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    • 专利摘要:
    Electric balancing method in a three-phase system. An electric balancing method is disclosed in a three-phase system. The steps are: obtain magnitude and phase of each simple output voltage; align a first simple tension with the real axis; choose two tensions and add a third conjugate complex voltage of the larger of the two above; calculate the sequences direct, inverse and homopolar annular the inverse sequence; calculate the direct and homopolar sequences of the new simple stress system; add direct sequence and homopolar sequence to the direct sequence and to the homopolar sequence calculate the new simple voltages from the new direct sequence voltage and the new homopolar sequence voltage with inverse sequence voltage equal to zero; repeat the previous two steps until the module of the new third simple voltage is equal to the module of the simple output voltage discarded in the third step. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2670472A1
    申请号:ES201631532
    申请日:2016-11-30
    公开日:2018-05-30
    发明作者:David SALVO LILLO；Abelardo Salvo Lillo；Antonio Poveda Lerma；José Luis Camps Soriano；Marcial ANTÓN PONS
    申请人:Power Electronics Espana SL；
    IPC主号:
    专利说明:

    image 1
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    being:
    image8
    image9
     rotate clockwise the system formed by simple tensions the angle
    image10 previously calculated:
    image11
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    Generally, at the output of the three-phase systems, what can be measured directly are the composite tensions. This second aspect of the invention is complementary to the first aspect of the invention but could also be used independently. In a third aspect of the invention, a three-phase system comprising the electric balancing method defined in the first aspect of the invention is disclosed. In a fourth aspect of the invention, a three-phase system comprising the electrical balancing method defined in the second aspect of the invention is disclosed. In an embodiment of the third aspect of the invention, the three-phase system comprises:
    image17 a three-phase power output (R, S, T);
     image18  power cells cascaded by each power line;
     image19  a control card for each power cell, which is configured to measure the voltage supplied by the cell to which it is associated and modify its voltage;
     image20  a control device connected with each control card and with the three-phase power output (R, S, T) to obtain the magnitude and phase of each simple voltage (UR, US, UT);
    in such a way that the control equipment modifies the magnitude and the phase of the tension of each cell through each control card until the output of the three-phase system reaches the new simple voltages (UR '', US '', UT '') .
    image21


    image22
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    In another embodiment of the third aspect of the invention, the power cell additionally comprises a bypass circuit, where the bypass circuit is closed when it receives a control instruction from the control card.
    BRIEF DESCRIPTION OF THE FIGURES
    Figure 1.- Medium voltage variator comprising a control equipment where the voltage balancing method of the present invention is implemented.
    Figure 2.- Power cell included in the medium voltage drive.
    Figure 3.- Representation of a five-cell inverter in phase and failure in three cells (cells C4, C5 and B5 that are not shown in the figure due to failure).
    Figure 4.- Medium voltage variator with imbalances caused by the inequality of the power cells in its manufacture.
    Figure 5.- Decomposition of an unbalanced system in its direct, inverse and homopolar sequences.
    Figure 6.- Vector decomposition of the Direct Sequence “SD”.
    Figure 7.- Vector decomposition of the Reverse Sequence “YES”.
    Figure 8.- Vector decomposition of the Inverse Sequence “SI” transformed to an anti-clockwise direction.
    Figure 9.- Vector decomposition of the Reverse Sequence “SI” in a vector system equivalent to that of Figure 8.
    Figure 10.-Vector decomposition of the Homopolar Sequence “SH”.
    Figure 11.- Flowchart of the electric balancing method in three-phase systems.
    Figure 12.- Vector representation of the simple output voltages of an unbalanced power inverter with alignment of an output voltage on the real axis.
    Figure 13.- Vector representation of the output voltages where one of them is the conjugate complex of the other.
    Figure 14.- Vector representation of the composite output voltages in equilibrium where the reversed inverse sequence condition is met.
    Figure 15.- Vector representation of the composite output voltages in equilibrium where the condition of the method stop is met.
    image28


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    PREFERRED EMBODIMENT OF THE INVENTION
    An exemplary embodiment of the invention is described below with an illustrative and non-limiting nature.
    For the exemplary embodiment, Figure 1 shows the topology of a medium voltage drive 1 whose three phase output (R, S, T) is connected to a motor 7. The medium voltage drive 1 comprises a phase change rectifier transformer 2, a power cell 3 connected in cascade, a control card 4, a control device 6 and a bypass circuit 5. The control card 4 is responsible for measuring the voltage supplied by the cell to which it is associated and detect, if any, a fault in the cell. The control card 4 communicates with the control equipment 6. The control equipment 6 can instruct the control card 4 to close the bypass circuit 5 in the event of a power cell failure. Alternatively, the control card 4 can close the bypass circuit 5 automatically when the card 4 detects a failure in the power cell 3. The control equipment 6 has implemented the method of balancing voltages (or currents) in such a way that acting on each of the power cells, the power output of the drive 1 is balanced. The operation of the control equipment 6 on each power cell 3 is carried out by modifying the magnitude and phase of the voltage or current of each of the power cells independently according to the method of the present invention. As described below, the method of the present invention allows to obtain a fully balanced power output in composite voltages or currents whether there is a failure in any of the power cells or if there are power variations in any of the power cells due to structural differences in their manufacturing and / or in the voltage / current supply received by the power cells.
    Power cell 3 is shown in Figure 2. Power cell 3 consists of a basic AC-DC-AC mono-polar inverter circuit. The cell has three alternating current inputs 8 L1, L2, L3, which are connected to a rectifier bridge 9, which is a diode bridge. The rectifier bridge 9 is connected to a continuous bus 10, and this to an inverter bridge 11. At the exit of the inverter bridge, the bypass circuit 5 is placed. The inverter bridge is composed of IGBT's that generate single-phase PWM voltage waves.
    image35
    image36


    image37
    In particular, an unbalanced three-phase electrical system in permanent regime can be decomposed into a balanced three-phase direct sequence system plus a balanced three-phase reverse sequence system plus a homopolar sequence system, see Figure 5.
      The Direct Sequence (
    image38 , or "SD", is a balanced three-phase sinusoidal system of voltages (or currents) of the same amplitude but decayed in electrical time and space 120º counterclockwise, see figure 6.
    The temporary electrical system can be expressed as a vector of three components:
    image39
    Each component of the system can be expressed as a temporary fasor that rotates in space counterclockwise:
    image40
    Another more compact way of representing the three-phase electrical system is through its spatial vector. To obtain it, it is enough to place the temporal magnitudes (not their phasors) on each spatial axis and add them:
    image41
    The Reverse Sequence
    image42 , or "YES", is a balanced three-phase sinusoidal system of voltages (or currents) of the same amplitude but decayed in electrical time and space 120º clockwise, see figure 7. Since the cosine function is even, the Tension system shown in Figure 7 is equivalent to a system whose temporary phasors rotate counterclockwise (in direct sequence) as follows (see Figure 8):
    image43
    image44


    image45
    This last system equivalent to the previous one, also has another equivalent (figure
    9):
    image46
    Although the direction of rotation of the temporal phasors changes, that of the associated spatial phasor does not change:
    image47
    Zero or Homopolar Sequence (
    , or "SH", is a system of three sinusoidal voltages (or currents) balanced of the same amplitude and phase and located in the same place in space, see figure 10. The temporary electrical system can be expressed as a vector of three components:
    image48
    image49
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    Each component of the system can be expressed as a temporary fasor that rotates in space counterclockwise:
    image51
    image52
    image53


    image54
    In the case of the zero or homopolar sequence, it is not possible to obtain a vector
    associated space, alreadythatthevectorsspace representexclusively
    complex polyphase systems.
    By so much,asystemelectricfromtensionsunbalanced,may
    decompose in the following sequences: direct, inverse and homopolar:
    image55
    If the inverse voltage system is subtracted from the inverse sequence voltage obtained from the previous expression, the new voltage system will not have an inverse sequence and therefore can be written as follows:
    image56
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    image62
    Step 8 (Figure 11; 38) The simple tensions (UR ’’, US ’’, UT ’’) associated with the S ’’ system are calculated. Therefore, UR ’’, US ’’ are equal in magnitude to UR, US ’, respectively, although different in phase.
    Step 9 (figure 11; 39) - The third simple voltage module (UT ’) calculated in step 8 is compared with the simple voltage module discarded in step 3 (see figure 15):
    image63
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    If both modules are equal, the method ends and the composite equilibrium tensions are UR ’’, US ’’, UT ’.
    If both modules are different, steps 7 and 8 are repeated modifying the direct sequence (SD) and homopolar (SH) voltages. This is equivalent to modifying “
    image67 "
    In figure 15 two equilateral triangles are shown. One of them T1 coincides with that shown in Figure 14 that would be formed by simple tensions (UR, US ’, U * S’). The second T2 is formed by turning an angle
    image68 counterclockwise UR (
    image69 UR ''), and by the turn that same angle
    image70 clockwise from US '(
    image71 US ''). Modification of the phase of the UR and US potentials at an angle
     image72 it is equivalent to adding a direct sequence potential and a homopolar sequence potential, which added to U * S ’results in UT’.
    Similar to what was done in step 5, in step 6, the UR vector is rotated an angle
     image73  counterclockwise (or time) and US ’the same angle, but in the opposite direction to the previous one, with the intention of maintaining the modules of these 2 vectors:
    image74
    image75
    This movement must correspond to the addition of a certain amount of direct sequence "SD" (UD) and homopolar sequence "SH" (UH). To calculate these quantities, remember that the direct sequence is a set of
    image76
    If you turn a certain angle:
    image77


    image78
    And the same goes for the homopolar sequence:
    image79
    Thus the following system of equations is obtained:
    image80
    These two equations unfold in a linear system of four:
    image81
    Separating terms:
    image82
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    权利要求:
    Claims (1)
    [1]
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    同族专利:
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20110134669A1|2009-12-07|2011-06-09|Kyosan Electric Mfg. Co., Ltd.|Unbalanced voltage compensation method, unbalanced voltage compensator, three-phase converter control method, and controller of three-phase converter|
    US5986909A|1998-05-21|1999-11-16|Robicon Corporation|Multiphase power supply with plural series connected cells and failed cell bypass|
    US8169107B2|2008-05-30|2012-05-01|Siemens Industry, Inc.|Method and system for reducing switching losses in a high-frequency multi-cell power supply|
    US8532230B2|2011-08-31|2013-09-10|Cisco Technology, Inc.|Instantaneous phasor determination for poly-phase electrical grids|CN109347350B|2018-11-14|2020-08-11|中南大学|Three-phase multi-level converter and battery SOC balance control method thereof|
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    ES201631532A|ES2670472B1|2016-11-30|2016-11-30|METHOD OF ELECTRICAL BALANCING IN A THREE-PHASE SYSTEM|ES201631532A| ES2670472B1|2016-11-30|2016-11-30|METHOD OF ELECTRICAL BALANCING IN A THREE-PHASE SYSTEM|
    EP17203046.2A| EP3331163B1|2016-11-30|2017-11-22|Method of electrical balancing in a three-phase system|
    ES17203046T| ES2759577T3|2016-11-30|2017-11-22|Electric balancing method in a three-phase system|
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