CA2950809A1 - Automatic droop control method for microgrid inverters based on small-signal stability analysis - Google Patents
Automatic droop control method for microgrid inverters based on small-signal stability analysis Download PDFInfo
- Publication number
- CA2950809A1 CA2950809A1 CA2950809A CA2950809A CA2950809A1 CA 2950809 A1 CA2950809 A1 CA 2950809A1 CA 2950809 A CA2950809 A CA 2950809A CA 2950809 A CA2950809 A CA 2950809A CA 2950809 A1 CA2950809 A1 CA 2950809A1
- Authority
- CA
- Canada
- Prior art keywords
- droop
- inverters
- voltage
- frequency
- curve
- 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
Classifications
-
- 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
-
- 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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
- Supply And Distribution Of Alternating Current (AREA)
Abstract
Disclosed is a microgrid inverter sagging automatic control method based on small-signal stability analysis. According to the control method, on the basis that the slope of a P-f sagging curve and the slope of the Q-V sagging curve are actively regulated, small-signal stability analysis is introduced, the feasibility of the slopes after the active regulation is verified, and no-deviating regulation of voltages and frequencies is implemented on the premise that the stability of a system is ensured. According to the present invention, for distributed generation under sagging control in an islanding state, the requirement of load changes is met by automatically regulating the slopes of the sagging curves and changing a reference active power value corresponding to a rated frequency in the sagging curves and a reference reactive power value corresponding to a rated voltage, and no-deviating frequency regulation and voltage regulation are implemented; the range of the slopes of the sagging curves allowed for stable operation of the system is obtained through the small-signal stability analysis, and when the sagging slopes are automatically regulated, the range needs to be met, and instability of the system caused by an operation of purely implementing the no-deviating frequency regulation and voltage regulation is avoided.
Description
J
AUTOMATIC DROOP CONTROL METHOD FOR MICROGRID
INVERTERS BASED ON SMALL-SIGNAL STABILITY ANALYSIS
Field of the Invention The invention relates to the field of microgrid control, and in particular to an automatic droop control method for microgrid inverters based on small-signal stability analysis.
Background of the Invention With the advent of energy crisis and the development requirements of energy saving and emission reduction, microgrids using lots of renewable energy are developing rapidly. Distributed power sources in microgrids are connected to the power grid by means of power electronic devices. When the microgrids are decoupled from the large grid to be in an islanding status in case of failures of the large grid, the distributed power sources within the microgrid systems are required to provide voltage and frequency supports to the microgrid systems; this objective is achieved extensively by simulating synchronous power source characteristic droop control, such as P-f and Q-V droop control, P-V and Q-f droop control and the like. However, with regard to the determined droop curves, operating points vary correspondingly when loads change; thus, no-deviating adjustment of voltage and frequency cannot be realized.
The existing method involves actively adjusting the slopes of the droop curves when the load changes cause changes in voltage and frequency, i.e., changing the value of the rated power PN corresponding to the rated frequency 50Hz in the P-f droop curve and the no-load voltage value in the Q-V droop curve, such that the voltage and the frequency of the system are recovered to the rated operating points to realize no-deviating adjustment. However, in this method, the limitations of constraint conditions of stable system operation to the droop slopes are not taken into account;
therefore, the steady-state operating points after automatic adjustment may cause instability in system operation.
It is disclosed in invention patent (application No. 201210107053.4) an island power , ' grid control and optimization method based on coordinate-rotated virtual impedance, which intends to design, for complex impedance characteristics in actual microgrids, the coordinate-rotated virtual impedance by using coordinate-rotated orthogonal transformation to improve the impedance characteristics of the microgrids.
However, this patent mainly aims at computational analysis on the steady-state operation of the microgrids and at optimization of the operation without considering the transient adjustment process of real-time fluctuation of new energy and loads of the microgrid systems within short time, and thus cannot realize no-deviating adjustment of voltage and frequency in the islanding microgrid systems.
Summary of the Invention An objective of the present invention is to solve the above problem and provides an automatic droop control method for a microgrid inverter based on small-signal stability analysis. On the basis of actively adjusting the slopes of P-f and Q-V droop curves, the control method introduces small-signal stability analysis to verify the feasibility of the actively adjusted slopes, thereby realizing no-deviating adjustment of voltage and frequency on the premise of guaranteeing system stability.
In order to achieve the above objective, the present invention employs the following technical solutions:
An automatic droop control method for microgrid inverters based on small-signal stability analysis includes the following steps:
(1) providing voltage and frequency supports by distributed power sources:
providing voltage and frequency supports by distributed power sources under droop control to an islanding microgrid, wherein the inverters are under P-f and Q-V control, i.e., adjusting a frequency of an output voltage of the inverters using active power and adjusting a magnitude of the output voltage of the inverters using reactive power; output characteristics of the inverters satisfy an active power-frequency droop characteristic curve and a reactive power-voltage droop characteristic curve;
AUTOMATIC DROOP CONTROL METHOD FOR MICROGRID
INVERTERS BASED ON SMALL-SIGNAL STABILITY ANALYSIS
Field of the Invention The invention relates to the field of microgrid control, and in particular to an automatic droop control method for microgrid inverters based on small-signal stability analysis.
Background of the Invention With the advent of energy crisis and the development requirements of energy saving and emission reduction, microgrids using lots of renewable energy are developing rapidly. Distributed power sources in microgrids are connected to the power grid by means of power electronic devices. When the microgrids are decoupled from the large grid to be in an islanding status in case of failures of the large grid, the distributed power sources within the microgrid systems are required to provide voltage and frequency supports to the microgrid systems; this objective is achieved extensively by simulating synchronous power source characteristic droop control, such as P-f and Q-V droop control, P-V and Q-f droop control and the like. However, with regard to the determined droop curves, operating points vary correspondingly when loads change; thus, no-deviating adjustment of voltage and frequency cannot be realized.
The existing method involves actively adjusting the slopes of the droop curves when the load changes cause changes in voltage and frequency, i.e., changing the value of the rated power PN corresponding to the rated frequency 50Hz in the P-f droop curve and the no-load voltage value in the Q-V droop curve, such that the voltage and the frequency of the system are recovered to the rated operating points to realize no-deviating adjustment. However, in this method, the limitations of constraint conditions of stable system operation to the droop slopes are not taken into account;
therefore, the steady-state operating points after automatic adjustment may cause instability in system operation.
It is disclosed in invention patent (application No. 201210107053.4) an island power , ' grid control and optimization method based on coordinate-rotated virtual impedance, which intends to design, for complex impedance characteristics in actual microgrids, the coordinate-rotated virtual impedance by using coordinate-rotated orthogonal transformation to improve the impedance characteristics of the microgrids.
However, this patent mainly aims at computational analysis on the steady-state operation of the microgrids and at optimization of the operation without considering the transient adjustment process of real-time fluctuation of new energy and loads of the microgrid systems within short time, and thus cannot realize no-deviating adjustment of voltage and frequency in the islanding microgrid systems.
Summary of the Invention An objective of the present invention is to solve the above problem and provides an automatic droop control method for a microgrid inverter based on small-signal stability analysis. On the basis of actively adjusting the slopes of P-f and Q-V droop curves, the control method introduces small-signal stability analysis to verify the feasibility of the actively adjusted slopes, thereby realizing no-deviating adjustment of voltage and frequency on the premise of guaranteeing system stability.
In order to achieve the above objective, the present invention employs the following technical solutions:
An automatic droop control method for microgrid inverters based on small-signal stability analysis includes the following steps:
(1) providing voltage and frequency supports by distributed power sources:
providing voltage and frequency supports by distributed power sources under droop control to an islanding microgrid, wherein the inverters are under P-f and Q-V control, i.e., adjusting a frequency of an output voltage of the inverters using active power and adjusting a magnitude of the output voltage of the inverters using reactive power; output characteristics of the inverters satisfy an active power-frequency droop characteristic curve and a reactive power-voltage droop characteristic curve;
(2) adjusting the droop curves: when a load change causes the frequency of the voltage to deviate from a rated value, automatically adjusting slopes of the droop =
curves by an adjuster;
curves by an adjuster;
(3) analyzing and verifying: obtaining upper and lower limits of the slopes of the droop curves by means of small-signal stability analysis, and verifying whether the adjusted slopes are within an allowed range via calculation by a comparator;
(4) executing operations: if the adjusted slopes are between the upper and lower limits and fall into the allowed range, recovering a stable operating point of the inverters to a rated voltage by the adjuster; if the adjusted slopes exceed one of the upper and lower limits, setting the droop curves according to a limiting value closest to the adjusted slopes.
In the step (1), an equation of the active power-frequency droop characteristic curve, namely the P-f droop curve, is f = fo¨ KpP , in which P represents the active power output by the inverters; f represents actual voltage frequency output by the inverters;
1.0 represents a no-load system frequency; Kp represents the droop slope of the P-f curve.
Besides, fn is system rated frequency 50Hz and corresponds to an active power reference value P.
In the step (1), an equation of the reactive power-voltage droop characteristic curve, namely a Q-V droop curve, is V = Vo ¨ KgQ , in which Q represents the reactive power output by the inverters; V represents the magnitude of an actual output voltage of the inverters; 170 represents a no-load system voltage; Kg represents the droop slope of the Q-V curve.
In the step (2), the slope Kp of the P-f curve is derived from a curve equation:
Kp = (A - f)I P, and during working, Kp is changed to a coefficient Kp, generated in real time according to system operating parameters:
K
p t-At 9 in which Pt_At represents the active power output by the inverters at time (t-At).
When the active power of loads is invariant, a system frequency is f=fn; when the active power of the loads increases at time t, the active power output by the inverters will increase to satisfy a system power balance; however, Kp, is calculated using the =
active power Pt-At of previous time At and thus kept unchanged, and the system frequency decreases; after a delay of time At, Kp starts to decrease until PP.
In other words, the active power reference value Pn corresponding to the rated frequency f0 in the P-f droop curve is increased by automatically decreasing the droop slope icp, such that the frequency of the output voltage is still fn even when the inverters generate more active power P. Nevertheless, the active power P output by the inverters cannot exceed a maximum Pmax allowed by normal operation of the inverters.
In the step (2), the droop slope Kg of the Q-V curve is derived from a curve equation:
K = (V, ¨V)1 Q . When the reactive power of the loads is invariant, the voltage is within a system allowed range [Vmin, Vrnax]; when the reactive power of the loads increases, the reactive power Q output by the inverters will increase to satisfy the system power balance; if the magnitude V of an outlet voltage exceeds [ Vmm, Vmad, Kg is changed to a coefficient Kcp generated in real time according to the system operating parameters:
v V
lµq1 = ¨ Qt-At After a delay of time At, Kg starts to decrease until Q=Qn. In other words, a reactive power reference value Qõ corresponding to a rated voltage G in the Q-V droop curve is increased by automatically decreasing the droop slope Kg, such that the magnitude of the output voltage is still kept within the range [V,,,n, Vmax] even when the inverters output more reactive power Q. Nevertheless, the reactive power Q output by the inverters cannot exceed a maximum Q. allowed by normal operation of the inverters.
In the step (3), the automatically adjusted slopes Kp, Kg of the droop curve satisfy the slope ranges [Kp miiõ lc max], [Kg niln, Kg mad of the droop curves obtained through the small-signal stability analysis. A microgrid system composed of the distributed power sources and the loads is described by n first-order nonlinear ordinary differential algebraic equations: , for an autonomous system: &y=f(x,u). Small disturbance is applied to the system and the equation is linearized into:
g37 = Ax I- Hu. x(t0) = x.
y¨Cx+Du, in which A, B, C, D are coefficient matrices. By an automatic control theory, when the characteristic roots 2=u+jco of the matrix A have negative real parts, the system has damped oscillation and then recovers to be stable. When other variables of the system are determined, 2 is a function of the droop coefficients Kp, Kg: 2=f(Kp,Kq).
The real part a of 2 is set below zero, and then the ranges [lc mm, Kp mad, [Kg imm konad of the slopes K, Kg of the droop curves are obtained.
The present invention has the following advantages:
for the distributed power sources under droop control in the islanding status, the active power reference value corresponding to the rated frequency and the reactive power reference value corresponding to the rated voltage in the droop curves are varied by automatically adjusting the slopes of the droop curves, thus meeting the requirements of the load changes and realizing no-deviating adjustment of frequency and voltage; besides, the slope ranges of the droop curves allowed by stable system operation are obtained through the small-signal stability analysis; the ranges should be satisfied during the automatic adjustment of the droop slopes so as to prevent system instability caused by unilateral realization of no-deviating adjustment of frequency and voltage.
Brief Description of the Drawings Fig. 1 is a structure diagram of a microgrid system;
Fig. 2 is a Thevenin's equivalent circuit of two inverters connected in parallel;
Fig. 3 is a schematic diagram of a P-f droop curve;
Fig. 4 is a schematic diagram of a Q-V droop curve;
Fig. 5 is a schematic diagram of the P-f droop curve during Kp adjustment;
Fig. 6 is a schematic diagram of the Q-V droop curve during Kg adjustment;
Fig. 7 is a structure diagram of a microgrid example for small-signal stability analysis;
Fig. 8 is a control block diagram of the present control method;
Fig. 9 are result figures based on PSCAD/EMTDC simulation software.
In the drawings, a represents active power generated by distributed power sources in the microgrid; b represents reactive power generated by the distributed power sources;
c represents the voltage of a microgrid bus; d represents the frequency of the microgrid system.
Detailed Description of the Embodiments The present invention will be further described by combining the accompanying drawings with embodiments.
An automatic droop control method for microgrid inverters based on small-signal stability analysis comprises the following steps:
Step (1): distributed power sources under droop control provide voltage and frequency supports to an islanding microgrid. Specific operations are as shown in Fig.
1. As a general structure of the microgrid, the distributed power source DG1 is under droop control, while DG2 and DG3 are under PQ control. When the microgrid is in a grid-connected operation mode, DG1 is in a grid-connected constant power status under droop control. When the microgrid is decoupled from a power distribution network to be in an islanding status due to power distribution network failures or other reasons, DG1 provides the voltage and frequency supports to the microgrid system under droop control.
As shown in Fig. 2, the Thevenin's equivalent circuit of two inverters connected in parallel is illustrated. A relation between power and impedance transmitted on the line can be derived:
V,U0 _____ cos(-8,)--- ,--8 ,) ¨ cos 6),(1) z, z, v u U2 Q Z, Z, ¨ sin(0, ) sin 0, (2) The line impedance angle is very small and it thus can be considered approximately that sin 8 8 and cos g R-.; 1. If the output impedance of the inverters is controlled to be inductive to keep the sum of the output impedance of the inverters and the line impedance still inductive, i.e., X0 R, ZzjX, then the following equations can be obtained:
P, =Vo,Uog, I X, (3) Q, = (Vo,t ¨UO2)1 X, (4) Further, the droop characteristics of frequency and voltage may be obtained as follows:
f, = KpP, (5) = Vo ¨ KqQ, (6) In other words, the frequency of the voltage across the ports of the inverters is approximately in a linear relation to active power, and the magnitude of the voltage is approximately in a linear relation to reactive power. Thus, P-f and Q-V droop characteristics are designed; the active power output by the inverters is adjusted to adjust the frequency, while the reactive power output by the inverters is adjusted to adjust the magnitude of the voltage.
As shown in Fig. 3, fo represents a no-load frequency; fn represents the rated frequency 50Hz of the system and corresponds to the reference active power Pn in the P-f droop curve; f represents the frequency of the actual output voltage of the inverters and corresponds to the actual active power P output by the inverters; Kp represents the droop slope of the P-f curve:
K =(fo¨ f) P (7) As shown in Fig. 4, Vo therein represents a no-load voltage; V,õõ and Vmax represent minimal and maximal voltages corresponding to the maximum reactive power output by the inverters and the maximum reactive power absorbed by the inverters, respectively; V represents the magnitude of the actual output voltage of the inverters and corresponding to the actual reactive power Q output by the inverters; Kg represents the droop slope of the Q-V curve:
K (V0 ¨V) Q (8) Step (2): When a change of loads occurs, the slopes of the droop curves are adjusted to realize no-deviating adjustment of frequency and voltage.
When the active load of the microgrid increases, the active power P output by the DG1 will increase to satisfy power balance.
As can be seen from Fig. 3, when the active power output by DG1 increases, the frequency f of the output voltage will decrease. If the droop slopes are adjusted approximately, the operating point of DG1 can be translated back to the rated frequency fn. Stated another way, as shown in Fig. 5, DG1 initially operates at point A
in accordance with the droop curve 1; after the output active power increases, the frequency drops to f and DG1 operates at point B; the slope Kp of the droop curve is adjusted such that DG1 operates in accordance with the droop curve 2, and then the operating point turns to C and the output frequency is recovered to fn.
When the reactive load of the microgrid increases, the reactive power Q output by DG1 will increase to satisfy power balance.
As can be seen from Fig. 4, the magnitude of the output voltage of DG1 will decrease and is prone to exceed the system allowed limit range [Vmin, Vniax]. If the droop slope is adjusted approximately, as shown in Fig. 6, DG1 initially operates in accordance with the droop curve 1, and has the minimal voltage value Vminl correspondingly when generating the maximum reactive power and the maximum voltage value Vmaxi correspondingly when absorbing the maximum reactive power. After the output reactive power increases, the magnitude of the output voltage decreases to exceed the system allowed range; then, the droop slope K4 is adjusted to result in an increase in the corresponding minimal voltage when the maximum reactive power is generated;
as a result, the magnitude of the output voltage falls back into the allowed range.
Step (3): the above automatically adjusted slopes are verified using small-signal stability analysis.
Taking the microgrid shown in Fig. 7 as an example, the status equation of the system is established as follows:
%
1DQ A mg XINV
iline ilkeDQ
iloadDQ = itoadDiz (9), in which _ -A, + /3/Nv RN MiNvCiNv, BiNv RNMNET BiNvRNMload Amg = B1NET RN MEW CINVc B2 NET CINV ro ANET + B1NET RN MNET B1NET RN
Mload _B1LOAD RN MINV CINVe + B2 LOAD CINV co B1 LOAD RN
MNET Aload + B1LOADRNMload _ Amg is the characteristic matrix of the system.
The characteristic roots of Amg are solved with the real parts set to be negative, and then the stable ranges of the droop coefficients of the microgrid system are as follows:
1.57x 10-5 < Kp < 1.90x 10-4 3.17x 104 < Kg < 4.79x 10-3 Step (4): determination and adjustment setting: if the slopes are within the allowed ranges, no-deviating adjustment of frequency and voltage can be realized; or otherwise, the droop curves are set according to the allowed maximum or minimal slopes obtained through the small-signal stability analysis.
As shown in Fig. 8, a microsource is connected with a microgrid bus by means of the inverters, an LC filter and a line. The outlet voltage and current of the filter are measured to obtain the output active power, the output reactive power, and the magnitude and frequency of the voltage. D represents a delay link with a delay of a time interval t. The solving boxes of Kp and Kg are automatic solving processes for realizing no-deviating adjustment of frequency and voltage of the islanding microgrid;
then, the small-signal stability analysis is performed to limit the magnitude.
V
represents the magnitude of the outlet voltage of the LC filter. PI represents a proportional-integral controller to improve the dynamic response characteristic of the magnitude of the voltage. Vm and 6m represent a space vector magnitude of three-phase output phase voltage synthesis and a phase angle reference value required for SPWM (Sinusoidal Pulse Width Modulation), respectively.
During working, the active power and reactive power output by the inverters are measured. After a delay of time At, the automatically adjustable droop coefficients Kp, =
=
Kg may be calculated. The system is modeled by the small-signal stability analysis, and then the slope ranges [Kp mm, Kp max] and [Kg nun, Kg max] of the droop curves capable of keeping the system stable may be calculated to limit the magnitudes of the previously calculated K, Kg. Reference voltage and frequency values for the inverters are calculated according to equations (5), (6) to further generate control pulses. As generation of the control pulses from the reference voltage and frequency is the prior art, it is not redundantly described herein.
PSCAD modeling is carried out on the microgrid as shown in Fig. 7, wherein DG1 is an energy storage system to which the automatic droop control method for the inverters with consideration to the small-signal stability analysis of the present patent is employed; DG2 is a photovoltaic power generation system to which constant power control may be employed within 12 seconds of simulation on the assumption of invariant illumination; DG3 is a wind power generation system to which constant power control may be employed within 12 seconds of simulation on the assumption of invariant wind speed.
At the fourth second, 10kW step pulse load is applied, and three distributed power sources output the active power, the reactive power, a bus voltage and a system frequency, as shown in Fig. 9.
As can be seen from Fig. 9, the automatic droop control method for the microgrid inverters based on the small-signal stability analysis has good adjustability:
for the distributed power sources under droop control in the islanding status, the reference active power value corresponding to the rated frequency and the reference reactive power value corresponding to the rated voltage in the droop curves are varied by automatically adjusting the slopes of the droop curves, thus meeting the requirements of the load changes and realizing no-deviating adjustment of frequency and voltage;
besides, the slope ranges of the droop curves allowed by stable system operation are obtained through the small-signal stability analysis; the ranges should be satisfied during the automatic adjustment of the droop slopes so as to prevent system instability caused by unilateral realization of no-deviating adjustment of frequency and voltage.
, t t Although the specific embodiments of the present invention are described above in conjunction with the accompanying drawings, they are not limit to the protection scope of the present invention. It will be understood by those skilled in the art that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution of the present invention still fall into the protection scope of the prevent invention.
In the step (1), an equation of the active power-frequency droop characteristic curve, namely the P-f droop curve, is f = fo¨ KpP , in which P represents the active power output by the inverters; f represents actual voltage frequency output by the inverters;
1.0 represents a no-load system frequency; Kp represents the droop slope of the P-f curve.
Besides, fn is system rated frequency 50Hz and corresponds to an active power reference value P.
In the step (1), an equation of the reactive power-voltage droop characteristic curve, namely a Q-V droop curve, is V = Vo ¨ KgQ , in which Q represents the reactive power output by the inverters; V represents the magnitude of an actual output voltage of the inverters; 170 represents a no-load system voltage; Kg represents the droop slope of the Q-V curve.
In the step (2), the slope Kp of the P-f curve is derived from a curve equation:
Kp = (A - f)I P, and during working, Kp is changed to a coefficient Kp, generated in real time according to system operating parameters:
K
p t-At 9 in which Pt_At represents the active power output by the inverters at time (t-At).
When the active power of loads is invariant, a system frequency is f=fn; when the active power of the loads increases at time t, the active power output by the inverters will increase to satisfy a system power balance; however, Kp, is calculated using the =
active power Pt-At of previous time At and thus kept unchanged, and the system frequency decreases; after a delay of time At, Kp starts to decrease until PP.
In other words, the active power reference value Pn corresponding to the rated frequency f0 in the P-f droop curve is increased by automatically decreasing the droop slope icp, such that the frequency of the output voltage is still fn even when the inverters generate more active power P. Nevertheless, the active power P output by the inverters cannot exceed a maximum Pmax allowed by normal operation of the inverters.
In the step (2), the droop slope Kg of the Q-V curve is derived from a curve equation:
K = (V, ¨V)1 Q . When the reactive power of the loads is invariant, the voltage is within a system allowed range [Vmin, Vrnax]; when the reactive power of the loads increases, the reactive power Q output by the inverters will increase to satisfy the system power balance; if the magnitude V of an outlet voltage exceeds [ Vmm, Vmad, Kg is changed to a coefficient Kcp generated in real time according to the system operating parameters:
v V
lµq1 = ¨ Qt-At After a delay of time At, Kg starts to decrease until Q=Qn. In other words, a reactive power reference value Qõ corresponding to a rated voltage G in the Q-V droop curve is increased by automatically decreasing the droop slope Kg, such that the magnitude of the output voltage is still kept within the range [V,,,n, Vmax] even when the inverters output more reactive power Q. Nevertheless, the reactive power Q output by the inverters cannot exceed a maximum Q. allowed by normal operation of the inverters.
In the step (3), the automatically adjusted slopes Kp, Kg of the droop curve satisfy the slope ranges [Kp miiõ lc max], [Kg niln, Kg mad of the droop curves obtained through the small-signal stability analysis. A microgrid system composed of the distributed power sources and the loads is described by n first-order nonlinear ordinary differential algebraic equations: , for an autonomous system: &y=f(x,u). Small disturbance is applied to the system and the equation is linearized into:
g37 = Ax I- Hu. x(t0) = x.
y¨Cx+Du, in which A, B, C, D are coefficient matrices. By an automatic control theory, when the characteristic roots 2=u+jco of the matrix A have negative real parts, the system has damped oscillation and then recovers to be stable. When other variables of the system are determined, 2 is a function of the droop coefficients Kp, Kg: 2=f(Kp,Kq).
The real part a of 2 is set below zero, and then the ranges [lc mm, Kp mad, [Kg imm konad of the slopes K, Kg of the droop curves are obtained.
The present invention has the following advantages:
for the distributed power sources under droop control in the islanding status, the active power reference value corresponding to the rated frequency and the reactive power reference value corresponding to the rated voltage in the droop curves are varied by automatically adjusting the slopes of the droop curves, thus meeting the requirements of the load changes and realizing no-deviating adjustment of frequency and voltage; besides, the slope ranges of the droop curves allowed by stable system operation are obtained through the small-signal stability analysis; the ranges should be satisfied during the automatic adjustment of the droop slopes so as to prevent system instability caused by unilateral realization of no-deviating adjustment of frequency and voltage.
Brief Description of the Drawings Fig. 1 is a structure diagram of a microgrid system;
Fig. 2 is a Thevenin's equivalent circuit of two inverters connected in parallel;
Fig. 3 is a schematic diagram of a P-f droop curve;
Fig. 4 is a schematic diagram of a Q-V droop curve;
Fig. 5 is a schematic diagram of the P-f droop curve during Kp adjustment;
Fig. 6 is a schematic diagram of the Q-V droop curve during Kg adjustment;
Fig. 7 is a structure diagram of a microgrid example for small-signal stability analysis;
Fig. 8 is a control block diagram of the present control method;
Fig. 9 are result figures based on PSCAD/EMTDC simulation software.
In the drawings, a represents active power generated by distributed power sources in the microgrid; b represents reactive power generated by the distributed power sources;
c represents the voltage of a microgrid bus; d represents the frequency of the microgrid system.
Detailed Description of the Embodiments The present invention will be further described by combining the accompanying drawings with embodiments.
An automatic droop control method for microgrid inverters based on small-signal stability analysis comprises the following steps:
Step (1): distributed power sources under droop control provide voltage and frequency supports to an islanding microgrid. Specific operations are as shown in Fig.
1. As a general structure of the microgrid, the distributed power source DG1 is under droop control, while DG2 and DG3 are under PQ control. When the microgrid is in a grid-connected operation mode, DG1 is in a grid-connected constant power status under droop control. When the microgrid is decoupled from a power distribution network to be in an islanding status due to power distribution network failures or other reasons, DG1 provides the voltage and frequency supports to the microgrid system under droop control.
As shown in Fig. 2, the Thevenin's equivalent circuit of two inverters connected in parallel is illustrated. A relation between power and impedance transmitted on the line can be derived:
V,U0 _____ cos(-8,)--- ,--8 ,) ¨ cos 6),(1) z, z, v u U2 Q Z, Z, ¨ sin(0, ) sin 0, (2) The line impedance angle is very small and it thus can be considered approximately that sin 8 8 and cos g R-.; 1. If the output impedance of the inverters is controlled to be inductive to keep the sum of the output impedance of the inverters and the line impedance still inductive, i.e., X0 R, ZzjX, then the following equations can be obtained:
P, =Vo,Uog, I X, (3) Q, = (Vo,t ¨UO2)1 X, (4) Further, the droop characteristics of frequency and voltage may be obtained as follows:
f, = KpP, (5) = Vo ¨ KqQ, (6) In other words, the frequency of the voltage across the ports of the inverters is approximately in a linear relation to active power, and the magnitude of the voltage is approximately in a linear relation to reactive power. Thus, P-f and Q-V droop characteristics are designed; the active power output by the inverters is adjusted to adjust the frequency, while the reactive power output by the inverters is adjusted to adjust the magnitude of the voltage.
As shown in Fig. 3, fo represents a no-load frequency; fn represents the rated frequency 50Hz of the system and corresponds to the reference active power Pn in the P-f droop curve; f represents the frequency of the actual output voltage of the inverters and corresponds to the actual active power P output by the inverters; Kp represents the droop slope of the P-f curve:
K =(fo¨ f) P (7) As shown in Fig. 4, Vo therein represents a no-load voltage; V,õõ and Vmax represent minimal and maximal voltages corresponding to the maximum reactive power output by the inverters and the maximum reactive power absorbed by the inverters, respectively; V represents the magnitude of the actual output voltage of the inverters and corresponding to the actual reactive power Q output by the inverters; Kg represents the droop slope of the Q-V curve:
K (V0 ¨V) Q (8) Step (2): When a change of loads occurs, the slopes of the droop curves are adjusted to realize no-deviating adjustment of frequency and voltage.
When the active load of the microgrid increases, the active power P output by the DG1 will increase to satisfy power balance.
As can be seen from Fig. 3, when the active power output by DG1 increases, the frequency f of the output voltage will decrease. If the droop slopes are adjusted approximately, the operating point of DG1 can be translated back to the rated frequency fn. Stated another way, as shown in Fig. 5, DG1 initially operates at point A
in accordance with the droop curve 1; after the output active power increases, the frequency drops to f and DG1 operates at point B; the slope Kp of the droop curve is adjusted such that DG1 operates in accordance with the droop curve 2, and then the operating point turns to C and the output frequency is recovered to fn.
When the reactive load of the microgrid increases, the reactive power Q output by DG1 will increase to satisfy power balance.
As can be seen from Fig. 4, the magnitude of the output voltage of DG1 will decrease and is prone to exceed the system allowed limit range [Vmin, Vniax]. If the droop slope is adjusted approximately, as shown in Fig. 6, DG1 initially operates in accordance with the droop curve 1, and has the minimal voltage value Vminl correspondingly when generating the maximum reactive power and the maximum voltage value Vmaxi correspondingly when absorbing the maximum reactive power. After the output reactive power increases, the magnitude of the output voltage decreases to exceed the system allowed range; then, the droop slope K4 is adjusted to result in an increase in the corresponding minimal voltage when the maximum reactive power is generated;
as a result, the magnitude of the output voltage falls back into the allowed range.
Step (3): the above automatically adjusted slopes are verified using small-signal stability analysis.
Taking the microgrid shown in Fig. 7 as an example, the status equation of the system is established as follows:
%
1DQ A mg XINV
iline ilkeDQ
iloadDQ = itoadDiz (9), in which _ -A, + /3/Nv RN MiNvCiNv, BiNv RNMNET BiNvRNMload Amg = B1NET RN MEW CINVc B2 NET CINV ro ANET + B1NET RN MNET B1NET RN
Mload _B1LOAD RN MINV CINVe + B2 LOAD CINV co B1 LOAD RN
MNET Aload + B1LOADRNMload _ Amg is the characteristic matrix of the system.
The characteristic roots of Amg are solved with the real parts set to be negative, and then the stable ranges of the droop coefficients of the microgrid system are as follows:
1.57x 10-5 < Kp < 1.90x 10-4 3.17x 104 < Kg < 4.79x 10-3 Step (4): determination and adjustment setting: if the slopes are within the allowed ranges, no-deviating adjustment of frequency and voltage can be realized; or otherwise, the droop curves are set according to the allowed maximum or minimal slopes obtained through the small-signal stability analysis.
As shown in Fig. 8, a microsource is connected with a microgrid bus by means of the inverters, an LC filter and a line. The outlet voltage and current of the filter are measured to obtain the output active power, the output reactive power, and the magnitude and frequency of the voltage. D represents a delay link with a delay of a time interval t. The solving boxes of Kp and Kg are automatic solving processes for realizing no-deviating adjustment of frequency and voltage of the islanding microgrid;
then, the small-signal stability analysis is performed to limit the magnitude.
V
represents the magnitude of the outlet voltage of the LC filter. PI represents a proportional-integral controller to improve the dynamic response characteristic of the magnitude of the voltage. Vm and 6m represent a space vector magnitude of three-phase output phase voltage synthesis and a phase angle reference value required for SPWM (Sinusoidal Pulse Width Modulation), respectively.
During working, the active power and reactive power output by the inverters are measured. After a delay of time At, the automatically adjustable droop coefficients Kp, =
=
Kg may be calculated. The system is modeled by the small-signal stability analysis, and then the slope ranges [Kp mm, Kp max] and [Kg nun, Kg max] of the droop curves capable of keeping the system stable may be calculated to limit the magnitudes of the previously calculated K, Kg. Reference voltage and frequency values for the inverters are calculated according to equations (5), (6) to further generate control pulses. As generation of the control pulses from the reference voltage and frequency is the prior art, it is not redundantly described herein.
PSCAD modeling is carried out on the microgrid as shown in Fig. 7, wherein DG1 is an energy storage system to which the automatic droop control method for the inverters with consideration to the small-signal stability analysis of the present patent is employed; DG2 is a photovoltaic power generation system to which constant power control may be employed within 12 seconds of simulation on the assumption of invariant illumination; DG3 is a wind power generation system to which constant power control may be employed within 12 seconds of simulation on the assumption of invariant wind speed.
At the fourth second, 10kW step pulse load is applied, and three distributed power sources output the active power, the reactive power, a bus voltage and a system frequency, as shown in Fig. 9.
As can be seen from Fig. 9, the automatic droop control method for the microgrid inverters based on the small-signal stability analysis has good adjustability:
for the distributed power sources under droop control in the islanding status, the reference active power value corresponding to the rated frequency and the reference reactive power value corresponding to the rated voltage in the droop curves are varied by automatically adjusting the slopes of the droop curves, thus meeting the requirements of the load changes and realizing no-deviating adjustment of frequency and voltage;
besides, the slope ranges of the droop curves allowed by stable system operation are obtained through the small-signal stability analysis; the ranges should be satisfied during the automatic adjustment of the droop slopes so as to prevent system instability caused by unilateral realization of no-deviating adjustment of frequency and voltage.
, t t Although the specific embodiments of the present invention are described above in conjunction with the accompanying drawings, they are not limit to the protection scope of the present invention. It will be understood by those skilled in the art that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution of the present invention still fall into the protection scope of the prevent invention.
Claims (5)
1. An automatic droop control method for microgrid inverters based on small-signal stability analysis, comprising the following steps:
(1) providing voltage and frequency supports by distributed power sources:
providing voltage and frequency supports by distributed power sources under droop control to an islanding microgrid, wherein the inverters are under P-f and Q-V control, i.e., adjusting a frequency of an output voltage of the inverters using active power and adjusting a magnitude of the output voltage of the inverters using reactive power; output characteristics of the inverters satisfy an active power-frequency droop characteristic curve and a reactive power-voltage droop characteristic curve;
(2) adjusting the droop curves: when a load change causes the frequency of the voltage to deviate from a rated value, automatically adjusting slopes of the droop curves by an adjuster;
(3) analyzing and verifying: obtaining upper and lower limits of the slopes of the droop curves by means of small-signal stability analysis, and verifying whether the adjusted slopes are within an allowed range via calculation by a comparator;
(4) executing operations: if the adjusted slopes are between the upper and lower limits and fall into the allowed range, recovering a stable operating point of the inverters to a rated voltage by the adjuster; if the adjusted slopes exceed one of the upper and lower limits, setting the droop curves according to a limiting value closest to the adjusted slopes;
wherein in the step (2), the slope K p of a P-f curve is derived from a curve equation:
K p = (.function.o ¨ .function.)/ P , and during working, K p is changed to a coefficient K pi generated in real time according to system operating parameters:
in which P t-.increment.t represents the active power output by the inverters at time (t-.increment.t);
when the active power of loads is invariant, a system frequency is .function.=.function. n; when the active power of the loads increases at time t, the active power output by the inverters will increase to satisfy a system power balance; however, K pi is calculated using the active power Pt-.increment.t of previous time .increment.t and thus kept unchanged, and the system frequency decreases; after a delay of time .increment.t, K p starts to decrease until P=P n; in other words, an active power reference value P n corresponding to a rated frequency .function.n in the P-f droop curve is increased by automatically decreasing the droop slope K p, such that the frequency of the output voltage is still .increment.n even when the inverters generate more active power P; nevertheless, the active power P output by the inverters cannot exceed a maximum P max allowed by normal operation of the inverters.
(1) providing voltage and frequency supports by distributed power sources:
providing voltage and frequency supports by distributed power sources under droop control to an islanding microgrid, wherein the inverters are under P-f and Q-V control, i.e., adjusting a frequency of an output voltage of the inverters using active power and adjusting a magnitude of the output voltage of the inverters using reactive power; output characteristics of the inverters satisfy an active power-frequency droop characteristic curve and a reactive power-voltage droop characteristic curve;
(2) adjusting the droop curves: when a load change causes the frequency of the voltage to deviate from a rated value, automatically adjusting slopes of the droop curves by an adjuster;
(3) analyzing and verifying: obtaining upper and lower limits of the slopes of the droop curves by means of small-signal stability analysis, and verifying whether the adjusted slopes are within an allowed range via calculation by a comparator;
(4) executing operations: if the adjusted slopes are between the upper and lower limits and fall into the allowed range, recovering a stable operating point of the inverters to a rated voltage by the adjuster; if the adjusted slopes exceed one of the upper and lower limits, setting the droop curves according to a limiting value closest to the adjusted slopes;
wherein in the step (2), the slope K p of a P-f curve is derived from a curve equation:
K p = (.function.o ¨ .function.)/ P , and during working, K p is changed to a coefficient K pi generated in real time according to system operating parameters:
in which P t-.increment.t represents the active power output by the inverters at time (t-.increment.t);
when the active power of loads is invariant, a system frequency is .function.=.function. n; when the active power of the loads increases at time t, the active power output by the inverters will increase to satisfy a system power balance; however, K pi is calculated using the active power Pt-.increment.t of previous time .increment.t and thus kept unchanged, and the system frequency decreases; after a delay of time .increment.t, K p starts to decrease until P=P n; in other words, an active power reference value P n corresponding to a rated frequency .function.n in the P-f droop curve is increased by automatically decreasing the droop slope K p, such that the frequency of the output voltage is still .increment.n even when the inverters generate more active power P; nevertheless, the active power P output by the inverters cannot exceed a maximum P max allowed by normal operation of the inverters.
2. The automatic droop control method for microgrid inverters based on small-signal stability analysis of claim 1, wherein in the step (1), an equation of the active power-frequency droop characteristic curve, namely the P-f droop curve, is .function. = .function.o¨K p P , in which P represents the active power output by the inverters; f represents an actual voltage frequency output by the inverters; f0 represents a no-load system frequency; K p represents the droop slope of the P-f curve; besides, .function.n is system rated frequency 50Hz and corresponds to the active power reference value P n.
3. The automatic droop control method for microgrid inverters based on small-signal stability analysis of claim 1, wherein in the step (1), an equation of the reactive power-voltage droop characteristic curve, namely a Q-V droop curve, is V =V0 ¨ K q Q in which Q represents the reactive power output by the inverters; V
represents the magnitude of an actual output voltage of the inverters; V0 represents a no-load system voltage; K q represents the droop slope of the Q-V curve.
represents the magnitude of an actual output voltage of the inverters; V0 represents a no-load system voltage; K q represents the droop slope of the Q-V curve.
4. The automatic droop control method for microgrid inverters based on small-signal stability analysis of claim 1, wherein in the step (2), the droop slope K q of the Q-V
curve is derived from a curve equation: K q = (V 0 ¨ V)/ Q; when the reactive power of the loads is invariant, the voltage is within a system allowed range [ V min, V max]; when the reactive power of the loads increases, the reactive power Q output by the inverters will increase to satisfy the system power balance; if the magnitude V of an outlet voltage exceeds [ V min, V max], K q is changed to a coefficient K qi generated in real time according to the system operating parameters:
after a delay of time .increment.t, K q starts to decrease until Q=Q n; in other words, a reactive power reference value Q n corresponding to a rated voltage V n in the Q-V
droop curve is increased by automatically decreasing the droop slope K q, such that the magnitude of the output voltage is still kept within the range [V min, V max] even when the inverters output more reactive power Q; nevertheless, the reactive power Q output by the inverters cannot exceed a maximum Q max allowed by normal operation of the inverters.
curve is derived from a curve equation: K q = (V 0 ¨ V)/ Q; when the reactive power of the loads is invariant, the voltage is within a system allowed range [ V min, V max]; when the reactive power of the loads increases, the reactive power Q output by the inverters will increase to satisfy the system power balance; if the magnitude V of an outlet voltage exceeds [ V min, V max], K q is changed to a coefficient K qi generated in real time according to the system operating parameters:
after a delay of time .increment.t, K q starts to decrease until Q=Q n; in other words, a reactive power reference value Q n corresponding to a rated voltage V n in the Q-V
droop curve is increased by automatically decreasing the droop slope K q, such that the magnitude of the output voltage is still kept within the range [V min, V max] even when the inverters output more reactive power Q; nevertheless, the reactive power Q output by the inverters cannot exceed a maximum Q max allowed by normal operation of the inverters.
5. The automatic droop control method for microgrid inverters based on small-signal stability analysis of claim 1, wherein in the step (3), the automatically adjusted slopes K p, K g of the droop curve satisfy the slope ranges [K p min, K p max], [K q min, K q max] of the droop curves obtained through the small-signal stability analysis; a microgrid system composed of the distributed power sources and the loads is described by n first-order nonlinear ordinary differential algebraic equations: , for an autonomous system:
&y=f(x,u); small disturbance is applied to the system and the equation is linearized into:
&y = Ax Bu, x(t o) = x o y=Cx+Du in which A, B, C, D are coefficient matrices; by an automatic control theory, when the characteristic roots .lambda.=.sigma.+j.omega. of the matrix A have negative real parts, the system has damped oscillation and then recovers to be stable; when other variables of the system are determined, A is a function of the droop coefficients K p, K q:
.lambda.=.function.(Kp,Kq);
the real part .sigma. of .lambda. is set below zero, and then the ranges [K p min, K p max], [K q mm, Kg max]
of the slopes K p, K q of the droop curves are obtained.
&y=f(x,u); small disturbance is applied to the system and the equation is linearized into:
&y = Ax Bu, x(t o) = x o y=Cx+Du in which A, B, C, D are coefficient matrices; by an automatic control theory, when the characteristic roots .lambda.=.sigma.+j.omega. of the matrix A have negative real parts, the system has damped oscillation and then recovers to be stable; when other variables of the system are determined, A is a function of the droop coefficients K p, K q:
.lambda.=.function.(Kp,Kq);
the real part .sigma. of .lambda. is set below zero, and then the ranges [K p min, K p max], [K q mm, Kg max]
of the slopes K p, K q of the droop curves are obtained.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310559711.8A CN103545810B (en) | 2013-11-12 | 2013-11-12 | Microgrid inverter sagging automatic control method based on small signal stability analysis |
| CN201310559711.8 | 2013-11-12 | ||
| PCT/CN2014/079930 WO2015070602A1 (en) | 2013-11-12 | 2014-06-16 | Microgrid inverter sagging automatic control method based on small-signal stability analysis |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2950809A1 true CA2950809A1 (en) | 2015-05-21 |
| CA2950809C CA2950809C (en) | 2019-02-12 |
Family
ID=49969002
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2950809A Expired - Fee Related CA2950809C (en) | 2013-11-12 | 2014-06-16 | Automatic droop control method for microgrid inverters based on small-signal stability analysis |
Country Status (3)
| Country | Link |
|---|---|
| CN (1) | CN103545810B (en) |
| CA (1) | CA2950809C (en) |
| WO (1) | WO2015070602A1 (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102017114306A1 (en) * | 2017-06-28 | 2019-01-03 | Sma Solar Technology Ag | METHOD FOR OPERATING AN ISLAND NETWORK AND ISLAND NETWORK |
| EP3496225A1 (en) * | 2017-12-11 | 2019-06-12 | General Electric Company | Method and system for droop control of power systems |
| CN110311375A (en) * | 2019-07-29 | 2019-10-08 | 东北大学 | A kind of micro-capacitance sensor transient stability control method containing more virtual synchronous machines |
| CN110460112A (en) * | 2019-09-18 | 2019-11-15 | 东北大学 | A kind of micro-capacitance sensor droop control method based on the control of power deviation amount consistency |
| CN112510749A (en) * | 2020-08-20 | 2021-03-16 | 国网山西省电力公司电力科学研究院 | Droop control method with network self-adaption capability in micro-grid island mode |
| CN113675895A (en) * | 2021-08-06 | 2021-11-19 | 阳光电源（上海）有限公司 | Power distribution method and system for optical storage multi-machine parallel system |
| CN115347582A (en) * | 2022-07-26 | 2022-11-15 | 合肥工业大学 | Micro-grid system based on state prediction consistency algorithm and frequency modulation strategy thereof |
Families Citing this family (27)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103545810B (en) * | 2013-11-12 | 2015-07-15 | 国家电网公司 | Microgrid inverter sagging automatic control method based on small signal stability analysis |
| CN104201667B (en) * | 2014-07-25 | 2016-04-13 | 华北电力大学（保定） | The optimal decentralized control method for coordinating of microgrid in a kind of New-energy power system |
| CN105896588B (en) * | 2014-10-16 | 2018-03-02 | 国家电网公司 | A kind of inverter parameters control method |
| CN105634309B (en) * | 2014-11-06 | 2018-06-22 | 台达电子工业股份有限公司 | A kind of control method and control device for inversion system |
| CN104601029B (en) * | 2015-01-14 | 2016-10-19 | 重庆大学 | Inverter parallel-control system droop control method |
| CN104897956B (en) * | 2015-05-18 | 2018-01-05 | 华南理工大学 | A kind of active power of online active measurement power network and the method for frequency characteristic coefficient |
| FR3046304B1 (en) * | 2015-12-23 | 2019-05-31 | Schneider Electric Industries Sas | METHOD FOR CONTROLLING AN ELECTRICAL DISTRIBUTION MICRO NETWORK |
| CN106684908A (en) * | 2016-11-28 | 2017-05-17 | 国网河南省电力公司郑州供电公司 | Drooping characteristic-based mode adaptive voltage source control method applied to microgrid |
| CN107482939B (en) * | 2017-09-08 | 2019-05-31 | 中南大学 | A kind of inverter control method |
| CN108306337B (en) * | 2018-01-11 | 2021-11-26 | 安徽工程大学 | Virtual synchronous generator control method based on droop coefficient self-adaptive adjustment |
| CN110323788A (en) * | 2018-03-30 | 2019-10-11 | 中国电力科学研究院有限公司 | A kind of control method and system of inertia generator |
| CN109038662B (en) * | 2018-08-01 | 2021-05-14 | 电子科技大学 | Virtual inertia control method of distributed power generation system |
| CN109474027B (en) * | 2018-11-05 | 2021-10-22 | 许继集团有限公司 | Droop control method and device and converter |
| CN109975610B (en) * | 2018-11-16 | 2021-12-14 | 国网江苏省电力有限公司盐城供电分公司 | Micro-grid dynamic frequency detection and adjustment method |
| CN110011321B (en) * | 2019-04-03 | 2023-02-14 | 国网江西省电力有限公司电力科学研究院 | Distributed photovoltaic variable slope droop control method based on head end voltage tracking |
| CN111064232B (en) * | 2019-10-31 | 2021-04-30 | 上海电力大学 | Virtual synchronous generator-based microgrid system inverter secondary frequency control method |
| CN111355234B (en) * | 2020-03-18 | 2024-06-04 | 国网浙江省电力有限公司嘉善县供电公司 | Micro-grid frequency control method based on reinforcement learning |
| CN113567871B (en) * | 2020-04-28 | 2024-03-15 | 中国电力科学研究院有限公司 | Frequency-voltage response consistency verification method and system for multi-type energy storage equipment |
| CN111786403A (en) * | 2020-06-02 | 2020-10-16 | 西门子工厂自动化工程有限公司 | Power control method and device of grid-connected inverter and grid-connected inverter |
| CN111682590B (en) * | 2020-07-17 | 2024-04-05 | 四川大学 | Island power grid optimized power distribution method based on fuzzy PI-PD sagging control |
| CN112152265B (en) * | 2020-09-17 | 2021-04-27 | 浙江大学 | Photovoltaic active power distribution network scheduling control method based on f-dp/dv |
| CN112510696B (en) * | 2020-11-25 | 2022-05-31 | 湖南大学 | Micro-grid transient voltage stability regulation and control system and method |
| CN112865062B (en) * | 2021-01-11 | 2022-11-25 | 河海大学 | Direct-current micro-grid damping enhancement control method considering multi-type load access |
| CN113410904B (en) * | 2021-03-29 | 2023-01-24 | 广东电网有限责任公司电力科学研究院 | Multi-module parallel emergency power supply and control method |
| CN113193245B (en) * | 2021-04-28 | 2022-10-18 | 太原科技大学 | SOH (State of health) balancing method for distributed battery energy storage system of micro-grid |
| CN114243798B (en) * | 2021-12-22 | 2023-10-17 | 国网河北省电力有限公司经济技术研究院 | Frequency recovery control method and device under decoupling of inverter output power |
| CN116933497A (en) * | 2023-06-16 | 2023-10-24 | 天津大学 | Grid-connected island detection method for photovoltaic virtual synchronous generator power station |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101976851B (en) * | 2010-10-27 | 2012-11-28 | 西安交通大学 | Method for improving wireless internet stability of multiple inverters in microgrid by utilizing virtual impedance |
| US8606424B2 (en) * | 2011-04-05 | 2013-12-10 | King Fahd University Of Petroleum And Minerals | Particle swarm optimization system and method for microgrids |
| CN102354974B (en) * | 2011-10-13 | 2014-12-10 | 山东大学 | Micro-grid multi-objective optimized operation control method |
| CN102510064B (en) * | 2011-11-08 | 2015-02-18 | 山东大学 | Improved droop control method in micro electric network detached island operation control system |
| CN102623992A (en) * | 2012-04-12 | 2012-08-01 | 山东大学 | Method for islanding microgrid control and optimization based on rotating coordinate virtual impedance |
| CN102723722B (en) * | 2012-06-06 | 2014-06-04 | 西安交通大学 | Parallel inverter droop control based reactive power control method |
| CN103545810B (en) * | 2013-11-12 | 2015-07-15 | 国家电网公司 | Microgrid inverter sagging automatic control method based on small signal stability analysis |
-
2013
- 2013-11-12 CN CN201310559711.8A patent/CN103545810B/en active Active
-
2014
- 2014-06-16 CA CA2950809A patent/CA2950809C/en not_active Expired - Fee Related
- 2014-06-16 WO PCT/CN2014/079930 patent/WO2015070602A1/en active Application Filing
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2019001986A1 (en) | 2017-06-28 | 2019-01-03 | Sma Solar Technology Ag | Method for operating an island network, and island network |
| DE102017114306B4 (en) | 2017-06-28 | 2019-01-17 | Sma Solar Technology Ag | METHOD FOR OPERATING AN ISLAND NETWORK AND ISLAND NETWORK |
| DE102017114306A1 (en) * | 2017-06-28 | 2019-01-03 | Sma Solar Technology Ag | METHOD FOR OPERATING AN ISLAND NETWORK AND ISLAND NETWORK |
| US11005270B2 (en) | 2017-06-28 | 2021-05-11 | Sma Solar Technology Ag | Method for operating an island system, and island system |
| EP3496225A1 (en) * | 2017-12-11 | 2019-06-12 | General Electric Company | Method and system for droop control of power systems |
| CN110311375B (en) * | 2019-07-29 | 2022-11-29 | 东北大学 | Micro-grid transient stability control method containing multiple virtual synchronous machines |
| CN110311375A (en) * | 2019-07-29 | 2019-10-08 | 东北大学 | A kind of micro-capacitance sensor transient stability control method containing more virtual synchronous machines |
| CN110460112A (en) * | 2019-09-18 | 2019-11-15 | 东北大学 | A kind of micro-capacitance sensor droop control method based on the control of power deviation amount consistency |
| CN110460112B (en) * | 2019-09-18 | 2023-02-28 | 东北大学 | Micro-grid sag control method based on power deviation value consistency control |
| CN112510749A (en) * | 2020-08-20 | 2021-03-16 | 国网山西省电力公司电力科学研究院 | Droop control method with network self-adaption capability in micro-grid island mode |
| CN112510749B (en) * | 2020-08-20 | 2023-11-24 | 国网山西省电力公司电力科学研究院 | Droop control method with network self-adaptive capacity in micro-grid island mode |
| CN113675895A (en) * | 2021-08-06 | 2021-11-19 | 阳光电源（上海）有限公司 | Power distribution method and system for optical storage multi-machine parallel system |
| CN113675895B (en) * | 2021-08-06 | 2024-04-12 | 阳光电源（上海）有限公司 | Power distribution method and system for optical storage multi-machine parallel system |
| CN115347582A (en) * | 2022-07-26 | 2022-11-15 | 合肥工业大学 | Micro-grid system based on state prediction consistency algorithm and frequency modulation strategy thereof |
| CN115347582B (en) * | 2022-07-26 | 2024-07-02 | 合肥工业大学 | Micro-grid system based on state prediction consistency algorithm and frequency modulation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| WO2015070602A1 (en) | 2015-05-21 |
| CA2950809C (en) | 2019-02-12 |
| CN103545810B (en) | 2015-07-15 |
| CN103545810A (en) | 2014-01-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2950809C (en) | Automatic droop control method for microgrid inverters based on small-signal stability analysis | |
| Hu et al. | A coordinated control of hybrid ac/dc microgrids with PV-wind-battery under variable generation and load conditions | |
| Elkhatib et al. | Evaluation of inverter-based grid frequency support using frequency-watt and grid-forming PV inverters | |
| Groß et al. | Increasing the resilience of low-inertia power systems by virtual inertia and damping | |
| Roy et al. | Dynamic stability analysis of hybrid islanded DC microgrids using a nonlinear backstepping approach | |
| Joung et al. | Decoupled frequency and voltage control for stand-alone microgrid with high renewable penetration | |
| Guan et al. | Frequency stability of hierarchically controlled hybrid photovoltaic-battery-hydropower microgrids | |
| CN105794066B (en) | Multivariable controller modulator for power generating equipment | |
| Zhong et al. | DC-side synchronous active power control of two-stage photovoltaic generation for frequency support in Islanded microgrids | |
| CN107732956A (en) | The two-stage type photovoltaic parallel in system low-voltage ride-through method of Variable power pursuit path | |
| Sun et al. | Novel temporary frequency support control strategy of wind turbine generator considering coordination with synchronous generator | |
| Abbassi et al. | Optimal energy management strategy and novel control approach for DPGSs under unbalanced grid faults | |
| Yap et al. | A novel adaptive virtual inertia control strategy under varying irradiance and temperature in grid-connected solar power system | |
| Arul et al. | Mitigating techniques for the operational challenges of a standalone hybrid system integrating renewable energy sources | |
| Kumar et al. | Wide-area damping control system for large wind generation with multiple operational uncertainty | |
| Rao et al. | Power quality improvement using ASO technique | |
| Soni | Solar PV plant model validation for grid integration studies | |
| Astero et al. | Improving PV hosting capacity of distribution grids considering dynamic voltage characteristic | |
| Ahmad et al. | Direct power control based on point of common coupling voltage modulation for grid-tied AC microgrid PV inverter | |
| Keshavarzi et al. | Disturbance resilience enhancement of islanded hybrid microgrid under high penetration of renewable energy resources by BESS | |
| Chandran et al. | A review on active & reactive power control strategy for a standalone hybrid renewable energy system based on droop control | |
| Pawar et al. | Grid-forming control for solar PV systems with real-time MPP estimation | |
| Arteaga et al. | Control of energy storage and photovoltaic systems using model predictive control | |
| Wasynczuk et al. | Voltage and frequency regulation strategies in isolated AC micro-grids | |
| Alosaimi et al. | Pv system control as statcom with svm-based islanding detection |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request |
Effective date: 20161130 |
|
| EEER | Examination request |
Effective date: 20161130 |
|
| MKLA | Lapsed |
Effective date: 20200831 |