Active Disturbance Rejection Grid-Connected Control Method Based on Periodic Harmonic Spread State Observer

Abstract

The present invention provides an auto-disturbance rejection grid-connected control method based on a periodic harmonic extended state observer, which relates to the technical field of grid-connected inverter control and includes: designing the structure of the extended state observer for a first-order controlled object according to the system extended state space equation; replacing the integrator for observing the generalized disturbance of the system in the structure of the extended state observer with a repetitive controller to observe the periodic harmonic disturbance through the repetitive controller; and connecting the proportional term gain h1 path for adjusting the response speed of the observer to the system state estimation in parallel with the repetitive controller to merge the disturbance observation effect of the proportional term gain h1 path into the generalized disturbance observation value, thereby obtaining a periodic harmonic extended state observer. The present invention realizes the precise compensation of grid voltage disturbance and inverter dead zone nonlinear disturbance, as well as high-precision grid-connected current control.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected inverter control, and in particular to an auto-disturbance-resistance grid-connected control method based on a periodic harmonic extended state observer. Background Art

[0002] Distributed power generation systems based on photovoltaic power generation and wind power generation have been widely built and put into use. With the rapid expansion of the scale of new energy distributed power generation systems, the requirements of distributed power generation systems for grid-connected power quality have also become an important standard. Therefore, it is very important to improve the power quality in the grid-connected new energy.

[0003] Linear active disturbance rejection control has been widely studied due to its model-free characteristics and simple design methods. The active disturbance rejection control strategy is an active disturbance compensation strategy based on the Extended State Observer (ESO), which can actively observe and compensate for disturbances. The generalized disturbance of the system is observed by ESO and compensated equivalently at the input end, eliminating the impact of the disturbance on the system and compensating the controlled object to an integral series type, and then controlling the controlled object through a linear feedback control law.

[0004] Since the power grid contains a large number of harmonics, the grid-connected inverter itself will also generate odd harmonics. These harmonics and the grid fundamental voltage are disturbances in the grid-connected inverter. They will act on the output filter of the inverter, causing the grid-connected current to be distorted. The anti-disturbance control technology can actively suppress disturbances, and because it does not rely on the controlled object model and has a simple design and is widely used in the field of motor control, but traditional anti-disturbance control is rarely used in single-phase grid-connected inverters. This is because the disturbance signals in the single-phase grid-connected inverter are all high-frequency harmonic periodic disturbance signals, and the traditional ESO only has the function of accurately observing DC disturbances, and the observation effect on periodic disturbances, especially high-frequency periodic disturbances, is poor. As the disturbance frequency increases, the traditional ESO's ability to observe disturbances will decrease rapidly, so it is impossible to accurately compensate for harmonic disturbances.

[0005] Repetitive Control (RC) based on the internal model principle is widely used due to its extremely high steady-state accuracy and excellent harmonic suppression ability. Repetitive control has a strong tracking and suppression effect on disturbances at the fundamental frequency and its multiples, and can achieve accurate grid-connected current control. However, the parameter design of repetitive control depends on the accurate mathematical model of the controlled object, and the design process is complicated. Summary of the invention

[0006] In view of this, an embodiment of the present application provides an anti-disturbance grid-connected control method based on a periodic harmonic extended state observer. By adding repetitive control based on an ideal compensator to the ESO (extended state observer), the ESO can observe the disturbances distributed at the fundamental frequency of the power grid and its positive integer multiple harmonic frequencies without difference, thereby achieving accurate compensation for the power grid voltage disturbance and the nonlinear disturbance of the inverter dead zone, and ultimately realizing high-precision grid-connected current control.

[0007] The embodiment of the present application provides the following technical solution: an auto-disturbance rejection grid-connected control method based on a periodic harmonic extended state observer, comprising:

[0008] According to the system extended state space equation, the structure of the extended state observer of the first-order controlled object is designed;

[0009] The integrator used for observing the generalized disturbance of the system in the structure of the extended state observer is replaced with a repetitive controller, so as to observe the periodic harmonic disturbance through the repetitive controller;

[0010] The proportional term gain h1 path in the structure of the extended state observer, which is used to adjust the observer's response speed to the system state estimation, is connected in parallel with the repetitive controller to merge the disturbance observation effect of the proportional term gain h1 path into the generalized disturbance observation value to obtain a periodic harmonic extended state observer.

[0011] According to an embodiment of the present application, the method further includes:

[0012] Establishing a mathematical model of a controlled object of the repetitive controller to obtain a transfer function of the controlled object;

[0013] The inverse of the transfer function of the controlled object is used as a repetitive control compensation function of the repetitive controller to obtain an ideal compensator of the repetitive controller.

[0014] According to an embodiment of the present application, establishing a mathematical model of a controlled object of the repetitive controller to obtain a transfer function of the controlled object includes:

[0015] The repetitive control branch in the periodic harmonic extended state observer structure is disconnected, and the loop and forward path in the structure of the periodic harmonic extended state observer remaining after the disconnection are analyzed to obtain mathematical expressions of the loop and the forward path, and the transfer function of the controlled object is obtained according to the Mason gain formula.

[0016] According to an embodiment of the present application, the transfer function of the controlled object is as follows:

[0017]

[0018] Among them, Ts is the sampling period, and h1 is the observer pole configuration gain.

[0019] According to an embodiment of the present application, the method further includes: adopting a zero-phase-shift low-pass filter as the internal model filter in the repetitive controller, and setting the observation bandwidth of the periodic harmonic expansion state observer according to the zero-phase-shift low-pass filter.

[0020] According to an embodiment of the present application, the discrete transfer function of the zero-phase-shift low-pass filter is Q ( z )for:

[0021]

[0022] in, is the coefficient of the zero-phase-shift low-pass filter, z is a discrete-time variable, and the coefficient is required satisfy: .

[0023] According to an embodiment of the present application, the method further includes: designing a linear control law according to the system control structure and control requirements of the periodic harmonic extended state observer, and setting a control bandwidth.

[0024] According to an embodiment of the present application, the structure of an extended state observer for a second-order controlled object is designed, wherein the discrete domain state space equation of the extended state observer is as follows:

[0025]

[0026] in, represents the observed value of the grid-connected current, is the first state variable observation value of the extended state observer, represents the generalized perturbation observation, is the second state variable observation value of the extended state observer, k represents the beat number of the discrete domain state variable, h1 and h2 are the observer pole configuration gains, b0 is the input gain of the controlled object, T s is the sampling period, e1 is the input signal, u k For control signal.

[0027] According to an embodiment of the present application, the discrete domain state space equation after replacing the integrator in the extended state observer structure with a repetitive controller is as follows:

[0028]

[0029] in, represents the observed value of the grid-connected current, is the first state variable observation value of the extended state observer, represents the generalized perturbation observation, is the second state variable observation value of the extended state observer, k represents the beat number of the discrete domain state variable, h1 and h2 are the observer pole configuration gains, b0 is the input gain of the controlled object, T s is the sampling period, e1 is the input signal, u k is the control signal, is the transfer function of the repetitive controller.

[0030] According to an embodiment of the present application, the transfer function of the repetitive controller is for:

[0031]

[0032] Where Q(z) represents the internal model filter, S(z) represents the repetitive control compensator, and z -N Represents the repeated control internal model delay link, N=f s / f0,f s is the sampling frequency, f0 is the grid frequency.

[0033] Compared with the prior art, the at least one technical solution adopted by the active disturbance rejection grid-connected control method based on periodic harmonic extended state observer (PHESO) in the embodiment of the present invention can achieve the following beneficial effects:

[0034] 1. The self-disturbance-resistance grid-connected technology based on the periodic harmonic expansion state observer can well observe and suppress the harmonic disturbance of the power grid. This effect comes from the following technical points:

[0035] a) The present invention adds repetitive control to the disturbance estimation loop of the ESO, and merges the disturbance estimation effect of the proportional gain h1 path into the disturbance estimation value.

[0036] b) A zero-phase-shift low-pass filter is used to ensure that the RC (repetitive control) obtains a sufficiently large open-loop gain at the harmonic frequency that needs to be suppressed.

[0037] 2. Based on the Periodic Harmonic Extended State Observer (PHESO), it can ensure that the estimation of ESO on disturbance can converge quickly. This effect comes from the following technical points:

[0038] The present invention introduces the idea of ​​perfect cancellation of repetitive control into ESO for the first time. Since the controlled object of RC in PHESO is essentially the integrator in the algorithm, its structure is a virtual ideal link, which enables perfect cancellation to be achieved, thereby obtaining a faster observer convergence speed.

[0039] 3. The periodic harmonic expanded state observer (PHESO) can effectively suppress the influence of high-frequency noise on the observer. This effect comes from the following technical points:

[0040] The present invention uses a zero-phase-shift low-pass filter to attenuate the high-frequency gain of the RC branch in the PHESO, so that the high-frequency noise is rejected in the RC branch, thereby reducing the influence of the noise on the PHESO.

[0041] In summary, the self-disturbance-resistance grid-connected control method based on the periodic harmonic expanded state observer of the present invention ultimately achieves accurate compensation of grid voltage disturbance and inverter dead zone nonlinear disturbance, as well as high-precision grid-connected current control, and can be well applied in inverter grid-connected control. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 1 is a flow chart of an active disturbance rejection grid-connected control method based on a periodic harmonic extended state observer according to an embodiment of the present invention;

[0044] Figure 2 It is the structural diagram of the traditional second-order ESO in the discrete domain;

[0045] Figure 3 It is the Bode plot of the generalized perturbation to generalized perturbation observation error of the traditional ESO;

[0046] Figure 4 is a structural diagram of an ESO after the first integrator in a traditional ESO is replaced with a repetitive controller in an embodiment of the present invention;

[0047] Figure 5 It is a structural diagram of PHESO obtained by merging the proportional term gain h1 path observation effect into the generalized disturbance observation value in an embodiment of the present invention;

[0048] Figure 6 is a structural diagram of a repetitive controller in an embodiment of the present invention;

[0049] Figure 7 is a repetitive control structure diagram after designing an ideal compensator in an embodiment of the present invention;

[0050] Figure 8 is a complete structural diagram of PHESO after an ideal compensator is designed for repetitive control in an embodiment of the present invention;

[0051] Fig. 9 is a Bode diagram of a repetitive control branch when the repetitive controller in an embodiment of the present invention adopts a first-order zero-phase low-pass filter;

[0052] Fig.10 is a Bode diagram of the PHESO disturbance-to-disturbance observation error in an embodiment of the present invention;

[0053] Fig.11 It is a Bode comparison diagram of the embodiment of the present invention in which the proportional term gain h1 path observation effect is incorporated into the generalized disturbance observation value and not incorporated into the generalized disturbance observation value;

[0054] Fig.12 is a structure diagram of the active disturbance rejection control based on PHESO in an embodiment of the present invention;

[0055] Fig.13 This is an oscilloscope waveform diagram of the grid-connected current based on the active disturbance rejection grid-connected control method according to an embodiment of the present invention;

[0056] Fig.14 It is a current waveform distortion spectrum diagram of a power quality analyzer based on the self-disturbance rejection grid-connected control method according to an embodiment of the present invention;

[0057] Fig.15 It is a dynamic response waveform diagram based on the active disturbance rejection grid-connected control method according to an embodiment of the present invention;

[0058] Fig.16 It is a flow chart of a specific embodiment of the self-disturbance rejection grid-connected control method of the present invention. DETAILED DESCRIPTION

[0059] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0060] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0061] like Figure 1 As shown, an embodiment of the present invention provides an active disturbance rejection grid-connected control method based on a periodic harmonic extended state observer, comprising:

[0062] S101. Design the structure of the extended state observer of the first-order controlled object according to the system extended state space equation;

[0063] S102. replacing the integrator used to observe the generalized disturbance of the system in the structure of the extended state observer with a repetitive controller, so as to observe the periodic harmonic disturbance through the repetitive controller;

[0064] S103. The proportional term gain h1 path in the structure of the extended state observer, which is used to adjust the observer's response speed to the system state estimation, is connected in parallel with the repetitive controller to merge the disturbance observation effect of the proportional term gain h1 path into the generalized disturbance observation value to obtain a periodic harmonic extended state observer.

[0065] Since traditional self-disturbance control observes and compensates for disturbances by setting up ESO, and the structure of traditional ESO determines that it can only observe DC disturbances without difference, as the disturbance frequency increases, the observation ability of traditional ESO for disturbances will decrease rapidly. Repetitive control has a strong tracking and suppression effect on disturbances at the fundamental frequency and its multiples, and can achieve accurate grid-connected current control effect. However, the parameter design of repetitive control depends on the accurate mathematical model of the controlled object, and the design process is complicated. Based on this, the self-disturbance control grid-connected control technology based on the periodic harmonic expanded state observer (PHESO) of the embodiment of the present invention, based on the internal model principle, introduces repetitive control into the disturbance observation loop of ESO to improve the observation ability of ESO for periodic disturbances, so that the self-disturbance control can play a better harmonic disturbance observation and compensation ability in the application scenario of high-frequency disturbances.

[0066] In one embodiment, the method further includes: establishing a mathematical model of the controlled object of the repetitive controller to obtain the transfer function of the controlled object; using the inverse of the transfer function of the controlled object as the repetitive control compensation function of the repetitive controller to obtain the ideal compensator of the repetitive controller. Wherein, establishing the mathematical model of the controlled object of the repetitive controller to obtain the transfer function of the controlled object specifically includes: disconnecting the repetitive control branch in the periodic harmonic expanded state observer structure, analyzing the loop and forward path in the structure of the periodic harmonic expanded state observer remaining after the disconnection, obtaining the mathematical expressions of the loop and forward path, and obtaining the transfer function of the controlled object according to the Mason gain formula. This embodiment is based on the idea of ​​perfect cancellation and sets an ideal compensator in the ESO so that the repetitive control can achieve the optimal convergence speed.

[0067] In one embodiment, the method further includes: using a zero-phase-shift low-pass filter as the internal model filter in the repetitive controller, and setting the observation bandwidth of the periodic harmonic expansion state observer according to the zero-phase-shift low-pass filter. In this embodiment, the internal model filter is set as a zero-phase low-pass filter, which attenuates the high-frequency gain of the RC branch in the PHESO, enables the observer to accurately observe the harmonic disturbance in the low-frequency band, and reduces the influence of high-frequency noise on the observer.

[0068] In one embodiment, the method further includes: designing a linear control law according to the system control structure and control requirements of the periodic harmonic extended state observer, and setting a control bandwidth.

[0069] The embodiment of the present invention adds repetitive control to the ESO based on the self-disturbance rejection grid-connected technology of the periodic harmonic extended state observer, and innovatively designs a perfect cancellation structure of repetitive control in the ESO to ensure the convergence speed of the PHESO, and innovatively designs a zero-phase shift low-pass filter to limit the observation bandwidth of the PHESO. This allows the PHESO to converge quickly, while maximally ensuring the difference-free characteristics of the observer's observation disturbance and the noise suppression capability of the PHESO.

[0070] like Fig.16 As shown, according to an embodiment of the present invention, the specific steps include:

[0071] Step 1: For the first-order system of the single-phase L-type grid-connected inverter, the structure diagram of the traditional second-order ESO in the discrete domain is given, as shown in Figure 2 As shown in Figure 1, the second-order ESO is obtained by expanding the state of the first-order system and establishing it. The second-order ESO consists of the following parts: two integrators, observer pole configuration gains h1 and h2, and control signal u k The first integrator is responsible for observing the generalized disturbance f, and the other integrator is responsible for observing the current i k The observed disturbance is used for equivalent compensation at the input, thereby eliminating the influence of the disturbance. The observed current is used for the control of the current loop.

[0072] The discrete domain state space equation of the traditional ESO is as follows:

[0073]

[0074] in, represents the observed value of the grid-connected current, is the first state variable observation value of the extended state observer, represents the generalized perturbation observation, is the second state variable observation value of the extended state observer, k represents the beat number of the discrete domain state variable, h1 and h2 are the observer pole configuration gains, b0 is the input gain of the controlled object, Ts is the sampling period, e1 is the input signal, u k For control signal.

[0075] The Bode plot of the generalized perturbation to generalized perturbation observation error of the traditional ESO is as follows: Figure 3 As shown in the figure, the Bode diagram analysis shows that the traditional ESO has a low observation error only in the low frequency band, and the observation error becomes 0dB in the high frequency band, and the disturbance observation effect completely disappears. Therefore, the traditional ESO cannot achieve accurate control effect when applied to grid-connected inverters.

[0076] Step 2: Replace the integration of the disturbance estimation loop with repetitive control to improve the ESO's observation capability of periodic harmonic disturbances.

[0077] The first integrator of the traditional second-order ESO is responsible for observing generalized disturbances. Replacing the first integrator in the traditional ESO with repetitive control actually increases the open-loop gain of the observation loop. The observer is a closed-loop system. The high open-loop gain brought by repetitive control in the loop will be manifested as high-precision observation capability after the loop is closed. The structure diagram of the ESO after replacing the first integrator in the traditional ESO with repetitive control is shown in the figure below. Figure 4 shown.

[0078] Its discrete domain state equation is as follows:

[0079]

[0080] in, represents the observed value of the grid-connected current, is the first state variable observation value of the extended state observer, represents the generalized perturbation observation, is the second state variable observation value of the extended state observer, k represents the beat number of the discrete domain state variable, h1 and h2 are the observer pole configuration gains, b0 is the input gain of the controlled object, T s is the sampling period, e1 is the input signal, u k is the control signal, is the transfer function of the repetitive controller.

[0081] Compared with the state equation of the traditional ESO, the only difference is the generalized perturbation observation value The generalized disturbance observation value is directly obtained by multiplying e1 by the repeated control transfer function and then by the gain h2.

[0082] Step 3: Further incorporate the proportional gain h1 path observation into the generalized disturbance observation value to obtain the structure diagram of PHESO as follows: Figure 5As shown. In PHESO, it can be seen intuitively that the generalized disturbance observation value is composed of repetitive control and parallel proportional term h1. Proportional parallel repetitive control is essentially equivalent to a proportional inertia multi-resonance controller, in which the proportional term is responsible for the rapidity of PHESO observation, the inertia link is responsible for the observation of DC disturbances, and the multi-resonance is responsible for the observation of periodic disturbances. Therefore, the application of PHESO in grid-connected inverters can ensure both rapidity and the suppression of non-periodic disturbances and periodic disturbances.

[0083] The corresponding PHESO state equation is as follows:

[0084]

[0085] Step 4: Repeat the basic structure of the control Figure 6 As shown, e1 is the input signal of repeated control, y rc is the output signal. The transfer function of RC is:

[0086]

[0087] Among them, Q(z) is the internal model filter, and S(z) is the repetitive control compensator. The role of Q(z) is to limit the open-loop gain of RC at different frequencies, so that RC has a larger open-loop gain at low frequencies and the open-loop gain decays rapidly at high frequencies. In this way, the zero-difference characteristics of RC can be maintained as much as possible while ensuring the stability of the system. The role of S(z) is to compensate the controlled object of RC to a frequency characteristic close to 0dB and 0 phase. This can optimize the performance of RC. Therefore, to design S(z), you first need to know the controlled object of RC. z -N To repeatedly control the internal model delay link, N=f s / f0,f s is the sampling frequency, f0 is the grid frequency.

[0088] Step 5: Repeat the control to establish the controlled object model.

[0089] If the RC branch in PHESO is disconnected, the loop in the structure diagram is:

[0090]

[0091] The forward path is:

[0092]

[0093] According to the Mersenne gain formula, from y rc arrive The transfer function is:

[0094]

[0095] Among them, Ts is the sampling period, and h1 is the observer pole configuration gain.

[0096] Step 6: Design an ideal compensator for repetitive control based on the idea of ​​perfect cancellation. Since repetitive control aims at 0 dB and 0 phase of the controlled object, the optimal compensator S(z) should be the inverse of the RC controlled object, which is called the ideal compensator. That is, the ideal compensation transfer function is obtained:

[0097] ;

[0098] The perfect cancellation concept is an input compensation method for a closed-loop system, which refers to completely eliminating errors and disturbances in the system output through a control strategy. Therefore, the embodiment of the present invention uses the perfect cancellation concept to design the ideal compensation transfer function S(z) of RC.

[0099] Usually, an ideal compensator cannot be physically realized, because the controlled object of RC cannot be completely accurately mathematically modeled, and the discretization of the controlled object will also bring modeling errors. However, the controlled object of RC here is not a real inverter model, but a standard paradigm obtained by summarizing the inverter model in ESO, so the controlled object of RC itself is an ideal model. Therefore, the ideal compensator can be realized in PHESO.

[0100] Step 7: Get perfect cancellation repetitive control, the structure diagram is as follows Figure 7 As shown in Figure 2, the complete structure of PHESO is shown in Figure 2. Figure 8 shown.

[0101] This structure enables PHESO to work in the optimal state. The poles of RC in PHESO are all distributed at the center of the unit circle. This feature enables PHESO to converge quickly and ensure system stability.

[0102] Step 8: Add a zero-phase-shift low-pass filter and set the observation bandwidth.

[0103] The bandwidth of the observer is determined by the internal model filter Q(z), which uses a zero-phase-shift low-pass filter with a discrete transfer function Q ( z )for:

[0104]

[0105] in, is the coefficient of the zero-phase-shift low-pass filter, z is a discrete time variable, and the coefficient is required to satisfy: .

[0106] In this embodiment, a first-order zero-phase low-pass filter is used. When the values ​​are 0.3, 0.5, and 0.7 respectively, the Bode diagram of the RC branch is as follows Fig. 9 As shown, with The gain of the RC branch decreases at high frequencies, and the gain change is not obvious at low frequencies. Therefore, by choosing a reasonable The value can suppress the high-frequency noise in the RC observation loop while ensuring high gain in the low-frequency band, thereby maintaining accurate disturbance observation capabilities.

[0107] The Bode diagram of the PHESO perturbation to perturbation observation error is as follows: Fig.10 As shown in the figure, the periodic harmonic expansion state observer can well observe the fundamental disturbance of the power grid and the harmonic disturbance at the positive integer multiple frequency of the fundamental frequency. After these disturbances are accurately observed, they can be equivalently compensated at the input end of the controlled object, thereby suppressing the impact of the disturbance on the system.

[0108] Analyze the effect of including the h1 pathway in the perturbation observations in step 3. Compare the structure without h1 in step 2 and the structure with h1 in step 3. The Bode plots are compared. Fig.11 As shown in Figure 2, the Bode plot analysis shows that the disturbance estimation error is smaller after considering the effect of h1, and it has almost no impact on the observation bandwidth.

[0109] Step 9: Based on the PHESO ADRC structure, design the linear control law and set the control bandwidth.

[0110] The structure diagram of the active disturbance rejection control based on PHESO is as follows: Fig.12 As shown, k c is the proportional coefficient of the linear control law, and b0 is the input gain of the controlled inverter.

[0111] The expression of the linear control law is as follows:

[0112]

[0113] in, is the reference signal differential feedforward. The control signal is composed of the linear proportional control signal, the reference differential feedforward signal, and the observation signal of PHESO to the generalized disturbance. c The larger the k is, the smaller the tracking error of the grid-connected current will be, but the stability margin will also be reduced. c The value should make the system reach the design target.

[0114] The method of this embodiment is experimentally verified. Fig.13 and Fig.14 They are the grid-connected current oscilloscope waveform and the current waveform distortion spectrum of the power quality analyzer. Fig.15 This is the dynamic response waveform of the grid-connected control algorithm.

[0115] It can be seen from the current waveform that when there are harmonics in the grid voltage, the grid current can be controlled to a sine wave with low distortion and maintain a low current error. The total current THD measured by the power quality analyzer is 0.9%, which is much lower than the grid standard of 5%. It can be seen from the dynamic experiment that the control algorithm can complete the regulation within two grid cycles.

[0116] The self-disturbance-resistance grid-connected control method based on the periodic harmonic expanded state observer in the embodiment of the present invention ultimately achieves accurate compensation of grid voltage disturbance and inverter dead zone nonlinear disturbance, as well as high-precision grid-connected current control, and can be well applied in inverter grid-connected control.

[0117] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An active disturbance rejection grid-connected control method based on periodic harmonic extended state observer, characterized in that: include: According to the system extended state space equation, the structure of the extended state observer of the first-order controlled object is designed; The integrator used for observing the generalized disturbance of the system in the structure of the extended state observer is replaced with a repetitive controller, so as to observe the periodic harmonic disturbance through the repetitive controller; The proportional term gain h1 path used to adjust the observer's response speed to the system state estimation in the structure of the extended state observer is connected in parallel with the repetitive controller to merge the disturbance observation effect of the proportional term gain h1 path into the generalized disturbance observation value to obtain a periodic harmonic extended state observer; The method further comprises: Establishing a mathematical model of a controlled object of the repetitive controller to obtain a transfer function of the controlled object; Taking the inverse of the transfer function of the controlled object as a repetitive control compensation function of the repetitive controller to obtain an ideal compensator of the repetitive controller; Establishing a mathematical model of the controlled object of the repetitive controller and obtaining a transfer function of the controlled object includes: The repetitive control branch in the periodic harmonic extended state observer structure is disconnected, and the loop and forward path in the structure of the periodic harmonic extended state observer remaining after the disconnection are analyzed to obtain mathematical expressions of the loop and the forward path, and the transfer function of the controlled object is obtained according to the Mason gain formula.

2. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 1 is characterized in that: The transfer function of the controlled object as follows: Among them, T s is the sampling period, and h1 is the observer pole configuration gain.

3. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 1 is characterized in that: The method further comprises: The internal model filter in the repetitive controller adopts a zero-phase-shift low-pass filter, and the observation bandwidth of the periodic harmonic expansion state observer is set according to the zero-phase-shift low-pass filter.

4. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 3 is characterized in that: The discrete transfer function of the zero-phase-shift low-pass filter is Q ( z )for: in, is the coefficient of the zero-phase-shift low-pass filter, z is a discrete-time variable, and the coefficient is required satisfy: .

5. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 1, characterized in that: The method further comprises: A linear control law is designed according to the system control structure and control requirements of the periodic harmonic expanded state observer, and a control bandwidth is set.

6. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 1, characterized in that: The structure of the extended state observer of the first-order controlled object is designed, wherein the discrete domain state space equation of the extended state observer is as follows: in, represents the observed value of the grid-connected current, is the first state variable observation value of the extended state observer, represents the generalized perturbation observation, is the second state variable observation value of the extended state observer, k represents the beat number of the discrete domain state variable, h1 and h2 are the observer pole configuration gains, b0 is the input gain of the controlled object, T s is the sampling period, e1 is the input signal, u k For control signal.

7. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 1, characterized in that: The discrete domain state space equation after replacing the integrator in the extended state observer structure with a repetitive controller is as follows: in, represents the observed value of the grid-connected current, is the first state variable observation value of the extended state observer, represents the generalized perturbation observation, is the second state variable observation value of the extended state observer, k represents the beat number of the discrete domain state variable, h1 and h2 are the observer pole configuration gains, b0 is the input gain of the controlled object, T s is the sampling period, e1 is the input signal, u k is the control signal, is the transfer function of the repetitive controller.

8. The active disturbance rejection grid-connected control method based on periodic harmonic extended state observer according to claim 7, characterized in that: The transfer function of the repetitive controller is for: Where Q(z) represents the internal model filter, S(z) represents the repetitive control compensator, and z -N Represents the repeated control internal model delay link, N=f s / f0,f s is the sampling frequency, f0 is the grid frequency.

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