Starting control loop and starting method of grid-connected wind turbine with additional energy storage

Abstract

The application relates to the technical field of electrical control, in particular to a starting control loop and a starting method of a grid-connected wind turbine with additional energy storage. The application provides a starting control loop of a grid-side converter and a starting control loop of an energy storage converter. In the starting process, the energy storage converter is started first and maintains the DC voltage of the wind turbine at a rated value; next, the grid-side converter is synchronized with the power grid by using a phase-locked loop first, and then switches to an autonomous synchronization operation state; finally, the machine-side converter is started, the captured wind power is gradually increased, and the wind turbine is transitioned to a rated operation state. The starting control loop and the starting method can make the grid-connected wind turbine with additional energy storage smoothly start from a shutdown state and transition to a grid-connected operation state, reduce the impact in the starting process, avoid the operation instability of the grid-connected wind turbine with additional energy storage in the starting process by adding a stability controller, and are beneficial to promoting the engineering application of the grid-connected wind turbine with additional energy storage.

Description

Technical Field

[0001] This invention relates to the field of electrical control technology, specifically to a starting control loop and starting method for a grid-connected wind turbine with additional energy storage. Background Technology

[0002] Currently, wind turbines typically employ a grid-following control method that uses phase-locked loops to observe the grid voltage phase. Under this control, the wind turbine exhibits external current source characteristics and cannot actively support the grid. This method is suitable for strong grid conditions with a low proportion of wind power integration. Grid-building control can enhance the wind turbine's ability to support the grid and is suitable for weak grid conditions with a high proportion of wind power connected to the grid.

[0003] However, existing grid-based control methods are mostly applicable to converters with stable power input, such as energy storage converters. For wind power converters with fluctuating input power, new grid-based control methods need to be studied. On the other hand, conventional wind turbines have a weak ability to participate in grid frequency regulation. Adding energy storage units to the DC side of wind turbines enables them to participate in primary grid frequency regulation.

[0004] Adding energy storage units to the DC side of grid-connected wind turbines enables them to participate in primary frequency regulation and inertia support. However, such grid-connected wind turbines with added energy storage lack the control loop and starting method for flexible grid-connected startup, which is not conducive to practical engineering applications. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by proposing a starting control loop and starting method for grid-connected wind turbines with additional energy storage, enabling flexible grid-connected starting, reducing the impact during the starting process, and improving the prospects for engineering applications.

[0006] To achieve the aforementioned objectives, the present invention employs the following technical solution: a start-up control loop for a grid-connected wind turbine with added energy storage, comprising a grid-side converter, an energy storage converter, and a turbine-side converter; the grid-side converter is a DC / AC converter, with its AC side being an LCL-type filter, which is connected to the power grid via a circuit breaker BRK; the turbine-side converter is an AC / DC converter; the energy storage converter is a bidirectional DC / DC converter, with one side connected to the DC capacitor of the wind turbine and the other side connected to the energy storage battery; the start-up controller of the turbine-side converter adopts a conventional start-up control loop;

[0007] The start-up controller of the grid-side converter adopts the following structure: a phase-locked loop (PLL) is used to observe the phase θ of the grid-connected voltage. p The output of the phase-locked loop (PLL) serves as the input to position 1 of the selector switch S1, and the DC voltage u of the observation network-side converter is... dc Multiply by the reference value ω of the power grid angular frequency BgDivide by the rated DC voltage u dcn It then enters an integrator, the output of which is θ. s As the input to position 2 of the selector switch S1; detect the output current i of the grid-side converter. 1abc LCL filter capacitor voltage u Cabc Grid connection point voltage u pabc And perform a coordinate transformation to obtain the d-axis component of the output current of the grid-side converter. 1d The output current q-axis component i of the grid-side converter 1q The d-axis component u of the LCL filter capacitor voltage Cd The q-axis component u of the LCL filter capacitor voltage Cq The d-axis component u of the grid connection point voltage pd q-axis component u of the grid connection point voltage pq The phase used for rotating coordinate transformation is the output θ of gating switch S1;

[0008] Reference value Q of reactive power output from grid-side converter gref Feedback value Q of reactive power g The difference is fed into a PI regulator, and the output of the PI regulator serves as the input to position 2 of the selector switch S6, while the input to position 1 of the selector switch S6 is 0; the DC voltage u of the grid-side converter is detected. dc This data is then input into a stabilizer controller, whose transfer function is sk. q / (Ts+1), where s is the Laplacian operator, T is the filtering time constant, and k is the filter time constant. q To stabilize the control gain, the output of the stabilizing controller serves as the input to position 2 of the selector switch S5, while the input to position 1 of the selector switch S5 is 0. The output of the selector switch S5 is superimposed with the output of the selector switch S6 and the effective value U of the grid phase voltage. t0 The value u is then used as a reference for the d-axis component of the LCL filter capacitor voltage. Cdref ;u Cdref The d-axis component u of the LCL filter capacitor voltage Cd The difference, after passing through a P regulator (proportional regulator), is used as the reference value i for the d-axis component of the grid-side converter output current. 1dref i 1dref The d-axis component of the output current of the grid-side converter 1d The difference, after passing through a PI regulator, outputs the signal as input to position 2 of selector switch S3, while the input to position 1 of selector switch S3 is the d-axis component u of the grid connection point voltage. pd Reference value u of the q-axis component of the LCL filter capacitor voltage. Cqref The q-axis component u of the LCL filter capacitor voltage CqThe difference, after passing through a P regulator (proportional regulator), is used as the reference value i for the q-axis component of the grid-side converter output current. 1qref i 1qref The output current q-axis component i of the grid-side converter 1q The difference, after passing through a PI regulator, is used as the input to position 2 of the selector switch S4, while the input to position 1 of the selector switch S4 is the q-axis component u of the grid connection point voltage. pq ;

[0009] The output of the selector switch S3 is the d-axis component of the modulated voltage of the grid-side converter. The output of the selector switch S4 is the q-axis component of the modulated voltage of the grid-side converter. The modulation voltage of the grid-side converter is transformed into a stationary coordinate system after rotation. The phase used for rotational transformation is θ; the modulation voltage of the grid-side converter. The trigger signal s for the grid-side converter is generated after sinusoidal pulse width modulation. gabc .

[0010] Furthermore, as a preferred embodiment of the present invention, the start-up controller of the energy storage converter adopts the following structure: the rated DC voltage u of the grid-side converter dcn DC voltage u of the grid-side converter dc The difference is passed through a transfer function K p +K I After the PI regulator of / s, it serves as the input to position 1 of the selector switch S2; the DC voltage rating of the grid-side converter is u. dcn DC voltage u of the grid-side converter dc The difference is passed through a transfer function K P After the PI regulator, it serves as the input to position 2 of the selector switch S2; the output of the selector switch S2 is the reference value i of the energy storage converter output current. esref i esref Feedback value i of the energy storage converter output current es The difference between the two signals passes through a PI regulator and then enters the modulation stage. The output of the modulation stage is the trigger signal s of the energy storage converter. es Among them, K P For proportional gain, K I Let s be the integral gain, and s be the Laplace operator.

[0011] Furthermore, as a preferred embodiment of the present invention, the reference value ω Bg The reference value u is 100π. Cqref It is 0.

[0012] The starting method for the starting control loop of a grid-connected wind turbine with additional energy storage is as follows: the energy storage converter starts first, followed by the grid-side converter, and finally the turbine-side converter. Before starting, the selector switches S1, S2, S3, S4, S5, and S6 are all in position 1. The starting process includes the following steps:

[0013] Step 1: Activate the trigger pulse of the energy storage converter. The energy storage converter starts up and controls the DC voltage of the grid-side converter to the rated value u. dcn ;

[0014] Step 2: Close circuit breaker BRK, connect the grid-side converter to the power grid, activate the grid-side converter trigger pulse, and connect the grid-side converter to the power grid through a phase-locked loop;

[0015] Step 3: Selector switches S3 and S4 are simultaneously switched from position 1 to position 2, and the grid-side converter enters the dual-loop control mode of the outer loop of the filter capacitor voltage and the inner loop of the inductor current.

[0016] Step 4: Selector switches S1 and S2 simultaneously switch from position 1 to position 2. The grid-side converter, controlled by the energy storage converter, switches the DC voltage to the autonomous synchronous grid operation mode. When selector switch S1 switches, position 2 receives the input phase θ. s The initial value is the input phase θ at position 1. p ;

[0017] Step 5: Switch S5 from position 1 to position 2 to add the stability controller to the control loop of the grid-side converter, thereby improving the stability of the wind turbine operation;

[0018] Step 6: Switch S6 is switched from position 1 to position 2 to add reactive power control to the outer control loop of the grid-side converter;

[0019] Step 7: The turbine-side converter starts up, the wind turbine captures wind power, and the output power of the turbine-side converter gradually increases. After the output power of the turbine-side converter increases to the rated value, the grid-type wind turbine with additional energy storage is started up.

[0020] The starting control loop and starting method of the grid-connected wind turbine with additional energy storage proposed in this invention have the following technical advantages compared with the prior art:

[0021] The start-up control loop and start-up method of the present invention enable grid-connected wind turbines with added energy storage to start smoothly from a shutdown state and transition to grid-connected operation, reducing the impact during the start-up process; the added stability controller can prevent the grid-connected wind turbines with added energy storage from becoming unstable during the start-up process, which is conducive to promoting the engineering application of grid-connected wind turbines with added energy storage. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the start-up control of the grid-type wind turbine with additional energy storage according to the present invention.

[0023] Figure 2 This is a block diagram of the start-up controller of the grid-side converter of the present invention;

[0024] Figure 3 This is a block diagram of the start-up controller of the energy storage converter of the present invention;

[0025] Figure 4 This is a simulation embodiment of the present invention—the startup waveform of a grid-type wind turbine with additional energy storage. Detailed Implementation

[0026] The present invention will be further explained in detail below with reference to the accompanying drawings, so that those skilled in the art can better understand and implement the present invention. However, the following examples are only used to explain the present invention and are not intended to limit the present invention.

[0027] like Figure 1 The diagram shows the startup control schematic of the grid-connected wind turbine with supplemental energy storage according to the present invention. The startup control loop of the grid-connected wind turbine with supplemental energy storage includes a grid-side converter, an energy storage converter, and a turbine-side converter. The grid-side converter is a DC / AC converter, with an LCL filter on its AC side, which is connected to the grid via a circuit breaker BRK. The turbine-side converter is an AC / DC converter. The energy storage converter is a bidirectional DC / DC converter, with one side connected to the DC capacitor of the wind turbine and the other side connected to the energy storage battery. The startup controller of the turbine-side converter uses a conventional startup control loop.

[0028] like Figure 2 The diagram shows the block diagram of the start-up controller of the grid-side converter of the present invention. The start-up controller of the grid-side converter adopts the following structure: a phase-locked loop (PLL) is used to observe the phase θ of the voltage at the grid connection point. p The output of the phase-locked loop (PLL) serves as the input to position 1 of the selector switch S1, and the DC voltage u of the observation network-side converter is... dc Multiply by the reference value ω of the power grid angular frequency Bg Divide by the rated DC voltage u dcn It then enters an integrator, the output of which is θ. s As the input to position 2 of the selector switch S1; detect the output current i of the grid-side converter. 1abc LCL filter capacitor voltage u Cabc Grid connection point voltage u pabc And perform a coordinate transformation to obtain the d-axis component of the output current of the grid-side converter. 1d The output current q-axis component i of the grid-side converter 1qThe d-axis component u of the LCL filter capacitor voltage Cd The q-axis component u of the LCL filter capacitor voltage Cq The d-axis component u of the grid connection point voltage pd q-axis component u of the grid connection point voltage pq The phase used for rotating coordinate transformation is the output θ of gating switch S1;

[0029] Reference value Q of reactive power output from grid-side converter gref Feedback value Q of reactive power g The difference is fed into a PI regulator, and the output of the PI regulator serves as the input to position 2 of the selector switch S6, while the input to position 1 of the selector switch S6 is 0; the DC voltage u of the grid-side converter is detected. dc This data is then input into a stabilizer controller, whose transfer function is sk. q / (Ts+1), where s is the Laplacian operator, T is the filtering time constant, and k is the filter time constant. q To stabilize the control gain, the output of the stabilizing controller serves as the input to position 2 of the selector switch S5, while the input to position 1 of the selector switch S5 is 0. The output of the selector switch S5 is superimposed with the output of the selector switch S6 and the effective value U of the grid phase voltage. t0 The value u is then used as a reference for the d-axis component of the LCL filter capacitor voltage. Cdref ;u Cdref The d-axis component u of the LCL filter capacitor voltage Cd The difference, after passing through a P regulator (proportional regulator), is used as the reference value i for the d-axis component of the grid-side converter output current. 1dref i 1dref The d-axis component of the output current of the grid-side converter 1d The difference, after passing through a PI regulator, outputs the signal as input to position 2 of selector switch S3, while the input to position 1 of selector switch S3 is the d-axis component u of the grid connection point voltage. pd Reference value u of the q-axis component of the LCL filter capacitor voltage. Cqref The q-axis component u of the LCL filter capacitor voltage Cq The difference, after passing through a P regulator (proportional regulator), is used as the reference value i for the q-axis component of the grid-side converter output current. 1qref i 1qref The output current q-axis component i of the grid-side converter 1q The difference, after passing through a PI regulator, is used as the input to position 2 of the selector switch S4, while the input to position 1 of the selector switch S4 is the q-axis component u of the grid connection point voltage. pq The output of the selector switch S3 is the d-axis component of the modulated voltage of the grid-side converter. The output of the selector switch S4 is the q-axis component of the modulated voltage of the grid-side converter. The modulation voltage of the grid-side converter is transformed into a stationary coordinate system after rotation. The phase used for rotational transformation is θ; the modulation voltage of the grid-side converter. The trigger signal s for the grid-side converter is generated after sinusoidal pulse width modulation. gabc Among them, the reference value ω Bg =100π; reference value u Cqref It is 0.

[0030] like Figure 3 The diagram shows a block diagram of the start-up controller for the energy storage converter of the present invention. The start-up controller of the energy storage converter adopts the following structure: the rated DC voltage u of the grid-side converter... dcn DC voltage u of the grid-side converter dc The difference is passed through a transfer function K p +K I After the PI regulator of / s, it serves as the input to position 1 of the selector switch S2; the DC voltage rating of the grid-side converter is u. dcn DC voltage u of the grid-side converter dc The difference is passed through a transfer function K P After the PI regulator, it serves as the input to position 2 of the selector switch S2; the output of the selector switch S2 is the reference value i of the energy storage converter output current. esref i esref Feedback value i of the energy storage converter output current es The difference between the two signals passes through a PI regulator and then enters the modulation stage. The output of the modulation stage is the trigger signal s of the energy storage converter. es Among them, K P For proportional gain, K I Let s be the integral gain, and s be the Laplace operator.

[0031] The starting method for the starting control loop of a grid-connected wind turbine with additional energy storage is as follows: the energy storage converter starts first, followed by the grid-side converter, and finally the turbine-side converter. Before starting, the selector switches S1, S2, S3, S4, S5, and S6 are all in position 1. The starting process includes the following steps:

[0032] Step 1: Activate the trigger pulse of the energy storage converter. The energy storage converter starts up and controls the DC voltage of the grid-side converter to the rated value u. dcn ;

[0033] Step 2: Close circuit breaker BRK, connect the grid-side converter to the power grid, activate the grid-side converter trigger pulse, and connect the grid-side converter to the power grid through a phase-locked loop;

[0034] Step 3: Selector switches S3 and S4 are simultaneously switched from position 1 to position 2, and the grid-side converter enters the dual-loop control mode of the outer loop of the filter capacitor voltage and the inner loop of the inductor current.

[0035] Step 4: Selector switches S1 and S2 simultaneously switch from position 1 to position 2. The grid-side converter, controlled by the energy storage converter, switches the DC voltage to the autonomous synchronous grid operation mode. When selector switch S1 switches, position 2 receives the input phase θ. s The initial value is the input phase θ at position 1. p ;

[0036] Step 5: Switch S5 from position 1 to position 2 to add the stability controller to the control loop of the grid-side converter, thereby improving the stability of the wind turbine operation;

[0037] Step 6: Switch S6 is switched from position 1 to position 2 to add reactive power control to the outer control loop of the grid-side converter;

[0038] Step 7: The turbine-side converter starts up, the wind turbine captures wind power, and the output power of the turbine-side converter gradually increases. After the output power of the turbine-side converter increases to the rated value, the grid-type wind turbine with additional energy storage is started up.

[0039] like Figure 4 As shown, the simulation embodiment of the present invention—the startup waveform of a grid-connected wind turbine with additional energy storage—is illustrated. The waveforms are as follows: 0 seconds to 0.5 seconds correspond to step 1 of the startup process; 0.5 seconds to 0.75 seconds correspond to step 2; 0.75 seconds to 1 second correspond to step 3; 1 second to 1.2 seconds correspond to step 4; 1.2 seconds to 1.5 seconds correspond to step 5; 1.5 seconds to 2.0 seconds correspond to step 6; and 2.0 seconds to 5.0 seconds correspond to step 7. Figure 4 The DC voltage waveform shown in (a) is as follows: Figure 4 As can be seen from the output active power waveform shown in (b), the grid-connected wind turbine with additional energy storage has a smooth and distortion-free startup process and can operate smoothly to its rated state.

[0040] During the startup process of this invention, the energy storage converter starts first and maintains the DC voltage of the wind turbine at the rated value; next, the grid-side converter first uses a phase-locked loop to synchronize with the grid, and then switches to autonomous synchronization operation; finally, the turbine-side converter starts and gradually increases the captured wind power to transition the wind turbine to the rated operation state.

[0041] The startup control loop and startup method proposed in this invention can smoothly start up grid-connected wind turbines with added energy storage from the shutdown state and transition to the grid-connected operation state, reducing the impact during startup; the added stability controller can prevent the grid-connected wind turbines with added energy storage from becoming unstable during startup, which is conducive to promoting the engineering application of grid-connected wind turbines with added energy storage.

[0042] The specific implementation schemes described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific implementation schemes of the present invention and are not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A start-up control loop for a grid-connected wind turbine with added energy storage, characterized in that, It includes a grid-side converter, an energy storage converter, and a turbine-side converter; the grid-side converter is a DC / AC converter, with an LCL filter on its AC side, which is connected to the grid via a circuit breaker BRK; the turbine-side converter is an AC / DC converter; the energy storage converter is a bidirectional DC / DC converter, with one side connected to the DC capacitor of the wind turbine and the other side connected to the energy storage battery; the start-up controller of the turbine-side converter adopts a conventional start-up control loop; The start-up controller of the grid-side converter adopts the following structure: a phase-locked loop (PLL) is used to observe the phase θ of the grid-connected voltage. p The output of the phase-locked loop (PLL) serves as the input to position 1 of the selector switch S1, and the DC voltage u of the observation network-side converter is... dc Multiply by the reference value ω of the power grid angular frequency Bg Divide by the rated DC voltage u dcn It then enters an integrator, the output of which is θ. s As the input to position 2 of the selector switch S1; detect the output current i of the grid-side converter. 1abc LCL filter capacitor voltage u Cabc Grid connection point voltage u pabc And perform a coordinate transformation to obtain the d-axis component of the output current of the grid-side converter. 1d The output current q-axis component i of the grid-side converter 1q The d-axis component u of the LCL filter capacitor voltage Cd The q-axis component u of the LCL filter capacitor voltage Cq The d-axis component u of the grid connection point voltage pd q-axis component u of the grid connection point voltage pq The phase used for rotating coordinate transformation is the output θ of gating switch S1; Reference value Q of reactive power output from grid-side converter gref Feedback value Q of reactive power g The difference is fed into a PI regulator, and the output of the PI regulator serves as the input to position 2 of the selector switch S6, while the input to position 1 of the selector switch S6 is 0; the DC voltage u of the grid-side converter is detected. dc This data is then input into a stabilizer controller, whose transfer function is sk. q / (Ts+1), where s is the Laplacian operator, T is the filtering time constant, and k is the filter time constant. q To stabilize the control gain, the output of the stabilizing controller serves as the input to position 2 of the selector switch S5, while the input to position 1 of the selector switch S5 is 0. The output of the selector switch S5 is superimposed with the output of the selector switch S6 and the effective value U of the grid phase voltage. t0 The value u is then used as a reference for the d-axis component of the LCL filter capacitor voltage. Cdref ;u Cdref The d-axis component u of the LCL filter capacitor voltage Cd The difference, after passing through a P regulator (proportional regulator), is used as the reference value i for the d-axis component of the grid-side converter output current. 1dref i 1dref The d-axis component of the output current of the grid-side converter 1d The difference, after passing through a PI regulator, outputs the signal as input to position 2 of selector switch S3, while the input to position 1 of selector switch S3 is the d-axis component u of the grid connection point voltage. pd Reference value u of the q-axis component of the LCL filter capacitor voltage. Cqref The q-axis component u of the LCL filter capacitor voltage Cq The difference, after passing through a P regulator (proportional regulator), is used as the reference value i for the q-axis component of the grid-side converter output current. 1qref i 1qref The output current q-axis component i of the grid-side converter 1q The difference, after passing through a PI regulator, is used as the input to position 2 of the selector switch S4, while the input to position 1 of the selector switch S4 is the q-axis component u of the grid connection point voltage. pq ; The output of the selector switch S3 is the d-axis component of the modulated voltage of the grid-side converter. The output of the selector switch S4 is the q-axis component of the modulated voltage of the grid-side converter. The modulation voltage of the grid-side converter is transformed into a stationary coordinate system after rotation. The phase used for rotational transformation is θ; the modulation voltage of the grid-side converter. The trigger signal s for the grid-side converter is generated after sinusoidal pulse width modulation. gabc .

2. The start-up control loop of the grid-connected wind turbine with additional energy storage according to claim 1, characterized in that, The start-up controller of the energy storage converter adopts the following structure: DC voltage rating of grid-side converter u dcn DC voltage u of the grid-side converter dc The difference is passed through a transfer function K p +K I After the PI regulator of / s, it serves as the input to position 1 of the selector switch S2; the DC voltage rating of the grid-side converter is u. dcn DC voltage u of the grid-side converter dc The difference is passed through a transfer function K P After the PI regulator, it serves as the input to position 2 of the selector switch S2; the output of the selector switch S2 is the reference value i of the energy storage converter output current. esref i esref Feedback value i of the energy storage converter output current es The difference between the two signals passes through a PI regulator and then enters the modulation stage. The output of the modulation stage is the trigger signal s of the energy storage converter. es Among them, K P For proportional gain, K I Let s be the integral gain, and s be the Laplace operator.

3. The start-up control loop of the grid-connected wind turbine with added energy storage according to claim 1, characterized in that, The reference value ω Bg The reference value u is 100π. Cqref It is 0.

4. A starting method for a grid-connected wind turbine generator with additional energy storage as described in any one of claims 1-3, characterized in that, The energy storage converter starts first, followed by the grid-side converter, and finally the generator-side converter. Before startup, selector switches S1, S2, S3, S4, S5, and S6 are all in position 1. The startup process includes the following steps: Step 1: Activate the trigger pulse of the energy storage converter. The energy storage converter starts up and controls the DC voltage of the grid-side converter to the rated value u. dcn ; Step 2: Close circuit breaker BRK, connect the grid-side converter to the power grid, activate the grid-side converter trigger pulse, and connect the grid-side converter to the power grid through a phase-locked loop; Step 3: Selector switches S3 and S4 are simultaneously switched from position 1 to position 2, and the grid-side converter enters the dual-loop control mode of the outer loop of the filter capacitor voltage and the inner loop of the inductor current. Step 4: Selector switches S1 and S2 simultaneously switch from position 1 to position 2. The grid-side converter, controlled by the energy storage converter, switches the DC voltage to the autonomous synchronous grid operation mode. When selector switch S1 switches, position 2 receives the input phase θ. s The initial value is the input phase θ at position 1. p ; Step 5: Switch S5 from position 1 to position 2 to add the stability controller to the control loop of the grid-side converter, thereby improving the stability of the wind turbine operation; Step 6: Switch S6 is switched from position 1 to position 2 to add reactive power control to the outer control loop of the grid-side converter; Step 7: The turbine-side converter starts up, the wind turbine captures wind power, and the output power of the turbine-side converter gradually increases. After the output power of the turbine-side converter increases to the rated value, the grid-type wind turbine with additional energy storage is started up.

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