Pulse Width Modulation Current Source Research Articles

New Adaptive Control Strategy for a Wind Turbine Permanent Magnet Synchronous Generator (PMSG)

Wind energy conversion systems have become a key technology to harvest wind energy worldwide. In permanent magnet synchronous generator-based wind turbine systems, the rotor position is needed for variable speed control and it uses an encoder or a speed sensor. However, these sensors lead to some obstacles, such as additional weight and cost, increased noise, complexity and reliability issues. For these reasons, the development of new sensorless control methods has become critically important for wind turbine generators. This paper aims to develop a new sensorless and adaptive control method for a surface-mounted permanent magnet synchronous generator. The proposed method includes a new model reference adaptive system, which is used to estimate the rotor position and speed as an observer. Adaptive control is implemented in the pulse-width modulated current source converter. In the conventional model reference adaptive system, the proportional-integral controller is used in the adaptation mechanism. Moreover, the proportional-integral controller is generally tuned by the trial and error method, which is tedious and inaccurate. In contrast, the proposed method is based on model predictive control which eliminates the use of speed and position sensors and also improves the performance of model reference adaptive control systems. In this paper, the proposed predictive controller is modelled in MATLAB/SIMULINK and validated experimentally on a 6-kW wind turbine generator. Test results prove the effectiveness of the control strategy in terms of energy efficiency and dynamical adaptation to the wind turbine operational conditions. The experimental results also show that the control method has good dynamic response to parameter variations and external disturbances. Therefore, the developed technique will help increase the uptake of permanent magnet synchronous generators and model predictive control methods in the wind power industry.

High Performance Single-Phase Single-Stage Grid-Tied PV Current Source Inverter Using Cascaded Harmonic Compensators

In this paper, a single-phase single-stage photovoltaic (PV) grid-tied system is investigated. The conventional pulse width modulated (PWM) voltage source inverter (VSI) is replaced by a PWM current source inverter (CSI) for its voltage boosting capabilities, inherent short-circuit proof and higher reliability features. Modeling, design, and analysis of the considered CSI are presented altogether with enhanced proposed control loops aided with a modified PWM technique. DC-link even current harmonics are commonly reflected as low-order odd harmonics in the grid resulting in a poor quality grid current. In order to overcome the latter, a high performance proportional resonant controller, applied in the inverter inner grid current loop, is proposed using cascaded resonant control units tuned at low-order frequencies to eliminate injected grid current harmonics. Hence, with a less-bulky smoothing inductor at the CSI DC-side, grid power quality and system efficiency are simultaneously improved. Simulation and experimental results verify the proposed controller effectiveness.

Modulation Schemes for Medium-Voltage PWM Current Source Converter-Based Drives: An Overview

Pulsewidth modulation current source converter (CSC)-based drive is one of the widely used drives in high-power (megawatt level) medium-voltage (MV) (2.3–6.6 kV) applications. The switching frequency of the MV CSC is limited to around 500 Hz to satisfy thermal requirement and reduce switching loss. Under such a condition, the overall performance of the used modulation scheme, especially its harmonics performance, is an important consideration for CSC-based drives. To date, a couple of modulation schemes have been proposed for MV CSCs, and this paper aims to present an overview of these modulation schemes. Traditional modulation schemes are reviewed, the recent advances are illustrated and analyzed, and the challenges and trends are discussed.

Distributed energy resources integration in single-phase microgrids: An application of IDA-PBC and PI-PBC approaches

This paper presents a unified Hamiltonian formulation for controlling distributed energy resources (DERs) in ac single-phase microgrids (SP-MGs) via proportional-integral passivity-based control (PI-PBC), and interconnection and damping assignment passivity-based control (IDA-PBC). The proposed Hamiltonian formulation allows us to consider both pulse-width modulated voltage source converters (PWM-VSC) and pulse-width modulated current source converters (PWM-CSC) under a unified model. Renewable generation and supercapacitor energy storage systems are integrated via PWM-VSC technologies, while superconducting coils are integrated through PWM-CSC technologies. IDA-PBC and PI-PBC theories enable us to design control strategies begin that consider Lyapunov’s stability theory combined with the well-known advantages of proportional and integral control actions. Our simulation’s results corroborate the applicability of the proposed control approaches under stability paradigm. MATLAB/Simulink is employed for computational implementations via begin the SimPowerSystems toolbox.

PBC Approach for SMES Devices in Electric Distribution Networks

This express brief presents a nonlinear active and reactive power control for a superconducting magnetic energy storage (SMES) system connected in three-phase distribution networks using pulse-width modulated current-source converter (PWM-CSC). The passivity-based control (PBC) theory is selected as a nonlinear control technique, since the open-loop dynamical model exhibits a port-Hamiltonian (pH) structure. The PBC theory exploits the pH structure of the open-loop dynamical system to design a general control law, which preserves the passive structure in closed-loop via interconnection and damping reassignment. Additionally, the PBC theory guarantees globally asymptotically stability in the sense of Lyapunov for the closed-loop dynamical system. Simulation results in a three-phase radial distribution network show the possibility to control the active and reactive power independently as well as the possibility to use the SMES system connected through a PWM-CSC as a dynamic power factor compensator for time-varying loads. All simulations are conducted in a MATLAB/ODE package.

Time-Domain Analysis for Current Control in Single-Phase Distribution Networks Using SMES Devices With PWM-CSCs

This paper presents a time-domain analysis for current control in single-phase distribution networks using superconducting magnetic energy storage devices connected through pulse-width modulated current source converters. The control law is designed through a combination of the classical feedback linearization control technique and the intrinsic Hamiltonian structure of the system. The stability analysis of the dynamical system is done through the temporal solution of the differential equations that represent the closed-loop dynamical system. The proposed controller does not require of the single phase-phase locked loop which does a strategy very attractive due to that avoids all the problems that these elements contain, increase the reliability of the system and reducing implementation costs. The effectiveness and the robustness of the proposed current control methodology are tested in a low-voltage single-phase distribution network. All simulation scenarios are conducted in MATLAB/ODE environment under time-domain reference frame.

Real‐time gating signal generation and performance analysis for fully controlled five‐phase, ten‐pulse, line‐commutated rectifier

Fossil fuel prices and air pollution impel many countries to concentrate on renewable energy sources, of which wind energy is considered to be a pillar. Owing to the numerous advantages when compared with its three-phase counterpart, five-phase direct-drive permanent magnet (PM) generators are a key area of focus in power generation with renewable and wind energy systems. The generator output requires a converter, such as an AC–DC rectifier, to match load requirements. The objective of this work is to generate in real time the gating signals of a fully controlled five-phase, line-commutated rectifier, fed from a five-phase PM generator. A mixed-reality environment is used to implement the gating signal generation algorithm for the five-phase rectifier, where the required gating signals are successfully generated, even with some distorted prototype generator voltage waveforms. The performance of the rectifier is investigated practically and validated by using the MATLAB/SIMULINK platform. Moreover, a comparison with a five-phase pulse-width modulated current source rectifier in terms of losses, size, weight, and cost is presented.

A generalized passivity-based control approach for power compensation in distribution systems using electrical energy storage systems

This paper presents a generalized interconnection and damping assignment passivity-based control (IDA-PBC) for electric energy storage systems (EESS) such as: superconducting magnetic energy storage (SMES) and supercapacitor energy storage (SCES). A general framework is proposed to represent the dynamical behavior of EESS interconnected to the electrical distribution system through forced commutated power electronic converters. A voltage source converter (VSC) and a pulse-width modulated current source converter (PWM-CSC) are used to integrate SCES and SMES systems to the electrical power systems respectively. The proposed control strategy allows active and reactive power interchange between the EESS and electric distribution grids independently, guaranteeing globally asymptotically convergence in the sense of Lyapunov via Hamiltonian formulation. Simulation results show the effectiveness and robustness of the generalized IDA-PBC to operate EESS as active and reactive power compensator in order to improve operative conditions in power distribution grids under balanced and unbalanced conditions.

A Generalized Model and Control forSupermagnetic and Supercapacitor EnergyStorage

This paper presents a generalized linear model based on LMI state-feedbackwith integral action, applicable to the control of Electric Energy Stora-ge Systems (EESS) such as Superconducting Magnetic Energy Storage(SMES) and Supercapacitor Energy Storage (SCES). A Voltage SourceConverter (VSC) and a Pulse-Width modulated Current Source Converter(PWM-CSC) are respectively used to integrate the SCES and the SMESsystems to the electrical distribution system. To represent the dynamicsbetween the EESS and the power distribution system a reduced generallinear model in the state-space representation is introduced. The proposedcontrol scheme regulates independently the active and reactive power flowbetween the EESS and ac the grid. Three case scenarios comparing a con-ventional PI controller and the proposed technique are conducted conside-ring grid voltage fluctuations. Extensive time-domain simulations demons-trate the robustness and proper performance of the proposed controller to operate the EESS as power compensator, in order to improve the operativeconditions of electrical distribution systems.

Common-Mode Resonance Suppression in Transformerless PWM Current-Source Drive

Among high-power pulsewidth modulation (PWM) current-source motor drives, the transformerless structure using the integrated dc choke has been widely acknowledged with superior advantages. A typical challenge faced by such transformerless PWM current-source drive systems is the potential common-mode resonance excited by the common-mode voltage (CMV). Since the implementation of power factor compensation (PFC) at low motor speeds may increase the CMV in such drives, the common-mode resonance could be serious and further aggravate the CMV stress on the system. In this paper, the critical factors on the common-mode resonance are thoroughly investigated. Based on the investigation, a solution based on average-value-reduction (AVR) space-vector modulation (SVM) is proposed to suppress the common-mode resonance while maintaining the PFC function. The investigation of common-mode resonance and the effectiveness of the proposed resonance suppression solution are verified through experiments on a transformerless PWM current-source drive system.

Simplified Model and Control Strategy of Three-Phase PWM Current Source Rectifiers for DC Voltage Power Supply Applications

Three-phase pulsewidth modulation (PWM) current source rectifiers (CSRs) that applied as dc voltage power supply include capacitors in the dc bus to obtain dc output voltage, which increase the system complexity and complicate the control strategy. In this paper, a dynamic model of the three-phase PWM CSR is first established in the dq -rotating frame for capacitive load applications. By aligning the vector of the ac capacitor voltage to the $d$ -axis, the model of the CSR can be simplified and decoupled into dc and ac side circuits, which can be controlled separately. Based on this model, a control strategy composed of a state-variable feedback control method for the dc side and an active-damping control method for the ac side is proposed. Moreover, a unity power factor of the CSR is achieved by regulating the $q$ component of the bridge currents. Simulation and experimental results are presented to validate the dynamic and static performance of the proposed control strategy.

A PWM Current Source-Based DC Transmission System for Multiple Wind Turbine Interfacing

A pulsewidth modulation (PWM) current source wind energy conversion system based on a parallel configuration for high voltage direct current application is proposed. A comparison between the parallel and series configurations for current source-based systems is investigated, which shows the merits of the proposed system. A new control technique for the PWM current source inverter is proposed. It can effectively control the average dc-link voltage with a feed-forward loop, while independently controlling reactive power according to grid code requirements. The system simulation confirms the performance of the proposed system with no interaction between wind turbine modules and satisfying performance with grid integration. Practical implementation further verifies the proposed inverter control. Finally, a brief comparison between conventional line-commutated converter-based systems and the proposed PWM current source converter-based system is presented.

An Adaptive Control Strategy for a Wind Energy Conversion System Based on PWM-CSC and PMSG

This paper proposes a new adaptive control strategy for a wind energy conversion system based on a permanent magnet synchronous generator and a pulse-width modulated current source converter. Most of the studies on wind farms are based on double fed induction technology. Nevertheless, the proposed conversion system is a good alternative due to its high efficiency and reliability. Electrolytic capacitors are not required in this type of converter and the voltage in the DC-link as well as the generated reactive power can be dynamically modified according to the wind velocity, being even negative if required. However, it is challenging from the control and stability standpoint. Capacitive filters placed on the AC side, which are required for safe commutation, can create resonances with the power grid. Reactive power is generated according to the capacity of the converter, the wind velocity and the load profile. The adaptive control strategy uses an adaptive PI which is self-tuned based on a linear approximation of the power system calculated at each sample time. A model reference is also proposed in order to reduce the post-fault voltages. Simulation results demonstrate the advantages of the proposed control.

Control Strategies for Balanced Three-phase Output in PWM Current Source Converter with Single-phase Input

This paper deals with a pulse width modulated (PWM) current source converter with single-phase input and three-phase output, and proposes control strategies for it. The converter circuit is a three-phase bridge circuit with three legs. The three-phase PWM method is used to obtain sinusoidal input and output. The single-phase-to-three-phase conversion can be achieved by using the phase-shifted PWM pattern. Moreover, to obtain a balanced three-phase output, the phase-angle control strategies of two PWM patterns are employed. The angle is determined with the feedback of the positive phase sequence component of the output currents. The paper describes in detail the circuit operation and the control method for balanced sinusoidal output. The RL static loads are used as three-phase loads to examine the performance of the converter. The experimental results prove that the three-leg converter with single-phase input can generate balanced three-phase output and includes sinusoidal waves in the input/output sides.

Direct Torque Control of Pulse Width Modulation Current Source Inverter-fed Induction Motor by Novel Switching Method

This article proposes a new approach for direct torque control of induction motors. This method is based on direct torque control with pulse width modulation of a current source inverter using SIMULINK/MATLAB simulators for its performance assessment. The proposed control system is realized based on stator-flux-oriented reference. It uses the same method as direct torque control drive systems with a voltage source inverter to estimate the stator flux and electromagnetic torque and, therefore, only needs the stator resistance to control the motor. In this method, stator current components are calculated to directly control the stator flux and electromagnetic torque. Simulation results show the excellent performance of this system. Using simulations, the proposed method is also compared with the direct torque control voltage source inverter system, and it is shown that the proposed method improves induction motor performance and decreases the inverter switching losses. Another main advantage of the proposed control method is that it seriously limits the starting current and feeds the motor with high power quality. A novel switching method in space vector modulation of current source inverter is also proposed, which effectively decreases motor torque ripple and harmonic losses.

A Simple Method for Suppression of Resonance Oscillation in PWM Current Source Converter

This paper deals with a suppression method for the resonance oscillation in the ac side of a pulse-width modulation (PWM) current source converter. The converter is operated with the PWM switching pattern which is generated by the full digital control of computer software. The resonance current, caused by the LC low pass filter at the step change of the pattern, can be effectively suppressed by one pulse control of the pattern. The proposed method does not need to have the feedback loop of the current/voltage and does not offer the switching stress of the devices. The switching timing of the control is determined by pre-calculation of the off-line in consideration of the circuit constants. The experimental and the simulated results in the single-phase and the three-phase PWM converters are given, compared with those without the control, and show good response of the supply current.

Modeling and analysis of common-mode voltages generated in medium voltage PWM-CSI drives

Common-mode voltages appear in pulse-width modulated current-source inverters (PWM-CSIs) drives due to the operating principles of the input rectifier and the output inverter. This paper presents the modeling and analysis of a medium voltage current-source inverter drive, using the Matlab software. Simulated results of the model are in close agreement with experimental waveforms obtained from an industrial AC drive, which shows overvoltages of up to 100%, generating important insulation stresses at the motor stator terminals.

Switched link PWM current source converters with harmonic elimination at the mains

Novel switched link pulse-width-modulated (PWM) current source converters are presented. These converters supply a controlled DC current to the load with a concurrent elimination of selected harmonics in the AC mains. The new topologies permit minimal constraints to be formulated resulting in significantly more efficient PWM patterns than hitherto reported in the literature. A higher number of harmonics are thus eliminated at the mains for a given switching frequency while maintaining a control capability of the output DC current in a wide range. Simulation results confirm the theoretical findings. Also discussed in the paper is the selection of capacitor filters to mitigate the residual harmonics.

A suitable single‐phase pulse width modulation current source inverter for utility interactive photovoltaic generation system

AbstractA suitable single‐phase inverter for the utility interactive photovoltaic generation system is proposed. The single‐phase Pulse Width Modulation (PWM) current source inverter has a novel circuit configuration in which an auxiliary branch is added to the normal single‐phase bridge circuit. To reduce the size and weight of the dc reactor, a double frequency parallel resonance circuit (LC tank circuit) is inserted in the dc side of the inverter. As a result, the double frequency voltage appearing in the dc side of the inverter due to the pulsation of the single‐phase instantaneous power is perfectly suppressed by the tank circuit. The constant dc current without pulsation is supplied from PV array to the inverter. The inverter provides a sinusoidal ac current for domestic loads and the utility line with unity power factor.The virtual maximum power of the PV array can be obtained without any feedback control. In the system, the PV array can play an important role as a current‐limiter due to its V‐I characteristics. Computed waveforms by simulation are shown. Excellent inverter equipment will be realized that is smaller in size and lighter in weight than is usual for a conventional inverter.

Input Filter Design for PWM Current-Source Rectifiers

Pulse-width modulated (PWM) rectifiers are increasingly used because they allow the elimination of low-order harmonics, and therefore a reduction in input filter components. Filtering requirements for PWM current-source rectifiers are usually satisfied through the use of low-pass LC input filters. This paper offers a systematic and user-friendly approach to choosing the filter components. Design of LC filters involves the positioning of the resonant frequency to meet the harmonic attenuation requirements (THD), and introducing damping at the resonant frequency to avoid amplification of residual harmonics. The problem is further complicated by considerations related to cost, power factor, voltage attenuation, system efficiency, and filter parameter variation. The systematic approach proposed in this paper focuses on PWM rectifiers, but can easily be extended to other classes of converters. Practical design considerations are detailed and design equations derived. Simulated results are presented to validate the design approach