Single-stage three-phase boost power factor correction circuit for AC ...

International Journal of Electronics

ISSN: 0020-7217 (Print) 1362-3060 (Online) Journal homepage: http://www.tandfonline.com/loi/tetn20

Single-stage three-phase boost power factor correction circuit for AC–DC converter Haitham Z. Azazi, Sayed M. Ahmed & Azza E. Lashine To cite this article: Haitham Z. Azazi, Sayed M. Ahmed & Azza E. Lashine (2017): Single-stage three-phase boost power factor correction circuit for AC–DC converter, International Journal of Electronics, DOI: 10.1080/00207217.2017.1335800 To link to this article: http://dx.doi.org/10.1080/00207217.2017.1335800

Published online: 12 Jun 2017.

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Date: 13 June 2017, At: 01:19

INTERNATIONAL JOURNAL OF ELECTRONICS, 2017 https://doi.org/10.1080/00207217.2017.1335800

Single-stage three-phase boost power factor correction circuit for AC–DC converter Haitham Z. Azazi, Sayed M. Ahmed and Azza E. Lashine Department of Electrical Engineering, Faculty of Engineering, Menoufiya University, Shebin El-Kom, Egypt ABSTRACT

ARTICLE HISTORY

This article presents a single-stage three-phase power factor correction (PFC) circuit for AC-to-DC converter using a single-switch boost regulator, leading to improve the input power factor (PF), reducing the input current harmonics and decreasing the number of required active switches. A novel PFC control strategy which is characterised as a simple and low-cost control circuit was adopted, for achieving a good dynamic performance, unity input PF, and minimising the harmonic contents of the input current, at which it can be applied to low/medium power converters. A detailed analytical, simulation and experimental studies were therefore conducted. The effectiveness of the proposed controller algorithm is validated by the simulation results, which were carried out using MATLAB/SIMULINK environment. The proposed system is built and tested in the laboratory using DSPDS1104 digital control board for an inductive load. The results revealed that the total harmonic distortion in the supply current was very low. Finally, a good agreement between simulation and experimental results was achieved.

Received 10 November 2016 Accepted 14 May 2017 KEYWORDS

AC–DC converter; boost regulator; single-stage; power factor correction

1. Introduction Diode rectifiers are usually utilised in the power converter circuits as an interface with the electric utility in most of the power electronics applications (Yao, Meng, Bo, & Hu, 2016). Bridge rectifier operation leads to a distortion in the input current, generates harmonics in the AC power source and causes various problems (Zhang, 2009). A number of problems in the sensitive electronic equipment and distribution are produced because of the non-sinusoidal input current drawn by the rectifiers. This operation also leads to a distortion in the supply voltage. Therefore, it requires high values of volt–ampere rating of the generator, transformer and transmission lines. The result of this problem is a high total harmonic distortion (THD) and malfunctioning of the sensitive electronic equipment (Ming, 2004). Single-stage power factor correction (PFC) topologies have been introduced for AC–DC converter, as PFC and regulator circuits can be combined into one stage in order to reduce the circuit and control system complexity and to lower the total cost. They have high efficiency, a near unity PF, low harmonic content, stable output voltage, simple control loop and a small size (Hirachi & Mutsuo, 1999; Pan et al., 2017; Park et al., 2014). Several PFC methods were proposed in the literature to improve the PF (Lee & Do, 2016; Pereira, Da Silva, Silva, & Tofoli, 2015). A harmonic current injection method was used as a new method for PFC (Itoh & Ashida, 2008). The topology consists of two filters, two electronic CONTACT Haitham Z. Azazi [email protected] Engineering, Menoufiya University, Shebin El-Kom 32511, Egypt © 2017 Informa UK Limited, trading as Taylor & Francis Group

Department of Electrical Engineering, Faculty of

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H. Z. AZAZI ET AL.

switches and a harmonic injection network. The control strategy in this circuit is complex and THD is high. Boosting PFC control without using input voltage sensor for three-phase AC-to-DC converter was proposed in Chattopadhyay and Ramanarayanan (2004). The main disadvantage of this circuit is using six switches, which results in a complicated control circuit. A simplified PFC control strategy for three-phase rectifier using Scott Transformer was proposed in Badin and Barbi (2006). Two controlled switches, two coils and two transformers were utilised in this circuit. An artificial intelligent technique was proposed in Hartmann, Ertland and Kolar (2012), where a fuzzy logic controller was applied. The main disadvantages of fuzzy controller are complex control, high THD and high cost. Three-phase delta switch rectifier was proposed in Rajan (2014), where six switches were required, leading to a complicated control and an increase in the cost. The three-phase boost PFC for the AC-to-DC converter was used due to existing continuous input currents and high-output voltages. It may be divided into two methods, six-switch boost rectifier, and a single-switch boost rectifier. The six-switch boost rectifier is used to achieve a nearly sinusoidal input current, resulting in features, which include nearly sinusoidal input current and high-PF (Huber, Kumar, & Jovanovic, 2014; Huber, Kumar, & Jovanović, 2015). However, the power and control circuits are very complicated. In the other method, six diodes and a single switch were used to control the supply currents (Bashi et al., 2005). This PFC circuit operates at discontinuous current mode. However, the disadvantage of this circuit is mainly dealing with fifth order and that the THD is relatively high (9.62%). In this paper, a novel control of a three-phase boost PFC converter using single switch is presented. Six diodes and single controlled switch are utilised. The principle of operation and control of the converter are also studied. Unity PF with low supply current harmonics can be obtained using the proposed control; furthermore, the output current and voltage are rectified as nearly pure DC voltage. Simulation results are presented for an inductive load. The concept of the control was to operate on the peaks of the input three-phase voltage. This results in reducing the variation of the voltage across the DC capacitor. Thus, a low value of the capacitor can be used to produce a practical circuit. The experimental system was implemented, and the results were taken to verify the effectiveness of the system.

2. System description 2.1 Power circuit Figure 1 shows a three-phase AC–DC boost-type voltage regulator. Only one unidirectional switch is used; a three-phase bridge rectifier consisting of six diodes is used in this circuit. An input threephase boost inductors (La, Lb, Lc) are located between the AC source and the bridge rectifier. The switch is located between the bridge rectifier and the load. This switch regulates the power delivered to the load at its off-state and provides a short circuit on both the source and boost inductors at its on-state. Since the single switch of the proposed circuit has a simple control circuit, this will simplify the controller design significantly.

2.2 Control circuit Figure 1 shows the block diagram of the proposed control technique. Only three independent hysteresis current controllers are used in the proposed regulator. The voltage reference signal, (Vref), is set according to the required load voltage. A mean value detector is used with the output voltage (Vo) for converting it to a corresponding dc value. This value is compared with the reference voltage signal, and the error signal is then passed through a Proportional Integral controller. The controller output is then multiplied by the unit vector of the supply phase voltages va, vb and vc to produce the command currents isac, isbc and iscc, respectively. The

INTERNATIONAL JOURNAL OF ELECTRONICS

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Figure 1. Block diagram of the proposed single-switch three-phase AC–DC boost voltage regulator.

supply currents isa, isb and isc are compared with their corresponding commands, and the errors are processed through three independent hysteresis controllers. The outputs of the hysteresis controllers are processed through three logic AND gates and compared with the outputs of the logic control signals, which detect the higher values of the supply phase voltage vsa, vsb and vsc, then passed through a logic OR gate to produce the logic signal pulse for g1. This logic signal will be used to control the switch (S). If the supply current is controlled to follow the reference current, it follows the supply voltage in its waveform. This control strategy ensures that the input PF is almost kept at nearly unity value.

3. Mathematical analysis The boost regulator shown in Figure 1 has two modes of operation. The following equations can be deduced for the two modes of operation:

3.1. Mode 1 In this mode, the switch (S) is turned on; the supply current is increased and the stored energy in the capacitor discharges in the load. This mode continues until each of the supply currents isa, isb and isc increases to a value more than or equal to {(isac, isbc and iscc) + 0.5H}; where H is the hysteresis band. The voltage equations: Figure 2 shows the waveforms of the three-phase input voltages, they are defined as: pffiffiffi vab ¼ 2Vl sinðωtÞ: (1) pffiffiffi 2Vl sinðωt 120Þ: pffiffiffi vca ¼ 2Vl sinðωt 240Þ; vbc ¼

where Vl is the peak line voltages, ω is the angular frequency of the line voltages. (i) The equation during (0,

π 3 ),

where D5 and D6 are on:

(2) (3)

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Figure 2. Three-phase input line-to-line voltage waveforms.

vcb ¼ isc Rc þ Lc

(ii) The equation during ( π3 ,

2π 3 ),

disc disb isb Rb Lb : dt dt

(4)


vab ¼ isa Ra þ La

disa disb isb Rb Lb : dt dt

(5)

(iii) The equation during ( 2π 3 , π), where D1 and D2 are on:

vac ¼ isa Ra þ La

4π 3 ),

(iv) The equation during (π,

5π 3 ),

(6)


vbc ¼ isb Rb þ Lb

(v) The equation during ( 4π 3 ,

disa disc isc Rc Lc : dt dt

disb disc isc Rc Lc : dt dt

(7)


vba ¼ isb Rb þ Lb

disb disa isa Ra La : dt dt

(8)


5

(vi) The equation during ( 5π 3 ,2π), where D5 and D4 are on: vca ¼ isc Rc þ Lc

disc disa isa Ra La : dt dt

(9)

The current equation is: isa þ isb þ isc ¼ 0:

(10)

1 dil ò ic dt þ vcO ¼ il Rl þ Ll : dt C

(11)

ic þ il ¼ 0:

(12)

The load equations:

3.2 Mode 2 In this mode, the switch (S) is turned off and the load is supplied from the ac source and this continues until each of the supply currents isa, isb and isc decreases to a valueless than or equal to {(isac, isbc and iscc) – 0.5 H}. The voltage equations: (i) The equation during (0,

π 3 ),

D5 and D6 are on:

vcb ¼ isc Rc þ Lc

(ii) The equation during ( π3 ,

2π 3 ),

disc disb þ Vo isb Rb Lb : dt dt

(13)

D1 and D6 are on:

vab ¼ isa Ra þ La

disa disb þ Vo isb Rb Lb : dt dt

(14)

(iii) The equation during ( 2π 3 , π), D1 and D2 are on: vac ¼ isa Ra þ La

(iv) The equation during (π,

4π 3 ),

disa disc þ Vo isc Rc Lc : dt dt

(15)

D3 and D2 are on:

vbc ¼ isb Rb þ Lb

disb disc þ Vo isc Rc Lc : dt dt

(16)

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H. Z. AZAZI ET AL.

(v) The equation during ( 4π 3 ,

5π 3 ),

D3 and D4 are on:

vba ¼ isb Rb þ Lb

disb disa þ Vo isa Ra La : dt dt

(17)

(vi) The equation during ( 5π 3 ,2π), D5 and D4 are on: vca ¼ isc Rc þ Lc

disc disa þ Vo isa Ra La ; dt dt

(18)

where isa ; isb and isc are the instantaneous values of the supply current, La ; Lb and Lc are the boost inductors. The input distortion factor THD is defined as: vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ! ffi u 1 u X Isn 2 =Is1 2 ; THD ¼ t (19) n¼2

where Is1 is the rms value of the fundamental component of the supply current, Isn is the rms value of the supply current at the (nth) harmonic. The input PF is given by: cos ϕ1 PF ¼ pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ; 1 þ THD2

(20)

where ϕ1 is the angle between the fundamental component of the current and the phase voltage of supply.

4. Simulation and experimental results The simulation was carried out for the proposed topology by MATLAB/SIMULINK software. The initial scheme of circuit parameters are listed in the Appendix. With the objective of evaluating the employed topology, a laboratory prototype has been set up. The real view of the complete control system is shown in Figure 3. Three-phase supply voltages are obtained from three-phase 3 KW autotransformer. The prototype PFC converter is implemented using single power switch IGBT MITSUBISHI Module (CM50DY-24H), and fast recovery diode (DESI 60). The output voltage is set according to the required load voltage. The voltage reference is set at 300 V. The required pulse g1 is generated using a dSPACE board (DS1104) Synchroniser with MATLAB/SIMULINK. A pulse amplifier circuit is used between the dSPACE board and the IGBT to achieve pulses of approximately 15 V to guarantee an effective IGBT switching. The three-phase supply voltages, three-phase supply currents and load voltage are measured using voltage and current sensors and their signals are fed to the dSPACE control board via the A/D converter ports. All the schemes in the threephase PFC for AC-to-DC converter illustrated in Figure 1 are realised digitally using a DSP board DS1104, which is based on 32-bit floating point DSP TMS32OC3I. The board is also integrated with a fixed point 16-bit TMS320P14 DSP, which is used as a slave processor. This DSP board-based system is used to experimentally evaluate the proposed control algorithms. The DSP board has facilitated capturing the experimental waveforms and exporting them numerically per sample.

4.1 Evaluation of the three-phase AC–DC converter performance without PFC Figure 4(a) shows the experimental waveforms of the phase supply voltage (Vsa) and current (isa) in the steady state for three-phase AC–DC converter without using the PFC technique. It is evident


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Figure 3. Hardware set-up for the experimental system.

(a)

(b)

Figure 4. Three-phase AC–DC converter performance without PFC: (a) Supply voltage (Vsa) and current (isa); and (b) Harmonics spectrum of supply current compared with IEC 1000-3-2.

from this figure that the supply current is relatively highly distorted. The supply current for this case has a high THD of 90.25% with a low PF of 0.6364, as shown in Figure 4(b). It is seen also from Figure 4(b) that the harmonics value of the supply current is higher than the standard limits of IEC 1000-3-2 class A.

4.2. Evaluation of the three-phase AC–DC converter performance using the proposed PFC technique Figure 5 shows the steady-state simulation and experimental results of the proposed circuit. It shows that the supply current (isa) has a nearly sinusoidal waveform and is in phase with the input voltage (va) as shown in the figure. Figure 5 confirms approaching a unity PF that the PF is 0.999. The proposed PFC technique enhances the THD more, so that it is extremely reduced to 2.32% in simulation and 4.32% in the experimental. It is also observed that the three-phase supply currents are symmetrical. Graphs show the current harmonics of the circuit and standard IEC 1000-3-2 limits for class-A equipment (Kessal, Rahmani, Gaubert, & Mostefai, 2012). It is seen that the THD of the input current is less than the standard limits. As can be observed, all harmonic components are lower than their respective standard limits. It is also clear that the load voltage is equal to the reference voltage, which ensures the validity of the proposed circuit. The load has been changed by ±40% in order to assess the stability of the system and its responsiveness as shown in Figure 6. As shown, the change in supply current is in a proportional relationship with load change. As obvious, the three-phase supply currents are symmetrical, and it could be indicated that the change in the supply current is increased when the load is increased and vice versa. It is evident that the load voltage (Vo) has a high response back to the reference

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H. Z. AZAZI ET AL.

2.5 Limits for Class A equipment in standard IEC 1000-3-2 THD for circuit with PFC (4.32%) PF=0.999

Mag (A)

2

1.5

1

0.5

0

(a)

2

3

4

5

6 7 8 9 Harmonic order

10

11 12 13

(b)

Figure 5. The steady-state simulation (a) and experimental (b) results.

value during the load change, so the figure shows that the circuit presents a high-performance response during a change in the load. The changes in the phase voltage, the supply current, three-phase supply currents, the load voltages and currents, due to a step change in the reference voltage from 230 to 250, then returning to 230 V again are shown in Figure 7. It is shown that, the supply voltage and current are in-phase. The three-phase supply currents and their changes during reference voltage change are in a proportional relationship; as shown in Figure 7. Also, it can be indicated from this figure,


9

Figure 6. The transient state simulation (a) and experimental (b) results (40% changes in the load): Supply voltage and current (upper); Three-phase supply currents (middle); and Load voltage and current (lower).

both the supply and load currents follow the variation in the reference voltage which ensures the high response of the proposed circuit. The proposed converter efficiency versus the load power is shown in Figure 8. It is shown that the proposed boost converter has a high efficiency. The performance of three-phase AC–DC converter without using PFC is compared with the proposed PFC technique as shown in Table 1. Table 1 illustrates the THD and PF values which are utilised in the comparison assessment. From the results in this table, the PF of three-phase AC–DC converter without PFC is very low. Also, the three-phase AC–DC converter with proposed PFC technique has a good performance, and the converter PF is nearly unity.

5. Conclusions The paper presents a novel PFC control strategy for three-phase AC-to-DC boost regulator. The proposed PFC technique is characterised as a low number of switches (only single switch), and provides a simple control design and implementation. This led to reducing the size and cost of the system. It is evident from the results that the AC/DC converter with a boost regulator has improved the dynamic performance. Supply current is continuous and close to a sine wave. As a result, nearly unity PF can be obtained. THD in the supply current was found to be very low (2.32%). The output

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H. Z. AZAZI ET AL.

Figure 7. The transient state simulation and experimental results (the step change in reference voltage): Supply voltage and current (upper); Three-phase supply currents (middle); and Load voltage and current (lower).

Figure 8. Converter efficiency variation with the load power.

voltage of the proposed converter is a smooth DC. The proposed circuit has a good dynamic response. The proposed PFC circuit is valid for resistance and inductive loads, as shown by


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Table 1. THD and PF for three-phase AC–DC converter. THD PF

Face of comparison Simulation Experimental Simulation Experimental

Without PFC 123% 90.25% 0.63 0.6364

proposed PFC technique 2.32% 4.32% 0.99973 0.999

simulation and experimental results. The proposed system has been built and tested in the laboratory using the DSP-DS1104 digital board.

Disclosure statement No potential conflict of interest was reported by the authors.

References Badin, A. A., & Barbi, I. (2006, July). Simplified control technique for three-phase rectifier PFC based on the Scott transformer. In Industrial Electronics, 2006 IEEE International Symposium on, 2, 931–936. Bashi, S. M., et al. (2005). Three-phase single switch power factor correction circuit with harmonic reduction. Journal of Applied Sciences, 5(1), 80–84. doi:10.3923/jas.2005.80.84 Chattopadhyay, S., & Ramanarayanan, V. (2004). Digital implementation of a line current shaping algorithm for three phase high power factor boost rectifier without input voltage sensing. IEEE Transactions on Power Electronics, 19(3), 709–721. doi:10.1109/TPEL.2004.826494 Hartmann, M., Ertland, H., & Kolar, J. (2012). A three-phase delta switch rectifier for use in modern aircraft. IEEE Transactions on Industrial Electronics, 59(9), 3635–3647. doi:10.1109/TIE.2011.2158770 Hirachi, K., & Mutsuo, N. (1999). Improved control strategy on single-phase buck-type power factor correction converter. International Journal of Electronics, 86(10), 1281–1293. doi:10.1080/002072199132806 Huber, L., Kumar, M., & Jovanovic, M. M. (2014). Performance comparison of PI and P compensation in averagecurrent-controlled three-phase six-switch boost PFC rectifier. In Applied Power Electronics Conference and Exposition (APEC), 2014 Twenty-Ninth Annual IEEE, 935–942. Huber, L., Kumar, M., & Jovanović, M. M. (2015). Implementation and performance comparison of five DSP-based control methods for three-phase six-switch boost PFC rectifier. In Applied Power Electronics Conference and Exposition (APEC), 101–108. Itoh, J. I., & Ashida, I. (2008). A novel three-phase PFC rectifier using a harmonic current injection method. IEEE Transactions on Power Electronics, 23(2), 715–722. doi:10.1109/TPEL.2007.915774 Kessal, A., Rahmani, L., Gaubert, J. P., & Mostefai, M. (2012). Experimental design of a fuzzy controller for improving power factor of boost rectifier. International Journal of Electronics, 99(12), 1611–1621. doi:10.1080/ 00207217.2012.680788 Lee, S. W., & Do, H. L. (2016). An isolated bridgeless AC-DC PFC converter using a LC resonant voltage doubler rectifier. International Journal of Electronics, 103(12), 2125–2139. doi:10.1080/00207217.2016.1178344 Ming, W. (2004). A novel single-stage full bridge buck-boost inverter. IEEE Transactions on Power Electronics, 19(1), 150– 158. doi:10.1109/TPEL.2003.820583 Pan, L., Wang, B., Li, M., Pang, Y., Yang, Z., & Zhang, J. (2017). One-cycle control for three-phase single-capacitor Zsource inverter with unity power factor. International Journal of Electronics, 104(4), 635–658. Park, C. Y., et al. (2014). Single-stage electronic ballast with high-power factor. International Journal of Electronics, 101 (3), 325–340. doi:10.1080/00207217.2013.780300 Pereira, D. D. C., Da Silva, M. R., Silva, E. M., & Tofoli, F. L. (2015). Comprehensive review of high power factor ac-dc boost converters for PFC applications. International Journal of Electronics, 102(8), 1361–1381. doi:10.1080/ 00207217.2014.981871 Rajan, G. (2014). Power factor correction of three phase diode rectifier at input stage using artificial intelligent techniques for DC drive applications. International Journal of Innovative Research in Science, 3(6), 13165–13173. Yao, K., Meng, Q., Bo, Y., & Hu, W. (2016). Three-phase single-switch DCM boost PFC converter with optimum utilization control of switching cycles. IEEE Transactions on Industrial Electronics, 63(1), 60–70. doi:10.1109/ TIE.2015.2472530 Zhang, H. (2009). Research and design of three-phase six-switch high power factor rectifier with one cycle control. In Power Electronics and Motion Control Conference, 2009. IPEMC’09, 1704–1707.

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Appendix The simulation and the experimental results for the proposed method are taken with the following specifications: The supply phase voltages (Vsa = Vsb = Vsc) is 80 V, Line frequency is 50 Hz, Coil resistance (Ra = Rb = Rc) is 1.3 Ω, Coil inductance (La = Lb = Lc) is 10 mH, Load capacitor (Cf) is 80 µF, Load resistance (R) is, and Load resistance (L) is 7 µF.