Fault simulation experiment system for wind power converter

Abstract

A wind power converter fault simulation experiment system comprises a converter and is composed of a driving part, an open-circuit fault simulation part, a control part and a measurement part. The driving part is composed of a converter main circuit and an alternating current motor, the converter controls the rotating speed of the alternating current motor and simulates load changes, and the alternating current motor is electrically connected with the output end of the converter; the open-circuit fault simulation part is an integrated power supply driving module of the converter and is composed of a three-phase IGBT converter bridge with a basic structure; the control part is a frequency input knob of the converter and is used for controlling the change of the input frequency of the converter; the measuring part is composed of a high-voltage probe and an oscilloscope, the high-voltage probe is electrically connected with the output end of the converter and the oscilloscope, and the output voltages Uab, Ubc and Uca of the converter are measured. According to the utility model, powerful support can be provided for fault research, diagnosis and repair of the wind power converter, and healthy development of the wind power generation technology is promoted.

Description

TECHNICAL FIELD

[0001] The utility model relates to doubly fed induction wind power generation technical field, especially wind power converter technical field, and is especially one kind of wind power converter fault simulation experiment system. BACKGROUND

[0002] With the wide application of wind power generation technology, wind power converter as the key equipment in wind power generation system, converts the unstable AC power generated by wind driven generator into frequency and voltage stable AC power to meet the grid connection requirements, and realizes the variable speed constant frequency control of wind driven generator, power regulation and protection of system, etc., to ensure the efficient, stable and reliable operation of wind power generation system. Its stable operation plays a crucial role in the performance and reliability of the whole wind power system. In the actual operation data of wind power field, the converter is the most important and vulnerable component in the wind power generation system, and its fault will affect the power quality, damage expensive equipment such as generator, and even pose a great threat to the whole power grid. In order to reduce the downtime of wind power generation system, improve the maintenance efficiency and reduce the management cost, research and analysis of fault mechanism is considered as a powerful tool for good operation and maintenance of wind power generation system.

[0003] In practice, wind power converter has high voltage and high power problems, which makes the analysis and research of fault mechanism difficult, high cost and dangerous.

[0004] (1) High voltage and high power problem. In reality, wind power converter usually works in high voltage and high power state. Taking the converter matched with common large wind driven generator group as an example, its rated voltage can reach several thousand volts, and the rated power can reach several megawatts. Under such high voltage and high power conditions, it is difficult to analyze the fault of the converter. On the one hand, the fault detection and diagnosis equipment needs to have the ability to withstand high voltage and large current, which greatly increases the cost of related detection equipment. For example, oscilloscope, power analyzer and other professional instruments used in high voltage environment, the price is often several times or even dozens of times of ordinary laboratory instruments. On the other hand, high voltage and high power also bring great safety risk to the operators. If not handled properly, it may cause electric shock, electric arc and other serious accidents, which threatens the safety of personnel life.

[0005] (2) Fault analysis cost problem. In order to determine the fault cause, it is often necessary to disassemble and check the converter in detail, which involves complex process flow and professional technical personnel. Moreover, during the disassembly and inspection process, some easily damaged parts may be damaged again, further increasing the maintenance cost. Secondly, due to the diversity and complexity of the fault of the wind power converter, it is necessary to equip various types of detection equipment and tools, and to reserve a large amount of spare parts, which undoubtedly increases the operating cost of the enterprise. For example, for some special power module faults, it may be necessary to import spare parts from abroad, which not only has high price, but also has long procurement cycle, which seriously affects the normal operation of the wind farm.

[0006] In view of the above problems, building a small power converter simulation experiment platform with the same circuit topology structure as the actual wind power converter becomes an effective solution. Practical new type content

[0007] The utility model provides a kind of wind power converter fault simulation experiment system, solve the difficulty of analysis and research of the fault mechanism of wind power converter in actual production, high cost and dangerous problem.

[0008] The technical scheme adopted by the utility model is as follows:

[0009] A kind of wind power converter fault simulation experiment system, including converter, it is composed of drive part, open circuit fault simulation part, control part, measurement part;The drive part is composed of converter main circuit and alternating current motor, the converter controls the rotating speed of alternating current motor, simulates load change, and the output end of the alternating current motor and the converter is electrically connected;The open circuit fault simulation part is the integrated power supply driving module of converter, which is composed of three-phase IGBT converter bridge with basic structure;The control part is the frequency input knob of the converter, controls the change of converter input frequency;The measurement part is composed of high-voltage probe and oscilloscope, the high-voltage probe is electrically connected with the output end of the converter and the oscilloscope, realizes the measurement of the output voltage Uab, Ubc and Uca of the converter.

[0010] The three-phase IGBT converter bridge of the converter includes three-phase bridge arm, each bridge arm is composed of two IGBTs and has anti-parallel diode;Each power switch is controlled by its gate signal: when the gate signal is equal to 1, the switch is turned on;When the gate signal is 0, the switch is turned off;The two IGBT switches on each bridge arm work in complementary mode.

[0011] The open circuit fault connection structure of single power switch is that the gate of power switch and ground terminal GND are short-circuited with each other, so that the gate signal is 0.

[0012] The open circuit fault connection structure of the two power switches is that the gates of the two power switches are connected with the ground terminal GND at the same time, so that the two gate control signals are 0.

[0013] The utility model discloses the beneficial effect that:

[0014] (1) reduce cost and risk

[0015] The low-power converter simulation experiment platform can operate under low voltage and small current conditions, which greatly reduces the equipment cost required for fault analysis. Ordinary electronic measuring instruments can meet the detection needs of the experiment platform, without the need to purchase expensive high-voltage and high-current detection equipment. At the same time, the safety risk of the operator is also significantly reduced in the low-voltage and small-current environment for experiment and fault analysis, avoiding the safety accidents that may be caused by high-voltage and high-power operation, and protecting the life safety of personnel and the property safety of enterprises.

[0016] (2) in-depth study of fault mechanism

[0017] Through the low-power converter simulation experiment platform, researchers can conveniently simulate various fault conditions under actual operating conditions and conduct in-depth research on the fault mechanism of wind power converters. For example, the waveforms and parameters of input voltage and current can be accurately controlled to simulate fault scenarios such as power grid voltage fluctuation and lightning strike, and to observe the response and fault characteristics of the converter under these conditions. Through analysis and summary of a large amount of simulated fault data, the fault law of wind power converters can be more accurately mastered, providing strong theoretical support for fault diagnosis and prevention.

[0018] (3) optimize fault diagnosis and repair strategy

[0019] Using the simulation experiment platform, different fault diagnosis methods and repair strategies can also be verified and optimized. In actual operation, various diagnostic algorithms and repair measures can be quickly tried out to compare their effectiveness and feasibility, so as to select the most suitable fault diagnosis and repair scheme. This helps to improve the operation and maintenance efficiency of wind power converters, reduce downtime, reduce operation and maintenance costs, and improve the overall economic benefits of wind farms.

[0020] In summary, due to the high failure rate of wind power converters and the high cost and danger of fault analysis in reality, the utility model, on the basis of studying the fault mode of the back-to-back converter of the doubly-fed wind power generation system and the influence of the open circuit fault of the converter on electric energy and other components, builds a low-power converter fault simulation experiment platform that is exactly the same as the circuit topology structure of the back-to-back converter, which can provide strong support for the fault research, diagnosis and repair of wind power converters and promote the healthy development of wind power technology. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A topology structure diagram of a doubly-fed wind power generator (DFIG) wind power system;

[0022] Figure 2 A structure block diagram of the utility model;

[0023] Figure 3 A composition schematic diagram of the integrated power supply driving module of the utility model;

[0024] Figure 4 A schematic diagram for realizing open circuit fault simulation of a single power switch in the utility model;

[0025] Figure 5 A schematic diagram for realizing open circuit fault simulation of two power switches in the utility model;

[0026] Figure 6 A voltage signal Uab, Ubc and Uca diagram of the converter output in the normal state Normal in the embodiment of the utility model;

[0027] Figure 7 A voltage signal Uab, Ubc and Uca diagram of the converter output when T1 occurs open circuit fault in the embodiment of the utility model;

[0028] Figure 8 A voltage signal Uab, Ubc and Uca diagram of the converter output when T2 occurs open circuit fault in the embodiment of the utility model;

[0029] Figure 9 A voltage signal Uab, Ubc and Uca diagram of the converter output when T1 and T2 occur open circuit fault simultaneously in the embodiment of the utility model. DETAILED DESCRIPTION

[0030] The utility model and its effects are further described below with reference to the drawings.

[0031] The utility model is based on the converter of a doubly-fed induction power generation system, and its topology structure is shown in Figure 1 The experimental platform is built, and the fault signals under different motor speeds are obtained.

[0032] As shown in Figure 1 The doubly-fed wind power system mainly comprises blades, a gear box, a generator, a control system, a power converter and a filter. The blades rotate under the push of wind power to convert wind energy into mechanical energy, drive the generator to rotate after speed change through the gear box, convert the mechanical energy into electrical energy, and emit alternating current with variable amplitude and frequency; then, the power converter converts the alternating current with unstable frequency and amplitude into alternating current with stable frequency and amplitude, which meets the requirements of the power grid, and sends the alternating current into the power grid through the transformer.

[0033] Converter is an indispensable energy conversion component in wind power generation system, and is the control center of the whole electrical system, which directly affects the power generation efficiency. The power converter usually adopts the converter combination of back-to-back structure, and the converter close to the generator side is called generator side converter, and the converter close to the grid side is called grid side converter. The generator side converter tracks the maximum wind energy, realizes variable speed constant frequency power generation, and improves the operation efficiency of the power generation system. The grid side converter prevents the grid side current harmonic and outputs high-quality electric energy. The structures of the two sides of the power converter are the same, and space vector pulse width modulation strategy is adopted. Statistical research shows that, in the wind power converter, open circuit fault of power semiconductor device is one of the main reasons leading to converter fault.

[0034] As shown in Figure 2 , a fault simulation experiment system capable of simulating wind power converter is built, including a converter, which is composed of a driving part, an open circuit fault simulation part, a control part and a measurement part. The driving part includes a converter main circuit and an alternating current motor, the converter controls the speed of the alternating current motor to simulate load change, the alternating current motor and the output end (A, B, C end) of the converter are electrically connected; the open circuit fault simulation part is an integrated power supply driving module of the converter, which is composed of a three-phase IGBT commutation bridge with a basic structure; the control part is a knob of the converter, which controls the change of the input frequency of the converter, thereby controlling the speed of the alternating current motor; the measurement part is composed of a high-voltage probe and an oscilloscope, the high-voltage probe and the output end (A, B, C end) of the converter, and the oscilloscope are electrically connected, and the measurement of the output voltage Uab, Ubc and Uca of the converter is realized.

[0035] Table 1 Main parameters of the experimental system

[0036]

[0037] As shown in Figure 3 , the structure diagram of the open circuit fault simulation part is shown, Ti represents IGBT, G-Ti represents the gate of the corresponding IGBT, and GND represents the ground end; six power switches are simulated to have open circuit faults, including single power switch open circuit fault and two power switch open circuit fault.

[0038] Operation and function realization of the utility model

[0039] Based on the function of the wind power converter in the wind power generation system, the wind power converter fault simulation experiment system needs to realize the following functions:

[0040] (1) Meet the fault mode of the power switch in the existing wind power converter

[0041] The internal failure mechanisms of IGBT (Insulated Gate Bipolar Transistor) open circuit mainly include gate drive failure and thermal stress failure. The external failure mechanisms of IGBT open circuit mainly include solder wire falling off, solder wire breaking, solder layer cracking and drive board open circuit. These failure mechanisms eventually manifest as IGBT open circuit failure. Different power switches have different open circuit failure modes. Taking a grid-side converter as an example, when all six power switches are healthy, the converter works in a normal state, which is recorded as Normal. When open circuit failure occurs only in one power switch, there are six failure modes: T1, T2, T3, T4, T5 and T6. When the upper and lower power switches of the same bridge arm have open circuit failure at the same time, there are three combinations: T1 and T2, T3 and T4, and T5 and T6. When the two power switches of the same half-bridge have open circuit failure at the same time, there are six combinations: T1 and T3, T1 and T5, T3 and T5, T2 and T4, T2 and T6, and T4 and T6. When the two power switches of different half-bridges have open circuit failure at the same time, there are also six combinations: T1 and T4, T1 and T6, T3 and T2, T3 and T6, T5 and T2, and T5 and T4. Since the simultaneous failure of three or more power switches is very rare, the utility model researches the failure diagnosis of single-switch open circuit failure and double-switch open circuit failure. Therefore, there are 5 types of 22 modes (Normal + 21 failure modes) in total, as shown in Table 2.

[0042] Table 2 Open circuit failure mode

[0043]

[0044] (2) Realize open circuit failure of power switch

[0045] Taking a grid-side converter as an example, the converter includes three-phase bridge arms, each phase bridge arm is composed of two IGBTs and has an anti-parallel diode (referred to as a reverse freewheeling diode). The power switch Ti is controlled by a gate signal: when the gate signal is equal to 1, the switch is turned on; when the gate signal is 0, the switch is turned off. The two IGBT switches on each bridge arm work in a complementary mode; in order to prevent the DC bus voltage from being short-circuited, only one IGBT switch is turned on.

[0046] In a short-circuit manner, the gate G-Ti of the switch is connected with the ground end GND, so that the gate signal is 0, and the open circuit failure of the power switch is simulated. In this way, different IGBT open circuit failures can be obtained. For example: to simulate T1 open circuit failure, only need to connect the gate G-T1 of T1 with the ground end GND, so that the gate signal is 0, as shown in Figure 5As shown in Fig. 4, when open-circuit fault occurs in T1 or T2, only need to connect the gate G-T1 and G-T2 of T1 and T2 to the ground terminal GND at the same time, so that the two gate signals are 0, as shown in Fig. 5. Figure 6

[0047] (3) Measurement of converter output voltage signal under different fault modes

[0048] The high-voltage probe and oscilloscope are used to realize the voltage signal of the converter output under different fault modes U ab , U bc and U ca , for example, T1 or T2 open-circuit fault, T1 and T2 open-circuit fault at the same time, as shown in Fig. 4 and Fig. 5. Figure 7 , Figure 8 , Figure 9 It can be seen that when the IGBT open-circuit fault occurs, the output voltage of the converter will be distorted, and the distortion is different for different fault modes.

[0049] (4) Collection of multi-fault sample data

[0050] Through the control part, the converter frequency input knob is rotated, and when the input frequency of the converter changes from 1 Hz to 50 Hz at an interval of 1 Hz, the output voltage Uab, Ubc and Uca of the converter under 22 fault modes are measured. There are 22*3*50=3300 samples in total. The sampling frequency is 50 kHz, the sampling time is 0.2 s, and therefore the sample size is 10000.

[0051] (5) Usage of fault sample data:

[0052] 1) Signal preprocessing. Including denoising and normalization. Among them, denoising, because the collected signal often contains noise, needs to use filtering method to remove noise interference. Common filtering methods include low-pass filtering, high-pass filtering, band-pass filtering and wavelet denoising, etc. Normalization, the amplitude of the signal is normalized to a certain range, so as to eliminate the difference of measurement range and unit of different sensors, and facilitate subsequent analysis and processing. Common normalization methods include minimum-maximum normalization and Z-score normalization, etc.

[0053] ​2) Signal analysis. Including time domain analysis, frequency domain analysis, time-frequency analysis. Time domain analysis, directly observe the waveform of the signal in the time domain, analyze its amplitude, mean, variance, peak, kurtosis and other statistical parameters. These parameters can reflect the overall characteristics and changes of the signal. Frequency domain analysis, through Fourier transform, the time domain signal is converted into frequency domain signal, get the frequency spectrum diagram of the signal, analyze the frequency components and energy distribution of the signal, in the frequency domain, it can be more easily identified that the characteristic frequency related to the fault; Or use power spectral density estimation method, further analyze the power distribution of the signal at different frequencies, more accurately determine the fault characteristic frequency and its corresponding energy size. Time-frequency analysis, the signal is analyzed in both time and frequency dimensions, and the time-frequency distribution image is obtained. This method can simultaneously show the frequency variation of the signal at different times, and more comprehensively capture the time-varying characteristics of the signal.

[0054] 3) Feature extraction, after signal analysis, various types of feature parameters are extracted from the time domain, frequency domain and time-frequency domain analysis results according to the requirements, such as: statistical feature extraction, transformation-based feature extraction, model-based feature extraction. Among them, the extraction of statistical features includes time domain features, frequency domain features, time-frequency statistical features. Transformation-based feature extraction includes wavelet transform features, empirical mode decomposition features, etc. Model-based features include autoregressive model features, artificial neural network features.

[0055] 4) Fault mode recognition. After extracting the fault features from the fault samples, the fault mode recognition mainly uses traditional machine learning, deep learning, expert system and other methods. After identifying the fault mode of the converter, the corresponding evaluation index is needed to evaluate the performance of the diagnosis model, such as the performance evaluation index based on confusion matrix, including accuracy, precision, recall, specificity, false positive rate, false negative rate, F1 score and Matthews correlation coefficient.

Claims

1. A wind power converter fault simulation experimental system, comprising a converter, characterized in that, It consists of a drive section, an open-circuit fault simulation section, a control section, and a measurement section. The drive section comprises the main circuit of the converter and an AC motor. The converter controls the speed of the AC motor to simulate load changes, and the AC motor is electrically connected to the output terminal of the converter. The open-circuit fault simulation section is the integrated power drive module of the converter, which is basically composed of a three-phase IGBT converter bridge. The control section is the frequency input knob of the converter, which controls the change of the input frequency of the converter. The measurement section consists of a high-voltage probe and an oscilloscope. The high-voltage probe is electrically connected to both the output terminal of the converter and the oscilloscope to measure the output voltages Uab, Ubc, and Uca of the converter.

2. The wind power converter fault simulation experimental system according to claim 1, characterized in that, The converter's three-phase IGBT converter bridge includes three-phase bridge arms, each phase bridge arm consisting of two IGBTs and equipped with anti-parallel diodes; each power switch is controlled by its gate signal: when the gate signal is equal to 1, the switch is turned on; When the gating signal is 0, the switch is turned off; the two IGBT switches on each bridge arm operate in complementary mode.

3. The wind power converter fault simulation experimental system according to claim 2, characterized in that, The open-circuit fault connection structure for a single power switch is as follows: short-circuit the gate of the power switch with the ground terminal GND to make the gate signal 0.

4. The wind power converter fault simulation experimental system according to claim 2, characterized in that, The open-circuit fault connection structure for the two power switches is as follows: connect the gates of both power switches to the ground terminal GND simultaneously, so that the two gate control signals are 0.

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