CN103116059B - Voltage fast detection algorithm suitable for grid power system low voltage ride through function - Google Patents
Voltage fast detection algorithm suitable for grid power system low voltage ride through function Download PDFInfo
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Abstract
The invention discloses a voltage fast detection algorithm suitable for a grid power system low voltage ride through function. The voltage fast detection algorithm suitable for the grid power system low voltage ride through function comprises the following steps: (1) acquiring amplitude value information under the normal operation of a power grid based on a phase-locked loop of a synchronous reference coordinate frame, (2) separating the voltage of a sampled power grid into three-phase of A, B, C, conducting a period of delay to the sampled power grid, and acquiring the absolute value of an difference value, (3) setting a voltage threshold value and comparing the difference value in the step (2) with the voltage threshold value, (4) if the difference value is smaller than the voltage threshold value, then judging that the voltage is normal, if the difference value is larger than the voltage threshold value, then turning to step (5), (5) sending real-time voltage signals into a maximumvalue tracking module and an over zero point tracking module through each of the phrases of voltage, after judging that the system enters into a low voltage status, and (6) recording the maximum value tracking module and the over zero point tracking module to acquire an amplitude value after the voltage of the power gird drops.
Description
Technical field
The present invention relates to a kind of voltage fast detection algorithm that the new energy grid-connected power system low-voltage passes through function that is applicable to, particularly for the voltage fast detection algorithm that is applicable to the grid-connected system low voltage ride-through function of the low voltage ride-through capability that improves generation of electricity by new energy.
Background technology
Low voltage crossing (LVRT) refers to be incorporated into the power networks when point voltage falls at aerogenerator the earliest, and blower fan can keep being incorporated into the power networks, even provide certain reactive power to electrical network, support power system restoration, until power system restoration is normal, thus " passing through " this low-voltage time (zone).And along with the fast development of generation of electricity by new energy technology, especially photovoltaic power generation technology develops rapidly, so that the generations of electricity by new energy such as photovoltaic generation also will improve the low voltage ride-through capability of self, namely the concept of low voltage crossing also has been applied to the generation of electricity by new energy fields such as photovoltaic plant.Low voltage crossing is that the generation of electricity by new energy equipment that is incorporated into the power networks is still kept a kind of specific operation function requirement of being incorporated into the power networks when electrical network voltage occurs and falls.The low voltage crossing that country variant (and area) proposes requires to be not quite similar.At present in the prevailing country of some generations of electricity by new energy, in succession formulated new operation of power networks criterion such as Denmark, Germany etc., provided quantitatively the off-grid condition of grid-connected power generation system (falling the degree of depth and dip duration such as minimum voltage), only have when line voltage falls and be lower than the regulation curve and just allow later on generation of electricity by new energy equipment off-grid, when voltage during at sunk part, generator should provide reactive power.
Improve the low voltage ride-through capability of various grid-connected power generation system, being exactly of at first will doing detected fast and accurately to the line voltage of system outlet side, and then to draw be that the three-phase voltage symmetry is fallen, or three-phase voltage is asymmetric to be fallen, if asymmetricly fall which phase also will tell what fall be, also to detect at last voltage and fall the degree of depth and dip duration.Traditional low-voltage detection method is to use phaselocked loop to detect falling of voltage.When drawing phase angle information, draw in the lump d-axis (d axle) component of line voltage based on the phaselocked loop of reference synchronization coordinate system, can draw the information of corresponding amplitude according to direct-axis component.Based on the schematic diagram of the phaselocked loop of reference synchronization coordinate system as shown in Figure 1.
PHASE-LOCKED LOOP PLL TECHNIQUE based on the reference synchronization coordinate system can be carried out in real time the amplitude information of line voltage under the electrical network normal operation, is extracted accurately and detects.And various faults appear especially during unbalanced fault (such as single-phase wire break, single-phase short circuit, line to line fault) when electrical network, line voltage three-phase voltage amplitude imbalance can occur and fall, meanwhile fall phase voltage and may also can follow the sudden change of phase angle, the above-mentioned amplitude detection method this moment effective amplitude of change detected.
For above problem, there have been some researchists to propose several solutions in the world wide, these methods mainly realize the fast detecting of low-voltage around the function of improved PLL.Below enumerate two kinds of more typical low-voltage detection modes.
The paper first method, as shown in Figure 2, the method is a kind of improved single-phase phase-locked loop, this phaselocked loop utilizes single-phase (A or B or the C phase) voltage in the three-phase voltage to construct two-phase (α β) voltage, after passing through again α β/dq conversion, utilize its quadratic sum to try to achieve the single-phase voltage amplitude, after meanwhile the q shaft voltage after the conversion being carried out the PI adjusting, compare with standard frequency again, draw the phase angle information of this phase, with its 1/4th cycles of phase shift, and draw the fundametal compoment of this phase voltage after multiplying each other with the amplitude that obtains, the fundametal compoment of trying to achieve can be used for constructing two phase voltages, and whole system consists of closed loop.
Secondly, it is second method, as shown in Figure 3, the method has proposed that on the basis based on the phaselocked loop of reference synchronization coordinate system three-phase voltage is carried out respectively the positive-negative sequence Park Transformation, and (d is direct-axis component, q is quadrature axis component) after, d axle and q axle component and the phase angle of the positive-negative sequence that obtains being mutually related.Meanwhile, d axle and the q axle component of positive-negative sequence are carried out mutual decoupling zero according to correlation formula, can obtain accurately d axle and the q axle component of positive-negative sequence, and then can draw amplitude and the phase angle information of three-phase positive sequence and negative sequence voltage, thus analyze three-phase voltage fall the degree of depth and drop-out time.
Improve one's methods in the advantage that detects low-voltage with not enough for two kinds that below analyze based on the phaselocked loop of reference synchronization coordinate system.First method is with single-phase two-phase (α β) voltage that constructs, and draws amplitude and phase angle information after passing through α β/dq again, finally can draw single-phase fundametal compoment.The research core of these class methods is single-phase phase-locked, and its advantage is to detect the amplitude information of single-phase voltage or phase-splitting detection three-phase voltage, can detect the phase angle sudden change of three-phase voltage simultaneously.But the shortcoming of this detection method is when the detection three-phase voltage falls, and needs three cover monophase systems, and module number wherein is a lot, and the resource that takies also increases thereupon.In addition, the method is on detection time, because added time delay module and low-pass filtering module, detection time at least will be more than 10ms, this difficult requirement of satisfying new low voltage crossing.Because low voltage crossing is not only to detect the degree of depth and the time that voltage falls to the new demand of grid-connected power generation system, also to carry out reactive power support to network system, so the time that detection voltage falls is short as far as possible.Second method is divided into positive-negative sequence with three-phase voltage, can clearly find out time and type that the imbalance of three-phase voltage fault continues.Simultaneously, utilize the positive-negative sequence voltage decoupling, can isolate positive sequence voltage, to finish phase-locked and to observe the positive sequence voltage amplitude.The negative sequence component that also needs to use separation in some control method is controlled accordingly.But the method need to align negative sequence voltage simultaneously carries out conversion and decoupling zero, the method that realizes is more loaded down with trivial details, and can't determine three-phase voltage amplitude and phase angle separately, also just can't measure accurately the drop information of phase voltage amplitude, and then can't carry out accurately reactive-load compensation.In addition, be subjected to its detection time the impact of coordinate transform and low-pass filter larger, so detection time is also longer.In sum, if at present three-phase voltage low-voltage detection Main Problems is to use three-phase phase-locked loop can't detect accurately three-phase voltage amplitude and phase angle separately, detection is subjected to the impact of Voltage unbalance larger, if the phaselocked loop quantity of using single-phase phase-locked loop then to need is three, the module that comprises like this rolls up, and realizes that difficulty is larger.In addition, the detection time of various existing detection methods is all partially long.
Summary of the invention
Purpose of the present invention overcomes the above problems exactly, the present invention proposes the voltage fast detection algorithm that is applicable to the grid-connected system low voltage ride-through function.
For realizing above purpose, the present invention adopts following technical scheme:
Be applicable to the voltage fast detection algorithm of grid-connected system low voltage ride-through function, may further comprise the steps:
Amplitude information when (1) obtaining electrical network and normally move based on the phaselocked loop of reference synchronization coordinate system;
(2) line voltage of sampling is pressed A, B, C three phase separation, the voltage of sampling is carried out the time-delay in a cycle in each of separating in mutually, then with each phase voltage and corresponding phase (the corresponding A phase of A, the corresponding B phase of B, the corresponding C phase of C) original signal (non-time delayed signal) subtracts each other, after obtaining difference, difference is asked absolute value;
(3) set a voltage threshold value, the difference of comparison step (2) and the size of voltage threshold value;
(4) if difference less than the voltage threshold value, then normal, think that system is in normal operating condition, continue to keep sampling and detect; If difference is more than or equal to the voltage threshold value, illustrative system may enter into low-voltage state, then forwards step (5) to;
(5) after the judgement system enters low-voltage state, and respectively every mutually real-time voltage signal is sent to maximal value tracing module and zero crossing tracing module simultaneously, two modules are processed real-time voltage signal simultaneously;
(6) record maximal value tracing module and zero crossing tracing module finally all can obtain the amplitude after line voltage falls, utilize the very fast voltage that obtains to fall voltage magnitude under the electrical network normal operation of rear amplitude and phaselocked loop acquisition, obtain to fall the degree of depth and drop-out time.
In the described step (2), by the mode in the cycle of delaying time, obtained line voltage before one cycle, i.e. the magnitude of voltage information of the corresponding point under the line voltage normal operation before the 0.02s, and then make comparisons with the voltage that current sampling obtains, judging fast whether voltage exists falls.
The processing procedure of described maximal value tracing module is: after the judgement system may enter low-voltage state, sampling apparatus is sent real-time voltage signal into the maximal value tracing module, and then the derivative value of the voltage signal when realistic, when derivative value is zero, then line voltage is crossed maximum of points, when recording the value of this point and it being remained to next time voltage jump.
It is worth mentioning that, because derivative value is just point of zero, if sample frequency is lower, then can't capture this point, in this case, derivative can be equalled zero be revised as derivative value absolute value less than a very little numerical value, can more be conducive to catch maximum of points like this.
The processing procedure of described zero crossing tracing module is, after the judgement system enters low-voltage state, real-time voltage signal is sent into the zero crossing tracing module, while triggering timing module, the beginning timing, when mains voltage signal equals zero, stop timing, utilize time that timing obtains and the information calculations triggering timing line voltage value constantly of current zero crossing, and then utilize count time and line voltage cycle (think that the line voltage frequency is 50 hertz, cycle is 0.02 second) try to achieve triggering timing line voltage unit amplitude sine value constantly, utilize at last the line voltage amplitude after triggering timing line voltage value constantly and unit amplitude sine value are tried to achieve sudden change, and then the calculating line voltage falls the degree of depth.
Equally, because the line voltage value is just point of zero, if sample frequency is lower, then can't capture this point, in this case, can be zero to be revised as its absolute value less than a very little numerical value with the line voltage value, can catch more easily zero crossing like this.
The described detailed process of step (6) is as follows:
(6-1) ask line voltage to fall a little phase angle, i.e. T
Eg/ T=ω t
e+ θ, ω are electrical network angular frequency and ω=50Hz, t
eRefer to the moment of falling a little, θ is initial phase angle, and T is line voltage cycle and T=0.02s, T
EgThe time that obtains for timing;
(6-2) phase angle of step (1) is asked sine value:
That is: sin (ω t
e+ θ);
(6-3) the zero crossing tracing module is sampled to real-time voltage, obtains timing finish time, namely from the voltage signal values U that falls a little nearest zero crossing
g, with this voltage signal values U
g=Asin (ω t+ θ), wherein A is voltage magnitude, t represents time variable, in addition known T
Eg, can in the hope of:
Asin (ω t
e+ θ)=U
e=Asin (ω (t-T
Eg)+θ), U
eFor falling point voltage, Asin (ω (t-T
Eg)+θ) can be tried to achieve by two jiaos of trigonometric function and formula, namely
Asin(ω（t－T
eg）+θ)＝Asin(ωt+θ)cos（ωT
eg）－Acos(ωt+θ)sin（ωT
eg）
Asin (ω t+ θ), ω, T
EgKnown, Acos (ω t+ θ) can be obtained by Asin (ω t+ θ) differentiate, to sum up Asin (ω+θ)
e, sin (ω+θ)
eAll known, can try to achieve voltage magnitude;
Voltage magnitude under the electrical network normal operation of (6-4) having determined in conjunction with phaselocked loop, the real-time grid information of voltage that recycling obtains after falling deducts the voltage magnitude under the electrical network normal operation, can try to achieve voltage and fall the degree of depth and time.
Maximal value tracing module and zero crossing tracing module finally all can obtain the amplitude after line voltage falls in the step (6), but because line voltage fall the diverse location that a little may be in the voltage sine wave (namely falling phase angle difference a little), so the voltage after falling may pass through first maximum point or pass through first zero crossing on its sinusoidal running orbit, so the maximal value tracing module is different from the amplitude required time after zero crossing tracing module calculating voltage falls, utilize the voltage magnitude under the electrical network normal operation of phaselocked loop acquisition in voltage magnitude and the step (1) behind the falling of comparatively fast calculating relatively can obtain to fall the degree of depth and drop-out time.
Beneficial effect of the present invention:
The present invention at first uses a kind of fairly simple three-phase voltage amplitude of three-phase phase-locked loop acquisition under the electrical network normal operation, design in addition a kind of voltage and fallen judgement and detection method, the party's ratio juris is when three phase network voltage is sampled, it is carried out a cycle (mains frequency 50Hz, one cycle 0.02s) time-delay, and then in sampling computation delay signal and original signal poor, if this difference is greater than the value of certain restriction, just think that line voltage may enter low-voltage state, follow the trail of maximal value or the zero crossing of line voltage.On this basis, according to the three-phase voltage amplitude under the electrical network normal operation that has obtained and corresponding computing formula, draw the drop-out time of line voltage and fall the degree of depth, and then according to drop-out time with fall the degree of depth and judge whether to enter low-voltage state, then carry out corresponding reactive-load compensation if enter, thereby improve the low voltage ride-through capability of grid-connected power generation system.Make advantage in this way be only to use a three-phase phase-locked loop, module number is few, realizes comparatively simply, simultaneously maximal value or zero crossing must occur in 1/4th cycles of 5ms(detection time) within, it is good to detect real-time.Compare with traditional low-voltage detection method, this detection method has shortening by a relatively large margin detection time, and only have 1/4th of the line voltage cycle the longest detection time, i.e. 5ms.Simultaneously, amplitude and phase angle that the method can divide three-phase to detect respectively every phase voltage have avoided voltage to fall rear Voltage unbalance to the impact of voltage detecting.
Description of drawings
Fig. 1 is the phaselocked loop based on synchronous coordinate system;
Fig. 2 is a kind of improved single-phase phase-locked loop;
Fig. 3 is a kind of phaselocked loop of positive-negative sequence decoupling zero;
Fig. 4 is low-voltage fast detecting process flow diagram;
Fig. 5 is the waveform synoptic diagram that is applicable to the voltage fast detection algorithm of grid-connected system low voltage ride-through function.
Embodiment
The below further sets forth the technical scheme that adopts with reference to the accompanying drawings.
1. at first adopt based on the amplitude information under the normal operation of phaselocked loop acquisition electrical network of reference synchronization coordinate system.Employing is that it is simple in structure, principle is clear, it is few to take resource based on the reason of the phaselocked loop of reference synchronization coordinate system, and under the electrical network normal operation, can detect rapidly and accurately the amplitude of three-phase voltage, for low-voltage state afterwards is provided by the information that provides.Based on the phaselocked loop of reference synchronization coordinate system as shown in Figure 1.
As shown in Figure 1, be the phaselocked loop based on synchronous coordinate system, its principle of work is, with three phase network voltage carry out successively abc/ α β (being that the three phase static coordinate system turns two perpendicular rest frames), α β/dq(two perpendicular rest frames turn the two-phase rotating coordinate system) conversion, the quadrature axis component of the Uq(two-phase rotating coordinate system that obtains).Under the electrical network normal operation, the Uq theoretical value is zero, so after Uq and zero balancing, the direction (large or little) that the positive and negative Uq of obtaining by numerical value should regulate is regulated through the PI controller, and then after comparing with standard electrical network angular frequency, be derived as and reach the direction that standard angle frequency actual angular frequency should be regulated, finally reach Uq and equal zero, angular frequency is the effect of standard electrical network angular frequency.Afterwards, the angular frequency that obtains is carried out the phase angle that integral operation draws electrical network.At last the phase angle of trying to achieve being used for α β/dq calculates.In addition, the direct-axis component of the Ud(two-phase rotating coordinate system that obtains of phaselocked loop) can characterize the amplitude information of line voltage.
2. the line voltage of sampling is pressed A, B, C three phase separation, the voltage of sampling is carried out the time-delay in a cycle in each of separating in mutually and (think that mains frequency is 50 hertz, namely delayed time 0.02 second), then take absolute value after subtracting each other with original signal, namely obtain the difference of current demand signal and a cycle front signal.Because delay time is one-period, so if there is not variation in line voltage, then tries to achieve corresponding difference and should be zero in theory.If there is voltage situation about falling, then this difference should be that the voltage of corresponding point falls value in the power frequency period in theory, this value of falling not necessarily peak value is fallen value, namely can not fall the degree of depth with this value of falling representative, but this value of falling can be used as the judgement signal that voltage falls, start computing module cited below, determine finally whether electrical network enters low-voltage state.But consider that can there be small size fluctuation in line voltage, can set a threshold value, in case the malfunction of locking system.
As shown in Figure 4, be low-voltage fast detecting process flow diagram.At first, phase voltage is carried out the time-delay in 0.02 second cycle after, with original signal do poor, ask absolute value.Then making comparisons to determine whether to start low-voltage with the threshold value of setting calculates.If start, then the real-time voltage value sent into maximum of points and zero crossing tracing module.
The maximum of points trace mode is for to differentiate to real-time grid voltage, when derivative value is zero, records current line voltage value (absolute value), and it is kept, until when this voltage changes next time, when namely the absolute value of maximum of points changes next time.
The zero crossing trace mode is for after calculating startup when low-voltage, the triggering timing module begins timing simultaneously, when the value of real-time grid voltage is zero, stops timing, obtain timing time, utilize this time and line voltage cycle 0.02 second can try to achieve triggering timing phase angle constantly.Simultaneously, can also utilize the line voltage sampled value of this timing time and current time, mode (calculating with two jiaos of trigonometric functions and formula) by phase shift is tried to achieve triggering timing magnitude of voltage constantly, comprehensively should be worth and angle values, can obtain the amplitude of line voltage.Equally, and it is kept, until when this voltage changes next time.
Maximal value tracing module and zero crossing tracing module finally all can obtain the amplitude after line voltage falls, but because line voltage fall the diverse location that a little may be in the voltage sinusoidal trajectory (namely falling phase angle difference a little), so the voltage after falling may pass through first maximum point or pass through first zero crossing on sine wave, so the maximal value tracing module is different from the voltage magnitude required time that the zero crossing tracing module calculates after falling, with comparatively fast obtain fall after the electrical network normal operation of voltage magnitude and phaselocked loop acquisition under voltage magnitude relatively can obtain to fall the degree of depth and drop-out time.
The direct-axis component of the Ud(two-phase rotating coordinate system that phaselocked loop partly obtains) after computing module starts, remains unchanged, namely keep the voltage magnitude under the electrical network normal operation.It is worth mentioning that, be in what phase angle when no matter line voltage falls, must cross maximum of points or zero crossing within 1/4th cycles, to fall long delay be 5ms so this mode detects voltage.
This is applicable to the waveform synoptic diagram of the voltage fast detection algorithm of grid-connected system low voltage ride-through function accompanying drawing 5, with the method for tracing of this figure labor maximum of points and zero crossing.
3. the tracking of maximum of points.If it is the moment shown in the A point in the accompanying drawing 5 constantly that line voltage falls, then according to above analysis, the voltage magnitude after can obtaining faster to fall to the tracking of maximum of points.At this moment, real-time grid voltage is in the A point, and the line voltage that postpones is in the corresponding point before a cycle, i.e. B point accordingly.Because the absolute value of the signal difference that A, B are 2 is greater than threshold value, so start low voltage detecting module.The maximum of points tracing module is sampled to real-time voltage, real-time voltage signal after the sampling was differentiated to the time, when derivative equals zero, the value of record sampled point, can try to achieve the voltage magnitude after falling, voltage magnitude under the electrical network normal operation of having determined in conjunction with phaselocked loop can be tried to achieve voltage and be fallen the degree of depth and time.
4. zero crossing is followed the trail of.If it is the moment shown in the E point in the accompanying drawing 5 constantly that line voltage falls, then according to above analysis, the voltage magnitude after can obtaining faster to fall to the tracking of zero crossing.At this moment, real-time grid voltage is in the E point, and the line voltage that postpones is in the corresponding point before a cycle, i.e. F point accordingly.Because the absolute value of the signal difference that E, F are 2 is greater than threshold value, so start low voltage detecting module and start timing module.When the real-time voltage signal equals zero, stop timing, the time of acquisition is the time T of EG section among the figure
Eg, the line voltage frequencies omega is 50 hertz in addition, cycle T=0.02 second utilizes T
Eg/ T can obtain the phase angle of corresponding E, and then obtains its sine value sin (ω t
e+ θ), ω is the electrical network angular frequency, and θ is initial phase angle, and the subscript e representative of time t is the moment that e is ordered, and t represents time variable.Meanwhile, tracing module is sampled to real-time voltage, can obtain the timing voltage signal values that G is ordered the finish time and be made as U
g=Asin (ω t+ θ), A is voltage magnitude, in addition known T
Eg, can in the hope of:
Asin (ω t
e+ θ)=U
e=Asin (ω (t-T
Eg)+θ), U
eBe the e point voltage, Asin (ω (t-T
Eg)+θ) can be tried to achieve by two jiaos of trigonometric function and formula, namely
Asin(ω（t－T
eg）+θ)＝Asin(ωt+θ)cos（ωT
eg）－Acos(ωt+θ)sin（ωT
eg）
Asin (ω t+ θ), ω, T
EgKnown, Acos (ω t+ θ) can be obtained by Asin (ω t+ θ) differentiate.Asin (ω+θ) to sum up
e, sin (ω+θ)
eAll known, can try to achieve line voltage amplitude A.Equally, the voltage magnitude under the electrical network normal operation of having determined in conjunction with phaselocked loop again can be tried to achieve voltage and be fallen the degree of depth and time.Because when the symbol of magnitude of voltage and angle values when negative, the absolute value that calculates and symbol are that the result of calculation of timing is identical, so can not consider before the symbol problem, simplify calculating.
Although above-mentionedly by reference to the accompanying drawings the specific embodiment of the present invention is described; but be not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme of the present invention, those skilled in the art do not need to pay various modifications that creative work can make or distortion still in protection scope of the present invention.
Claims (4)
1. be applicable to the voltage fast detection algorithm of grid-connected system low voltage ride-through function, it is characterized in that, may further comprise the steps:
(1) based on the amplitude information under the normal operation of phaselocked loop acquisition electrical network of reference synchronization coordinate system;
(2) line voltage of sampling press A, B, C three phase separation, the voltage of sampling is carried out the time-delay in a cycle in each of separating in mutually, then each phase voltage is subtracted each other with the original signal of corresponding phase, obtain difference after, difference is asked absolute value;
(3) set a voltage threshold value, the difference of comparison step (2) and the size of voltage threshold value;
(4) if difference less than the voltage threshold value, then normal, think that system is in normal operating condition, continue to keep sampling and detect; If difference is more than or equal to the voltage threshold value, illustrative system may enter into low-voltage state, then forwards step (5) to;
(5) after the judgement system enters low-voltage state, respectively every mutually real-time voltage signal is sent to maximal value tracing module and zero crossing tracing module simultaneously, two modules are processed real-time voltage signal simultaneously;
(6) record maximal value tracing module and zero crossing tracing module finally all can obtain the amplitude after line voltage falls, utilize the very fast voltage that obtains to fall voltage magnitude under the electrical network normal operation of rear amplitude and phaselocked loop acquisition, obtain to fall the degree of depth and drop-out time;
The described detailed process of step (6) is as follows:
(6-1) ask line voltage to fall a little phase angle, i.e. T
Eg/ T=ω t
e+ θ, ω are electrical network angular frequency and ω=50Hz, t
eRefer to the moment of falling a little, θ is initial phase angle, and T is line voltage cycle and T=0.02s, T
EgThe time that obtains for timing;
(6-2) phase angle of step (1) is asked sine value:
That is: sin (ω t
e+ θ);
(6-3) the zero crossing tracing module is sampled to real-time voltage, obtains timing finish time, namely from the voltage signal values U that falls a little nearest zero crossing
g, with this voltage signal values U
g=Asin (ω t+ θ), wherein A is voltage magnitude, t represents time variable, in addition known T
Eg, can in the hope of:
Asin (ω t
e+ θ)=U
e=Asin (ω (t-T
Eg)+θ), U
eFor falling point voltage, Asin (ω (t-T
Eg)+θ) can be tried to achieve by two jiaos of trigonometric function and formula, namely
Asin(ω（t－T
eg）+θ)＝Asin(ωt+θ)cos（ωT
eg）－Acos(ωt+θ)sin（ωT
eg）
Asin (ω t+ θ), ω, T
EgKnown, Acos (ω t+ θ) can be obtained by Asin (ω t+ θ) differentiate, to sum up Asin (ω+θ)
e, sin (ω+θ)
eAll known, can try to achieve voltage magnitude;
Voltage magnitude under the electrical network normal operation of (6-4) having determined in conjunction with phaselocked loop, the real-time grid information of voltage that recycling obtains after falling deducts the voltage magnitude under the electrical network normal operation, can try to achieve voltage and fall the degree of depth and time.
2. the voltage fast detection algorithm that is applicable to the grid-connected system low voltage ride-through function according to claim 1, it is characterized in that: in the described step (2), mode by the cycle of delaying time, obtained line voltage before one cycle, be the magnitude of voltage information of the corresponding point under the line voltage normal operation before the 0.02s, and then make comparisons with the voltage that current sampling obtains, judging fast whether voltage exists falls.
3. the voltage fast detection algorithm that is applicable to the grid-connected system low voltage ride-through function as claimed in claim 1, it is characterized in that: the processing procedure of the maximal value tracing module described in the step (5) is: after the judgement system may enter low-voltage state, sampling apparatus is sent real-time voltage signal into the maximal value tracing module, and then the derivative value of the voltage signal when realistic, when derivative value is zero, then line voltage is crossed maximum of points, when recording the value of this point and it being remained to next time voltage jump.
4. the voltage fast detection algorithm that is applicable to the grid-connected system low voltage ride-through function as claimed in claim 1, it is characterized in that: the processing procedure of the described zero crossing tracing module of step (5) is, after the judgement system enters low-voltage state, sampling apparatus is sent real-time voltage signal into the zero crossing tracing module, while triggering timing module, the beginning timing, when mains voltage signal equals zero, stop timing, utilize time that timing obtains and the real-time voltage calculated signals triggering timing line voltage value constantly of current zero crossing, and then utilize count time and line voltage cycle, try to achieve triggering timing line voltage unit amplitude sine value constantly, utilize at last the line voltage amplitude after triggering timing line voltage value constantly and unit amplitude sine value are tried to achieve sudden change, and then the calculating line voltage falls the degree of depth.
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| CN105116195B (en) * | 2015-07-13 | 2018-07-06 | 中国人民解放军海军工程大学 | Suitable for the big method for detecting voltage drop of Voltage Harmonic content |
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