CN112260319B - Power grid synchronization method, system and medium based on open loop - Google Patents

Power grid synchronization method, system and medium based on open loop Download PDF

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CN112260319B
CN112260319B CN202011027471.3A CN202011027471A CN112260319B CN 112260319 B CN112260319 B CN 112260319B CN 202011027471 A CN202011027471 A CN 202011027471A CN 112260319 B CN112260319 B CN 112260319B
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CN112260319A (en
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徐勇
谢学渊
单周平
陈宏�
向运琨
向洁
黎菁
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National Network Hunan Integrated Energy Service Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H02J3/44—Synchronising a generator for connection to a network or to another generator with means for ensuring correct phase sequence
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]

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Abstract

The invention discloses a power grid synchronization method, a system and a medium based on open loop, and the method comprises the following steps of calculating output frequency, phase and amplitude parameters required by inverter control: calculating two-phase input signals under a static coordinate system according to the three-phase input signals, calculating two-phase input signals under a two-phase rotating coordinate system, respectively obtaining filtered two-phase input signals through filtering, calculating input signals under the two-phase static coordinate system, carrying out amplitude normalization to obtain normalized two-phase input signals, calculating estimated input parameters, and calculating estimated output frequency parameters, output phase parameters and output amplitude parameters according to the estimated input parameters. The method has no stability problem, and does not need to set complex parameters; the dynamic response speed is high, and the transient state has no particularly large fluctuation; the realization is simple, and the calculation amount and the storage requirement are low; different pre-MAF filters can be designed to meet the requirements according to the grid environment.

Description

Open-loop-based power grid synchronization method, system and medium
Technical Field
The invention relates to a power grid synchronization technology, in particular to a power grid synchronization method, a power grid synchronization system and a power grid synchronization medium based on open loop.
Background
The grid synchronization technology is a necessary link for inverter control, and then with penetration of distributed power generation and improvement of nonlinear load, grid signals are subjected to different pollution, such as voltage amplitude drop, phase angle jump, frequency shift, harmonic waves, imbalance and the like. How to effectively deal with the adverse power grid environment plays an extremely important role in inverter control and power grid operation. The power grid synchronization technology can be mainly divided into closed-loop synchronization and open-loop synchronization.
The closed-loop synchronization technology is mainly represented by a three-phase-locked loop based on a synchronous rotating coordinate system and a generalized integrator frequency-locked loop based on a static coordinate system. They are essentially a complex coefficient band-pass IIR filter, or a fixed-gain kalman filter. They therefore face mainly two problems: on one hand, stability analysis and parameter design both need good compromise design, and parameter setting is mainly performed on the basis of a small signal model and an extended symmetric optimal rule of a linear time invariant system at present. However, such a design requires a highly accurate small-signal model, and the dynamic response speed of the design cannot be faster than two power frequency periods on the premise of considering a good stability margin. On the other hand, standard phase-locked loops and frequency-locked loops generally have poor disturbance rejection capability, and if high disturbance rejection capability is required, the bandwidth of the system needs to be designed to be low, so that the dynamic performance is sacrificed. To improve their disturbance rejection capabilities, the most common practice is to structurally pre-filter or add filters within the loop. Placing the filter in the loop is more popular because it causes the phase of the phase/frequency locked system to lag, resulting in reduced stability and dynamic performance. These filters mainly include generalized integrators (second and reduced order), sliding window filters MAF, delay signal cancellation operators DSC. The generalized integrator usually requires adaptively detected frequency information, thus increasing the complexity of the whole structure, making stability and parameter design more difficult. The sliding window filter MAF and the delay signal cancellation operator DSC are effective choices in three-phase systems due to their flexibility and high disturbance rejection capability, and their main disadvantages are that the disturbance rejection capability is weak when the memory requirement and frequency shift are relatively high. In general, both the pll/pflc and the prefilter must be analyzed for stability and parameter design in detail to achieve good compromise performance.
Unlike closed-loop synchronization techniques, open-loop synchronization techniques avoid the presence of feedback loops and the tuning of parameters, so they are completely free of stability problems and do not require parameter tuning. Considering that the calculation of a high-order matrix is introduced in the modeling containing the unbalanced and harmonic signals, the calculation load is larger, and therefore the unbalanced and harmonic components are less considered. The open-loop synchronization technology mainly establishes a parameter solving model by using a fundamental frequency signal, and simultaneously improves the disturbance suppression capability by using a pre-filter. In the prior art, documents propose open-loop synchronization of differentiators, which, despite the consideration of accurate differentiation-step compensation, are nevertheless complex to implement. In the prior art, frequency information reflected by a phase deviation caused by MAF is used for solving the frequency, but the signal used in the method has an unfiltered component, so that the disturbance suppression capability is poor. There are documents in the prior art that use the detuning/frequency shifting principle to calculate the frequency, however these approaches introduce additional frequency doubling components and therefore require additional filters to suppress them, thus limiting their flexibility. The literature uses the principle of discrete resonance to calculate the frequency, however this approach faces the problem of computational ill-conditioning, requiring additional logic to avoid it, but can cause the frequency estimate to oscillate. The prior art references utilize two-phase signals while applying the principle of discrete resonance to avoid the ill-conditioned problem, however this increases the complexity of the implementation. In general, although past open-loop synchronization techniques have improved variously, they still achieve complex and performance-compromised performance.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: aiming at the problems in the prior art, the invention provides a power grid synchronization method, a system and a medium based on open loop, and the method has no stability problem and does not need to set complex parameters; the dynamic response speed is high, and the transient state has no particularly large fluctuation; the realization is simple, and the calculation amount and the storage requirement are low; different pre-MAF filters can be designed to meet the requirements according to the grid environment.
In order to solve the technical problems, the invention adopts the technical scheme that:
an open-loop based grid synchronization method, comprising the following steps of calculating output frequency, phase and amplitude parameters required for inverter control:
1) from three-phase input signals va(k),vb(k),vc(k) Calculating two-phase input signal v under static coordinate systemα0(k),vβ0(k)；
2) According to twoPhase input signal vα0(k),vβ0(k) Calculating two-phase input signal v under two-phase rotating coordinate systemd(k),vq(k)；
3) From two-phase input signals vd(k),vq(k) Respectively filtering to obtain filtered two-phase input signals vd1(k),vq1(k)；
4) From two-phase input signals vd1(k),vq1(k) Calculating an input signal v in a two-phase stationary coordinate systemα1(k),vβ1(k)；
5) According to an input signal vα1(k),vβ1(k) Carrying out amplitude normalization to obtain a normalized two-phase input signal vα(k),vβ(k)；
6) From two-phase input signals vα(k),vβ(k) Calculating estimated input parameters
Figure BDA0002702546740000021
Based on estimated input parameters
Figure BDA0002702546740000022
Calculating an estimated output frequency parameter
Figure BDA0002702546740000023
From two-phase input signals vα(k),vβ(k) Estimated input parameters
Figure BDA0002702546740000024
Calculating an estimated output phase parameter
Figure BDA0002702546740000025
From two-phase input signals vα(k),vβ(k) Estimated input parameters
Figure BDA0002702546740000026
Calculating an estimated output amplitude parameter
Figure BDA0002702546740000027
Optionally, calculating the two-phase input signal v in the stationary coordinate system in step 1)α0(k),vβ0(k) The function expression of (a) is as follows:
Figure BDA0002702546740000028
in the above formula, va(k),vb(k),vc(k) Is a three-phase input signal.
Optionally, calculating a two-phase input signal v in the two-phase rotation coordinate system in step 2)d(k),vq(k) The function expression of (a) is shown as follows:
Figure BDA0002702546740000031
in the above formula, θNInstantaneous phase, theta, representing nominal frequencyN＝∫ωNdt, where ωNFor rated grid frequency, t is time, vα0(k),vβ0(k) Is a two-phase input signal in a stationary coordinate system.
Optionally, the filtering in step 3) specifically refers to filtering by a MAF filter, and the discrete expression of the transfer function of the MAF filter is shown as follows:
Figure BDA0002702546740000032
in the above formula, GMAF(z) denotes the transfer function, z denotes the operator of the z-transform, and N denotes the number of points of the fundamental period.
Optionally, calculating the input signal v in the two-phase stationary coordinate system in step 4)α1(k),vβ1(k) The function expression of (a) is as follows:
Figure BDA0002702546740000033
in the above formula, the first and second carbon atoms are,θNinstantaneous phase, theta, representing nominal frequencyN＝∫ωNdt, where ωNFor rated grid frequency, t is time, vd1(k),vq1(k) Is a filtered two-phase input signal.
Optionally, the amplitude normalization in step 5) is performed to obtain a normalized two-phase input signal vα(k),vβ(k) The function expression of (a) is as follows:
Figure BDA0002702546740000034
in the above formula, vα1(k),vβ1(k) Is an input signal in a two-phase stationary coordinate system.
Optionally, calculating estimated input parameters in step 6)
Figure BDA0002702546740000035
The function expression of (a) is as follows:
Figure BDA0002702546740000036
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000037
for estimated angular frequency, klNumber of points for signal delay, TsIs a sampling period, vα(k),vβ(k) For normalized two-phase input signals, vα(k-kl),vβ(k-kl) Is vα(k),vβ(k) After a delay of klA signal of a point number;
calculating an estimated output frequency parameter
Figure BDA0002702546740000038
The function expression of (a) is as follows:
Figure BDA0002702546740000039
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000041
for the estimated input parameters, fsTo sample frequency, klThe number of points of signal delay.
Optionally, calculating an estimated output phase parameter in step 6)
Figure BDA0002702546740000042
The function expression of (a) is shown as follows:
Figure BDA0002702546740000043
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000044
for the estimated phase, N is the number of sample points in the fundamental period, TsIn order to be the sampling period of time,
Figure BDA0002702546740000045
for estimated angular frequency, ωNIs the rated grid frequency;
calculating an estimated output amplitude parameter in step 6)
Figure BDA0002702546740000046
The function expression of (a) is as follows:
Figure BDA0002702546740000047
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000048
for the estimated amplitude, N is the number of sampling points in the fundamental frequency period, TsIn order to be the sampling period of time,
Figure BDA0002702546740000049
for estimated angular frequency, ωNIs the nominal grid frequency.
Furthermore, the present invention also provides an open-loop based grid synchronization system, comprising a computer device programmed or configured to perform the steps of the open-loop based grid synchronization method, or having a computer program programmed or configured to perform the open-loop based grid synchronization method stored on a memory of the computer device.
Furthermore, the present invention also provides a computer readable storage medium having stored thereon a computer program programmed or configured to perform the open loop based grid synchronization method.
Compared with the prior art, the invention has the following advantages: the method comprises the steps of calculating two-phase input signals under a static coordinate system according to three-phase input signals, calculating two-phase input signals under a two-phase rotating coordinate system, obtaining filtered two-phase input signals through filtering, calculating input signals under the two-phase static coordinate system, carrying out amplitude normalization to obtain normalized two-phase input signals, calculating estimated input parameters, and calculating estimated output frequency parameters, output phase parameters and output amplitude parameters according to the estimated input parameters. The method has no stability problem, and does not need to set complex parameters; the dynamic response speed is high, and the transient state has no particularly large fluctuation; the realization is simple, and the calculation amount and the storage requirement are low; different pre-MAF filters can be designed to meet the requirements according to the grid environment.
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FIG. 1 is a schematic diagram of a basic flow of a method according to an embodiment of the present invention.
FIG. 2 is a graph of the frequency waveforms estimated under test 1 for the method of the present invention and three comparative methods.
Fig. 3 is a graph of the phase deviation waveforms estimated under test 1 by the method of the embodiment of the present invention and three comparative methods thereof.
FIG. 4 is a waveform of the amplitude estimated under test 1 for the method of the embodiment of the present invention and three comparative methods thereof.
FIG. 5 is a graph of the frequency waveforms estimated under test 2 for the method of the present invention and three comparative methods.
Fig. 6 is a graph of the phase deviation waveforms estimated under test 2 for the method of the present invention and its three comparative methods.
FIG. 7 is a waveform of the amplitude estimated under test 2 for the method of the present embodiment and three comparative methods thereof.
FIG. 8 is a graph of the frequency waveforms evaluated under test 3 for the method of the present embodiment and three comparative methods thereof.
Fig. 9 is a graph of the phase deviation waveforms estimated under test 3 for the method of the embodiment of the present invention and three comparative methods thereof.
FIG. 10 is a graph of the amplitude waveform estimated under test 3 for the method of the present invention and three comparative methods.
FIG. 11 is a graph of the frequency waveforms estimated under test 4 for the method of the present invention and three comparative methods.
Fig. 12 is a graph of the phase deviation waveforms estimated under test 4 for the method of the embodiment of the present invention and three comparative methods thereof.
FIG. 13 is a waveform of the amplitude estimated at test 4 for the method of the embodiment of the present invention and three comparative methods thereof.
Detailed Description
As shown in fig. 1, the open-loop-based grid synchronization method of the present embodiment includes the following steps of calculating output frequency, phase and amplitude parameters required for inverter control:
1) from three-phase input signals va(k),vb(k),vc(k) Calculating two-phase input signal v under static coordinate systemα0(k),vβ0(k)；
2) From two-phase input signals vα0(k),vβ0(k) Calculating a two-phase input signal v under a two-phase rotating coordinate systemd(k),vq(k)；
3) From two-phase input signals vd(k),vq(k) Respectively filtering to obtain filtered two-phase input signals vd1(k),vq1(k)；
4) From two-phase input signals vd1(k),vq1(k) MeterCalculating an input signal v in a two-phase stationary coordinate systemα1(k),vβ1(k)；
5) According to the input signal vα1(k),vβ1(k) Carrying out amplitude normalization to obtain a normalized two-phase input signal vα(k),vβ(k)；
6) From two-phase input signals vα(k),vβ(k) Calculating estimated input parameters
Figure BDA0002702546740000051
Based on estimated input parameters
Figure BDA0002702546740000052
Calculating an estimated output frequency parameter
Figure BDA0002702546740000053
From two-phase input signals vα(k),vβ(k) Estimated input parameters
Figure BDA0002702546740000054
Calculating an estimated output phase parameter
Figure BDA0002702546740000055
From two-phase input signals vα(k),vβ(k) Estimated input parameters
Figure BDA0002702546740000056
Calculating an estimated output amplitude parameter
Figure BDA0002702546740000057
V of three-phase input signals of ideal three-phase systema(k),vb(k),vc(k) The discrete signal is shown as follows:
Figure BDA0002702546740000058
in the above formula, va(k),vb(k),vc(k) For a three-phase input signal, A represents the amplitude, ω represents the angular frequency, k represents the coefficient, TsWhich represents the period of the sampling,
Figure BDA0002702546740000059
indicating the phase.
In this embodiment, the two-phase input signal v in the stationary coordinate system is calculated in step 1)α0(k),vβ0(k) The function expression of (a) is as follows:
Figure BDA0002702546740000061
in the above formula, va(k),vb(k),vc(k) Is a three-phase input signal. The above formula is a function expression of Clark transformation, wherein the matrix of Clark is a transformation matrix, A represents amplitude, ω represents angular frequency, k represents coefficient, and T represents coefficientsWhich represents the period of the sampling,
Figure BDA0002702546740000062
indicating the phase. According to the characteristics of two-phase orthogonal signals, the following relationship can be derived to calculate the frequency parameter:
Figure BDA0002702546740000063
in the above formula, ω represents angular frequency, klNumber of points for signal delay, TsDenotes the sampling period, vα0(k),vβ0(k) Is a two-phase input signal in a stationary coordinate system, vα(k-kl),vβ(k-kl) Is v isα0(k),vβ0(k) Through klDelaying the signals of the points. It is noted that the above formula introduces the sum of squares of two-phase signals, and in order to simplify the implementation and reduce the sensitivity of the synchronization link to voltage drop, an amplitude normalization link is introduced, that is, the signal v after amplitude normalization is definedα(k),vβ(k) Are respectively shown as a formula (4);
Figure BDA0002702546740000064
in the above formula, vα1(k),vβ1(k) Is an input signal in a two-phase stationary coordinate system.
Meanwhile, the calculation of the frequency parameter can be further simplified:
Figure BDA0002702546740000065
the frequency parameter can be found by the above equation, and further the frequency:
Figure BDA0002702546740000066
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000067
for the estimated input parameters, fsTo sample the frequency, klThe number of points of signal delay.
Considering that equations (3), (6) require knowledge of specific klSo that further pairs of k are requiredlAnd (5) designing. First, it is easy to see if k islThe larger the value of (c), the longer the time for obtaining the frequency parameter, i.e. the slower the dynamic performance of the open-loop frequency calculation method. Thus it klThe smaller should be the better from the viewpoint of dynamic speed. However, if it is too small, it will be extremely sensitive to the disturbance component, which can be seen from the following analysis:
modeling harmonic components on the basis of original ideal three-phase voltage signals to obtain the following functional expression:
Figure BDA0002702546740000071
in the above formula, V1 +Is the amplitude of the fundamental frequency signal and,
Figure BDA0002702546740000072
is the initial phase of the fundamental signal, h is the number of negative sequence components and harmonics of the fundamental frequency, Vh ±,
Figure BDA0002702546740000073
The amplitude and the initial phase of the positive and negative sequence components of the order h are respectively, and Q is a set of h. For equation (7), the fundamental negative-sequence component and harmonics correspond primarily to h ═ 1, -5, +7, -11, +13, the set Q including the above components. And the signal satisfies the following equation:
Figure BDA0002702546740000074
in the above formula, a parameter k is introduced1And k2The remaining symbols are as defined above. Parameter k1And k2Defined as describing the impact factors on the negative sequence component and harmonics of the fundamental frequency. It can be seen that when k is1And k2The larger the influence of the negative sequence component of the fundamental frequency and the harmonics on the frequency calculation formula. And k is1And k2Mainly depending on klCan see klThe smaller, the k thereof1A small variation, and k2It becomes significantly larger. Thus can obtain klIt is not well suited to be so small that the frequency calculation formula is extremely sensitive to the disturbance component. Therefore to klThe value of (a) needs to be selected in a compromise, which is recommended to be one tenth of the rated sampling point number in the embodiment.
While the phase and amplitude can be calculated directly from:
Figure BDA0002702546740000075
Figure BDA0002702546740000076
however, the above calculation frequency is only considered in the case of three-phase ideal voltage, so when there is disturbance component in the actual grid voltage signal, it is necessary to introduce a pre-filter to improve the disturbance rejection capability, and herein, the MAF filter with low calculation load is introduced as the pre-filter to improve the disturbance rejection capability. It is noted that MAF is very flexible, it can design different delay lengths according to the characteristics of the actual grid signal, if the number of delay points is the number of sampling points N of a fundamental frequency cycle, it can effectively suppress direct current, unbalanced components and integer sub-harmonics. If N/2, imbalance and odd harmonics can be suppressed. If it is N/6, the harmonic can be effectively suppressed. If the cascade MAF suppression method is applied to weak grid and micro-grid environments, good suppression capability can be achieved by cascading MAF. Note that MAF is actually a recursive DFT filter, so to avoid rounding errors causing numerical stability problems of the filter, its delay length does not employ frequency adaptation, while also avoiding interpolation techniques. The filtering in step 3) in this embodiment specifically refers to filtering by a MAF filter (moving average filter, see the content of the upper dashed box in fig. 1), and the discrete expression of the transfer function of the MAF filter is shown as follows:
Figure BDA0002702546740000081
in the above formula, GMAF(z) denotes the transfer function, z denotes the operator of the z-transform, and N denotes the number of points of the fundamental frequency period. Referring to FIG. 1, the MAF filter input signal is vx(k) The output signal is vy(k) The output signal v can be obtained by the MAF filter by constructing each module in the content of the upper dotted line frame in FIG. 1 by using MATLAB/Simluniky(k)。
From the transfer function of the MAF filter, the functional expression of its amplitude and phase can be derived:
Figure BDA0002702546740000082
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000083
denotes the amplitude of the MAF filter, ω denotes the angular frequency, TsRepresenting the sampling period, and N is the number of sampling points in the fundamental frequency period.
Figure BDA0002702546740000084
In the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000085
denotes the phase of the MAF filter, ω denotes the angular frequency, TsRepresenting the sampling period, and N is the number of sampling points in the fundamental frequency period.
Since the non-adaptive MAF filter may cause the signal to have phase and amplitude offset when the frequency is shifted, in order to solve the above technical problem, the present embodiment adopts a method of adding a phase and amplitude compensator, as shown in the following formula:
Figure BDA0002702546740000086
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000087
for the estimated phase, N is the number of sample points in the fundamental period, TsIn order to be the sampling period of time,
Figure BDA0002702546740000088
for the estimated frequency, ωNIs the rated grid frequency; in this embodiment, the rated grid frequency ωN＝100πrad/s。
Figure BDA0002702546740000089
In the above formula, the first and second carbon atoms are,
Figure BDA00027025467400000810
for the estimated amplitude, N is the number of sampling points in the fundamental frequency period, TsIn order to be the sampling period of time,
Figure BDA00027025467400000811
for the estimated frequency, ωNIs the nominal grid frequency. In this embodiment, the estimated output phase parameter is calculated in step 6)
Figure BDA00027025467400000812
Is expressed as formula (14), in this embodiment, the estimated output amplitude parameter is calculated in step 6)
Figure BDA00027025467400000813
The functional expression of (b) is represented by the following formula (15).
In this embodiment, the two-phase input signal v under the two-phase rotation coordinate system is calculated in step 2)d(k),vq(k) The function expression of (a) is as follows:
Figure BDA0002702546740000091
in the above formula, θNInstantaneous phase, θ, representing frequencyN＝∫ωNdt, where ωNFor rated grid frequency, t is time, vα0(k),vβ0(k) Is a two-phase input signal in a stationary coordinate system.
In this embodiment, the input signal v in the two-phase stationary coordinate system is calculated in step 4)α1(k),vβ1(k) The function expression of (a) is shown as follows:
Figure BDA0002702546740000092
in the above formula, θNInstantaneous phase, θ, representing nominal frequencyN＝∫ωNdt, where ωNFor rated grid frequency, t is time, vd1(k),vq1(k) Is a filtered two-phase input signal.
In this embodiment, the amplitude normalization in step 5) is performed to obtain a normalized two-phase input signal vα(k),vβ(k) The function expression of (a) is as follows:
Figure BDA0002702546740000093
in the above formula, vα1(k),vβ1(k) Is an input signal in a two-phase stationary coordinate system. The above formula is substantially the same as formula (4), and the main difference is the signal v in formula (4)α0(k),vβ0(k) Subscript is converted into signal vα1(k),vβ1(k) To correspond to the signal subscripts shown in figure 1.
In this embodiment, the estimated input parameters are calculated in step 6)
Figure BDA0002702546740000094
The function expression of (a) is as follows:
Figure BDA0002702546740000095
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000096
for estimated angular frequency, klNumber of points for signal delay, TsIs the sampling period, vα(k),vβ(k) For normalized two-phase input signals, vα(k-kl),vβ(k-kl) Is vα(k),vβ(k) After a delay of klA signal of a point number; the above formula is substantially the same as formula (5), and its main difference is the signal v in formula (5)α0(k),vβ0(k) Subscript is converted into signal vα1(k),vβ1(k) To correspond to the signal subscripts shown in figure 1.
In this embodiment, the estimated output frequency parameter is calculated
Figure BDA0002702546740000097
The function expression of (a) is as follows:
Figure BDA0002702546740000098
in the above formula, the first and second carbon atoms are,
Figure BDA0002702546740000099
for the estimated input parameters, fsTo sample the frequency, klThe number of points of signal delay. The above equation is the same as the above equation (6), and is only the estimated output frequency parameter
Figure BDA00027025467400000910
The sign form of (a) is changed.
In order to verify the effectiveness of the open-loop-based grid synchronization method of the present embodiment, the open-loop synchronization technology OLS1 based on a differentiator, the open-loop synchronization technology OLS2 based on MAF deviation, and the three-phase SRF-PLL (PMAF-PLL) based on MAF are compared in the present embodiment. To ensure a fair comparison, the MAF filters in the present embodiment, the PMAF-PLL and the OLS2 all use a window length of 1 nominal period, and the delay signal cancellation operator in the OLS1 uses filters cascaded with α β DSC2, α β DSC4, α β DSC8, α β DSC16 and α β DSC 32. Namely, the delay lengths of the four methods are all ensured to be about 1 period, and table 1 shows the parameter selection of the method of the embodiment of the present invention and the three comparison methods thereof, and the sampling frequency is 12 kHz.
Table 1: the method of the embodiment of the invention and a parameter table of three comparison methods thereof.
Figure BDA0002702546740000101
Tests 1 to 4 times were carried out below.
Test 1: and (4) phase jump, wherein the phase angle jumps by +30 degrees when the three-phase voltage is 0.5 s.
Fig. 2 to 4 show waveforms of frequency, phase deviation and amplitude estimated under test 1 by the method of the embodiment of the present invention and three comparative methods thereof, respectively. It can be seen that the four structures can track the phase angle jump of the upper three-phase voltage without error, but the method and the OLS2 have the fastest dynamic response speed, and the OLS2 has smoother transient state during phase adjustment, which is mainly due to the compensator. They take about 20ms to reach steady state, while the PMAF-PLL takes about 40ms, while the OLS1 has large transient fluctuations in frequency, amplitude and phase.
And (3) testing 2: the amplitude is asymmetrically dropped, and the amplitude of the A phase voltage drops by 90% when the time t is 0.5 s.
Fig. 5-7 show waveforms of frequency, phase deviation and amplitude, respectively, estimated under test 2 for the method of the present invention and three comparative methods thereof. It can be seen that the OLS1, the PMAF-PLL and the method of the present invention can track the voltage drop of the single-phase voltage without error, i.e. effectively suppress the three-phase imbalance. While the OLS2 cannot suppress the unbalanced component, so there is a large steady-state error in the detected frequency, phase and amplitude. In addition, the time for the method to reach the steady state is only about 20ms, while the PMAF-PLL needs about 40 ms. Although the OLS1 also has a fast dynamic response speed, its transient process has large frequency, amplitude and phase fluctuations.
And (3) testing: and (3) frequency deviation, wherein the frequency of the three-phase voltage jumps to +2Hz when the time t is 0.5 s.
Fig. 8 to 10 are waveform diagrams of the frequency, phase deviation and amplitude values estimated under test 3 by the method of the embodiment of the present invention and three comparative methods thereof, respectively. It can be seen that the four methods can track the frequency jump of the upper single-phase voltage, however, in terms of frequency, the method and the PMAF-PLL provided by the invention achieve high error precision, and the steady-state error is almost 0. While OLS1 has a steady state error of 0.0001Hz due to the approximation of the differential, OLS2 has a steady state error of 0.015Hz due to the approximation of MAF. From the dynamic response of frequency, phase and amplitude, the method of the present invention still has a fast adjustment time of 20ms, and although the OLS2 has a good advantage in phase detection, it still has a steady-state error problem, which is about 0.02 deg. However, the amplitude detection of the four structures has certain errors, which are mainly caused by the approximate operation of the amplitude compensator of the MAF.
And (4) testing: the three-phase voltage is mixed with harmonic and direct current components at time t of 0.5s, and the specific magnitudes of-5, +7, -11, +13 and direct current components are 0.06, 0.05, 0.035, 0.03, 0.05, respectively.
Fig. 11-13 show waveforms of frequency, phase deviation and amplitude, respectively, estimated under test 4 for the method of the present invention and three comparative methods thereof. It can be seen that the method and the PMAF-PLL, OLS1 of the present invention are both effective in suppressing harmonic and dc components, whereas OLS2 shows poor accuracy. In terms of dynamic performance, the method provided by the present invention still can maintain a fast adjustment time of 20ms, and meanwhile, large transient fluctuations do not occur, while the OLS1 has a serious impact on its transient due to the introduction of differential operation by its structure.
After comparing their performance, the computational burden and storage requirements of the inventive method and its three comparative methods are also statistically shown in table 2.
Table 2: the method of the embodiment of the invention and the comparison of the calculated loss of the three comparison methods are disclosed.
+/- × ÷ Cutting method Reverse triangle Triangular shape Storage requirements
The method of the present invention 14 20 2 1 2 0 6T/(5Ts)
PMAF-PLL 18 23 2 0 2 4 T/Ts
OLS1
20 26 3 1 1 3 31T/(32Ts)+T/(2Ts)
OLS2 16 22 2 1 1 0 T/Ts
It can be seen that the method proposed by the present invention has extremely low computational burden and memory requirement, and especially the avoidance of differentiator makes the proposed method have significant advantages in implementation and performance over OLS 1.
In summary, the present embodiment provides a simple and fast three-phase open-loop power grid synchronization technique, which utilizes a discrete time domain expression of two-phase orthogonal signals to deduce the calculation of frequency parameters, instead of utilizing a traditional differentiator to calculate frequency, and utilizes a pre-adaptive sliding average filter to improve the disturbance rejection capability of the three-phase open-loop power grid synchronization technique. The present embodiment avoids the consideration of differentiation by modeling from discrete representations of signals, rather than modeling continuous signals, and proposes a new open-loop synchronization technique that has simpler implementation and ensures fast dynamic performance. Meanwhile, in order to improve the disturbance suppression capability, a simple and flexible pre-filter is designed. The method of the embodiment has the following advantages: (1) and no stability problem exists, and complicated parameters do not need to be set. (2) The dynamic response speed is high, and the transient state does not fluctuate particularly greatly. (2) The method is simple to implement and low in calculation amount and storage requirements. (3) Different pre-MAF filters can be designed to meet the requirements according to the grid environment.
Furthermore, the present invention also provides an open-loop based grid synchronization system, comprising a computer device programmed or configured to perform the steps of the open-loop based grid synchronization method, or having a computer program programmed or configured to perform the open-loop based grid synchronization method stored on a memory of the computer device.
Furthermore, the present invention also provides a computer readable storage medium having stored thereon a computer program programmed or configured to perform the open loop based grid synchronization method.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The present application is directed to methods, apparatus (systems), and computer program products according to embodiments of the application wherein instructions, which execute via a flowchart and/or a processor of the computer program product, create means for implementing functions specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims (9)

1. An open-loop-based grid synchronization method is characterized by comprising the following steps of calculating output frequency, phase and amplitude parameters required by inverter control:
1) from three-phase input signals va(k)、vb(k)、vc(k) Calculating two-phase input signal v under static coordinate systemα0(k)、vβ0(k)；
2) From two-phase input signals vα0(k)、vβ0(k) Calculating a two-phase input signal v under a two-phase rotating coordinate systemd(k)、vq(k)；
3) From two-phase input signals vd(k)、vq(k) Respectively obtaining two-phase input signals v after filteringd1(k)、vq1(k)；
4) From two-phase input signals vd1(k)、vq1(k) Calculating an input signal v in a two-phase stationary coordinate systemα1(k)、vβ1(k)；
5) According to an input signal vα1(k)、vβ1(k) Carrying out amplitude normalization to obtain a normalized two-phase input signal vα(k)、vβ(k)；
6) From two-phase input signals vα(k)、vβ(k) Calculating estimated input parameters
Figure FDA0003573408720000011
Based on estimated input parameters
Figure FDA0003573408720000012
Calculating an estimated output frequency parameter
Figure FDA0003573408720000013
From two-phase input signals vα(k) And vβ(k) Estimated input parameters
Figure FDA0003573408720000014
Calculating an estimated output phase parameter
Figure FDA0003573408720000015
From two-phase input signals vα(k) And vβ(k) Estimated input parameters
Figure FDA0003573408720000016
Calculating an estimated output amplitude parameter
Figure FDA0003573408720000017
Wherein estimated input parameters are calculated
Figure FDA0003573408720000018
The function expression of (a) is as follows:
Figure FDA0003573408720000019
in the above formula, the first and second carbon atoms are,
Figure FDA00035734087200000110
for estimated angular frequency, klNumber of points for signal delay, TsIs a sampling period, vα(k)、vβ(k) For normalized two-phase input signals, vα(k-kl)、vβ(k-kl) Is vα(k)、vβ(k) After a delay of klCounting the number of signals; calculating an estimated output frequency parameter
Figure FDA00035734087200000111
The function expression of (a) is as follows:
Figure FDA00035734087200000112
in the above formula, the first and second carbon atoms are,
Figure FDA00035734087200000113
for the estimated input parameters, fsTo sample the frequency, klThe number of points of signal delay.
2. An open-loop-based grid synchronization method according to claim 1, wherein the two-phase input signal v in the stationary coordinate system is calculated in step 1)α0(k)、vβ0(k) The function expression of (a) is as follows:
Figure FDA00035734087200000114
in the above formula, va(k),vb(k),vc(k) Is a three-phase input signal.
3. Open-loop-based grid synchronization method according to claim 1, wherein the two-phase input signal v in the two-phase rotating coordinate system is calculated in step 2)d(k)、vq(k) The function expression of (a) is shown as follows:
Figure FDA00035734087200000115
in the above formula, θNInstantaneous phase, theta, representing nominal grid frequencyN＝∫ωNdt, where ωNFor rated grid frequency, t is time, vα0(k),vβ0(k) The two-phase input signal is in a static coordinate system.
4. An open-loop-based grid synchronization method as claimed in claim 1, wherein the filtering in step 3) is specifically performed by a MAF filter, and the discrete expression of the transfer function of the MAF filter is as follows:
Figure FDA0003573408720000021
in the above formula, GMAF(Z) denotes a transfer function, Z denotes a Z transform operator, and N denotes the total number of sample points for one fundamental period.
5. Open-loop-based grid synchronization method according to claim 1, characterized in that the input signal v in the two-phase stationary coordinate system is calculated in step 4)α1(k)、vβ1(k) The function expression of (a) is as follows:
Figure FDA0003573408720000022
in the above formula, θNInstantaneous phase, θ, representing nominal grid frequencyN＝∫ωNdt, where ωNFor rated grid frequency, t is time, vd1(k)、vq1(k) Is a filtered two-phase input signal.
6. An open-loop-based grid synchronization method according to claim 1, characterized in that the amplitude normalization in step 5) results in a normalized two-phase input signal vα(k),vβ(k) The function expression of (a) is as follows:
Figure FDA0003573408720000023
in the above formula, vα1(k)、vβ1(k) Is an input signal in a two-phase stationary coordinate system.
7. Open loop based grid synchronization method according to claim 1, characterized in that the estimated output phase parameter is calculated in step 6)
Figure FDA0003573408720000024
The function expression of (a) is as follows:
Figure FDA0003573408720000025
in the above-mentioned formula, the compound has the following structure,
Figure FDA0003573408720000026
for the estimated phase, N is the number of sampling points of the fundamental frequency period, TsIn order to be the sampling period of time,
Figure FDA0003573408720000027
for estimated angular frequency, ωNIs the rated grid frequency;
calculating an estimated output amplitude parameter in step 6)
Figure FDA0003573408720000028
The function expression of (a) is as follows:
Figure FDA0003573408720000029
in the above-mentioned formula, the compound has the following structure,
Figure FDA00035734087200000210
for the estimated amplitude, N is the number of sampling points in the fundamental frequency period, TsIs a time period of the sampling, and,
Figure FDA00035734087200000211
for estimated angular frequency, ωNIs the nominal grid frequency.
8. An open-loop based grid synchronization system comprising a computer device, characterized in that the computer device is programmed or configured to perform the steps of the open-loop based grid synchronization method according to any of claims 1 to 7, or that the computer device has stored on its memory a computer program programmed or configured to perform the open-loop based grid synchronization method according to any of claims 1 to 7.
9. A computer readable storage medium having stored thereon a computer program programmed or configured to perform the open loop based grid synchronization method according to any of claims 1-7.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN2882076Y (en) * 2006-02-24 2007-03-21 清华大学 Static sync compensator based on crystal brake tube
CN103036462A (en) * 2012-11-26 2013-04-10 天津大学 Model prediction control method of voltage source type rectifier when network voltage is unbalanced

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2425496C (en) * 2002-04-04 2012-06-05 Chunlin Li Fast phase synchronization and retrieval of sequence components in three-phase networks
CN101964527B (en) * 2009-07-22 2012-08-22 河南森源电气股份有限公司 Non-balanced type active filtering compensation method for voltage on power grid side
CN107831365A (en) * 2017-07-03 2018-03-23 中国农业大学 A kind of open loop synchronous method based on moving average filter to power network phase-angle detection
CN110011312B (en) * 2019-05-27 2020-11-10 河北交通职业技术学院 Frequency self-adaptive phase-locked loop modeling method based on internal model
CN110289852B (en) * 2019-07-12 2021-04-23 中南大学 Three-phase frequency locking ring based on L-M algorithm and implementation method thereof

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN2882076Y (en) * 2006-02-24 2007-03-21 清华大学 Static sync compensator based on crystal brake tube
CN103036462A (en) * 2012-11-26 2013-04-10 天津大学 Model prediction control method of voltage source type rectifier when network voltage is unbalanced

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