Bidirectional AC-DC converters are used in many applications such as renewable energy systems, communication systems, and grid connection of electric vehicles. In this paper, a non-linear controller based on the Lyapunov-based model reference adaptive control approach is proposed for single-phase bidirectional AC-DC converters that incorporate active power factor correction circuits. The proposed controller dynamically adjusts the output power according to the grid conditions and user preferences while maintaining a nearly unitary power factor and a constant output DC voltage set as the reference value. The proposed controller also ensures the stability and robustness of the system under various operating conditions and disturbances. The performance of the proposed controller is compared with another Lyapunov-based control proposed in the literature to show that the proposed controller performs at least on par with the other controller in all aspects

Chicco, Gianfranco

Mazza, Andrea

Musumeci, Salvatore

Qureshi, Muhammad Ahmed

Reatti, Alberto

Torelli, Francesco

English

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

11 February 2024POLITECNICO DI TORINORepository ISTITUZIONALEApplication of Advanced Model Reference Adaptive Control for Bidirectional AC-DC Converters / Qureshi, MuhammadAhmed; Musumeci, Salvatore; Torelli, Francesco; Reatti, Alberto; Mazza, Andrea; Chicco, Gianfranco. - ELETTRONICO.- (2023), pp. -5. (Intervento presentato al  convegno 58th International Universities Power Engineering Conference(UPEC) tenutosi a Dublin (Ireland) nel 30 August 2023 - 1 September 2023) [10.1109/UPEC57427.2023.10294442].OriginalApplication of Advanced Model Reference Adaptive Control for Bidirectional AC-DC ConvertersIEEE postprint/Author's Accepted ManuscriptPublisher:PublishedDOI:10.1109/UPEC57427.2023.10294442Terms of use:Publisher copyright©2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in anycurrent or future media, including reprinting/republishing this material for advertising or promotional purposes, creatingnew collecting works, for resale or lists, or reuse of any copyrighted component of this work in other works.(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2984650 since: 2024-01-09T14:19:14ZIEEEApplication of Advanced Model Reference AdaptiveControl for Bidirectional AC-DC ConvertersMuhammad Ahmed QureshiDip. Energia ”Galileo Ferraris”Politecnico di TorinoTorino, Italymuhammad.qureshi@polito.itSalvatore MusumeciDip. Energia ”Galileo Ferraris”Politecnico di TorinoTorino, Italysalvatore.musumeci@polito.itFrancesco TorelliDip. Ing. Elettrica e dell’InformazionePolitecnico di BariTorino, Italyfrancesco.torelli@poliba.itAlberto ReattiDip. Ingegneria dell’InformazioneUniversity of FlorenceFlorence, Italyalberto.reatti@unifi.itAndrea MazzaDip. Energia ”Galileo Ferraris”Politecnico di TorinoTorino, Italyandrea.mazza@polito.itGianfranco ChiccoDip. Energia ”Galileo Ferraris”Politecnico di TorinoTorino, Italygianfranco.chicco@polito.itAbstractBidirectional AC-DC converters are used in many applications such as renewable energy systems, communication systems,and grid connection of electric vehicles. In this paper, a non-linear controller based on the Lyapunov-based model referenceadaptive control approach is proposed for single-phase bidirectional AC-DC converters that incorporate active power factorcorrection circuits. The proposed controller dynamically adjusts the output power according to the grid conditions and userpreferences while maintaining a nearly unitary power factor and a constant output DC voltage set as the reference value. Theproposed controller also ensures the stability and robustness of the system under various operating conditions and disturbances.The performance of the proposed controller is compared with another Lyapunov-based control proposed in the literature to showthat the proposed controller performs at least on par with the other controller in all aspects.Index TermsPower converter, Model reference, Tracking control, Lyapunov theory, Sensitivity theory, Torelli Control Box, AC-DCConverter, Vehicle to GridI. INTRODUCTIONBidirectional converters are an integral part of many modern-day electronics used in power system applications. They finduses in a multitude of applications, ranging from photovoltaic-based renewable energy systems to the latest grid connection ofelectric vehicles (EVs). For example, recently EVs have become popular as they are considered beneficial for the environmentin many contexts, with various advantages over conventional vehicles, such as lower emissions, lower fuel costs, lowermaintenance costs, and higher efficiency. Under the hood, the power transfer system of the EVs consists of bidirectionalDC-AC converters and DC-DC converters, among other power electronic components.The EVs are also able to contribute to the stability and security of the power grid by providing ancillary services through theiroperation in Vehicle-to-Grid (V2G) mode [1], which enables bidirectional power flow between EVs and the grid. Therefore,EVs can act as distributed energy resources that can supply or absorb power from the grid depending on the grid conditionsand user preferences. The energy flow during the two operations is shown in Fig. 1. When the vehicle is charging, the modeof operation is called Grid to Vehicle (G2V) mode, while the vehicle supports the grid from appropriately operating in theV2G mode.V2G can offer multiple benefits, such as peak shaving, frequency regulation, voltage support, renewable energy integration,and emergency backup [2]. To offer these V2G services, the EVs use bidirectional converters to transfer power from thebattery to the grid and vice versa. This bidirectional transfer of the power still faces some technical issues. One importantchallenge is to overcome the decrease in power quality caused by the non-linear behaviour of the EV chargers. This happensbecause these converters are prone to drawing non-sinusoidal currents from the grid, which can distort the grid voltage andreduce the power factor. This low power factor then leads to higher losses, higher currents, and lower voltage levels in thegrid [3].A typical V2G system consists of a bidirectional AC-DC power converter and a DC-DC power converter as shown in Fig.2. The AC-DC converters used in EV chargers, in addition to converting AC power from the grid to DC power for chargingthe batteries, are also responsible for Power Factor Correction (PFC). Fig. 3 shows a single phase AC-DC power converterusually used in EV chargers. During the charging mode, it acts as a boost rectifier using the controller to maintain the outputvoltage at the reference value, while the DC-DC converter attached to it operates in buck mode. During the discharging mode,the DC-DC converter steps up the output voltage of the battery while AC-DC converter acts as an inverter and controls theactive and reactive power injected into the grid.The controller of the PFC circuit plays a crucial role in improving not only the power quality but also the efficiency of theV2G system. Several linear controllers have been proposed in the literature, such as Proportional Integral Derivative (PID)and linear quadratic based controller for regulating the charging and discharging of electric vehicles (EVs) [4], [5]. Althoughthese controllers can perform adequately, they have a limited range of operation that is confined to a small region near theoperating point. Additionally, these controllers are not robust against external disturbances and uncertainties. Lyapunov-basedcontrollers have also been proposed in the literature [6]–[8]. The sliding mode controllers proposed offer robustness againstuncertainties, however, they suffer from the issue of chattering which results in power losses of the system. An alternative isthe use of higher-order sliding mode control techniques but those require the use of additional integrators or derivatives in thecontrol law, which give rise to additional complexity in their practical implementation.In this paper, a Lyapunov-based model reference adaptive control is applied by using an advanced controller based on theTorelli Control Box (TCB) formulation for a single-phase V2G technology. The system incorporates an active PFC circuit toimprove the power quality and efficiency of EV chargers. The TCB methodology has been previously used for the regulationof DC-DC converters [9] and for maximum power point tracking applications in [10]. Its application to bidirectional convertersis shown in this paper for the first time. The proposed controller can dynamically adjust the output power of the EV chargeraccording to the grid conditions and user preferences, while maintaining a high power factor. The proposed controller alsoensures the stability and robustness of the V2G system under various operating conditions and disturbances.The rest of this paper is organized as follows. Section II presents the system model and assumptions. Section III describes thedesign of the proposed controller and its Lyapunov stability analysis. Section IV shows the simulation results and performanceevaluation of the proposed controller. Section V concludes the paper and indicates future work.Fig. 1. Energy flow direction during V2G and G2V operating modesFig. 2. Block diagram of an Electric Vehicle chargerII. DERIVATION OF THE AC-DC CONVERTER MODELThe scheme of the AC-DC converter is shown in Fig. 3. The full-bridge bidirectional AC-DC power converter works byusing four switches to control the flow of the current between the input source and the output. When the current flows fromthe grid to the DC converter output, the converter shown in Fig. 3 acts as a boost rectifier, increasing the output voltage(Vdc) to be higher than the input source voltage E. The inductor and capacitor are used to filter the grid current and voltagerespectively, to reduce ripples and ensure a smooth and stable output.A. System SchemeThe converter, as shown in Fig. 3 has two switching legs. The switches S1 and S4 are operated in a complementary waywith respect to the switches S2 and S3. The duty cycle u is used by the pulse width modulation (PWM) circuit to generatethe signals as shown in Fig. 4 to operate the switches.Fig. 3. Bidirectional AC-DC converterFig. 4. PWM signal generationDuring the positive half part of the cycle, in the first switching mode, the direction of current flow is shown in Fig. 5 bythe arrows. The starting arrow is shown in green while the switches that are in operation during the first switching mode areshown in blue color. As seen from Fig. 5, the switches S1 and S4 are operational, while the other switches remain off.During the negative half part of the cycle, in the second switching mode, the other pair of switches S2 and S3 are operatedwith a duty cycle, while the switches S1 and S4 are off. The direction of the current flow during this mode is shown in Fig.6.Using the Kirchhoff’s voltage and current laws, following averaged mathematical model of the converter has been derivedin literature [6], [11]: ẋ1 =1L[−x1r − x2(2u − 1) + E]ẋ2 =1C[x1(2u − 1)− Idc](1)where x1 and x2 are the average grid current and the average DC bus voltage, respectively, and u is the duty ratio that isused to generate the PWM signals for the switches.III. CONTROLLER FORMULATION OF THE TCB CONTROL APPROACH FOR THE AC-DC CONVERTERThis paper shows the applications of the technique whose mathematical formulation has been shown in [9] and [10].As mentioned in the above papers, the approach consists of the following three steps. The first step is the generation ofreference values that govern the behavior of the converter parameters. The vector of the state variables is x = { x1, x2},the control variable vector is u = {u}, and the algebraic variable, is y = {yr0}. Here yr0 is the main output variable that isconsidered as variable of interest.In the second step, the coordinates of the equilibrium point in the composite domain (x, u), denoted as (x*, u*), aredetermined. This step is done by setting the derivatives in Equation (1) to zero and, hence, finding the steady-state values ofthe equilibrium point:Fig. 5. Direction of current flow during the first switching mode in the positive half cycleFig. 6. Direction of current flow during the second switching mode in the negative half cyclex∗1 = αEx∗2 = yr0u∗ =E+2yr0−√E21−4Idcryr04yr0(2)where α is given by:α =yr0V 2(−c2ex2C + iDC) (3)This expression has been derived in [6] and establishes the relationship between the desired grid current and the grid voltage.The third step is to design the adaptation mechanism for the minimization of the following tracking errors:ex1 = α1(x1 − x∗1)ex2 = α2(x2 − x∗2)eu = β(u− u∗)(4)Based on Equation (2) and the error vectors defined above, the expression for the control equation becomes:u̇ = −K[dx1duα12(x1 − x∗1) +dx2duα22(x2 − x∗2) + β(u− u∗)](5)where K is the gain factor, with constant value and α1, α2 and β are weights defined for the errors, respectively.The sensitivity parameters s1 = dx1du and s2 =dx2du are calculated based on the converter model given in Equation (1):ṡ1 = −1L(−s1r − 2s2u− 2x2 + s2)ṡ2 =1C(2s1u+ 2x1 − s1)(6)IV. SIMULATION RESULTS FOR THE AC-DC CONVERTERThe simulation for the bidirectional converter has been executed in the Matlab/Simulink environment using the ODE 45solver. The parameters used for the converter and the values of controller gains are given in Table I and Table II. The testbench for the system is shown in Fig. 7.Fig. 7. Test bench setup for controller testingFig. 8. DC load currentFig. 9. DC bus VoltageAs mentioned before, the aim of the controller design is to ensure constant reference voltage tracking of the DC voltageand unitary power factor of the grid voltage and current in face of variations in the load conditions.In each test result, the load current of the converter has been varied as shown in Fig. 8. The load current is kept constant at5 A for time t = 0 to t = 0.4 s, before being increased to 10 A till time t = 0.7 s. At this moment, the load current is steppeddown to -5 A to show the performance of the controller in the reverse mode as well. The large sudden variations in the loadcurrent have been introduced to test the robustness of the controller under stressed conditions.Fig. 9 shows the DC output voltage of the converter with the reference voltage set to 400 V, while Fig. 10 shows the gridcurrent under conditions of variable load current. The starting point for the voltage in the simulation has been set to 350 V toshow the initial fast adaptation to the reference target. Both figures show the effects of sudden variations in the load current.Fig. 10. Grid CurrentFig. 11. Grid Voltage and Grid CurrentAt 0.4 s as the load current requirement is increased, the grid current also increases, but as the load current requirement isreversed the phase of the grid current shifts. This change in phase of the grid current can be better seen in Fig. 11, whichshows that the phase of the grid current is opposite to that of grid voltage after t = 0.7 s.Fig. 12. DC Voltage output comparison of both controllersTABLE ISPECIFICATIONS OF AC-DC CONVERTERDescription of parameters Nominal valueInput voltage, E (RMS) 230 VReference output voltage, Vo 400 VCapacitance, C 3000 uFInductance, L 4.06 mHLoad Current, A 5 ASwitching frequency, fs 10 kHzInductor resistance, RL 0.1 ΩTABLE IICONTROLLER GAINSDescription of parameters Nominal valueTCB Gain, K 0.035α1 3α2 0.5β 7c2 50A. Comparison with other controllersTo judge the performance of the proposed controller, a Lyapunov redesign based controller (LC) proposed in the literature[6] has been replicated. Both controllers were once again subject to the same external disturbances in the load current. TheDC output voltage of both controllers is shown in Fig. 12.As seen in Fig. 12, both controllers perform satisfactorily under the given circumstances. There is no overshoot voltage forboth controllers with almost comparable rise time. For the TCB controller, in the case shown, there is the additional benefitof slightly smaller ripple magnitude. Both controllers have no steady state errors.For the practical implementation of both controllers, the number of sensors required will be the same as both of them needinductor current and output DC voltage as an input. However, the LC control law implemented in [6] requires the use ofderivative of the reference current which can give rise to additional complexity as derivatives of signals can be very sensitiveto noise. The TCB controller does not need information on the derivatives of the signals.V. CONCLUSIONThis paper has presented the application of a Lyapunov-based TCB controller on a bidirectional converter that acts asa single-phase active PFC circuit. The proposed controller can dynamically adjust the output power according to the gridconditions and user preferences while maintaining a high power factor, i.e., voltages and currents remain in phase in thedifferent operational modes.The simulations have been performed in the MATLAB/ Simulink environment. The robustness of the controller has beenthoroughly tested by imposing large and stressful changes in the load current demanded from the AC-DC bidirectional converter.The results show that the proposed TCB controller performs at the same level as the other Lyapunov redesign based controllerproposed in the literature, taken as the benchmark. Overall, exploiting the TCB controller appears a promising approach forimproving the effectiveness of bidirectional converters such as the one considered in this paper. Our findings will be useful forresearchers and practitioners working in the field of electric vehicles and power systems. In future work, the TCB methodologywill be extended to three-phase systems and its performance under different grid conditions will be validated experimentallythrough a hardware in the loop setup.REFERENCES[1] “Electric vehicles – analysis - iea,” International Energy Agency, 2022. [Online]. Available: https://www.iea.org/reports/electric-vehicles[2] M. Yilmaz and P. T. Krein, “Review of the impact of vehicle-to-grid technologies on distribution systems and utility interfaces,” IEEE Transactions onPower Electronics, vol. 28, no. 12, pp. 5673–5689, 2013.[3] M. Bharathidasan and V. Indragandhi, “Review of power factor correction (pfc) ac/dc-dc power electronic converters for electric vehicleapplications,” IOP Conference Series: Materials Science and Engineering, vol. 906, no. 1, p. 012006, aug 2020. [Online]. Available:https://dx.doi.org/10.1088/1757-899X/906/1/012006[4] L. Pan and C. Zhang, “An integrated multifunctional bidirectional ac/dc and dc/dc converter for electric vehicles applications,” Energies, vol. 9, no. 7,2016. [Online]. Available: https://www.mdpi.com/1996-1073/9/7/493[5] K. Sayed and H. A. Gabbar, “Electric vehicle to power grid integration using three-phase three-level ac/dc converter and pi-fuzzy controller,” Energies,vol. 9, no. 7, 2016. [Online]. Available: https://www.mdpi.com/1996-1073/9/7/532[6] A. Rachid, H. EL Fadil, F. Z. Belhaj, K. Gaouzi, and F. Giri, “Lyapunov-based control of single-phase ac–dc power converter for bev charger,” inRecent Advances in Electrical and Information Technologies for Sustainable Development, S. El Hani and M. Essaaidi, Eds. Springer InternationalPublishing, 2019.[7] R. Sabzehgar, Y. M. Roshan, and P. Fajri, “Modelling and sliding-mode control of a single-phase single-stage converter with application to plug-inelectric vehicles,” IET Power Electronics, vol. 12, no. 3, p. 620–626, 2019.[8] G. Mohebalizadeh, H. Alipour, L. Mohammadian, and M. Sabahi, “An improved sliding mode controller for dc/dc boost converters used in ev batterychargers with robustness against the input voltage variations,” International Journal of Industrial Electronics Control and Optimization, vol. 4, no. 2,pp. 257–266, 2021.[9] M. A. Qureshi, S. Musumeci, F. Torelli, A. Reatti, A. Mazza, and G. Chicco, “Application of a novel adaptive control approach for the regulation ofpower converters,” in 2022 57th International Universities Power Engineering Conference (UPEC), 2022, pp. 1–6.[10] M. A. Qureshi, F. Torelli, S. Musumeci, A. Reatti, A. Mazza, and G. Chicco, “A novel adaptive control approach for maximum power-point trackingin photovoltaic systems,” Energies, vol. 16, no. 6, 2023. [Online]. Available: https://www.mdpi.com/1996-1073/16/6/2782[11] I. Ahmed, I. Ahmad, S. Ahmed, and H. M. M. Adil, “Robust nonlinear control of battery electric vehicle charger in grid to vehicle applications,”Journal of Energy Storage, vol. 42, p. 103039, 2021.

Application of Advanced Model Reference Adaptive Control for Bidirectional AC-DC Converters

https://iris.polito.it/bitstream/11583/2984650/2/Inverter_Conference_Paper_26_05_2023.pdf

Application of Advanced Model Reference Adaptive Control for Bidirectional AC-DC Converters

Abstract

Similar works

Full text

Available Versions

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)