CN108397347B - Rotating speed control method for ensuring stable inertia response control of large wind turbine generator - Google Patents

Abstract

A rotating speed control method for ensuring stable inertia response control of a large-scale wind turbine generator comprises the following steps: 1) detecting the frequency of a power grid by a converter of the wind turbine generator; 2) the wind turbine generator main control system judges whether the wind turbine generator enters an inertia response control mode or not according to the power grid frequency and the inertia response control dead zone; 3) if so, the wind turbine generator simulates an inertia response effect by releasing the rotation kinetic energy stored by the wind turbine generator impeller and the generator; 4) when the frequency of the power grid is judged to be restored to the range of the dead zone or the wind turbine generator judges that the wind turbine generator is in the critical capacity of inertia support, the wind turbine generator starts to restore the rotating speed and adopts a constant rotating speed restoration control method; 5) and when the output power of the set is recovered to be within 90-110% of the theoretical power of the variable speed and variable pitch control operation, the set enters a smooth and continuous acceleration switching control mode. The invention solves the problems of unit halt and secondary impact on a power grid caused by unstable rotating speed of the wind turbine generator.

Description

Rotating speed control method for ensuring stable inertia response control of large wind turbine generator

Technical Field

The invention relates to a control method of a wind generating set, in particular to a rotating speed control method for ensuring the inertia response control stability of a large-scale wind generating set.

Background

Wind power participating in power system frequency modulation has many benefits for the power grid: the method has the advantages of adjusting the frequency pressure of the power grid in a link, improving the frequency stability of the power grid, improving the wind power permeability, increasing the new energy ratio, reducing the rotating reserve capacity of the power grid and reducing the operating cost of the power grid. More and more power companies require wind power generation energy to provide auxiliary services like a conventional power plant, and some latest published power grid guides at home and abroad definitely propose that a grid-connected wind power plant needs to provide auxiliary functions such as rotary standby, inertial response, primary frequency modulation and the like the conventional power plant. The wind power participating in the power system frequency modulation is the inevitable trend of the power grid requirement.

The stator of the variable-speed constant-frequency wind turbine generator based on the doubly-fed induction generator is directly connected into a power grid, and the rotor is indirectly connected into the power grid through the frequency converter. When the system frequency changes, the frequency converter controls the electromagnetic power to be kept unchanged as much as possible, and because the wind speed is constant, the rotating speed of the wind turbine is unchanged, and the output mechanical power is unchanged, the electromagnetic power and the mechanical power can be kept balanced, the rotating speed of the generator is unchanged, and the kinetic energy cannot be released. In this case, the inherent inertia of the doubly-fed wind turbine hardly contributes to the inertia of the whole system, that is, the doubly-fed wind turbine is connected to the grid, so that the rotational inertia of the whole system is reduced, and therefore, the recovery of the grid frequency is not facilitated.

Therefore, when no additional energy storage system exists, the active power output of the wind turbine generator is controlled and adjusted by utilizing the kinetic energy stored in the rotor of the wind turbine generator, so that the wind turbine generator and the synchronous motor in the system participate in the frequency modulation process of the system together, the integral frequency modulation capability of the system is improved, and the frequency stability of the system is improved. When the system frequency changes, the frequency converter adjusts the electromagnetic power of the generator set, and as the wind speed is basically kept constant, the wind turbine set releases kinetic energy and outputs mechanical power to be increased, the electromagnetic power and the mechanical power can not be kept balanced, so that the rotating speed of the generator changes. Meanwhile, after the inertia response supporting process is finished, the change of the rotating speed affects the power output of the wind generation set along with the process of rotating speed recovery of the wind generation set, and secondary impact and influence are generated on the frequency of a power grid.

Disclosure of Invention

The invention provides a control method capable of stabilizing the rotating speed of a wind turbine generator in an inertia response control process, aiming at solving the problems of unstable rotating speed of the wind turbine generator in the inertia response control of the wind turbine generator and solving the problems of unit halt and secondary impact on a power grid caused by unstable rotating speed of the wind turbine generator.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a rotating speed control method for ensuring stable inertia response control of a large-scale wind turbine generator comprises the following steps:

1) the wind turbine converter detects the frequency of a power grid and uploads a frequency signal to a wind turbine main control system;

2) the wind turbine generator main control system judges whether the wind turbine generator enters an inertia response control mode or not according to the power grid frequency and the inertia response control dead zone;

3) if the wind turbine generator enters an inertia response control mode, the wind turbine generator utilizes kinetic energy stored in a rotor to carry out power support, active power output by the wind turbine generator is improved, and a large wind turbine generator simulates an inertia response effect by releasing rotating kinetic energy stored by an impeller of the wind turbine generator and a generator; during the inertia response period, the wind speed is constant, and the energy captured by the wind turbine generator is kept constant, so that the rotating speed of the wind turbine generator is reduced;

4) when the frequency of the power grid is judged to be restored to the range of the dead zone or the wind turbine generator judges that the wind turbine generator is in the critical capacity of inertia support, the large wind turbine generator starts to restore the rotating speed and adopts a constant rotating speed restoration control method;

5) and when the output power of the set is recovered to be within 90-110% of the theoretical power of the variable speed and variable pitch control operation, the set enters a smooth and continuous acceleration switching control mode.

Further, in the step 4), the wind turbine generator simultaneously monitors the power grid frequency and the rotating speed of the generator, and when any one condition triggers the threshold, the wind turbine generator enters a constant rotating speed stable recovery mode and enters the step 5).

Preferably, the grid frequency monitoring trigger threshold is set as follows: the unit inertia response frequency trigger dead zone is delta f, namely when the power grid frequency is restored to 50-delta f Hz in the unit inertia response process, the unit enters a stable rotating speed restoration mode;

the generator speed trigger thresholds are set as follows: the lowest rotating speed of the generator set is omega_minWhen the rotating speed of the wind turbine generator is lower than omega, the early warning threshold of the rotating speed of the generator is delta omega_minWhen the speed is + delta omega, the unit enters a stable rotating speed recovery mode;

during the speed recovery period, the expected acceleration is calculated by a proportional-integral control algorithm by adopting a constant speed recovery control mode as follows:

a_{i_exp}＝k_p(v_ref-v)+k_i∫(v_ref-v)dt

wherein: a is_{i_exp}Response of inertia to desired acceleration, k_pIs a proportionality coefficient, k_iIs an integral coefficient, v_refAnd controlling the target rotating speed for the unit, and v is the actual rotating speed of the unit.

Still further, in the step 5), the variable speed and variable pitch control is operated, and the control algorithm is adopted to calculate the expected acceleration as follows:

a_{v_exp}＝k_p(v_ref-v)

wherein: a is_{v_exp}Desired acceleration, k, for variable speed pitch control_pIs a proportionality coefficient, v_refControlling a target rotating speed for the unit, and v is an actual rotating speed of the unit;

continuously processing the control quantity in the switching process, and continuously processing the output quantity of the controller, namely the expected acceleration by using a weighted average algorithm in the transition process, wherein the formula is as follows:

a_exp＝k₁a_{i_exp}+k₂a_{v_exp}

wherein: a is_expIs the control quantity of the controller in the transition region, a_{i_exp}In response to desired acceleration for inertia, a_{v_exp}Desired acceleration, k, for variable speed pitch control₁And k₂Is a weight coefficient, k₁≥0，k₂1 and k is ≦ 1₁+k₂＝1。

Further, in the step 5), k₁And k₂The selection rules of (2) are as follows:

the closer the current state of the unit is to a certain control mode, the larger the weight coefficient corresponding to the mode is, and when the constant speed recovery mode and the variable speed power generation control mode of the unit are switched, k₁And k₂The values of (a) are as follows:

k₁、k₂＝0.5±Δv_i/(2δ_v)

wherein, Δ v_iFor the corresponding ordinate axis value, delta, of the unit operating state in the transition region_vThe offset of the transition zone boundary line.

The technical conception of the invention is as follows: through the rotation speed control of the wind turbine generator in the inertia response process or the recovery process, the stability of output power of the wind turbine generator is ensured while the wind turbine generator is stably and safely operated in the whole inertia response process, and the secondary impact of the wind turbine generator on the power grid frequency caused by shutdown or output power jitter due to too low rotation speed is avoided.

The invention has the following beneficial effects: 1. the rotation speed control can avoid the shutdown of the wind turbine generator due to the over-low rotation speed caused by the inertia response of the wind turbine generator, and prevent the reduction of the service life of the wind turbine generator and the impact on a power grid; 2. the rotation speed control can realize quick and stable recovery to the optimal rotation speed of the unit variable speed and variable pitch control operation, thereby ensuring the safe and stable operation of the unit and preventing the unit from vibrating; 3. the operating conditions of the power grid and the unit are fully considered in the rotating speed point judgment, so that the optimal effect of the unit for supporting the power grid is realized, and the safety of the unit and the stability of the power grid are ensured.

Drawings

Fig. 1 is a rotation speed control mode determination map.

Fig. 2 is a transition region explanatory diagram.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to fig. 1 and 2, a rotating speed control method and system for ensuring stable inertia response control of a large-scale wind turbine generator, the control method includes the following steps:

1) the method comprises the following steps that a wind turbine converter quickly and accurately (with high precision) detects the frequency of a power grid and uploads a frequency signal to a wind turbine main control system;

2) the wind turbine generator main control system judges whether the wind turbine generator enters an inertia response control mode or not according to the power grid frequency and the inertia response control dead zone;

3) if the wind turbine generator enters an inertia response control mode, the wind turbine generator utilizes kinetic energy stored in the rotor to carry out rapid power support, active power output by the wind turbine generator is improved, and the large wind turbine generator simulates an inertia response effect by releasing rotating kinetic energy stored by an impeller of the wind turbine generator and a generator. During the inertia response, the wind speed is constant (the constant is basically constant, namely is within a small fluctuation range), the energy captured by the wind turbine set is kept constant (the constant is basically constant, namely is within a small fluctuation range), and then the rotating speed of the wind turbine set is reduced;

4) and when the frequency of the power grid is judged to be restored to the range of the dead zone or the wind turbine generator is judged to be in the critical capacity of inertia support, the large wind turbine generator starts to restore the rotating speed, and a constant rotating speed restoration control method is adopted.

And (3) simultaneously monitoring the power grid frequency and the rotating speed of the generator by the wind turbine, and when any one condition triggers a threshold, enabling the wind turbine to enter a constant rotating speed stable recovery mode and entering the step 5).

Setting a power grid frequency monitoring trigger threshold as follows: the unit inertia response frequency trigger dead zone is delta f (default value is 0.2Hz), namely, when the power grid frequency is restored to 49.8Hz in the unit inertia response process, the unit enters a stable rotating speed restoring mode.

The generator speed trigger thresholds are set as follows: the lowest rotating speed of the generator set is omega_minWhen the rotating speed of the wind turbine generator is lower than omega, the early warning threshold of the rotating speed of the wind turbine generator is delta omega (the default value is 50rpm)_minAnd when the speed is + delta omega, the unit enters a stable rotating speed recovery mode.

During the speed recovery period, the expected acceleration is calculated by a proportional-integral control algorithm by adopting a constant speed recovery control mode as follows:

a_{i_exp}＝k_p(v_ref-v)+k_i∫(v_ref-v)dt

wherein: a is_{i_exp}Response of inertia to desired acceleration, k_pIs a proportionality coefficient, k_iIs an integral coefficient, v_refAnd controlling the target rotating speed for the unit, and v is the actual rotating speed of the unit.

5) When the output power of the set is recovered to be within 90% -110% of the theoretical power of variable speed and variable pitch control operation, the set enters a smooth and continuous switching control mode of acceleration, the angular acceleration of the wind turbine generator is not suddenly changed, the operation is stable, and vibration is avoided.

And (3) controlling and operating the variable speed and the variable pitch, and calculating the expected acceleration by adopting a control algorithm as follows:

a_{v_exp}＝k_p(v_ref-v)

wherein: a is_{v_exp}Desired acceleration, k, for variable speed pitch control_pIs a proportionality coefficient, v_refAnd controlling the target rotating speed for the unit, and v is the actual rotating speed of the unit.

Continuously processing the control quantity in the switching process, and continuously processing the output quantity of the controller, namely the expected acceleration by using a weighted average algorithm in the transition process, wherein the formula is as follows:

a_exp＝k₁a_{i_exp}+k₂a_{v_exp}

wherein: a is_expIs the control quantity of the controller in the transition region, a_{i_exp}In response to desired acceleration for inertia, a_{v_exp}Desired acceleration, k, for variable speed pitch control₁And k₂Is a weight coefficient, k₁≥0，k₂1 and k is ≦ 1₁+k₂＝1。

k₁And k₂The selection rules of (2) are as follows:

the closer the current state of the unit is to a certain control mode, the larger the weight coefficient corresponding to the mode is. When the unit constant speed recovery mode and the variable speed power generation control mode are switched, k₁And k₂Values of such asThe following:

k₁、k₂＝0.5±Δv_i/(2δ_v)

wherein, Δ v_iFor the corresponding ordinate axis value, δ, of the unit operating state in the transition region of fig. 2_vThe offset of the transition zone boundary line.

Dynamically selecting a weight coefficient k₁And k₂The method and the device can enable the unit to control the expected acceleration to change smoothly in the switching process, and avoid unit buffeting caused by sudden change of the acceleration caused in mode switching.

Claims (5)

1. A rotating speed control method for ensuring stable inertia response control of a large-scale wind turbine generator is characterized by comprising the following steps:

1) the wind turbine converter detects the frequency of a power grid and uploads a frequency signal to a wind turbine main control system;

2) the wind turbine generator main control system judges whether the wind turbine generator enters an inertia response control mode or not according to the power grid frequency and the inertia response control dead zone;

3) if the wind turbine generator enters an inertia response control mode, the wind turbine generator utilizes kinetic energy stored in a rotor to carry out power support, active power output by the wind turbine generator is improved, and a large wind turbine generator simulates an inertia response effect by releasing rotating kinetic energy stored by an impeller of the wind turbine generator and a generator; during the inertia response period, the wind speed is constant, and the energy captured by the wind turbine generator is kept constant, so that the rotating speed of the wind turbine generator is reduced;

4) when the frequency of the power grid is judged to be restored to the range of the dead zone or the wind turbine generator judges that the wind turbine generator is in the critical capacity of inertia support, the large wind turbine generator starts to restore the rotating speed and adopts a constant rotating speed restoration control method;

5) and when the output power of the set is recovered to be within 90-110% of the theoretical power of the variable speed and variable pitch control operation, the set enters a smooth and continuous acceleration switching control mode.

2. The rotating speed control method for ensuring the inertia response control stability of the large-scale wind turbine generator set according to claim 1, characterized in that: in the step 4), the wind turbine generator simultaneously monitors the power grid frequency and the rotating speed of the generator, and when any one condition triggers the threshold, the wind turbine generator enters a constant rotating speed stable recovery mode and enters the step 5).

3. The rotating speed control method for ensuring the inertia response control stability of the large-scale wind turbine generator set according to claim 2, characterized in that: setting a power grid frequency monitoring trigger threshold as follows: the unit inertia response frequency trigger dead zone is delta f, namely when the power grid frequency is restored to 50-delta f Hz in the unit inertia response process, the unit enters a stable rotating speed restoration mode;

the generator speed trigger thresholds are set as follows: the lowest rotating speed of the generator set is omega_minWhen the rotating speed of the wind turbine generator is lower than omega, the early warning threshold of the rotating speed of the generator is delta omega_minWhen the speed is + delta omega, the unit enters a stable rotating speed recovery mode;

during the speed recovery period, the expected acceleration is calculated by a proportional-integral control algorithm by adopting a constant speed recovery control mode as follows:

a_{i_exp}＝k_p(v_ref-v)+k_i∫(v_ref-v)dt

wherein: a is_{i_exp}Response of inertia to desired acceleration, k_pIs a proportionality coefficient, k_iIs an integral coefficient, v_refAnd controlling the target rotating speed for the unit, and v is the actual rotating speed of the unit.

4. The rotating speed control method for ensuring the inertia response control stability of the large-scale wind turbine generator set according to any one of claims 1 to 3, characterized in that: in the step 5), the step of processing the raw material,

and (3) controlling and operating the variable speed and the variable pitch, and calculating the expected acceleration by adopting a control algorithm as follows:

a_{v_exp}＝k_p(v_ref-v)

wherein: a is_{v_exp}Desired acceleration, k, for variable speed pitch control_pIs a proportionality coefficient, v_refControlling a target rotating speed for the unit, and v is an actual rotating speed of the unit;

continuously processing the control quantity in the switching process, and continuously processing the output quantity of the controller, namely the expected acceleration by using a weighted average algorithm in the transition process, wherein the formula is as follows:

a_exp＝k₁a_{i_exp}+k₂a_{v_exp}

wherein: a is_expIs the control quantity of the controller in the transition region, a_{i_exp}In response to desired acceleration for inertia, a_{v_exp}Desired acceleration, k, for variable speed pitch control₁And k₂Is a weight coefficient, k₁≥0，k₂1 and k is ≦ 1₁+k₂＝1。

5. The rotating speed control method for ensuring the inertia response control stability of the large-scale wind turbine generator set according to claim 4, characterized in that: in said step 5), k₁And k₂The selection rules of (2) are as follows:

the closer the current state of the unit is to a certain control mode, the larger the weight coefficient corresponding to the mode is, and when the constant speed recovery mode and the variable speed power generation control mode of the unit are switched, k₁And k₂The values of (a) are as follows:

k₁、k₂＝0.5±Δv_i/(2δ_v)

wherein, Δ v_iFor the corresponding ordinate axis value, delta, of the unit operating state in the transition region_vThe offset of the transition zone boundary line.