Microsoft Word - ETASR_V12_N5_pp9178-9185 Engineering, Technology & Applied Science Research Vol. 12, No. 5, 2022, 9178-9185 9178 www.etasr.com Gopan K & Shree: Implementation of a High Power Quality BLDC Motor Drive Using Bridgeless DC to … Implementation of a High Power Quality BLDC Motor Drive Using Bridgeless DC to DC Converter with Fuzzy Logic Controller Vishnu Gopan K. Department of Electrical and Electronics Engineering Coimbatore Institute of Technology, Coimbatore Tamil Nadu, India gopan1vishnu@gmail.com J. Devi Shree Department of Electrical and Electronics Engineering Coimbatore Institute of Technology, Coimbatore Tamil Nadu, India devishreecit@gmail.com Received: 20 July 2022 | Revised: 28 July 2022 | Accepted: 29 July 2022 Abstract-Electric motor drives based on electronic power converters having good power quality parameters are getting huge acceptance. Conventional Diode Bridge Rectifier (DBR) and DC to DC converter-based methods have become obsolete, as they provide low power quality indices which hamper the supply by introducing current harmonics and conduction losses. Although there are many developments in motors and control strategies, the risk and complexity of such drives become bottlenecks in implementation. This study implemented a drive scheme with a brushless DC Motor. The new improved bridgeless topology was modified with an advanced fuzzy logic controller to further improve its power quality and performance. Due to low power, a high-speed application of Brush Less (BLDC) motor was selected for the drive scheme. This combination could achieve almost Unity Power Factor (UPF) and significantly improve control compared to conventional topologies. A circuit- wise analysis was conducted to design the converter's components. The modifications were elaborated through mathematical expressions, and the parameters of power quality were analyzed and validated. Keywords-Brush-Less Direct Current Motor (BLDC); Diode Bridge Rectifier (DBR); High-Frequency Transformer (HFT); Total Harmonic Distortion (THD); Discontinuous Inductor Current Mode (DICM); Bridgeless Dual Cuk (BDC); Fuzzy Logic Controller (FLC); Unity Power Factor (UPF) I. INTRODUCTION The need for quality AC supplies and their efficiency is becoming a primary concern in modern power electronics [1], especially in the development of various DC-DC and AC-DC converters. This paper discusses DC-DC converters, as they are more flexible and versatile in terms of power quality and efficiency. Improved power quality is mandatory for electrical equipment nowadays by the international Power Quality (PQ) standard IEC 61000-3-2. This standard also stipulates high power factor and low Total Harmonic Distortion (THD) of the AC main current for Class-A applications (<600W, <16A) [2]. Due to their advantages of high efficiency, high flux density per unit volume, low maintenance requirement, low EMI problems, high ruggedness, and a wide range of speed control, Brush-Less DC (BLDC) motors are recommended for many low- and medium-power drive applications [3]. BLDC motors are used in numerous areas such as household applications [4], transportation (hybrid vehicles) [5], aerospace [6], heating, etc. This study implemented and evaluated a variety of power electronic circuits to drive a BLDC motor. An AC Supply is essential for domestic loads. Conventionally, a Diode Bridge Rectifier (DBR), followed by a filter capacitor is used for the generation of a DC supply. Today, many applications continue to use them due to their simplicity of construction and cost- effective production. The high value of the filter capacitor draws a high non-sinusoidal current from the supply. In addition, DBRs with their inherent flaw of high conduction losses reduce the efficiency of converter circuits, and increased harmonic levels cause a rise in the THD levels between 45- 65% [7]. Many Power Factor Correction (PFC) converters have been developed to reduce the THD levels to permissible limits and improve the power factor of the supply, and most of them serve their purpose on their performance levels. Therefore, more reliable drive control is performed through the control of the DC link voltage by controlling the switches on the PFC converter side [8]. To implement such a control, the converter has to be chosen from an array of DC-DC converters divided into isolated or nonisolated and bridged or bridgeless topologies [9, 10]. Moreover, it has to be decided in which mode the converter should operate to achieve Unity Power Factor (UPF). This study selected a Cuk converter, after examining various topologies with different types of loads and applications of PFC converters, intending to improve the power quality of AC to DC conversion. This study also presents the bridgeless topology with a proposed modification. Additionally, a fuzzy logic-based advanced linguistic controller was implemented for the bridgeless topology to further enhance the performance of the converter and improve power quality at the main supply. The simulated results along with their mathematical validation, were used to analyze the improvements. Performance analysis and input power quality Corresponding author: Vishnu Gopan K. Engineering, Technology & Applied Science Research Vol. 12, No. 5, 2022, 9178-9185 9179 www.etasr.com Gopan K & Shree: Implementation of a High Power Quality BLDC Motor Drive Using Bridgeless DC to … of the operation of the converter were used to conduct the harmonic analysis of the topology. As there are many speed control drive schemes for various applications, this study allowed the operation of a motor drive with quick response and very low speed variations from the reference value. Moreover, the incorporation of FLC into a bridgeless configuration further improved performance and power quality. II. CONFIGURATION For speed control, the selection of the front-end converter and its operation configuration are equally important to achieve a high power factor at the supply mains. The Cuk converter was selected due to its many advantages [12]. There are multiple approaches for the conversion of AC input to variable DC for the drive scheme. A DBR followed by a high DC link capacitor was used, which due to its high losses was replaced by "DBR-Power Factor Correction (PFC)" converter configuration. In such circuits, the speed control of the drive can be achieved in several ways. One way is to control the switching of the 6 individual switches of the motor-end Voltage Source Inverter (VSI). Due to the increased number of control switches and the high frequency of motor operation, it is not preferred due to high switching losses [8]. Another solution could be a PFC converter to control the DC link voltage. The PFC converter can be controlled by 2 methods: a voltage follower or a current multiplier method [13]. These methods depend on which mode the PFC converters operate. This study discussed the 2 modes of operation and attempted to compare their results with the bridgeless topology. PID controllers were used for the three types of converters, using a linearized modeling technique to standardize the results. In the voltage follower approach [13], the converter operates in DCM and is further divided into DICM and DVCM where the respective inductor currents or capacitive voltages become discontinuous during a switching period of the converter switch [13]. The advantage of this mode is that it requires only one sensor for control. The need for 2 voltage sensors and 1 current sensor makes this multiplier method more complex [13]. In this configuration, the converter operates in CCM and ensures more robust control [14]. The configuration consists of a DBR followed by a power factor correction Cuk converter designed to operate in CCM operation. The DC output of the converter is fed to the input side of the voltage source inverter that controls the speed of the BLDC motor. Even though both configurations have their advantages, the main drawback of lack of isolation between the high- and low- frequency switching parts hampers the smooth operation by introducing harmonics in the circuit. This reduces the converter's efficiency and the purported operation in power factor correction. The proposed configuration, shown in Figure 1, resolves this inherent problem by providing high-frequency isolation [9]. This is done by providing 2 High-Frequency Transformers (HFT) in the respective positive and negative side converters of the modified Cuk converter topology. The modification of the proposed converter eliminates the need for a DBR and avoids any conduction losses. The converter operates in DICM, where the current through the output side inductor becomes discontinuous over a switching period. Three converters were constructed and analyzed in Matlab 2018 and their performance was compared during changes in speed conditions. Fig. 1. Proposed isolated coupled Cuk converter-fed BLDC motor drive III. OPERATION OF THE CONFIGURATION The input side DBR was eliminated in the proposed converter-fed BLDC motor drive. This was achieved by incorporating another Cuk converter in parallel with the existing one so that one works in the positive half-cycle and the other in the negative half-cycle of the supply, by implementing a zero-crossing detector on the input side. Another major advantage of this method was that the AC input and the output side BLDC motor drive were completely isolated with the help of an HFT. Hence, the speed control of the drive was hassle- free and the amount of noise present in the control signals could also be reduced. The converter was designed in such a way that the current through the output inductors Lo1 and Lo2 becomes discontinuous over a switching period in either half cycle of the input supply, as shown in Figure 2. Therefore, the converter operated in Discontinuous Inductor Current Mode Engineering, Technology & Applied Science Research Vol. 12, No. 5, 2022, 9178-9185 9180 www.etasr.com Gopan K & Shree: Implementation of a High Power Quality BLDC Motor Drive Using Bridgeless DC to … (DICM) [15]. Even though there are many categories of discontinuous conduction modes, such as DICM on input, DICM on output, and DCVM [16], applying DICM on the output side inductor was simpler and lowered harmonics. Several advantages can be gained by operating the rectifier in DICM, such as a natural near-unity power factor and at zero current the power switches are turned ON and the output diodes are turned OFF. (a) (b) (c) (d) Fig. 2. Operating modes of the proposed converter at different intervals of the switching period during the positive half cycle: (a) switch closed, (b) switch open – inductor discharging, (c) switch closed – inductor fully discharged, and (d) associated waveforms. In the first mode, switch Sw1 is turned ON and the inductors Li1, Lo1, and magnetizing inductance Lm1 start charging. The capacitor Ci1 charges Lm1, and Co1 delivers DC link voltage. In the second mode, the switch is being turned OFF, inductors Li1 and Lo1 discharge thereby charging Ci1 and Co1, and the magnetizing inductance Lm1 discharges through Cd. In the third mode, the output side inductor Lo1 is completely discharged and the input inductor Li1 and the magnetizing inductance of HFT Lm1 continue to discharge. Figure 3 shows the negative half operation of the converter. The converter operates in such a way that the input side energy storage components remain in non-conducting mode and the output side components remain non-discharged. The converter is designed so that the positive sinusoidal input from the AC supply at the fundamental frequency of 50Hz is split into a large number of cycles of operation of the upper Cuk converter switch. (a) (b) (c) (d) Fig. 3. Operating modes of the proposed converter at different intervals of switching period during the negative half cycle: (a) switch closed, (b) switch open – inductor discharging, (c) switch closed – inductor fully discharged, and (d) associated waveforms. A. Motor Speed Control An electronic commutation of the BLDC motor includes the proper switching of the Voltage Source Inverter (VSI) to Engineering, Technology & Applied Science Research Vol. 12, No. 5, 2022, 9178-9185 9181 www.etasr.com Gopan K & Shree: Implementation of a High Power Quality BLDC Motor Drive Using Bridgeless DC to … draw a symmetrical DC from the DC link capacitor for 120° [17] and placed symmetrically at the center of the back Electro- Motive Force (EMF) of each phase. A Hall-effect position sensor was used to sense the rotor position on a span of 60°; which is required for the electronic commutation of the BLDC motor [18]. The front-end converter was controlled by feeding back the DC voltage. The control scheme was comprised of feedback DC voltage, reference voltage generator, and PWM generator. The reference voltage was obtained by multiplying the reference speed by the motor speed constant Kv: ��� ∗ � �� . This reference voltage was compared with the actual DC link value of the converter and the error was used for PWM generation in 3 different ways for the front-end converter switches to obtain speed control [19]. Table I illustrates the switching signals to be sent to the phase 3 VSI. The controller logic was designed to send the ON pulses to the respective switches following the rotor position in a single direction. TABLE I. SWITCHING STATES FOR THE VSI Angular Placement State of Switches T1 T2 T3 T4 T5 T6 NA 0 0 0 0 0 0 0-60 0 0 0 1 1 0 60–120 0 1 1 0 0 0 120–180 0 1 0 0 1 0 180–240 1 0 0 0 0 1 240–300 1 0 0 1 0 0 300–360 0 0 1 0 0 1 NA 0 0 0 0 0 0 IV. DESIGN The basic CUK converter is shown in Figure 4. Fig. 4. CUK converter circuit. For this Cuk converter, the output equation is given as [21]: VDC= - D 1-D Vin In the case of the shown converter topology, the negative output at the output changes to a positive value by interchanging the terminals. In this type of arrangement, the average AC voltage applied across the input side can be obtained as: ��� �� � |�� ��� ��| � �230√2 ��� 340��� (1) using the following parameter values: Vmin=100V, Vmax=200V, Vsmin=170V, Vsmax=270V, Pmax=250W, and Pmin=125W. The selected switching frequency fs was 20kHz for the operation of all 3 converters. A. Design of the BDC Converter The output voltage is obtained as [21]: ��� � ������ � !�� ��� (2) Transformer ratio, ������ was taken as 0.5. Let D(t) be the instantaneous value of the duty ratio, then we have [16]: " �� � #$%&�� ��' (#)* +�,#$% � #$%&�� ��' (∗|#)* -�� .+�|,#$% (3) Instantaneous power is given by: /� � 0 1234#$%_234 ��� 6 (4) 1) Inductor Design [20]: 7� � 7�8 � #)* +�.� +�9:)* +�;< � 9.;< & #<� 1) ( & #$% �#)* +�,#$%( (5) where η is the input current ripple, which was taken as 50%, and n is the turns ratio of the HFT, taken as 1:2. 7= � 7=8 � &#< � 1) ( #$% 8#)* +�;< & #$% �#)* +�,#$%( (6) Both equations are used under the assumption that Pi=Pi-max and Vin= √2 Vs_min.The value of the input side inductor was 7mH. The value of the output side inductor was obtained as 1.502mH for VDC=200V, and 0.546mH for VDC=100V, so a value lower than 0.546mH should be chosen. The selected value selected was 0.1mH. The magnetizing inductances are [16]: 7� � 7�8 � &#< � 1) ( >.;< & #$% �#)* +�,#$%( (7) where ς is the permitted ripple current on the output side, taken as 50%, were obtained as 7mH. 2) Capacitor Design ?� � ?�8 � �.1)@.√8#<.;<. �√8#<,#$%� (8) where Ci1=Ci2=220nF. ?= � ?=8 � 1)A.#$%.;< �√8#<,#$%� (9) where Co1=Co2=2.2μF. The output side DC link capacitor was given as: ?� � :$%8.B#$% � & 1) #$%( 8..C.#$%� (10) where k is the input side ripple voltage (25%), x is the ripple voltage at the converter side (10%), and ρ=ΔVDC is the permitted output ripple (5%). The obtained value of CD was 1000μF. 3) Filter Design A low pass LC filter was used to avoid higher order harmonics in the supply system. The maximum value of the filter's capacitance was given by [13]: Engineering, Technology & Applied Science Research Vol. 12, No. 5, 2022, 9178-9185 9182 www.etasr.com Gopan K & Shree: Implementation of a High Power Quality BLDC Motor Drive Using Bridgeless DC to … Cmax= Im ωLV m tan θ = √2 Pmax / Vs ωL√2 Vs tan θ (11) where θ is the displacement angle between the fundamental value of supply voltage and supply current, taken as 2°. The maximum value of the filter capacitor was calculated using (11) at 574.4nF and was selected as 330nF. This value was selected for all 3 configurations as there is no variation in input voltage, and the capacitor always acts across one-half of the input supply at any given time. The value of the filter inductor was designed by considering the source impedance Ls as 4-5% of the base impedance. Hence, the additional value of required inductance was given as: 7; � 7DEF + 7- => 7DEF = 7; − 7- 7DEF = J K� ;L��M − 0.025 & .O( & #<� 1P ( (12) where fc is the cut-off frequency, selected such that fL