Electrical protection device and method for offshore double-fed wind turbine and supporting boost equipment

Abstract

The present invention discloses an offshore double-fed wind turbine and supporting boost equipment electrical protection device and method, including a first current transformer, a second current transformer, an incomplete differential protection device and a first circuit breaker, wherein the first current transformer is installed on the high-voltage side line of the boost transformer, the second current transformer is installed on the stator current output line of the wind turbine, the incomplete differential protection device is electrically connected to the first current transformer and the second current transformer respectively, the high-voltage side current I1 of the boost transformer and the stator current I2 of the wind turbine are taken as input signals, the first circuit breaker is installed on the ring network cabinet line and electrically connected to the incomplete differential protection device to realize circuit breaking protection. The present invention significantly improves the sensitivity, reliability, selectivity and speed of protection of equipment such as offshore wind turbines, frequency converters, boost transformers and their connecting cables, and is not affected by the low voltage ride-through working conditions of the wind turbine, 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 offshore doubly-fed wind turbine and an electrical protection device and method for supporting boosting equipment. Background Art

[0002] China's offshore wind power industry has experienced rapid growth in recent years. By the end of June 2020, China had a cumulative installed offshore wind power capacity of 6.99 million kilowatts, including 1.06 million kilowatts of newly installed capacity. As wind turbines evolve toward longer blades and larger unit capacities, the cost of individual wind turbines is increasing, and the impact of downtime and failure is also growing. The harsh offshore environment severely hinders equipment maintenance, resulting in significant safety risks and economic losses.

[0003] At present, electrical faults in offshore wind turbines are mainly cut off by tower-bottom circuit breakers and ring network cabinet circuit breakers equipped with overcurrent protection. However, wind turbines are at the end of the power grid, and the fault current is relatively small. In addition, they are affected by the current of low voltage ride-through, resulting in large existing protection settings and low sensitivity.

[0004] As can be seen, the existing offshore wind turbine and supporting booster protection devices and methods still have inconveniences and defects, and are in urgent need of further improvement. Creating a new offshore doubly-fed wind turbine and supporting booster protection device and method is currently one of the most important research and development topics. Summary of the Invention

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

[0006] To solve the above technical problems, the present invention provides an electrical protection device for an offshore doubly-fed wind turbine and its supporting boosting equipment, 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 high-voltage side line of the boost 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 high-voltage side current I1 of the boost transformer and the stator current I2 of the wind turbine generator set as input signals. The first circuit breaker is installed on the ring network cabinet line and 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 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|, rated current of wind turbine is Ie, preset slope is k, preset proportional differential starting value is Iqd, preset quick-break differential setting value is Isd;

[0012] The preset proportional differential starting value Iqd is set according to the sum of the absolute values ​​of the rotor side current I3 and the maximum distribution load current I4 when the wind turbine is running at full load, and is set according to the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine;

[0013] The quick-break differential setting value Isd is set according to the maximum excitation inrush current that may be generated by the step-up transformer and the maximum unbalanced current that can be reliably avoided due to 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 device is provided with harmonic braking lockout and CT disconnection lockout.

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

[0021] To solve the above technical problems, the present invention provides an electrical protection method for an offshore doubly-fed wind turbine and its supporting boosting equipment, which uses the above-mentioned electrical protection device for the offshore doubly-fed wind turbine and its supporting boosting equipment, including proportional differential protection and fast-break differential protection, wherein:

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

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

[0024] The setting is based on the sum of the absolute value of the rotor side current I3 and the maximum distribution load current I4 when the wind turbine is running at full load.

[0025] And adjust the current in accordance with the maximum differential unbalance that can be reliably avoided 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] The setting is based on the maximum excitation inrush current that may be generated by the step-up transformer.

[0028] And set according to the maximum unbalanced current to reliably avoid external faults;

[0029] The operating conditions of proportional differential protection are:

[0030] When Ir≤Ie, Id>Iqd, the proportional differential protection is activated.

[0031] When Ir>Ie, Id>Iqd+k×(Ir-Ie), the proportional differential protection is activated;

[0032] The operating conditions for the quick-trip differential protection are:

[0033] When Id>Isd, the quick-trip differential protection is activated.

[0034] As a further improvement, the electrical protection method for the offshore doubly-fed wind turbine and its supporting boosting equipment is provided with harmonic braking lockout and CT line break lockout.

[0035] After adopting such a design, the present invention has at least the following advantages:

[0036] The present invention significantly improves the sensitivity, reliability, selectivity and speed of protection for equipment such as offshore wind turbines, frequency converters, step-up transformers and their connecting cables, while being unaffected by the low voltage ride-through conditions of wind turbines, effectively reducing the probability of electrical damage to the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] 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.

[0038] Figure 1 This is a schematic diagram of the composition of the offshore doubly-fed wind turbine generator set and the electrical protection device of the supporting boosting equipment provided by the present invention.

[0039] Figure 2 It is a schematic coordinate diagram of the protection action conditions triggering of the incomplete differential protection device.

[0040] Figure 3 It is the protection logic diagram of the incomplete differential protection device. DETAILED DESCRIPTION

[0041] See also Figure 1 The present invention provides an electrical protection device for an offshore doubly-fed wind turbine and its associated boosting equipment, 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 high-voltage side of the boost transformer, and the second current transformer CT2 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 and second current transformers, respectively, and takes the high-voltage side current I1 of the boost transformer and the stator current I2 of the wind turbine generator set as input signals. The first circuit breaker Q1 is installed on the ring main unit line and electrically connected to the incomplete differential protection device, receiving an action signal to implement circuit-breaking protection. In addition, a second circuit breaker Q2 is provided, installed at the base of the wind turbine tower and also electrically connected to the incomplete differential protection device to implement circuit-breaking protection.

[0042] 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.

[0043] See also Figure 2 The incomplete differential 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 rated current of the wind turbine is Ie, the preset slope is k, the preset proportional differential starting value is Iqd, and the preset quick-break differential setting value is Isd;

[0044] The operating conditions of proportional differential protection are:

[0045] When Ir≤Ie, Id>Iqd, the proportional differential protection is activated.

[0046] When Ir>Ie, Id>Iqd+k×(Ir-Ie), the proportional differential protection is activated;

[0047] The operating conditions for the quick-trip differential protection are:

[0048] When Id>Isd, the quick-trip differential protection is activated.

[0049] The setting method of the preset proportional differential starting value Iqd is:

[0050] (1) The setting is based on the sum of the absolute value of the rotor side current I3 and the maximum distribution load current I4 when the wind turbine is running at full load, that is;

[0051] (2) The setting should be based on the ability to reliably avoid the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine.

[0052] The setting method of the quick-break differential setting value Isd is as follows:

[0053] (1) According to the setting to reliably avoid the maximum excitation inrush current that may be generated by the step-up transformer

[0054] (2) Adjust according to the maximum unbalanced current that can reliably avoid external faults.

[0055] See also Figure 3 In addition to proportional differential protection and quick-break differential protection, the protection logic of the incomplete differential device also includes harmonic braking lockout and CT line break lockout.

[0056] 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 different 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.

[0057] The CT line break lockout is only activated at a smaller current or differential current (such as 1.1×Ie) and exited at a larger current or differential current (such as 1.2×Ie).

[0058] In addition, the present invention also provides a protection method for an offshore doubly fed wind turbine and supporting boosting equipment. The above-mentioned offshore doubly fed wind turbine and supporting boosting equipment protection device is adopted. The protection logic, proportional differential protection action conditions, quick-break protection action conditions, proportional differential starting value Iqd setting method, and quick-break differential set value Isd setting method have all been described in detail in the functional settings of the above-mentioned incomplete differential device and will not be repeated again.

[0059] The present invention is also applicable to the wiring configuration of an onshore double-fed wind turbine generator set, a step-up transformer and a ring network cabinet.

[0060] 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 offshore double-fed wind turbine and its supporting booster equipment electrical protection device, characterized in that: It includes a first current transformer, a second current transformer, an incomplete differential protection device and a first circuit breaker, wherein the first current transformer is installed on the high-voltage side line of the step-up transformer, the second current transformer is installed on the stator current output line of the wind generator set, the incomplete differential protection device is electrically connected to the first current transformer and the second current transformer respectively, and takes the high-voltage side current I1 of the step-up transformer and the stator current I2 of the wind generator set as input signals, the first circuit breaker is installed on the ring main unit line and electrically connected to the incomplete differential protection device, and receives the action signal to implement circuit breaking protection; 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; The incomplete differential protection device is provided with proportional differential protection action conditions and quick-break differential action conditions, wherein: Braking current Ir=|I1+I2|, differential current Id=|I1-I2|, rated current of wind turbine is Ie, preset slope is k, preset proportional differential starting value is Iqd, preset quick-break differential setting value is Isd; The preset proportional differential starting value Iqd is set according to the sum of the absolute values ​​of the rotor side current I3 and the maximum distribution load current I4 when the wind turbine is running at full load, and is set according to the maximum differential unbalanced current during the start-up, operation and shutdown of the wind turbine. The quick-break differential setting value Isd is set according to the maximum excitation inrush current that may be generated by the step-up transformer and the maximum unbalanced current that can be reliably avoided under 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 of the fast-trip differential protection are: When Id>Isd, the quick-trip differential protection is activated.

2. The electrical protection device for offshore double-fed wind turbine and supporting booster equipment 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.

3. The electrical protection device for offshore double-fed wind turbine and supporting booster equipment 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.

4. According to the electrical protection device for offshore doubly-fed wind turbines and supporting boosting equipment in claim 1, the incomplete differential protection device is provided with harmonic braking interlock and CT line break interlock.

5. According to the electrical protection device for offshore doubly-fed wind turbines and supporting boosting equipment according to claim 2 or 3, the incomplete differential protection device is provided with harmonic braking interlock and CT line break interlock.

6. A protection method applied to the electrical protection device of the offshore doubly-fed wind turbine set and the supporting boosting equipment as described in any one of claims 1 to 5.

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