CN101005267A - Frequency converter for different mains voltages - Google Patents
Frequency converter for different mains voltages Download PDFInfo
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- CN101005267A CN101005267A CNA2007100072917A CN200710007291A CN101005267A CN 101005267 A CN101005267 A CN 101005267A CN A2007100072917 A CNA2007100072917 A CN A2007100072917A CN 200710007291 A CN200710007291 A CN 200710007291A CN 101005267 A CN101005267 A CN 101005267A
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Abstract
The invention concerns a method for speed controlling an electric motor by means of a frequency converter, and a frequency converter applying the method. The frequency converter can be connected to one of several different mains voltages and is a socalled multi-voltage unit. When connected to a lower nominal mains voltage than the one, for which the frequency converter is dimensioned, or when the mains voltage drops, the frequency converter will demand a larger current from the mains to meet the power demands of the motor. However, this may damage the input of the frequency converter due to a too large current. According to the invention, the problem is solved in limiting the maximum output power of the frequency converter, when the actual mains voltage is lower that the maximum nominal mains voltage, for which the frequency converter is designed, and that during the limitation the frequency converter controls the speed of the motor within a power range up to the limited maximum output power. This gives a genuine multi-voltage unit, which can be connected to a wide range of mains voltages. Further, an adaptive current limit is described, said limit adapting to either temperature, frequency or load profile.
Description
This case is to divide an application, and female case is that international filing date is the application for a patent for invention 02823279.8 (its international application no is PCT/DK02/00785) of on November 21st, 2002, identical denomination of invention.
Technical field
The present invention relates to a kind of frequency converter, it can be connected on one of several different supply voltages, the invention still further relates to a kind of method of coming motor is carried out speed control by frequency converter.
Background technology
Because need product differentiation, the difference of US and European supply voltage has increased production cost.Therefore, for many years, make the frequency converter that can be connected to different electrical power voltage, (for example) sees US4,656,571.
But when frequency converter was connected to frequency converter supply voltage that can handle, that be lower than maximum nominal supply voltage, this had caused a problem.Electric current in the equipment will increase to keep the electrical power output identical to motor in this case.The electric current that increases may the damage frequency transducer.For fear of the generation of this situation, can be designed for high electric current to frequency converter, but this is a kind of relatively more expensive solution, and needs more space, because (for example) intermediate circuit coil can be bigger.Thereby, need protect frequency converter.
But, in another connects, can know from EP0431563B1 and frequency converter, to reduce electric current.When overload, when promptly being used in electrical consumption in the compressor reducer of HVAC system here and crossing multiple current, a control appliance reduces the output frequency of inverter.Detect the amplitude of electric current by the current measurement of power end (that is, before frequency converter).When reducing output frequency, just reduce flowing to the electric current of rectifier, and protected the unlikely overcurrent that suffers of the device in the private home thus from power supply.But described frequency converter is not to be used for being connected to of several different electrical power voltages.
US4 above-mentioned has described a kind of supply voltage adaptive frequency transducer in 656,571.Placed a voltage detector before rectifier, it provides the information relevant with the supply voltage amplitude to control appliance.Control appliance comprises memory element, has wherein stored a table for every kind of possible supply voltage.Every table comprises a plurality of U/f relations, and its essence is the electric moter voltage that applied by inverter and the relation between the electric machine frequency.In order to obtain optimum motor operation, it is constant that this relation must keep.To supply voltage 100V, 115V, 200V, 230V, the table that has comprised the U/f relation is all arranged, and by selecting suitable U/f relation, the power output of frequency converter is adjusted to a steady state value.In this solution, attempt to keep intermediate circuit voltage constant, input circuit has comprised a conversion equipment for this purpose, and it switches to voltage and doubles pattern when equipment is connected to 115V, and conversion equipment remains unchanged when connecting this equipment to 230V.Thereby motor receives identical voltage, but the shortcoming of this system is that input circuit must receive higher electric current when using the 115V supply voltage.Be necessary for the complete input circuit of minimum power supply voltage, design, this means some waste that will seem of this equipment of higher supply voltage.This designs further problem is not consider off-standard voltage.Thereby do not know that the supply voltage how control appliance will be handled from 230V to 170V descends.The operation of no classification is not described.
The adaptivity of frequency converter should not only limit to adapt to supply voltage.In addition, the adaptation to current limitation also is interested.Today, frequency converter comprises three current limitations usually, and the higher limit is a short-circuit protection, when electric current reach the nominal frequency converter current 300% the time it can be activated, its response time is 1 to 2 μ s.This limit can be activated when ground connection or short circuit occurring between phase coil.Second limit is hardware limit, it normally nominal current 220%, the response time is 15 μ s.Hardware limit is represented the semiconductor of frequency converter and the maximum current that coil can bear.Short-circuit limit and hardware limit all realize with electronic component, and the 3rd limit (software limit) is programme controlled by frequency converter.Usually software limit is 160% of a nominal current, and the response time is 60s, and frequency converter reduces load by reducing electric machine frequency after 60s.
Usually, just in frequency converter, pinned hardware current limit during manufacture, but US4,525,660 disclose a kind of current circuit of crossing, and current limitation is variable during operation in this circuit.Here import the current measurement signal that receives from the electric current of measuring in intermediate circuit or the motor lines for one of comparator, another input received current reference signal, it changes according to the voltage frequency ratio (U/f) of frequency converter.When current measurement signal surpassed current reference, comparator sent signal, so that reduce electric current or complete stop frequency transducer.Variable current reference signal is made up of two parts, and first standing part is by potentiometer setting, and second part is determined as the function of U/f ratio.Second part is by tabling look-up or function calculation finds, and U/f is than the key assignments that is record, and the current limitation part increases along with increasing U/f.Thereby the current reference signal that is produced changed in the operating period of frequency converter.But.The shortcoming of this circuit is that the variation of current limitation is locked into the U/f ratio, and it determines the feature of current reference, i.e. curved profile separately.
WO97/36777 has also described a kind of circuit that is used to produce current reference, and current reference is in Electric Machine Control operating period variation, and this variation is the function of machine speed.Table in the memory component of the combination of current reference generator by comprising speed and electric current produces hardware limit, and microprocessor forms software current limit.By data wire, microprocessor links to each other with the memory component of current reference generator, thereby can change the profile of hardware characteristics.With US4,525,660 compare, and the advantage of this circuit is only just can change the current limitation feature by the programming that changes microprocessor.This has given manufacturer the bigger degree of freedom.When manufacturer wanted to make the general-purpose machine driver of the motor that can be used for different sizes, they especially needed the bigger degree of freedom.Common problem is that the high-power frequency converter that series is made is connected to low-power motor.The hardware current limit of frequency converter is lockable immediately, and compares with motor and to seem too high.With regard to application (promptly using the field of frequency converter), need the further degree of freedom.For example, the HVAC (heating, ventilation, air conditioning) and the belt applications of different current limitation features arranged, but they have been fixed in the frequency converter during manufacture usually.Thereby frequency converter manufacturer is forced to make multiple variant, and each has its specific hardware current limit.
Summary of the invention
Based on above argumentation, target of the present invention be the design a kind of universal frequency transducer, it on electricity, can adapt to surrounding environment or at an easy rate by around environmental adaptation.
According to the present invention, this target is solved by a method, adjust the DC/DC transducer that is placed between rectifier and the inverter in the method, with the output dc voltage that operating period remains unchanged on any of several supply voltages, limiting value signal and one or more parameter that measure or that calculate compare, control appliance limits peak power output by reducing the electric machine frequency that is produced by inverter, and frequency converter is during limited from the power output of inverter, in the speed of the power bracket inner control motor that is up to limited peak power output.
This solution provides a general frequency converter, and it can be connected on a large scale in principle, on the continuous supply voltage special case.This frequency converter is by limiting power output according to the supply voltage that it connected, thereby adapts to available supply voltage automatically.For example, if frequency converter is (maximum nominal supply voltage can appear in the specification of electric machine controller) that the maximum nominal supply voltage for 230V designs, control appliance will reduce power output when being connected to the practical power voltage of 115V.More precisely, control appliance will limit peak power output, so that frequency converter is moved on to another working point by the working point from an expectation, frequency converter will continue to operate in the new working point then.The present invention can be used in the following situation: be connected on the power supply with low initial voltage when frequency converter is initial and use this voltage power supply in the operational phase subsequently, perhaps AC supply voltage descends during operation.In the duration of this low voltage, peak power output is limited, reaches its nominal value once more up to AC supply voltage.Adopt this mode, control appliance protection frequency converter is not done harm to by super-high-current, consequently general electric machine controller.Though motor off-load operation under many circumstances can be more practical concerning the OEM manufacturer that only needs to handle a kind of frequency converter and motor in its warehouse and terminal use.Do not consider the kind of used limiting value, by reducing the power output that electric machine frequency can reduce inverter.Electric machine frequency is applied by inverter, and its mode essence is directly related with motor speed.Because (for example) power consumption of pump or fan motor becomes than direct ratio with speed in the 3rd power, the reduction of electric machine frequency will have tangible influence to power consumption, and thereby frequency converter institute consumed current also be had tangible influence.The present invention uses and is installed in rectifier amplification converter afterwards, rather than uses in check rectifier, and the output voltage of amplification converter is controlled to be constant by control appliance, and controlled rectifier is used with multi-phase AC power usually.Operating period keeps the constant unexpected variation that can deal with supply voltage of dc voltage in the intermediate circuit on a kind of voltage in several supply voltages, and provide by the design platform of explication because power limit technology of the present invention its might use cheap parts.When this is particularly useful for dc voltage and on different electrical power voltage identical uniform amplitude is arranged.The advantage of bringing like this is no matter the amplitude of supply voltage how, all has complete velocity interval.Another variant is to change the amplitude of dc voltage according to different supply voltages, but keeps dc voltage constant during operation.DC/DC transducer (preferably amplification converter) is controlled power factor control and intermediate circuit voltage to lump together in known manner and is provided.
Be that in so-called weak mains zone (being insulation layer), the amplitude of supply voltage is especially responsive to the electric current of being controlled according to the very big advantage that method of the present invention provided.The frequency converter of imagining according to the prior art development level is connected between motor and the weak mains, and it is low that the weak mains voltage ratio is expected, this will cause increasing from the current absorption of power supply, cause degradation under the voltage immediately.The present invention has broken this vicious circle, because the decline of inverter power output has protected supply voltage can further not descend.Thereby the present invention has improved operating reliability.
In principle, control appliance can reduce predetermined fixed value with power output, is the designed maximum nominal supply voltage of frequency converter if practical power voltage is lower than.The amplitude of supply voltage is known in the setting that control appliance is carried out in the time of subsequently will be by user's starting device.But, preferably control appliance realizes that frequency converter independently and automatically adapts to supply voltage, and therefore control appliance comprises a limiting value, and this limiting value and one or several Electric Machine Control parameter that measure or that calculate (for example rectifier current) compares.If comparative result shows the parameter of measuring or calculating and is higher than limiting value, just reduces power output.
The reduction of power output can connect frequency converter very fast generation after power supply.If the startup stage ending, the parameter of measuring or calculating is higher than limiting value, control appliance is with regard to the peak power output of limit frequency transducer, and all will keep this new value in principle in the remaining operational phase.Use has avoided control appliance to use rated output during operation to this interassay of maximum permission power output.
Can store different limiting values in a table rather than only use a limiting value, control appliance can be selected one according to one or more measurements or the parameter that calculates from these limiting values.For example, the size of limiting value can change with near the temperature that measures semiconductor.
By control appliance being calculated during operation continuously or definite limiting value can obtain point-device formula of limiting value.Even this needs rated output, the raising that this also can through performance remedies, because frequency converter will be operated on its optimal working point on the supply voltage of being discussed.In other words, the control motor is so that it provides the maximum power accepted on given supply voltage.
Advantageously, limiting value can be represented as current limitation, for example, and by the electric current after electric current in the motor phase (preferably) or the rectifier.Because the correlation between electric machine frequency and the input current (high-frequency causes high electric current) can be provided with the function that current limitation is an electric machine frequency easily, also can combine with measured temperature.
Reduced electric machine frequency by the electric machine frequency of establishment expectation and the difference on the frequency between the frequency attenuation term, the frequency attenuation term is to calculate according to differing between parameter of measuring or calculating and the limiting value.Difference on the frequency is provided for inverter as reference signal subsequently.
Control means that mainly based on U/f control the reduction of frequency f also will cause electric moter voltage U to descend, and relation is constant in to guarantee the correct magnetization because expectation keeps U/f.
Use lower electric moter voltage, can reduce intermediate circuit voltage.This reduction is finished by the DC/DC transducer, and intermediate voltage will keep constant once more during operation after this reduces.The advantage that intermediate circuit voltage reduces is, be the heating electrical power in the intermediate circuit parts, put aside still less, make heat load reduce.
Supply voltage can directly be measured by the voltage sensor in the rectifier input, but also can be by the indirect expression formula that current sensor obtains the supply voltage amplitude is installed in the intermediate circuit of frequency converter.
By respectively inserting a measurement resistor between rectifier and the amplification converter and between amplification converter and inverter, just obtained two current values, they and two limiting values can be compared.Electric current in first limiting value and the rectifier compares, and determines when the power output that reduce inverter.Electric current in second limiting value and the inverter compares, and relates to the overcurrent protection of inverter.Advantageously, can make second limiting value as the function of the torque load(ing) on nominal power rated value, real electrical machinery frequency or the motor shaft of motor and change.
The invention still further relates to the frequency converter that is used for motor is carried out speed control.Comprise amplification converter between rectifier and the inverter according to frequency converter of the present invention, amplification converter is created in that operating period all keeps constant dc voltage on each of several supply voltages, frequency converter also comprises control appliance, this control appliance reduces the power output of frequency converter so that adapt to supply voltage by first limiting value of having described, but except first limiting value, also introduced second limiting value, the hardware electric current of its expression inverter and be adjustable in the operating period of frequency converter.Second limiting value and current measurement signal compare, and just provide overcurrent signal in case current measurement signal exceeds second limiting value.
Adopt this mode can design general frequency converter.At the AC power end, frequency converter adapts to available supply voltage by the restriction peak power output, thereby and adapts to motor at the motor side frequency converter by the limiting value that changes overcurrent signal according to motor size, electric machine frequency or the load that is connected with motor shaft.
Preferably, second limiting value is to produce according to the reference characteristic of storing in the memory.By making current reference characteristic depend on different variablees, the degree of freedom that frequency converter manufacturer can obtain to expect.Current reference characteristic almost is wide-open to change, because can replace with the another feature with second variable with a feature of first variable.A frequency converter that is suitable for motor size can be arranged, perhaps have one to comprise the inverter power unit of (inter alia), same power unit can be used for the frequency converter of different sizes.Unique part that will be replaced is a control assembly, just in time with the current limitation of the power unit that is applied to discussing it is programmed.Will be crossed the highland design though the power supply unit parts are compared with motor under many circumstances, for example 250W frequency converter and the 150W motor that links to each other have a spot of variant can be more cheap concerning frequency converter manufacturer.Realized a large amount of advantages and flexibility, can take place during fabrication or take place in OEM manufacturer or end user location because adapt to.Current reference characteristic is stored in the memory component, and the substitutability of feature has been brought the flexibility of expectation.Thereby, can be in a kind of variant to a feature programming, it depends on one or two variable, and can programme to another feature according to two other variablees in another variant.Can carry out formulism to feature according to a plurality of variablees, and it is expressed as arbitrary function with formula or form.For example, feature can be stored as the fixed character in the microprocessor program, also can be several optional features if want.Second limiting value is by reference generator pulse width modulation and produces.This has brought simple accurate signal control.Doing further advantage like this is, except that short-circuit limit, frequency converter can be only with an additional current limitation job, because software current limit and hardware current limit have been combined in the limit.This means the quantity that has reduced needed parts.
These variablees can be chosen from Control Parameter and (as electric machine frequency, U/f ratio and temperature) or application parameter (as motor size or bearing axle feature).(for example) if selected temperature as input variable, second limiting value will increase and reduce with temperature.In addition, current limitation also can be formulated as the two function of Control Parameter and application parameter.
Control and application parameter or their mixing are sent to reference generator as input signal, and reference generator is made of FPGA (field programmable gate array), ASIC (application-specific integrated circuit (ASIC)), DSP (digital signal processor) or microprocessor.
Preferably, use electric machine frequency at least, because electric machine frequency is the better expression to the electric current in frequency converter and the motor as the variable in the feature.Usually, this means that improving frequency will cause electric current to increase, and different current limitations belongs to different frequencies.
If current reference characteristic with temperature and electric machine frequency as variable and formulism can obtain the point-device expression to hardware current limit so.
A problem is the starting current that is approximately equal to motor by the electric current that the rotor of blocking produces.Therefore, the overcurrent circuit can not be distinguished both of these case usually, but changes second limiting value so that level is increased to limiting frequency from startup to be lowered again subsequently, has avoided possible error detection.To one very short period, hardware current limit is increased on the amplitude of starting current simply.
Before comparison, pulse width modulating signal should be converted into analog signal, by this easiest finishing of low pass filter.Should carry out the speed of comparison with analogue technique needing to realize to the electric current measured and current reference.
The control and/or the application parameter that are used for forming the basis of current reference characteristic will mainly be determined during the manufacturing of frequency converter, but it is optional also can be set to the user, for example OEM client the switch installed in the frequency converter or wire jumper are set or by serial communication interface to frequency converter programming (as by using PLC).
In addition, frequency converter self can be adjusted current reference characteristic.Frequency converter is measured motor, determines its electrical parameter and calculates motor size.Parameter measurement is automatically known from the prior art development level, and was normally carried out before starter motor.
Advantageously, the current signal that is measured by frequency converter is carried out standardization with normalization circuit, so that control needn't be known the absolute value of electric current.This means that identical control can be used for the frequency converter of different sizes.
Be separated and be placed in two frequency converter types on the different printing circuit board at power unit and control section, normalization circuit can be installed in these the card in any one on.This means that equally (for example) identical power unit can be used for different control cards, and perhaps identical control card can be used for different power cards, because in a sense, all adaptive functionals all are placed on the control card.Preferably, normalization circuit is installed in power unit.
Normalization circuit can be realized in simple mode with the in parallel of current signal by the resistance of two series connection.Preferably, current signal is to be produced by the measuring resistance in the intermediate circuit that is installed in frequency converter.
Also realize this target by a kind of method that is used to produce overcurrent signal.
Description of drawings
Below, will set forth the present invention with reference to the accompanying drawings, in the accompanying drawing:
The circuit of the frequency converter that Fig. 1 is connected with motor
Time dependent first curved profile of Fig. 2 power limit
Time dependent second curved profile of Fig. 3 power limit
First embodiment of controller used thereby among Fig. 4 the present invention
Second embodiment of controller used thereby among Fig. 5 the present invention
The 3rd embodiment of controller used thereby among Fig. 6 the present invention
Fig. 7 overcurrent sensing circuit figure
The time dependent curved profile of Fig. 8 overcurrent limiting value
The curved profile of Fig. 9 overcurrent limiting value during as the function of electric machine frequency
The circuit of Figure 10 power controlling factor correction device.
Embodiment
The present invention is by following works.Suppose that motor size is 750W, the supply voltage U of 230V
NTo cause being about 4.The feeder circuit I of 8A
NInput current as rectifier.If supply voltage is 115V, identical motor load will cause the input current of about 9.6A to satisfy the power demand of motor.Unless rectifier 2 and coil 10 are customized in view of the above, otherwise they will wreck, and perhaps coil will produce very high loss heat, and it will destroy remaining circuit.In addition, can make full the closing of core of coil, this will cause self-induced loss.This will cause high peak current, and high peak current will cause further loss, and loss may destroy semiconductor.When frequency converter is installed in the fully sheathed case in the washing machine thus refrigeration be a big problem, and this problem further worsens when supply voltage is low.In the first possible embodiment, the electric current I of control appliance by relatively after rectifier, measuring
RecWith the current limit value I that has applied the 230V supply voltage
LimThe power output that adapts to frequency converter.Control appliance is adjusted frequency the power output of transducer so that be no more than the electric current I of 4.8A
N, thereby the maximum power of limit frequency transducer is output as 375W.Fig. 2 has showed this situation.At time t0, frequency converter is with the limit P of the maximum power power output of 750W
Max1Beginning.At t0 to t1 stage (this stage is longer than start-up time slightly and continues about 3 seconds), detect supply voltage or intermediate circuit voltage and with table in the limiting value of storage compare.If voltage is lower than limiting value, control appliance just concludes that AC supply voltage is lower than the voltage that frequency converter is designed to, and the peak power output that limits it is P
Max2=375W.This value remained unchanged in the remaining operating time, and restricted frequency converter is in the speed of the power bracket inner control motor that reaches as high as limited peak power output Pmax2 in the remaining operating time.
As mentioned above, do not need direct measurement, because can be that basic calculation is come out with the voltage in the electric current in the rectifier and (for example) intermediate circuit by control appliance to the supply voltage amplitude.Also needn't know the accurate amplitude of supply voltage, because the indication of the amplitude of supply voltage is just enough, and this indication can (for example) be made up of the electric current of measuring after rectifier just by measuring resistance 20.The moment of the power output limit can be after frequency converter starts soon, for example when amplifying that switch 11 has been started working and capacitor 13 has been finished and charged and when having obtained the indication of supply voltage amplitude.Simultaneously, control appliance can be provided with suitable limiting value, and it is applied to the remaining time of frequency converter operational phase.This solution has been saved rated output.Perhaps, as previously mentioned, control appliance can carry out continuous supervision during operation, and if exceeded limiting value and can reduce electric output power.
If mains fluctuations also can the starting power restriction scheme.Usually, can add/subtract fluctuation range design frequency transducer for nominal supply voltage, for example 230V+/-10%.But when relating to special weak mains, for example voltage may be reduced to 180V, and input current will increase to satisfy the power demand of motor here.But according to the present invention, control appliance will reduce size to a frequency converter acceptable value of peak power output.Suppose the motor that has connected 1500W, the nominal voltage of 230V is with the electric current of 9.5A.Fig. 3 has showed that t0 is to the maximum power limit P of t1 in the stage
Max1. at time t1, supply voltage is reduced to 180V, because limiting value has been set to 9.5A, control appliance restriction power output is P
Max2=1200W.The throttling of peak power output occurs in t1 during the t2.Motor properties has reduced, but motor is still worked rather than controlled device stops with the protection frequency converter.This is corresponding to the reduction of maximum centrifugal speed in the washing machine.Usually terminal use and to be indifferent to centrifugal speed be 1100RPM or 800RPM.This technology also can be used for other to be used, for example with the loaded work piece that reduces rather than pumping system that stops fully (pump is to move so that can extract at least some water out than low velocity) or chilling unit.Get back among Fig. 3, slightly descend, promptly to 200 at time t2 supply voltage.Control appliance increases maximum power limit P now
Max3To 1320W.The power limit that this can bear less than motor, but still be to be higher than the power limit of t1 to the t2 stage.
Fig. 4 has showed the control algolithm that how to realize reducing power output with the block diagram form.Controller shown in Fig. 4 is the part of control appliance 6, and power output is to reduce by reducing electric machine frequency according to the measurement to rectifier current.Suppose intermediate circuit voltage U
DcConstant.The rectifier current I that measures
RecIn filter 30, in subtracter 31, therefrom deducted current limit value I by mean deviation
LimIn converting unit 32, current deviation is converted into frequency f
Lim, it is that frequency reduces item and represents its quantity, limits electric machine frequency with it, for example 10HZ.Converting unit 32 comprises mathematical transfer function, but it also can be implemented as controller.At frequency translation unit 33 (it comprises mathematical transfer function), frequency limitation item f
LimElectric machine frequency f with expectation
SetBe converted into an output signal f
RefConverting unit 33 is a subtracter in the simplest embodiment, but preferably it is the filter function that is used for by time unit controls frequency change.Output signal from 33 is reference frequency f
Ref, it is directly oriented to pwm unit 35, the semiconductor device in this unit controls inverter 4.In addition, f
RefBe admitted to U/f control unit 34, this unit produces modulation index signal m on the basis of this signal and the intermediate circuit voltage Udc that measures
aSignal, i.e. the benchmark of electric moter voltage and intermediate circuit voltage U
DcBetween relation.In addition, can use occupation efficiency D, promptly semiconductor device on time and the relation between cycle time, but also there is an occupation efficiency (that is, altogether three) in each motor coil, it makes with D restive.In addition, the inversion frequency of inverter remains unchanged.
Another control algolithm of having showed the power output of restriction frequency converter when low-voltage among Fig. 5.Here suppose also that intermediate circuit voltage is constant.Measure rectifier voltage U afterwards
RecAnd in filter 40, make it level and smooth.This signal is imported into unit 41 subsequently, and it is this voltage transitions success rate limiting value signal P
LimUnit 41 comprises the limiting value P of different sizes
LimTable, voltage U in this table
RecBe used as inlet.This fiducial value is imported into subtracter 42, always exports P from the actual power of transducer
InvDeduct limiting value.In unit 43 based on the intermediate circuit electric current I of measuring
DcFiltration after value calculate actual power output.Perhaps, power calculation can also comprise the intermediate circuit voltage U that measures
DcThis is to be shown by the dotted line in the frame 44 that comprises filter.P
LimAnd P
InvBetween difference be imported into converting unit 45 subsequently, it converts deviation to frequency f
Limf
LimThe size of expression frequency limits electric machine frequency with it.Converting unit 45 is implemented as adjuster or transfer function.Remaining circuit is identical with Fig. 4.Power P
InvAlso can on the basis of electric moter voltage and current of electric, calculate.
Although the adjuster among Fig. 4 and Fig. 5 is according to the fixedly intermediate circuit voltage U that is produced by amplification converter
DcWork, but the control circuit among Fig. 5 is based on variable intermediate circuit voltage.Amplify switch 11 by controlling, thereby make intermediate circuit voltage U according to the fluctuation of supply voltage
DcChange simultaneously with supply voltage.Thereby the voltage after the amplification converter is used as the indirect expression formula of AC power amplitude.Use the advantage of the intermediate circuit of such intermediate circuit rather than voltage constant to be, intermediate circuit voltage only need be amplified to required value, and needn't be higher.The RMS-value and the difference between the intermediate circuit voltage of supply voltage are big more, and loss is big more.By measuring voltage U
RecDetect the fluctuation of supply voltage.Variable voltage U
DcBe imported into converting unit 50, it becomes frequency f to this voltage transitions
Lim, f
LimExpression must limit the quantity of electric machine frequency.Subsequently, circuit is worked as Fig. 4 and Fig. 5 are described.In addition, frequency limitation f
LimCan be confirmed as the function of modulation index by converting unit 51.For Show Options, those frames all with dashed lines draw.If supply voltage descends, thereby makes intermediate circuit voltage U
DcReduce, just can not provide correct voltage to motor again, but reduce electric machine frequency by the function as modulation index or intermediate circuit voltage, can realize providing correct voltage to motor, simultaneously power output also is lowered as the function of supply voltage.
We get back to Fig. 4 and limiting value I now
LimThis limiting value can be dynamic and depend on different parameters that for example the temperature T of being measured by temperature sensor 24 (Fig. 1) also can be stored as the fixed value in the master meter, is perhaps calculated continuously during operation by control appliance.
Fig. 4 has also showed signal OC, and it is imported into pwm unit 35.This signal is overcurrent or cut-off signal, and it just closes inverter if reached absolute extremes that electronic equipment can bear.In the prior art development level, hardware current limit signal OC produces when exceeding fixed current limit value usually, but advantageously, the current limitation that is used to trip can be variable and depend on electric machine frequency.Fig. 7 has showed the circuit 60 that produces overcurrent signal OC.Circuit block 61,63 and 70 is parts of control appliance 6.Reference generator 61 produces the variable limit value based on one or more variablees (being parameter A 1, A2, AN or S1, S2, Sn)." A " means application-specific parameters, for example secondary torque load(ing) of the motor shaft of pump, and " S " means Control Parameter, for example electric machine frequency, motor temperature and inverter temperature.These parameters all have base value 62.In output 63, reference generator provides suitable frequency, for example 2kHZ to pulse width modulating signal.Occupation efficiency is set to 50%, and this causes current limitation to be lowered 50%.In low pass filter 64, pwm signal is converted into the direct voltage signal I in the input 65 of comparator 66
OCThe variable limiting value of signal representative in the input 65.In input 67, there is one to be used for the signal that actual current is measured, for example represent the signal of the size of current of intermediate circuit.The output signal of comparator 66 is imported into reference generator by connecting 71, and the form of reference generator is FPGA or microprocessor.Although produce hardware current limit with digital technology (being slower than the corresponding simulating technology), also realized the acceptable response time, because digital processing is subject to the variation of current reference signal (promptly exporting the signal on 63).This circuit is enough fast, takes place in output 69 because the generation of overcurrent signal is an analog circuit.The circuit of being made up of ohmic resistor 68 is guaranteed current signal standardization always, and in present case, the 220mV in the output 67 is corresponding to the maximum permissible current in the inverter.If signal is 150mV, it is corresponding to the actual current utilization of frequency converter power unit 68.2%.Like this, control appliance does not need to know the watt level of the power unit of frequency converter.As shown in Figure 7, the normalization circuit of having realized in parallel by the measuring resistance in the negative conductor of two bypass resistances and intermediate circuit.The size of measuring resistance is 18 milliohms, but the varying in size of bypass resistance.Bypass resistance serves as voltage divider and in the scope of several megaohms.Normalization circuit 68 preferably is installed on the printed circuit board (PCB) of power unit, and forms the interface section with control board when the circuit that needs power unit and control section is connected.
Concerning the manufacturer of frequency converter, normalization circuit means that the same printed circuit board (PCB) that comprises control section can be used for the power unit of different sizes.When the direct voltage signal in the input 65 had exceeded the current measurement signal of importing on 67, the comparator output OC on the circuit 69 became high level and indication " overcurrent ", and whether control appliance 6 decisions subsequently close frequency converter.Variable current limit I
OCMainly be expressed as the real electrical machinery frequency f
RefFunction with the possible one or more electrical parameters of motor.These parameter A 1, A2, An and S1, S2 and Sn among Fig. 5 can be the power of motor or the nominal current of motor, can directly read from motor nameplate.In addition, the parameter of electric machine as similar stator resistance, rotor resistance and inductance (for example home court inductance and leakage inductance) can be the part that current reference characteristic is determined.The size of the motor that is connected to frequency converter can directly be read or calculate to reference generator 61 on the basis of these parameters, and thereby the definite limiting value that will use.In other words, reference current generator 61 adapts to the current limitation IOC of motor, so that different motor size can both be connected to identical frequency converter.This is especially suitable when the less motor of rated power is connected to the higher frequency converter of rated power.Thereby the user needn't readjust current limitation, and this is finished automatically by frequency converter.The information relevant with motor size can be imported by keyboard, serial communication connection, wire jumper or at the dual-in-line switch (dip-switch) that is installed in the factory on the control board by the user, and each dual-in-line switch is represented a motor size.But, particularly preferably be control appliance and measure the electrical parameter of motor and create limiting value I with this information by frequency converter
OCThe electrical parameter of measuring motor before operation is known, and is realized by input DC and AC signal in stator coil.
The variable current limit among Fig. 7 in the input 65 also can be by reference generator according to the typical load curve setting of using.Memory 70 comprises a table of relevant current limit value and load curve, and (for example) will be a parabola for this curve of pump application.In another example, current reference characteristic is the single function of the inverter temperature measured by transducer 24 (Fig. 1), and the process of curve is negative parabola, and its peak value is at 0 ℃, and increases with temperature and to descend.In described example, current reference can (for example) be followed this feature:
(1)I
OC＝-0.0085*T
2+100
Wherein T is a temperature, I
OCIt is current reference signal.In practice, this curve will be piece-wise linear so that IOC has fixing constant value up to 90 ℃, and this curve will increase and descends with temperature subsequently.Transfer function (1) can be implemented as the function in the microprocessor or is embodied as look-up table.
As previously mentioned, can make current reference signal depend on the reference signal (f among Fig. 4 of electric machine frequency or electric machine frequency
Ref).This feature will be presented among Fig. 9 subsequently, and the there current limitation increased up to the frequency f that reaches capacity between the starting period of motor
g
In addition, reference generator can be changed current limitation by the function as the time between the starting period of motor.Fig. 8 has shown from starting up to the over and done with current limitation I of one specific operation period
OCIndicatrix.By the dual-in-line switch on the control board current limitation of current limitation for coupling particular motor size can be set.In fact, frequency converter can provide much bigger electric current, but the rated power of motor is less.In the t0-t1 stage, reference generator 61 increases limiting value to I
OC2With allow bigger starting current by and can not cause tripping operation.At time t1, reference generator reduces current limitation once more to I
OC1. at time t2, ambient temperature raises, and it causes the more high heat load of electronic unit, and therefore current limitation further is reduced to I
OC3Current limitation can also be lowered owing to the decline of supply voltage.Reduction in the t2-t3 stage can be substep or continuous.Using an advantage of the variable current limit is limiting value I
OCNeedn't customize according to starting current, and this can detect the fault of generation more accurately.The overcurrent that is produced by the rotor that blocks can have approximate amplitude with starting current, and is similar in fixed current limit that this overcurrent can not be counted as fault under the situation of starting current.
In addition, can come formulistic current reference characteristic as variable with temperature and electric machine frequency.
As relate to as shown in the argumentation of Fig. 7, split circuit is digital flexibility and analog rate for the numerical portion of handling non-time-critical function and the advantage of carrying out quick operating simulation part.In Figure 10, further set forth this principle with the circuit of control amplification converter 9.Amplification converter is carried out as preceding foregoing PFC function.The PFC control circuit is made up of (low) voltage control loop, multiplier (the line voltage waveform is multiply by in the output of voltage control loop) and (fast) current control loop.The output of multiplier is the benchmark of current control loop.Current control loop can be Average Current Control or peak current control.For example PFC control can be the mixing of analog circuit, pure digi-tal control (for example DSP) or digital control and analog circuit.
Even (use microprocessor to produce low-pass filter and enter the numerical reference signal of analog reference signal) when using the digital-to-analog Configuration Type that separates shown in Fig. 7 to control amplification converter, PFC control occupies the major part of microprocessor processes ability.In addition, the resolution of the reference current waveshape that is produced by microprocessor is very poor, because PWM output can only per 1 millisecond is updated once.1 millisecond also causes phase deviation unnecessary in the electric current.
Can alleviate this problem by multiplier being moved on to outside the microprocessor and it being embodied as analog multiplier.
This will reduce the needs to Gao Gengxin speed, and discharge the disposal ability of processor thus.In addition, waveform resolution will be improved, and phase deviation will reduce.Analogue multiplication can be undertaken by the PWM modulation of modulation lines waveform signal.
Voltage U among Figure 10 after the rectification
RECBe divided into level of signal by resistor 82 and 83.Pwm signal from microprocessor 61 is fed by resistor 80 and 81 via connecting 88, and by transistor 85 and diode 84 control U
RECSignal is for opening and closing.Look from the capacitor 92 of open and closed, diode 84 is guaranteed identical impedance (being similar to resistor 82) in fact.In off status, the voltage in diode 84 compensation transistors 85 descends.Opening state, the voltage of diode 84 descends and complete UREC Voltage Series, does not therefore have what meaning.The low frequency component of signal on resistor 82 and capacitor 92 filter circuits 90.This signal is a voltage U
RECWith ' product of the occupation efficiency that provides, this signal can be envisioned as a series of digit pulses of the amplitude of constant width and variation by microprocessor 61.But capacitor 92 and resistor 82 call I to this signal smoothing among Figure 10
RefThe analog D C signal of variation.I
RefRepresent the reference current of amplification converter 87, it provides the in-phase current of power end and voltage and compares with signal that the resistor 95 that is placed on the lead-in wire that amplifies switch is measured.The output of comparator is sent to Signal Conditioning Equipment 93, and it is connected to the door that amplifies switch again.Signal Conditioning Equipment 93 comprises rest-set flip-flop and amplifier.The output of comparator 87 is trigger reset, from connecting 88 pwm signal then with trigger set.Have the frame 86 of dotted line to represent early the multiplication function of a funtion part of microprocessor 61 ' before this, but it is the fast discrete analog component now.Circuit shown in Figure 10 is used as peak current controller, but also can convert the Average Current Control device to.
Having handled above with variable current limit value serves as that the basis produces overcurrent signal OC, and we get back under the low supply voltage situation restriction to power output now.Note current limit value I
LimWith current reference I
OCSeparate work is because I
LimBe an in house software current limitation, I
OCIt is hardware current limit.The major function of IOC is the protection semiconductor, and therefore signal OC can also be transferred to and amplify switch 11.
As previously mentioned, by the reduction influence of control appliance by electric machine frequency power output is applied restriction, this is that (via connecting 14) realizes by pulse emission pause (pu1se-pause) ratio of the power semiconductor in the change inverter 4.Because realized U/f control, also reduced electric moter voltage.This means and to reduce intermediate circuit voltage U simultaneously
DcTo avoid the unnecessary amplification of intermediate circuit voltage.Thereby can limit, because motor need descend simultaneously to electric moter voltage with reducing electric machine frequency by the combination that frequency reduces and intermediate circuit voltage reduces.The function that can be the power output of frequency converter by the average pulse time-out ratio on the reduction amplification switch 11 reduces intermediate circuit voltage.
The maximum reduction of power output has been protected the input of frequency converter to be unlikely and has been suffered excessive electric current.Available supply voltage is controlled the speed of motor in the input according to frequency converter.Thereby motor can not produce the torque identical with being connected to higher supply voltage, but OEM manufacturer certainly takes into account the performance of this reduction when design system.
Claims (2)
1. method that in the frequency converter that motor is carried out speed control, produces overcurrent signal, this overcurrent signal is to produce when the current value of measuring surpasses the value of current reference signal, described current reference signal changed in frequency converter operating period, the method is characterized in that the feature of the current reference signal in the memory element of frequency converter is interchangeable and depends on different variablees.
2. frequency converter, comprise the circuit that is used for detection of excessive current, this circuit is made up of comparator (66), the current reference signal that comparator (66) compares current measurement signal and produced by reference generator, when current measurement signal during greater than current reference signal comparator send overcurrent signal, current reference signal changed in frequency converter operating period, this frequency converter is characterised in that, current reference characteristic is stored in the programmable storage element (70), this feature depends at least one first variable and can be replaced by another feature, described another feature depends at least one second variable, and reference generator (61) is written into current reference characteristic and produces pulse-width-modulated current reference signal (63) from memory element.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DKPA200101751 | 2001-11-23 | ||
| DKPA200101750 | 2001-11-23 | ||
| DK200101750A DK174880B1 (en) | 2001-11-23 | 2001-11-23 | Procedure for control of frequency converter for various line voltages and a frequency converter |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB028232798A Division CN100334802C (en) | 2001-11-23 | 2002-11-21 | Frequency converter for different mains voltages |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN101005267A true CN101005267A (en) | 2007-07-25 |
Family
ID=8160853
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2007100072917A Pending CN101005267A (en) | 2001-11-23 | 2002-11-21 | Frequency converter for different mains voltages |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN101005267A (en) |
| DK (1) | DK174880B1 (en) |
Cited By (11)
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| CN102948062A (en) * | 2010-06-22 | 2013-02-27 | 株式会社理光 | Multi-phase converter |
| CN103368374A (en) * | 2012-03-22 | 2013-10-23 | 迪尔航空航天有限公司 | Electrical supply apparatus |
| CN103475243A (en) * | 2013-09-09 | 2013-12-25 | 泓芯泰业科技(北京)有限公司 | Control system and method for inverter |
| WO2014075414A1 (en) * | 2012-11-16 | 2014-05-22 | 中山大洋电机股份有限公司 | Fan motor |
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| CN105024560A (en) * | 2015-08-05 | 2015-11-04 | 哈尔滨工业大学 | Automatic conversion device of alternating current power supply |
| CN105099322A (en) * | 2015-08-05 | 2015-11-25 | 广东美的制冷设备有限公司 | Variable-frequency air-conditioner current frequency limiting method and device |
| CN105515473A (en) * | 2016-01-26 | 2016-04-20 | 珠海格力节能环保制冷技术研究中心有限公司 | Current control method and device for direct-current draught fan |
| CN106452102A (en) * | 2016-11-10 | 2017-02-22 | 成都信息工程大学 | Frequency converter |
| CN106982023A (en) * | 2016-01-18 | 2017-07-25 | Ls 产电株式会社 | Inverter |
| WO2018188027A1 (en) * | 2017-04-13 | 2018-10-18 | 深圳市海浦蒙特科技有限公司 | Control method and control system for multi-speed multi-power electric motor |
-
2001
- 2001-11-23 DK DK200101750A patent/DK174880B1/en not_active IP Right Cessation
-
2002
- 2002-11-21 CN CNA2007100072917A patent/CN101005267A/en active Pending
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102948062A (en) * | 2010-06-22 | 2013-02-27 | 株式会社理光 | Multi-phase converter |
| CN102948062B (en) * | 2010-06-22 | 2015-07-01 | 株式会社理光 | Multi-phase converter |
| CN103368374A (en) * | 2012-03-22 | 2013-10-23 | 迪尔航空航天有限公司 | Electrical supply apparatus |
| CN103368374B (en) * | 2012-03-22 | 2017-04-26 | 迪尔航空航天有限公司 | Electrical supply apparatus |
| WO2014075414A1 (en) * | 2012-11-16 | 2014-05-22 | 中山大洋电机股份有限公司 | Fan motor |
| CN104919695B (en) * | 2012-12-13 | 2020-02-18 | 威伯科有限公司 | Compressor, control method thereof, compressed air supply device and pneumatic system |
| CN104919695A (en) * | 2012-12-13 | 2015-09-16 | 威伯科有限公司 | Compressor for producing compressed air, compressed air supply system, pneumatic system and method for operating a compressor |
| US11156220B2 (en) | 2012-12-13 | 2021-10-26 | Zf Cv Systems Europe Bv | Compressor for compressed air supply and pneumatic systems |
| CN103475243B (en) * | 2013-09-09 | 2016-06-22 | 泓芯泰业科技(北京)有限公司 | A kind of control system and method for inverter |
| CN103475243A (en) * | 2013-09-09 | 2013-12-25 | 泓芯泰业科技(北京)有限公司 | Control system and method for inverter |
| CN105099322B (en) * | 2015-08-05 | 2018-02-02 | 广东美的制冷设备有限公司 | The electric current limit frequency method and device of convertible frequency air-conditioner |
| CN105099322A (en) * | 2015-08-05 | 2015-11-25 | 广东美的制冷设备有限公司 | Variable-frequency air-conditioner current frequency limiting method and device |
| CN105024560A (en) * | 2015-08-05 | 2015-11-04 | 哈尔滨工业大学 | Automatic conversion device of alternating current power supply |
| US11296639B2 (en) | 2016-01-18 | 2022-04-05 | Lsis Co., Ltd. | Inverter |
| CN106982023A (en) * | 2016-01-18 | 2017-07-25 | Ls 产电株式会社 | Inverter |
| CN106982023B (en) * | 2016-01-18 | 2019-05-31 | Ls 产电株式会社 | Inverter |
| CN105515473B (en) * | 2016-01-26 | 2018-11-23 | 珠海格力电器股份有限公司 | A kind of current control method and device of DC fan |
| CN105515473A (en) * | 2016-01-26 | 2016-04-20 | 珠海格力节能环保制冷技术研究中心有限公司 | Current control method and device for direct-current draught fan |
| CN106452102A (en) * | 2016-11-10 | 2017-02-22 | 成都信息工程大学 | Frequency converter |
| WO2018188027A1 (en) * | 2017-04-13 | 2018-10-18 | 深圳市海浦蒙特科技有限公司 | Control method and control system for multi-speed multi-power electric motor |
Also Published As
| Publication number | Publication date |
|---|---|
| DK200101750A (en) | 2002-11-21 |
| DK174880B1 (en) | 2004-01-19 |
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