CA1185653A - Stabilizing circuit for controlled inverter-motor system - Google Patents
Stabilizing circuit for controlled inverter-motor systemInfo
- Publication number
- CA1185653A CA1185653A CA000384532A CA384532A CA1185653A CA 1185653 A CA1185653 A CA 1185653A CA 000384532 A CA000384532 A CA 000384532A CA 384532 A CA384532 A CA 384532A CA 1185653 A CA1185653 A CA 1185653A
- Authority
- CA
- Canada
- Prior art keywords
- voltage
- inverter
- frequency
- steady state
- bus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
-
- 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
- H02M5/40—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 with intermediate conversion into dc
- H02M5/42—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 with intermediate conversion into dc by static converters
- H02M5/44—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 with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—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 with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—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 with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—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 with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2201/00—Indexing scheme relating to controlling arrangements characterised by the converter used
- H02P2201/03—AC-DC converter stage controlled to provide a defined DC link voltage
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/047—V/F converter, wherein the voltage is controlled proportionally with the frequency
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
- Control Of Ac Motors In General (AREA)
Abstract
STABILING CIRCUIT FOR CONTROLLED INVERTER-MOTOR
SYSTEM
Abstract:
Stabilized operation of an inverter (25) and an a-c motor (412, driven by the inverter, is obtained in the presence of sudden undesired load changes by controlling the inverter so that both the amplitude and frequency of the inverter output a-c voltage will be functions of, and will vary directly with, the d-c bus voltage, with the result that anytime an abrupt abnormal load change causes the d-c bus voltage to vary, a frequency change occurs to compensate for the load change and to stabilize the bus voltage. By employing the d-c bus voltage to regulate the inverter frequency, if there is a sudden decrease, for example, in the mechanical load (43) on the motor, the d-c bus voltage, which will tend to increase, causes the frequency of the inverter output voltage to increase, thereby increasing the motor speed so that the electrical load change across the d-c bus (26,27) is reduced. As a result, the d-c bus voltage tends to remain relatively constant in spite of the abrupt mechanical load change. When there is a normal variation in load demand, necessitating a different steady state motor speed, a set point or reference voltage may be adjusted to change the amplitude and frequency of the inverter output voltage to the levels needed to drive the motor at the new required speed.
SYSTEM
Abstract:
Stabilized operation of an inverter (25) and an a-c motor (412, driven by the inverter, is obtained in the presence of sudden undesired load changes by controlling the inverter so that both the amplitude and frequency of the inverter output a-c voltage will be functions of, and will vary directly with, the d-c bus voltage, with the result that anytime an abrupt abnormal load change causes the d-c bus voltage to vary, a frequency change occurs to compensate for the load change and to stabilize the bus voltage. By employing the d-c bus voltage to regulate the inverter frequency, if there is a sudden decrease, for example, in the mechanical load (43) on the motor, the d-c bus voltage, which will tend to increase, causes the frequency of the inverter output voltage to increase, thereby increasing the motor speed so that the electrical load change across the d-c bus (26,27) is reduced. As a result, the d-c bus voltage tends to remain relatively constant in spite of the abrupt mechanical load change. When there is a normal variation in load demand, necessitating a different steady state motor speed, a set point or reference voltage may be adjusted to change the amplitude and frequency of the inverter output voltage to the levels needed to drive the motor at the new required speed.
Description
073073-BWL ~ 1 -STABILIZING CIRCUIT FOR CONTROhLED
INVERTER-MOTOR SYSTEM
Description This invention rela~es to a control system for stabilizing the operation of an inverter-motor system during transients or disturbances, thereby greatly improving its dynamic behavior, and during steady state when the operating conditions are appropriate to cause system oscillation.
- 10 Inverter-motor systems have a tendency to oscillate at low frequencies under certain operating conditions, at which time the inverter appears as a negative resistance to the d-c bus over which the inverter receives its energizing voltage~
This invention serves to make the inverter appear as a more positive resistance, thus reducing the tendency to oscillate.
In ad~dition, the inverter-motor systems may have load torques which change abruptly, causing significant deviations from the desired steady state d-c bus voltage. This invention also serves to reduce the effect that the sudden load torque change has on the d-c bus voltage, thereby reducing the deviations ~rom the desired d-c bus voltage.
The cause of the undesired bus voltage change is attributable to the presence o~ the filter, comprising a series-connected choke and a shunt-connected capacitor, which is usually included in the d-c power supply that produces the bus voltage.
s~
During normal steady state operation no average current flows to the filter capacitor and all of the current flows to the inverter and then to the motor windings. If the~e is a sudden drop, for example, in the load torque on the motor; the motor cuxrent abruptly decreases and the inductor current flows into the filter capacitor, charging - it to a considerably higher voltage. Since the d G bus is coupled across the capacitor, the bus voltage likewise increases significantly. The high bus voltage, in addition to deleteriously affecting the operation of the motor, may also - destroy the switching devices (which may be transistors~
in the inverter. To prevent such destruction, oversized switching devices are customarily employed having performance characteristics sufficient to withstand the highest bus voltage that could occur in the event of a very sudden load change.
The control system of the present invention achieves significantly improved dynamic performance and overcomes the instability problem by effectively regulating the d-c bus voltage to provide motor stability, while at the same time avoiding the necessity oE oversizing the switching devices.
With the present invention, the negative resistance of the inverter is made more positive to eliminate the tendency to oscillate. At the same time, the invention effects the way the motor torque changes with time to reduce the d-c bus voltage deviation 3~ from the desir~d value.
The control system of the invention controls the operation of an a-c motor driven by the output a-c voltage from an inverter which in turn is energiæea by an adjus-table d-c bus voltage received over a d-c bus from a controlled d--c power supply. The control system comprises means for providing a set point voltage representing a desired steady state of amplitude and a desired steady state f.requency for the a-c voltage proa--uced by the inverter. There are first utilizing means for utilizing the set point voltage to ad~ust the d-c ~us voltage to establish the inverter output voltage at the desired steady state amplitude~ and including a frequency insensitive feedback circuit, having a pr~de-term.ined first gain factor, from the d-c bus for determin-ing the ratio of steady state d-c bus voltage to steady state inver-ter fre~uency. Second utilizing means are provided for utilizing the set point voltage to establish the frequency of the inverter output voltage at the desired steady state level. Stabilizing means are also provided including a frequency insensitive circuit having a predetermined second gain factor, responsive to a deviation in the d-c bus voltage from the desired steady state amplitude for varying the inverter frequency to change the electrical load across the d-c bus to maintain the bus voltage constant under changing conditions, the second gain factor determining the ratio of d-c bus voltage deviation to inverter frequency deviat~on under changing conditions, thereby permitting the employment of different ratios for steady state and changing conditionsO
The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further advantages and features thereof, may hest ~e unaerstood, however, by reference to the following description in conjunction with the accompanying drawing in which:
FIGURE 1 schematically illustrates a control system, constructed in accordance with one embodiment of the present invention, and the manner in which that control system is coupled to an inverter-motor system to control and to bm~ ^
, J\~ . ~
~s~s,~
stabili~e the operation thereof; and FIGURES 2 and 3 show portions of the control sys-tem oE FIGURE 1 modified in acc~rdance with two other embodiments of the invention~
bm~ - 3a -~' ~
`' ~
~L~ilS~i~i3 Referring to FIGURE 1~ l.ine conductors Ll, L2 and L3 connect to a conventional three-phase a~c power system an~ thus provide three-phase a-c voltage, namely three alternating voltages that $ are phase-displaced with respect to each other by 120 and have a frequency of 60 hertz. Each of the three phase voltages is a line-to-line voltage and appears on one of the line conductors Ll, L2 and L3 relative to another one of the line conductors.
The a-c energy received over the line conductors is converted to d-c power by a controlled rectifier bridge 10 which is of well-known construction.
Specifically, the bridge has a family of six silicon controlled rectifiers or SCR's 11-16 ~hich, when fired into conduction by gate current from recti:Eier controller 17, rectify the applied a-c voltage and develop across the bridge's positive and negative output terminals (designated 13 and 19, respectively) rectified vol-tage of a magnitude determined by the conduction angles of the SCR's during each half cycle of the applied a-c voltage~
To explain, each SCR in bridge 10 can conduct, during each positive polarity half cycle of the voltage applied thereto from the a-c power system, when the SCR's anode is positive relative to i.ts cathode. However, conduct.ion will not occur during a positive half cycle ~mtil gate current is supplied to the SCR's gate from rectifier controller 17. At that instant, the SCR fires into conduction, or turns on, and permits load current to flow therethrough until the end of the positive half cycle. The greater the phase angle or time delay 079073~BWL ~ 5 -between the start of a positive half cycle and the firing of the SCR into conduction, the less the conduction angle and the less average voltage will be rectified and supplied to the load. Of course, the rectified voltage will be of positive polarity at terminal 18 with respect to terminal 19.
A filter 20 comprising series-connected choke 21 and shunt-connected capacitor 22 filter the rectified voltage from the bridge to develop a filtered d-c voltage for application to inverter 25 over the d-c bus provided by lines 26 and 27.
A positive-polarity d-c bus voltage will therefore appear on line 26 with respect to line 27 which is connected to a ground plane of reference potential or circuit common, zero volts in the illustratad embodimentO By controlling the conduction angles of SCR's l:L-16 the d-c bus voltage applied to inverter 2'i, via bus 26, 27, is controlled.
Invert:er 25 has a well-known circuit con-figuration. It includes three pairs of NPN bipolar : power transistors 31-36, each pair being series-connected across the d-c bus 26, 27. The circuit junctions 37, 38 and 39 of the three transistor pairs connect to the windings of a-c induction motor 41, whose output shaft 42 drives some mechanical load 43. By supplying drive current to the bases of the six bipolar transistors 31-36 at prescribed times, the d-c vol-tage across the d c bus is effectively changed to a-c voltage as applied to the windi.ngs of the motor, thereby delivering alternating current to the windings to effect rotation of motor 41 at a speed determined hy and directl~ proportional to the frequency of t~e inverter output a-c voltage~ For example, if base drive current îS simultaneously supplied to transistors 31 and 35 to drive those transistors into their saturation modes, current will flow from line 26 and through, in the order named, the emitter-collector conduction path of transistor 31, junction 37, a winding of motor 41, junction 38 and the emitter-collector conduction path of transistor 35 to line 27 or ground.
If transistors 31 and 35 are then cut off and tran-sistors 32 and 34 are turned on instead, current will flow through the same motor winding in the opposite direction. Of course, control circuitry for supplying base drive current to switch the transistors 31-36 on and off in the correct sequence, at the correc~ times and at the correct frequency in order to provide the required a-c energy for rotating motor 41 and driving load 43 in the desired manner is well understood by those skilled in the art. In the illustrated embo diment this control circuitry is shown by the block 45 labelled "inverter control circuit". Usually, such a control circuit will include logic circuitry and a controlled oscillator whlch, in response to a control voitage received over line 47, supplies programmed periodically recurring timing pulses, or base drive signals, to transistors 31-36 tc establish the fre-quency of the inverter output voltage and consequently the speed of motor 41. The pulse repetition requency of the timing pulses will be a function of the control voltage on line 47. Hence, the inverter frequency is controlled by varying the magnitude of that control voltage.
~8~i~S3 The emitter-collector conduction path of each of the six power transistors 31-36 is shunted by a res-pective one of a series of six oppositely poled feed-back diodes 51-56 which are employed to circulate the motor reactive current back to filter capacitor 22O
Feedback diodes 51-56 are also effective to cla:mp the motor terminal voltage so that it will never exceed the d-c bus voltage.
Although not shown in the drawing, prefera.bly each of transistors 31-36 will also be shunted by a ,-on-ventional snubber network to prevent the inductive energy in the motor windings from damaging the tran-sistors when they are switched off by inverter control circuit 45 during normal operation.
While each of power bipolar transistors 31--36 is illustrated as a conventional NPN transistor (to simplify the drawing), in reality it would preerably take the fo:rm of a well-known power darlington tran-sistor. In the darlington arrangement, each of tran-sistors 31-36 comprises a combination of two trcm-sistors, while still having only three connections, i namely base, emitter and collector connections clS is the case in the drawing. Of course, while power bipolar transistors are shown as the switching clevices, other devices can be used such as thyristors, field effect transistors, etc.
To control the operation of rectifier controller 17 in order to adjust the amplitude of the inverter output a-c voltage and to control the operation of control circuit 45 to :regulate the frequency of the inverter voltage, an adjustable set point or reference d~c voltage is provided at the junction 57 of fixed resistor 58 and adjustab,le resistor 59. As will be made apparent, the set pOillt voltage from voltage divIder 58, 59 determines the s~eady state operating conditions and represents a desired amplitude and a desired frequency for the a-c voltage produced by inverter 25 for application to motor 41. Preferably, the set point will be selected to satisfy the speed demanded by mechanical load 43. Comparator 61 compares the set point voltage with a voltage proportional to the d-c bus voltage (due to the presence of gain factor K62) to provide an error voltage which is a fwnction of - the difference between the compared voltages. K62 sets the gain between the d-c bus voltage and the set point voltage. Rectifier controller 17 responds to the error voltage to produce properly timed gate current pulses for application to the gates of SCR's 11-16 to control the conduction angles of the SCR's as required to establish the d-c bus voltage across lines 26 and 27 at the magnitude necessary to establish and to maintain the inverter output voltage at the desired amplitude.
If the d-c bus voltage tends to vary from the requisite steady state level, the error voltage changes and causes rectifier controller 17 to vary the conduction angles as necessary to adjust the d-c bus voltage until the correct steady state amplitude level is re-established.
In the meantime, the control voltage for regu-lating the operation of control circuit 45 is developed by adding, in summing circuit 63, the set point voltage and a voltage proportional to the error voltage. K64 represents a transfer function and indicates the gain S65~
079073-BWL - g in the feedhack loop. The value of K64 is selected for ~est system performance. Too low a value will defeat the positive featllre of the control system, whereas too high a value for K64 can cause instability. The control voltage will thus be a function of the error voltage and the set point voltage, as a result of which the programmed timing or base drive signals supplied to transistors 31-36 will have the ~requency required to set the frequency of the inverter output voltage at the desired steady state level. Since both the amplitude and frequency of the inverter output vcltage ,are determined by the set point voltage, those two - characteristics of the inverter voltage will have a ixed ratio with respect to each other when no error voltage i5 present. This steady state ratio can ~e set by gain factor 62. A fixed ratio is desirable in order to avoid overheating of motor 41 and to provide the motor with a constant torque output capability xegardless of motor speed.
When there is a normal variation in load demand, thereby dictating a different steady state motor speed, resistor 59 may be adjusted to vary the set pcint - voltage to the extent necessary to change the control voltage as required to establish the frequency of the inverter voltage at the level necessary to drive motor ~1 at the new desired speed. At the same time, the new set point voltage varies the d-c bus volta~e as needed to maintain the same fixed ratio of the amplitude and frequency characteristics of the inverter output voltage.
Of course, while the motor speed may be changed by manually adjusting resistor 59, the set point voltage 3LlB5653 may be derived by sensing some parameter or character istic of the system~ in which the controlled inverter-motor system is inco~porated, in order to automatically control the motor speed in response to that sensed informationO
It is also to be recognized that the d-c power supply (namely rectifier bridge 10 and filter 20) may operate in response to single-phase rather than three-phase a-c energy. In the single-phase environment, line conductor L3 and SCR's 13 and 16 would be omitted.
: Of course, a d-c bus voltage of positive polarity will - still be produced on line 26 with respect to line 27.
It should also be appreciated that the constructions of ~he d-c power supply and the inver-ter may take a variety of different forms. For example, the con-trolled d-c bus could be provided by a DC-DC converter supplied by a d-c bus.
In the event that the mechanical load on motor 41 ~: undergoes a sudden change, in the absence of the disclosed stabilizing circuit the d-c bus voltage would change. To explain, assume that the load torque on motox 41 i.s abxuptly decreased, or removed entirely, causing sharply decreased average d-c bus current to the inverter. The ~ilter choke current thereupon flows into filter capacitor 22 to charge that capacitor to a voltagQ significantly higher than the desired d-c bus voltage. The tendency of the bus voltage to increase will be compensated, however, by the present invention by increasing the motor speed in response to increasing ~us voltage so that the inverter-motor system will not ~35~i53 079073-B~L - 11 -be deleteriously affected and stable operation will ensue. In effect, the invention operates to maintain, in the presence of sudden abnormal mechanical load changes on motor 41, an electrical load across d-c bus 26, 27 which causes the d-c bus voltage to tend to remain relatively fixed.
This immunization to abrupt or transient load torque ahanges is obtained ~y controlling the inverter frequency so that it i6 a function ofl and will varv directly with, the d-c bus voltage. If the bus voltage tends to increasè, a~ the load torque drops, the error voltage will increase and cause the control voltage to increase, whereupon inverter control circuit 45 will efect an increase in the frequency of the inverter output voltage. As a consequence, the motor speed increases and this effectively increases the electrical load on the d-c bus to compensate for the decreased electrical load which occurred when the mechanical load decreased. In short, the motor is accelerated anytime the mechanical load drops, thereby presenting a reduced change in electrical load to the d-c bus. The error voltage is then decreased to zero by the d-c bus re~ulating circuit and the system is once again operative at the frequency and voltage called for by the set point voltage. The gain for the ratio of the transient change or deviation in the bus voltage relative to the resulting frequency deviation for the inverter will be adjusted by gain factor K64 and can be adjusted differently than, and independently rom, the steady state gain factor 62.
6~3 079073~BWL - 12 -Of course, if motor 41 experiences a sudden increase in load torque resulting in an increased electrical load and a reduced d-c bus voltaye, the error voltage will drop and cause the inverter frequency and motor speed to decrease so that the electrical load on the d-c bus wïll drop and the bus voltage will increase.
To summarize the operation of the invention j as embodied in Figure 1, under normal steady state conditions rectifier controller 17 serves to reduce the error voltage to zero. The d-c ~us - voltage then is reIated to the set point voltage by the gain factor K62. At that time, the control voltage, which determines the inverter frequency, is equal to the set point voltage. Hence, the ratio of d-c bus voltage to inverter frequency can be adjustecl by K62. Under transient conditions, the error voltage will not be zero. Gain factor K64 determines the amount of control voltage deviation from the set point that will occur for a given error voltage. As a consequence, K64 determines the magnitude of the frequency deviation from the steady state frequency value that will occur under transient conditions. The ratio of the d-c bus voltage deviation from the desired steady state value to the deviation of the inverter frequency from the desired steady state value is, therefore, adjusted by gain factor K64. As a result, the ratio of steady state d-c bus voltage to inverter frequency can be set independently of the ratio of d-c bus voltage deviation to inverter frequency deviation under trans-ient conditions.
35i6~3 079073-BWL - 13 ~
It should be understood ~hat the invention may be practiced in a variety of di.fferent manners ïn order to cause a devi.ati.on of the frequency control voltage proportional to the dev;ation o~
the d-c bus voltage from its desired value. In the Figure 1 em~odiment, transient bus voltage changes result in trans.ient error voltage ch.anges which are then used to vary the inverter frequency.
The sta~ilizing means: of the invention can, of ~: 10 course, respond directly to a transient variation in the d~c bus: voltage. This is shown in the embodiment of Figure 2. There, the feedback loop from the d-c bus. to the inverter excludes the comparator 61, unlike the case in Figure 1. Also, in accordance with the Figure 2 embodiment, K64 is pxeceded by a band-pass filter 65 to r~move any steady state ef~ect of the control system. With such a filter, the stabilizing circuit will respond only to transie.nt bus voltage changes. In other 20: words, for normal operation when the inverter-~:~ motor system is operated at different stea.dy state conditionsv no vol-tage is applied, through ~ilter 6~, to sur~ning circuit 63 and the inverter frequency is established entirely by the set point voltage.
However, when the hus voltage experiences an undesired transient change, that change will pass : through filter 65 to summing circuit 63. In effect, summing circuit 63 is made unresponsive to relatively slow changes in the bus voltage but 3G responsive to relatively fast changes~ The control voltage, produced by the summing circuit, will ~ 35~;~3 -therefore be ~ari~ed and the inverter frequency will be altered, in accordance with the invention, to CO~QenSate for the sudden bus voltage change.
Of ~ourse, any transient change in the d-c bus voltage will also appear as a transient change in the motor voltage or the inverter output voltage, which are essentially the same. ~ence, the invention may be practiced ~y providing a feedback loop from a-c motor 41 to the inverter 25 for adjusting the inverter frequency in response to transient changes in the inverter output voltage.
T~is is shown in t~e embodiment of Figure 3. The three-phase voltage produced by inverter 25 is rectified by rectifier 67 to develop a d-c voltage which will have su~stantially the same magnitude as the d-c bus voltage applied to the inverter.
Moreover, any transient change in the d-c bus ~
voltage will manifest itself as a transient change în the d-c output voltage of rectifier 67O Hence, such a d-c voltage may be applied to comparator 61 and the system will operate substantially the same as described in connectïon with Figure 1.
It is thus apparent that the present invention ~; not only stabilizes the operation Gf an inverter-~ 25 motor system, but by preventing the d-c bus voltage ; from increasing, in response to a sudden drop in load torque, the transistors in the inverter need not be oversized.
While a particular embodiment of the invention has been shown and described, modif;cations may ~e made, and it îs intended ;n the appended claims to cover all such modifications as may fall within the true spirit and scope Gf the inventïon.
INVERTER-MOTOR SYSTEM
Description This invention rela~es to a control system for stabilizing the operation of an inverter-motor system during transients or disturbances, thereby greatly improving its dynamic behavior, and during steady state when the operating conditions are appropriate to cause system oscillation.
- 10 Inverter-motor systems have a tendency to oscillate at low frequencies under certain operating conditions, at which time the inverter appears as a negative resistance to the d-c bus over which the inverter receives its energizing voltage~
This invention serves to make the inverter appear as a more positive resistance, thus reducing the tendency to oscillate.
In ad~dition, the inverter-motor systems may have load torques which change abruptly, causing significant deviations from the desired steady state d-c bus voltage. This invention also serves to reduce the effect that the sudden load torque change has on the d-c bus voltage, thereby reducing the deviations ~rom the desired d-c bus voltage.
The cause of the undesired bus voltage change is attributable to the presence o~ the filter, comprising a series-connected choke and a shunt-connected capacitor, which is usually included in the d-c power supply that produces the bus voltage.
s~
During normal steady state operation no average current flows to the filter capacitor and all of the current flows to the inverter and then to the motor windings. If the~e is a sudden drop, for example, in the load torque on the motor; the motor cuxrent abruptly decreases and the inductor current flows into the filter capacitor, charging - it to a considerably higher voltage. Since the d G bus is coupled across the capacitor, the bus voltage likewise increases significantly. The high bus voltage, in addition to deleteriously affecting the operation of the motor, may also - destroy the switching devices (which may be transistors~
in the inverter. To prevent such destruction, oversized switching devices are customarily employed having performance characteristics sufficient to withstand the highest bus voltage that could occur in the event of a very sudden load change.
The control system of the present invention achieves significantly improved dynamic performance and overcomes the instability problem by effectively regulating the d-c bus voltage to provide motor stability, while at the same time avoiding the necessity oE oversizing the switching devices.
With the present invention, the negative resistance of the inverter is made more positive to eliminate the tendency to oscillate. At the same time, the invention effects the way the motor torque changes with time to reduce the d-c bus voltage deviation 3~ from the desir~d value.
The control system of the invention controls the operation of an a-c motor driven by the output a-c voltage from an inverter which in turn is energiæea by an adjus-table d-c bus voltage received over a d-c bus from a controlled d--c power supply. The control system comprises means for providing a set point voltage representing a desired steady state of amplitude and a desired steady state f.requency for the a-c voltage proa--uced by the inverter. There are first utilizing means for utilizing the set point voltage to ad~ust the d-c ~us voltage to establish the inverter output voltage at the desired steady state amplitude~ and including a frequency insensitive feedback circuit, having a pr~de-term.ined first gain factor, from the d-c bus for determin-ing the ratio of steady state d-c bus voltage to steady state inver-ter fre~uency. Second utilizing means are provided for utilizing the set point voltage to establish the frequency of the inverter output voltage at the desired steady state level. Stabilizing means are also provided including a frequency insensitive circuit having a predetermined second gain factor, responsive to a deviation in the d-c bus voltage from the desired steady state amplitude for varying the inverter frequency to change the electrical load across the d-c bus to maintain the bus voltage constant under changing conditions, the second gain factor determining the ratio of d-c bus voltage deviation to inverter frequency deviat~on under changing conditions, thereby permitting the employment of different ratios for steady state and changing conditionsO
The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further advantages and features thereof, may hest ~e unaerstood, however, by reference to the following description in conjunction with the accompanying drawing in which:
FIGURE 1 schematically illustrates a control system, constructed in accordance with one embodiment of the present invention, and the manner in which that control system is coupled to an inverter-motor system to control and to bm~ ^
, J\~ . ~
~s~s,~
stabili~e the operation thereof; and FIGURES 2 and 3 show portions of the control sys-tem oE FIGURE 1 modified in acc~rdance with two other embodiments of the invention~
bm~ - 3a -~' ~
`' ~
~L~ilS~i~i3 Referring to FIGURE 1~ l.ine conductors Ll, L2 and L3 connect to a conventional three-phase a~c power system an~ thus provide three-phase a-c voltage, namely three alternating voltages that $ are phase-displaced with respect to each other by 120 and have a frequency of 60 hertz. Each of the three phase voltages is a line-to-line voltage and appears on one of the line conductors Ll, L2 and L3 relative to another one of the line conductors.
The a-c energy received over the line conductors is converted to d-c power by a controlled rectifier bridge 10 which is of well-known construction.
Specifically, the bridge has a family of six silicon controlled rectifiers or SCR's 11-16 ~hich, when fired into conduction by gate current from recti:Eier controller 17, rectify the applied a-c voltage and develop across the bridge's positive and negative output terminals (designated 13 and 19, respectively) rectified vol-tage of a magnitude determined by the conduction angles of the SCR's during each half cycle of the applied a-c voltage~
To explain, each SCR in bridge 10 can conduct, during each positive polarity half cycle of the voltage applied thereto from the a-c power system, when the SCR's anode is positive relative to i.ts cathode. However, conduct.ion will not occur during a positive half cycle ~mtil gate current is supplied to the SCR's gate from rectifier controller 17. At that instant, the SCR fires into conduction, or turns on, and permits load current to flow therethrough until the end of the positive half cycle. The greater the phase angle or time delay 079073~BWL ~ 5 -between the start of a positive half cycle and the firing of the SCR into conduction, the less the conduction angle and the less average voltage will be rectified and supplied to the load. Of course, the rectified voltage will be of positive polarity at terminal 18 with respect to terminal 19.
A filter 20 comprising series-connected choke 21 and shunt-connected capacitor 22 filter the rectified voltage from the bridge to develop a filtered d-c voltage for application to inverter 25 over the d-c bus provided by lines 26 and 27.
A positive-polarity d-c bus voltage will therefore appear on line 26 with respect to line 27 which is connected to a ground plane of reference potential or circuit common, zero volts in the illustratad embodimentO By controlling the conduction angles of SCR's l:L-16 the d-c bus voltage applied to inverter 2'i, via bus 26, 27, is controlled.
Invert:er 25 has a well-known circuit con-figuration. It includes three pairs of NPN bipolar : power transistors 31-36, each pair being series-connected across the d-c bus 26, 27. The circuit junctions 37, 38 and 39 of the three transistor pairs connect to the windings of a-c induction motor 41, whose output shaft 42 drives some mechanical load 43. By supplying drive current to the bases of the six bipolar transistors 31-36 at prescribed times, the d-c vol-tage across the d c bus is effectively changed to a-c voltage as applied to the windi.ngs of the motor, thereby delivering alternating current to the windings to effect rotation of motor 41 at a speed determined hy and directl~ proportional to the frequency of t~e inverter output a-c voltage~ For example, if base drive current îS simultaneously supplied to transistors 31 and 35 to drive those transistors into their saturation modes, current will flow from line 26 and through, in the order named, the emitter-collector conduction path of transistor 31, junction 37, a winding of motor 41, junction 38 and the emitter-collector conduction path of transistor 35 to line 27 or ground.
If transistors 31 and 35 are then cut off and tran-sistors 32 and 34 are turned on instead, current will flow through the same motor winding in the opposite direction. Of course, control circuitry for supplying base drive current to switch the transistors 31-36 on and off in the correct sequence, at the correc~ times and at the correct frequency in order to provide the required a-c energy for rotating motor 41 and driving load 43 in the desired manner is well understood by those skilled in the art. In the illustrated embo diment this control circuitry is shown by the block 45 labelled "inverter control circuit". Usually, such a control circuit will include logic circuitry and a controlled oscillator whlch, in response to a control voitage received over line 47, supplies programmed periodically recurring timing pulses, or base drive signals, to transistors 31-36 tc establish the fre-quency of the inverter output voltage and consequently the speed of motor 41. The pulse repetition requency of the timing pulses will be a function of the control voltage on line 47. Hence, the inverter frequency is controlled by varying the magnitude of that control voltage.
~8~i~S3 The emitter-collector conduction path of each of the six power transistors 31-36 is shunted by a res-pective one of a series of six oppositely poled feed-back diodes 51-56 which are employed to circulate the motor reactive current back to filter capacitor 22O
Feedback diodes 51-56 are also effective to cla:mp the motor terminal voltage so that it will never exceed the d-c bus voltage.
Although not shown in the drawing, prefera.bly each of transistors 31-36 will also be shunted by a ,-on-ventional snubber network to prevent the inductive energy in the motor windings from damaging the tran-sistors when they are switched off by inverter control circuit 45 during normal operation.
While each of power bipolar transistors 31--36 is illustrated as a conventional NPN transistor (to simplify the drawing), in reality it would preerably take the fo:rm of a well-known power darlington tran-sistor. In the darlington arrangement, each of tran-sistors 31-36 comprises a combination of two trcm-sistors, while still having only three connections, i namely base, emitter and collector connections clS is the case in the drawing. Of course, while power bipolar transistors are shown as the switching clevices, other devices can be used such as thyristors, field effect transistors, etc.
To control the operation of rectifier controller 17 in order to adjust the amplitude of the inverter output a-c voltage and to control the operation of control circuit 45 to :regulate the frequency of the inverter voltage, an adjustable set point or reference d~c voltage is provided at the junction 57 of fixed resistor 58 and adjustab,le resistor 59. As will be made apparent, the set pOillt voltage from voltage divIder 58, 59 determines the s~eady state operating conditions and represents a desired amplitude and a desired frequency for the a-c voltage produced by inverter 25 for application to motor 41. Preferably, the set point will be selected to satisfy the speed demanded by mechanical load 43. Comparator 61 compares the set point voltage with a voltage proportional to the d-c bus voltage (due to the presence of gain factor K62) to provide an error voltage which is a fwnction of - the difference between the compared voltages. K62 sets the gain between the d-c bus voltage and the set point voltage. Rectifier controller 17 responds to the error voltage to produce properly timed gate current pulses for application to the gates of SCR's 11-16 to control the conduction angles of the SCR's as required to establish the d-c bus voltage across lines 26 and 27 at the magnitude necessary to establish and to maintain the inverter output voltage at the desired amplitude.
If the d-c bus voltage tends to vary from the requisite steady state level, the error voltage changes and causes rectifier controller 17 to vary the conduction angles as necessary to adjust the d-c bus voltage until the correct steady state amplitude level is re-established.
In the meantime, the control voltage for regu-lating the operation of control circuit 45 is developed by adding, in summing circuit 63, the set point voltage and a voltage proportional to the error voltage. K64 represents a transfer function and indicates the gain S65~
079073-BWL - g in the feedhack loop. The value of K64 is selected for ~est system performance. Too low a value will defeat the positive featllre of the control system, whereas too high a value for K64 can cause instability. The control voltage will thus be a function of the error voltage and the set point voltage, as a result of which the programmed timing or base drive signals supplied to transistors 31-36 will have the ~requency required to set the frequency of the inverter output voltage at the desired steady state level. Since both the amplitude and frequency of the inverter output vcltage ,are determined by the set point voltage, those two - characteristics of the inverter voltage will have a ixed ratio with respect to each other when no error voltage i5 present. This steady state ratio can ~e set by gain factor 62. A fixed ratio is desirable in order to avoid overheating of motor 41 and to provide the motor with a constant torque output capability xegardless of motor speed.
When there is a normal variation in load demand, thereby dictating a different steady state motor speed, resistor 59 may be adjusted to vary the set pcint - voltage to the extent necessary to change the control voltage as required to establish the frequency of the inverter voltage at the level necessary to drive motor ~1 at the new desired speed. At the same time, the new set point voltage varies the d-c bus volta~e as needed to maintain the same fixed ratio of the amplitude and frequency characteristics of the inverter output voltage.
Of course, while the motor speed may be changed by manually adjusting resistor 59, the set point voltage 3LlB5653 may be derived by sensing some parameter or character istic of the system~ in which the controlled inverter-motor system is inco~porated, in order to automatically control the motor speed in response to that sensed informationO
It is also to be recognized that the d-c power supply (namely rectifier bridge 10 and filter 20) may operate in response to single-phase rather than three-phase a-c energy. In the single-phase environment, line conductor L3 and SCR's 13 and 16 would be omitted.
: Of course, a d-c bus voltage of positive polarity will - still be produced on line 26 with respect to line 27.
It should also be appreciated that the constructions of ~he d-c power supply and the inver-ter may take a variety of different forms. For example, the con-trolled d-c bus could be provided by a DC-DC converter supplied by a d-c bus.
In the event that the mechanical load on motor 41 ~: undergoes a sudden change, in the absence of the disclosed stabilizing circuit the d-c bus voltage would change. To explain, assume that the load torque on motox 41 i.s abxuptly decreased, or removed entirely, causing sharply decreased average d-c bus current to the inverter. The ~ilter choke current thereupon flows into filter capacitor 22 to charge that capacitor to a voltagQ significantly higher than the desired d-c bus voltage. The tendency of the bus voltage to increase will be compensated, however, by the present invention by increasing the motor speed in response to increasing ~us voltage so that the inverter-motor system will not ~35~i53 079073-B~L - 11 -be deleteriously affected and stable operation will ensue. In effect, the invention operates to maintain, in the presence of sudden abnormal mechanical load changes on motor 41, an electrical load across d-c bus 26, 27 which causes the d-c bus voltage to tend to remain relatively fixed.
This immunization to abrupt or transient load torque ahanges is obtained ~y controlling the inverter frequency so that it i6 a function ofl and will varv directly with, the d-c bus voltage. If the bus voltage tends to increasè, a~ the load torque drops, the error voltage will increase and cause the control voltage to increase, whereupon inverter control circuit 45 will efect an increase in the frequency of the inverter output voltage. As a consequence, the motor speed increases and this effectively increases the electrical load on the d-c bus to compensate for the decreased electrical load which occurred when the mechanical load decreased. In short, the motor is accelerated anytime the mechanical load drops, thereby presenting a reduced change in electrical load to the d-c bus. The error voltage is then decreased to zero by the d-c bus re~ulating circuit and the system is once again operative at the frequency and voltage called for by the set point voltage. The gain for the ratio of the transient change or deviation in the bus voltage relative to the resulting frequency deviation for the inverter will be adjusted by gain factor K64 and can be adjusted differently than, and independently rom, the steady state gain factor 62.
6~3 079073~BWL - 12 -Of course, if motor 41 experiences a sudden increase in load torque resulting in an increased electrical load and a reduced d-c bus voltaye, the error voltage will drop and cause the inverter frequency and motor speed to decrease so that the electrical load on the d-c bus wïll drop and the bus voltage will increase.
To summarize the operation of the invention j as embodied in Figure 1, under normal steady state conditions rectifier controller 17 serves to reduce the error voltage to zero. The d-c ~us - voltage then is reIated to the set point voltage by the gain factor K62. At that time, the control voltage, which determines the inverter frequency, is equal to the set point voltage. Hence, the ratio of d-c bus voltage to inverter frequency can be adjustecl by K62. Under transient conditions, the error voltage will not be zero. Gain factor K64 determines the amount of control voltage deviation from the set point that will occur for a given error voltage. As a consequence, K64 determines the magnitude of the frequency deviation from the steady state frequency value that will occur under transient conditions. The ratio of the d-c bus voltage deviation from the desired steady state value to the deviation of the inverter frequency from the desired steady state value is, therefore, adjusted by gain factor K64. As a result, the ratio of steady state d-c bus voltage to inverter frequency can be set independently of the ratio of d-c bus voltage deviation to inverter frequency deviation under trans-ient conditions.
35i6~3 079073-BWL - 13 ~
It should be understood ~hat the invention may be practiced in a variety of di.fferent manners ïn order to cause a devi.ati.on of the frequency control voltage proportional to the dev;ation o~
the d-c bus voltage from its desired value. In the Figure 1 em~odiment, transient bus voltage changes result in trans.ient error voltage ch.anges which are then used to vary the inverter frequency.
The sta~ilizing means: of the invention can, of ~: 10 course, respond directly to a transient variation in the d~c bus: voltage. This is shown in the embodiment of Figure 2. There, the feedback loop from the d-c bus. to the inverter excludes the comparator 61, unlike the case in Figure 1. Also, in accordance with the Figure 2 embodiment, K64 is pxeceded by a band-pass filter 65 to r~move any steady state ef~ect of the control system. With such a filter, the stabilizing circuit will respond only to transie.nt bus voltage changes. In other 20: words, for normal operation when the inverter-~:~ motor system is operated at different stea.dy state conditionsv no vol-tage is applied, through ~ilter 6~, to sur~ning circuit 63 and the inverter frequency is established entirely by the set point voltage.
However, when the hus voltage experiences an undesired transient change, that change will pass : through filter 65 to summing circuit 63. In effect, summing circuit 63 is made unresponsive to relatively slow changes in the bus voltage but 3G responsive to relatively fast changes~ The control voltage, produced by the summing circuit, will ~ 35~;~3 -therefore be ~ari~ed and the inverter frequency will be altered, in accordance with the invention, to CO~QenSate for the sudden bus voltage change.
Of ~ourse, any transient change in the d-c bus voltage will also appear as a transient change in the motor voltage or the inverter output voltage, which are essentially the same. ~ence, the invention may be practiced ~y providing a feedback loop from a-c motor 41 to the inverter 25 for adjusting the inverter frequency in response to transient changes in the inverter output voltage.
T~is is shown in t~e embodiment of Figure 3. The three-phase voltage produced by inverter 25 is rectified by rectifier 67 to develop a d-c voltage which will have su~stantially the same magnitude as the d-c bus voltage applied to the inverter.
Moreover, any transient change in the d-c bus ~
voltage will manifest itself as a transient change în the d-c output voltage of rectifier 67O Hence, such a d-c voltage may be applied to comparator 61 and the system will operate substantially the same as described in connectïon with Figure 1.
It is thus apparent that the present invention ~; not only stabilizes the operation Gf an inverter-~ 25 motor system, but by preventing the d-c bus voltage ; from increasing, in response to a sudden drop in load torque, the transistors in the inverter need not be oversized.
While a particular embodiment of the invention has been shown and described, modif;cations may ~e made, and it îs intended ;n the appended claims to cover all such modifications as may fall within the true spirit and scope Gf the inventïon.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A control system for controlling and stabilizing the operation of an a-c motor driven by the output a-c voltage developed by an inverter from an adjustable a-c bus voltage received over a d-c bus from a controlled d-c power supply, the d-c bus voltage being subject to un-desired variations under changing conditions, said control system comprising:
means for providing a set point voltage represent-ing a desired steady state amplitude and a desired steady state frequency for the a-c voltage produced by the inverter;
first utilizing means for utilizing the set point voltage to adjust the d-c bus voltage to establish the inverter output voltage at the desired steady state ampli-tude, and including a frequency insensitive feedback circuit, having a predetermined first gain factor, from the d-c bus for determining the ratio of steady state a-c bus voltage to steady state inverter frequency;
second utilizing means for utilizing the set point voltage to establish the frequency of the inverter output voltage at the desired steady state level; and stabilizing means, including a frequency insensitive circuit having a predetermined second gain factor, respon-sive to a deviation in the d-c bus voltage from the desired steady state amplitude for varying the inverter frequency to change the electrical load across the d-c bus to maintain the bus voltage constant under changing conditions, the second gain factor determining the ratio of d-c bus voltage deviation to inverter frequency deviation under changing conditions , thereby permitting the employment of different ratios for steady state and changing conditions.
means for providing a set point voltage represent-ing a desired steady state amplitude and a desired steady state frequency for the a-c voltage produced by the inverter;
first utilizing means for utilizing the set point voltage to adjust the d-c bus voltage to establish the inverter output voltage at the desired steady state ampli-tude, and including a frequency insensitive feedback circuit, having a predetermined first gain factor, from the d-c bus for determining the ratio of steady state a-c bus voltage to steady state inverter frequency;
second utilizing means for utilizing the set point voltage to establish the frequency of the inverter output voltage at the desired steady state level; and stabilizing means, including a frequency insensitive circuit having a predetermined second gain factor, respon-sive to a deviation in the d-c bus voltage from the desired steady state amplitude for varying the inverter frequency to change the electrical load across the d-c bus to maintain the bus voltage constant under changing conditions, the second gain factor determining the ratio of d-c bus voltage deviation to inverter frequency deviation under changing conditions , thereby permitting the employment of different ratios for steady state and changing conditions.
2. A control system according to claim 1 wherein said first utilizing means includes means for comparing the set point voltage with a voltage proportional to the d-c bus voltage to produce an error voltage having amplitude changes which reflect changes in the d-c bus voltage from the desired steady state amplitude and which error voltage is used during steady state conditions to adjust the bus voltage as necessary to maintain it at the desired steady state amplitude, and wherein said stabilizing means responds to changes in the error voltage to vary the inverter frequency as required to hold the bus voltage constant under changing conditions.
3. A control system according to claim 2 wherein a summing circuit adds the set point voltage and a voltage proportional to the error voltage to produce a control voltage for controlling the inverter frequency, the error voltage being zero during steady state as a result of which the control voltage equals the set point voltage under steady state conditions.
4. A control system according to claim 3 wherein the frequency of the inverter output a-c voltage is determined by the frequency of timing pulses applied to the inverter, wherein a controller, operated in response to the error voltage, controls the d-c power supply to adjust the d-c bus voltage to the level required to establish the inver-ter output voltage at the desired steady state amplitude, wherein summing means adds the set point voltage and a voltage proportional to the error voltage to provide a control voltage and wherein an inverter control circuit operates in response to the control voltage to supply periodically recurring timing pulses to the inverter to establish the inverter output voltage at the desired steady state frequency thereby setting the motor speed at a desired level, changes in the error voltage, caused by variations in the bus voltage during changing conditions, effecting changes in the frequency of the timing pulses to vary the inverter frequency with, and in the same direction as the d-c bus voltage.
5. A control system for controlling and stabilizing the operation of an a-c motor driven by the output a-c voltage developed by an inverter from an adjustable d-c bus voltage received over a d-c bus from a controlled d-c power supply, the inverter output a-c voltage being subject to undesired variations under changing conditions, said control system comprising:
means for providing a set point voltage represent-ing a desired steady state amplitude and a desired steady state frequency for the a-c voltage produced by the inverter;
first utilizing means for utilizin the set point voltage to adjust the d-c bus voltage to establish the inverter output voltage at the desired steady state amplitude, and including a frequency insensitive feedback circuit, having a predetermined first gain factor, from the output of the inverter for determining the ratio of steady state inverter output voltage to steady state inverter frequency;
second utilizing means for utilizing the set point voltage to establish the frequency of the inverter output voltage at the desired steady state level; and stabilizing means, including a frequency insensitive circuit having a predetermined second gain factor, respon-sive to a deviation in the inverter output voltage from the desired steady state amplitude for varying the inverter fre-quency to change the electrical load across the d-c bus to maintain the inverter output voltage constant under changing conditions, the second gain factor determining the ratio of inverter output voltage deviation to inverter frequency deviation under changing conditions, thereby permitting the employment of different ratios for steady state and changing conditions.
means for providing a set point voltage represent-ing a desired steady state amplitude and a desired steady state frequency for the a-c voltage produced by the inverter;
first utilizing means for utilizin the set point voltage to adjust the d-c bus voltage to establish the inverter output voltage at the desired steady state amplitude, and including a frequency insensitive feedback circuit, having a predetermined first gain factor, from the output of the inverter for determining the ratio of steady state inverter output voltage to steady state inverter frequency;
second utilizing means for utilizing the set point voltage to establish the frequency of the inverter output voltage at the desired steady state level; and stabilizing means, including a frequency insensitive circuit having a predetermined second gain factor, respon-sive to a deviation in the inverter output voltage from the desired steady state amplitude for varying the inverter fre-quency to change the electrical load across the d-c bus to maintain the inverter output voltage constant under changing conditions, the second gain factor determining the ratio of inverter output voltage deviation to inverter frequency deviation under changing conditions, thereby permitting the employment of different ratios for steady state and changing conditions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US18944580A | 1980-09-22 | 1980-09-22 | |
| US189,445 | 1988-05-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1185653A true CA1185653A (en) | 1985-04-16 |
Family
ID=22697362
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000384532A Expired CA1185653A (en) | 1980-09-22 | 1981-08-25 | Stabilizing circuit for controlled inverter-motor system |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5791680A (en) |
| CA (1) | CA1185653A (en) |
| DE (1) | DE3135764A1 (en) |
| FR (1) | FR2490893B1 (en) |
| GB (2) | GB2084357B (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH645220A5 (en) * | 1981-12-28 | 1984-09-14 | Spincor Sa | DEVICE FOR STABILIZING THE TORQUE OF AN ELECTRIC MOTOR WITH ELECTRONIC COMMUTATION. |
| US4511835A (en) * | 1982-12-23 | 1985-04-16 | Borg-Warner Corporation | Voltage-controlled, inverter-motor system |
| US4511834A (en) * | 1982-12-23 | 1985-04-16 | Borg-Warner Corporation | Control and stabilizing system for damperless synchronous motor |
| US4473790A (en) * | 1983-01-03 | 1984-09-25 | General Electric Company | Control circuit for suppression of line resonances in current feedback pulse width modulation control systems with a minimum d-c filter |
| DE3313124C1 (en) * | 1983-04-12 | 1984-07-12 | Danfoss A/S, Nordborg | Stabilization circuit for an inverter motor control |
| DE3501615A1 (en) * | 1985-01-17 | 1986-07-17 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Method and arrangement for compensation of current fluctuations resulting from sudden motor-data changes |
| EP0244186A3 (en) * | 1986-04-29 | 1989-03-08 | David C. Hoffmann | Electronic power supply |
| FI78202C (en) * | 1987-01-13 | 1989-06-12 | Kone Oy | FOERFARANDE FOER STYRNING AV HALVLEDARKOPPLINGAR I EN TILL VAEXELSPAENNINGSNAET KOPPLAD LIKRIKTARBRYGGA SAMT EN FOER TILLAEMPNING AV FOERFARANDET AVSEDD STYRENHET. |
| US4823068A (en) * | 1987-06-23 | 1989-04-18 | General Electric Company | Cross tie for induction motor drive |
| DE69013095T2 (en) * | 1989-07-27 | 1995-03-16 | Seiko Epson Corp | Pulse width modulated converter / inverter system and method to control the same. |
| DE4110225C2 (en) * | 1991-03-28 | 1994-07-21 | Abb Patent Gmbh | Control method and control arrangement for an inverter |
| JP2903863B2 (en) * | 1992-05-29 | 1999-06-14 | 三菱電機株式会社 | Inverter device |
| DE4231347C1 (en) * | 1992-09-18 | 1993-10-07 | Siemens Ag | Multiprocessor system for the control and regulation of a converter |
| JP5427845B2 (en) | 2011-07-08 | 2014-02-26 | 山洋電気株式会社 | Power supply system |
| CN104993770A (en) * | 2015-07-05 | 2015-10-21 | 中能世华(北京)节能科技有限公司 | Multi-power permanent magnet motor energy-saving device |
| CN116505535B (en) * | 2023-06-26 | 2024-04-09 | 深圳市德兰明海新能源股份有限公司 | Energy storage system and direct current bus voltage stable control method |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3546551A (en) * | 1969-03-27 | 1970-12-08 | Cutler Hammer Inc | Adjustable frequency control system having feedback for voltage and frequency regulation |
| DE2234681C3 (en) * | 1972-07-14 | 1975-07-31 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Method and circuit arrangement for reducing the torque ripple of an induction machine |
| US4186334A (en) * | 1978-02-07 | 1980-01-29 | Tokyo Shibaura Denki Kabushiki Kaisha | Control systems of alternating current motors |
| DE2808616A1 (en) * | 1978-02-28 | 1979-08-30 | Alsthom Cgee | Speed control circuit for async. motor - has limiter diode in series with operational amplifier producing voltage proportional to difference between reference and motor voltages |
-
1981
- 1981-08-25 CA CA000384532A patent/CA1185653A/en not_active Expired
- 1981-09-09 DE DE19813135764 patent/DE3135764A1/en not_active Ceased
- 1981-09-10 GB GB8127342A patent/GB2084357B/en not_active Expired
- 1981-09-22 JP JP15049581A patent/JPS5791680A/en active Pending
- 1981-09-22 FR FR8117880A patent/FR2490893B1/en not_active Expired
-
1984
- 1984-01-17 GB GB8401118A patent/GB2136168B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2084357A (en) | 1982-04-07 |
| GB8401118D0 (en) | 1984-02-22 |
| FR2490893B1 (en) | 1985-07-26 |
| FR2490893A1 (en) | 1982-03-26 |
| JPS5791680A (en) | 1982-06-07 |
| GB2136168A (en) | 1984-09-12 |
| GB2084357B (en) | 1984-08-08 |
| GB2136168B (en) | 1985-03-13 |
| DE3135764A1 (en) | 1982-05-27 |
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