Reactive current adaptive control method and system for wind power system

Abstract

The present invention discloses a method for adaptive reactive current control of a wind power system, comprising obtaining operating 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 based on the current operating state of the target wind power system; and completing adaptive reactive current control of the target wind power system based on the reactive current control coefficient. The present invention also discloses a system for implementing the method for adaptive reactive current control of a wind power system. By establishing a reactive voltage control state space of the target wind power system and calculating the reactive current control coefficient in the corresponding fine interval, the present invention not only realizes adaptive reactive current control of the wind power system, but also achieves higher reliability and better accuracy.

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 daily life, bringing endless convenience to people's production and life. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system. Currently, wind power systems account for an increasing proportion of the power system, so ensuring the stable and reliable operation of wind power systems is of great significance to the power system.

[0003] Currently, large-scale wind power systems are typically transmitted and consumed over long distances via high-voltage direct current (HVDC). During DC transmission, changes in active power, such as commutation failures and single / double-pole blocking, can lead to significant fluctuations in reactive power imbalance, causing serious transient voltage issues. Fault ride-through capability is key to the safe grid connection of wind farms. In the event of a grid fault, wind turbines continue to operate without disconnecting from the grid and inject reactive current into the grid to support grid voltage recovery and mitigate 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 electric power systems.

[0004] Currently, during faults, most existing standards and solutions for wind power systems use a fixed current coefficient as the benchmark for reactive current output. However, this solution cannot fully utilize the dynamic regulation capabilities of the wind power system. 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 objectives of the present invention is to provide a method for adaptively controlling reactive current of a wind power system with high reliability, good accuracy and good effect.

[0006] A second object 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 operating data information of the target wind power system;

[0009] S2. Establishing the reactive voltage control state space of the target wind power system according to the data information obtained 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. Based on the reactive current control coefficient obtained in step S3, the reactive current adaptive control of the target wind power system is completed.

[0012] Step S2, in accordance with the data information acquired in step S1, establishes the reactive power and voltage control state space of the target wind power system, including the following steps:

[0013] With the goal of 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 target voltage 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 Number of control strategy records in the state space, N o and N a are all positive integers;

[0020] 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.

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

[0022] Determining, based on the current grid connection point voltage value of the target wind power system, whether the operating state of the target wind power system is 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 based on 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 based on 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 the low voltage ride-through state;

[0030] If 0.9pu≤Us (t k )<1.1pu, the operating state of the target wind power system is determined to be the recovery state;

[0031] If 1.1pu≤U s (t k )<U lmax , 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 lowest voltage for the wind power system to operate without disconnecting from the grid; U lmax The highest voltage at which the wind power system can operate without being disconnected from the grid;

[0032] In the low voltage ride-through state and the grid voltage change rate C tk When it is less than the set threshold, the voltage change value 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 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 ), 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 ), calculate the reactive current control coefficient of the target wind power system for K min is the minimum coefficient for 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 ), calculate the reactive current control coefficient of the target wind power system for

[0036] The reactive current adaptive control of the target wind power system is completed according to the reactive current control coefficient obtained in step S3 in step S4, and 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 includes 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 ), calculate the dynamic reactive current reference value I of the wind power system gqref (t k ):

[0046]

[0047] According to the obtained 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 voltage deviation value ΔU(t k+1 ), and make a judgment:

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

[0050] If ΔU(t k+1 )>δ1, then 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 according to 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 for a wind power system provided by the present invention not only realizes the reactive current adaptive control of the wind power system by establishing the reactive voltage control state space of the target wind power system and calculating the reactive current control coefficient in the corresponding fine interval, but also has higher reliability and better accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 Schematic diagram of the process 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 figure shows a flow chart of the method of the present invention: The method for adaptively controlling reactive current of a wind power system disclosed in the present invention comprises the following steps:

[0056] S1. Obtaining operating 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 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 taken:

[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 target voltage 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 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 k The grid connection point voltage value, ΔU(tk ) 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, 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; comprising the following steps:

[0067] Determining, based on the current grid connection point voltage value of the target wind power system, whether the operating state of the target wind power system is 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 based on 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 based on 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 based on the grid connection point voltage value;

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

[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 the low voltage ride-through state;

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

[0076] If 1.1pu≤U s (t k )<U lmax, 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 lowest voltage for the wind power system to operate without disconnecting from the grid; U lmax The highest voltage at which the wind power system can operate without being disconnected from the grid;

[0077] In the low voltage ride-through state and the grid voltage change rate C tk When it is less than the set threshold, the voltage change value 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 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 ), 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 ), calculate the reactive current control coefficient of the target wind power system for K min is the minimum coefficient for 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 ), 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 taken:

[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 ), calculate the dynamic reactive current reference value I of the wind power system gqref (t k ):

[0091]

[0092] According to the obtained 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 voltage deviation value ΔU(t k+1 ), and make a judgment:

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

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

[0096] like Figure 2 Shown is 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 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.

[0097] The present invention combines the grid-connected point voltage and voltage change rate of the wind power system to design a reactive current control coefficient for the entire voltage range of the wind power system to adapt to the changing reactive power requirements at each stage of voltage recovery: During the low voltage ride-through 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 approaches the 0.9 per unit value, 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 0.9 to 1.1 per unit value range, that is, during the voltage recovery period, the wind power system reactive current control strategy is designed to support the voltage to continuously recover to its initial level. The present invention can overcome the defect of existing wind power systems that only consider dynamic reactive power support when the grid-connected point voltage is below 0.9 pu or above 1.1 pu, and has higher reliability and better accuracy.

Claims

1. A method for adaptively controlling reactive current in a wind power system, comprising the following steps: S1. Obtaining operating data information of the target wind power system; S2. Establishing the reactive voltage control state space of the target wind power system according to the data information obtained in step S1; specifically comprising the following steps: Select the current voltage value U of the grid connection point s (t), grid connection point voltage deviation value ΔU(t) as state space variables; The calculation formula of ΔU(t) is ΔU(t)=U ref -U s (t), U ref is the target voltage 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 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; 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, o tk =[U s (t k ),ΔU(t k ),P g (t k ),I g (t k )],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; 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. Based on 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 S3 of calculating the reactive current control coefficient of the target wind power system based on the reactive voltage control state space established in step S2 and according to the current operating state of the target wind power system includes the following steps: Determining, based on the current grid connection point voltage value of the target wind power system, whether the operating state of the target wind power system is 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 based on 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 based on 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.

3. The method for adaptive reactive current control of a wind power system according to claim 2, 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 the low voltage ride-through state; If 0.9pu≤U s (t k )<1.1pu, the operating state of the target wind power system is determined to be the recovery state; If 1.1pu≤U s (t k )<U lmax , then the target wind power system is determined to be in a high voltage ride-through state; pu represents per unit value; U lmin The lowest voltage for the wind power system to operate without disconnecting from the grid; U lmax The highest voltage at which the wind power system can operate without being disconnected from the grid; In the low voltage ride-through state and the grid voltage change rate C tk When it is less than the set threshold, the voltage change value 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 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 ), 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 ), calculate the reactive current control coefficient of the target wind power system for K min is the minimum coefficient for reactive current control of wind power system; In the high voltage ride-through state, according to the grid voltage value U s (t k ), calculate the reactive current control coefficient of the target wind power system for 4. The method for adaptive reactive current control of a wind power system according to claim 3, characterized in that The reactive current adaptive control of the target wind power system is completed according to the reactive current control coefficient obtained in step S3 in step S4, and 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.

5. The method for adaptive reactive current control of a wind power system according to claim 4, characterized in that The step S4 specifically includes 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 ), 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 voltage deviation value ΔU(t k+1 ), and make a judgment: If ΔU(t k+1 )≤δ1, the adaptive control of the reactive current of the target wind power system is terminated; δ1 is the set threshold; If ΔU(t k+1 )>δ1, then the reactive current adaptive control of the wind power system is performed according to steps S2 to S4.

6. A system for implementing the method for adaptive reactive current control of a wind power system according to any one of claims 1 to 5, 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 obtain 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 based on 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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