A wind turbine generator power control method and system for inhibiting ultra-high voltage direct current blocking

Abstract

This invention relates to a power control method and system for wind turbines to suppress UHVDC (Ultra-High Voltage Direct Current) blocking, comprising: Step 1. Determining whether a short circuit has occurred in the power grid based on the per-unit value of the positive sequence component of the grid voltage; Step 2. If a short circuit has occurred in the grid, switching the control mode of the converter corresponding to the wind turbine in the grid to current control mode until the grid returns to normal and proceeding to Step 3; otherwise, returning to Step 1; Step 3. Switching the control mode of the converter corresponding to the wind turbine in the grid to power control mode and returning to Step 1. The technical solution of this invention is simple and easy to implement in engineering, reducing the risk of high-voltage grid disconnection of near-field wind turbines due to DC transmission system faults, improving the wind power transmission capacity of the UHVDC system, and promoting cross-regional wind power consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system operation control, in particular to a wind turbine power control method and system for inhibiting UHVDC blocking. BACKGROUND

[0002] Due to the complex voltage regulation characteristics of wind turbine and dynamic reactive power compensation system of wind power base, the control target is scattered and lacks of coordinated control, the overall wind power base in the actual power grid presents the opposite voltage regulation characteristics to the conventional power source, and the power grid adaptability is not strong. When the DC commutation failure, blocking and other faults cause overvoltage in the DC sending end power grid, it may lead to large-scale cascading trip of wind turbines in the DC near area.

[0003] At present, the wind turbine adopts reactive power priority control strategy after entering low voltage ride through control, that is, during the fault, the wind farm provides dynamic reactive power support according to the requirements of the standard GB / T 19963-2011 Technical Regulation for Wind Farm Integration into Power System on the low voltage ride through capability of wind farm, and after the reactive current meets the standard requirements, the other capacity is used to output active power. Simulation analysis and actual operation experience show that under the existing fault ride through control strategy of wind turbine, the larger the wind power output of the DC weak sending end is, the more serious the near area transient overvoltage problem under AC / DC fault is, and the more serious the DC transmission capacity limitation is, which seriously restricts the ability of UHVDC cross-regional consumption of new energy, and directly affects the overall situation of energy transformation and development in China. SUMMARY

[0004] In view of the defects of the prior art, the purpose of the present application is to provide a wind turbine power control method and system for inhibiting UHVDC blocking, which optimizes the control target value of active current and reactive current of wind turbine during fault, reduces the influence of wind farm operation on overvoltage of AC system caused by DC system blocking, thereby reducing the high voltage trip risk of wind turbine in the near area of UHVDC caused by DC transmission system fault, improving the wind power sending capacity of UHVDC system, and promoting the cross-regional consumption of wind power.

[0005] The purpose of the present application is achieved by adopting the following technical solutions:

[0006] The present application provides a wind turbine power control method for inhibiting UHVDC blocking, which is improved in that the method comprises:

[0007] Step 1. Determine whether the power grid has a power grid short circuit according to the positive sequence component per unit value of the power grid voltage;

[0008] Step 2. If the power grid has a short circuit, switch the control mode of the converter corresponding to the wind turbine in the power grid to current control mode until the power grid returns to normal and go to step 3, otherwise, return to step 1;

[0009] Step 3. Switch the control mode of the converter corresponding to the wind turbine in the power grid to the power control mode, and return to Step 1.

[0010] Preferably, the determination of whether the power grid has a short circuit according to the positive-sequence component per-unit value of the grid voltage comprises:

[0011] If the positive-sequence component per-unit value of the grid voltage is lower than a threshold value at which the wind turbine converter enters the low-voltage ride-through control, the power grid has a short circuit.

[0012] If the positive-sequence component per-unit value of the grid voltage is higher than a threshold value at which the wind turbine converter exits the low-voltage ride-through control, the power grid is in normal operation.

[0013] Further, the threshold value at which the wind turbine converter enters the low-voltage ride-through control is 0.85 p.u.

[0014] The threshold value at which the wind turbine converter exits the low-voltage ride-through control is 0.9 p.u.

[0015] Preferably, when the control mode of the converter corresponding to the wind turbine in the power grid is the current control mode, the target value i q_ref of the reactive current control of the wind turbine is determined according to the following formula:

[0016] i q_ref = i q0

[0017] In the above formula, i q0 is the reactive current emitted by the wind turbine in normal operation.

[0018] The target value i p_ref of the active current control of the wind turbine is determined according to the following formula:

[0019] i p_ref = U T × i p0

[0020] In the above formula, U T is the positive-sequence component per-unit value of the bus voltage at the terminal of the wind turbine; and i p0 is the active current emitted by the wind turbine in normal operation.

[0021] Preferably, when the control mode of the converter corresponding to the wind turbine in the power grid is the power control mode, the target value i q_ref of the reactive current control of the wind turbine is determined according to the following formula:

[0022] i q_ref = i q0

[0023] In the above formula, i q0The active power control target value P of the wind turbine is determined by the following formula

[0024] The active power control target value P of the wind turbine is determined by the following formula p_ref :

[0025] P p_ref =P p0

[0026] In the above formula, P p0 is the active power emitted by the wind turbine in normal operation.

[0027] The wind turbine power control system for inhibiting UHVDC blocking provided by the application has the improvement that the system comprises:

[0028] A judging module is configured to determine whether the power grid has a short circuit according to the positive sequence component per unit value of the grid voltage.

[0029] A first switching module is configured to switch the control mode of the converter corresponding to the wind turbine in the power grid to a current control mode if the power grid has a short circuit, until the power grid returns to normal and the second switching module is entered, otherwise, the judging module is returned.

[0030] A second switching module is configured to switch the control mode of the converter corresponding to the wind turbine in the power grid to a power control mode, and the judging module is returned.

[0031] Preferably, the judging module comprises:

[0032] A first judging unit is configured to determine that the power grid has a short circuit if the positive sequence component per unit value of the grid voltage is lower than the threshold value at which the wind turbine converter enters low voltage ride through control.

[0033] A second judging unit is configured to determine that the power grid is in normal operation if the positive sequence component per unit value of the grid voltage is greater than the threshold value at which the wind turbine converter exits low voltage ride through control.

[0034] Further, the threshold value at which the wind turbine converter enters low voltage ride through control is 0.85 p.u.

[0035] The threshold value at which the wind turbine converter exits low voltage ride through control is 0.9 p.u.

[0036] Preferably, when the control mode of the converter corresponding to the wind turbine in the power grid is a current control mode, the reactive power control target value i q_ref of the wind turbine is determined by the following formula

[0037] i q_ref =i q0

[0038] In the above formula, i q0a reactive current generated by the wind turbine when the wind turbine is in normal operation;

[0039] The active current control target value i of the wind turbine is determined according to the following formula: p_ref

[0040] i p_ref = U T × i p0

[0041] In the above formula, U T is the positive sequence component unit value of the bus voltage at the terminal of the wind turbine; and i p0 is the active current generated by the wind turbine when the wind turbine is in normal operation.

[0042] Preferably, when the control mode of the converter corresponding to the wind turbine in the power grid is a power control mode, the reactive current control target value i of the wind turbine is determined according to the following formula: q_ref

[0043] i q_ref = i q0

[0044] In the above formula, i q0 is the reactive current generated by the wind turbine when the wind turbine is in normal operation.

[0045] The active power control target value P of the wind turbine is determined according to the following formula: p_ref

[0046] P p_ref = P p0

[0047] In the above formula, P p0 is the active power generated by the wind turbine when the wind turbine is in normal operation.

[0048] Compared with the closest prior art, the present application has the beneficial effects that:

[0049] The wind turbine power control method and system for inhibiting UHVDC blocking provided by the present application comprises the following steps: 1. determining whether a power grid short circuit occurs according to the positive sequence component unit value of the grid voltage; 2. if the power grid short circuit occurs, switching the control mode of the converter corresponding to the wind turbine in the power grid to a current control mode until the power grid returns to normal and the step 3 is reached, otherwise, returning to the step 1; and 3. switching the control mode of the converter corresponding to the wind turbine in the power grid to a power control mode and returning to the step 1. The technical solution of the present application controls the output ratio of the active power and the reactive power of the wind turbine during a fault, reduces the influence of the wind farm operation on the overvoltage of the alternating current system caused by the blocking of the direct current system, thereby reducing the high voltage off-grid risk of the wind turbine in the vicinity of the UHVDC caused by the fault of the direct current transmission system, improving the wind power sending capacity of the UHVDC system, and promoting the cross-regional consumption of wind power.​​​BRIEF DESCRIPTION OF DRAWINGS BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 is a flow chart of a wind turbine power control method for inhibiting UHVDC blocking provided by the present application;

[0051] Figure 2 is a structural diagram of a wind turbine power control system for inhibiting UHVDC blocking provided by the present application. DETAILED DESCRIPTION

[0052] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings.

[0053] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of the present application.

[0054] The present application provides a wind turbine power control method for inhibiting UHVDC blocking, as shown in Figure 1 The method comprises the following steps:

[0055] Step 1. Determine whether the power grid has a short circuit according to the positive sequence component per unit value of the grid voltage.

[0056] Step 2. If the power grid has a short circuit, switch the control mode of the converter corresponding to the wind turbine in the power grid to a current control mode until the power grid returns to normal and go to Step 3, otherwise, return to Step 1.

[0057] Step 3. Switch the control mode of the converter corresponding to the wind turbine in the power grid to a power control mode and return to Step 1.

[0058] Specifically, the determination of whether the power grid has a short circuit according to the positive sequence component per unit value of the grid voltage comprises:

[0059] If the positive sequence component per unit value of the grid voltage is lower than the threshold value at which the wind turbine converter enters low voltage ride through control, the power grid has a short circuit.

[0060] If the positive sequence component per unit value of the grid voltage is higher than the threshold value at which the wind turbine converter exits low voltage ride through control, the power grid is in normal operation.

[0061] Further, the threshold value at which the wind turbine converter enters low voltage ride through control is 0.85 p.u.

[0062] The threshold value for the wind turbine converter to exit the low voltage ride through control is 0.9 p.u.

[0063] Specifically, when the control mode of the converter corresponding to the wind turbine in the power grid is a current control mode, the wind turbine reactive current control target value i q_ref :

[0064] i q_ref =i q0

[0065] In the above formula, i q0 is the reactive current emitted by the wind turbine when it is in normal operation;

[0066] The wind turbine active current control target value i p_ref is determined by the following formula:

[0067] i p_ref =U T ×i p0

[0068] In the above formula, U T is the positive sequence component of the wind turbine terminal bus voltage in per unit; i p0 is the active current emitted by the wind turbine when it is in normal operation.

[0069] Specifically, when the control mode of the converter corresponding to the wind turbine in the power grid is a power control mode, the wind turbine reactive current control target value i q_ref is determined by the following formula:

[0070] i q_ref =i q0

[0071] In the above formula, i q0 is the reactive current emitted by the wind turbine when it is in normal operation;

[0072] The wind turbine active power control target value P p_ref is determined by the following formula:

[0073] P p_ref =P p0

[0074] In the above formula, P p0 is the active power emitted by the wind turbine when it is in normal operation.

[0075] In the optimal embodiment of the present application, the active control target is to restore the active power when it is in normal operation, and the wind turbine is required to restore at least 90% of the active power when it is in normal operation within 60 ms.

[0076] The present application also provides a wind turbine power control system for inhibiting UHV DC blocking, which comprises a wind turbine and a power control system.Figure 2 The system comprises:

[0077] a judging module, configured to judge whether a short circuit of a power grid occurs according to a positive sequence component per unit value of a grid voltage;

[0078] a first switching module, configured to switch a control mode of a converter corresponding to a wind turbine generator in the power grid to a current control mode if the short circuit of the power grid occurs, until the power grid returns to normal and the second switching module is entered, otherwise, the judging module is returned;

[0079] a second switching module, configured to switch the control mode of the converter corresponding to the wind turbine generator in the power grid to a power control mode, and return to the judging module.

[0080] Specifically, the judging module comprises:

[0081] a first judging unit, configured to judge that the short circuit of the power grid occurs if the positive sequence component per unit value of the grid voltage is lower than a threshold value at which the converter of the wind turbine generator enters a low voltage ride through control;

[0082] a second judging unit, configured to judge that the power grid is in normal operation if the positive sequence component per unit value of the grid voltage is greater than a threshold value at which the converter of the wind turbine generator exits the low voltage ride through control.

[0083] Further, the threshold value at which the converter of the wind turbine generator enters the low voltage ride through control is 0.85 p.u.

[0084] The threshold value at which the converter of the wind turbine generator exits the low voltage ride through control is 0.9 p.u.

[0085] Specifically, when the control mode of the converter corresponding to the wind turbine generator in the power grid is the current control mode, a reactive current control target value i q_ref of the wind turbine generator is determined according to the following formula:

[0086] i q_ref = i q0

[0087] In the above formula, i q0 is a reactive current emitted by the wind turbine generator in normal operation;

[0088] an active current control target value i p_ref of the wind turbine generator is determined according to the following formula:

[0089] i p_ref = U T × i p0

[0090] In the above formula, U T is a positive sequence component per unit value of a terminal bus voltage of the wind turbine generator; and i p0 is an active current emitted by the wind turbine generator in normal operation.

[0091] Specifically, when the control mode of the converter corresponding to the wind turbine in the power grid is the power control mode, the reactive current control target value i of the wind turbine is determined according to the following formula: q_ref

[0092] i q_ref =i q0

[0093] In the above formula, i q0 is the reactive current generated by the wind turbine in normal operation;

[0094] The active power control target value P of the wind turbine is determined according to the following formula: p_ref

[0095] P p_ref =P p0

[0096] In the above formula, P p0 is the active power generated by the wind turbine in normal operation.

[0097] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) containing computer-usable program code.

[0098] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a system for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks Figure 1 The system that implements the functions specified in a flow or multiple flows and / or blocks.

[0099] These computer program instructions can also be stored in a computer-readable memory that can direct the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction system that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in a flow or multiple flows and / or blocks​​Figure 1 the function specified in the one or more blocks.

[0100] These computer program instructions can also be loaded into computer or other programmable data processing devices, so that a series of operation steps are performed on the computer or other programmable data processing devices to generate computer-implemented processes, thus the instructions executed on the computer or other programmable data processing devices provide a process for implementing the flow Figure 1 the flow or flows and / or blocks Figure 1 the steps of the function specified in the one or more blocks.

[0101] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it, although the above embodiments of the present application have been described in detail, those skilled in the art should understand: the specific embodiments of the present application can be modified or replaced by the same, without departing from the spirit and scope of the present application, any modification or equivalent replacement, which should be covered in the protection scope of the claims of the present application.

Claims

1. A power control method for wind turbines to suppress UHVDC blocking, characterized in that, The method includes: Step 1. Determine whether a short circuit has occurred in the power grid based on the per-unit value of the positive sequence component of the power grid voltage; Step 2. If a short circuit occurs in the power grid, switch the control mode of the converter corresponding to the wind turbine in the power grid to the current control mode until the power grid returns to normal and proceed to Step 3; otherwise, return to Step 1. Step 3. Switch the control mode of the converter corresponding to the wind turbine in the power grid to power control mode, and return to step 1; When the control mode of the converter corresponding to the wind turbine in the power grid is current control mode, the target value of reactive current control for the wind turbine is determined by the following formula: q_ref : i q_ref =i q0 In the above formula, i q0 This refers to the reactive current generated by the wind turbine during normal operation. The target value i for active current control of the wind turbine is determined by the following formula. p_ref : and p_ref =U T ×and p0 In the above formula, U T i represents the per-unit value of the positive sequence component of the wind turbine terminal bus voltage; p0 This refers to the active current generated by the wind turbine during normal operation. When the control mode of the converter corresponding to the wind turbine in the power grid is power control mode, the reactive current control target value i of the wind turbine is determined by the following formula. q_ref : i q_ref =i q0 In the above formula, i q0 This refers to the reactive current generated by the wind turbine during normal operation. The target value P for active power control of the wind turbine is determined by the following formula. p_ref : P p_ref =P p0 In the above formula, P p0 This refers to the active power generated by the wind turbine during normal operation.

2. The method as described in claim 1, characterized in that, The method of determining whether a short circuit has occurred in the power grid based on the per-unit value of the positive sequence component of the power grid voltage includes: If the per-unit value of the positive sequence component of the grid voltage is lower than the threshold for the wind turbine converter to enter low voltage ride-through control, a short circuit will occur in the grid. If the per-unit value of the positive sequence component of the grid voltage is greater than the threshold for the wind turbine converter to exit low voltage ride-through control, the grid will operate normally.

3. The method as described in claim 2, characterized in that, The threshold for the wind turbine converter to enter low voltage ride-through control is 0.85 pu; The threshold for the wind turbine converter to exit low voltage ride-through control is 0.9 pu.

4. A wind turbine power control system for suppressing UHVDC blocking, characterized in that, The system includes: The judgment module is used to determine whether a short circuit has occurred in the power grid based on the per-unit value of the positive sequence component of the power grid voltage. The first switching module is used to switch the control mode of the converter corresponding to the wind turbine in the power grid to the current control mode if a short circuit occurs in the power grid, until the power grid returns to normal and switches to the second switching module; otherwise, it returns to the judgment module. The second switching module is used to switch the control mode of the converter corresponding to the wind turbine in the power grid to the power control mode and return to the judgment module. When the control mode of the converter corresponding to the wind turbine in the power grid is current control mode, the target value of reactive current control for the wind turbine is determined by the following formula: q_ref : i q_ref =i q0 In the above formula, i q0 This refers to the reactive current generated by the wind turbine during normal operation. The target value i for active current control of the wind turbine is determined by the following formula. p_ref : and p_ref =U T ×and p0 In the above formula, U T i represents the per-unit value of the positive sequence component of the wind turbine terminal bus voltage; p0 This refers to the active current generated by the wind turbine during normal operation. When the control mode of the converter corresponding to the wind turbine in the power grid is power control mode, the reactive current control target value i of the wind turbine is determined by the following formula. q_ref : i q_ref =i q0 In the above formula, i q0 This refers to the reactive current generated by the wind turbine during normal operation. The target value P for active power control of the wind turbine is determined by the following formula. p_ref : P p_ref =P p0 In the above formula, P p0 This refers to the active power generated by the wind turbine during normal operation.

5. The system as described in claim 4, characterized in that, The judgment module includes: The first judgment unit is used to determine if a short circuit occurs in the power grid if the per-unit value of the positive sequence component of the grid voltage is lower than the threshold for the wind turbine converter to enter low voltage ride-through control. The second judgment unit is used to determine if the grid is operating normally if the per-unit value of the positive sequence component of the grid voltage is greater than the threshold for the wind turbine converter to exit low voltage ride-through control.

6. The system as described in claim 5, characterized in that, The threshold for the wind turbine converter to enter low voltage ride-through control is 0.85 pu; The threshold for the wind turbine converter to exit low voltage ride-through control is 0.9 pu.

Images