Virtual Vector Research Articles

An Angle-Based Virtual Vector Model Predictive Current Control for IPMSM Considering Overmodulation

The conventional model predictive control method suffers from large current and torque harmonics due to the limited voltage vectors. To increase the control performance, in many papers, the methods of extending the predictive control set by adding virtual vectors are proposed. However, constructing virtual vectors will bring extra computational burden for vector optimization. To solve this problem, this paper proposes an angle-based virtual vector model predictive current control (ABVV-MPCC) method for interior permanent magnet synchronous motor (IPMSM). In this method, a hexagonal coordinate system is introduced to define the virtual vectors. After obtaining the composite relationship between the reference voltage vector and the adjacent basic vector, the vector optimization range is reduced from six voltage sectors to one voltage sector. And the optimal voltage vector is directly obtained by searching for the closest candidate voltage vector. After adopting the proposed method, the exhaustive optimization is avoided and the calculation burden is independent from the virtual voltage vectors number. Therefore, virtual voltage vectors number can be set arbitrarily, which greatly reduces current harmonics. Besides, a simple overmodulation dealing method by finding the optimal reachable voltage vector is proposed. And the dynamic performance under overmodulation is increased without adding additional control module.

A phase-field simulation of easily switchable vortex structure for multilevel low-power ferroelectric memory

Ferroelectric materials with multi-directional polarization orders can form a variety of special domain structures, which have a wide range of applications. In this work, lead-free potassium sodium niobate ferroelectric thin films were simulated by solving the Time-Dependent-Landau-Ginzburg (TDLG) equation. Based on vortex topological structure characteristic of perovskite-type ferroelectric, domain types are simplified from 26 to 9 through virtual polarization vectors. By temperature selection, we accomplished a large easily switchable vortex structure with 20% side length. Based on this, as low as 0.04V/nm electric-field pulse was applied to explore vortex domain structures change. Under different low external electric-field pulses, conductance states change in vortex have been calculated and discussed systematically. Free energy computation results reveal that the domain wall (DW) conductance states primarily originate from the competition between electrostatic energy, gradient energy, and elastic energy. Finally, we propose the multilevel data ferroelectric memory through easily switchable vortex topological structures for the first time. Under electric-field pulses, diverse storage states were presented through 0/1 measurement of 8 positions. By achieving an easy-to-distinguish and robust-to-switch data map at the vortex structure, this work might provide a significant idea of vortex structure on low-power ferroelectric memory applications.

An Enhanced Discrete Virtual Vector-Based Direct Torque Control of PMSM Drives

An Enhanced Discrete Virtual Vector-Based Direct Torque Control of PMSM Drives

Zero-Sequence-Current Suppression of Open-End Winding PMSM With Common DC Bus Based on Virtual Vector Control

Zero-Sequence-Current Suppression of Open-End Winding PMSM With Common DC Bus Based on Virtual Vector Control

A Comprehensive Review on Space Vector Based-PWM Techniques for Common Mode Voltage Mitigation in Photovoltaic Multi-Level Inverters

Nowadays, transformer-less photovoltaic (PV) multi-level inverters (MLIs) are commonly employed in both industrial and residential settings. This structure has attracted increased attention due to its unique advantages, such as higher efficiency, lower cost and size, better waveform quality, and inherent fault tolerance. However, due to the removal of the transformer, the common mode voltage (CMV) becomes one of the crucial issues in transformer-less PV MLIs. The high-frequency variation in CMV results in a leakage current that deteriorates the line current quality, increases the PV power system losses, leads to severe electromagnetic emissions (EMI), reduces the PV array lifespan, and causes personal safety problems. In this regard, this paper presents a review of the existing and recent research on modulation techniques based on space vector pulse width modulation (SVPWMs) that overcome this issue in transformer-less three-level NPC-MLIs (3L-NPC-MLIs). The reduced CMV-SVPWM (RCMV-SVPWM) can be mainly categorized as an RCMV-SVPWM based on the vector type, based on virtual vectors, and based on the two-level SVPWM (2L-SVPWM). Their features and their limitations in terms of several main criteria are discussed. In the final section of this paper, some challenges and future trends for this research area are projected.

A Novel Common-Mode Voltage Suppression Strategy for Current Source Converter

The problem of common-mode voltage (CMV) in current source converter (CSC) has been concerned with the development and application of CSC, such as in the transformerless motor drive system. Using a common-mode choke is a popular solution to suppressing CMV. The high-frequency harmonics of the CMV can be eliminated by the common-mode filter. However, the low-order harmonics cannot be eliminated effectively, especially at low modulation index, which may cause common-mode resonance and increase the size of the choke. In this paper, a novel virtual space vector modulation (VSVM) method is proposed, which constructs virtual space vectors by the original vectors. The average value of the CMV produced by each virtual vector is zero. The proposed method can reduce the amplitude and third-order harmonic component of the CMV. In addition, the number of switching transitions in a switching sequence of the proposed method is the same as the conventional 5-segment SVM. The suppression effects of different methods on the low-order harmonics of CMV are compared through simulation and experiments, and the effectiveness of the proposed methods is verified.

A Novel Virtual Space Vector Modulation With Optimized Neutral-Point Voltage Control Capability for Ten-Switch Three-Phase Three-Level Inverter

Ten-switch three-phase three-level inverter (TP-TLI) is receiving more attentions owing to the reduced system cost compared to traditional TP-TLIs. However, it still faces serious neutral-point voltage (NPV) balance problem. This article proposes a novel virtual space vector modulation (NVSVM) with optimized neutral-point voltage control (NPVC) capability. A set of virtual vectors are selected to generate zero NP current. By analyzing the vector synthesis principle over the full modulation areas, a new control degree, which is utilized to optimize the NPVC capability and reduce line voltage THD, is introduced. Besides, a dead time compensation method based on volt-second balance is also given to reduce the switching loss. The NVSVM not only improves the NPVC capability without dc offset and obvious ac oscillations in NPV under full range of modulation index and power factor (PF) conditions, but also reduces line voltage THD and the switching loss. Theoretical analysis shows that the available NP current for the proposed NVSVM is about 2.75 times greater at most than that for traditional VSVM. Simulation and experimental results are given to validate the effectiveness of the NVSVM and control strategies.

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.

ZSCC suppression method for parallel three-level inverters based on model predictive control with virtual location vector

ZSCC suppression method for parallel three-level inverters based on model predictive control with virtual location vector

Improved Feedback Quantizer with Discrete Space Vector.

The use of advanced modulation and control schemes for power converters, such as a Feedback Quantizer and Predictive Control, is widely studied in the literature. This work focuses on improving the closed-loop modulation scheme called Feedback Quantizer, which is applied to a three-phase voltage source inverter. This scheme has the natural behavior of mitigating harmonics at low frequencies, which are detrimental to electrical equipment such as transformers. This modulation scheme also provides good tracking for the voltage reference at the fundamental frequency. On the other hand, the disadvantage of this scheme is that it has a variable switching frequency, creating a harmonic spectrum in frequency dispersion, and it also needs a small sampling time to obtain good results. The proposed scheme to improve the modulation scheme is based on a Discrete Space Vector with virtual vectors to obtain a better approximation of the optimal vectors for use in the algorithm. The proposal improves the conventional scheme at a high sampling time (200 μs), obtaining a THD less than 2% in the load current, decreases the noise created by the conventional scheme, and provides a fixed switching frequency. Experimental tests demonstrate the correct operation of the proposed scheme.

Improved virtual space vector modulation for neutral point voltage oscillation and common-mode voltage reduction in neutral point clamped three-level inverter

Improved virtual space vector modulation for neutral point voltage oscillation and common-mode voltage reduction in neutral point clamped three-level inverter

Trajectory Tracking Control for Quadrotor Slung Load System With Unknown Load's Linear Velocity and Cable Length

This paper addresses the trajectory tracking control problem for a quadrotor suspended load system without load's linear velocity measurement and cable length information. Firstly, the cable length is estimated by designing an immersion and invariance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf{I\&amp;I}$</tex-math></inline-formula> )-based adaptive law. Secondly, a virtual thrust force vector is designed for the load position subsystem with the denoted auxiliary variables in the lack of load's linear velocity measurement. Then, through the cable direction subsystem and quadrotor attitude subsystem, the angular velocity input is presented to drive the real thrust input to virtual thrust input via the backstepping method. Thereafter, the uniformly boundedness of the whole closed-loop system is obtained by means of building suitable Lyapunov functions. Ultimately, numerical simulations attest to the performance of the proposed trajectory tracking control law.

Quasi-Z-Source Three-Phase Voltage Source Inverter with Virtual Space Vector Modulation to Increase the Voltage Gain and for the Reduction of Common Mode Voltage

Abstract A quasi-Z-source network is used to boost the DC bus voltage of a voltage source two-level H-bridge inverter to increase the voltage gain. With the increase in the DC bus voltage, the common mode voltage (CMV) also increases. The CMV is reduced using virtual space vector pulse width modulation (SVPWM). Due to the presence of a quasi-Z-source network, the expression of the CMV changes significantly with respect to the conventional voltage source two-level H-bridge inverter fed from a pure DC supply. In this paper, a detailed analysis of the origin of the CMV for the quasi-Z-source two-level H-bridge inverter is presented. Additionally, it is shown how the CMV is affected for a DC input supply taken from a three-phase diode bridge rectifier. The work also details the scheme for suitable placement of shoot-through time intervals required for boosting within the non-active time intervals in virtual SVPWM. The simulation and experimental results show the scheme is effective in increasing the voltage gain and reducing the CMV arising at the third harmonic of the desired output frequency by at least 33.33%.

A Computationally Efficient Model Predictive Control Method for Dual Three-Phase PMSM of Electric Vehicle With Fixed Switching Frequency

Aiming at the problems of large harmonic current, unfixed switching frequency and heavy calculation burden in the model predictive current control (MPCC) methods of dual three-phase permanent magnet synchronous motor (DT-PMSM). This paper presents a computationally efficient MPCC method with a fixed switching frequency. Firstly, the virtual voltage vectors (V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s) are synthesized by two large vectors and two medium-small vectors. The V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s effectively reduce the harmonic currents, and the goal of the synthetic V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> is that the harmonic current in the x-y subspace is zero. Therefore, the weighting factor of the harmonic term is eliminated in the cost function. Secondly, an optimal voltage vector selection method is designed to reduce the candidate voltage vectors in the control set and relieves the calculation burden. In addition, to further reduce ripple current and torque ripple, the duty cycle modulation method is introduced to calculate the dwell time of the V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The zero vector is inserted in the middle and both sides of the V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s to achieve the purpose of fixing the switching frequency. Finally, the effectiveness of the proposed method is verified by experiments.

Attitude Estimation From Vector Measurements: Necessary and Sufficient Conditions and Convergent Observer Design

The paper addresses the problem of attitude estimation for rigid bodies using (possibly time-varying) vector measurements, for which we provide a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">necessary and sufficient</i> condition of distinguishability. Such a condition is shown to be strictly weaker than those previously used for attitude observer design. Thereafter, we show that even for the single vector case the resulting condition is sufficient to design almost globally convergent attitude observers, and two explicit designs are obtained. To overcome the weak excitation issue, the first design employs to make full use of historical information, whereas the second scheme dynamically generates a virtual reference vector, which remains non-collinear to the given vector measurement. Simulation results illustrate the accurate estimation despite noisy measurements.

Supporting a Virtual Vector Instruction Set on a Commercial Compute-in-SRAM Accelerator

Supporting a Virtual Vector Instruction Set on a Commercial Compute-in-SRAM Accelerator

Model-Free Predictive Current Controller for Common Mode Voltage Stabilization by Finite odd Virtual Vector set

Model-Free Predictive Current Controller for Common Mode Voltage Stabilization by Finite odd Virtual Vector set

Low Complexity Model Predictive Flux Control Based on Discrete Space Vector Modulation and Optimal Switching Sequence for Induction Motors

In this paper, a low-computational burden model predictive flux control (MPFC) based on discrete space vector modulation (DSVM) and the optimal switching sequence (OSS) is proposed for achieving switching frequency (SF) and computational burden efficiencies in motor drives fed by two-level voltage source inverter. The DSVM is used to extend the prediction candidates of MPFC and greatly improve the performance of the controller. A generalized minimum flux error method independent of the number of virtual vectors is derived to cancel the exhaustive optimization method and lower the execution time of the proposed algorithm. In addition, new over-modulation and OSS schemes are designed to optimize the use of DC-link voltage and mitigate the inverter SF when implementing the optimal control action into switching states. The comparative experimental results show that without significant performance degradation, the proposed strategy provided about 50% SF and 25% execution time reductions compared to the classic MPFC methods.

Optimized Virtual Vector Technique with Loss Minimization of Six Phase IM Under Low-Speed Operation for Electric Vehicles

Optimized Virtual Vector Technique with Loss Minimization of Six Phase IM Under Low-Speed Operation for Electric Vehicles

A Hybrid Active Damping Strategy for Improving the Adaptability of LCL Converter in Weak Grid

In a weak grid, the line impedance variation will cause the resonant frequency of the LCL filter to shift towards lower frequencies, thus reducing the quality of the grid-connected current and affecting the power grid stability. To solve this problem, a hybrid active damping strategy with feedforward compensation is proposed for the neutral point clamped (NPC) LCL grid-connected inverter system. In order to reshape the output conductance of the grid-connected system, suppress the resonance spikes of the LCL filter and improve the adaptability of the grid-connected system to the weak grid. A first-order low-pass filter is designed in the grid-connected current loop, and an active damping control of grid-connected current based on a first-order high-pass filter is also proposed. Compared with the conventional capacitive current active damping, no additional sensors are required, and the use of a differential is avoided, which reduces the high-frequency noise. The use of passive resistors is reduced, which reduces the power loss of the grid-connected system. In addition, a point of common coupling (PCC) voltage feedforward strategy based on a low-pass filter is designed to suppress the background higher harmonics at PCC and improve the quality of grid-connected current. In this work, the robustness of the system is analyzed when the parameters of the LCL filter change. Finally, the virtual space vector modulation strategy is used to balance the neutral voltage of the DC bus. Simulation and experimental results show that the control strategy can effectively improve the adaptability of the system to the weak power grid, improve the quality of grid-connected current, and demonstrate strong stability. The THD can be decreased by 0.2% at least, and the improvements are more significant with larger line impedance; the THD is only 2.33% even at 10 mH line impedance.