Permanent magnet synchronous generator power generation and voltage stabilization control strategy considering high resistance contact fault

Abstract

The application relates to a permanent magnet synchronous generator power generation voltage stabilization control strategy considering high-resistance contact faults, and steps are as follows: based on a dq rotating coordinate system, a permanent magnet synchronous generator mathematical model considering high-resistance contact faults is established; combined with the permanent magnet synchronous generator mathematical model considering high-resistance contact faults, an instantaneous power equation considering high-resistance contact faults is derived based on instantaneous power theory; combined with the instantaneous power equation considering high-resistance contact faults, a quantitative relationship between a direct-current terminal voltage double-frequency ripple and a cross-axis current is derived based on a small signal analysis method; combined with the quantitative relationship between the direct-current terminal voltage double-frequency ripple and the cross-axis current, a cross-axis current integral average compensation method is designed by taking the characteristic that a sine signal is integrated to zero in an integral period, and a compensated current is obtained to perform permanent magnet synchronous generator power generation voltage stabilization control. The application can inhibit the double-frequency ripple of the cross-axis current, and further reduce the double-frequency ripple of the direct-current terminal voltage, so that the purpose of voltage stabilization control is achieved.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, and in particular relates to a quadrature axis current compensation strategy based on the integral mean method to reduce the DC terminal voltage double frequency ripple that occurs after a high-resistance contact fault in a permanent magnet synchronous generator. It is applicable to permanent magnet synchronous generators and can be applied to situations where the single-phase stator branch resistance changes abruptly after a high-resistance contact fault. Background Technology

[0002] With the development of drone technology, quality assurance drones have extremely high application and promotion value in the field of agricultural production. Among the many types of agricultural drones, multi-rotor gasoline-powered drones have the advantages of long endurance and large payload. Replacing the starter motor on the original multi-rotor gasoline-powered drone with a starter / generator can effectively improve its shortcomings such as lack of power source and insufficient power supply. Due to its advantages of simple structure, reliable operation, small size, light weight, and high power density, permanent magnet synchronous motors are often used in starter / generator systems.

[0003] As a motor mounted on an agricultural drone, it should possess high reliability, safety, and stability. However, facing complex operating environments, motors inevitably experience some malfunctions, affecting their normal operation and system stability. Among these, high-resistance contact faults can cause the equivalent resistance of the three-phase stator branches to become asymmetrical, resulting in additional double-frequency ripple in the DC load voltage and impacting system performance.

[0004] Agricultural drones have high power requirements, so some methods need to be adopted to reduce the second harmonic ripple generated on the DC terminal voltage after a high-resistance contact fault, thereby reducing its impact on system performance. Summary of the Invention

[0005] Purpose of the invention: This invention proposes a voltage regulation control strategy for permanent magnet synchronous generators (PMSGs) that considers high-resistance contact faults. The purpose is to solve the problem of DC terminal voltage fluctuations caused by high-resistance connection faults in existing PMSGs. This invention provides a voltage regulation method based on quadrature-axis current compensation using the integral averaging method. This method reduces the second harmonic ripple of the DC terminal voltage by suppressing the second harmonic ripple of the quadrature-axis current, thereby achieving the purpose of voltage regulation control.

[0006] Technical solution:

[0007] The voltage regulation control strategy for permanent magnet synchronous generators under high-resistance contact faults involves the following steps:

[0008] Step 1: Based on the dq rotating coordinate system, establish a mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults;

[0009] Step 2: Combining the mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults, and based on instantaneous power theory, derive the instantaneous power equation considering high-resistance contact faults; combining the instantaneous power equation considering high-resistance contact faults, and based on small-signal analysis, derive the quantitative relationship between the second harmonic ripple of the DC terminal voltage and the quadrature axis current.

[0010] Step 3: Combining the quantitative relationship between the DC terminal voltage second harmonic ripple and the quadrature-axis current, and taking advantage of the characteristic that the integral of a sinusoidal signal is zero over the entire cycle, design a quadrature-axis current integral mean compensation method to obtain the compensated current. Perform voltage stabilization control for permanent magnet synchronous generators.

[0011] Furthermore, the mathematical model of the permanent magnet synchronous generator in step one is as follows:

[0012]

[0013] in,

[0014] In the formula, u d ,u q Let i be the voltage across the dq axis. d i q L is the dq-axis current. d ,L q For the dq axis inductance, ω e Let ψ be the electric angular velocity of the motor. f For rotor flux linkage, R dd ,R qq ,R dq The stator resistances R are respectively s The dq-axis components and coupling components, θ e Let be the electrical angle of the motor. Furthermore, the instantaneous power equation in step two is:

[0015]

[0016] In the formula, ω e Let ψ be the electric angular velocity of the motor. f For rotor flux linkage, R s θ is the stator resistance, ΔR0 is the additional stator branch resistance caused by a high-resistance contact fault, and θ is the stator resistance. e R is the electrical angle of the motor, C is the parallel capacitor at the DC end, and R is the electric angle of the motor. L U is the DC load resistor. dc The DC terminal voltage, i q This is the q-axis current.

[0017] Furthermore, the quantitative relationship between the DC terminal voltage second harmonic ripple and the quadrature-axis current in step two is as follows:

[0018]

[0019] In the formula, ΔU dc Δi represents the fluctuation in DC terminal voltage caused by a high-impedance fault. q This represents the fluctuation in quadrature-axis current caused by a high-resistance fault. The steady-state quantity of DC terminal voltage affected by high-impedance faults. The steady-state quantity of the quadrature-axis current affected by a high-resistance fault is given by ΔR0, where ΔR0 is the additional resistance of the stator branch due to the high-resistance contact fault, C is the parallel capacitor at the DC terminal, and ω is the constant. e This represents the electric angular velocity of the motor.

[0020] Furthermore, the control structure of the quadrature-axis current integral averaging compensation method is as follows: the output terminals of the DC-side load reference voltage and the actual voltage are both connected to the input terminal of the voltage outer-loop PI controller. The output terminal of the voltage outer-loop PI controller is connected to the input terminal of the first integral stage and the input terminal of the delay stage, respectively. The output terminal of the delay stage is connected to the input terminal of the second integral stage. The output terminals of the first and second integral stages are both connected to the input terminal of the averaging stage. The output terminal of the averaging stage and the output terminal of the current inverse Park transform are both connected to the input terminal of the q-axis current inner-loop PI controller. The output terminals of the d-axis reference current and the current inverse Park transform are both connected to the input terminal of the d-axis current inner-loop PI controller. The output terminal of the q-axis current inner-loop PI controller is connected to the input terminal of the q-axis current inner-loop PI controller. The output terminals of the d-axis current inner loop voltage compensation structure are all connected to the input terminal of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system. The output terminals of the d-axis current inner loop PI controller and the d-axis current inner loop voltage compensation structure are all connected to the input terminal of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system. The output terminal of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system is connected to the input terminal of the SVPWM controller. The output terminal of the SVPWM controller is connected to the input terminal of the third PWM rectifier. The third PWM rectifier is connected to the input terminal of the permanent magnet synchronous generator. The output terminal of the permanent magnet synchronous generator is connected to the input terminal of the current inverse Park transformation, the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system, and the SVPWM controller, respectively.

[0021] Furthermore, the quadrature-axis current integral mean compensation method is as follows: DC terminal load reference voltage given signal With the actual voltage signal U dc The input signal of the voltage outer loop PI controller is obtained after subtraction, and the output signal of the voltage outer loop PI controller is the given q-axis current. The input signal is the integral average compensation controller, and the output signal of the integral average compensation controller is the compensated q-axis current. With the actual q-axis current signal i q The input signal for the q-axis current inner loop PI controller is obtained by subtraction, and the d-axis given current is obtained by subtraction. With the actual d-axis current signal i d The input signal of the d-axis current inner loop PI controller is obtained by subtracting the output signal of the q-axis current inner loop PI controller from the voltage compensation signal of the q-axis current inner loop. The d-axis setpoint voltage is obtained by summing the output signal of the d-axis current inner loop PI controller 8 and the output signal of the d-axis current inner loop voltage compensation structure. As the input signal for the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system, the output signal αβ, the given voltage, is the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system. The signals are respectively used as input signals to the SVPWM controller, the output signal of the SVPWM controller is used as input signals to the third PWM rectifier, the output signal of the third PWM rectifier is used as input signals to the permanent magnet synchronous generator, and the output signal of the permanent magnet synchronous generator is the three-phase current i of phases A, B, and C. abc The rotation angle information θ serves as the input signal for the inverse Park transformation of the current. The output signal of the permanent magnet synchronous generator, along with the rotation angle information θ, also serves as the input signal for the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system and the SVPWM controller. The actual d-axis current i... d With the actual q-axis current i q As the output signal of the inverse Park transform of the current;

[0022] Within the integral average compensation controller, the voltage outer loop PI controller outputs a signal that sets the q-axis current. The input signals for the integrator and delay stages are respectively used as input signals for the integrator and delay stages. The output signal of the delay stage is used as the input signal for the integrator. The difference between the output signals of the integrator and the delay stage is used as the input signal for the averaging stage. The output signal of the averaging stage is the q-axis compensation current.

[0023] Furthermore, the compensated current in step three for:

[0024]

[0025] In the formula, To provide the compensated q-axis current, The voltage outer loop PI controller outputs the q-axis current, Δi. q This represents the fluctuation in quadrature-axis current caused by a high-resistance fault. ω is the steady-state quantity of the quadrature-axis current affected by a high-resistance fault. e C1 is the electric angular velocity of the motor, and C1 is the quadrature-axis current second harmonic ripple amplitude coefficient.

[0026] Beneficial effects:

[0027] This invention uses the integral average compensation method to compensate and control the AC current, suppressing the second harmonic ripple of the quadrature-axis current, thereby reducing the second harmonic ripple of the DC terminal voltage. This invention is relatively simple to operate and can run online. Furthermore, this invention also derives the quantitative relationship between the second harmonic ripple of the DC terminal voltage and the quadrature-axis current when a high-resistance contact fault occurs in a permanent magnet synchronous generator. Attached Figure Description

[0028] Figure 1 This is a topology diagram of the DC power supply structure of a permanent magnet synchronous generator considering high-resistance contact faults.

[0029] Figure 2 It is an instantaneous power flow diagram;

[0030] Figure 3 This is a block diagram of the control method proposed in this invention;

[0031] Figure 4 The DC terminal voltage U is when the resistance of the three-phase stator branch is unbalanced. dc Waveform;

[0032] Figure 5 The quadrature-axis current i is the current when the resistance of the three-phase stator branch is unbalanced. q Waveform;

[0033] Figure 6 The direct-axis current i is when the resistance of the three-phase stator branch is unbalanced. d Waveform;

[0034] Figure 7 This is the three-phase current waveform when the resistance of the three-phase stator branch is unbalanced;

[0035] Figure 8 This is a comparison of the waveforms of various physical quantities when the resistance of the three-phase stator branch is unbalanced;

[0036] Figure 9 The DC terminal voltage U under the compensation strategy proposed in the application paper invention. dc Comparison chart;

[0037] Figure 10 The quadrature-axis current i under the compensation strategy proposed in this invention. q Comparison chart.

[0038] Explanation of reference numerals in the attached figures:

[0039] 1. Permanent magnet synchronous generator; 2. First PWM rectifier; 3. Second PWM rectifier; 4. Additional resistor; 5. Voltage outer loop PI controller; 6. Integral averaging compensation controller; 7. q-axis current inner loop PI controller; 8. d-axis current inner loop PI controller; 9. q-axis current inner loop voltage compensation structure; 10. d-axis current inner loop voltage compensation structure; 11. Transformation from dq two-phase rotating coordinate system to αβ two-phase stationary coordinate system; 12. SVPWM controller; 13. Third PWM rectifier; 14. Inverse Park transformation; 15. Permanent magnet synchronous generator; 16. First integrator; 17. Delay element; 18. Second integrator; 19. Averaging element; 20. Voltage outer loop. Detailed Implementation

[0040] The following description, in conjunction with the accompanying drawings, provides a further illustration of one embodiment of the present invention.

[0041] This invention proposes a voltage regulation control strategy for permanent magnet synchronous generators (PMSGs) considering high-resistance contact faults. Based on instantaneous power theory and small-signal analysis, the quantitative relationship between the second harmonic ripple of the DC terminal voltage and the quadrature-axis current of the PMSG load is derived. Furthermore, based on the mean-integral compensation method, a method for reducing DC terminal voltage fluctuations caused by high-resistance contact faults is presented. For ease of research, [further details are provided]. Figure 1 , Figure 2 , Figure 3 To elaborate.

[0042] Step 1: Based on the dq rotating coordinate system, establish a mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults.

[0043] When the permanent magnet synchronous motor is in normal operating condition and no faults occur, the three-phase voltage equations are as follows:

[0044]

[0045] In equation (1), u a ,u b ,u c For the three-phase stator voltage, i a i b i c For the three-phase stator current, Ψ a ,Ψ b ,Ψ c For the three-phase winding flux linkage, R a ,R b ,R c This refers to the three-phase stator resistance.

[0046] After coordinate transformation, the voltage equation along the dq axis is obtained, which is the mathematical model of the permanent magnet synchronous generator:

[0047]

[0048] In equation (2), u d ,u q Let i be the voltage across the dq axis. d i q L is the dq-axis current. d ,L q For the dq axis inductance, ω e Let θ be the electric angular velocity of the motor. e Let ψ be the electrical angle of the motor. f R represents the rotor flux linkage. dd ,R qq ,R dq The stator resistances R are respectively s The dq axis components and coupling components are shown in equations (3) and (4) respectively:

[0049]

[0050]

[0051] When considering high-resistance contact faults, the three-phase stator resistance R of the permanent magnet synchronous generator a R b R c The values ​​are not equal. Due to the spatial symmetry of the windings, the methods and results for analyzing high-resistance contact faults in any one phase stator branch are similar. Here, we assume a high-resistance contact fault occurs in phase A stator branch (as shown in the attached diagram). Figure 1 (as shown), Figure 1 The diagram shows the topology of the DC power supply structure for a permanent magnet synchronous generator considering high-resistance contact faults. Figure 1 In the middle, e, L s R s These represent the electromotive force, inductance, and resistance in each phase stator branch, respectively. ΔR0 is the additional resistance in the stator branch considering a high-resistance contact fault in phase A. C and R L U dc These are the DC-end capacitor, DC-end load, and DC-end voltage, respectively. A PWM rectifier is connected between the permanent magnet synchronous generator and the DC-end load.

[0052] Figure 1 In this invention, when a high-resistance contact fault occurs between phase A and phase A of the permanent magnet synchronous generator 1, the additional resistor 4 is connected to the branch. When a high-resistance contact fault occurs in phase A, the additional resistor 4, phases B and C of the permanent magnet synchronous generator 1 are connected to the first PWM rectifier 2, and the second PWM rectifier 3 is connected to the additional resistor 4. This invention uses a high-resistance contact fault in phase A as an example. If a high-resistance contact fault occurs in phase B or phase C, the additional resistor 4 may also be located on the branch of phase B or phase C.

[0053] Let the original resistance of the three-phase stator be R. s The additional resistance in the stator branch due to the high-resistance contact fault is ΔR0. That is, the resistance of phase A branch after the high-resistance contact fault is R. a =R s +ΔR0, the resistance of the B and C phase branches is R a =R b =R s Substituting this into equation (4), we obtain the stator resistance dq component and its coupling component in the mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults:

[0054]

[0055] Special note: When high-resistance contact faults occur in phases B and C respectively, the power generation voltage stabilization control strategy proposed in this invention is also applicable. The analysis is consistent with the analysis method for high-resistance contact faults in phase A considered in this invention, so it will not be described again.

[0056] Step 2: Combining the mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults, and based on instantaneous power theory, derive the instantaneous power equation considering high-resistance contact faults; combining the instantaneous power equation considering high-resistance contact faults, and based on small-signal analysis, derive the quantitative relationship between the second harmonic ripple of the DC terminal voltage and the quadrature axis current.

[0057] Combination Figure 2 Instantaneous power flow diagram: When the motor is in generating mode, the active power provided by the motor's electromotive force is P. E The instantaneous power consumed by the three-phase stator resistors (copper loss) is: The instantaneous power absorbed by the increase in energy stored in the magnetic field within the inductor is: The power loss generated is P r Generally, this can be ignored; the instantaneous power absorbed by the DC terminal capacitor is P. C The instantaneous power absorbed by the DC-side load is Based on instantaneous power theory, the quantitative relationships between the various powers are shown in equations (6)-(11).

[0058]

[0059]

[0060]

[0061]

[0062]

[0063]

[0064] Within the scope of permanent magnet synchronous motors to which this invention applies, due to L s Too small, therefore in equation (7) It can be ignored. And because it uses i... d The control strategy is 0, therefore, by combining equations (5) and (8), the copper loss can be derived. Specifically:

[0065]

[0066] Therefore, if i q If the copper consumption is constant or does not change much, then the copper loss will be low. It contains a second harmonic ripple of the motor's electrical angular velocity, the magnitude of which is related to the additional resistance ΔR0 of phase A and the q-axis current i. q related.

[0067] Substituting equations (6), (9), (10), and (12) into equation (11) yields the instantaneous power equation considering high-resistance contact faults:

[0068]

[0069] In equation (13), ω e Let ψ be the electric angular velocity of the motor. f For rotor flux linkage, R s θ is the stator resistance, ΔR0 is the additional stator branch resistance caused by a high-resistance contact fault, and θ is the stator resistance. e R is the electrical angle of the motor, C is the parallel capacitor at the DC end, and R is the electric angle of the motor. L U is the DC load resistor. dc The DC terminal voltage, i q This is the q-axis current.

[0070] Based on the small-signal analysis method, assuming the q-axis current changes due to a high-resistance contact fault, the variation is as follows: DC terminal voltage change is in, and For steady-state quantities, Δi q With ΔU dc The variable is denoted as . Under normal operating conditions, the steady-state equation of the permanent magnet synchronous generator is:

[0071]

[0072] When a high-resistance contact fault occurs, its instantaneous power equation is:

[0073]

[0074] Ignore quadratic minor terms and have to:

[0075]

[0076] Combining equation (14) to separate the direct current, we get:

[0077]

[0078] Analyzing equation (17), when Δi q Compared to When smaller, It can be approximated as a constant, while also considering the generator's electrical angle θ. e =ω e t, therefore we have equation (18):

[0079]

[0080] In equation (18), K = ΔR0i q (i q +2Δi q ) / 2CU dc Since is a constant, we can then obtain information about the DC voltage fluctuation ΔU. dc More specifically, the quantitative relationship between the second harmonic ripple of the DC terminal voltage and the quadrature-axis current is:

[0081]

[0082] In equation (19), ΔU dc Δi represents the fluctuation in DC terminal voltage caused by a high-impedance fault. q This represents the fluctuation in quadrature-axis current caused by a high-resistance fault. The steady-state quantity of DC terminal voltage affected by high-impedance faults. The steady-state quantity of the quadrature-axis current affected by a high-resistance fault is given by ΔR0, where ΔR0 is the additional resistance of the stator branch due to the high-resistance contact fault, C is the parallel capacitor at the DC terminal, and ω is the constant. e This represents the electric angular velocity of the motor.

[0083] From equation (19), it can be seen that the DC terminal voltage fluctuation ΔU dc This is a second-harmonic ripple based on the electric angular velocity of the motor, and its magnitude is related to the quadrature-axis current. The quadrature-axis current ripple Δi can be suppressed. q This reduces the DC terminal voltage ripple ΔU. dc .

[0084] Step 3: Combining the quantitative relationship between the DC terminal voltage second harmonic ripple and the quadrature-axis current, and taking advantage of the characteristic that the integral of a sinusoidal signal is zero over the entire cycle, design a quadrature-axis current integral mean compensation method to obtain the compensated current. Perform voltage stabilization control for permanent magnet synchronous generators.

[0085] exist In control strategies, the outer voltage loop often uses a PI controller, which measures the difference between the given DC terminal voltage and the actual DC terminal voltage. The output value is the given q-axis current. Assuming perfect current tracking, then:

[0086]

[0087] Combining equation (19), we can derive the quadrature axis current fluctuation Δi. q This is a second harmonic ripple based on the electric angular velocity of the motor, namely:

[0088] Δi q =C1sin(2ω) e t)+C2 (21)

[0089] From equation (21), it can be seen that the quadrature axis current ripple Δi q It is a second harmonic ripple sinusoidal signal based on the electric angular velocity of the motor.

[0090] Based on the characteristic that the integral of a sinusoidal signal is 0 over a full cycle, given the known electric angular velocity ω of the motor... e Given a period T, the output of the outer loop PI controller under normal voltage conditions... The integral mean over the rounding period, as shown in equation (22), suppresses the quadrature-axis current ripple Δi. q In equation (22), The current is given to the q-axis after compensation.

[0091]

[0092] In equation (22), To provide the compensated q-axis current, The voltage outer loop PI controller outputs the q-axis current, Δi. q This represents the fluctuation in quadrature-axis current caused by a high-resistance fault. ω is the steady-state quantity of the quadrature-axis current affected by a high-resistance fault. e C1 is the electric angular velocity of the motor, and C1 is the quadrature-axis current second harmonic ripple amplitude coefficient.

[0093] Since the integral of the sine function is 0 over an integer period, the compensated q-axis current obtained through equation (7) is... Can The second harmonic ripple is eliminated, and its DC value is extracted, thereby making... This reduces, and consequently, reduces, the DC terminal voltage ripple ΔU caused by high-resistance contact faults. dc .

[0094] The quadrature-axis current integral mean compensation method adopts, as follows: Figure 3 The control structure shown.

[0095] Figure 3 This is a block diagram of the control method proposed in this invention. The connections between the various structures are as follows: the output terminals of the DC-side load reference voltage and the actual voltage are both connected to the input terminal of the outer voltage loop PI controller 5; the outer voltage loop PI controller 5 is connected to the input terminal of the integral averaging compensation controller 6; the output terminal of the integral averaging compensation controller 6 and the output terminal of the current inverse Park transform 14 are both connected to the input terminal of the q-axis current inner loop PI controller 7; the output terminals of the d-axis reference current and the current inverse Park transform 14 are both connected to the input terminal of the d-axis current inner loop PI controller 8; and the output terminals of the q-axis current inner loop PI controller 7 and the q-axis current inner loop voltage compensation structure 9 are both connected to the dq two-phase rotating coordinate system transformed to the αβ two-phase stationary coordinate system. The 11 input terminals are connected. The output terminals of the d-axis current inner loop PI controller 8 and the d-axis current inner loop voltage compensation structure 10 are both connected to the input terminal of the dq two-phase rotating coordinate system to αβ two-phase stationary coordinate system transformation 11. The output terminal of the dq two-phase rotating coordinate system to αβ two-phase stationary coordinate system transformation 11 is connected to the input terminal of the SVPWM controller 12. The output terminal of the SVPWM controller 12 is connected to the input terminal of the third PWM rectifier 13. The third PWM rectifier 13 is connected to the input terminal of the permanent magnet synchronous generator 15. The output terminal of the permanent magnet synchronous generator 15 is connected to the input terminal of the current inverse Park transformation 14, the dq two-phase rotating coordinate system to αβ two-phase stationary coordinate system transformation 11, and the SVPWM controller 12, respectively.

[0096] Figure 3 The integral averaging compensation controller 6 in the outer voltage loop 20 further refines the structural connection relationship. The output terminals of the DC load reference voltage and the actual voltage are both connected to the input terminal of the outer voltage loop PI controller 5. The output terminal of the outer voltage loop PI controller 5 is connected to the input terminal of the first integral stage 16 and the input terminal of the delay stage 17, respectively. The output terminal of the delay stage 17 is connected to the input terminal of the second integral stage 18. The output terminals of the first integral stage 16 and the second integral stage 18 are both connected to the input terminal of the averaging stage 19. The output terminal of the averaging stage 19 is connected to the input terminal of the outer voltage loop PI controller 5.

[0097] Figure 3 This is a block diagram of the control method proposed in this invention, wherein the relationship between each input terminal and output terminal is as follows: In the outer voltage loop, the DC terminal load reference voltage is given by the signal. With the actual voltage signal U dc The input signal of the voltage outer loop PI controller 5 is obtained after subtraction, and the output signal of the voltage outer loop PI controller 5 is the given q-axis current. The input signal is the integral averaging compensation controller 6, and the output signal of the integral averaging compensation controller 6 is the compensated q-axis given current. With the actual q-axis current signal i q The input signal of the q-axis current inner loop PI controller 7 is obtained after subtraction, and the d-axis given current is obtained. (Note: Here) ) and the actual d-axis current signal i d The input signal of the d-axis current inner loop PI controller 8 is obtained by subtracting the output signal of the q-axis current inner loop PI controller 7 and the q-axis current inner loop voltage compensation signal 9. The d-axis setpoint voltage is obtained by summing the output signal of the d-axis current inner loop PI controller 8 with the d-axis current inner loop voltage compensation signal 10. As the input signal for the transformation 11 from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system, the output signal αβ of the transformation 11 from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system is the given voltage. The signals are respectively used as input signals to the SVPWM controller 12, the output signal of the SVPWM controller 12 is used as input signal to the third PWM rectifier 13, the output signal of the third PWM rectifier 13 is used as input signal to the permanent magnet synchronous generator 15, and the output signal of the permanent magnet synchronous generator 15 is the three-phase current i of phases ABC. abc The rotation angle information θ serves as the input signal for the inverse Park transformation 14 of the current. The output signal of the permanent magnet synchronous generator 15, along with the rotation angle information θ, also serves as the input signal for the transformation 11 from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system and the SVPWM controller 12. The actual d-axis current i... d With the actual q-axis current i q As the output signal of the inverse Park transform 14.

[0098] Figure 3 In the voltage outer loop and mean-integral compensation structure shown in voltage outer loop 20, the DC-side load reference voltage given signal With the actual voltage signal U dc The input signal of the voltage outer loop PI controller 5 is obtained after subtraction, and the output signal of the voltage outer loop PI controller 5 is the given q-axis current. The output signals of the delay stage 17 and the integrator 16 and delay stage 18 are used as input signals, respectively. The output signal of the delay stage 17 is used as input signal of the integrator 18. The difference between the output signals of the integrator 16 and the integrator 18 is used as input signal of the averaging stage 19. The output signal of the averaging stage 19 is the compensated q-axis reference current.

[0099] The actual implementation of the above compensation control strategy is as follows: the original given quadrature shaft current output from the outer voltage loop of the permanent magnet synchronous generator is sampled to obtain... The generator speed n is obtained from the speed sensor of the permanent magnet synchronous generator, and then the generator's electrical angular velocity ω is obtained. e This leads to the mean calculation period T. Where: ω e =npπ / 30, where p is the number of pole pairs of the permanent magnet synchronous generator; T = 2π / ω e Let the initial sampling calculation time be t0, and the current time be t. Calculate the following respectively. Substituting the integral over the intervals (t0, t) and (t0, tT) into equation (22) yields the compensated q-axis current.

[0100] Implementation Cases

[0101] To verify the correctness of the control strategy and derivation results mentioned in this invention, the relevant parameters of a 42-pole permanent magnet synchronous motor are shown in Table 1.

[0102] Table 1

[0103]

[0104] This invention utilizes MATLAB / Simulink to simulate and analyze the above model. A high-resistance contact fault is introduced in the stator branch of phase A at 1 second, forming an equivalent additional resistance of ΔR0 = 0.3Ω in the series branch of phase A, i.e., R... a =0.581Ω, R b =R c =0.281Ω. Simulation results are as follows: Figure 4-8 As shown.

[0105] Depend on Figure 4 It can be seen that after a high-resistance contact fault occurs in phase 1sA, the DC terminal voltage drops to approximately 23.85V, and a ripple of approximately 0.11V still appears after tracking the given value, which is significantly different from before the high-resistance contact fault occurred; from Figure 5 It can be seen that the quadrature-axis current drops to approximately -8.5A, and a ripple of approximately 1.2A still appears after tracking the given value, which is significantly different from before the high-resistance contact fault occurred. Figure 6 It can be seen that since the direct-axis current does not participate in the transmission of active power, there is no significant change before and after the high-resistance contact fault occurs in phase A.

[0106] Depend on Figure 7 It can be seen that the three-phase current also changed significantly after the high-resistance contact fault occurred in phase A. The amplitudes of the three-phase currents were not equal, changing from 6.8A before the fault to 7.69, 7.34 and 7.71A respectively. Moreover, each phase showed a third harmonic with an amplitude of about 0.25A after the stator branch resistance was unbalanced. Figure 7 The third harmonic and the three-phase current of the ABC phases appear in the middle. Figure 8 The quadrature-axis current i after coordinate transformation q The secondary ripples that appear corroborate each other.

[0107] exist Figure 8 The value displayed is the DC terminal voltage U. dc Cross-axis current i q And the electric angular velocity ω calculated based on the number of pole pairs p and the rotational speed n of the permanent magnet synchronous generator. e The fitted sin(2ω) e t) Waveform changes over a time interval of 1.80s to 1.82s. (From...) Figure 8 It can be seen that the DC terminal voltage U dc Cross-axis current i q The ripple caused by the asymmetry in the three-phase stator branch resistance due to a high-resistance contact fault and sin(2ω) e t) The phase remains consistent, verifying the derivation conclusions of equations (19) and (21), namely, the DC terminal voltage U dc and cross-axis current i q The asymmetry in the three-phase stator branch resistance caused by a high-resistance contact fault will generate a second harmonic based on the motor's electrical angle, and this harmonic will remain synchronized.

[0108] To verify the permanent magnet synchronous generator voltage regulation control strategy proposed in this invention that considers high-resistance contact faults, in Figures 4-8 Based on this, the compensation control strategy proposed in this invention is applied after a high-resistance contact fault occurs in phase 1sA. The DC terminal voltage U under different conditions is compared with and without the application of the compensation strategy proposed in this invention. dc and cross-axis current i q To verify the correctness and feasibility of the proposed strategy, the comparison time interval was 1.80s to 1.81s. The simulation results are as follows: Figures 9-10 As shown.

[0109] Depend on Figures 9-10 It can be seen that after applying the compensation control strategy proposed in this invention, the quadrature-axis current i q The voltage stabilizes at around -7.60A, and compared to not applying the compensation strategy proposed in this invention, the second harmonic is significantly reduced. DC terminal voltage U dc The second harmonic amplitude decreased from 0.110V to 0.082V, a reduction of approximately 26.3%.

[0110] In summary, the compensation control strategy proposed in this paper can effectively eliminate the second harmonic of the quadrature axis current and suppress the second harmonic of the DC terminal voltage in a permanent magnet synchronous generator system with three-phase stator branch resistance asymmetry caused by a high-resistance contact fault. The simulation results verify the correctness and feasibility of the compensation control strategy proposed in this invention.

Claims

1. A control strategy for a permanent magnet synchronous generator for power generation and voltage stabilization, taking into account high resistance contact faults, characterized in that: The steps are as follows: Step 1: Based on the dq rotating coordinate system, establish a mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults; Step 2: Combining the mathematical model of the permanent magnet synchronous generator considering high-resistance contact faults, and based on instantaneous power theory, derive the instantaneous power equation considering high-resistance contact faults; combining the instantaneous power equation considering high-resistance contact faults, and based on small-signal analysis, derive the quantitative relationship between the second harmonic ripple of the DC terminal voltage and the quadrature axis current. Step three: combine the quantity relation between the DC terminal voltage double frequency ripple and the quadrature axis current, and design the quadrature axis current integral average compensation method with the characteristics of the integral of the sine signal in the whole period being zero, to obtain the compensated current Permanent magnet synchronous generator power generation and voltage stabilization control is performed; The quantitative relationship between the DC terminal voltage second harmonic ripple and the quadrature axis current in step two is as follows: ； In the formula, This represents the fluctuation in DC terminal voltage caused by a high-impedance fault. This represents the fluctuation in quadrature-axis current caused by a high-resistance fault. The steady-state quantity of DC terminal voltage affected by high-impedance faults. This represents the steady-state quantity of the quadrature-axis current affected by a high-resistance fault. This is an additional resistor in the stator branch caused by a high-resistance contact fault. A capacitor connected in parallel to the DC terminal. The electric angular velocity of the motor; The current compensated in step three Is: ； wherein, is the compensated q-axis given current, is the q-axis given current output by the voltage outer loop PI controller, is the fluctuation of the quadrature axis current affected by the high impedance fault, is the steady state of the quadrature axis current affected by the high impedance fault, is the electrical angular velocity of the motor, is the quadrature axis current double frequency ripple amplitude coefficient.

2. The permanent magnet synchronous generator power generation and voltage regulation control strategy considering high resistance contact faults according to claim 1, characterized in that: The mathematical model of the permanent magnet synchronous generator in step one is as follows: ； wherein ; In the formula, This is the dq-axis voltage. For dq axis current, For dq axis inductance, The electric angular velocity of the motor. For rotor flux linkage, Stator resistors The dq-axis components and coupling components, The electric angle is the motor angle.

3. The permanent magnet synchronous generator voltage regulation control strategy considering high-resistance contact faults according to claim 1, characterized in that: The instantaneous power equation in step two is: ； In the formula, The electric angular velocity of the motor. For rotor flux linkage, For stator resistance, This is an additional resistor in the stator branch caused by a high-resistance contact fault. For the electric angle of the motor, A capacitor connected in parallel to the DC terminal. For DC load resistor, DC terminal voltage This is the q-axis current.

4. The permanent magnet synchronous generator power generation and voltage regulation control strategy considering high resistance contact faults according to claim 1, characterized in that: The control structure of the quadrature-axis current integral mean compensation method is as follows: the output terminals of the DC-end load reference voltage and the actual voltage are both connected to the input terminal of the voltage outer loop PI controller (5). The output terminal of the voltage outer loop PI controller (5) is connected to the input terminal of the first integral element (16) and the input terminal of the delay element (17), respectively. The output terminal of the delay element (17) is connected to the input terminal of the second integral element (18). The output terminals of the first integral element (16) and the second integral element (18) are both connected to the input terminal of the mean element (19). The output terminal of the mean element (19) and the output terminal of the current inverse Park transform (14) are both connected to the input terminal of the q-axis current inner loop PI controller (7). The output terminals of the d-axis reference current and the current inverse Park transform (14) are both connected to the input terminal of the d-axis current inner loop PI controller (8). The output terminal of the q-axis current inner loop PI controller (7) is connected to the input terminal of the d-axis current inner loop PI controller (8). The output terminals of the q-axis current inner loop voltage compensation structure (9) are connected to the input terminals of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11). The output terminals of the d-axis current inner loop PI controller (8) and the d-axis current inner loop voltage compensation structure (10) are connected to the input terminals of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11). The output terminals of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11) are connected to the input terminals of the SVPWM controller (12). The output terminals of the SVPWM controller (12) are connected to the input terminals of the third PWM rectifier (13). The third PWM rectifier (13) is connected to the input terminals of the permanent magnet synchronous generator (15). The output terminals of the permanent magnet synchronous generator (15) are connected to the input terminals of the current inverse Park transformation (14), the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11), and the SVPWM controller (12), respectively.

5. The permanent magnet synchronous generator power generation and voltage regulation control strategy considering high resistance contact faults according to claim 1, characterized in that: The quadrature-axis current integral mean compensation method is as follows: DC terminal load reference voltage given signal With actual voltage signal The input signal of the voltage outer loop PI controller (5) is obtained after subtraction, and the output signal of the voltage outer loop PI controller (5) is the given q-axis current. The input signal of the integral average compensation controller (6) is the q-axis given current after compensation. With the actual q-axis current signal The input signal of the q-axis current inner loop PI controller (7) is obtained after subtraction, and the d-axis given current is obtained. With the actual d-axis current signal The input signal of the d-axis current inner loop PI controller (8) is obtained by subtracting the output signal of the q-axis current inner loop PI controller (7) from the voltage compensation signal of the q-axis current inner loop. The d-axis given voltage is obtained by summing the output signal of the d-axis current inner loop PI controller 8 with the output signal of the d-axis current inner loop voltage compensation structure (10). As the input signal for the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11), the output signal αβ of the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11) is the given voltage. The signals are respectively used as input signals to the SVPWM controller (12), the output signal of the SVPWM controller (12) is used as input signals to the third PWM rectifier (13), the output signal of the third PWM rectifier (13) is used as input signals to the permanent magnet synchronous generator (15), and the output signal of the permanent magnet synchronous generator (15) is the three-phase current of ABC. With corner information As the input signal of the inverse Park transform (14), the output signal of the permanent magnet synchronous generator (15) is the rotation angle information. It also serves as the input signal for the transformation from the dq two-phase rotating coordinate system to the αβ two-phase stationary coordinate system (11) and the SVPWM controller (12), representing the actual current along the d-axis. With q-axis actual current As the output signal of the inverse Park transform of the current (14); Within the integral average compensation controller (6), the output signal of the voltage outer loop PI controller (5) provides the q-axis current. The output signals of the delay stage (17) and the integral stage (18) are respectively used as input signals for the integral stage (16) and the delay stage (17). The output signal of the delay stage (17) is used as the input signal for the integral stage (18). The difference between the output signals of the integral stage (16) and the integral stage (18) is used as the input signal for the averaging stage (19). The output signal of the averaging stage (19) is the current for q-axis compensation. .

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