CN107423261A - The separation method of positive and negative order components based on OVPR under the conditions of non-ideal micro-capacitance sensor - Google Patents
The separation method of positive and negative order components based on OVPR under the conditions of non-ideal micro-capacitance sensor Download PDFInfo
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Abstract
The present invention provides the positive and negative order components separation method based on OVPR under the conditions of a kind of non-ideal micro-capacitance sensor, is become by Clark change commanders microgrid voltage from three-phase abc coordinate system transformations to the static α β coordinate systems of two-phase first；Then positive-sequence component, the negative sequence component of voltage are obtained by Signal separator subsystem, is specially：The microgrid voltage and isolated each component sum for transforming to the static α β coordinate systems of two-phase subtract each other, fundamental positive sequence detection unit, the negative phase-sequence detection unit formed respectively through single order vector resonant controller OVPR forms negative-feedback, and the output of each unit is respectively the positive-sequence component of voltage, negative sequence component.This method has response very fast, is not required to Instantaneous Symmetrical Components separation, realizes the features such as simple, can fast and accurately be directly realized by positive and negative sequence and harmonic wave separation.Simulation result and the analytical proof correct and validity of proposed method.
Description
Technical Field
The invention relates to a separation method of positive and negative sequence components based on OVPR under the condition of a non-ideal microgrid.
Background
The microgrid can overcome the adverse effect of distributed power generation, and the microgrid gives full play to the advantages of the microgrid and is widely concerned. However, due to the characteristics of the micro-grid, the micro-grid is easily affected by nonlinear and high-power loads in the grid, so that the voltage of the grid is unbalanced and harmonic distortion occurs. Therefore, higher demands are made on the control of power electronic converters as micro power source interfaces, so that multiple control targets, such as no fluctuation of active power, no fluctuation of reactive power, no harmonic of output current, and the like, can be achieved. The need to achieve multiple control objectives requires efficient and fast separation of the voltage positive and negative sequence and harmonic components. Therefore, the voltage detection separation method has a great influence on the implementation of the multi-target control strategy, and further influences the grid-connected operation of the micro power supply.
The currently used separation methods include a method using an instantaneous symmetric component method and an improved delay Cancellation (DSC) detection method thereof, a method based on dq synchronous rotating coordinate system detection, and a method using a wave trap and an integrator with a filtering function.
Svensson J, Bongiorno M, sanino a.practical implementation method for phase-sequence separation [ J ]. ieee transaction Power separation, 2007,22 (1): 18-26, adopt time delay to cancel and extract the positive and negative sequence components of the voltage, the method has 1/4 time delay in time, and is susceptible to the influence of harmonic wave, in order to eliminate the influence of multiple harmonic wave, it needs to adopt multiple DSC cascades.
The method comprises the following steps of (1) a detection method [ J ] of grid voltage synchronous signals of a decoupling multi-synchronous reference coordinate system, namely, Licoral, Duxiong, Wanglinu, and the like: 183-189, the proposed method using multi-synchronous dq rotation coordinate system realizes the voltage conversion and harmonic elimination by decoupling method in multiple positive and negative sequence rotation coordinate systems, but the structure is complicated, and the additional LPF filter is needed to filter out the harmonic, which affects the dynamic response performance of the system.
A positive and negative sequence component detection system formed on the basis of a second order generalized integrator SOGI (second order generalized integrator) and a complex integrator can effectively detect voltage signals in a non-ideal power grid environment, but the method cannot directly distinguish positive and negative sequence components, needs instantaneous symmetric component calculation to separate the positive and negative sequence components, and is easy to influence the detection result under the condition of high harmonic content. To eliminate the effect of harmonics, Yazdani D, Mojiri M, BakhshaiA, et al.A fast and acid synchronization technique for the extraction of systematic components [ J ]. IEEE Transactions on Power Electronics,2009,24(3):674 684 is compared with Culin, Tangningping. 2350 SOGI is adopted in the auxiliary 2356 to form a harmonic elimination module, then a plurality of modules are cascaded in sequence to eliminate each subharmonic in sequence, thereby realizing the separation detection of the positive and negative sequence components of the fundamental wave of the voltage of the power grid and each subharmonic signal, but the cascade of a plurality of modules increases the order of the system, the system becomes more complex, the difficulty of the system analysis and parameter design is increased, meanwhile, the phase margin may be reduced to reduce the system stability, and the method still needs to utilize the instantaneous symmetric component for calculation.
Disclosure of Invention
Based on the problems, in order to improve the operation control performance of the microgrid inverter in a non-ideal microgrid environment, the invention aims to provide the separation method of positive and negative sequence components based on the OVPR under the non-ideal microgrid condition, which has higher performance, can realize positive and negative sequence and harmonic detection, and enables the microgrid inverter to realize different control targets.
The invention discloses a method for separating positive and negative sequence components based on OVPR under the condition of a non-ideal microgrid. The method can eliminate the influence of the negative sequence component and the harmonic component on the detection result, can directly and quickly detect the positive sequence component, the negative sequence component and the harmonic of the voltage without separating instantaneous symmetrical components, and has strong capability of adapting to non-ideal power grid environment.
The technical solution of the invention is as follows:
a separation method of positive and negative sequence components based on OVPR under the condition of a non-ideal microgrid comprises the following steps,
step 1, carrying out Clark transformation on collected unbalanced and harmonic-containing microgrid voltage uabc＝(ua，ub，uc) Conversion from the three-phase abc coordinate system to the two-phase stationary αβ coordinate system to uαβ＝(uα,uβ)；
Step 2, converting the microgrid voltage u to a two-phase static αβ coordinate systemαβThrough the separation of each signal separation subsystem, a positive sequence component, a negative sequence component and a harmonic component of the voltage are respectively obtained, in particular to the microgrid voltage u of a two-phase static αβ coordinate systemαβSubtracting the sum of the separated negative sequence and each subharmonic component; u. ofαβAnd subtracting the sum of the positive sequence and each subharmonic component, and forming negative feedback by a fundamental positive sequence detection unit and a negative sequence detection unit which are respectively composed of a first-order vector resonance controller OVPR, wherein the output of each unit is respectively the positive sequence component and the negative sequence component of the voltage.
Further, the step 2 further comprises a harmonic detection unit, namely a microgrid voltage u of a two-phase static αβ coordinate systemαβAnd subtracting the sum of the separated components, and forming negative feedback by a fundamental wave positive sequence detection unit, a fundamental wave negative sequence detection unit and a fundamental wave harmonic detection unit which are respectively formed by a first-order vector resonance controller OVPR, wherein the output of each unit is respectively a positive sequence component, a negative sequence component and a harmonic component of the voltage.
Furthermore, a positive sequence controller and a positive and negative sequence controller are respectively adopted to separate positive sequence components from negative sequence components, the formed fundamental wave positive sequence controller and the positive and negative sequence controller adopt a first-order vector resonance controller OVPR, and the transfer function of the OVPR is as follows:
wherein,is a fundamental wave positive and negative sequence controller, kPIs a proportionality coefficient, kIIs an integral coefficient, s represents a continuous domain transfer function complex variable, j represents a complex number, and omega is a fundamental frequency;
when the voltage passes through the positive sequence controller, the gain of the positive sequence component reaches the maximum, the amplitude of the negative sequence component is approximately attenuated to 0, and similarly, when the voltage passes through the negative sequence OVPR controller, the gain of the negative sequence component reaches the maximum, and the amplitude of the positive sequence component is approximately attenuated to 0, so that the selection of the positive sequence component and the negative sequence component is realized by the first-order vector resonance controller OVPR, and further, the detection and separation of the positive sequence component, the negative sequence component and the harmonic components with different frequencies with the same frequency are realized under the non-ideal power grid condition.
Further, a first order vector resonance controllerThe difference equation of (a) is that,
in the formula, TsIs a sampling period; u. ofα、uβIs the voltage under the two-phase static αβ coordinate system as the input of the first order vector resonance controller OVPR, yα、yβThe output of the first order vector resonance controller OVPR in the two-phase stationary αβ coordinate system, z represents the discrete transfer function variable, and ω is the fundamental frequency.
Furthermore, a frequency domain mathematical model is established according to the relation between the input and the output of the signal separation subsystem in the step 2 as follows,
in the formula, the upper corner mark h is p, n, 5,7 … 6k-1,6k +1, where k is 1,2,3 …, and represents the fundamental positive and negative sequence and 5,7, 6k-1,6k +1 subharmonics, respectively. Wherein,Uα(s)、Uβ(s) is a time domain variable uα、uβA complex frequency domain variable after laplace transformation;OVPR transfer functions representing different frequencies; is the time domain variable e in FIG. 5hAnd (4) carrying out Laplace transform on the complex frequency domain variable.
Further, the transfer function corresponding to the signal separation subsystem obtained from equation (11) is,
wherein,OVPR transfer functions representing different frequencies;representing the sum of the OVPR transfer functions at different frequencies.
The invention has the beneficial effects that: according to the separation method of the positive and negative sequence components based on the OVPR under the non-ideal microgrid condition, the corresponding components are directly obtained by utilizing the frequency selection characteristics of the positive sequence signal, the negative sequence signal and the harmonic signal of a first-order vector resonance controller; by adopting the sub-system constructed by the first-order vector resonance controllers with different frequencies, the influence of unbalanced network voltage and harmonic waves is eliminated. The method has the characteristics of quick response, no need of instantaneous symmetrical component separation, simple realization and the like, and can quickly and accurately directly realize the positive and negative sequence and harmonic separation. Simulation results and analysis demonstrate the correctness and effectiveness of the proposed method.
Drawings
FIG. 1 is a Baud diagram of a conventional VPI controller.
Fig. 2 is a diagram of OVPR control baud in an embodiment.
FIG. 3 is a diagram of OVPR baud with different values of parameters in the embodiment.
Fig. 4 is a schematic diagram illustrating the implementation of the OVPR structure in the embodiment.
FIG. 5 is a schematic diagram of positive and negative sequence separation according to an embodiment.
FIG. 6 is a Baud diagram of a closed loop subsystem for signal positive sequence separation in an embodiment.
FIG. 7 is a waveform diagram of an embodiment method for three-phase voltage imbalance detection.
FIG. 8 is a waveform diagram of voltage detection under unbalanced, harmonic conditions by an embodiment method.
Fig. 9 is a diagram of a conventional SOGI method detection waveform.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
The embodiment provides a voltage positive sequence, negative sequence and harmonic component detection method based on an OVPR controller in order to meet the requirement of a microgrid inverter for realizing multiple control targets under the non-ideal microgrid voltage condition. LPF or other filtering links are not required to be added, and multiple rotation coordinate changes or extra calculation is not required. Simulation verification results show that the method can quickly and accurately extract the positive sequence component and the negative sequence component of the fundamental wave of the power grid voltage under the non-ideal voltage condition.
A separation method of positive and negative sequence components based on OVPR under the condition of a non-ideal microgrid comprises the following steps,
step 1, carrying out Clark transformation on collected unbalanced and harmonic-containing microgrid voltage uabcTransformation from three-phase abc coordinate system to two-phase stationary αβ coordinate system to uαβ；
Step 2, converting the microgrid voltage u to a two-phase static αβ coordinate systemαβThrough the separation of each signal separation subsystem, a positive sequence component, a negative sequence component and a harmonic component of the voltage are respectively obtained, in particular to the microgrid voltage u of a two-phase static αβ coordinate systemαβSubtracting the sum of the separated negative sequence and each subharmonic component; u. ofαβAnd subtracting the sum of the positive sequence and each subharmonic component, and forming negative feedback by a fundamental positive sequence detection unit and a negative sequence detection unit which are respectively composed of a first-order vector resonance controller OVPR, wherein the output of each unit is respectively the positive sequence component and the negative sequence component of the voltage.
The positive sequence component and the negative sequence component are separated by respectively adopting a positive sequence controller and a positive and negative sequence controller, the formed fundamental wave positive sequence controller and the positive and negative sequence controller adopt a first-order vector resonance controller OVPR, and the transfer function of the OVPR is as follows:
wherein,a fundamental wave positive and negative sequence controller, and omega is the fundamental wave frequency;
when the voltage passes through the positive sequence controller, the gain of the positive sequence component reaches the maximum, the amplitude of the negative sequence component is approximately attenuated to 0, and similarly, when the voltage passes through the negative sequence OVPR controller, the gain of the negative sequence component reaches the maximum, and the amplitude of the positive sequence component is approximately attenuated to 0, so that the selection of the positive sequence component and the negative sequence component is realized by the first-order vector resonance controller OVPR, and further, the detection and separation of the positive sequence component, the negative sequence component and the harmonic components with different frequencies with the same frequency are realized under the non-ideal power grid condition.
The differential equation for the first order vector resonant controller OVPR is,
the relation between the input and the output of the signal separation subsystem in the step 2 is used for establishing a frequency domain mathematical model as follows,
in the formulaRespectively represent OVPR transfer functions of different frequencies such as positive and negative sequences of fundamental waves, 5 th harmonic waves, 7 th harmonic waves and the like.
The transfer function corresponding to the signal separation subsystem is obtained from equation (11),
the principle of the separation method based on positive and negative sequence components of OVPR under the condition of non-ideal microgrid is illustrated as follows:
principle of positive and negative sequence separation of voltage
Under the non-ideal condition that the voltage of the micro-grid is unbalanced and harmonic waves exist, the zero sequence component is not considered, the voltage has positive and negative sequence components, as shown in the following formula,
in which the positive and negative sequence components of the voltageAndrespectively, are shown as being, respectively,
in the formula, the upper corner marks p and n represent positive and negative sequences. Wherein x is 1,2 … m,respectively representing the amplitudes of the positive and negative sequence and harmonic components, "omegapx、ωnx"angular frequencies representing positive and negative sequence and harmonic components, respectively," + "px”、“φnx"represents the phases of the positive and negative sequence and harmonic components, respectively.
For u is pairedabcClark transformation is carried out, the three-phase abc coordinate system is transformed into a two-phase static αβ coordinate system,
in the formula, Tabc/αβRepresenting Clark transformation, voltageRespectively represent positive sequence components under a two-phase static αβ coordinate systemRespectively, represent the negative sequence components under the two-phase stationary αβ coordinate system.
Wherein,
in the formula,respectively represent positive and negative sequence components of different frequencies under a two-phase static αβ coordinate system,representing positive and negative sequence and harmonic component magnitudes.
In the above formula, omegapx＝-ωnxIn addition to the fundamental positive and negative sequence components, the voltage contains 6k-1(k is 1,2,3 …) subharmonic as the negative sequence component; the 6k +1 th harmonic is the positive sequence component.
As can be seen from equation (4)q＝e-jπ/2A phase shift operator with a lag of 90. Thus, as can be derived from equation (3),
according to the above formulas (3), (4) and (5), it can be seen that, in order to realize the separation of the positive sequence, the negative sequence and the harmonic component, a filtering method for filtering signals except for specific frequencies can be adopted, or a 90-degree phase shift construction quadrature signal can be realized based on the SOGI or an improved structure thereof, and then the separation of the voltage positive sequence, the voltage negative sequence and the harmonic can be realized through instantaneous symmetrical component calculation.
OVPR-based positive and negative sequence detection method
The positive sequence, negative sequence and harmonic separation is realized by adopting a filtering method for filtering signals except for specific frequencies, and the filter is required to have a frequency selection characteristic and a positive and negative frequency selection characteristic.
The OVPR complex controller and the realization thereof are as follows: equation (6) is vector proportional-integral (VPI), a resonant controller with filtering function, and the bode diagram of the VPI controller is shown in fig. 1.
As can be seen from fig. 1, the VPI controller simultaneously and respectively realizes resonance of the positive and negative sequence components at ± ω resonance points (+ ω and — ω frequencies respectively corresponding to the fundamental positive and negative sequence components), and can realize attenuation of components of other frequencies, but has a frequency selection characteristic, but does not have positive and negative frequency selectivity, and thus cannot realize separation of the positive and negative sequence components of the same frequency.
In the combination of (6) and fig. 1, it can be seen that the second-order VPI controller is actually formed by connecting a first-order positive controller and a first-order negative controller in parallel. Therefore, the separation of positive sequence components and negative sequence components by respectively adopting a positive sequence controller and a positive and negative sequence controller can be considered to obtain a first-order vector resonance controller (OVPR) after reducing the order,
is a fundamental wave positive and negative controller, omega is the fundamental wave frequency, and figure 2 is a bode diagram of the positive sequence OVPR controller at the frequency of +/-50 Hz.
It can be seen from equation (7) and fig. 2 that when the voltage passes through the positive sequence OVPR controller, the gain of the positive sequence component reaches the maximum, and the amplitude of the negative sequence component is approximately attenuated to 0, and similarly, when the voltage passes through the negative sequence OVPR controller, the gain of the negative sequence component reaches the maximum, and the amplitude of the positive sequence component is approximately attenuated to 0, which proves that the OVPR controller not only can realize the filtering function, but also has the positive and negative frequency selection characteristics, and can realize the selection of the positive and negative sequence components, thereby realizing the detection and separation of the positive, negative and harmonic components with the same frequency under the non-ideal power grid conditions of voltage imbalance, harmonic wave and the like.
In FIG. 3, each is kp＝0.1，kIValues of 100, 200, 300; k is a radical ofI＝100，kpAnd taking values of 0.1, 0.5 and 1 to obtain a positive sequence OVPR controller Baud diagram. It can be seen that kp，kIThe gain of the value-increasing controller is increased along with the gain, the frequency selection characteristic is poor, and the robustness to frequency fluctuation is enhanced; with kpIncreasing the controller phase lag decreases, and kIIncreasing the controller phase lag increases. Thus, the parameter kIIncreasing decreases the phase margin of the OVPR controller and may affect the stability of the system.
As can be seen from equation (7), although the OVPR controller is difficult to implement in digital control due to the existence of the complex number j, the variable x in the coordinate system of the two-phase stationary αβ can be known from the knowledge related to the complex variable functionα、xβThere is a relationship of the formula (8),
j can therefore be realized by means of equation (8), the specific structural realization is shown in figure 4,
a proven effective discretization method is adopted in digital control[6]The bilinear transformation method shown in the formula (9) realizes the discretization of complex frequency domain variables,
the z-transformation is performed by adopting (9) in the formula (7), and the difference equation of the OVPR controller can be obtained as follows,
the positive and negative sequence separation method based on OVPR is as follows: according to the analysis, the OVPR controller can quickly and accurately realize the separation of positive, negative sequence and harmonic components in unbalanced and harmonic voltages. For a brief explanation of the implementation, the low order 5,7 harmonics are mainly considered, and the specific implementation is shown in fig. 5.
In fig. 5, the microgrid voltage is first transformed from the three-phase abc coordinate system to the two-phase stationary α β coordinate system by a Clark transformation. Then subtracting the sum of the components obtained by separation, forming negative feedback by fundamental wave positive and negative sequence formed by OVPR, 5 th and 7 th harmonic detection unit subsystems respectively, wherein the output of each unit is the positive sequence component, the negative sequence component, the 5 th and 7 th harmonic component of the voltage respectively. If only the fundamental component is separated, the harmonic detection unit may not be included, and likewise if other harmonics are to be detected, only the corresponding harmonic detection unit needs to be added.
Third, the detection mechanism and parameter design
From the relationship between input and output of fig. 5, a frequency domain mathematical model can be constructed as follows,
in the formula, the upper corner mark h ═ p, n, 5,7 … 6k-1,6k +1(k ═ 1,2,3 …) represents the fundamental positive and negative sequences and the 5,7, 6k-1,6k +1 subharmonics, respectively. Wherein,Uα(s)、Uβ(s) is a time domain variable uα、uβA complex frequency domain variable after laplace transformation;OVPR transfer functions representing different frequencies; is the time domain variable e in FIG. 5hAnd (4) carrying out Laplace transform on the complex frequency domain variable.Respectively represent OVPR transfer functions of different frequencies such as positive and negative sequences of fundamental waves, 5 th harmonic waves, 7 th harmonic waves and the like. The transfer function corresponding to each signal separation subsystem can be obtained from the formula (11),
separating subsystem T in positive sequence by fundamental wavep αβFor example, it can be seen from equation (12) that when the input voltage is the fundamental positive sequence, the negative sequence, the 5 th harmonic, and the 7 th harmonic, and the frequencies are ω, - ω, 5 ω, and 7 ω, respectively, T isp αβ(s)|s＝jω＝1，Tp αβ(s)|s＝-jω＝Tp αβ(s)|s＝j5ω＝Tp αβ(s)|s＝j7ωAt 0, it turns out that the fundamental positive sequence voltage can be completely detected by the fundamental positive sequence voltage separation subsystem, while the fundamental negative sequence component and harmonics of other frequencies are attenuated to 0. The results for the other subsystems are similar. Therefore, the signal separation method shown in fig. 5 can directly separate the positive sequence, the negative sequence and the harmonic components of the voltage without constructing an additional filtering module with a complex structure or trigonometric function operation.
Analyzing the parameter design and selection principle of the system by taking a fundamental wave positive sequence separation subsystem as an example through a functional formula (11), considering the closed-loop transfer function of the positive sequence separation subsystem as shown in the following formula (13),
shown in FIG. 6 as kI1＝100，kp1Values of 0.01, 0.5, 2 and k, respectivelyp1＝0.1，ki1And taking values of 50, 100 and 200 respectively to obtain a Baud diagram of the closed-loop transfer function of the formula (13).
As can be seen from fig. 6, the input signal gain of the closed loop system to the resonant frequency is 1 and the phase offset is 0. k is a radical ofp1The frequency selection characteristic is increased to be poor, and the harmonic attenuation capability in the input signal is poor; likewise, kI1The frequency-selecting characteristic is increased and the frequency-selecting characteristic is also deteriorated, and the harmonic attenuation capability in the input signal is also correspondingly deteriorated. But in comparison with respect to kI1Parameter kp1The influence on the frequency selection characteristic is larger, kp1The frequency selection characteristic is better when the value is smaller, but the dynamic performance of the system is correspondingly poor.
The above results are combined and the analysis shows that: parameter kp1Mainly aiming at the frequency selection characteristic and the dynamic performance, the design is carried out, and the value k is usually takenp1Less than 1; parameter kI1The design is typically at 10 for the steady state performance of the system primarily2Magnitude order value. The design of system parameters should comprehensively consider the requirements of frequency selection characteristic, dynamic performance, robustness to frequency fluctuation and the like of the system to be selected in a compromise way. The determination of other channel parameters is similar.
Verification and analysis
Example simulation verification is performed, wherein in order to verify the effectiveness and the performance of the positive sequence detection method, the negative sequence detection method and the harmonic detection method, simulation verification is performed under the conditions of unbalanced voltage and harmonic of the microgrid. The micro-grid and the large-grid are connected in a grid, the three-phase line voltage is 380v, and the working conditions are as follows: 1, C phase voltage falls to 40%; 2. 5,7 harmonics appear on the voltage drop to 40%, wherein the content of the 5 harmonics is 20%, and the content of the 7 harmonics is 10%.
Under the condition of voltage unbalance of the condition 1, the positive and negative sequence components of the voltage are separated and extracted. As shown in fig. 7, the voltage dropped to 40% at 0.2s and continued until 0.3 s. It can be seen that when the voltage is unbalanced, the detected voltage is stable within 1/2 fundamental wave period time, and the fast and accurate detection of the fundamental wave positive and negative sequence components can be realized.
Under the condition 2 that the voltage is unbalanced and harmonic waves are generated, waveforms of positive and negative sequences and harmonic wave components of the voltage are separated and extracted as shown in fig. 8. An imbalance occurs in the voltage drop of 0.3s, and the harmonic mainly comprises a large amount of 5 and 7 harmonics and lasts to 0.4 s. It can be seen that the voltage reaches a stable value in 1/2 fundamental wave cycle time, so that the positive and negative sequence components of the fundamental wave can be rapidly and accurately detected, and 5 and 7 harmonics can be effectively and accurately separated.
From the above, the method provided by the embodiment can quickly and accurately detect the positive and negative sequence components of the fundamental voltage and simultaneously separate out the harmonic wave under the non-ideal voltage condition of the microgrid.
Comparative analysis, fig. 9 shows positive and negative sequence waveforms detected using the existing SOGI-based method under operating condition 2. Comparing fig. 8 and fig. 9, it can be seen that under the same operating condition, the dynamic response speed of the two methods is the same, but the fundamental positive and negative sequence voltages detected based on the SOGI method contain harmonics, and particularly, the negative sequence voltage detection is affected more severely by the harmonics. The SOGI detection method is proved to be influenced when the harmonic content of the power grid voltage is large, and the fundamental wave positive sequence voltage and the fundamental wave negative sequence voltage detected and separated by the method are not influenced.
Claims (6)
1. A separation method of positive and negative sequence components based on OVPR under the condition of a non-ideal microgrid is characterized by comprising the following steps: comprises the following steps of (a) carrying out,
step 1, carrying out Clark transformation on collected unbalanced and harmonic-containing microgrid voltage uabc＝(ua，ub，uc) Conversion from the three-phase abc coordinate system to the two-phase stationary αβ coordinate system to uαβ＝(uα,uβ)；
Step 2, converting the microgrid voltage u to a two-phase static αβ coordinate systemαβBy means of signalsSeparating the subsystem to obtain the positive sequence component, the negative sequence component and the harmonic component of the voltage respectively, specifically to obtain the microgrid voltage u of a two-phase static αβ coordinate systemαβSubtracting the sum of the separated negative sequence and each subharmonic component; u. ofαβAnd subtracting the sum of the positive sequence and each subharmonic component, and forming negative feedback by a fundamental positive sequence detection unit and a negative sequence detection unit which are respectively composed of a first-order vector resonance controller OVPR, wherein the output of each unit is respectively the positive sequence component and the negative sequence component of the voltage.
2. The method for separating positive and negative sequence components based on OVPR under the condition of the non-ideal microgrid as claimed in claim 1, characterized in that the step 2 further comprises a harmonic detection unit, and the microgrid voltage u of a two-phase static αβ coordinate systemαβAnd subtracting the sum of the separated components, and forming negative feedback by a fundamental wave positive sequence detection unit, a fundamental wave negative sequence detection unit and a fundamental wave harmonic detection unit which are respectively formed by a first-order vector resonance controller OVPR, wherein the output of each unit is respectively a positive sequence component, a negative sequence component and a harmonic component of the voltage.
3. The method for separating positive and negative sequence components based on OVPR under the non-ideal microgrid condition of claim 1, characterized in that: the positive sequence controller and the negative sequence controller are respectively adopted to separate positive sequence components from negative sequence components, the formed fundamental wave positive sequence controller and the negative sequence controller adopt a first-order vector resonance controller OVPR, and the OVPR transfer function is as follows:
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msubsup> <mi>G</mi> <mrow> <mi>O</mi> <mi>V</mi> <mi>P</mi> <mi>R</mi> </mrow> <mi>p</mi> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <msub> <mi>k</mi> <mi>P</mi> </msub> <mi>s</mi> <mo>+</mo> <msub> <mi>k</mi> <mi>I</mi> </msub> </mrow> <mrow> <mi>s</mi> <mo>-</mo> <mi>j</mi> <mi>&omega;</mi> </mrow> </mfrac> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msubsup> <mi>G</mi> <mrow> <mi>O</mi> <mi>V</mi> <mi>P</mi> <mi>R</mi> </mrow> <mi>n</mi> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <msub> <mi>k</mi> <mi>P</mi> </msub> <mi>s</mi> <mo>+</mo> <msub> <mi>k</mi> <mi>I</mi> </msub> </mrow> <mrow> <mi>s</mi> <mo>+</mo> <mi>j</mi> <mi>&omega;</mi> </mrow> </mfrac> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow>
wherein,is a positive and negative sequence controller of fundamental wave,kPis a proportionality coefficient, kIIs an integral coefficient, s represents a continuous domain transfer function complex variable, j represents a complex number, and omega is a fundamental frequency;
when the voltage passes through the positive sequence controller, the gain of the positive sequence component reaches the maximum, the amplitude of the negative sequence component is approximately attenuated to 0, and similarly, when the voltage passes through the negative sequence OVPR controller, the gain of the negative sequence component reaches the maximum, and the amplitude of the positive sequence component is approximately attenuated to 0, so that the selection of the positive sequence component and the negative sequence component is realized by the first-order vector resonance controller OVPR, and further, the detection and separation of the positive sequence component, the negative sequence component and the harmonic components with different frequencies with the same frequency are realized under the non-ideal power grid condition.
4. The method for separating positive and negative sequence components based on OVPR under the condition of the non-ideal microgrid according to claim 3, characterized in that: first order vector resonance controllerThe difference equation of (a) is that,
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <msub> <mi>y</mi> <mi>&alpha;</mi> </msub> <mrow> <mo>(</mo> <mi>z</mi> <mo>)</mo> </mrow> <mo>-</mo> <msub> <mi>y</mi> <mi>&alpha;</mi> </msub> <mrow> <mo>(</mo> <mi>z</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>+</mo> <mfrac> <mrow> <msub> <mi>&omega;T</mi> <mi>s</mi> </msub> </mrow> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msub> <mi>y</mi> <mi>&beta;</mi> </msub> <mo>(</mo> <mi>z</mi> <mo>)</mo> <mo>+</mo> <msub> <mi>y</mi> <mi>&beta;</mi> </msub> <mo>(</mo> <mrow> <mi>z</mi> <mo>-</mo> <mn>1</mn> </mrow> <mo>)</mo> <mo>)</mo> </mrow> <mo>=</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>p</mi> </msub> <mo>+</mo> <mfrac> <mrow> <msub> <mi>k</mi> <mi>I</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mn>2</mn> </mfrac> <mo>)</mo> <msub> <mi>u</mi> <mi>&alpha;</mi> </msub> <mo>(</mo> <mi>z</mi> <mo>)</mo> <mo>-</mo> <mo>(</mo> <msub> <mi>k</mi> <mi>p</mi> </msub> <mo>-</mo> <mfrac> <mrow> <msub> <mi>k</mi> <mi>I</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mn>2</mn> </mfrac> <mo>)</mo> <msub> <mi>u</mi> <mi>&alpha;</mi> </msub> <mo>(</mo> <mi>z</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <msub> <mi>y</mi> <mi>&beta;</mi> </msub> <mrow> <mo>(</mo> <mi>z</mi> <mo>)</mo> </mrow> <mo>-</mo> <msub> <mi>y</mi> <mi>&beta;</mi> </msub> <mrow> <mo>(</mo> <mi>z</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>-</mo> <mfrac> <mrow> <msub> <mi>&omega;T</mi> <mi>s</mi> </msub> </mrow> <mn>2</mn> </mfrac> <mrow> <mo>(</mo> <msub> <mi>y</mi> <mi>&alpha;</mi> </msub> <mo>(</mo> <mi>z</mi> <mo>)</mo> <mo>+</mo> <msub> <mi>y</mi> <mi>&alpha;</mi> </msub> <mo>(</mo> <mrow> <mi>z</mi> <mo>-</mo> <mn>1</mn> </mrow> <mo>)</mo> <mo>)</mo> </mrow> <mo>=</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mi>p</mi> </msub> <mo>+</mo> <mfrac> <mrow> <msub> <mi>k</mi> <mi>I</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mn>2</mn> </mfrac> <mo>)</mo> <msub> <mi>u</mi> <mi>&beta;</mi> </msub> <mo>(</mo> <mi>z</mi> <mo>)</mo> <mo>-</mo> <mo>(</mo> <msub> <mi>k</mi> <mi>p</mi> </msub> <mo>-</mo> <mfrac> <mrow> <msub> <mi>k</mi> <mi>I</mi> </msub> <msub> <mi>T</mi> <mi>s</mi> </msub> </mrow> <mn>2</mn> </mfrac> <mo>)</mo> <msub> <mi>u</mi> <mi>&beta;</mi> </msub> <mo>(</mo> <mi>z</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>10</mn> <mo>)</mo> </mrow> </mrow>
in the formula, TsIs a sampling period; u. ofα、uβIs the voltage under the two-phase static αβ coordinate system as the input of the first order vector resonance controller OVPR, yα、yβThe output of the first order vector resonance controller OVPR in the two-phase stationary αβ coordinate system, z represents the discrete transfer function variable, and ω is the fundamental frequency.
5. The method for separating positive and negative sequence components based on OVPR under the non-ideal microgrid condition of claim 1, characterized in that: the relation between the input and the output of the signal separation subsystem in the step 2 is used for establishing a frequency domain mathematical model as follows,
<mrow> <mfenced open = "{" close = ""> <mtable> <mtr> <mtd> <mrow> <mo>(</mo> <msub> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> </msub> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <munder> <mo>&Sigma;</mo> <mrow> <mi>h</mi> <mo>=</mo> <mi>p</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>7</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </munder> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>p</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msubsup> <mi>E</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>P</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>p</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>p</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>p</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msub> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> </msub> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <munder> <mo>&Sigma;</mo> <mrow> <mi>h</mi> <mo>=</mo> <mi>p</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>7</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </munder> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>n</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msubsup> <mi>E</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>n</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>n</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>n</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>n</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msub> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> </msub> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <munder> <mo>&Sigma;</mo> <mrow> <mi>h</mi> <mo>=</mo> <mi>p</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>7</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </munder> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>5</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msubsup> <mi>E</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>5</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>5</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>5</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>5</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msub> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> </msub> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <munder> <mo>&Sigma;</mo> <mrow> <mi>h</mi> <mo>=</mo> <mi>p</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>7</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </munder> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>7</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <msubsup> <mi>E</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>7</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>-</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>7</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>)</mo> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>7</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> <mo>=</mo> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mn>7</mn> </msubsup> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mo>.</mo> </mtd> </mtr> <mtr> <mtd> <mo>.</mo> </mtd> </mtr> <mtr> <mtd> <mo>.</mo> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>11</mn> <mo>)</mo> </mrow> </mrow>
in the formula, the upper corner mark h is p, n, 5,7 … 6k-1,6k +1, where k is 1,2,3 …, and represents the fundamental positive and negative sequence and 5,7, 6k-1,6k +1 subharmonics, respectively. Wherein,Uα(s)、Uβ(s) is a time domain variable uα、uβA complex frequency domain variable after laplace transformation;OVPR transfer functions representing different frequencies; as a time domain variable ehAnd (4) carrying out Laplace transform on the complex frequency domain variable.
6. The method for separating positive and negative sequence components based on OVPR under the non-ideal microgrid condition of claim 5, characterized in that: the transfer function corresponding to the signal separation subsystem is obtained from equation (11),
<mrow> <msubsup> <mi>T</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> <msub> <mo>|</mo> <mrow> <mi>h</mi> <mo>=</mo> <mi>p</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>7</mn> </mrow> </msub> <mo>=</mo> <mfrac> <mrow> <msubsup> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mrow> <mrow> <msub> <mi>U</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>h</mi> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mrow> <mrow> <mn>1</mn> <mo>+</mo> <munder> <mo>&Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mi>p</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>7</mn> <mo>,</mo> <mn>...</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mn>6</mn> <mi>k</mi> <mo>+</mo> <mn>1</mn> </mrow> </munder> <msubsup> <mi>G</mi> <mrow> <mi>&alpha;</mi> <mi>&beta;</mi> </mrow> <mi>i</mi> </msubsup> <mrow> <mo>(</mo> <mi>s</mi> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>12</mn> <mo>)</mo> </mrow> <mo>.</mo> </mrow>
wherein,OVPR transfer functions representing different frequencies;representing the sum of the OVPR transfer functions at different frequencies.
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