CN111679128A - Power grid impedance measurement method based on variable PWM carrier frequency - Google Patents
Power grid impedance measurement method based on variable PWM carrier frequency Download PDFInfo
- Publication number
- CN111679128A CN111679128A CN202010498849.1A CN202010498849A CN111679128A CN 111679128 A CN111679128 A CN 111679128A CN 202010498849 A CN202010498849 A CN 202010498849A CN 111679128 A CN111679128 A CN 111679128A
- Authority
- CN
- China
- Prior art keywords
- frequency
- carrier
- inverter
- power grid
- pwm
- 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.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/08—Measuring resistance by measuring both voltage and current
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measurement Of Resistance Or Impedance (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses a power grid impedance measuring method based on variable PWM carrier frequency, in inverter PWM modulation, the frequency of a variable carrier changes near a set frequency, and a carrier frequency spectrum with harmonic amplitude gradually increasing from low frequency to the set frequency is obtained by setting the change rule of the carrier frequency; the carrier signal with the changed frequency is used as a carrier wave of PWM modulation, and is modulated with a modulation wave generated by an inverter controller to generate a PWM signal to control an inverter switch tube, so that the controlled inverter alternating current power supply also comprises a plurality of carrier frequencies, and the closer the frequency is to the set frequency, the larger the amplitude is; and sampling and analyzing the output voltage and current signals of the inverter to obtain the power grid impedance under various frequencies. The invention can effectively solve the problem that the amplitude of the injected harmonic wave is attenuated along with the increase of the frequency in the existing broadband harmonic wave injection method.
Description
The application is application number: 201710962594.8, filing date: 2017.10.17 divisional application entitled "a method for measuring grid impedance based on variable PWM carrier frequency".
Technical Field
The invention relates to a power grid impedance measuring method based on variable PWM carrier frequency.
Background
Because power electronic equipment is used in a large amount in a power grid, especially the access of new energy grid-connected power generation, the impedance of the power grid is more complicated than before. In order to maintain the stability of the power system, some grid-connected devices need to adjust control parameters based on the grid impedance, and therefore online measurement of the grid impedance is needed. The method for measuring the impedance of a power grid based on the harmonic injection mode of an inverter is the current main mode.
The inverter is a converter device which converts a direct current power supply into an alternating current power supply and is widely applied to the fields of new energy power generation and the like, the basic principle of the inverter is that firstly, the direct current power supply is chopped into high-frequency pulse power supplies with different widths, the power supply waveforms with different pulse widths comprise low-frequency alternating current of transmission power and high-frequency alternating current for current conversion, and then, high-frequency components in the power supply waveforms are filtered by a filter so as to obtain the required low-frequency alternating current power supply waveforms. The control of the inverter mainly comprises two parts of inverter control and Pulse Width Modulation (PWM).
Modulation principle of PWM: the modulation wave is a reference signal of the waveform of the alternating current power supply of the inverter and is generated by an inverter controller. The modulated wave is compared with the carrier wave to generate control signals PWM1 and PWM2 of the switching tube, the control signals can control the inverter to generate a power waveform in a high-frequency pulse form, and the power waveform is filtered to become low-frequency alternating current consistent with the reference signal waveform.
The carrier frequency in PWM modulation is usually fixed, the invention injects extra harmonic waves into the power grid by changing the carrier frequency in PWM modulation, and then obtains the power grid impedance by calculating the extra harmonic waves in the voltage and the current of the power grid.
The existing power grid impedance detection method comprises the following steps:
mainly includes two major categories of passive and active methods [1 ]. The passive method is to analyze a large amount of data of voltage and current signals existing in the power grid to obtain the impedance of the power grid, and the passive method is generally low in precision, large in calculated amount and long in time consumption. More, an active method is adopted, wherein the active method is to inject characteristic harmonic waves into the power grid and measure the voltage and the current of the characteristic harmonic waves at two ends of the power grid to analyze the impedance of the power grid.
The characteristic harmonic injection comprises two modes of current harmonic injection and voltage harmonic injection. For a common voltage source inverter, voltage harmonic injection is simple and can be realized only by changing a modulation wave in a PWM (pulse width modulation) link; and current harmonic injection needs to be realized through a current control loop, and needs to be realized by changing a current reference in an inverter controller. Because the impedance of the power grid in a low-frequency band is small, current harmonic injection is usually needed to avoid generating excessive harmonic current interference on the power grid; in a high-frequency band, the current control bandwidth of the inverter is limited, and voltage harmonic injection is simpler and more effective.
The injected characteristic harmonics include single harmonic injection, several subharmonic injection, and broadband harmonic injection. In the single harmonic injection method, typically, for example, 75Hz harmonic current injection is selected, the harmonic is close to the power frequency of 50Hz, and the power grid has almost no interference signal of the subharmonic, so that the power grid impedance detection precision for the power frequency is high. However, the grid impedance is not a first-order system or even non-linear, so that the relationship between the grid impedance and the frequency can be obtained more accurately by adopting a harmonic injection method of multiple frequencies, but the multiple harmonic injections increase the calculation amount, require longer time, and increase the interference to the grid. Therefore, if a broadband harmonic signal is injected, the signal can be injected only once, and the power grid impedance in a wide frequency range can be obtained through analysis. Typical broadband harmonics are square wave signals, which include harmonic signals with rich frequencies.
However, in a broadband signal, the amplitude of the harmonic wave is usually attenuated as the frequency increases, so in practical application, the harmonic wave of the high frequency part is very weak, and the measurement accuracy is very low. Often it is necessary to inject several square wave signals of different frequencies to measure the low and high frequency impedances separately. The grid impedance can also be calculated by measuring the voltage and current of the parasitic PWM carrier frequency in the PWM inverter, but the PWM frequency is relatively high and is relatively far from the grid characteristic frequency.
Disclosure of Invention
The invention aims to provide a power grid impedance measuring method based on variable PWM carrier frequency, which can effectively solve the problem that the injected harmonic amplitude is attenuated along with the increase of frequency in the existing broadband harmonic injection method.
The technical solution of the invention is as follows:
a power grid impedance measurement method based on variable PWM carrier frequency is characterized in that: in the inverter PWM modulation, the frequency of a changed carrier wave is changed near a set frequency, and a carrier frequency spectrum with harmonic amplitude gradually increasing from a low frequency to the set frequency is obtained by setting the change rule of the carrier frequency;
the carrier signal with the changed frequency is used as a carrier wave of PWM modulation, and is modulated with a modulation wave generated by an inverter controller to generate a PWM signal to control an inverter switch tube, so that the controlled inverter alternating current power supply also comprises a plurality of carrier frequencies, and the closer the frequency is to the set frequency, the larger the amplitude is;
and sampling and analyzing the output voltage and current signals of the inverter to obtain the power grid impedance under various frequencies.
The invention can effectively solve the problem that the injection harmonic amplitude is attenuated along with the increase of frequency in the existing broadband harmonic injection method; the invention adopts a method of changing PWM carrier frequency, and can generate an injection harmonic amplitude value which is increased along with the frequency.
Drawings
The invention is further illustrated by the following figures and examples.
FIG. 1 is a system block diagram of the present invention.
Fig. 2 is a schematic diagram of carrier frequency variation law.
Fig. 3 is a schematic diagram of a carrier waveform.
Fig. 4 is a waveform diagram of an inverter output current using a carrier signal according to the present invention.
Fig. 5 is a waveform diagram of an output current at a constant carrier frequency.
Detailed Description
A power grid impedance measuring method based on variable PWM carrier frequency is characterized in that in inverter PWM modulation, the frequency of a variable carrier changes near a set frequency, and a carrier frequency spectrum with harmonic amplitude gradually increasing from low frequency to the set frequency is obtained through the change rule of the set carrier frequency;
the carrier signal with the changed frequency is used as a carrier wave of PWM modulation, and is modulated with a modulation wave generated by an inverter controller to generate a PWM signal to control an inverter switch tube, so that the controlled inverter alternating current power supply also comprises a plurality of carrier frequencies, and the closer the frequency is to the set frequency, the larger the amplitude is;
and sampling and analyzing the output voltage and current signals of the inverter to obtain the power grid impedance under various frequencies.
The practical application system is shown in fig. 1, a dashed line box is a part of the invention, and usually, a power grid impedance calculation module does not always run, and power grid impedance calculation can be started at regular time. When the power grid impedance calculation is started, the carrier frequency starts to change according to a rule, and the power grid impedance calculation unit calculates the power grid impedance in real time according to the sampling of the voltage and the current of the power grid.
As an example, a carrier frequency variation rule and a carrier waveform are shown in fig. 2 and 3.
The output current waveform of the inverter using this carrier signal is shown in fig. 4, and it can be seen that harmonics of an integral multiple of 1kHz are included in addition to the 10kHz carrier frequency. As a comparison fig. 5 shows the output current waveform at a constant carrier frequency, which contains only harmonic currents around the carrier frequency.
Therefore, the power grid impedance of the integral multiple of 1kHz can be further obtained according to the analysis of the harmonic voltage and current of the integral multiple of 1kHz in the power grid.
Claims (1)
1. A power grid impedance measurement method based on variable PWM carrier frequency is characterized in that: in the inverter PWM modulation, the frequency of a changed carrier wave is changed near a set frequency, and a carrier frequency spectrum with harmonic amplitude gradually increasing from a low frequency to the set frequency is obtained by setting the change rule of the carrier frequency;
the carrier signal with the changed frequency is used as a carrier wave of PWM modulation, and is modulated with a modulation wave generated by an inverter controller to generate a PWM signal to control an inverter switch tube, so that the controlled inverter alternating current power supply also comprises a plurality of carrier frequencies, and the closer the frequency is to the set frequency, the larger the amplitude is;
sampling and analyzing the output voltage and current signals of the inverter to obtain the power grid impedance under various frequencies;
starting the calculation of the impedance of the power grid at regular time; according to the analysis of harmonic voltage and current of 1kHz integral multiple, the impedance of the power grid of 1kHz integral multiple is obtained.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010498849.1A CN111679128B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710962594.8A CN107782972B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
| CN202010498849.1A CN111679128B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710962594.8A Division CN107782972B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111679128A true CN111679128A (en) | 2020-09-18 |
| CN111679128B CN111679128B (en) | 2022-05-13 |
Family
ID=61434519
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710962594.8A Active CN107782972B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
| CN202010498849.1A Active CN111679128B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201710962594.8A Active CN107782972B (en) | 2017-10-17 | 2017-10-17 | Power grid impedance measurement method based on variable PWM carrier frequency |
Country Status (1)
| Country | Link |
|---|---|
| CN (2) | CN107782972B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113328648A (en) * | 2021-04-13 | 2021-08-31 | 浙江大学 | Inverter PWM modulation method and device |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110554242A (en) * | 2019-10-14 | 2019-12-10 | 江苏为恒智能科技有限公司 | Impedance measuring device for grid-connected inverter |
| CN111239491B (en) * | 2019-12-31 | 2021-01-26 | 浙江大学 | Generalized impedance real-time experimental measurement method adopting physical controller disturbance injection |
| CN113075452B (en) * | 2021-03-11 | 2022-09-09 | 国网浙江余姚市供电有限公司 | High-precision rapid frequency detection system and method |
| CN117310293B (en) * | 2023-11-28 | 2024-03-01 | 广东电网有限责任公司 | Power grid impedance measurement method and device |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080084219A1 (en) * | 2006-10-05 | 2008-04-10 | Mohamed Belkhayat | Impedance Measurement Using Line-to-Line Current Injection |
| CA2831576A1 (en) * | 2011-06-01 | 2012-12-06 | Enphase Energy, Inc. | Method and apparatus for grid impedance detection |
| CN103630749A (en) * | 2013-11-11 | 2014-03-12 | 西安交通大学 | Harmonic injection device for harmonic impedance measurement of power grid |
| CN104090182A (en) * | 2014-06-23 | 2014-10-08 | 北京交通大学 | Alternating current electrified railway traction network impedance frequency characteristic testing device |
| JP2017034739A (en) * | 2015-07-28 | 2017-02-09 | 株式会社ダイヘン | System impedance estimation device, inverter and system impedance estimation method |
| CN106771786A (en) * | 2017-02-28 | 2017-05-31 | 合肥工业大学 | The verification method and experimental provision of electric network impedance identification |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7421356B2 (en) * | 2006-09-29 | 2008-09-02 | Gm Global Technology Operations, Inc. | Method and apparatus for measurement of fuel cell high frequency resistance in the presence of large undesirable signals |
| CN104155555B (en) * | 2014-08-27 | 2017-02-15 | 阳光电源股份有限公司 | Active island detection method and device |
-
2017
- 2017-10-17 CN CN201710962594.8A patent/CN107782972B/en active Active
- 2017-10-17 CN CN202010498849.1A patent/CN111679128B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20080084219A1 (en) * | 2006-10-05 | 2008-04-10 | Mohamed Belkhayat | Impedance Measurement Using Line-to-Line Current Injection |
| CA2831576A1 (en) * | 2011-06-01 | 2012-12-06 | Enphase Energy, Inc. | Method and apparatus for grid impedance detection |
| CN103630749A (en) * | 2013-11-11 | 2014-03-12 | 西安交通大学 | Harmonic injection device for harmonic impedance measurement of power grid |
| CN104090182A (en) * | 2014-06-23 | 2014-10-08 | 北京交通大学 | Alternating current electrified railway traction network impedance frequency characteristic testing device |
| JP2017034739A (en) * | 2015-07-28 | 2017-02-09 | 株式会社ダイヘン | System impedance estimation device, inverter and system impedance estimation method |
| CN106771786A (en) * | 2017-02-28 | 2017-05-31 | 合肥工业大学 | The verification method and experimental provision of electric network impedance identification |
Non-Patent Citations (2)
| Title |
|---|
| MICHAEL JORDAN等: "Frequency Dependent Grid-Impedance Determination with Pulse-Width-Modulation-Signals", 《2011 7TH INTERNATIONAL CONFERENCE-WORKSHOP COMPATIBILITY》 * |
| 岳小龙等: "一种基于调制脉冲叠加的快速电网谐波阻抗测量方法", 《大功率变流技术》 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113328648A (en) * | 2021-04-13 | 2021-08-31 | 浙江大学 | Inverter PWM modulation method and device |
Also Published As
| Publication number | Publication date |
|---|---|
| CN107782972B (en) | 2020-07-03 |
| CN107782972A (en) | 2018-03-09 |
| CN111679128B (en) | 2022-05-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107782972B (en) | Power grid impedance measurement method based on variable PWM carrier frequency | |
| CN107121609B (en) | Power grid impedance online identification method and device based on PRBS disturbance injection | |
| US10122355B2 (en) | High-power adjustable high-frequency fractional-order capacitor with order greater than 1 and control method thereof | |
| US9977094B2 (en) | Islanding operation detection and islanding operation detection method | |
| CN103812135A (en) | Control method for improving adaptability of LCL type grid-connected inverter for weak grid | |
| Shen et al. | Current control optimization for grid-tied inverters with grid impedance estimation | |
| CN104428963A (en) | Method of controlling in stable fashion pulse light source and phase difference of pulse laser light | |
| CN109004649A (en) | A kind of LCL filter resonance inhibition device and method based on active damping | |
| CN103605002A (en) | Harmonic impedance measurement apparatus of electric power system | |
| CN110266009A (en) | A kind of exchange micro-capacitance sensor higher hamonic wave active stabilization device and method | |
| CN106533404B (en) | A kind of triangular carrier slope random distribution pulse-width modulation circuit | |
| CN106452028B (en) | A kind of triangular carrier slope random distribution pulse duration modulation method | |
| CN207472983U (en) | A kind of electric network impedance on-line identification device based on PRBS disturbance injections | |
| CN109839540B (en) | RPWM-based online weak network impedance measurement method for single-phase grid-connected inverter | |
| CN203672975U (en) | Harmonic-impedance measuring device for power system | |
| Krishnakumar et al. | A new random PWM technique for conducted-EMI mitigation on Cuk converter | |
| CN105572452A (en) | Gaussian beam bunch average current measuring method of particle accelerator in quasi-continuous running state | |
| Cvetanovic et al. | High frequency passivity properties of grid-connected admittance with double-sampling asymmetric dual-edge modulator | |
| CN207442691U (en) | A kind of electric vehicle single phase bidirectional DC/AC converter adaptive controllers | |
| CN113740609A (en) | Self-adaptive current source impedance measuring device and measuring method | |
| CN103023291A (en) | Resonance suppression method based on voltage-type grid-connected inverter | |
| CN113804936B (en) | Triangular wave signal parameter measurement method | |
| CN113067372A (en) | Active damping method and circuit for improving LCL filtering grid-connected control performance | |
| CN113346551A (en) | Grid-connected converter control system and control method | |
| CN206209455U (en) | HF signal generator |
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 |