# A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation

^{*}

## Abstract

**:**

## 1. Introduction

## 2. SRB Fundamentals

_{min}) between two level changes. In the case of a sinusoidal waveform of period (T) and maximum peak value of the number of levels connected in series (N

_{max}), the steepest part is reached at the zero crossing where TimeStep

_{min}can be estimated from the derivative of the signal, as given by the formula shown in Figure 1.

_{max}reaches 128 and the related minimum time step is then about 25 µs, which corresponds to an equivalent switching frequency of 40 kHz. This frequency can be reduced if more than one level can be switched at each control time step. Note that the battery pack could include additional cells that could be used to provide the maximum voltage output in case of cell failures; therefore, the number of cells could be greater than N

_{max}without affecting TimeStep

_{min}.

_{SRB}). This induces a current exchange approximately proportional to that voltage difference which can reaches 0.5 A/V for a SRB of 128 levels of single 18,650 NMC cells, such as Sony VTC6. Therefore, generating a waveform for charging purpose implies a tight synchronization with the electrical network voltage waveform to avoid any excessive current exchange due to control time delay, as detailed in Section 4.2. The periodic aspect of the electrical network voltage facilitates this control. However, it can present stochastic deformations, which is why a power filtering stage is usually required in existing SRBs to filter out these unpredictable disturbances.

_{1}to t

_{4}according to the reference signal. At time t

_{5}, a fault occurs on cell B, which is associated with the third level. This faulty cell is disconnected and instantly removed from the list of available cells list in the ranking X(t). This ranking gives cell G as the next available cell to be connected in replacement of the faulty cell. At time t

_{6}, the cell ranking X(t) is updated by the balancing algorithm. Cell G, now with rank five, is immediately replaced by cell J that has now rank four. Then cell J is disconnected at t

_{7}when only three levels are required in order to follow the theoretical waveform. At time t

_{8}, only two levels are required and cell C is disconnected as requested by the ranking X(t). At time t

_{9}, only one level is required and the cell D is disconnected. At time t

_{10}, the zero-crossing point of the voltage is reached. The cell A is disconnected and then all cells are bypassed. The negative part of the waveform is generated using the inverter H-bridges distributed on each module containing 4 cells (see Figure 3), while cells are connected successively in the order given by the cell ranking X(t) (cell A first). The following sections show how the CEA has implemented the innovations presented above.

## 3. Hardware Architecture

#### 3.1. Master/Slave Organization

_{out}is the output-to-com voltage of the HF SRB, V

_{N}is the line-to-neutral voltage into which the AC charger voltage comes in and V

_{G}is the generated AC voltage for the battery discharging.

#### 3.2. Communication Buses

#### 3.3. SRB Control Strategy

#### 3.4. Slave Switches’ Choices and Thermal Considerations

#### 3.5. Master

## 4. Software Architecture

#### 4.1. Real Time Architecture

#### 4.2. Nearest Level Control Loop

_{MAX}is the maximum number of series cells that the system can be applied to at the same time (cells added if positive and cells removed if negative) and V

_{cellMax}is the maximum voltage of one cell (4.2V for NMC Lithium battery). The discharge control system (DCS) includes two sub-control loops: a current limit control (CLC) to ensure that I

_{out}amplitude never exceeds I

_{LIMIT}, and a voltage control (VC) to ensure that V

_{out}follows V

_{ref}. The target AC voltage data points, which are obtained by sampling a 230VAC-50 Hz sinusoidal signal at 20 kHz, are stored in a look-up-table (LUT). The latter is then multiplied by a factor α to produce V

_{ref}with 0 ≤ α ≤ 1. α is decreased by CLC to lower V

_{out}when the output current I

_{out}is too high.

_{out}when it lags behind V

_{out}in the case of inductive load. As the derivative function is sensitive to the measurement noises, a low-pass filter (LPF) is added to make it a filtered PID.

_{out}with the same pace and in phase with the charge voltage V

_{N}, while ensuring an instantaneous charge current in phase with voltages V

_{out}and V

_{N}. As a result, the potential reactive power consumed by any inductive components in the system, such as L

_{1}and L

_{2}, will be removed. Hence, the CCS includes three main blocs: a current reference generator (CRG) bloc, a phase control (PC) bloc and a voltage drop control (VDC) bloc. The CRG bloc generates two current reference signals obtained from V

_{N}, and then in phase with it: i

_{ref}is the instantaneous current that I

_{out}should look like (same pace and effective value I

_{EFF}) and i

_{ref^*}is the normalized value of i

_{ref}. The PC bloc determines and controls the delay ∅

_{adv}of the feedback current I

_{out^*}with respect to i

_{ref^*}(simultaneously V

_{N}) to make the charge current and voltage in phase. The LPF is a first-order filter where τ = 100 µs.

_{N}and V

_{out}to keep I

_{out^*}close to i

_{ref}. To obtain ∆V, the control loop estimates the equivalent resistor R

_{eq}between batteries and the AC charger that includes batteries ESR, inductors internal resistance, wire resistance and so on. In practice, V

_{N}is not directly connected to V

_{out}at the start-up of the control system to avoid short-circuiting and damaging the charger and the HF SRB system. The solution is to synchronize V

_{N}and V

_{out}when I

_{out}= 0 A (SW

_{1}off) and to make V

_{N}’s amplitude slightly higher than V

_{out}’s one to allow current flows from AC charger to HF SRB after switching on SW

_{1}. To do this, I

_{out^*}is first equal to the modelled current I

_{outModel}until |∅

_{adv}| < 0.01—the necessary condition to switch on the power relay SW

_{1}—and then uses I

_{out}as a feedback input current.

## 5. Experimental Results

#### 5.1. Cell Balancing

#### 5.2. Waveform Generation

#### 5.3. Efficiency

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Lu, L.; Han, X.; Li, J.; Hua, J.; Ouyang, M. A review on the key issues for lithium-ion battery management in electric vehicles. J. Power Sources
**2013**, 226, 272–288. [Google Scholar] [CrossRef] - Bentley, W.F. Cell balancing considerations for lithium-ion battery systems. IEEE Proc. Annu. Battery Conf. Appl. Adv.
**1997**, 223–226. [Google Scholar] - Baumhöfer, T.; Brühl, M.; Rothgang, S.; Sauer, D.U. Production caused variation in capacity aging trend and correlation to initial cell performance. J. Power Sources
**2014**, 247, 332–338. [Google Scholar] [CrossRef] - Andrea, D. Battery Management Systems for Large Lithium-Ion Battery Packs; Artech House: Norwood, MA, USA, 2010. [Google Scholar]
- Han, W.; Zou, C.; Zhou, C.; Zhang, L. Estimation of Cell SOC Evolution and System Performance in Module-Based Battery Charge Equalization Systems. IEEE Trans. Smart Grid
**2019**, 10, 4717–4728. [Google Scholar] [CrossRef] - Ci, S.; Lin, N.; Wu, D. Reconfigurable Battery Techniques and Systems: A Survey. IEEE Access
**2016**, 4, 1175–1189. [Google Scholar] [CrossRef] - He, L.; Gu, L.; Kong, L.; Gu, Y.; Liu, C.; He, T. Exploring Adaptive Reconfiguration to Optimize Energy Efficiency in Large-Scale Battery Systems. In Proceedings of the 2013 IEEE 34th Real-Time Systems Symposium, Vancouver, BC, Canada, 3–6 December 2013; pp. 118–127. [Google Scholar]
- Davis, A.; Salameh, Z.M.; Eaves, S.S. Evaluation of lithium-ion synergetic battery pack as battery charger. IEEE Trans. Energy Convers.
**1999**, 14, 830–835. [Google Scholar] [CrossRef] - Davis, A.; Salameh, Z.M.; Eaves, S.S. Comparison of a synergetic battery pack drive system to a pulse width modulated AC induction motor drive for an electric vehicle. IEEE Trans. Energy Convers.
**1999**, 14, 245–250. [Google Scholar] [CrossRef] - Genovese, A.; Ortenzi, F.; Villante, C. On the energy efficiency of quick DC vehicle battery charging. World Electr. Veh. J.
**2015**, 7, 540–576. [Google Scholar] - Zheng, Z.; Wand, K.; Xu, L.; Li, Y. A hybrid cascaded multilevel converter for battery energy management applied in electric vehicles. IEEE Trans. Power Electron.
**2014**, 29, 3537–3546. [Google Scholar] [CrossRef] - D’Arco, S.; Quraan, M.; Tricoli, P.; Piegari, L. Low frequency operation of Modular Multilevel Converters with embedded battery cells for traction drives. In Proceedings of the 2016 International Symposium on Power Electronics, Electrical Drives, Automation and Motion, SPEEDAM, Anacapri, Italy, 22–24 June 2016; pp. 1375–1382. [Google Scholar]
- Simone, D.D.; Piegari, L. Integration of stationary batteries for fast charge EV charging stations. Energies
**2019**, 12, 4638. [Google Scholar] [CrossRef] [Green Version] - Akagi, H.; Maharjan, L. A battery energy storage system based on a multilevel cascade PWM converter. In Proceedings of the 2009 Brazilian Power Electronics Conference, Bonito-Mato Grosso do Sul, Brazil, 27 September–1 October 2009; pp. 9–18. [Google Scholar]
- Quraan, M.; Yeo, T.; Tricoli, P. Design and Control of Modular Multilevel Converters for Battery Electric Vehicles. IEEE Trans. Power Electron.
**2016**, 31, 507–517. [Google Scholar] [CrossRef] - Gao, F.; Gu, X.; Ma, Z.; Zhang, C. Redistributed Pulsewidth Modulation of MMC Battery Energy Storage System under Submodule Fault Condition. IEEE Trans. Power Electron.
**2020**, 35, 2284–2294. [Google Scholar] [CrossRef] - Han, W.; Wik, T.; Kersten, A.; Dong, G.; Zou, C. Next-Generation Battery Management Systems: Dynamic Reconfiguration. IEEE Ind. Electron. Mag.
**2020**, 14, 20–31. [Google Scholar] [CrossRef] - Simone, D.D.; Piegari, L.; D’Arco, S. Comparative Analysis of Modulation Techniques for Modular Multilevel Converters in Traction Drives. In Proceedings of the 2020 IEEE 14th International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG), Setubal, Portugal, 8–10 July 2018; pp. 593–600. [Google Scholar]
- Kraus, D.; Specht, E.; Merz, T.; Hiller, M. Optimized Real-Time Control for Modular Multilevel Converters using Adaptive Neural Networks. In Proceedings of the 2019 21st European Conference on Power Electronics and Applications (EPE ’19 ECCE Europe), Genova, Italy, 3–5 September 2019. [Google Scholar]
- Kim, H.; Shin, K.G. On Dynamic Reconfiguration of A Large-Scale Battery System. In Proceedings of the 2009 15th IEEE Real-Time and Embedded Technology and Applications Symposium, San Francisco, CA, USA, 13–16 April 2009; pp. 87–96. [Google Scholar]
- Kim, H.; Shin, K.G. DESA: Dependable, efficient, scalable architecture for management of large-scale batteries. IEEE Trans. Ind. Inform.
**2012**, 8, 406–417. [Google Scholar] [CrossRef] [Green Version] - Morstyn, T.; Momayyezan, M.; Hredzak, B.; Agelidis, V.G. Distributed Control for State-of-Charge Balancing Between the Modules of a Reconfigurable Battery Energy Storage System. IEEE Trans. Power Electron.
**2016**, 31, 7986–7995. [Google Scholar] [CrossRef] - Gao, Z.; Lu, Q. A Hybrid Cascaded Multilevel Converter Based on Three-Level Cells for Battery Energy Management Applied in Electric Vehicles. IEEE Trans. Power Electron.
**2019**, 7326–7349. [Google Scholar] [CrossRef]

**Figure 8.**Cells balancing of HF SRB on direct charge with electrical grid (

**a**); the master and one slave unit (

**b**); and control process period (

**c**).

**Figure 9.**HF SRB 230Vac 50Hz experimental waveforms discharging on a resistive load (

**a**) and direct charging on the electrical grid at 280 Wrms (

**b**).

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Thomas, R.; Despesse, G.; Bacquet, S.; Fernandez, E.; Lopez, Y.; Ramahefa-Andry, P.; Cassarino, L.
A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation. *World Electr. Veh. J.* **2021**, *12*, 8.
https://doi.org/10.3390/wevj12010008

**AMA Style**

Thomas R, Despesse G, Bacquet S, Fernandez E, Lopez Y, Ramahefa-Andry P, Cassarino L.
A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation. *World Electric Vehicle Journal*. 2021; 12(1):8.
https://doi.org/10.3390/wevj12010008

**Chicago/Turabian Style**

Thomas, Rémy, Ghislain Despesse, Sylvain Bacquet, Eric Fernandez, Yan Lopez, Prince Ramahefa-Andry, and Léandro Cassarino.
2021. "A High Frequency Self-Reconfigurable Battery for Arbitrary Waveform Generation" *World Electric Vehicle Journal* 12, no. 1: 8.
https://doi.org/10.3390/wevj12010008