Fault-tolerant operation method and device for an alternating-current excited motor

Abstract

The present invention relates to a fault-tolerant operation method and device for an alternating current excited motor. The converter of the alternating current excited motor comprises multiple groups of parallel-connected ANPC three-level inverters. When a fault occurs in one phase of a single ANPC three-level inverter, by controlling the voltage of the faulty phase to be zero and the voltages of the two non-faulty phases to be line voltages, a three-phase symmetrical voltage is output by the ANPC three-level inverter, and the remaining non-faulty ANPC three-level inverters equally divide the remaining power, so that the power of the converter meets the requirements of the alternating current excited motor, and uninterrupted fault-tolerant operation of the alternating current excited generator is realized.

Description

Technical Field

[0001] The present invention relates to a fault-tolerant operation method and device for an alternating current excited motor. Background Art

[0002] An alternating current excited generator belongs to a wound-rotor induction motor. By injecting alternating current into the rotor winding, three-phase excitation current with variable frequency, adjustable amplitude, and controllable phase can be provided, enabling the motor to have a wider operating range and better efficiency. Compared with traditional synchronous motors, the adjustable amount of the excitation current of a synchronous generator is only the amplitude, so generally only the reactive power can be adjusted; while for an alternating current excited motor, there are three adjustable amounts of the excitation current: one is the amplitude of the excitation current; the second is the frequency of the excitation current; the third is the phase of the excitation current.

[0003] To match the volatility and intermittency of new energy, variable-speed pumped storage units using alternating current excited motors have been widely used. With the development of the power grid and the progress of pumped storage technology, the single-machine capacity of alternating current excited motors has increased rapidly. Increasing the head of a pumped storage power station can store a large amount of energy when the water storage volume decreases. With the increase of the single-machine capacity, the pump-turbine has a tendency to develop towards higher heads, and the speed of the alternating current excited motor also increases accordingly. However, limited by the capacity of the power electronic converter, it is difficult to use a single power electronic converter to provide excitation current for an alternating current excited motor. Currently, the parallel connection of multiple power electronic converters (inverters) is usually adopted to expand the equivalent capacity of the excitation converter to meet the excitation capacity required by a large-capacity alternating current excited motor. In high-power medium-voltage scenarios, active-clamped ANPC three-level inverters are mostly used. In summary, the application of multi-converter parallel connection and multi-level converters increases the number of power devices, and the topological structure is more complex, increasing the probability of failure. However, this structure has the advantage of power device redundancy. When a fault occurs, it can work at a low voltage level using its own redundancy. When one or more converters are in a fault state due to some reason, the existing control method is to withdraw the faulty inverter from operation. The existing control method will reduce the overall power output of the alternating current excited motor. In some application environments, it is necessary to ensure that the alternating current excited motor outputs a certain power. However, if an inverter withdraws from operation, it will lead to a power deficit. Summary of the Invention

[0004] The object of the present invention is to provide a fault-tolerant operation method and device for an alternating current excited motor, which can operate in a fault-tolerant manner and effectively ensure power output in the case of a fault in the inverter.

[0005] Based on the same inventive concept, the present invention has two independent technical solutions:

[0006] 1. A fault-tolerant operation method for an AC-excited motor. The AC-excited motor converter includes multiple groups of parallel ANPC three-level inverters. When a phase of a single ANPC three-level inverter fails, by controlling the voltage of the faulty phase to zero and the voltages of the two non-faulty phases to the line voltage, a three-phase symmetrical voltage is output by this ANPC three-level inverter, and the remaining non-faulty ANPC three-level inverters evenly divide the remaining power, so that the power of the converter meets the requirements of the AC-excited motor, realizing the uninterrupted fault-tolerant operation of the AC-excited generator.

[0007] Further, when a phase of a single ANPC three-level inverter fails, the output terminal of the faulty phase is connected to the midpoint of the DC bus, making the output voltage of the faulty phase zero; modulating the voltages of the other two phases so that the amplitudes of the other two phases are times that in normal operation, and the amplitudes of the output line voltages are the same, then the output power of a single ANPC three-level inverter is where P m represents the power of a single inverter in normal operation.

[0008] Further, when an A-phase fault occurs in a single ANPC three-level inverter, modulating the three-phase voltages of the ANPC three-level inverter, the specific formulas are as follows.

[0009]

[0010] In the formula, U mA , U mB , U mC are the modulation voltages of the A, B, and C phases of the ANPC three-level inverter, ω is the grid angular frequency, is the initial phase angle of the A-phase voltage before the fault, and m is the modulation ratio;

[0011] If a B-phase fault occurs, the three-phase modulation voltages of the ANPC three-level inverter can be expressed as

[0012]

[0013] If a C-phase fault occurs, the three-phase modulation voltages of the ANPC three-level inverter can be expressed as

[0014]

[0015] Further, when a single ANPC three-level inverter fails,

[0016] If n represents the number of inverters of the parallel ANPC three-level inverters, P m represents the power of a single ANPC three-level inverter in normal operation, P eLet \(P_{total}\) represent the required total power, then modulate the single ANPC three-level inverter with a fault to make its output power The remaining ANPC three-level inverters evenly divide the remaining power, where the remaining power is \(P\) e and the difference between them.

[0017] Furthermore, when a single ANPC three-level inverter has a fault, if \(P\) e \(<(n - 1)\times P\) m , then the single ANPC three-level inverter with a fault stops operating, and the remaining \(n - 1\) ANPC three-level inverters evenly divide the required total power \(P\) e .

[0018] Furthermore, when a single ANPC three-level inverter has a fault, if \(P\) e \(<(n - 1)\times P\) m , then modulate the single ANPC three-level inverter with a fault to make its output power The remaining ANPC three-level inverters evenly divide the remaining power, where the remaining power is \(P\) e and the difference between them.

[0019] Furthermore, when \(k\) ANPC three-level inverters have faults, \(k>1\),

[0020] If Let \(n\) represent the number of parallel ANPC three-level inverters, \(P\) m represent the power of a single ANPC three-level inverter during normal operation, \(P\) e represent the required total power,

[0021] then modulate \(p\) ANPC three-level inverters with faults, where \(m + 1\leq p\leq k\), so that the output power of each of the \(p\) ANPC three-level inverters with faults is The \(n - k\) non-faulty ANPC three-level inverters evenly divide the remaining power, where the remaining power is \(P\) e and the difference between them.

[0022] Furthermore, when \(k\) ANPC three-level inverters have faults, \(k>1\), if \(P\) e \(<(n - k)\times P\) m , \(n\) represents the number of parallel ANPC three-level inverters, \(P\) m represents the power of a single ANPC three-level inverter during normal operation, \(P\) eIf \(P\) represents the required total power, then the \(k\) faulty ANPC three-level inverters stop operating, and the remaining \(n - k\) ANPC three-level inverters evenly divide the required total power \(P\). e 。

[0023] Further, when \(k\) ANPC three-level inverters fail, where \(k>1\), if \(P\) e <(n - k)×P m , \(n\) represents the number of parallel ANPC three-level inverters, \(P\) m represents the power of a single ANPC three-level inverter during normal operation, and \(P\) e represents the required total power, then modulate the \(q\) faulty ANPC three-level inverters so that the output power of each of the \(q\) faulty ANPC three-level inverters is The \(n - k\) non-faulty ANPC three-level inverters evenly divide the remaining power, and the remaining power is the difference between \(P\) e and .

[0024] 2. An inverter fault-tolerant operation device for an AC-excited motor, which is used to execute the above method.

[0025] The beneficial effects of the present invention are as follows:

[0026] When a phase of a single ANPC three-level inverter fails, by controlling the faulty phase voltage to zero and the non-faulty two-phase voltages to line voltages, the ANPC three-level inverter outputs three-phase symmetrical voltages, and the remaining non-faulty ANPC three-level inverters evenly divide the remaining power, so that the converter power meets the requirements of the AC-excited motor, realizing the uninterrupted fault-tolerant operation of the AC-excited generator. Through the above operation method, the present invention ensures that when a phase of the ANPC three-level inverter fails, it can still operate in a fault-tolerant manner and effectively guarantees the power output.

[0027] When a phase-A fault occurs, at this time the output of phase A is zero. If it is desired to achieve a sinusoidal current on the output side, the phase voltage modulation wave needs to be modified. Then the three-phase modulation voltages of the ANPC inverter can be expressed as

[0028]

[0029] In the formula, \(U\) mA , \(U\) mB , \(U\) mC are the three-phase voltage modulation waves of phases A, B, and C of the ANPC three-level inverter, \(\omega\) is the grid angular frequency, is the initial phase angle of the phase-A voltage before the fault, and \(m\) is the modulation ratio.

[0030] If a phase-B fault occurs, then the three-phase modulation voltages of the ANPC inverter can be expressed as

[0031]

[0032] If a C-phase fault occurs, the three-phase modulation voltages of the ANPC inverter can be expressed as

[0033]

[0034] Through the above inverter modulation method, the present invention further effectively ensures the reliability of the fault-tolerant operation of the inverter when a single-phase fault occurs, and ensures the power output ability.

[0035] When a single ANPC three-level inverter fails in the present invention, if n represents the number of ANPC three-level inverters connected in parallel, and P m represents the power of a single ANPC three-level inverter during normal operation, and P e represents the total required power, then modulate the faulty single ANPC three-level inverter so that its output power is The remaining ANPC three-level inverters equally divide the remaining power, and the remaining power is P e and The difference between them. When a single ANPC three-level inverter fails, if P e <(n - 1)×P m , then the faulty single ANPC three-level inverter exits the operation, and the remaining n - 1 ANPC three-level inverters equally divide the total required power P e . When a single ANPC three-level inverter fails, if P e <(n - 1)×P m , then modulate the faulty single ANPC three-level inverter so that its output power is The remaining ANPC three-level inverters equally divide the remaining power, and the remaining power is P e and The difference between them. The present invention gives different fault-tolerant operation methods when a single ANPC three-level inverter fails according to different power output and power demand situations, further ensures the reliability of the overall operation of the inverter, realizes the redistribution of the excitation power of the AC excited motor, maintains the constant excitation power of the AC excited motor, and further ensures the normal operation and power output of the unit.

[0036] When k ANPC three-level inverters fail in the present invention, k > 1, if n represents the number of ANPC three-level inverters connected in parallel, and P m represents the power of a single ANPC three-level inverter during normal operation, and P eLet \(P_{total}\) represent the required total power. If \(m + 1\leq p\leq k\) ANPC three-level inverters with faults occur among the modulated \(P\) ANPC three-level inverters, then the output power of each of the \(P\) faulty ANPC three-level inverters is The remaining power is shared equally among the \(n - k\) non-faulty ANPC three-level inverters, and the remaining power is \(P_{total}\) e And The difference between them. When \(k\gt1\) ANPC three-level inverters have faults, if \(P_{total}\) e \(<(n - k)\times P_{single}\) m where \(n\) represents the number of parallel ANPC three-level inverters, and \(P_{single}\) m represents the power of a single ANPC three-level inverter during normal operation, and \(P_{total}\) e represents the required total power. Then the \(k\) faulty ANPC three-level inverters are taken out of operation, and the remaining \(n - k\) ANPC three-level inverters share the required total power \(P_{total}\) e equally. When \(k\gt1\) ANPC three-level inverters have faults, if \(P_{total}\) e \(<(n - k)\times P_{single}\) m where \(n\) represents the number of parallel ANPC three-level inverters, and \(P_{single}\) m represents the power of a single ANPC three-level inverter during normal operation, and \(P_{total}\) e represents the required total power. Then \(q\) faulty ANPC three-level inverters are modulated so that the output power of each of the \(q\) faulty ANPC three-level inverters is The remaining power is shared equally among the \(n - k\) non-faulty ANPC three-level inverters, and the remaining power is \(P_{total}\) e And the difference between them. According to different power output and power demand situations, the present invention gives different fault-tolerant operation methods when \(K\) ANPC three-level inverters have faults, further ensuring the reliability of the overall operation of the inverter, realizing the redistribution of the excitation power of the AC excited motor, maintaining the constant excitation power of the AC excited motor, and thus ensuring the normal operation and power output of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the circuit schematic diagram of the existing ANPC three-level inverter;

[0038] Figure 2 is the schematic diagram of the parallel operation of the machine-side converters of the existing AC excited motor;

[0039] Figure 3 is the flowchart of the inverter fault-tolerant operation method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will be described in detail below in conjunction with the embodiments shown in the accompanying drawings. It should be noted, however, that these embodiments do not limit the present invention, and any equivalent transformation or substitution in terms of function, method, or structure made by those of ordinary skill in the art based on these embodiments shall fall within the protection scope of the present invention.

[0041] Embodiment 1:

[0042] Fault-tolerant operation method for an AC-excited motor

[0043] The converter of the AC-excited motor includes multiple groups of parallel ANPC three-level inverters. When a phase of a single ANPC three-level inverter fails, by controlling the voltage of the faulty phase to zero and the voltages of the non-faulty two phases to the line voltage, a three-phase symmetrical voltage is output by this ANPC three-level inverter, and the remaining non-faulty ANPC three-level inverters evenly divide the remaining power, so that the power of the converter meets the requirements of the AC-excited motor, realizing the uninterrupted fault-tolerant operation of the AC-excited generator.

[0044] In multiple groups of parallel ANPC three-level inverters (active-clamped three-level inverters), when a phase of a single ANPC three-level inverter fails, the output terminal of the faulty phase is connected to the midpoint of the DC bus, making the output voltage of the faulty phase zero; modulating the voltages of the other two phases so that the amplitudes of the other two phases are times that in normal operation, and the amplitudes of the output line voltages are the same, then the output power of a single ANPC three-level inverter is P m represents the power of a single inverter in normal operation.

[0045] Taking the fault of phase A of a single ANPC three-level inverter as an example, as Figure 1 shown, the schematic diagram of a single-phase circuit of the existing ANPC three-level inverter (schematic diagram of phase A circuit) is given. If phase A fails, the faults can be divided into three categories:

[0046] The first category: The switch tube VTa1 or the switch tube VTa4 fails;

[0047] The second category: The switch tube VTa2 or the switch tube VTa3 fails;

[0048] The third category: The clamping tube VTa5 or the clamping tube VTa6 fails.

[0049] When the above-mentioned first or second type of fault occurs, connect the output terminal of the faulty phase to the midpoint of the DC bus, and modulate the phase voltage through the clamping diodes VTa5 and VTa6 of the ANPC three-level inverter. When the phase voltage is operating normally, it is a sine wave with a 120° phase difference among phases A, B, and C. When a fault occurs in phase A, the output of phase A is zero at this time. If a sinusoidal current is to be achieved on the output side, the phase voltage modulation wave needs to be modified. Then, the three-phase modulation voltages of the ANPC inverter can be expressed as

[0050]

[0051] where U mA 、U mB 、U mC are the three-phase voltage modulation waves of phases A, B, and C of the ANPC three-level inverter, ω is the grid angular frequency, is the initial phase angle of phase A voltage before the fault, and m is the modulation ratio.

[0052] If a fault occurs in phase B, the three-phase modulation voltages of the ANPC inverter can be expressed as

[0053]

[0054] If a fault occurs in phase C, the three-phase modulation voltages of the ANPC inverter can be expressed as

[0055]

[0056] Therefore, after adopting the above method, in the new modulation mode, the available capacity of the converter becomes times the original. As shown in Figure 2 , when a single ANPC three-level inverter fails, if n represents the number of parallel ANPC three-level inverters, P m represents the power of a single ANPC three-level inverter during normal operation, and P e represents the total required power, then modulate the faulty single ANPC three-level inverter so that its output power is The remaining ANPC three-level inverters equally divide the remaining power, and the remaining power is the difference between P e and .

[0057] When a single ANPC three-level inverter fails, if P e < (n - 1) × P m , then modulation can be carried out in the following two ways.

[0058] In the first method, the single ANPC three-level inverter with a fault exits the operation, and the remaining n - 1 ANPC three-level inverters equally divide the total required power P. e .

[0059] In the second method, modulate the single ANPC three-level inverter with a fault so that its output power is The remaining ANPC three-level inverters equally divide the remaining power, where the remaining power is the difference between P e and .

[0060] If at this time the single faulty inverter operates at a derated power, and the total output of the n inverters still cannot meet the required power output.

[0061] As Figure 3 shown, when k ANPC three-level inverters have faults, k > 1,

[0062] If n represents the number of parallel ANPC three-level inverters, P m represents the power of a single ANPC three-level inverter when operating normally, P e represents the total required power, then modulate p faulty ANPC three-level inverters, where m + 1 ≤ p ≤ k, so that the output power of each of the p faulty ANPC three-level inverters is The n - k non-faulty ANPC three-level inverters equally divide the remaining power, where the remaining power is the difference between P e and .

[0063] When k ANPC three-level inverters have faults, k > 1, if P e < (n - k) × P m , n represents the number of parallel ANPC three-level inverters, P m represents the power of a single ANPC three-level inverter when operating normally, P e represents the total required power, then modulation can be performed in the following two ways.

[0064] In the first method, the k faulty ANPC three-level inverters exit the operation, and the remaining n - k ANPC three-level inverters equally divide the total required power P e .

[0065] In the second method, modulate q faulty ANPC three-level inverters so that the output power of each of the q faulty ANPC three-level inverters is n - k non - faulty ANPC three - level inverters equally divide the remaining power, where the remaining power is P e and the difference between

[0066] If at this time, k faulty inverters operate at derated power, and the total output of n inverters still cannot meet the required power output.

[0067] Embodiment 2:

[0068] An inverter fault - tolerant operation device for an AC - excited motor

[0069] The device is used to execute the method described in Embodiment 1

[0070] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not used to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

[0071] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above - mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non - restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A fault-tolerant operation method for an AC-excited motor, wherein the converter of the AC-excited motor comprises multiple groups of parallel ANPC three-level inverters, and is characterized in that: When a single-phase fault occurs in one phase of a single ANPC three-level inverter, by controlling the voltage of the faulty phase to zero and the voltages of the two non-faulty phases to the line voltage, a three-phase symmetrical voltage is output by the ANPC three-level inverter, and the remaining non-faulty ANPC three-level inverters evenly divide the remaining power, so that the converter power meets the requirements of the AC excited motor, and the uninterrupted fault-tolerant operation of the AC excited generator is realized; When a single-phase fault occurs in one phase of a single ANPC three-level inverter, the output terminal of the faulty phase is connected to the midpoint of the DC bus, so that the output voltage of the faulty phase is zero; Modulate the voltages of the remaining two phases so that the amplitudes of the remaining two-phase voltages are times that in normal operation, and the amplitudes of the output line voltages are the same. Then the output power of a single ANPC three-level inverter is where P m represents the power of a single inverter in normal operation.

2. The fault-tolerant operation method for an alternating current excited motor according to claim 1, characterized in that: When a phase-A fault occurs in a single ANPC three-level inverter, the three-phase voltages of the ANPC three-level inverter are modulated, and the specific formula is as follows. Wherein, U mA , U mB , U mC are the voltage modulation voltages of three phases A, B, and C of the ANPC three-level inverter, ω is the grid angular frequency, is the initial phase angle of phase A voltage before the fault, m is the modulation ratio, and t represents time; If a phase-B fault occurs, the three-phase modulated voltages of the ANPC three-level inverter can be expressed as If a phase-C fault occurs, the three-phase modulated voltages of the ANPC three-level inverter can be expressed as 3. The fault-tolerant operation method for an AC-excited motor according to claim 1, characterized in that: When a single ANPC three-level inverter has a fault; If n represents the number of inverter units of the parallel ANPC three-level inverter, and P m represents the power of a single ANPC three-level inverter during normal operation, and P e represents the total required power, then modulate the single ANPC three-level inverter that has failed so that its output power is and the remaining ANPC three-level inverters evenly divide the remaining power, where the remaining power is the difference between P e and the difference between them.

4. The fault-tolerant operation method for an AC-excited motor according to claim 3, characterized in that: When a single ANPC three-level inverter fails, if P e <(n - 1)×P m , then the single ANPC three-level inverter with the fault exits the operation, and the remaining n - 1 ANPC three-level inverters equally divide the total required power P e .

5. The fault-tolerant operation method for an AC-excited motor according to claim 3, characterized in that: When a single ANPC three-level inverter fails, if P e <(n - 1)×P m , then modulate the faulty single ANPC three-level inverter to make its output power The remaining ANPC three-level inverters evenly divide the remaining power, and the remaining power is the difference between P e and .

6. The fault-tolerant operation method for an alternating current excited motor according to claim 1, characterized in that: When k ANPC three-level inverters have faults, k > 1; If 0 ≤ m ≤ k - 1, n represents the number of inverter units of the parallel ANPC three-level inverter, and P m represents the power of a single ANPC three-level inverter during normal operation, and P e represents the total required power Then, for the ANPC three-level inverters with faults occurring in P units, where m + 1 ≤ p ≤ k, the output power of each of the P ANPC three-level inverters with faults is The remaining power is equally divided among the n - k ANPC three-level inverters without faults, and the remaining power is P e and the difference between them.

7. The fault-tolerant operation method for an alternating current excited motor according to claim 1, characterized in that: When k ANPC three-level inverters have faults, k > 1; If P e <(n - k)×P m , n represents the number of inverter units of the parallel ANPC three-level inverter, P m represents the power of a single ANPC three-level inverter during normal operation, P e represents the total required power Then the k ANPC three-level inverters with faults will withdraw from operation, and the remaining n - k ANPC three-level inverters will equally divide the total required power P e .

8. The fault-tolerant operation method for an alternating current excited motor according to claim 1, characterized in that: When k ANPC three-level inverters have faults, k > 1; If P e <(n - k)×P m , where n represents the number of inverter units of the parallel ANPC three-level inverter, and P m represents the power of a single ANPC three-level inverter during normal operation, and P e represents the total required power. Then, modulate q ANPC three-level inverters with faults so that the output power of each inverter among the q ANPC three-level inverters with faults is The remaining power is evenly divided among n - k non-faulty ANPC three-level inverters. The remaining power is the difference between P e and .

9. An inverter fault-tolerant operation device for an AC-excited motor, characterized in that: For performing the method according to any one of claims 1 to 8.

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