Voltage Vector Research Articles

A High-Precision Position Estimation Method for Low Saliency Ratio Machine Based on Convolutional Neural Networks

Sensorless control of surface permanent magnet synchronous motor (SPMSM) faces great challenges in achieving high precision of rotor position estimation at low speed because the saliency of an SPMSM is only a minor secondary effect. In order to extract accurate position information for SPMSM with low and ultra-low saliency ratios, this paper presents a method that implements image recognition techniques with high-frequency (HF) rotating voltage vector injection. For building an image of the induced current vector, the information of the negative-sequence and the second harmonic of positive-sequence HF current signals in the stationary reference frame is extracted. Then, convolutional neural networks (CNN) are applied to the current vector images to establish the relationship between the vector image and the rotor position. Subsequently, the rotor position can be obtained from the result of image recognition from the neural network. Benefiting from CNN’s excellent performance in image classification, the proposed method is able to recognize subtle position signatures even under low saliency. This confirms the opportunity to increase position estimation accuracy for sensorless control of SPMSM. Finally, the experimental results have provided proof that the proposed method has significantly enhanced estimation accuracy.

MPC Based Position Sensorless SRM Drive for Light Electric Vehicles With Optimized Voltage Vectors and Reduced Torque Ripple

MPC Based Position Sensorless SRM Drive for Light Electric Vehicles With Optimized Voltage Vectors and Reduced Torque Ripple

Enhanced Model Predictive Control for Induction Motor Drives in Marine Electric Power Propulsion System

Marine electric propulsion is an important topic in the research of modern ships and underwater vehicles. The propulsion motor drives based on model predictive control (MPC) are becoming increasingly popular in marine propulsion systems as an emerging technology. However, the multi-objective optimization in conventional MPC requires cumbersome weighting factor tuning. The relatively large computational cost is also detrimental to the industrial application of MPC. Aiming at reducing the computational complexity of multi-objective optimization without weighting factors, this paper proposes an enhanced ranking-based MPC method for induction motor drives in marine electric power propulsion. The presented control set pre-optimization aims to reduce the computational complexity of enumeration and ranking. Based on the sign of torque prediction deviation, the proposed method avoids enumerating all fundamental voltage vectors. Consequently, the number of candidate elements in the initial control set are reduced to four without excessively excluding feasible solutions. By converting predicted numerical errors into ranking results, the proposed MPC seeks the optimal solution among the candidates through improved ranking evaluation. Considering the situation of simultaneous optimal ranking, the normalization error judgment is developed to further optimize the optimal solution selection process. The simulation and experimental results confirm that the proposed MPC is simple and effective. Without the involvement of tuning the weighting factors, the proposed method achieves good performance.

Modulation Techniques and Coordinated Voltage Vector Distribution: Effects on Efficiency in Dual-Inverter Topology-Based Electric Drives

The increasing popularity of electric drives employing an isolated dual-inverter (DI) topology is motivated by their superior DC-link voltage and power utilization, fault-tolerant operation, and potential for multilevel operation. These attributes are significant in battery-powered transportation, such as electric vehicles and aviation. Given the considerable freedom in modulation and control of the DI topology, this paper researches the impact of reference voltage vector distribution between the two individual inverters. The study also evaluates the influence of two well-established asynchronous modulation strategies—Space Vector PWM (SVPWM) and Depenbrock’s Discontinuous Modulation (DPWM1). Since simulation tools nowadays play a crucial role in power electronics design and concept verification, the results are based on extensive and detailed models in Matlab/Simulink. Employing the basic field-oriented control of a 12 kW induction motor with precisely parameterized SiC switching devices for accurate loss calculation, this research reveals the possibility of significant energy savings at multiple operating points. Notably, optimal efficiency is achieved when one inverter operates up to half of the nominal speed while the other solely establishes a neutral point for the winding. Moreover, the results highlight DPWM1 as a superior strategy for the DI topology, showcasing reduced converter losses. Overall, it is shown that the system’s losses can be significantly reduced just by the design of the voltage vector distribution in the drive’s operating range and the modulation strategy selection.

An enhanced predictive current control technique for interior permanent magnet synchronous motor drives with extended voltage space vectors for electric vehicles

SummaryPermanent magnet synchronous motors (PMSM) are widely employed in the application of electric vehicles (EVs) due to their simplicity of operation. Model predictive current control (MPCC) is an advanced technique used to control the PMSM owing advantages like multi‐variable cost function and good dynamic performance. Cost function of predictive current control (PCC) does not require the flux weighting factor; hence, it is simple in the selection of suitable voltage vector (VV). The conventional PCC (C‐PCC) applied to interior PMSM (IPMSM) contains more torque and flux ripples as it includes only one set of voltage vectors for all speed ranges. In proposed PCC (P‐PCC), the magnitude and location of voltage vectors is to be selected as large and small VVs to reduce torque ripples. The P‐PCC in this article utilizes two set of extended voltage vectors (large and small VVs) based on the applied speed change in dynamic conditions and hence reduces the ripple content. Incorporating maximum torque per ampere (MTPA) control in this article serves the purpose of optimizing the machine performance. By adding MTPA to the proposed method, it is aimed to enhance the machine performance with less ripples and improved torque response. Simulation results are presented for conventional and P‐PCC to highlight the effectiveness and efficacy of the P‐PCC. The P‐PCC is experimentally verified with 3.7 kW PMSM using d‐SPACE controller.

Efficiency Improvement of Permanent Magnet Synchronous Motors Using Model Predictive Control Considering Core Loss

The highway cycle is an important consideration in the EV’s new European driving cycles (NEDCs) range, as the steady-state efficiency improvement in such conditions can be greatly beneficial. In the model predictive control (MPC) of the permanent magnet synchronous motors (PMSMs), the predicted next-step feedback reference generated by the equivalent circuit model (ECM) will contribute directly to the voltage vector selection, therefore influencing the performance of the motor control. In the current MPC scheme, when the conventional ECM is applied, it only considers copper loss, and the core loss is usually disregarded. In some circumstances, such as the highway cycle of EVs, the motors are at high speed, the torque is low, and the core loss can be significant in the losses, thus affecting the accuracy of control and the efficiency of the system; hence, the introduction of core loss ECM into the MPC would be beneficial. This paper aims to investigate the steady-state efficiency improvement of a novel ECM of PMSM considering core loss ECM, and the comparison will be based on model predictive direct torque control (MPDTC) using the core loss ECM, which will be compared to MPDTC with the conventional ECM of the PMSM. The results demonstrate the proposed ECM’s efficiency improvement in various conditions, the limitations of the model and the simulation are discussed, and future work is proposed.

Research on three-level PWM Rectifier without grid voltage sensor

Traditional three-level PWM rectification technology usually uses voltage sensors to sample the grid voltage, and then obtains the angle information of the voltage vector through a phase-locked loop, thereby achieving the d/q axis control function of voltage and current. However, the use of voltage sensors not only increases system costs, but also increases system volume and debugging difficulty. In addition, when the voltage sensor is damaged, it can cause system shutdown and affect system reliability. After analyzing the three-level control method of PWM rectifiers, a sensorless control strategy for grid voltage based on sliding mode observer method is proposed. By using the sliding mode observer method to estimate the amplitude and phase of the power grid voltage at the voltage and current values of each PWM cycle, a phase-locked loop is used to determine the position of its voltage vector. The simulation results all demonstrate that the proposed method can accurately and effectively estimate the voltage vector angle of the power grid, and ensure that the output of the rectification system meets the standard voltage waveform.

Integrated Voltage Vector–Based SVPWM for Reliability and Performance Enhancement of Five-Level HANPC Inverters

Power converters are designed to operate over a wide range of voltages to meet various industrial demands. Recently, multilevel inverters have been receiving considerable attention owing to their ability to reduce the current ripple and its associated harmonic distortion. However, for applications requiring high voltage/power ratings, large electrolytic capacitors are essential, which are significantly affected by the ripple in the DC-link current. This causes a significant reduction in the lifespan and reliability of the power converter and necessitates expensive diagnosis and maintenance procedures. Therefore, an effective method of integrated voltage vector-based space vector pulse-width modulation is proposed in this study for minimizing the ripple in the DC-link and common-mode voltage of five-level hybrid active neutral-point-clamped (5L-HANPC) inverters. The proposed method uses a unique control algorithm that can smoothly select the required voltage vectors without a noticeable distortion in the output current waveforms. Moreover, the proposed method can be applied without modifying the original topology of the 5L-HANPC inverter or adding complex compensations to the control algorithm. Extensive simulation and experimental results are provided to demonstrate the capability of the proposed approach to reduce the DC-link current ripple over a wide range of modulation indices.

A Simple Multistep Solution for Model Predictive Control in Multiphase Electric Drives

The multiphase electric drive field of research is rather young, and most of the efforts in this area have been focused on appropriately extending different techniques that were already popular in three-phase systems. This is the case of finite-control set model predictive control (FCS-MPC), which has been a hot topic since 2009. Despite the numerous contributions on FCS-MPC for multiphase systems, all of them assume a single-step horizon in the predictions. This paper shows the first attempt to include multistep predictions within the FCS-MPC that performs the current regulation. The extension from the three-phase case is not direct at all because the number of voltage vectors and subspaces is higher, this adding further complexity and eventually leading to issues related to the secondary current regulation. A smart selection of different subsets of voltage vectors is used to ease the implementation, and a modified cost function is developed to jeopardize the high instantaneous voltage values that significantly worsens the current quality at steady state. Experimental results confirm that the use of multistep FCS-MPC is feasible in multiphase electric drives, showing at the same time that some measures must be taken to minimize the distortion in the low-impedance secondary subspaces.

Permanent magnet synchronous motor stator flux trajectory tracking control based on switching time correction

In this paper, aiming at the problems that the existing stator flux trajectory tracking control method often needs to design complex fundamental wave component observers and the switching time correction based on steady-state solution lacks accurate theoretical calculation equations, a permanent magnet synchronous motor stator flux trajectory tracking control method using optimal PWM (Pulse Width Modulation) is proposed. The outer loop is the speed regulator, whose output is combined with the flux linkage of the permanent magnet of the motor as the reference vector of the stator flux linkage. And the motor speed with the rotor position is combined to calculate the amplitude and phase angle of the reference stator voltage vector, which is used to optimize PWM pulse mode and to determine switching action. Meanwhile, the switching time of optimal PWM is corrected in real time through the stator flux deviation to eliminate the deviation between the stator flux reference value and the actual value. This method does not need to estimate the fundamental component of voltage, current or flux linkage. And unlike the traditional vector method, there is no current inner loop, which can significantly improve the dynamic response speed while simplifying the control structure. Simulation and experiments also fully verify the effectiveness of the proposed control method.

A Direct Power Controller for Doubly-Fed Induction Generator

This paper proposes a direct power control scheme for doubly-fed induction generator for variable speed wind power generation. Using a stator flux decoupling and deadbeat control loops the algorithm calculates the rotor voltage vector to be supplied to the rotor in order to eliminate the active and reactive power errors that can achieve high accuracy and fast dynamic power response based on the estimated stator flux, the active and reactive power and their errors. Simulations results are carried out for validation of the digital controller operation.

Model predictive current control based on hybrid control set for permanent magnet synchronous motor drives

AbstractModel predictive current control (MPCC) has been widely recognized as a high‐performance scheme for permanent magnet synchronous motor drives because of its simple control structure. This article proposes a novel multivector MPCC (MMPCC) method based on a hybrid control set, which includes both original basic voltage vectors (VVs) and synthesized VVs. The two active VVs and one null VV are considered as an initial control set, and the exact combination of them depends on their corresponding durations, which are calculated by stator current slopes in frame with the use of the prediction formula. Contrary to the traditional cost function, an alternative hybrid control set can achieve superior voltage precision. This is due to the involved cost function that minimizes the maximum of prediction current errors, which typically occur at non‐integer sample instants during the control period. The performance of the proposed MMPCC method has been experimented to confirm its effectiveness, compared with the conventional MPCC (CMPCC) and duty‐cycle MPCC (DMPCC). The results indicated an anticipated enhancement in both dynamic and steady‐state performance at a low rotor speed, alongside a significant robustness against parameter mismatch.

Model Predictive Virtual Flux Control Method for Low Switching Loss Performance in Three-Phase AC/DC Pulse-width-Modulated Converters

Three-phase AC/DC pulse-width-modulated (PWM) converters have been widely employed in various renewable energy systems and industrial applications, which require a high-efficiency power converter operation. This article proposes a technique to reduce switching loss in AC/DC converters by integrating a voltage vector preselection strategy to model predictive virtual flux control. The voltage vector preselection strategy preselects available voltage vectors corresponding to switching states that lead to minimum switching loss in the phase leg, which conducts the highest current. By using preselected voltage vectors, clamping intervals are generated at every fundamental period to maintain the present switching states of the power switches, resulting in the reduction in switching loss. Additionally, by using virtual flux control, the proposed approach can effectively be used under both ideal and distorted source voltage conditions. The proposed method is compared with the conventional model predictive current control and the conventional model predictive virtual flux control. Both a simulation and experiment are performed to validate the correctness and effectiveness of the proposed method, which has been found to decrease the switching loss of an AC/DC converter by up to 15% compared to conventional control schemes at a negligible increase in the input current total harmonic distortion and DC output voltage ripple.

Analytical modelling and implementation of a new four-switch hybrid power filter topology.

This paper presents a new three-phase four-switch shunt hybrid power filter with the new circuit topology aimed at compensating reactive power and higher harmonics of the load. A space-vector PWM scheme is adopted to reduce the switching state of power switches. In the proposed control scheme, proper voltage vectors are generated on the ac terminal for drawing nearly sinusoidal line currents with controllable power factor. An original closed-form solution of line currents, based on the mixed p-z approach is presented. The analytical procedure is verified by experimental results to confirm the effectiveness of the proposed control scheme

New Space-vector hysteresis current control with neutral point voltage balancing applied on three-level VSI for wind power conversion

This paper presents a new space-vector hysteresis current control (SV-HCC) with neutral point voltage balancing applied on a three-level NPC-VSI. The last supplies a rotor winding of the doubly fed induction generator (DFIG). The proposed control technique controls the power delivered from the wind generator to the electrical network by controlling the rotor currents of the DFIG. It is based firstly on the detection of area and sector in which the error vector tip of the rotor current can be located, secondly, on the neutral voltage sensing. And then on the application of an appropriate voltage vector among the 27 voltage vectors of the three-level NPC-VSI to accomplish two main goals: 1- Controlling the active and reactive powers delivered by the wind generator to the electrical network. 2- Balancing the neutral point voltage of the three-level VSI.

Hexagonal zoning deadbeat model predictive control of induction motor

AbstractDeadbeat model predictive control is known as a precise control method in motor control applications. Recently, finite set deadbeat control is applied to power electronics applications. A voltage‐based cost function is used to select the closest voltage vector to the reference vector by examining all possible states in the cost function. This method needs a high amount of computation when it is applied to multilevel inverters or virtual voltage vectors due to a considerable increase in the number of candidates. Some studies have been done to reduce the number of candidate voltage vectors and computation burden. The methodology in these methods is based on finding the adjacent area and applying the vertex vectors to the cost function. So, these strategies are multi‐step and complex. The hexagonal zoning deadbeat model predictive control is proposed and introduced. The basic idea of the proposed method is that each zone should contain only one vector. In this way, the area identification is equal to finding the optimum voltage selection. Hexagonal zoning is used, which simplifies the process of identifying the area. A simple area identification method is developed based on the reference voltage phase angle. The proposed method can be applied to different inverters with different spatial vector diagrams. Furthermore, the synthesis of the virtual vector is manipulated to reduce the torque and flux ripple. The proposed method is experimentally evaluated by applications to the virtual voltage switching of a two‐level inverter for the induction motor drive in this research.

Orthogonal decomposition of currents, power definitions and energy transmission in three-phase systems treated in the time domain.

This paper deals with the orthogonal decomposition of currents in a three-phase system. Currents and voltages of the three-phase system are treated as instantaneous values and as continuous functions defined in given interval. In both cases current and voltage vectors are defined. They are decomposed into two orthogonal components. The first one is collinear with the voltage vector while the second one is orthogonal to it. It is shown, that only the current vector component collinear with the voltage vector contributes to the energy transmission and to active power while the current vector component orthogonal to the voltage vector causes reciprocal energy exchange between source and load whose average value equals zero.

A new flux and multilevel hysteresis torque band DTC with lookup table‐based switched reluctance motor drive to suppress torque ripple

SummaryThe switched reluctance motor (SRM) is a prominent electrical machine drive with low cost and good performance in different drive applications. This machine's main drawbacks are torque ripple and flux ripple. However, the existing SRM‐operated direct torque control (DTC) Voltage vectors (VVs) give high torque ripples due to improper sector division and minimum selection of VVs switching states. On the other hand, a two‐level hysteresis torque band can result in torque ripples. Therefore, this paper proposed DTC using 16 partitions, active small and large VVs, and a multilevel hysteresis torque band (MHTB) strategy to mitigate the torque ripple further. More active VVs (i.e., 16) are employed in the modified sector‐based switching tables, suppressing the torque ripples. The proposed strategy is verified and validated using MATLAB/Simulink. The detailed result discusses the response of torque, flux, and speed of SRM. The DTC‐operated SRM drive experimental results prove the effective minimization of torque ripples in the proposed DTC compared to the existing DTC.

Bidirectional PWM Converter to Interface AC Part to DC Microgrid with Neutral Potential Balancing

This research presents a description of a bidirectional pulse width modulated converter that functions as a rectifier by using the direct power control strategy and space vector modulation technology. In contrast to the voltage-oriented control strategy, this method minimises the number of internal current loops and requires more tuning. While functioning as an inverter, it applies the space vector modulation technique as well. The approach, on the other hand, is not the same as rectifiers since it calculates the duty ratio of the neighbouring voltage vectors in each small triangle that is generated in each sector that has a period of 60 degrees. In both situations, the neutral point potential has been brought back into equilibrium.

Modified direct torque control algorithm for regeneration capability of IM driven electric vehicle by using hybrid energy storage system

The direct torque control (DTC) algorithm of a 3-phase voltage source inverter (VSI) has been implemented to drive induction motor (IM) for EV applications. However, the conventional DTC for IM is distressed due to large torque ripple, high current total harmonic distortion, and variable switching frequency. So, in this manuscript, a modified direct torque control (MDTC) algorithm is proposed to tackle the said challenges. A three-level hysteresis controller is proposed in modified DTC to optimize the duty ratio of the fundamental voltage vector to minimize the error between the reference and final voltage vector imposed on IM terminals. To improve the efficiency of the EVs by developing a system that uses the energy produced during regenerative braking. The proposed method recovers electric energy produced by the EV without using any additional power converter. The switching patterns allow power flow in both directions. Later, a hybrid energy storage system (HESS) is integrated to supply and store the energy in an optimal way. Extensive studies have been performed to show the efficacy of the proposed MDTC technique in IM based EV application with HESS. The key findings indicate that the proposed MDTC provides better dynamic and steady-state performance.