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© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works This article presents two algorithms to control the speed of doubly-fed induction motors. The controllers are designed using the complex-valued sliding mode methodology to track either the rotor or the stator current. An outer loop controls the mechanical speed. The control schemes are validated experimentally and compared in a laboratory setup.

A multiple-reference complex-based controller is proposed for three-phase power converters feeding nonlinear and unbalanced loads. The control scheme incorporates a stable multiple-complex coefficient filter with bandwidths that are set arbitrarily and independently for every harmonic under consideration. The multiple-reference complex-based control scheme is applied to an uninterruptible power supply system with a voltage source converter. Each harmonic is controlled using a standard complex proportional-resonant controller that is designed for stability and robustness using the Nyquist criterion. Similar stability and robustness properties follow for the overall system due to the frequency-domain properties of the filter and of the controllers. The proposed methodology is validated in simulation and experimental tests.

International audience; This paper presents a new state-space model (SSM) to represent the four types of currents flowing through a Modular Multilevel Converter (MMC). In line with the converter topology, the model itself is modular. In other words, its configuration adapts itself to the number of AC phases, to the active or passive nature of the AC-side grid, to the connection between the AC and DC neutral points, and to the number of submodules. The model describes the influence of the MMC arm voltages on the currents using an average behavior of the submodules. Simulations performed using a software dedicated to electrical engineering systems demonstrate the value and the accuracy of the proposed model.

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works In this work, a complex-valued controller for a three-phase VSC with an LC output filter is proposed. The system is first transformed into its complex representation with the consequent order reduction and simpler analysis. The proposed complex controller places all the poles at desirable locations in the complex plane. Unlike classical controllers with an inner current-control loop and outer voltage-control loop, the proposed controller considers the complete dynamics of the system, thus ensuring the closed-loop stability. Furthermore, the complex representation facilitates the pole placement in the complex plane compared to the real domain. The performance of the proposed controller is validated through simulations and experiments.

This paper develops a systematic comparison of two nonlinear models of induction machines in magnetic saturation using stator and rotor currents as state variables. One of the models accounts for dynamic cross-saturation effects, whereas the other neglects them. Analytic derivations yield an explicit description of the difference between the models showing that differences can only be observed through transient responses in the saturated region. To refine the comparison, and exclude conditions in the linear magnetic region, the dynamics of self-excited induction generators around stable operating points is analyzed. Unexpected and interesting features of the models are revealed through their linearization in the reference frame aligned with the stator voltage vector, followed by computation of the transfer functions from perturbations to state deviations. The analysis predicts a slower exponential convergence of the simplified model compared to the full model, despite very close responses in the initial period. The comparison is validated via thorough experiments and simulations. This paper provides experimental evidence of the higher accuracy of the full model for transients deep into the saturated region. For realistic operating conditions, the difference is found to be rather small, and often comparable to the steady-state error caused by inaccuracies in the parameters.

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. A large class of three-phase electrical power systems possess symmetry conditions that make it possible to describe their behavior using single-input single-output transfer functions with complex coefficients. In such cases, an extended root locus method can be used to design control laws, even though the actual systems are multi-input multi-output. In this paper, the symmetric conditions for a large class of power systems are analyzed. Then, the root locus method is revisited for systems with complex coeffcients and used for the analysis and control design of power systems. To demonstrate the benefits of the approach, this paper includes two examples: 1) a doubly fed induction machine and 2) a three-phase LCL inverter.

The complexity and strong nonlinearity of the model of a self-excited induction generator hinder the systematic design of a voltage regulation system. Using a special reference frame aligned with the stator voltage vector, the paper succeeds in developing a control-oriented linearized model that relates small deviations of the capacitance, load admittance, and angular velocity, to corresponding deviations of the voltage amplitude. Transfer functions are also computed based on the linear model. A stability analysis predicts rapidly decaying oscillatory transients combined with a primary component with slower exponential decay. Simulated transient responses of the full and linearized models demonstrate the validity of the approximation and are in good agreement with experiments.\ud

International audience; The paper presents a new sensorless parameter identification method for permanent magnet stepper motors. Current sensors are assumed available, but mechanical sensors are not. Data is obtained with open-loop commands at multiple speeds. A new frame is proposed that presents advantages similar to the d-q frame, but without the need for a position sensor. The method exploits derived linear parameterizations and least-squares algorithms. In some cases, overparameterization is resolved using elimination theory. The parameters identified using the new procedure are found to be very close to those obtained with sensors. The approach is potentially applicable to other types of synchronous motors.

In this note a globally stable methodology is proposed to estimate the frequency, phase, and amplitude of a sinusoidal signal affected by additive structured and bounded unstructured disturbances. The structured disturbances belong to the class of time-polynomial signals incorporating both bias and drift phenomena. Stability and robustness results are given by resorting to Input-to-State stability arguments. Simulation comparative results show the effectiveness of the proposed technique.

In this brief, a new control scheme is presented for the doubly fed induction machine (DFIM). The proposed control algorithm offers the advantages of proven stability and remarkable simplicity. In contrast to the classical vector control method, where the DFIM is represented in a stator- flux-oriented frame, a model wit h orientation of the stator voltage is adopted. This approach allows the decomposition of the active and reactive powers on the stator side and their regulation on the rotor side. A main contribution of this brief is the use of the Hurwitz test for polynomials with complex coefficients that has had little prior application in control theory. This results in a proof that a proportional-integral (PI) control regulating the stator currents ensures global stability for a feedback-linearized DFIM. The specific condition that the PI gains must satisfy is derived as a simple inequality. The PI controller has a particular structure that directly relates the d -component of the rotor voltages to the q -component of the stator currents and vice versa. The feedback linearization stage only uses the direct measurement of the rotor and stator currents and is thus easily implementable. Furthermore, it is also shown that the PI controller (without the feedback linearization terms) is also stable for a large range of control gains and does not require the knowledge of the machine parameters. Finally, the control system is validated in simulations and in experiments.

International audience; The paper presents a new sensorless parameter identification method for permanent magnet stepper motors. Current sensors are assumed available, but position and velocity sensors are not. Data is obtained with open-loop voltage com- mands at multiple speeds. A new reference frame is proposed that presents advantages similar to the standard d − q frame, but without the need for a position sensor. The method exploits carefully derived linear parameterizations and a least-squares algorithm. In one case, overparameterization is resolved using elimination theory. Overall, the parameters identified using the new procedure are found to be very close to those obtained with position sensors. The approach is potentially applicable to other types of synchronous motors as well.