Experimental Study of Shoot-Through Control Methods for Z-Source Inverter

Omar Ellabban, Joeri Van Mierlo, and Philippe Lataire

Experimental Study of the Shoot-Through Boost Control Methods for the Z-Source Inverter Omar Ellabban, Joeri Van Mierlo, and Philippe Lataire: The department of Electrical Engineering and Energy Technology (ETEC), Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium Keywords: Z-source inverter, shoot-through control, simple boost, maximum boost, maximum constant boost and modified space vector modulation boost

Abstract This paper presents a simulation and experimental comparative analysis of the Z-source inverter (ZSI) with four different shoot-through (ST) control methods, namely: the simple boost control, the maximum boost control, the maximum constant boost control and the modified space vector modulation boost control methods. A review of these methods is presented with a summary of all expressions. A prototype of a 30 kW ZSI is designed and implemented. The eZdsp™ F2808 evaluation board is used for the realization of the shoot-through control methods and the real time workshop (RTW) is used for automatic code generation. The paper compares between the different four shoot-through control methods in terms of: the line voltage harmonic, the phase current harmonic, the d.c. link voltage ripples, the switch voltage stress, the inductor current ripples, the obtainable a.c.output phase voltage and the overall efficiency with detailed simulation and experimental results. In addition, the paper presents the effect of varying the d.c. input voltage and the shoot-through duty ratio on the overall inverter efficiency. The maximum constant shoot-through boost control method seems to be the most suitable shoot-through control method for the ZSI. Also, it is shown that the efficiency of the ZSI improves with increasing the d.c. input voltage and degrades with increasing the shoot-through duty ratio.

Introduction The demand for the electric energy is never ending and with this rapid increase in energy demand, more generation resources are needed. Because of environmental concerns and limited fossil fuel resources, the renewable energy sources such as: fuel cells, PV and Wind etc., which are environmentally clean, are gaining increasing impetus across the globe. The output voltage of these renewable energy sources has a wide voltage variation rang. In these situations an additional d.c.-d.c. boost converter or step-up transformer is usually needed, increasing the system complexity and cost. The ZSI is an emerging topology for power electronics converters with very interesting properties such as buck-boost characteristics and single stage conversion. As a result, the ZSI has received a lot of attention recently [1]. The special Z-network, comprising two capacitors and two inductors, connected to the well known three phase bridge, as shown in Fig. 1, allows working in buck or boost modes using the ST state. The ZSI advantageously utilizes the ST states to boost the d.c.link voltage by gating on both the upper and lower switches of a phase leg. In addition, a ST state caused by electromagnetic interference (EMI) noise does not destroy the circuit. Therefore a more reliable single stage power converter for both buck and boost power conversion is obtained. Many PWM control methods have been developed and used for the voltage source inverter (VSI). The VSI has six active states, when the d.c. voltage is impressed across the load, and two zero states when the load terminals are shorted through the lower or upper switches. The ZSI has an additional zero state, the ST state. How to insert this ST state becomes the key point of the PWM control methods for the ZSI. Since the ZSI was proposed in 2003

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[1], lots of work have been done in this subject, especially for ST control methods [2-12]. Four different ST boost control methods have been proposed, which are: simple boost control [2], maximum boost control [3], maximum constant boost control [4], and modified space vector modulation (MSVM) boost control [5, 6]. In [7, 8], the authors present a simulation efficiency comparison between two different ST control methods, which are: two ST states insertion per switching cycle and six ST states insertion per switching cycle. Therefore the authors did not distinguish between the simple boost, the maximum boost, and the maximum constant boost control methods. In [9], the authors present a simu-lation comparison between the above four mentioned ST control methods for the different ZSI topologies (the basic, the bidirectional and the high-performance ZSI). In [10], the author proposed the application of the discontinuous PWM modulation methods for improving the efficiency of the ZSI, but the paper did not present the effect of the application of these modulation methods on the voltage gain, switch voltage stress and output current and voltage harmonic content. A simulation comparison of the voltage gain of different ST control methods of the ZSI, without the modi-

Fig. 1 : The basic ZSI topology

EPE Journal ⋅ Vol. 21 ⋅ no 2 ⋅ June 2011

Experimental Study of the Shoot-Through Boost Control Methods for the Z-Source Inverter fied space vector modulation method, was presented in [11]. The simple and the maximum constant ST boost control methods are compared by simulation in terms of voltage gain and voltage stress in [12]. The aim of this paper is to present a review of the four ST boost control methods and presents a simulation and experimental comparison of them. In addition, loss model based calculation and experimental measurement of the ZSI efficiency with the different ST control methods for different output power levels are presented and compared, Also, the effects of varying the input voltage and the ST duty ratio on the ZSI efficiency are theoretically and experimentally studied.

(a)

Operation of the ZSI Fig. 1 shows the basic ZSI topology, which consists of inductors (L1 and L2) and capacitors (C1 and C2) connected in X shape to couple the inverter to the d.c. voltage source. The ZSI can produce any desired a.c. output voltage regardless of the d.c. input voltage. Because of this special structure, the ZSI has an additional switching state, when the load terminals are shorted through both the upper and lower switching devices of any phase leg, which called the shoot-through (ST) state besides the eight traditional non-shoot through(NST) states. The ZSI has two operating modes: nonshoot-through mode and shoot-through mode, as shown in Fig. 2. During the ST switching state, the input diode is reverse biased; the input d.c. source is isolated from the load, and the two capacitors discharge energy to the inductors and to the load. During the NST switching states, the input diode turns ON, and the d.c. input voltage source as well as the inductors transfer energy to the load and charge the capacitors, as a result the d.c.-link voltage of bridge is boosted.

(b)

Fig. 2: The ZSI operation modes: (a) non-shoot-through state, (b) shoot-through state

In steady state, the capacitor voltage, the d.c.-link voltage and the output a.c. peak phase voltage of the ZSI are given by [1]: VC =

Vin 1 − D0

Vˆi = B ⋅ Vin =

(1)

Vin 1 − 2 D0

Vˆ V Vˆac = M ⋅ i = M ⋅ B ⋅ in 2 2

(2)

(3)

where D0 = T0/Ts is the ST duty ratio, T0 is the ST time per the switching period, Ts, B = 1/1 – 2D0 is the boost factor and M is the modulation index. From (3), the peak a.c. output phase voltage can be controlled both by adjusting the modulation index or ST time, and it can be larger than the input d.c. voltage by adjust the ST time. That is the main advantage of the ZSI.

Review of PWM control methods for ZSI Simple ST boost control method The simple ST boost control method, [2], uses two straight lines equal to or greater than the peak value of the three phase references to control the ST duty ratio in a traditional sinusoidal PWM, as shown in Fig. 3. When the triangular waveform is greater than the upper line, Vp, or lower than the bottom line, Vn, the circuit


Fig. 3: Simple ST boost control method waveforms turns into ST state. Otherwise it operates just as traditional carrier based PWM. This method is very straightforward; however, the resulting voltage stress across the switches is relatively high because some traditional zero states are not utilized. Maximum ST Boost Control Method Reducing the voltage stress under a desired voltage gain becomes more important to control the ZSI, this can be achieved by making the ST duty ratio as large as possible. The maximum ST boost control, [3], turns all the traditional zero states into ST state. As shown in Fig. 4, the circuit is in ST state when the triangular carrier wave is either greater than the maximum curve of the references (Va, Vb and Vc) or smaller than the minimum of the references. The ST duty ratio varies at six times of the output frequency. The ripples in the ST duty ratio will result in ripple in the inductor current and the capacitor voltage. This will cause a higher

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Fig. 4: Waveforms of the maximum ST boost control method

(a)

(b) Fig. 5 : Maximum constant ST boost control method with third harmonic injection requirement of the passive components when the output frequency becomes very low. Therefore, the maximum ST boost control method is suitable for applications that have a fixed or relatively high output frequency. Maximum constant ST boost control method In order to reduce the volume and the cost, it is important always to keep the ST duty ratio constant. At the same time, a greater voltage boost for any given modulation index is desired to reduce the voltage stress across the switches. The maximum constant ST boost control method achieves the maximum voltage gain while always keeping the ST duty ratio constant [4]. Fig. 5 shows the sketch map of the maximum constant ST boost control with third harmonic injection. Using the third harmonic injection, only two straight lines, Vp and Vn, are needed to control the ST time with 1/6 of the third harmonic injected. Modified space vector modulation ST control method The space vector PWM (SVPWM) techniques are widely used in industrial applications of the PWM inverter because of lower current harmonics and a higher modulation index. The SVPWM is suitable to control the ZSI. Unlike the traditional SVPWM, the modified space vector modulation (MSVM) has an additional ST time T0 for boosting the d.c.-link voltage of the inverter beside the time intervals T1, T2 and Tz. The ST states are evenly assigned to each phase with T0 /6 within zero voltage period Tz. The zero voltage period should be diminished for generating a ST time, and

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Fig. 6: Switching pattern for the MSVPWM: (a) MSVPWM1, (b) MSVPWM2 the active states T1 and T2 are unchanged. So, the ST time does not affect the PWM control of the inverter, and it is limited to the zero state time Tz. The MSVM can be applied using two patterns. The MSVPWM1 as shown in Fig. 6 (a), at this switch pattern, the ST time T0 is limited to (3/4)Tz, because the period (Tz/4-2Ts) should be greater than zero. The MSVPWM2 as shown in Fig. 6 (b), where the distribution of zero state time is changed into (Tz/6) and (Tz/3). The maximum ST time is increased to the zero state time Tz, [5, 6]. Table 1 shows a summary of all relations for the different ST boost control methods, where D0 is the ST duty ratio, M is the modulation index, B is the boost factor, G is the voltage gain, and Vs is the voltage stress across the switch. Fig. 7(a) shows the voltage gain versus the modulation index and Fig. 7(b) shows the voltage stress versus the voltage gain for different ST boost control methods. At high voltage gain, the MSVPWM1 has the highest voltage stress.

Efficiency comparison Efficiency evaluation is an important task during inverter design. The losses of the inverter mainly distributed on the semiconductor devices. The semiconductor device losses mainly include conduction losses and switching losses.


Experimental Study of the Shoot-Through Boost Control Methods for the Z-Source Inverter Table 1 : Summary of the different ST boost control methods expressions [9] ST boost control method

Simple

Max.

MSVPWM2 2π − 3 3M 2π

1 3M − 1

4π 9 3M − 2π

π 3 3M − π

πM 3 3M − π

M 3M − 1

4 πM 9 3M − 2π

πM 3 3M − π

πG 3 3G − π

G 3G − 1

2 πG 9 3G − 4 π

πG 3 3G − π

(9 3G − 4 π ) Vin 2π

(3 3G − π) Vin π

1− M −

B

1 2M −1

π 3 3M − π

G

M 2 M −1

Mmax

G 22G − 1 2 (2G − 1)Vin

MSVPWM1 3 2π − 3 3M ⋅ 4 2π

2π − 3 3M 2π

D0

Vs

Max. Con.

2 − 3M 2

3 3G − π Vin π

( 3G − 1)Vin

(a) (b) Fig. 7: (a) Voltage gain versus modulation index, (b) Voltage stress versus voltage gain for different PWM control methods [9] The unique operation principle makes the losses evaluation of the ZSI is complex and different from that of the VSI, and different ST boost control methods have a great influence on the losses evaluation. When The ZSI is operating in buck mode, it operates like a VSI and the losses of the IGBTs and the freewheeling diodes (FWDs) are calculated in the same way as the VSI. Going into the boost mode, the ST states are required to boost the input voltage. During the ST state all six IGBTs (for simple, maximum and constant maximum ST boost control methods) or two IGBTs (for modified space vector modulation ST boost control method) are conducting simultaneously and the d.c.-link is short circuited. In this case the current through one IGBT is the superimposition of the sinusoidal a.c. current and the high-frequency ST current. Therefore, there is a different way to calculate the losses for the ZSI when operating in boost mode [13, 14]. The conduction losses are calculated according to the well known equations [15]:

and iav, irms are the average and RMS current passing through the IGBT or the FWD. Using a linearized model of the switching losses, the switching losses are directly proportional to the switching frequency and they depend on the chosen ST boost control method and the switching loss energies of the IGBT (Eon, Eoff) and the diode (Erec), can be given by [15]: PSIGBT =

V I 1 fs ( Eon + Eoff ) v ⋅ v π Vref I ref

(6)

PSDiode =

V I 1 fs Erec v ⋅ v π Vref I ref

(7)

2 PCIGBT = VCE0 ⋅ iav + rCE irms

(4)

In datasheets, the switching loss energy are only given for a reference voltage Vref and a current Iref.

2 PCDiode = VF0 ⋅ iav + rF irms

(5)

In this paper, the 1200 V IGBT module SKM 400GB12T4 is chosen as the switch devices for the inverter bridge and the input diode. The device parameters specified for junction temperature T = 150 °C are extracted from the datasheet as indicated in Table 2.

where VCE0 and VF0 constitute the IGBT's and diode's threshold voltages, rCE and rF constitute their differential ohmic resistance


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Omar Ellabban, Joeri Van Mierlo, and Philippe Lataire Table 2 : Characteristics of SKM 400GB12T4 IGBT module IGBT

FW Diode

VCES (v)

IC (A)

VCES (v)

rCE (mΩ)

Eon (mJ)

Eoff (mJ)

IF (A)

VF0 (V)

rF (mΩ)

Err (mJ)

1200

610

0.7

3.8

33

42

440

0.9

3

30.5

Eon, Eoff and Erec are given at Vref = 600 V, IC = 400 A. Table 3 : Experimental prototype and simulation model parameters of the ZSI Parameter Input voltage Inductance Inductance internal resistance Capacitance Capacitance internal resistance Switching frequency Steady state shoot-through ratio AC load inductance AC load resistance

Fig. 8: Experimental setup of a 30 kW ZSI

Fig. 9: DSP based control circuit of the proposed ZSI

Fig. 10: Simulink model used for code generation for the TMS320F2808 DSP

Simulation and experimental results The dynamic performance of the ZSI with the four different ST boost control methods has been compared using MATLAB simulation and experimental verification using the parameters in Table 3. A 30 kW prototype of the ZSI, as shown in Fig. 8, has been designed and implemented. For the realization of the ST control

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Value 220 V 650 µH 0.22 Ω 320 µF 0.9 mΩ 10 kHz 0.24 340 µH 8.3 Ω

methods the evaluation board eZdsp™ F2808 based on the TMS320F2808 DSP by Texas Instruments has been chosen [16]. The eZdsp evaluation board is connected to a PC using USB cable and the PC has MATLAB, real time workshop (RTW) and code composer studio (CCS) installed on it for automatic code generation and real time control, as shown in Fig. 9. Fig. 10 shows the Simulink model used for automatic code generation. Figs. 11-14 compare the simulation and the experimental results of the ZSI performance using the different four ST boost control methods. Each figure shows the waveforms of the a.c. output line voltage and its harmonic spectrum, the a.c. output phase current and its harmonic spectrum and the d.c. input voltage, the Z-network capacitor voltage, the d.c. link voltage and the Z-network inductor current waveforms in terms of output and switching frequencies. Where, the figure parts a, c, e and g represent the simulation results and the parts b, d, f and h represents the experimental results. Fig. 15 shows the obtainable a.c. output phase voltage with constant ST duty ratio for different ST control methods. Fig. 16 shows the measured and calculated efficiency of the ZSI at different load levels with different ST boost control methods. The calculated efficiency is based on the conduction and switching linearized loss models, and it is calculated at constant input voltage. Fig. 17 shows the losses distribution of the ZSI at nominal input and 10 kW output power, where the input diode conduction and switching losses are included, which are neglected in most publications, the extra losses of the MSVM boost method mainly come from the switching losses of IGBTs and reverse recovery losses of the input diode which are about three times of other methods. Table 4 presents a comparison between the different four ST control methods. By comparing the simulation and experimental results, one finds a great matching between the simulation and experimental results. But the measured efficiency is lower than the calculated one, because the measured efficiency included the Z-network inductors and capacitors which are not included in the calculated efficiency. These results show that the constant maximum ST boost control method seems to be the most suitable ST control method for the ZSI. It requires less inductor value and results in less switch voltage stress, less output current total harmonic distortion, better Z-network behavior, high obtainable ac output voltage and higher efficiency.


Experimental Study of the Shoot-Through Boost Control Methods for the Z-Source Inverter

(a)

(b)

(c)

(e)

(e)

(f)

(g)

(h)

Fig. 11: Simulation and experimental results of the ZSI topology using the simple ST boost control method Fig. 18 shows the relationship of the input d.c. voltage and the ZSI efficiency at 10 kW output power. One can find that lower the input d.c. voltage brings lower efficiency, this because the lower input d.c. voltage means the larger ST duty cycle and higher ST


current, as indicated in Fig.19, the efficiency of the simple ST boost control method is strongly affected by increasing the ST duty ratio.

23


(a)

(b)

(c)

(e)

(e)

(f)

(g)

(h)

Fig. 12: Simulation and experimental results of the ZSI topology using the maximum ST boost control method

24



(a)

(b)

(c)

(e)

(e)

(f)

(g)

(h)

Fig. 13: Simulation and experimental results of the ZSI topology using the maximum constant ST boost control method


25


(a)

(b)

(c)

(e)

(e)

(f)

(g)

(h)

Fig. 14: Simulation and experimental results of the ZSI topology using the MSVM ST boost control method

26



Fig. 15: Output phase voltage of the ZSI for different ST boost control methods

Fig. 17: Losses distribution of the ZSI at 10 kW output power

(a)

(b) Fig. 16: Calculated, (a), and measured, (b) ZSI efficiency for different ST boost control methods

Table 4: Different ST control methods comparison - (+, 0 and -) represents the best, the moderate and the lowest performance, respectively Line voltage harmonic Phase current harmonic dc link voltage ripples Switch voltage stress Inductor current ripples Efficiency Obtainable ac voltage Total

Simple Boost

Max. boost

Max. Cont. boost

MSVM boost

0 0 0 0 0 0 -

+ 0 + + 0 +++--

0 + + 0 + + + +++++

+ 0 +----

(a) (b) Fig. 18: The ZSI efficiency for different input voltage: (a) calculated efficiency, (b) measured efficiency using the maximum constant ST boost method


27


(a) (b) Fig. 19: ZSI efficiency for different ST duty ratio: (a) calculated efficiency, (b) measured efficiency using the maximum constant ST boost method

Conclusion In this paper, four ST boost control methods are reviewed and compared, using MATLAB simulation and experimental results, under the same input voltage, the same ST duty ratio, the same switching frequency and the same output load. A prototype of a 30 kW ZSI is designed and implemented with a DSP controller based on the eZdsp™ F2808 evaluation board. The simulation and the experimental comparison results show that the constant maximum ST boost control method seems to be the most suitable method for the ZSI. Also, the ZSI efficiency improves by increasing the d.c. input voltage of and it worsens by increasing the ST duty ratio.

References [1] F. Z. Peng: Z-source inverter, IEEE Transactions on Industry Applications, Vol. 39, No. 2, March/April 2003, pp. 504-510. [2] FY 2005 report : Z-source inverter for fuel cell vehicles, Oak Ridge National Laboratory, September 2005, pp. 1-77. [3] F. Z. Peng, M. Shen, and Z. Qian: Maximum boost control of the Z-source inverter, IEEE Transactions on Power Electronic, Vol. 20, No. 4, July 2005, pp. 833-838. [4] Miaosen Shen, Jin Wang, A. Joseph, Fang Zheng Peng, L.M. Tolbert, and D.J. Adams, D.J: Constant boost control of the Zsource inverter to minimize current ripple and voltage stress, IEEE Transactions on Industry Applications, Vol. 42, No. 3, , May/June 2006, pp. 770-778. [5] Poh Chiang Loh, D. Mahinda Vilathgamuwa, Yue Sen Lai, Geok Tin Chua, and Yunwei Li: Pulse-Width Modulation of Z-Source Inverters, IEEE Transactions on power electronics, Vol. 20, No. 6, November 2005, pp. 1346-1355. [6] T.W. Chun, Q.V. Tran, J.R. Ahn, and J.S. Lai: AC Output Voltage Control with Minimization of Voltage Stress Across Devices in the Z-Source Inverter Using Modified SVPWM, IEEE Power Electronics Specialists Conference, PESC, Jeju, Korea, June 2006, pp. 3030-3034. [7] Jin Li, Jinjun Liu, and Zeng Liu: Loss Oriented Evaluation and Comparison of Z-Source Inverters Using Different Pulse Width Modulation Strategies, the twenty-fourth annual IEEE applied power electronics conference and exposition, APEC, Feb. 2009, pp. 851-856. [8] Jin Li, Jinjun Liu, and Zeng Liu: Comparison of Z-source inverter and traditional two-stage boost-buck inverter in grid-tied renewable energy generation, IEEE 6th International Power Electronics and Motion Control Conference, IPEMC, May 2009, pp. 1493-1497.

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[9] Omar Ellabban, Joeri Van Mierlo and Philippe Lataire: Comparison between Different PWM Control Methods for Different Z-Source Inverter Topologies, The 13th European Conference on Power Electronics and Applications, Sept. 2009, Barcelona-Spain, pp. 1-11. [10] Jacek Rabkowski: Improvement of Z-source inverter properties using advanced PWM methods, the 13th European Conference on Power Electronics and Applications, Sept. 2009, Barcelona-Spain, pp. 1-9. [11] H. Rostami and D. A. Khaburi: Voltage Gain Comparison of Different Control Methods of the Z-Source Inverter, International Conference on Electrical and Electronics Engineering, ELECO, Nov. 2009, pp. 268-272. [12] T. Meenakshi and K. Rajambal: Identification of an Effective Control Scheme for Z-source Inverter, The Asian Power Electronics Journal, Vol. 4,No.1, April 2010, pp. 22-28. [13] W.-T. Franke, M. Mohr and F. W. Fuchs: Comparison of a ZSource Inverter and a Voltage-Source Inverter Linked with a DC/DC Boost-Converter for Wind Turbines Concerning Their Efficiency and Installed Semiconductor Power, IEEE 39th Power Electronics Specialists Conference, PESC08, June 2008, Rhodes, pp. 1814 - 1820. [14] Keping You and M. F. Rahman: Analytical Model of Conduction and Switching Losses of Matrix-Z-Source Converter, Journal of Power Electronics, Vol. 9, No. 2, March 2009, pp.275-287. [15] Malte Mohr, and Friedrich W. Fuchs: Comparison of Three Phase Current Source Inverters and Voltage Source Inverters Linked with DC to DC Boost Converters for Fuel Cell Generation Systems, the European Conference on Power Electronics and Applications, 2005, Dresden, pp. 1-10. [16] Texas Instruments, Inc.: eZdspTM F2808 USB, Technical Reference, 2005.

The authors Omar Ellabban was born in Egypt in 1975. He received the B.Sc. from Helwan University, Egypt in 1998 and the M.Sc. degree from Cairo University, Egypt in 2005, both in Electric Power and Machines Engineering, and the Ph.D. degree in Electrical Engineering from Vrije Universiteit Brussel, Belgium in May 2011 with the greatest distinction. He is a member at the IEEE, JPE and EPE journals. His research interests include motor drives, artificial intelligent, power electronics converters design, modeling and control, electric and hybrid electric vehicles control,


Experimental Study of the Shoot-Through Boost Control Methods for the Z-Source Inverter DSP-based system control and switched reluctance motor control for automotive applications. Joeri Van Mierlo obtained his Ph.D. in Electromechanical Engineering Sciences from Vrije Universiteit Brussel in 2000. He is now a Full Time Professor at this university, where he leads the MOBI - Mobility and Automotive Technology Research Group. His current research interests include the development of hybrid propulsion systems (converters, supercaps, energy-management, etc.) as well as the environmental comparison of vehicles with different kinds of drive trains and fuels (LCA, WTW). He is the author of more than 100 scientific publications. He chairs the EPE chapter on “Hybrid and Electric Vehicles” (www.epe-association.org). He is the Secretary of the Board of the Belgian section of AVERE (ASBE) and is a Board Member of

AVERE. He is a Co-Editor of the Journal of Asian Electric Vehicles. He is an active Member of EARPA - the Association of Automotive R&D Organizations. Furthermore he is a Member of Flanders Drive and of VSWB - the Flemish Cooperative on Hydrogen and Fuels Cells. Prof. Van Mierlo is Chairman of the International Program Committee of the International Electric, Hybrid and Fuel Cell Symposium (EVS24). Philippe Lataire received a degree in Electromechanical Engineering in 1975 and his Ph.D. in 1982, both from Vrije Universiteit Brussel (VUB), Brussels, Belgium. He is presently a Full Time Professor at VUB. His current research interests include electric drives, power electronics and control.

Book New publication: Power Conversion and Control of Wind Energy Systems Authors: Bin Wu, Yongqiang Lang, Navid Zargari, Samir Kouro IEEE Press Series on Power Engineering and John Wiley & Sons, Inc., Publication ISBN Book: 978-1-118-02900-8 PDF: 978-1-118-02899-5 Pub: 978-1-118-02898-8 The conversion of wind kinetic energy into electric energy is of a multidisciplinary nature, involving aerodynamics, mechanical systems, electric machines, power electronics, control theory, and power systems. In the past, a number of books have addressed some of these subjects. This book explores the power conversion and control of wind energy conversion systems (WECS) from the electrical engineering perspective. It provides a comprehensive and in-depth analysis of wind generators, system configurations, power converters, control schemes, and dynamic/steady-state performance of various practical wind energy systems. The book contains nine chapters. Chapter 1 provides a market survey and an overview of wind turbine technology, wind energy system classifications, costs, and grid codes for wind power integration. Chapter 2 introduces the fundamentals and control principles of wind energy systems, including wind turbine components, aerodynamics, stall and pitch controls, and maximum power tracking schemes. Chapter 3 presents commonly used wind generators, including squirrel cage induction generators, doubly fed induction generators, and synchronous generators. The dynamic and steady-state models of these generators are also derived to facilitate the analysis of wind energy systems in the subsequent chapters. Chapter 4 discusses various power converters and PWM schemes used in wind energy systems. Both voltage and current source converters are presented with an emphasis on high-power wind energy system. Chapter 5 presents a general overview of configurations and characteristics of major practical WECS. Chapter 6 focuses on fixed-speed, inductor generator based wind energy systems; important issues such as grid connection, two-speed operation, and reactive power compensation are discussed.


Chapter 7 deals with wind energy systems with variable-speed, squirrel cage induction generators (SCIG), in which typical systems configurations and advanced control schemes such as field oriented control (FOC) and direct torque control (DTC) are elaborated. Chapter 8 discusses doubly fed induction generator (DFIG) systems, where the subsynchronous modes of operation are investigated. Chapter 9 is dedicated to variable-speed, synchronous generator wind systems, in which various control schemes, including zero d-axis current (ZDC) control, maximum torque per ampere (MTPA) control, and unity power factor (UPF) control, are analyzed in detail. Throughout, important concepts are illustrated with simulations and experiments, and design guidance is provided with tables, charts, and graphs. To help the reader understand the principle and operation of various WECS, more than 30 case studies are given in various chapters and more that 100 solved problems are included in a dedicated appendix. This book not only serves as a valuable reference for academic researchers, practicing engineers, and consultants, but also as a textbook and senior-year undergraduate students. BIN WU, PhD, is a Professor in the Department of Electrical and Computer Engineering at Ryerson University (Canada). He is an NSERC/Rockwell Automation Industrial Research Chair and the founder of the Laboratory for Electric Drive Applications and Research (LEDAR). He is a Fellow of the Institute of Electrical and Electronics Engineers, Engineering Institute of Canada, and Canadian Academy of Engineering. YONGQIANG LANG, PhD, is a Senior Engineer in the State Grid Electric Power Research Institute (China). He worked in the LEDAR WindTech Laboratory at Ryerson University from November 2006 to June 2009 as a postdoctoral fellow in the area of wind power. NAVID ZARGARI, PhD, is a leading expert in medium voltage drives and a practicing engineer for fifteen years. He has been with the Medium Voltage Business of Rockwell Automation Canada since 1994, and has in-depth knowledge of many aspects of adjustable speed drives and wind energy systems. SAMIR KOURO, PhD, is a research academic in the Electronics Engineering Department of Universidad Tecnica Federico Santa Maria (Chile).

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Experimental Study of Shoot-Through Control Methods for Z-Source Inverter

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