A method, system and device for power supply voltage stabilization of microgrid island system

Abstract

The present invention relates to the technical field of microgrid voltage stabilization, and more particularly to a method, system, and device for power supply voltage stabilization of a microgrid island system. The method determines the coupling term of the SG-VSG parallel power supply system based on its output power, the rotor motion equation, and the AC voltage. To address the coupling problem of the SG-VSG parallel power supply system, the calculated decoupling term is applied to the synchronous generator control loop and the virtual synchronous generator control loop, respectively, effectively suppressing power angle changes of the SG-VSG parallel power supply system. When the active power of the electrical load suddenly increases, the method ensures that the voltage of the microgrid island system remains stable, thereby improving the stability of the microgrid island system.

Description

Technical Field

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

[0002] With the continuous acceleration of the construction of new power systems and the 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) or a power electronic converter. In an island system, the power electronic converter is generally controlled by a virtual synchronous generator (VSG). Both can be used as the power supply for the island system.

[0004] When the two jointly supply power to the microgrid island system, 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, power coupling occurs between the synchronous generator and the virtual synchronous generator, causing 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, existing solutions typically passively increase the output damping of synchronous generators or virtual synchronous generators to suppress voltage oscillations. Consequently, these solutions often provide suboptimal control, requiring repeated adjustments to the required damping under different operating conditions. This makes them difficult to adapt to the complex and ever-changing microgrid island systems and fails to meet actual voltage stabilization requirements. Summary of the Invention

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

[0007] The present invention solves the above-mentioned technical problems by:

[0008] A method for stabilizing power supply voltage of a microgrid island system, comprising the following steps:

[0009] S1. Calculate the parallel admittance parameters of the transmission line of the SG-VSG parallel power supply system;

[0010] S2. Calculate the output power of the SG-VSG parallel power supply system based on the parallel admittance parameters of the SG-VSG parallel power supply system transmission lines;

[0011] 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;

[0012] S4. Calculate the apparent power of the SG-VSG parallel power supply system;

[0013] S5. Calculate the coupled power of the SG-VSG parallel power supply system based on the apparent power of the SG-VSG parallel power supply system and the output power of the SG-VSG parallel power supply system;

[0014] S6. Calculate the AC voltage of the SG-VSG parallel power supply system according to the coupled power of the SG-VSG parallel power supply system;

[0015] S7. 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.

[0016] It is further defined that 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 and the second line are connected in parallel, 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, and the output end of the first line and the output end of the second line are both connected to the input end of the electrical load;

[0017] The step S1 comprises:

[0018] S11. Calculate the line admittance Y of the first line respectively s , the line admittance Y of the second line ls and the admittance Y of the electrical load lv :

[0019]

[0020] 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;

[0021] 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 to conduct the .

[0022] It is further defined that step S2 includes:

[0023] S21, according to the parallel admittance Y of the first circuit and the power load ss The parallel admittance Y of the first and second lines 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 :

[0024]

[0025] Among them, E s is the output voltage of the synchronous generator, G ss The parallel admittance Y of the first line and the 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 and second lines sv The amplitude, δ sv is the power angle of the SG-VSG parallel power supply system, Y is the parallel admittance of the first and second lines sv The phase angle, B ss Y is the parallel admittance of the first line and the load ss of susceptance;

[0026] S22, according to the parallel admittance Y of the first circuit and the second circuit sv The second line and the power load parallel admittance Y 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 :

[0027]

[0028] Among them, E v is the electromotive force of the synchronous generator, G vv Y is the parallel admittance of the second line and the load vv The conductivity, B vv Y is the parallel admittance of the second line and the load vv of the electrical impedance.

[0029] Further defined, the step S3 is specifically as follows:

[0030] 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 is constructed:

[0031]

[0032] 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.

[0033] It is further defined 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 :

[0034]

[0035] 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 circuit, I line2 is the current of the second circuit, and j is an imaginary number.

[0036] It is further defined that step S5 is specifically as follows:

[0037] 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 active power P coupled between the synchronous generator and the virtual synchronous generatorsv =P se +P ve -P line1 -P line2 ;

[0038] S52, according to the reactive power Q output by the synchronous generator se , the reactive power Q output by the virtual synchronous generator ve , 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 .

[0039] It is further defined that step S6 is specifically as follows:

[0040] According to the active power P output by the SG-VSG parallel power supply system sv 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 .

[0041] It is further defined that step S7 includes:

[0042] S71. Determine the dq decoupling current term applied to the synchronous generator control loop based on 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:

[0043]

[0044]

[0045] in, i SG_d is the d-axis decoupling current term applied to the synchronous generator control loop, i SG_q is the q-axis decoupling 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;

[0046] S72. Determine a decoupling power term applied to a virtual synchronous generator control loop based on 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:

[0047]

[0048]

[0049] in, 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.

[0050] A microgrid island system power supply voltage stabilization device, used to implement the above-mentioned microgrid island system power supply voltage stabilization method, comprising:

[0051] The parallel admittance parameter calculation module is used to calculate the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system;

[0052] An output power calculation module is used to calculate the output power of the SG-VSG parallel power supply system based on the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system;

[0053] A 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;

[0054] Apparent power calculation module, used to calculate the apparent power of the SG-VSG parallel power supply system;

[0055] The system output power calculation module is used to calculate the coupled 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;

[0056] An AC voltage calculation module, used to calculate the AC voltage of the SG-VSG parallel power supply system according to the coupled power of the SG-VSG parallel power supply system;

[0057] The SG-VSG parallel power supply system decoupling module is used to calculate the decoupling term of the SG-VSG parallel power supply system based on 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.

[0058] A microgrid island system power supply and voltage stabilization device includes a non-volatile storage medium and a central processing unit. The non-volatile storage medium stores executable code. When the central processing unit executes the executable code, the microgrid island system power supply and voltage stabilization method as described above is implemented.

[0059] The beneficial effects of the present invention are:

[0060] The present invention determines the coupling term of the SG-VSG parallel power supply system based on 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 term is applied to the synchronous generator control loop and the virtual synchronous generator control loop respectively, so as to effectively suppress the power angle change of the SG-VSG parallel power supply system. When the active power of the power load suddenly increases, the voltage of the microgrid island system is ensured to be continuously stable, thereby improving the stability of the microgrid island system. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 This is a structural diagram of the SG-VSG parallel power supply system of the present invention;

[0062] Figure 2 This is a step diagram of the power supply and voltage stabilization method for a microgrid island system of the present invention;

[0063] Figure 3 This is a block diagram of the rotor motion equation of the SG-VSG parallel power supply system of the present invention;

[0064] Figure 4 This is a block diagram of the AC side voltage of the SG-VSG parallel power supply system of the present invention;

[0065] Figure 5 This is the coupling model of the SG-VSG parallel power supply system of the present invention;

[0066] Figure 6 This is a block diagram of the synchronous generator control loop of the present invention;

[0067] Figure 7 This is a block diagram of the virtual synchronous generator control loop of the present invention;

[0068] Figure 8 This is a comparison chart showing the impact of the virtual synchronous motor power supply on the power supply stability of the microgrid island system;

[0069] Figure 9 This is a comparison diagram of the impact of a sudden increase in active power on the power supply stability of the microgrid island system in the present invention. DETAILED DESCRIPTION

[0070] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0071] 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 serve as power sources; wherein the first line is connected to the second line 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 end of the first line and the output end of the second line are both connected to the input end of the electrical load.

[0072] Among them, the impedance of the electrical load is Z load ; The filter impedance in the first circuit is Z d , the line impedance is Z line1 , the filter impedance of the second line is Z filter , the line impedance is Z line2 .

[0073] 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, i dc is the DC bus current of the virtual synchronous generator VSG.

[0074] Example 1

[0075] refer to Figure 2 The present invention provides a method for stabilizing power supply of a microgrid island system, comprising the following steps:

[0076] S1. Calculate the parallel admittance parameters of the transmission line of the SG-VSG parallel power supply system;

[0077] S2. Calculate the output power of the SG-VSG parallel power supply system based on the parallel admittance parameters of the SG-VSG parallel power supply system transmission lines;

[0078] 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;

[0079] S4. Calculate the apparent power of the SG-VSG parallel power supply system;

[0080] S5. Calculate the coupled power of the SG-VSG parallel power supply system based on the apparent power of the SG-VSG parallel power supply system and the output power of the SG-VSG parallel power supply system;

[0081] S6. Calculate the AC voltage of the SG-VSG parallel power supply system according to the coupled power of the SG-VSG parallel power supply system;

[0082] S7. 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.

[0083] Specific, combined Figure 1 , it can be obtained that step S1 includes the following steps:

[0084] S11. Calculate the admittance Y of the first line respectively s , the admittance Y of the second line ls and the admittance Y of the electrical load lv :

[0085]

[0086] 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 +Z line2 ;

[0087] 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 to conduct the .

[0088] To further illustrate, step S2 includes:

[0089] S21, according to the parallel admittance Y of the first circuit and the power load ss The parallel admittance Y of the first and second lines sv , calculate, calculate the active power P output of the synchronous generator se And the reactive power Q output by the synchronous generator se :

[0090]

[0091] Among them, E s is the output voltage of the synchronous generator, G ss Y is the parallel admittance of the first line and the 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 and second lines sv The amplitude, δ sv is the power angle of the SG-VSG parallel power supply system, Y is the parallel admittance of the first and second lines sv The phase angle, B ss Y is the parallel admittance of the first line and the load ss of susceptance;

[0092] S22, according to the parallel admittance Y of the first circuit and the second circuit 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 :

[0093]

[0094] Among them, E v is the electromotive force of the synchronous generator, G vv Y is the parallel admittance of the second line and the load vv The conductivity, B vv Y is the parallel admittance of the second line and the load vv of the electrical impedance.

[0095] Since the reactance of the transmission line in the SG-VSG parallel power supply system is much greater than its resistance, the parallel admittance Y of the first line and the second line is sv Phase angle ≈0°.

[0096] When the first line and the second line are connected in parallel, the admittance Y sv Phase angle ≈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 at their maximum values. Therefore, when the power angle δ of the SG-VSG parallel power supply system is sv When ≠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.

[0097] To further illustrate, step S3 is specifically as follows:

[0098] 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 is constructed:

[0099]

[0100] 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, 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 pv is the proportional regulation coefficient of the virtual synchronous generator, σ i is the integral regulation coefficient of the synchronous generator, and t is the time.

[0101] According to T se =P se / ω0,T ve =P ve / ω0, and further obtain the rotor motion equation of the SG-VSG parallel power supply system:

[0102]

[0103] in, 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, .

[0104] To further illustrate, step S4 is specifically as follows:

[0105] 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 :

[0106]

[0107] 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 circuit, I line2 is the current of the second circuit, and j is an imaginary number.

[0108] To further illustrate, step S5 is specifically as follows:

[0109] 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 active power P coupled between the synchronous generator and the virtual synchronous generator sv =P se +P ve -P line1 -P line2 ;

[0110] S52, according to the reactive power Q output by the synchronous generator se, the reactive power Q output by the virtual synchronous generator ve , 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 .

[0111] To further illustrate, step S6 is specifically as follows:

[0112] When the SG-VSG parallel power supply system operates in a steady state, the load power and the power supply power are balanced, that is, the power provided by the power supply and the power consumed by the load are kept in balance. The AC voltage of the SG-VSG parallel power supply system can be obtained. .

[0113] Further deduction can be obtained:

[0114] U ac =

[0115] According to the rotor motion equation of the SG-VSG parallel power supply system, the active power output by the synchronous generator and the active power output by the virtual synchronous generator will 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, such as Figure 3 shown.

[0116] 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 the input quantities of the rotor motion equation of the SG-VSG parallel power supply system, the power angle δ of the SG-VSG parallel power supply system sv is the output of the rotor motion equation of the SG-VSG parallel power supply system, which is related to the line impedance Z line1 and line impedance Z line2 There is no correlation. When the power load of the SG-VSG parallel power supply system experiences a sudden power surge or a short circuit fault, 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 change.

[0117] According to the calculation of the AC voltage of the SG-VSG parallel power supply system, the AC voltage U ac 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 It is also related to the active power P of the first line. line1 , the active power P of the second line line2 , reactive power Q of the first line line1 and the reactive power Q of the second line line2 related.

[0118] According to the AC voltage calculation formula 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 shown in the figure: Figure 4 shown.

[0119] refer to Figure 4 , we can get the AC voltage U of the SG-VSG parallel power supply system ac 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 , reactive power Q of the first line line1 and the reactive power Q of the second line line2 impact.

[0120] Due to the power angle δ of the SG-VSG parallel power supply system sv AC voltage U of the SG-VSG parallel power supply system ac They are all related to the electromagnetic power of the synchronous generator and the electromagnetic power of the virtual synchronous generator. Therefore, combined with 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 shown in Figure 5 shown.

[0121] refer to Figure 5, dotted line I indicates that the reactive power of the synchronous generator has a coupling effect on the active power of the synchronous generator, and dotted 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; dotted line III indicates that the active power of the synchronous generator has a coupling effect on the reactive power of the synchronous generator, and dotted 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.

[0122] Therefore, it can be obtained that the power angle δ of the SG-VSG parallel power supply system sv Stability and AC voltage U of SG-VSG parallel power supply system ac The stability of the SG-VSG parallel power supply system is affected by each other.

[0123] According to power system analysis, active power is generally related to frequency, while reactive power is related to voltage. The AC voltage of the SG-VSG parallel power supply system is associated with active power through the two coupling branches formed by dotted lines I and II, that is, reactive power will affect active power; similarly, active power can also affect reactive power through the two coupling branches formed by dotted lines III and IV. Therefore, it is shown that in the SG-VSG parallel power supply system, there is power coupling between the synchronous motor and the virtual synchronous motor, and the coupling term of the SG-VSG parallel power supply system is determined.

[0124] Due to the existence of these four coupling branches in the SG-VSG parallel power supply system, the AC voltage of the SG-VSG parallel power supply system and the AC voltage power angle of the SG-VSG parallel power supply system are coupled with each other, resulting in continuous superposition of coupling interference during the AC voltage control process of the SG-VSG parallel power supply system, causing AC voltage instability of the microgrid island system under the power supply condition of the SG-VSG parallel power supply system.

[0125] To further illustrate, step S7 includes:

[0126] S71. Determine the dq decoupling current term applied to the synchronous generator control loop based on 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:

[0127]

[0128]

[0129] in, i SG_d is the d-axis decoupling current term applied to the synchronous generator control loop, i SG_qis the q-axis decoupling 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.

[0130] refer to Figure 6 Specifically, the dq decoupling current term is superimposed on the dq axis current reference value of the synchronous motor control to generate a regulating voltage in the SG control loop, which can eliminate the coupling power generated by the dotted line I and dotted line III coupling branches, thereby eliminating the coupling effect of the dotted line I and dotted line III coupling branches on the SG-VSG parallel power supply system.

[0131] Figure 6 middle, 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 d-axis output current sampling value of the synchronous motor, i q is the q-axis output current sampling value of the synchronous motor, i α Output current for synchronous motor α Quantity, i β Output current for synchronous motor β Quantity, i a 、 i b and i c are the three-phase currents output by the synchronous motor, ω s is the angular frequency of the synchronous motor, Ψ f is the magnetic flux of the synchronous motor, L d is the coupled inductance of the synchronous motor.

[0132] PI For 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 synchronous motor output voltage d-axis reference, u * q is the synchronous motor output voltage q-axis reference, uα Output voltage for synchronous motor Axis sampling, u β Output voltage for synchronous motor Axis sampling, θ r is the rotor angle of the permanent magnet synchronous generator (PMSG).

[0133] The dq decoupling current terms are superimposed on the given dq current reference values, and the control loop of the synchronous motor generates a regulated voltage that can offset the coupling branches of dotted lines I and III, thereby eliminating the coupling influence of the coupling branches of dotted lines I and III on the SG-VSG parallel power supply system.

[0134] S72. Determine a decoupling power term applied to a virtual synchronous generator control loop based on 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:

[0135]

[0136]

[0137] in, P decoupling is the active power decoupling term applied to the virtual synchronous generator control loop, Q decoupling is the active power decoupling term applied to the virtual synchronous generator control loop.

[0138] refer to Figure 7 Specifically, by superimposing the active power decoupling term and the reactive power decoupling term on the virtual synchronous motor active power reference value and the virtual synchronous motor reactive power reference value in the virtual synchronous motor control loop, the influence of the dotted line II and dotted line IV coupling branches on the SG-VSG parallel power supply system can be eliminated, thereby improving the stability of the microgrid island system; wherein, the virtual synchronous motor control loop includes the active power loop of the virtual synchronous motor and the reactive power loop of the virtual synchronous motor.

[0139] Figure 7 middle, 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 feedforward controller transfer function, G cc is the current regulator transfer function, G vc is the voltage regulator transfer function; 1 / sis the differential operator, ω is the output angular frequency of the virtual synchronous motor, P ref is the reference value of the virtual synchronous motor active power, ΔP is the virtual synchronous motor active power conversion amount, u od is the d-axis component of the virtual synchronous motor output voltage, u oq is the q-axis component of the virtual synchronous motor output voltage, u od.ref is the reference of the d-axis component of the virtual synchronous motor output voltage, Q ref is the virtual synchronous motor reactive power reference value, k q is the droop coefficient.

[0140] The calculated decoupling power term is superimposed on the active power loop of the virtual synchronous motor and the reactive power loop of the virtual synchronous motor. By interacting with the active power loop of the virtual synchronous motor and the reactive power loop of the virtual synchronous motor, a pair of active power and reactive power with equal magnitude and opposite direction on the coupling branches of dotted line II and dotted line IV can be generated, which can cancel each other out and eliminate the influence of the coupling branches of dotted line II and dotted line IV on the SG-VSG parallel power supply system.

[0141] refer to Figure 8 In actual use, when the microgrid island system is operating normally, the microgrid island system is first powered by a synchronous motor alone. At the 4th second, the virtual synchronous motor is used to power the SG-VSG parallel power supply system. It can be seen that the AC voltage of the SG-VSG parallel power supply system can significantly reduce fluctuations and oscillations through the microgrid island system power supply stabilization method provided by the present invention.

[0142] refer to Figure 9 When the microgrid island system is powered by both the synchronous motor and the virtual synchronous motor, the active power of the electrical load in the microgrid island system suddenly increases at 5.5 seconds. The power supply voltage stabilization method for the microgrid island system provided by the present invention can effectively reduce the fluctuation of the AC voltage of the SG-VSG parallel power supply system.

[0143] The microgrid island system power supply voltage stabilization method provided by the present invention eliminates the influence of the four coupling branches on the SG-VSG parallel power supply system by applying decoupling terms in the synchronous motor control loop and the virtual synchronous motor control loop, thereby improving the voltage stability of the microgrid island system.

[0144] Example 2

[0145] Based on Example 1, this embodiment provides a power supply voltage stabilizing device for a microgrid island system, including:

[0146] The parallel admittance parameter calculation module is used to calculate the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system;

[0147] An output power calculation module is used to calculate the output power of the SG-VSG parallel power supply system based on the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system;

[0148] A 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;

[0149] Apparent power calculation module, used to calculate the apparent power of the SG-VSG parallel power supply system;

[0150] The system output power calculation module is used to calculate the coupled 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;

[0151] An AC voltage calculation module, used to calculate the AC voltage of the SG-VSG parallel power supply system according to the coupled power of the SG-VSG parallel power supply system;

[0152] The SG-VSG parallel power supply system decoupling module is used to calculate the decoupling term of the SG-VSG parallel power supply system based on 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.

[0153] Example 3

[0154] Based on Example 1, this embodiment provides a microgrid island system power supply and voltage stabilization device, including a non-volatile storage medium and a central processing unit. The non-volatile storage medium stores executable code. When the central processing unit executes the executable code, the microgrid island system power supply and voltage stabilization method described in Example 1 is implemented.

[0155] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the present invention.

Claims

1. A method for stabilizing power supply of a microgrid island system, characterized in that: The following steps are involved: S1. Calculate the parallel 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 based on the parallel admittance parameters of the SG-VSG parallel power supply system transmission lines; 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 coupled power of the SG-VSG parallel power supply system based on the apparent power of the SG-VSG parallel power supply system 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 coupled power of the SG-VSG parallel power supply system; S7. Calculate a 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; The step S3 is specifically as follows: 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 is constructed: 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, ω0 is the initial angular frequency of the SG-VSG parallel power supply system; The step S7 comprises: S71. Determine the dq decoupling current term applied to the synchronous generator control loop based on 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: in, i SG_d is the d-axis decoupling current term applied to the synchronous generator control loop, i SG_q is the q-axis decoupling 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; E s is the output voltage of the synchronous generator; G ss The parallel admittance Y of the first line and the load ss conductivity; B ss Y is the parallel admittance of the first line and the load ss Susceptance; δ sv is the power angle of the SG-VSG parallel power supply system, Y sv is the parallel admittance of the first line and the second line; Y is the parallel admittance of the first and second lines sv The phase angle; S72. Determine a decoupling power term applied to a virtual synchronous generator control loop based on 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: in, P decoupling is the active power decoupling term applied to the virtual synchronous generator control loop, G vv Y is the parallel admittance of the second line and the load vv The conductivity, B vv Y is the parallel admittance of the second line and the load vv The electrical susceptance, Q decoupling is the reactive power decoupling term applied to the virtual synchronous generator control loop.

2. The power supply voltage stabilization method for a microgrid island system according to claim 1, characterized in that: 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, wherein the first line is connected 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, and the output end of the first line and the output end of the second line are both connected to the input end of the electrical load; The step S1 comprises: S11. Calculate the line admittance Y of the first line respectively 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, 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 to conduct the .

3. The power supply voltage stabilization method for a microgrid island system according to claim 2, characterized in that: The step S2 comprises: S21, according to the parallel admittance Y of the first circuit and the power load ss The parallel admittance Y of the first and second lines sv , 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 Y is the parallel admittance of the first line and the 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 and second lines sv The amplitude, δ sv is the power angle of the SG-VSG parallel power supply system, Y is the parallel admittance of the first and second lines sv The phase angle, B ss Y is the parallel admittance of the first line and the load ss of susceptance; S22, according to the parallel admittance Y of the first circuit and the second circuit 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 : Among them, E v is the electromotive force of the synchronous generator, G vv Y is the parallel admittance of the second line and the load vv The conductivity, B vv Y is the parallel admittance of the second line and the load vv of the electrical impedance.

4. The power supply voltage stabilization method for a microgrid island system according to claim 3, 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 circuit, I line2 is the current of the second circuit, and j is an imaginary number.

5. The power supply and voltage stabilization method for a microgrid island system according to claim 4, characterized in that: The step S5 is specifically as follows: 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 active power P coupled 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 , 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 .

6. The power supply voltage stabilization method for a microgrid island system according to claim 5, characterized in that: The step S6 is specifically as follows: According to the active power P output by the SG-VSG parallel power supply system sv 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 .

7. A power supply voltage stabilizing device for a microgrid island system, characterized in that: A method for stabilizing power supply of a microgrid island system according to any one of claims 1 to 6, comprising: The parallel admittance parameter calculation module is used to calculate the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system; An output power calculation module is used to calculate the output power of the SG-VSG parallel power supply system based on the parallel admittance parameters of each transmission line in the SG-VSG parallel power supply system; A 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; Apparent power calculation module, used to calculate the apparent power of the SG-VSG parallel power supply system; The system output power calculation module is used to calculate the coupled 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, used to calculate the AC voltage of the SG-VSG parallel power supply system according to the coupled 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 based on 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.

8. A power supply voltage stabilizing device for a microgrid island system, characterized in that: The microgrid island system power supply stabilization method comprises a non-volatile storage medium and a central processing unit, wherein the non-volatile storage medium stores executable code, and when the central processing unit executes the executable code, the microgrid island system power supply stabilization method according to any one of claims 1 to 6 is implemented.

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