Onshore doubly-fed wind turbine generator set, box-type transformer electrical protection device and method

Abstract

The present invention discloses an electrical protection device and method for an onshore doubly-fed wind turbine and a box-type transformer. The protection device includes a first current transformer, a second current transformer, an incomplete differential protection device, and a first circuit breaker. The first current transformer is installed on the low-voltage side line of the box-type transformer, and the second current transformer is installed on the stator current output line of the wind turbine generator set. The incomplete differential protection device is electrically connected to the first current transformer and the second current transformer, respectively, and takes the low-voltage side current of the box-type transformer and the stator current of the wind turbine generator set as input signals to control the first circuit breaker to achieve circuit breaker protection. The present invention significantly improves the sensitivity, reliability, selectivity, and speed of protection for equipment such as wind turbines, frequency converters, box-type transformers, and their connecting cables. At the same time, it is not affected by the low-voltage ride-through working conditions of the wind turbine generator set, effectively reducing the probability of electrical damage to the equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbines, and in particular to an onshore doubly-fed wind turbine, a box-type transformer electrical protection device and method. Background Art

[0002] China's wind power industry has experienced rapid growth in recent years. By the end of June 2020, China had a cumulative installed wind power capacity of 217 million kilowatts, firmly ranking first in the world. At the same time, as wind turbines have evolved toward longer blades and larger unit capacities, the cost of individual wind turbines has increased, and the resulting downtime losses have also increased. Failure statistics show that electrical failures in wind turbines, inverters, box-type transformers (hereinafter referred to as "box-type transformers"), and other electrical systems account for over half of all wind farm failures. Dozens of wind turbine burns and burns in the wind power industry in recent years have been caused by electrical failures. This demonstrates the high prevalence and serious consequences of electrical failures in wind turbines.

[0003] Currently, electrical faults in wind turbines are primarily isolated by circuit breakers at the base of the tower and on the low-voltage side of the transformer. However, these circuit breaker protection devices have poor maintainability and low reliability, often failing to operate during faults, leading to escalating accidents. Furthermore, wind turbines are located at the end of the grid, where fault currents are relatively small. Furthermore, due to the influence of low-voltage ride-through currents, existing protection settings at all levels are high and have low sensitivity.

[0004] As can be seen from the above, the existing wind turbine and box-type transformer electrical protection devices and methods still have inconveniences and defects, and are in urgent need of further improvement. How to create a new onshore doubly-fed wind turbine and box-type transformer electrical protection device and method is indeed one of the important research and development topics. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an onshore doubly-fed wind turbine and box-type transformer electrical protection device, so as to achieve more reliable and sensitive protection for wind turbines, frequency converters, box-type transformers and related cables, so as to avoid major electrical accidents of wind turbines and box-type transformers, thereby overcoming the shortcomings of existing wind turbine and box-type transformer electrical protection devices.

[0006] To solve the above technical problems, the present invention provides an onshore doubly-fed wind turbine and a box-type transformer electrical protection device, comprising a first current transformer, a second current transformer, an incomplete differential protection device, and a first circuit breaker. The first current transformer is installed on the low-voltage side line of the box-type transformer, and the second current transformer is installed on the stator current output line of the wind turbine generator set. The incomplete differential protection device is electrically connected to the first current transformer and the second current transformer, respectively, and takes the low-voltage side current I1 of the box-type transformer and the stator current I2 of the wind turbine generator set as input signals. The first circuit breaker is installed on the low-voltage side line of the box-type transformer and is electrically connected to the incomplete differential protection device, and receives an action signal to implement circuit-breaking protection.

[0007] As an improvement of the present invention, the incomplete differential protection device is electrically connected to a second circuit breaker, and the second circuit breaker is installed at the bottom of the wind turbine tower.

[0008] Furthermore, the stator winding of the wind turbine generator set is star-connected, and the second current transformer is installed on the neutral point side.

[0009] Furthermore, the stator winding of the wind turbine generator set is connected in a delta connection manner, and the second current transformer is installed near the generator outlet side.

[0010] Furthermore, the incomplete differential protection device is provided with a proportional differential protection action condition and a quick-break differential action condition, wherein:

[0011] Braking current Ir=|I1+I2|, differential current Id=|I1-I2|, wind turbine rated current Ie, preset slope k, preset proportional differential starting value Iqd, preset quick-break differential setting value Isd;

[0012] The preset proportional differential starting value Iqd is set in accordance with the reliable avoidance of the rotor side current I3 when the wind turbine is running at full load, with a reliability coefficient of not less than 1.2, and in accordance with the reliable avoidance of the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine;

[0013] The fast-break differential setting value Isd is adjusted according to the maximum unbalanced current that can reliably avoid external faults;

[0014] The operating conditions of proportional differential protection are:

[0015] When Ir≤Ie, Id>Iqd, the proportional differential protection is activated.

[0016] When Ir>Ie, Id>Iqd+k×(Ir-Ie), the proportional differential protection is activated;

[0017] The operating conditions for the quick-trip differential protection are:

[0018] When Id>Isd, the quick-trip differential protection is activated.

[0019] Furthermore, the incomplete differential protection device is provided with harmonic braking lockout and CT disconnection lockout.

[0020] In addition, the present invention also provides an electrical protection method for onshore doubly-fed wind turbines and box-type transformers, which enables more reliable and sensitive protection of wind turbines, frequency converters, box-type transformers and related cables to avoid major electrical accidents of wind turbines and box-type transformers, thereby overcoming the shortcomings of existing wind turbine and box-type transformer protection methods.

[0021] To solve the above technical problems, the present invention provides an onshore doubly-fed wind turbine generator set and a box-type transformer electrical protection method, characterized in that the onshore doubly-fed wind turbine generator set and the box-type transformer electrical protection device described above are adopted, including proportional differential protection and fast-break differential protection, wherein:

[0022] Braking current Ir = | I1 + I2 |, differential current Id = | I1 - I2 |, wind turbine rated current Ie, preset slope k, preset proportional differential starting value Iqd, preset quick-break differential setting Isd;

[0023] The setting method of the preset proportional differential starting value Iqd is:

[0024] The reliability coefficient is not less than 1.2, according to the setting of the rotor side current I3 when the wind turbine is running at full load.

[0025] And according to the reliable avoidance of the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine;

[0026] The setting method of the quick-break differential setting value Isd is as follows:

[0027] Adjust according to the maximum unbalanced current to reliably avoid external faults;

[0028] The operating conditions of proportional differential protection are:

[0029] When Ir≤Ie, Id>Iqd, the proportional differential protection is activated.

[0030] When Ir>Ie, Id>Iqd+k×(Ir-Ie), the proportional differential protection is activated;

[0031] The operating conditions for the quick-trip differential protection are:

[0032] When Id>Isd, the quick-trip differential protection is activated.

[0033] As a further improvement, the electrical protection method for the onshore doubly-fed wind turbine generator set and box-type transformer is provided with harmonic braking lockout and CT line break lockout.

[0034] After adopting such a design, the present invention has at least the following advantages:

[0035] The present invention significantly improves the sensitivity, reliability, selectivity and speed of protection for equipment such as wind turbines, frequency conversion cabinets, box-type transformers and their connecting cables. At the same time, it is not affected by the low voltage ride-through conditions of wind turbines, effectively reducing the probability of electrical damage to equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] Figure 1 This is a schematic diagram of the composition of the onshore doubly-fed wind turbine generator set and the box-type transformer electrical protection device provided by the present invention.

[0038] Figure 2 It is a schematic coordinate diagram of the protection action conditions triggering of the incomplete differential protection device.

[0039] Figure 3 It is the protection logic diagram of the incomplete differential protection device. DETAILED DESCRIPTION

[0040] See also Figure 1 The present invention provides an onshore doubly-fed wind turbine generator set and a box-type transformer electrical protection device, comprising a first current transformer CT1, a second current transformer CT2, an incomplete differential protection device, and a first circuit breaker Q1. The first current transformer CT1 is installed on the low-voltage side circuit of the box-type transformer, and the second current transformer CT2 is installed on the stator current output circuit of the wind turbine generator set. The incomplete differential protection device is electrically connected to the first current transformer CT1 and the second current transformer CT2, respectively, and takes the box-type transformer low-voltage side current I1 and the wind turbine generator set stator current I2 as input signals. The first circuit breaker Q1 is installed on the low-voltage side circuit of the box-type transformer and is electrically connected to the incomplete differential protection device. In other embodiments of the present invention, a second circuit breaker is further provided, installed at the bottom of the wind turbine tower, and is also electrically connected to the incomplete differential protection device.

[0041] Preferably, if the stator winding of the wind turbine is connected in star, the second current transformer CT2 is installed on the neutral point side. If the stator winding of the wind turbine is connected in delta, the second current transformer CT2 is installed near the generator outlet.

[0042] See also Figure 2 , the incomplete differential protection device is provided with a proportional differential protection action condition and a quick-break differential action condition, in the figure, the braking current Ir = | I1 + I2 |, the differential current Id = | I1 - I2 |, the wind turbine rated current is Ie, the preset slope is k, the preset proportional differential starting value is Iqd, the preset quick-break differential value is Isd;

[0043] The operating conditions of proportional differential protection are:

[0044] When Ir≤Ie, Id>Iqd, the proportional differential protection is activated;

[0045] When Ir>Ie, Id>Iqd+k×(Ir-Ie), and the proportional differential protection is activated.

[0046] The operating conditions for the quick-trip differential protection are:

[0047] When Id>Isd, the quick-trip differential protection is activated.

[0048] The setting method of the preset proportional differential starting value Iqd is:

[0049] (1) The reliability coefficient shall be no less than 1.2 according to the setting of the rotor side current I3 when the wind turbine is running at full load;

[0050] (2) Adjust the current in such a way as to reliably avoid the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine.

[0051] The setting method of the quick-break differential setting value Isd is as follows:

[0052] Adjust according to the maximum unbalanced current to reliably avoid external faults.

[0053] See also Figure 3 In addition to proportional differential protection and quick-break differential protection, the protection logic of the incomplete differential protection device also includes harmonic braking lockout and CT line break lockout.

[0054] Harmonic braking lockout should fully consider the harmonic conditions during wind turbine startup, operation, shutdown, and external fault high current (such as low voltage ride-through), and make a differentiated judgment from the harmonics during internal faults to prevent false operation during normal operating conditions and external faults, and refusal to operate during internal faults.

[0055] The CT line break lockout is activated only at a relatively small current or differential current (such as 1.1×Ie) and is exited at a relatively large current or differential current (such as 1.2×Ie).

[0056] In addition, the present invention also provides an onshore doubly-fed wind turbine and box-type transformer protection method, which adopts the above-mentioned onshore doubly-fed wind turbine and box-type transformer electrical protection device. The protection logic, proportional differential protection action conditions, quick-break protection action conditions, proportional differential starting value Iqd setting method, and quick-break differential setting value Isd setting method have been described in detail in the functional setting of the above-mentioned incomplete differential protection device and will not be repeated again.

[0057] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art can make some simple modifications, equivalent changes or modifications based on the technical content disclosed above, which all fall within the scope of protection of the present invention.

Claims

1. An onshore doubly-fed wind turbine generator set and box-type transformer electrical protection device, characterized in that: The device comprises a first current transformer, a second current transformer, an incomplete differential protection device and a first circuit breaker. The first current transformer is installed on the low-voltage side line of the box-type transformer, the second current transformer is installed on the stator current output line of the wind turbine generator set, the incomplete differential protection device is electrically connected to the first current transformer and the second current transformer respectively, and takes the low-voltage side current I1 of the box-type transformer and the stator current I2 of the wind turbine generator set as input signals. The first circuit breaker is installed on the low-voltage side line of the box-type transformer and is electrically connected to the incomplete differential protection device, and receives an action signal to implement circuit breaking protection. The incomplete differential protection device is provided with a proportional differential protection action condition and a quick-break differential action condition, wherein: Braking current Ir=|I1+I2|, differential current Id=|I1-I2|, wind turbine rated current Ie, preset slope k, preset proportional differential starting value Iqd, preset quick-break differential setting value Isd; The preset proportional differential starting value Iqd is set in accordance with the reliable avoidance of the rotor side current I3 when the wind turbine is running at full load, with a reliability coefficient of not less than 1.2, and in accordance with the reliable avoidance of the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine; The fast-break differential setting value Isd is adjusted according to the maximum unbalanced current that can reliably avoid external faults; The operating conditions of proportional differential protection are: When Ir≤Ie, Id>Iqd, the proportional differential protection is activated. When Ir>Ie, Id>Iqd+k×(Ir-Ie), the proportional differential protection is activated; The operating conditions for the quick-trip differential protection are: When Id>Isd, the quick-trip differential protection is activated.

2. The onshore doubly-fed wind turbine generator set and box-type transformer electrical protection device according to claim 1, characterized in that: The incomplete differential protection device is electrically connected to a second circuit breaker, and the second circuit breaker is installed at the bottom of the wind turbine tower.

3. The onshore doubly-fed wind turbine generator set and box-type transformer electrical protection device according to claim 1, characterized in that: The stator winding of the wind turbine generator set is star-connected, and the second current transformer is installed on the neutral point side.

4. The onshore doubly-fed wind turbine generator set and box-type transformer electrical protection device according to claim 1, characterized in that: The stator winding of the wind turbine generator set is connected in a delta connection manner, and the second current transformer is installed near the generator outlet side.

5. The onshore doubly-fed wind turbine generator set and box-type transformer electrical protection device according to claim 1, wherein the incomplete differential protection device is provided with harmonic braking lockout and CT disconnection lockout.

6. An electrical protection method for an onshore doubly-fed wind turbine generator set and a box-type transformer, characterized in that: The onshore doubly-fed wind turbine generator set and box-type transformer electrical protection device according to any one of claims 1 to 5 includes proportional differential protection and quick-break differential protection, wherein: Braking current Ir = | I1 + I2 |, differential current Id = | I1 - I2 |, wind turbine rated current Ie, preset slope k, preset proportional differential starting value Iqd, preset quick-break differential setting Isd; The setting method of the preset proportional differential starting value Iqd is: The reliability coefficient is not less than 1.2, according to the setting of the rotor side current I3 when the wind turbine is running at full load. And according to the reliable avoidance of the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine; The setting method of the quick-break differential setting value Isd is as follows: Adjust according to the maximum unbalanced current to reliably avoid external faults; The operating conditions of proportional differential protection are: When Ir≤Ie, Id>Iqd, the proportional differential protection is activated. When Ir>Ie, Id>Iqd+k×(Ir-Ie), the proportional differential protection is activated; The operating conditions for the quick-trip differential protection are: When Id>Isd, the quick-trip differential protection is activated.

7. The electrical protection method for onshore doubly-fed wind turbine generator system and box-type transformer according to claim 6, characterized in that: Equipped with harmonic braking lockout and CT disconnection lockout.

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