CN116896121B - Island alternating-current micro-grid reactive power sharing method based on sagging control - Google Patents
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Abstract
The invention discloses a reactive power sharing method of an island alternating current micro-grid based on droop control, which comprises the following steps: firstly, interface line impedance between an inverter and a load busbar is identified by a recursive least square method, secondly, all line impedance identification values are compared, the maximum value is obtained to serve as a reference virtual complex impedance, then, the difference value between each line impedance identification value and a basic virtual complex impedance is obtained, the difference value is taken as the optimal virtual complex impedance of each inverter, finally, the optimal virtual complex impedance is multiplied by output current to serve as virtual voltage to compensate a voltage reference value generated by micro-grid droop control, and the voltage reference value for finally controlling dq axis voltage is obtained, so that reactive power sharing is finally realized. Compared with the prior art, the micro-grid voltage is prevented from being further reduced, the actual line impedance is not required to be known in advance in the design stage, and the current high-frequency disturbance caused by the output current differentiation is avoided according to the available measurement on-line estimation.
Description
Technical Field
The invention relates to the field, in particular to an island alternating current micro-grid reactive power sharing method based on droop control.
Background
The rapid growth of global power demand and the need to utilize environmentally friendly energy has accelerated the development of power electronics systems. The number of distributed power generation systems increases substantially each year. Furthermore, the clusters of small-scale generator sets form a micro-grid providing reliable and optimal integration for inverter-based distributed power generation systems, as they may be in grid-tie or island mode.
Conventional frequency and voltage drop control techniques are widely used for control of island micro-grids. This control method of the distributed power generation system simulates the operation of a synchronous generator. Although the conventional droop control can realize proper active power sharing, the conventional droop control has serious limitation in reactive power sharing in a low-voltage island micro-grid. This is mainly due to the mismatch of the feeder impedance and the differences in the inverter design parameters. In micro-grids, the adverse effect of feed impedance mismatch on reactive sharing has been a major problem. In island ac microgrids, when conventional frequency and voltage drop control techniques are employed, the interface line impedance mismatch between the inverter and the load bus leads to failure to achieve reactive power sharing. This operation jeopardizes the reliability of the whole micro-grid, as it may cause some inverters to be overloaded, triggering protection relays and causing cascading failures.
Among the many proposed methods aimed at enhancing reactive power sharing of island micro-grids, the virtual output impedance method has gained tremendous popularity due to its simple implementation. This technique relies on reshaping the characteristics of the inverter output impedance by creating an additional control loop. Thus, the coupling between active and reactive is minimized. Therefore, even in the case where the feeder impedances are not matched, the reactive sharing accuracy can be improved. Although there is a great deal of work available in the literature to address reactive power sharing using the virtual impedance approach, the process of assigning optimal values to the virtual impedance of each inverter has not been thoroughly studied. It is therefore particularly important to find a suitable way to study the optimum value of the virtual impedance distribution.
Disclosure of Invention
The invention aims to: in order to solve the problems in the prior art, the invention provides an island alternating current micro-grid reactive power sharing method based on droop control. And obtaining the identification value of the line impedance through a recursive least square algorithm, and comparing all the identification values of the line impedance to obtain the maximum value serving as the reference virtual complex impedance. And then obtaining a difference value between each line impedance identification value and the basic virtual complex impedance, and taking the difference value as the optimal virtual complex impedance of each inverter. And multiplying the optimal virtual complex impedance by the output current to serve as virtual voltage to compensate a voltage reference value generated by the micro-grid droop control, and obtaining a voltage reference value of final control dq axis voltage, thereby realizing reactive power average division. The method not only solves the problem of difficult obtaining of the circuit impedance in practical engineering, but also researches the optimal value of virtual impedance distribution.
The technical scheme is as follows: the invention discloses a reactive power sharing method of an island alternating current micro-grid based on droop control, which comprises the following steps:
Step 1: obtaining the voltage of the inverter and the voltage of the load bus, obtaining the output current obtained between the inverter and the load bus, and obtaining an interface line impedance identification value between the inverter and the load bus by a recursive least square method;
Step 2: obtaining line impedance identification values according to the step1, comparing all the line impedance identification values to obtain a maximum value serving as a reference virtual complex impedance;
Step 3: obtaining a difference value between each line impedance identification value and the reference virtual complex impedance according to the reference virtual complex impedance in the step 2, and taking the difference value as the optimal virtual complex impedance of each inverter;
Step 4: and 3, multiplying the optimal virtual complex impedance obtained in the step 3 by the output current to obtain virtual voltage, compensating a voltage reference value generated by the micro-grid droop control, obtaining a voltage reference value for finally controlling the dq axis voltage, and finally realizing the equipartition of reactive power.
Further, the specific operation of step 1 to obtain the interface line impedance identification value between the inverter and the load bus is as follows:
first, a mathematical model of steady-state operation of the jth inverter is derived:
Wherein v j and i j are the output voltage and current measurements of the jth inverter, respectively, and v pcc is the load bus voltage;
Let v j and v pcc be system input variables, i j be state variables, get continuous time state space model:
The above formula is written in discrete time form as follows:
Considering the measured sampling interval T s, a solution of the state equation written in discrete time is obtained by mapping the input and output:
The above formula is written as a linear regression form:
where y (k) is an output vector comprising i (k), Is an input vector consisting of two variables, namely a delay voltage v j (k-1) and a current i j (k-1) vector for one sample; θ is the regression vector of the unknown parameter (R fj,Lfj);
The equation at sample instance k for the recursive least squares algorithm used is expressed as:
Wherein ρ is a forgetting factor, and the value is between 0 and 1;
According to the estimated regression vector theta, directly calculating the resistance and inductance components of the jth line, which are expressed as:
further, the reference virtual complex impedance in the step 2 is expressed as:
Wherein, The identification value of the line impedance is represented by R v-base、Xv-base, the resistance and reactance of the reference virtual complex impedance are represented by the number of lines, j.
Further, step 3 obtains a difference value between each line impedance identification value and the reference virtual complex impedance by using the reference virtual complex impedance, and takes the difference value as the optimal virtual complex impedance of each inverter:
wherein R v-base、Xv-base represents the resistance and reactance of the reference virtual complex impedance respectively, Representing the identification value of the first line resistance,/>Representing an identification of the reactance of the first line.
Further, the step 4 compensates the voltage reference value generated by the micro-grid droop control by multiplying the obtained optimal virtual complex impedance by the output current as a virtual voltage, and obtains a voltage reference value of the final control dq axis voltage:
first, a mathematical model of the virtual impedance in the abc coordinate system is given:
Wherein u refa,urefb,urefc represents the actual output voltages of the three phases a, b, c respectively, Reference output voltages of a, b and c phases are respectively represented, R v,Lv represents virtual resistance values and virtual inductance values, and i oa,iob,ioc represents output current values of a, b and c phases;
The realization equation of virtual impedance under the dq rotation coordinate system can be obtained as follows:
Wherein u refd,urefq represents the actual output voltages of the d-axis and q-axis, respectively, Reference output voltages respectively representing d-axis and q-axis, R v,Lv representing virtual resistance value and virtual inductance value respectively, ω representing rated angular frequency, and i od and i oq representing output currents respectively representing d-axis and q-axis.
The beneficial effects are that:
1. The invention firstly adds a recursive least square algorithm to identify the line impedance, has simple estimation technology, and ensures high precision and low calculation burden by using the existing measurement method.
2. The invention provides an optimal tuning method of virtual complex impedance of each inverter, which comprises the steps of comparing all line impedance identification values according to the line impedance identification values to obtain a maximum value as a reference virtual complex impedance, taking the difference between each line impedance identification value and the reference virtual complex impedance as the optimal virtual complex impedance of each inverter. It has physical significance, taking into account the exact mismatch value in the physical feeder impedance.
3. The invention avoids unnecessary voltage degradation in the micro-grid, and establishes a clear relation between the unmatched value of the actual line impedance and the virtual complex impedance distribution value of each inverter. Thus, further reduction of the microgrid voltage is prevented. Second, there is no need to know the actual line impedance in advance during the design phase, as they are estimated on-line from the available measurements. Finally, the high-frequency disturbance of the current caused by the differentiation of the output current is avoided in the virtual complex impedance part, and meanwhile, a low-pass filter is not used, so that the dynamic performance of the system is not affected.
Drawings
FIG. 1 is a reactive power equipartition control block diagram of an island alternating current micro-grid based on droop control;
FIG. 2 is a diagram showing the identification of the line resistance according to the present invention;
FIG. 3 is a diagram showing the line inductance identification according to the present invention;
FIG. 4 is a graph of virtual resistance optima in accordance with the present invention;
FIG. 5 is a graph of virtual inductance optima in accordance with the present invention;
FIG. 6 is a reactive power diagram of the present invention;
Fig. 7 is a graph of the output voltage of the inverter of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, but are not to be construed as limiting the scope of the present invention
The invention discloses a reactive power sharing method of an island alternating current micro-grid based on droop control, which comprises the following steps:
Step 1: the voltage of the inverter and the voltage of the load bus are measured through the voltmeter and the ammeter, the output current between the inverter and the load bus is measured, and the interface line impedance identification value between the inverter and the load bus is obtained through a recursive least square method.
Step 1 first derives a mathematical model of steady state operation of the jth inverter:
Where v j and i j are the output voltage and current measurements, respectively, of the jth inverter and v pcc is the load bus voltage.
Let v j and v pcc be system input variables and i j be state variables, a continuous time state space model can be obtained:
The above formula is written in discrete time form as follows:
considering the measured sampling interval T s, the solution of the above-mentioned state equation is obtained by mapping the input and output:
the above formula can be written as a linear regression form:
where y (k) is an output vector containing i (k). Is an input vector consisting of two variables, namely a delay voltage v j (k-1) and a current i j (k-1) vector for one sample. θ is the regression vector of the unknown parameter (R fj,Lfj).
A recursive least squares algorithm can now be applied to estimate the line impedance based on three measurements (v j,ij,vpcc).
The equation for the recursive least squares algorithm used in the above equation at sample instance k is expressed as:
wherein ρ is a forgetting factor, and the value is between 0 and 1.
According to the estimated regression vector theta, directly calculating the resistance and inductance components of the jth line, which are expressed as:
Step 2: and (3) obtaining line impedance identification values according to the step (1), comparing all the line impedance identification values, and obtaining a maximum value serving as a reference virtual complex impedance. The reference virtual complex impedance is expressed as:
Wherein, The identification value of the line impedance is represented by R v-base、Xv-base, the resistance and reactance of the reference virtual complex impedance are represented by the number of lines, j.
Step 3: and (3) obtaining a difference value between each line impedance identification value and the reference virtual complex impedance according to the reference virtual complex impedance in the step (2), and taking the difference value as the optimal virtual complex impedance of each inverter.
Wherein R v-base、Xv-base represents the resistance and reactance of the reference virtual complex impedance respectively,Representing the identification value of the first line resistance,/>Representing an identification of the reactance of the first line.
Step 4: and 3, multiplying the optimal virtual complex impedance obtained in the step 3 by the output current to obtain virtual voltage, compensating a voltage reference value generated by the micro-grid droop control, obtaining a voltage reference value for finally controlling the dq axis voltage, and finally realizing the equipartition of reactive power.
First, a mathematical model of the virtual impedance in the abc coordinate system is given:
Wherein u refa,urefb,urefc represents the actual output voltages of the three phases a, b, c respectively, Reference output voltages of a, b, and c phases are respectively represented, R v,Lv represents a virtual resistance value and a virtual inductance value, and i oa,iob,ioc represents output current values of a, b, and c phases.
Clark transformation is carried out on the formula to obtain the following components:
Assume that the three-phase currents output by the inverter are:
Where i om is the magnitude of the line current.
The three-phase current is converted into an alpha beta coordinate system to obtain the following components:
Obtaining an expression of the virtual impedance in an alpha beta coordinate system:
the virtual impedance realization equation under the dq rotation coordinate system can be finally obtained by Park transformation of the formula as follows:
Wherein u refd,urefq represents the actual output voltages of the d-axis and q-axis, respectively, Reference output voltages respectively representing d-axis and q-axis, R v,Lv representing virtual resistance value and virtual inductance value respectively, ω representing rated angular frequency, and i od and i oq representing output currents respectively representing d-axis and q-axis.
Referring to fig. 1, fig. 1 is a reactive power equipartition control block diagram of an island ac micro-grid based on droop control, and the structure of the island ac micro-grid mainly comprises an LC filter, a PI controller, a power calculation module, a droop control module, a virtual impedance module, an on-line estimated line impedance module and a virtual impedance optimal value module. Firstly, estimating line impedance, then outputting virtual impedance through a virtual impedance optimal value module, and outputting virtual voltage through a virtual impedance module to compensate a voltage reference value generated by micro-grid droop control, so as to obtain a voltage reference value for finally controlling dq axis voltage.
Fig. 2 is a line resistance identification chart, and the identification method proposed in the present experiment starts at 3s, where the line resistance is set to 0.04 Ω and the actual resistance is set to 0.04 Ω. It can be seen from the figure that when the proposed identification method is enabled, the identified resistance can converge very accurately to the actual value, proving the feasibility of the recursive least squares algorithm.
Fig. 3 is a diagram showing the identification of the line inductance, the identification method proposed in the present experiment starts at 3s, the line inductance is set to 0.4mH, and the actual resistance is set to 0.4mH. It can be seen from the figure that when the proposed identification method is enabled, the identified inductance can converge very accurately to the actual value, proving the feasibility of the recursive least squares algorithm.
Fig. 4 is a graph of virtual resistance optimum values, and the method proposed in this experiment starts at 3 s. The optimal value of the virtual resistor is consistent with the theoretical optimal value, is-0.016 omega, and proves the feasibility of the method.
Fig. 5 is a graph of virtual inductance optimum values, and the method proposed in this experiment starts at 3 s. The optimal value of the virtual inductor is consistent with the theoretical optimal value and is minus 0.094mH, and the feasibility of the method is proved.
Fig. 6 is a reactive power diagram, the method proposed in this experiment starting at time 3 s. Reactive power cannot be equally divided due to mismatching of line impedance, and reactive power equally division can be achieved, so that feasibility of the method is proved.
Fig. 7 is a graph of inverter output voltage, and the method proposed in this experiment starts at time 3 s. It can be seen that unnecessary voltage degradation in the microgrid is avoided. The voltage drop in the microgrid is reduced due to the adoption of the optimal value of the proposed virtual impedance.
The invention is understood and implemented in accordance therewith and is not to be construed as limited in scope. All equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of the present invention.
Claims (5)
1. The island alternating current micro-grid reactive power sharing method based on droop control is characterized by comprising the following steps of:
Step 1: obtaining the voltage of the inverter and the voltage of the load bus, obtaining the output current obtained between the inverter and the load bus, and obtaining an interface line impedance identification value between the inverter and the load bus by a recursive least square method;
Step 2: obtaining line impedance identification values according to the step1, comparing all the line impedance identification values to obtain a maximum value serving as a reference virtual complex impedance;
Step 3: obtaining a difference value between each line impedance identification value and the reference virtual complex impedance according to the reference virtual complex impedance in the step 2, and taking the difference value as the optimal virtual complex impedance of each inverter;
Step 4: and 3, multiplying the optimal virtual complex impedance obtained in the step 3 by the output current to obtain virtual voltage, compensating a voltage reference value generated by the micro-grid droop control, obtaining a voltage reference value for finally controlling the dq axis voltage, and finally realizing the equipartition of reactive power.
2. The droop control-based island alternating current micro-grid reactive power sharing method according to claim 1, wherein the specific operation of obtaining the interface line impedance identification value between the inverter and the load bus in the step 1 is as follows:
first, a mathematical model of steady-state operation of the jth inverter is derived:
Wherein v j and i j are the output voltage and current measurements of the jth inverter, respectively, and v pcc is the load bus voltage;
Let v j and v pcc be system input variables, i j be state variables, get continuous time state space model:
The above formula is written in discrete time form as follows:
Considering the measured sampling interval T s, a solution of the state equation written in discrete time is obtained by mapping the input and output:
The above formula is written as a linear regression form:
where y (k) is an output vector comprising i (k), Is an input vector consisting of two variables, namely a delay voltage v j (k-1) and a current i j (k-1) vector for one sample; θ is the regression vector of the unknown parameter (R fj,Lfj);
The equation at sample instance k for the recursive least squares algorithm used is expressed as:
Wherein ρ is a forgetting factor, and the value is between 0 and 1;
According to the estimated regression vector theta, directly calculating the resistance and inductance components of the jth line, which are expressed as:
3. the droop control-based island ac micro-grid reactive power sharing method according to claim 1, wherein the reference virtual complex impedance in the step 2 is expressed as:
Wherein, The identification value of the line impedance is represented by R v-base、Xv-base, the resistance and reactance of the reference virtual complex impedance are represented by the number of lines, j.
4. The droop control-based island ac micro-grid reactive power sharing method according to claim 3, wherein step 3 uses a reference virtual complex impedance to obtain a difference value between each line impedance identification value and the reference virtual complex impedance, and takes the difference value as an optimal virtual complex impedance of each inverter:
wherein R v-base、Xv-base represents the resistance and reactance of the reference virtual complex impedance respectively, Representing the identification value of the first line resistance,/>Representing an identification of the reactance of the first line.
5. The reactive power sharing method of the island ac micro-grid based on droop control according to claim 1, wherein the step 4 uses multiplication of the obtained optimal virtual complex impedance and the output current as the virtual voltage to compensate the voltage reference value generated by the micro-grid droop control, so as to obtain the voltage reference value of the voltage of the dq axis of final control:
first, a mathematical model of the virtual impedance in the abc coordinate system is given:
Wherein u refa,urefb,urefc represents the actual output voltages of the three phases a, b, c respectively, Reference output voltages of a, b and c phases are respectively represented, R v,Lv represents virtual resistance values and virtual inductance values, and i oa,iob,ioc represents output current values of a, b and c phases;
The realization equation of virtual impedance under the dq rotation coordinate system can be obtained as follows:
Wherein u refd,urefq represents the actual output voltages of the d-axis and q-axis, respectively, Reference output voltages respectively representing d-axis and q-axis, R v,Lv representing virtual resistance value and virtual inductance value respectively, ω representing rated angular frequency, and i od and i oq representing output currents respectively representing d-axis and q-axis.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10395897B1 (en) * | 2018-04-24 | 2019-08-27 | Newpowerplasma Co., Ltd. | Virtual impedance auto matching method |
| CN114039379A (en) * | 2021-10-22 | 2022-02-11 | 中冶赛迪电气技术有限公司 | Control system and method of energy storage converter in island operation mode |
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| GB201613956D0 (en) * | 2016-08-15 | 2016-09-28 | Univ Swansea | Dynamic active and reactive power sharing schemes in islanded microgrids |
| KR102238340B1 (en) * | 2019-05-28 | 2021-04-08 | 효성중공업 주식회사 | PCS Droop Control Device and Energy Storage System using the Same |
| CN110190608A (en) * | 2019-06-27 | 2019-08-30 | 上海电力学院 | A kind of isolated island micro-capacitance sensor of no interconnected communication is idle to divide equally control method and device |
| CN112018807A (en) * | 2020-08-03 | 2020-12-01 | 江苏斯帕沃电子技术有限公司 | Distributed island microgrid power control method |
| CN113824160A (en) * | 2021-09-18 | 2021-12-21 | 长沙理工大学 | Adaptive virtual inductor-based micro-grid parallel inverter power regulation method |
| CN115589036A (en) * | 2022-10-31 | 2023-01-10 | 南京工程学院 | Method for adjusting parallel active power equalization of multiple inverters based on self-adaptive virtual impedance |
-
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10395897B1 (en) * | 2018-04-24 | 2019-08-27 | Newpowerplasma Co., Ltd. | Virtual impedance auto matching method |
| CN114039379A (en) * | 2021-10-22 | 2022-02-11 | 中冶赛迪电气技术有限公司 | Control system and method of energy storage converter in island operation mode |
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