Automatic grid-connected filtering adjustment system and method for doubly-fed wind turbine
A doubly-fed wind turbine, automatic adjustment technology, applied in AC network to reduce harmonics/ripple, harmonic reduction device, single-network parallel feeding arrangement, etc., can solve problems such as reducing filtering performance and increasing system loss, etc. Achieve the effect of avoiding active power loss, high reliability, improving overall reliability and grid-connected power quality
Active Publication Date: 2019-11-15
NANJING POLYTECHNIC INSITUTE
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However, increasing the resistance will reduce the filtering performance on the one hand, and increase the system loss on the other hand.
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[0029] The calculation formula of double-fed motor tooth harmonic frequency is where f 1 Indicates the grid voltage frequency after grid connection, S indicates the number of rotor cogging of the motor, N P Indicates the number of poles of the motor, and s indicates the slip rate of the motor. The number of slots commonly used in the design of doubly-fed wind turbines is 60 slots or 48 slots, and the number of poles is usually 4 poles. where n 1 is the synchronous speed, and n is the current running speed of the motor. For a 4-pole motor running on a 50Hz power grid, the synchronous speed is 1500 rpm, and the normal operating slip range of the doubly-fed wind turbine is generally -0.3 to 0.2. Taking the 48-slot motor as an example, the relationship between the running speed of the doubly-fed wind turbine and the harmonic frequency of the teeth is shown in the attached Figure 4 shown.
[0030] Implementation steps of the present invention are:
[0031] 1) Measure the s...
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The invention discloses an automatic grid-connected filtering adjustment system of a doubly-fed wind turbine. An LC branch is connected in parallel with a filtering capacitor of an original LC filter.The LC branch comprises an inductor LZ, a capacitor CZ and a switching switch QZ, wherein the inductor LZ, the capacitor CZ and the switching switch QZ are connected in series. The switching of the QZ is controlled by a processor. When the harmonic frequency of the motor teeth and the filter resonance frequency at the current rotational speed of the processor are close, the switching switch QZ ofthe added LC branch is controlled to change the current switching status. The invention further provides an automatic adjustment method. By measuring the rotational speed of the generator, the harmonic frequency of the motor teeth at the current rotational speed is calculated. When the tooth harmonic frequency is close to the current resonance frequency of the filter, the switching of the added LC branch is controlled, and the resonance frequency of the filter is changed to realize automatic adjustment. According to the invention, the problem of excessive harmonic current and resonance causedby the coupling of the tooth harmonics of the double-fed wind turbine and the LCL filter is solved, and the overall reliability of the unit and the quality of grid-connected power are improved.
Description
technical field [0001] The invention relates to the technical field of wind power generation, in particular to a doubly-fed wind turbine grid-connected filtering automatic adjustment system and method. Background technique [0002] With the rapid development of power electronic technology, a large number of wind power generation equipment uses power electronic converters to connect to the grid. Since power electronic equipment works in a switch mode, a filter needs to be configured at the output end, and LCL filters are widely used at present. The LCL filter belongs to the third-order filter, which has strong harmonic attenuation ability in the high frequency band, but at the same time, it also presents a very low impedance at the natural resonance frequency. When there is a harmonic source in this frequency band, it is easy to cause harmonic current overshoot large phenomena, and even cause resonance problems. For double-fed wind turbines, due to the cogging effect of dou...
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IPC IPC(8): H02J3/01H02J3/38
CPCH02J3/01Y02E40/40
Inventor 陈琳冀俊茹
Owner NANJING POLYTECHNIC INSITUTE