Dc-link Voltage Measurement Research Articles

Improved Extended EMF-Based Sensorless Control for IPMSMs With Small DC-Link Capacitor Considering DC-Link Voltage Measurement Error

Improved Extended EMF-Based Sensorless Control for IPMSMs With Small DC-Link Capacitor Considering DC-Link Voltage Measurement Error

Analysis, Diagnosis and Reconfiguration of a Synchronous Motor Control With Faulty DC Link Voltage Measurement

This paper discusses the effects of an incorrectly measured DC link voltage in a synchronous drive system. As the investigations show, the control algorithm can become unstable when the measured value for the DC link voltage is much smaller than the actual value. Therefore, this paper also presents two approaches for estimating the DC link voltage based on the measured currents, the motor speed and the duty cycle. If measured and estimated values of the DC link voltage deviate too much from each other, a fault diagnosis system detects this fault and enables different flags based on the fault scenario. The flags are then used to reconfigure the control algorithm, so that instead of the measured current its estimated value is used. The analysis shows the need for the reconfiguration of a faulty DC link voltage measurement and the experimental results demonstrate the effectiveness of the approach.

Improved crowbar protection technique for DFIG using fuzzy logic

<span lang="EN-US">A doubly-fed induction generator is the most widely used as a wind turbine generator. Due to its drawbacks, doubly fed induction generator (DFIG) is extremely sensitive to grid disturbances, and the fragility of some components which are costly to the producer. Also, its acquisition value is very high in terms of maintenance time or component cost, causing substantial harm to both the energy production and power supplier. It is required that the DFIG components must be protected, especially power electronics devices and DC-Link capacitor. Therefore, this paper presents an improved crowbar strategy for DFIG. This method is based on the AI technique concept of utilizing a fuzzy logic controller. The main goal of this project is to improve the system performance by reducing the dangerous oscillations of electromagnetic torque, DC-link voltage, and rotor current during fault. This work consists of replacing the hysteresis control for the crowbar with fuzzy logic to realize crowbar-FLC. The proposed crowbar is based on free light chain (FLC) depending on rotor currents and DC-link voltage measurements. The control strategy is simulated in the MATLAB Simulink platform to evaluate the efficiency of the suggested technique.</span>

Development of a Didactic Platform for Flexible Power Electronic Converters

Power electronic converters are the subject of several studies and applications. Knowledge about those converters is essential for several technical and undergraduate courses in the field of Electrical Engineering and related areas. The presence of converter modules in laboratories can be beneficial for experimental validations in academic research and educational purposes, for allowing students to have practical contact with different converter topologies and applications. However, the commercially available power converters are generally manufactured for specific applications, with poor versatility and high cost, when applied for academic purposes. For this reason, several laboratories propose the design of versatile converters, mainly for multilevel converter research. Nevertheless, most of these projects present module designs based on half bridge topology due to their low cost. Therefore, this project topology requires more modules to operate as topologies based on a full-bridge converter. Besides, modules based on full-bridge topology can also work in a half-bridge configuration. Thus, this work presents the design of full-bridge modules capable of operating as different types of converters, as well as the project of the dc-link voltage measurement, isolated power supply and bypass circuits. Moreover, this work addresses the heatsink choice, the thermal evaluation for the semiconductor devices and the realization of galvanic isolation between the signal and power circuits.

A Novel Rotor Initial Position Detection Method Utilizing DC-Link Voltage Sensor

A new simple rotor initial position detection method for permanent magnet machines is proposed in this article. It is based on the magnetic saturation effect, which is commonly used by existing methods. Different from the conventional methods utilizing phase current or phase voltage sensors, the dc-link voltage sensor is used to estimate the rotor initial position. In the proposed method, a specific excitation approach is used to enhance the performance and a so-called “equivalent injection position” is developed to simplify the estimation process. The proposed method can achieve a 30° estimation resolution. Besides, practical considerations, including the dc-link voltage measurement errors, dc-link resistance, dc-link capacitance, and dc-link voltage ripples, are discussed in this article. A guideline of voltage pulse selection is presented to minimize the impact of these practical issues. Moreover, it is found that as the dc-link resistance increases, the proposed method shows a better estimation performance than the conventional methods. Besides, the proposed method is insensitive to sensor measurement errors. The experimental results are given to verify the effectiveness of the proposed method.

Cascaded Control of Back-to-Back Converter DC Link Voltage Robust to Grid Parameters Variation

The article elaborates on the mathematical modeling and control structure design of a grid-connected back-to-back voltage source inverter with a complex dc link and an LC filter for the current harmonics reduction. A cascaded, three-loop control structure is designed for controlling the converter current, the grid current, and the dc link voltage. The derived control structure, utilizing two sets of current sensors and a dc link voltage measurement, is based on proportional-integral controllers and a Truxal–Guillemin model-based controller for the dc link voltage control. The chosen control structure provides consistent results for great variations of the grid impedance. Robustness is tested for various scenarios of variations in grid filter parameters, controller parameters, chosen operating point for linearization, and grid impedance. Results are validated by simulations and experiments on a 7.5 kW converter and show highly robust performance for $\pm$ 20% parameter change and a large span of grid impedance variation.

Enhancement of low-voltage ride-through capability of permanent magnet synchronous generator wind turbine by applying state-estimation technique

Purpose The purpose of this study is to propose a control scheme based on state estimation algorithm to improve zero or low-voltage ride-through capability of permanent magnet synchronous generator (PMSG) wind turbine. Design/methodology/approach Based on the updated grid codes, during and after faults, it is necessary to ensure wind energy generation in the network. PMSG is a type of wind energy technology that is growing rapidly in the network. The control scheme based on extended Kalman filter (EKF) is proposed to improve the low voltage ride-through (LVRT) capability of the PMSG. In the control scheme, because the state estimation algorithm is applied, the requirement of DC link voltage measurement device and generator speed sensor is removed. Furthermore, by applying this technique, the extent of possible noise on measurement tools is reduced. Findings In the proposed control scheme, zero or low-voltage ride-through capability of PMSG is enhanced. Furthermore, the requirement of DC link voltage measurement device and generator speed sensor is removed and the amount of possible noise on the measurement tools is minimized. To evaluate the ability of the proposed method, four different cases, including short and long duration short circuit fault close to PMSG in the presence and absence of measurement noise are studied. The results confirm the superiority of the proposed method. Originality/value This study introduces EKF to enhance LVRT capability of a PMSG wind turbine.

Plug-and-Play Voltage Ripple Mitigator for DC Links in Hybrid AC–DC Power Grids With Local Bus-Voltage Control

In this paper, a straightforward plug-and-play voltage ripple mitigator (RM) is proposed. Unlike existing voltage ripple reduction methods, the proposed device can be attached to the dc link of a hybrid ac–dc power system without modifying the host system itself. In particular, a local bus-voltage control scheme is employed to achieve the plug-and-play operation. With the requirement of the dc-link voltage measurement only, this device can be operated as a standalone module. Theoretical analysis and experimental work on a boost-type power factor correction rectification system have been successfully performed to validate the effectiveness of the ripple-mitigating function, the hot-swap operation and the nonintrusive property of the RM. Practical results obtained from a 110-W miniature hybrid ac–dc power system comprising an ac/dc converter and two resistive loads are included to demonstrate some of the functions of the RM.

DC-Link Voltage Measurement Method Suitable for Power Converter Systems Controlled by a μ-Controller

A dc-link voltage measurement method is proposed in this letter. The proposed method is suitable for a power converter with μ-processor control. The dc-link voltage is directly measured so that the measurement error caused by the resistive voltage divider can be removed. The circuit is designed as simply as possible to avoid errors caused by inaccuracies in the components. DC-link voltage sampling and A/D conversion are synchronized with the timing of the PWM modulator to avoid instances where power-converter switching generates strong electromagnetic noise. The validity of the proposed method is verified through an experiment.

Two Sliding Mode Based Observers for Sensorless Control of PMSM Drives

This paper develops two sliding mode-based observers for sensorless control of permanent magnet synchronous motor (PMSM) drives. These observers estimate the rotor position and speed from the stator currents and the DC-link voltage measurements. The first observer uses the f g stator reference, while the second observer uses an estimated dq rotor reference. Both observer structures have two main parts. The first part is a sliding mode-based observer that uses the equivalent control to estimate a disturbance term containing information on the position and speed. The second part is a specific observer used to extract these desired variables. The observer designs the implementation aspects, and a comparative study on the extensive experimental results are given.