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Improved reactive power disturbance island detection algorithm

A technology of power disturbance and island detection, applied in the direction of measuring electricity, measuring devices, measuring electrical variables, etc., can solve the problems of difficult threshold setting, unfavorable power quality of power grid, and increase of current harmonics, etc., to achieve one-way large disturbance Effect

Inactive Publication Date: 2020-03-24
JIAOZUO POWER SUPPLY COMPANY OF STATE GRID HENAN ELECTRIC POWER +1
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Problems solved by technology

[0002] Although the passive island detection method has the advantages of fast detection speed, good economy, and simple implementation, it usually has the disadvantages that the threshold is difficult to set, and it is easy to fall into the detection blind spot when power matching, which greatly restricts the passive island detection method. Widely used, so the passive detection method is often used in conjunction with the active detection method; although the active island detection method reduces the detection blind area through the introduction of the disturbance strategy, when the power grid is in normal operation for a long time, the inverter The disturbance of the output current frequency of the inverter will lead to the increase of current harmonics, which will have an adverse effect on the power quality of the grid.
At the same time, the islanding detection algorithm based on active current disturbance may cause grid voltage fluctuations due to active current amplitude disturbances, and even lead to instability of the entire system; An improved reactive power disturbance islanding detection algorithm is very necessary

Method used

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  • Improved reactive power disturbance island detection algorithm
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  • Improved reactive power disturbance island detection algorithm

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Embodiment 1

[0038] In order to verify the correctness and effectiveness of this algorithm, an island detection model based on reactive power disturbance is built in the Matlab / Simulink simulation environment to simulate and verify the anti-islanding strategy proposed in this chapter. The three-phase photovoltaic grid-connected inverter is The constant power control strategy is adopted, the peak voltage of the three-phase grid is 311V, the frequency is 50Hz, the DC bus voltage is 700V, the rated power of the inverter is 10kW, and the switching frequency is 10kHz.

[0039] According to the worst case defined in the IEEE Std.929-2000 standard, the island needs to be detected within 2s; the RLC load resonance frequency is 50Hz, and the quality factor is Q f =2.5, R=7.26Ω, C=1096.1μF, L=9.24mH, according to the algorithm proposed in this chapter, the periodic low distortion positive and negative disturbance time is 100ms respectively, and the disturbance period is 1s. Under the condition of ba...

Embodiment 2

[0048] An improved reactive power disturbance islanding detection algorithm, which includes the following steps:

[0049] Step 1): When islanding occurs, detect the positive zero crossing of the PCC point voltage. At this time, the disturbance quantity Q based on the reactive power reference value dis and PCC point voltage frequency stable value f i The relationship between them is as follows:

[0050]

[0051] In the formula, Δf is the difference of island stable frequency at PCC before and after reactive power disturbance is applied;

[0052] Step 2): Add periodic reactive power disturbance, in order to reduce the impact of periodic reactive power disturbance on grid-connected power quality, and at the same time, the power grid may produce frequency fluctuations (±0.1Hz) due to load switching during normal operation, as To avoid misjudgment, in the normal state, the periodic reactive power disturbance is as follows:

[0053]

[0054] Q ref1 is the periodic reactive...

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Abstract

The invention relates to an improved reactive power disturbance island detection algorithm, which comprises the following steps: 1) when an island occurs, detecting the forward zero crossing of the voltage of a PCC point; 2) adding a periodic reactive disturbance quantity to reduce the influence of the periodic reactive disturbance quantity on the grid-connected power quality; 3) detecting the voltage amplitude and frequency of the PCC point, and judging whether an island occurs or not according to the voltage amplitude or voltage frequency of the PCC point when one of the following four conditions is met; 4) if the voltage frequency fi of the PCC point is greater than or equal to 49.5 Hz and less than or equal to 50.5 Hz after the island occurs, setting a disturbance quantity conversion criterion, realizing unidirectional large disturbance according to the local load property through the disturbance quantity conversion criterion, and quickly increasing the disturbance quantity along with the frequency change so as to trigger an island protection device. The algorithm has the advantages of being high in stability, high in detection speed and small in influence on electric energy quality.

Description

technical field [0001] The invention relates to the technical field of distributed photovoltaic grid-connected island detection, in particular to an improved reactive power disturbance island detection algorithm. Background technique [0002] Although the passive island detection method has the advantages of fast detection speed, good economy, and simple implementation, it usually has the disadvantages that the threshold is difficult to set, and it is easy to fall into the detection blind spot when power matching, which greatly restricts the passive island detection method. Widely used, so the passive detection method is often used in conjunction with the active detection method; although the active island detection method reduces the detection blind area through the introduction of the disturbance strategy, when the power grid is in normal operation for a long time, the inverter The disturbance of the output current frequency of the inverter will lead to the increase of cur...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/08
CPCG01R31/088
Inventor 胡丹丹赵倩朱哲然
Owner JIAOZUO POWER SUPPLY COMPANY OF STATE GRID HENAN ELECTRIC POWER
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