Fault diagnosis and fault-tolerant control method of position sensor of permanent magnet hydroelectric generator

Abstract

The present invention discloses a method for position sensor fault diagnosis and fault-tolerant control of a permanent magnet hydroelectric generator, comprising: obtaining detection values ​​of generator rotor position and speed; obtaining observation values ​​of generator rotor position and speed according to measured voltage and current values ​​in combination with a pre-built PMSG position observer; performing position sensor fault diagnosis according to the observation values ​​of the generator rotor position and speed and the detection values ​​of the generator rotor position and speed; and performing fault-tolerant control based on the observation values ​​of the generator rotor position and speed when diagnosing a position sensor fault. The present invention adopts a fault diagnosis method based on position observation of a surface-mounted permanent magnet synchronous generator back electromotive force model, and the residual obtained by comparing the detection value of the sensor with the observation value of the observer with a threshold value completes the fault diagnosis of the drive system, and the estimated value obtained by the position observer can realize fault-tolerant control after a sensor fault, which has great engineering practical value.

Description

Technical Field

[0001] The invention relates to the field of motor control, and in particular to a method for diagnosing and fault-tolerantly controlling a position sensor of a permanent magnet hydroelectric generator. Background Art

[0002] At present, most small hydropower stations generally use a hydropower generation system that is directly connected to the grid with a synchronous generator. The reactive power is adjusted by adjusting the rotor winding excitation current to meet the power factor requirements of hydropower grid connection. However, adjusting the excitation current will change the voltage of the connected grid, thereby affecting the quality of power. In addition, the rotor speed of the synchronous generator must be relatively static with the armature rotating magnetic field. Constrained by the grid frequency, the turbine operates at a fixed speed regardless of the working conditions. However, most small hydropower stations are run-of-river hydropower stations with a wide working head range and large flow changes. They cannot operate stably under a certain working condition, and fixed speed operation cannot maximize the efficiency of the turbine. Therefore, in order to improve the working efficiency of the turbine under different working conditions and improve the turbine's water energy capture capacity, a variable speed constant frequency technology is adopted, that is, when the working conditions of the turbine change, the operating speed is changed to track the maximum working efficiency of the turbine and improve the turbine output power. At the same time, the power generation system introduces power electronic power devices, so that the speed of the turbine generator is no longer related to the grid frequency, and the turbine always generates electricity at a frequency of 50Hz when the turbine changes speed.

[0003] The current mainstream variable speed hydropower generation systems include hydropower generation systems based on doubly fed induction motors and hydropower generation systems based on permanent magnet synchronous generators (PMSG). Among them, the permanent magnet synchronous hydropower generation system has the advantages of high power density, wide speed regulation range, and does not require gearboxes and slip rings, and has excellent adaptability to grid faults. The control method of permanent magnet synchronous generators generally adopts vector control based on magnetic field orientation, which is flexible and stable. In the variable speed hydropower generation system, PMSG is a multi-pole generator. High-performance vector control requires accurate rotor position and speed information to achieve accurate magnetic field orientation. Photoelectric encoders or rotary transformers are required to detect the position and speed of the rotor, which requires high performance of the detection device. At the same time, the installation of mechanical sensors will increase system cost, increase volume, reduce operating reliability, and be easily affected by the working environment. Its accuracy and performance are easily affected by the harsh operating environment around it, and it is easy to malfunction or even fail. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies in the prior art, the present invention provides a method for diagnosing and fault-tolerantly controlling a position sensor of a permanent magnet hydroelectric generator, so as to solve at least one of the above-mentioned technical problems.

[0005] The present invention is achieved according to the following technical solutions:

[0006] The method for fault diagnosis and fault-tolerant control of position sensors of permanent magnet hydraulic generators includes:

[0007] Obtain detection values ​​of generator rotor position and speed;

[0008] According to the measured voltage and current values, combined with the pre-built PMSG position observer, the observed values ​​of the generator rotor position and speed are obtained;

[0009] Performing position sensor fault diagnosis based on the observed values ​​of the generator rotor position and speed and the detected values ​​of the generator rotor position and speed;

[0010] When a position sensor failure is diagnosed, fault-tolerant control is performed based on the observed values ​​of the generator rotor position and speed.

[0011] The above technical solution adopts a fault diagnosis method based on the position observation of the back-electromotive force model of the surface-mounted permanent magnet synchronous generator. The residual obtained by the detection value of the sensor and the observation value of the observer is compared with the threshold to complete the fault diagnosis of the drive system. The estimated value obtained by the position observer can realize fault-tolerant control after the sensor failure, which has great engineering practical value.

[0012] As a further technical solution, the construction of the PMSG position observer includes: obtaining a rotor electrical angle and electrical angular velocity observation model based on a phase-locked loop controller according to a mathematical model of the permanent magnet synchronous generator, the observation value of the rotor electrical angle corresponds to the observation value of the rotor position, and the observation value of the rotor electrical angular velocity corresponds to the observation value of the speed.

[0013] As a further technical solution, the method also includes: obtaining a residual of the rotor position based on the observed value and the detected value of the rotor position, and comparing the residual of the rotor position with a threshold value of the rotor position to obtain a rotor position comparison result; obtaining a residual of the speed based on the observed value and the detected value of the speed, and comparing the residual of the speed with a threshold value of the speed to obtain a speed comparison result; and performing position sensor fault diagnosis based on the rotor position comparison result and the speed comparison result.

[0014] As a further technical solution, when the residual of the rotational speed exceeds a rotational speed threshold or the residual of the rotor position exceeds a rotor position threshold, it is diagnosed as a position sensor failure.

[0015] As a further technical solution, after diagnosing a position sensor fault, the position sensor fault diagnosis flag is set to position 1, and the operating mode of the generator system is switched to a fault-tolerant operating mode, in which the rotor position and speed values ​​obtained by the observer are used as the output of the operating mode switch.

[0016] As a further technical solution, after the fault flag of the position sensor is set to 1, the generator system keeps the fault flag set to 1 until the fault flag is set to 0 again.

[0017] As a further technical solution, after the fault-tolerant control strategy is implemented, regardless of whether the position sensor fails, the system can obtain the accurate position of the generator back-EMF vector, and then obtain the actual speed of the motor. At the same time, the position signal is used to decompose the current vector to form the torque excitation component under the orthogonal dq axis. Through the PI adjustment of the outer speed loop, the torque current given instruction is output, and the excitation current given instruction is set to zero. Then, through the PI adjustment of the current inner loop, the dq axis voltage given instruction is output. Finally, by using vector synthesis and vector transformation, it is restored to the stator voltage given vector instruction under the three-phase shaft system. After vector modulation, the PWM pulse that drives the converter is output, so that the actual speed and current track the given speed and current instructions, and the system is adjusted without static error.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] In order to solve the position sensor failure in the variable speed hydroelectric power generation system, the present invention adopts a position observer sensorless algorithm based on rotor position angle estimation as a redundant solution. The algorithm has good dynamic and steady-state performance and high parameter robustness. At the same time, the estimated value obtained by the position observer realizes the fault diagnosis and fault-tolerant control of the position sensor in the full speed range. The solution is simple, reliable and has strong engineering practicality. It significantly improves the reliability of the permanent magnet synchronous generator rotor position angle acquisition and ensures the stability and safety of the permanent magnet hydroelectric power generation system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of a method according to an embodiment of the present invention.

[0021] Figure 2 Schematic diagram of a PMSG vector coordinate system according to an embodiment of the present invention.

[0022] Figure 3 4 is a structural block diagram of a PMSG position observer according to an embodiment of the present invention.

[0023] Figure 4 4 is a schematic diagram of a position sensor fault diagnosis principle according to an embodiment of the present invention.

[0024] Figure 5 4 is a schematic diagram of a position sensor fault-tolerant control principle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions of various embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] The present invention provides a method for diagnosing and controlling a position sensor fault of a permanent magnet hydraulic generator. Figure 1 As shown, it includes: obtaining detection values ​​of generator rotor position and speed; obtaining observation values ​​of generator rotor position and speed based on measured voltage and current values ​​in combination with a pre-built PMSG position observer; performing position sensor fault diagnosis based on the observation values ​​of generator rotor position and speed and the detection values ​​of generator rotor position and speed; when a position sensor fault is diagnosed, performing fault-tolerant control based on the observation values ​​of generator rotor position and speed.

[0027] The method compares the residual obtained by the detection value of the sensor and the estimated value of the observer with a threshold to complete the fault diagnosis of the drive system. The estimated value obtained by the position observer can also realize fault-tolerant control after sensor failure, which has great engineering practical value.

[0028] The method mainly includes three parts: PMSG rotor position observation, position sensor fault diagnosis and position sensor fault tolerant control.

[0029] PMSG vector coordinate system is as follows Figure 2 As shown, the α-β axis represents a fixed reference system, and the dq axis represents a synchronously rotating reference system. The axis represents the synchronously rotating observation coordinate system, in the dq reference system:

[0030]

[0031] where u d 、u q are the components of the stator voltage in the synchronously rotating dq axis, i d 、i q is the component of the stator current in the synchronously rotating dq axis, R is the stator winding resistance, L d , L q They represent the components of the stator winding inductance in the synchronously rotating dq axis, ψ f is the rotor permanent magnet flux, ω e is the rotor electrical angular velocity, and D is the differential operator.

[0032] Transform (3-1) into:

[0033]

[0034] according to Figure 1 The dq and Correspondence between coordinate systems, voltage and current u in dq coordinate system d 、u q 、i d 、i q and Voltage and current in the coordinate system The transformation relationship between them is:

[0035]

[0036] Among them, Δθ e is the difference between the real rotor electrical angle and the observed rotor electrical angle. Substituting equation (3-3) into equation (3-2), we can get The voltage equation of the coordinate system is:

[0037]

[0038] From (3-4), we can get the difference Δθ between the real rotor electrical angle and the observed rotor electrical angle e It is expressed as:

[0039]

[0040] The ideal state of the PMSG position observer is the rotor electrical angle observation value and the real rotor electrical angle θ e The same, because the mechanical time constant is relatively large, when the rotor electrical angle observation value and the real rotor electrical angle θ e When approximating, Δθ can be ignored e The effect of the rate of change, i.e. DΔθ e ≈0. For the electromechanical control system of the variable speed hydroelectric generator, the sampling frequency of the control system is high enough, and the current change rate within a sampling period is It can be considered equal to zero. PMSG adopts i d =0, then formula (3-5) can be simplified to

[0041]

[0042] The PMSG position observer aims to observe the rotor electrical angle. and the real rotor electrical angle θ e The difference Δθ e →0, so the real electrical angular velocity ω in equation (3-6) e The electrical angular velocity can be observed using Substitution. Using the application of inverse trigonometric functions in infinitesimal substitution formulas, we can obtain:

[0043]

[0044] The rotor electrical angle observation error Δθ obtained according to formula (3-7) e , the rotor electrical angle and electrical angular velocity observation model based on the phase-locked loop controller can be obtained, such as Figure 3 As shown. By estimating the rotor electrical angle error Δθ e PI regulation is used to obtain the estimated rotor electrical angular velocity After integration, the observed rotor electrical angle is obtained At this point, the construction of the PMSG position observer is completed.

[0045] In the present invention, the generator rotor position signal observation may be replaced by other solutions, and the present invention does not limit the specific implementation method of the generator rotor position signal observation.

[0046] By adopting the above-mentioned model-based method, a corresponding position observer is established according to the mathematical model of the permanent magnet synchronous generator to obtain an estimated value of the sensor measurement value, thereby performing fault diagnosis on the position sensor.

[0047] Specific fault diagnosis principles such as Figure 4 As shown. According to the measured voltage value u ab 、u bc And the current value i a 、i b 、i c , the observed values ​​of the generator rotor position and speed are obtained through the position observer, and the observed position The position θ detected by the sensor e , the observed speed The speed detected by the sensor ω e The residuals are then compared with the position and speed thresholds ε θ and ε ω By comparison, fault diagnosis of the position sensor can be performed.

[0048] Among them, the speed residual is specifically used to diagnose the position sensor stuck fault. When the position sensor is stuck, the speed detected by the sensor will drop to 0, and the observed speed is still the actual running speed of the motor. The speed residual will exceed the corresponding threshold. At this time, the position sensor is judged to be faulty, and the fault diagnosis flag position is 1. The position residual is mainly used to diagnose the position sensor offset fault. When the position sensor has an offset fault, a constant offset is generated between the detected position and the actual position, and the position estimated by the observer can still follow the actual position. Therefore, the position difference will be larger than the position threshold, and the position sensor is judged to be faulty, and the fault diagnosis flag position is 1.

[0049] For position sensor failure, the position observer is used to obtain the rotor position and speed signals as the position and speed signals required for fault-tolerant control. The specific position sensor fault-tolerant control principle diagram is as follows: Figure 5 shown.

[0050] When the sensor detection value is normal, the position sensor fault flag is 0, the generator system works in normal operation mode, θ et =θ e ,ω et =ω e , that is, the position and speed signal detection values ​​of the position sensor are used as the output of the working mode switch, thereby performing closed-loop vector control of the motor.

[0051] After the position sensor fault diagnosis strategy diagnoses the position sensor fault, the position sensor fault diagnosis flag is set to 1, and the working mode of the generator system is switched to the fault-tolerant operation mode. That is, the position and speed estimation values ​​obtained by the designed observer are switched to the output of the working mode switcher to ensure fault-tolerant control after a fault. After the fault flag is set to 1, the generator system keeps the fault flag set to 1 until the fault flag is set to 0 again.

[0052] When the position sensor is working normally, the diagnostic algorithm detects the rotor position information obtained from the position sensor in real time, which is equivalent to the fault diagnosis state. Once the position sensor is diagnosed to have a fault, the fault type is located and the power generation system is guaranteed to switch to the fault-tolerant control mode without large jitter. After the fault-tolerant control strategy is implemented, regardless of whether the position sensor fails, the system can obtain the accurate position of the generator back-EMF vector, and then obtain the actual speed of the motor. At the same time, the position signal is used to decompose the current vector to form the orthogonal dq axis torque excitation component. Through the PI adjustment of the speed outer loop, the torque current given instruction is output, and the excitation current given instruction is set to zero. Then, through the PI adjustment of the current inner loop, the dq axis voltage given instruction is output. Finally, vector synthesis and vector transformation are used to restore it to the stator voltage given vector instruction under the three-phase shaft system. After vector modulation, the PWM pulse of the drive converter is output, so that the actual speed and current track the given speed and current instructions, and the system is adjusted without static error.

[0053] The turbine provides driving torque for the generator, thereby generating electrical energy. When the turbine power changes, the speed will also change. The machine-side rectifier needs to stabilize the generator speed to convert the mechanical power generated by the turbine into electrical power. In the PMSG control system, by controlling the q-axis torque current, the generator output torque can be controlled, and then the speed can be controlled, and the generator output power can also be controlled accordingly. At this time, combined with the turbine MPPT algorithm, the generator speed can be adjusted to make the system run at the maximum power output state.

[0054] In order to solve the position sensor failure in the variable speed hydroelectric power generation system, the present invention adopts a position observer sensorless algorithm based on rotor position angle estimation as a redundant solution. The algorithm has good dynamic and steady-state performance and high parameter robustness. At the same time, the estimated value obtained by the position observer realizes the fault diagnosis and fault-tolerant control of the position sensor in the full speed range. The solution is simple, reliable and has strong engineering practicality. It significantly improves the reliability of the permanent magnet synchronous generator rotor position angle acquisition and ensures the stability and safety of the permanent magnet hydroelectric power generation system operation.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for fault diagnosis and fault-tolerant control of a position sensor of a permanent magnet hydroelectric generator, characterized in that: include: Obtain detection values ​​of generator rotor position and speed; According to the measured voltage and current values, combined with the pre-built PMSG position observer, the observed values ​​of the generator rotor position and speed are obtained; The construction of the PMSG position observer includes: obtaining a rotor electrical angle and electrical angular velocity observation model based on a phase-locked loop controller according to a permanent magnet synchronous generator mathematical model, wherein the observed value of the rotor electrical angle corresponds to the observed value of the rotor position, and the observed value of the rotor electrical angular velocity corresponds to the observed value of the rotational speed. The construction formula of the PMSG position observer is as follows: ； Said for The voltage in the coordinate system, for Coordinate system The shaft current, is the stator winding inductance in synchronous rotation The weight of the axis, is the stator winding resistance, is the real rotor electrical angular velocity, is the difference between the real rotor electrical angle and the observed rotor electrical angle; The PMSG position observer aims to observe the rotor electrical angle. The actual rotor electrical angle difference , so the real rotor electrical angular velocity in the above formula is The rotor electrical angular velocity can be observed Substitution; using the application of inverse trigonometric functions in infinitesimal substitution formulas, we can get: ； The rotor electrical angle observation error obtained according to the above formula , we can get the rotor electrical angle and electrical angular velocity observation model based on the phase-locked loop controller, and calculate the rotor electrical angle estimation error by PI regulation is used to obtain the estimated rotor electrical angular velocity , after integration, the observed rotor electrical angle is obtained ; Performing position sensor fault diagnosis based on the observed values ​​of the generator rotor position and speed and the detected values ​​of the generator rotor position and speed; When a position sensor failure is diagnosed, fault-tolerant control is performed based on the observed values ​​of the generator rotor position and speed.

2. The method for fault diagnosis and fault-tolerant control of position sensors of a permanent magnet hydroelectric generator according to claim 1, characterized in that: The method also includes: obtaining a residual of the rotor position based on the observed value and the detected value of the rotor position, and comparing the residual of the rotor position with a threshold value of the rotor position to obtain a rotor position comparison result; obtaining a residual of the speed based on the observed value and the detected value of the speed, and comparing the residual of the speed with a threshold value of the speed to obtain a speed comparison result; and performing position sensor fault diagnosis based on the rotor position comparison result and the speed comparison result.

3. The method for fault diagnosis and fault-tolerant control of position sensors of a permanent magnet hydroelectric generator according to claim 2, characterized in that: When the residual error of the rotational speed exceeds a rotational speed threshold or the residual error of the rotor position exceeds a rotor position threshold, a position sensor failure is diagnosed.

4. The method for fault diagnosis and fault-tolerant control of position sensors of a permanent magnet hydroelectric generator according to claim 1, characterized in that: After the position sensor fault is diagnosed, the position sensor fault diagnosis flag is set to position 1, and the working mode of the generator system is switched to a fault-tolerant operation mode, in which the rotor position and speed values ​​obtained by the observer are used as the output of the working mode switch.

5. The method for fault diagnosis and fault-tolerant control of position sensors of permanent magnet hydroelectric generators according to claim 4, characterized in that: After the fault flag of the position sensor is set to 1, the generator system keeps the fault flag set to 1 until the fault flag is set to 0 again.

6. The method for fault diagnosis and fault-tolerant control of position sensors of permanent magnet hydroelectric generators according to claim 5, characterized in that: After the fault-tolerant control strategy is implemented, regardless of whether the position sensor fails, the system can obtain the accurate position of the generator back-EMF vector, and then obtain the actual speed of the motor. At the same time, the position signal is used to decompose the current vector to form the torque excitation component under the orthogonal dq axis. Through the PI adjustment of the speed outer loop, the torque current given instruction is output, and the excitation current given instruction is set to zero. Then, through the PI adjustment of the current inner loop, the dq axis voltage given instruction is output. Finally, by using vector synthesis and vector transformation, it is restored to the stator voltage given vector instruction under the three-phase shaft system. After vector modulation, the PWM pulse that drives the converter is output, so that the actual speed and current track the given speed and current instructions, and the system is adjusted without static error.

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