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A method and system for compensating busbar voltage unbalance and harmonics in isolated island microgrid

A technology of bus voltage and compensation method, applied in AC network to reduce harmonics/ripple, harmonic reduction device, single-network parallel feeding arrangement, etc., can solve problems such as unbalance, voltage unbalance, voltage distortion, etc. Achieving the effect of wide application, reducing system cost and improving output voltage quality

Active Publication Date: 2022-04-19
CECEP WIND POWER
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] Aiming at the voltage unbalance problem that occurs when the inverter operates with three-phase unbalanced loads, the unbalanced suppression research method for three-phase inverters in the prior art proposes to add a Δ / The Y transformer can provide a current path for the unbalanced current generated by the three-phase unbalanced load to solve the problem of unbalanced inverter output voltage, but this will undoubtedly increase additional costs
Aiming at the voltage distortion problem that occurs when the inverter operates with nonlinear loads, the control method for unbalanced nonlinear mixed loads of micro-source inverters in the prior art proposes to transform the output voltage of the inverter into DC flow through d-q rotation coordinates After filtering, it is sent to the PI (proportional-integral) controller to achieve the purpose of output voltage tracking the fundamental reference voltage and filtering out harmonics in the output voltage. However, this control method can only suppress the 5th and 7th harmonics , when there are 3k harmonics, this control method is not applicable
The existing technology also proposes a method of feeding back the inductor current through an integrator to adjust the output impedance of the inverter to be capacitive. This method can improve the distortion rate of the output voltage, but the selection of the optimal virtual capacitance value is cumbersome.
The existing technology also proposes a droop control method to reduce the distortion rate of the inverter output voltage, and share the harmonic current through the parallel inverters to achieve the purpose of reducing the distortion rate of the output voltage. However, the droop control method in this control method The selection of the equation needs to depend on the inverter output impedance type
[0004] To sum up, the above methods are all aimed at the quality problem of inverter output voltage when the load is single nonlinear or unbalanced, without considering the coexistence of nonlinear and unbalanced mixed loads in the actual distribution network

Method used

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  • A method and system for compensating busbar voltage unbalance and harmonics in isolated island microgrid
  • A method and system for compensating busbar voltage unbalance and harmonics in isolated island microgrid
  • A method and system for compensating busbar voltage unbalance and harmonics in isolated island microgrid

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Embodiment 1

[0064] Based on the above description, if image 3 As shown, this embodiment provides a bus voltage unbalance and harmonic compensation method for an island microgrid, including the following steps:

[0065] 1) Select the inverter with the largest capacity in the microgrid as the master inverter, and use the rest of the inverters in the microgrid as slave inverters, where the master inverter and the slave inverter both use three-phase Four-leg topology.

[0066] 2) Obtain the load current i in the microgrid oabc , and for the acquired load current i oabc Separate the components to get the load current i oabc The components of each, where the load current i oabc The components of include fundamental positive sequence current, fundamental negative sequence current, zero sequence current and each harmonic current, specifically:

[0067] 2.1) Obtain the load current i in the microgrid oabc :

[0068]

[0069] in, and are the fundamental positive-sequence current, fun...

Embodiment 2

[0097] This embodiment provides an island microgrid bus voltage unbalance and harmonic compensation system, including:

[0098] The inverter selection module is used to select an inverter with the largest capacity in the microgrid as the master inverter, and use the remaining inverters in the microgrid as slave inverters;

[0099] The component separation module is used to obtain the current in the load of the microgrid, and perform component separation on the obtained load current to obtain each component of the load current;

[0100] A reference current command generating module, configured to generate a reference current command value from the inverter according to each component of the load current;

[0101] The current tracking error determination module is used to obtain the actual output current value of the slave inverter, and make a difference with the reference current command value of the slave inverter to obtain the current tracking error of the slave inverter;

...

Embodiment 3

[0105] This embodiment provides a processor, including computer program instructions, wherein, when the computer program instructions are executed by the processor, they are used to implement the steps corresponding to the above-mentioned isolated microgrid bus voltage unbalance and harmonic compensation method.

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Abstract

The present invention relates to a method and system for compensating bus voltage imbalance and harmonics of an isolated island microgrid. The rest of the inverters in the power grid are used as slave inverters; 2) obtain the current in the load of the microgrid, and separate the components of the obtained load current; 3) generate the reference of the slave inverter according to each component of the load current Current command value; 4) Obtain the current tracking error from the inverter; 5) Generate a PWM modulation signal from the obtained current tracking error through the current inner loop controller of the inverter; 6) Generate a PWM modulation signal from the inverter according to the generated The PWM modulation signal controls the shut-off of its IGBT, and then controls the output compensation current from the inverter to complete the bus voltage imbalance and harmonic compensation of the island microgrid. The present invention can be widely used in the research field of microgrid power quality control.

Description

technical field [0001] The invention relates to a bus voltage unbalance and harmonic compensation method and system of an isolated island microgrid, belonging to the research field of microgrid power quality control. Background technique [0002] There are a large number of nonlinear unbalanced mixed loads in the microgrid. When the inverter is connected to such loads, if the inverter algorithm is not improved, the output voltage of the inverter will be due to the nonlinear unbalanced mixed load. The existence of unbalanced and distorted microgrid leads to unbalanced and distorted bus voltage of the connected microgrid. Unbalanced and distorted voltage will not only cause great harm to the electrical equipment in the microgrid, but also affect the stable operation of the inverter. Therefore, while the inverter completes the form conversion of electric energy, it must also ensure that it can still provide high-quality electric energy under nonlinear and unbalanced mixed load...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38H02J3/26H02J3/01H02J3/24
CPCH02J3/388H02J3/26H02J3/01H02J3/24H02J3/241Y02E40/40Y02E40/50
Inventor 申红帅菅永曹彬曹雪源
Owner CECEP WIND POWER
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