Reactive current adaptive control method and system of wind power system

Abstract

The invention discloses a reactive current self-adaptive control method for a wind power system. The method comprises the following steps: acquiring working data information of a target wind power system; establishing a reactive voltage control state space of the target wind power system; calculating a reactive current control coefficient of the target wind power system according to the current operation state of the target wind power system; and completing reactive current adaptive control of the target wind power system according to the reactive current control coefficient. The invention also discloses a system for realizing the reactive current adaptive control method of the wind power system. Through establishment of the reactive voltage control state space of the target wind power system and calculation of the reactive current control coefficient of the corresponding fine interval, not only is reactive current adaptive control of the wind power system realized, but also the reliability is higher and the accuracy is better.

Description

Technical Field

[0001] The present invention belongs to the field of electrical automation, and in particular relates to a reactive current adaptive control method and system for a wind power system. Background Art

[0002] With the development of economy and technology and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and life, bringing endless convenience to people's production and life. Therefore, ensuring the stable and reliable supply of electricity has become one of the most important tasks of the power system. At present, the proportion of wind power systems in the power system is increasing, so ensuring the stable and reliable operation of wind power systems is of great significance to the power system.

[0003] At present, large-scale wind power systems usually use high-voltage direct current to achieve long-distance transmission and utilization. During the operation of direct current transmission, changes in active power such as commutation failure and single / double-pole blocking will lead to large changes in reactive imbalance, thus causing serious transient voltage problems. Fault ride-through capability is the key to the safe grid connection of wind farms; when a grid fault occurs, wind turbines continue to operate without being disconnected from the grid and inject reactive current into the grid to support the recovery of grid voltage and reduce the impact of the fault. Therefore, the transient reactive voltage support capability of wind turbines is of great significance to both wind power systems and power systems.

[0004] At present, during faults, most of the existing standards and solutions for wind power systems use a fixed current coefficient as the benchmark for reactive current output, but this solution cannot fully utilize the dynamic regulation capabilities of the wind power system; and simply increasing the reactive current control coefficient can easily cause a large overshoot at the moment of fault removal, thereby affecting the safe and stable operation of the wind power system and the power system. Summary of the invention

[0005] One of the purposes of the present invention is to provide a reactive current adaptive control method for a wind power system with high reliability, good accuracy and good effect.

[0006] A second objective of the present invention is to provide a system for implementing the reactive current adaptive control method of the wind power system.

[0007] The reactive current adaptive control method of the wind power system provided by the present invention comprises the following steps:

[0008] S1. Obtaining the working data information of the target wind power system;

[0009] S2. Establishing reactive voltage control state space of target wind power system according to data information acquired in step S1;

[0010] S3. Based on the reactive voltage control state space established in step S2, the reactive current control coefficient of the target wind power system is calculated according to the current operating state of the target wind power system;

[0011] S4. According to the reactive current control coefficient obtained in step S3, the reactive current adaptive control of the target wind power system is completed.

[0012] The step S2 of establishing the reactive voltage control state space of the target wind power system according to the data information obtained in the step S1 includes the following steps:

[0013] With the goal of the fastest voltage tracking and recovery, the voltage variable at the grid connection point is selected as the state space variable;

[0014] The control scheme of the wind power system is the grid-side converter priority control scheme, and the power data and current data of the grid side are selected as state space variables;

[0015] Finally, the reactive power and voltage control state space of the target wind power system is constructed.

[0016] The step S2 specifically includes the following steps:

[0017] Select the current voltage value U of the grid connection point s (t), the grid-connected point voltage deviation value ΔU(t) is used as the state space variable; the calculation formula of ΔU(t) is ΔU(t)=U ref -U s (t), U ref is the voltage target value of the grid connection point;

[0018] Select the grid-side power P g (t), q-axis current I g (t) as a state space variable;

[0019] Construct the reactive power and voltage control state space S of the target wind power system at time t t for Among them t is the observed value at time t, o t =[U s (t),ΔU(t),P g (t),I g (t)],a t-1 is the reactive current control coefficient at time t-1, N o is the number of consecutive observations in the state space, N a The number of control strategy records in the state space, N o and N a All are positive integers;

[0020] At sampling time tk , the corresponding reactive power and voltage control state space of the target wind power system is for is the sampling time t k The observed quantity, U s (t k ) is the sampling time t k The grid connection point voltage value, ΔU(t k ) is the sampling time t k The grid connection point voltage deviation value, P g (t k ) is the sampling time t k The grid-side power, I g (t k ) is the sampling time t k The q-axis current.

[0021] The step S3, based on the reactive voltage control state space established in step S2, calculates the reactive current control coefficient of the target wind power system according to the current operating state of the target wind power system, including the following steps:

[0022] According to the current grid connection point voltage value of the target wind power system, determining the operation state of the target wind power system as a low voltage ride-through state, a recovery state or a high voltage ride-through state;

[0023] In the low voltage ride-through state, the reactive current control coefficient of the target wind power system is calculated according to the change value of the grid connection point voltage or the grid connection point voltage value;

[0024] In the recovery state, the reactive current control coefficient of the target wind power system is calculated according to the voltage deviation value of the grid connection point;

[0025] In the high voltage ride-through state, the reactive current control coefficient of the target wind power system is calculated based on the voltage value of the grid connection point.

[0026] The step S3 specifically includes the following steps:

[0027] Set the current time as sampling time t k ;

[0028] According to the current grid connection point voltage value U of the target wind power system s (t k ), determine the operating status of the target wind power system:

[0029] If U lmin ≤U s (t k )<0.9pu, the target wind power system is determined to be in a low voltage ride-through state;

[0030] If 0.9pu≤U s (t k )<1.1pu, it is determined that the operating state of the target wind power system is a recovery state;

[0031] If 1.1pu≤U s (t k )<U lmax , then the target wind power system is determined to be in the high voltage ride-through state; pu represents the per unit value; U lmin The minimum voltage for the wind power system to operate without disconnecting from the grid; U lmax The highest voltage for wind power system to operate without disconnecting from the grid;

[0032] In the low voltage ride-through state and the grid connection point voltage change rate C tk When it is less than the set threshold, according to the change value of the grid connection point voltage U s (t k )-U s (t k -1), and calculate the reactive current control coefficient of the target wind power system for Where K max is the maximum coefficient of reactive current control of wind power system;

[0033] In the low voltage ride-through state and the grid connection point voltage change rate C tk When it is greater than or equal to the set threshold, according to the grid voltage value U s (t k ), and calculate the reactive current control coefficient of the target wind power system for T k is the sampling period;

[0034] In the recovery state, according to the grid voltage deviation value ΔU(t k ), and calculate the reactive current control coefficient of the target wind power system for K min is the minimum coefficient of reactive current control of wind power system;

[0035] In the high voltage ride-through state, according to the grid voltage value U s (t k ), and calculate the reactive current control coefficient of the target wind power system for

[0036] The step S4 described in which the reactive current control coefficient obtained in step S3 is used to complete the reactive current adaptive control of the target wind power system includes the following steps:

[0037] According to the reactive current control coefficient obtained in step S3, the maximum reactive current output value and reactive current control value of the grid-side converter are calculated;

[0038] According to the maximum reactive current output value and reactive current control value of the grid-side converter, the dynamic reactive current reference value of the wind power system is calculated;

[0039] The reactive current of the target wind power system is adaptively controlled according to the obtained dynamic reactive current reference value of the wind power system, and the reactive current of the target wind power system at the next sampling moment is adaptively controlled according to the grid connection point voltage deviation value at the next sampling moment.

[0040] The step S4 specifically comprises the following steps:

[0041] Set the current time as sampling time t k ;

[0042] According to the reactive current control coefficient obtained in step S3, the maximum reactive current output value I of the grid-side converter is calculated using the following formula: gqmax (t k ) and reactive current control value I gqr (t k ):

[0043]

[0044] Where I g-max is the maximum current on the grid side; I N is the rated current of the grid-side converter; I o is the initial current of the grid-side converter;

[0045] According to the maximum reactive current output value I gqmax (t k ) and reactive current control value I gqr (t k ), and calculate the dynamic reactive current reference value I of the wind power system gqref (t k ):

[0046]

[0047] According to the obtained wind power system dynamic reactive current reference value I gqref (t k ) adaptively controlling the reactive current of the target wind power system;

[0048] At the next sampling time t k+1 , obtain the grid connection point voltage deviation value ΔU(t k+1 ), and make a judgment:

[0049] If ΔU(t k+1 )≤δ1, the adaptive control of reactive current of the target wind power system is terminated; δ1 is the set threshold;

[0050] If ΔU(t k+1 )>δ1, the reactive current adaptive control of the wind power system is performed according to steps S2 to S4.

[0051] The present invention also provides a system for implementing the reactive current adaptive control method of the wind power system, comprising a data acquisition module, a space establishment module, a coefficient calculation module and an adaptive control module; the data acquisition module, the space establishment module, the coefficient calculation module and the adaptive control module are connected in series in sequence; the data acquisition module is used to acquire the working data information of the target wind power system, and upload the data information to the space establishment module; the space establishment module is used to establish the reactive voltage control state space of the target wind power system according to the received data information, and upload the data information to the coefficient calculation module; the coefficient calculation module is used to calculate the reactive current control coefficient of the target wind power system according to the received data information, based on the established reactive voltage control state space and the current operating state of the target wind power system, and upload the data information to the adaptive control module; the adaptive control module is used to complete the reactive current adaptive control of the target wind power system according to the received data information and the obtained reactive current control coefficient.

[0052] The reactive current adaptive control method and system of the wind power system provided by the present invention not only realizes the reactive current adaptive control of the wind power system but also has higher reliability and better accuracy by establishing the reactive voltage control state space of the target wind power system and calculating the reactive current control coefficient of the corresponding fine interval. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The figure is a schematic diagram of the method flow of the present invention.

[0054] Figure 2 Schematic diagram of the functional modules of the system of the present invention. DETAILED DESCRIPTION

[0055] like Figure 1 The method flow chart of the method of the present invention is shown as follows: The reactive current adaptive control method of the wind power system disclosed in the present invention comprises the following steps:

[0056] S1. Obtaining the working data information of the target wind power system;

[0057] S2. Establishing the reactive voltage control state space of the target wind power system according to the data information obtained in step S1; comprising the following steps:

[0058] With the goal of the fastest voltage tracking and recovery, the voltage variable at the grid connection point is selected as the state space variable;

[0059] The control scheme of the wind power system is the grid-side converter priority control scheme, and the power data and current data of the grid side are selected as state space variables;

[0060] Finally, the reactive power and voltage control state space of the target wind power system is constructed;

[0061] When it is implemented, the following steps are adopted:

[0062] Select the current voltage value U of the grid connection point s (t), the grid-connected point voltage deviation value ΔU(t) is used as the state space variable; the calculation formula of ΔU(t) is ΔU(t)=U ref -U s (t), U ref is the voltage target value of the grid connection point;

[0063] Select the grid-side power P g (t), q-axis current I g (t) as a state space variable;

[0064] Construct the reactive power and voltage control state space S of the target wind power system at time t t for Among them t is the observed value at time t, o t =[U s (t),ΔU(t),P g (t),I g (t)],a t-1 is the reactive current control coefficient at time t-1, N o is the number of consecutive observations in the state space, N a The number of control strategy records in the state space, N o and N a are all positive integers; N o and N a are all positive integers; N o The preferred value of is 2, N a The preferred value of is 1;

[0065] At sampling time t k , the corresponding reactive power and voltage control state space of the target wind power system is for is the sampling time t k The observed quantity, U s (t k ) is the sampling time t kThe grid connection point voltage value, ΔU(t k ) is the sampling time t k The grid connection point voltage deviation value, P g (t k ) is the sampling time t k The grid-side power, I g (t k ) is the sampling time t k The q-axis current;

[0066] S3. Based on the reactive voltage control state space established in step S2, according to the current operating state of the target wind power system, calculate the reactive current control coefficient of the target wind power system; comprising the following steps:

[0067] According to the current grid connection point voltage value of the target wind power system, determining the operation state of the target wind power system as a low voltage ride-through state, a recovery state or a high voltage ride-through state;

[0068] In the low voltage ride-through state, the reactive current control coefficient of the target wind power system is calculated according to the change value of the grid connection point voltage or the grid connection point voltage value;

[0069] In the recovery state, the reactive current control coefficient of the target wind power system is calculated according to the voltage deviation value of the grid connection point;

[0070] In the high voltage ride-through state, the reactive current control coefficient of the target wind power system is calculated according to the grid connection point voltage value;

[0071] When it is implemented, the following steps are adopted:

[0072] Set the current time as sampling time t k ;

[0073] According to the current grid connection point voltage value U of the target wind power system s (t k ), determine the operating status of the target wind power system:

[0074] If U lmin ≤U s (t k )<0.9pu, the target wind power system is determined to be in a low voltage ride-through state;

[0075] If 0.9pu≤U s (t k )<1.1pu, it is determined that the operating state of the target wind power system is a recovery state;

[0076] If 1.1pu≤U s (t k )<U lmax, then the target wind power system is determined to be in the high voltage ride-through state; pu represents the per unit value; U lmin The minimum voltage for the wind power system to operate without disconnecting from the grid; U lmax The highest voltage for wind power system to operate without disconnecting from the grid;

[0077] In the low voltage ride-through state and the grid connection point voltage change rate C tk When it is less than the set threshold, according to the change value of the grid connection point voltage U s (t k )-U s (t k -1), and calculate the reactive current control coefficient of the target wind power system for Where K max is the maximum coefficient of reactive current control of wind power system;

[0078] In the low voltage ride-through state and the grid connection point voltage change rate C tk When it is greater than or equal to the set threshold, according to the grid voltage value U s (t k ), and calculate the reactive current control coefficient of the target wind power system for T k is the sampling period;

[0079] In the recovery state, according to the grid voltage deviation value ΔU(t k ), and calculate the reactive current control coefficient of the target wind power system for K min is the minimum coefficient of reactive current control of wind power system;

[0080] In the high voltage ride-through state, according to the grid voltage value U s (t k ), and calculate the reactive current control coefficient of the target wind power system for

[0081] S4. According to the reactive current control coefficient obtained in step S3, the reactive current adaptive control of the target wind power system is completed; comprising the following steps:

[0082] According to the reactive current control coefficient obtained in step S3, the maximum reactive current output value and reactive current control value of the grid-side converter are calculated;

[0083] According to the maximum reactive current output value and reactive current control value of the grid-side converter, the dynamic reactive current reference value of the wind power system is calculated;

[0084] Adaptively control the reactive current of the target wind power system according to the obtained dynamic reactive current reference value of the wind power system, and adaptively control the reactive current of the target wind power system at the next sampling moment according to the grid connection point voltage deviation value at the next sampling moment;

[0085] When it is implemented, the following steps are adopted:

[0086] Set the current time as sampling time t k ;

[0087] According to the reactive current control coefficient obtained in step S3, the maximum reactive current output value I of the grid-side converter is calculated using the following formula: gqmax (t k ) and reactive current control value I gqr (t k ):

[0088]

[0089] Where I g-max is the maximum current on the grid side; I N is the rated current of the grid-side converter; I o is the initial current of the grid-side converter;

[0090] According to the maximum reactive current output value I gqmax (t k ) and reactive current control value I gqr (t k ), and calculate the dynamic reactive current reference value I of the wind power system gqref (t k ):

[0091]

[0092] According to the obtained wind power system dynamic reactive current reference value I gqref (t k ) adaptively controlling the reactive current of the target wind power system;

[0093] At the next sampling time t k+1 , obtain the grid connection point voltage deviation value ΔU(t k+1 ), and make a judgment:

[0094] If ΔU(t k+1 )≤δ1, the adaptive control of reactive current of the target wind power system is terminated; δ1 is the set threshold;

[0095] If ΔU(t k+1 )>δ1, the reactive current adaptive control of the wind power system is performed according to steps S2 to S4.

[0096] like Figure 2 The figure shows a schematic diagram of the functional modules of the system of the present invention: the system disclosed in the present invention for realizing the reactive current adaptive control method of the wind power system comprises a data acquisition module, a space establishment module, a coefficient calculation module and an adaptive control module; the data acquisition module, the space establishment module, the coefficient calculation module and the adaptive control module are connected in series in sequence; the data acquisition module is used to acquire the working data information of the target wind power system, and upload the data information to the space establishment module; the space establishment module is used to establish the reactive voltage control state space of the target wind power system according to the received data information, and upload the data information to the coefficient calculation module; the coefficient calculation module is used to calculate the reactive current control coefficient of the target wind power system according to the received data information, based on the established reactive voltage control state space and the current operating state of the target wind power system, and upload the data information to the adaptive control module; the adaptive control module is used to complete the reactive current adaptive control of the target wind power system according to the received data information and the obtained reactive current control coefficient.

[0097] The scheme of the present invention combines the grid-connected point voltage and voltage change rate of the wind power system, and designs the reactive current control coefficient of the wind power system in the entire voltage range to adapt to the changing reactive power demand in each stage of voltage recovery: in the low voltage crossing stage, the reactive current control coefficient is appropriately increased to enhance the reactive voltage support capability of the power grid and improve the system voltage recovery speed; when the grid-connected point voltage is close to recovering to 0.9 per unit, the reactive current coefficient should be appropriately reduced to reduce the risk of voltage overshoot caused by excess reactive power; when the grid-connected point voltage is within the per unit range of 0.9 to 1.1, that is, in the voltage recovery period, the reactive current control strategy of the wind power system is designed to support the voltage to continue to recover to the initial level. The scheme of the present invention can make up for the defect of the existing wind power system that only considers the grid-connected point voltage below 0.9pu or above 1.1pu for dynamic reactive support, and has higher reliability and better accuracy.

Claims

1. A reactive current adaptive control method for a wind power system, comprising the following steps: S1. Obtaining the working data information of the target wind power system; S2. Establishing reactive voltage control state space of target wind power system according to data information acquired in step S1; S3. Based on the reactive voltage control state space established in step S2, the reactive current control coefficient of the target wind power system is calculated according to the current operating state of the target wind power system; S4. According to the reactive current control coefficient obtained in step S3, the reactive current adaptive control of the target wind power system is completed.

2. The method for adaptive reactive current control of a wind power system according to claim 1, characterized in that The step S2 of establishing the reactive voltage control state space of the target wind power system according to the data information obtained in the step S1 includes the following steps: With the goal of the fastest voltage tracking and recovery, the voltage variable at the grid connection point is selected as the state space variable; The control scheme of the wind power system is the grid-side converter priority control scheme, and the power data and current data of the grid side are selected as state space variables; Finally, the reactive power and voltage control state space of the target wind power system is constructed.

3. The method for adaptive reactive current control of a wind power system according to claim 2, characterized in that The step S2 specifically includes the following steps: Select the current voltage value U of the grid connection point s (t), grid connection point voltage deviation ΔU(t) as state space variables; The calculation formula of ΔU(t) is ΔU(t)=U ref -U s (t), U ref is the voltage target value of the grid connection point; Select the grid-side power P g (t), q-axis current I g (t) as a state space variable; Construct the reactive power and voltage control state space S of the target wind power system at time t t for Among them t is the observed value at time t, o t =[U s (t),ΔU(t),P g (t),I g (t)],a t-1 is the reactive current control coefficient at time t-1, N o is the number of consecutive observations in the state space, N a The number of control strategy records in the state space, N o and N a are all positive integers; N o and N a All are positive integers; At sampling time t k , the corresponding reactive power and voltage control state space of the target wind power system is for is the sampling time t k The observed quantity, U s (t k ) is the sampling time t k The grid connection point voltage value, ΔU(t k ) is the sampling time t k The grid connection point voltage deviation value, P g (t k ) is the sampling time t k The grid-side power, I g (t k ) is the sampling time t k The q-axis current.

4. The method for adaptive reactive current control of a wind power system according to claim 3, characterized in that The step S3, based on the reactive voltage control state space established in step S2, calculates the reactive current control coefficient of the target wind power system according to the current operating state of the target wind power system, including the following steps: According to the current grid connection point voltage value of the target wind power system, determining the operation state of the target wind power system as a low voltage ride-through state, a recovery state or a high voltage ride-through state; In the low voltage ride-through state, the reactive current control coefficient of the target wind power system is calculated according to the change value of the grid connection point voltage or the grid connection point voltage value; In the recovery state, the reactive current control coefficient of the target wind power system is calculated according to the voltage deviation value of the grid connection point; In the high voltage ride-through state, the reactive current control coefficient of the target wind power system is calculated based on the voltage value of the grid connection point.

5. The method for adaptive reactive current control of a wind power system according to claim 4, characterized in that The step S3 specifically includes the following steps: Set the current time as sampling time t k ; According to the current grid connection point voltage value U of the target wind power system s (t k ), determine the operating status of the target wind power system: If U lmin ≤U s (t k )<0.9pu, the target wind power system is determined to be in a low voltage ride-through state; If 0.9pu≤U s (t k )<1.1pu, it is determined that the operating state of the target wind power system is a recovery state; If 1.1pu≤U s (t k )<U lmax , then the operating state of the target wind power system is determined to be a high voltage ride-through state; pu means per unit value; U lmin The minimum voltage for the wind power system to operate without disconnecting from the grid; U lmax The highest voltage for wind power system to operate without disconnecting from the grid; In the low voltage ride-through state and the grid connection point voltage change rate C tk When it is less than the set threshold, according to the change value of the grid connection point voltage U s (t k )-U s (t k -1), and calculate the reactive current control coefficient of the target wind power system for Where K max is the maximum coefficient of reactive current control of wind power system; In the low voltage ride-through state and the grid connection point voltage change rate C tk When it is greater than or equal to the set threshold, according to the grid voltage value U s (t k ), and calculate the reactive current control coefficient of the target wind power system for T k is the sampling period; In the recovery state, according to the grid voltage deviation value ΔU(t k ), and calculate the reactive current control coefficient of the target wind power system for K min is the minimum coefficient of reactive current control of wind power system; In the high voltage ride-through state, according to the grid voltage value U s (t k ), and calculate the reactive current control coefficient of the target wind power system for 6. The method for adaptive reactive current control of a wind power system according to claim 5, characterized in that The step S4 described in which the reactive current control coefficient obtained in step S3 is used to complete the reactive current adaptive control of the target wind power system includes the following steps: According to the reactive current control coefficient obtained in step S3, the maximum reactive current output value and reactive current control value of the grid-side converter are calculated; According to the maximum reactive current output value and reactive current control value of the grid-side converter, the dynamic reactive current reference value of the wind power system is calculated; The reactive current of the target wind power system is adaptively controlled according to the obtained dynamic reactive current reference value of the wind power system, and the reactive current of the target wind power system at the next sampling moment is adaptively controlled according to the grid connection point voltage deviation value at the next sampling moment.

7. The method for adaptive reactive current control of a wind power system according to claim 6, characterized in that The step S4 specifically comprises the following steps: Set the current time as sampling time t k ; According to the reactive current control coefficient obtained in step S3, the maximum reactive current output value I of the grid-side converter is calculated using the following formula: gqmax (t k ) and reactive current control value I gqr (t k ): Where I g-max is the maximum current on the grid side; I N is the rated current of the grid-side converter; I o is the initial current of the grid-side converter; According to the maximum reactive current output value I gqmax (t k ) and reactive current control value I gqr (t k ), and calculate the dynamic reactive current reference value I of the wind power system gqref (t k ): According to the obtained wind power system dynamic reactive current reference value I gqref (t k ) adaptively controlling the reactive current of the target wind power system; At the next sampling time t k+1 , obtain the grid connection point voltage deviation value ΔU(t k+1 ), and make a judgment: If ΔU(t k+1 )≤δ1, the adaptive control of reactive current of the target wind power system is terminated; δ1 is the set threshold; If ΔU(t k+1 )>δ1, the reactive current adaptive control of the wind power system is performed according to steps S2 to S4.

8. A system for implementing the reactive current adaptive control method of a wind power system according to any one of claims 1 to 7, characterized in that It includes a data acquisition module, a space establishment module, a coefficient calculation module and an adaptive control module; the data acquisition module, the space establishment module, the coefficient calculation module and the adaptive control module are connected in series in sequence; the data acquisition module is used to acquire the working data information of the target wind power system, and upload the data information to the space establishment module; the space establishment module is used to establish the reactive voltage control state space of the target wind power system according to the received data information, and upload the data information to the coefficient calculation module; The coefficient calculation module is used to calculate the reactive current control coefficient of the target wind power system according to the received data information, based on the established reactive voltage control state space and the current operating state of the target wind power system, and upload the data information to the adaptive control module; The adaptive control module is used to complete the reactive current adaptive control of the target wind power system according to the received data information and the obtained reactive current control coefficient.

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