Grid connection method and system of electro-magnetic synchronous motor gravity energy storage system

Abstract

The invention discloses a grid-connected method and system of an electrically excited synchronous motor gravity energy storage system, the grid-connected method considers improvement of a control mode of a gravity energy storage back-to-back converter, during grid connection, a grid-side converter in an inversion state adopts a voltage and current double-loop control strategy of a virtual synchronous motor, and a grid-side converter in an inversion state adopts a grid-side converter in an inversion state; an active power calculated value and a reactive power calculated value used for supporting operation of a power grid are obtained, a grid-side converter absorbs active power from a direct-current bus and feeds the active power and the reactive power into the power grid according to the active power calculated value and the reactive power calculated value, so that the converter has inertia and dynamic reactive power supporting capacity, and the reactive power is obtained. And the fluctuation of the new energy is better inhibited. And meanwhile, the machine side converter in the rectification state adopts a direct current control strategy to determine an output voltage calculation value for stabilizing the direct current bus voltage, and the machine side converter controls the direct current bus voltage to reach the output voltage calculation value, so that the stability of the voltage on the direct current bus of the back-to-back converter is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of gravity energy storage, and in particular to a grid-connected method and system for an electrically excited synchronous motor gravity energy storage system. Background Art

[0002] Traditional gravity energy storage systems mostly use permanent magnet synchronous motors to connect back-to-back converters to the grid, and the goal of grid connection is to achieve more active input. Therefore, the machine-side converter adopts a direct current control strategy, and the grid-side converter adopts a voltage and current dual closed-loop control strategy. Due to the presence of a phase-locked loop on the grid side, the output frequency of the grid-side converter is related to the grid frequency, and there is no active droop characteristic; the output voltage of the grid-side converter is related to the grid voltage, and there is no reactive droop characteristic. The machine-side converter is connected to a permanent magnet synchronous motor and has no excitation system. It is impossible to raise the machine-end voltage and then raise the converter output voltage. This traditional method is suitable for areas with relatively stable power grids and can transmit energy to the grid well. When this traditional method is applied to new energy power generation scenarios such as photovoltaics and wind power, it is difficult to effectively alleviate the impact of new energy fluctuations on the power grid. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention proposes a grid-connected method and system for an electrically excited synchronous motor gravity energy storage system.

[0004] The technical solution of the present invention is as follows:

[0005] A grid-connected method for an electrically excited synchronous motor gravity energy storage system, wherein the electrically excited synchronous motor in the gravity energy storage system is connected to a power grid via a back-to-back converter and an LCL filter; the back-to-back converter includes a machine-side converter and a grid-side converter, and the method includes:

[0006] The grid-side converter adopts a voltage-current dual-loop control strategy of a virtual synchronous motor based on a grid-side converter control signal obtained by converting a three-phase voltage signal on the grid side to obtain an active power calculation value and a reactive power calculation value for supporting grid operation. The grid-side converter feeds active power and reactive power into the grid according to the active power calculation value and the reactive power calculation value.

[0007] The machine-side converter adopts a direct current control strategy based on the machine-side converter control signal obtained by converting the DC bus voltage signal to determine an output voltage calculation value for stabilizing the DC bus voltage, and the machine-side converter controls the DC bus voltage to reach the output voltage calculation value.

[0008] Furthermore, the control links of the voltage-current dual-loop control strategy of the virtual synchronous motor include active power control, reactive power control, virtual impedance control, current inner loop control and voltage outer loop control.

[0009] Furthermore, the active power regulation equation of the virtual synchronous motor is expressed as:

[0010]

[0011] Where P m , P e are the mechanical power and electromagnetic power of the synchronous generator respectively; J is the moment of inertia; D is the damping coefficient; ω is the angular velocity; ω ref is the rated angular frequency;

[0012] The power-frequency droop relationship is expressed as:

[0013] P m =P ref +k p (ω ref -ω)

[0014] Where P ref Indicates the active power given value; k p is the active power control coefficient; ω ref is the rated angular velocity;

[0015] Define angular momentum H = Jω, damping torque D p =Dω, then the control equation of the virtual speed regulator of the virtual synchronous motor is obtained:

[0016]

[0017] The above control equation is further adjusted as follows:

[0018]

[0019] Regulating virtual potential E in virtual synchronous motor m From the no-load potential E0 and reactive power ΔE Q , terminal voltage ΔE u Common control; among them, reactive power ΔE Q The droop relationship between reactive power and voltage can be expressed as:

[0020] ΔE Q =E ref -E0=k q (Q e -Q ref )

[0021] Terminal voltage ΔE u It is simplified to proportional control:

[0022] ΔE u =k u (U ref -U)

[0023] E=E0+ΔE Q +ΔE U

[0024] E m =E0+ΔE Q +ΔE u

[0025] The angular velocity ω is obtained by active frequency control, and the virtual potential E is obtained by reactive voltage control. m ; After Parker transformation, the virtual potential E is obtained m The d-axis component E d , virtual potential E m The q-axis component E q And for virtual impedance control:

[0026]

[0027] Where i d 、i q are the d-axis component and q-axis component of the converter output current obtained after Parker transformation; R s , L s are the virtual resistance and virtual reactance of the converter respectively; u dref 、u qref They are respectively the d-axis component reference value and the q-axis component reference value obtained after the grid-side voltage Parker transformation through the virtual impedance link;

[0028] The reference value after the grid-side voltage Parker transformation is controlled by the voltage outer loop and the current inner loop to stabilize the converter output voltage; the voltage outer loop control equation is as follows:

[0029]

[0030] Among them, u d 、u q are the actual values ​​of the grid-side output voltage of the converter respectively;

[0031] The current inner loop control equation is as follows:

[0032]

[0033] The virtual potential E is obtained through voltage and current double closed-loop control m :

[0034] E m =E0+k q (Q e -Q ref )+k u (U ref -U)

[0035] Virtual potential Em After Parker transformation, the virtual potential E is obtained m The d-axis component E d and the q-axis component E q , and calculate the active power value P according to the following formula m And reactive power calculation value Q m :

[0036] In the formula, i d 、i q They are the d-axis component and q-axis component of the converter output current obtained after Park transformation.

[0037] Further, the direct current control strategy includes current inner loop control and voltage outer loop control;

[0038] The input of the current inner loop control is the d-axis component V' of the DC side voltage d and the q-axis component of the DC voltage V' q The output is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q ;

[0039] The input of the voltage outer loop control is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q , the output is the machine-side converter output voltage U dc .

[0040] Furthermore, the current inner loop is controlled as follows:

[0041]

[0042] In the formula, i' d 、i' q are the d-axis component and q-axis component of the three-phase AC current of the synchronous motor obtained by Parker transformation; L' and r' are the resistance and reactance between the synchronous motor and the machine-side converter respectively; e' d 、e' q are the d-axis component and q-axis component of the synchronous motor terminal voltage obtained by Park transformation; V' d =S d V dc 、V' q =S q V dc ; Among them, S d , S q is the switch function;

[0043] Introduce feedforward compensation to decouple the q-axis component and the d-axis component:

[0044]

[0045] in, V' d 、V' q The steady-state given value of

[0046] Combining the above two equations, we can get:

[0047]

[0048] therefore, It can be adjusted by PI controller

[0049]

[0050] Combining the above equations, the decoupling control method of the current inner loop is obtained:

[0051]

[0052]

[0053] The voltage outer loop control is as follows:

[0054] The AC side circuit equation in the dq coordinate system is:

[0055]

[0056] DC node KCL equation:

[0057] i dc =i c +i L

[0058] Among them, i c The current flowing through the capacitor C; i L is the load current; then i dc It is expressed as:

[0059]

[0060] According to the power balance equation:

[0061]

[0062] To achieve feedback stability, the machine-side converter voltage setting value is required. The output voltage of the replacement machine-side converter is U dc , we get the final control link, and from the above equation we can get:

[0063] Then the control strategy of the voltage outer loop can be obtained, and the current inner loop control and the voltage outer loop control are connected in series to achieve stable control of the machine-side converter;

[0064]

[0065] Where U dc is the output voltage of the machine-side converter; P is the output voltage setting value of the receiving side converter; L is the active power of the gravity energy storage synchronous motor on the AC side; e' d is the d-axis component of the synchronous motor terminal voltage, i' d is the d-axis component of the synchronous motor terminal current.

[0066] Furthermore, the grid connection method further comprises: when a fault occurs on the grid side causing a voltage drop, enhancing the excitation current of the electrically excited synchronous motor.

[0067] Furthermore, when a fault occurs on the grid side causing a voltage drop, the specific method for enhancing the excitation current of the electrically excited synchronous motor includes:

[0068] When the grid voltage U at the grid-connected node of the gravity energy storage system is lower than 90% of the rated value, it is considered that a voltage drop fault occurs on the grid side, and the terminal voltage U of the electro-excitation synchronous motor is increased by the excitation current. LL Increase the upper limit of the DC bus voltage maximum value; adjust the DC bus voltage through the DC bus voltage adjustment coefficient K θ To increase the DC bus voltage reference value of the machine-side converter output Thereby raising the DC bus voltage U dc , thereby increasing the grid-side converter output reactive power Q e Upper limit; through droop control, the grid-side converter outputs reactive power Q e Increase, and finally the grid voltage U at the grid-connected node of the gravity energy storage system;

[0069] Among them, the DC bus voltage reference value output by the machine-side converter is Related to DC bus voltage regulation coefficient K θ The calculation formula is:

[0070]

[0071] The output power of the back-to-back converter is constrained as follows:

[0072]

[0073] A grid-connected system of an electrically excited synchronous motor gravity energy storage system, wherein the electrically excited synchronous motor in the gravity energy storage system is connected to a power grid via a back-to-back converter and an LCL filter; the back-to-back converter includes a machine-side converter and a grid-side converter, and the system includes a grid-side converter control module and a machine-side converter control module;

[0074] The grid-side converter control module is used to control the grid-side converter based on the grid-side converter control signal obtained by converting the three-phase voltage signal on the grid side, adopt the voltage and current dual-loop control strategy of the virtual synchronous motor, obtain the active power calculation value and reactive power calculation value used to support the operation of the grid, and the grid-side converter feeds the active power and reactive power into the grid according to the active power calculation value and reactive power calculation value;

[0075] The machine-side converter control module is used to control the machine-side converter based on the machine-side converter control signal obtained by converting the DC bus voltage signal, adopt a direct current control strategy, determine the output voltage calculation value used to stabilize the DC bus voltage, and the machine-side converter controls the DC bus voltage to reach the output voltage calculation value.

[0076] Furthermore, the control links of the voltage-current dual-loop control strategy of the virtual synchronous motor include active power control, reactive power control, virtual impedance control, current inner loop control and voltage outer loop control.

[0077] Furthermore, the active power regulation equation of the virtual synchronous motor is expressed as:

[0078]

[0079] Where P m , P e are the mechanical power and electromagnetic power of the synchronous generator respectively; J is the moment of inertia; D is the damping coefficient; ω is the angular velocity; ω ref is the rated angular frequency;

[0080] The power-frequency droop relationship is expressed as:

[0081] P m =P ref +k p (ω ref -ω)

[0082] Where P ref Indicates the active power given value; k p is the active power control coefficient; ω ref is the rated angular velocity;

[0083] Define angular momentum H = Jω, damping torque D p=Dω, then the control equation of the virtual speed regulator of the virtual synchronous motor is obtained:

[0084]

[0085] The above control equation is further adjusted as follows:

[0086]

[0087] Regulating virtual potential E in virtual synchronous motor m From the no-load potential E0 and reactive power ΔE Q , terminal voltage ΔE u Common control; among them, reactive power ΔE Q The droop relationship between reactive power and voltage can be expressed as:

[0088] ΔE Q =E ref -E0=k q (Q e -Q ref )

[0089] Terminal voltage ΔE u It is simplified to proportional control:

[0090] ΔE u =k u (U ref -U)

[0091] E=E0+ΔE Q +ΔE U

[0092] E m =E0+ΔE Q +ΔE u

[0093] The angular velocity ω is obtained by active frequency control, and the virtual potential E is obtained by reactive voltage control. m ; After Parker transformation, the virtual potential E is obtained m The d-axis component E d , virtual potential E m The q-axis component E q And for virtual impedance control:

[0094]

[0095] Where i d 、i q are the d-axis component and q-axis component of the converter output current obtained after Parker transformation; R s , L s are the virtual resistance and virtual reactance of the converter respectively; udref 、u qref They are respectively the d-axis component reference value and the q-axis component reference value obtained after the grid-side voltage Parker transformation through the virtual impedance link;

[0096] The reference value after the grid-side voltage Parker transformation is controlled by the voltage outer loop and the current inner loop to stabilize the converter output voltage; the voltage outer loop control equation is as follows:

[0097]

[0098] Among them, u d 、u q are the actual values ​​of the grid-side output voltage of the converter respectively;

[0099] The current inner loop control equation is as follows:

[0100]

[0101] The virtual potential E is obtained through voltage and current double closed-loop control m :

[0102] E m =E0+k q (Q e -Q ref )+k u (U ref -U)

[0103] Virtual potential E m After Parker transformation, the virtual potential E is obtained m The d-axis component E d and the q-axis component E q , and calculate the active power value P according to the following formula m And reactive power calculation value Q m :

[0104] In the formula, i d 、i q They are the d-axis component and q-axis component of the converter output current obtained after Park transformation.

[0105] Further, the direct current control strategy includes current inner loop control and voltage outer loop control;

[0106] The input of the current inner loop control is the d-axis component V' of the DC side voltage d and the q-axis component of the DC voltage V' q The output is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q ;

[0107] The input of the voltage outer loop control is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q , the output is the machine-side converter output voltage U dc .

[0108] Furthermore, the current inner loop is controlled as follows:

[0109]

[0110] In the formula, i' d 、i' q are the d-axis component and q-axis component of the three-phase AC current of the synchronous motor obtained by Parker transformation; L' and R' are the resistance and reactance between the synchronous motor and the machine-side converter respectively; e' d 、e' q are the d-axis component and q-axis component of the synchronous motor terminal voltage obtained by Park transformation; V' d =S d V dc 、V' q =S q V dc ; Among them, S d , S q is the switch function;

[0111] Introduce feedforward compensation to decouple the q-axis component and the d-axis component:

[0112]

[0113] in, V' d 、V' q The steady-state given value of

[0114] Combining the above two equations, we can get:

[0115]

[0116] therefore, It can be adjusted by PI controller

[0117]

[0118] Combining the above equations, the decoupling control method of the current inner loop is obtained:

[0119]

[0120] The voltage outer loop control is as follows:

[0121] The AC side circuit equation in the dq coordinate system is:

[0122]

[0123] DC node KCL equation:

[0124] i dc =i c +i L

[0125] Among them, i c The current flowing through the capacitor C; i L is the load current; then i dc It is expressed as:

[0126]

[0127] According to the power balance equation:

[0128]

[0129] To achieve feedback stability, the machine-side converter voltage setting value is required. The output voltage of the replacement machine-side converter is U dc , we get the final control link, and from the above equation we can get:

[0130] Then the control strategy of the voltage outer loop can be obtained, and the current inner loop control and the voltage outer loop control are connected in series to achieve stable control of the machine-side converter;

[0131]

[0132] Where U dc is the output voltage of the machine-side converter; P is the output voltage setting value of the receiving side converter; L is the active power of the gravity energy storage synchronous motor on the AC side; e' d is the d-axis component of the synchronous motor terminal voltage, i' d is the d-axis component of the synchronous motor terminal current.

[0133] Furthermore, the grid connection method further comprises: when a fault occurs on the grid side causing a voltage drop, enhancing the excitation current of the electrically excited synchronous motor.

[0134] Furthermore, when a fault occurs on the grid side causing a voltage drop, the specific method for enhancing the excitation current of the electrically excited synchronous motor includes:

[0135] When the grid voltage U at the grid-connected node of the gravity energy storage system is lower than 90% of the rated value, it is considered that a voltage drop fault occurs on the grid side, and the terminal voltage U of the electro-excitation synchronous motor is increased by the excitation current. LL Increase the upper limit of the DC bus voltage maximum value; adjust the DC bus voltage through the DC bus voltage adjustment coefficient K θ To increase the DC bus voltage reference value of the machine-side converter output Thereby raising the DC bus voltage U dc , thereby increasing the grid-side converter output reactive power Q e Upper limit; through droop control, the grid-side converter outputs reactive power Q e Increase, and finally the grid voltage U at the grid-connected node of the gravity energy storage system;

[0136] Among them, the DC bus voltage reference value output by the machine-side converter is Related to DC bus voltage regulation coefficient K θ The calculation formula is:

[0137]

[0138] The output power of the back-to-back converter is constrained as follows:

[0139]

[0140] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to execute any of the methods described above.

[0141] A computer-readable storage medium stores a computer program, wherein the computer program implements the steps of any of the above methods when executed by a processor.

[0142] Compared with the prior art, the present invention has the following beneficial effects:

[0143] The present invention proposes a grid-connected method and system for an electrically excited synchronous motor gravity energy storage system. The grid-connected method considers improving the control mode of the gravity energy storage back-to-back converter. When connected to the grid, the grid-side converter in the inverter state adopts the voltage and current dual-loop control strategy of the virtual synchronous motor to obtain the active power calculation value and the reactive power calculation value used to support the operation of the power grid. The grid-side converter absorbs the active power from the DC bus and feeds the reactive power into the power grid according to the active power calculation value and the reactive power calculation value, so that the converter has inertia and dynamic reactive support capabilities, and better suppresses the volatility of new energy. At the same time, the machine-side converter in the rectification state adopts a direct current control strategy to determine the output voltage calculation value for stabilizing the DC bus voltage. The machine-side converter controls the DC bus voltage to reach the output voltage calculation value, thereby achieving the stability of the voltage on the DC bus of the back-to-back converter.

[0144] When the grid-side voltage drops, the grid-connected method of the present invention can also utilize the electrically excited synchronous motor to output more reactive power to raise the output voltage to support the grid and prevent the fault from spreading. BRIEF DESCRIPTION OF THE DRAWINGS

[0145] Figure 1 It is a structural schematic diagram of the gravity energy storage system of the electrically excited synchronous motor;

[0146] Figure 2 It is the current inner loop control strategy diagram;

[0147] Figure 3 It is the voltage outer loop control strategy diagram;

[0148] Figure 4 This is the voltage and current dual-loop control strategy diagram. DETAILED DESCRIPTION

[0149] Embodiment 1:

[0150] A grid-connected method for an electrically excited synchronous motor gravity energy storage system of the present invention, such as Figure 1 As shown, the electrically excited synchronous motor in the gravity energy storage system is connected to the grid via a back-to-back converter and an LCL filter; when connected to the grid, the back-to-back converter includes a machine-side converter in a rectifying state and a grid-side converter in an inverter state. The grid-connected method includes:

[0151] The grid-side converter uses a voltage-current dual-loop control strategy of a virtual synchronous motor based on a grid-side converter control signal converted from a three-phase voltage signal on the grid side to obtain active power calculation values ​​and reactive power calculation values ​​used to support grid operation. The grid-side converter feeds the active power and reactive power absorbed from the DC bus into the grid according to the active power calculation values ​​and reactive power calculation values.

[0152] The machine-side converter adopts a direct current control strategy based on the machine-side converter control signal obtained by converting the DC bus voltage signal to determine the calculated output voltage value used to stabilize the DC bus voltage. The machine-side converter controls the DC bus voltage to reach the calculated output voltage value, which is generally controlled by absorbing power from the synchronous motor and inputting the power into the DC bus.

[0153] Embodiment 2:

[0154] This embodiment is further designed on the basis of the first embodiment in that the control links of the voltage-current dual-loop control strategy of the virtual synchronous motor in this embodiment include active power control, reactive power control, virtual impedance control, current inner loop control and voltage outer loop control.

[0155] Embodiment three:

[0156] This embodiment is further designed on the basis of the second embodiment in that the active power regulation equation of the virtual synchronous motor (VSG) in this embodiment is expressed as:

[0157]

[0158] Where P m , P e are the mechanical power and electromagnetic power of the synchronous generator respectively; J is the moment of inertia; D is the damping coefficient; ω is the angular velocity; ω ref is the rated angular frequency;

[0159] The power-frequency droop relationship is expressed as:

[0160] P m =P ref +k p (ω ref -ω)

[0161] Where P ref Indicates the active power given value; k p is the active power control coefficient; ω ref is the rated angular velocity;

[0162] Define angular momentum H = Jω, damping torque D p =Dω, then the control equation of the virtual speed regulator of the virtual synchronous motor is obtained:

[0163]

[0164] The above control equation is further adjusted as follows:

[0165]

[0166] Regulating virtual potential E in virtual synchronous motor mFrom the no-load potential E0 and reactive power ΔE Q , terminal voltage ΔE u Common control; among them, reactive power ΔE Q The droop relationship between reactive power and voltage can be expressed as:

[0167] ΔE Q =E ref -E0=k q (Q e -Q ref )

[0168] Terminal voltage ΔE u It is simplified to proportional control

[0169] ΔE u =k u (U ref -U)

[0170] E=E0+ΔE Q +ΔE U

[0171] E m =E0+ΔE Q +ΔE u

[0172] Since there is an LC filter between the converter port and the grid, the converter output voltage is not equal to the grid voltage. Virtual impedance control is required in the control link.

[0173] The angular velocity ω is obtained by active frequency control, and the virtual potential E is obtained by reactive voltage control. m ; After Parker transformation, the virtual potential E is obtained m The d-axis component E d , virtual potential E m The q-axis component E q And for virtual impedance control:

[0174]

[0175] Where i d 、i q are the d-axis component and q-axis component of the converter output current obtained after Parker transformation; R s , L s are the virtual resistance and virtual reactance of the converter respectively; u dref 、u qref They are respectively the d-axis component reference value and the q-axis component reference value obtained after the grid-side voltage Parker transformation through the virtual impedance link;

[0176] The reference value after the grid-side voltage Parker transformation is controlled by the voltage outer loop and the current inner loop to stabilize the converter output voltage; the voltage outer loop control equation is as follows:

[0177]

[0178] Among them, u d 、u q are the actual values ​​of the grid-side output voltage of the converter respectively;

[0179] The current inner loop control equation is as follows:

[0180]

[0181] After voltage and current double closed-loop control, the final output voltage is obtained, that is, the virtual potential E m :

[0182] E m =E0+k q (Q e -Q ref )+k u (U ref -U)

[0183] The final output voltage amplitude of the grid-side converter is E m The grid voltage U at the energy storage system connection node and the converter output reactive power Q e Common control, virtual potential E m After Parker transformation, the virtual potential E is obtained m The d-axis component E d and the q-axis component E q , and calculate the active power value P according to the following formula m And reactive power calculation value Q m :

[0184] In the formula, i d 、i q They are the d-axis component and q-axis component of the converter output current obtained after Park transformation.

[0185] Embodiment 4:

[0186] This embodiment is further designed on the basis of the second embodiment in that the direct current control strategy in this embodiment includes current inner loop control and voltage outer loop control;

[0187] The input of the current inner loop control is the d-axis component of the DC voltage V' d and the q-axis component of the DC voltage V' q The output is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation dThe d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q ;

[0188] The input of the voltage outer loop control is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation. d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q , the output is the machine-side converter output voltage U dc .

[0189] Embodiment five:

[0190] This embodiment is further designed on the basis of the fourth embodiment in that: Figure 2 As shown, in this example, the current inner loop control is as follows:

[0191]

[0192] In the formula, i' d 、i' q are the d-axis component and q-axis component of the three-phase AC current of the synchronous motor obtained by Parker transformation; L' and R' are the resistance and reactance between the synchronous motor and the machine-side converter respectively; e' d 、e' q are the d-axis component and q-axis component of the synchronous motor terminal voltage obtained by Park transformation; V' d =S d V dc 、V' q =S q V dc ; Among them, S d , S q is the switch function;

[0193] Introduce feedforward compensation to decouple the q-axis component and the d-axis component:

[0194]

[0195] in, V' d 、V' q The steady-state given value of

[0196] Combining the above two equations, we can get:

[0197]

[0198] therefore, It can be adjusted by PI controller

[0199]

[0200] Combining the above equations, the decoupling control method of the current inner loop is obtained:

[0201]

[0202] like Figure 3 As shown, the voltage outer loop control is as follows:

[0203] The AC side circuit equation in the dq coordinate system is:

[0204]

[0205] DC node KCL equation:

[0206] i dc =i c +i L

[0207] Among them, i c The current flowing through the capacitor C; i L is the load current; then i dc It is expressed as:

[0208]

[0209] According to the power balance equation:

[0210]

[0211] To achieve feedback stability, the machine-side converter voltage setting value is required. The output voltage of the replacement machine-side converter is U dc , we get the final control link, and from the above equation we can get:

[0212] Then the control strategy of the voltage outer loop can be obtained, and the current inner loop control and the voltage outer loop control are connected in series to achieve stable control of the machine-side converter, such as Figure 4 As shown;

[0213]

[0214] Where U dc is the output voltage of the machine-side converter; P is the output voltage setting value of the receiving side converter; L is the active power of the gravity energy storage synchronous motor on the AC side; e' d is the d-axis component of the synchronous motor terminal voltage, i' d is the d-axis component of the synchronous motor terminal current. The output voltage of the machine-side converter is U dc , output voltage setting value of the receiving side converter Active power P of gravity energy storage synchronous motor on AC side L, synchronous motor terminal voltage d-axis component e' d , synchronous motor terminal current d-axis component i' d control.

[0215] Embodiment six:

[0216] This embodiment is further designed on the basis of the first embodiment in that the grid connection method in this example also includes: when a fault occurs on the grid side causing a voltage drop, enhancing the excitation current of the electrically excited synchronous motor to raise the machine-end voltage to support the grid.

[0217] Embodiment seven:

[0218] This embodiment is further designed on the basis of the sixth embodiment in that, in this embodiment, when a fault occurs on the grid side causing a voltage drop, the specific method of enhancing the excitation current of the electrically excited synchronous motor to raise the terminal voltage to support the grid includes:

[0219] When the grid voltage U at the grid-connected node of the gravity energy storage system is lower than 90% of the rated value, it is considered that a voltage drop fault occurs on the grid side, and the terminal voltage U of the electro-excitation synchronous motor is increased by the excitation current. LL Increase the upper limit of the DC bus voltage maximum value; adjust the DC bus voltage through the DC bus voltage adjustment coefficient K θ To increase the DC bus voltage reference value of the machine-side converter output Thereby raising the DC bus voltage U dc , thereby increasing the grid-side converter output reactive power Q e Upper limit; through droop control, the grid-side converter outputs reactive power Q e Increase, and finally the grid voltage U at the grid-connected node of the gravity energy storage system;

[0220] Among them, the DC bus voltage reference value output by the machine-side converter is Related to DC bus voltage regulation coefficient K θ The calculation formula is:

[0221]

[0222] The output power of the back-to-back converter is constrained as follows:

[0223]

[0224] Embodiment eight:

[0225] A grid-connected system of an electrically excited synchronous motor gravity energy storage system of the present invention, wherein the electrically excited synchronous motor in the gravity energy storage system is connected to the power grid via a back-to-back converter and an LCL filter; when connected to the grid, the back-to-back converter includes a machine-side converter in a rectifying state and a grid-side converter in an inverting state, and the grid-connected system includes a grid-side converter control module and a machine-side converter control module;

[0226] Among them, the grid-side converter control module is used to control the grid-side converter based on the grid-side converter control signal obtained by converting the three-phase voltage signal on the grid side, adopt the voltage and current dual-loop control strategy of the virtual synchronous motor, obtain the active power calculation value and reactive power calculation value used to support the operation of the grid, and the grid-side converter feeds the active power and reactive power absorbed from the DC bus into the grid according to the active power calculation value and reactive power calculation value;

[0227] The machine-side converter control module is used to control the machine-side converter based on the machine-side converter control signal obtained by converting the DC bus voltage signal. It adopts a direct current control strategy to determine the output voltage calculation value used to stabilize the DC bus voltage. The machine-side converter controls the DC bus voltage to reach the output voltage calculation value, which is generally controlled by absorbing power from the synchronous motor and inputting the power into the DC bus.

[0228] Furthermore, the control links of the voltage-current dual-loop control strategy of the virtual synchronous motor include active power control, reactive power control, virtual impedance control, current inner loop control and voltage outer loop control.

[0229] Furthermore, the active power regulation equation of the virtual synchronous motor is expressed as:

[0230]

[0231] Where P m , P e are the mechanical power and electromagnetic power of the synchronous generator respectively; J is the moment of inertia; D is the damping coefficient; ω is the angular velocity; ω ref is the rated angular frequency;

[0232] The power-frequency droop relationship is expressed as:

[0233] P m =P ref +k p (ω ref -ω)

[0234] Where P ref Indicates the active power given value; k p is the active power control coefficient; ω ref is the rated angular velocity;

[0235] Define angular momentum H = Jω, damping torque D p =Dω, then the control equation of the virtual speed regulator of the virtual synchronous motor is obtained:

[0236]

[0237] The above control equation is further adjusted as follows:

[0238]

[0239] Regulating virtual potential E in virtual synchronous motor m From the no-load potential E0 and reactive power ΔE Q , terminal voltage ΔE u Common control; among them, reactive power ΔE Q The droop relationship between reactive power and voltage can be expressed as:

[0240] ΔE Q =E ref -E0=k q (Q e -Q ref )

[0241] Terminal voltage ΔE u It is simplified to proportional control:

[0242] ΔE u =k u (U ref -U)

[0243] E=E0+ΔE Q +ΔE U

[0244] E m =E0+ΔE Q +ΔE u

[0245] The angular velocity ω is obtained by active frequency control, and the virtual potential E is obtained by reactive voltage control. m ; After Parker transformation, the virtual potential E is obtained m The d-axis component E d , virtual potential E m The q-axis component E q And for virtual impedance control:

[0246]

[0247] Where i d 、i q are the d-axis component and q-axis component of the converter output current obtained after Parker transformation; E s , L s are the virtual resistance and virtual reactance of the converter respectively; u dref 、u qref They are respectively the d-axis component reference value and the q-axis component reference value obtained after the grid-side voltage Parker transformation through the virtual impedance link;

[0248] The reference value after the grid-side voltage Parker transformation is controlled by the voltage outer loop and the current inner loop to stabilize the converter output voltage; the voltage outer loop control equation is as follows:

[0249]

[0250] Among them, u d 、u q are the actual values ​​of the grid-side output voltage of the converter respectively;

[0251] The current inner loop control equation is as follows:

[0252]

[0253] The virtual potential E is obtained through voltage and current double closed-loop control m :

[0254] E m =E0+k q (Q e -Q ref )+k u (U ref -U)

[0255] Virtual potential E m After Parker transformation, the virtual potential E is obtained m The d-axis component E d and the q-axis component E q , and calculate the active power value P according to the following formula m And reactive power calculation value Q m :

[0256] In the formula, i d 、i q They are the d-axis component and q-axis component of the converter output current obtained after Park transformation.

[0257] Furthermore, the direct current control strategy includes current inner loop control and voltage outer loop control;

[0258] The input of the current inner loop control is the d-axis component of the DC voltage V' d and the q-axis component of the DC voltage V' q The output is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q ;

[0259] The input of the voltage outer loop control is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation. dThe d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q , the output is the machine-side converter output voltage U dc .

[0260] Furthermore, the current inner loop is controlled as follows:

[0261]

[0262] In the formula, i' d 、i' q are the d-axis component and q-axis component of the three-phase AC current of the synchronous motor obtained by Parker transformation; L' and R' are the resistance and reactance between the synchronous motor and the machine-side converter respectively; e' d 、e' q are the d-axis component and q-axis component of the synchronous motor terminal voltage obtained by Park transformation; V' d =S d V dc 、V' q =S q V dc ; Among them, S d , S q is the switch function;

[0263] Introduce feedforward compensation to decouple the q-axis component and the d-axis component:

[0264]

[0265] in, V' d 、V' q The steady-state given value of

[0266] Combining the above two equations, we can get:

[0267]

[0268] therefore, It can be adjusted by PI controller

[0269]

[0270] Combining the above equations, the decoupling control method of the current inner loop is obtained:

[0271]

[0272] The voltage outer loop control is as follows:

[0273] The AC side circuit equation in the dq coordinate system is:

[0274]

[0275] DC node KCL equation:

[0276] i dc =i c +i L

[0277] Among them, i c The current flowing through the capacitor C; i L is the load current; then i dc It is expressed as:

[0278]

[0279] According to the power balance equation:

[0280]

[0281] To achieve feedback stability, the machine-side converter voltage setting value is required. The output voltage of the replacement machine-side converter is U dc , we get the final control link, and from the above equation we can get:

[0282] Then the control strategy of the voltage outer loop can be obtained, and the current inner loop control and the voltage outer loop control are connected in series to achieve stable control of the machine-side converter;

[0283]

[0284] Where U dc is the output voltage of the machine-side converter; P is the output voltage setting value of the receiving side converter; L is the active power of the gravity energy storage synchronous motor on the AC side; e' d is the d-axis component of the synchronous motor terminal voltage, i' d is the d-axis component of the synchronous motor terminal current.

[0285] Furthermore, the grid connection method also includes: when a fault occurs on the grid side causing a voltage drop, enhancing the excitation current of the electrically excited synchronous motor.

[0286] Furthermore, when a fault occurs on the grid side causing a voltage drop, a specific method of enhancing the excitation current of the electrically excited synchronous motor includes:

[0287] When the grid voltage U at the grid-connected node of the gravity energy storage system is lower than 90% of the rated value, it is considered that a voltage drop fault occurs on the grid side, and the terminal voltage U of the electro-excitation synchronous motor is increased by the excitation current. LL Increase the upper limit of the DC bus voltage maximum value; adjust the DC bus voltage through the DC bus voltage adjustment coefficient K θ To increase the DC bus voltage reference value of the machine-side converter output Thereby raising the DC bus voltage U dc , thereby increasing the grid-side converter output reactive power Q e Upper limit; through droop control, the grid-side converter outputs reactive power Q e Increase, and finally the grid voltage U at the grid-connected node of the gravity energy storage system;

[0288] Among them, the DC bus voltage reference value output by the machine-side converter is Related to DC bus voltage regulation coefficient K θ The calculation formula is:

[0289]

[0290] The output power of the back-to-back converter is constrained as follows:

[0291]

[0292] Embodiment nine:

[0293] An electronic device of the present invention includes a memory and a processor, wherein the memory stores a computer program, and the processor is used to call and run the computer program stored in the memory to execute the method described in any of the above embodiments.

[0294] A computer-readable storage medium of the present invention stores a computer program, and when the computer program is executed by a processor, the steps of the method described in any of the above embodiments are implemented.

Claims

1. A grid-connected method for an electrically excited synchronous motor gravity energy storage system, wherein the electrically excited synchronous motor in the gravity energy storage system is connected to the power grid via a back-to-back converter and an LCL filter; the back-to-back converter includes a machine-side converter and a grid-side converter, characterized in that: The method comprises: The grid-side converter adopts a voltage-current dual-loop control strategy of a virtual synchronous motor based on a grid-side converter control signal obtained by converting a three-phase voltage signal on the grid side to obtain an active power calculation value and a reactive power calculation value for supporting grid operation. The grid-side converter feeds active power and reactive power into the grid according to the active power calculation value and the reactive power calculation value. The machine-side converter adopts a direct current control strategy based on the machine-side converter control signal obtained by converting the DC bus voltage signal to determine an output voltage calculation value for stabilizing the DC bus voltage, and the machine-side converter controls the DC bus voltage to reach the output voltage calculation value.

2. The grid-connected method of the electrically excited synchronous motor gravity energy storage system according to claim 1, characterized in that: The control links of the voltage-current dual-loop control strategy of the virtual synchronous motor include active power control, reactive power control, virtual impedance control, current inner loop control and voltage outer loop control.

3. The grid-connected method of the electrically excited synchronous motor gravity energy storage system according to claim 2, characterized in that: The active power regulation equation of the virtual synchronous motor is expressed as: Where P m , P e are the mechanical power and electromagnetic power of the synchronous generator respectively; J is the moment of inertia; D is the damping coefficient; ω is the angular velocity; ω ref is the rated angular frequency; The power-frequency droop relationship is expressed as: P m =P ref +k p (oh ref -oh) Where P ref Indicates the active power given value; k p is the active power control coefficient; ω ref is the rated angular velocity; Define angular momentum H = Jω, damping torque D p =Dω, then the control equation of the virtual speed regulator of the virtual synchronous motor is obtained: The above control equation is further adjusted as follows: Regulating virtual potential E in virtual synchronous motor m From the no-load potential E0 and reactive power ΔE Q , terminal voltage ΔE u Common control; among them, reactive power ΔE Q The droop relationship between reactive power and voltage can be expressed as: ΔE Q =E ref -E0=k q (Q e -Q ref ) Terminal voltage ΔE u It is simplified to proportional control: ΔE u =k u (IN ref -IN) E=E0+ΔE Q +ΔE U E m =E0+ΔE Q +ΔE u The angular velocity ω is obtained by active frequency control, and the virtual potential E is obtained by reactive voltage control. m ; After Parker transformation, the virtual potential E is obtained m The d-axis component E d , virtual potential E m The q-axis component E q And for virtual impedance control: Where i d 、i q are the d-axis component and q-axis component of the converter output current obtained after Parker transformation; R s , L s are the virtual resistance and virtual reactance of the converter respectively; u dref 、u qref They are respectively the d-axis component reference value and the q-axis component reference value obtained after the grid-side voltage Parker transformation through the virtual impedance link; The reference value after the grid-side voltage Parker transformation is controlled by the voltage outer loop and the current inner loop to stabilize the converter output voltage; the voltage outer loop control equation is as follows: Among them, u d 、i q are the actual values ​​of the grid-side output voltage of the converter respectively; The current inner loop control equation is as follows: The virtual potential E is obtained through voltage and current double closed-loop control m : E m =E0+k q (Q e -Q ref )+k u (U ref -U) Virtual potential E m After Parker transformation, the virtual potential E is obtained m The d-axis component E d and the q-axis component E q , and calculate the active power value P according to the following formula m And reactive power calculation value Q m : In the formula, i d 、i q They are the d-axis component and q-axis component of the converter output current obtained after Park transformation.

4. The grid-connected method of the electrically excited synchronous motor gravity energy storage system according to claim 1, characterized in that: The direct current control strategy includes current inner loop control and voltage outer loop control; The input of the current inner loop control is the d-axis component V' of the DC side voltage d and the q-axis component of the DC voltage V' q The output is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q ; The input of the voltage outer loop control is the d-axis component i' of the three-phase AC current of the synchronous motor obtained by Park transformation d The d-axis component i' of the three-phase current of the synchronous motor is obtained by Park transformation q , the output is the machine-side converter output voltage U dc .

5. The grid-connected method of the electrically excited synchronous motor gravity energy storage system according to claim 4, characterized in that: The current inner loop control is as follows: In the formula, i' d 、i' q are the d-axis component and q-axis component of the three-phase AC current of the synchronous motor obtained by Parker transformation; L' and R' are the resistance and reactance between the synchronous motor and the machine-side converter respectively; e' d 、e' q are the d-axis component and q-axis component of the synchronous motor terminal voltage obtained by Park transformation; V' d =S d V dc 、V' q =S q V dc ; Among them, S d , S q is the switch function; Introduce feedforward compensation to decouple the q-axis component and the d-axis component: in, V' d 、V' q The steady-state given value of Combining the above two equations, we can get: therefore, It can be adjusted by PI controller Combining the above equations, the decoupling control method of the current inner loop is obtained: The voltage outer loop control is as follows: The AC side circuit equation in the dq coordinate system is: DC node KCL equation: i dc =i c +i L Among them, i c The current flowing through the capacitor C; i L is the load current; then i dc It is expressed as: According to the power balance equation: To achieve feedback stability, the machine-side converter voltage setting value is required. The output voltage of the replacement machine-side converter is U dc , we get the final control link, and from the above equation we can get: Then the control strategy of the voltage outer loop can be obtained, and the current inner loop control and the voltage outer loop control are connected in series to achieve stable control of the machine-side converter; Where U dc is the output voltage of the machine-side converter; P is the output voltage setting value of the receiving side converter; L is the active power of the gravity energy storage synchronous motor on the AC side; e' d is the d-axis component of the synchronous motor terminal voltage, i' d is the d-axis component of the synchronous motor terminal current.

6. The grid-connected method of the electrically excited synchronous motor gravity energy storage system according to claim 1, characterized in that: The grid connection method further includes: when a fault occurs on the grid side causing a voltage drop, enhancing the excitation current of the electrically excited synchronous motor.

7. The grid-connected method of the electrically excited synchronous motor gravity energy storage system according to claim 6, characterized in that: The specific method of enhancing the excitation current of the electrically excited synchronous motor when a fault occurs on the grid side and causes a voltage drop includes: When the grid voltage U at the grid-connected node of the gravity energy storage system is lower than 90% of the rated value, it is considered that a voltage drop fault occurs on the grid side, and the terminal voltage U of the electro-excitation synchronous motor is increased by the excitation current. LL Increase the upper limit of the DC bus voltage maximum value; adjust the DC bus voltage through the DC bus voltage adjustment coefficient K θ To increase the DC bus voltage reference value of the machine-side converter output Thereby raising the DC bus voltage U dc , thereby increasing the grid-side converter output reactive power Q e Upper limit; through droop control, the grid-side converter outputs reactive power Q e Increase, and finally the grid voltage U at the grid-connected node of the gravity energy storage system; among them, the DC bus voltage reference value output by the machine-side converter Related to DC bus voltage regulation coefficient K θ The calculation formula is: The output power of the back-to-back converter is constrained as follows:

8. A grid-connected system of an electrically excited synchronous motor gravity energy storage system, wherein the electrically excited synchronous motor in the gravity energy storage system is connected to the power grid via a back-to-back converter and an LCL filter; the back-to-back converter includes a machine-side converter and a grid-side converter, characterized in that: The system includes a grid-side converter control module and a machine-side converter control module; The grid-side converter control module is used to control the grid-side converter based on the grid-side converter control signal obtained by converting the three-phase voltage signal on the grid side, adopt the voltage and current dual-loop control strategy of the virtual synchronous motor, obtain the active power calculation value and reactive power calculation value used to support the operation of the grid, and the grid-side converter feeds the active power and reactive power into the grid according to the active power calculation value and reactive power calculation value; The machine-side converter control module is used to control the machine-side converter based on the machine-side converter control signal obtained by converting the DC bus voltage signal, adopt a direct current control strategy, determine the output voltage calculation value used to stabilize the DC bus voltage, and the machine-side converter controls the DC bus voltage to reach the output voltage calculation value.

9. An electronic device, characterized in that: The electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor is configured to call and run the computer program stored in the memory to execute the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method as claimed in any one of claims 1 to 7 are implemented.

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