• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The inventive method is used to drive an n-phase inverter with n bridge arms for feeding an n-phase electric machine, wherein between the inverter and machine an n-phase low-pass output filter is arranged. The bridge branches each have the function of a changeover switch, and control commands for the switches of each bridge branch, and thus each phase, are effected by means of sine undershoot modulation, i. is formed by intersecting a switching frequency triangular carrier signal which is the same for all phases and having a sinusoidal phase modulation function which is in phase with a desired output phase voltage fundamental of the respective phase. In this case, each of the n total phase modulation functions is formed by adding a respective offset-free basic phase modulation function and an offset, the offset having the same value for all n phases.
    公开号:CH714100A2
    申请号:CH01071/17
    申请日:2017-08-29
    公开日:2019-03-15
    发明作者:Walter Kolar Johann；Bortis Dominik；Marios Antivachis Michail
    申请人:Eth Zuerich；
    IPC主号:
    专利说明:

    Description [0001] Three-phase DC / AC converters, i.A. termed three-phase inverters, are industrially used for feeding three-phase electrical machines from the input DC windings, the star point of the windings being insulated, since due to the three-phase nature, a return conductor from the star point to the DC input side of the inverter can be dispensed with, with a reduction the realization costs result. This advantage also remains upright if a three-phase low-pass output filter is arranged between the inverter and the machine in order to avoid steep voltage edges which can impair the service life of the machine insulation and secondly to avoid switching-frequency harmonics of the stator current or high-frequency losses in the stator windings. Then, at each phase, branching from the output terminal of the associated inverter bridge branch, a filter inductance against the associated machine terminal, i. put the associated phase terminal of the stator winding; Furthermore, filter capacitors are arranged in a star connection branching off from the machine phase terminals, the filter capacitor star point being connected to the negative rail of the DC input DC voltage (referred to below as a negative DC rail). In addition to this lower filter capacitor star circuit can be additionally provided another, upper star circuit of filter capacitors whose star point is connected to the positive DC rail, then in each phase, the parallel connection of the associated capacitors of the lower and upper star connection is effective.
    The three-phase inverter is formed by three bridge arms, each bridge branch has two in series of the positive against the negative DC rail switch, for example, transistors with antiparallel freewheeling diodes, and the connection point of both transistors forms the output terminal of the bridge branch, and always only one the two transistors is in the through state, or both transistors are locked. In the turn-on of the upper transistor, the output terminal is then connected to the positive DC bus and in the turn-on of the lower transistor to the negative DC rail, which seen each branch bridge starting from the output terminal has the function of a switch between positive and negative DC rail. According to the state of the art, the switches of the individual phases are now operated at a constant clock frequency such that a pulse width modulated alternating voltage is formed at a phase output terminal measured against the virtual center of the DC voltage supplying the inverter (hereafter referred to as virtual DC voltage center) whose basic oscillation (hereafter referred to as Output phase voltage fundamental) denotes the desired output frequency and whose amplitude has the required output phase voltage amplitude. The control commands of the switch of each phase are thereby in the simplest case by means of sine undershoot modulation, i. is formed by intersecting a switching frequency triangular carrier signal which is the same for all phases with a sinusoidal phase modulation function (sinusoidal phase modulation function) in phase with the desired output phase voltage fundamental having the desired output frequency and the desired relative amplitude, the limit of the linear modulation range (hereinafter referred to as the sine modulation output limit ) is reached, or the maximum output phase voltage fundamental oscillation in the amount of half the DC input voltage is generated when the phase modulation function amplitude is selected equal to the amplitude of the triangular carrier signal. The linear modulation range is characterized in that the amplitude of the fundamental output phase voltage oscillation formed directly from the multiplication of the ratio of the amplitude of the phase modulation function and the amplitude of the triangular carrier signal with half the DC input voltage.
    An increase of the drive limit by about 15% can be achieved by adding a third harmonic equal to all the phase modulation functions - the third harmonic is to see as a common-mode signal with triple output frequency, the phase relationship is chosen so that the resulting sum phase modulation functions in the vicinity of the maxima are reduced in value and raised in value before and after the zero crossings and thus have a trapezoidal course. The amplitude of the third harmonic is optimally to be selected equal to one fourth of the amplitude of the sinusoidal phase modulation function.
    As mentioned above, a smooth phase terminal voltage is formed by the low pass output filter for the powered alternator. At the filter inductance, the difference of the inverter output phase voltage and the machine phase terminal voltage accordingly occurs in each phase. The switching-frequency component of this voltage results in a switching-frequency ripple of the filter inductance current or in high-frequency losses of the filter inductance, or a minimum value of the filter inductance is to be provided for limiting the ripple. The critical case relevant for the selection of the filter inductance value is given when the inverter output phase fundamental voltages or the bridge branch output phase voltages or the machine phase terminal voltages have a very small amplitude or a low degree of modulation. The output of each inverter bridge branch then has approximately a 50% duty cycle, i. the bridge leg outputs are then connected to the negative DC rail nearly during the entire first half of a clock period with the positive and almost throughout the entire second half of a clock period. Accordingly, at the filter inductances switching frequency, there are alternatingly high positive and negative voltage time areas and thus high switching-frequency current fluctuations. Accordingly, for controlling this operating point, relatively high inductance values are to be provided, which result in a relatively high constructional volume of the filter inductances, or a relatively high current fibrillation occurs in the filter inductances, which leads to a reduction of the energy conversion efficiency due to high-frequency losses.
    The object of the invention is therefore to provide a control method for the inverter bridge arms such that the occurring across the filter inductance voltage time surfaces or the switching frequency Stromrippei is minimized in the filter inductances, whereby the inductance and thus the construction volume of the filter inductances can be reduced or for a given filter inductance over conventional control lower high frequency losses of the filter inductances occur.
    The object is achieved by a method according to the claims.
    Thus, the method is used to drive an n-phase inverter with n bridge arms for feeding an n-phase electric machine (the winding star point is carried out in isolation), wherein between inverter and machine an n-phase low-pass output filter is arranged, the bridge branches respectively have the function of a switch, and control commands for the switches of each bridge branch and thus each phase by means of sine undershoot modulation, ie are formed by intersecting a switching frequency triangular carrier signal which is the same for all phases and having a sinusoidal phase modulation function (sinusoidal phase modulation function) which is in phase with a desired output phase voltage fundamental of the respective phase. In this case, each of the n total phase modulation functions is formed by adding a respective offset-free basic phase modulation function and an offset, and the offset has the same value for all n phases.
    The basic phase modulation function is thus a phase modulation function without DC component, the total phase modulation function is that which is used to drive the switch.
    In the method, therefore, the phase modulation functions are modified such that low-frequency common-mode components of the bridge branch output phase voltages are maximized, wherein the modification is made so that the maximum generated by the inverter amplitude of the fundamental of the bridge branch output phase voltages remains unchanged.
    The applicability of the above outlined concept is explained by the fact that due to the free neutral point of the stator windings of the three-phase machine fed ultimately only the differences of the measured against the virtual center of the DC input voltage filter capacitor voltages, i. the chained low-pass filter output voltages or, again relative to phase magnitudes, the differential mode components of the filter capacitor voltages take effect. Common mode components (each filter capacitor voltage can be seen in the sense of a three-phase system as the sum of a push-pull and a common mode component) have no influence on the current consumption of the alternator or their power consumption. If a common-mode voltage is added to a phase modulation function, the resulting pulse width modulated output voltage of the associated bridge branch has a low frequency and a switching frequency (high frequency) differential mode and a low frequency and a switching frequency (high frequency) common mode component, wherein the low frequency balanced component equal to the interest for feeding the machine , Bridge branch output phase fundamental oscillation mentioned in the beginning which must have a defined value depending on the operation of the machine. If now taken into account that the pulse width modulated always has the same spectral power due to the amplitude always equal to half the intermediate circuit voltage regardless of the pulse width ratios, or in other words the sum of all voltage components results in any case the pulse width modulated inverter output phase voltage, it is clear that the magnification of a In any case, the low-frequency voltage component must lead to a reduction in the switching-frequency voltage components. Since the low-frequency push-pull component is defined by the operation as mentioned above, the low-frequency common-mode voltage component remains for minimizing the sum of the switching-frequency DC and negative-mode voltage component, which ultimately represents the switching-frequency voltage across the filter inductance and is thus responsible for the switching-frequency current ripple in the filter inductance , whose value is limited by the fact that within each pulse period, an intersection of each phase modulation function must take place in the triangular carrier signal, ie the phase modulation function may have at most the positive or negative value of the (positive) amplitude of the triangular carrier signal.
    In the simplest case, a constant (frequency zero) voltage value (offset) can be selected for the low-frequency common mode component. The sine modulation function of the phases of a prior art system is characterized by a positive offset, i. for all phases equal in each case shifted such that the maximum values of the resulting total phase modulation functions become equal to the amplitude of the triangular carrier signal. For a modulation, i. a relative sine (negative) output voltage amplitude (based on half the input DC voltage) of 10% is thus added a common mode shift of 90%. Thereby, the duty cycle of the pulse width modulated bridge branch output voltages of 0.4 to 0.6 is shifted to 0.8 to 1.0, which results in significant smaller switching frequency voltage time across the Filterinduktvitäten and thus in a massive reduction of the Filterinduktivitätsstromrippei or for a comparison with the prior art ripple the inductance value significantly reduced or the switching frequency can be lowered, whereby a reduction of the switching losses of the inverter or improving the efficiency of energy conversion is achievable.
    Increases the modulation, we offset the offset back so far that the total phase modulation functions again reach the triangular carrier signal amplitude only in discrete points and are otherwise below this level. However, correspondingly higher output phase fundamental oscillations are then formed, which also act in the direction of a reduction of the switching-frequency filter inductance voltages.
    In sum, by using the inventive method a significant advantage in terms of design of the output filter (volume) or the efficiency of the overall system (inverter and output filter) can be achieved.
    In addition to a positive offset can be used in a mutually analogous manner, a negative offset application, in which case the value of the offset is chosen in each case so that the Gesamphasenmodulationsfunktionen reach only in discrete points the negative value of the amplitude of the triangular carrier signal and otherwise smaller in magnitude Have values.
    The displacement (addition of an offset) previously described for sinusoidal phase modulation functions can advantageously also be used for sum phase modulation functions, in which case a magnitude slightly higher offset value can be selected and thus a slight further improvement of the performance is possible.
    As mentioned above, in systems implemented according to the prior art, a third harmonic (typically also a sine function) with an amplitude equal to% of the amplitude of the sinusoidal phase modulation function is used to extend the modulation range by 15% with respect to sine modulation. It is now possible to maximize the amplitude of the third harmonic in the sense of maximizing the low-frequency component of the pulse width-modulated bridge branch output voltages (or maximum reduction of switching-frequency components). be so large that the resulting from addition of the sinusoidal phase modulation functions and the maximum 3rd harmonic total phase modulation functions in discrete points reach the positive or negative peak (amplitude) of the triangular carrier signal of the pulse width modulation and remain limited to smaller values. Accordingly, the amplitude of the 3rd harmonic is to decrease with increasing modulation level and becomes equal to the amplitude of a third harmonic according to the prior art at the modulation limit.
    As a closer analysis shows, this principle in the entire modulation range applicable method at high Aussteuergraden (about 50% maximum modulation) is preferable to an offset shift of the modulation functions.
    The previously described offset shift of the phase modulation functions or extension of the sinusoidal phase modulation functions with a maximum 3rd harmonic can be advantageously coupled with a reduction of the switching frequency (reducing the frequency of the triangular carrier signal), which is a corresponding reduction in the switching losses of the inverter or improvement the efficiency of the energy conversion leads, wherein the frequency reduction can be selected with regard to a ripple of the current in the filter inductances which is equal to the prior art control, and is then set as a function of the modulation level.
    It should be noted that the offset shift of modulation signals can also be used advantageously for inverters of a load with two phase terminals. The inverter therefore has two bridge branches in this case. Analogously, the offset shift can also be applied more than three phases.
    In the following, the subject invention based on preferred embodiments, which are illustrated in the accompanying drawings, explained in more detail. It shows schematically in each case:
    Fig. 1: Circuit diagram of the power part of a three-phase inverter with three-phase load with isolated neutral point (equivalent circuit diagram of the stator winding system of a three-phase alternator, induced voltages not shown).
    Fig. 2: Switching frequency triangular carrier signal of the pulse width modulation and sinusoidal phase modulation functions (left) and resulting current in an inductance of the output low-pass filter shown for small modulation over an output voltage period; (a) Conditions in realization according to the prior art; (b) ratios for positive off-set displacement and (c) ratios for negative offset shift of sinusoidal phase modulation functions. The achievable with the use of the method reduction of the switching frequency Rippeis the Filterinduktivitätsstromes immediately becomes clear.
    Fig. 3: Switching frequency triangular carrier signal of the pulse width modulation and sum phase modulation functions (left) and resulting current in an inductance of the output low pass filter shown for small modulation over an output voltage period; (a) Conditions in realization according to the prior art; (b) ratios for addition of a 3rd harmonic of maximum amplitude. The achievable with the use of the method reduction of the switching frequency Rippeis the Filterinduktivitätsstromes immediately becomes clear.
    FIG. 4 shows the rms value of the current in the inductances of the output low-pass filter, above the modulation level for control of the inverter according to the prior art (a); FIG. with positive offset shift (b) and (c) for addition of a third harmonic with maximum amplitude. It becomes clear that, starting at a modulation level of 50%, the maximization of the amplitude of the third harmonic of an offset
    Displacement leads to a greater reduction in Ripple RMS. For small modulation levels, the offset shift clearly has a higher performance.
    权利要求:
    Claims (9)
    [1]
    claims
    1. A method for driving an n-phase inverter (1) with n bridge arms for feeding an n-phase electric machine (2), wherein between the inverter (1) and machine (2) arranged an n-phase low-pass output filter (3) is, with the bridge branches each having the function of a switch, and control commands for the switches of each bridge branch and thus each phase by means of sinusoidal modulation, ie by forming a switching frequency triangular carrier signal which is the same for all phases and having a sinusoidal phase modulation function in phase with a desired output phase voltage fundamental of each phase, characterized in that each of the n total phase modulation functions is formed by addition of a respective offset-free basic phase modulation function and an offset, and the offset has the same value for all n phases.
    [2]
    2. The method according to claim 1, wherein the offset has a constant value.
    [3]
    3. The method according to claim 2, wherein the offset has a positive value.
    [4]
    4. The method according to claim 3, wherein the offset has a negative value.
    [5]
    5. The method according to claim 1, wherein the offset varies while having three times the frequency of the Ausgangsphasenspan fundamental oscillations.
    [6]
    6. The method according to claim 3, wherein an amplitude of the offset, to maximize a low-frequency portion of the pulse width modulated bridge branch output voltages, is chosen so large that the resulting from addition of the basic phase modulation function and the offset total phase modulation functions in discrete points a positive or negative peak reach the triangular carrier signal of the pulse width modulation and remain limited to smaller values.
    [7]
    7. The method according to any one of the preceding claims, wherein a switching frequency of the switching-frequency triangular carrier signal in response to a Aussteuergrades the total phase modulation functions is reduced.
    [8]
    8. The method according to any one of claims 1 to 7, wherein n is equal to two.
    [9]
    9. The method according to any one of claims 1 to 7, wherein n is equal to three.
    类似技术:
    公开号 | 公开日 | 专利标题
    EP2391522B1|2021-07-07|Dc/dc converter and ac/dc converter
    DE102008014898A1|2009-09-24|Method for controlling a multiphase power converter with distributed energy stores at low output frequencies
    DE112008001796B4|2022-03-10|Inverter system and control method
    DE10108766A1|2001-10-25|Pulse width modulation controlled power conversion unit
    WO2014206704A1|2014-12-31|Converter assembly having multi-step converters connected in parallel and method for controlling said multi-step converters
    DE102017115639A1|2019-01-17|Reduction of ripple current during switching operations of a bridge circuit
    DE102017212462A1|2019-01-24|Galvanically coupled electrical converter
    DE102011116593B4|2014-11-13|Inverter with asymmetrical chokes and a control unit for asymmetric operation of the chokes
    EP2928060A1|2015-10-07|Modular frequency converter circuit with submodules having different switching capacities
    EP3602762B1|2021-07-28|Inverter
    CH714100A2|2019-03-15|Method for controlling a polyphase inverter.
    CH715005B1|2021-10-29|Device for converting a DC voltage that varies within wide limits into a multi-phase AC voltage with variable frequency and amplitude.
    EP2928054A1|2015-10-07|Modular power converter circuit with submodules which are operated in linear mode
    EP2409394B1|2016-05-18|Method for operating an inverter circuit and device for performing the method
    WO2019057771A1|2019-03-28|Ac/dc converter having step-up/step-down converter phase modules
    EP2985896B1|2017-01-25|System for increasing the network-side power factor of three phase ec motors
    EP2536019B1|2018-01-03|Method for controlling an inverter
    EP3806314A1|2021-04-14|Inverter for an alternating current grid
    DE102012112902A1|2013-06-27|Method for controlling multi-phase inverter bridge switches of inverter for photovoltaic system, involves setting upper fixed value by adding another correction value, if predetermined upper threshold value exceeds duty cycle
    DE102011116615A1|2012-12-20|Method for controlling three-phase converter for supply of voltage to three-phase system e.g. induction machine, involves switching operation of converter between modulation techniques, based on operating state of three-phase system
    AT523973A1|2022-01-15|DC converter with extended voltage range
    CH715813A2|2020-08-14|Method for regulating a three-phase pulse rectifier system with an intermediate circuit.
    WO2013116885A2|2013-08-15|Ac/dc voltage transformer and method of operation therefor
    AT412179B|2004-10-25|METHOD FOR MINIMIZING THE SWITCHING FREQUENCY CURRENT CURRENT HARMONICS OF A TRIANGULAR CIRCUIT OF SINGLE-PHASE PULSE RECTIFIER SYSTEMS
    WO2013092034A1|2013-06-27|Method for controlling a power converter circuit
    同族专利:
    公开号 | 公开日
    CH714100B1|2021-10-29|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CH01071/17A|CH714100B1|2017-08-29|2017-08-29|Method for controlling a multi-phase inverter.|CH01071/17A| CH714100B1|2017-08-29|2017-08-29|Method for controlling a multi-phase inverter.|
    [返回顶部]