Pulse Width Modulated Voltage Source Research Articles

Analytical Modeling of Sideband Current Harmonic Components in Induction Machine Drive With Voltage Source Inverter by an SVM Technique

The sideband current harmonic components are practically inevitable in induction motor drive systems with voltage source inverter and pulse width modulation technique. However, those particular harmonic components would increase the losses, torque ripple, and electromagnetic noise so as to deteriorate the overall performance of the electric machine. In this paper, the main sideband current harmonic components in induction machines driven by voltage source inverter with space vector pulse width modulation technique are analytically derived and expressed in both stator and synchronous dq reference frames, which could be employed as a rapid analytical tool to study the corresponding harmonic losses, torque pulsations, and electromagnetic noises. The validity of the analytical models has been confirmed by the experimental results. Finally, both the load characteristics and impact factors on the sideband current harmonics in induction machine drives are comprehensively investigated and discussed based on the analytical models.

Universal active and reactive power control of electronically interfaced distributed generation sources in virtual power plants operating in grid‐connected and islanding modes

The control paradigms of the distributed generation (DG) sources in the smart grid are realised by either utilising virtual power plant (VPP) or by employing MicroGrid structures. Both VPP and MicroGrid are presented with the problem of control of power flow between their comprising DG sources. This study depicts this issue for VPP and proposes a novel and improved universal active and reactive power flow controllers for three-phase pulse width modulated voltage source inverters (PWM-VSI) operating in the VPP environment. The proposed controller takes into account all cases of R–X relationship, thus allowing it to function in systems operating at high, medium (MV) and low-voltage (LV) levels. Also proposed control scheme for the first time in an inverter control takes into account the capacitance of the transmission line which is an important factor to accurately represent medium length transmission lines. This allows the proposed control scheme to be applied in VPP structures, where DG sources can operate at MV LV levels over a short/medium length transmission line. The authors also conducted small signal stability analysis of the proposed controller and compared it against the small signal study of the existing controllers.

Performance Study of Field Oriented Controlled Induction Machine in Field Weakening Using SPWM and SVM Fed Inverters

One of the main reasons for adopting the field oriented controlled (FOC) induction machine for high performance application is its capability for easy implementation in field weakening. In a sensorless FOC induction machine, the speed estimation in Field Weakening (FW) region and the sensitivity to parameter error of the motor is a major problem. Model Reference Adaptive System (MRAS) approach is one of the best techniques to estimate the rotor speed due to its straight forward stability approach. Space vector pulse width modulated (SVM) voltage source inverter is preferred to feed the FOC induction machine rather than the traditional sinusoidal pulse width modulated (SPWM) inverter due to the full utilization of voltage and current rating of the inverter. In this paper, a sensorless FOC induction machine with MRAS scheme based on sliding mode (SM) technique to estimate the rotor speed in the FW region using SVM fed inverter is modeled. The drive system is simulated by MATLAB/Simulink and the performance of the technique is evaluated by comparing the model with FOC induction machine with sensor using SVM inverter.

Common-Mode Voltage Reduction Pulsewidth Modulation Techniques for Three-Phase Grid-Connected Converters

This paper experimentally investigates the performance of three-phase voltage source pulsewidth modulation (PWM) converter, with the grid interfaced photovoltaic energy conversion system being the main application. In such applications the ground leakage current [common mode current (CMC)] should be much less than an ampere and this is difficult to obtain in transformerless (direct) connected systems. With the target being the reduction of the common mode voltage (CMV) and CMC, the converter performance is investigated thoroughly. Conventional PWM methods [space vector PWM (SVPWM) and discontinuous PWM (DPWM)] and recently developed reduced common mode voltage PWM (RCMV-PWM) methods [active zero state PWM (AZSPWM) and near state PWM (NSPWM)] are considered. The performance of a 1-kW rated PWM rectifier with additional common-mode capacitor emulating a PV system has been experimentally investigated. It is shown that the CMV and CMC of the tested RCMV-PWM methods is significantly less than conventional methods. In particular, NSPWM yields the best overall performance including low ground leakage current, low inverter output (phase current) and input (dc-link current) ripple, and low switching losses. Accounting for the parasitic capacitance effect, the resonant frequency of the common-mode circuit is identified and it is used in the converter design for the purpose of avoiding resonances involving large CMV-CMC. This paper aims help the design engineer select the appropriate PWM method for grid-connected applications and provides some design rules of thumb.

New Active Damping Strategy for LCL-Filter-Based Grid-Connected Inverters with Harmonics Compensation

The use of LCL filters in pulse width modulation voltage source converters is a standard solution for providing proper attenuation of high-order grid-current harmonics. However, these filters can cause the undesired effect of resonance. This paper proposes an active damping strategy with harmonics compensation. It can alleviate the harmonics around the resonance frequency caused by the LCL filters. The proposed strategy is attractive since it is simple, does not depend on grid parameters and does not increase the number of sensors. Simulation and experimental results verify the effectiveness of the proposed active damping strategy.

Electrical and Thermal Computation of Stress Grading System in Inverter-Driven Medium Voltage Motors

This paper focuses on analyzing the electric field and the temperature distribution in a typical stress grading system used in medium voltage rotating machines under pulse width modulation voltage source conditions. Two analysis models for electric field and heat transfer processes are developed to take into account the nonlinear relationship between the electric field and the electrical conductivity of Silicon Carbide (SiC) semi-conductive tape. The simulation results give a fundamental background to explain the failure of the stress grading system in inverter-driven medium voltage motors.

A New Approach for Controlling Direct-Driven PMSG Wind Turbines

This paper presents control of wind energy conversion system (WECS) with permanent magnet synchronous generator (PMSG). With the modern power electronic technology, direct-driven PMSG have been increasingly used in wind turbine manufactures. In PMSG wind turbine with two back-to-back voltage source converter (VSC) are used like a commercial passive rectifier followed by an insulated gate bipolar transistor (IGBT) inverter. This paper investigates the new approach for controlling the direct-driven PMSG wind turbines; it has two side-by-side voltage source pulse width modulation (PWM) converters. The paper investigates new approach based on direct current vector control method and also investigates the conventional vector control. Thisnew approach has to control both the machine side converter (MSC) and grid side converter (GSC). The control strategy is developed for integrated control of PMSG for maximum power extraction, dc-link voltage control and grid voltage support control. The WECS have been developed using Matlab Simulink software to compare the conventional vector control method with proposed approach under steady state and gusty wind conditions.

Novel Control Strategy for Voltage Source Converters Based on Energy Function

This paper proposes a nonlinear control strategy for pulse-width modulated voltage source converters (VSCs). A passivity-based approach, resulting from the Lyapunov direct method, is presented for designing an effective nonlinear VSC controller to improve their dynamic behaviors under perturbed conditions. The differential equations of the converters are obtained and then transformed into a d − q frame. Considering the nonlinearity of the transformed equations, the Lyapunov direct method is utilized to find a solution to improve the transient response. The time derivative of the Lyapunov function guarantees that increasing its dissipative term will result in the trajectory of the VSC system returning to the equilibrium point more quickly. The proposed control strategy can be simultaneously applied to multiVSC devices, such as a unified power flow controller (UPFC). Moreover, it is shown that the proposed strategy meets the steady-state requirements without using any other control loop. As an example, a 3-machine system with a UPFC is studied to verify the effectiveness of the proposed strategy.

Adaptive Current Control for Grid-Connected Converters With LCL Filter

This paper presents a discrete-time adaptive current controller for grid-connected pulse width modulation voltage source converters with LCL filter. The main attribute of the proposed current controller is that, in steady state, the damping of the LCL resonance does not depend on the grid characteristic since the adaptive feedback gains ensure a predefined behavior for the closed-loop current control. An overview of model reference adaptive state feedback theory is presented aiming to give the reader the required background for the adaptive current control design. The digital implementation delay is included in the model, and the stability concerning the variation of the grid parameters is analyzed in detail. Furthermore, current distortions due to the grid background voltage are rejected without using the conventional stationary resonant controllers or the synchronous proportional-plus-integral controllers. Simulation and experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed controller for grid-connected converters subjected to large grid impedance variation and grid voltage disturbances.

Characteristics analysis of IPM motor applied by voltage source using 3‐D finite element method with prismatic elements

PurposeThe purpose of this paper is to clarify the usefulness of characteristics analysis of an interior permanent magnet (IPM) motor using the 3‐D finite element method (FEM) with prismatic elements from the view point of the accuracy and the calculation time.Design/methodology/approachThe authors analyzed characteristics of an IPM motor applied by the pulse width modulation (PWM) voltage source using the 3‐D FEM with prismatic elements and with tetrahedral elements; then compared the calculated results and the calculation time using prismatic elements with those using tetrahedral elements.FindingsIt was found that the calculated current and torque, and eddy current loss using prismatic elements are almost the same as those using tetrahedral elements. The calculation time using prismatic elements is shorter than that using tetrahedral elements.Originality/valueThis paper verifies the usefulness of the 3‐D FEM with prismatic elements through characteristics analysis of an IPM motor driven by the PWM voltage source.

A Study on Nonlinear Control Strategy for Three-phase Voltage Source PWM DC/AC Inverter based on the PCH Model

The mathematical model of a three-phase voltage source pulse-width modulation (PWM) DC/AC inverter is non-linear, and in view of the traditional linear control strategy it can not meet the requirements of designing a high-performance inverter. What's more, when the loads are not pure resistive loads, the inverter further requires that the controller possess high-performance. This paper proposes a nonlinear control strategy for the inverter called Passivity-based Control. We can alter the inverter model in three-phase abc coordinate to two-phase synchronous rotating dq coordinate for establishing the port-control Hamiltonian (PCH) model for this system. We can control the distribution of energy in the system to achieve the control aim. Simulation results show that the passivity-based control method can make this system possess a level of high-performance that is both robust and dynamic.

Optimal and Direct-Current Vector Control of Direct-Driven PMSG Wind Turbines

With the advances of power electronic technology, direct-driven permanent magnet synchronous generators (PMSGs) have increasingly drawn the interest of wind turbine manufacturers. At the present time, a commercial PMSG wind turbine primarily makes use of a passive rectifier followed by an insulated gate bipolar transistor (IGBT) inverter. Although a PMSG wind turbine with two back-to-back voltage source IGBT converters is considered more efficient, it has not been widely adopted by the wind power industry. This paper investigates both the conventional and a novel vector control mechanism for a PMSG wind turbine that has two side-by-side voltage source pulsewidth modulation converters. The proposed approach is based on a direct-current vector control mechanism for control of both machine- and grid-side converters of a PMSG wind turbine. Then, an optimal control strategy is developed for integrated control of PMSG maximum power extraction, reactive power, and grid voltage support controls. A transient system simulation using SimPowerSystem is built to investigate the performance of the conventional and proposed control techniques for the PMSG wind turbine under steady and gusty wind conditions. This paper shows that when using the direct-current vector control structure, a PMSG system has excellent performance in various aspects.

Derivation of a Small-Signal Harmonic Model for Closed-Loop Power Converters Based on the State-Variable Sensitivity Method

An admittance or impedance matrix of a power converter is highly desirable for harmonic analysis of a power system. However, power converters are inherently nonlinear and time-varying systems. Therefore, a small-signal harmonic model needs to be derived. While there have been many methods to obtain the small-signal models of DC-DC converters, most of these methods cannot be directly applied to AC-DC converters. Moreover, while accurate methods exist for obtaining accurate models of open-loop AC-DC converters, there are few existing methods for obtaining accurate models for closed-loop AC-DC converters. This paper proposes an analytical method for obtaining an accurate small-signal harmonic model for a power converter. The proposed method is based on state-variable sensitivity methods, which have been previously used to derive a transfer function of a DC-DC converter. This paper will show what modifications are required to extend it to derive the small-signal harmonic model of a closed-loop AC-DC converter. A small-signal harmonic model of a closed-loop pulse-width modulated (PWM) voltage source converter (VSC) with synchronous frame current controllers and a dc voltage controller is derived based on the proposed method. The results are in good agreement with large-signal simulations by means of PSCAD/EMTDC.

Anti-Windup PID Controller With Integral State Predictor for Variable-Speed Motor Drives

The windup phenomenon appears and results in performance degradation when the proportional-integral-derivative (PID) controller output is saturated. Integral windup is analyzed on the PI plane, and a new anti-windup PID controller is proposed to improve control performance of variable-speed motor drives and is experimentally applied to the speed control of a vector-controlled induction motor driven by a pulse width-modulated voltage source inverter. The steady-state value of the integral state is predicted while the PID controller output is saturated, and this value is utilized as an initial value of the integral state when the PID controller begins to operate in a linear range. Simulation and experiments result in more similar speed responses against load conditions and step reference change over conventional anti-windup schemes. Control performance, such as overshoot and settling time, is very similar to that determined by PID gain in the linear range.

Robust Input-Output Linearisation Control of Insulated Gate Bipolar Transistor Based Voltage Source Converters for Stabilisation of High Voltage DC Transmission Link

In this paper, a robust non-linear controller for a two-area voltage source converter high voltage DC (VSC-HVDC) transmission system is proposed subject to model uncertainties and external disturbances. The non-linear controller uses a robust feedback linearisation control for the voltage source pulse-width modulation (PWM) converter and inverter system of the DC-link along with a linear H > control strategy. The purpose of the converter control is to ensure independent control of the active and reactive power flow in the system while maintaining a constant DC voltage at the same time. For achieving robust feedback linearisation unlike the classical one requires the control of the square of the DC voltage rather than the DC voltage itself. This control strategy may provide the insight for the design of input-output linearised system, in which zero dynamics contain some desirable state variables. The controlled PWM has the global stability, fast tracking of DC bus voltage with zero steady-state error, rejection of exogenous disturbances, and stabilisation of synchronous generators connected to the VSC-HVDC systems at the two ends.

High-power CSI-fed induction motor drive with optimal power distribution based control

In this article, a current source inverter (CSI) fed induction motor drive with an optimal power distribution control is proposed for high-power applications. The CSI-fed drive is configured with a six-step CSI along with a pulsewidth modulated voltage source inverter (PWM–VSI) and capacitors. Due to the PWM–VSI and the capacitor, sinusoidal motor currents and voltages with high quality as well as natural commutation of the six-step CSI can be obtained. Since this CSI-fed drive can deliver required output power through both the six-step CSI and PWM–VSI, this article shows that the kVA ratings of both the inverters can be reduced by proper real power distribution. The optimal power distribution under load requirements, based on power flow modelling of the CSI-fed drive, is proposed to not only minimise the PWM–VSI rating but also reduce the six-step CSI rating. The dc-link current control of the six-step CSI is developed to realise the optimal power distribution. Furthermore, a vector controlled drive for high-power induction motors is proposed based on the optimal power distribution. Experimental results verify the high-power CSI-fed drive with the optimal power distribution control.

Modeling and Control of a Three-Phase Four-Switch PWM Voltage-Source Rectifier in d-q Synchronous Frame

Controller design for six-switch pulse width-modulated (PWM) voltage source rectifiers (VSRs) is often accomplished in the rotating d-q frame coordinates in order to achieve a high-performance control. In contrast, the development of a d-q frame controller for a four-switch PWM VSR is rarely reported in the literature. In this regard, this paper introduces a control design approach in rotating d-q frame for the four-switch PWM VSRs. For this purpose, a mathematical model of the four-switch PWM VSR in rotating d-q frame is first derived. Its success is relied on performing a so-called “reduced Park Transformation” on switching functions. The derived model shares much structural property with that of a six-switch VSR. Then, two d-q frame current controller designs, input-output feedback linearization (IOFL) and linear proportional-plus-integral (LPI) control, are performed based on the derived model as application examples. Their effectiveness is verified via computer simulation and hardware experiment. Responses of an LPI a-b-c frame controller originated from the six-switch VSR are also documented for comparative study. Test results evidence the superiority of the d-q frame controllers.

Filter-Based Active Damping of Voltage Source Converters With $LCL$ Filter

Pulsewidth modulation (PWM) voltage source converters are becoming a popular interface to the power grid for many applications. Hence, issues related to the reduction of PWM harmonics injection in the power grid are becoming more relevant. The use of high-order filters like <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filters is a standard solution to provide the proper attenuation of PWM carrier and sideband voltage harmonics. However, those grid filters introduce potentially unstable dynamics that should be properly damped either passively or actively. The second solution suffers from control and system complexity (a high number of sensors and a high-order controller), even if it is more attractive due to the absence of losses in the damping resistors and due to its flexibility. An interesting and straightforward active damping solution consists in plugging in, in cascade to the main controller, a filter that should damp the unstable dynamics. No more sensors are needed, but there are open issues such as preserving the bandwidth, robustness, and limited complexity. This paper provides a systematic approach to the design of filter-based active damping methods. The tuning procedures, performance, robustness, and limitations of the different solutions are discussed with theoretical analysis, selected simulation, and experimental results.

Voltage-Source PWM Rectifier–Inverter Based on Direct Power Control and Its Operation Characteristics

This paper describes a novel control strategy of direct power-control-based voltage-source pulsewidth modulation (PWM) rectifier-inverter. The key of this strategy is direct selection of a switching state of the PWM rectifier-inverter on basis of instantaneous power errors. A relationship between the instantaneous power and the switching state of the PWM rectifier-inverter is theoretically analyzed, which is essential to compose a switching-state table. Effectiveness of the proposed technique is examined through several experimental tests, using a 1.6-kW prototype. As a result, unity power factor operation is achieved by the proposed method, and the output currents are confirmed to be sinusoidal waveforms without large distortion under balanced and unbalanced power-source condition.

A Cost-Effective High-Efficiency Power Conditioner With Simple MPPT Control Algorithm for Wind-Power Grid Integration

In this paper, a novel grid integration system for a variable-speed wind turbine using an interior permanent-magnet synchronous generator (IPMSG) is developed. The power conditioner system (PCS) consists of a series-type 12-pulse uncontrolled diode rectifier powered by a phase-shifting transformer and then cascaded to a pulsewidth-modulated (PWM) voltage source inverter. The active current of the grid-side PWM inverter is only controlled to follow the optimal active current reference which is determined by using a simple maximum power point tracking (MPPT) control strategy. The MPPT algorithm requires only three sensors in order to track the maximum power of the wind turbine. The most significant advantage of the proposed system is that the passive filter together with a series-type 12-pulse rectifier provides high efficiency by compensating the power factor angle of the IPMSG and suppresses distortions presented in the IPMSG voltages and currents. The laboratory results indicate that the proposed construction and scheme are simple, cheap, and efficient.