Network following-constructing integration control method based on doubly-fed flywheel energy storage

Abstract

The invention discloses a doubly-fed flywheel energy storage-based network following-construction fusion control method, which comprises the following steps of: 1, acquiring electrical parameters of a stator and a rotor of a doubly-fed fan, performing coordinate transformation to obtain dq-axis components, and calculating real-time output power of the stator; 2, a virtual internal potential phase is generated through virtual synchronous control, a phase-locked loop obtains a power grid phase, modulation voltage reference values are output respectively, and a final modulation voltage reference value is obtained through weighted sum so as to realize dynamic fusion control of network following and network construction characteristics, and in the network following control, a modulation voltage is obtained through a rotating speed-active and reactive outer loop and a current inner loop, and the current inner loop is added to the rotating speed-active and reactive outer loop; in the network construction control, instantaneous power is calculated through electrical parameters, a reference phase and voltage are obtained through virtual synchronous control, and modulation voltage is output through a single voltage loop. According to the method, the characteristics of the network following current source and the network construction voltage source are fused, advantage complementation is achieved, the method has fast power adjustment and power grid supporting performance, the method is adaptive to a wide-short-circuit-ratio power grid scene, and therefore the weak power grid stability and the new energy consumption capacity can be effectively improved.

Description

A grid-connected control method based on doubly-fed flywheel energy storage Technical Field

[0001] This invention relates to the field of wind power generation, and more specifically to a fusion control method for enhancing and optimizing the grid adaptability and power response capabilities of wind power grid-connected units. Background Technology

[0002] With the continuous advancement of my country's dual-carbon goals, a new power system with a high proportion of renewable energy generation is expected to take shape. This will present multiple challenges to grid stability, primarily due to the weakening of the power system's inertia damping as a large number of renewable energy units replace traditional synchronous generators. Simultaneously, in renewable energy distributed low-voltage access systems, the renewable energy units are located at the end of the grid, with a significant electrical distance from synchronous generators and multiple transformer stages, resulting in a weak grid characteristic with a low short-circuit ratio at the renewable energy grid connection point. In traditional doubly-fed induction generator (DFIG) flywheel energy storage control, the generator-side converters employ conventional phase-locked loop (PLL)-oriented vector control, meaning they follow the grid, also known as grid-following control. Under grid-following control, renewable energy units cannot actively support the grid's voltage and frequency. Furthermore, under weak grid conditions, traditional PLL synchronous control can lead to a series of instability risks, threatening the operational stability of the wind power system and the grid's voltage / frequency stability. Therefore, the weak grid stability and active support capabilities of DFIG wind turbines urgently need improvement.

[0003] To enable doubly-fed induction generator (DFIG) flywheel energy storage to achieve stable operation and active grid support under weak grid conditions, grid-connected converter technology, which combines active support capability with strong stability in weak grids, has become a focus of attention and research hotspot in academia and industry. However, the grid-connected control of this technology still faces many challenges: slow power regulation speed, significant multi-machine coupling effect, and poor stability under strong grid scenarios. Therefore, it is necessary to reconstruct a control scheme for DFIG flywheel energy storage that combines stability in both strong and weak grids with active support capability. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention proposes a grid-connected and grid-building integrated control method based on doubly-fed flywheel energy storage. This method aims to combine the rapid power response of grid-connected control with the grid support characteristics of grid-building control, thereby improving the system's stability and active support capabilities under both strong and weak grid conditions.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: The characteristic of the grid-grid integrated control method based on doubly-fed flywheel energy storage is that it is applied to a doubly-fed phase-modulation system composed of a doubly-fed motor, flywheel, rotor-side converter, and grid-side converter, and is performed according to the following steps: Step 1: Acquire the three-phase stator current of the doubly-fed wind turbine. , , With three-phase stator voltage , , After coordinate transformation, the instantaneous active power output from the stator side of the doubly-fed induction generator (DFIG) is calculated. With instantaneous reactive power Step 2: Collect the three-phase rotor current of the doubly-fed wind turbine. , , With rotor electric angular velocity After coordinate transformation, the d-axis DC component of the rotor current in the synchronous rotating coordinate system of the rotor converter is obtained. q-axis DC component Step 3, and After processing by a low-pass filter, the filtered instantaneous active power is obtained. and filtered instantaneous reactive power Then, the data is input into the VSG circuit, thereby utilizing the rotor motion equations of the doubly-fed wind turbine in VSG control mode to obtain the virtual mechanical power. Step 4: Calculate the virtual mechanical power With filtered active power deviation and the deviation The input is processed in the active power controller (APC) to obtain the stator voltage control angle under grid control. Step 5: Calculate the stator-side reactive power command. With filtered instantaneous reactive power deviation and the deviation Input the stator-side reactive power controller (RPC) to obtain the stator voltage amplitude command. Step 6: Calculate the stator voltage amplitude command. Phase voltage amplitude relative to grid connection point voltage deviation and the deviation The input voltage is processed in a single-voltage loop controller to obtain the modulation voltage amplitude of the output under network control. Step 7: Collect the rotational speed ω of the doubly-fed motor and calculate the outer loop speed command. Deviation from rotational speed ω and the deviation The input is processed in the speed controller to obtain the active power command value. Step 8: Calculate the active power command value. Deviation from instantaneous active power P under grid control and the deviation The input is processed in the stator-side active power controller (APC) to obtain the rotor d-axis setpoint. Step 9: Obtain the grid phase through a phase-locked loop. and calculate with The instantaneous reactive power Q is used as input, and then the reactive power outer loop command under grid control is calculated. Deviation from instantaneous reactive power Q and the deviation The input is processed by the stator-side reactive power controller (RPC) to obtain the rotor q-axis setpoint. Step 10: Calculation and Deviation between and and The deviation between them is input into the PI regulator of the inner loop of the rotor current for processing, and the corresponding d-axis rotor voltage command in the dq coordinate system is obtained. q-axis rotor voltage command After the coordinate transformation process, the modulation voltage amplitude output under grid control is obtained. Step 11: Based on the network coefficients And network coefficient ,right and After weighted summation, the final modulation voltage reference value is obtained, which is then input into the PWM stage for modulation to generate the machine-side converter switching control signals S1-S6, thereby realizing the integrated control of the doubly-fed flywheel energy storage.

[0006] The feature of the grid-connected control method based on doubly-fed flywheel energy storage described in this invention is that step 1 includes: step 1.1, using the coordinate transformation link shown in equation (1) to center the three-phase stator current. , , With three-phase stator voltage , , The process is performed to obtain the d-axis DC component of the stator current in the synchronous rotating coordinate system. q-axis DC component and the DC component of the stator voltage along the d-axis in a synchronous rotating coordinate system q-axis DC component : (1) Step 1.2: Obtain the instantaneous active power output on the stator side of the doubly fed wind turbine according to equation (2). With instantaneous reactive power : (2) In equations (1) and (2), This is the reference angle for coordinate transformation in rotor converter control, obtained from the virtual synchronization element of the network control. , , This represents the three-phase stator voltage / three-phase stator current of the doubly-fed induction generator in a three-phase stationary coordinate system. , The d-axis and q-axis DC components represent the three-phase stator voltage / three-phase stator current in the synchronous rotating coordinate system of the rotor converter.

[0007] Furthermore, in step 2, equation (3) is used to measure the three-phase rotor current. , , With rotor electric angular velocity Perform coordinate transformation to obtain the d-axis DC component of the rotor current in the synchronous rotating coordinate system of the rotor converter. q-axis DC component : In equation (3), The phase of the power grid is obtained by the phase-locked loop in the grid control.

[0008] Furthermore, in step 3, the following steps are performed: and After processing by a low-pass filter, the filtered instantaneous active power is obtained. and filtered instantaneous reactive power The virtual mechanical power is then input into the VSG stage and obtained using equation (4). ; In equation (4), It is the synchronous angular velocity of the power grid; This represents the virtual mechanical power injected into the doubly-fed induction generator; the coefficient m is the active power-frequency droop coefficient. It is the power reference value obtained by the speed outer loop control under the grid control.

[0009] Furthermore, step 4 involves using virtual mechanical power. With filtered active power The input is processed in the active power controller (APC) to obtain the reference angle under grid control using equation (5). : (5) In equation (5), s represents the complex frequency variable of the Laplace transform, J is the virtual inertia coefficient, and D is the damping coefficient.

[0010] Furthermore, step 5 involves sending the stator-side reactive power command. With filtered instantaneous reactive power The input is processed in the stator-side reactive power controller RPC, thereby obtaining the stator voltage amplitude command using equation (6). : In equation (6), is the given command value for reactive power, and n is the reactive power-voltage droop coefficient.

[0011] Furthermore, step 6 involves setting the stator voltage amplitude command. Phase voltage amplitude relative to grid connection point voltage The input voltage is processed in a single-voltage loop controller, and the amplitude of the modulated voltage output under network control is obtained using equation (7). : In equation (7), k is the integral parameter of the voltage controller.

[0012] Furthermore, step 7 involves setting the rotational speed outer loop command. The motor speed ω is input to the speed controller for processing, thereby obtaining the active power command value using equation (8). : In equation (8), These are the proportional parameters of the speed controller; These are the integral parameters of the speed controller.

[0013] Furthermore, in step 8, the active power command value is... The instantaneous active power P under grid control is input to the stator-side active power controller APC for processing, thereby obtaining the rotor d-axis setpoint using equation (9). : In equation (9), These are the proportional parameters of the active power controller; These are the integral parameters of the active power controller.

[0014] Furthermore, in step 9, the rotor q-axis setpoint is obtained using equation (10). : In equation (10), This refers to the proportional parameters of the reactive power controller. These are the integral parameters of the reactive power controller.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention adopts a network-network fusion control strategy, using a weighted sum formula. The dynamic fusion of the two modulation voltage modes solves the problems of traditional grid-following control being unable to actively support grid voltage / frequency, being prone to instability in weak grids, and the slow power regulation and poor stability in strong grid scenarios of single grid-following control. It achieves the complementarity of the rapid power regulation of the "current source" and the grid support characteristics of the "voltage source", adapts to grid scenarios with wide short-circuit ratios, and effectively improves the stability of weak grids and the ability to absorb new energy.

[0016] 2. The grid control of this invention adopts a virtual synchronous control (VSG) + single voltage loop design. After processing the instantaneous power through low-pass filtering, it is input into the VSG link to simulate the rotor motion law of the synchronous generator. Combined with the reactive power-voltage control loop that draws on the droop characteristics of the synchronous generator, it solves the problems of insufficient voltage amplitude control accuracy and significant multi-machine coupling effect in existing grid control. It can actively provide grid inertia and damping support, and improve grid frequency and voltage stability.

[0017] 3. The grid-following control of this invention adopts a closed-loop structure of "speed-active power outer loop + current inner loop". It derives the active power command through speed deviation, adjusts the rotor current setpoint through power deviation, and then outputs the rotor voltage command through PI regulation of the current inner loop. This solves the problems of low power response accuracy and lag in rotor current regulation of traditional grid-following vector control, significantly improves the power regulation response speed and output accuracy in grid-following mode, and reduces grid power fluctuations.

[0018] 4. This invention converts the voltage / current in the three-phase stationary coordinate system into DC components on the dq axis through coordinate transformation, and performs low-pass filtering on the instantaneous power, which solves the problem of control command deviation caused by harmonic interference in the original signal, improves the stability and accuracy of the control basic data, provides reliable support for subsequent power calculation, phase and voltage command generation, and reduces the overall control error. Attached Figure Description

[0019] Figure 1 is a strategy diagram of the fusion control method of the present invention. Detailed Implementation

[0020] In this embodiment, a grid-connected integrated control method based on doubly-fed flywheel energy storage is applied to a doubly-fed phase-modulation system composed of a doubly-fed motor, flywheel energy storage, rotor-side converter, and grid-side converter, as shown in Figure 1, and is performed according to the following steps: Step 1: Collect the three-phase stator current of the doubly-fed wind turbine. , , With three-phase stator voltage , , Substituting these values ​​into the coordinate transformation step shown in equation (1), we obtain the DC components isd and isq of the stator current in the synchronous rotating coordinate system, and the d-axis DC component of the stator voltage in the synchronous rotating coordinate system. q-axis DC component And according to equation (2), the above DC components are calculated to obtain the instantaneous active power output on the stator side of the doubly-fed wind turbine. With instantaneous reactive power : (1) (2) In equations (1) and (2), This is the reference angle for coordinate transformation in rotor converter control, obtained from the virtual synchronization element of the network control. , , This represents the three-phase stator voltage / three-phase stator current of the doubly-fed induction generator in a three-phase stationary coordinate system. , The d-axis and q-axis DC components represent the three-phase stator voltage / three-phase stator current in the synchronous rotating coordinate system of the rotor converter.

[0021] Step 2: Collect the three-phase rotor current i of the doubly-fed wind turbine. ra i rb i rc With rotor electric angular velocity Substituting this into the coordinate transformation step shown in equation (3), we obtain the d-axis DC component ird and the q-axis DC component irq of the rotor current in the synchronous rotating coordinate system of the rotor converter: In equation (3), The phase of the power grid is obtained by the phase-locked loop in the grid control.

[0022] Step 3, and After processing by a low-pass filter, the filtered instantaneous active power is obtained. and filtered instantaneous reactive power Then, it is input into the VSG stage, thereby obtaining the virtual mechanical power using equation (4). It consists of two superimposed parts: the active power setpoint and the virtual speed governor output adjustment.

[0023] In equation (4), It is the synchronous angular velocity of the power grid; This represents the virtual mechanical power injected into the doubly-fed induction generator; the coefficient m is the active power-frequency droop coefficient. It is the power reference value obtained by the speed outer loop control under the grid control.

[0024] Step 4: Calculate virtual mechanical power With filtered active power deviation and the deviation The input is processed in the active power controller (APC) to obtain the stator voltage control angle under grid control using equation (5). .

[0025] (5) In equation (5), s represents the complex frequency variable of the Laplace transform, J is the virtual inertia coefficient, and D is the damping coefficient.

[0026] Step 5: To achieve precise control of the output voltage amplitude of the grid-type doubly-fed wind turbine, the reactive power-voltage control loop is designed based on the inherent droop characteristic of synchronous generators (i.e., the output voltage amplitude decreases as reactive power output increases). Based on this characteristic, the calculation formula for the voltage command is derived as shown in equation (6), and finally the stator voltage amplitude command is obtained. : In equation (6), is the given command value for reactive power, and n is the reactive power-voltage droop coefficient.

[0027] Step 6: Calculate the stator voltage amplitude command Phase voltage amplitude relative to grid connection point voltage deviation and the deviation The input single-voltage loop control is shown in equation (7): In equation (7), k represents the integral parameter of the voltage controller. The amplitude of the modulated voltage output under network control.

[0028] Step 7: Collect the rotational speed ω of the doubly-fed motor and calculate the outer loop speed command. Deviation from rotational speed ω and the deviation The input is processed in the speed controller to obtain the active power command value using equation (8). ; Calculate the active power command value Deviation from instantaneous active power P under grid control and the deviation The input is processed in the stator-side active power controller (APC) to obtain the rotor d-axis setpoint using equation (9). : (8) (9) In equation (8), These are the proportional parameters of the speed controller; For the integral parameters of the speed controller; in equation (9), This refers to the proportional parameters of the reactive power controller. These are the integral parameters of the reactive power controller.

[0029] Step 8: Calculate The instantaneous reactive power Q is used as input, and the reactive power outer loop command under grid control is calculated. Deviation from instantaneous reactive power Q and the deviation The input is fed into the stator-side reactive power controller RPC, thereby obtaining the rotor q-axis setpoint using equation (10). : In equation (10), , These are the proportional and integral parameters of the reactive power controller.

[0030] Step 9: Calculate the rotor current command in the dq coordinate system under grid control. With rotor current feedback Deviations and instructions and The deviation between them is input into the PI regulator of the inner loop of the rotor current, and the corresponding d-axis rotor voltage command in the dq coordinate system is obtained. q-axis rotor voltage command After the coordinate transformation process, the modulation voltage amplitude output under grid control is obtained. .

[0031] Step 10: Calculate the final input modulation voltage reference value to the rotor-side converter, and use equation (11) to determine the amplitude of the modulation voltage output under grid control. The amplitude of the modulated voltage output under network control The weighted sum is used to obtain the final modulation voltage reference value. After modulation by the PWM stage, the control signals S1-S6 of the machine-side converter switching tube are generated, thereby realizing the integrated control of the doubly-fed flywheel energy storage.

[0032] In equation (11), For the network coefficient, The network coefficient is denoted as .

[0033] In this embodiment, an electronic device includes a memory and a processor. The memory stores a program that supports the processor in executing the above-described method, and the processor is configured to execute the program stored in the memory.

[0034] In this embodiment, a computer-readable storage medium stores a computer program, which is executed by a processor to perform the steps of the above method.

Claims

1. A grid-connected integrated control method based on doubly-fed flywheel energy storage, characterized in that, This is applied to a doubly-fed phase-modulation system consisting of a doubly-fed motor, flywheel, rotor-side converter, and grid-side converter, and is performed according to the following steps: Step 1, collect the three-phase stator current of the doubly-fed wind turbine. 、 、 With three-phase stator voltage 、 、 After coordinate transformation, the instantaneous active power output from the stator side of the doubly-fed induction generator (DFIG) is calculated. With instantaneous reactive power Step 2: Collect the three-phase rotor current of the doubly-fed wind turbine. 、 、 With rotor electric angular velocity After coordinate transformation, the d-axis DC component of the rotor current in the synchronous rotating coordinate system of the rotor converter is obtained. q-axis DC component Step 3, and After processing by a low-pass filter, the filtered instantaneous active power is obtained. and filtered instantaneous reactive power Then, the data is input into the VSG circuit, thereby utilizing the rotor motion equations of the doubly-fed wind turbine in VSG control mode to obtain the virtual mechanical power. Step 4: Calculate the virtual mechanical power With filtered active power deviation and the deviation The input is processed in the active power controller (APC) to obtain the stator voltage control angle under grid control. Step 5: Calculate the stator-side reactive power command. With filtered instantaneous reactive power deviation and the deviation Input the stator-side reactive power controller (RPC) to obtain the stator voltage amplitude command. Step 6: Calculate the stator voltage amplitude command. Phase voltage amplitude relative to grid connection point voltage deviation and the deviation The input voltage is processed in a single-voltage loop controller to obtain the modulation voltage amplitude of the output under network control. Step 7: Collect the rotational speed ω of the doubly-fed motor and calculate the outer loop speed command. Deviation from rotational speed ω and the deviation The input is processed in the speed controller to obtain the active power command value. Step 8: Calculate the active power command value. Deviation from instantaneous active power P under grid control and the deviation The input is processed in the stator-side active power controller (APC) to obtain the rotor d-axis setpoint. ； Step 9: Obtain the grid phase through a phase-locked loop. and calculate with The instantaneous reactive power Q is used as input, and then the reactive power outer loop command under grid control is calculated. Deviation from instantaneous reactive power Q and the deviation The input is processed by the stator-side reactive power controller (RPC) to obtain the rotor q-axis setpoint. Step 10: Calculation and Deviation between and and The deviations between them are input into the PI regulator of the inner loop of the rotor current for processing, and the corresponding d-axis rotor voltage command in the dq coordinate system is obtained. q-axis rotor voltage command After the coordinate transformation process, the modulation voltage amplitude output under grid control is obtained. Step 11: Based on the network coefficients And network coefficient ,right and After weighted summation, the final modulation voltage reference value is obtained, which is then input into the PWM stage for modulation to generate the control signals S1-S6 for the switching transistors of the generator-side converter, thereby realizing the integrated control of the doubly-fed flywheel energy storage.

2. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 1, characterized in that, Step 1 includes: Step 1.1, using the coordinate transformation link shown in equation (1) to center the three-phase stator current. 、 、 With three-phase stator voltage 、 、 The process is performed to obtain the d-axis DC component of the stator current in the synchronous rotating coordinate system. q-axis DC component and the DC component of the stator voltage along the d-axis in the synchronous rotating coordinate system q-axis DC component ： (1) Step 1.2: Obtain the instantaneous active power output on the stator side of the doubly fed wind turbine according to equation (2). With instantaneous reactive power ： (2) In equations (1) and (2), This is the reference angle for coordinate transformation in rotor converter control, obtained from the virtual synchronization element of the network control. 、 、 This represents the three-phase stator voltage / three-phase stator current of the doubly-fed induction generator in a three-phase stationary coordinate system. 、 The d-axis and q-axis DC components represent the three-phase stator voltage / three-phase stator current in the synchronous rotating coordinate system of the rotor converter.

3. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 2, characterized in that, In step 2, equation (3) is used to measure the three-phase rotor current. 、 、 With rotor electric angular velocity Perform coordinate transformation to obtain the d-axis DC component of the rotor current in the synchronous rotating coordinate system of the rotor converter. q-axis DC component ： In equation (3), The phase of the power grid is obtained by the phase-locked loop in the grid control.

4. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 3, characterized in that, In step 3, the following is to... and After processing by a low-pass filter, the filtered instantaneous active power is obtained. and filtered instantaneous reactive power The virtual mechanical power is then input into the VSG stage and obtained using equation (4). ； In equation (4), It is the synchronous angular velocity of the power grid; Represents the virtual mechanical power injected into the doubly-fed motor; The coefficient m is the active power-frequency droop coefficient. It is the power reference value obtained by the speed outer loop control under the grid control.

5. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 4, characterized in that, Step 4 involves using virtual mechanical power. With filtered active power The input is processed in the active power controller (APC) to obtain the reference angle under grid control using equation (5). ： (5) In equation (5), s represents the complex frequency variable of the Laplace transform, J is the virtual inertia coefficient, and D is the damping coefficient.

6. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 5, characterized in that, Step 5 involves sending the stator-side reactive power command. With filtered instantaneous reactive power The input is processed in the stator-side reactive power controller RPC, thereby obtaining the stator voltage amplitude command using equation (6). ： In equation (6), is the given command value for reactive power, and n is the reactive power-voltage droop coefficient.

7. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 6, characterized in that, Step 6 involves sending the stator voltage amplitude command. Phase voltage amplitude relative to grid connection point voltage The input voltage is processed in a single-voltage loop controller, and the amplitude of the modulated voltage output under network control is obtained using equation (7). ： In equation (7), k is the integral parameter of the voltage controller.

8. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 7, characterized in that, Step 7 involves transferring the speed outer loop command. The motor speed ω is input to the speed controller for processing, thereby obtaining the active power command value using equation (8). ： In equation (8), These are the proportional parameters of the speed controller; These are the integral parameters of the speed controller.

9. The grid-connected control method based on doubly-fed flywheel energy storage according to claim 8, characterized in that, Step 8 involves setting the active power command value. The instantaneous active power P under grid control is input to the stator-side active power controller APC for processing, thereby obtaining the rotor d-axis setpoint using equation (9). ： In equation (9), These are the proportional parameters of the active power controller; These are the integral parameters of the active power controller.

10. A grid-connected control method based on doubly-fed flywheel energy storage according to claim 9, characterized in that, In step 9, the rotor q-axis setpoint is obtained using equation (10). ： In equation (10), For the proportional parameters of the reactive power controller; These are the integral parameters of the reactive power controller.

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