CN109839540B - RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter - Google Patents
RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter Download PDFInfo
- Publication number
- CN109839540B CN109839540B CN201910209955.0A CN201910209955A CN109839540B CN 109839540 B CN109839540 B CN 109839540B CN 201910209955 A CN201910209955 A CN 201910209955A CN 109839540 B CN109839540 B CN 109839540B
- Authority
- CN
- China
- Prior art keywords
- disturbance
- rpwm
- measurement
- carrier frequency
- condition
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Measurement Of Resistance Or Impedance (AREA)
Abstract
The invention discloses an RPWM-based weak network impedance measurement method for an online single-phase grid-connected inverter, which is characterized by comprising the following steps of: combining active measurement and passive measurement, carrying out passive measurement in real time, and carrying out active measurement by applying disturbance when a disturbance condition is met; the weak network impedance is taken as an active measurement value after disturbance is applied and a passive measurement value when the disturbance condition is not met; the disturbance condition is based on the current distortion degree; the active measurement is to switch the PWM mode from SPWM modulation timing to RPWM modulation, so as to achieve the purpose of disturbing and dispersing harmonic spectrum and then calculate. The invention realizes more time-efficient THD measurement and real-time and accurate inductive reactance measurement. The invention does not need to additionally add equipment, and has dispersed frequency spectrum and small electromagnetic interference after disturbance; and a variable carrier frequency RPWM modulation mode is selected to effectively excite disturbance, and the inductive reactance is accurately measured in real time.
Description
Technical Field
The invention belongs to the technical field of grid-connected inverter control, and particularly relates to an online weak grid harmonic impedance measuring method.
Background
With the increase of grid-connected power of the distributed power source and the wide distribution of positions of access to a power grid, the power grid increasingly shows the characteristics of a weak power grid in consideration of factors such as a long power transmission and distribution line, more isolation transformers, a large number of distributed power generation devices connected to a grid-connected point in a hanging mode, and the impedance of the power grid is not negligible.
The large impedance causes impedance mismatch, which in turn generates harmonic currents. The method for adjusting the controller parameters to adapt to different power grid conditions by detecting the impedance can effectively inhibit the power grid impedance influence, accurate parameter online detection is needed, for example, filter resonance is excited and specific subharmonic current is injected to detect the voltage of a common coupling point, extra hardware equipment is needed for realizing detection, so that the cost is increased, some excited harmonic frequency spectrums are too concentrated, larger electromagnetic interference is caused, and adverse influence can be generated on the quality of the current entering the power grid.
In the method for measuring impedance by actively applying disturbance, the judgment of the time length for applying the disturbance is an especially important factor. In order to reduce the interference on the current quality of the power grid as much as possible, the total harmonic distortion rate THD can be used as a reference for measuring the time length. However, the conventional THD measurement method always analyzes waveforms of integral multiples of a period, that is, the measured THD value always contains harmonic information of at least one period in the past, and cannot meet the requirement of judging the time duration of disturbance on the time effectiveness of THD.
Disclosure of Invention
The invention provides an RPWM-based online single-phase grid-connected inverter weak grid impedance measurement method for avoiding the defects in the prior art, no additional equipment is needed, and the disturbed frequency spectrum is dispersed and the electromagnetic interference is small; the traditional THD measuring mode is improved, THD measurement with time effectiveness is achieved, a variable carrier frequency RPWM modulation mode is selected, disturbance is effectively excited, and impedance is accurately measured in real time.
The invention adopts the following technical scheme for solving the technical problems:
the RPWM-based online weak network impedance measurement method for the single-phase grid-connected inverter is characterized by comprising the following steps: combining active measurement and passive measurement, carrying out passive measurement in real time, and carrying out active measurement by applying disturbance when the condition of applying disturbance is met; the weak network impedance is taken as an active measurement value after disturbance is applied and a passive measurement value when the condition of applying the disturbance is not met; the disturbance applying condition is based on the current distortion degree represented by the THD value;
the passive measurement refers to: sampling to obtain PCC point voltage and PCC point current during grid-connected operation, carrying out FFT analysis on the PCC point voltage and the PCC point current, calculating to obtain an impedance value, and realizing passive measurement of weak network impedance when current distortion is large; the active measurement is carried out according to the following steps:
fi＝fmax+Ri·Δf (1)
In the formula (1), fmaxThe carrier frequency of the SPWM is shown, and delta f is the variable quantity of the carrier frequency of the RPWM;
carrier frequency f according to the RPWMiObtaining a carrier signal;
The RPWM-based online weak network impedance measurement method of the single-phase grid-connected inverter is characterized in that: setting the RPWM modulation mode as an RPWM modulation mode with variable carrier frequency change rate; defining the carrier frequency rate of change as fRAnd then: at a value from t characterized by formula (2)kCarrier frequency f of k-th RPWM in t period from timekObtained by calculation of equation (3):
fk＝fmax+Rk·Δf (3)
in the formula (3), k is 1,2,3 …, RkIs [ -1,0 [ ]]The random number of (2);
setting the carrier frequency change rate fRComprises the following steps: f. ofR＝m·fkM is [1,2 ]]。
The RPWM-based online single-phase grid-connected inverter weak grid impedance measurement method is also characterized in that: determining a disturbance time period in the following mode, wherein the condition of applying disturbance is that a condition I and a condition II are simultaneously met;
the first condition is as follows: in the disturbance judgment interval;
the second condition is as follows: total harmonic distortion rate THD < 3%;
the disturbance judgment interval is as follows: 1/4 cycles from the time of the timed application of the perturbation;
the total harmonic distortion rate THD is calculated as follows:
extracting fundamental waves from a sampling waveform as a reference waveform by using a wavelet packet transform mode, intercepting a section of length of the sampling waveform and the reference waveform respectively, and combining the sections of length of the sampling waveform and the reference waveform into a waveform with a period length for calculation to obtain a Total Harmonic Distortion (THD), wherein in the waveform with the period length, the front section is the reference waveform, and the rear section is the sampling waveform;
and defining the time length contained in the disturbance judgment interval as the judgment time length, and judging that the interception length of the sampling waveform is not less than the judgment time length.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, when disturbance is actively applied, hardware equipment is not required to be added, the cost is saved, only the carrier frequency is required to be changed, and the implementation mode is simple;
2. the carrier frequency is determined by random numbers, and the disturbed waveform frequency spectrum is dispersed, so that calculation fitting is facilitated, and electromagnetic interference is effectively reduced;
3. the variable carrier frequency and variable rate RPWM selected by the invention has the characteristics that the frequency value has long duration time at low frequency and short duration time at high frequency, and can effectively excite disturbance;
4. the segmented THD measuring method can realize faster response to the change of the waveform and has better timeliness;
5. the passive measurement part can actively apply disturbance kinetic energy to effectively correct the current impedance measurement value when the impedance changes and feed back the measurement value outside the period of actively applying disturbance, the disturbance time is short, and external interference is not introduced.
Drawings
FIG. 1 is an RPWM-based impedance measurement block diagram of active and passive combination method
FIG. 2 is a diagram of the connection of the measurement module to the main circuit in the present invention;
FIGS. 3a and 3b are graphs comparing the rate of change of two carrier frequencies in the present invention;
FIG. 4 is a waveform of inverter output current in accordance with the present invention;
FIG. 5 shows a measured inductance L according to the present invention;
FIG. 6 shows the feedback inductance L of the control circuit;
FIG. 7 is a graph of segmented THD measurements in accordance with the present invention;
FIG. 8 is a conventional THD measurement;
FIG. 9 shows the FFT analysis result of the THD variation caused by the weak network impedance variation under the SPWM modulation in the present invention;
FIG. 10 shows the FFT analysis results of the RPWM perturbation of the present invention;
table 1 shows the inverter parameters given in the present invention;
table 2 shows the lower frequency limit test of the present invention;
table 3 shows RPWM parameters selected in the present invention;
Detailed Description
In the method for measuring the impedance of the weak network of the online single-phase grid-connected inverter based on RPWM (reverse pulse width modulation) in the embodiment, active measurement and passive measurement are combined, passive measurement is carried out in real time, and active measurement is carried out by applying disturbance when the condition of applying disturbance is met; the weak network impedance is taken as an active measurement value after disturbance is applied and a passive measurement value when the condition of applying the disturbance is not met; the conditions under which the perturbation is applied are based on the degree of current distortion as characterized by the THD value.
Fig. 1 and fig. 2 show a block diagram of a method for measuring weak grid impedance of an online single-phase grid-connected inverter based on an active-passive combination method of Random Pulse Width Modulation (RPWM) in the present embodiment and a connection diagram of the weak grid impedance and a main circuit.
Passive measurements refer to: and sampling to obtain a public coupling point, namely PCC point voltage and PCC point current, during grid-connected operation, carrying out FFT analysis on the PCC point voltage and the PCC point current, calculating to obtain an impedance value, and realizing passive measurement of the weak network impedance when the current distortion is large.
The active measurement is carried out as follows:
fi＝fmax+Ri·Δf (1)
In the formula (1), fmaxThe carrier frequency of the SPWM is shown, and delta f is the variable quantity of the carrier frequency of the RPWM; carrier frequency f according to the RPWMiA carrier signal is obtained.
And 2, carrying out pulse width modulation on the modulated wave signal and the carrier signal obtained in the step 1 to obtain a pulse signal for driving an inverter switching tube in a disturbance period.
In the specific implementation, the RPWM mainly plays a role in low frequency band disturbance, and the THD can be raised by large enough disturbance to play a role in timing active disturbance. In order to generate a sufficiently large disturbance, the random frequency should be made short in duration when the frequency is high and long in duration when the frequency is low. Therefore, the RPWM modulation mode is set as the RPWM modulation mode with variable carrier frequency change rate; defining the carrier frequency rate of change as fRAnd then: at a value from t characterized by formula (2)kCarrier frequency f of k-th RPWM in t period from timekObtained by calculation of equation (3):
fk＝fmax+Rk·Δf (3)
in the formula (3), k is 1,2,3 …, RkIs [ -1,0 [ ]]The random number of (2); setting the carrier frequency change rate fRComprises the following steps: f. ofR＝m·fkM is [1,2 ]]I.e. 0.5,1 of the duration of any frequency in the corresponding period]Doubling; when m is large, the duration of high and low frequenciesShortening; on the contrary, the duration of high and low frequencies is longer, so the value of m should not be too large or too small.
In specific implementation, a disturbance time period is determined as follows, and the condition for applying disturbance is that a condition I and a condition II are simultaneously met;
the first condition is as follows: in the disturbance judgment interval;
the second condition is as follows: total harmonic distortion rate THD < 3%;
the disturbance judgment interval is as follows: 1/4 cycles from the time of the timed application of the perturbation;
the total harmonic distortion rate THD is calculated as follows: extracting fundamental waves from a sampling waveform as a reference waveform by using a wavelet packet transform mode, intercepting a section of length of the sampling waveform and the reference waveform respectively, and combining the sections of length of the sampling waveform and the reference waveform into a waveform with a period length for calculation to obtain a Total Harmonic Distortion (THD), wherein in the waveform with the period length, the front section is the reference waveform, and the rear section is the sampling waveform; and defining the time length contained in the disturbance judgment interval as the judgment time length, and judging that the interception length of the sampling waveform is not less than the judgment time length.
The segment THD detection length is one period, and assuming that the truncation length from the reference wave is α, the sampling waveform should be retained with a length (T- α), and T is the modulation wave period 0.02 s. Because the length of the reserved sampling waveform is always less than one period, the THD value measured by the method is always less than that of the traditional THD measurement mode, in order to reduce errors, if the index specifies that the oscillation time of the current waveform is not more than T, the oscillation length of a certain section of the oscillation can be contained in the intercepted sampling waveform only if (T- α) > T is met, and because the judgment disturbance module has the judgment duration, the time length of the sampling waveform is more than or equal to the judgment duration, so that the value before the THD is reduced is close to the result of the traditional THD measurement mode, as shown in fig. 3a and fig. 3 b.
In a specific implementation, the variation range of the carrier frequency is determined as follows: the carrier frequency maximum is selected as the carrier frequency during SPWM modulation, so the carrier frequency variation range is determined only by the minimum of the carrier frequency, and the selection of the carrier frequency minimum is discussed below.
At selected carrier frequencyThere is an upper limit at the minimum
The upper limit value is that when the carrier frequency is selected as the frequency during SPWM modulation, THD in a disturbance period can be ensured>The minimum frequency value of 3 is:
in addition to the constraint condition, the RPWM has the function of dispersing the spectrum, and the harmonic spectrum is mainly distributed at the integral multiple of the switching frequency, so the spectrum range selected when calculating the impedance value should be considered, so as to give the optimal value.
In order to verify the effectiveness of the method, a single-phase grid-connected inverter model with the rated capacity of 6kw is built in Matlab/simulink; inverter parameters are given in table 1:
TABLE 1 inverter parameters given
| Description of the parameters | Parameter value |
| Effective value of electric network voltage (V) | 220 |
| Grid voltage frequency (Hz) | 50 |
| DC side voltage (V) | 360 |
| Rated power (W) | 6K |
| SPWM switching frequency (Hz) | 10K |
| Inverter side inductor (mH) | 0.6 |
| Network side inductor (mH) | 0.15 |
| Filter capacitor (mu F) | 10 |
| P | 0.45 |
| I | 2200 |
| Ke | 0.1 |
| Ki | 0.15 |
Firstly, selecting the frequency fitting range of FFT result as 1K-2K, and then testing the THD result when using fixed low-frequency SPWM for modulation under different conditions, as shown in Table 2:
TABLE 2
In Table 2, LgRepresents the actual value, LtestAre assumed measured values. In the test, the low-frequency duration is the whole fundamental wave period, and when the RPWM is disturbed, the low-frequency duration is short, and after the disturbanceThe THD of (a) is smaller than the values given in the table, and the segmented THD measurement also results in a slightly smaller THD value, so the lower limit of the RPWM carrier frequency is practically 2000Hz, as shown in table 3. After later-stage simulation identification, the value is reasonable, and when 2300Hz is adopted, THD does not reach the standard in a part of disturbance time period.
TABLE 3
| Description of the parameters | Parameter value |
| RPWM Carrier frequency maximum (Hz) | 10K |
| RPWM Carrier frequency minimum (Hz) | 2K |
| Carrier frequency change |
1 |
| Sampling waveform intercept length(s) | 0.01 |
In the simulation, the load impedance (neglecting resistance) rises to 0.5mH at 0.04s, 1mH at 0.1s, 1.5mH at 0.16s, and the disturbance is applied and the disturbance determination module is activated at 0.08s, 0.14s, 0.18 s. The simulation results are shown in fig. 4 to 9.
As shown in fig. 4, the inverter outputs a current waveform, the method of the present invention has short disturbance time, small influence on the output current of the inverter, and a good output current waveform.
As can be seen from the measured inductance L curve shown in fig. 5, the measured impedance curves after applying the disturbances at 0.08s, 0.14s and 0.18s are distributed around the theoretical value, i.e. the method of the present invention has high measurement accuracy, and particularly, the feedback value can be effectively corrected after actively applying the disturbances. As can be seen from the observation of the waveform, even if the active measurement value is obtained after the disturbance is actively applied for 0.08s, the active measurement result is more accurate and the fluctuation degree is smaller compared with the passive measurement result before 0.08 s.
As shown in fig. 6, the control circuit feeds back the inductance curve, the feedback value is not updated after the disturbance, and the feedback value is a fixed value. It should be noted that in the system selected for verification, the measured impedance value needs to be applied to the control circuit, and since the control is intended to reduce the distortion degree of the output waveform, the absolute value and averaging processing is performed on the measured value, and the feedback value is updated only when the THD value is greater than 3%.
Comparing fig. 7 and fig. 8, it can be known that the time efficiency of the segmented THD measurement mode in the method of the present invention is higher than that of the conventional THD measurement mode; 4-7, the method of the present invention has been shown to be advantageous in measuring impedance; fig. 9 and fig. 10 show the FFT analysis results of THD variation caused by weak network impedance variation and RPWM disturbance under SPWM modulation, and it is easy to find that the spectrum is relatively dispersed when RPWM disturbance occurs after comparison.
The method makes up the defects of the existing harmonic impedance detection technology, and has the advantages of simple and feasible disturbance applying mode, short disturbance time, small influence on the current of the power grid and high impedance value measurement precision. The effectiveness of the method is verified by simulation.
Claims (2)
1. An RPWM-based online single-phase grid-connected inverter weak grid impedance measurement method is characterized by comprising the following steps: combining active measurement and passive measurement, carrying out passive measurement in real time, and carrying out active measurement by applying disturbance when the condition of applying disturbance is met; the weak network impedance is taken as an active measurement value after disturbance is applied and a passive measurement value when the condition of applying the disturbance is not met; the disturbance applying condition is based on the current distortion degree represented by the THD value;
the passive measurement refers to: sampling to obtain PCC point voltage and PCC point current during grid-connected operation, carrying out FFT analysis on the PCC point voltage and the PCC point current, calculating to obtain an impedance value, and realizing passive measurement of weak network impedance when current distortion is large; the active measurement is carried out according to the following steps:
step 1, generating a value of [ -1,0 [)]Random number R betweeniThe carrier frequency f of RPWM is obtained by calculation of formula (1)i：
fi＝fmax+Ri·Δf (1)
In the formula (1), fmaxThe carrier frequency of the SPWM is shown, and delta f is the variable quantity of the carrier frequency of the RPWM;
carrier frequency f according to the RPWMiObtaining a carrier signal;
step 2, carrying out pulse width modulation on the modulated wave signal and the carrier signal obtained in the step 1 to obtain a pulse signal for driving an inverter switching tube in a disturbance period;
step 3, switching the inverter switching tube between an SPWM (sinusoidal pulse width modulation) mode and an RPWM (sinusoidal pulse width modulation) mode at regular time, and applying active disturbance in a disturbance period; sampling to obtain a PCC point voltage during disturbance and a PCC point current during disturbance, carrying out FFT analysis on the PCC point voltage during disturbance and the PCC point current during disturbance, calculating to obtain an impedance value, and realizing the active measurement of the weak network impedance;
determining a disturbance time period in the following mode, wherein the condition of applying disturbance is that a condition I and a condition II are simultaneously met;
the first condition is as follows: in the disturbance judgment interval;
the second condition is as follows: total harmonic distortion rate THD < 3%;
the disturbance judgment interval is as follows: 1/4 cycles from the time of the timed application of the perturbation;
the total harmonic distortion rate THD is calculated as follows:
extracting fundamental waves from a sampling waveform as a reference waveform by using a wavelet packet transform mode, intercepting a section of length of the sampling waveform and the reference waveform respectively, and combining the sections of length of the sampling waveform and the reference waveform into a waveform with a period length for calculation to obtain a Total Harmonic Distortion (THD), wherein in the waveform with the period length, the front section is the reference waveform, and the rear section is the sampling waveform;
and defining the time length contained in the disturbance judgment interval as the judgment time length, and judging that the interception length of the sampling waveform is not less than the judgment time length.
2. The RPWM-based online single-phase grid-connected inverter weak grid impedance measurement method as claimed in claim 1, wherein the method comprises the following steps: setting the RPWM modulation mode as an RPWM modulation mode with variable carrier frequency change rate; defining the carrier frequency rate of change as fRAnd then: at a value from t characterized by formula (2)kCarrier frequency f of k-th RPWM in t period from timekObtained by calculation of equation (3):
fk＝fmax+Rk·Δf (3)
in the formula (3), k is 1,2,3 …, RkIs [ -1,0 [ ]]The random number of (2);
setting the carrier frequency change rate fRComprises the following steps: f. ofR＝m·fkM is [1,2 ]]。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910209955.0A CN109839540B (en) | 2019-03-19 | 2019-03-19 | RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910209955.0A CN109839540B (en) | 2019-03-19 | 2019-03-19 | RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109839540A CN109839540A (en) | 2019-06-04 |
| CN109839540B true CN109839540B (en) | 2021-02-05 |
Family
ID=66886082
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910209955.0A Active CN109839540B (en) | 2019-03-19 | 2019-03-19 | RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109839540B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ES2867349A1 (en) * | 2019-11-28 | 2021-10-20 | Convergrid S L | SYSTEM AND PROCEDURE FOR THE INTEGRATION AND SUPERVISION OF ELECTRICAL EQUIPMENT FOR THE STABILIZATION OF ELECTRICAL NETWORKS (Machine-translation by Google Translate, not legally binding) |
| CN111025023B (en) * | 2019-12-19 | 2021-03-23 | 西南交通大学 | Disturbance energy limit value selection method for injection type harmonic impedance measurement |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006238573A (en) * | 2005-02-24 | 2006-09-07 | Meidensha Corp | Method and apparatus for measuring insulation resistance of frequency converter |
| CN105259414A (en) * | 2015-11-23 | 2016-01-20 | 上海电力学院 | Power grid impedance on-line detection method on the basis of inverter |
| CN107121609A (en) * | 2017-05-22 | 2017-09-01 | 广西大学 | A kind of electric network impedance on-line identification method and device that injection is disturbed based on PRBS |
| CN107870266A (en) * | 2017-10-18 | 2018-04-03 | 江苏固德威电源科技股份有限公司 | Three-phase photovoltaic grid-connected inverting device electric network impedance inductance detection method |
| CN207200599U (en) * | 2017-05-31 | 2018-04-06 | 珠海格力电器股份有限公司 | Single-phase grid-connected inverter and single-phase grid-connected inverter circuit |
| CN108414838A (en) * | 2018-02-06 | 2018-08-17 | 西安交通大学 | A kind of inverter parallel system line impedance measurement method |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5012803B2 (en) * | 2006-08-04 | 2012-08-29 | トヨタ自動車株式会社 | Insulation resistance detection system, insulation resistance detection device, and insulation resistance detection method |
-
2019
- 2019-03-19 CN CN201910209955.0A patent/CN109839540B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006238573A (en) * | 2005-02-24 | 2006-09-07 | Meidensha Corp | Method and apparatus for measuring insulation resistance of frequency converter |
| CN105259414A (en) * | 2015-11-23 | 2016-01-20 | 上海电力学院 | Power grid impedance on-line detection method on the basis of inverter |
| CN107121609A (en) * | 2017-05-22 | 2017-09-01 | 广西大学 | A kind of electric network impedance on-line identification method and device that injection is disturbed based on PRBS |
| CN207200599U (en) * | 2017-05-31 | 2018-04-06 | 珠海格力电器股份有限公司 | Single-phase grid-connected inverter and single-phase grid-connected inverter circuit |
| CN107870266A (en) * | 2017-10-18 | 2018-04-03 | 江苏固德威电源科技股份有限公司 | Three-phase photovoltaic grid-connected inverting device electric network impedance inductance detection method |
| CN108414838A (en) * | 2018-02-06 | 2018-08-17 | 西安交通大学 | A kind of inverter parallel system line impedance measurement method |
Non-Patent Citations (2)
| Title |
|---|
| 并网逆变器的阻抗自适应控制方法;杜燕 等;《电力系统自动化》;20180325;第42卷(第6期);第120-127页 * |
| 考虑谐波电流的并网逆变器阻抗模型研究;王喜莲 等;《北京交通大学学报》;20170430;第41卷(第2期);第90-97、105页 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109839540A (en) | 2019-06-04 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107121609B (en) | Power grid impedance online identification method and device based on PRBS disturbance injection | |
| CN111506869B (en) | Grid-connected inverter frequency coupling impedance characteristic extraction method based on multi-sine-wave signal injection | |
| CN103605002A (en) | Harmonic impedance measurement apparatus of electric power system | |
| CN108318852B (en) | Square wave influence test method for intelligent electric energy meter | |
| CN103545838A (en) | Method for adaptively controlling hybrid damping of grid-connection inverter applicable to weak grid access conditions | |
| CN109839540B (en) | RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter | |
| CN107782972B (en) | Power grid impedance measurement method based on variable PWM carrier frequency | |
| Nian et al. | Design method of multisine signal for broadband impedance measurement | |
| Shen et al. | Current control optimization for grid-tied inverters with grid impedance estimation | |
| CN113156214B (en) | Dual-mode broadband disturbance device and control method | |
| CN109902347B (en) | Grid-connected system short circuit ratio measuring method and device based on fundamental wave impedance identification | |
| CN109245171A (en) | Harmonic suppressing method, device and the realization device of photovoltaic generating system | |
| CN111308207B (en) | Dq impedance measuring method for single-phase alternating current system | |
| CN207472983U (en) | A kind of electric network impedance on-line identification device based on PRBS disturbance injections | |
| Li et al. | An improved impedance measurement method based on multi-sine signal considering the suppression of noise interference | |
| CN203672975U (en) | Harmonic-impedance measuring device for power system | |
| Li et al. | Adaptive frequency adjustment method for impedance measurement | |
| CN115236404B (en) | Grid-connected inverter port impedance self-measurement method | |
| CN116609597A (en) | Nonlinear load power loss metering method and device for power distribution network | |
| CN116087623A (en) | Method and device for measuring overall impedance of new energy grid-connected system | |
| Davari et al. | Impedance analysis of single-phase PFC converter in the frequency range of 0–150 kHz | |
| CN111025023B (en) | Disturbance energy limit value selection method for injection type harmonic impedance measurement | |
| Liu et al. | Dead-Time Compensation Based on Current Phase Estimation for High-Frequency Cascaded Transformer Multilevel Inverter | |
| Vickery et al. | Wideband Measurement of Grid Impedance Using Chirp Signals in Grid-Connected Inverters | |
| Wang et al. | Multi-stage Design Method of Broadband Perturbation Signal for Impedance Measurement |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |