Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M5/00—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases
  • H02M5/02—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC
  • H02M5/04—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters
  • H02M5/22—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M5/275—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
  • H02M5/293—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M5/00—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases
  • H02M5/02—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC
  • H02M5/04—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters
  • H02M5/10—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters using transformers
  • H02M5/14—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into DC by static converters using transformers for conversion between circuits of different phase number

Definitions

• TITLE AC/AC CONVERTER FOR CONVERSION BETWEEN THREE PHASE AND SINGLE PHASE POWER SUPPLIES
• the present disclosure generally relates to AC/AC converters.
• AC/AC converters convert an AC waveform into another AC waveform having a predetermined voltage and frequency.
• AC/AC converters based on various topologies including voltage-source inverter converters, current-source inverter converters, cyclo- converters and matrix converters are known in the art. Voltage-source inverter converters and current-source inverter converters are generally associated with conduction losses and poor power factor which reduces their efficiency. Cyclo- converters find limited use, typically in systems wherein output frequency is required to be lower than input frequency. Generally, AC/AC matrix converters comprise at least nine bi-directional semiconductor switches along with other circuit components. The topology of matrix converters known in the art is complex and expensive, and necessitates the use of a large number of components.
• An object of the present disclosure is to provide a bi-directional AC/AC converter with lesser number of bi-directional switches.
• Another object of the present disclosure is to provide a bi-directional AC/AC converter that provides high frequency output voltage using lesser number of bidirectional switches.
• Still another object of the present disclosure is to provide an optimized bidirectional AC/AC converter with reduced switching losses.
• Yet another. object of the present disclosure is to provide a simple optimized bidirectional AC/AC converter.
• Still another object of the present disclosure is to provide an efficient optimized bi-directional AC/AC converter.
• One more object of the present disclosure is to provide an optimized bidirectional AC/AC converter that eliminates the need for energy storage elements.
• an object of the present disclosure is to provide an optimized bidirectional AC/AC converter with improved power factor.
• One more objective of the present disclosure is to provide an optimized bidirectional AC/AC converter with reduced total harmonic distortion.
• a converter selectively converting an input AC voltage into an output AC voltage, the converter connected between the terminals of a three phase AC supply and the terminals of a single phase AC supply, the converter comprising:
• a first switch set comprising three bidirectional switches connected in a one to one correspondence with the terminals of the three phase AC supply at one end ' and the other end being connected to a terminal of ' the single phase AC supply;
• a second switch set comprising three bidirectional switches connected in a one to one correspondence with the terminals of the three phase AC supply at one end and the other end being connected to another terminal of the single phase AC supply; and • a controller connected to each switch of the switch pairs constituting each of the bidirectional switches, the controller adapted to sequentially turn ON one switch of the switch pair of a predetermined bidirectional switch of the first switch set and another switch of the switch pair of a predetermined bidirectional switch of the second switch set, for every phase angle displacement of 60 degrees corresponding to the input AC voltage thereby generating the output AC voltage having a frequency in the range of 50Hz to 30kHz.
• the converter can be a single stage converter wherein the frequency of said single phase AC output is in the range of 1 kHz to 30 kHz. However, it could be higher or lower depending on the frequency capability of the power devices, losses and application. Theoretically, there is no limit to the frequency or frequency range.
• the converter comprises bi-directional switches that are sequentially turned ON to provide bidirectional flow of power. For instance, when the input AC voltage is a three phase AC voltage, the output AC voltage is a high frequency single phase AC voltage. Alternatively, when the input AC voltage is a single phase AC voltage, the output AC voltage is a high frequency three phase AC voltage.
• the bi-directional switch constituting the switch pair can be a pair of antiparallel common emitter configuration of IGBTs with series diode.
• the controller as described herein above comprises:
• each of the comparators being adapted to compare a carrier waveform with at least one reference signal corresponding to a phase of the three phase AC supply and generate a unipolar switching signal (SPWM);
• each of the AND-ing means being adapted to logically AND the unipolar switching signal with a frequency signal to generate a signal corresponding to each of the switches constituting the bi-directional switches;
• each of the OR-ing means being adapted to receive and logically OR the signals corresponding to switches constituting each of the pairs and further adapted to generate trigger signals for the sequential turning ON of switches.
• a method for converting an input AC voltage into an output AC voltage comprising the steps of:
• the step of sequentially turning ON one switch can further comprise the following steps:
• SPWM unipolar switching signal
• FIGURE 1 illustrates a conventional indirect AC-AC converter topology
• FIGURE 2 illustrates a direct AC/AC converter topology
• FIGURE 3 illustrates a power circuit of a bi-directional AC/AC converter in accordance with an embodiment of the present disclosure
• FIGURE 4 is a control circuit diagram that illustrates generation of trigger signals for bi-directional switches of FIGURE 3;
• FIGURE 5 illustrates a single phase output voltage waveform across a load
• FIGURE 6 and FIGURE 7 illustrate output voltage waveforms corresponding to different input voltages applied to a bi-directional AC/AC converter in accordance with an embodiment of the present disclosure.
• FIGURE 1 illustrates a conventional indirect AC -AC converter topology.
• the topology implements an energy storage element (10), typically a capacitor or an inductor.
• an AC input to the converter is first converted into a DC output which is stored in the energy storage element (10).
• the energy stored by the energy storage element (10) is then further converted into a desired AC output to be supplied to a connected load.
• FIGURE 1 It is apparent from the aforementioned description of FIGURE 1 that the topology requires at least two stages of power conversion, thereby necessitating the use of more power semiconductor devices. Moreover, increased conduction and switching losses lead to higher total harmonic distortion, low power factor and poor efficiency in converters based on indirect AC-AC converter topology.
• FIGURE 2 illustrates a direct AC/AC converter topology. As illustrated, this converter topology is used to convert an AC input voltage into another AC output voltage without any direct DC link as required in the conventional indirect AC -AC converter described in FIGURE 1.
• This topology overcomes the limitations of a conventional indirect AC-AC converter of FIGURE 1 by replacing the multiple conversion stages and an intermediate energy storage element by a single power conversion stage, therefore reducing losses in converters based on matrix converter topology.
• FIGURE 3 illustrates a power circuit of a bi-directional AC/AC converter in accordance with an embodiment of the present disclosure.
• the converter is connected between the terminals of a three phase AC supply and the terminals of a single phase AC supply.
• the power circuit (300) comprises six bidirectional switches, each switch comprising a pair of antiparallel common emitter configuration of IGBTs with series diode.
• the six bi-directional switches are grouped in to two switch sets.
• the three bi-directional switches constituting the first switch set are connected to one of the phases of the three phase AC input at one end, in a one to one correspondence, and at the other end connected to a terminal (302) of the single phase AC supply.
• the three bidirectional switches constituting the second switch set are connected to one of the phases of the three phase AC input at one end, in a one to one correspondence, and at the other end to another terminal (304) of the single phase AC supply.
• a first bi-directional switch comprises IGBTs Tl and T2 along with series diodes Dl and D2 respectively
• a second bi-directional switch comprises IGBTs T3 and T4 along with series diodes D3 and D4 respectively
• a third bidirectional switch comprises IGBTs T5 and T6 along with series diodes D5 and D6 respectively
• a fourth bi-directional switch comprises IGBTs T7 and T8 along with series diodes D7 and D8 respectively
• a fifth bi-directional switch comprises IGBTs T9 and T10 along with series diodes D9 and D10 respectively
• a sixth bi-directional switch comprises IGBTs Ti l and T12 along with series diodes Dl 1 and D12 respectively.
• a controller is connected to each switch of the switch pairs constituting each of the bidirectional switches.
• the controller sequentially turns ON one switch of the switch pair of a predetermined bidirectional ' switch of the first switch set and another switch of the switch pair of a predetermined bidirectional switch of the second switch set, for every phase angle displacement of 60 degrees corresponding to the input AC voltage thereby generating the output AC voltage having a frequency in the range of 50Hz to 30kHz.
• a 360 degree cycle of the input AC waveform only two switches of the 12 switches constituting the 6 bidirectional switches conduct in a sequential pattern in each of the six time intervals (I, II, III, IV, V, VI) based on trigger signals generated by the controller.
• the switching pattern of each switch is predetermined in accordance with Table 1 provided herein below.
• R and B phases are connected to the input power supply, IGBTs T6 and T7 are turned ON and provide an output to the terminals (302) and (304) respectively.
• Y and R phases are connected to the input power supply, IGBTs T2 and T9are turned ON and provide an output to the terminals (302) and (304) respectively.
• FIGURE 4 is a control circuit (400) that illustrates generation of trigger signals for bi-directional switches of FIGURE 3.
• the circuit (400) illustrates an integration of the power circuit of FIGURE 3 with the control circuits (phase R, phase Y and phase B respectively) for the converter of FIGURE 3.
• the control circuit associated with each phase comprises two comparators compl and comp2.
• Each of the comparators compl and comp2 receive a positive reference signal and a negative reference signal respectively at one input and a carrier voltage signal CV, generally a triangular waveform, at the second input.
• the positive reference signal is connected to a non-inverting terminal of the comparator compl and the negative reference signal is connected to a non- inverting terminal of the comparator comp2.
• the comparators compl and comp2 compare the reference signals with the carrier voltage signal CV and generate unipolar voltage switching signals SPWM at the output.
• the unipolar voltage switching signals SPWM along with a frequency logic signal (f logic) are provided to two pairs of AND-ing means, typically AND gates. Each AND gate receives an SPWM signal at one input terminal and the frequency logic (f logic), at the other input terminal.
• One pair of AND gates receives the frequency logic signal (f logic) and the other pair of AND gates receives the inverted frequency logic signal (f logic).
• the frequency logic signal (f logic) generally, a square wave, determines the output frequency of the bi-directional AC/AC converter.
• OR- ing means typically OR gates for logically OR-ing the signals corresponding to switches constituting each of the bidirectional switch pairs and generate trigger signals for the sequential turning ON of switches in accordance with the. predetermined switching sequence of Table 1 provided herein above.
• the circuit (400) incorporates OR gates configured to connect:
• bi-directional switches, the connection scheme and the switching sequence enable the converter of the present disclosure to be applicable for bi-directional power flow, thereby making the converter of the present disclosure suitable to regenerate energy back to the utility. Accordingly, when the input AC voltage is a three phase AC voltage, the output AC voltage is a single phase AC voltage and vice versa.
• the converter of the present disclosure is particular capable of generating high
• a single phase AC input voltage is required to be converted into a three phase AC output voltage
• a single phase high frequency AC input power is fed to the power circuit comprising switching devices and a three phase AC output with fundamental line frequency is fed to the AC mains supply.
• the generated three phase AC output is line synchronized, thereby necessitating the presence (grid connectivity) of mains supply to the bidirectional AC/AC converter of the present disclosure.
• FIGURE 5 illustrates a single phase output voltage waveform across a load, the single phase output voltage being obtained from a three phase input voltage supply.
• FIGURE 6 and FIGURE 7 illustrate output voltage waveforms corresponding to different input voltages applied to a bi-directional AC/AC converter in accordance with an embodiment of the present disclosure.
• the waveforms corresponding to each phase is displaced by 120 degrees.
• the AC/AC converters of the present disclosure typically find application in traction locomotives, DC motor control in process industries (DC drives), AC motor control (AC drives), battery chargers, rectifiers - high voltage for electrostatic precipitations, rectifiers - high current for electrochemical applications, rectifiers - metal finishing rectifiers, HV DC transmission, renewable energy sources and regeneration of electrical supply.
• TEST DATA A test report of a prototype of a bi-directional AC/AC converter of the present disclosure is provided herein below in Table 3.
• Triangular frequency 7 KHz.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Ac-Ac Conversion (AREA)

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Publications (2)

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• 2014
  • 2014-06-20 IN IN6MU2013 patent/IN2013MU00006A/en unknown
  • 2014-06-20 EP EP14814235.9A patent/EP3011665A4/en not_active Ceased
  • 2014-06-20 WO PCT/IN2014/000414 patent/WO2014203282A2/en active Application Filing
  • 2014-06-20 CN CN201480046397.6A patent/CN105765846B/zh not_active Expired - Fee Related

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