Multi-frequency adaptive wave trap rotor position estimation method applied to direct-driven wave power generation

Abstract

The invention discloses a multi-frequency adaptive wave trap rotor position estimation method applied to direct-driven wave power generation, which is characterized in that an error signal in high-frequency current is extracted through a PMLG mathematical model which is simplified under excitation of a high-frequency pulsating signal and an adaptive wave trap which is designed by combining a minimum mean square root algorithm, so that accurate estimation of the rotor position is realized. In order to overcome the limitation of a traditional single-frequency wave trap in complex sea conditions, the ANF is expanded to be of a multi-frequency structure so as to suppress multi-frequency interference signals, and it is ensured that a system stably operates in an offshore power generation scene with frequent dynamic wave load change. Through the designed signal modulation and demodulation method, the system can separate a direct-current error component from high-frequency harmonic waves, and precise rotor position tracking without a position sensor is achieved in combination with closed-loop control. The invention provides an innovative solution, the control precision of the direct-driven wave power generation system is remarkably improved, and noise interference and system maintenance cost are reduced.

Description

Technical Field

[0001] This invention relates to the field of wave energy generation technology, specifically to a method for estimating the rotor position of a multi-frequency adaptive notch filter applied to direct-drive wave power generation. Background Technology

[0002] Floating wave energy generation systems have important applications in the marine energy sector, but current wave power generation technology still faces challenges such as structural design, control strategies, and sea condition adaptability. Especially in the marine environment, traditional mechanical position sensors are susceptible to temperature, humidity, and corrosion, leading to high failure rates and high maintenance costs. Therefore, sensorless control technology has become an important development direction for direct-drive wave power generation systems.

[0003] Currently, the application of sensorless control technology in wave power generation still faces challenges, especially at low speeds. Existing methods struggle to cope with noise and interference in complex sea conditions, leading to insufficient accuracy in rotor position estimation. Therefore, researching a novel sensorless control method is of paramount importance. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the purpose of this invention is to provide a multi-frequency adaptive notch wave generator rotor position estimation method for direct-drive wave power generation, aiming to improve the robustness and control accuracy of wave power generation systems under complex sea conditions through efficient and stable sensorless control technology.

[0005] The objective of this invention can be achieved through the following steps:

[0006] A method for estimating the rotor position of a multi-frequency adaptive notch filter applied to direct-drive wave power generation includes:

[0007] Step 1: In the direct-drive wave power generation system, based on the mathematical model of the high-frequency pulse signal excitation and permanent magnet linear generator, under low-speed conditions and when the injected signal is much greater than the fundamental frequency, the resistance voltage drop and electric angular velocity terms are ignored to obtain the simplified mathematical model of the motor.

[0008] Step 2: Based on the mathematical model of the motor and the dq coordinate system, design an adaptive notch filter based on the least mean square algorithm to extract the linearization error signal from the high-frequency current.

[0009] Step 3: Extend the adaptive notch filter to a multi-frequency structure, design a multi-frequency adaptive notch filter, and filter different frequencies to suppress multi-frequency interference signals at sea.

[0010] Step 4: Modulate the q-axis high-frequency current signal, input the error signal regulated by the multi-frequency adaptive notch filter into the phase-locked loop, extract the rotor angle error signal, and realize accurate estimation of the rotor position.

[0011] Furthermore, the low-speed operating condition is when the speed of the permanent magnet linear generator is less than 200 revolutions per minute.

[0012] Furthermore, the simplified mathematical model of the motor is as follows:

[0013]

[0014] Among them, u d and u q Represents the high-frequency voltage components along the d-axis and q-axis, i d and i q L represents the high-frequency current components along the d-axis and q-axis. d L q These are the d-axis and q-axis inductances.

[0015] Furthermore, the transfer function of the adaptive notch filter is:

[0016]

[0017] Where μ is the adjustable gain, ω h For the target frequency, I sx (s) is the initial signal, I sx (s) is the notch output signal.

[0018] Furthermore, the linearization error signal is:

[0019]

[0020] in, For rotor estimation error, θ e This is the actual angle of the rotor. Estimate the rotor angle.

[0021] Furthermore, the adaptive notch filter is extended to a multi-frequency structure: multiple independent adaptive notch filters are connected in parallel, and each adaptive notch filter has a transfer function designed for a different frequency.

[0022] Furthermore, for dual-frequency notch filters, the transfer function of the multi-frequency adaptive notch filter is:

[0023]

[0024] Where ω and 2ω are the different frequencies that need to be filtered out.

[0025] Furthermore, by employing a multi-frequency adaptive notch filter, the high-frequency current signal is modulated as follows:

[0026]

[0027] in, For rotor estimation error, θ e The angle between the dq coordinate system and the α-β coordinate system. For θ e The estimated value, HF(ω) h t) represents the first high-frequency harmonic, HF(2ω) h t) represents the second high-frequency harmonic and HF(ω) s t) represents the PW current harmonic term, ω h For the target frequency, ω s This refers to the harmonic frequency.

[0028] Furthermore, the relationship between the target frequency and the harmonic frequency is: ω h =nω s , n>6.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention solves the reliability problem of traditional position sensors in marine environments by combining high-frequency pulse injection method with multi-frequency adaptive notch filter technology, significantly improving the control accuracy of direct-drive wave power generation systems. Firstly, this invention extracts the rotor angle error signal through high-frequency current response and uses the LMS algorithm to dynamically adjust the notch filter parameters, overcoming the limitations of traditional ANF single-frequency filtering. The further extended MANF can simultaneously suppress multi-frequency interference signals, ensuring the stability of filtering performance under complex sea conditions. Through the designed signal modulation and demodulation method, the system can separate the DC error component from high-frequency harmonics, and combined with closed-loop control, achieve accurate rotor position tracking without position sensors. Compared with existing technologies, this invention retains the speed of the high-frequency injection method while significantly reducing the misjudgment rate caused by noise interference, reducing system maintenance costs, and is suitable for offshore power generation scenarios with frequent changes in dynamic wave loads. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0033] Figure 2 This is a block diagram of an adaptive notch filter based on the LMS algorithm.

[0034] Figure 3 This is a graph showing the amplitude-frequency response of MANF in dual-frequency form.

[0035] Figure 4 Loop diagram for rotor position estimation. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, a method for estimating the rotor position of a multi-frequency adaptive notch filter applied to direct-drive wave power generation includes the following steps:

[0038] Step 1: In a direct-drive wave power generation system, a mathematical model based on high-frequency pulsed signal excitation and a permanent magnet linear generator (PMLG) is established. This is under low-speed operating conditions with a high-frequency injected signal (frequency ω). h When the frequency is much greater than the fundamental frequency, the voltage drop across the resistor and the electric angular velocity term are ignored, resulting in a simplified mathematical model of the motor.

[0039] In direct-drive wave power generation systems, the operating characteristics of the permanent magnet linear generator (PMLG) directly affect the energy conversion efficiency. To accurately estimate the rotor position, a mathematical model of the PMLG needs to be established using the high-frequency pulse injection method. In the dq coordinate system, the voltage equation of the PMLG is:

[0040]

[0041] The mathematical model of PMLG is simplified under high-frequency pulse signal excitation, and the high-frequency injected signal (frequency ω) is applied in the low-speed domain. h When the frequency is much greater than the fundamental frequency, neglecting the voltage drop across the resistor and the electrical angular velocity term, a simplified model is obtained:

[0042]

[0043] In the formula, u d and u q Represents the high-frequency voltage components along the d-axis and q-axis, i d and i q This represents the high-frequency current components along the d-axis and q-axis. Through the inverse Park transform, the high-frequency voltage in the α-β coordinate system can be expressed as:

[0044]

[0045] The angle between the dq coordinate system and the α-β coordinate system is θ. e dq coordinate system and The angle between the coordinate systems is The high-frequency voltage equation in the α-β coordinate system is obtained through the inverse Park transformation. By analogy, the equation in the estimated rotor coordinate system of the motor can be obtained. Lower high-frequency voltage equation:

[0046]

[0047] In the observation coordinate system dq, the following high-frequency voltage is injected along the d-axis.

[0048]

[0049] The resulting q-axis high-frequency current response is:

[0050]

[0051] In the formula, The amplitude of the high-frequency response current. The rotor estimation error is given by L, where L is the average inductance, ΔL is the half-differential inductance, and the q-axis high-frequency current amplitude includes the angle error signal. When the error θ... e When the value is extremely small, the linearization error signal can be obtained:

[0052]

[0053] By injecting high frequency, the q-axis current directly contains the angle error signal, which provides a linearization basis for subsequent error extraction and solves the problem of weak signal under low-speed conditions.

[0054] Step 2: Based on linearized error signal analysis, the error signal is extracted from the high-frequency current by an adaptive notch filter (ANF) based on the least mean square (LMS) algorithm. The adjustable gain μ is dynamically adjusted to achieve error tracking and enable the direct-drive wave power generation system to adapt to changes in marine interference in real time.

[0055] To extract subtle rotor position errors from complex current signals, a high-precision filter needs to be designed. Traditional fixed-bandwidth notch filters are ill-suited to the dynamic interference of the marine environment. Therefore, an adaptive notch filter (ANF) based on the least mean square (LMS) algorithm is designed to extract error signals from high-frequency currents. This invention employs an adaptive notch filter based on the LMS algorithm, as shown in the attached figure. Figure 2 As shown. The input signal i s (t) includes the target frequency ω h With noise components, through the orthogonal reference signal sin(ω) h t) and cos(ω) h t) Separate the sine and cosine components. Error tracking is achieved by adjusting the adjustable gain μ:

[0056] p1=∫[μ·e r(t)·sin(ω h t)]dt

[0057] The closed-loop transfer function of the filter output is derived using the Laplace transform and Euler's formula:

[0058]

[0059] By subtracting the reference input signal from the filtered output signal, the transfer function of the notch filter output can be obtained as follows:

[0060]

[0061] The ANF notch filter output transfer function is an equivalent second-order transfer function. The difference lies in the fact that the ANF has time-varying coefficients, especially the adjustable gain μ, which enables adaptive weighting coefficients. By changing μ, the bandwidth of the filter can be altered. Substituting s = jωh into the above equation, we obtain G. sx (jωh)=0, meaning ANF operates at frequency ω h The gain of the input signal is 0, thus filtering out signals of that frequency.

[0062] Increasing μ can improve the convergence speed, but it will introduce steady-state error. In practical applications, μ needs to be dynamically adjusted according to the operating conditions (such as the wave frequency fluctuation range) to control the bandwidth and convergence speed of the filter.

[0063] Step 3: Extend the ANF to a multi-frequency structure (MANF), and design a control scheme based on the transfer function of the multi-frequency MANF to filter different frequencies, thereby effectively suppressing multi-frequency interference signals at sea.

[0064] To address multi-frequency interference (such as PWM harmonics) present in practical systems, the ANF (Application-Related Function) is extended into a multi-frequency structure. Taking a dual-frequency notch filter (frequency ω and 2ω) as an example, in a dual-frequency MANF, two independent ANF units are connected in parallel, and transfer functions are designed for the ω and 2ω frequencies respectively:

[0065] The transfer function of MANF is:

[0066]

[0067] Simulation verification shows that at ω h =100Hz and 2ω h At 200Hz, MANF's amplitude attenuation reaches -40dB with minimal impact on other frequency bands, indicating its highly efficient multi-frequency suppression capability, as shown in the attached figure. Figure 3 As shown.

[0068] Step 4: Modulate the q-axis high-frequency current signal, and use the demodulated error signal to input into the phase-locked loop to extract the rotor angle error signal, thereby achieving accurate estimation of the rotor position.

[0069] Finally, rotor position estimation is achieved through error signal demodulation and position observation strategies. The loop diagram for rotor position estimation based on MANF is attached. Figure 4 As shown. The actual high-frequency current response includes a DC component, high-frequency harmonics, and PWM noise. The modulated signal can be decomposed into:

[0070]

[0071] In the formula, HF(.) represents the high-frequency harmonic term. This is achieved by setting ω... h =nω s (n>6), making the interfering component ω h The error signal f(θ) is an integer multiple thereof and is filtered out by MANF. e )=2kθ e The input is sent to the position observer to estimate the rotor position, and the PWM signal is generated through closed-loop control.

[0072] Combination Figure 1 It can be seen that the known switching frequency ω s and the injected high-frequency signal frequency ω h Then, through the designed MANF, the target position error signal f(θ) can be extracted. e Furthermore, the designed MANF can adapt to different ω s With ω h Adaptive adjustment requires filtering out frequencies, thus achieving adaptive frequency filtering.

[0073] To overcome the limitations of traditional single-frequency notch filters in complex sea conditions, this invention extends the ANF (Anti-Ambient Fluid Filter) to a multi-frequency structure (MANF) to suppress multi-frequency interference signals and ensure stable system operation in offshore power generation scenarios with frequently changing dynamic wave loads. Through the designed signal modulation and demodulation method, the system can separate the DC error component from high-frequency harmonics, and combined with closed-loop control, achieve precise rotor position tracking without position sensors. This invention provides an innovative solution that significantly improves the control accuracy of direct-drive wave power generation systems while reducing noise interference and system maintenance costs.

[0074] The present invention also provides a computer storage medium storing an executable program, which is executed by a processor to implement the steps of the multi-frequency adaptive notch filter rotor position estimation method.

[0075] It should be noted that the high-frequency voltage and high-frequency current in this embodiment are common terms in the art, and refer to current and voltage relative to the 50Hz AC power frequency. No range needs to be given. The innovation of this invention lies in the design of the controller in the closed loop. The control loop is well known in the art and will not be described in detail here.

[0076] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] The foregoing has shown and described the basic principles, main features, and advantages of this disclosure. Those skilled in the art should understand that this disclosure is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this disclosure. Various changes and modifications can be made to this disclosure without departing from its spirit and scope, and all such changes and modifications fall within the scope of this disclosure as claimed.

Claims

1. A multi-frequency adaptive notch filter rotor position estimation method applied to direct drive wave power generation, characterized by, The application relates to a multi-frequency adaptive notch filter rotor position estimation method. Step 1. In a direct-drive wave power generation system, based on a high-frequency pulse signal excitation and a mathematical model of a permanent magnet linear generator, a simplified motor mathematical model is obtained under low-speed working conditions and when an injected signal is far greater than a fundamental frequency, resistance voltage drop and electric angular velocity items are ignored; Step 2. Based on the motor mathematical model and a dq coordinate system, an adaptive notch filter based on a least mean square root algorithm is designed to extract a linearization error signal from a high-frequency current; Step 3. The adaptive notch filter is expanded into a multi-frequency structure, a multi-frequency structure adaptive notch filter is designed, different frequencies are filtered respectively, and offshore multi-frequency interference signals are suppressed; Step 4. A q-axis high-frequency current signal is modulated, an error signal of the multi-frequency structure adaptive notch filter is input into a phase-locked loop, a rotor angle error signal is extracted, and accurate estimation of a rotor position is realized.

2. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 1, characterized in that, The low-speed working condition in step 1 is that the speed of the permanent magnet linear generator is less than 200 revolutions per minute.

3. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 1, characterized in that, The simplified motor mathematical model in step 1 is as follows: wherein u d and u q represent the high-frequency voltage components of the d-axis and q-axis, i d and i q represent the high-frequency current components of the d-axis and q-axis, L d and L q are the d-axis and q-axis inductances.

4. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 1, characterized in that, The transfer function of the adaptive notch filter in step 2 is as follows: where μ is an adjustable gain, ω h is the target frequency, I sx (s) is the initial signal, I sx (s) is the notch output signal.

5. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 4, characterized in that, The linearization error signal in step 2 is as follows: wherein, is the rotor estimation error, θ e is the rotor actual angle, is the rotor estimation angle.

6. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 5, characterized in that, In step 3, the adaptive notch filter is expanded into a multi-frequency structure, that is, a plurality of independent adaptive notch filters are connected in parallel, and each adaptive notch filter is designed to have a transfer function for different frequencies.

7. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 6, characterized in that, For a double-frequency notch, the transfer function of the multi-frequency structure adaptive notch filter is as follows: Wherein, omega and 2omega are different frequency frequencies that need to be filtered out.

8. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 7, characterized in that, The modulated high-frequency current signal is as follows: wherein, is the estimation error for the rotor, θ e is the angle between the d-q coordinate system and the α-β coordinate system, is the estimation value of θ e , HF(ω h t) is the first high frequency harmonic, HF(2ω h t) is the second high frequency harmonic and HF(ω s t) is the PW current harmonic term, ω h is the target frequency, ω s is the harmonic frequency.

9. A method for rotor position estimation of a multi-frequency adaptive notch filter applied to direct drive wave power generation according to claim 8, characterized in that, The relationship of the target frequency and the harmonic frequency is: ω h = nω s , n > 6.

10. A computer storage medium, characterized in that, The computer storage medium stores an executable program, and the executable program is executed by the processor to realize the steps of the multi-frequency adaptive notch filter rotor position estimation method in any one of claims 1-9.

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