Harmonic injection-based accurate reactive power allocation method of island microsource without interconnection line
A technology of harmonic injection and distribution method, which is applied in the field of microgrid, can solve the problems of inability to distribute, burn out of inverters, difficult to accurately distribute reactive power, etc., and achieve the effect of saving cost and reducing complexity
Active Publication Date: 2017-05-17
YANSHAN UNIV
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Problems solved by technology
When droop control is used, since f is a global variable, the active power of each micro-source can be allocated accurately; however, due to the influence of line impedance, the voltage drop on each line impedance is different, which makes it difficult to accurately allocate reactive power. The problem of distribution, which will cause reactive power cannot be distributed according to the capacity of the micro-source, and in serious cases will cause the inverter to burn out
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[0029] The method of the present invention will be further described below in conjunction with the accompanying drawings:
[0030] like figure 1 As shown, taking a system composed of two inverters in parallel as an example, the steps of the distribution method of the present invention are as follows:
[0031] Step 1. Construct a parallel system of two inverters controlled by the P-f / Q-v droop control algorithm;
[0032] Step 2. According to the droop relationship of the traditional P-f / Q-v droop control algorithm, that is, f=f * -m(P-P * ), V=V * -n(Q-Q * ) to control the output voltage amplitude and frequency of the inverter;
[0033] In the formula, f is the output voltage frequency, f * is the rated frequency of droop control, m is the active droop coefficient, P is the active power output by the inverter, P * is the rated active power for droop control; V is the output voltage amplitude, V * is the rated voltage amplitude of the droop control, n is the reactive pow...
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A harmonic injection-based accurate reactive power allocation method of an island microsource without an interconnection line comprises the steps of constructing a two-inverter parallel system controlled by employing a P-f / Q-v droop control algorithm; performing control to obtain output voltage amplitudes and frequencies of invertors according to a droop relation of a traditional P-f / Q-v droop control algorithm; adding a harmonic voltage which is constant in frequency and of which the amplitude is relevant to a reactive power output from a first inverter to the parallel system through a harmonic injection module; reversely calculating the reactive power output from the first inverter according to the amplitude of a harmonic current extracted by a harmonic extraction module of a second inverter; multiplying the reactive power value which is reversely calculated in the second inverter by a coefficient K and then subtracting the reactive power which is output from the second inverter so as to be used as an input of a proportion integral (PI) regulator; and adding an output of the PI regulator into a voltage rated value in the droop relation of the second inverter, and achieving accurate reactive power allocation by voltage regulation. The method has the advantages of high flexibility, fast dynamic response and the like, the system is simplified, and the control is simple.
Description
technical field [0001] The invention relates to the field of micro-grid, in particular to a method for accurately distributing reactive power of island micro-sources. Background technique [0002] With the increasingly serious energy and environmental problems in recent years, distributed micro-sources have been developed on a large scale. In order to realize the dual-mode operation of islanding and grid-connected micro-sources, the inverters in distributed micro-sources mostly use droop control, that is, P-f / Q-v control. When droop control is used, since f is a global variable, the active power of each micro-source can be accurately distributed; however, due to the influence of line impedance, the voltage drop on each line impedance is different, which makes it difficult to accurately reactive power The problem of distribution, which will cause the reactive power to not be distributed according to the micro-source capacity, will cause the inverter to burn out in severe cas...
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IPC IPC(8): H02J3/50
CPCH02J3/50
Inventor 王晓寰刘聪哲张纯江张莹
Owner YANSHAN UNIV