NB/T 31015-2018Technical specification for converter of permanent magnet wind turbine generator (English PDF)

3.1 permanent magnet wind turbine converter

AC-DC-AC voltage source static converter matched with permanent magnet wind turbine generator and connected between stator winding and grid

Note: It has the functions of, for example, sending the stator winding energy into the grid, etc. It mainly consists of generator-side converter, DC link, grid-side converter and its control system. Some types of converters may make energy flow in both directions, while others may only make energy flow to the grid side.

3.2 generator-side converter

static converter connected with the stator winding of the permanent magnet wind turbine generator and used for converting alternating current with variable voltage, current amplitude and frequency from the wind turbine into direct current

Note: It is also called stator-side converter or generator-side converter, which may be of full control bridge type or uncontrolled bridge type + boost type, including filters that likely present.

3.3 DC link

DC circuit interconnected between the generator-side converter and the line-side converter

3.4 line-side converter

full control bridge static converter connected with the grid to realize the exchange control of active power and reactive power between the DC link and the grid

Note: It is also called grid-side converter, including filters that likely present.

3.5 wind turbine generator system; WTGS

system converting wind energy into electric energy (excluding grid-connected transformer), hereinafter referred to as "WTGS”

3.6 output of WTGS

connection port between WTGS and grid-connected transformer

3.7 rated operation condition of WTGS

working state of the WTGS operating at rated rotational speed and rated power under the condition of rated voltage and rated frequency of the grid

3.8 rated operation condition of converter

working state of the converter under the rated operation condition of the WTGS, hereinafter referred to as "rated operation condition"

3.9 line-side rated current

root-mean-square value of the maximum fundamental current on the AC side of the line-side converter under rated operation condition

3.10 line-side rated voltage

root-mean-square value of line voltage on the AC side of the line-side converter

3.11 line-side rated frequency

frequency of the fundamental voltage on the AC side of the line-side converter, i.e., the power frequency

3.12 line-side rated capacity

apparent power of line-side converter at line-side rated frequency, line-side rated voltage and line-side rated current

3.13 line-side power factor

ratio of the active power to the apparent power on the AC side of the line-side converter or at the output of WTGS, also called the WTGS power factor

The power factor formula is as follows:

(1) where,

lambda - - the power factor;

P - - the active power;

S - - the apparent power.

3.14 total harmonic distortion; THD

total harmonic distortion is related to the fundamental component of the vector under consideration the total harmonic distortion (THD) is defined by the following formula:

(2) where,

Q1 - - the r.m.s value of fundamental harmonic;

Q - - the total r.m.s value, which may represent current or voltage.

The total harmonic contains inter-harmonic. When inter-harmonic exists, the waveform is no longer periodic, and the influence of inter-harmonic may be more complex than that of harmonic.

If inter-harmonic is ignored, Formula (2) may also be expressed as:

(3) where, h - - the harmonic order, where the number h is even, kTHD is called even harmonic distortion, where h is odd, kTHD is called odd harmonic distortion;

Qh - - the r.m.s value of the h-th order harmonic component.

3.15 generator-side rated current

root-mean-square value of fundamental current of the generator-side converter under the rated operation condition

3.16 generator-side rated voltage

root-mean-square value of fundamental line voltage on the AC side of the generator-side converter under the rated operation condition

3.17 generator-side rated frequency

frequency of fundamental voltage on the AC side of the generator-side converter under the rated operation condition

3.18 generator-side frequency range

fundamental voltage frequency range on the AC side of the generator-side converter corresponding to the permanent magnet wind turbine generator within the specified rotational speed range

3.19 generator-side converter rated apparent power

apparent power of generator-side converter at generator-side rated frequency, generator-side rated voltage and generator-side rated current

3.20 converter efficiency

ratio of the output active power to the input active power of the converter, which is expressed as a percentage the converter efficiency formula is:

(4) where,

eta - - the converter efficiency;

Pout - - the output active power;

Pin - - the input active power.

3.21 converter cut in current

maximum peak current generated when the line-side converter is switched on on the AC side

3.22 overload capability

root-mean-square value of the maximum fundamental current supplied within a specified period of time and not exceeding the specified limit under the rated operation condition of the converter

3.23 generator filter

filter consisting of common-mode voltage suppression link, differential mode voltage suppression link and du/dt suppression link, connected between the converter and the generator, and used for reducing the voltage value at the motor side and suppressing the overvoltage (such as high common-mode voltage, high differential mode voltage and the like) at the generator side caused by superposition of long cable reflected waves

3.24 nominal current

root-mean-square value of maximum fundamental current that the converter may continuously supply and that does not exceed the allowable value

3.25 common-mode voltage

average of phasor voltages occurring between each conductor and a specified reference point (generally the earth or rack) or 1/3 the input voltage applied at both measuring terminals of the voltmeter and at the specified common terminal

3.26 differential mode voltage

potential difference between phases

3.27 du/dt value

derivative of voltage with time:

du/dt=deltaUi/deltati=(U90%-U10%)/(t90%-t10%) where, du/dt - - the derivative of voltage with time;

deltaUi - - the voltage change value;

deltati - - the time change value;

U90% - - 90% of average voltage;

t90% - - the time corresponding to 90% of average voltage.

4.1 Product type and main parameter

4.1.1 Product type

The types of products shall be classified as:

- - Low-temperature type and normal-temperature type according to the ambient temperature;

- - Air cooling type, liquid cooling type and mixed cooling type according to the cooling method of the power module.

4.1.2 Line-side voltage grade

The following series shall be preferred for the line-side voltage grade of the converter:

0.38 (0.4), 0.6 (0.62), 0.66 (0.69), 1 (1.05), 1.14 (1.2), 2.3 (2.4), 3 (3.15) and 6 (6.3).

Note: The unit is kV. Voltage grades exceeding the above preferred series shall be determined by the user and the manufacturer through negotiation.

4.2 Operating conditions

4.2.1 Environment conditions for normal operation

The converter shall operate under the specified air cooling or liquid cooling environment conditions.

a) Working ambient temperature:

- - Normal temperature type: -20°C~45°C.

- - Low temperature type: -40°C~45°C.

b) Relative humidity: <=95% (below 20°C) c) Altitude: <=2,000m.

4.2.2 Environment condition for normal test

It mainly includes the operating climatic conditions, and the converter shall be tested under the following atmospheric environment:

a) Ambient temperature: -5°C~40°C.

b) Relative humidity: <=90% (below 20°C).

c) Atmospheric pressure: 86kPa~106kPa.

4.2.3 Ambient temperature for storage and transport

During storage and transport of the converter, the ultimate temperature of the ambient air shall be -40°C~70°C.

4.2.4 Electrical conditions for normal operation

4.2.4.1 Variation range of grid frequency

Variation range of grid frequency: 47.5Hz~51.5Hz.

4.2.4.2 Fluctuation range of grid voltage

The converter shall operate normally when the grid voltage is within ±10% of the rated value.

Where the grid voltage exceeds the above range, it shall be determined by the user and the manufacturer through negotiation.

4.2.4.3 Grid voltage unbalance degree

According to the requirement in clause 4 of GB/T 15543-2008, the grid voltage unbalance degree shall not exceed 2%, and the short-time voltage unbalance degree shall not exceed 4%.