Full-current harmonic detection method based on bisecond-order generalized integrator

Abstract

The invention discloses a total current harmonic detection method based on a double-second-order generalized integrator, and relates to the field of photovoltaic power generation and adaptive compensation control, and the method comprises the following steps: constructing an ip-iq method system, and extracting a three-phase current at a load side; processing the three-phase current of the load side through Clark transformation to obtain a current under a two-phase static coordinate system; processing the current under the two-phase static coordinate system through DSOGI-QSG to obtain a fundamental wave positive sequence current; processing the fundamental wave positive sequence current through Clark inverse transformation to obtain a three-phase fundamental wave positive sequence current; extracting harmonic current according to the three-phase fundamental wave positive sequence current; a Park transformation link is omitted, the structure of the system is simplified, and meanwhile the accuracy of the system is improved; through a detection method without a phase-locked loop, the system detection speed is improved; and the DSOGI-QSG is adopted to extract the fundamental wave positive sequence current and obtain the harmonic current, so that the extraction accuracy of the harmonic current is higher.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic power generation and adaptive compensation control, and in particular to a full current harmonic detection method based on a biquadric generalized integrator. Background Art

[0002] In the field of photovoltaic power generation, the widespread use of power electronic devices and nonlinear loads causes a large amount of harmonic current to be injected into the power grid, seriously affecting the safe operation of the power grid. Therefore, active power filters are introduced to suppress harmonics.

[0003] In the existing technology, the main harmonic detection method is based on the instantaneous reactive power theory. p -i q This method uses a phase-locked loop (PLL) to perform Clark and Park transformations and utilizes a low-pass filter to obtain the fundamental current, thereby extracting the harmonic current.

[0004] First, the traditional method relies on a low-pass filter to extract the fundamental component. The cutoff frequency of the low-pass filter is inconsistent with the response speed. A cutoff frequency that is too low will lead to dynamic response delays, making it difficult to track rapidly changing harmonics. Second, when the grid voltage is distorted, the traditional phase-locked loop will have a phase tracking error, resulting in inaccurate coordinate system of the Park transform, which in turn leads to a decrease in the accuracy of fundamental wave separation. In addition, when the frequency suddenly changes, the phase-locked loop needs to be relocked. During the relocking period, the detection function fails and the system performance will be restricted. Finally, the traditional method has high computational complexity and structural complexity. It needs to fully execute the Clark transform, Park transform and inverse transform, involving a large number of trigonometric function operations, which will significantly increase the computational burden of the DSP.

[0005] Therefore, a full current harmonic detection method based on a biquad generalized integrator is provided to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a full current harmonic detection method based on a biquad generalized integrator, which eliminates the Park transform and low-pass filter in the traditional scheme and adopts a phase-locked loop-free design to simplify the system structure, make the detection results more accurate, and achieve faster dynamic response.

[0007] To achieve the above object, the present invention provides a full current harmonic detection method based on a biquad generalized integrator, comprising the following steps:

[0008] S1: Build i p -i q Method system, extract the load side three-phase current i a 、i b and i c ;

[0009] S2: Clark transformation of the load side three-phase current i a 、i b and i c Processing is performed to obtain the current i in the two-phase stationary coordinate system α and i β ;

[0010] S3: The current i in the two-phase stationary coordinate system is calculated by DSOGI-QSG. α and i β Processing is performed to obtain the fundamental positive sequence current and

[0011] S4: fundamental positive sequence current through Clark inverse transformation and Processing is performed to obtain the three-phase fundamental positive sequence current and

[0012] S5: According to the fundamental positive sequence current of the three phases and Extracting harmonic currents and

[0013] Preferably, in step S2, the Clark transform is specifically set to:

[0014]

[0015] Preferably, step S3 specifically includes the following steps:

[0016] S31: Through the SOGI transfer function, the current i in the two-phase stationary coordinate system is respectively α 、i β Perform SOGI processing, which includes bandpass filtering D(s) and low-pass filtering Q(s);

[0017] S32: Calculate the amplitude |D(s)| of the bandpass filter, the phase ∠D(s) of the bandpass filter, the amplitude |Q(s)| of the lowpass filter, and the phase ∠Q(s) of the lowpass filter;

[0018] S33: Perform positive sequence component synthesis to obtain fundamental positive sequence current and

[0019] Preferably, in step S31, the band-pass filter D(s) and the low-pass filter Q(s) are respectively set to:

[0020]

[0021] Where i represents the input current, i′ represents the in-phase output current, qi′ represents the quadrature output current, q represents the proportional coefficient, ζ represents the damping ratio, ω0 represents the undamped natural frequency, and s represents the Laplace complex variable.

[0022] Preferably, step S32 specifically includes the following steps:

[0023] Step 1: Calculate the amplitude of the bandpass filter |D(s)|. The amplitude of the bandpass filter |D(s)| is specifically set to:

[0024]

[0025] Where ω represents the system frequency;

[0026] Step 2: Calculate the phase ∠D(s) of the bandpass filter. The specific setting of the phase ∠D(s) of the bandpass filter is:

[0027]

[0028] Step 3: Calculate the amplitude of the low-pass filter |Q(s)|. The amplitude of the low-pass filter |Q(s)| is specifically set to:

[0029]

[0030] Step 4: Calculate the phase ∠Q(s) of the low-pass filter. The phase ∠Q(s) of the low-pass filter is specifically set to:

[0031]

[0032] Preferably, in step S33, positive sequence component synthesis is performed, and the positive sequence component synthesis is specifically configured as follows:

[0033]

[0034] Among them, i′ α Represents the current i α The in-phase current, qi′ α Represents the current i α The quadrature current, i′ β Represents the current i β The in-phase current, qi′ β Represents the current i β of the quadrature current.

[0035] Preferably, step S4 specifically includes the following steps:

[0036] S41: Calculate the fundamental positive sequence current of phase a Fundamental positive sequence current of phase a The specific settings are:

[0037]

[0038] S42: Calculate the fundamental positive sequence current of phase b Fundamental positive sequence current of phase b The specific settings are:

[0039]

[0040] S43: Calculate the fundamental positive sequence current of phase c Fundamental positive sequence current of phase c The specific settings are:

[0041]

[0042] Preferably, in step S5, the harmonic current and Set to:

[0043]

[0044] Therefore, the present invention adopts the above-mentioned full current harmonic detection method based on a biquad generalized integrator, which has the following beneficial effects:

[0045] (1) This solution omits the Park transformation link. First, since the coordinate rotation calculation module required for the Park transformation is eliminated, it not only reduces the hardware resource usage but also improves the reliability and stability of the system. Second, omitting the Park transformation avoids the phase error introduced by coordinate rotation and eliminates the problem of low detection accuracy in traditional methods. Finally, reducing the processing delay of the coordinate transformation link can effectively improve the response speed of the system and enable the system to better adapt to dynamic working conditions such as load mutations.

[0046] (2) This solution is a detection method without a phase-locked loop, which simplifies the system structure, increases the system's speed, and achieves a significant simplification of the system structure and an overall improvement in detection performance;

[0047] (3) This solution uses DSOGI-QSG to extract the fundamental positive sequence current and obtain the harmonic current. Through the innovative signal processing architecture, high-precision fundamental positive sequence current extraction and harmonic separation are achieved, avoiding the phase error and calculation delay introduced by the Park transform and phase-locked loop links in the traditional method, making the extraction of harmonic current more accurate and fast.

[0048] The method scheme of the present invention is further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of a full current harmonic detection method based on a biquad generalized integrator according to the present invention;

[0050] Figure 2 It is a block diagram of the overall structure of the present invention;

[0051] Figure 3 For the present invention p -i q Law structure diagram;

[0052] Figure 4 Schematic diagram of the DSOGI-QSG of the present invention;

[0053] Figure 5 is the Bode diagram of the DSOGI-QSG transfer function of the present invention;

[0054] Figure 6 This is a schematic diagram of the DSOGI-QSG quadrature signal generator of the present invention;

[0055] Figure 7 This is a diagram of the harmonic current acquisition of the present invention. DETAILED DESCRIPTION

[0056] The method scheme of the present invention is further described below through the drawings and examples.

[0057] Unless otherwise defined, technical terms or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0058] The words “include” or “comprising” and similar words used in the present invention mean that the elements before the word include the elements listed after the word, and do not exclude the possibility of also including other elements. The orientation or position relationship indicated by the terms “inside”, “outside”, “upper”, “lower”, etc. is based on the orientation or position relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. When the absolute position of the described object changes, the relative position relationship may also change accordingly. In the present invention, unless otherwise clearly stipulated and limited, the terms such as “attachment” should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral whole; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0059] Example

[0060] like Figure 1-Figure 2 and Figure 4-Figure 7As shown, the present invention provides a full current harmonic detection method based on a biquad generalized integrator, comprising the following steps:

[0061] S1: Build i p -i q Method system, extract the load side three-phase current i a 、i b and i c ;

[0062] S2: Clark transformation of the three-phase current i on the load side a 、i b and i c Processing is performed to obtain the current i in the two-phase stationary coordinate system α and i β ;

[0063] In step S2, the Clark transform is specifically set as:

[0064]

[0065] S3: The orthogonal signal generator DSOGI-QSG composed of DSOGI is used to measure the current i in the two-phase stationary coordinate system. α and i β Processing is performed by using the characteristics of the two outputs of SOGI to form a bandpass filter and a low-pass filter for the input transfer function, and the fundamental positive sequence current is obtained. and

[0066] Step S3 specifically includes the following steps:

[0067] S31: Through the SOGI transfer function, the current i in the two-phase stationary coordinate system is respectively α 、i β Perform SOGI processing, which includes bandpass filtering D(s) and low-pass filtering Q(s);

[0068] In step S31, the bandpass filter D(s) and the lowpass filter Q(s) are respectively set to:

[0069]

[0070] Where i represents the input current, i′ represents the in-phase output current, qi′ represents the quadrature output current, q represents the proportional coefficient, ζ represents the damping ratio, ω0 represents the undamped natural frequency, and s represents the Laplace complex variable.

[0071] S32: Calculate the amplitude |D(s)| of the bandpass filter, the phase ∠D(s) of the bandpass filter, the amplitude |Q(s)| of the lowpass filter, and the phase ∠Q(s) of the lowpass filter;

[0072] Step S32 specifically includes the following steps:

[0073] Step 1: Calculate the amplitude of the bandpass filter |D(s)|. The amplitude of the bandpass filter |D(s)| is specifically set to:

[0074]

[0075] Where ω represents the system frequency;

[0076] Step 2: Calculate the phase ∠D(s) of the bandpass filter. The specific setting of the phase ∠D(s) of the bandpass filter is:

[0077]

[0078] Step 3: Calculate the amplitude of the low-pass filter |Q(s)|. The amplitude of the low-pass filter |Q(s)| is specifically set to:

[0079]

[0080] Step 4: Calculate the phase ∠Q(s) of the low-pass filter. The phase ∠Q(s) of the low-pass filter is specifically set to:

[0081]

[0082] From the Bode plot of the SOGI transfer function, it can be seen that there is a resonant peak at the center angular frequency, which has an attenuation effect on signals of other frequencies and a polarity-selective effect on the 50Hz positive sequence component.

[0083] S33: Perform positive sequence component synthesis to obtain fundamental positive sequence current and

[0084] In step S33, positive sequence component synthesis is performed, and the specific setting of positive sequence component synthesis is:

[0085]

[0086] Among them, i′ α Represents the current i α The in-phase current, qi′ α Represents the current i α The quadrature current, i′ β Represents the current i β The in-phase current, qi′ β Represents the current i β of the quadrature current.

[0087] The fundamental positive sequence component is accurately extracted using DSOGI-QSG, and the fundamental positive sequence current is obtained under the full current harmonic detection method of the second-order generalized integrator without phase-locked loop and low-pass filter. and is the harmonic current and Extraction lays the foundation.

[0088] S4: fundamental positive sequence current through Clark inverse transformation and Processing is performed to obtain the three-phase fundamental positive sequence current and

[0089] Step S4 specifically includes the following steps:

[0090] S41: Calculate the fundamental positive sequence current of phase a Fundamental positive sequence current of phase a The specific settings are:

[0091]

[0092] S42: Calculate the fundamental positive sequence current of phase b Fundamental positive sequence current of phase b The specific settings are:

[0093]

[0094] S43: Calculate the fundamental positive sequence current of phase c Fundamental positive sequence current of phase c The specific settings are:

[0095]

[0096] S5: According to the fundamental positive sequence current of the three phases and Extracting harmonic currents and Thus achieving full current compensation.

[0097] In step S5, the harmonic current and Set to:

[0098]

[0099] like Figure 3 As shown, the traditional p -i q The structural diagram of the method, three-phase load current i a 、i b 、ic Under Clark transformation, the current i in the two-phase stationary coordinate system is formed α and i β The phase angle of the output voltage of the phase-locked loop is used for Park transformation, and the current i after Park transformation is converted by the low-pass filter. p and i q Filter and obtain the DC component of the current in the two-phase rotating coordinate system Then, Park and Clark inverse transform to form the three-phase fundamental current i af 、i bf 、i cf , and finally get the harmonic current i * ca 、i * cb 、i * cc .

[0100] Compared with this embodiment, the system is more complex, and the phase-locked loop and Park transformation links are added, which reduces the accuracy of the system to a certain extent, and the use of the low-pass filter has a delay effect on the system.

[0101] The full current harmonic detection method based on a biquad generalized integrator proposed in this embodiment greatly simplifies the structure of the system and increases the speed of the system.

[0102] Therefore, the present invention adopts the above-mentioned full-current harmonic detection method based on a dual-quadratic generalized integrator, omitting the Park transformation link, simplifying the system structure, and increasing the accuracy of the system; through a detection method without a phase-locked loop, the system detection speed is improved; and DSOGI-QSG is used to extract the fundamental positive sequence current and obtain the harmonic current, so that the extraction accuracy of the harmonic current is higher.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the method scheme of the present invention and not to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary method personnel in this field should understand that they can still modify or replace the method scheme of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified method scheme to deviate from the spirit and scope of the method scheme of the present invention.

Claims

1. A full current harmonic detection method based on a biquad generalized integrator, characterized in that: The following steps are involved: S1: Build i p -i q Method system, extract the load side three-phase current i a 、i b and i c ; S2: Clark transformation of the load side three-phase current i a 、i b and i c Processing is performed to obtain the current i in the two-phase stationary coordinate system α and i β ; S3: The current i in the two-phase stationary coordinate system is calculated by DSOGI-QSG. α and i β Processing is performed to obtain the fundamental positive sequence current and S4: fundamental positive sequence current through Clark inverse transformation and Processing is performed to obtain the three-phase fundamental positive sequence current and S5: According to the fundamental positive sequence current of the three phases and Extracting harmonic currents and 2. The full current harmonic detection method based on a biquad generalized integrator according to claim 1, characterized in that: In step S2, the Clark transform is specifically set as:

3. The full current harmonic detection method based on a biquad generalized integrator according to claim 1, characterized in that: Step S3 specifically includes the following steps: S31: Through the SOGI transfer function, the current i in the two-phase stationary coordinate system is respectively α 、i β Perform SOGI processing, which includes bandpass filtering D(s) and low-pass filtering Q(s); S32: Calculate the amplitude |D(s)| of the bandpass filter, the phase ∠D(s) of the bandpass filter, the amplitude |Q(s)| of the lowpass filter, and the phase ∠Q(s) of the lowpass filter; S33: Perform positive sequence component synthesis to obtain fundamental positive sequence current and 4. The full current harmonic detection method based on a biquad generalized integrator according to claim 3, characterized in that: In step S31, the bandpass filter D(s) and the lowpass filter Q(s) are respectively set to: Where i represents the input current, i′ represents the in-phase output current, qi′ represents the quadrature output current, q represents the proportional coefficient, ζ represents the damping ratio, ω0 represents the undamped natural frequency, and s represents the Laplace complex variable.

5. The full current harmonic detection method based on a biquad generalized integrator according to claim 3, characterized in that: Step S32 specifically includes the following steps: Step 1: Calculate the amplitude of the bandpass filter |D(s)|. The amplitude of the bandpass filter |D(s)| is specifically set to: Where ω represents the system frequency; Step 2: Calculate the phase ∠D(s) of the bandpass filter. The specific setting of the phase ∠D(s) of the bandpass filter is: Step 3: Calculate the amplitude of the low-pass filter |Q(s)|. The amplitude of the low-pass filter |Q(s)| is specifically set to: Step 4: Calculate the phase ∠Q(s) of the low-pass filter. The phase ∠Q(s) of the low-pass filter is specifically set to:

6. The full current harmonic detection method based on a biquad generalized integrator according to claim 3, characterized in that: In step S33, positive sequence component synthesis is performed, and the specific setting of positive sequence component synthesis is: Among them, i′ α Represents the current i α The in-phase current, qi′ α Represents the current i α The quadrature current, i′ β Represents the current i β The in-phase current, qi′ β Represents the current i β of the quadrature current.

7. The full current harmonic detection method based on a biquad generalized integrator according to claim 1, characterized in that: Step S4 specifically includes the following steps: S41: Calculate the fundamental positive sequence current of phase a Fundamental positive sequence current of phase a The specific settings are: S42: Calculate the fundamental positive sequence current of phase b Fundamental positive sequence current of phase b The specific settings are: S43: Calculate the fundamental positive sequence current of phase c Fundamental positive sequence current of phase c The specific settings are:

8. The full current harmonic detection method based on a biquad generalized integrator according to claim 1, characterized in that: In step S5, the harmonic current and Set to:

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