Current Control Method Research Articles

An Improved Three-Vector-Based Model Predictive Current Control Method for Surface-Mounted PMSM Drives

The conventional model predictive control method suffers from large torque ripples and harmonic current. Moreover, the modulation range of output is limited, leading to the deterioration of performance. To address these problems, this article proposes an improved three-vector model predictive current control method for surface-mounted permanent magnet synchronous motor (SPMSM) drives. First, virtual vectors are introduced to increase the number of available voltage vectors, in which the voltage vector control set can be extended. Furthermore, a hierarchical multilevel optimization control algorithm is adopted to obtain the main control set and the extended control set. According to two different control sets, the first and second vectors can be obtained by the cost function, respectively, which can realize modulation range extension. Then, the zero vectors are added to adjust the magnitude of the output voltage vector, and the output vector action time is obtained based on the deadbeat principle. The ripples can be minimized, and the modulation range can be extended with the proposed method. Finally, a comparative analysis of both the simulation and experimental tests is investigated. The comparative investigation verifies the effectiveness and feasibility of the proposed method.

Grid Current Quality Improvement for Three-Phase Diode Rectifier-Fed Small DC-Link Capacitance IPMSM Drives

In order to improve the grid current quality of the small dc-link capacitance (SDC) motor drives fed by three-phase diode rectifier, a grid current control method based on regulation of the rectifier current sixth harmonic is proposed in this paper. Considering the 120° maximum conduction angle of the rectifier diodes, a 120° rectangular waveform with low total harmonic distortion (THD) is selected as the grid current reference. Based on the relationship between the grid current and the rectifier current, the proposed scheme shapes the grid current into the selected 120° rectangular waveform by regulating the rectifier current sixth harmonic. In this way, the grid current THD of the SDC system is significantly reduced. Since the regulation of the rectifier current harmonic is independent of the speed and motor current control loops, the proposed method avoids the complicated controller and the cumbersome parameter tuning in the grid current control process. The experimental results demonstrate the effectiveness of the proposed method.

Research on Torque Current Error Control of PMSM Based on Model Predictive Control

To solve the problem that the torque pulsation is serious due to the large current error in the period when the duty cycle is calculated by the deadbeat method in the duty cycle dual-vector model predictive current control method, a vector switching method is proposed. The control objective of the proposed method is not to equate the predicted torque current with the reference value under the dead-beat idea, but to reduce the torque current control error by changing the switching time of the voltage vector and ensuring the symmetry of the positive and negative current errors. By deducing the duty cycle, the maximum current errors in a single control cycle before and after vector switching is compared and analyzed. The vector switching method is verified on the Simulink simulation platform and compared with the duty cycle double vector method. The results show that the vector switching method can effectively reduce the intra-cycle torque current tracking error and realize the optimal process control in each cycle.

Less is more: Vital roles of bioactive equivalency in assessing food quality

Less is more: Vital roles of bioactive equivalency in assessing food quality

Stabilized Double-Stranded RNA Strategy Improves Cotton Resistance to CBW (Anthonomus grandis).

Cotton is the most important crop for fiber production worldwide. However, the cotton boll weevil (CBW) is an insect pest that causes significant economic losses in infested areas. Current control methods are costly, inefficient, and environmentally hazardous. Herein, we generated transgenic cotton lines expressing double-stranded RNA (dsRNA) molecules to trigger RNA interference-mediated gene silencing in CBW. Thus, we targeted three essential genes coding for chitin synthase 2, vitellogenin, and ecdysis-triggering hormone receptor. The stability of expressed dsRNAs was improved by designing a structured RNA based on a viroid genome architecture. We transformed cotton embryos by inserting a promoter-driven expression cassette that overexpressed the dsRNA into flower buds. The transgenic cotton plants were characterized, and positive PCR transformed events were detected with an average heritability of 80%. Expression of dsRNAs was confirmed in floral buds by RT-qPCR, and the T1 cotton plant generation was challenged with fertilized CBW females. After 30 days, data showed high mortality (around 70%) in oviposited yolks. In adult insects fed on transgenic lines, chitin synthase II and vitellogenin showed reduced expression in larvae and adults, respectively. Developmental delays and abnormalities were also observed in these individuals. Our data remark on the potential of transgenic cotton based on a viroid-structured dsRNA to control CBW.

Thrombospondin-Related Anonymous Protein (TRAP) Family Expression by Babesia bovis Life Stages within the Mammalian Host and Tick Vector.

The tick-transmitted disease bovine babesiosis causes significant economic losses in many countries around the world. Current control methods include modified live-attenuated vaccines that have limited efficacy. Recombinant proteins could provide effective, safe, and low-cost alternative vaccines. We compared the expression of the Babesia bovis thrombospondin-related anonymous protein (TRAP) family from parasites in bovine blood, in vitro induced sexual stages, and kinetes from tick hemolymph. Quantitative PCR showed that in blood and sexual stages, TRAP3 was highly transcribed as compared to the other TRAPs. In contrast, the TRAP1 gene was highly transcribed in kinetes as compared to the other TRAPs. Fixed immunofluorescence assays showed that TRAP2, 3, and 4 proteins were expressed by both blood and sexual stages. Conversely, TRAP1 protein, undetected on blood and induced sexual stages, was the only family member expressed by kinetes. Live IFA revealed that TRAP2, 3, and 4 proteins were expressed on the surface of both B. bovis blood and sexual stages. Modeling of B. bovis TRAP1 and TRAP4 tertiary structure demonstrated both proteins folded the metal-ion-dependent adhesion site (MIDAS) domain structure of Plasmodium TRAP. In conclusion, TRAP proteins may serve as potential vaccine targets to prevent infection of bovine and ticks with B. bovis essential for controlling the spread of bovine babesiosis.

Optimal Operation of WL-RC-QLMS and Luenberger Observer Based Disturbance Rejection Controlled Grid Integrated PV-DSTATCOM System

This article deals with a widely linear reduced-complexity quaternion least mean square (WL-RC-QLMS) controlled two-stage photovoltaic (PV) grid system. The WL-RC-QLMS-based current control method is developed, and the function of this control technique is to attenuate the higher order and suborder harmonic components from the distorted load currents, even when the load currents are nonlinear and/or unbalanced. Moreover, the Luenberger observer is used to control the dc-link voltage. The Luenberger observer is equipped with the cascaded state observers, which can reject the overshoot and undershoot at the dc bus voltage rapidly and precisely. The proposed WL-RC-QLMS controller is modeled and the controller is developed in a Simulink environment and validated on a laboratory prototype. The grid current condition measured in terms of total harmonics distortion is found under the restraint of IEEE 519 standard in different working conditions, which exhibits the efficacy of the implemented control.

A current sensorless control method for multi‐level active front‐end rectifiers with LCL filter

AbstractThis paper presents a current sensorless control strategy for a three‐phase multi‐level active front‐end rectifier with an LCL filter. The proposed control strategy is based on the mathematical model of the system. Opposed to the existing control methods that measure three‐phase currents as well as three‐phase voltages, the proposed control eliminates the current measurement requirement which leads to cost reduction. Moreover, unlike the existing current control methods that use two proportional‐integral (PI) controllers, the proposed current control does not use any PI controller in the current loop. The elimination of two PI controllers simplifies the controller design. The resonance damping requirement arising due to the LCL filter is tackled by active damping that is realized by using filter capacitor voltage feedback. The steady‐state and dynamic performances of the proposed control strategy are investigated experimentally under balanced, unbalanced and distorted grid conditions.

Single current sensor based fault tolerant control of interior permanent magnet synchronous machine for drive applications

This paper presents an integrated method for current sensor fault detection and fault tolerant control (FTC) for traction interior permanent magnet synchronous motor (IPMSM). The proposed current sensor fault detection method is based on detecting changes in the d-q axis current. The FTC is based on d-q axis current estimation from the reference d-q axis current and the phase current measured by the surviving current sensor. The current estimation process is independent of machine parameters. Hence the estimation is robust and requires less computational cost. The effectiveness of the FTC method is verified by the transient analysis. Such FTC is suitable for electric vehicle traction applications to ensure non-stop control operation of the drive in the entire range of speed. The efficacy of the proposed FTC method is tested through extensive simulations in MATLAB/Simulink environment. The real-time applicability of the proposed FTC method using the cost-effective digital signal processor (DSP) is verified on Texas Instruments© TMSF28379D through the processor in loop (PIL) simulation model.

Waveform harmonic suppression technology for electromagnetic standard vibration actuators based on current feedback control

To realize high-precision calibration of vibration sensors, the total harmonic distortion (THD) of the output waveform of a standard vibration actuator should be as small as possible, so a harmonic suppression technique based on current feedback control is presented. A low-cost, easy-to-implement feedback control loop of driving current is established in an electromagnetic standard vibration actuator (EVA), and the rationality of driving current in place of acceleration in the acceleration characteristic frequency band to achieve the feedback is analyzed. The influence of different values of the key parameters on the system is studied, and the acceleration characteristic frequency band of low-frequency vibration is effectively extended so that the THD of the output waveform is immensely alleviated. The effectiveness of the proposed method is verified by experiments and compared with traditional control methods, the harmonic distortion of acceleration waveform can be reduced by more than 40% without using any feedback sensors, which proves the superiority of the current feedback control method.

Buffered Microgrids with Modular Back-to-Back Converter Grid Interface

This paper proposes a buffered microgrid with a modular grid interface consisting of a modular back-to-back converter. The proposed method provides a flexible strategy that enables both the load and generation expansion of the microgrid, with no sizing constraints on the initial stage. The method maintains the physical separation of the buffered microgrid from the grid by using back-to-back converters, which ensures a safe, secure and seamless operation in both islanded and grid-connected operation modes. The proposed modular structure allows an energy exchange prioritization either between the energy storage systems and the grid or between the energy storage units themselves, depending on the recommended/desired operational strategy. The prioritizations are achieved by using sets of dead zones in the control of the interfacing converters. In order to control the voltage and frequency, an inverse-droop-based dq-frame current control method was implemented in PSCAD/EMTDC to substantiate the proposed method. The simulation results of different scenarios show the operational flexibility, control simplicity and communication-free operation of the microgrid with different types of sources.

Input voltage estimation method and suppression of distortion caused by DC voltage ripple for input current control of PFC

AbstractThis paper proposes a new method for input current control of power factor correction (PFC) with continuous conduction mode (CCM), which does not require input voltage detection. As a control method that does not use input voltage detection, pulse width modulation (PWM) with the inductor current as the modulated signal is already in practical use however, this approach has limitations for the range of inductance values used. In CCM‐PFC, the input rectified voltage and low‐frequency component of the voltage of the switching circuit are approximately equal in the stable state as well as proportional to the PWM signal. This study uses the previous modulated signal as the estimated voltage value to generate an instantaneous current command for feedback control. In addition, a method to suppress the influence of the DC voltage ripple by changing the voltage control gain according to the value of the DC voltage was employed. From the evaluation, it was confirmed that the harmonics of the input current were suppressed within the specified range of values.

Susceptibility of primary, secondary and suspected vectors to Plasmodium vivax and Plasmodium falciparum infection in Ethiopia

BackgroundInsecticide-based vector control interventions in combination with case management with artemisinin-based combination therapy has reduced malaria incidence and prevalence worldwide. Current control methods focus on the primary malaria vectors, Anopheles gambiae sensu lato (s.l.) and the An. funestus group; however, the impact of secondary and suspected vectors has been either sidelined or received limited attention. Defining the susceptibility of secondary, suspected vector species to different parasites in time and space is essential for efficient malaria control and elimination programs. The aim of this study was to assess the susceptibility of An. gambiae s.l., An. coustani complex and An. pharoensis to Plasmodium vivax and P. falciparum infection in Ethiopia.MethodsLarvae of Anopheles spp. were collected from different aquatic habitats and reared to adults under laboratory conditions, with the temperature and humidity maintained at 27 ± 1 °C and 75 ± 5%, respectively. Adult female mosquitoes were identified to species as An. gambiae s.l., An. coustani complex and An. pharoensis. Females of these three Anopheles spp. were allowed to feed in parallel feeding assays on infected blood containing the same gametocytes isolated from P. falciparum and P. vivax gametocyte-positive patients by indirect membrane feeding assays. All blood-fed mosquitoes were held under laboratory conditions. After 7 days, all surviving mosquitoes were dissected to detect mid-gut oocyst and enumerated under a microscope.ResultsOf 5915 female Anopheles mosquitoes exposed to gametocyte-infected blood, 2106 (35.6%)s fed successfully in the 32 independent infection experiments. There was a significant variation in feeding rates among An. gambiae s.l., An. pharoensis and An. coustani complex (G-test = 48.43, P = 3.049e-11). All three exposed mosquito species were receptive to P. vivax and P. falciparum infection development. The percentage of infected mosquitoes following feeding on an infected blood meal was significantly different among species (G-test = 6.49, P = 0.03886). The median infection intensity (II) for An. coustani complex, An. gambiae s.l. and An. pharoensis was 1.16, 2.00 and 1.25, respectively. Although the proportion of infected mosquitoes significantly differed in terms of II, infection rate (IR) and mean oocyst density among the species, mean oocyst density and IR were highly correlated with gametocyte density in all tests (P < 0.001).ConclusionPrimary, secondary and suspected vectors were experimentally susceptible to both P. vivax and P. falciparum infection. An effective malaria elimination program might include surveillance and control tools which target secondary and suspected vectors that might play an outdoor transmission role, possibly resulting in reduced focal malaria transmission.Graphical Comparison of the three species’ mean infection rates with standard deviation

Real-Time Nondestructive Evaluation of Additive Manufacturing Using a Laser Vibrometer and Shock Tube

Abstract Additive manufacturing (AM) parts retain a certain degree of individuality and could suffer from a combination of different defect types, and therefore the nondestructive evaluation on AM parts remains a challenging task. Engineering non-contact and nondestructive real-time inspection and in situ quality assurance of AM parts would be a net improvement compared to current quality control methods that are conducted post-production. Here, the authors propose to combine the use of a laser vibrometer with a compression-driven shock tube to assess the quality of AM parts through the evaluation of the vibration spectra of the part. An AM of a cylindrical part was selected for the study, along with different defect types and sizes. These defects include internal voids of different sizes at different locations, local changes in thickness (infill), and local changes in melting temperatures. A numerical model was created and validated using experimental data to conduct model-assisted probability of detection (MAPOD). Results were analyzed by evaluating correlation matrices between different models. Results showed that vibration spectra induced by a shock wave were sensitive to different types and sizes of defects under the studied geometry. The defect index yielded an approximately linear relationship with respect to defect void severity. MAPOD curve studies revealed a minimum detectable void defect of 0.039% of the AM part’s volume.

Study on quality control of Zuojin pill by HPLC fingerprint with quantitative analysis of multi-components by single marker method and antioxidant activity analysis

Current quality control methods for Zuojin Pill (ZJP) lack comprehensiveness and practicability. This study aimed to develop a comprehensive strategy for the quality evaluation of ZJP and the prediction of potential bioactive components in ZJP. First, an HPLC method with excellent separation of main components was developed and was used to establish the chromatographic fingerprint of ZJP. Similarities were calculated by comparing 28 batches of ZJPs with the reference fingerprint and the resulting similarity values were all greater than 0.976. The 28 samples were classified into different groups according to their origins by Hierarchical Cluster Analysis, Principal component analysis, and orthogonal partial least squares discriminant analysis. Based on the classification, eight quality markers (Q-Markers) affecting the quality of ZJP were discovered. Then, using berberine as an internal standard substance, quantitative analysis of multi-components by single marker method (QAMS) for the determination of eight Q-markers was developed. The results showed that there was no significant difference between QAMS and external standard method (P＞0.05). Finally, using an off-line antioxidant system and partial least-squares model (PLS), the fingerprint-efficacy relationship of ZJP was constructed to explore and predict the bioactive components in ZJP. The present study strategy could be also applied to comprehensive quality study of other TCMs.

Reduction of chickens use to perform in vitro pre-screening of novel anticoccidials by miniaturisation and increased throughput of the current Eimeria tenella compound-screening model

We have developed an in vitro model for the evaluation of potential anticoccidial properties of novel compounds aimed to control chicken coccidiosis, a costly disease for the poultry industry. This disease is caused by protozoan parasites of the genus Eimeria (Apicomplexa), and it is mainly controlled by chemoprophylaxis with ionophores and chemical anticoccidials; however, there is an overall agreement about the limitation of these traditional drugs and the need to improve current methods of control. Anticoccidial activities of novel compounds is currently evaluated by expensive experiments that involve large numbers of chickens. The use of our in vitro model for the pre-screening of essential oils led to a reduction of 67% of the chickens used in the in vivo trials for validation. Eimeria parasites can only complete their life cycle in their animal host, therefore chickens are required for their propagation as they cannot be propagated in vitro. In this study, we describe how further optimisation of this in vitro model by miniaturisation can have an additional impact in reduction of the number of chickens used for the generation of parasite stocks for provision of the in vitro model. We have estimated that the use of one chicken could support the evaluation of 10 compounds with a 96-well plate format versus only two compounds with a 24-well plate format, which means an 80% reduction in chicken use. In this study we have proved that the miniaturisation into a 96-well plate format perfectly mimics the invasion and replication observed before in the 24-well plate format. In addition, the 96-well plate format has allowed the simultaneous pre-screening of higher numbers of anticoccidial drugs at different concentrations following streamlined protocols in a more cost-effective way, factors that are beneficial for a wider uptake of the model by other researchers investigating anticoccidial compounds.

PV용 Interleaved Converter의 MPPT 및 전류 평형을 위한 DSP 기반의 제어기 설계 및 HILS 검증

This paper proposes a digital controller designed for maximum power point tracking control and phase current balancing control for PV system. A variable-step incremental conductance method is applied for maximum power point tracking. For phase current balance of the interleaved boost converter, an average current balance control method that reduces the control instability due to phase difference of the phase currents and A/D conversion is proposed. The ADC frequency is set to 2 times the switching frequency and 10 times the MPPT frequency. The designed controller is implemented in the TMS320F28335 DSP, and through PLECS simulation, the superiority of the proposed controller compared to the open loop and the proposed average current balance control method compared to the general control method are verified. Finally, the performance of the proposed controller under dc and sine wave insolation conditions is verified through HIL-Simulation.

Photoinactivation of Colletotrichum truncatum, Corynespora cassiicola, Sclerotinia sclerotiorum and Rhizoctonia solani in soybean seeds by cationic porphyrins

AbstractGrain legume production is of great importance in the world economy, with soybeans being a major agricultural product. Among the main causes of crop losses are diseases caused by pathogens that infect seeds, such as Colletotrichum truncatum, Corynespora cassiicola, Sclerotinia sclerotiorum and Rhizoctonia solani. The fungicides used are not fully effective in controlling these diseases, and new control options are necessary. Photodynamic inactivation (PDI) may be an alternative. PDI consists of the association of a photosensitizer (PS), light and molecular oxygen aimed at the destruction of microbial cells. Porphyrins and their derivatives are aromatic tetrapyrrolic macrocyclic compounds with photosensitizing capacity. The aim of the present study was to evaluate the efficiency of PDI in the photoinactivation of C. truncatum, C. cassiicola, S. sclerotiorum and R. solani, using a mixture of cationic meso‐tetra‐aryl porphyrins as PS, being the first study to consider this formulation as PS in the photoinactivation of these pathogens. Assays were carried out with soybean seeds artificially inoculated with the different fungi, treated with the PS at 10, 50, 100 and 200 μg/ml and submitted to light under an irradiance of 50 mW/cm2. The assays were set up following the blotter test methodology. The evaluations showed significant reductions in the infection rates of the seeds in relation to the controls. The greatest reductions were 46% for C. truncatum, 95.5% for S. sclerotiorum, 87% for C. cassiicola and 92% for R. solani. The results suggest that PDI can be an important alternative to current control methods against these pathogens.

Predictive deadbeat average model control for phase‐shifted full‐bridge DC/DC converter

Digital current control method is the mainstream method for high-power DC/DC converters. However, digital controllers require additional filters for noise suppression to ensure their proper operation in the complicated electromagnetic environment. The filtering processes coupled with the inherent time delays of digital systems significantly degrade dynamic performance. Thus, steady-state performance is improved at cost of dynamic performance in conventional current control. To solve the problems, this paper establishes a deadbeat average control model based on application of the oversampling technique for phase-shifted full-bridge (PS-FB) DC/DC converter and proposes a predictive deadbeat average model control method by incorporating predictive control into the proposed control model. Simulation and experimental results verify the effectiveness of the proposed control method in mitigating the contradiction between steady-state performance and dynamic performance in the digital system.

Shunt active power filter with MSRF-PI-AHCC technique for harmonics mitigation in a hybrid energy system under load changing condition

ABSTRACT In this study, a shunt active power filter (SAPF) is used to measure the harmonics level of a hybrid power system based on solar PV (SPV) and wind system. The SAPF employs a modified synchronous reference frame technology, an adaptive hysteresis current controller method, and a conventional proportional and integral based voltage regulator for the generation of reference current. The recommended SAPF performs extremely well in suppressing harmonics under varied load and source conditions. The results show that the proposed model outperforms earlier approaches in terms of harmonic mitigation and dc-link voltage stability. It was created in MATLAB/Simulink. The SAPF can minimise harmonics of the source current from 26.74% to 1.565% and 20.25% to 1.80% for inductive and capacitive load case respectively under ideal source condition and 30.05% to 3.82% (inductive) and 25.25% to 3.56% (capacitive) under non-ideal source condition. The proposed controller also reduces the ripples from the dc-link capacitor voltage from 22 V to 8 V and 9 V under both the source condition, respectively, based on the numerical comparison of findings.