CN106208138B - It is a kind of based on the distributed generation resource of virtual impedance without ac sensor control method - Google Patents
It is a kind of based on the distributed generation resource of virtual impedance without ac sensor control method Download PDFInfo
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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
- H02J3/381—Dispersed generators
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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
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- H02J3/388—Islanding, i.e. disconnection of local power supply from the network
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention discloses a kind of based on the distributed generation resource of virtual impedance without ac sensor control method, it is adapted to the grid-connected and isolated island double mode operation of micro-capacitance sensor, in micro-grid connection operation, it joined virtual impedance control on the basis of sagging control, Control system resolution and stability are not influenced by mains by harmonics in the case where being not necessarily to voltage sensor；In micro-capacitance sensor isolated operation, by being further improved virtual impedance and active damping method being added, so that nonlinear load and LCL be inhibited to filter harmonic wave interference caused by link, while the problem of filter resonates is avoided.The control method proposed through the invention reduces the computation burden of system cost and control system, improves the accuracy and stability of control system in the case of harmonic wave interference, has great significance for the further genralrlization of distributed power generation and micro-capacitance sensor.
Description
Technical Field
The invention belongs to the technical field of distributed power supply control, and particularly relates to a distributed power supply AC-free sensor control method based on virtual impedance.
Background
It is generally considered that distributed generation dg (distribution generation) refers to a generator set which meets the specific needs of users, supports the economic operation of the existing power distribution network, or meets both of the needs, and the power configured at or near the user site is small and compatible with the environment, so that the concept of a micro-grid is proposed, and the micro-grid refers to a small power generation and distribution system composed of a distributed power supply, an energy storage device, an energy conversion device, a load, a monitoring and protection device, and the like. The micro-grid is an autonomous system capable of realizing self control, protection and management, and can be operated in a grid-connected mode with an external power grid or in an isolated mode. The micro-grid aims to realize flexible and efficient application of distributed power supplies and solve the problem of grid connection of the distributed power supplies with large quantity and various forms.
In the past, the output current or voltage of a distributed power supply in a microgrid is synchronized with the voltage of an external power grid through a phase-locked loop, the voltage at a grid-connected point of the distributed power supply needs to be accurately measured under the control strategy, and a synchronous phase angle of the voltage is detected through an alternating-current voltage sensor, but the sampling cost of the alternating-current voltage is high, and the operation burden of a distributed power supply control system is large; if the control strategy without the alternating voltage sensor is adopted, the measurement of the alternating voltage and the phase-locked loop can be effectively reduced, and meanwhile, the calculation burden of the distributed power supply control system is reduced. In the prior art, there is a control strategy that does not require a voltage sensor, and a patent with application number CN201010109338.2 proposes a direct power control method of a grid-connected inverter without an ac voltage sensor.
However, the direct power control method of the grid-connected inverter without the ac voltage sensor described in the above patent document has the following disadvantages: the control method of the patent essentially utilizes an algorithm for indirectly obtaining the voltage and the phase of the power grid, and the algorithm is complex and has large calculation workload; in addition, the method mentioned in the patent is sensitive to harmonic interference of the power grid, and if a load with a large harmonic distortion rate is accessed into the power grid, the accuracy and stability of system control are affected. Meanwhile, the distributed power supply increasingly attaches importance to the requirements of dual-mode operation of grid connection and isolated island of the micro-grid, and in the isolated island operation mode, the distributed power supply in the micro-grid needs to provide voltage support and resist the influence of nonlinear load harmonic waves.
Disclosure of Invention
The invention provides a distributed power supply AC-free sensor control method based on virtual impedance to solve the problems, and the method effectively solves the problems that a micro-grid is high in cost due to the adoption of an AC voltage sensor and a phase-locked loop under grid-connected and island dual-mode operation, a control system is large in operation amount, and AC voltage calculation accuracy is influenced by a power grid or load harmonic.
In order to achieve the purpose, the invention adopts the following technical scheme:
a distributed power supply AC-free sensor control method based on virtual impedance comprises the following steps:
(1): and (3) a power control link of the distributed power supply: the reference frequency f of the current period of the system is obtained through a control link of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude ErefThen obtaining the reference voltage through a sine signal generator
(2): and a voltage control link: firstly, the output current I of the distributed power supply is detected1Obtaining PWM reference voltage by adopting control strategy based on virtual impedance
(3): passing the reference voltage in the step (1) of the current periodAnd the output current I in the step (2)1Calculating the output active power P of the distributed power supply of the next periodDGAnd reactive power QDGAnd (3) calculating the control link of the active power-frequency and the reactive power-voltage amplitude in the step (1) of the next period.
In the step (1), the concrete steps include:
(1-1) in a micro-grid-connected operation mode, a power control link of the distributed power supply can obtain a reference frequency f of the current period of the system through droop control of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude Eref：
fref＝DP(Pref-PDG)
Wherein, PrefAnd QrefSetting reference values of active power and reactive power according to the capacity of the distributed power supply; dPIs a proportionality coefficient of active power-frequency; dqAnd KiProportional coefficient and integral coefficient of reactive power-voltage amplitude; pDGAnd QDGReal-time active power and reactive power output for the distributed power supply; f. ofrefAnd ErefIs a reference voltageVia a sinusoidal signal generator to generate a reference voltage
(1-2): in a micro-grid island operation mode, a distributed power supply power control link can obtain the reference frequency f of the current period of the system through droop control of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude Eref：
fref＝DP·PDG
Eref＝Dq·QDG
Wherein D isPIs a proportionality coefficient of active power-frequency; dqIs a proportional coefficient of reactive power-voltage amplitude; pDGAnd QDGReal-time active power and reactive power output for the distributed power supply; f. ofrefAnd ErefIs a reference voltageVia a sinusoidal signal generator to generate a reference voltage
In the step (2), the specific step of adopting the control strategy based on the virtual impedance includes:
(2-1) in a microgrid grid-connected operation mode, a virtual impedance control strategy is adopted in a voltage control link of the distributed power supply, specific times of harmonic waves are obtained through a resonance harmonic current observer, and a PWM reference voltage is calculated by connecting virtual resistors in series on the output side of the distributed power supply:
wherein, I1For output current, h is the number of harmonics, Rv,hAs a virtual resistance at the h harmonic, ωcTo cut-off frequency, ωoTo output the voltage frequency, omegao＝2π·50＝100πrad/s；
(2-2) in the isolated island operation mode of the micro-grid, the voltage control link of the distributed power supply adopts virtual impedance control, and the voltage drop generated by the virtual impedanceIs composed of
In the formula Rv,hIs a virtual resistance with harmonic order h, Lv,hIs a virtual reactance with harmonic order h.
To avoid the resonance problem of LCL filter, an appropriate high frequency gain is generated by using the active damping theory
RADActive damping at high frequencies, omegaHPFIs the cut-off frequency of a high-pass filter, I1Is the output current of the current cycle.
Finally, the improved PWM reference voltage is:
in the step (3), PDGAnd QDGThe calculation formula of the active power and the reactive power output by the distributed power supply is as follows:
wherein,and I1_delayRespectively, the reference voltage and the output current of the last calculation cycle.
The invention has the beneficial effects that:
(1) the distributed power supply control method is applicable to a grid-connected operation mode and an island operation mode of a micro-grid. When the micro-grid is connected to the power grid, the voltage amplitude and the phase can still be accurately calculated under the condition that the harmonic wave of the power grid is serious, and the reasonable distribution of the load among distributed power supplies can be realized; in a micro-grid island operation mode, accurate voltage support can be provided and the influence of nonlinear load harmonic waves can be resisted.
(2) The distributed power control system does not need alternating voltage sampling, an alternating voltage detection part and a phase-locked loop can be omitted, the cost is reduced, and the operation burden of the control system is reduced.
(3) The voltage control link of the distributed power supply adopts virtual impedance control, which is equivalent to that proper impedance is connected in series on the output harmonic frequency band of the distributed power supply on the physical characteristic, so that the distributed power supply has good harmonic interference resistance, and the stability and the accuracy of a control system are ensured.
(4) When the island operates, the virtual impedance is further improved and an active damping method is added, so that the interference caused by the load and the LCL filtering link is restrained, and the problem of filter resonance is avoided.
Drawings
FIG. 1 is a schematic diagram of a microgrid configuration having multiple distributed power sources;
FIG. 2(a) is a circuit diagram of a single distributed power supply in a microgrid grid-connected mode;
fig. 2(b) is a block diagram of a single distributed power control system in a microgrid grid-connected mode;
fig. 3(a) is a circuit diagram of two distributed power sources in an islanding mode of a microgrid;
fig. 3(b) is a structural block diagram of two distributed power control systems in a microgrid island mode;
fig. 4(a) is a simulation waveform diagram of a distributed power supply in a microgrid grid-connected mode;
fig. 4(b) is a simulation waveform diagram of the virtual impedance distributed power supply not added in the microgrid grid-connected mode;
fig. 4(c) is a simulation waveform diagram of adding a virtual impedance distributed power supply in a microgrid grid-connected mode;
fig. 5(a) is a simulation waveform diagram of a distributed power supply in an islanding mode of a microgrid;
fig. 5(b) is a simulation waveform diagram of a distributed power supply without adding virtual impedance in a microgrid island mode;
fig. 5(c) is a simulation waveform diagram of adding a virtual impedance distributed power supply in a microgrid island mode.
The specific implementation mode is as follows:
the invention is further described with reference to the following figures and examples.
As shown in fig. 1, when a static switch is closed, the micro-grid is connected to operate, and feeds power to the large power grid; when the large power grid fails, the static switch is disconnected, the micro-grid operates independently, and power is supplied to loads in the micro-grid through the distributed power supply. However, when power is supplied to loads in a microgrid, the nonlinear loads generate harmonic waves, which affect the power quality of a control system and seriously affect the stability of the system. Therefore, a control method is needed, which is suitable for operation in a grid-connected mode and an isolated island mode of a micro-grid, does not need an alternating voltage sensor, does not influence the alternating voltage calculation precision by the grid or load harmonic, reduces the input cost of a distributed power supply system, resists adverse influence of the harmonic, and improves the stability of system operation; when the micro-grid is connected to the power grid, the voltage amplitude and the phase can still be accurately calculated under the condition that the harmonic wave of the power grid is serious, and the reasonable distribution of the load among distributed power supplies can be realized; in a micro-grid island operation mode, accurate voltage support can be provided and the influence of nonlinear load harmonic waves can be resisted.
A distributed power supply AC-free sensor control method based on virtual impedance comprises the following steps:
(1): the power control link of the distributed power supply can obtain the reference frequency f of the current period of the system through the control links of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude ErefThen the instantaneous reference voltage can be obtained by a sine signal generator
(2): a voltage control link, which adopts a control strategy based on virtual impedance to obtain PWM reference voltage
(3): calculating the output active power P of the distributed power supply in the next period according to the voltage reference value and the output current value of the current periodDGAnd reactive power QDGAnd (3) controlling active power-frequency and reactive power-voltage amplitude in the step (1) of the next period.
The power control link of the distributed power supply in the step (1) and the voltage control link in the step (2) are respectively divided into two aspects of grid-connected operation of the micro-grid and isolated operation of the micro-grid:
the typical equivalent circuit structure of a single distributed power supply during the grid-connected operation of the micro-grid is shown in fig. 2(a), the distributed power supply is a single-phase inversion full-bridge topology consisting of four power switch modules, the distributed power supply is connected to a public connection point PoC through an LCL filter and is connected with the large grid, and the LCL filter is composed of a filter inductor L2Filter resistor R2Filter capacitor CfAnd (4) forming. V in FIG. 2(a)dcIs a DC side voltage, VPWMIs a pulse width modulated voltage, VcIs the filter capacitor voltage, I1Is the output current of the distributed power supply, I2Is the filter inductor current, CB is the static switch, VgridIs the grid voltage. The method only detects the output current I of the distributed power supply1And a DC side voltage VdcCompared with the traditional method, the output voltage of the distributed power supply does not need to be detected.
The structural block diagram of a single distributed power control system in a grid-connected mode of the invention is shown in fig. 2(b), and in a micro-grid-connected mode:
(1) in the power control link, the reference frequency f of the current period of the system can be obtained through droop control of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude Eref：
fref＝DP(Pref-PDG)
Wherein f isrefAnd ErefIs a reference voltageVia a sinusoidal signal generator to generate a reference voltage
PrefAnd QrefThe reference values of the active power and the reactive power can be set according to the capacity of the distributed power supply; dPIs a proportionality coefficient of active power-frequency; dqAnd KiProportional coefficient and integral coefficient of reactive power-voltage amplitude; pDGAnd QDGThe real-time active power and reactive power output by the distributed power supply are calculated by the following formula:
wherein,and I1_delayRespectively, a reference voltage value and an output current value of the last calculation period.
Through the steps, active power and reactive power can be obtained in a low-cost mode, and alternating voltage does not need to be measured.
(2) In order to avoid adverse effects of power grid harmonics on accuracy and stability of a control system, a virtual impedance control strategy is adopted in a voltage control link, harmonics of specific times are obtained through a resonant harmonic current observer, and a PWM reference voltage is calculated by connecting virtual resistors in series on an output side of a distributed power supply:
wherein R isv,hAs a virtual resistance at the h harmonic, ωcIs the cut-off frequency.
Through virtual impedance control, the physical characteristics of the distributed power supply are equivalent to that proper impedance is connected in series on a harmonic frequency band output by the distributed power supply, so that the distributed power supply has good harmonic interference resistance, and the stability and accuracy of a control system are ensured.
In the invention, two distributed power supplies in a microgrid are taken as a typical structure for analysis in a microgrid mode, the typical equivalent circuit structure is shown in fig. 3(a), the distributed power supplies are single-phase inversion full-bridge topologies consisting of four power switch modules, the distributed power supplies are connected with loads through LCL filters, the Load loads are nonlinear loads in the microgrid, a large number of nonlinear Load harmonics can be generated in an island mode, the LCL filters are composed of filter inductors L2Filter resistor R2Filter capacitor CfAnd (4) forming. V in FIG. 3(a)dcIs a DC side voltage, VPWMIs a pulse width modulated voltage, VcIs the filter capacitor voltage, I1Is a filter inductor current, I1While being the output current of the distributed power supply, CB being the static switch, ILoadIs the load current. The method still only detects the output current and the direct current voltage of the distributed power supply, and compared with the traditional method, the method does not need to detect the output voltage of the distributed power supply.
The structural block diagram of two distributed power control systems in the power grid island mode is shown in fig. 3(b), and in the micro-power grid island mode:
(1) in the power control link, the reference frequency f of the current period of the system can be obtained through droop control of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude Eref：
fref＝DP·PDG
Eref＝Dq·QDG
Wherein f isrefAnd ErefIs a reference voltageVia a sinusoidal signal generator to generate a reference voltage
DPIs a proportionality coefficient of active power-frequency; dqIs a proportional coefficient of reactive power-voltage amplitude; pDGAnd QDGThe real-time active power and reactive power output by the distributed power supply are calculated by the following formula:
wherein,and I1_delayRespectively, the voltage reference value and the output current value of the last calculation period.
Through the steps, active power and reactive power can be obtained in a low-cost mode, and alternating voltage does not need to be measured.
(2) In order to avoid the adverse effect of nonlinear load harmonic on the accuracy and stability of the control system, the voltage control link adopts virtual impedance control, and the voltage drop generated by the virtual impedanceComprises the following steps:
in the formula Rv,hIs a virtual resistance with harmonic order h, Lv,hIs a virtual reactance with harmonic order h.
To avoid the resonance problem of LCL filter, an appropriate high frequency gain is generated by using the active damping theory
RADActive damping at high frequencies, omegaHPFThe cut-off frequency of the high-pass filter.
Finally, the improved PWM reference voltage is:
through virtual impedance control, the physical characteristics of the distributed power supply are equivalent to that proper impedance is connected in series on a harmonic frequency band output by the distributed power supply, so that the distributed power supply has good harmonic interference resistance, and the stability and accuracy of a control system are ensured. And active damping is added, so that the resonance problem of the LCL filter is avoided.
After the calculation of the previous period is completed, calculating the active power P output by the distributed power supply of the next period according to the voltage reference value and the output current value of the current periodDGAnd reactive power QDG：
Wherein,and I1delayRespectively, the voltage reference value and the output current value of the last calculation period.
The invention verifies the correctness and the effectiveness of the method through tests:
matlab/simulink is used for building a simulation model shown in fig. 2(a) and 3(a), and parameters of a main circuit and a control system are detailed in a table 1.
| Circuit parameter | Numerical value |
| Rated voltage of power grid | 220V/50HZ |
| Voltage on the direct current side | 450V |
| LCL filtering link | L2＝＝6.5MH；R2＝8MΩ；Cf＝6UF； |
| Control parameter | Numerical value |
| Switching frequency | 10KHZ |
| Cut-off frequency of resonant filter | ωc＝2.5RAD/S |
| Rv,h(grid-connected mode) | 50Ω |
| Droop control (grid-connected mode) | DP＝1/500；DP＝1/1500；Ki＝1/500 |
| Rv,h(island mode) | 1Ω |
| Lv,h(island mode) | 5MH |
TABLE 1
Fig. 4(a), 4(b), and 4(c) are simulation waveforms of the distributed power system in the microgrid interconnection mode.
Fig. 4(a) is a simulated waveform diagram in the time period from 0.5s to 5s, only droop control is used in the initial stage, a virtual impedance link is added at 0.6s, and the active power is changed from 2500W to 3500W at 3.5 s. As can be seen from fig. 3(a), the virtual impedance does not cause any significant transient current, and the dynamic response of the power control is fast.
Fig. 4(b) and fig. 4(c) are graphs obtained by amplifying waveforms of the non-virtual impedance element and the virtual impedance element, and by comparing the results, the THD of the line current before the non-virtual impedance element is added is 11.41%, and the THD after the virtual impedance element is added is 4.36%.
Fig. 5(a), 5(b) and 5(c) are simulation waveforms of the parallel distributed power system in the microgrid island mode.
Fig. 5(a) shows waveforms in island operation. The amplitude and frequency of the reference voltage are set, and the virtual impedance link is default. As shown in fig. 5(b), the voltage amplitude is only 213V, which is significantly lower than the set value, while the THD is 8.51%. Meanwhile, the phenomenon of uneven current obviously exists due to mismatching of the output impedances of the current transformers 1 and 2.
In contrast, when the droop control strategy based on the virtual impedance is utilized, as shown in fig. 5(c), the voltage quality is improved by only 4.71%, the voltage amplitude is changed to 218V close to the set value of 220V, and the dual-channel power distribution can be better realized.
The droop control based on the virtual impedance can save a capacitor voltage detection part and a phase-locked loop, reduce the cost, reduce the operation burden of a control system and effectively inhibit harmonic waves, can better realize the distribution of power in an island mode, and is a distributed power supply variable control method which is worthy of popularization and is suitable for a micro-grid.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.
Claims (6)
1. A distributed power supply AC-free sensor control method based on virtual impedance is characterized in that: the method comprises the following steps:
(1): and (3) a power control link of the distributed power supply: the reference frequency f of the current period of the system can be obtained through the control link of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude ErefThen, the reference voltage can be obtained by a sine signal generator
(2): and a voltage control link: firstly, detecting the output current I of the distributed power supply1Obtaining PWM reference voltage by adopting control strategy based on virtual impedance
(3): by reference voltage of the current cycleAnd an output current I1Calculating the output active power P of the distributed power supply of the next periodDGAnd reactive power QDGThe control link of the active power-frequency and the reactive power-voltage amplitude in the step (1) of the next period is used;
in the step (3), PDGAnd QDGThe calculation formula of the active power and the reactive power output by the distributed power supply is as follows:
wherein,and I1_delayRespectively, the voltage reference value and the output current value of the previous period.
2. The virtual impedance-based distributed power supply ac-sensorless control method of claim 1, wherein: the distributed power supply power control link in the step (1) comprises a micro-grid-connected operation mode and a micro-grid island mode.
3. The virtual impedance-based distributed power supply ac-sensorless control method of claim 2, wherein:
in a micro-grid-connected operation mode, a power control link of the distributed power supply can obtain a reference frequency f of the current period of the system through droop control of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude Eref：
fref＝DP(Pref-PDG)
Wherein, PrefAnd QrefSetting reference values of active power and reactive power according to the capacity of the distributed power supply; dPIs a proportionality coefficient of active power-frequency; dqAnd KiProportional coefficient and integral coefficient of reactive power-voltage amplitude; pDGAnd QDGReal-time active power and reactive power output for the distributed power supply; f. ofrefAnd ErefIs a reference voltageVia a sinusoidal signal generator to generate a reference voltage
4. The virtual impedance-based distributed power supply ac-sensorless control method of claim 2, wherein: in a micro-grid island operation mode, a distributed power supply power control link can obtain the reference frequency f of the current period of the system through droop control of active power-frequency and reactive power-voltage amplituderefAnd a reference voltage amplitude Eref：
fref＝DP·PDG
Eref＝Dq·QDG
Wherein D isPIs a proportionality coefficient of active power-frequency; dqIs a proportional coefficient of reactive power-voltage amplitude; pDGAnd QDGReal-time active power and reactive power output for the distributed power supply; f. ofrefAnd ErefIs a reference voltageVia a sinusoidal signal generator to generate a reference voltage
5. The virtual impedance-based distributed power supply ac-sensorless control method of claim 1, wherein: under the grid-connected operation mode of a micro-grid, a voltage control link of a distributed power supply adopts a virtual impedance control strategy, harmonic waves of specific times are obtained through a resonance harmonic current observer, and PWM reference voltage is calculated by connecting virtual resistors in series at the output side of the distributed power supply:
wherein, I1For output current, h is the number of harmonics, Rv,hAs a virtual resistance at the h harmonic, ωcTo cut-off frequency, ωoTo output the voltage frequency, omegao＝2π·50＝100πrad/s。
6. The virtual impedance-based distributed power supply ac-free transmission method according to claim 1The sensor control method is characterized in that: in a micro-grid island operation mode, a voltage control link of a distributed power supply adopts virtual impedance control, and voltage drop generated by the virtual impedanceIs composed of
In the formula Rv,hIs a virtual resistance with harmonic order h, Lv,hA virtual reactance with harmonic number h;
to avoid the resonance problem of LCL filter, an appropriate high frequency gain is generated by using the active damping theory
RADActive damping at high frequencies, omegaHPFIs the cut-off frequency of a high-pass filter, I1The current value is the output current value of the current period;
finally, the improved PWM reference voltage is:
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| CN108574298A (en) * | 2017-12-21 | 2018-09-25 | 国网江苏省电力有限公司南京供电分公司 | A kind of alternating current-direct current mixing micro-capacitance sensor interface converter Control method based on virtual synchronous motor technology |
| CN109861271A (en) * | 2018-11-27 | 2019-06-07 | 国网山东省电力公司青岛供电公司 | Distributed control method and system under accumulation energy type micro-capacitance sensor island mode |
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