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High Voltage DC systems are gaining widespread attention due to the advances in power electronic devices and converters. MMCs are very popular nowadays in this type of application. This paper first revisits the dynamic equations of the circulating current of a MMC to incorporate a disturbance term. Based on the modified equations, a disturbance rejection controller is proposed to eliminate the double...
Modular multilevel converter (MMC) is an attractive topology for transformer-less high voltage applications due to its capability to reach high voltage levels by the use of power semiconductors. Each submodule can be considered as a controlled voltage source where capacitor's voltage should be maintained at a certain level for proper operation of the MMC and for fault detection and protection purposes...
Rotational speed sensorless drives need to estimate a rotor speed before an inverter starts when an induction motor is running freely with high inertia load. In this paper new estimation method for the initial rotor speed estimation in particularly low rotational speed has been proposed. To avoid over current and re-generating torque, the double derivation of the secondary flux is utilized. The effectiveness...
Full speed sensorless Interior Permanent Magnet Synchronous Motor (IPM-SM) drives estimate the rotor speed and position by means of a HF voltage injection at standstill or low speed operation and by some form of back-electromotive force or PM flux estimator at the medium and high speed range. Both the estimation strategies include an inner loop closed by a PI+I regulator for extracting speed and position,...
Traditionally, the current control of grid-tied converters with LCL filter is based on proportional-resonant or proportional-integral controllers, which often need an additional active damping method to achieve stability. These solutions do not permit to place the closed-loop poles in convenient locations when dealing with such high-order plants. This constraint results in degraded reference-tracking...
This paper proposes a nonlinear control system based on a nonlinear observer to manage the active and reactive power within a single-phase-frequency-modulated Dual-Active-Bridge DC/DC converter directly. It is accomplished by employing a nonlinear controller to regulate the direct and quadrature current, id(t) and iq (t), as they are directly proportional to two power components, respectively. A nonlinear...
Online parameter estimation could improve the performance of sensorless control. In this paper, a super-twisting algorithm (STA) based second-order sliding-mode observer (SMO) sensorless control with online stator resistance estimation is proposed. The chattering problem and time delay, which could not be avoided in conventional SMO, are eliminated in this STA based second-order SMO. At the same time,...
This paper deals with a novel robust current control scheme for Permanent Magnet Synchronous Machine based on the conventional cascade structure. The main idea is to substitute the commonly used decoupling network, which requires the precise knowledge of the system parameters in any working condition, with a more flexible and robust scheme. In particular, the traditional configuration is improved...
This paper proposes a permanent magnet (PM) machine position sensorless drive for high speed (>10-krpm) applications. A fully discretized back electromotive force (EMF) estimator is designed to overcome several high speed rotor position estimation issues, including the voltage error due to pulse-width-modulation (PWM), dq inductance cross-coupling effect and the deviation between the estimated...
This paper proposes a novel current/voltage sensor fault detection and isolation (FDI) method for wind energy conversion systems (WECSs) based on the power balance principle. The proposed method uses the sensor-measured signals to calculate the imbalanced power in the power converters of a WECS, which is then used as the indicator for sensor fault detection. The fault isolation process is started...
This paper proposes the use of the feedback-linearization control technique for the regulation of the voltage amplitude and frequency of power-electronic converters. This control strategy linearize the trajectory of a nonlinear system between any two equilibrium points, and thus allowing to use linear control technique. The reference tracking robustness of the proposed control technique is assessed...
Model predictive current control uses a model of the machine and an appropriate cost function to indirectly control electromagnetic torque and reactive power. However, due to sensitivity of model predictive control (MPC) to system parameters, need for high sampling frequency, and high torque and flux ripples, this method is not employed in a wide variety of commercial drives. Incorporating the concept...
In this article, the local trajectory tracking control problems are reformulated as adaptive control problems. This approach gives rise to a robust decentralized solution, with virtually no information on local plants interaction dynamics. It is shown that when the interconnection effects are viewed as exogenous, unstructured, disturbances, such disturbance can be actively estimated and canceled from...
Image tracking self-sensing, which utilizes cross-correlation to detect the rotor position by evaluating the orientation of the current image across a full injection cycle can enhance estimated accuracy and improve tolerance to noise. Cross-correlation over a full injection cycle replaces the classical heterodyning demodulation used in traditional point-tracking methods and is known to produce significant...
The aim of this paper is to reduce the low-speed limitation of PMSM drives that use low-resolution position sensors. It is recognized, for the first time, that this may be overcome by merging signal-injection-based self-sensing and low-resolution sensor technologies, if the machine possesses a detectable amount of electromagnetic saliency. The supplementary information coming from the injection of...
Voltage reference that contains cross-coupling term between the q- and d-axis is commonly utilized as input of sensorless schemes, and this might cause coupling between speed and position estimation and deteriorate system dynamic performance, which is unacceptable in some applications such as electric vehicle and industrial robot. By employing decoupled voltage reference as observer input, this paper...
Back-EMF self-sensing is commonly used in induction machine (IM) drive systems for its maintenance cost and safety considerations. In recent years, deadbeat-direct torque and flux control (DB-DTFC) has been shown to be a highly effective method for induction machine control. It has advantages such as the fastest possible torque dynamics, dynamically loss manipulation capability independent of torque...
This paper deals with grid-voltage sensorless synchronization and control under unbalanced grid conditions. A three-phase grid-connected converter equipped with an LCL filter is considered, and no other signals than the converter currents and the DC-link voltage are measured for control. An augmented adaptive state observer is proposed for estimation of the positive- and negative-sequence components...
Modular multilevel converter (MMC) has drawn tremendous attention in the academia and industry since its invention, and it is considered as a very suitable solution for the high-power applications. It is usually composited by a large number of half-bridge or full-bridge sub-modules (SMs), which makes the reliability as one of the most important challenges for MMC. Besides, due to the DC side short-circuit...
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