| CPC H02J 1/02 (2013.01) [H02J 2310/42 (2020.01)] | 5 Claims |
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1. A tracking and adaptive compensation method for power fluctuation of a pulse load of a ship, the tracking and adaptive compensation method comprising:
based on a microgrid topology model of the ship, a pulse load model of the pulse load, and an interharmonic power and pulse parameter relationship model, performing power fluctuation tracking, frequency selection and a power spectrum analysis to obtain filtering parameters of a low-pass filter and filtering parameters of a band-pass filter;
performing waveform adaptation to eliminate a phase delay caused by the low-pass filter and the band-pass filter, and obtaining a control command for a power compensation strategy; and
generating, by a power loop, a pulse width modulation (PWM) signal to control a switching tube in a bidirectional direct current (DC)/DC converter of each of an energy storage battery pack and a supercapacitor of a hybrid energy storage system;
wherein the microgrid topology model of the ship comprises: a diesel generator, multiple loads connected in parallel to a DC bus through converters, and the hybrid energy storage system comprising the energy storage battery pack and the supercapacitor; the diesel generator is connected to the DC bus through an alternating current (AC)/DC rectifier converter and is configured to supply power to the DC bus; each of the energy storage battery pack and the supercapacitor is connected to the DC bus through the bidirectional DC/DC converter and is controlled by the bidirectional DC/DC converter; the multiple loads comprise a propulsion load, the pulse load, and a daily use load; and a power consumption of the propulsion load and the pulse load accounts for a majority of a power consumption of the propulsion load, the pulse load, and the daily use load;
wherein the pulse load model comprises a controlled current source (CCS) used to equivalently replace a surge current, a control signal of the CCS is composed of a pulse square wave, a pulse period of the pulse square wave represents a change frequency of the pulse load, a pulse power of the pulse square wave represents a maximum impact amplitude of the pulse load, and a pulse duty cycle of the pulse square wave represents a duration ratio of a peak power of the pulse load;
wherein the interharmonic power and pulse parameter relationship model refers to a relationship between three pulse parameters and an interharmonic power shock generated during operation of the pulse load, the interharmonic power and pulse parameter relationship model is obtained through formula derivation and theoretical analysis, the three pulse parameters consist of a pulse power of the pulse load, a pulse duty ratio of the pulse load and a pulse period of the pulse load, and an interharmonic oscillation component is expressed as follows:
 wherein a peak power amplitude of an interharmonic is obtained by analysis of a harmonic power modeling formula for the pulse load, and the peak power amplitude of the interharmonic is expressed as follows:
 where PnΩ0, represents a spectral amplitude at a frequency of nΩ0, Ω0 represents an angular frequency of the pulse load, k represents a conversion coefficient, and n is a positive integer;
wherein a ratio of the peak power amplitude of the interharmonic to an average total power value Ptotal of an integrated power system of the ship is expressed as follows:
 and the average total power value Ptotal of the integrated power system of the ship is decomposed into an average power PM of a propulsion motor and an average power p of the pulse load;
wherein the performing power fluctuation tracking and frequency selection comprises:
predicting and calculating approximate fluctuation amplitudes and frequencies of the interharmonic power generated at the diesel generator according to an amplitude ratio of the interharmonic power at each of the frequencies, and obtaining a fluctuation frequency curve fn(x)=εnΩ0−λn(x−nΩ0)2, where n is a positive integer and a value range of n is εnΩ0≥flim(nΩ0), and the fluctuation frequency curve fn(x) and an amplitude limiting curve flim(x) are combined to make fn(x)=flim(x), to thereby obtain spectral overrun ranges fncLow and fncHigh;
wherein a fluctuation range redundancy is added according to a fluctuation decline rate at an intersection of the fluctuation frequency curve fn(x) and the amplitude limiting curve flim(x) to the spectral overrun ranges fncLow and fncHigh, to update the spectral overrun ranges fncLow and fncHigh:
 where Kcom represents a compensation coefficient;
wherein respond and track are performed as per the spectral overrun ranges fncLow and fncHigh calculated according to the above formula after an interharmonic power shock of the pulse load occurs, which reduces the shock of the pulse load on the integrated power system of the ship; and
wherein the performing power spectrum analysis comprises: using the power spectrum analysis to monitor the power fluctuation of the pulse load in real time, correcting the filtering parameters of the low-pass filter and the band-pass filter according to results of the power spectrum analysis, and after adaptive compensation for a power change of the pulse load is realized, confirming the filtering parameters of the low-pass filter and the band-pass filter by two analysis methods: the spectral overrun ranges fncLow and fncHigh are obtained according to the results of the power spectrum analysis, and the filtering parameters of the low-pass filter and the band-pass filter are determined according to the results of the power spectrum analysis and results of a fluctuation range analysis.
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