Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique

Introduction. Resonant inverters are indispensable in demanding applications such as induction heating, wireless energy transfer, and high-frequency power conversion systems. Problem. The main topologies for realizing resonant inverters are the half-bridge and full-bridge configurations, but the mul...

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Дата:2026
Автори: Garmat, A., Toubal Maamar, A. E., Abdelouahed, T., Bensafi, N.
Формат: Стаття
Мова:Англійська
Опубліковано: National Technical University "Kharkiv Polytechnic Institute" and Аnatolii Pidhornyi Institute of Power Machines and Systems of NAS of Ukraine 2026
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Назва журналу:Electrical Engineering & Electromechanics
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Electrical Engineering & Electromechanics
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author Garmat, A.
Toubal Maamar, A. E.
Abdelouahed, T.
Bensafi, N.
author_facet Garmat, A.
Toubal Maamar, A. E.
Abdelouahed, T.
Bensafi, N.
author_institution_txt_mv [ { "author": "A. Garmat", "institution": "Ziane Achour University of Djelfa" }, { "author": "A. E. Toubal Maamar", "institution": "University of M’hamed Bougara of Boumerdes" }, { "author": "T. Abdelouahed", "institution": "University of M’hamed Bougara of Boumerdes" }, { "author": "N. Bensafi", "institution": "University of M’hamed Bougara of Boumerdes" } ]
author_sort Garmat, A.
baseUrl_str http://eie.khpi.edu.ua/oai
collection OJS
datestamp_date 2026-07-01T21:42:56Z
description Introduction. Resonant inverters are indispensable in demanding applications such as induction heating, wireless energy transfer, and high-frequency power conversion systems. Problem. The main topologies for realizing resonant inverters are the half-bridge and full-bridge configurations, but the multilevel topology is not well-known for resonant inverters because their modeling and control design are challenging steps. The goal of this study is to investigate a five-level resonant inverter combined with the selective harmonic elimination (SHE) technique to eliminate the third harmonic and minimize the total harmonic distortion (THD). Methodology. The structure of the proposed inverter and the SHE modulation technique are presented to illustrate harmonic reduction in the applied voltage. To address the inherent nonlinearities of the system, the extended describing function (EDF) method is employed to derive a generalized small-signal state-space model from any defined input to any desired output. This model enables accurate prediction of system behavior around the operating point. Based on this model, an adaptive I-PD controller incorporating a model reference adaptive control (MRAC) mechanism, designed according to the Massachusetts Institute of Technology (MIT) rule, is developed. The adaptive mechanism continuously tunes the proportional, derivative, and integral gains to maintain the desired performance despite load and parameter changes. Results. Numerical simulations validate the accuracy of the developed model and demonstrate that the adaptive I-PD control significantly ensures the system’s robustness. The results indicate that the THD of voltage and current are 25.46 %, and 9.43 %, respectively. The third harmonic is well eliminated. The model prediction error, when compared to full MATLAB/Simulink nonlinear simulations, did not exceed 4.1 %, thereby validating the effectiveness and precision of the modeling approach. The presented MRAC-based adaptive I-PD controller demonstrates high performance in tracking reference signal and responds to abrupt changes of load parameter (30 % change of the resistance value), highlighting its effectiveness for current control in five-level resonant inverter system. Scientific novelty. The proposed framework combines SHE-based harmonic mitigation, EDF-based modeling, and MRAC-based adaptive I-PD control for multilevel resonant inverters. This integration provides a generalized and flexible approach for handling system nonlinearities and improving dynamic performance. Practical value. The results confirm the feasibility of implementing adaptive I-PD control for five-level resonant inverters. The proposed scheme ensures high efficiency, stable power regulation, and reliable operation, paving the way for industrial applications requiring precise temperature control and robust performance under varying load conditions. References 28, table 1, figures 17.
doi_str_mv 10.20998/2074-272X.2026.4.07
first_indexed 2026-07-02T01:00:24Z
format Article
fulltext Electrical Engineering & Electromechanics, 2026, no. 4 47 © A. Garmat, A.E. Toubal Maamar, T. Abdelouahed, N. Bensafi UDC 621.314 https://doi.org/10.20998/2074-272X.2026.4.07 A. Garmat, A.E. Toubal Maamar, T. Abdelouahed, N. Bensafi Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique Introduction. Resonant inverters are indispensable in demanding applications such as induction heating, wireless energy transfer, and high- frequency power conversion systems. Problem. The main topologies for realizing resonant inverters are the half-bridge and full-bridge configurations, but the multilevel topology is not well-known for resonant inverters because their modeling and control design are challenging steps. The goal of this study is to investigate a five-level resonant inverter combined with the selective harmonic elimination (SHE) technique to eliminate the third harmonic and minimize the total harmonic distortion (THD). Methodology. The structure of the proposed inverter and the SHE modulation technique are presented to illustrate harmonic reduction in the applied voltage. To address the inherent nonlinearities of the system, the extended describing function (EDF) method is employed to derive a generalized small-signal state- space model from any defined input to any desired output. This model enables accurate prediction of system behavior around the operating point. Based on this model, an adaptive I-PD controller incorporating a model reference adaptive control (MRAC) mechanism, designed according to the Massachusetts Institute of Technology (MIT) rule, is developed. The adaptive mechanism continuously tunes the proportional, derivative, and integral gains to maintain the desired performance despite load and parameter changes. Results. Numerical simulations validate the accuracy of the developed model and demonstrate that the adaptive I-PD control significantly ensures the system’s robustness. The results indicate that the THD of voltage and current are 25.46 %, and 9.43 %, respectively. The third harmonic is well eliminated. The model prediction error, when compared to full MATLAB/Simulink nonlinear simulations, did not exceed 4.1 %, thereby validating the effectiveness and precision of the modeling approach. The presented MRAC-based adaptive I-PD controller demonstrates high performance in tracking reference signal and responds to abrupt changes of load parameter (30 % change of the resistance value), highlighting its effectiveness for current control in five-level resonant inverter system. Scientific novelty. The proposed framework combines SHE-based harmonic mitigation, EDF-based modeling, and MRAC-based adaptive I-PD control for multilevel resonant inverters. This integration provides a generalized and flexible approach for handling system nonlinearities and improving dynamic performance. Practical value. The results confirm the feasibility of implementing adaptive I-PD control for five-level resonant inverters. The proposed scheme ensures high efficiency, stable power regulation, and reliable operation, paving the way for industrial applications requiring precise temperature control and robust performance under varying load conditions. References 28, table 1, figures 17. Key words: resonant multilevel inverter, adaptive control, selective harmonic elimination, induction heating. Вступ. Резонансні інвертори є невід’ємною складовою сучасних високотехнологічних застосувань, зокрема систем індукційного нагрівання, бездротового передавання енергії та високочастотних систем перетворення електроенергії. Проблема. Основними топологіями реалізації резонансних інверторів є напівмостові та мостові схеми. Водночас багаторівнева топологія для резонансних інверторів залишається недостатньо дослідженою через складність математичного моделювання та синтезу систем керування. Мета. Дослідження п’ятирівневого резонансного інвертора у поєднанні з методом селективного усунення гармонік (SHE) для пригнічення третьої гармоніки та мінімізації повного гармонічного спотворення (THD). Методика. Представлено структуру запропонованого інвертора та метод модуляції SHE для демонстрації зменшення гармонічних складових прикладеної напруги. Для врахування притаманних системі нелінійностей застосовано метод розширеної описувальної функції (EDF), за допомогою якого отримано узагальнену малосигнальну модель у просторі станів для довільно визначених входів і виходів. Розроблена модель забезпечує точне прогнозування поведінки системи поблизу робочої точки. На її основі синтезовано адаптивний I-PD-регулятор із механізмом адаптивного керування за еталонною моделлю (MRAC), побудованим відповідно до правила Массачусетського технологічного інституту (MIT). Адаптивний механізм забезпечує безперервне налаштування пропорційного, диференціального та інтегрального коефіцієнтів для підтримання необхідних показників роботи за зміни навантаження та параметрів системи. Результати. Чисельне моделювання підтвердило точність розробленої моделі та показало, що адаптивне I-PD-керування суттєво підвищує робастність системи. Отримані результати свідчать, що THD напруги та струму становлять відповідно 25,46 % і 9,43 %. Третя гармоніка ефективно усувається. Похибка прогнозування моделі порівняно з повною нелінійною моделлю MATLAB/Simulink не перевищувала 4,1 %, що підтверджує ефективність і точність запропонованого підходу до моделювання. Представлений адаптивний I-PD-регулятор на основі MRAC демонструє високу якість відстеження опорного сигналу та ефективно реагує на різкі зміни параметрів навантаження (зміна опору на 30 %), що підтверджує його придатність для керування струмом у системі п’ятирівневого резонансного інвертора. Наукова новизна. Запропонований підхід поєднує метод селективного усунення гармонік SHE, моделювання на основі EDF та адаптивне I- PD-керування на основі MRAC для багаторівневих резонансних інверторів. Така інтеграція забезпечує узагальнений і гнучкий підхід до врахування нелінійностей системи та покращення її динамічних характеристик. Практична значимість. Отримані результати підтверджують можливість практичної реалізації адаптивного I-PD-керування для п’ятирівневих резонансних інверторів. Запропонована схема забезпечує високу ефективність, стабільне регулювання потужності та надійну роботу, що відкриває перспективи її застосування у промислових системах, які потребують точного температурного регулювання та робастної роботи за змінних умов навантаження. Бібл. 28, табл. 1, рис. 17. Ключові слова: резонансний багаторівневий інвертор, адаптивне керування, селективне усунення гармонік, індукційне нагрівання. Introduction. High-frequency power electronic converter, typically a resonant inverter, is a widely adopted circuit in industrial manufacturing, such as telecommunication systems, the induction heating, wireless energy transfer, and high-frequency power conversion systems [1, 2]. However, the most high-frequency applications are highly nonlinear. The electrical parameters of these systems, such as their equivalent resistance and inductance, vary significantly with temperature and magnetic field intensity [3]. These variations shift the resonant frequency and the load impedance, leading to fluctuations in output power and potential detuning from the optimal zero voltage switching (ZVS) operation, which is crucial for efficiency [4]. Consequently, a fixed-gain controller, such as a standard PID controller, is often inadequate to maintain consistent performance across the entire operating range. Its performance degrades under parameter variations, leading to poor disturbance rejection and potential instability [5]. 48 Electrical Engineering & Electromechanics, 2026, no. 4 Therefore, the problem addressed in this paper is the design of a robust control strategy for a multilevel resonant inverter that can ensure stable output power and dynamic performance despite the nonlinear and time- varying nature of the load. Solving this problem is highly relevant for advancing industrial manufacturing processes that demand precise control and high reliability. Multilevel converters have garnered significant attention in recent years for medium and high power applications [6]. Compared to traditional inverters, they offer superior performances, including reduced output voltage harmonic distortion, lower electromagnetic interference, and the ability to operate at higher voltages with devices of lower voltage rating [7]. For high-frequency applications, multilevel topologies can provide a stepped voltage waveform that more closely approximates a sinusoid, reducing the stress on the resonant tank components. Review of recent publications demonstrate that an extensive research have been conducted on both multilevel inverter topologies and resonant inverters. In terms of topologies, reduced-switch-count multilevel inverters are an active area of research to minimize cost and complexity [8]. The topology proposed in [9] presents a 7-level inverter with 6 switches, which is less than a conventional cascaded H-bridge. This work aligns with the trend of topological simplification. The authors [10] discussed the resent advances in resonant converters. The study establishes the current level of knowledge, technology, and advancement in converters, which helps researchers identify knowledge gaps, and confirm the novelty of their own research. In [11] the authors proposed an extended topology for series resonant inverter with high quality control for induction heating applications. Furthermore, authors [12] presented the analysis of 5-level LLC resonant converter with design method for battery chargers. The discussed results demonstrated the performance of the resonant converter topologies. For inverters modulation, various techniques are employed, such as the carrier-based pulse width modulation (PWM) technique, space vector PWM technique, and selective harmonic elimination (SHE) technique are employed [13–15]. SHE is the well- established, offering the advantage of direct elimination of specific order harmonics. Recent works, such as [16], employ optimization algorithms like particle swarm optimization (PSO) to solve the nonlinear SHE equations efficiently. Regarding modeling, the nonlinear nature of resonant converters necessitates advanced modeling techniques for controller design. The extended describing function (EDF) method is a powerful tool for deriving large-signal and small-signal models of resonant converters, accurately predicting behavior around the operating point [17]. The small-signal modeling approach has demonstrated its effectiveness across a wide range of systems, including LLC converters [18] and chopper [19]. In the domain of control, adaptive control techniques have been proposed to handle system uncertainties. The model reference adaptive control (MRAC) scheme, particularly using the Massachusetts Institute of Technology (MIT) rule for adaptation, is a direct method to make a system’s output track that of a reference model [20]. This approach has been explored for DC-DC converters [21] and motor drives [22]. Integral-Proportional-Derivative (I-PD) controller, a variant of the PID structure where the integral action is on the reference and the proportional- derivative actions are on the feedback, is known to reduce overshoot and improve set-point response compared to the parallel form [23–25]. Despite these advancements, several challenges remain unsolved or are not fully addressed in the current literature, including: Lack of comprehensive studies that integrate a reduced-switch-count multilevel inverter, SHE modulation for harmonic mitigation, an accurate EDF- based dynamic model, and an advanced adaptive controller for the specific challenges of resonant inverters. Also, the application of MRAC-based adaptive I-PD control, which combines the benefits of improved set- point response I-PD with online parameter tuning MRAC, to multilevel resonant inverters for induction heating as example is not thoroughly explored. Thus, the unsolved problem is the development and validation of a unified control strategy that synergistically combines these advanced techniques to achieve robust, stable, and high- performance operation of a multilevel resonant inverter under realistic, varying operating conditions. The goal of this study is to investigate a five-level resonant inverter combined with SHE technique to eliminate the third harmonic and minimize the total harmonic distortion (THD). In addition, this work presents the development of a small-signal model to handle the intrinsic nonlinear behavior of the system. This model is then used for the design of an adaptive I-PD controller through a simple and accurate approach. Adaptive control is employed to ensure the system’s robustness in the presence of parameter variations. To achieve the goal, an emerging inverter topology employing only 6 power switches is used, which is fewer than the usual number of switches in a cascaded H-bridge multilevel inverter. To generate a high-quality output voltage waveform with minimized lower-order harmonics, SHE technique is suggested. To address the modeling issue, the EDF method is employed to create a small signal model of the load with the proposed five- level multilevel resonant inverter. This model makes it possible to get a good idea of how the system will behave around the operating point when the load changes. The second objective of this paper is to synthesize an adaptive I-PD controller based on MRAC structure, with adaptation mechanisms governed by the MIT rule, to autonomously adjust controller gains and maintain desired performance. Finally purpose is to validate the accuracy of the developed model and the efficacy of the proposed control strategy through numerical simulations, demonstrating improved disturbance rejection and robust tracking performance under load variations. The proposed five-level inverter. Figure 1 shows the proposed single phase 5-levels multilevel resonant inverter topology used in this study. The proposed topology includes a DC power supply (Vi), 4 main switches T1 – T4 and 2 auxiliary switches T5 and T6. IGBT switches have external freewheeling diodes. The oscillating circuit has a series inductor Ls and a parallel resonant capacitor Cp. The workpiece is put inside the N turns cooper coil with a certain amount of air space. A capacitor Cb is put in series with the primary of the transformer. Electrical Engineering & Electromechanics, 2026, no. 4 49 Fig. 1. Proposed five-level multilevel resonant inverter To make sure that the ZVS works during the heating cycle, the converter is run above the system’s natural frequency. The proposed inverter’s main task is to create 5 different levels of output voltage based on the state of switches is on or off. Table 1 illustrates the output voltage levels. Table 1 The switches on-off condition uab T1 T2 T3 T4 T5 T6 –Vi 0 1 1 0 1 0 –0.5Vi 0 1 1 0 0 1 0 0 1 0 1 0 0 0 0 1 0 1 0 0 0.5Vi 1 0 0 1 0 1 Vi 1 0 0 1 1 0 The typical waveforms for the five-level inverter output voltage uab(t) with PWM operation modes are illustrated in Fig. 2, where T is the period, f is frequency, θ1, θ2 are the switching angles. Fig. 2. Typical output voltage waveform SHE strategy. The output voltage in Fig. 2 is a stepped waveform, and θ1 and θ2 are the angles at which the waveform switches. These angles need to be set so that certain harmonics (3, 5, 7, etc.) are removed. Using Fourier series analysis, we can write the output voltage as:           1 21 )sin()cos()cos( 2 )( n s i ab tnnn n V tu   , (1) where n is the natural number; s is the angular switching frequency; t is the time. The switching angles θ1 and θ2 must meet the following condition: 20 21   . We use SHE to get rid of some harmonic components. In this instance, the analysis of the output voltage waveform through Fourier theory yields a collection of non-linear transcendental equations. If these equations have a solution, it gives the switching angles needed for a certain fundamental component and a chosen harmonic profile. In 5-level multilevel inverter, to eliminate the 3rd harmonic order the angles θ1 and θ2 are chosen to satisfy:          ,0)3cos()3cos( ; 1 )cos()cos( 21 21   m k (2) where m is the modulation index (m = πh1/2kVi); k is the number of switching angles (in our study k = 2); h1 is the fundamental harmonic. This equation is not linear and has trigonometric terms. To solve these sets of equations, iterative methods like Newton-Raphson or Gauss Jordan are well used. But, the initial values must be chosen near to the optimal solution. In this study PSO method is applied to find the desired switching angles: θ1 and θ2. The PSO method is well detailed in several previous researches, including [16]. Figure 3 shows the switching angles as a function of the modulation index m. m Fig. 3. Switching angles θ1 and θ2 vs modulation index m The five-level resonant inverter under SHE control is simulated, where the simulation parameters are summarized in Appendix A. The applied output voltage waveform uab(t) and the corresponding harmonic spectrum that revealed elimination of 3rd harmonic are shown in Fig. 4, 5, respectively. The output voltage has 5 levels: Vi, 0.5Vi, 0, –0.5Vi, –Vi, and the wave shape is near sinusoidal. The output voltage has a THD of 25.46 %. From the harmonic spectrum the 3rd harmonic is absent from the waveform as predicted. Figure 6 shows the resulting current is(t) from applying the voltage of Fig. 4 to the LLC load. The corresponding harmonic spectrum is shown in Fig. 7. From the harmonic spectrum, the THD of the current waveform equals 9.43 %. t, ms uab, V Fig. 4. Output voltage waveform of the proposed inverter Fig. 5. Harmonic spectrum of the applied voltage 50 Electrical Engineering & Electromechanics, 2026, no. 4 t, ms is, A Fig. 6. Output current waveform of the proposed inverter Fig. 7. Harmonic spectrum of the output current is(t) Generalized small signal model. To create the control system for the five-level multilevel resonant inverter shown in Fig. 1, it’s necessary to make a linear mathematical model of the real system. It is possible to model the induction heating load (the copper coil and the workpiece) by putting together its equivalent resistance R0 and equivalent inductance L0 [26]. The equivalent circuit of the proposed inverter is given in Fig. 8. Fig. 8. The equivalent circuit of the proposed inverter The primary side of the transformer is denoted by the following equivalents R, L and C: pC n n CL n n LR n n R 2 1 2;0 2 2 1;0 2 2 1                    , where (n1/n2) refers to the turns ratio of the transformer. The resonant frequency ω0, the quality factor Q and the inductance ratio Le of the system are given by: L L L C L R Q LCL LL s e s s     , 1 ,0 . Theoretically, the current gain of the inverter can be given as: 22 0)( QLL QL I I H ee e s i    . (3) Figure 9, which was obtained from (3), shows the values of |Hi| for different inductance ratio Le and Q factors. From Fig. 9, when ωs ≈ ω0 and Q >> 1 (Q ≈ 30), the current is amplified over the heating coil with gain which can be simplified by: |Hi| ≈ Le. The circuit’s differential nonlinear equations can be expressed using the symbols in Fig. 8, as follows: Le Hi Fig. 9. Current gain as function of Le and Q               .d)()( 1 )( ; d )(d )()( );( d )(d )( ttiti c tv t ti LtRitv tv t ti Ltu sc c c s sab (4) The state vector is chosen as:  tcs titvtitx )()()()(  . The input u(t) and the output y(t) variables are given as: u(t) = uab(t), y(t) = vc(t). In order to provide the generalized small signal model, we need to calculate the coefficients of Fourier series for the circuit state variables. In this case, the state variables are complex values which can be defined as:          . ; ; 331 221 111 qd qdc qds jxxi jxxv jxxi (5) The 1st harmonic of the input voltage is given by:  211 coscos 2    i ab V u . (6) The initial harmonic approximation of is(t), vc(t) and i(t) is valid under the conditions: Q >> 1 and ωs ≈ ω0. We can break down 12 into 6 equations by replacing (5) and (6) into (4) and using the harmonic balance method. The large signal model of the system is constructed as follows:                           . 1 ; 1 ; 11 ; 11 ; 1 ;)cos()cos( 21 2333 2333 3122 3122 211 21211 qdsqq dqsdd qqdsq ddqsd q s dsq s i d s qsd x L xx L R x x L xx L R x x C x C xx x C x C xx x L xx L V x L xx               (7) The new state variables become:  tqdqdqd xxxxxxtx 332211)(  . The input controls are defined as:  tis Vtu 21)(  . The output variable is expressed as: 2 3 2 3)( qd xxty  . Electrical Engineering & Electromechanics, 2026, no. 4 51 Digital simulations were conducted in MATLAB/Simulink to validate the accuracy of the developed large-signal model. The responses of the proposed mathematical model and the simulated circuit were compared under identical operating conditions. The comparative results are presented in Fig. 10, 11. t, ms vc, V Fig. 10. Comparison of voltage between the large signal model and the simulated circuit t, ms i, A Fig. 11. Comparison of current between the large signal model and the simulated circuit These results show the good concordance existing between the developed mathematical model and the simulated circuit. Keep in mind that the large signal model is a nonlinear equation because it has the product (ωs xid) and (ωs xiq), where ωs, xid and xiq are all independent variables. It is hard to use this model to make the control system. Once the system’s large signal model has been found, the nonlinear equations in (7) can be linearized around the operating point. This lets us make the small signal transfer function from any input Vi, θ1, θ2, ωs to any desired output is, vc, i, P. To find the system’s equilibrium operation point, we can solve the equation above by setting the derivatives of the system equations (7) equal to zero. Using Taylor series, we get the small signal model of the system by perturbing and linearizing the large signal model around the operating point (U0, X0, Y0):         .)(~,)(~)( ;)(~,)(~)( ;)(~,)(~)( 00 00 00 YtytyYty UtutuUtu XtxtxXtx (8) The small signal model’s state equations are written in matrix form as follows:       ),(~)(~ );(~)(~)(~ txCty tuBtxAtx s ss  (9) where:     )( ~ )(~ ;~~~~)(~ ;~~~~~~)(~ 21 332211 tity vtu xxxxxxtx t si t qdqdqd     The matrix’s As, Bs and Cs are given in Appendix B. Adaptive I-PD control. Adaptive control has been successfully utilized in control practice for a diverse range of engineering challenges, including DC-DC converters. This method is used when the system is hard to model because it is complicated or not linear. The suggested resonant inverters induction heating systems are in this group because they have a structure that changes over time and parts that are not linear. Putting 1 ~ , 2 ~ , s ~ equal to zeros, the small signal transfer function from the input voltage )(~ svi to the output inductor current )( ~ si is derived as follow:   sss i BASIC sv si sG 1 )(~ )( ~ )(  . (10) In order to confirm the accuracy of the resulting small-signal model, the dynamic response )( ~ ti of G(s) is compared with the response of the simulated circuit for the same random input signal where the magnitude is varied between –5 % and +5 % of Vi. Simulation results are given in Fig. 12. t, ms i, A Fig. 12. Comparison between the small signal model and the simulated circuit From the results shown in Fig. 12, there is a small deviation between the response output of the resulting mathematic model and the response of the simulated circuit. This confirms that around the operation point, the resulting model G(s) agrees well with the dynamics of the simulated resonant inverter. The transfer function (10) is a 6 order system, which has 6 poles:       .100152.00315.0 ;107071.00127.0 ;103990.10315.0 5 6,5 5 4,3 5 2,1    jp jp jp To determine graphically the phase margin and the gain margin of the open loop system (8), the magnitude vs phase plot is sketched on the Nichols chart given in Fig. 13. From the Nichols charts, the minimum gain margin Gm, the phase margin Pm, and the associated frequencies ωgm and ωpm are given by: Gm = 0.106 dB; Pm = [94.6°, 64.5°, –109.8°, –135.5°, 100.9°]; ωgm = 7.01104 rad/s; ωpm = [1.2104, 5.6104, 8.4104, 1.3105, 1.4105]. Figure 14 shows the schematic diagram of the proposed adaptive I-PD control structure. The system has 2 loops. The inner loop is consisting of the system G(s) and the I-PD controller. In order to force the system to 52 Electrical Engineering & Electromechanics, 2026, no. 4 track the reference the outer loop (adaptive mechanism) is used the adjust the controller parameters Kp, Ki, and Kd. In this instance, the required performance specifications are articulated through a reference model GRM(s). Fig. 13. Nichols chart of the open loop system G(s) Fig. 14. MRAC I-PD controller block diagram The output signal )(~ svi is calculated as: )( ~ 1 )()(~ si sT sK Ks s K sv f d p i i            , (11) where Tf is the filter time constant. Based on the popular MIT rule, the adaptive mechanism needs the following signals ε(s), e(s) and )( ~ si to adjust the I-PD controller [27, 28]. In our case, the controller parameter β is adjusted to minimizing the cost function J given by: )( 2 1 )( 2  eJ  , (12) where: )( ~ )( ~ )( sisise m ;  dip KKK ,, . The MIT rule affirms that the rate of change of β is directly related to the negative gradient of J [28]. The controller parameter β is calculated by:           )()( d d e e J t , (13) where   )(e is the sensitivity derivative of error with regard to β; γ is the adaptation gain. In practice, the choice of adaptation gain is very important, and its value depends on the levels of the signals. The closed-loop transfer function of the system with the suggested I-PD structure in control theory is given by: )( )( )( ~ )( ~ sD sN si si r  , (14) where: )()()( sGsGKsN fi ;   )()()()()( 2 sGsKssGKsGKssGsD dfpfif  ;  1)(  sTsG ff . Using (13), the controller parameters Kp, Ki and Kd can be determinate by:                                      . ~ ~ d d ; ~ ~ d d ; ~ ~ d d d d d i i i p p p K i i e e J t K K i i e e J t K K i i e e J t K    (15) From (15), the adaptation I-PD law can be described with respect to the original controller parameters as:                   ).( ~ )( )( d d ;)( ~ )( ~ )( )()1( d d );( ~ )( )()1( d d 2 si sD sGs e t K sisi sD sGsT e t K si sD sGsTs e t K d d r f i i f p p    (16) It is important to choose the reference model so that the closed loop response has an overshoot of less than 5 % and a settling time < 5 ms. To test how well the proposed adaptive I-PD controller works, we compare the response results of the real system and the reference model. Figures 15, 16 display the results of the comparison and the associated tracking error e(t), respectively. t, ms i, A Fig. 15. Output current responses i(t) under sinus input reference t, ms e Fig. 16. Tracking error variation with adaptive I-PD controller These figures show that the suggested control method can make the system output current follow the reference model. This is justified by the correct selection of the adaptation gains γp, γi and γd, which ensure the transient performance of the output current regarding rise time, overshoot, and settling time. The controller demonstrates a fast and well-damped response, with an estimated rise time of 1.4 ms, a low overshoot of approximately 5 %, and a settling time of about 5 ms. These results confirm the Electrical Engineering & Electromechanics, 2026, no. 4 53 ability of the controller to achieve rapid tracking while maintaining system stability and robustness. We tested the proposed adaptive I-PD control under load variation, where the load changes from 0.107 Ω to 0.0749 Ω at t = 40 ms, to make sure it was sufficiently robust. Figure 17 shows that the tracking works well and the disturbances are very well rejected. t, ms i, A Fig. 17. Output current responses i(t) with disturbance rejection To reject the disturbance, the system has to follow the output of the reference model by changing the input the input )(~ svi . In this case, the control parameters come together to form a constant value, and the tracking error e(t) is getting closer to zero. Conclusions. This paper describes the modeling and control of a five-level resonant inverter using SHE technique and an adaptive I-PD strategy based on MRAC. A five-level resonant inverter topology with a reduced number of switches (6 switches instead of 8 in the conventional H-bridge topology) was successfully tested. This resulted in a 25 % reduction in power semiconductor devices compared to the conventional cascaded H-bridge structure, leading to lower hardware complexity and reduced cost. SHE technique successfully eliminated the 3rd harmonic component from the output voltage waveform. THD of the inverter output voltage equals 25.46 %, while the load current THD equals 9.43 %. An accurate generalized small-signal dynamic model of the inverter was derived using the EDF method. The model prediction error, when compared to full MATLAB/Simulink nonlinear simulations, did not exceed 4.1 %, thereby validating the effectiveness and precision of the proposed modeling approach. The proposed MRAC-based adaptive I-PD controller demonstrates excellent performance in tracking reference signal. The controller ensures a fast and well-damped response, with an estimated rise time of 1.4 ms, a low overshoot of approximately 5 %, and a settling time of about 5 ms. The controller demonstrates high responds to abrupt changes of load parameter (30 % change of the resistance value). These results confirm the ability of the controller to achieve rapid tracking while maintaining system stability and robustness, highlighting its effectiveness for current control in five-level resonant inverter system. The future work will focus on building a hardware prototype of the proposed circuit to validate the simulation results and assess practical implementation challenges. The next step is developing more mathematically rigorous adaptation laws, potentially grounded in Lyapunov stability theory to reinforce the theoretical stability guarantees of the proposed control strategy, and extending the control strategy to simultaneously optimize multiple performance indices, such as efficiency and tracking error. On the other hand, to explore new research topics, it is paving the way to study other related systems such as the extension of the system with other converter topologies and the integration of renewable energy such as photovoltaic solar, wind, or hybrid systems like photovoltaic-wind, which have garnered significant attention due to their sustainability. Appendix A. The equivalent parameters used in numerical simulation are: resistor R = 0.107 Ω; inductance L = 14.13 μH; capacitance C = 17.7 μF; inductance Ls = 70 μH; DC power source Vi = 540 V; switching angles θ1 = 25°, θ2 = 34°; factor Q = 8.35; ωs = 7.07104 rad/s. Appendix B. The matrices As, Bs, Cs are:                                        L R L L R L CC CC L L A s s s s s s s s s 0 0 0 0 0 0 1 000 0 1 00 1 00 1 0 0 1 00 1 00 1 00 000 1 0       ; t svs BBBBB ][ 21  ;             2 03 2 03 03 2 03 2 03 030000 qd q qd d s xx x xx x C , where:      t s v L B        00000coscos 4 2010   ;   t s i L V B        00000cos 4 101   ;   t s i L V B        00000cos 4 202   ;  tdqdqdqs XXXXXXB 030302020101  . Conflict of interest. The authors declare that they have no conflicts of interest. REFERENCES 1. Jaafari B., Namadmalan A. Design and parameter estimation of series resonant induction heating systems using self-oscillating tuning loop. Journal of Applied Research in Electrical Engineering, 2022, vol. 1, no. 1, pp. 42-49. doi: https://doi.org/10.22055/jaree.2021.36904.1025. 2. Irwanto M., Kita L.K.W. 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Robust I-PD Controller Design with Case Studies on Boiler Steam Drum and Bioreactor. 2023 15th International Conference on Computer and Automation Engineering (ICCAE), 2023, pp. 486-491. doi: https://doi.org/10.1109/ICCAE56788.2023.10111205. 26. Ahmed N.A. High-Frequency Soft-Switching AC Conversion Circuit With Dual-Mode PWM/PDM Control Strategy for High-Power IH Applications. IEEE Transactions on Industrial Electronics, 2011, vol. 58, no. 4, pp. 1440-1448. doi: https://doi.org/10.1109/TIE.2010.2050752. 27. Sachit S., Vinod B.R. MRAS Based Speed Control of DC Motor with Conventional PI Control – A Comparative Study. International Journal of Control, Automation and Systems, 2022, vol. 20, no. 1, pp. 1- 12. doi: https://doi.org/10.1007/s12555-020-0470-1. 28. Swarnkar P., Jain S., Nema R.K. Effect of Adaptation Gain in Model Reference Adaptive Controlled Second Order System. Engineering, Technology & Applied Science Research, 2011, vol. 1, no. 3, pp. 70-75. doi: https://doi.org/10.48084/etasr.11. Received 02.03.2026 Accepted 12.05.2026 Published 02.07.2026 A. Garmat1, PhD, Associate Professor, A.E. Toubal Maamar2, PhD, Associate Professor, T. Abdelouahed 2, PhD, Associate Professor, N. Bensafi 2, PhD, Associate Professor, 1 Ziane Achour University of Djelfa, Algeria, e-mail: a.garmat@univ-djelfa.dz (Corresponding Author) 2 University of M’hamed Bougara of Boumerdes, Algeria. How to cite this article: Garmat A., Toubal Maamar A.E., Abdelouahed T., Bensafi N. Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique. Electrical Engineering & Electromechanics, 2026, no. 4, pp. 47-54. doi: https://doi.org/10.20998/2074-272X.2026.4.07
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spelling eiekhpieduua-article-3429982026-07-01T21:42:56Z Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique Garmat, A. Toubal Maamar, A. E. Abdelouahed, T. Bensafi, N. резонансний багаторівневий інвертор адаптивне керування селективне усунення гармонік індукційне нагрівання resonant multilevel inverter adaptive control selective harmonic elimination induction heating Introduction. Resonant inverters are indispensable in demanding applications such as induction heating, wireless energy transfer, and high-frequency power conversion systems. Problem. The main topologies for realizing resonant inverters are the half-bridge and full-bridge configurations, but the multilevel topology is not well-known for resonant inverters because their modeling and control design are challenging steps. The goal of this study is to investigate a five-level resonant inverter combined with the selective harmonic elimination (SHE) technique to eliminate the third harmonic and minimize the total harmonic distortion (THD). Methodology. The structure of the proposed inverter and the SHE modulation technique are presented to illustrate harmonic reduction in the applied voltage. To address the inherent nonlinearities of the system, the extended describing function (EDF) method is employed to derive a generalized small-signal state-space model from any defined input to any desired output. This model enables accurate prediction of system behavior around the operating point. Based on this model, an adaptive I-PD controller incorporating a model reference adaptive control (MRAC) mechanism, designed according to the Massachusetts Institute of Technology (MIT) rule, is developed. The adaptive mechanism continuously tunes the proportional, derivative, and integral gains to maintain the desired performance despite load and parameter changes. Results. Numerical simulations validate the accuracy of the developed model and demonstrate that the adaptive I-PD control significantly ensures the system’s robustness. The results indicate that the THD of voltage and current are 25.46 %, and 9.43 %, respectively. The third harmonic is well eliminated. The model prediction error, when compared to full MATLAB/Simulink nonlinear simulations, did not exceed 4.1 %, thereby validating the effectiveness and precision of the modeling approach. The presented MRAC-based adaptive I-PD controller demonstrates high performance in tracking reference signal and responds to abrupt changes of load parameter (30 % change of the resistance value), highlighting its effectiveness for current control in five-level resonant inverter system. Scientific novelty. The proposed framework combines SHE-based harmonic mitigation, EDF-based modeling, and MRAC-based adaptive I-PD control for multilevel resonant inverters. This integration provides a generalized and flexible approach for handling system nonlinearities and improving dynamic performance. Practical value. The results confirm the feasibility of implementing adaptive I-PD control for five-level resonant inverters. The proposed scheme ensures high efficiency, stable power regulation, and reliable operation, paving the way for industrial applications requiring precise temperature control and robust performance under varying load conditions. References 28, table 1, figures 17. Вступ. Резонансні інвертори є невід’ємною складовою сучасних високотехнологічних застосувань, зокрема систем індукційного нагрівання, бездротового передавання енергії та високочастотних систем перетворення електроенергії. Проблема. Основними топологіями реалізації резонансних інверторів є напівмостові та мостові схеми. Водночас багаторівнева топологія для резонансних інверторів залишається недостатньо дослідженою через складність математичного моделювання та синтезу систем керування. Мета. Дослідження п’ятирівневого резонансного інвертора у поєднанні з методом селективного усунення гармонік (SHE) для пригнічення третьої гармоніки та мінімізації повного гармонічного спотворення (THD). Методика. Представлено структуру запропонованого інвертора та метод модуляції SHE для демонстрації зменшення гармонічних складових прикладеної напруги. Для врахування притаманних системі нелінійностей застосовано метод розширеної описувальної функції (EDF), за допомогою якого отримано узагальнену малосигнальну модель у просторі станів для довільно визначених входів і виходів. Розроблена модель забезпечує точне прогнозування поведінки системи поблизу робочої точки. На її основі синтезовано адаптивний I-PD-регулятор із механізмом адаптивного керування за еталонною моделлю (MRAC), побудованим відповідно до правила Массачусетського технологічного інституту (MIT). Адаптивний механізм забезпечує безперервне налаштування пропорційного, диференціального та інтегрального коефіцієнтів для підтримання необхідних показників роботи за зміни навантаження та параметрів системи. Результати. Чисельне моделювання підтвердило точність розробленої моделі та показало, що адаптивне I-PD-керування суттєво підвищує робастність системи. Отримані результати свідчать, що THD напруги та струму становлять відповідно 25,46 % і 9,43 %. Третя гармоніка ефективно усувається. Похибка прогнозування моделі порівняно з повною нелінійною моделлю MATLAB/Simulink не перевищувала 4,1 %, що підтверджує ефективність і точність запропонованого підходу до моделювання. Представлений адаптивний I-PD-регулятор на основі MRAC демонструє високу якість відстеження опорного сигналу та ефективно реагує на різкі зміни параметрів навантаження (зміна опору на 30 %), що підтверджує його придатність для керування струмом у системі п’ятирівневого резонансного інвертора. Наукова новизна. Запропонований підхід поєднує метод селективного усунення гармонік SHE, моделювання на основі EDF та адаптивне I-PD-керування на основі MRAC для багаторівневих резонансних інверторів. Така інтеграція забезпечує узагальнений і гнучкий підхід до врахування нелінійностей системи та покращення її динамічних характеристик. Практична значимість. Отримані результати підтверджують можливість практичної реалізації адаптивного I-PD-керування для п’ятирівневих резонансних інверторів. Запропонована схема забезпечує високу ефективність, стабільне регулювання потужності та надійну роботу, що відкриває перспективи її застосування у промислових системах, які потребують точного температурного регулювання та робастної роботи за змінних умов навантаження. Бібл. 28, табл. 1, рис. 17. National Technical University &quot;Kharkiv Polytechnic Institute&quot; and Аnatolii Pidhornyi Institute of Power Machines and Systems of NAS of Ukraine 2026-07-02 Article Article application/pdf https://eie.khpi.edu.ua/article/view/342998 10.20998/2074-272X.2026.4.07 Electrical Engineering &amp; Electromechanics; No. 4 (2026); 47-54 Электротехника и Электромеханика; № 4 (2026); 47-54 Електротехніка і Електромеханіка; № 4 (2026); 47-54 2309-3404 2074-272X en https://eie.khpi.edu.ua/article/view/342998/351644 Copyright (c) 2025 A. Garmat, A. E. Toubal Maamar, T. Abdelouahed, N. Bensafi http://creativecommons.org/licenses/by-nc/4.0
spellingShingle resonant multilevel inverter
adaptive control
selective harmonic elimination
induction heating
Garmat, A.
Toubal Maamar, A. E.
Abdelouahed, T.
Bensafi, N.
Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title_alt Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title_full Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title_fullStr Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title_full_unstemmed Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title_short Design of an adaptive I-PD controller for a five-level resonant inverter with selective harmonic elimination technique
title_sort design of an adaptive i-pd controller for a five-level resonant inverter with selective harmonic elimination technique
topic resonant multilevel inverter
adaptive control
selective harmonic elimination
induction heating
topic_facet резонансний багаторівневий інвертор
адаптивне керування
селективне усунення гармонік
індукційне нагрівання
resonant multilevel inverter
adaptive control
selective harmonic elimination
induction heating
url https://eie.khpi.edu.ua/article/view/342998
work_keys_str_mv AT garmata designofanadaptiveipdcontrollerforafivelevelresonantinverterwithselectiveharmoniceliminationtechnique
AT toubalmaamarae designofanadaptiveipdcontrollerforafivelevelresonantinverterwithselectiveharmoniceliminationtechnique
AT abdelouahedt designofanadaptiveipdcontrollerforafivelevelresonantinverterwithselectiveharmoniceliminationtechnique
AT bensafin designofanadaptiveipdcontrollerforafivelevelresonantinverterwithselectiveharmoniceliminationtechnique