Papers by Jesús Doval-Gandoy
AC Voltage Sensorless Method With Bumpless Start for Current-Controlled Converters Connected to Microgrids
This paper presents a novel grid synchronization method with bumpless start which requires minima... more This paper presents a novel grid synchronization method with bumpless start which requires minimal computational load and can selectively track the positive sequence of the grid voltage in an unbalanced and distorted three-phase weak grid. Only twelve floating-point operations (flops) are required to obtain the in-phase and quadrature components that define a synchronous frame which tracks the positive sequence of the grid voltage. Contrarily to a phase-locked loop (PLL), the presented scheme does not require to measure any ac voltages. Therefore, this sensorless method is particularly suitable in weak-grid conditions in which the voltage at the point of common coupling (PCC) is different from the grid voltage and may contain significant noise. The error in the estimated phase depends on the accuracy of the plant model. If the grid-impedance is assumed to be zero and the LCL filter parameters are known, both the proposal and a PLL-based scheme result in the same steady-state error. Experimental results show the advantages of the proposal compared to a moving average filter (MAF)-based PLL.
AC-Voltage Controller for Grid-Forming Converters
IEEE Transactions on Power Electronics, Apr 1, 2023
Robust AC Voltage Controller with Harmonic Elimination for Stand-Alone and Weak-Grid-Connected Operation
This paper presents an ac voltage controller with a high robustness to plant model variations whi... more This paper presents an ac voltage controller with a high robustness to plant model variations which can operate under a wide range of loads. A robust voltage controller is required in a droop-controlled inverter which operates in island mode with other generators or is connected to a grid. In such modes of operation, the voltage source converter (VSC) can experience a large variation in the load impedance depending on the number of parallel generators or the grid impedance value. The proposal improves the transient performance by selectively minimizing the output impedance of the system at the frequencies which typically contain the largest components of the output current. Complete harmonic control is achieved due to its zero output impedance at a set of design-selected frequencies. The design process only requires, as input parameters, the LC filter values, the sampling frequency, and a set of harmonics where load-current circulation is expected.
Proceedings of IEEE Power Engineering Society
IEEE Power Engineering Society General Meeting, 2007
Discrimination Between Eccentricity and Interturn Faults Using Current or Voltage-Reference Signature Analysis in Symmetrical Six-Phase Induction Machines
IEEE Transactions on Power Electronics
Two common defects in induction machines (IMs) are eccentricity and interturn faults, which shoul... more Two common defects in induction machines (IMs) are eccentricity and interturn faults, which should be diagnosed to prevent performance degradation and further damage. A popular fault-detection approach is the current signature analysis (CSA), because of its simplicity and non-intrusiveness. Under closed-loop control, it is combined with analogous voltage-reference (VR) signature analysis (VRSA). However, by using these methods in three-phase IMs it is difficult to discriminate between these faults, which cause similar symptoms. Multiphase machines provide remarkable advantages such as inherent tolerance to open-phase faults. Six-phase IMs are particularly attractive since they allow adopting three-phase converters. Among them, those with symmetrical spatial arrangement of the stator phases offer superior fault tolerance. Nonetheless, the distinction between eccentricity and interturn failures in these IMs has not been addressed so far. This paper studies the discrimination between eccentricity and interturn faults in symmetrical six-phase (S6) IMs by CSA or VRSA. It is shown that, conversely to three-phase IMs and most other multiphase IMs, in S6 ones these two types of failures can be easily distinguished: interturn faults considerably alter the currents or VRs in the so-called x-y plane, whereas eccentricity leads to current/voltage symptoms only in the alpha1-beta1 plane. Experimental results confirm the theory.
Evaluation of Current Distortion Improvement in an Asymmetrical Six-Phase Induction Motor Drive by Using SiC MOSFETs With Reduced Dead Time
2020 IEEE Energy Conversion Congress and Exposition (ECCE)
Multiphase drives offer significant benefits, e.g., better fault tolerance. However, current dist... more Multiphase drives offer significant benefits, e.g., better fault tolerance. However, current distortion tends to be larger than for three-phase ones, since voltage harmonics (e.g., due to dead time) see very low impedance in their additional subspaces. This has previously been addressed by active compensation, but at the cost of extra sensors and complexity. On the other hand, wide-bandgap devices (WBDs) are receiving increasing attention due to advantages such as higher efficiency and power density. WBDs yield shorter turn-on/off time than traditional Si IGBTs. Hence, in multiphase applications, WBDs may be adopted with switching frequency similar to Si IGBTs, but using smaller dead time; thus, besides exploiting the well-known advantages of the former, dead-time current distortion may be substantially improved. This approach has not been considered or tested so far in multiphase drives. Given the particular characteristics of multiphase machines, with different impedance per subspace, a specific study is necessary. In this paper, such possibility is experimentally evaluated for the first time in an asymmetrical six-phase induction motor supplied by a SiC-MOSFET inverter with 10-kHz switching frequency and reduced dead time. It is shown that this strategy substantially diminishes the large current distortion that tends to arise in multiphase drives.
Extension to Symmetrical and Asymmetrical n-Phase AC Drives of Simple Carrier-Based PWM for Prolonged High DC-Link Utilization
IECON 2020 The 46th Annual Conference of the IEEE Industrial Electronics Society, 2020
Recently, it was proposed to combine circulating-current (x-y) filters with a carrier-based pulse... more Recently, it was proposed to combine circulating-current (x-y) filters with a carrier-based pulsewidth-modulation (PWM) method, which injects harmonics in no-torque x-y subspaces (attenuated by the filter) of five-phase motors to achieve high dc-link utilization (DLU). The filter allows prolonged high DLU without overheating. Unlike square-wave switching, no torque ripple is introduced by the PWM. Compared with other PWM techniques capable of high-DLU operation (often called overmodulation), the one proposed for said filters is especially convenient because of its simplicity. However, it is unclear if this PWM method can be extended to machines of any phase number n and winding arrangement (symmetrical or asymmetrical). This paper extends this simple carrier-based PWM strategy to n-phase (symmetrical or asymmetrical) drives, and evaluates its behavior in terms of DLU. The improvement in DLU, compared with conventional PWM with zero-sequence injection, is considerable in most cases. Current distortion is negligible with suitable filter, and no torque ripple (unlike square-wave switching) is generated.
Overmodulation Method With Adaptive $x$-$y$ Current Limitation for Five-Phase Induction Motor Drives
IEEE Transactions on Industrial Electronics, 2021
Five-phase induction machines are attractive due to inherent benefits such as lower current ratin... more Five-phase induction machines are attractive due to inherent benefits such as lower current rating than three-phase ones. On the other hand, ac motor drives often need to operate in the overmodulation (OVM) region, e.g., to increase the maximum speed or to work with reduced dc-link voltage. Most of the existing OVM strategies for five-phase drives are based on injecting low-order harmonics in the no-torque <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula><inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> plane while avoiding low-order <inline-formula><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> harmonics (at least up to a modulation index of <inline-formula><tex-math notation="LaTeX">$\text{1.2311}\,{\;}\text{p.u.}$</tex-math></inline-formula>), so as to prevent the torque ripple associated with the <inline-formula><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> components. However, in practice the <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> impedance is very small, and hence, this approach can easily lead to overcurrent. This article proposes an OVM method for five-phase induction motors that adaptively modifies the injected components so that at each moment the addition of low-order <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> harmonics is favored over <inline-formula><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> ones but without surpassing the maximum current rms of the drive. In case the total stator copper loss (SCL) tends to exceed its rating during OVM in a given scenario, the proposed scheme automatically reduces the <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> injection to keep the SCL at its rated value. Experimental results verify the theory.
Improvement in DC-Link Utilization With Reduced Current and Torque Deterioration for Five-Phase Drives by Combination of Circulating-Current Filters and Simple Carrier-Based PWM Based on Closed-Form Expressions
IEEE Transactions on Industrial Electronics, 2020
Multiphase drives offer important advantages over three-phase ones. With pulsewidth modulation (P... more Multiphase drives offer important advantages over three-phase ones. With pulsewidth modulation (PWM), zero-sequence and <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> signals can be injected to enhance dc-link utilization (DLU). For example, in five-phase drives, for given dc-link voltage, the fundamental is raised by <inline-formula><tex-math notation="LaTeX">$\text{23.1}\%$</tex-math></inline-formula>. For sinusoidally distributed windings, although <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> currents increase losses, torque is unaffected. However, no simple carrier-based PWM methods based on closed-form expressions have been presented for this purpose so far. Most importantly, <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> currents may be unacceptably large, due to the small <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> impedance. This is particularly troublesome when high fundamental voltage is needed continuously. Applying square waveform instead of PWM raises the fundamental from <inline-formula><tex-math notation="LaTeX">$\text{23.1}$</tex-math></inline-formula> to <inline-formula><tex-math notation="LaTeX">$\text{27.3}\%$</tex-math></inline-formula>. Given the square-voltage distortion, filters with large <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> impedance were devised for this approach. However, some square-waveform harmonics map into the torque-producing plane without attenuation, generating torque ripple. This article proposes to use a simple carrier-based PWM method in five-phase drives combined with a circulating-current filter. The <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> voltages, which see large filter impedance, are exploited to achieve a high DLU similar to previous solutions, but without torque ripple or excessive <inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>–<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula> currents. Guidelines are given for designing the filter when used with the presented PWM strategy. Experimental results verify the proposal.
IEEE Transactions on Transportation Electrification, 2019
Wide bandgap (WBG) device-based power electronics converters are more efficient and lightweight t... more Wide bandgap (WBG) device-based power electronics converters are more efficient and lightweight than Silicon-based converters. WBG devices are an enabling technology for many motor drive applications and new classes of compact and efficient motors. This paper reviews the potential applications and advances enabled by WBG devices in ac motor drives. Industrial motor drive products using WBG devices are reviewed and the benefits are highlighted. This paper also discusses the technical challenges, converter design considerations and design trade-offs in realizing the full potential of WBG devices in motor drives. There is a trade-off between high switching frequency and other issues such as high dv/dt and electromagnetic interference. The problems of high common mode currents and bearing and insulation damage, which are caused by high dv/dt, and the reliability of WBG devices are discussed.
IEEE Transactions on Power Electronics, 2019
Multiphase drives offer important advantages over three-phase ones; e.g., lower per-phase rating ... more Multiphase drives offer important advantages over three-phase ones; e.g., lower per-phase rating and enhanced fault tolerance. For multiphase machines, multifrequency current control (MCC) is often required, e.g., for harmonic cancellation or injection. In certain situations, converter output voltage (OV) saturation occurs, which can cause windup and additional OV distortion. For MCC, obtaining antiwindup and distortionfree OV saturation, with full dc-bus exploitation, entails extra complexity. Recent publications address this problem in threephase and dual three-phase (treated as two independent threephase) systems with one and two isolated neutrals, respectively. However, extending such solutions to drives of any phase number n, winding arrangement (symmetrical or asymmetrical) and neutral configuration is not straightforward. This paper proposes a general MCC scheme, including antiwindup and distortionfree OV saturation with full dc-link utilization, for n-phase machines with different winding arrangements (symmetrical or asymmetrical) and neutral configurations. The computational burden required by the proposed antiwindup and saturation strategy is studied; it is concluded that, although it is significant in comparison with the resources needed by the rest of the MCC, the total computational load is acceptable in most cases. Experimental results with two multiphase machines are provided, including a comparison with other approaches. Index Terms-Current control, digital control, machine control, motor drives, multiphase ac drives, variable speed drives. ACRONYMS BEMF Back electromotive force. IMC Internal model control. MCC Multifrequency current control. OV Output voltage. OVSB OV saturation to the boundary. PWM Pulse width modulation.
IEEE Transactions on Industrial Informatics, 2016
Synchronization techniques can be broadly classified into two major categories: Closed-loop and o... more Synchronization techniques can be broadly classified into two major categories: Closed-loop and open-loop methods. The open-loop synchronization (OLS) techniques, contrary to the closed-loop ones, are unconditionally stable and benefit from a fast dynamic response. Their performance, however, tends to worsen in the presence of frequency drifts. To deal with this problem, two approaches are often recommended in the literature: Adapting OLS techniques to grid frequency variations by feeding back the frequency estimated by them or using the frequency estimated by a secondary frequency detector in a parallel manner. In the presence of the frequency feedback loop, nevertheless, the OLS technique may not be truly openloop, which makes a deep study of stability necessary. Using the secondary frequency detector, on the other hand, increases the computational effort and implementation complexity. Another drawback of most of the available OLS techniques is that their implementation involves the computation of sine and cosine functions, which is undesirable from the computational standpoint, particularly when the implementation with low-cost digital signal processors is intended. The aim of this paper is to develop a true OLS (and therefore, unconditionally stable) technique without any need for the calculation of sine and cosine functions. The effectiveness of the proposed synchronization technique is confirmed through the simulation and experimental results.
Reduction of saturation-induced distortion and antiwindup in multifrequency current control
2015 17th European Conference on Power Electronics and Applications (EPE'15 ECCE-Europe), 2015
Preventing voltage waveform distortion and integrator windup in multifrequency current control du... more Preventing voltage waveform distortion and integrator windup in multifrequency current control during saturated operation is a difficult combined problem, which so far has only partially been solved. In this paper, a scheme based on distortion-free saturation of the resonant-part outputs is proposed. Its effectiveness is experimentally verified.
Multifrequency Current Control With Distortion-Free Saturation
IEEE Journal of Emerging and Selected Topics in Power Electronics, 2016
Preventing voltage waveform distortion in multifrequency current control during saturated operati... more Preventing voltage waveform distortion in multifrequency current control during saturated operation is a difficult problem, which so far has been only partially solved. In this paper, a scheme based on the principle of realizable references is proposed. As the converter enters saturated operation, an algorithm recalculates the converter-current reference such that unsaturated operation returns, i.e., the converter-voltage reference does not exceed the space-vector-modulation hexagon. Distortion is thereby avoided, as is integrator windup.
Leakage current evaluation of a single-phase transformerless PV inverter connected to the grid
Apec 2007: Twenty-Second Annual Ieee Applied Power Electronics Conference and Exposition, Vols 1 and 2, 2007
Abstract-For low-power grid connected applications a single phase converter can be used. In PV ap... more Abstract-For low-power grid connected applications a single phase converter can be used. In PV applications it is possible to remove the transformer in the inverter in order to reduce losses, costs and size. Galvanic connection of the grid and the DC sources in ...
Four-dimensional space vector PWM algorithm for multilevel four-leg converters
2008 34th Annual Conference of IEEE Industrial Electronics, 2008
Abstract Four-leg voltage-source converters provide an effective neutral connection in three-phas... more Abstract Four-leg voltage-source converters provide an effective neutral connection in three-phase systems with neutral wire. They can be applied to inverters, rectifiers or active filters to control the neutral current caused by unbalanced or nonlinear loads as well as ...
Harmonic Identification Methods Based on Moving Average Filters for Active Power Filters
2008 IEEE Industry Applications Society Annual Meeting, 2008
ABSTRACT Harmonic detection is very important in the control of active power filters (APFs). This... more ABSTRACT Harmonic detection is very important in the control of active power filters (APFs). This paper presents a technique for harmonic identification, based on moving average filters (MVAs) and heterodyning, very suitable for digital implementation. The approach of fundamental component identification is contributed both for single-phase and three-phase voltage/current systems. Selective harmonic identification is also feasible. Due to the rapid step-response, good harmonic/noise cancellation of MVAs, and good frequency adaptation of the proposed algorithms, they have a very good performance compared with other alternatives. Experimental results of digital implementation in a rapid prototyping platform (dSpace DS1103), including an APF prototype are contributed proving the theoretical approaches. Details and experimental results of FPGA implementation, a clear trend in the field of digital control, are also contributed.
New algorithm for grid synchronization based on Fourier series
2007 European Conference on Power Electronics and Applications, 2007
This paper presents a new digital open loop architecture as an alternative to Phase locked loops ... more This paper presents a new digital open loop architecture as an alternative to Phase locked loops (PLLs) for grid synchronization. The system calculates in real time the Fourier coefficients of the input signal fundamental component using a heterodyning algorithm. Once the fundamental components are calculated the system can reconstruct the input fundamental signal and calculate its phase angle, frequency and
Reference generation techniques for active power line conditioners
2008 34th Annual Conference of IEEE Industrial Electronics, 2008
Reference generation is very important in the control of power line conditioners. This paper pres... more Reference generation is very important in the control of power line conditioners. This paper presents some algorithms both for single-phase and three-phase systems very suitable for reference generation and digital implementation. The key of the proposed algorithm is the implementation and tuning of Moving Average FIR filters (MVAs). Thanks to the rapid step-response and good harmonic/noise cancellation of MVAs, proposed
Control algorithm for a SSSC
2009 Compatability and Power Electronics, 2009
The power grid in most of the countries is aging and under increasing stress. The modern industri... more The power grid in most of the countries is aging and under increasing stress. The modern industrial infrastructure demands increasing amounts of affordable and reliable electricity. Solutions based on flexible AC transmission systems (FACTS) can be used to control power flow on the grid. Shunt VARs compensators provide grid voltage support, while series VARs compensators are required to control active
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Papers by Jesús Doval-Gandoy