# A BL-CC Converter-Based BLDC Motor Drive for Marine Electric Vehicle Applications

Authors: Tanmay Shukla; Ujjwal Kumar Kalla
Journal: International Transactions on Electrical Energy Systems
 (2022)

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## Abstract

This article presents a BLDC (permanent magnet brushless DC) motor drive for marine electric vehicle (MEV) application. The presented scheme uses bridgeless canonical cell (BL-CC) converter with center-tapped inductor (shown as two separate inductors for analysis purpose) for source-side power factor correction (PFC); however, the BL-CC converter requires two inductors. In the presented scheme use of one center-tapped inductor eliminates the requirement of one extra inductor. Thus, center-tapped inductor usage in BLDC motor drive results in decrement in components count. The BL-CC converter-based BLDC motor drive scheme do not require extra back-feeding diodes like other bridgeless (BL) schemes, but it uses inbuilt antiparallel diodes of insulated gate bipolar transistor (IGBT) switches for the same purpose this again leads to decrement in required component count. In this work, PFC BL-CC converter is operated in discontinuous inductor current (DIC) mode to attain better power quality. The DIC mode operation requires only one voltage sensor to sense DC-link voltage, whereas in continuous conduction mode (CCM), the sensor requirement increases to three (two voltage sensors and one current sensor). The PFC BL-CC converter also eliminates the diode bridge rectifier stage. The elimination of one extra inductor, two extra back-feeding diodes, DBR stage and also requirement of only one voltage sensor in DIC mode operation instead of three sensors for CCM implies reduction in components count which implies the reduction in cost and also the volume and weight of the BLDC motor drive. The weight reduction for marine (on-board) electric vehicle is very important as this enhances the vehicle performance. This paper also presents the detailed mathematical modeling and stability analysis of presented BL-CC converter using pole zero map and Bode plot. The BL-CC converter-based BLDC motor driving system for MEV application for DIC mode operation has been developed in the laboratory as well as on MATLAB/Simulink platform and simulated MATLAB and real-time experimental results have been presented to validate the presented BLDC motor drive under steady-state and dynamic operating conditions.


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## Body

## 1. Introduction

Advantages such as higher reliability, greater efficiency, low EMI (electro-magnetic interference) issue, high ruggedness, and its exceptional performance in comparison with other motors [1] over a wide range of speed control [2, 3] makes BLDC motor an ideal choice for many medium and low-power applications like medical equipments, household appliances, air conditioners, motion controllers, position actuators, and transport sector (vehicle applications) [4–7]. Nowadays the application of BLDC in MEVs has become very common. The marine electric vehicles (MEVs) having diesel engine generators (DEGs) produces AC, and this AC voltage has to be converted into useable form by BLDC motor for MEV applications. BLDC motors are a type of synchronous motors having three-phase concentrated windings on stator and permanent magnets on rotor. Hall-effect sensor-based electronic commutation technique is used in this motor, which diminishes or reduces certain issues associated with traditional DC motors such as maintenance issue, sparking and noise problem, and EMI [8]. Hall-effect sensors are utilized to sense the rotor position. A diode bridge rectifier (DBR), fed voltage source inverter (VSI)-based traditional BLDC motor drive draws a peaky input current [9, 10]. This peaky supply current does not resemble the input AC voltage waveform. This gives rise to serious power quality (PQ) issue. The input current THD (total harmonic distortion) with traditional charger is found approximately equal to 65%, which is not acceptable as per IEC 61000-3-2 standard of PQ [11]. So the inclusion of power factor correction (PFC) power converters in drive becomes must, to increase the supply-side PQ. Many PQ enhancement schemes for BLDC motor drive system using different power converters of different orders have been reported in literature [12–21]. Boost PFC converter-fed BLDC motor drive has been presented by Ho et al. [12]. The main advantage of employing the boost PFC converters is availability of inductance at input side, which lessens the supply current harmonics. However, boost converter suffers a drawback that it can only boost up the voltage level but cannot reduce. The buck-boost second-order PFC converter is given by Aishwarya and Gnana Sheela [13]. The advantages of buck-boost PFC converter over boost converter is that it can step up or step down the voltage levels depending on the duty cycle value, but utilization of buck-boost converter in PFC application requires additional/external filter to improve input side PQ. This requirement of external filter adds extra energy storage elements which increases the order of the system. PFC Cuk converter-based BLDC motor drive is reported by Singh and Singh [14]. The Cuk converter is garnished with output- and input-side inductors, which improves the output current and input current waveforms respectively. No external filters are required with PFC Cuk converters due to the presence of inductors at both the ends. However, fourth-order SEPIC and Zeta power converter-based BLDC motor drive are reported in previous studies [15–17]. Like Cuk converter, SEPIC converter is also garnished with output- and input-side inductances. The SEPIC converter also gives noninverted output unlike Cuk converter. A PFC Luo converter-based BLDC motor drive is presented in previous studies [18, 22, 23]. However, PQ-improved canonical cell (CC) converter-based BLDC driver system is reported by Bist and Singh [19]. For EMI problem, various resonant converters have been reported in literature [20, 21, 24, 25]. The soft switching technique to increase the performance from reliability, reduction in switching losses, and EMI interference point of view, is presented by Pahlevani and Jain [26]. Williams [27] presents various types of DC-DC converters. The interleaving of converters provides certain advantages like better power distribution, quicker response to transients, current ripple cancellation, and reduction in passive component size but interleaved arrangement does not have any significant impact on EMI interference [28, 29]. The Interleaved DC-DC converter-based BLDC motor drive configuration also uses DBR which increases the nonlinearity. The answer to DBR-related problem is bridgeless configuration of converter. Various types of bridgeless converter-based BLDC motor drives have been reported in literature [30–39]. The advantage of using such configuration are DBR elimination, simple controlling, and low electrical stress, as the average current across the components conducting during each half cycle of bridgeless PFC converters reduces. Different control schemes for BLDC motor drive are discussed by Ashok and Kumar [40]. The BLDC motor sensorless control schemes are discussed in literature [41, 42]. The speed control scheme of BLDC motor drive with calculation of controller tuning parameters using modified genetic algorithm approach is presented by Vanchinathan et al. [41]. The sensorless fuzzy logic precise commutation control scheme for speed control of BLDC motor drive using equal area criteria approach is presented by Soni and Tripathi [42].This paper presents a BL-CC converter-based reduced component count drive for BLDC motor for MEV application. The presented CC converter-based BLDC motor drive is shown in Figure 1. The BLDC motor drive for MEV application is divided into three parts in addition to two controlling loops. The filter is connected to DEG output, which is input to the BLDC motor drive VIN. The filter is made of filtering inductance (Lf) and capacitance (Cf). Next stage to filter is PF correction stage, which incorporate BL-CC converter. The third stage consists of voltage source converter-fed BLDC motor. The rotor position of BLDC motor is sensed by Hall-effect sensors. These sensed signals are then used to generate the gating pulse of VSI. The gating pulses to switches of BL-CC converter are generated with a simple voltage follower controlling technique using proportional-integral controller.Figure 1
BL-CC AC-DC converter-based BLDC motor drive for MEV applications.The contributing and notable features of the presented BL-CC converter-based BLDC motor drive for MEV applications are being listed as follows:(1)
The BL-CC converter in BL configuration uses a single-center tapped inductor (shown as two different inductors, i.e.,L1 and L2 in Figure 1) which conducts partially and fully in different modes of each half cycle of generator output voltage. The usage of this tapped inductance eliminates one extra inductor requirement.(2)
BL-CC converter-fed BLDC motor drive uses inbuilt antiparallel diodes of insulated gate bipolar transistor (IGBT) switches for back-feeding during both positive and negative cycle of generator output voltage. So, no separate additional back feeding diodes are required in the presented scheme whereas conventional BL schemes require separate/additional back feeding diodes.(3)
The CC converter uses three energy storage elements where as other converters such as Cuk, SEPIC, Zeta, Luo, Landsman, Sheppard Taylor uses more number of energy storage elements as compared to CC converter which witnesses the lower-order of CC converter.(4)
PFC is achieved with a simple control (voltage follower) technique as both the switches of the BL-CC converter are needed to be fed with same gate pulse. DIC mode operation reduces the sensors requirement to one which reduces the cost of MEV drive with respect to CCM operation which requires three sensors (two voltage sensors and one current sensor).(5)
The presence of inductance in output current loop increases the load current profile and the usage of CC converter for both half cycles of DEG output voltage maintains symmetry of BL-CC converter so analysis of any half cycle (either positive or negative) is sufficient to analyze the operation of PF corrected BL-CC converter. This reduces the calculative as well as analysis burden by 50%.The presented BL-CC converter operating in DIC mode works as inbuilt PF preregulator of the drive system for obtaining a linear voltage to current profile at generator output voltage (90–260 V). A variable DC-link bus voltage to VSI is used to control the speed of BLDC motor. This reduces the switching losses due to low-frequency electronically commutated switching of VSI. These switching losses at six IGBT switches of VSI shares a significant portion of total losses in BLDC motor drive system.


## 2. BL-CC Converter Configuration

The CC converter with bridgeless configuration used in BLDC motor drive system with reduced components count has been shown in Figure2. The converter is symmetrical for both half cycles of input AC voltage. For MEV applications, the input voltage to the BLDC motor drive is output voltage of DEG denoted by VIN. The presented PF-corrected converter uses a single-center tapped inductor (shown as two different inductors i.e. L1 and L2 in Figure 1) which conducts partially and fully in different modes of each half cycle of input AC voltage. Also the converter uses the inbuilt antiparallel diodes of IGBT switches which eliminate the usage of extra diodes for completion of conduction loops during different half cycles of input AC voltage.Figure 2
BL-CC AC-DC converter.


### 2.1. Operation of PQ-Enhanced BL-CC AC-DC Converter

In this section, DIC mode operation of BL-CC converter has been described. For DIC mode operation of BL-CC converter, total six possible cases exists-three during positive cycle and other three during negative cycle of input AC voltage. Owing to symmetrical configuration of BL-CC converter, only positive half cycle operation is elaborated in this section. However, the conduction loop during all six possible cases has been depicted in Figures3(a) to 3(f).Figure 3
Operating modes of BL-CC converter during (a) mode I, (b) mode II, (c) DIC mode during positive half cycle, (d) mode IV, (e) mode V, and (f) mode VI.
(a)(b)(c)(d)(e)(f)The six cases/modes arising with BL-CC converter when operated in DIC mode are as follows:(i)
Positive half cycle of DEG output voltage.(1)
SwitchSP is conducting (supplied with gating pulse).(2)
SwitchSP is not conducting (off).(3)
SwitchSP is off and also no diode current through diode D1 vanishes (DIC mode of positive half cycle).(ii)
Negative half cycle of DEG output voltage.(4)
SwitchSN conducts.(5)
SwitchSN is off.(6)
SwitchSN is off and also inductor L2 current vanishes (DIC mode of negative half cycle).To unfold the CC converter working in BL configuration, different operating modes of presented PF-corrected BL-CC converter, are explicated in present section.(1)
Mode-I—The conduction loops during this mode has been shown in Figure3(a) for more clarity and better understanding. Switch SP is supplied with gate pulse. The inductor current can be estimated using the following relation:(1)VL=LdiLdt.In the ongoing mode, the capacitorC1 getting discharged through the switch (acting as short circuit for this mode) SP and the loop getting completed as C1 − L1 − Load||CDC on the other hand another conduction loop during this mode consists of VIN − Lf − L1 − L2 and the loops getting completed through antiparallel diode of another switch (SN). The maximum stress (electric current stress) on switch SP during mode-1 is given as follows:(2)iSp_peak=VC1−VCDCd1TsL1,where,TS is time interval and d1 is duty cycle.(2)
Mode-II—In this mode, switchSP is turned off and conduction loops are deployed in Figure 3(b). In this mode, diode D1 conducts and converter conduction loops consists of Cf − C1 − L1 − L2 and another loop also got completed through diode D1 consisting of inductor L1 and DC-link capacitor in parallel with load. Maximum value current through diode D1 can be evaluated using the following relation:(3)iD1_peak=−VCDCd2TsL1,where,d2=Time elapsed in this mode/Total time period.Peak voltage across switchSP is given as follows:(4)VQp_peak=−VCDC−VL1.This operating mode also shows the conduction of inbuilt antiparallel diodes of switchSN.(3)
Mode-III—In this mode, the switchSP remains off, and this mode begins just after the complete vanish of inductor energy where as the capacitor C1 holds energy and retain its charge; however, the load is supplied with DC-link capacitor and the conduction path for this mode is depicted in Figure 3(c). The diode D1 also stops conducting so, the current through inductor L2 and capacitor C1 is same and the conduction loop during this mode consists of VIN − L1 − C1 − L2 − R||CDC − C2. In this mode, capacitor CDC discharges.The DIC mode can be expressed mathematically as follows:(5)d1Ts+d2Ts<Ts,where,dON = d1 and dOFF = d2 + dDICM.Also,(6)d1+d2+dDICM=1.The same operational behavior of the presented BL-CC converter can be realized for other half cycle of input AC voltage due to the presence of symmetry in bridgeless converter configuration.


### 2.2. Differential Factors of Presented BL-CC Converter

The differential factors with the presented BL-CC converter are PQ improvement, DBR elimination, efficiency enhancement, component count reduction, elimination of back feeding diode, simple control input, and availability of output inductances in output current loop for both half cycles. A brief comparison of various BL converter-based BLDC motor drive is tabulated in Table1. It shows total components count along with required inductors, capacitors, switches, diodes, and components conducting each half cycle of input voltage.Table 1
Comparative analysis of presented bridgeless-CC converter with different existing BL configuration.
S. no.ConfigurationDevice countLCDSwitchTotal(1)BL-buck-boost [30]21429(2)BL-cuk [31]654217(3)BL-SEPIC [32]434213(4)BL-Zeta [33]323210(5)BL-Luo [34]434213(6)BL-Sheppard Taylor [35]4310421(7)BL-CSC [36]234211(8)BL-Landsman [37]434213(9)BL-Zeta [39]544215(10)Presented BL-CC1∗32281∗ in Table 1 represents the tapped inductor.


### 2.3. Designing and Selection of Components for BL-CC Converter

The presented PF-corrected BL-CC converter is operated in DIC mode such that the energy through the inductor vanishes before completion of cycle and the inductorL1 and L2 current becomes discontinuous. However, the voltage across the energy storage capacitor C1 and C2 remain continuous throughout the switching period. A 425 W BLDC motor (specification of motor is given in Appendix) is being used in this article to validate the drive system at MATLAB platform. So, a front-end PF-corrected converter with maximum power rating equal to 500 W is designed for BLDC motor drive. For wide range speed variation using DC-link voltage in BLDC motor, the rated value for DC-link voltage is taken as 200 V and minimum value of DC-link voltage is taken as 70 V. The applied input voltage to the PF-corrected converter can be written as follows:(7)VIN=VmaxsinωLt=2202sin2πfLt,where, Vmax is the peak input voltage and ωL is the line frequency in radian/second and fL is the line frequency equal to 50 Hz.Now, the instantaneous value across the inductor and switch combination can be evaluated as follows:(8)VINt=VmaxsinωLt=2202sin314t.For CC converter, on applying the voltage-second balance across the inductors, the converter transfer function comes out to be the following:(9)VCDCVIN=d11−d1.The duty ratio instantaneous value depends on DC-link capacitor voltage and instantaneous value of input AC voltage.(10)d1t=VCDCVCDC+VINt=VCDCVCDC+VmaxsinωLt.Since, the BLDC motor speed control is achieved by varying the voltage across DC-link capacitor at the input side of VSI. So, the power at DC link can be taken as a linear function of DC-link capacitor voltage.(11)PDC_link=PmaxVCDC_max×VCDC,where VCDCmax represents maximum value of DC-link voltage and Pmax represents rated power for PF correction converter. Using relation equation (11), the minimum value of power (Pmin) at minimum value of DC-link capacitor voltage, that is, 70 V comes out to be 112.90 W.The value of CC converter inductanceLCC(LCC = L1 + L2) for operation in DIC mode do require the selection of switching frequency which is one of the critical parameter which decides the switching losses and also the inductor value and size. With higher switching frequency, the inductor size and value reduces but the switching losses across solid-state devices increases and thus require a heat sink of larger size; however, with lower switching frequency, the switching losses reduces significantly, but the value and size of the required inductor increases. Taking both the things into consideration, the switching frequency for this work is taken as 20,000 Hz. The value CC converter inductance LCC can be calculated using the following formula:(12)LCC=VINtd1t2IINtfs=RINd1t2fs.For the calculation of inductance value of CC converter to operate in DCM mode (i.e. inductance value less than critical value), thed1(t) and RIN_min values are required, which can be calculated as follows:(13)RIN_min=VIN_min2PRated=852500,d1t=200200+852=0.621.The inductance value for DIC mode operation can be evaluated as follows:(14)LCC<RIN_mind1t2fs=14.45×0.6212×20,000=224μH.The inductor,LCC value chosen as 70 µH. So, the value of inductor L1 and L2 comes out to be 35 µH each.The expression to evaluate energy storage intermediate capacitance in continuous capacitor voltage mode value with allowed 10% of voltage ripple (λ) at maximum AC input voltage value 270 × 1.414 and rated DC-link voltage is given as follows:(15)C1,2>VDC_ratedd1tλ2VIN_max+VDC_ratedRLfs,C1,2>200×0.3440.12702+200×20,000×5002002,C1,2>0.74μF,where, at this instant d1(t) can be calculated as follows:(16)d1t=200200+2702=0.344.The value of capacitor for CC converterC1,2 is taken as 0.67 µF. The capacitor utilized in the present application must be capable of operating at high frequency and greater surge-current application, so generally polypropylene film energy storage capacitors which have lower series inductance and resistance are used in such applications.The value of capacitor used at DC-link (CDC) can be evaluated using the following equation:(17)ΔVDC=∫iCDCtdt=−iCDC2ωCDCsin2ωt,CDC=iCDC2ωΔVDC=PVDC×12ωκVDC,where, ΔVDC represents the allowed ripple in voltage across DC-link. The CDC is needed to be designed at worse case. Which occurs at 70 V (minimum value) DC-link voltage and minimum power is given as follows:(18)CDC=PminVDC_min×12ωκVDCCDC=11370×12×2π×50×0.02×70=1836.10μF.The value of DC-link capacitor is chosen to be 2.1 mF. As the capacitor needs to be used at low switching (due to second harmonic influence in its calculation) and relatively greater value of current and the capacitor is also required to have higher value of capacitance per unit volume due to larger value of capacitance, so electrolytic capacitors could be suited for this application.


### 2.4. Designing and Selection of Filter Components

As depicted in Figure1, a low-pass (L-C) filter is used at the input side of BLDC motor drive to avoid the entry of the higher-order harmonics in the input current waveform. The maximum filter capacitance value can be estimated as given as follows:(19)Cf=P/VmaxωLVmaxtanθ=5002/220100π×2202tan1°=573.98nF.So, a capacitor of 430 nF is chosen as one of the filter element. The filter inductor value is designed by taking the source input impedance (LIN) of 3% to 5% of the base impedance value. Therefore, additional inductance required to be used as filter inductance Lf can be calculated as follows:(20)Lreq=Lf−LIN.where,(21)Lf=14π2fcut−off2Cf=14π2×18002×430×10−9H=18.18×10−3H,LIN=0.051ωL×VIN2P=0.05×12πfL×2202500=15.41mH.Using equation (18), Lreq can be calculated, and its value comes out to be 2.77 mH.Where, filter cut-off frequency should be in between line frequency and switching frequency. The filter cut-off frequency is taken as 1800 Hz for this work. To withstand current ripples with high frequency switching, the polypropylene film capacitor should be used for this purpose.


## 2.1. Operation of PQ-Enhanced BL-CC AC-DC Converter

In this section, DIC mode operation of BL-CC converter has been described. For DIC mode operation of BL-CC converter, total six possible cases exists-three during positive cycle and other three during negative cycle of input AC voltage. Owing to symmetrical configuration of BL-CC converter, only positive half cycle operation is elaborated in this section. However, the conduction loop during all six possible cases has been depicted in Figures3(a) to 3(f).Figure 3
Operating modes of BL-CC converter during (a) mode I, (b) mode II, (c) DIC mode during positive half cycle, (d) mode IV, (e) mode V, and (f) mode VI.
(a)(b)(c)(d)(e)(f)The six cases/modes arising with BL-CC converter when operated in DIC mode are as follows:(i)
Positive half cycle of DEG output voltage.(1)
SwitchSP is conducting (supplied with gating pulse).(2)
SwitchSP is not conducting (off).(3)
SwitchSP is off and also no diode current through diode D1 vanishes (DIC mode of positive half cycle).(ii)
Negative half cycle of DEG output voltage.(4)
SwitchSN conducts.(5)
SwitchSN is off.(6)
SwitchSN is off and also inductor L2 current vanishes (DIC mode of negative half cycle).To unfold the CC converter working in BL configuration, different operating modes of presented PF-corrected BL-CC converter, are explicated in present section.(1)
Mode-I—The conduction loops during this mode has been shown in Figure3(a) for more clarity and better understanding. Switch SP is supplied with gate pulse. The inductor current can be estimated using the following relation:(1)VL=LdiLdt.In the ongoing mode, the capacitorC1 getting discharged through the switch (acting as short circuit for this mode) SP and the loop getting completed as C1 − L1 − Load||CDC on the other hand another conduction loop during this mode consists of VIN − Lf − L1 − L2 and the loops getting completed through antiparallel diode of another switch (SN). The maximum stress (electric current stress) on switch SP during mode-1 is given as follows:(2)iSp_peak=VC1−VCDCd1TsL1,where,TS is time interval and d1 is duty cycle.(2)
Mode-II—In this mode, switchSP is turned off and conduction loops are deployed in Figure 3(b). In this mode, diode D1 conducts and converter conduction loops consists of Cf − C1 − L1 − L2 and another loop also got completed through diode D1 consisting of inductor L1 and DC-link capacitor in parallel with load. Maximum value current through diode D1 can be evaluated using the following relation:(3)iD1_peak=−VCDCd2TsL1,where,d2=Time elapsed in this mode/Total time period.Peak voltage across switchSP is given as follows:(4)VQp_peak=−VCDC−VL1.This operating mode also shows the conduction of inbuilt antiparallel diodes of switchSN.(3)
Mode-III—In this mode, the switchSP remains off, and this mode begins just after the complete vanish of inductor energy where as the capacitor C1 holds energy and retain its charge; however, the load is supplied with DC-link capacitor and the conduction path for this mode is depicted in Figure 3(c). The diode D1 also stops conducting so, the current through inductor L2 and capacitor C1 is same and the conduction loop during this mode consists of VIN − L1 − C1 − L2 − R||CDC − C2. In this mode, capacitor CDC discharges.The DIC mode can be expressed mathematically as follows:(5)d1Ts+d2Ts<Ts,where,dON = d1 and dOFF = d2 + dDICM.Also,(6)d1+d2+dDICM=1.The same operational behavior of the presented BL-CC converter can be realized for other half cycle of input AC voltage due to the presence of symmetry in bridgeless converter configuration.


## 2.2. Differential Factors of Presented BL-CC Converter

The differential factors with the presented BL-CC converter are PQ improvement, DBR elimination, efficiency enhancement, component count reduction, elimination of back feeding diode, simple control input, and availability of output inductances in output current loop for both half cycles. A brief comparison of various BL converter-based BLDC motor drive is tabulated in Table1. It shows total components count along with required inductors, capacitors, switches, diodes, and components conducting each half cycle of input voltage.Table 1
Comparative analysis of presented bridgeless-CC converter with different existing BL configuration.
S. no.ConfigurationDevice countLCDSwitchTotal(1)BL-buck-boost [30]21429(2)BL-cuk [31]654217(3)BL-SEPIC [32]434213(4)BL-Zeta [33]323210(5)BL-Luo [34]434213(6)BL-Sheppard Taylor [35]4310421(7)BL-CSC [36]234211(8)BL-Landsman [37]434213(9)BL-Zeta [39]544215(10)Presented BL-CC1∗32281∗ in Table 1 represents the tapped inductor.


## 2.3. Designing and Selection of Components for BL-CC Converter

The presented PF-corrected BL-CC converter is operated in DIC mode such that the energy through the inductor vanishes before completion of cycle and the inductorL1 and L2 current becomes discontinuous. However, the voltage across the energy storage capacitor C1 and C2 remain continuous throughout the switching period. A 425 W BLDC motor (specification of motor is given in Appendix) is being used in this article to validate the drive system at MATLAB platform. So, a front-end PF-corrected converter with maximum power rating equal to 500 W is designed for BLDC motor drive. For wide range speed variation using DC-link voltage in BLDC motor, the rated value for DC-link voltage is taken as 200 V and minimum value of DC-link voltage is taken as 70 V. The applied input voltage to the PF-corrected converter can be written as follows:(7)VIN=VmaxsinωLt=2202sin2πfLt,where, Vmax is the peak input voltage and ωL is the line frequency in radian/second and fL is the line frequency equal to 50 Hz.Now, the instantaneous value across the inductor and switch combination can be evaluated as follows:(8)VINt=VmaxsinωLt=2202sin314t.For CC converter, on applying the voltage-second balance across the inductors, the converter transfer function comes out to be the following:(9)VCDCVIN=d11−d1.The duty ratio instantaneous value depends on DC-link capacitor voltage and instantaneous value of input AC voltage.(10)d1t=VCDCVCDC+VINt=VCDCVCDC+VmaxsinωLt.Since, the BLDC motor speed control is achieved by varying the voltage across DC-link capacitor at the input side of VSI. So, the power at DC link can be taken as a linear function of DC-link capacitor voltage.(11)PDC_link=PmaxVCDC_max×VCDC,where VCDCmax represents maximum value of DC-link voltage and Pmax represents rated power for PF correction converter. Using relation equation (11), the minimum value of power (Pmin) at minimum value of DC-link capacitor voltage, that is, 70 V comes out to be 112.90 W.The value of CC converter inductanceLCC(LCC = L1 + L2) for operation in DIC mode do require the selection of switching frequency which is one of the critical parameter which decides the switching losses and also the inductor value and size. With higher switching frequency, the inductor size and value reduces but the switching losses across solid-state devices increases and thus require a heat sink of larger size; however, with lower switching frequency, the switching losses reduces significantly, but the value and size of the required inductor increases. Taking both the things into consideration, the switching frequency for this work is taken as 20,000 Hz. The value CC converter inductance LCC can be calculated using the following formula:(12)LCC=VINtd1t2IINtfs=RINd1t2fs.For the calculation of inductance value of CC converter to operate in DCM mode (i.e. inductance value less than critical value), thed1(t) and RIN_min values are required, which can be calculated as follows:(13)RIN_min=VIN_min2PRated=852500,d1t=200200+852=0.621.The inductance value for DIC mode operation can be evaluated as follows:(14)LCC<RIN_mind1t2fs=14.45×0.6212×20,000=224μH.The inductor,LCC value chosen as 70 µH. So, the value of inductor L1 and L2 comes out to be 35 µH each.The expression to evaluate energy storage intermediate capacitance in continuous capacitor voltage mode value with allowed 10% of voltage ripple (λ) at maximum AC input voltage value 270 × 1.414 and rated DC-link voltage is given as follows:(15)C1,2>VDC_ratedd1tλ2VIN_max+VDC_ratedRLfs,C1,2>200×0.3440.12702+200×20,000×5002002,C1,2>0.74μF,where, at this instant d1(t) can be calculated as follows:(16)d1t=200200+2702=0.344.The value of capacitor for CC converterC1,2 is taken as 0.67 µF. The capacitor utilized in the present application must be capable of operating at high frequency and greater surge-current application, so generally polypropylene film energy storage capacitors which have lower series inductance and resistance are used in such applications.The value of capacitor used at DC-link (CDC) can be evaluated using the following equation:(17)ΔVDC=∫iCDCtdt=−iCDC2ωCDCsin2ωt,CDC=iCDC2ωΔVDC=PVDC×12ωκVDC,where, ΔVDC represents the allowed ripple in voltage across DC-link. The CDC is needed to be designed at worse case. Which occurs at 70 V (minimum value) DC-link voltage and minimum power is given as follows:(18)CDC=PminVDC_min×12ωκVDCCDC=11370×12×2π×50×0.02×70=1836.10μF.The value of DC-link capacitor is chosen to be 2.1 mF. As the capacitor needs to be used at low switching (due to second harmonic influence in its calculation) and relatively greater value of current and the capacitor is also required to have higher value of capacitance per unit volume due to larger value of capacitance, so electrolytic capacitors could be suited for this application.


## 2.4. Designing and Selection of Filter Components

As depicted in Figure1, a low-pass (L-C) filter is used at the input side of BLDC motor drive to avoid the entry of the higher-order harmonics in the input current waveform. The maximum filter capacitance value can be estimated as given as follows:(19)Cf=P/VmaxωLVmaxtanθ=5002/220100π×2202tan1°=573.98nF.So, a capacitor of 430 nF is chosen as one of the filter element. The filter inductor value is designed by taking the source input impedance (LIN) of 3% to 5% of the base impedance value. Therefore, additional inductance required to be used as filter inductance Lf can be calculated as follows:(20)Lreq=Lf−LIN.where,(21)Lf=14π2fcut−off2Cf=14π2×18002×430×10−9H=18.18×10−3H,LIN=0.051ωL×VIN2P=0.05×12πfL×2202500=15.41mH.Using equation (18), Lreq can be calculated, and its value comes out to be 2.77 mH.Where, filter cut-off frequency should be in between line frequency and switching frequency. The filter cut-off frequency is taken as 1800 Hz for this work. To withstand current ripples with high frequency switching, the polypropylene film capacitor should be used for this purpose.


## 3. Controlling of PF-Corrected BL-CC Converter-Fed BLDC Motor Drive

The control scheme for BL-CC AC-DC converter-fed BLDC motor drive for MEV application is explained in this section. The complete BLDC motor driver scheme uses two different controls: one for PF-corrected converter and another for BLDC motor.


### 3.1. Control Scheme for PF-Corrected BL-CC Converter

A voltage follower (tracking) approach is employed to achieve PF correction at input side using BL-CC converter in DIC mode in this work. For this control technique, only one sensor is needed to control the voltage drop across DC-link capacitor for speed control of BLDC motor. The block diagram of control loop to control DC-link voltage has been depicted in Figure4. This control technique uses a reference voltage generator (RVG), an error generator (comparator), a pulse width modulation generator (PWMG) and a proportional-integral (P-I) controller. RFG generates reference voltage VDC∗ on multiplying the BLDC motor voltage constant (KVϕ) with reference speed ω∗ and the equation can be expressed as follows:(22)VDC∗=KVφω.Figure 4
Control loop for PF-corrected BL-CC converter.The resultant reference voltage is applied to error generator along with DC-link-sensed voltage the error generator compares both the DC-link-sensed voltage and RFG output and generate error signal (Verr) which is given at jth sample instant as follows:(23)Verrj=VDC∗j−VDCj.The generated error signal is applied to P-I controller so that a controlled output voltage (VC) can be generated. The controller output voltage, VC can be expressed as follows:(24)VCj=VCj−1+KPVerrj−Verrj−1+KIVerrj,where, KI and KP are integral and proportional gains of P-I controllers, respectively. On comparison of VC with high-frequency saw-tooth wave, YST (from saw-tooth generator) and then using relational operator to get final gate pulse to be fed to switches SP and SN of the PF-corrected BL-CC converter. The operation of relational operator is described as follows:ForVIN > 0.IfYST ≤ VC then switch SP is “ON.”IfYST > VC then switch SP is “OFF.”ForVIN < 0.IfYST ≤ VC then switch SN is “ON”IfYST > VC then switch SN is “OFF.”


### 3.2. Control Scheme for VSI-Fed BLDC Motor

Electronic commutation technique is used for speed control of BLDC motor. Owing to the usage of electronic commutation circuit, problems such as maintenance issue, sparking and noise problem, and EMI are eliminated or reduced significantly. The rotor positions of BLDC are sensed by Hall-effect (position) sensors. In a BLDC motor at any instant of time, only two stator phases are exited. The information of rotor position (provided by Hall sensors) is being used to decide the state (ON or OFF) of different switches of VSI. This rotor position is helpful to ensure proper current flow direction in different winding of trapezoidal back-electromotive force (B-EMF) BLDC motor at different instant. A conduction loop at instant when VSI switchesS1 and S5 conduct is shown in Figure 5. At this instant, a current is drawn by VSI-fed BLDC motor from DC-link applied voltage VDC. So the current magnitude and direction both depend on DC-link voltage VDC, mutual inductance (MAB), and self-inductances (LA and LB) of conducting windings, resistances of both windings (RA and RB) and also the back EMFs (EAN and EBN). Also, the switching states of all six switches of VSI based on all three Hall-sensors (HA, HB, and HC) signals feeding BLDC motor have been shown in Table 2.Figure 5
VSI feeding BLDC with switchS1 and S6 conducting.Table 2
Hall-signal-based switching states of VSI for BLDC motor electronic commutation.
θ(radians)Hall sensor signalsVSI switching statesHAHBHCS1S2S3S4S5S60 − (π/3)101100010(π/3) − (2π/3)100100001(2π/3) − π110010001π − (4π/3)010010100(4π/3) − (5π/3)011001100(5π/3) − 2π001001010NA000000000


## 3.1. Control Scheme for PF-Corrected BL-CC Converter

A voltage follower (tracking) approach is employed to achieve PF correction at input side using BL-CC converter in DIC mode in this work. For this control technique, only one sensor is needed to control the voltage drop across DC-link capacitor for speed control of BLDC motor. The block diagram of control loop to control DC-link voltage has been depicted in Figure4. This control technique uses a reference voltage generator (RVG), an error generator (comparator), a pulse width modulation generator (PWMG) and a proportional-integral (P-I) controller. RFG generates reference voltage VDC∗ on multiplying the BLDC motor voltage constant (KVϕ) with reference speed ω∗ and the equation can be expressed as follows:(22)VDC∗=KVφω.Figure 4
Control loop for PF-corrected BL-CC converter.The resultant reference voltage is applied to error generator along with DC-link-sensed voltage the error generator compares both the DC-link-sensed voltage and RFG output and generate error signal (Verr) which is given at jth sample instant as follows:(23)Verrj=VDC∗j−VDCj.The generated error signal is applied to P-I controller so that a controlled output voltage (VC) can be generated. The controller output voltage, VC can be expressed as follows:(24)VCj=VCj−1+KPVerrj−Verrj−1+KIVerrj,where, KI and KP are integral and proportional gains of P-I controllers, respectively. On comparison of VC with high-frequency saw-tooth wave, YST (from saw-tooth generator) and then using relational operator to get final gate pulse to be fed to switches SP and SN of the PF-corrected BL-CC converter. The operation of relational operator is described as follows:ForVIN > 0.IfYST ≤ VC then switch SP is “ON.”IfYST > VC then switch SP is “OFF.”ForVIN < 0.IfYST ≤ VC then switch SN is “ON”IfYST > VC then switch SN is “OFF.”


## 3.2. Control Scheme for VSI-Fed BLDC Motor

Electronic commutation technique is used for speed control of BLDC motor. Owing to the usage of electronic commutation circuit, problems such as maintenance issue, sparking and noise problem, and EMI are eliminated or reduced significantly. The rotor positions of BLDC are sensed by Hall-effect (position) sensors. In a BLDC motor at any instant of time, only two stator phases are exited. The information of rotor position (provided by Hall sensors) is being used to decide the state (ON or OFF) of different switches of VSI. This rotor position is helpful to ensure proper current flow direction in different winding of trapezoidal back-electromotive force (B-EMF) BLDC motor at different instant. A conduction loop at instant when VSI switchesS1 and S5 conduct is shown in Figure 5. At this instant, a current is drawn by VSI-fed BLDC motor from DC-link applied voltage VDC. So the current magnitude and direction both depend on DC-link voltage VDC, mutual inductance (MAB), and self-inductances (LA and LB) of conducting windings, resistances of both windings (RA and RB) and also the back EMFs (EAN and EBN). Also, the switching states of all six switches of VSI based on all three Hall-sensors (HA, HB, and HC) signals feeding BLDC motor have been shown in Table 2.Figure 5
VSI feeding BLDC with switchS1 and S6 conducting.Table 2
Hall-signal-based switching states of VSI for BLDC motor electronic commutation.
θ(radians)Hall sensor signalsVSI switching statesHAHBHCS1S2S3S4S5S60 − (π/3)101100010(π/3) − (2π/3)100100001(2π/3) − π110010001π − (4π/3)010010100(4π/3) − (5π/3)011001100(5π/3) − 2π001001010NA000000000


## 4. State-Space Model and Small Signal Analysis of BL-CC Converter

The dynamics of the BL-CC converter can be well understood by resolving the BL-CC converter conduction circuit of each conduction mode into first-order differential equations (FDEs) using basic laws of circuit theory; for stability analysis, these FDEs are expressed in standard state-space form [31]. The standard state-space equations are as follows:(25)x•=AQx+BQVINy=CQx+DQVIN,where, Q equals F1, F2, and F3 for positive cycle of input AC voltage and G1,G2,andG3 for negative cycle of input AC voltage, but due to presence of symmetry in circuit and symmetrical operation in both half cycle cycles of input AC voltage only, the stability analysis of positive cycle converter is done using Bode-plot and Pole-zero map. The BL-CC converter under stability test is shown in Figure 6.Figure 6
Presented PF-corrected BL-CC converter.The matrix-vectors for positive cycle of BL-CC converter are follows:(26)BF1=BF2=BF3=0−1L200T,CF1=CF2=CF3=0001,DF1=DF2=DF3=0,AF1=000−1L1001L2−1L2−1C1−1C1001CDC1CDC0−1RCDC,AF2=−1L1000001L2−1L20−1C1001CDC1CDC0−1RCDC,AF3=0000001L2−1L20−1C10001CDC0−1RCDC.The state-space matrix to incorporate in standard state-space equation for positive cycle converter in DIC mode is obtained using the following relation:(27)AF=AF1d1+AF2d2+AF31−d1−d2,BF=BF1d1+BF2d2+BF31−d1−d2,CF=CF1d1+CF2d2+CF31−d1−d2,DF=DF1d1+DF2d2+DF31−d1−d2.Now the transfer function for positive cycle of BL-CC converter is given as follows:(28)TFBL−CSC,poss=VDC•sVIN•s=CFsI−AF−1BF.Calculating the transfer function by entering the values (magnitudes) of components used in BL-CC converter for DIC mode operation lead to transfer function having two zeros and four poles and is given by the following equation:(29)VDC•sVIN•s=−5.195×1010s2+1.512s+8.10×1020s4+a1s3+a2s2+a3s+2.70×1020,where, a1 = 109.10, a2 = 1.818 × 1011, and a3 = 9.633 × 1012Two zeros and four poles can also be seen in pole zero map of TFBL-CC,pos, shown in Figure 7(a). In pole zero map, none of the four poles is seen on the right side of the y-axis which witnesses the stability of the positive cycle converter circuit of BL-CC converter. For closed-loop operation, the converter is cascaded with P-I controller and the P-I controller transfer function is given as follows:(30)TFct=KP+KIs,where, KP and KI are proportional and integral tuned parameters and KI and KP are selected as 0.05 and 0.001, respectively. Using the BL-CC converter positive-cycle transfer function and TFct, bode-plot of complete function is plotted and shown in Figure 7(b). Positive and large values of phase and gain margins are obtained of values 24.3° and 64.2 dB respectively, which confirm good stability of positive half cycle converter. Similarly, the stability for the converter circuit operating in negative half cycle can be seen and due to symmetry in BL configuration exactly same results will be gained after following same method so, in this paper, negative cycle converter is not discussed.Figure 7
Positive cycle BL-CC converter analysis using (a) pole-zero map and (b) bode-plot.
(a)(b)


## 5. Result and Discussion

Performance of BL-CC AC-DC converter-based drive system for BLDC motor for MEV application is examined in this section with motor specifications as in Appendix using MATLAB/Simulink. The simulated results of drive system are also discussed in this section.


### 5.1. Simulation Results

In this section, MATLAB simulation results of BL-CC converter-based BLDC motor drive are presented and discussed in detail under steady state as well as dynamic condition.


#### 5.1.1. Performance of Presented BLDC Motor Drive at Steady-State

The steady-state performance of BL-CC converter-based BLDC motor drive with input AC voltage 220 V and DC-link voltage 200 V at rated load is shown in Figure8. In which Figures 8(a) and 8(b) shows input AC voltage and current, respectively. DC-link voltage and BLDC motor stator current is shown in Figures 8(c) and 8(d), respectively. BLDC motor drive performance with 80 V DC-link voltage and input AC voltage 220 V at rated load is depicted in Figure 9.Figure 8
BLDC motor drive performance at rated load with input AC voltage 220 V and DC-link voltage 200 V: (a) input AC voltage, (b) input AC current, (c) DC- link capacitor voltage, and (d) stator current of BLDC motor.
(a)(b)(c)(d)Figure 9
BLDC motor drive performance at rated load with input AC voltage 220 V and DC-link voltage 80 V: (a) input AC voltage, (b) input current, (c) DC-link capacitor voltage, and (d) stator current of BLDC motor.
(a)(b)(c)(d)


#### 5.1.2. Performance of PF-Corrected BL-CC Converter

The current across both the inductors (L1 and L2) of the CC converter in BL configuration is depicted in Figures 10(c) and 10(d), respectively. The DIC mode operation of the PF correction converter can be well seen in Figures 10(c) and 10(d) due to zero inductor current for some instant in current waveforms of both the inductors. The voltages across the intermediate energy storage capacitors C1 and C2 are depicted in Figure 11 along with input AC voltage and current. Voltages and current across both the switches of BL-CC converter is depicted in Figure 12. The voltage and current across positive cycle switch SP is shown in Figures 12(a) and 12(b); however, the voltage and current through negative cycle switch is shown in Figures 12(c) and 12(d). The conduction operation of inbuilt antiparallel diode can be clearly seen in Figures 12(b) and 12(d). The current and voltage across switch, SP of BLDC motor drive system is enlarged and shown in Figure 13. The peak values of voltage and current across the switch SP from the results shown in Figures 13(a) and 13(b) comes out to be 470 V and 43 A, respectively.Figure 10
Performance of BL-CC converter: (a) input AC voltage, (b) input current, (c) current through inductorL1, and (d) current through inductor L2.Figure 11
BL-CC converter parameters: (a) input AC voltage, (b) input current, (c) voltage across capacitorC1, (d) voltage across capacitor C2.
(a)(b)(c)(d)Figure 12
BL-CC converter switches parameters: (a) voltage across switchSP, (b) current across switch SP, (c) voltage across switch SN, and (d) current across switch SN.
(a)(b)(c)(d)Figure 13
Enlarged waveforms of (a) voltage across switchSP and (b) current through switch SN.
(a)(b)


#### 5.1.3. Dynamic-Performance of Presented BL-CC Converter-Based BLDC Motor Drive

The dynamic performance results of presented BL-CC converter-based BLDC motor drive is incorporated in this section. Figure14(a) shows the decrease in magnitude of supply current with the sudden rise in voltage from 110 V to 220 V. However, initial and final value of DC-link voltage under this step rise in supply voltage is the same. The DC-link voltage is restored to their previous value under varying supply voltage. The stator current and back EMF of BLDC motor are almost unaffected under varying supply voltage. Figure 14(b) also shows the same initial and final value of DC-link voltage with sudden drop in supply voltage from 220 V to 110 V. However, the supply current and back EMF increases. The stator current is unaffected for the step decrease in supply voltage. The BL-CC converter-based drive performance with sudden variation in DC-link voltage can be seen in Figures 14(c) and 14(d). When DC-link voltage is reduced from 220 V to 150 V, the supply current and back EMF got reduced which can be seen in Figure 14(c). If the DC-link voltage is increased from 150 V to 200 V, the increment in current as well as back EMF are observed in Figure 14(d). The dynamic performance of the BL-CC converter-based BLDC drive under variation in load torque can be seen in Figure 14(e) and 14(f). When the load torque is suddenly increased from 1 N m to 1.55 N m, the back EMF decreases with an increase in supply and stator currents. The final and initial value of the DC-link voltage is also maintained at same value which can be seen in Figure 14(e). Figure 14(f) shows the dynamic results with sudden decrement in load. The results clearly show that the supply current and stator current both decreases with decrement in load torque. However, the back EMF increases with dip in load.Figure 14
Dynamic performance of BL-CC converter-based BLDC drive under sudden variation in (a) supply voltage from 220 V to 110 V, (b) supply voltage from 110 V to 220 V, (c) DC-link voltage from 200 V to 150 V, (d) DC-link voltage from 150 V to 200 V, (e) load torque from 1 to 1.5 N m, and (f) load torque from 1.5 to 1 N m.
(a)(b)(c)(d)(e)(f)


### 5.2. Hardware Validation of Presented BL-CC Converter-Based BLDC Drive

In this section, steady-state and dynamic performance real-time experimental results of BL-CC converter-based BLDC motor drive are presented and discussed in detail. PQ results are also shown in this section.


#### 5.2.1. Steady-State Results

Figure15 shows the experimental results of BL-CC converter-based BLDC motor drive under steady-state operation. The supply current seems to follow the supply voltage profile with DC-link voltage of 200 V.Figure 15
Steady-state performance of BL-CC converter-based BLDC motor drive.


#### 5.2.2. PQ Results

Figure16 shows the obtained PQ results with unity power factor operation of the presented BLDC motor drive. The performance indices such as supply input voltage (VIN), supply current (IIN), apparent (S), active (P), and reactive (Q) powers, displacement power factor (DPF), power factor (PF), and THD of supply current are measured on a “Fluke.” The THD of supply current is 2.9%; therefore, the presented system is meeting the IEC standard 61000-3-2 of PQ.Figure 16
Power quality performance of the MEV system: (a)P, Q, S, and P.F. and (b) harmonic spectrum of supply current.


#### 5.2.3. Experimental Dynamic Performance of the Presented System

Hardware validation of dynamic performance results with step change in supply voltage is shown in Figure17(a). The results show the increment in supply current with same initial and final value of DC-link voltage on sudden decrement in supply voltage. The results with sudden variation in DC-link voltage is shown in Figure 17(b). The results show the increment in supply current and stator current with sudden increment in DC-link voltage.Figure 17
Dynamic performance of BL-CC converter-based BLDC drive under sudden variation in (a) supply voltage and (b) DC-link voltage.
(a)(b)


### 5.3. Efficiency Comparison

In conventional converter powered BLDC motor drive, the losses in the VSI are very high due to high-frequency switching operation to generate the PWM pulses for speed control of BLDC motor. The switching frequency is of order of 20 kHz. This high switching frequency causes higher switching losses in VSI and thus, harnesses the efficiency. The conventional PFC converter and DBR + CSC converter-based CSC converter both uses DBR. The maximum efficiency of DBR is 81.2%, so the efficiency of the DBR-based system will be quite less than 81.2%. In the presented scheme, the VSI used to generate the pulses for BLDC motor is switched at fundamental frequency and the speed control of BLDC motor in the presented BL-CC converter-based PFC scheme is done by varying DC-link voltage and thus, the switching losses are significantly reduced. The presented scheme completely eliminates the DBR stage and therefore the losses associated with DBR are also eliminated and the significant increment (6%–8%) in efficiency is achieved with the present configuration.The comparison in PFC converter efficiency between conventional PFC, DBR + CSC converter-based PFC and presented BL-CC converter-based PFC scheme under varying power levels is presented in Figure18. The efficiency under varying power level for presented BL-CC converter-based PFC scheme used in this work is greater than both DBR + CSC converter and conventional converter-based PFC scheme as shown in Figure 18.Figure 18
Efficiency variation with varying power levels for different converters.


## 5.1. Simulation Results

In this section, MATLAB simulation results of BL-CC converter-based BLDC motor drive are presented and discussed in detail under steady state as well as dynamic condition.


### 5.1.1. Performance of Presented BLDC Motor Drive at Steady-State

The steady-state performance of BL-CC converter-based BLDC motor drive with input AC voltage 220 V and DC-link voltage 200 V at rated load is shown in Figure8. In which Figures 8(a) and 8(b) shows input AC voltage and current, respectively. DC-link voltage and BLDC motor stator current is shown in Figures 8(c) and 8(d), respectively. BLDC motor drive performance with 80 V DC-link voltage and input AC voltage 220 V at rated load is depicted in Figure 9.Figure 8
BLDC motor drive performance at rated load with input AC voltage 220 V and DC-link voltage 200 V: (a) input AC voltage, (b) input AC current, (c) DC- link capacitor voltage, and (d) stator current of BLDC motor.
(a)(b)(c)(d)Figure 9
BLDC motor drive performance at rated load with input AC voltage 220 V and DC-link voltage 80 V: (a) input AC voltage, (b) input current, (c) DC-link capacitor voltage, and (d) stator current of BLDC motor.
(a)(b)(c)(d)


### 5.1.2. Performance of PF-Corrected BL-CC Converter

The current across both the inductors (L1 and L2) of the CC converter in BL configuration is depicted in Figures 10(c) and 10(d), respectively. The DIC mode operation of the PF correction converter can be well seen in Figures 10(c) and 10(d) due to zero inductor current for some instant in current waveforms of both the inductors. The voltages across the intermediate energy storage capacitors C1 and C2 are depicted in Figure 11 along with input AC voltage and current. Voltages and current across both the switches of BL-CC converter is depicted in Figure 12. The voltage and current across positive cycle switch SP is shown in Figures 12(a) and 12(b); however, the voltage and current through negative cycle switch is shown in Figures 12(c) and 12(d). The conduction operation of inbuilt antiparallel diode can be clearly seen in Figures 12(b) and 12(d). The current and voltage across switch, SP of BLDC motor drive system is enlarged and shown in Figure 13. The peak values of voltage and current across the switch SP from the results shown in Figures 13(a) and 13(b) comes out to be 470 V and 43 A, respectively.Figure 10
Performance of BL-CC converter: (a) input AC voltage, (b) input current, (c) current through inductorL1, and (d) current through inductor L2.Figure 11
BL-CC converter parameters: (a) input AC voltage, (b) input current, (c) voltage across capacitorC1, (d) voltage across capacitor C2.
(a)(b)(c)(d)Figure 12
BL-CC converter switches parameters: (a) voltage across switchSP, (b) current across switch SP, (c) voltage across switch SN, and (d) current across switch SN.
(a)(b)(c)(d)Figure 13
Enlarged waveforms of (a) voltage across switchSP and (b) current through switch SN.
(a)(b)


### 5.1.3. Dynamic-Performance of Presented BL-CC Converter-Based BLDC Motor Drive

The dynamic performance results of presented BL-CC converter-based BLDC motor drive is incorporated in this section. Figure14(a) shows the decrease in magnitude of supply current with the sudden rise in voltage from 110 V to 220 V. However, initial and final value of DC-link voltage under this step rise in supply voltage is the same. The DC-link voltage is restored to their previous value under varying supply voltage. The stator current and back EMF of BLDC motor are almost unaffected under varying supply voltage. Figure 14(b) also shows the same initial and final value of DC-link voltage with sudden drop in supply voltage from 220 V to 110 V. However, the supply current and back EMF increases. The stator current is unaffected for the step decrease in supply voltage. The BL-CC converter-based drive performance with sudden variation in DC-link voltage can be seen in Figures 14(c) and 14(d). When DC-link voltage is reduced from 220 V to 150 V, the supply current and back EMF got reduced which can be seen in Figure 14(c). If the DC-link voltage is increased from 150 V to 200 V, the increment in current as well as back EMF are observed in Figure 14(d). The dynamic performance of the BL-CC converter-based BLDC drive under variation in load torque can be seen in Figure 14(e) and 14(f). When the load torque is suddenly increased from 1 N m to 1.55 N m, the back EMF decreases with an increase in supply and stator currents. The final and initial value of the DC-link voltage is also maintained at same value which can be seen in Figure 14(e). Figure 14(f) shows the dynamic results with sudden decrement in load. The results clearly show that the supply current and stator current both decreases with decrement in load torque. However, the back EMF increases with dip in load.Figure 14
Dynamic performance of BL-CC converter-based BLDC drive under sudden variation in (a) supply voltage from 220 V to 110 V, (b) supply voltage from 110 V to 220 V, (c) DC-link voltage from 200 V to 150 V, (d) DC-link voltage from 150 V to 200 V, (e) load torque from 1 to 1.5 N m, and (f) load torque from 1.5 to 1 N m.
(a)(b)(c)(d)(e)(f)


## 5.1.1. Performance of Presented BLDC Motor Drive at Steady-State

The steady-state performance of BL-CC converter-based BLDC motor drive with input AC voltage 220 V and DC-link voltage 200 V at rated load is shown in Figure8. In which Figures 8(a) and 8(b) shows input AC voltage and current, respectively. DC-link voltage and BLDC motor stator current is shown in Figures 8(c) and 8(d), respectively. BLDC motor drive performance with 80 V DC-link voltage and input AC voltage 220 V at rated load is depicted in Figure 9.Figure 8
BLDC motor drive performance at rated load with input AC voltage 220 V and DC-link voltage 200 V: (a) input AC voltage, (b) input AC current, (c) DC- link capacitor voltage, and (d) stator current of BLDC motor.
(a)(b)(c)(d)Figure 9
BLDC motor drive performance at rated load with input AC voltage 220 V and DC-link voltage 80 V: (a) input AC voltage, (b) input current, (c) DC-link capacitor voltage, and (d) stator current of BLDC motor.
(a)(b)(c)(d)


## 5.1.2. Performance of PF-Corrected BL-CC Converter

The current across both the inductors (L1 and L2) of the CC converter in BL configuration is depicted in Figures 10(c) and 10(d), respectively. The DIC mode operation of the PF correction converter can be well seen in Figures 10(c) and 10(d) due to zero inductor current for some instant in current waveforms of both the inductors. The voltages across the intermediate energy storage capacitors C1 and C2 are depicted in Figure 11 along with input AC voltage and current. Voltages and current across both the switches of BL-CC converter is depicted in Figure 12. The voltage and current across positive cycle switch SP is shown in Figures 12(a) and 12(b); however, the voltage and current through negative cycle switch is shown in Figures 12(c) and 12(d). The conduction operation of inbuilt antiparallel diode can be clearly seen in Figures 12(b) and 12(d). The current and voltage across switch, SP of BLDC motor drive system is enlarged and shown in Figure 13. The peak values of voltage and current across the switch SP from the results shown in Figures 13(a) and 13(b) comes out to be 470 V and 43 A, respectively.Figure 10
Performance of BL-CC converter: (a) input AC voltage, (b) input current, (c) current through inductorL1, and (d) current through inductor L2.Figure 11
BL-CC converter parameters: (a) input AC voltage, (b) input current, (c) voltage across capacitorC1, (d) voltage across capacitor C2.
(a)(b)(c)(d)Figure 12
BL-CC converter switches parameters: (a) voltage across switchSP, (b) current across switch SP, (c) voltage across switch SN, and (d) current across switch SN.
(a)(b)(c)(d)Figure 13
Enlarged waveforms of (a) voltage across switchSP and (b) current through switch SN.
(a)(b)


## 5.1.3. Dynamic-Performance of Presented BL-CC Converter-Based BLDC Motor Drive

The dynamic performance results of presented BL-CC converter-based BLDC motor drive is incorporated in this section. Figure14(a) shows the decrease in magnitude of supply current with the sudden rise in voltage from 110 V to 220 V. However, initial and final value of DC-link voltage under this step rise in supply voltage is the same. The DC-link voltage is restored to their previous value under varying supply voltage. The stator current and back EMF of BLDC motor are almost unaffected under varying supply voltage. Figure 14(b) also shows the same initial and final value of DC-link voltage with sudden drop in supply voltage from 220 V to 110 V. However, the supply current and back EMF increases. The stator current is unaffected for the step decrease in supply voltage. The BL-CC converter-based drive performance with sudden variation in DC-link voltage can be seen in Figures 14(c) and 14(d). When DC-link voltage is reduced from 220 V to 150 V, the supply current and back EMF got reduced which can be seen in Figure 14(c). If the DC-link voltage is increased from 150 V to 200 V, the increment in current as well as back EMF are observed in Figure 14(d). The dynamic performance of the BL-CC converter-based BLDC drive under variation in load torque can be seen in Figure 14(e) and 14(f). When the load torque is suddenly increased from 1 N m to 1.55 N m, the back EMF decreases with an increase in supply and stator currents. The final and initial value of the DC-link voltage is also maintained at same value which can be seen in Figure 14(e). Figure 14(f) shows the dynamic results with sudden decrement in load. The results clearly show that the supply current and stator current both decreases with decrement in load torque. However, the back EMF increases with dip in load.Figure 14
Dynamic performance of BL-CC converter-based BLDC drive under sudden variation in (a) supply voltage from 220 V to 110 V, (b) supply voltage from 110 V to 220 V, (c) DC-link voltage from 200 V to 150 V, (d) DC-link voltage from 150 V to 200 V, (e) load torque from 1 to 1.5 N m, and (f) load torque from 1.5 to 1 N m.
(a)(b)(c)(d)(e)(f)


## 5.2. Hardware Validation of Presented BL-CC Converter-Based BLDC Drive

In this section, steady-state and dynamic performance real-time experimental results of BL-CC converter-based BLDC motor drive are presented and discussed in detail. PQ results are also shown in this section.


### 5.2.1. Steady-State Results

Figure15 shows the experimental results of BL-CC converter-based BLDC motor drive under steady-state operation. The supply current seems to follow the supply voltage profile with DC-link voltage of 200 V.Figure 15
Steady-state performance of BL-CC converter-based BLDC motor drive.


### 5.2.2. PQ Results

Figure16 shows the obtained PQ results with unity power factor operation of the presented BLDC motor drive. The performance indices such as supply input voltage (VIN), supply current (IIN), apparent (S), active (P), and reactive (Q) powers, displacement power factor (DPF), power factor (PF), and THD of supply current are measured on a “Fluke.” The THD of supply current is 2.9%; therefore, the presented system is meeting the IEC standard 61000-3-2 of PQ.Figure 16
Power quality performance of the MEV system: (a)P, Q, S, and P.F. and (b) harmonic spectrum of supply current.


### 5.2.3. Experimental Dynamic Performance of the Presented System

Hardware validation of dynamic performance results with step change in supply voltage is shown in Figure17(a). The results show the increment in supply current with same initial and final value of DC-link voltage on sudden decrement in supply voltage. The results with sudden variation in DC-link voltage is shown in Figure 17(b). The results show the increment in supply current and stator current with sudden increment in DC-link voltage.Figure 17
Dynamic performance of BL-CC converter-based BLDC drive under sudden variation in (a) supply voltage and (b) DC-link voltage.
(a)(b)


## 5.2.1. Steady-State Results

Figure15 shows the experimental results of BL-CC converter-based BLDC motor drive under steady-state operation. The supply current seems to follow the supply voltage profile with DC-link voltage of 200 V.Figure 15
Steady-state performance of BL-CC converter-based BLDC motor drive.


## 5.2.2. PQ Results

Figure16 shows the obtained PQ results with unity power factor operation of the presented BLDC motor drive. The performance indices such as supply input voltage (VIN), supply current (IIN), apparent (S), active (P), and reactive (Q) powers, displacement power factor (DPF), power factor (PF), and THD of supply current are measured on a “Fluke.” The THD of supply current is 2.9%; therefore, the presented system is meeting the IEC standard 61000-3-2 of PQ.Figure 16
Power quality performance of the MEV system: (a)P, Q, S, and P.F. and (b) harmonic spectrum of supply current.


## 5.2.3. Experimental Dynamic Performance of the Presented System

Hardware validation of dynamic performance results with step change in supply voltage is shown in Figure17(a). The results show the increment in supply current with same initial and final value of DC-link voltage on sudden decrement in supply voltage. The results with sudden variation in DC-link voltage is shown in Figure 17(b). The results show the increment in supply current and stator current with sudden increment in DC-link voltage.Figure 17
Dynamic performance of BL-CC converter-based BLDC drive under sudden variation in (a) supply voltage and (b) DC-link voltage.
(a)(b)


## 5.3. Efficiency Comparison

In conventional converter powered BLDC motor drive, the losses in the VSI are very high due to high-frequency switching operation to generate the PWM pulses for speed control of BLDC motor. The switching frequency is of order of 20 kHz. This high switching frequency causes higher switching losses in VSI and thus, harnesses the efficiency. The conventional PFC converter and DBR + CSC converter-based CSC converter both uses DBR. The maximum efficiency of DBR is 81.2%, so the efficiency of the DBR-based system will be quite less than 81.2%. In the presented scheme, the VSI used to generate the pulses for BLDC motor is switched at fundamental frequency and the speed control of BLDC motor in the presented BL-CC converter-based PFC scheme is done by varying DC-link voltage and thus, the switching losses are significantly reduced. The presented scheme completely eliminates the DBR stage and therefore the losses associated with DBR are also eliminated and the significant increment (6%–8%) in efficiency is achieved with the present configuration.The comparison in PFC converter efficiency between conventional PFC, DBR + CSC converter-based PFC and presented BL-CC converter-based PFC scheme under varying power levels is presented in Figure18. The efficiency under varying power level for presented BL-CC converter-based PFC scheme used in this work is greater than both DBR + CSC converter and conventional converter-based PFC scheme as shown in Figure 18.Figure 18
Efficiency variation with varying power levels for different converters.


## 6. Conclusion

The detailed mathematical and stability analysis of the BL-CC AC-DC converter used in BLDC motor drive system for MEV application has been shown in this paper. Stability of the converter has been studied with the help of Bode plot and pole-zero maps. The simulated model of the scheme on MATLAB platform has been developed and their simulated analysis using simulated results has also been included in the paper along with the experimental results of the developed prototype in the laboratory. A presented BL-CC AC–DC converter having reduced components count, higher efficiency, and enhanced PQ designed in DIC mode of operation has been verified with the help of experimental results as well as MATLAB simulation results. The presented drive system with reduced components count is garnished with advantages like size reduction and simple controlling. Moreover, the input voltage and current seems to be following linear relation resulting in PQ enhancement and the input current THD is found to be 2.58% at rated load with input AC voltage 220 V and DC-link capacitor voltage 300 V and THD found to be 2.87% with 220 V input AC voltage and DC-link voltage 80 V at rated load. The presented BLDC motor drive is validated using the results obtained to justify the satisfactory closed-loop performance of BLDC motor drive system.



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*Source: 7026462-2022-06-01.xml*