decide the power flow from RES to the load and to suppress the harmonic and reactive power in the grid making grid current sinusoidal. In this paper, the reference current generation techniques like instantaneous p-q method and extension p-q method are implemented and compared. Linear Quadratic Regulator (LQR) is used to track the reference current. The control law of LQR is designed in a simple way using simplified equivalent circuit of a three-phase grid integrated renewable energy system. The system is tested experimentally under balanced and unbalanced conditions in two different modes such as insufficient renewable power and excess renewable power. The supremacy of extension p-q method over instantaneous p-q method is proved by getting low total harmonic distortion and better power factor under balanced and unbalanced conditions experimentally.

PERFORMANCE ASSESSMENT OF IMPROVED CURRENT CONTROL STRATEGY BASED SHUNT ACTIVE POWER FILTER: A REVIEW

The most powerful solution to current harmonics is a shunt active power filter (SAPF). Because of its simple implementation features, the Synchronous Reference Frame (SRF) concept has been commonly used in current harmonics extraction algorithms in its controller. The traditional SRF algorithm, on the other hand, has a significant time delay due to its heavy dependency on slow numerical filters. Furthermore, the algorithm is still thought to have unnecessary features that place an undue computational burden on the controller. Active control filters are commonly used in the power system to reduce harmonics induced by nonlinear loads. The Shunt Active Power Filter (SAPF) injects a suitable compensating current at a line point known as the point of common coupling (PCC) to cancel out the line's harmonics and restore the sinusoidal existence of voltage and current waveforms. As an active filter, a three-phase current-controlled voltage source inverter (VSI) with a DC connection capacitor across it is used. Shunt active power filter (SAPF) is the best solution that minimises the harmonic problems in power systems, but how fast and how effective it is. This paper describes a detailed study about the various types of power quality disturbances and their mitigation techniques and their comparative details.

Novel Single Inverter-Controlled Brushless Wound Field Synchronous Machine Topology

This paper proposes a novel brushless excitation topology for a three-phase synchronous machine based on a customary current-controlled voltage source inverter (VSI). The inverter employs a simple hysteresis-controller-based current control scheme that enables it to inject a three-phase armature current to the stator winding which contains a dc offset. This dc offset generates an additional air gap magneto-motive force (MMF). On the rotor side, an additional harmonic winding is mounted to harness the harmonic power from the air gap flux. Since a third harmonic flux is generated in this type of topology, the machine structure is also modified to accommodate the third harmonic rotor winding to have a voltage induced as the rotor rotates at synchronous speed. Specifically, four-pole armature and field winding patterns are used, whereas the harmonic winding is configured for a twelve-pole pattern. A diode rectifier is also mounted on the rotor between the harmonic and field windings. Therefore, the generated voltage on the harmonic winding feeds the current to the field winding for excitation. A 2D-finite element analysis (FEA) in JMAG-Designer was carried out for performance evaluation and verification of the topology. The simulation results are consistent with the proposed theory. The topology could reduce the cost and stator winding volume compared to a conventional brushless machine, with good potential for various applications.

Grid Integration of Renewable Energy Sources using GA Technique for Improving Power Quality

Hybrid Renewable energy sources (HRES) are rapidly increasingly compared to the traditional system since they are less effective to the environment and meet the huge demand required by the utilities. In the proposed paper the modelling, control and design analysis is implemented with PV, wind and battery as an energy storing device. The grid-interfacing inverter is regulated with a single-stage, three-phase RES-based distributed generation (DG) system. A genetic algorithm (GA) based shunt active power filter (SHAPF) is used to mitigate the power quality issues under nonlinear and unbalanced load conditions. The DG is grid-connected through a current-controlled –voltage source inverter (CC-VSI) via a DC link capacitor. Here the VSI is utilized to transfer the power from DG to the point of common coupling (PCC), SAPF to compensate for load current harmonics, under distorted supply voltage conditions, reactive power demand and load current imbalance. Both of these functions are important either individually or concurrently. As a result, the proposed controller regulates the power flow, controls it and acts as a SHAPF or does both at the same time. The proposed method is employed in the MATLAB/Simulink platform and performances were analysed.

Modeling and Control of a Single-Phase Grid-Connected Inverter with LCL Filter

The increasing penetration of renewable energy sources is pushing low-voltage electrical grids to become predominantly power electronic-based. Consequently, the design and operation of the related grid-connected converters must be achieved under proper manner, in order to maintain stability and support reliable operation of the entire power system. Thus, this work presents the modeling and control of a single-phase grid-connected multifunctional converter, which operates as a current-controlled voltage source inverter using an LCL-type output filter. An active damping approach is employed for attenuation of oscillations occurring from interactions between the grid and the inductances and capacitance of the LCL filter. Additionally, the voltage and current control loops of the inverter are addressed in this paper, along with the design of their respective controllers, considering that the grid impedance is unknown. Experimental results demonstrate stable operation of the inverter and show its satisfactory behavior under steady state conditions, proving its capability to offer ancillary services such as active filtering.

Event-Driven Distributed Active and Reactive Power Dispatch for CCVSI-Based Distributed Generators in AC Microgrids

This article presents a novel distributed event-driven control strategy that will dispatch and share the active and reactive power outputs of massive current-controlled voltage source inverter (CCVSI)-based distributed generators (DGs) in an ac microgird. The proposed distributed power sharing control strategy is fully distributed and only driven at their own event time, which effectively reduces the frequency of controller updates compared with continuous-time feedback control. Moreover, each CCVSI-based DG only requires the local voltage and current measurement from its own and some nearest neighbors (but not all) for the distributed power sharing control at the last event-driven time by using low-bandwidth communication links and then, updates the control inputs to restore the active and reactive powers to desired values for further reducing the consumption of computing and communication resources to some extent. The Lyapunov technique is employed to derive the stability and convergence analysis of the proposed dynamic event-driven conditions. The effectiveness of the proposed control strategy is verified under various scenarios by a modified IEEE 34-bus test network in MATLAB/SimPowerSystems.

Fixed Point Implementation of Grid Tied Inverter in Digital Signal Processing Controller

Power inverters are one of the devices of great importance used in power grids to convert DC to AC, especially for grids with attached solar panels or wind turbines. The world is getting warmer due to coal- and oil-based power generation. So human existence is threatened due to the increased amount of carbon-dioxide in the air. As a result, integration of renewable energy sources (RESs) with the grid became mandatory. So, the demand of grid-connected inverters is increasing as more RESs are connecting with the grid; this necessitates developing a low-cost grid connected inverter system. This paper presents a comprehensive study and hardware implementation of a grid tied inverter. In this research, we have demonstrated a cost-efficient grid tied inverter design using low cost DSP controller applying fixed point arithmetic. The fixed-point arithmetic and Digital Signal Processing (DSP) implementation results in superior performance over conventional methods of calculation. This paper also proposes a hardware model of such a bi-directional grid tied inverter. A current controlled Voltage Source Inverter(VSI) is used in the paper and a PI controller is suggested for current error compensation. To generate gating pulse for appropriate voltage, Space Vector Pulse Width Modulation (SVPWM) technique is employed. Synchronous Reference Frame Phase Locked Loop (SRF-PLL) is chosen for performing grid synchronization. The feasibility of the hardware model is verified by performing simulations on Simulink.

Impact of Inverter Controller-Based Grid-Connected PV System in the Power Quality

In a Grid-Connected Photovoltaic System (GCPS), the inverters are applied for integration with the power grid. This integration brings some issues at the connection point. Therefore, grid-tied inverter control performs a vital role in feeding the power system with good power quality. This study presents a current-controlled Voltage Source Inverter (VSI) strategy for large-scale GCPS generates 1000 kW rated of power. The methodology and structure of the control system are presented. The power quality issues such as harmonics, voltage fluctuation, voltage unbalance, and power factor are limited at the interfacing point into the required limits as imposed by the standards. This study also discusses the controller design and the simulation results are introduced to show its effectiveness. Furthermore, the values obtained may be used to evaluate the power supply quality of various inverter controllers.

Cost-Effective Single-Inverter-Controlled Brushless Technique for Wound Rotor Synchronous Machines

This paper proposes a cost-effective brushless technique for wound rotor synchronous machines (WRSMs). The proposed technique involves a traditional current-controlled voltage source inverter that utilizes a simple hysteresis-controller-based current control scheme and supplies three-phase currents to the armature winding of the machine. The supplied armature currents inherently contain fundamental-harmonic and third-harmonic current components. These unique armature current waveforms were previously realized by using dual-inverter-controlled schemes achieved with and without thyristor switches to develop brushless WRSM topologies. The fundamental-harmonic current component is applied to develop the main stator field, whereas the third-harmonic component is employed to realize the harmonic magnetomotive force, which induces a back electromotive force (EMF) in the harmonic winding located at the rotor periphery. The induced harmonic EMF is rectified to deliver a DC current to the rotor field winding through a full-bridge diode rectifier to achieve brushless operation. The proposed cost-effective brushless technique for WRSMs is validated using 2-D finite element analysis employing JMAG-Designer 19.1 to investigate the electromagnetic and electromechanical behaviors of the machine. Furthermore, the proposed technique is employed in machine topologies with different pole/slot combinations for the armature winding to achieve better performance.

Power Quality Enhancement Using Lyapunov Based Voltage Source Inverter for the Grid Integrated Renewable Energy System

Abstract The evolution of high performance power electronic converters makes a feasible way to integrate the Renewable Energy System (RES) to the grid. High performance in terms of stability, good transient and steady state response, load variations is achieved in this work using Current Controlled Voltage Source Inverters (CCVSI) by deriving the control law using Lyapunov function at the expense of a time varying reference current. In this work, a single phase equivalent circuit is represented for the three phase grid connected renewable energy system, and mathematical modeling is developed to design the controller. Analysis using Lyapunov based controller is carried out to ensure the real and reactive power flow from the renewable energy system to the grid connected with the non linear load. The reference current for the controller is generated using the Symmetrical Component theory. This theory requires no transformation and desired source power factor can be achieved. To exhibit the efficacy of the Lyapunov controller, the simulation is carried out using MATLAB/Simulink environment. It is observed that the desired power factor is obtained and Total Harmonic Distortion (THD) is within the IEEE limits in the grid side. The performance of the system is validated experimentally and the results are compared with the conventional hysteresis controller for the same application.

Control shunt active filter based on dq frame using current model prediction

The nonlinear loads present more in the power systems in the practice today by developing of electronic technology and using the small distributed power sources (solar power, wind power etc.), this causes the increasing the high frequency switch devices etc. in the power network. Nonlinear loads cause non-sinusoidal currents and voltages with harmonic components, increasing the reactive power, overload of power lines and electrical devices, low power factor and affecting badly to the networks. Shunt active filters (SAF) with current controlled voltage source inverters (CCVSI) are used effectively to reduce the harmonics and to balance the phases sinusoidal source currents by generating the currents to compensate the harmonic currents caused by the nonlinear loads. In this paper we suppose a control strategy to generate the compensation currents of SAF by using the current model predictive engineering. This method is better than the control strategy using PI controller in term of transient time. The desired compensation currents can track exactly the reference compensation currents on the dq frame. The simulation results implemented on the nonlinear load, a full bridge rectifier and 3 phase unbalance load, show that the transient period decrease from 0.1s to 0.02s in comparing with PI controller. The experimental results proof that the THD of source currents decrease from 24.8% to 5.4% when using the proposed method.

Performance Analysis of ANN Based three-phase four-wire Shunt Active Power Filter for Harmonic Mitigation under Distorted Supply Voltage Conditions

This paper presents the design and implementation of three-phase four-wire shunt active power filter (SAPF). It consists of insulated gate bipolar transistors, IGBT based current-controlled voltage source inverter (CC-VSI), series coupling inductor and self-supported DC bus. Power electronics based converters and non-linear loads generate waveform-driven power quality issue as harmonics. Three-phase four-wire SAPF mitigates harmonics, compensates for reactive power, neutral current and power factor correction. Conventionally, the positive sequence detection control strategy using phase-locked loop (PLL) is applied as the synchronizing unit vector element to generate reference source currents. Conventional controller tuning process is difficult and fails to perform satisfactorily under supply voltage variation conditions. In this paper, Levenberg-Marquardt back propagation training algorithm based artificial neural network (ANN) controller is proposed to regulate DC link voltage due to its self-adapting and rapid calculation characteristics that allow the controller to handle high nonlinearity and uncertainty in a non-linear system. Weights of a neuron are adapted to minimize total harmonic distortion (THD) of source current under the step, ramp, time series amplitude variation and frequency and amplitude of modulation conditions. The proposed system is modelled in MATLAB/SIMULINK environment and laboratory prototype with dSpace1104 control card is developed. Experimentation results validate the simulated results of the proposed scheme under supply voltage variations for three-phase four-wire distribution system.

SEIG-Based Renewable Generation for MVDC Ship Power System with Improved Power Quality

The global energy consumption is increasing day by day. This increased energy demand can only be fulfilled through large-scale renewable energy integration. This article presents the mathematical modeling, control, and integration of a bio-fuel prime mover fed self-excited induction generator (SEIG) for medium voltage direct current (MVDC) ship power system. A three-phase current controlled voltage source inverter (VSI) working as a static synchronous compensator (STATCOM) injects compensating currents at the point of common coupling (PCC) for harmonic elimination and regulation of the generated voltage under varying load. The VSI is connected at the PCC through a three-phase zig-zag/star transformer which reduces the voltage stress at the DC link. An indirect current technique based controller is used to generate gating pulses for the STATCOM. The MVDC load zone is modeled as an integral sliding mode controlled DC-DC converter feeding ship service loads in shipboard system. Hardware realization of the proposed system has been implemented with 3.7kW induction generator.

Active Disturbance Rejection Control of LCL-Filtered Grid-Connected Inverter Using Padé Approximation

In this paper, a simplified robust control is proposed to improve the performance of a three-phase current controlled voltage source inverter connected to the grid through an inductive–capacitive–inductive ( LCL ) filter. The presence of the LCL -filter resonance complicates the dynamics of the control system and limits its overall performance, particularly when disturbances and parametric uncertainty are considered. To solve this problem, a robust active damping method based on the linear active disturbance rejection control (LADRC) is proposed. The simplification is made possible by order reduction in the plant transfer function using Pade approximation. Simulation results show that the proposed LADRC-based current controller achieves high power quality and good dynamic performance, in the presence of parameters uncertainties as well as external disturbances. An experimental prototype is built to verify the effectiveness and practicality of the proposed control strategy.

Simulation of an Indirect Rotor Flux Oriented Induction Motor Drive using Matlab/Simulink

Indirect Field Oriented Control (IFOC) is very popular technique in industries due to its simple designing and structure, in comparison to the direct method since it requires flux and torque estimators. This paper presents detail calculation of all values needed for the development of an indirect rotor flux oriented induction motor model fed by a current-controlled voltage source inverter. With the calculated values for 1 hp 50 Hz 3 phase induction motor; an indirect rotor flux oriented model is developed using MATLAB/Simulink. The simulation results are outlined and discussed.