Power supply voltage stabilization method, system and equipment for micro-grid island system

Abstract

The invention relates to the technical field of microgrid voltage stabilization, in particular to a microgrid island system power supply voltage stabilization method, system and equipment, and the method comprises the steps: determining a coupling term of an SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system and the AC voltage of the SG-VSG parallel power supply system; for the coupling problem of the SG-VSG parallel power supply system, decoupling items obtained through calculation are applied to a synchronous generator control loop and a virtual synchronous generator control loop respectively, the power angle change of the SG-VSG parallel power supply system is effectively restrained, when the active power of an electricity load is suddenly increased, it is ensured that the voltage of a micro-grid island system is continuously stable, and the stability of the micro-grid island system is improved. And the stability of the micro-grid island system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrid voltage regulation, and particularly relates to a power supply voltage regulation method, system and device for a microgrid island system. Background Art

[0002] With the continuous acceleration of the construction of the new power system, in the scenario of large-scale application of renewable energy, more and more microgrid island systems will be formed.

[0003] In a microgrid island system, the power supply can be either a synchronous generator (SG, Synchronous Generator) or a power electronic converter. Under the island system, the power electronic converter generally uses virtual synchronous generator (VSG, Virtual Synchronous Generator) control, and both can be used as the power supply of the island system.

[0004] When both of them supply power to the microgrid island system together, the synchronous generator and the virtual synchronous generator form an SG-VSG parallel power supply system. When the active power in the microgrid island system suddenly increases, there is power coupling between the synchronous generator and the virtual synchronous generator, which causes a drastic change in the power angle of the parallel system, resulting in unstable output voltage of the SG-VSG parallel power supply system and causing the microgrid island system to fail to operate normally.

[0005] Currently, the existing solutions usually passively increase the output damping of the synchronous generator or the virtual synchronous generator to suppress voltage oscillation. Therefore, the existing solutions often have unsatisfactory control effects, and the required damping needs to be repeatedly adjusted under different working conditions. It is difficult to cope with the complex and changeable microgrid island system and cannot meet the actual voltage regulation requirements. Summary of the Invention

[0006] The purpose of the present invention is to provide a power supply voltage regulation method, system and device for a microgrid island system, and solve the technical problem that the output voltage of the SG-VSG parallel power supply system is unstable due to the increase of the active power in the current microgrid island system.

[0007] The solution of the present invention to the above technical problem: A power supply voltage regulation method for a microgrid island system includes the following steps: S1. Calculate the shunt admittance parameter of the transmission line of the SG-VSG parallel power supply system; S2. Calculate the output power of the SG-VSG parallel power supply system according to the shunt admittance parameter of the transmission line of the SG-VSG parallel power supply system; S3. Construct the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system; S4. Calculate the apparent power of the SG-VSG parallel power supply system; S5. Calculate the coupling power of the SG-VSG parallel power supply system according to the apparent power and the output power of the SG-VSG parallel power supply system; S6. Calculate the AC voltage of the SG-VSG parallel power supply system according to the coupling power of the SG-VSG parallel power supply system; S7. Calculate the decoupling term of the SG-VSG parallel power supply system according to the output power, the rotor motion equation and the AC voltage of the SG-VSG parallel power supply system, and superimpose the calculated decoupling term on the SG-VSG parallel power supply system.

[0008] Further defined, the SG-VSG parallel power supply system includes a synchronous generator control loop, a virtual synchronous generator control loop, a synchronous generator, a virtual synchronous generator, a first line, a second line and an electrical load. The first line is in parallel with the second line. The synchronous generator control loop is connected to the input end of the first line through the synchronous generator, and the virtual synchronous generator control loop is connected to the input end of the second line through the virtual synchronous generator. The output ends of the first line and the second line are both connected to the input end of the electrical load; The step S1 includes: S11. Calculate the line admittance Y s of the first line, the line admittance Y ls of the second line and the admittance Y lv of the electrical load respectively:

[0009] wherein, Z ls is the line impedance of the first line, Z lv is the line impedance of the second line, and Z load is the impedance of the electrical load; S12. Calculate the parallel admittance s of the first line and the electrical load, the parallel admittance ls of the first line and the second line, and the parallel admittance lv of the second line and the electrical load according to the line admittance Y of the first line, the line admittance Y of the second line and the admittance Y of the electrical load.

[0010] Further defined, the step S2 includes: S21. According to the parallel admittance Y ss of the first line and the electrical load and the parallel admittance Y sv, calculate and determine the active power \(P\) output by the synchronous generator se and the reactive power \(Q\) output by the synchronous generator se :

[0011] where \(E\) s is the output voltage of the synchronous generator, \(G\) ss is the conductance of the shunt admittance \(Y\) of the first line and the electrical load, \(U\) ss is the output voltage of the virtual synchronous generator, \(|Y|\) v is the magnitude of the shunt admittance \(Y\) of the first line and the second line, \(\delta\) sv is the power angle of the SG-VSG parallel power supply system, sv is the phase angle of the shunt admittance \(Y\) of the first line and the second line, \(B\) sv is the susceptance of the shunt admittance \(Y\) of the first line and the electrical load; is the shunt admittance \(Y\) of the first line and the second line sv is the phase angle, \(B\) ss is the susceptance of the shunt admittance \(Y\) of the first line and the electrical load ss ; S22. According to the shunt admittance \(Y\) of the first line and the second line sv and the shunt admittance \(Y\) of the second line and the electrical load vv , calculate and determine the active power \(P\) output by the virtual synchronous generator ve and the reactive power \(Q\) output by the virtual synchronous generator ve :

[0012] where \(E\) v is the electromotive force of the synchronous generator, \(G\) vv is the conductance of the shunt admittance \(Y\) of the second line and the electrical load vv is the susceptance, \(B\) vv is the susceptance of the shunt admittance \(Y\) of the second line and the electrical load vv ;

[0013] It is further specified that the step S3 is specifically: Construct the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system:

[0014] where \(J\) sv is the equivalent virtual inertia of the SG-VSG parallel power supply system, is the angular acceleration between the synchronous generator and the virtual synchronous generator, is the power angle difference between the synchronous generator and the virtual synchronous generator, \(T\) M is the equivalent mechanical torque of the SG-VSG parallel power supply system, \(T\) EThe equivalent electromagnetic torque of the SG-VSG parallel power supply system, J s The inertia coefficient of the synchronous generator, J v The virtual inertia coefficient of the virtual synchronous generator, D ps The damping coefficient of the synchronous generator, D pv The virtual damping coefficient of the virtual synchronous generator, t is time, ω s The sampled value of the angular frequency of the synchronous generator, ω v The sampled value of the angular frequency of the virtual synchronous generator, ω0 is the initial angular frequency of the SG-VSG parallel power supply system.

[0015] Further limited, the apparent power of the SG-VSG parallel power supply system includes the apparent power S of the first line line1 and the apparent power S of the second line line2 :

[0016] Wherein, P line1 is the active power of the first line, P line2 is the active power of the second line, Q line1 is the reactive power of the first line, Q line2 is the reactive power of the second line, I line1 is the current of the first line, I line2 is the current of the second line, j is the imaginary number.

[0017] Further limited, the step S5 is specifically: S51. According to the active power P output by the synchronous generator se , the active power P output by the virtual synchronous generator ve , the active power P of the first line line1 and the active power P of the second line line2 , calculate the coupled active power P between the synchronous generator and the virtual synchronous generator sv =P se +P ve -P line1 -P line2 ; S52. According to the reactive power Q output by the synchronous generator se , the reactive power Q output by the virtual synchronous generator ve , the reactive power Q of the first line line1 and the reactive power Q of the second line line2 , calculate the coupled reactive power Q between the synchronous generator and the virtual synchronous generator sv =Q se +Q ve -Q line1 -Qline2 。

[0018] Further defined, the step S6 is specifically: According to the active power P output by the SG-VSG parallel power supply system sv and the reactive power Q output by the SG-VSG parallel power supply system sv , calculate the AC voltage of the SG-VSG parallel power supply system 。

[0019] Further defined, the step S7 includes: S71. Determine the d-q decoupled current terms applied to the synchronous generator control loop according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system, and the AC voltage of the SG-VSG parallel power supply system:

[0020]

[0021] Among them, i SG_d is the d-axis decoupled current term applied to the synchronous generator control loop, i SG_q is the q-axis decoupled current term applied to the synchronous generator control loop; u ac is the instantaneous AC voltage of the SG-VSG parallel power supply system, u v is the instantaneous output voltage of the virtual synchronous generator; S72. Determine the decoupled power terms applied to the virtual synchronous generator control loop according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system, and the AC voltage of the SG-VSG parallel power supply system:

[0022]

[0023] Among them, P decoupling is the active power decoupled term applied to the virtual synchronous generator control loop, Q decoupling is the reactive power decoupled term applied to the virtual synchronous generator control loop.

[0024] A power supply voltage stabilizing device for a microgrid island system, which is used to implement the above-mentioned power supply voltage stabilizing method for the microgrid island system, includes: The shunt admittance parameter calculation module is used to calculate the shunt admittance parameters of each transmission line in the SG-VSG parallel power supply system; The output power calculation module is used to calculate the output power of the SG-VSG parallel power supply system according to the shunt admittance parameters of each transmission line in the SG-VSG parallel power supply system; The rotor motion equation construction module is used to construct the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system; The apparent power calculation module is used to calculate the apparent power of the SG-VSG parallel power supply system; The power calculation module of the system output is used to calculate the coupling power of the SG-VSG parallel power supply system according to the apparent power of the SG-VSG parallel power supply system and the output power of the SG-VSG parallel power supply system; The AC voltage calculation module is used to calculate the AC voltage of the SG-VSG parallel power supply system according to the coupling power of the SG-VSG parallel power supply system; The SG-VSG parallel power supply system decoupling module is used to calculate the decoupling term of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system and the AC voltage of the SG-VSG parallel power supply system, and superimpose the calculated decoupling term on the SG-VSG parallel power supply system.

[0025] A power supply voltage stabilizing device for a microgrid island system includes a non-volatile storage medium and a central processing unit. An executable code is stored in the non-volatile storage medium. When the central processing unit executes the executable code, the power supply voltage stabilizing method for the microgrid island system as described above is implemented.

[0026] The beneficial effects of the present invention are as follows: The present invention determines the coupling term of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system and the AC voltage of the SG-VSG parallel power supply system. Aiming at the coupling problem of the SG-VSG parallel power supply system, the calculated decoupling terms are respectively applied to the synchronous generator control loop and the virtual synchronous generator control loop, effectively suppressing the power angle change of the SG-VSG parallel power supply system. When the active power of the electrical load suddenly increases, it ensures the continuous stability of the voltage of the microgrid island system and improves the stability of the microgrid island system. Description of the Drawings

[0027] Figure 1 It is the structure diagram of the SG-VSG parallel power supply system of the present invention; Figure 2 It is the flowchart of the power supply voltage stabilizing method for the microgrid island system of the present invention; Figure 3 It is the rotor motion equation block diagram of the SG-VSG parallel power supply system of the present invention; Figure 4 It is the AC side voltage block diagram of the SG-VSG parallel power supply system of the present invention; Figure 5 It is the coupling model of the SG-VSG parallel power supply system of the present invention; Figure 6 It is the synchronous generator control loop block diagram of the present invention; Figure 7 It is the virtual synchronous generator control loop block diagram of the present invention; Figure 8 It is the comparison diagram of the influence of the virtual synchronous motor connecting to the power supply on the power supply stability of the microgrid island system of the present invention; Figure 9 It is the comparison diagram of the influence of the sudden increase in active power in the microgrid island system on the power supply stability of the microgrid island system of the present invention. Detailed implementation manners

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Refer to Figure 1 , the SG-VSG parallel power supply system includes a synchronous generator SG, a virtual synchronous generator VSG, a first line line1, a second line line2, and an electrical load, and also includes a synchronous generator control loop for controlling the synchronous generator and a virtual synchronous generator control loop for controlling the virtual synchronous generator; the synchronous generator SG and the virtual synchronous generator VSG are used as power sources; wherein, the first line and the second line are in parallel, the output end of the synchronous generator is connected to the input end of the first line, the output end of the virtual synchronous generator is connected to the input end of the second line, and the output ends of the first line and the second line are both connected to the input end of the electrical load.

[0030] Among them, the impedance of the electrical load is Z load ; the filter impedance in the first line is Z d , the line impedance is Z line1 , the filter impedance in the second line is Z filter , the line impedance is Z line2 .

[0031] The output voltage of the synchronous generator is E s ∠δ s, the output voltage of the virtual synchronous generator is U v ∠δ v , u dc is the DC bus voltage of the virtual synchronous generator VSG, and i dc is the DC bus current of the virtual synchronous generator VSG.

[0032] Embodiment 1 Reference Figure 2 , the present invention provides a power supply voltage stabilization method for a microgrid island system, including the following steps: S1. Calculate the shunt admittance parameters of the transmission line of the SG-VSG parallel power supply system; S2. Calculate the output power of the SG-VSG parallel power supply system according to the shunt admittance parameters of the transmission line of the SG-VSG parallel power supply system; S3. Construct the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system; S4. Calculate the apparent power of the SG-VSG parallel power supply system; S5. Calculate the coupling power of the SG-VSG parallel power supply system according to the apparent power and the output power of the SG-VSG parallel power supply system; S6. Calculate the AC voltage of the SG-VSG parallel power supply system according to the coupling power of the SG-VSG parallel power supply system; S7. Calculate the decoupling term of the SG-VSG parallel power supply system according to the output power, the rotor motion equation and the AC voltage of the SG-VSG parallel power supply system, and superimpose the calculated decoupling term on the SG-VSG parallel power supply system.

[0033] Specifically, combined with Figure 1 , it can be obtained that step S1 includes the following steps: S11. Calculate the admittance Y of the first line s , the admittance Y of the second line ls and the admittance Y of the electrical load lv :

[0034] Among them, Z ls is the line impedance of the first line, Z lv is the line impedance of the second line, Z load is the impedance of the electrical load, Z ls =Z d +Z line1 , Z lv =Z filter +Zline2 ; S12, according to the line admittance Y of the first line s , the line admittance Y of the second line ls and the admittance Y of the electrical load lv , calculate the parallel admittance of the first line and the power load , the parallel admittance of the first line and the second line The second line and the electrical load are connected in parallel. .

[0035] To further illustrate, step S2 includes: S21, according to the parallel admittance Y of the first line and the power load ss The parallel admittance Y of the first line and the second line sv , calculate, calculate the active power P output by the synchronous generator se And the reactive power Q output by the synchronous generator se :

[0036] Among them, E s is the output voltage of the synchronous generator, G ss The parallel admittance Y of the first line and the power load ss The conductivity, U v is the output voltage of the virtual synchronous generator, |Y sv | is the parallel admittance Y of the first line and the second line sv The amplitude, δ sv is the power angle of the SG-VSG parallel power supply system, is the parallel admittance Y of the first line and the second line sv The phase angle, B ss The parallel admittance Y of the first line and the power load ss of electrical susceptance; S22, according to the parallel admittance Y of the first line and the second line sv The second line and the power load parallel admittance Y vv , calculate the active power P output by the virtual synchronous generator ve and the reactive power Q output by the virtual synchronous generator ve :

[0037] Among them, E v is the electromotive force of the synchronous generator, G vv The parallel admittance Y of the second line and the load vv The conductivity, B vv The parallel admittance Y of the second line and the power load vv The electrical conductivity.

[0038] In the SG-VSG parallel power supply system, the reactance of the transmission line is much greater than its resistance. Therefore, the phase angle of the parallel admittance Y of the first line and the second line sv is ≈0°.

[0039] When the phase angle of the parallel admittance Y of the first line and the second line sv is ≈0°, in the SG-VSG parallel power supply system, the active power and reactive power of the synchronous generator, as well as the active power and reactive power of the virtual synchronous generator, are all at their maximum values. Therefore, when the power angle δ of the SG-VSG parallel power supply system sv ≠0°, the active power of the synchronous generator, the reactive power of the synchronous generator, and the active power and reactive power of the virtual synchronous generator will all decrease.

[0040] Further explanation: Step S3 is specifically as follows: Based on the output power of the SG-VSG parallel power supply system, construct the rotor motion equation of the SG-VSG parallel power supply system:

[0041] where J sv is the equivalent virtual inertia of the SG-VSG parallel power supply system, ; is the angular acceleration between the synchronous generator and the virtual synchronous generator, J s is the inertia coefficient of the synchronous generator, J v is the virtual inertia coefficient of the virtual synchronous generator, T sm is the mechanical torque of the synchronous generator, ; T vm is the mechanical torque of the virtual synchronous generator, ; T se is the electromagnetic torque of the synchronous generator, T ve is the electromagnetic torque of the virtual synchronous generator, J sv is the equivalent virtual inertia of the SG-VSG parallel power supply system, D ps is the damping coefficient of the synchronous generator, D pv is the virtual damping coefficient of the virtual synchronous generator, ω s is the angular frequency sampling value of the synchronous generator, ω v is the angular frequency sampling value of the virtual synchronous generator, ω0 is the initial angular frequency of the SG-VSG parallel power supply system; T s0 is the initial torque of the synchronous generator, k ps is the proportional regulation coefficient of the synchronous generator, T v0 is the initial torque of the virtual synchronous generator, k pvis the proportional regulation coefficient of the virtual synchronous generator, σ i is the integral regulation coefficient of the synchronous generator, and t is time.

[0042] According to T se =P se / ω0, T ve =P ve / ω0, the rotor motion equation of the SG-VSG parallel power supply system is further obtained:

[0043] Among them, is the angular acceleration between the synchronous generator and the virtual synchronous generator, is the power angle difference between the synchronous generator and the virtual synchronous generator, ; is the initial power angle difference between the synchronous generator and the virtual synchronous generator, T M is the equivalent mechanical torque of the SG-VSG parallel power supply system, ; T E is the equivalent electromagnetic torque of the SG-VSG parallel power supply system, .

[0044] Further explanation, step S4 is specifically: The apparent power of the SG-VSG parallel power supply system includes the apparent power S line1 of the first line and the apparent power S line2 of the second line:

[0045] Among them, P line1 is the active power of the first line, P line2 is the active power of the second line, Q line1 is the reactive power of the first line, Q line2 is the reactive power of the second line, I line1 is the current of the first line, I line2 is the current of the second line, and j is the imaginary number.

[0046] Further explanation, step S5 is specifically: S51. According to the active power P se output by the synchronous generator, the active power P ve output by the virtual synchronous generator, the active power P line1 of the first line, and the active power P line2 of the second line, calculate the coupled active power P sv between the synchronous generator and the virtual synchronous generator = P se +P ve -Pline1 -P line2 ; S52. According to the reactive power Q output by the synchronous generator se , the reactive power Q output by the virtual synchronous generator ve , the reactive power Q of the first line line1 and the reactive power Q of the second line line2 , calculate the reactive power Q coupled between the synchronous generator and the virtual synchronous generator sv = Q se + Q ve - Q line1 - Q line2 .

[0047] Further explanation, step S6 is specifically as follows: When the SG-VSG parallel power supply system operates in a steady state, the power of the electrical load and the power of the power supply are balanced, that is, the power provided by the power supply and the power consumed by the electrical load maintain the balance principle, and the AC voltage of the SG-VSG parallel power supply system can be obtained .

[0048] Further derivation can obtain: U ac =

[0049] According to the rotor motion equation of the SG-VSG parallel power supply system, it can be obtained that the active power output by the synchronous generator and the active power output by the virtual synchronous generator will both affect the power angle δ of the SG-VSG parallel power supply system sv ; at the same time, according to the rotor motion equation of the SG-VSG parallel power supply system, the rotor motion equation block diagram of the SG-VSG parallel power supply system is obtained, as Figure 3 shown

[0050] Refer to Figure 3 , the active power P output by the synchronous generator se and the active power P output by the virtual synchronous generator ve are both input quantities of the rotor motion equation of the SG-VSG parallel power supply system, and the power angle δ of the SG-VSG parallel power supply system sv is the output quantity of the rotor motion equation of the SG-VSG parallel power supply system. The rotor motion equation of the SG-VSG parallel power supply system has no association with the line impedance Z line1 and the line impedance Z line2 . When there is a power mutation or a short-circuit fault in the electrical load of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system only changes with the active power P output by the synchronous generator se and the active power P output by the virtual synchronous generator ve .

[0051] According to the calculation of the AC voltage of the SG-VSG parallel power supply system, the AC voltage U of the SG-VSG parallel power supply system can be obtained ac and the active power P output by the synchronous motor se , the reactive power Q output by the synchronous generator se , the active power P output by the virtual synchronous motor ve and the reactive power Q output by the virtual synchronous generator ve are related, and are also related to the active power P of the first line line1 , the active power P of the second line line2 , the reactive power Q of the first line line1 and the reactive power Q of the second line line2 .

[0052] According to the calculation formula of the AC voltage of the SG-VSG parallel power supply system, the AC side voltage block diagram of the SG-VSG parallel power supply system can be obtained, as Figure 4 shown.

[0053] Referring to Figure 4 , the AC voltage U of the SG-VSG parallel power supply system can be obtained ac is also related to the admittance Y of the electrical load lv . At the same time, the SG-VSG parallel power supply system is also affected by the active power P output by the synchronous generator se , the reactive power Q output by the synchronous generator se , the active power P output by the virtual synchronous generator ve , the reactive power Q output by the virtual synchronous generator ve , the active power P of the first line line1 , the active power P of the second line line2 , the reactive power Q of the first line line1 and the reactive power Q of the second line line2 .

[0054] Since the power angle δ of the SG-VSG parallel power supply system sv and the AC voltage U of the SG-VSG parallel power supply system ac are both related to the electromagnetic power of the synchronous generator and the electromagnetic power of the virtual synchronous generator, therefore, combining the output power calculation formula of the SG-VSG parallel power supply system, the coupling model diagram of the SG-VSG parallel power supply system can be obtained, as Figure 5 shown.

[0055] Referring to Figure 5, the dashed line Ⅰ indicates that the reactive power of the synchronous generator has a coupling effect on the active power of the synchronous generator, and the dashed line Ⅱ indicates that the reactive power of the virtual synchronous generator has a coupling effect on the active power of the virtual synchronous generator; the dashed line Ⅲ indicates that the active power of the synchronous generator has a coupling effect on the reactive power of the synchronous generator, and the dashed line Ⅳ indicates that the active power of the virtual synchronous generator has a coupling effect on the reactive power of the virtual synchronous generator.

[0056] Therefore, it can be obtained that the power angle δ sv of the SG-VSG parallel power supply system and the stability of the AC voltage U ac of the SG-VSG parallel power supply system have an impact on each other, affecting the stability of the SG-VSG parallel power supply system.

[0057] According to the analysis of the power system, the active power is generally related to the frequency, and the reactive power is related to the voltage. The AC voltage of the SG-VSG parallel power supply system is associated with the active power through two coupling branches formed by the dashed line Ⅰ and the dashed line Ⅱ respectively, that is, the reactive power will have an impact on the active power; similarly, the active power can also have an impact on the reactive power through two coupling branches formed by the dashed line Ⅲ and the dashed line Ⅳ respectively. Therefore, it shows that there is a power coupling phenomenon between the synchronous motor and the virtual synchronous motor in the SG-VSG parallel power supply system, and the coupling terms of the SG-VSG parallel power supply system are determined.

[0058] Due to the existence of these four coupling branches in the SG-VSG parallel power supply system, it constitutes the interaction of coupling between the AC voltage of the SG-VSG parallel power supply system and the power angle of the AC voltage of the SG-VSG parallel power supply system, resulting in continuous superimposed coupling interference in the AC voltage control process of the SG-VSG parallel power supply system, causing the AC voltage of the microgrid island system to be unstable under the power supply condition of the SG-VSG parallel power supply system.

[0059] Furthermore, it is explained that step S7 includes: S71. Determine the d-q decoupled current terms applied to the control loop of the synchronous generator according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system, and the AC voltage of the SG-VSG parallel power supply system:

[0060]

[0061] Among them, i SG_d is the d-axis decoupled current term applied to the control loop of the synchronous generator, i SG_q is the q-axis decoupled current term applied to the control loop of the synchronous generator; u acis the instantaneous AC voltage of the SG-VSG parallel power supply system, u v is the instantaneous output voltage of the virtual synchronous generator.

[0062] Reference Figure 6 , specifically, the d-q decoupled current term is superimposed on the d-q axis current reference values of the synchronous motor control, generating a regulating voltage in the SG control loop, which can eliminate the coupling power generated by the coupling branches of dotted line Ⅰ and dotted line Ⅲ. Therefore, the coupling influence of the coupling branches of dotted line Ⅰ and dotted line Ⅲ on the SG-VSG parallel power supply system can be eliminated.

[0063] Figure 6 In i derf is the d-axis current reference value of the synchronous motor, i qref is the q-axis current reference value of the synchronous motor, i d is the sampled value of the d-axis output current of the synchronous motor, i q is the sampled value of the q-axis output current of the synchronous motor, i α is the α component of the synchronous motor output current, i β is the β component of the synchronous motor output current, i a , i b and i c are the three-phase currents output by the synchronous motor respectively, ω s is the angular frequency of the synchronous motor, Ψ f is the magnetic flux of the synchronous motor, L d is the coupling inductance of the synchronous motor.

[0064] PI is the regulator, u d is the d-axis sampling of the synchronous motor output voltage, u q is the q-axis sampling of the synchronous motor output voltage, u * d is the d-axis reference of the synchronous motor output voltage, u * q is the q-axis reference of the synchronous motor output voltage, u α is the axis sampling of the synchronous motor output voltage,u β For the output voltage of the synchronous motor Axis sampling, θ r is the rotor angle of the permanent magnet synchronous generator (PMSG, Permanent Magnet Synchronous Generator).

[0065] Superimpose the d-q decoupled current terms on the given d-q current reference values respectively, and generate a regulating voltage through the control loop of the synchronous motor that can cancel the coupling branches of the dashed line Ⅰ and the dashed line Ⅲ, eliminating the coupling influence of the coupling branches of the dashed line Ⅰ and the dashed line Ⅲ on the SG-VSG parallel power supply system.

[0066] S72. Determine the decoupled power term applied to the control loop of the virtual synchronous generator according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system, and the AC voltage of the SG-VSG parallel power supply system:

[0067]

[0068] Among them, P decoupling is the active power decoupling term applied to the control loop of the virtual synchronous generator, Q decoupling is the active power decoupling term applied to the control loop of the virtual synchronous generator.

[0069] Reference Figure 7 , specifically, superimpose the active power decoupling term and the reactive power decoupling term on the active power reference value of the virtual synchronous motor and the reactive power reference value of the virtual synchronous motor in the control loop of the virtual synchronous motor, then the influence of the coupling branches of the dashed line Ⅱ and the dashed line Ⅳ on the SG-VSG parallel power supply system can be eliminated, and the stability of the microgrid island system can be improved; among them, the control loop of the virtual synchronous motor includes the active power loop of the virtual synchronous motor and the reactive power loop of the virtual synchronous motor.

[0070] Figure 7 In θ is the angular frequency of the virtual synchronous motor, ω g is the grid angular frequency, Lc is the coupling inductance of the virtual synchronous motor, G f is the transfer function of the feedforward controller, G cc is the transfer function of the current regulator, G vc is the transfer function of the voltage regulator; 1 / s is the differential operator, ω is the output angular frequency of the virtual synchronous motor, Pref is the active power reference value of the virtual synchronous generator, and ΔP is the active power transformation amount of the virtual synchronous generator. u od is the d-axis component of the output voltage of the virtual synchronous generator. u oq is the q-axis component of the output voltage of the virtual synchronous generator. u od.ref is the reference of the d-axis component of the output voltage of the virtual synchronous generator. Q ref is the reactive power reference value of the virtual synchronous generator. k q is the droop coefficient.

[0071] The decoupled power terms obtained by calculation are correspondingly superimposed on the active power loop of the virtual synchronous generator and the reactive power loop of the virtual synchronous generator. By acting on the active power loop of the virtual synchronous generator and the reactive power loop of the virtual synchronous generator, a pair of active power and reactive power with equal magnitudes and opposite directions on the coupling branches of the dotted line Ⅱ and the dotted line Ⅳ can be generated, achieving mutual cancellation and eliminating the influence of the coupling branches of the dotted line Ⅱ and the dotted line Ⅳ on the SG-VSG parallel power supply system.

[0072] Reference Figure 8 , in actual use, when the microgrid island system is operating normally, the synchronous generator supplies power to the microgrid island system alone first. When the virtual synchronous generator is put into power supply at the 4th second and the SG-VSG parallel power supply system is formed, it can be seen that the AC voltage of the SG-VSG parallel power supply system can significantly reduce fluctuations and oscillations through the power supply voltage stabilization method of the microgrid island system provided by the present invention.

[0073] Reference Figure 9 , when the microgrid island system is jointly powered by the synchronous generator and the virtual synchronous generator, when the active power of the electrical load in the microgrid island system suddenly increases at the 5.5th second, the power supply voltage stabilization method of the microgrid island system provided by the present invention can effectively reduce the fluctuations of the AC voltage of the SG-VSG parallel power supply system.

[0074] The power supply voltage stabilization method of the microgrid island system provided by the present invention eliminates the influence of the four coupling branches on the SG-VSG parallel power supply system by applying the decoupling terms in the control loops of the synchronous generator and the virtual synchronous generator, and improves the voltage stability of the microgrid island system.

[0075] Embodiment 2 Based on Embodiment 1, this embodiment provides a power supply voltage stabilization device for a microgrid island system, including: A parallel admittance parameter calculation module for calculating the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system; An output power calculation module, configured to calculate the output power of the SG-VSG parallel power supply system according to the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system; A rotor motion equation construction module, configured to construct a rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system; An apparent power calculation module, configured to calculate the apparent power of the SG-VSG parallel power supply system; A power calculation module for system output, configured to calculate the coupling power of the SG-VSG parallel power supply system according to the apparent power of the SG-VSG parallel power supply system and the output power of the SG-VSG parallel power supply system; An AC voltage calculation module, configured to calculate the AC voltage of the SG-VSG parallel power supply system according to the coupling power of the SG-VSG parallel power supply system; An SG-VSG parallel power supply system decoupling module, configured to calculate the decoupling term of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system, and the AC voltage of the SG-VSG parallel power supply system, and superimpose the calculated decoupling term on the SG-VSG parallel power supply system.

[0076] Embodiment 3 Based on Embodiment 1, this embodiment provides a power supply voltage stabilizing device for a microgrid island system, including a non-volatile storage medium and a central processing unit. An executable code is stored in the non-volatile storage medium. When the central processing unit executes the executable code, the power supply voltage stabilizing method for the microgrid island system described in Embodiment 1 is implemented.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting the present invention; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present invention.

Claims

1. A power supply voltage stabilization method for a microgrid islanding system, characterized in that, It includes the following steps: S1. Calculate the shunt admittance parameters of the transmission lines of the SG-VSG parallel power supply system; S2. Calculate the output power of the SG-VSG parallel power supply system according to the shunt admittance parameters of the transmission lines of the SG-VSG parallel power supply system; S3. Construct the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system; S4. Calculate the apparent power of the SG-VSG parallel power supply system; S5. Calculate the coupling power of the SG-VSG parallel power supply system according to the apparent power and the output power of the SG-VSG parallel power supply system; S6. Calculate the AC voltage of the SG-VSG parallel power supply system according to the coupling power of the SG-VSG parallel power supply system; S7. Calculate the decoupling terms of the SG-VSG parallel power supply system according to the output power, the rotor motion equation and the AC voltage of the SG-VSG parallel power supply system, and superimpose the calculated decoupling terms on the SG-VSG parallel power supply system.

2. The power supply voltage stabilization method of the microgrid island system according to claim 1, wherein The SG-VSG parallel power supply system includes a synchronous generator control loop, a virtual synchronous generator control loop, a synchronous generator, a virtual synchronous generator, a first line, a second line and an electrical load. The first line is in parallel with the second line. The synchronous generator control loop is connected to the input end of the first line through the synchronous generator. The virtual synchronous generator control loop is connected to the input end of the second line through the virtual synchronous generator. The output ends of the first line and the second line are both connected to the input end of the electrical load; The step S1 includes: S11. Calculate the line admittance Y of the first line s , the line admittance Y of the second line ls and the admittance Y of the electrical load lv : Among them, Z ls is the line impedance of the first line, Z lv is the line impedance of the second line, Z load is the impedance of the electrical load; S12. Calculate the parallel admittance of the first line and the electrical load, the parallel admittance of the first line and the second line, and the parallel admittance of the second line and the electrical load according to the line admittance Y of the first line, the line admittance Y of the second line, and the admittance Y of the electrical load. s of the second line ls and the admittance Y of the electrical load lv . The parallel admittance of the first line and the electrical load , the parallel admittance of the first line and the second line and the parallel admittance of the second line and the electrical load.

3. The power supply voltage stabilization method of the microgrid island system according to claim 2, characterized in that The step S2 includes: S21. Calculate the active power \(P\) and the reactive power \(Q\) output by the synchronous generator according to the shunt admittance \(Y\) of the first line and the electrical load and the shunt admittance \(Y\) of the first line and the second line: ss and the shunt admittance \(Y\) of the first line and the second line sv to calculate the active power \(P\) output by the synchronous generator se and the reactive power \(Q\) output by the synchronous generator se : Among them, E s is the output voltage of the synchronous generator, G ss is the conductance of the parallel admittance Y ss of the first line and the electrical load, U v is the output voltage of the virtual synchronous generator, |Y sv | is the amplitude of the parallel admittance Y sv of the first line and the second line, δ sv is the power angle of the SG-VSG parallel power supply system, is the phase angle of the parallel admittance Y sv of the first line and the second line, B ss is the susceptance of the parallel admittance Y ss of the first line and the electrical load; S22. Calculate the active power \(P\) output by the virtual synchronous generator and the reactive power \(Q\) output by the virtual synchronous generator according to the shunt admittance \(Y\) of the first line and the second line and the shunt admittance \(Y\) of the second line and the electrical load. sv and the shunt admittance \(Y\) of the second line and the electrical load vv : ve Calculate the active power \(P\) output by the virtual synchronous generator and the reactive power \(Q\) output by the virtual synchronous generator ve : Among them, E v is the electromotive force of the synchronous generator, G vv is the conductance of the shunt admittance Y vv of the second line and the electrical load, B vv is the susceptance of the shunt admittance Y vv of the second line and the electrical load.

4. The power supply voltage stabilization method for the microgrid island system according to claim 3, wherein The specific content of the step S3 is: Construct the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system: Among them, J sv is the equivalent virtual inertia of the SG-VSG parallel power supply system, is the angular acceleration between the synchronous generator and the virtual synchronous generator, is the power angle difference between the synchronous generator and the virtual synchronous generator, T M is the equivalent mechanical torque of the SG-VSG parallel power supply system, T E is the equivalent electromagnetic torque of the SG-VSG parallel power supply system, J s is the inertia coefficient of the synchronous generator, J v is the virtual inertia coefficient of the virtual synchronous generator, D ps is the damping coefficient of the synchronous generator, D pv is the virtual damping coefficient of the virtual synchronous generator, t is time, ω s is the angular frequency sampling value of the synchronous generator, ω v is the angular frequency sampling value of the virtual synchronous generator, and ω0 is the initial angular frequency of the SG-VSG parallel power supply system.

5. The power supply voltage stabilization method for the microgrid island system according to claim 4, characterized in that, The apparent power of the SG-VSG parallel power supply system includes the apparent power S of the first line line1 and the apparent power S of the second line line2 : Among them, P line1 is the active power of the first line, P line2 is the active power of the second line, Q line1 is the reactive power of the first line, Q line2 is the reactive power of the second line, I line1 is the current of the first line, I line2 is the current of the second line, and j is the imaginary unit.

6. The power supply voltage stabilization method for the microgrid island system according to claim 5, characterized in that The specific content of the step S5 is: S51. Calculate the active power \(P_{coupled}\) coupled between the synchronous generator and the virtual synchronous generator according to the active power \(P\) output by the synchronous generator, the active power \(P\) output by the virtual synchronous generator, the active power \(P\) of the first line, and the active power \(P\) of the second line, where \(P_{coupled}=P + P - P - P\); se the active power \(P\) output by the virtual synchronous generator ve the active power \(P\) of the first line line1 and the active power \(P\) of the second line line2 where \(P_{coupled}=P + P - P - P\); sv =P se +P ve -P line1 -P line2 ; S52. According to the reactive power Q output by the synchronous generator se and the reactive power Q output by the virtual synchronous generator ve , the reactive power Q of the first line line1 and the reactive power Q of the second line line2 , calculate the reactive power Q coupled between the synchronous generator and the virtual synchronous generator sv =Q se +Q ve -Q line1 -Q line2 .

7. The power supply voltage stabilization method of the microgrid island system according to claim 6, characterized in that The specific content of the step S6 is: According to the active power P output by the SG-VSG parallel power supply system sv and the reactive power Q output by the SG-VSG parallel power supply system sv , calculate the AC voltage of the SG-VSG parallel power supply system .

8. The power supply voltage stabilization method of the microgrid island system according to claim 7, characterized in that, The step S7 includes: S71. Determine the d-q decoupling current terms applied to the synchronous generator control loop according to the output power, the rotor motion equation and the AC voltage of the SG-VSG parallel power supply system; Among them, i SG_d is the d-axis decoupling current term applied to the control loop of the synchronous generator, i SG_q is the q-axis decoupling current term applied to the control loop of the synchronous generator; u ac is the instantaneous AC voltage of the SG-VSG parallel power supply system, u v is the instantaneous output voltage of the virtual synchronous generator; S72. Determine the decoupling power terms applied to the virtual synchronous generator control loop according to the output power, the rotor motion equation and the AC voltage of the SG-VSG parallel power supply system; Among them, P decoupling is the active power decoupling term applied to the virtual synchronous generator control loop, Q decoupling is the reactive power decoupling term applied to the virtual synchronous generator control loop.

9. A power supply voltage stabilizing device for a microgrid islanding system, characterized in that, To implement the power supply voltage stabilization method for the microgrid island system described in any one of claims 1 to 8, it includes: A shunt admittance parameter calculation module for calculating the shunt admittance parameters of each transmission line in the SG-VSG parallel power supply system; An output power calculation module for calculating the output power of the SG-VSG parallel power supply system according to the shunt admittance parameters of each transmission line in the SG-VSG parallel power supply system; A rotor motion equation construction module for constructing the rotor motion equation of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system; An apparent power calculation module, configured to calculate the apparent power of the SG-VSG parallel power supply system; A power calculation module for the system output, configured to calculate the coupling power of the SG-VSG parallel power supply system according to the apparent power of the SG-VSG parallel power supply system and the output power of the SG-VSG parallel power supply system; An AC voltage calculation module, configured to calculate the AC voltage of the SG-VSG parallel power supply system according to the coupling power of the SG-VSG parallel power supply system; An SG-VSG parallel power supply system decoupling module, configured to calculate the decoupling term of the SG-VSG parallel power supply system according to the output power of the SG-VSG parallel power supply system, the rotor motion equation of the SG-VSG parallel power supply system, and the AC voltage of the SG-VSG parallel power supply system, and superimpose the calculated decoupling term on the SG-VSG parallel power supply system.

10. A power supply voltage stabilizing device for a microgrid island system, characterized in that, It includes a non-volatile storage medium and a central processing unit. An executable code is stored in the non-volatile storage medium. When the central processing unit executes the executable code, the power supply voltage stabilization method of the microgrid island system as described in any one of claims 1 to 8 is implemented.

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