Five-phase induction motor drive for electric vehicle with high gain switched-inductor quasi impedance source inverter

Received Jul 19, 2021 Revised Jan 25, 2022 Accepted Feb 1, 2022 Switched-inductor quasi-impedance source inverter (SL-qZSI) with high gain fed five-phase induction motor drive for electric vehicle (EV) applications is proposed in this paper. Multi-phase electric machines have been predicted for application where the entire system should have better reliability and demanded power per phase is low especially for autonomous applications like EVs. To supply variable voltage and frequency to multiphase machines, multi-phase inverters are required. SL-qZSI offers enhanced boost capability with respect to traditional impedance source converters by inserting three diodes and only one inductor to the basic quasiimpedance source inverter (qZSI). Also, SL-qZSI offers withstanding capability during voltage dip results line harmonics are diminished; enhances reliability of inverter; and extended output voltage range. The key idea of this paper is to design and develop a high performance and highly reliable SL-qZSI fed five-phase Induction Motor drive and validate the proposed system depends on results of Simulation with the help of MATLAB; these findings were comparable to the similar type of existing converters. We can notice from the performance analysis of the proposed system that it can provide enhanced voltage boosting capability and proved that it has significant potential for the suggested multi-phase variable speed drive (VSD) system.


INTRODUCTION
In the past few years, the benefits offered by the three-phase induction motor made it apt for the application of adjustable speed drive (ASD) [1]. Nevertheless, the perturbed operation of the three-phase machine has to be taken into account during the faulty condition. In such situation modification of hardware for the drive system is expensive [2]. These days, the focus is grabbed by multi-phase induction motors (IM) because of their added benefits compared to the deep-rooted three-phase machines [3]. Benefits offered by it are better torque density, reduced power rating of switches, decreased pulsations in torque, improved efficiency, harmonics get reduced in DC link current, [4]− [5]. The most attractive feature of multi-phase motor is inherent fault-tolerant capability without any requirement of extra hardware [6]. Hence multi-phase machines are employed in applications where the requirement of high power and safety is essential such as ship propulsion, electric vehicle (EV), electric aircraft, hybrid electric vehicles (HEVs) [7], [8].  Babu) 413 Therefore, the paper attempts to fill the gap by investigating the five-phase induction motor driven by the SL-qZSI. This paper aims to unite the benefits of both the SL-qZSI and five-phase machines. The suggested five-phase VSD system driven by the SL-qZSI provides improved reliability and transient response, efficiency. The results obtained from the simulation are evaluated for assessing the system performance. Here, the paper introduces an innovative high gain switched-inductor quasi impedance source inverter (SL-qZSI) fed five-phase IM drive suitable for EV that fulfills nearly all of the aforesaid features. In the section 2, described the proposed system, the simulation results are presented and analyzed in section 3. Conclusion of this effort is presented in section 4.

PROPOSED SL-qZSI FED INDUCTION MOTOR 2.1. Modeling of five-phase phase induction motor
Consider the phase angle displacement between any two adjacent phases of a five-phase IM. The below assumptions are taken into account for deriving a mathematical model of a five-phase machine. − In a winding, the MMF produced is distributed sinusoidal along the diameter of the air gap. − The air gap is constant. − The saturation of the main flux can be ignored since the iron core has a linear B-H curve. − Iron core losses can be ignored. − Resistance and inductance of the winding are constant.
In accordance with the winding transformation ratio, assuming that rotor winding is talk about the stator winding. Flux linkage, rotor, and stator voltage equations are conveyed as: The voltage, current, flux linkages in (1) and (2) can be defined as: Stator and rotor inductance matrices are given as: Mutual inductance matrix is given by: ' 'represents the instantaneous location of the rotor phase 'a' magnetic axis regarding the stator phase 'a' magnetic axis. In five-phase IM, the matrices of rotor and stator resistances are diagonal in nature, and their order is 5 × 5.
Decoupling transformation: to obtain a simplified model, for eliminating the variation of inductances with respect to time, a coordinate conversion is applied. Power invariant form of co-ordinate conversion is employed. Thus, the transformation matrix is applied to five-phase winding of the stator.
Where a transformation matrix of power invariant form is chosen in order that ̱ −1 = ̱ . The decoupling transformation matrix is given as: Machine model in a standard arbitrary reference frame: Flux linkage is shown in (12): Here again Lm= (n/2) M.
Under the transformation mechanical equations of rotor motion is constant and is given by (14).
Where, 'P' is the number of poles in machine and 'J' is inertia.

Operation of SL-qZSI [24]
The power topology of the introduced SL-qZSI fed five-phase IM drive system is appeared in Figure 1. SL-qZSI contains three inductors (viz., L1, L2, & L3), four diodes (viz., Din, D1, & D2), and two capacitors (viz., C1&C2). Switched Inductor cell comprises of L2, L3, D1, D2, &D3. In contrast to SL-ZSI topology, inrush current flow is eliminated in SL-qZSI topology, since the current flowing through the principle circuit is zero during the start-up; nevertheless, in SL-qZSI the capacitors and inductors still resonate. When compared to the traditional continuous current qZSI, the boost factor in SL-qZSI is enhanced from 1/(1-2D) to (1+ D)/(1−2D−D 2 ) by adding one inductor and three diodes to its power circuit. Boost factor for basic ZSI and qZSI can be written as: where T0 is shoot-through interval state, D = T0 /T is the duty cycle. Circuit analysis: analogous to the traditional ZSI, the five-phase SL-qZSI has typically thirty dynamics and two zero states apart from shoot-through zero states. Hence, the working principle of the suggested is analogous to the conventional ZSI. To simplify the study, the switching states are divided into shoot-through and non-shoot through states (NST). Equivalent circuit diagram of SL-qZSI shown in Figure 2. Figures 2 (a) and 2 (b) shows equivalent circuit during shoot-through state and non-shoot through state respectively. The five-phase SL-qZSI has thirty non-zero and two zero states during non-shoot through condition. In this condition, Din and D1 are conducting whereas D2 and D3 are open. L2 and L3 are associated in series. The energy is supplied from DC source to AC circuit by the inductors are of L1, L2, and L3; during this condition, the capacitors C1&C2 are charged. Also, 2_ and 3_ are voltages across the inductors L2 and L3, respectively. We get: (a) (b) Figure 2. Equivalent circuit diagram of SL-qZSI (a) shoot-through state (b) non-shoot through state [24] When both the lower and upper switches of the similar leg are conducting simultaneously, the shootthrough state can be accomplished in an inverter. During shoot-through state, Din&D1 are open whereas D2&D3 are conducting and inductors L2& L3 are associated in parallel. While the inductors L1, L2& L3 are charging, then the capacitors C1& C2 are getting discharged. We get: By applying volt-second stability principle to inductors L2&L3 then we get: In the same manner, the volt-second stability principle is applied to L1 then: Substituting (25) in (20) we obtain: Where, B is defined as the boost factor of the inverter, it is: Compared to conventional ZSI, the suggested SL-qZSI has superior boost capability, but it has reduced boost capability compared to SL-ZSI.

Bidirectional DC-DC converter
Bi-directional DC to DC converter along with the SL-qZSI is placed in between the DC link and the battery of the inverter, as shown in Figure 1. This bidirectional converter is used as a backup option, and it helps the battery to charge during regenerative braking of the motor. Either of the switches in the bidirectional converter is turned ON to step-down or step-up the voltage. The duty cycle of switches is controlled based on the terminal voltage of the solar PV. If solar energy is low or it is absent, then the battery and bidirectional converter combination maintain constant DC link voltage.

SIMULATION RESULTS
To approve the exhibition of the proposed structure, solar-powered 1-phase power modulating unit for five-phase IM drive is simulated on the MATLAB/Simulink environs. The determined parameters of simulation are tabularized in the Table 1. In the results section, the simulation results of solar PV voltage and PV current; input voltage and current of the battery; and the output voltages and currents are introduced. It additionally introduces the motor side simulation results, i.e., stator currents and speed of the five-phase IM. DC bus is provided by considering arrangement of PV array of 5kW rating with MPPT system in shunt with battery fed bi-directional buck-boost D.C to D.C converter.

Table 1. Simulation parameters
In these simulations, the two instabilities are in the usage of speed of the IM drive and solar irradiation is presented to approve the active performance of the introduced structure. PV temperature stays steady all over the simulation time. From Figure 3 (a) it tends to be seen that at 0.5-sec, the solar irradiation is reduced, so accordingly IPV diminished. Both the PV current and voltage are appeared in Figures 3 (a) and (b) correspondingly. Likewise, the voltage and current of the battery is appeared in Figures 3 (c) and 3 (d). Figures 4 and 5 show the inverter currents and voltages during the both steady state and transient state.
Stator currents inconsistent state are sinusoidal waveforms as appeared in the zoomed view portion of corresponding phase currents of Figure 5 and Figure 6 displays the results of the simulation of stator flux of five-phase IM drive using a 10 N-m load under-rated and reduced-speed conditions. It can be noticed that, under both speeds, the drive is able to operate at constant flux conditions. Reference speed at the time of zero sec is 1430rpm and it is decreased to 1200 rpm at the time of 1.5 seconds. It tends to be seen from Figure 7 that the genuine speed of the motor precisely tracks the reference speed. Till 1.5s, the reference speed is remains unchanged, but the source is changed, consistently detect the instabilities of speed momentarily. In such conditions, the drive is able to track the reference speed precisely under steady-state conditions. From Figure 8, power accessible since the PV is 5000 W, from beginning moment to t=0.5 second. So, the abundance in accessible power is deposited in battery up to the time 0.5 seconds. At the time t=0.5 sec, PV current is diminished meanwhile irradiation is decreased, however the PV voltage stays constant, so power accessible from PV is diminished, which is inadequate to reach the load. From t=0.5 sec to t=2 sec, inadequacy in power is exists from PV to satisfy the load demand, that inadequate power is acquired from the battery. The equivalent can be seen from the Figure 8.

Variation of duty cycle
As stated previously, the adjustment in the impedance network setup, boost factors of every single topology possibly will vary from others. Hypothetically, the extreme boost factor of every single topology is immeasurable. Boost factors are essential for the conversion DC to AC from 1 to 1.75, i.e., while 200 V D.C is changed over 350 V AC to 600 V AC (RMS line), are intended and illustrated in the Figure 9. From this Figure 9, it is evident that the projected inverter is capable to alter the input D.C into essential A.C with the necessity of a low boost factor.
Variations of duty cycle are intended as the variations in the middle of the maximum and minimum duty cycles essential for the conversion DC to AC in a definite variety. For the determination of contrast of various topologies, the maximum and minimum duty ratios are intended for the 200 V D.C to 600 V A.C conversion (RMS line) and 200 V D.C to 350 V AC conversion (line RMS) respectively. These values are introduced in a bar diagram, as appeared in Figure 10. From the bar diagram, it is evident that the variation of duty cycle range for the essential D.C to A.C conversion is huge on account of SL-qZSI; therefore, the duty cycle control is likely to be smooth on behalf of the introduced converter.

Peak DC-link voltages
For the D.C to A.C conversion from 1 to 1.75 i.e., 200V, D.C is altered from 350V AC to 600V A.C (RMS line). D.C-links of every single topology are diverse from others, as appeared in Figure 11. From this outcome, it is extremely evident that the values of D.C-link voltage are low on account of introduced converter when contrasted to others. Figure 11. Peak DC link voltages in different topology

Capacitor voltages and switching stresses
Meanwhile capacitors utilized in different topologies are altered, total voltage stresses are determined for the sake of comparison in all capacitors. Here in Figure 12, the entire capacitor stresses are designed though 200 V DC is changed over a range of A.C from 350 V to 600 V (RMS line). From Figure  12, it is evident that the stresses of capacitors are extreme low on account of the introduced inverter. Switching stresses in different topologies are illustrated in Figure 13. It is evident that from this figure, relatively the switching voltage stresses are low on account of the introduced inverter.

CONCLUSION
A high performance, highly reliable, and greater efficient SL-qZSI fed five-phase IM drive is introduced in the paper. In contrast to the counterpart i.e., classical VSI fed 3-phase IM drive, the combination of SL-qZSI five-phase IM attains best reliability and efficiency. Various attributes of the fivephase IM drive system are investigated with SL-qZSI. Desired performance is accomplished by the suggested system, and it is verified using simulations with V/f control. The suggested system can be implemented in the systems where better efficiency and reliability are of more concern. Its agreement validates the simulation results.