1. Chapter 1 Power Electronic Devices
Outline
1.1 An introductory overview of power electronic devices
1.2 Uncontrolled device—power diode
1.3 Half- controlled device—thyristor
1.4 Typical fully- controlled devices
1.5 Other new power electronic devices

2. 1.1 An introductory overview of power electronic devices
The concept and features
Power electronic devices: are the electronic devices that can be directly used in the power processing circuits to convert or control electric power.
Very often: Power electronic devices= Power semiconductor devices
Major material used in power semiconductor devices——Silicon

3. Features of power electronic devices
a) The electric power that power electronic device deals with is usually much larger than that the information electronic device does.
b) Usually working in switching states to reduce power losses
c)Need to be controlled by information electronic circuits.
d)Very often, drive circuits are necessary to interface between information circuits and power circuits.
e)Dissipated power loss usually larger than information electronic devices —special packaging and heat sink are necessary.

4. 2) Configuration of systems using power electronic devices
Power electronic system:
Protection circuit is also very often used in power electronic system especially for the expensive power semiconductors.

5. Terminals of a power electronic device
Control signal from drive circuit must be connected between the control terminal and a fixed power circuit terminal (therefore called common terminal

6. Major topics for each device
Appearance, structure, and symbol
Physics of operation
Specification
Special issues
Devices of the same family
Passive components in power electronic circuit
Transformer, inductor, capacitor and resistor: these are passive components in a power electron
ic circuit since they can not be controlled by control signal and their characteristics are usually constant and linear.
The requirements for these passive components by power electronic circuits could be very different from those by ordinary circuits.

7. 1.2 Uncontrolled device Power diode
Appearance

8. PN junction

9. PN junction with voltage applied in the forward direction

10. PN junction with voltage applied in the reverse direction

11. Construction of a practical power diode

12. Features different from low-power (information electronic) diodes
–Larger size
–Vertically oriented structure
–n drift region (p-i-n diode)
–Conductivity modulation
Junction capacitor
The positive and negative charge in the depletion region is variable with the changing of external voltage. variable with the changing of external voltage.
—–Junction capacitor C Junction capacitor CJ .
Junction capacitor influences the switching characteristics of
power diode.

13. Static characteristics of power diode
Turn-off transient Turn- on transient

14. Examples of commercial power diodes

15. 1.3 Half- controlled device—Thyristor
Another name: SCR—silicon controlled rectifier
Thyristor Opened the power electronics era
–1956, invention, Bell Laboratories
–1957, development of the 1st product, GE
–1958, 1st commercialized product, GE
–Thyristor replaced vacuum devices in almost every power processing area.
Still in use in high power situation. Thyristor till has the
highest power-handling capability.

16. Appearance and symbol of thyristor

17. Structure and equivalent circuit of thyristor

18. Physics of thyristor operation

19. Quantitative description of thyristor operation
When IG =0, α1+α2 is small.
When IG >0, α1 +α2 will approach 1, IA will be very large.

20. Other methods to trigger thyristor on
High voltage across anode and cathode—avalanche breakdown
High rising rate of anode voltagte —du/dt too high
High junction temperature
Light activation
Static characteristics of thyristor
Blocking when reverse biased, no matter if there is gate current applied.
Conducting only when forward biased and there is triggering current
applied to the gate.
Once triggered on, will be latched on conducting even when the gate current is no longer applied.

21. Switching characteristics of thyristor

22. 1.4 Typical fully- controlled devices
Features
–IC fabrication technology, fully- controllable, high frequency
Applications
–Begin to be used in large amount in 1980s
–GTR is obsolete and GTO is also seldom used today.
–IGBT and power MOSFET are the two major power
semiconductor devices nowadays.

23. 1.4.1 Gate- turn- off thyristor—GTO
Major difference from conventional thyristor:
The gate and cathode structures are highly interdigitated , with various types of geometric forms being used to layout the gates and cathodes.

24. Physics of GTO operation
The basic operation of GTO is the same as that of the conventional
thyristor. The principal differences lie in the modifications in the
structure to achieve gate turn- off capability.
–Large α2
–α1+α2 is just a little larger than the critical value 1.
–Short distance from gate to cathode makes it possible to drive current out of gate.

25. 1.4.2 Giant Transistor—GTR
GTR is actually the bipolar junction transistor that can handle
high voltage and large current.
So GTR is also called power BJT, or just BJT.

26. Structures of GTR different from its information-processing counterpart

27. Static characteristics of GTR

28. Second breakdown of GTR

29. Basic structure Symbol
1.4.3 Power metal- oxide- semiconductor field effect transistor—Power MOSFET
A classification
Basic structure Symbol

30. Physics of MOSFET operation (Off- state)
p-n- junction is
reverse-biased
off-state voltage
appears across
n- region

31. Physics of MOSFET operation (On-state)
p-n- junction is slightly reverse biased positive gate voltage induces conducting channel drain current flows through n- region an conducting channel on resistance = total resistances of n- region,conducting channel,source and drain contacts, etc.

32. Static characteristics of power

33. Switching characteristics of power MOSFET
Turn- on transient Turn- off transient
–Turn- on delay time td(on) –Turn- off delay time td(off)
–Rise time tr –Falling time tf

34. Examples of commercial power MOSFET

35. 1.4.4 Insulated- gate bipolar transistor—IGBT
Combination of MOSFET and GTR

36. Features
On- state losses are much smaller than those of a power MOSFET, and are comparable with those of a GTR
Easy to drive —similar to power MOSFET
Faster than GTR, but slower than power MOSFET
Structure and operation principle of IGBT
Also multiple cell structure Basic structure similar to power MOSFET, except extra p region On- state: minority carriers
are injected into drift region, leading to conductivity modulation
compared with power MOSFET: slower switching times, lower on- resistance, useful at higher voltages (up to 1700V)

37. Equivalent circuit and circuit symbol of IGBT

38. Switching characteristics of IGBT

39. Examples of commercial IGBT

40. 1.5 Other new power electronic devices
Static induction transistor —SIT
Static induction thyristor —SITH
MOS controlled thyristor —MCT
Integrated gate- commutated thyristor —IGCT
Power integrated circuit and power module
Static induction transistor—SIT
Another name: power junction field effect transistor—power JFET Features
–Major- carrier device
–Fast switching, comparable to power MOSFET
–Higher power- handling capability than power MOSFET
–Higher conduction losses than power MOSFET
–Normally- on device, not convenient (could be made normally- off, but with even higher on-state losses)

41. 2) Static induction thyristor—SITH
other names
–Field controlled thyristor—FCT
–Field controlled diode
Features
–Minority- carrier device, a JFET structure with an additional
injecting layer
–Power- handling capability similar to GTO
–Faster switching speeds than GTO
–Normally- on device, not convenient (could be made
normally- off, but with even higher on- state losses)

42. 3) MOS controlled thyristor—MCT
Essentially a GTO with integrated MOS- driven gates controlling both turn- on and turn- off that potentially will significantly simply the design of circuits using GTO.
The difficulty is how to design a MCT that can be turned on and turned off equally well.
Once believed as the most promising device, but still not commercialized in a large scale. The future remains uncertain.
4) Integrated gate- commutated thyristor — IGCT
The newest member of the power semiconductor family, introduced in 1997 by ABB
Actually the close integration of GTO and the gate drive circuit with multiple MOSFETs in parallel providing the gate currents
Short name: GCT
Conduction drop, gate driver loss, and switching speed are superior to GTO
Competing with IGBT and other new devices to replace GTO

43. Review of device classifications

44. Chapter 2 AC to DC Converters
Outline
2.1 Single-phase controlled rectifier
2.2 Three-phase controlled rectifier
2.3 Effect of transformer leakage inductance on rectifier circuits
2.4 Capacitor-filtered uncontrolled rectifier
2.5 Harmonics and power factor of rectifier circuits
2.6 High power controlled rectifier
2.7 Inverter mode operation of rectifier circuit
2.8 Thyristor-DC motor system
2.9 Realization of phase-control in rectifier

45. 2. 1 Single- phase controlled (controllable) rectifier 2. 1
2.1 Single- phase controlled (controllable) rectifier Single-phase half-wave controlled rectifier

46. Inductive (resistor-inductor) load

47. Basic thought process of time-domain analysis for power electronic circuits
The time- domain behavior of a power electronic circuit is actually the combination of consecutive transients of the different linear circuits when the power semiconductor devices are in different states.

48. Single- phase half- wave controlled rectifier with freewheeling diode
load (L is large enough) Inductive

49. Maximum forward voltage, maximum reverse voltage
Disadvantages:
–Only single pulse in one line cycle
–DC component in the transformer current

50. 2.1.2 Single- phase bridge fully-controlled rectifier
Resistive load

51. Average output (rectified) voltage:
Average output current:
For thyristor:
For transformer:

52. Inductive load (L is large enough)

53. Electro- motive-force (EMF) load With resistor

54. With resistor and inductor
When L is large enough, the output voltage and current waveforms are the same as ordinary inductive load.
When L is at a critical value

55. 2.1.3 Single- phase full- wave controlled rectifier

56. 2.1.4 Single- phase bridge half-controlled rectifier

57. Another single- phase bridge half-controlled rectifier
Comparison with previous circuit:
–No need for additional freewheeling diode
–Isolation is necessary between the drive circuits of the two thyristors

58. Summary of some important points in analysis
When analyzing a thyristor circuit, start from a diode circuit with the same topology. The behavior of the diode circuit is exactly the same as the thyristor circuit when firing angle is 0.
A power electronic circuit can be considered as different linear circuits when the power semiconductor devices are in different states. The time- domain behavior of the power electronic circuit is actually the combination of consecutive transients of the different linear circuits.
Take different principle when dealing with different load
– For resistive load: current waveform of a resistor is the same as the voltage waveform
–For inductive load with a large inductor: the inductor current can
be considered constant

59. 2.2 Three- phase controlled (controllable) rectifier
2.2.1 Three- phase half- wave controlled rectifier
Resistive load, α= 0º

60. Resistive load, α= 30º

61. Resistive load, α= 60º

62. Resistive load, quantitative analysis
When α≤ 30º , load current id is continuous.
When α > 30º , load current id is discontinuous.
Average load current
Thyristor voltages

63. Inductive load, L is large enough

64. Thyristor voltage and currents, transformer current :

65. 2.2.2 Three- phase bridge fully-controlled rectifier
Circuit diagram
Common- cathode group and common- anode group of thyristors
Numbering of the 6 thyristors indicates the trigger sequence.

66. Resistive load, α= 0º

68. Resistive load, α= 30º

70. Resistive load, α= 60º

72. Resistive load, α= 90º

74. Inductive load, α= 0º

76. Inductive load, α= 30º

78. Inductive load, α= 90º

80. Quantitative analysis
Average output voltage:
For resistive load, When a > 60º, load current id is discontinuous.
everage output current (load current):
Transformer current:

81. 2.3 Effect of transformer leakage inductance on rectifier circuits
In practical, the transformer leakage inductance has to be taken into account.
Commutation between thyristors, thus can not happen instantly,but with a commutation process.

82. Commutation process analysis
Circulating current ik during commutation
Output voltage during commutation

83. Quantitative calculation
Reduction of average output voltage due to the commutation process
Calculation of commutation angle
– Id ↑,γ↑
– XB↑, γ↑
– For α ≤ 90۫ , α↓, γ↑

84. Summary of the effect on rectifier circuits

85. Conclusions
–Commutation process actually provides additional working states of the circuit.
–di/dt of the thyristor current is reduced.
–The average output voltage is reduced.
–Positive du/dt
– Notching in the AC side voltag

86. 2.4 Capacitor- filtered uncontrolled (uncontrollable) rectifier
2.4.1 Capacitor- filtered single- phase uncontrolled rectifier
Single-phase bridge, RC load:

87. Single-phase bridge, RLC load

88. 2.4.2 Capacitor- filtered three- phase uncontrolled rectifier
Three-phase bridge, RC load

89. Three- phase bridge, RC load Waveform when ωRC≤1.732

90. Three- phase bridge, RLC load

91. 2.5 Harmonics and power factor of rectifier circuits
2.5.1 Basic concepts of harmonics and reactive power
For pure sinusoidal waveform
For periodic non-sinusoidal waveform
where

92. Harmonics-related specifications
Take current harmonics as examples
Content of nth harmonics
In is the effective (RMS) value of nth harmonics.
I1 is the effective (RMS) value of fundamental component.
Total harmonic distortion
Ih is the total effective (RMS) value of all the harmonic components.

93. Definition of power and power factor for sinusoidal circuits
Active power
Reactive power
Apparent power
Power factor

94. Definition of power and power factor For non- sinusoidal circuit
Active power:
Power factor:
Distortion factor (fundamental- component factor):
Displacement factor (power factor of fundamental component):
Definition of reactive power is still in dispute

95. Review of the reactive power concept
The reactive power Q does not lead to net transmission of energy between the source and load. When Q ≠ 0, the rms current and apparent power are greater than the minimum amount necessary to transmit the average power P.
Inductor: current lags voltage by 90°, hence displacement factor is zero. The alternate storing and releasing of energy in an inductor leads to current flow and nonzero apparent power, but P = 0. Just as resistors consume real (average) power P, inductors can be viewed as consumers of reactive power Q.
Capacitor: current leads voltage by 90°, hence displacement factor is zero. Capacitors supply reactive power Q. They are often placed in the utility power distribution system near inductive loads. If Q supplied by capacitor is equal to Q consumed by inductor, then the net current (flowing from the source into the capacitor- inductive- load combination) is in phase with the voltage, leading to unity power factor and minimum rms current magnitude.

96. 2.5.2 AC side harmonics and power factor of controlled rectifiers with inductive load
Single- phase bridge fully-controlled rectifier

97. AC side current harmonics of single- phase bridge fully-controlled rectifier with inductive load
Where
Conclusions
–Only odd order harmonics exist
– In∝1/n
– In / I1 = 1/n

98. A typical gate triggering control circuit

99. Three- phase bridge fully-controlled rectifier

101. AC side current harmonics of three- phase bridge fully- controlled rectifier with inductive load
where

102. 2.5.3 AC side harmonics and power factor of capacitor- filtered uncontrolled rectifiers
Situation is a little complicated than rectifiers with inductive load.
Some conclusions that are easy to remember:
–Only odd order harmonics exist in single- phase circuit, and only 6k±1 (k is positive integer) order harmonics exist in three- phase circuit.
–Magnitude of harmonics decreases as harmonic order increases.
–Harmonics increases and power factor decreases as capacitor increases.
–Harmonics decreases and power factor increases as inductor increases.

103. 2.5.4 Harmonic analysis of output voltage and current

104. Ripple factor in the output voltage
Output voltage ripple factor
where UR is the total RMS value of all the harmonic components in the output voltage
and U is the total RMS value of the output voltage

105. Harmonics in the output current
where

106. Conclusions
for α = 0º
Only mk (k is positive integer) order harmonics exist in the output voltage and current of m- pulse rectifiers
Magnitude of harmonics decreases as harmonic order increases when m is constant.
The order number of the lowest harmonics increases as m increases. The corresponding magnitude of the lowest harmonics decreases accordingly.
For α ≠ 0º
Quantitative harmonic analysis of output voltage and current is very
complicated for α ≠ 0º.
As an example,for 3- phase bridge fully- controlled rectifie

107. 2.6 High power controlled rectifier
2.6.1 Double- star controlled rectifier
Circuit Waveforms When α= 0º

108. Effect of interphase reactor(inductor, transformer)

109. Quantitative analysis when α = 0º

110. Waveforms when α > 0º

111. 2.6.2 Connection of multiple rectifiers

112. Phase-shift connection of multiple rectifiers
Parallel connection

113. Series connection

114. Sequential control of multiple series-connected rectifiers

115. 2.7 Inverter mode operationof rectifiers
Review of DC generator- motor system

116. Inverter mode operation of rectifiers
Rectifier and inverter mode operation of single- phase full- wave converter

117. Necessary conditions for the inverter mode operation of controlled rectifiers
There must be DC EMF in the load and the direction of the DC EMF must be enabling current flow in
thyristors. (In other word EM must be negative if taking the ordinary output voltage direction as positive.)
α > 90º so that the output voltage Ud is also negative.

118. Inverter mode operation of 3- phase bridge rectifier

119. Inversion angle (extinction angle) β
α+ β=180º
Inversion failure and minimum inversion angle
Possible reasons of inversion failures
–Malfunction of triggering circuit
–Failure in thyristors
–Sudden dropout of AC source voltage
–Insufficient margin for commutation of thyristors
Minimum inversion angle (extinction angle)
βmin= δ + γ+ θ′（2-109）

121. 2.8 Thyristor- DC motor system
2.8.1 Rectifier mode of operation

122. Speed- torque (mechanic) characteristic when load current is continuous

123. Speed- torque (mechanic) characteristic when load current is discontinuous
EMF at no load (taking 3- phase half-wave as example)

124. 2.8.2 Inverter mode of operation

125. 2.8.3 Reversible DC motor drive system(4-quadrant operation)

127. 2.9 Gate triggering control circuit for thyristor rectifiers
A typical gate triggering control circuit

128. Chapter 3 DC to DC Converters
Outline
3.1 Basic DC to DC converters
3.1.1 Buck converter (Step- down converter)
3.1.2 Boost converter (Step-up converter)
3.2 Composite DC/DC converters and connection of multiple DC/DC converters
3.2.1 A current-reversible chopper
3.2.2 Bridge chopper (H-bridge DC/DC converter)
3.2.3 Multi-phase multi-channel DC/DC converters

129. 3.1 Basic DC to DC converters
3.1.1Buck converter
SPDT switch changes dc component
Switch output voltage waveform
Duty cycle D: 0 ≤ D ≤ 1
complement D: D´ = 1 - D

130. Dc component of switch output voltage

131. Insertion of low- pass filter to remove switching harmonics and pass only dc component

132. Basic operation principle of buck converter

133. Thought process in analyzing basic DC/DC converters
1) Basic operation principle (qualitative analysis)
–How does current flows during different switching states
–How is energy transferred during different switching states
2) Verification of small ripple approximation
3) Derivation of inductor voltage waveform during different switching states
4) Quantitative analysis according to inductor volt-second balance or capacitor charge balance

134. Actual output voltage waveform of buck converter

135. Buck converter analysis: inductor current waveform

136. Inductor voltage and current subinterval 1: switch in position 1

137. Inductor voltage and current subinterval 2: switch in position 2

138. Inductor voltage and current waveforms

139. Determination of inductor current ripple magnitude

140. Inductor current waveform during start-up transient

141. The principle of inductor volt- second balance: Derivation
Inductor defining relation:
Integrate over one complete switching period:
In periodic steady state, the net changes in inductor current is zero:
Hence, the total area(or volt-seconds)under the inductor voltage waveform is zero whenever the converter operates in steady state.
An equivalent form:
The average inductor voltage is zero in steady state.

142. Inductor volt-second balance:Buck converter example
Integral of voltage waveform is area of rectangles:
average voltage is
Equate to zero and solve for V:

143. 3.1.2Boost converter
Boost converter example

144. Boost converter analysis

145. Subinterval 1: switch in position 1

146. Subinterval 2: switch in position 2

147. Inductor voltage and capacitor current waveforms

148. Inductor volt- second balance

149. Conversion ratio M(D) of the boost converter

150. Determination of inductor current dc component

151. Continuous- Conduction- Mode (CCM) and Discontinuous Conduction-Mode (DCM) of boost

152. 3.2 Composite DC/DC converters and connection of multiple DC/DC converters
3.2.1 A current reversible chopper

153. 3.2.2Bridge chopper (H-bridge chopper)

154. 3.2.3Multi-phase multi-channel DC/DC converter

155. Chapter 4 AC to AC Converters
Outline
4.1 AC voltage controllers
4.2 Other AC controllers
4.3 Thyristor cycloconverters
4.4 Matrix converters

156. 4.1.1 Single-phase AC voltage controller

157. Resistive load, quantitative analysis
RMS value of output voltage
RMS value of output current
RMS value of thyristor current
Power factor of the circuit

158. Inductive (Inductor- resistor) load , operation principle

159. Inductive load, quantitative analysis
Differential equation
The RMS value of output voltage, output current, and thyristor current can then be calculated.

160. 4.1.2 Three-phase AC voltage controller
Classification of three- phase circuits

161. 3- phase 3- wire Y connection AC voltage controller
For a time instant, there are 2 possible conduction states:
–Each phase has a thyristor conducting. Load voltages are the same as the source voltages.
–There are only 2 thyristors conducting, each from a phase. The load voltages of the two conducting phases are half of the corresponding line to line voltage, while the load voltage of the other phase is 0.

162. 4.2 Other AC controllers
4.2.1 Integral cycle control—AC power controller
Circuit topologies are the same as AC voltage controllers.
Only the control method is different.
Load voltage and current are both sinusoidal when thyristors are conducting.

163. Spectrum of the current inAC power controller
There is NO
harmonics in the
ordinary sense.
There is harmonics
as to the control
frequency. As to the
line frequency, these
components become
fractional harmonics.

164. 4.2.2 Electronic AC switch
Circuit topologies are the same as AC voltage controllers. But the back- to- back thyristors are just used like a switch to turn the equipment on or off.
Application—Thyristor-switched capacitor (TSC)

165. TSC waveforms when the capacitor is switched in/out
The voltage across the thyristor must be nearly zero when switching in the capacitor, and the current of the thyristor must be zero when switching out the capacitor.

166. TSC with the electronic switch realized by a thyristor and an anti-parallel diode
The capacitor voltage will be always charged up to the peak of source voltage.
The response to switching- out command could be a little slower (maximum delay is one line-cycle).

167. 4.2.3 Chopping control—AC chopper
Modes of operation

168. 4.3 Thyristor cycloconverters
4.3.1 Single- phase thyristor-cycloconverter
Circuit configuration and operation principle

169. Single- phase thyristor-cycloconverter
Modes of operation

170. Typical waveforms

171. Modulation methods for firing delay angle Calculation method
– For the rectifier circuit

173. 4.3.2 Three- phase thyristor-cyclo converter
The configuration with common input line

174. The configuration with star-connected output

175. Typical waveforms

176. Input and output characteristics
The maximum output frequency and the harmonics in the output voltage are the same as in single-phase circuit. Input power factor is a little higher than single-phase circuit. Harmonics in the input current is a little lower thanthe single- phase circuit due to the cancellation of some harmonics among the 3 phases.
To improve the input power factor:
–Use DC bias or 3k order component bias on each of the 3 output phase voltages
Features and applications
Features:
–Direct frequency conversion—high efficiency
–Bidirectional energy flow, easy to realize 4- quadrant operation
–Very complicated—too many power semiconductor devices
–Low output frequency
–Low input power factor and bad input current waveform
Applications:
–High power low speed AC motor drive

177. 4.4 Matrix converter
Circuit configuration

178. Usable input voltage

179. Features
Direct frequency conversion—high efficiency can realize good input and output waveforms, low harmonics, and nearly unity displacement factor
Bidirectional energy flow, easy to realize 4- quadrant operation
Output frequency is not limited by input frequency
No need for bulk capacitor (as compared to indirect frequency converter)
Very complicated—too many power semiconductor devices
Output voltage magnitude is a little lower as compared to indirect frequency converter.

180. Chapter 5 DC to AC Converters
Outline
5.1 Commutation
5.2 Voltage source inverters
5.3 Current source inverters
5.4 Multiple- inverter connections and multi- level inverters

181. 5.1 Commutation types Basic operation principle of inverters
A classification of inverters
–Square- wave inverters (are discussed in this chapter)
–PWM inverters ( will be discussed in Chapter 6)
The concept of commutation

182. 4 types of commutation
1)Device commutation:
Fully- controlled devices: GTO, IGBT, MOSFET
2)Line commutation:
Phase- controlled rectifier,Phase- controlled AC controller,
Thyristor cycloconverter
3)Load commutation
4)Forced commutation

183. (1) Load commutation

184. (2) Forced commutation (capacitance commutation)

185. Another classification of commutations

186. 2 classes of inverters

187. 5.2 Voltage source inverter (VSI)
Features
DC side is constant voltage, low impedance (voltage source, or bulk cap)
AC side voltage is square wave or quasi- square wave.
AC side current is determined by the load.
Anti- parallel diodes are necessary to provide energy feedback path.
(freewheeling diodes , feedback diodes)

188. Single-phase half bridge VSI
The current conducting path is determined by the polarity of load voltage and load current. (This is true for analysis of many power electronics circuits.)
The magnitude of output square- wave voltage is Ud/2.

189. Single-phase full bridge VSI
Operation principle

190. Quantitative analysis
Fourier series extension of output voltage
Magnitude of output voltage fundamental component
Effective value of output voltage fundamental component

191. Output voltage control by phase-shift

192. Inverter with center- tapped transformer—push-pull inverter

193. Three-phase VSI

194. Basic equations to obtain voltage

195. Quantitative analysis
Fourier series extension of output line- to- line voltage
Magnitude of output voltage (line- to- line) fundamental component
Effective value of output voltage (line- to- line) fundamental component

196. 5.3 Current source inverter (CSI)
Features
DC side is constant current , high impedance (current source, or large inductor)
AC side current is quasis-quare wave. AC side voltage is determined by the load.
No anti-parallel diodes are needed. sometimes series diodes are needed to block reverse voltage for other power semiconductor devices.

197. Single-phase bridge CSI
Parallel Resonant Inverter

198. Three- phase self-commutated CSI

199. Three- phase force- commutated CSI

200. Three- phase load-commutated CSI

201. 5.4 Multiple- inverter connections and multi-level inverters
Series connection of 2 single- phase VSIs

202. Series connection of 2 3- phase VSIs

203. Multi-level Inverters 3- level inverter