Space Vector Theory Research Articles

A Simple Method for Detection of Voltage Sags and their Mitigation using a Dynamic Voltage Restorer

Power quality is the major focus of progressive nations.In the era of smart grid,power quality receives a lot of thrust at all voltage levels namely,medium ,high and low.The objective of this paper is to present a simple and cost effective method of sag detection and mitigation in three phase systems at the consumer's end. The use of the concept of space vector representation of three phase quantities, effectively in the detection ,quantification and mitigation of short duration voltage disturbances such as sags in three phase supply systems under both balanced and unbalanced conditions of operation is presented.Three phase balanced quantities can be represented by a synchronously rotating space vector of constant magnitude .The two phase equivalent of which on a stationary reference frame are orthogonal to each other.When balanced sags occur,the magnitude of the rotating space vector obtained as a resultant of its orthogonal components is sensed for magnitude deviations from its constant nominal value.A trigger signal of varying amplitude is generated in proportional response to the detection of the deviation in its magnitude . In case of sags occurring on one or two phases of the supply, (unblanced),the positive sequence components of the unbalanced three phase quanities are determined using mathematical transformations and the magnitude of the resultant is found out. This resultant is sensed and its deviations from nominal value are measured and used to generate the trigger after processing.The trigger thus generated, initiates the control system of a Dynamic Voltage Restorer(DVR).When a sag is detected,the trigger signal generated, switches on the control circuit of the inverter which uses the space vector pwm control using sampled phase amplitudes of the control signal to generate the modulating wave in proportion to the deviation of the sag voltage from the reference value.The fundamental component of the output voltage which in proportion to the deviation from the nominal value is injected in series with the three phase disturbed signal through a transformer of suitable gain .The results show the successful operation of the DVR in maintaining nominal value of the voltage across the load through out the duration of the disturbance for all cases of balanced and unbalanced operation. The paper presents the detection algorithm as well as the control algorithm for restoration of voltage which are simple and easy to implement .

Performance of an OVT inverter reliant on the switching frequency of the filtering inverter

The paper presents an inverter based on the orthogonal space vectors theory (OVT inverter) and its performance. The OVT inverter consists of two constituent twolevel 3-phase inverters: the main inverter (MI) and the auxiliary one (AI). The MI is controlled in a simple way to generate the stepped output voltage and the AI works as an active filter limiting the higher harmonics in the OVT output voltage. The filtering process is formed by the use of the orthogonal space vector theory. The output voltage of the OVT inverter takes the shape of a stepped voltage comparable to the voltage generated by multilevel inverters. The AI operates as a very effective active power filter (APF) of the OVT inverter output voltage. The AI power is significantly lower in comparison to the MI power nevertheless its switching frequency affects the OVT performance. The article describes studies in which the impact of changes in the switching frequency filter inverter on the operation of the orthogonal inverter and the output voltage THD. Increasing the filter inverter switching frequency improved performance and reduced the transformer size, which acts as a summing node.

Active Filtering of Inverter Output Waveforms Based on Orthogonal Space Vector Theory

This paper presents a DC/AC converter consisting of two two-level inverters. The complex converter is built using two standard three-phase inverters: the main inverter (MI) and the auxiliary one (AI). The MI is controlled in a simple way to generate the stepped output voltage and the AI works as an active filter limiting the higher harmonics in the MI output voltage. The filtering process is based on the orthogonal space vector theory. A development and modification of the basic solution are presented here. The output voltage of the MI takes the shape of a stepped voltage comparable to the voltage generated by multilevel inverters. The AI operates as a very effective active power filter (APF) of the MI output voltage. The AI power is significantly lower in comparison to the MI power.

Synchronverter-Based STATCOM With Voltage Imbalance Compensation Functionality

In this work, a synchronverter-based D-STATCOM with self-synchronization and voltage imbalance compensation capability with operation independent of the power operating modes is proposed. The S-STATCOM's synchronverter base model is firstly presented in space-vector representation together with its control strategy with standard D-STATCOM control structure. Then, the Voltage Imbalance Compensation Loop (VICL) is proposed, which uses two well known resonant control structures, the Double Second-Order Generalized Integrator (DSOGI) and a Proportional plus Resonant controller (PR), in an innovative way to effectively turn the S-STATCOM into a specialized active filter for negative sequence voltage, compensating the voltage imbalance at the PCC by supplying the corresponding oscillating power locally. Simulation and experimental results on a small scale prototype are presented to validate the control strategy, which successfully reduced voltage imbalances from up to 10% to bellow the 2% acceptable levels.

Modeling and Evaluation of Mutual Coupling Effect in Conventional Switched Reluctance Machines Using Space Vector Representation

This paper presents a non-linear model for conventional switched reluctance machines (CSRMs) that considers the mutual coupling between phases. Although CSRMs are based on single-phase excitation, there is usually an overlapping between the excited phases. During this overlapping, the CSRM is at 2-phase excitation and the single-phase representation of motor dynamics is not accurate. Hence, a dynamic model is presented in this paper that that accounts for the the mutual coupling between phases in addition to the effects of saturation and spatial harmonics. The proposed method is based on modeling the resultant current vector due to 2-phase excitation in space. The relationship between the resultant current and flux linkage vectors is obtained at different rotor positions using finite element method (FEM). This relationship is saved as a 3D lookup table (LUT). These 3D LUTs are reduced into 2D LUTs independent of rotor position by representing the phase currents as vectors instead of instantaneous values. Similarly, the relationship between the resultant current vector and the electromagnetic torque is obtained and saved as a 3D lookup table. The proposed method is compared with a conventional model where the mutual coupling is not considered. This comparison is conducted using FEM on two different motors; the first motor is 12/8 3-phase 2kW CSRM and the second motor is 24/16 3-phase 75kW CSRM. FEM results show that the mutual coupling is significant for high power motors. The proposed dynamic model is compared with experimental results using the 12/8 3-phase 2kW CSRM.

Performance Analysis of Three-Phase Inverter Using Different Techniques for the Grid- Connected Pv System

The model of a three-phase voltage source inverter is examined based on space vector theory. SVPWM offers an improved outcome with the inverter as compared to the conservative SPWM technique for the inverter. There is a 15.5% upsurge in the line voltage of the inverter. SVPWM better exploits the available DC-link power with the SVPWM inverter. It has been revealed that the SVPWM method utilizes DC bus voltage extra competently and produces a smaller amount of harmonic distortion and easier digital realization in a three-phase voltage-source inverter. For converter‘s gating signals generation, the space-vector pulse width modulation (SVPWM) strategy lessens the switching losses by restricting the switching to two-thirds of the pulse duty cycle. A hypothetical study regarding the use of the SVPWM the three-level voltage inverter and simulation results are offered to prove the usefulness of the SVPWM in the involvement in the switching power losses lessening, output voltages with fewer harmonics. Nevertheless, despite all the above-cited benefits that SVPWM enjoys over SPWM, the SVPWM technique used in three-level inverters is more difficult on account of a large number of inverter switching states. The attained simulation outcomes were satisfactory. As prospects, future experimental works will authenticate the simulation results. A software simulation model is developed in Matlab/Simulink.

Advance speed control of three phase induction motor using field oriented control method

The report illustrates a stepwise execution for system for an electric drive having a control system using the software ‘Simulink’ on MATLAB. The induction motor (IM) presented in the report is constructed after an circuit in the stator reference frame that is actually based on space vector theory. The control system for motor is prepared via the (indirect) vector control (field oriented control) which is used for the rotor flux reference frame. It makes use of a converter.The prepared simulink model can be potentially implemented as model for illustrating electrical motors. Especially in terms of schooling where the output is centered and focused on getting introduced to new things by doing them and where the outcome is to get introduced to new things by the help of a practical real life approach. The following application thus correlates the space vector theory and practice.

RETRACTED: Research on motor control and simulation based on PID and Internet of Things system

A motor application consists of a Single Phase Induction Motor, and it has single-phase winding, which is winding on the stator of the motor and a winding placed on the rotor. A pulsating magnetic field is produced when a phase supply energizes the single-phase induction motor's stator winding shown below. In the existing method, DTC (Direct Torque Control) is based on converting alternating source and fed to the desired source motor low efficiency and high speed. So in this proposed method, Induction Motor Using Proportional-Integral-Derivative (PID) and IOT (Internet of Thing) for Inverter based achieving an efficiency output voltage or with the lowest amount of ripple content, the high switching frequency. Proportional Integral Derivative (PID) is an emerging technique for controlling PWM (Pulse Width Modulation) Inverter-Fed Induction Motor (IM) drives. The precise and quick inspection of the IM (Induction Motor) flux and torque without calling for complex control algorithms. In principle, moreover, it requires only the knowledge of the stator resistance. The application reviews an IM (Induction Motor) essential operation and a PWM (Pulse Width Modulation) inverter using the space vector theory. The IOT (Internet of Thing) control is a monitoring application of a Checking and controlling compliance and boundary is essential in many applications. The reliable functionality Policies available for equivalents and handles Observing different boundaries and three control.

Impact of Star Connection Layouts on the Control of Multiphase Induction Motor Drives Under Open-Phase Fault

This article presents a postfault control algorithm that minimizes the stator Joule losses in multiphase induction machines under an open-phase fault and for different star connection layouts. The key novelty is that the algorithm can be applied to any configuration of a multi- n -phase machine, independently of the connection of the neutral points. The latter is analytically derived and is based on the space vector representation of the machine model. In addition, it is shown that a low number of neutral points helps to reduce the winding losses in case of an open-phase fault but requires additional control regulators and computational efforts. The theory is applied to an asymmetrical quadruple-three-phase induction machine, which is configured to represent five different motor layouts. Finally, experimental results are presented to validate the control algorithm. The optimal solution that is given in this article can be employed for the control of symmetrical or asymmetrical multiphase machines with different star connection layouts and in any open-phase postfault operation.

IMPLEMENT DIRECT TORQUE AND FLUX CONTROL (DTC) INDUCTION MOTOR DRIVE MODEL: A REVIEW

Direct torque control ( DTC ) is considered one of the modern control methods, which wildly used in industrial variable speed drive systems to govern behaviors of induction motors. The main objective of this paper is to introduce a comprehensive study of a conventional direct torque of three phase induction motors. Moreover, the paper also aims to enhance and improve the transient response of the conventional DTC by proposing a novel design of its switching table, which considered as an essential component of DTC control circuit. At first, Space Vector theory was implemented to derive a mathematical model of a threephase induction motor. Second, the model was simulated by using Matlab Simulink software due to its simplicity. The conventional DTC and proposed DTC were applied on the computer model of the motor at no-load and when the motor shaft is loaded respectively. It was observed from the results that the transient response of the proposed DTC is better than the response of the conventional one. The paper concluded with number of important results, which obtained from the computer model of the two DTC control methods. Ripple

Modeling and Simulation of English Speech Rationality Optimization Recognition Based on Improved Particle Filter Algorithm

As one of the most important communication tools for human beings, English pronunciation not only conveys literal information but also conveys emotion through the change of tone. Based on the standard particle filtering algorithm, an improved auxiliary traceless particle filtering algorithm is proposed. In importance sampling, based on the latest observation information, the unscented Kalman filter method is used to calculate each particle estimate to improve the accuracy of particle nonlinear transformation estimation; during the resampling process, auxiliary factors are introduced to modify the particle weights to enrich the diversity of particles and weaken particle degradation. The improved particle filter algorithm was used for online parameter identification and compared with the standard particle filter algorithm, extended Kalman particle filter algorithm, and traceless particle filter algorithm for parameter identification accuracy and calculation efficiency. The topic model is used to extract the semantic space vector representation of English phonetic text and to sequentially predict the emotional information of different scales at the chapter level, paragraph level, and sentence level. The system has reasonable recognition ability for general speech, and the improved particle filter algorithm evaluation method is further used to optimize the defect of the English speech rationality and high recognition error rate Related experiments have verified the effectiveness of the method.

Analysis and Control of PV Cascaded H-Bridge Multilevel Inverter With Failed Cells and Changing Meteorological Conditions

This article proposes an approach to control a photovoltaic cascaded H-bridge multilevel inverter with failed cells and changing meteorological conditions for large-scale grid-connected applications. The controller development is based on an analysis of the interaction between the inverter common-mode and differential-mode quantities, which is done in the time domain, supported by a space vector representation analysis. The proposed approach is able to produce balanced three-phase line-to-line voltages and currents even if there is a failed cell or if the fluctuating meteorological conditions cause uneven power distribution among the bridges. This is achieved through the modification of the pulsewidth modulation reference phase voltage angles combined to the injection of a dynamic homopolar component. Such an approach avoids tripping the system due to the protective functions #25 and #87 for per grid applicable codes and standards. Numerical simulations and laboratory experiments performed on a seven-level converter with different abnormal conditions to confirm the effectiveness of the suggested control strategy.

A Study on Input Power Factor Compensation Capability of Matrix Converters

In practice, the input filter is an important component in matrix converter (MC) systems for removing high harmonic components from input currents. Due to the input filter, the input power factor (IPF) at the main power supply does not always achieve unity. To investigate the behavior of the IPF, this paper analyzes the IPF compensation capacity of MCs with an LC input filter based on space vector theory and the conservation of energy law. The study shows that the range of voltage transfer ratio (VTR) to achieve unity IPF depends strongly on the quality factor, which is determined by the system parameters. If the quality factor is greater than 0.375, the MC can never achieve unity IPF for the whole range of VTR. If the quality factor is lower than 0.375, the MC can only achieve unity IPF for a certain range of VTR, except at a very low or very high VTR. Experimental results are provided to confirm the correctness of the study.

An Improved Reduced Complexity Model Predictive Current Controller for Grid-Connected Four-Leg Multilevel Inverter

Model predictive current controller offers numerous benefits over the traditional controllers in grid-tied inverters. However, the real-time execution duration reduction of model predictive controller in multilevel inverters is a big challenge, which has been investigated by several researchers. The work presented in this article exploits the three-dimensional space vector representation of a four-leg neutral point clamped three-level inverter in a-b-c coordinates to lower the real-time execution duration of model predictive controller. The objective function determination counts of model predictive controller in the process of controlling neutral point voltage and source current of four-leg neutral point clamped inverter are significantly reduced in the proposed scheme. Therefore, real-time execution duration is reduced as well. In the proposed scheme, three virtual mutually orthogonal sliding planes decide the objective functions to be determined. This method evades the use of any weighing factor in the objective function, which completely obviates the parameter tuning requirement for the control of the four-leg inverter. The extension procedure for higher level four-leg inverter is also explained. Experimental evidence is presented to prove the superiority of the core idea with respect to a recent work.

Torque Calculation of Permanent Magnet Spherical Motor Based on Virtual Work Method

A double-layer permanent magnet spherical motor (PMSM) with same spatial distribution of stator poles and rotor poles is designed based on spherical harmonic theory in this article. The stator coils are equivalent to permanent magnets to simplify the calculation, and the torque model based on virtual work method is derived. First, the torque model of single pair of poles is derived on the premise of considering the fundamental component of the magnetic field. Then, the relative positions of stator poles and rotor poles, the direction angles of torque components are discussed. Finally, the torque model is obtained by space vector theory and superposition theorem. Moreover, the simulation and experiment are implemented to verify the feasibility and correctness of the proposed torque model. The obtained torque model in this article has similar expression with that of traditional motor, which lays a theoretical foundation for the structure optimization and control strategy of PMSM.

The Relationship Between Root Locus and Transient Field Components of AC Machines

The dynamic analysis of induction motors is supported by well-known theories: the two-axes transformation, and the space vector theory. Yet some inconsistencies with the theory of dynamic systems exist. The machine eigenvalues suggest the existence of two damped oscillators, physically not understandable. The respective eigenfrequencies change with the angular velocity of the reference frame. This contradicts the understanding that eigenfrequencies are inherent system properties. Physically, the dynamics depend on the continuous distribution of magnetic energy and its spatial displacement during transient processes. Information on the system dynamics is lost when dividing the continuum of magnetic energy into discrete portions. Complex state variables associate the dynamics to the propagation in space of distributed magnetic fields. The dynamic analysis reveals the existence single-complex eigenvalues. These define a novel class of system identifiers. They are characterized by having only one imaginary part instead of a conjugate complex pair. The use of complex state variables conveys insight and physical understanding of the dynamic processes within the machine. The approach constitutes an extension to the theory of dynamic systems.

SVM algorithm oriented for implementation in a low-cost Xilinx FPGA

The paper proposes an idea of hardware realization of a space vector modulation (SVM) and transistor commutation method in the direct matrix converter (MC). The presented technique is oriented to an implementation in a single, low-cost programmable logic device (namely, field programmable gate array, FPGA). The SVM method is based on the instantaneous space-vector representation of input currents and output voltages. The traditional computation algorithms usually involve digital signal processors (DSPs) which drive the large number of power transistors (18 transistors and 18 independent PWM outputs) and “non-standard positions of control pulses” during the switching sequence. Therefore, hardware implementations are becoming popular since computed operations may be executed much faster and more efficiently due to the concurrent nature of the digital devices. In the paper a hardware algorithm of the SVM computation is proposed. Contrary to the existing hardware methods, the presented solution neither requires specialized modeling tools (such as Matlab/Simulink, ISE EDK), nor advanced converters to achieve the hardware representation. It is assumed that the system is prepared in a pure hardware description language (namely, Verilog). Furthermore, the proposed technique permits concurrent execution of most operations. The presented algorithm has been verified experimentally with the low-cost Xilinx FPGAs (in particular, the devices from Artix-7 family). The results of the physical implementation are presented and discussed.

New advanced concept of the flying capacitor asymmetric multilevel voltage source inverter

PurposeTo improve the voltage quality in AC adjustable high-power-speed-drive applications, the purpose of the paper is to provide a large number of output levels without increasing the number of commutation cells in the three-phase, n-cells flying capacitor voltage source asymmetric Multilevel Inverter (MI). The concept is based on the selection of different ratios between the breakdown voltages of two successive power devices. The new mathematical model is developed under various ratios, allows a thorough investigation of the harmonic distortions, flying capacitor energy storage, flying capacitor voltage balancing controllability and blocking voltage insulated gate bipolar transistor (IGBT) capability.Design/methodology/approachThe asymmetrical design provides a large number of output levels without increasing the number of commutation cells. The important new analytical expression of capacitors voltage distribution is derived and extended to any ratio between the switch breakdown voltages of two successive power devices.FindingsThe detailed simulation study of the proposed concept has been carried out using MATLAB/Simulink. The power switches control of the three-phase three-cell MI is assured by new phase-shifted-multi-carrier pulse width modulation. The space vector representation is used to show the regular and irregular step output voltage in the complex plan (α,β).Originality/valueIn the paper, the n cells flying capacitor inverter, which typically operates in the (n + 1) levels mode, was extended to (n + 2), (n + 3) … until 2n levels with regular or irregular step output voltage. Consequently, the claimed advantages of the asymmetric MI are to improve power quality by reducing harmonic distortions and to reduce the requirement on capacitive energy storage in the circuit.

Voltage sag source identification based on the sign of internal resistance in a “Thevenin's equivalent circuit”

Summary This paper briefly introduces the existing methods for voltage sag source location and theoretically analyzes some reasons why high accuracy cannot be achieved by using these methods. Based on the redefined voltage sag source location “reference direction” and the analysis of voltage sag source's influences in power network, it is pointed out that observing from disturbance source point to both sides of monitoring services, any power network can be equivalent to 2 active single-port networks and the networks can be equally replaced by “Thevenin's equivalent circuit.” By judging the sign of the internal resistance in Thevenin' s equivalent circuit, the origin of voltage sag disturbance can be easily identified. The calculation of internal transient resistance is given based on the application of space vector theory. This method can locate voltage sag source with an accuracy of 100% verified by simulation experiments. It is a very practical method that is not only applicable in radial and nonradial power systems but also in networks of neutral grounded effectively or ineffectively.

Motor-Converter Synchronization Phenomena in a Subsynchronous Cascade Drive

In the past, subsynchronous cascade drive behavior at slips that are a multiple of 1/6 has caused controversy among researchers. A new approach for predicting and interpreting drive behavior at these slips is presented in this paper. With the help of the space vector theory, an analytical investigation that shows a specific synchronization of the induction motor with the diode rectifier is carried out. The method of analysis presented can also be generally applied when a specific symmetry of the space vectors of the motor electromagnetic quantities is imposed by a power electronic converter or other sources.