400Hz inverter repetitive control loop parameter adaptive adjustment method suitable for inductance parameter disturbance

Abstract

The invention discloses a 400 Hz inverter repetitive control loop parameter adaptive adjustment method suitable for inductance parameter disturbance, and belongs to the field of inverter control. The method comprises the following steps of: establishing a mathematical relationship among a voltage outer loop proportional integral (PI) parameter, a damping ratio of a physical controlled object Po and a natural resonant frequency of an LC filter by taking a Peq amplitude-frequency characteristic of an RC controlled object under the condition that a system operates at a power which is three times of a designed output power, namely three times of an overload condition as a reference; and the PI parameter and the damping ratio are dynamically adjusted on line to realize the amplitude and phase angle matching of the physical controlled object Po at the resonant frequency when the inductance value changes. According to the invention, good stability and harmonic suppression effect of the repetitive control system under the fluctuation of the filter inductance value can be realized, and the output voltage quality of the intermediate-frequency inverter power supply under different loads can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of medium frequency inverter power supply control, and particularly relates to applications such as aviation, aerospace and navigation. The medium frequency inverter power supply achieves low-order harmonic suppression in a wide frequency range while ensuring good system stability. Background Art

[0002] Medium frequency inverter is a device that uses power electronic devices to convert electric energy. It can be input with AC or DC and obtain a constant voltage and frequency 115V / 400Hz AC output. It is widely used in many fields such as industry, national defense, navigation, aviation, etc. 400Hz inverter fundamental frequency f 0 Higher than the traditional 50Hz inverter, making it low harmonic n f 0 Usually it is outside the control bandwidth. Low-order harmonics outside the control bandwidth will greatly reduce the output voltage quality.

[0003] Repetitive Control (RC) eliminates harmonics by constructing an internal model of periodic signals. The advantage is that the N-beat delay link in the repetitive control internal model is easy to implement in the z domain, but the adjustment time of an independent RC system is not less than one fundamental wave cycle, and the system dynamic response is slow. To this end, by adding a PI fast response outer loop to form an inserted RC or parallel RC, a dynamic and steady-state control effect similar to that of the Harmonic Resonant Regulator (HRr) which is also based on the internal model principle is achieved.

[0004] In 400Hz medium frequency applications, the inverter power supply needs to have a certain overload capacity. Even if the iron-nickel core with good DC bias resistance is selected, the filter inductance value fluctuation range is still large, and the LC filter resonant frequency will still shift over a large range, thus affecting the inverter control stability and output voltage quality; in addition, the change of the filter inductance value will also cause the inverter physical control object P o The damping ratio is offset, making the RC controlled object P eq The amplitude-frequency response of the RC controlled object varies in a wide range. Therefore, obtaining a relatively smooth amplitude-frequency characteristic with a small variation range is the basis for achieving good stability and harmonic suppression performance of the 400Hz inverter system. Summary of the invention

[0005] Purpose of the invention: In order to solve the problem of amplitude-phase characteristic change of RC controlled object caused by inductance parameter disturbance under overload condition, the present invention provides a method for adaptively adjusting parameters of 400Hz inverter repetitive control loop under inductance parameter disturbance, which can dynamically adjust PI parameters and damping ratio online to realize the physical controlled object P when the inductance value changes. oThe amplitude and phase angle are matched at the natural resonant frequency.

[0006] Technical solution: The present invention provides a method for adaptively adjusting parameters of a repetitive control loop under inductance parameter disturbance, the method comprising step 1: setting the system to operate at three times the designed output power, i.e., three times overload, by the transfer function H 1 (s) and the inductor current feedback G AD (z) The phase margin of the inner current loop Adjust the current inner loop feedback gain and calculate P o The damping ratio is ξ o3 Step 2: Set P under triple overload o The control bandwidth is calculated as k. p and zero is ω z3 Step 3: Calculate when the controlled object P o Only under PI independent control, the system open-loop transfer function G o_PI (s), amplitude and phase angle under triple overload. Step 4: Set the actual operating range of inductance parameters [L min L max ], calculate L x The physical controlled object P o Step 5: G at three times overload o_PI3 The amplitude and phase angle of (s) are used as the basis to calculate the PI zero point ω at each natural resonant frequency. zx and the damping ratio ξ of the RC controlled object ox Step 6: Calculate the results (ω zx ,f rx ) and (ξ ox , f rx ) Use quadratic polynomial fitting to establish the LC filter's inherent resonant frequency and the voltage outer loop PI coefficient, P o Mathematical relationship between damping ratios.

[0007] The PI expression is:

[0008]

[0009] where k p is the proportional gain coefficient, s is the Laplace operator, ω zx It is zero point.

[0010] When the controlled object P o Open-loop transfer function G under PI independent control only o_PI The constraint relationship of (s) is:

[0011]

[0012] Among them G o_PI3 (s) is the open-loop transfer function of the system under triple overload, G o_PIx (s) is the open-loop transfer function of the system when the output power is less than three times the overload condition.

[0013] Based on the zero point ω of this constraint relationship zx The LC filter has a natural resonant frequency ω rx The mathematical relationship is:

[0014]

[0015] where ω z3 is the selected zero point under triple overload, ω r3 is the resonant angular frequency of the system under triple overload, ξ o3 is the damping ratio of the system under triple overload. The open-loop transfer function of the system is:

[0016]

[0017] Where ω r is the natural resonant angular frequency of the LC filter, K 2 Represents the physical controlled object P o The transfer function, ξ o represents the damping ratio of the system, ξ ox The LC filter has a natural resonant frequency ω rx The mathematical relationship is as follows:

[0018]

[0019] Where ω z3 is the selected zero point under triple overload, ω r3 is the resonant angular frequency of the system under triple overload, ω zx According to the LC filter's natural resonant frequency ω rx Calculated zero point.

[0020] By dynamically adjusting the PI parameters and damping ratio online, the physical controlled object P can be realized when the inductance value changes. o The amplitude and phase angle are matched at the resonant frequency.

[0021] The beneficial effects brought by adopting the above technical solution are:

[0022] (1) The control scheme is simple to implement digitally and the code execution time is short.

[0023] (2) The inverter of the present invention dynamically adjusts the PI parameters and damping ratio online to achieve the physical controlled object P when the inductance value changes. oMatching the amplitude and phase angle at the resonant frequency can ensure that the system has good stability and harmonic suppression capabilities when RC is used. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the implementation diagram of the repetitive control method for medium frequency inverter power supply.

[0025] Figure 2 Flow chart for quick response outer loop PI parameter setting and damping coefficient adjustment.

[0026] Figure 3 For the current inner loop, when the controlled object P o Open-loop transfer function G when running at three times overload only under PI independent control o_PI3 and the equivalent controlled object P under triple overload eq3 Frequency response curve.

[0027] Figure 4 is the PI controller zero point ω z The natural resonant frequency f r The quadratic polynomial fit plot between .

[0028] Figure 5 is the damping ratio ξ o The LC filter has a natural resonant frequency f r The quadratic polynomial fit plot between .

[0029] Figure 6 The RC equivalent controlled object P to which the dynamically adjusted PI parameters and damping ratio are applied under the condition of the resonant frequency changing is eq The Bode diagram. DETAILED DESCRIPTION

[0030] In order to make the purpose and technical solution of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The present invention provides a PI fast response outer loop in a medium frequency inverter repetitive control loop and a controlled object P o Damping ratio parameter setting process.

[0032] Figure 1 This is an implementation diagram of a repetitive control method for a medium frequency inverter power supply. The inductor current is sampled to control the inner loop of the system current. The sampled output voltage is provided to a repetitive controller and a proportional-integral controller to control the output voltage.

[0033] Figure 2 The flow chart of the fast response outer loop PI parameter setting and damping coefficient adjustment is shown below. Figure 2 As shown, the proportional gain, zero point and damping coefficient are selected to minimize the change in the amplitude and phase characteristics of the system.

[0034] Figure 2 Step 1: First set the phase margin of the current inner loop under triple overload is 25°, the damping coefficient ξ is calculated o3 It is 0.38.

[0035] Step 2: Further design of G under triple overload o_PI The bandwidth of (s) is controlled at 900 Hz, at which point the proportional gain k of the PI controller is p =2π·880rad / s, zero point ω z3 =2π·15000rad / s.

[0036] Calculate each resonant frequency f rx The corresponding ξ ox and ω zx The following constraints need to be met:

[0037]

[0038] G o_PI3 (s) is the open-loop transfer function of the system under triple overload, G o_PIx (s) is the open-loop transfer function of the system when the output power is less than three times the overload condition.

[0039] Physical controlled object P o The open-loop transfer function P o (s) is as follows:

[0040]

[0041] Where ω r is the resonant natural frequency of the LC filter, K 2 Represents the physical controlled object P o The transfer function, ξ o Represents the damping ratio of the system.

[0042] Based on the constraint relation of formula (1), the zero point ω zx The LC filter has a natural resonant frequency ω rx The mathematical relationship is:

[0043]

[0044] where ω z3 is the selected zero point under triple overload, ωrx is the resonant angular frequency of the LC filter under the corresponding inductance parameters, ω r3 is the resonant angular frequency of the system under triple overload, ξ o3 is the damping ratio of the system under three times overload.

[0045] Based on equations (1) and (2), ξ ox The natural resonant frequency of the LC filter ω rx The mathematical relationship is:

[0046]

[0047] Where ω z3 is the selected zero point under triple overload, ω r3 is the resonant angular frequency of the system under triple overload, ω zx According to the LC filter's natural resonant frequency ω rx Calculated zero point.

[0048] Step 3: Calculate when the controlled object P o Only under PI independent control, the system open-loop transfer function G o_PI (s) Amplitude and phase angle under triple overload condition. Figure 3 is the phase margin of the inner current loop The open-loop transfer function when the controlled object is 25° o Only in proportional gain k p =2π·880rad / s, zero point ω z3 =2π·15000rad / s PI independent control system open loop transfer function G o_PI (S), and the equivalent controlled object P under triple overload eq 3 Frequency response curve

[0049] Step 4: Set the actual operating range of inductance parameters [L min L max ], calculate L x The physical controlled object P o The natural resonant frequency f rx ∈(f r0 , f r3 ), based on equations (3) and (4), the corresponding resonant frequency f is calculated rx The next ox and ω zx The initial value of the design calculation is the resonant frequency f when the system is unloaded. r0 The calculated termination value is the resonant frequency f when the system is three times overloaded r3 .

[0050] Step 5: Increase the resonant angular frequency value and determine the f at this time rx Does it satisfy f rx ∈(f r0 , f r3 ) and repeat the calculation in step 3.

[0051] Step 6: When f rx >f r3 When , terminate the calculation and draw (ω zx ,f rx ) and (ξ ox , f rx ) and perform a quadratic polynomial fit. Figure 4 For when f r When the damping coefficient ξ changes o The image and polynomial fitting results of Figure 5 For when f r When the PI controller zero point ω changes z The image and polynomial fitting results.

[0052] Apply the fitted dynamically adjusted PI parameters and damping ratio to the RC equivalent controlled object P eq , P eq Birdtower Figure 6 As shown, within the range of the LC filter's inherent resonant frequency, P eq The amplitude and phase angle show good uniformity in the low harmonic frequency band.

[0053] The inverter of the present invention dynamically adjusts the PI parameters and the damping ratio online to achieve the physical controlled object P when the inductance value changes. o Matching the amplitude and phase angle at the resonant frequency can ensure that the system has good stability and harmonic suppression capabilities when RC is used.

[0054] The above embodiments are only for illustrating the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for adaptively adjusting parameters of a 400Hz inverter repetitive control loop under inductance parameter disturbance, the method comprising online dynamic adjustment of PI parameters, physical controlled object P o The damping ratio is characterized by: The system is operated at three times the design output power, that is, three times the overload condition. o The amplitude / phase-frequency characteristic curve is used as a reference to dynamically adjust the PI parameters and damping ratio online to achieve the physical controlled object P when the inductance value changes. o The amplitude and phase angle are matched at the resonant frequency.

2. The method for adaptively adjusting parameters of a 400Hz inverter repetitive control loop under inductance parameter disturbance according to claim 1 is characterized in that: The adjustment steps are: Step 1: Set the system to operate at three times the designed output power, that is, three times the overload condition, which is determined by the transfer function H1(s) and the inductor current feedback G AD (z) The phase margin of the inner current loop Adjust the feedback gain of the current inner loop and calculate P o The damping ratio is ξ o3 ; Step 2: Set P under triple overload o The control bandwidth is calculated as k. p and zero is ω z3 ; Step 3: Calculate when the physical controlled object P o Only under PI independent control, the system open-loop transfer function G o_PI (s) Amplitude and phase angle under triple overload; Step 4: Set the actual operating range of inductance parameters [L min L max ], calculate L x The physical controlled object P o The natural resonant frequency f x ; Step 5: Triple G overload o_PI3 The amplitude and phase angle of (s) are used as the basis to calculate the PI zero point ω at each natural resonant frequency. zx and the damping ratio ξ of the RC controlled object ox ; Step 6: Calculate the results (ω zx , f rx ) and (ξ ox , f rx ) Use quadratic polynomial fitting to establish the inherent resonant frequency of the LC filter and the voltage outer loop PI coefficient, P o Mathematical relationships between damping ratios; The physical controlled object P is connected in series o Only under PI independent control, the system open-loop transfer function G o_PI The constraint relationship of (s) is: Among them G o_PI3 (s) is the open-loop transfer function of the system under triple overload, G o_PIx (s) is the open-loop transfer function of the system when the output power is less than three times the overload condition.

3. According to the adjustment step of the method for adaptively adjusting parameters of a 400Hz inverter repetitive control loop under inductance parameter disturbance as described in claim 2, the voltage outer loop PI coefficient in step 2 is related to the inherent resonant angular frequency ω of the LC filter. rx The mathematical relationship between is characterized by The expression of PI controller is: where k p is the proportional gain coefficient, s is the Laplace operator, and the zero point ω zx The LC filter has a natural resonant frequency ω rx The mathematical relationship is: where ω z3 is the selected zero point under triple overload, ω r3 is the resonant frequency of the system under triple overload, ξ o3 is the damping ratio of the system under three times overload.

4. According to the adjustment step of the method for adaptively adjusting parameters of a 400 Hz inverter repetitive control loop under inductance parameter disturbance as described in claim 2, the P in step 2 o Damping ratio and LC filter natural resonant angular frequency ω rx The mathematical relationship between is characterized by: P o The open-loop transfer function is as follows: Where ω r is the natural resonant frequency of the LC filter, K2 represents the physical controlled object P o The transfer function, ξ o represents the damping ratio of the system, ξ ox The LC filter has a natural resonant frequency ω rx The mathematical relationship is as follows: Where ω z3 is the selected zero point under triple overload, ω r3 is the resonant angular frequency of the system under triple overload, ω zx According to the LC filter's natural resonant angular frequency ω rx Calculated zero point.

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