Chiller Load Forecasting Using Hyper-Gaussian Nets

Energy load forecasting for optimization of chiller operation is a topic that has been receiving increasing attention in recent years. From an engineering perspective, the methodology for designing and deploying a forecasting system for chiller operation should take into account several issues regarding prediction horizon, available data, selection of variables, model selection and adaptation. In this paper these issues are parsed to develop a neural forecaster. The method combines previous ideas such as basis expansions and local models. In particular, hyper-gaussians are proposed to provide spatial support (in input space) to models that can use auto-regressive, exogenous and past errors as variables, constituting thus a particular case of NARMAX modelling. Tests using real data from different world locations are given showing the expected performance of the proposal with respect to the objectives and allowing a comparison with other approaches.Unión Europea RTI2018-101897-B-I00Ministerio de Ciencia e Innovación RTI2018-101897-B-I0

Adaptive Cost Function FCSMPC for 6-Phase IMs

In this paper, an adaptive cost function FCSMPC is derived from newly obtained results concerning the distribution of figures of merits used for the assessment of stator current model-based control of multi-phase induction machines. A parameter analysis of FCSMPC is carried out for the case of a six-phase motor. After extensive simulation and Pareto screening, a new structure has been discovered linking several figures of merit. This structure provides an simple explanation for previously reported results concerning the difficulty of cost function tuning for FCSMPC. In addition, the newly discovered link among figures of merit provides valuable insight that can be used for control design. As an application, a new cost function design scheme is derived and tested. This new method avoids the usual and cumbersome procedure of testing many different controller parameters.Unión Europea RTI2018-101897-B-I00Ministerio de Ciencia e Innovación RTI2018-101897-B-I00Agencia Estatal de Investigación RTI2018-101897-B-I0

Online Adaptive Set of Virtual Voltage Vectors for Stator Current Regulation of a Six-Phase Induction Machine Using Finite State Model Predictive Controllers

(This article belongs to the Special Issue Electric Power Applications II) // "This article is an open access article distributed under the terms and conditions of the Creative Commons ttribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/"Virtual voltage vectors (VVV) have been used for the control of multi-phase induction machines, where different sub-spaces appear related to the torque production and losses generation. In the literature, several sets of VVV have been used, aiming at reducing harmonic content while maintaining a low computational burden. This paper proposes the use of different sets of VVV to regulate the stator current of multi-phase drives using finite-state model predictive controllers. In the proposal, only one set is active at each control period. This active set is obtained through a preliminary analysis using performance maps. As a result, a method is derived for the online selection using the current operating point. The selection is based on a simple computation from variables usually measured on variable-speed drives. Results are provided for a symmetrical six-phase IM, showing that the proposal improves the closed-loop performance of the multi-phase drive with a low computational cost

Predictive Stator Current Control of a Five-Phase Motor Using a Hybrid Control Set

Finite state model predictive control (FSMPC) of multiphase drives can use an extra number of inverter configurations compared with the three-phase case. This, however, requires more computing power for the optimization phase. The application time of each selected voltage vector (VV) is then increased, which can result in higher harmonic content. Reducing the allowed VVs can speed up the computations, thus ameliorating the current tracking/regulation in different orthogonal subspaces. However, the flexibility offered by the reduced set of VVs is less than that of the full set. Furthermore, a lower sampling time can result in an increase in the switching frequency, especially for some speed-load combinations. This article proposes the use of a hybrid scheme where the set of allowed VVs is not fixed but rather selected on-line according to the actual speed and torque producing stator current which are computed by the outer loop. A five-phase induction machine (IM) is used as a test bed for the proposal, showing improved results with respect to the nonhybrid case.Ministerio de Ciencia e Innovación RTI2018-101897-B-I0

Fast finite-state predictive current control of electric drives

This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/This work presents a novel optimization method for the implementation of finite-state modelbased predictive current controllers in electrical drives. The proposal avoids the usual exhaustive search to find the control action, reducing the computational burden. The method is based on physical considerations of the power converter voltage vectors and is easy to implement on digital signal processors. The proposal is applied to a five-phase induction machine. Experimental results are compared with those obtained by a standard model-based controller, showing the feasibility of the proposal and the improvements in terms of sampling time reduction and control accuracy

Predictive Control of Multi-Phase Motor for Constant Torque Applications

Constant torque motors are needed for rotary screw compressors that are used for cooling and other applications. In such systems, the torque demanded by the load is approximately the same over the whole range of mechanical speeds. In this paper, the use of multi-phase induction machines is investigated for this type of application. The requirement of low stator current distortion is considered. A scheduled approach is used to provide the best possible tuning for each operating point, similar to the concept of gain scheduling control. Simulations and laboratory tests are used to assess the proposal and compare it with finite-state predictive control. The experiments show that a trade-off situation appears between the ripple content in stator currents in the torque-producing and harmonic planes. As a consequence, the controller tuning appears as an important step. The proposed method considers various figures of merit with cost function tuning, resulting in a scheduled scheme that provides improved results. It is shown that the approach leads to a reduction in current ripple, which is advantageous for this particular applicationMinisterio de Ciencia e Innovación - FEDER RTI2018-101897-B-I00Junta de Andalucía -FEDER P20_0054

Evolutionary Gaps Stator Current Control of Multi-phase Drives Balancing Harmonic Content

Multiphase machines are increasingly used in research and industry applications due to their inherent advantages. Stator current control is a common strategy for this type of systems. The most important issue it must face is regulation of currents in the torque producing plane and the harmonic plane. For this task, finite control set model predictive control (FCS-MPC) constitutes an interesting alternative to methods using modulation. However, the implementation of FCS-MPC is characterized by a high computational demand, limiting the sampling frequency. This work proposes a predictive algorithm that needs less computation time. As a result, the sampling period can be reduced while producing predictive control. This brings about several benefits resulting from improved current tracking. The proposed method avoids the combinatorial optimization phase of standard FCS-MPC, which is the most time-consuming part. The algorithm is based on physical insights obtained from the application of FCS-MPC to multiphase drives leading to the concept of evolutionary gaps regions. The experimental results for a five-phase motor demonstrate improved performance. Moreover, the method is flexible enough to balance the tradeoff appearing between the torque producing plane and the harmonic plane.Ministerio de Ciencia e Innovación TED2021-129558B-C22 PID2021-125189OBI0

Control predictivo polifásico mediante dos constelaciones de vectores virtuales de tensión

En el campo de los accionamientos eléctricos de velocidad variable ha aparecido recientemente el método predictivo basado en vectores virtuales de tensión. Este método permite reducir la contribuci´on del voltaje en el subespacio x-y, en el cual no se produce par, sino pérdidas. De este modo no sólo se limitan las pérdidas sino que se reduce la complejidad de sintonía del controlador predictivo. Los vectores virtuales de tensión se obtienen mediante combinación de vectores de tensión pertenencientes a distintas coronas pequeña, media y grande además de los vectores nulos. En una aplicación típica se elige en primer lugar la(s) corona(s) a usar y después se desarrollan los vectores virtuales. El controlador predictivo usa en cada periodo de muestreo el vector virtual más adecuado. En este trabajo se propone el uso de varios conjuntos de vectores virtuales provenientes de diferentes  combinaciones de coronas. Para cada punto de operación del accionamiento eléctrico se utiliza el conjunto que proporciona mejores valores de cierto criterio de bondad. El método propuesto es validado experimentalmente usando una máquina de inducción de seis fases

Multi-phase predictive control using two virtual-voltage-vector Constellations

En el campo de los accionamientos eléctricos de velocidad variable ha aparecido recientemente el m´etodo predictivo basado en vectores virtuales de tensión. Este método permite reducir la contribución del voltaje en el subespacio x-y, en el cual no se produce par, sino pérdidas. De este modo no sólo se limitan las pérdidas sino que se reduce la complejidad de sintonía del controlador predictivo. Los vectores virtuales de tensión se obtienen mediante combinación de vectores de tensión pertenencientes a distintas coronas pequeña, media y grande además de los vectores nulos. En una aplicación típica se elige en primer lugar la(s) corona(s) a usar y después se desarrollan los vectores virtuales. El controlador predictivo usa en cada periodo de muestreo el vector virtual más adecuado. En este trabajo se propone el uso de varios conjuntos de vectores virtuales provenientes de diferentes combinaciones de coronas. Para cada punto de operacón del accionamiento eléctrico se utiliza el conjunto que proporciona mejores valores de cierto criterio de bondad. El método propuesto es validado experimentalmente usando una máquina de induccón de seis fases.In the field of variable speed electric drives, the predictive method based on virtual voltage vectors has recently appeared. This method allows to reduce the voltage contribution in the x-y subspace, in which no torque is produced, but losses. This not only limits the losses but also reduces the tuning complexity of the predictive controller. The virtual voltage vectors are obtained by combining tension vectors belonging to different small, medium and large crowns in addition to the null vectors. In a typical application, first the crown(s) to be used are chosen and then the virtual vectors are developed. The predictive controller uses in each sampling period the most suitable virtual vector. In this work we propose the use of several sets of virtual vectors coming from different combinations of crowns. For each operating point of the electric drive, the set that provides the best values of a certain goodness criterion is used. The proposed method is experimentally validated using a six-phase induction machine

Pointing performance evaluation of control strategies for high concentration photovoltaic sun trackers

[EN] In this article the pointing performance of several control strategies for high concentration sun trackers is evaluated. Due to the high accuracy required in real pointing, below the global acceptance half-angle of the energy harvesting system, the article sumarizes the most characteristic uncertainty sources of mounting a solar tracker. A theoretical framework is established that let us represent assembly imperfections in the form of rotational relationships among reference frames associated to the elements of the tracker. A two-stage system calibration process is exposed, which allows estimating parametric uncertainties of the rotations. Finally, five control strategies and the experimental results obtained with them when implemented on a high-performance industrial-grade HCPV solar tracker are analyzed. The results show an appropriate performance for all strategies whether the system is well calibrated. However, only the one based on power feedback is robust enough to provide a good performance when the system becomes uncalibrated.[ES] En este artí­culo se evalua el desempeño por apuntamiento de una serie de estrategias de control para seguidores solares de alta concentracion. Dado el alto grado de precisión que se necesita en el apuntamiento real, por debajo del semi ángulo de aceptancia global del sistema de captacion de energí­a, en el artí­culo se revisan las incertidumbres mas caracterí­sticas del montaje de un seguidor solar, y se establece un marco teorico que permite representar imperfecciones de montaje en forma de relaciones de rotación de marcos de referencias asociados a los elementos del seguidor. Se expone un proceso de calibracion del sistema en dos etapas, que permite estimar incertidumbres parametricas de las rotaciones. Finalmente, se analizan cinco estrategias de control y los resultados experimentales obtenidos con ellas al implementarlas sobre un seguidor solar HCPV industrial de altas prestaciones. Los resultados muestran que con el sistema bien calibrado, todas las estrategias proporcionan un desempeno similar. Sin embargo, solo la basada en realimentacion en potencia es suficientemente robusta como para proporcionar buen desempeño cuando el sistema de descalibra.Esta publicación es parte del proyecto de I+D+i PID2020-115561RB-C32, financiado por Ministerio de Ciencia e Innovación/ Agencia Estatal de Investigación/10.13039/501100011033/ “FEDER Una manera de hacer Europa”.Garrido Satué, M.; Castaño Castaño, F.; Ortega Linares, MG.; Rodríguez Rubio, F. (2022). Evaluación del desempeño por apuntamiento de estrategias de control para seguidores solares fotovoltaicos de alta concentración. Revista Iberoamericana de Automática e Informática industrial. 19(2):174-185. https://doi.org/10.4995/riai.2022.16905OJS17418519