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A control method for parallel power sharing of multiple inverters in islanded microgrid

A multi-inverter and micro-grid technology, applied in the direction of single-network parallel feeding arrangement, etc., can solve the problem of harmonic power, feeder impedance inconsistency, inverter power sharing control, affecting the system's fast response speed, and complex implementation process, etc. problem, to achieve the effect of eliminating harmonic voltage and asymmetrical voltage, easy to separate, and easy to transmit

Inactive Publication Date: 2017-04-05
STATE GRID CORP OF CHINA +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, this patent needs to perform fast Fourier transform FFT on the instantaneous active power and instantaneous reactive power, and detect the power of each characteristic sub-harmonic by frequency division, and then calculate and synthesize the harmonic reference voltage for each characteristic sub-harmonic respectively. Such a specific implementation process is too complicated, and the amount of program calculation is relatively large, which may affect the fast response speed of the system.
[0010] To sum up, the prior art has not solved the problem of inverter power sharing control in low-voltage microgrids due to actual complex factors such as harmonic power, inconsistency of feeder impedance, and inconsistency of inverter rated capacity. technical challenge

Method used

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  • A control method for parallel power sharing of multiple inverters in islanded microgrid
  • A control method for parallel power sharing of multiple inverters in islanded microgrid
  • A control method for parallel power sharing of multiple inverters in islanded microgrid

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Embodiment 1

[0087] A control method for parallel power sharing control of multiple inverters in an island microgrid, the method is applicable to a control system for parallel power sharing of multiple inverters in an island microgrid, and the control system for parallel power sharing of multiple inverters in an island microgrid includes Several parallel inverters, common busbars, linear and non-linear loads, and centralized controller; the main circuit of the inverter includes sequentially connected DC regulated power supplies, H-bridge inverter circuits, LC filter circuits, and feeders, The H-bridge inverter circuit features a S 1 -S 4 Four power switching tubes, the inverter also includes a drive and protection circuit, and a local controller; several parallel inverters are connected to a common bus through the feeder, and linear and nonlinear loads are connected to the common bus , there is also a centralized controller on the common bus; the structure of the island microgrid multi-in...

Embodiment 2

[0105] According to the method for controlling parallel power sharing of multiple inverters in an island microgrid in Embodiment 1, it is further defined as, in the step (1), the centralized controller controls the common bus voltage u pcc Carry out sampling, processing and calculation to obtain the d coordinate component value u of the h order harmonic component of the common bus voltage in the dq coordinate system pcch_d and the q-coordinate component value u pcch_q , the specific steps include:

[0106] a. The centralized controller extracts the common bus voltage u through the sliding window discrete Fourier transform SDFT pcc Fundamental component u pccf_α and the h harmonic component u pcch_α , for u pccf_α Delay a quarter of the power frequency cycle to get the corresponding conjugate value u pccf_β , for u pcch_α Delay a quarter of the h-th harmonic frequency period to obtain the corresponding conjugate value u pcch_β ; The transfer function H of the sliding win...

Embodiment 3

[0116] According to the method for parallel power sharing control of multiple inverters in an island microgrid described in Embodiment 1, it is further defined as, in the step (4), for u pcch_d and u pcch_q Carry out dq / αβ coordinate transformation to get u pcch_α and u pcch_β , the calculation formula is shown in formula (Ⅳ):

[0117]

[0118] Due to the common bus voltage u pcc Phase angle θ pcc and filter capacitor voltage u c_α Phase angle θ c The phase angle difference between them is extremely small, and the filter capacitor voltage u c_α Phase angle θ c to u pcch_d and u pcch_q Carrying out dq / αβ coordinate transformation can avoid common bus voltage u pcc Phase angle θ pcc Transmission via low-bandwidth communication, so use θ c substitute theta pcc Carry out dq / αβ coordinate transformation.

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Abstract

The invention discloses an equalization control method for the power of a plurality of parallel inverters in an island microgrid. The equalization control method comprises the following steps: constructing an alpha-beta coordinate system in a single-phase control system, and calculating the voltage and the power without need of low-pass filtering in the calculation process; and extracting a phase angle of a filtering capacitor voltage in a local controller of all the inverters, and by using the phase angle as reference, transforming a dq coordinate system back to the alpha-beta coordinate system, wherein electric signals are easily transmitted to the local controller from a centralized controller by low-bandwidth communication. The fundamental component of the voltage of the filtering capacitor participates in adjustment of a first quasi-proportional resonance control for the fundamental voltage; the filtering capacitor voltage containing harmonic voltage participates in adjustment of second quasi-proportional resonance control for the characteristic subharmonic voltage. By application of the equalization control method in an equalization control system for the plurality of parallel inverters in the island microgrid under the complex conditions with non-linear loads, different impedances of feeder lines of all the inverters and inconsistent rated capacities, the inverters also can realize equalization control for the output power, and the loop current among all the inverters is effectively inhibited.

Description

technical field [0001] The invention relates to a method for controlling parallel power equalization of multi-inverters in an isolated island microgrid, and belongs to the technical fields of distributed power generation and smart grids. Background technique [0002] In order to solve the technical problems of connecting distributed power sources to the power grid, scholars related to power systems have proposed the concept of micro-grids. A microgrid is a local power generation system that is composed of distributed micro sources, energy conversion devices, and local loads interconnected through a network, and can realize self-control, protection, and management. In the microgrid, most distributed micro-sources are connected to the AC bus through the inverter interface, thus forming a multi-inverter parallel operation environment. [0003] Due to the variety of local loads on the AC bus, there are inevitably nonlinear loads, which brings great challenges to the inverter co...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M7/493H02J3/38
CPCH02J3/38H02M7/493
Inventor 张庆海吕志鹏刘安华郭维明蔡军于雪光郭亚峰徐跃东董海涛
Owner STATE GRID CORP OF CHINA
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