System for extracting positive and negative sequence fundamental wave components of power grid voltage signal
阅读说明:本技术 电网电压信号的正负序基波分量提取系统 (System for extracting positive and negative sequence fundamental wave components of power grid voltage signal ) 是由 黄文俊 易龙强 林伟民 叶永发 于 2019-10-31 设计创作,主要内容包括:本发明适用于电力电子及电力系统技术领域,提供了电网电压信号的正负序基波分量提取系统,包括:坐标变换模块、降阶谐振调节模块和锁频环模块;坐标变换模块用于将三相电网电压信号变换为αβ坐标系的输入电压信号;降阶谐振调节模块用于对输入电压信号进行正负序分离,得到正负序基波分量;锁频环模块用于获取所述三相电网电压信号,并根据锁频环的闭环反馈原理及所述三相电网电压信号对所述降阶谐振调节模块的电压基波频率进行自适应跟踪。本申请通过降阶谐振调节模块对输入电压信号进行电压正负序分离,可完全消除电网特定的低次谐波和直流分量对正负序分量提取结果的影响,改善电网电压的正负序分量的提取效果。(The invention is suitable for the technical field of power electronics and power systems, and provides a system for extracting positive and negative sequence fundamental wave components of a power grid voltage signal, which comprises the following steps: the system comprises a coordinate transformation module, a reduced order resonance adjusting module and a frequency locking ring module; the coordinate transformation module is used for transforming the three-phase power grid voltage signal into an input voltage signal of an alpha beta coordinate system; the reduced order resonance adjusting module is used for carrying out positive and negative sequence separation on the input voltage signal to obtain positive and negative sequence fundamental wave components; and the frequency locking loop module is used for acquiring the three-phase power grid voltage signal and carrying out self-adaptive tracking on the voltage fundamental frequency of the reduced-order resonance adjusting module according to the closed-loop feedback principle of the frequency locking loop and the three-phase power grid voltage signal. The positive and negative sequence separation of voltage is carried out on the input voltage signal through the reduced order resonance adjusting module, the influence of specific low-order harmonic waves and direct current components of a power grid on the positive and negative sequence component extraction result can be completely eliminated, and the positive and negative sequence component extraction effect of the power grid voltage is improved.)
1. A positive and negative sequence fundamental component extraction system of a grid voltage signal, comprising: the system comprises a coordinate transformation module, a reduced order resonance adjusting module and a frequency locking ring module;
the coordinate transformation module is used for transforming the three-phase power grid voltage signal into an input voltage signal of an alpha beta coordinate system;
the reduced order resonance adjusting module is used for carrying out positive and negative sequence separation on the input voltage signal to obtain positive and negative sequence fundamental wave components;
and the frequency locking loop module is used for acquiring the three-phase power grid voltage signal and carrying out self-adaptive tracking on the voltage fundamental frequency of the reduced-order resonance adjusting module according to the closed-loop feedback principle of the frequency locking loop and the three-phase power grid voltage signal.
2. The system for positive and negative sequence fundamental component extraction of a grid voltage signal as claimed in claim 1, wherein said reduced order resonance tuning module comprises a first reduced order resonance tuning sub-module and a second reduced order resonance tuning sub-module;
the first reduced order resonance adjusting submodule is used for obtaining a positive order fundamental component according to the input voltage signal;
and the second reduced order resonance adjusting submodule is used for obtaining a negative sequence fundamental component according to the input voltage signal.
3. The system of claim 2, wherein the first reduced order harmonic adjustment sub-module comprises a first feedback unit, a first positive order fundamental harmonic adjustment, a first negative order fundamental harmonic adjustment, a first integrator, a first summing unit, a first subtracting unit, and a first gain unit;
the first feedback unit is used for acquiring the input voltage signal and a last positive sequence fundamental component, and subtracting the last positive sequence fundamental component from the input voltage signal to obtain a first voltage;
the first positive sequence fundamental wave resonance regulator is used for regulating the first voltage to obtain a first output value;
the first negative sequence fundamental wave resonance regulator is used for obtaining a last positive sequence fundamental wave component and regulating the last positive sequence fundamental wave component to obtain a second output value;
the first integrator is used for outputting a first integral value according to the last positive-sequence fundamental component;
the first summing unit is used for summing the second output value and the first integrated value to obtain a third output value;
the first subtraction unit is used for subtracting the third output value from the first output value to obtain a fourth output value;
the first gain unit is used for solving the product of the fourth output value and the gain parameter to obtain the current positive sequence fundamental wave component, and feeding the current positive sequence fundamental wave component back to the first feedback unit for the next calculation.
4. The system for positive and negative sequence fundamental component extraction of a grid voltage signal of claim 3, wherein the first reduced order resonance adjustment submodule further comprises at least one first Nmultiplied resonance adjustment unit;
each first N frequency multiplication resonance adjusting unit comprises a first positive sequence N frequency multiplication resonance adjuster and a first negative sequence N frequency multiplication resonance adjuster respectively;
the first positive sequence N frequency multiplication resonance adjuster is used for acquiring a previous positive sequence fundamental component, adjusting the previous positive sequence fundamental component to obtain a first adjusting value, and inputting the first adjusting value into the first summing unit;
the first negative sequence N frequency multiplication resonance adjuster is used for obtaining a last positive sequence fundamental component, adjusting the last positive sequence fundamental component to obtain a second adjusting value, and inputting the second adjusting value into the first summation unit.
5. The system for positive and negative sequence fundamental component extraction of a grid voltage signal of claim 4, wherein the transfer function of the first positive sequence fundamental resonant regulator is:
the transfer function of the first negative-sequence fundamental resonance regulator is as follows:
the transfer function of the first positive sequence frequency multiplication resonant regulator is as follows:
the transfer function of the first negative-sequence frequency-N multiplication resonance regulator is as follows:
wherein N represents the harmonic order of the first positive-sequence frequency multiplication resonant regulator and the first negative-sequence frequency multiplication resonant regulator, and the N values of the first frequency multiplication resonant regulating units are different.
6. The system of claim 2, wherein the second reduced order harmonic adjustment sub-module includes a second feedback unit, a second negative order fundamental harmonic adjustment, a second positive order fundamental harmonic adjustment, a second integrator, a second summing unit, a second subtracting unit, and a second gain unit;
the second feedback unit is used for acquiring the input voltage signal and a last negative sequence fundamental component, and subtracting the last negative sequence fundamental component from the input voltage signal to obtain a second voltage;
the second negative-sequence fundamental wave resonance regulator is used for regulating the second voltage to obtain a fifth output value;
the second positive sequence fundamental wave resonance regulator is used for obtaining a last negative sequence fundamental wave component and regulating the last negative sequence fundamental wave component to obtain a sixth output value;
the second integrator is used for outputting a second integral value according to the last negative-sequence fundamental component;
the second summing unit is used for summing the sixth output value and the second integrated value to obtain a seventh output value;
the second subtracting unit is configured to subtract the seventh output value from the fifth output value to obtain an eighth output value;
and the second gain unit is used for solving the product of the eighth output value and the gain parameter to obtain the current negative sequence fundamental wave component, and feeding the current negative sequence fundamental wave component back to the second feedback unit for next calculation.
7. The system for positive and negative sequence fundamental component extraction of a grid voltage signal of claim 6, wherein the second reduced order resonance adjustment submodule further comprises at least one second Nmultiplied resonance adjustment unit;
each second N frequency multiplication resonance adjusting unit comprises a second positive sequence N frequency multiplication resonance adjuster and a second negative sequence N frequency multiplication resonance adjuster respectively;
the second positive sequence N frequency multiplication resonance adjuster is used for acquiring a last negative sequence fundamental component, adjusting the last negative sequence fundamental component to obtain a third adjusting value, and inputting the third adjusting value into the second summation unit;
the second negative sequence N frequency multiplication resonance adjuster is used for obtaining a last negative sequence fundamental component, adjusting the last negative sequence fundamental component to obtain a fourth adjusting value, and inputting the fourth adjusting value into the second summation unit.
8. The system for positive and negative sequence fundamental component extraction of a grid voltage signal as claimed in claim 7, wherein the transfer function of the second negative sequence fundamental resonant regulator is:
the transfer function of the second positive sequence fundamental wave resonance regulator is as follows:
the transfer function of the second positive-sequence frequency multiplication resonant regulator is as follows:
the transfer function of the second negative-sequence frequency-N multiplication resonance regulator is as follows:
and N represents the harmonic order of the second positive-sequence N frequency multiplication resonance adjuster and the second negative-sequence N frequency multiplication resonance adjuster, and the N values of the second N frequency multiplication resonance adjusting units are different.
9. The system according to claim 1, wherein the frequency-locked loop module is configured to obtain a positive-sequence fundamental component from the three-phase grid voltage signal, and adaptively track the voltage fundamental frequency of the reduced-order resonance adjustment module according to a closed-loop feedback principle of the frequency-locked loop and the positive-sequence fundamental component.
10. The system of claim 9, wherein the frequency locked loop module comprises a Park transform unit, a q-axis subtraction unit, a PI controller, a third integrator, and an addition unit;
the Park conversion unit is used for converting the previous positive sequence fundamental wave component into a d-axis positive sequence fundamental wave component and a q-axis positive sequence fundamental wave component in a dq coordinate system according to the previous frequency integral value;
the q-axis subtraction unit is used for subtracting the q-axis positive sequence fundamental component from a target positive sequence control quantity to obtain a positive sequence control deviation;
the PI controller is used for obtaining a positive sequence control output value according to the positive sequence control deviation;
the addition unit is used for summing the positive sequence control output value and the initial power grid voltage frequency to obtain a voltage fundamental wave frequency;
the third integrator is used for integrating the current voltage fundamental frequency to obtain a current frequency integral value, and inputting the current frequency integral value to the Park transformation unit, and the Park transformation unit performs the next dq coordinate transformation according to the current frequency integral value.
Technical Field
The invention belongs to the technical field of power electronics and power systems, and particularly relates to a positive-negative sequence fundamental component extraction system for a power grid voltage signal.
Background
In an electric power system, factors such as asymmetrical faults of a power grid, unbalanced three-phase loads and the like can cause unbalanced three-phase voltage. In recent years, renewable energy is increasingly used, but due to intermittency and uncertainty of new energy power generation such as wind power generation and photovoltaic power generation, imbalance of grid voltage and generation of harmonics are increased after the new energy power generation is integrated into a power grid. In order to ensure the stable operation of a power grid system, the grid-connected standards of various countries all require that the grid-connected system has certain fault ride-through capability, and the control of the grid-connected system becomes a research hotspot when the voltage of the power grid is unbalanced.
In order to control the harmonic wave of the grid-connected current and the active and reactive power, it is necessary to be able to quickly and accurately detect the amplitude and phase information of the positive and negative sequence components of the grid voltage. How to rapidly separate positive and negative sequence components of the voltage, researchers have made extensive research. Currently, a Synchronous Frame phase-locked loop (SRF-PLL) is one of the most common methods. When the three-phase voltage is symmetrical, the SRF-PLL can well extract the fundamental positive sequence component, but when the three-phase voltage is asymmetrical, the negative sequence component can generate an alternating current component of 2 times of power frequency on a dq axis, and the SRF-PLL positive and negative sequence separation result is difficult to satisfy.
Disclosure of Invention
In view of this, the embodiment of the present invention provides a system for extracting positive and negative sequence fundamental wave components of a grid voltage signal, so as to solve the problem in the prior art that the separation effect of the positive and negative sequence fundamental wave components of the grid voltage is poor.
The embodiment of the invention provides a system for extracting positive and negative sequence fundamental wave components of a power grid voltage signal, which comprises:
the system comprises a coordinate transformation module, a reduced order resonance adjusting module and a frequency locking ring module;
the coordinate transformation module is used for transforming the three-phase power grid voltage signal into an input voltage signal of an alpha beta coordinate system;
the reduced order resonance adjusting module is used for carrying out positive and negative sequence separation on the input voltage signal to obtain positive and negative sequence fundamental wave components;
and the frequency locking loop module is used for acquiring the three-phase power grid voltage signal and carrying out self-adaptive tracking on the voltage fundamental frequency of the reduced-order resonance adjusting module according to the closed-loop feedback principle of the frequency locking loop and the three-phase power grid voltage signal.
In one embodiment, the reduced order resonance adjustment module includes a first reduced order resonance adjustment sub-module and a second reduced order resonance adjustment sub-module;
the first reduced order resonance adjusting submodule is used for obtaining a positive order fundamental component according to the input voltage signal;
and the second reduced order resonance adjusting submodule is used for obtaining a negative sequence fundamental component according to the input voltage signal.
In one embodiment, the first reduced order resonance adjustment sub-module comprises a first feedback unit, a first positive order fundamental resonance adjuster, a first negative order fundamental resonance adjuster, a first integrator, a first summing unit, a first subtracting unit, and a first gain unit;
the first feedback unit is used for acquiring the input voltage signal and a last positive sequence fundamental component, and subtracting the last positive sequence fundamental component from the input voltage signal to obtain a first voltage;
the first positive sequence fundamental wave resonance regulator is used for regulating the first voltage to obtain a first output value;
the first negative sequence fundamental wave resonance regulator is used for obtaining a last positive sequence fundamental wave component and regulating the last positive sequence fundamental wave component to obtain a second output value;
the first integrator is used for outputting a first integral value according to the last positive-sequence fundamental component;
the first summing unit is used for summing the second output value and the first integrated value to obtain a third output value;
the first subtraction unit is used for subtracting the third output value from the first output value to obtain a fourth output value;
the first gain unit is used for solving the product of the fourth output value and the gain parameter to obtain the current positive sequence fundamental wave component, and feeding the current positive sequence fundamental wave component back to the first feedback unit for the next calculation.
In one embodiment, the first reduced order resonance adjustment submodule further comprises at least one first frequency doubling resonance adjustment unit;
each first N frequency multiplication resonance adjusting unit comprises a first positive sequence N frequency multiplication resonance adjuster and a first negative sequence N frequency multiplication resonance adjuster respectively;
the first positive sequence N frequency multiplication resonance adjuster is used for acquiring a previous positive sequence fundamental component, adjusting the previous positive sequence fundamental component to obtain a first adjusting value, and inputting the first adjusting value into the first summing unit;
the first negative sequence N frequency multiplication resonance adjuster is used for obtaining a last positive sequence fundamental component, adjusting the last positive sequence fundamental component to obtain a second adjusting value, and inputting the second adjusting value into the first summation unit.
In one embodiment, the transfer function of the first positive sequence fundamental resonance regulator is:
the transfer function of the first negative-sequence fundamental resonance regulator is as follows:
the transfer function of the first positive sequence frequency multiplication resonant regulator is as follows:
the transfer function of the first negative-sequence frequency-N multiplication resonance regulator is as follows:
wherein N represents the harmonic order of the first positive-sequence frequency multiplication resonant regulator and the first negative-sequence frequency multiplication resonant regulator, and the N values of the first frequency multiplication resonant regulating units are different.
In one embodiment, the second reduced order resonance adjustment submodule includes a second feedback unit, a second negative sequence fundamental resonance adjuster, a second positive sequence fundamental resonance adjuster, a second integrator, a second summing unit, a second subtracting unit, and a second gain unit;
the second feedback unit is used for acquiring the input voltage signal and a last negative sequence fundamental component, and subtracting the last negative sequence fundamental component from the input voltage signal to obtain a second voltage;
the second negative-sequence fundamental wave resonance regulator is used for regulating the second voltage to obtain a fifth output value;
the second positive sequence fundamental wave resonance regulator is used for obtaining a last negative sequence fundamental wave component and regulating the last negative sequence fundamental wave component to obtain a sixth output value;
the second integrator is used for outputting a second integral value according to the last negative-sequence fundamental component;
the second summing unit is used for summing the sixth output value and the second integrated value to obtain a seventh output value;
the second subtracting unit is configured to subtract the seventh output value from the fifth output value to obtain an eighth output value;
and the second gain unit is used for solving the product of the eighth output value and the gain parameter to obtain the current negative sequence fundamental wave component, and feeding the current negative sequence fundamental wave component back to the second feedback unit for next calculation.
In one embodiment, the second reduced order resonance adjustment submodule further comprises at least one second N multiplied resonance adjustment unit;
each second N frequency multiplication resonance adjusting unit comprises a second positive sequence N frequency multiplication resonance adjuster and a second negative sequence N frequency multiplication resonance adjuster respectively;
the second positive sequence N frequency multiplication resonance adjuster is used for acquiring a last negative sequence fundamental component, adjusting the last negative sequence fundamental component to obtain a third adjusting value, and inputting the third adjusting value into the second summation unit;
the second negative sequence N frequency multiplication resonance adjuster is used for obtaining a last negative sequence fundamental component, adjusting the last negative sequence fundamental component to obtain a fourth adjusting value, and inputting the fourth adjusting value into the second summation unit.
In one embodiment, the transfer function of the second negative sequence fundamental resonance regulator is:
the transfer function of the second positive sequence fundamental wave resonance regulator is as follows:
the transfer function of the second positive-sequence frequency multiplication resonant regulator is as follows:
the transfer function of the second negative-sequence frequency-N multiplication resonance regulator is as follows:
and N represents the harmonic order of the second positive-sequence N frequency multiplication resonance adjuster and the second negative-sequence N frequency multiplication resonance adjuster, and the N values of the second N frequency multiplication resonance adjusting units are different.
In one embodiment, the frequency-locked loop module is configured to obtain a positive-sequence fundamental component according to the three-phase grid voltage signal, and perform adaptive tracking on the voltage fundamental frequency of the reduced-order resonance adjustment module according to a closed-loop feedback principle of a frequency-locked loop and the positive-sequence fundamental component.
In one embodiment, the frequency-locked loop module comprises a Park transformation unit, a q-axis subtraction unit, a PI controller, a third integrator and an addition unit;
the Park conversion unit is used for converting the previous positive sequence fundamental wave component into a d-axis positive sequence fundamental wave component and a q-axis positive sequence fundamental wave component in a dq coordinate system according to the previous frequency integral value;
the q-axis subtraction unit is used for subtracting the q-axis positive sequence fundamental component from a target positive sequence control quantity to obtain a positive sequence control deviation;
the PI controller is used for obtaining a positive sequence control output value according to the positive sequence control deviation;
the addition unit is used for summing the positive sequence control output value and the initial power grid voltage frequency to obtain a voltage fundamental wave frequency;
the third integrator is used for integrating the current voltage fundamental frequency to obtain a current frequency integral value, and inputting the current frequency integral value to the Park transformation unit, and the Park transformation unit performs the next dq coordinate transformation according to the current frequency integral value.
Compared with the prior art, the embodiment of the invention has the following beneficial effects: the system for extracting the positive and negative sequence fundamental wave components of the power grid voltage signal provided by the embodiment comprises: the system comprises a coordinate transformation module, a reduced order resonance adjusting module and a frequency locking ring module; the coordinate transformation module is used for transforming the three-phase power grid voltage signal into an input voltage signal of an alpha beta coordinate system; the reduced order resonance adjusting module is used for carrying out positive and negative sequence separation on the input voltage signal to obtain positive and negative sequence fundamental wave components; and the frequency locking loop module is used for acquiring the three-phase power grid voltage signal and carrying out self-adaptive tracking on the voltage fundamental frequency of the reduced-order resonance adjusting module according to the closed-loop feedback principle of the frequency locking loop and the three-phase power grid voltage signal. According to the embodiment, the positive and negative sequence separation of the voltage is carried out on the input voltage signal through the reduced-order resonance adjusting module, the influence of specific low-order harmonic and direct-current components of the power grid on the positive and negative sequence component extraction result can be completely eliminated, and the positive and negative sequence component extraction effect of the power grid voltage is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of a system for extracting positive and negative sequence fundamental wave components of a grid voltage signal according to an embodiment of the present invention;
fig. 2 is a schematic diagram of the amplitude-frequency characteristic of the ROR regulator provided in the embodiment of the present invention;
FIG. 3 is a schematic diagram of a ROR regulator provided by an embodiment of the present invention;
FIG. 4 is a block diagram of extracting positive and negative sequence fundamental components of a complex plane according to an embodiment of the present invention;
fig. 5 is a block diagram of extracting positive and negative sequence fundamental wave components in an α β coordinate system according to an embodiment of the present invention;
fig. 6 is a block diagram of a frequency-locked loop module according to an embodiment of the present invention;
FIG. 7 shows a transfer function G provided by an embodiment of the present inventionp(s) and Gn(s) frequency domain characteristics;
FIG. 8 is a graph of three-phase voltage signals when the input three-phase voltage drops by 50% according to an embodiment of the present invention;
FIG. 9 is a graph of three phase voltage signals with the input A, B phase voltage dropping 50% simultaneously, according to an embodiment of the present invention;
FIG. 10 is a graph of three-phase voltage signals when 10% of 2, 3, 5, 7 harmonics are injected into the input three-phase voltage simultaneously, according to an embodiment of the present invention;
fig. 11 is another schematic structural diagram of the ROR regulator according to the embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
In order to explain the technical means of the present invention, the following description will be given by way of specific examples.
As shown in fig. 1, fig. 1 is a schematic structural diagram of a system for extracting positive and negative sequence fundamental wave components of a grid voltage signal, which is provided by an embodiment of the present invention, and includes:
the system comprises a coordinate
the coordinate
In a three-phase three-wire system, there is no zero sequence component. Regardless of the harmonic components, the three-phase grid voltage may be represented as the sum of three-phase positive and negative sequence components, as shown in equation (1).
In the formula (1), UpRepresenting a positive sequence component, U, of the voltage amplitudenRepresenting a voltage magnitude negative sequence component;representing the phase of the positive sequence component of the voltage,
phase representing negative sequence component of voltageA bit; ω is the fundamental angular frequency of the three-phase grid voltage signal.The actual three-phase grid voltage signal is often superimposed with components such as harmonic and direct-current components, and the three-phase grid voltage signal with the harmonic and direct-current components can be expressed as follows:
in the formula (2), UpiRepresenting the ith multiplied voltage amplitude positive sequence component, UniA negative sequence component of voltage amplitude representing the ith frequency multiplication;
the phase of the voltage positive sequence component representing the ith frequency multiplication,representing the phase, U, of the ith frequency-multiplied voltage negative sequence componentda、Udb、UdcEach representing a dc component of the three-phase network voltage.In this embodiment, the coordinate
In the formula (3), uαpiPositive sequence fundamental component, u, representing the ith multiple of the alpha axisβpiPositive sequence fundamental component, u, representing the ith multiple of the beta axisαniNegative-sequence fundamental component, u, representing the ith multiple of the alpha axisβniA negative-sequence fundamental component representing the ith multiple of the beta axis; t isabc/αβRepresents a Clarke transformation matrix, and
in the embodiment, the reduced order resonant regulator (ROR) has polarity selectivity, and can extract signals with specific frequencies, and the structure of the ROR regulator is shown in fig. 3. according to the structure of the ROR regulator shown in fig. 3, a transfer function of the ROR regulator is obtained
Specifically, when ω is 100 π rad/s in equation (4), the amplitude-frequency characteristic of the corresponding ROR regulator is shown in FIG. 2(a), and the phase-frequency characteristic is shown in FIG. 2(b), as can be seen from FIG. 2, HR(s) has frequency selective characteristic, has resonance peak at frequency 50Hz, and has infinite output gain and attenuation effect on other frequency signals. Similarly, when ω is-100 π rad/s, H can be passedR(s) the extraction of the negative sequence component is realized.
In this embodiment, the ROR regulator has a complex field transfer function, and equation (5) can be obtained by the structure shown in fig. 3:
discretizing the formula (5) by using a bilinear transformation formula to obtain a discrete difference equation (6) of the ROR regulator.
In the formula (6), TsRepresenting the sampling period of the system. y isα(n) and yβ(n) coupling with each other, each by x, in order to eliminate the influence of the couplingα(n)、xa(n-1)、xβ(n)、xβ(n-1)、ya(n-1)、yβ(n-1) represents ya(n) and yβ(n) to give formula (7):
specifically, the coefficient in the formula (7) can be obtained from the following formula (8).
In the formula (8), TsRepresenting the sampling period of the system.
In this embodiment, the structure of the ROR regulator may also be as shown in fig. 11, and the transfer function corresponding to the ROR regulator shown in fig. 11 is as shown in equation (9):
in the present exemplary embodiment, the three-phase system voltage signal (u)aubuc)TTransforming the coordinates to an alpha beta coordinate system to obtain (u)αuβ)TThe three-phase grid voltage is used as input, and the influence of second harmonic and direct-current components can be eliminated by using the reduced-order
In the present embodiment, the frequency-locked
As can be seen from the foregoing embodiments, the system for extracting positive and negative sequence fundamental wave components of a grid voltage signal provided by this embodiment includes: the system comprises a coordinate
Fig. 4 shows a block diagram of extracting positive and negative sequence fundamental wave components of the complex plane provided in the present embodiment, and the block diagram shown in fig. 4 is a block diagram drawn by taking an example in which an input voltage signal contains a harmonic of
As shown in fig. 4, in one embodiment, the reduced order
the first reduced order
the second reduced order
In one embodiment, the first reduced order resonance adjustment sub-module includes a
the
the first positive-sequence
the first negative sequence
the
the first summing
the
the
In this embodiment, the last positive-sequence fundamental component is the positive-sequence fundamental component calculated last time by the first reduced-order
In the present embodiment, the first positive-sequence
Specifically, the input voltage signal is data of an α β coordinate system, which includes uα、uβFig. 5 shows a block diagram of the extraction of the positive and negative sequence fundamental wave components of the system on the α β coordinate system. Specifically, in the
Similarly, the last positive-sequence fundamental component fed back to the first Nmultiplying resonance adjusting unit includes uαp1And
the second output value comprises a second a-axis output valueAnd a second beta-axis output value, wherein the first integral value comprises a first a-axis integral value and a first beta-axis integral value, the second a-axis output value is added with the first a-axis integral value to obtain a third a-axis output value, and the second beta-axis output value is added with the first beta-axis integral value to obtain a third beta-axis output value, wherein the third output value comprises the third a-axis output value and the third beta-axis output value. In theThe gain parameter of the
In one embodiment, the first reduced order resonance adjustment submodule further comprises at least one first frequency doubling resonance adjustment unit;
each first N-fold frequency resonance adjusting unit comprises a first positive sequence N-fold
the first positive sequence N frequency
the first negative-sequence frequency-N
In this embodiment, the ROR regulators are used to eliminate the influence of low-order harmonics and dc components, and therefore, it is necessary to determine the order of the low-order harmonics of the three-phase power grid voltage, and respectively use ROR reduced-order resonance regulators with different n values to perform regulation to eliminate the harmonics and dc components of the corresponding order.
In one embodiment, the transfer function of the first positive sequence
the transfer function of the first negative-sequence
the transfer function of the first positive-sequence frequency-N
the transfer function of the first negative-sequence frequency-N multiplication
wherein N represents the harmonic order of the first positive-sequence N-
Specifically, the number of the first N-times frequency resonance adjusting units is the same as the number of the low-order harmonics, for example, when only the second harmonic needs to be eliminated, only one first N-times frequency resonance adjusting unit is needed, and the N values of the two reduced order resonance adjusters corresponding to the first N-times frequency resonance adjusting unit are both 2. When the input voltage signal contains 2, 3 and 5 harmonics, 3 first N-fold frequency resonance adjusting units are needed, and the N values of the reduced order resonance adjusters of the first N-fold frequency resonance adjusting units are 2, 3 and 5 in sequence.
In one embodiment, the second reduced order resonance adjustment sub-module includes a
the
the second negative-sequence
the second positive-sequence
the
the second summing
the
the second gain unit 324 is configured to calculate a product of the eighth output value and the gain parameter to obtain a current negative-sequence fundamental component, and feed the current negative-sequence fundamental component back to the
In one embodiment, the second reduced order resonance adjustment submodule further comprises at least one second N multiplied resonance adjustment unit;
each second N-frequency multiplication resonance adjusting unit includes a second positive-sequence N-frequency
the second positive-sequence frequency-N
the second negative-sequence frequency-N
In this embodiment, as shown in fig. 5, the extraction process of the negative-sequence fundamental component of the second reduced-order resonance adjustment sub-module is similar to the extraction process of the positive-sequence fundamental component of the first reduced-order resonance adjustment sub-module, and is not described herein again.
In one embodiment, the transfer function of the second negative sequence
the transfer function of the second positive sequence
the transfer function of the second positive-sequence frequency-N multiplication
the transfer function of the second negative-sequence frequency-N multiplication
wherein N represents the harmonic order of the second positive-sequence N-
In this embodiment, the number of the second N-times frequency resonance adjusting units is the same as the number of the low-order harmonics, and when only the second harmonic needs to be eliminated, only one second N-times frequency resonance adjusting unit is needed, and the N values of the two reduced order resonance adjusters corresponding to the second N-times frequency resonance adjusting unit are 2. When the input voltage signal contains 2, 3, 5 harmonics, 3 second N-fold frequency resonance adjusting units are needed, and the N values of the reduced order resonance adjuster of each second N-fold frequency resonance adjusting unit are 2, 3, 5 respectively.
In this embodiment, if the transfer function of the ROR regulator is shown in equation (9), the transfer function of the first positive-sequence fundamental wave
In one embodiment, the frequency-locked loop module is configured to obtain a positive-sequence fundamental component according to the three-phase grid voltage signal, and perform adaptive tracking on the voltage fundamental frequency of the reduced-order resonance adjustment module according to a closed-loop feedback principle of a frequency-locked loop and the positive-sequence fundamental component.
In this embodiment, the three-phase grid voltage signal may be directly converted into an input voltage signal of an α β coordinate system, and the input voltage signal of the α β coordinate system is input to the frequency-locked loop module, so as to obtain a voltage fundamental frequency corresponding to the input voltage signal. The input voltage signal can also be input into the reduced order resonance adjusting module to obtain a positive sequence fundamental wave component and a negative sequence fundamental wave component, and then the positive sequence fundamental wave component/the negative sequence fundamental wave component is input into the frequency locking ring module to obtain the voltage fundamental wave frequency of the power grid voltage signal.
In one embodiment, fig. 6 shows a block diagram of a frequency locked loop module. As shown in fig. 6, in one embodiment, the frequency-locked loop module includes a
the
the q-
the
the adding
the
In this embodiment, the gain characteristic of the ROR regulator is determined by its resonant frequency, and in order to accurately retain the fundamental component of the grid voltage while filtering out the high-frequency harmonic component, the resonant frequency of the regulator must be made equal to the frequency of the grid voltage signal. In order to obtain the real-time frequency of the power grid, a frequency locking ring based on Park transformation is adopted, and the method has the characteristics of high calculation speed and strong harmonic interference resistance.
As shown in FIG. 6, the positive-sequence fundamental component u extracted previously is usedαβ1And
as input, the input is input to aIn the present embodiment, the target positive sequence control amount
Initial grid voltage frequency ωcAnd may be 50 Hz. Through the Park transformation, theIn this embodiment, an input vector u of the system in the frequency domain is definedαβ(s) fundamental positive sequence output vector uαβpsThe fundamental wave negative sequence output vector is uαβnsThen, it can be expressed as formula (10) on the complex plane.
From the above equation (10) and the block diagram shown in fig. 4, the following equation (11) can be obtained.
The system transfer function G of the block diagram 4 can be obtained from equation (11)p(s) and Gn(s) Namely, formula (12). When ω is 100 π rad/s, k is 110, G is plottedp(s) and GnThe frequency domain characteristic curve of(s) is shown in FIG. 7, wherein FIG. 7(a) shows Gp(s) and GnAmplitude-frequency characteristics of(s), and FIG. 7(b) shows Gp(s) and Gn(s) phase frequency characteristics.
From FIG. 7, the transfer function G for the positive sequence fundamental component extractionp(s) gain at f-50 Hz is 0dB, and gain at-100 Hz, -50Hz, 0Hz, 100Hz frequency points is-infinity dB, indicating Gp(s) the input u can be retained without attenuationαβThe fundamental positive sequence component u contained in(s)αβpsAnd simultaneously, the fundamental negative sequence component, the double-frequency positive and negative sequence component and the direct current component are attenuated. Transfer function G for negative sequence component extractionn(s) also have similar properties.
Taking a specific application scenario as an example, the TMS320F28335 chip of TI is adopted to implement signal sampling and data processing in this embodiment, and the effectiveness of the algorithm is verified through experiments under various working conditions. In the experiment, the sampling frequency f of the systemsTaking 5kHz as the reference, taking 110 as the gain coefficient k extracted from the positive sequence and the negative sequence, and taking the proportionality coefficient k of the frequency locking ringpTake 2.5X 10-2Integral coefficient kiTake 2.5
When t is 0.02s, the a-phase voltage of the input voltage drops by 50%, and the experimental result is shown in fig. 8, where fig. 8(a) shows the corresponding input three-phase voltage when the input three-phase voltage drops by 50%, fig. 8(b) shows the positive and negative sequence voltage amplitudes when the input three-phase voltage drops by 50%, fig. 8(c) shows the positive and negative sequence voltage phases when the input three-phase voltage drops by 50%, where,
which represents the phase of the positive sequence voltage,representing the negative sequence voltage phase. The algorithm can accurately extract the positive and negative sequence amplitude and the phase of the fundamental wave of the power grid voltage within 0.02 s.When t is 0.02s, A, B phase voltages of the input voltage drop 50% at the same time, and the experimental result is shown in fig. 9, wherein fig. 9(a) shows the corresponding input three-phase voltages when the input A, B phase voltages drop 50% at the same time; FIG. 9(b) shows the positive and negative sequence voltage amplitudes at which the input A, B phase voltage drops 50% simultaneously, where up1Representing positive sequence voltage amplitude, un1Representing a negative sequence voltage magnitude; fig. 9(c) shows the positive and negative sequence voltage phases with the input A, B phase voltage dropping 50% simultaneously, where,which represents the phase of the positive sequence voltage,
representing the negative sequence voltage phase. The algorithm can accurately extract the positive and negative sequence amplitude and the phase of the fundamental wave of the power grid voltage within 0.02 s.When t is 0.02s, the A phase voltage of the input voltage drops by 50%, and 10% of 2, 3, 5 and 7 harmonics are injected into the input three-phase voltage. The ROR regulator structure for
From the above embodiments, in order to effectively extract the positive and negative sequence amplitude and phase of the fundamental wave of the input voltage under the condition of containing harmonic wave and direct current component, the application provides a positive and negative sequence fundamental wave component extraction system of the grid voltage signal. According to the method, the frequency selectivity of the ROR regulator is utilized, the influence of specific low-order harmonics and direct-current components of a power grid on the positive and negative sequence component extraction result can be completely eliminated by constructing an algorithm structure based on a plurality of ROR regulators and an integration link, and a certain inhibiting effect on non-specific high-order harmonics is achieved due to the low-pass characteristic of a closed-loop transfer function of the controller. Experimental results show that the algorithm can rapidly and accurately extract the amplitude and phase information of the positive and negative sequence components of the power grid voltage under the conditions that the power grid voltage amplitude falls and contains direct-current components and a large number of low-order harmonics.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.
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