A High-Voltage Gain Non-Isolated DC–DC Converter Designed for Bipolar DC Microgrids

Abstract

DC microgrids are now starting to attract huge attention from researches and engineers. Among the several DC microgrid architectures, bipolar DC microgrids are advantageous to accommodate a wider range of DC loads. However, due to mismatched loads connected to the two poles, bipolar DC microgrids may show voltage balancing issues. In this context, this article presents a new high input-to-output voltage gain, non-isolated DC–DC converter specifically designed for bipolar DC Microgrids. The proposed converter supports the balance of voltages at both bipolar DC microgrid poles, as the converter can transfer energy between the two poles in an unbalanced way. The description, theoretical support, and operation of the proposed converter will be presented. The theoretical assumptions will be complemented with several results obtained from computer simulation tests. The simulation tests will be compared to laboratory results from an experimental prototype. The obtained results confirm the theoretical properties of the proposed converter.

Keywords:

• bipolar DC microgrid
• voltage unbalance
• DC–DC converters
• voltage balancer
• high gain

1. Introduction

Electrical infrastructures, especially at low voltage (LV), are facing a paradigm change. In fact, now instead of always using the classical AC grid, engineers have started to consider using DC grids (or microgrids) [1–5]. DC grids present strong advantages over the classical AC grids, such as increased efficiency, no reactive power, and higher power transfer capability [6–9]. In particular, the bipolar microgrid architecture provides two symmetrical DC voltages (+V, –V) and presents several advantages over most of the unipolar DC microgrid architectures [10–13], namely the possibility to fed a broader range of power loads. Nevertheless, a bipolar microgrid may present a significant disadvantage related to the unbalance of the absolute values of the voltages in the positive (+V) and negative (–V) poles. This unbalance may be originated by asymmetries in the loads, generators, and storage systems connected to the two DC poles. For example, typical PV generators use a single input, single output DC–DC converter, therefore, feeding only one of the bipolar microgrid poles. Even if there are two PV generators, each one feeding its own DC microgrid pole, to avoid pole voltage unbalances, each PV generator must inject the exact energy needed for pole voltage balancing, considering the loads at each pole, therefore, impairing the PV generators maximum renewable power transfer capability. Hence, specifically designed DC–DC microgrid converters able to eliminate or mitigate microgrid pole unbalance issues are welcome.

Unbalance issues in bipolar DC microgrids can be mitigated through careful balancing over time, the power distribution among the two poles of devices, like generators, storage systems, and loads [14, 15]. However, due to random variations in consumption and renewable generation, it is difficult, without using extra power converters, to ensure that the number of connected devices and their powers are such that the net power in both poles is exactly balanced over time. Therefore, the simple static equalizing balancing strategy will not ensure the balance of a bipolar DC microgrid as the number and power of loads and renewable generators change stochastically. A better strategy to balance the two voltages of bipolar DC microgrid poles uses an extra power electronic converter called a voltage balancer (VB) [16–18]. A VB converter allows transferring the energy from one pole to the other pole, dynamically ensuring the balance of the two bipolar DC microgrid poles. However, besides the extra cost of the VB converter, it also introduces additional power losses. A third strategy to address the unbalance issue is to change the type of DC–DC converter used in generators like photovoltaic and/or fuel-cells. Instead of using the usual single-input single-output DC–DC converter, a multiport (single-input dual-output) DC–DC converter is devised. The multiport converter must be designed to transfer the energy as a function of the pole voltage unbalance [19–25]. Thus, if the bipolar DC microgrid is balanced, supposing unbalanced loads, then, the energy must be transferred to the positive and negative poles in an unbalanced way. Otherwise, the multiport converter should transfer most of the energy to the pole with lower absolute voltage value.

Not many multiport converter topologies have been proposed for this type of bipolar DC microgrids, the subject still being a new area under study. As photovoltaic panels and fuel-cells present relatively low output voltage values, usually DC–DC converters processing the output power of these generators must have voltage boost characteristics [26–30]. Consequently, the majority of the proposed topologies for bipolar DC microgrids are boost type converters. Additional features related to boost converters are galvanic isolation and high input-to-output voltage gain. Several high gain topologies based on high frequency transformers were proposed [31–33]. However, transformer isolation presents some disadvantages like lower efficiency and core saturation issues. Thus, several proposals were made to use topologies without high frequency transformers. Some of these topologies are characterized by a typical boost feature, with the standard Boost DC–DC converter static input-to-output voltage gain or the double considering pole to pole voltage [34–37]. However, although under the theoretical point of view the boost voltage gain can be very high, in practice due to the losses and voltage drops the standard boost presents a very limited voltage gain (<5). This limitation led to the proposal of several converters with extended static input-to-output voltage gains [38–43]. Nevertheless, the high majority of the proposed converters with extended voltage gains are not well suited for bipolar DC microgrids since they have only a single output. Nevertheless, some extended gain converters were designed for two outputs and with the capability to operate in different conditions to support the balance of the microgrid. An interleaved Boost converter with Greinacher voltage multiplier cells was revealed in Ref. [44]. A topology with an additional inductor added to a conventional three-level-boost converter was disclosed in Ref. [45]. Another topology based on a boost converter integrated with a bipolar Dickson voltage multiplier was proposed in Ref. [46]. A converter that allows for some extended voltage gain was also presented in work [47]. An extended gain topology with continuous input current was also proposed in Ref. [48]. However, some limitations of the aforementioned topologies include relatively high losses, discontinuous input current, high number of active semiconductor switches, or many passive components, especially inductors.

Regarding the importance of the development of DC–DC converters suited to address the unbalance issue of bipolar DC microgrids, this article proposes a new converter topology with capability to support the voltage balance of bipolar DC microgrids. The proposed self-balance dual output (SBDO) converter is characterized by high static input–output voltage gain, as well as, continuous input current (Section 2). The proposed self-balance dual output converter, developed aiming to reduce the number of passive components, is designed in Section 3. To show the claimed features and theoretical assumptions, the article includes several tests carried out by computer simulations (Section 4) and by a laboratory prototype (Section 5).

2. Proposed DC–DC SBDO Converter for Bipolar DC Microgrids

To mitigate voltage unbalances between the positive and negative poles of a DC bipolar microgrid, DC–DC power electronic converters, fed from PV panels or fuel cells, should have continuous input current and dual outputs to supply a bipolar DC microgrid. Taking into consideration these requirements, the new DC–DC power electronic SBDO converter topology is proposed, as shown in Figure 1. The SBDO converter has a single inductive input for continuous input current and a double voltage source output to allow the transfer of the input power to the two poles of the bipolar DC microgrid in a balanced or unbalanced way. This feature contributes to the microgrid pole voltage balance. The proposed SBDO converter also features a boost characteristic with high input-to-output voltage gain.

FIGURE 1. Topology of the DC–DC SBDO converter designed to support the balancing of bipolar DC microgrids.

For continuous input current, the proposed topology must operate in the continuous conduction mode (CCM). In CCM, if the two switches (S₁ and S₂) operate synchronously, that is, when S₁ is in the ON state S₂ is also in the ON state and vice-versa, the SBDO converter has only two operation modes, as described hereafter:

• First operation mode - Mode 1 - (switches S₁ and S₂ ON, t₀–t₁): During the time span where both switches are ON (Figure 2(a)), inductor L will receive energy from the DC source (e.g., PV panel), aided by the discharge of capacitor C₁ in series with said DC source via S₁ and S₂. If the absolute value of the negative pole voltage V_o2 is smaller or equals the capacitor C₂ voltage V_C2, then, some energy from capacitor C₂ will be transferred to the negative pole capacitor C_o2, via S₂ D₅, up to the equilibrium of these two capacitor voltages. Therefore, the negative pole voltage V_o2 is linked to the capacitor C₂ voltage V_C2, except if |V_o2|> V_C2. In this case, there is no energy transfer from capacitor C₂, up to the moment where the discharge of C_o2 will lead to V_C2>|V_o2|.

• Second operation mode - Mode 2 - (both switches OFF, t₁–T): During this time span both switches are OFF (Figure 2(b)). In Mode 2, the energy stored in inductor L can be transferred, via D₁, to capacitor C₁, to capacitor C₂ and to the output positive pole capacitor C_o1, via diodes D₂, D₃, and D₄, respectively. These three capacitors are connected in parallel through the diodes. Therefore, the positive pole voltage V_o1 is linked to the capacitor C₂ voltage V_C2, except if V_o1 > V_C2. In this case, there is no energy transfer from capacitor C₂ to capacitor C_o1, until V_o1 < V_C2.

FIGURE 2. First (a) and second (b) operation modes of the SBDO converter designed to be used in bipolar DC microgrids.

The proposed SBDO converter addresses the voltage balancing issues of bipolar DC microgrids in the following ways:

• In Mode 1, if |V_o2| > V_C2 no power is transferred from C₂ to C_o2, until C_o2 is sufficiently discharged, therefore, promoting |V_o2| ≈ V_C2;

• In Mode 2, if V_o1> V_C2 no power is transferred to C_o1, until C_o1 is sufficiently discharged, therefore, promoting V_o1 ≈ V_C2;

• if |V_o2|> V_C2 power is only transferred to the positive pole (during Mode 2);

• if V_o1> V_C2 power is only transferred to the negative pole (during Mode 1);

• if |V_o2| ≈ V_o1 ≈ V_C2 power is transferred to the positive pole during Mode 2 and to the negative pole during Mode 1.

The combined effect of the two modes gives |V_o2| ≈ V_o1 ≈ V_C2, therefore, self-eliminating voltage unbalances in the bipolar microgrid.

Regarding the typical waveforms (Figure 3) associated to the proposed SBDO converter, it can be seen that the current in inductor L, i_L, rises during Mode 1 and decreases during Mode 2, being i_L(t) > 0 to guarantee operation in CCM. The current variation can be made small enough for the PV or fuel-cell generator optimum operation by designing the inductance value for a given switching frequency. The microgrid output voltages |V_o2|, V_o1, and capacitor voltage V_C2 are nearly constant and show nearly equal average values. The voltages at the terminals of the active semiconductors V_S1, V_S2, and diodes V_D1, V_D2, V_D3, V_D4, and V_D5, show semiconductors have to sustain only half of the total output voltage.

FIGURE 3. Current and voltage waveforms associated to the CCM of the proposed SBDO converter to be used in bipolar DC microgrids.

To determine the static input-to-output voltage gain, steady-state is considered at nearly constant capacitor voltages to apply the inductor volt-second balance principle. The inductor average voltage is zero in steady-state. Considering the duty cycle δ of both switches, (being δ = (t₁/T)), the average value of the inductor voltage is: (1) $$V_{\mathit{Lav}}=0=\frac{1}{T}\left[\underset{0}{\overset{\delta T}{\int }}\left(V_i+V_{C1}\right)dt+\underset{\delta T}{\overset{T}{\int }}\left(V_i-V_{C1}\right)dt\right]\Rightarrow V_{C1}=V_i\frac{1}{1-2\delta }$$(1)

From Mode 2, it is concluded that V_C2 ≈ V_C1 and V_o1 ≈ V_C2. From Mode 1, it is concluded that |V_o2| ≈ V_C2. Therefore, V_o1 ≈ |V_o2| ≈ V_C1: (2) $$V_{o1}\approx \left|V_{o2}\right|\approx V_i\frac{1}{1-2\delta }$$(2)

The total static input-to-output voltage gain of the proposed SBDO converter, it is given by: (3) $$V_o=V_{o1}-\left(-V_{o2}\right)\approx V_i\frac{2}{1-2\delta }$$(3)

From the static input-to-output voltage gain of the SBDO converter given in (3)(3) $$V_o=V_{o1}-\left(-V_{o2}\right)\approx V_i\frac{2}{1-2\delta }$$(3) , it is seen that the SBDO converter allows a relatively high gain. Figure 4 presents a comparison of the static input-to-output voltage gain of the SBDO converter regarding the classical Boost, the dual Boost, and the Z-source converter.

FIGURE 4. Comparison of the static input-to-output voltage gain function of the duty cycle between the classical Boost, the dual Boost, the Z-source converter, and the proposed SBDO converter.

3. Design of the SBDO Converter

The design of the SBDO converter assumes the CCM operation, ideal semiconductor devices and circuit components together with the relationships presented in the previous section.

As the SBDO converter is assumed to be conservative, the input power equals the output power. Therefore, the inductor current average value is expressed by (9)(9) $$C_2=C_3=\frac{t_2{I}_{C_2}}{\Delta V_{C_2}}=\frac{\left(1-\delta \right)I_o}{f_s\Delta V_{C_2}}$$(9) . (4) $$V_i{I}_L=V_o{I}_o=\frac{2}{1-2\delta }{V}_i{I}_o\Rightarrow I_L=\frac{2}{1-2\delta }{I}_o$$(4)

The design of the inductor and capacitors will take into consideration the rated voltages and current in these components, as well as, the limitation of the ripples of the current in the inductor and of the voltage in the capacitors. Considering expressions (1)(1) $$V_{\mathit{Lav}}=0=\frac{1}{T}\left[\underset{0}{\overset{\delta T}{\int }}\left(V_i+V_{C1}\right)dt+\underset{\delta T}{\overset{T}{\int }}\left(V_i-V_{C1}\right)dt\right]\Rightarrow V_{C1}=V_i\frac{1}{1-2\delta }$$(1) and (5)(5) $$L=\frac{t_1\left(V_i+V_{C_1}\right)}{\Delta I_L}=\frac{\delta \left(1-\delta \right)V_i}{\left(1-2\delta \right)f_s\Delta I_L}$$(5) , the condition to size the inductance is: (5) $$L=\frac{t_1\left(V_i+V_{C_1}\right)}{\Delta I_L}=\frac{\delta \left(1-\delta \right)V_i}{\left(1-2\delta \right)f_s\Delta I_L}$$(5)

To size the capacitances, the rate of change of the capacitor voltage (6)(6) $$\frac{\Delta v_C}{\Delta t}=\frac{i_C}{C}$$(6) is assumed to be proportional to the capacitor current. Then, the equations to size the capacitances C_o1 = C_o2, C₁, C₂ = C₃, are given by (7)(7) $$C_{o1}=C_{o2}=\frac{t_1{I}_o}{\Delta V_{C_{o1,o2}}}=\frac{\delta I_o}{f_s\Delta V_{C_{o1,o2}}}$$(7) , (8)(8) $$C_1=\frac{t_1{I}_{C_1}}{\Delta V_{C_1}}=\frac{2\delta I_o}{\left(1-2\delta \right)f_s\Delta V_{C_1}}$$(8) , and (9)(9) $$C_2=C_3=\frac{t_2{I}_{C_2}}{\Delta V_{C_2}}=\frac{\left(1-\delta \right)I_o}{f_s\Delta V_{C_2}}$$(9) , respectively. (6) $$\frac{\Delta v_C}{\Delta t}=\frac{i_C}{C}$$(6) (7) $$C_{o1}=C_{o2}=\frac{t_1{I}_o}{\Delta V_{C_{o1,o2}}}=\frac{\delta I_o}{f_s\Delta V_{C_{o1,o2}}}$$(7) (8) $$C_1=\frac{t_1{I}_{C_1}}{\Delta V_{C_1}}=\frac{2\delta I_o}{\left(1-2\delta \right)f_s\Delta V_{C_1}}$$(8) (9) $$C_2=C_3=\frac{t_2{I}_{C_2}}{\Delta V_{C_2}}=\frac{\left(1-\delta \right)I_o}{f_s\Delta V_{C_2}}$$(9)

The previous assumptions will also be used to determine the power semiconductor ratings. The power semiconductors (transistors and diodes) current ratings will be given by expressions (10)(10) $$I_{S_1}=I_{S_2}=\left(\frac{4\delta }{1-2\delta }+\frac{1}{\delta }\right)I_o$$(10) to (13)(13) $$I_{D_5}=\frac{1}{\delta }{I}_o$$(13) . (10) $$I_{S_1}=I_{S_2}=\left(\frac{4\delta }{1-2\delta }+\frac{1}{\delta }\right)I_o$$(10) (11) $$I_{D_1}=\left[\frac{4\left(1-\delta \right)}{1-2\delta }+\frac{1}{1-\delta }\right]I_o$$(11) (12) $$I_{D_2}=I_{D_3}=I_{D_4}=\frac{1}{1-\delta }{I}_o$$(12) (13) $$I_{D_5}=\frac{1}{\delta }{I}_o$$(13)

The power semiconductors voltage ratings are estimated neglecting the voltage ripple in the capacitors. The minimum voltage capability required for each power semiconductor is given by expressions (14)(14) $$V_{S_1}=V_{S_2}=V_{D_1}=V_{D_2}=V_{D_4}=V_{C_{o1}}=\frac{V_o}{2}$$(14) and (15)(15) $$V_{S_2}=V_{D_4}=V_{C_{o1}}=\frac{V_o}{2}$$(15) . (14) $$V_{S_1}=V_{S_2}=V_{D_1}=V_{D_2}=V_{D_4}=V_{C_{o1}}=\frac{V_o}{2}$$(14) (15) $$V_{S_2}=V_{D_4}=V_{C_{o1}}=\frac{V_o}{2}$$(15)

4. Simulation Results

This section presents some simulation results of the proposed DC–DC SBDO converter using the MATLAB/Simulink software. The proposed SBDO converter component values for capacitors are C_o1 = C_o2 = 470 µF, C₁ = C₂ = 48 µF and for inductor L = 600 µH. The SBDO converter is supplied by a single DC voltage source of 48 V_DC and the output of the bipolar DC microgrid was adjusted through the duty cycle to obtain ±170 V_DC, which is a quite common voltage for bipolar DC microgrids. The switching frequency selected was 20 kHz and the initial load was considered to equal 140 Ω in each pole. The operation mode of the DC–DC SBDO converter was tested in CCM and steady-state. The first simulation result presents the input and output voltages of the SBDO converter (Figure 5(a)) showing the obtained voltage gain from 48 V_DC to 340 V_DC (total voltage). Figure 5(b) shows the voltage over the power devices with a switching frequency of 20 kHz and a duty-cycle of 0.36. This figure shows that the maximum hold-off voltage in each power device is around 170 V. The input current (see Figure 5(c)) in the inductor L of the SBDO converter shows the CCM operation at an average value around 15 A. The nearly 7 A peak-to-peak ripple allows expecting CCM operation of the SBDO converter down to nearly 3.5 A input inductor averaged current.

FIGURE 5. Results obtained by simulation of the SBDO converter designed for the bipolar DC microgrid: (a) voltages of the input source and SBDO converter output; (b) voltages over transistors S₁ and S₂; (c) input current of the proposed SBDO converter.

The capability of the proposed SBDO converter to support the bipolar DC microgrid voltages with unbalanced loads was evaluated creating a simulated transient test. Prior to the transient test, the microgrid was balanced (considering the same load in each pole). After t = 1.2 msec the load of the negative pole changed from 140 Ω to 100 Ω, resulting in a current increment as can be seen in Figure 6(a). This figure shows that only the output current (I_o2) associated to the negative pole increases while the current of the positive pole (I_o1) remains constant. Figure 6(a) confirms that the positive output voltage average value is not affected by the unbalance in the negative pole load, as the average values of |V_o2| ≈ V_o1 do not change significantly, in spite of the shown transient in the instantaneous pole voltages to accommodate the load unbalance. This confirms that the operation of the SBDO converter allows more energy transfer for the pole that most requires it.

FIGURE 6. Results obtained by simulation of the SBDO converter designed for the bipolar DC microgrid when there is a suddenly change in the load connected to the negative pole: (a) Output currents of the proposed SBDO converter and (b) voltages across capacitors C₁ and C₂.

5. Experimental Results

This section presents some experimental tests and obtained results using a laboratory prototype. These experiments tests were made using components with similar values to those presented in the simulation section. All the tests were executed with a duty-cycle providing CCM operation.

Similarly to the simulation tests, the first experimental test was performed in steady state conditions and balanced loads in the bipolar DC microgrid. The obtained voltage gain can be seen in Figure 7(a). Considering an input voltage of 48 V_DC, it was obtained a total output voltage over 340 V_DC which demonstrates the high input-to-output voltage gain of the proposed SBDO converter. Similarly, the voltage over the power devices and input current can be seen in Figures 7(b) and 7(c). Observing these results it is possible to conclude that they are similar to those shown in the simulation and with agreement with the theoretical analysis.

FIGURE 7. Results obtained through laboratory tests of the SBDO converter designed for the bipolar DC microgrid: (a) voltages of the input source and SBDO converter output; (b) voltages over transistors S₁ and S₂; (c) input current of the proposed SBDO converter.

An experimental transient analysis was also made to demonstrate the proposed SBDO converter capability to support unbalanced loads in the bipolar DC microgrid. In the beginning of this second experimental test, the loads connected to the two microgrid DC poles were nearly equal to obtain balanced operation. Then, after some time, in the microgrid negative pole an additional resistive load was manually switched on to create an unbalanced condition. Figure 8(a) shows the abrupt increase in the negative DC pole current at the instant in which the load was switched on. As the added load is resistive almost no current establishing transient can be seen. After the fast transient mode the input current stabilizes around a higher average value. Conversely, the current in the positive remains constant, which indicates that the positive output voltage is not affected by the unbalance in the negative pole load. This demonstrates that a load change in one DC pole, does not affect the other pole, implying only current variations in the pole current itself and in the SBDO converter input current. Figure 8(b) also shows the transient behavior of the SBDO converter voltages to load variation, which present dynamics with acceptable transient response.

FIGURE 8. Results obtained through laboratory tests of the SBDO converter designed for the bipolar DC microgrid when there is a suddenly change in the load connected to the negative pole: (a) Output currents of the proposed SBDO converter and (b) voltages across capacitors C₁ and C₂.

6. Conclusions

This work addressed the problem of bipolar microgrids voltage unbalance, through the proposal of a new self-balance dual output converter to be powered from photovoltaic panels or fuel cells. The proposed SBDO converter presents boost characteristics with high input-to-output voltage gain, continuous input current, and dual complementary output. Since in bipolar DC microgrids voltage unbalances between their poles may appear, mainly due to load unbalance, the proposed SBDO converter allows to transfer of energy to the dual output in a balanced or unbalanced way. If the voltage absolute value at one of the poles is lower than the voltage at the other pole, then the SBDO converter will only transfer energy to the pole with the lower voltage helping to achieve the microgrid balance. Another characteristic of the SBDO converter is that it uses only two active switches that operate synchronously. Besides the description of the operation of the proposed SBDO converter, the article also presented the design of the topology. To confirm the referred characteristics of the proposed SBDO converter, several tests were performed. These tests were made in two different ways, namely through computer simulations and using a laboratory prototype. The results obtained in simulations and in the laboratory confirmed the important SBDO converter feature to correctly operate in balanced or unbalanced load conditions. In fact, when the DC microgrid was balanced, the SBDO converter delivered the energy in a balanced way to the positive and negative poles. However, when the microgrid was unbalanced, the results showed that the energy was only transferred to the pole with the voltage with a lower absolute value. The shown results confirm the suitability of the SBDO converter to be used in bipolar DC microgrids.

Additional information

Funding

This work was supported by national funds through FCT – Fundação para a Ciência e a Tecnologia, under project UIDB/50021/2020 and UIDB/00066/2020.

Notes on contributors

Vitor Fernão Pires

Vitor Fernão Pires received the B.S. degree in Electrical Engineering from Institute Superior of Engineering of Lisbon, Portugal, in 1988 and the M.S. and Ph.D. Degrees in Electrical and Computer Engineering from Technical University of Lisbon, Portugal, in 1995 and 2000, respectively. Since 1991 he is a member of the teaching staff at Electrical Engineering Department of Superior Technical School of Setúbal – Polytechnic Institute of Setúbal. Presently he is a Professor, teaching Power Electronics and Control of Power Converters. He is also researcher at Instituto de Engenharia de Sistemas e Computadores, Investigação e Desenvolvimento em Lisboa (INESC-ID). His work has resulted in more than 300 publications. His present research interests include the areas of power-electronic converters, fault diagnosis and fault tolerant operation, renewable energy, electrical vehicles, electrical drives, and power quality.

Armando Cordeiro

Armando Cordeiro was born in Portugal in 1976, received his B.S. degree in Electrical Engineering from Instituto Superior de Engenharia de Lisboa in 1999. He received the M.Sc. and Ph.D. degrees in Electrical Engineering from IST, Technical University of Lisbon, in 2004 and 2015, respectively. His research interests include power electronics, variable speed drives, automation systems and electrical vehicles. He is also professor at the Department of Electrical Engineering and Automation of Instituto Superior de Engenharia de Lisboa for the area of Automation since 2006. His present research interests include the areas of power-electronic converters, industrial automation and robotics.

Daniel Foito

Daniel Foito received the Dipl. Ing. and M.S. degrees in electrical engineering from Instituto Superior Técnico, Technical University of Lisbon, Lisbon, Portugal in 1993 and 2002, respectively. He received Ph.D. degrees in electrical engineering from Faculty of Sciences and Technology, Universidade Nova de Lisboa, Portugal in 2015. Since 1997 he is a member of the teaching staff at Electrical Engineering Department of Superior Technical School of Setúbal – Polytechnic Institute of Setúbal. Presently he is a Adjoint Professor, teaching Power Electronics and Electric Drives. His research interests include renewable energy generation, electrical machines, electric drives, electric vehicle, fault diagnosis and fault tolerant operation.

José Fernando Silva

José Fernando Silva was born in Monção Portugal in 1956. He received the Dipl. Ing. in electrical engineering (1980) and the Doctor degree in electrical and computer engineering (power electronics and control) in 1990, from Instituto Superior Técnico (IST), Universidade Técnica de Lisboa (UTL), Lisbon, Portugal. He is a full professor of Power Electronics and Energy Storage in the scientific area of Energy, Department of Electrical and Computer Engineering of Instituto Superior Técnico (IST), Universidade de Lisboa (UL). He is senior researcher at Instituto de Engenharia de Sistemas e Computadores - Investigação e Desenvolvimento em Lisboa (INESC-ID) and currently the leader of the Research Line Energy Systems and the leader of the research group Power Electronics and Power Quality. He is IEEE Senior Member since 2001, Associate Editor of IEEE Transactions on Industrial Electronics from 2000 to 2019, member of the Industrial Electronics Magazine editorial board since 2010, and a member of the Portuguese Engineering Society. His research interests include electric power components and systems.