Method for detecting and separating positive and negative sequence components of grid voltage of three-phase neutral-line-free system

A grid voltage and separation method technology, applied in the direction of measuring current/voltage, measuring electrical variables, measuring devices, etc., can solve problems such as complex structure, complex digital realization of harmonic parameter design, and influence on system dynamic performance

Active Publication Date: 2014-12-03
HEFEI UNIV OF TECH
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  • Claims
  • Application Information

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Problems solved by technology

Many existing literatures have proposed different solutions, which can be summarized into three types: ① The second harmonic filtering method uses the second harmonic filter to filter out the second harmonic in the dq coordinate system, but the parameters of the harmonic The design and digital implementation are complicated, and the dynamic performance of the system is affected; ②Dual coordinate system decoupling and sequence method, the asymmetric grid voltage is transformed through double dq, and the positive and negative

Method used

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  • Method for detecting and separating positive and negative sequence components of grid voltage of three-phase neutral-line-free system
  • Method for detecting and separating positive and negative sequence components of grid voltage of three-phase neutral-line-free system
  • Method for detecting and separating positive and negative sequence components of grid voltage of three-phase neutral-line-free system

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example 1

[0048] see figure 1 , this example is a photovoltaic three-phase non-neutral line grid-connected control system, when the C-phase voltage of the grid drops, the three-phase asymmetric grid voltage is sampled, and the method for detecting and separating positive and negative sequence components provided by the present invention is used. The specific steps as follows:

[0049]A) Obtain the three-phase instantaneous grid phase voltage of the system detected by the voltage sensor through the sampling unit, and use Park transformation to convert the grid voltage from the three-phase static coordinate system to the instantaneous grid voltage e in the two-phase static αβ coordinate system α (n), e β (n), the method is shown in the following formula ①:

[0050] e α ( n ) = 2 ...

example 2

[0069] In order to verify the performance of the method described in the present invention, in the photovoltaic three-phase grid-connected control system without a neutral line described in Example 1, when the C-phase voltage of the power grid drops, the method provided by the present invention and the existing method are respectively adopted Separate the detection of the positive and negative sequence components of the grid voltage, and use the model MSO-X 3014A oscilloscope produced by the American Aglient company to output the voltage waveforms of the detection and separation of the positive and negative sequence components for comparison.

[0070] see image 3 , the three-phase grid voltage at t s At this moment, the phase C voltage drops, and the collection results are as follows: Figure 4 ~ Figure 7 shown. Figure 4 ~ Figure 7 Respectively, adopting the method provided by the present invention and the existing method to separate the detection and separation of the pos...

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Abstract

The invention provides a method for detecting and separating positive and negative sequence components of grid voltage of a three-phase neutral-line-free system. According to the method, grid voltage of each phase is sampled so as to acquire an instantaneous value and a corresponding differential value of the current grid voltage, thereby being capable of separating the positive and negative sequence components of the current voltage of the grid voltage of the phase, and calculating so as to acquire the sine and the cosine of a positive-negative sequence instantaneous phase angle of the current grid voltage. The method provided by the invention is simple in calculation, small in time delay, high in real-time performance, convenient for engineering realization, applied to a software phase-locked loop of a three-phase grid-connected converter control system, and capable of effectively avoiding overcurrent and fluctuation of DC-side voltage caused by asymmetry of three-phase voltage.

Description

technical field [0001] The invention relates to the field of power systems, in particular to a method for detecting electrical control parameters. Background technique [0002] When the grid voltage drops, to achieve good control of the three-phase grid-connected converter without a neutral line, the system is required to accurately and quickly detect the grid voltage amplitude and phase, and provide accurate system parameter information for the control system in time. This requires the phase-locked loop (PLL) to have steady-state accuracy and dynamic fastness, so that the control system can take effective measures to avoid overcurrent and DC side voltage fluctuations caused by three-phase voltage asymmetry. In order to meet the needs of the asymmetric control strategy of the three-phase grid-connected converter, the positive and negative sequence components of the instantaneous value of the grid voltage can be quickly and accurately extracted under the condition of grid vol...

Claims

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Application Information

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IPC IPC(8): G01R19/00
Inventor 姜卫东吴志清李王敏佘阳阳胡杨赵德勇
Owner HEFEI UNIV OF TECH
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