KR20080077170A - Electronic control transformer using dc link voltage - Google Patents

Electronic control transformer using dc link voltage Download PDF

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Publication number
KR20080077170A
KR20080077170A KR1020087014048A KR20087014048A KR20080077170A KR 20080077170 A KR20080077170 A KR 20080077170A KR 1020087014048 A KR1020087014048 A KR 1020087014048A KR 20087014048 A KR20087014048 A KR 20087014048A KR 20080077170 A KR20080077170 A KR 20080077170A
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KR
South Korea
Prior art keywords
voltage
dc
fixed
dc link
input
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KR1020087014048A
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Korean (ko)
Inventor
하롤드 로버트 쉐네츠카
무하메트 코산
Original Assignee
요크 인터내셔널 코포레이션
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Priority to US11/324,368 priority Critical
Priority to US11/324,368 priority patent/US20070151272A1/en
Application filed by 요크 인터내셔널 코포레이션 filed Critical 요크 인터내셔널 코포레이션
Publication of KR20080077170A publication Critical patent/KR20080077170A/en

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B49/00Arrangement or mounting of control or safety devices
    • F25B49/02Arrangement or mounting of control or safety devices for compression type machines, plant or systems
    • F25B49/025Motor control arrangements
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B2600/00Control issues
    • F25B2600/02Compressor control
    • F25B2600/021Inverters therefor
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00Energy efficient heating, ventilation or air conditioning [HVAC]
    • Y02B30/70Efficient control or regulation technologies
    • Y02B30/74Technologies based on motor control
    • Y02B30/741Speed regulation of the compressor

Abstract

In a chiller system, an electronic control transformer is powered by the DC link of a variable speed drive that drives a compressor motor. The electronic control transformer converts the DC voltage to a constant 120 VAC at 60 Hz, for providing power to auxiliary electrical devices associated with the chiller system. The electronic transformer includes four semiconductor switches to convert the DC voltage to AC. The energy stored in the compressor motor is transferred to the DC link of the VSD during an input voltage sag. The electronic control transformer maintains the control voltage and prevents the system auxiliary loads from dropping out during a voltage sag. The chiller system is able to ride through the input voltage sag or interruption. A boost converter may be provided at the input of the VSD to increase ride through capability.

Description

ELECTRICAL CONTROL TRANSFORMER USING DC LINK VOLTAGE}

The present invention relates to an electronic transformer for supplying a control voltage. In particular, the present invention relates to an electronically controlled transformer powered by a DC link of a variable speed drive for a chiller.

In the past, motors for driving compressors in chillers have been designed to operate at standard line-to-line voltages and frequencies available from the power distribution system of the facility in which the motor operates. The use of line voltage and frequency limits the options for modulating the compressor's capacity with less efficient mechanical devices such as inlet guide vanes and slide valves as a result of the motor being limited to one operating speed, typically based on the motor's input frequency. Was done.

Also, if the operating speed of the motor is not equal to the desired operating speed of the compressor, a "step up" or "step down" gearbox may be used between the motor and the compressor to achieve the desired operating speed of the compressor. Inserted.

Next, variable speed drives (VSDs) were developed that could change the frequency and voltage provided to the motor of the chiller. This can change the input frequency and voltage applied to the motor, so that the motor can provide a variable output speed to the corresponding compressor of the cooling device. The shifting operation of the motor (and compressor) allows the chiller to take advantage of the efficiencies that occur during the partial loading process of the compressors when the complete design load speed is operating at lower than desired levels. The use of variable speed drives also allows the use of other types of motors that require their own electronic drive in the chiller, in addition to older motors that can operate directly from three-phase power lines, ie induction motors or synchronous motors.

Generally, a chiller includes a number of auxiliary devices that cooperate with a compressor. These aids are usually specified at a fixed voltage that is different from the fixed voltage of the compressor motor and include control panels, contactors, relays, pumps and fans operating at a fixed frequency, ie at a frequency of 60 Hz or 50 Hz. Since the auxiliary devices cannot operate with the variable voltage and frequency output of the VSD, the power for the control voltage is provided by a conventional winding magnetic control transformer connected to the VSD as input AC power or from another input power source. The output voltage of the control transformer secondary winding is proportional to the primary winding input voltage, so that a voltage drop or blackout on the primary winding reflects the output voltage of the control transformer almost simultaneously. A voltage drop or power outage, if sufficient in size and / or cycle, may cause the contactor or relay of the chiller to drop out, or cause the control panel or pump to shut down, resulting in chiller operation. It stops.

The VSD powering the compressor will experience an input voltage drop or power failure for the same reason. VSDs typically include a converter that converts an AC input voltage into a DC voltage for the DC link. The inverter is connected to the DC link and converts the DC link voltage into a variable voltage, variable frequency AC power output. The DC link is supported by a capacitor that supplies limited stored energy, and in some instances an active rectifier or converter will be employed to boost the input voltage to a peak of the RMS value, i.e., 1.414 times the nominal value of the input voltage source. These parts of the VSD provide a measure of the ride-through capability. However, very often, the power failure compensation capability is insufficient to maintain cooler operation for input voltage drops or interruptions greater than a few cycles on a 60 Hz utility line.

In such a case, where the VSD is configured to have the capability of compensating for the power failure, the control transformer can be left to be damaged by the voltage drop even though the VSD and the compressor motor maintain the voltage drop. One limitation of a chiller with separate AC input power sources for the compressor and auxiliary devices is that the chiller fails if the VSD output voltage or control voltage drop or BRIEF power failure occurs. Another limitation of a chiller with separate AC input control power sources for the compressor and auxiliary devices is that different control transformers must be used for power devices with different distribution voltages and the design of the control transformer is an input applied to the chiller. It depends on AC voltage and frequency.

Therefore, there is a need for a control transformer powered by a VSD driving a compressor of a chiller and having improved instantaneous power compensation capability.

The present invention includes an electronic transformer configured to provide a single phase AC control power from a DC link of a VSD to power at least one accessory associated with the chiller. The electronically controlled transformer includes an inverter module for converting the DC voltage into an AC voltage to power the load. The inverter module includes a plurality of pairs of power switches, each pair including a plurality of pairs of power switches including an insulated gate bipolar transistor connected in anti-parallel to the diode; An input DC connection for connecting an electronically controlled transformer to the DC link of the variable speed drive; An input AC connection for connecting the electronically controlled transformer to the AC input of the variable speed drive; And an output AC connection for connecting at least one auxiliary device. The inverter module may be controlled to provide a fixed output AC voltage and a fixed frequency to power at least one auxiliary device.

In a preferred embodiment, the invention relates to a drive for powering a number of components of a cooling device which have different voltage requirements than the drive itself. The drive includes an active rectifier or converter stage coupled to an AC power source to receive input AC power at a fixed input AC voltage and a fixed input frequency. The active converter or rectifier is configured with a charging circuit for controlling the inrush current applied to the DC link at start up. The active converter stage is configured to convert a fixed input AC voltage into a boosted DC voltage, where the boosted DC voltage is greater than the peak value of the fixed input AC voltage. The DC link is connected to the converter stage. The DC link is configured to filter the boosted DC voltage and store energy coming from the converter stage. The first inverter stage is also connected to the DC link. The first inverter stage is configured to convert the boosted DC voltage coming from the DC link to provide a variable voltage and an output voltage as a variable frequency to the motor of the cooling device. The variable voltage has a maximum voltage capability greater than the fixed input AC voltage. The variable frequency has a maximum frequency capability greater than the fixed input frequency. Active converters provide additional momentary compensation capability to the extent that the AC input voltage decreases without a corresponding decrease in the DC link. When the active converter reaches saturation, the inverter responds to the decreasing fixed input AC voltage to drive power from the energy stored in the rotating mass of the motor connected to the first inverter stage to maintain the voltage level of the DC link. It is controlled to divert the flow of energy coming from the DC link stage direction. An electronically controlled transformer configured to convert a boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency for at least one component of the chiller, connected to the DC link. The fixed output AC voltage is less than the fixed input AC voltage applied to the drive's converter. In addition, the output AC voltage and the fixed output frequency of the electronically controlled transformer are maintained when a temporary decrease in the fixed input AC voltage occurs.

In another embodiment, the VSD includes a conventional rectifier or converter at the input. There is a DC link connected to the converter stage, which is configured to filter the DC voltage and store energy coming from the converter stage. The first inverter stage is connected to the DC link. The first inverter stage is configured to convert the DC voltage coming from the DC link into an output voltage for the motor.

The first inverter stage is adapted to switch in power flow from the first inverter stage to the DC link stage to transfer power from the energy stored in the rotating mass of the motor to maintain the voltage level of the DC link stage in response to the decreasing input AC voltage. Controlled. An electronically controlled transformer configured to convert a DC voltage from a DC link into a secondary output power source having a fixed output AC voltage and a fixed output frequency for at least one component of the chiller. The fixed output AC voltage is connected to the drive. Is less than the fixed input AC voltage applied to the converter. In addition, the output AC voltage and the fixed output frequency of the electronically controlled transformer are maintained when a temporary decrease in the fixed input AC voltage occurs.

In another embodiment of the invention, there is a cooling device comprising an electronically controlled transformer. The chiller comprises a refrigeration circuit comprising a compressor, a condenser and an evaporator connected to a closed refrigeration circuit. The motor is coupled to the compressor to power the compressor. The variable speed drive is connected to the motor. The variable speed drive is configured to receive input AC power at a fixed input AC voltage and a fixed input frequency and provide output power to the motor at variable voltages and variable frequencies.

The variable voltage has a variable frequency having a maximum voltage capability greater than a fixed input AC voltage and a maximum frequency capability greater than a fixed input frequency.

Variable speed drives include an active converter or rectifier stage connected to an AC power source providing input AC power. The converter stage is configured to convert the input AC voltage into a boosted DC voltage. The boosted DC voltage is greater than the fixed input AC voltage. There is a DC link connected to the converter stage, the DC link configured to filter the boosted DC voltage and to store energy from the converter stage. The first inverter stage is connected to the DC link. The first inverter stage is configured to convert the boosted DC voltage coming from the DC link into an output voltage for the motor. The first inverter stage receives a power flow flowing from the first inverter stage to the DC link stage to deliver power from the energy stored in the rotating mass of the motor to maintain the voltage level of the DC link stage in response to the decreasing input AC voltage. Configured to switch.

The electronically controlled transformer is connected to the DC link. The electronically controlled transformer is configured to convert the boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency, wherein the fixed output voltage is greater than the fixed input AC voltage for the active converter or rectifier. small. The fixed output AC voltage and fixed output frequency of the electronically controlled transformer are maintained in case of a temporary decrease in the input AC voltage.

In another embodiment, the present invention relates to an electronically controlled transformer for powering at least one auxiliary device associated with a cooling device. The electronically controlled transformer includes an inverter module for converting a DC voltage to provide a fixed output AC voltage and a fixed frequency to power at least one auxiliary device. The inverter has a plurality of pairs of power switches, each pair of power switches comprising an insulated gate bipolar transistor connected to the diode in anti-parallel. An input DC connection is provided to connect the electronically controlled transformer to the DC link of the variable speed drive. An input AC connection is also provided for connecting the electronically controlled transformer to the AC input of the drive. An output AC connection is provided for connecting at least one auxiliary device to the inverter module.

One advantage of the present invention is that an electronic transformer having improved instantaneous power compensation capability as an auxiliary component of the cooling device provides an improved reliability of the cooling device as an auxiliary component of the cooling device.

Another advantage of the present invention is the use of an electronically controlled transformer with independent input AC voltage magnitude and input frequency for a single electronically controlled transformer, ie VSD equipment chiller, to power the cooling control.

Another advantage of the present invention is that the electronic transformer of the present invention eliminates the need for conventional control transformers and provides a common source of power for the entire chiller.

Other features and advantages of the present invention will become apparent from the following more detailed description of the preferred embodiments which illustrate, by way of example, the principles of the invention with reference to the accompanying drawings.

1 is a view schematically showing a general device configuration of the present invention.

2 is a view schematically showing an embodiment of the variable speed drive and the electronically controlled transformer of the present invention.

3 is a view schematically showing a refrigeration system that can be used in the present invention.

4 is a circuit diagram of one embodiment of an electronically controlled transformer.

5 is a view showing another example of an electronically controlled transformer.

6 shows another example of an active converter arrangement.

The same reference numerals will be used for the same or similar parts throughout the drawings.

1 and 2 generally illustrate the device configuration of the present invention. The electronic transformer 108 is configured to provide AC power from the DC link 204 of the variable speed drive (VSD) 104. The electronic transformer 108 has at least four semiconductor switches and converts the DC link voltage into a fixed voltage, fixed frequency AC output. The AC power source 102 supplies AC power to the VSD 104, which in turn supplies AC power to the motor 106. In other embodiments of the invention, the VSD 104 may power one or more motors 106. The motor 106 is preferably used to drive the corresponding compressor of the refrigeration system or chiller. The VSD 104 also powers the electronic transformer 108 from the DC link 204. The electronic transformer 108 directs the DC power from the DC link 204 to various auxiliary devices 110, namely control panels, contactors, relays, pumps and fans, which are components of the chiller (generally shown in FIG. 3). Converts to AC controlled power source with fixed voltage and frequency. The AC power source 102 provides three phase fixed voltage and fixed frequency AC power from the on-site AC power grid or distribution device to the VSD 104. The AC power grid may be supplied directly from the electrical utility or may be supplied from one or more conversion substations between the electrical utility and the AC power grid. AC power source 102 is preferably capable of supplying a three-phase AC or line voltage of 200 V, 230 V, 380 V, 460 V, or 600 V at a line frequency of 50 Hz or 60 Hz, depending on the corresponding AC power grid. Can be. It will be appreciated that the AC power source 102 can supply any suitable fixed line voltage or fixed line frequency to the VSD 104 in accordance with the AC power grid. In addition, a particular site may have multiple AC power grids that can meet different line voltage and line frequency requirements. For example, a site may have a 230 VAC power grid to handle certain applications and a 460 VAC power grid to handle other applications.

Referring next to FIG. 2, the VSD 104 receives AC power having a particular fixed line voltage and a fixed line frequency from the AC power source 102, and the AC power can be changed to meet specific requirements. To the motor 106 at the desired voltage and desired frequency. Preferably, the VSD 104 may provide the motor 106 with AC power having a voltage and frequency higher or lower than the fixed voltage and fixed frequency received from the AC power source 102. 2 schematically illustrates some of the components in one embodiment of the VSD 104. VSD 104 comprises three stages; The converter stage 202, the DC link stage 204, and the inverter stage 206 may be provided. Converter 202 converts AC power at a fixed line frequency, fixed line voltage from AC power source 102, into DC power. DC link 204 filters the DC power coming from converter 202 and provides energy storage components such as capacitor 208 and / or inductor (not shown). The inverter 206 converts the DC power coming from the DC link 204 into AC power of variable frequency, variable voltage for the motor 106.

The electronic transformer 108 is also connected to the DC link 204 of the VSD 104. Although the fixed voltage and / or frequency may be changed to meet various site conditions or operating requirements, the electronic transformer 108 converts the DC power from the DC link 204 at a fixed frequency, preferably 60 Hz, at a fixed frequency. Voltage, preferably 120 VAC. The auxiliary device 110 for the cooling device is connected to the output of the electronic transformer 108 and may include a control panel, a contactor, a relay, a pump and a fan. If necessary, the electronic transformer 108 will be configured to supply three phase power to the auxiliary devices. The electronic transformer 108 has the ability to provide control power at the boosted voltage of the auxiliary device 110 as long as the DC voltage of the DC link is maintained at a sufficient level. As will be discussed in more detail below, the benefits of the VSD 104's ability to compensate for momentary power are delivered to the auxiliary device 110 of the cooling device. The electronic transformer 108 will be installed in the same enclosure that surrounds the VSD 104. Alternatively, the electronic transformer 108 may be installed into a control panel or housed in an enclosure with distribution circuit breakers and switches to feed to the control panel 308 (see FIG. 3) and / or the auxiliary device 110. . Preferably, motor 106 is an induction motor that can be driven at a variable speed. Induction motors may have any suitable arrangement of poles, including two, four or six poles. Induction motors are used to drive the load, preferably the compressor of the refrigeration or cooling device as shown in FIG. 3. Figure 3 generally shows a device of the invention connected to a refrigeration device.

As shown in FIG. 3, the HVAC, refrigeration system or liquid cooling device 300 includes a compressor 302, a condenser 304, an evaporator 306 and a control panel 308. The control panel 308 may include various other components such as analog to digital converters, microprocessors, nonvolatile memory, and interface boards to control the operation of the refrigeration system 300. The control panel 308 may be used to control the operation of the VSD 104 and the motor 106. The electronic transformer 108 provides control power to the control panel 308 as well as other single phase aids 110 for the chiller 300.

The compressor 302 compresses the cooling vapor and sends it to the condenser 304 through the discharge line. The compressor 302 preferably consists of a centrifugal compressor, but may be any other suitable type of compressor, namely a screw compressor, a reciprocating compressor, or the like. The cooling vapor carried by the compressor 302 to the condenser 304 is in heat exchange with the fluid, ie air or water, and undergoes a phase change as a cooling liquid as a result of the heat exchange with the fluid. Condensed liquid coolant from condenser 304 flows to evaporator 306 through an expander (not shown).

Evaporator 306 may comprise a connection of a supply line and a return line of the cooling load. A secondary liquid, ie water, ethylene, calcium chloride brine or sodium chloride brine, moves through the return line into the evaporator 306 and exits the evaporator 306 via the feed line. The liquid coolant in the evaporator 306 will heat exchange with the secondary liquid to lower the temperature of the secondary liquid. The cooling liquid in the evaporator 306 undergoes a phase change to cooling steam as a result of heat exchange with the secondary liquid. The vapor coolant in the evaporator 306 exits the evaporator 306 and returns to the compressor 302 by the suction line to complete the cycle. It will be appreciated that suitable configurations of the condenser 304 and evaporator 306 may be used in the apparatus 300 and appropriate phase changes of the coolant in the condenser 304 and the evaporator 306 may be obtained.

The HVAC, refrigeration system or liquid chiller 300 may include other features not shown in FIG. 3. These features have been omitted for simplicity of explanation. In addition, FIG. 3 shows an HVAC, refrigeration system or chiller 300 with one compressor connected to a single refrigeration circuit, although the device 300 is connected to each of one or more refrigeration circuits and is a single VSD or multiple VSDs. It will be appreciated that it is possible to have multiple compressors powered by.

Preferably, control panel 308, microprocessor or controller provides VSD 104 to provide suitable operating settings for VSD 104 and motor 106 depending on the particular sensor readings received by control panel 308. FIG. (And possibly the control of the motor 106) may provide a control signal to the VSD 104. For example, in the refrigerating device 300 of FIG. 3, the control panel 308 may adjust the output voltage and frequency of the VSD 104 to correspond to changes in conditions in the refrigerating device. That is, in response to the increase or decrease of the load conditions on the compressor 302 to obtain the desired operating speed of the motor 106 and the desired load output of the compressor 302, the control panel 308 outputs the output of the VSD 104. You can increase or decrease the voltage and frequency.

Referring back to FIG. 2, the transformer 202 may be a conventional diode or thyristor rectifier connected to the DC link 204. In another example, converter 202 is insulated to provide a boosted DC voltage to DC link 204 to obtain a maximum base RMS output voltage from VSD 104 that is greater than the normal RMS base input voltage of VSD 104. It can be a pulse width modulated boost converter or rectifier with gated bipolar transistors (IGBTs). In a preferred embodiment of the present invention, VSD 104 has a maximum output voltage greater than the fixed base RMS input voltage provided to VSD 104 and a maximum greater than the fixed normal base RMS input frequency provided to VSD 104. It can provide a basic RMS output frequency. It will also be appreciated that the VSD 104 can incorporate other components than those shown in FIG. 2 as long as the VSD 104 can provide the appropriate output voltage and frequency for the motor 106.

In addition, the active converter or rectifier 202 can be used to improve the VSD 104's ability to compensate for the momentary power while the AC input voltage is decreasing, as referred to as a voltage drop. Active converter or rectifier 202 may be controlled to provide the desired desired output voltage to DC link 204 independent of the AC input voltage. By providing a DC voltage that is independent of the AC input voltage, the active converter or rectifier 202 (and the VSD 104) is not affected by the voltage drop at the AC input voltage and thereby the VSD 104. Improved power failure compensation capability is provided. The active converter or rectifier 202 can continue to provide the desired DC voltage to the DC link 204 even when the AC input voltage drops. This capability of the active converter or rectifier 202 may allow the VSD 104 to continue to operate without interruption or momentary power outages during times when the AC input voltage drops.

As an additional means to improve the instantaneous power compensation in the chiller, when the active converter or rectifier 202 reaches its current limit during voltage drop, the compressor control unit (not shown) is removed from the DC link capacitor 208. The mechanical no load device of the compressor 302 is operated to minimize the power consumed by the resulting mechanical load. In addition, an inverter control unit (not shown) is intended to transfer energy from the energy stored in the rotating mass of the motor 106 to the DC link capacitor 208 at approximately the same time that no mechanical load is connected by the compressor control unit. Control the DC link and control the motor speed.

The motor speed decreases during the momentary power compensation, while the DC link voltage remains at or near the promoted voltage. If the energy stored in the rotating mass is sufficiently depleted before the line input voltage returns to its normal range, the device will actually shut down to prevent damage to the chiller components. Once the line input AC voltage has recovered to within a range of normal input AC voltages, the inverter 206 regulates the speed of the motor 106 as required by the HVACR & R's control until the next voltage drop occurs, Converter 202 regulates the DC voltage of DC link 204.

As will be described in detail below, electronic transformer 108 consists of four power semiconductor switches (not shown) such as insulated gate bipolar transistors (IGBTs) or MOSFETs. Preferably, the electronic transformer 108 is configured to convert the DC voltage coming from the DC link to provide 120V 60Hz of a single phase. AC supplies control power to auxiliary device 110. If the auxiliary device 110 includes a three phase motor for pumps and fans, the electronic transformer 108 will be configured to provide three phase power and other fixed voltages and fixed frequencies if desired. The electronic transformer 108 is set for a fixed output voltage and frequency, and once set, does not adjust the voltage and frequency of the output power.

In a preferred embodiment of the present invention, VSD 104 includes a charging configuration for charging capacitors connected to a DC link. Referring to FIG. 4, the charging of the capacitors 208 of the DC link 204 is controlled using the active converter or rectifier module 202 shown in FIG. 4. The active converter or rectifier module 202 includes three pairs of power switches or transistors (one pair for each input phase). The active converter or rectifier module 202 also includes corresponding control connections (not shown for simplicity) to control the switching of the power switches in a manner similar to that described below for the electronic transformer 108. In a preferred embodiment of the active converter or rectifier module 202, the power switches are controlled by pulse width modulation techniques to generate the desired output voltage for the DC link 204, as described in detail below. IGBT power switches. Preferably, the active converter or rectifier module 202 may operate as a boost rectifier to provide a boosted DC voltage to the DC link 204 to obtain an output voltage from the VSD 104 that is greater than the input voltage of the VSD 104. Can be.

In the active converter or rectifier module 202, one of the power switches in each pair of power switches is an IGBT 450 connected to the anti-parallel diode 452. The antiparallel diode 452 is used to conduct current after the other power switch, IGBT 454, is turned off when the VSD 104 is operating in pulse width modulation mode. As shown in FIG. 4, the IGBTs 450 and the reverse diode 452 are connected between the output of the circuit protection device and the three-phase line inductor 416 and the negative rail of the DC booth 412. However, in another embodiment of the present invention, the plurality of IGBTs 450 and the inverse diode 452 may include the output of the circuit protection device, the three-phase line inductor 416, and the DC bus booth 412a as shown in FIG. Is connected between the negative rails. Circuit protection device 416 may include inductors, circuit breakers, fuses, and other devices for protecting VSD circuit components connected to the load side of device 416.

The other power switch in the pair of power switches is a reverse blocking IGBT 454, i. Reverse blocking IGBT 454 is connected to an anti-balance or anti-parallel IGBT 456, which is also a reverse blocking IGBT. Anti-parallel IGBT 456 is preferably controlled during the charging process to ensure that only small pulses of inrush current can reach the DC link. After the charging operation is complete, the anti-parallel IGBT 456 can be controlled to conduct throughout, similar to the anti-parallel diode 452. Reverse blocking IGBT 454 blocks the positive emitter-to-collector voltage approximately equal to the peak line-to-line voltage seen across IGBT 454 as long as the conduction of anti-parallel IGBT 456 is delayed for charging purposes. . In another embodiment of the active converter 202, as shown in FIG. 6, the converter includes three power switches per phase. Each of the three power switches per phase consists of a conventional IGBT 450 that cannot block the reverse voltage connected to the anti-balance or anti-parallel diode 452. Two of the power switches are connected in series oppositely between the output of the circuit protection device and the three phase line reactor 416 and the positive rail. In each phase, the top power switch (A top ) is charged so that only small pulses of inrush current can reach the DC link 204 through the intermediate opposing series power switch (A mid ) reverse diode. It is preferably controlled during operation. After the preliminary operation is completed, the first power switch switch A top may be controlled to conduct throughout, similar to the antiparallel diode 452. The third power switch of each phase A bot is connected between the output of the circuit protection device and the three-phase line reactor 416 and the negative rail.

Referring to FIG. 4, in another embodiment of the converter 202, the anti-parallel IGBT 456 is replaced with a silicon carbide controlled rectifier (SiCCR). Reverse blocking IGBTs 454 are connected in anti-parallel to SiCCR. The SiCCR is preferably controlled during the charging operation so that only small pulses of inrush current can reach the DC link 204. After the charging operation is complete, the SiCCR can be controlled to conduct throughout, similar to the antiparallel diode 452. The reverse blocking IGBT 454 blocks the positive emitter-collector voltage that is approximately equal to the peak line-to-line voltage seen across the IGBT 454 as long as the conduction of the SiCCR is delayed for charging purposes. In addition, SiCCR exhibits no reverse recovery phenomenon or characteristics when operating as a conventional diode. The presence of a reverse recovery characteristic in SiCCR prevents significant reverse current from flowing in the SiCCR whenever the IGBT 450 is turned on in the same phase, thereby preventing significant reverse recovery losses occurring in the SiCCR. In the case of charging the DC link, in a preferred embodiment, the electronic transformer 108 is coupled to a pair of diodes 430 connected to any two of the three phases (Ll, L2, L3) of the input AC power 102. Include. This arrangement provides power to the control circuit immediately in case the active converter or rectifier is not working or when charging the DC link 204. While the DC link 204 of the converter 202 is charging, the diodes 430 are connected to the DC booth 440 of the electronic transformer to convert the input AC voltage 102 into the DC voltage of the DC booth 440. . Diodes 432 block current from flowing from DC bus 440 to DC link 202 during the charging process. After charging of the DC link 204 is completed, the active converter 202 is activated, and the boosted DC voltage of the DC link 202 is greater than the DC voltage provided by the diode 430, which means that the DC current is equal to the DC bus ( Flow from 440 to DC link 204. Therefore, diodes 430 are reverse biased when the voltage of DC link 204 exceeds the peak of the input AC voltage and stops conducting current to DC bus 440. Diodes 430 shield the DC link with respect to input AC line 102. Preferably, capacitor 442 is connected across DC booth 440 to filter DC energy and store energy for electronic transformer 108. Although no additional diode 430 is shown, a three-phase AC power source may be included with the voltage to provide an electronically controlled transformer in case the active converter or rectifier is not operating.

The electronic transformer 108 essentially includes an inverter that converts the DC voltage of the DC booth 440 into a control voltage for the auxiliary device 110 for power typically of 120 Volt, 60 Hz. The voltage transformer 108 has four pairs of power switches or transistors. One of the power switches in each pair of power switches is an IGBT 444 connected to an antibalance or antiparallel diode 446. The anti-balance or anti-parallel diode 446 is used to conduct current after the other switch, IGT 444, is turned off when the electronic transformer 108 is operating in pulse width modulation mode.

As shown in FIG. 4, IGBTs 444 and inverse diode 446 are coupled between DC booth 440 and inductors 460 at the output of electronic transformer 108. Inductors 460 and capacitor C2 form a low pass filter to filter the switching frequency generated by IGBT's 444 and diode 446 in the inverter. The electronic transformer 108 uses an modulation method to “on” or enable position and “off” or deactivate each of the IGBT power switches in the electronic transformer 108 using a modulation method to obtain the desired AC voltage and frequency from the electronic transformer 108. The DC voltage is converted in the DC bus 440 by selectively switching between positions. A gating signal or switching signal is applied to the IGBT power switches by a control circuit, not shown based on the modulation method, to selectively switch the IGBT power switches between the "on" and "off" positions. IGBT power switches are placed in the "on" position if the switching signal is "high", ie logic one, and in the "off" position if the switching signal is "low", ie logic zero. . However, it will be appreciated that activation and deactivation of IGBT power switches may be based on the corresponding state of the switching signal.

Capacitor C2 filters across the output voltage of electronic transformer 108 and connects across the load terminals of inductor 460 to store electrical energy for the load, such as solenoid valves and relays that require inrush current when activated. do. Optionally, the isolation transformer 464 is connected across the capacitor 462 at the output of the electronic transformer 108 to provide electrical shielding such as, for example, the grounding of the control circuit. If shielded transformer 464 is needed, inductor 460 and capacitor C2 are connected to the load side of transformer 464. This causes high frequency to be applied to the primary of the transformer 464, allowing the use of a small, low cost transformer 464.

In another embodiment of the present invention, the VSD 104 is not provided with a charging configuration. Where the inrush current for the DC link is not important, it is not necessary to control the charging of the capacitors of the DC link. Referring to FIG. 5, in this configuration, the DC link 204 is directly connected to the DC bus 440 of the electronic transformer 108. The converter module 202 includes three pairs (one pair for each input phase) of power switches or transistors. The converter module 202 also includes a corresponding control connection as mentioned above to control the switching of the power switches. The power switches are controlled by pulse width modulation techniques to generate the desired output voltage for the DC link 204. Preferably, converter module 202 may operate as a boost rectifier to provide boosted DC power to DC link 204 to obtain an output voltage from VSD 104 that is greater than the input voltage of VSD 104. .

In the converter module 202 shown in FIG. 5, each pair of power switches is an IGBT 450 connected to an antibalance or antiparallel diode 452. Anti-balance or anti-parallel diode 452 is used to conduct current after the other power switch, IGBT 450, is turned off when VSD 104 is operating in pulse width modulation mode. As shown in FIG. 4, in each pair of power switches, one set of IGBTs 450 and inverse diode 452 is a circuit protection device and a three-phase line reactor 416 and a negative rail of DC booth 412. Is connected between. In each pair of power switches, a different set of IGBTs 450 and reverse diode 452 are connected between the output of the circuit protection device and the positive rail of the three-phase line reactor 416 and the DC busbar 412. Since 452 is always conducting in one direction, charging capacitor 208 is uncontrollable.

The configuration of the electronic transformer 108 shown in FIG. 5 is also modified to remove the direct connection to the AC input line 102. The capacitor 442 of the electronic transformer 108 is connected in parallel with the DC link 204 and the capacitor of the VSD 104, and the DC bus 440 of the electronic transformer 440. There are four pairs of power switches that operate as mentioned above in connection with the configuration shown in FIG. Similarly, inductors 460, capacitor 462, and any shielding transformer 464 are configured the same as shown in FIG. 4.

The connection of the electronic transformer to the DC link 204 provides additional momentary compensation capability to the chiller aid that is not useful when using conventional winding transformers. If a voltage drop occurs in the input AC power source 102, the DC link 204 is caused by the energy stored in the rotating mass of the motor 106 and the compressor 302 and / or the active converter 202 as described above. As long as it is supported, the output voltage of the electronic transformer 108 is maintained as a rated output voltage. Therefore, the operation of the chiller is not affected by the failure of auxiliary devices such as control panels, pumps, relays and contactors during voltage drops and faults.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will understand that various modifications and changes can be made without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to practice the invention without departing from the essential scope thereof. Therefore, the invention is not limited to the specific embodiments of the invention which are described as best mode for carrying out the invention, and the invention will include all embodiments falling within the scope of the appended claims.

Claims (28)

  1. A drive for powering multiple parts of a chiller having different voltage requirements,
    The drive device is a converter stage connected to an AC power source to receive a fixed input AC voltage and an input AC voltage of a fixed input frequency, the converter stage being configured to convert the fixed input AC voltage into a boosted DC voltage, wherein the boosted DC voltage is A converter stage greater than the fixed input AC voltage;
    A DC link coupled to the converter stage and configured to filter the boosted DC voltage and the stored energy exiting the converter stage; And
    Coupled to the DC link and configured to convert a boosted DC voltage from the DC link to provide a variable voltage and an output voltage of variable frequency to a motor of a cooling device, wherein the variable voltage is a maximum greater than a fixed input AC voltage. A first inverter stage having a voltage, said variable frequency having a maximum frequency greater than a fixed input frequency, said first inverter stage maintaining said voltage level of said DC link in response to a decreasing fixed input AC voltage. A first inverter stage configured inversely to the power flowing through the first inverter stage to the DC link stage to transfer energy stored in a rotating mass of a motor coupled to the inverter stage; And
    A second inverter stage coupled to the DC link and configured to convert a boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency for at least one component of a cooling device; And a second inverter stage wherein the fixed output AC voltage is less than the fixed input AC voltage and the fixed output AC voltage and the fixed output frequency of the second inverter stage are maintained even in the case of a temporary decrease in the fixed input AC voltage.
  2. 2. The drive device of claim 1, wherein the converter stage is controllable to charge the DC link.
  3. The drive device of claim 1, wherein the second inverter stage is comprised of at least four power semiconductor switches configured to conduct a boosted DC voltage to a fixed output AC voltage and a fixed output frequency.
  4. The drive device of claim 1, wherein the first inverter stage and the second inverter stage are disposed in a single enclosure.
  5. The driving device of claim 1, wherein the first inverter stage and the second inverter stage are disposed in separate enclosures.
  6. The drive device of claim 1, wherein the auxiliary output power source fixed output AC voltage is 120 VAC and the fixed output frequency is 60 Hz.
  7. The drive device of claim 1, wherein the second inverter stage provides fixed output AC power to a control panel and a power distribution panel, and at least one auxiliary electrical component is connected to the power distribution panel.
  8. 9. A drive device according to claim 8, wherein said at least one auxiliary electrical component is selected from the group consisting of pumps, relays, solenoids, heaters, contactors, fans and combinations thereof.
  9. 4. The drive device of claim 3, wherein the second inverter stage further comprises circuitry for providing a DC power source directly from the input AC power while the converter stage charges the DC link.
  10. 10. The driving device of claim 9, wherein the circuit of the second inverter stage comprises a plurality of diodes connected to the input AC power and a diode connected to the DC link.
  11. As a chiller,
    (Iii) a cooling circuit comprising a compressor, a condenser and an evaporator connected as closed cooling circuits;
    (Ii) a motor coupled to the compressor to power the compressor;
    (Iii) a variable speed drive coupled to the motor, the variable speed drive configured to receive a fixed input AC voltage and an input AC voltage of a fixed input frequency, the variable voltage having a maximum voltage greater than the fixed input AC voltage, the variable frequency being a fixed input Having a maximum frequency greater than frequency, the variable speed drive is a converter stage connected to an AC power source providing input AC power, the converter stage being configured to convert an input AC voltage into a boosted DC voltage, the boosted DC voltage being fixed; A converter stage larger than the input AC voltage; A DC link coupled to the converter stage and configured to filter the boosted DC voltage and the stored energy exiting the converter stage; And connected to the DC link and configured to convert a boosted DC voltage from the DC link into an output voltage for the motor and also maintain a voltage level of the DC link stage in response to a decreasing input AC voltage. A variable speed drive including a first inverter stage configured to reverse power relative to power flowing through the first inverter stage to the DC link stage to transfer energy stored in the rotating mass of the motor; And
    (Iii) an electronically controlled transformer connected to the DC link and configured to convert a boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency, wherein the fixed output AC voltage is a fixed input. And an electronic control transformer smaller than an AC voltage, wherein the fixed output AC voltage and the fixed output frequency of the electronic control transformer are maintained even when the fixed input AC voltage is temporarily reduced.
  12. 12. The cooling device of claim 11 wherein the converter stage is controllable to charge the DC link.
  13. 12. The apparatus of claim 11, wherein the electronically controlled transformer is comprised of at least four power semiconductor switches configured to conduct a boosted DC voltage to a fixed output AC voltage and a fixed output frequency.
  14. 12. The cooling device of claim 11 wherein the first inverter stage and the electronically controlled transformer are disposed in a single enclosure.
  15. 12. The cooling device of claim 11, wherein said first inverter stage and said electronically controlled transformer are disposed in separate enclosures.
  16. The chiller of claim 1, wherein the auxiliary output power source fixed output AC voltage is 120 VAC and the fixed output frequency is 60 Hz.
  17. The cooling device of claim 1, wherein the electronically controlled transformer provides fixed output AC power to the control panel and the power distribution panel, and at least one auxiliary electrical component is connected to the power distribution panel.
  18. 18. A drive device according to claim 17, wherein said at least one auxiliary electrical component is selected from the group consisting of pumps, relays, solenoids, heaters, contactors, fans and combinations thereof.
  19. 13. The drive system of claim 12, wherein the electronically controlled transformer further comprises circuitry for providing a DC power source directly from the input AC power while the converter stage charges the DC link.
  20. The driving device of claim 11, wherein the circuit of the electronically controlled transformer comprises a plurality of diodes connected to the input AC power and a plurality of diodes connected to the DC link.
  21. An electronically controlled transformer for powering at least one auxiliary device associated with a chiller, the inverter module converting a DC voltage to provide a fixed output AC voltage and a fixed frequency for powering the at least one auxiliary device. The inverter module includes a plurality of pairs of power switches, each pair of power switches including an insulated gate bipolar transistor connected in anti-parallel with respect to a diode; An input DC connection for connecting the electronically controlled transformer to a DC link of a variable speed drive; And an output AC connection for connecting the at least one auxiliary device to the inverter module.
  22. 22. The electronically controlled transformer of claim 21, wherein said inverter module is controllable by pulse width modulation techniques.
  23. 22. The electronically controlled transformer of claim 21, wherein the plurality of pairs of power switches comprise two pairs of power switches.
  24. 22. The apparatus of claim 21, further comprising an input AC connection for connecting an input AC power source used to power the variable speed drive, wherein the input AC connection also includes a pair of converter diodes and a reverse blocking diode, The converter diode is configured to rectify the input AC voltage coming from the input AC power source into a DC voltage, and the reverse blocking diode is connected between the converter diode and the input DC connection to prevent a short circuit of the charging circuit of the variable speed drive. Connected electronically controlled transformer.
  25. 25. The electronically controlled transformer as recited in claim 24, further comprising an input capacitor coupled across said input DC connection for filtering a DC input and storing electrical energy.
  26. 22. The electronically controlled transformer of claim 21, further comprising an input capacitor coupled across an input DC connection for filtering the DC input and storing electrical energy.
  27. 22. The electronically controlled transformer as in claim 21, further comprising an isolation transformer coupled to the output AC connection for electrical isolation of the load.
  28. 28. The electronically controlled transformer of claim 27, further comprising a filter circuit connected in series with the isolation transformer, the filter circuit comprising at least one series connected inductor, at least one parallel connected capacitor, and combinations thereof.
KR1020087014048A 2006-01-03 2006-12-14 Electronic control transformer using dc link voltage KR20080077170A (en)

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US11/324,368 US20070151272A1 (en) 2006-01-03 2006-01-03 Electronic control transformer using DC link voltage

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JP4741009B2 (en) 2011-08-03
TW200737679A (en) 2007-10-01
JP2009521903A (en) 2009-06-04
US20070151272A1 (en) 2007-07-05
WO2007133289A2 (en) 2007-11-22
WO2007133289A3 (en) 2008-03-27
EP1972050A2 (en) 2008-09-24
CN101351953A (en) 2009-01-21

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