Active Voltage Vectors Research Articles

A Novel Finite-Set Ultra-Local Model-Based Predictive Current Control for AC/DC Converters of Direct-Driven Wind Power Generation with Enhanced Steady-State Performance

Compared with the standard finite-set model-based predictive current control (FS-MPCC), the finite-set ultra-local model-based predictive current control (FS-ULMPCC) removes the use of actual system parameters and thus has some advantages like good robustness and easy implementation. However, the steady-state performance of FS-ULMPCC is relatively weak. In this paper, a novel FS-ULMPCC method is proposed and applied to the AC/DC converter of a direct-driven wind power generation system. The proposed method is designed based on a linear-extended state observer (LESO). In particular, a new control set reconstruction strategy is proposed to improve the steady-state performance. Only three options are included in the reconstructed control set, and each one is associated with two independent, active voltage vectors and their durations. The proposed FS-ULMPCC method is compared with the traditional one through experiments. The proposed method includes enhanced steady-state performance and reduced computational burden.

Improved performance of linear induction motors based on optimal duty cycle finite-set model predictive thrust control

Linear induction machines (LIMs) find widespread adoption in various applications, owing to their inherent advantages such as low noise, compact turning radius, and excellent climbing capability. LIMs are extensively utilized in linear metro applications. However, in practical operations, the output thrust shrinks with the increase in speed, which is attributed to end effects. This phenomenon leads to a reduction in efficiency. In addition, fluctuations in the normal force impact system stability, posing disturbances to the suspension system. To address these challenges, this paper suggests a finite-set model predictive thrust control (FS-MPTC) for a drive system employing a linear induction motor (LIM). The FS-MPTC optimizes the duty cycle for the active voltage vector and allocates the remaining period to one of the zero voltage vectors. The selected zero voltage vector reduces the switching transition between it and the active voltage vectors. The duty cycle is calculated for the six voltage vectors by incorporating the deadbeat concept and the derivative value for the electromagnetic thrust. In the prediction stage of the FS-MPTC, the computed duty cycle and the corresponding voltage vector are used simultaneously and repeated for the six voltage vectors. The cost function comprises two terms: the error between the reference thrust and predicted thrust value as the first term and the error between the rated primary flux linkage and its predicted value as the second term. The reference thrust is generated from the outer speed control loop. To validate the effectiveness of the proposed control approach, Japanese 12000 linear induction machine parameters are employed for verification. Comparative analysis of the performance between the suggested control method with the optimal duty cycle and the same process with a fixed duty cycle demonstrates superior performance when utilizing the optimal duty cycle. Finally, the proposed FS-MPTC with the optimal duty cycle offers a promising solution to enhance the operational efficiency of the LIM-based drive systems.

A Model Predictive Control Scheme with Minimum Common-Mode Voltage for PMSM Drive System Fed by VSI

Common-mode voltage (CMV) brings shaft voltage and shaft current, and corrodes the bearings of the permanent-magnet synchronous machine (PMSM), which affects the reliability of the whole PMSM drive system. Since the CMV applied by the zero voltage vectors (ZVVs) is three times that applied by the active voltage vectors (AVVs), a modulation scheme achieving minimum CMV without ZVV is proposed and introduced into the model predictive control structure for the PMSM drive system. Firstly, the whole modulation range is divided into three regions, including the low voltage modulation region (LVMR), high voltage modulation region (HVMR), and over-voltage modulation region (OVMR). Meanwhile, the regional boundary expression is derived. Then, the active zero-state pulse width modulation (AZSPWM) is adopted in LVMR. To improve the steady-state performance, near-state pulse width modulation (NSPWM) without opposite ZVVs is applied to the HVMR. Furthermore, when the reference voltage vector (VV) is located in OVMR, an optimal scheme is proposed to improve the dynamic response. Under the premise of no ZVV existing in the whole modulation region, simulation and experimental results show that the proposed hybrid modulation method can improve the steady-state and dynamic performance of the PMSM drive system.

Improved Zero-Sequence Current Hysteresis Control-Based Space Vector Modulation for Open-End Winding PMSM Drives With Common DC Bus

Through the zero-sequence current (ZSC) hysteresis controller, the existing ZSC hysteresis control-based space vector modulation (SVM) strategy can provide a satisfactory ZSC suppression effect and greatly reduce the complexity for the open-end winding permanent magnet synchronous machine (OW-PMSM) drive with common dc bus. However, the corresponding linear modulation range is reduced by 12.7% compared with the middle hexagon space vector modulation (MH-SVM) for the OW-PMSM drive. To this end, this letter improves the linear modulation range of the existing strategy. The candidate voltage vectors for each sector are re-selected, and three active voltage vectors will be employed in the extended feasible region. While ensuring the ZSC hysteresis control, the linear modulation range of the proposed strategy is the same as the MH-SVM. At last, experimental results verify the feasibility and effectiveness of the proposed strategy. The proposed strategy can suppress the ZSC effectively, and the corresponding maximum speed is the same as the counterpart of the MH-SVM.

Current fluctuations reduction strategy based on optimal three‐space‐vector pulse‐width modulation for service‐life improvement of DC‐link electrolytic capacitors in three‐phase voltage‐source inverter system

AbstractThe authors propose a current fluctuation reduction strategy based on optimal three‐space‐vector pulse‐width modulation (TSVPWM), which is used to improve the service‐life of the dc‐link electrolytic capacitors in two‐level three‐phase voltage‐source inverter (VSI) system. Differing from the typical SVPWM‐based method that employs two adjacent active voltage vectors and zero voltage vectors to synthesise the reference voltage, the proposed strategy selects the required voltage vectors based on the minimum dc‐link electrolytic capacitor current fluctuation. With the proposed strategy, an objective function for the root‐mean‐square value of dc‐link electrolytic capacitor current is first constructed under the constraint of eight permissible voltage vectors. And then, by solving the minimum of the objective function through the piecewise linear programming, the optimal three voltage vectors under the different modulation ratios and load power factors are obtained accordingly, so as to achieve the minimum dc‐link electrolytic capacitor current fluctuations during each switching period. Meanwhile, a PWM implementation scheme based on positive–negative double carrier signals is presented, which not only simplifies the implementation process but also effectively reduces the switching losses of power devices. Finally, the experimental results demonstrate that the proposed strategy can minimise the dc‐link electrolytic capacitor current fluctuation under different working conditions.

A New Four-Step Commutation Method for Indirect Matrix Converter With Active-Voltage Vectors Being Applied

The existing two commutation methods of the rectifier stage for indirect matrix converter (IMC) are zero-current commutation and four-step commutation. The premise of zero-current commutation is that the inverter stage of IMC uses a zero-voltage vector, but when the inverter stage cannot use zero-voltage vectors (such as space overmodulation, common mode suppression modulation, etc.), the four-step commutation is adopted. The conventional four-step commutation method has a complex switching sequence and requires additional sensors. Based on the natural freewheeling characteristic of IMC and the switching sequence of zero-current commutation, a new four-step commutation method is proposed when active-voltage vectors are applied in the inverter stage, first turn off the two switches at 1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> and 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nd</sup> steps, and then turn on the two switches at 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> and 4 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> steps. The switching sequence of the new four-step commutation is not affected by the polarity of input voltage or output current direction, thus solving the complexity switching sequence problem of the conventional four-step commutation, and does not require additional voltage or current sensors, making the IMC commutation process safer and more reliable. Finally, this paper verifies the effectiveness of the new four-step commutation method of IMC through experiments.

Three-Vector Model Predictive Suspension Force Control for Bearingless Permanent Magnet Slice Motor

Aiming at the defects of signal detection and transmission delay leading to the reduction of control accuracy in the digital control of bearingless permanent magnet slice motor(BPMSM), a three-vector model predictive suspension force control(MPSFC) strategy is proposed. Firstly, the suspension force prediction model of the BPMSM is established and the dead-beat principle is used to calculate two active voltage vectors and a null vector duty cycle. Then, according to the principle of the minimum switching state in one control cycle, simplifying the candidate voltage vector combinations, which effectively reduces the calculation amount and inverter switching frequency. Finally, the simulation and experimental results show that the proposed three-vector MPSFC strategy of the BPMSM can not only effectively improve the control accuracy, but also implement the stable suspension of the rotor. In addition, it has good static and dynamic response characteristics.

Overall Electrical Parameters Identification for IPMSMs Using Current Derivative to Avoid Rank Deficiency

An approach to identify overall electrical parameters for interior permanent magnet synchronous motors (IPMSMs) in steady state is proposed in this paper using current derivative, with which the concerns of rank deficiency can be avoided. It is found that the conventional IPMSM models under d-q frame always neglected the PWM switching effect of inverter and the quantities in these models are always regarded as constant values in steady state, making it untoward to identify all motor parameters simultaneously. Instead, the switching IPMSM model is built to analyze the details of PWM, and full-rank current derivative functions during zero and active voltage vectors are given respectively. Without any injected signals, all electrical parameters including d/q-axis inductance, stator resistance and permanent magnet flux linkage are able to be figured out in steady state by measuring the phase current derivatives. Simulations and experiments are implemented to validate the proposed approach.

Topology and Modulation for a New Indirect Matrix Converter to Reduce the Common-Mode Voltage

In this paper, a new indirect matrix converter (IMC) topology with two insulated gate bipolar transistors (IGBT) set in the upper and lower dc-link is proposed to suppress the common-mode voltage (CMV). Meanwhile, two new space vector modulation (SVM) strategies are redesigned to control this topology. The first strategy utilizes the equivalent zero voltage vectors to replace the zero voltage vectors for reducing the CMV, while the second strategy selects and utilizes specific active voltage vectors and equivalent zero voltage vectors to suppress the CMV based on the input current sector. Comparative simulation and experimental research for the two strategies are carried out for the new IMC topology, which validates that the CMV can be reduced to 57.7% or 37.1% of the one in the conventional IMC system. Besides, the proposed new IMC system is experimentally verified that it can keep a satisfied CMV suppression performance when feeding an induction motor. Moreover, the efficiency analysis also indicates that the new topology will not bring in obvious additional power loss under the proposed SVM strategies even though two IGBTs are added in the dc-link.

Multivector-Based Model Predictive Current Control With Zero-Sequence Current Suppression for Three-Phase Series-End Winding Permanent Magnet Synchronous Motor Drives

To suppress the zero-sequence current and enhance the steady-state performance of the three-phase series-end winding permanent magnet synchronous motor (TPSW-PMSM) drives, a multi-vector-based model predictive current control scheme with zero-sequence current suppression is developed in this paper. The concept of the desired voltage is utilized to preselect the candidate voltage vectors and offer the guidance of the geometric division of the sector. In one sampling period, multi-voltage vectors are employed, and the combinations include one active voltage vector and one null voltage vector, and two active voltage vectors, which improves the steady-state performance. Meanwhile, the duty cycle of each voltage vector is derived based on an intuitive geometric expression of the cost function. Further, the relationship between the zero-sequence voltage injection and the switching sequence is revealed, and it is employed to suppress the zero-sequence current actively. In addition, overmodulation operation is also taken into consideration in the proposed scheme. Finally, the experimental study validates the effectiveness of the proposed scheme.

An Improved High-Frequency Voltage Injection Method for Interturn Short-Circuit Fault Detection in PMSMs

The inter-turn short-circuit fault (ITSCF) is a common incipient fault for the permanent magnet synchronous machine (PMSM) drive system. In recent years, the high-resolution ITSCF detection method that combines the high frequency (HF) signal injection and zero-sequence voltage measurement has been put forward. However, for the traditional HF signal injection technique, nonnegligible voltage distortion may occur when the injection frequency is close to the PWM carrier-frequency. In addition, the injected voltage varies with the operating conditions of the PMSM. These drawbacks of the traditional HF signal injection technique greatly limit the ITSCF detection performance using HF signal injection. To further improve the ITSCF detection performance, an improved HF injection scheme is proposed in this paper. In the proposed method, the six active voltage vectors are injected into the PMSM in certain orders to realize a rotating voltage injection, and the injection frequency is up to five-sixth of the PWM carrier-frequency. By employing the proposed injection method, the ITSCF detection sensitivity can be much improved. And the ITSCF detection performance is not affected by the operation conditions of the PMSMs. Finally, the simulations and experiments are carried out to verify the proposed method.

A Low-Complexity Modulated Model Predictive Torque and Flux Control Strategy for PMSM Drives Without Weighting Factor

This article proposes a modulated model predictive torque and flux control (M2PTFC) method with low complexity for a two-level voltage source inverter (2L-VSI)-fed permanent magnet synchronous motor (PMSM). The proposed strategy aims to reduce the computation burden and simplify the control implementation of the conventional M2PTFC scheme by reducing the number of candidate voltage vectors at every control sample to the minimum (i.e., only two candidates) and eliminating the weighting factor of the cost function and its corresponding tuning procedures. For these purposes, the proposed method devotes different control objectives to the duty modulation and the cost function evaluation processes while executing them sequentially. First, aiming at torque ripple reduction, a duty modulation strategy is proposed based on the analysis of torque deviations produced by different voltage vectors, which ensures proper selection of the two candidates and restricts active voltage vectors (AVVs) that cause high deviations. Then, these candidates are evaluated based on a cost function assigned to achieve the stator flux control objective. The effectiveness of the proposed control scheme is verified through comparative assessment with the conventional M2PTFC and two existing simplified methods by means of simulation and experimental results.

Integration of Reference Current Slope Based Model-Free Predictive Control in Modulated PMSM Drives

Conventional model-based predictive current control (MBPCC) suffers from high current ripple and system parameter dependence problem. To address these issues, a novel reference current slope-based modulated model-free predictive control (MFPC) is proposed in this article. In the proposed method, a reference current slope is obtained based on the current deadbeat solution. A reduced amount of active voltage vectors can then be determined in a straightforward way according to the reference current slope and the current slopes for the possible voltage vectors, thus avoiding enumerating operation in the conventional MBPCC. To reduce the current ripples, a two-vector modulation strategy is introduced to the proposed method. In addition, the current slopes for the possible voltage vectors are obtained in a model-free manner based on online measured data only to reduce the influence of parameter uncertainties on the controller. Here, the principles of the two-vector modulation are well-considered, and the current variations with the input voltage vectors from two sampling time intervals are used to estimate the current slopes for all the voltage vectors. As a result, even though two voltage vectors with variable time durations are applied in each control period, the current slope information can be refreshed every half control period, thus guaranteeing the reliability and accuracy of current predictions. The proposed method is verified on a permanent magnet synchronous machine (PMSM) setup to demonstrate its improved parameter robustness and steady-state performance.

Improved Model Predictive Current Control for Linear Vernier Permanent-Magnet Motor With Efficient Voltage Vectors Selection

In order to relieve the computational burden and reduce the ripples in thrust force and current of linear vernier permanent-magnet motors, this article proposes three-vector-based model predictive current control (MPCC) with efficient voltage vectors selection. The proposed method avoids the traversal of all the possible voltage vectors. Only three nonadjacent active voltage vectors are predicted and evaluated by the cost function. Two active voltage vectors can be precisely determined according to the relationship of three cost function values. The prediction workload can be reduced with the efficient voltage vectors selection. Also, the two active voltage vectors along with the null voltage vector are used to synthesize the final applied voltage vector based on deadbeat principle. The proposed three-vector-based MPCC method extends the modulation area from discrete points to the whole regular hexagon. Thus, the ripples in thrust force and current can be minimized. Theoretical analyses and experimental results are given to verify the effectiveness of the proposed MPCC.

Space Vector Pulsewidth Modulation Strategy for Multilevel Cascaded H-Bridge Inverter With DC-Link Voltage Balancing Ability

Space vector pulsewidth modulation (SVPWM) algorithms for cascaded H-bridge multilevel (CHB ML) inverter usually provide the possibility of using several combinations of active voltage vectors to generate the same output voltage vector. For preselected H-bridges, some of them may generate output voltages opposite to the assumed direction. This results in the change of the dc-link voltages of these H-bridges in the opposite direction to the assumed direction in the ordering algorithm. Consequently, these algorithms are characterized by undue constraints and narrow possibilities of dc-link voltage balancing. In the proposed control algorithm, CHB ML inverter is treated as groups of successively activated three-level inverters; depending on the length of the reference voltage vector. These three-level inverters consist of three H-bridges selected from each phase. The proposed extended selection method enables firm-grip control of the dc-link voltages. For a given direction of phase currents, the possibility of using H-bridges with lowest and highest dc-link voltages is simultaneously analyzed. Additionally, each of the three-level inverters is controlled by one of three proposed alternative modulation methods for which both the attainable output voltage vectors and unbalanced dc-link voltages are predicted. Simulation and experimental results confirm the correctness of the algorithm execution.

Sensorless Control and Inductances Estimation of IPMSMs Using FPGA and High Bandwidth Current Measurement

This paper presents a sensorless control method and a very fast on-line inductances identification of an IPMSM. The current slopes (derivatives) at one active-voltage vector and one zero-voltage vector are measured every PWM cycle to estimate the rotor speed and position with the aim of increasing the estimation accuracy and reducing total harmonic distortion. In addition to these current slopes, the DC bus voltage of the inverter is measured to estimate the machine inductances on-line. The proposed on-line parameter identification method can overcome the drawback of the existing off-line methods, such as: the requirement of a robust mechanical clamping system and test signal generators. The proposed on-line method also addresses the limit of the existing on-line methods, such as slow update and the possibility of incorrect convergence of the estimated parameters. Extensive experimental studies were conducted to verify the effectiveness and robustness of the proposed sensorless control and parameters identification of the IPMSM.

An Improved PWM Method of Five-Leg VSI Fed Dual-PMSM System With Duty Cycles Regulation

The five-leg voltage source inverter dual motors system has been widely studied in recent years for its advantage of fewer power switching devices. The traditional modulation method generates the voltage vectors needed by the two motors alternately in one control period, in which active voltage vectors of one motor can operate for a short time thus limit the speed ranges of the two motors. Regarding the deficiency, the relationship between the basic active voltage vectors of the two motors is futher analyzed and an improved pulsewidth modulation (PWM) method is proposed in this article, by which the duty cycles of five-phase PWM signals are modified as a whole. Under the premise that the common leg pulse width meets the requirements of the two motors in one control period, the effective time of the active voltage vectors of the two motors is tremendously expanded with no hardware added, and the speed ranges of the two motors are thus greatly expanded. When one motor runs at a relatively low speed, the speed range of the other motor can be effectively expanded with this method, compared with the traditional one. Simulations and experiments also verify the accuracy of the theoretical analysis and the feasibility of the proposed method.

Second Harmonic Seamless Splicing Technique Based on Maximum Active-Voltage Vector for Online MTPA Tracking Control of SynRM

Maximum-torque-per-ampere (MTPA) control strategy is widely employed to achieve the optimal efficiency control of synchronous reluctance machines (SynRMs). However, the control efficiency of the conventional method that the optimal current distribution angle is directly calculated based on the knowledge of the machine parameters is seriously affected by the highly nonlinear and time-varying characteristics of SynRMs. Therefore, in order to effectively resolve this problem, a novel MTPA control scheme based on the second harmonic splicing technique is proposed in this article. Differing from the conventional method, the proposed solution utilizes the transient response current slopes of fundamental maximum active-voltage vector to splice a specific second harmonic signal that contains the optimal current distribution angle. After selecting two available and different splicing coefficients in each sector to guarantee the continuity of the spliced second harmonic signal, the optimal current distribution angle can be obtained accurately without any machine parameters through a simple signal demodulation, which significantly enhances the robustness to machine parameter variations. Furthermore, the influence of rotor position acquisition errors caused by the position sensor's limited accuracy and installation misalignment is analyzed in detail. Finally, the experimental results demonstrate the effectiveness and feasibility of the proposed MTPA control scheme.

A DPWM Modulation Strategy to Reduce Common-Mode Voltage for Indirect Matrix Converters Based on Active-Current Vector Amplitude Characteristics

Based on the characteristics that the amplitude of active-current vector in the rectifier stage is zero when the zero-voltage vector is used in the inverter stage, and any one from the six active-current vectors can be selected, a novel discontinuous pulsewidth modulation (DPWM) strategy for the indirect matrix converter is proposed in this article to reduce the common-mode voltage (CMV). In this DPWM strategy, the reference current vector in the rectifier stage is synthesized by two adjacent active-current vectors, and the reference voltage vector in the inverter stage is synthesized by two adjacent active-voltage vectors and one zero-voltage vector. When zero-voltage vectors are used in the inverter stage, an appropriate active-current vector with the lowest input phase voltage among the two adjacent active-current vectors is used to produce a lower CMV. Under the same switching loss, the proposed strategy has a better input performance and better output performance in high voltage transfer ratio than conventional SVM. Finally, the effectiveness of the modulation strategy is verified by simulation and experiments.

Finite Control Set–Model Predictive Control of H8 Inverter Considering Dead-Time Effect for PMSM Drive Systems With Reduced Conducted Common-Mode EMI and Current Distortions

To reduce the conducted common-mode (CM) electromagnetic interference (EMI) and current total harmonic distortion (THD) in permanent magnet synchronous motor drive systems, this article proposes a finite control set–model predictive control (FCS–MPC) method for an H8 inverter considering the dead-time (DT) effect. In a real system, the DT causes unexpected peak common-mode voltages (CMVs) and distortion of the inverter output voltage, which deteriorates both the CM EMI and current THD. The conventional double active voltage vector (VV) based MPC methods with an H6 inverter may not be a good solution because of the numerous CMV variations and the limit of the VV transitions. In contrast, the proposed FCS–MPC method allows all VV transitions possible without the peak CMVs by instantly operating the series-connected switch of the H8 inverter based on the previous VV, predicted current sector, and next optimal VV. Furthermore, the nonlinearity of the inverter output voltage due to the DT is compensated in a discrete-time model used for the current prediction, considering the calculation delay of the digital controller. Consequently, the current THD as well as the CM EMI can be improved. The simulation and experimental results are presented to verify the effectiveness of the proposed method.