Study On Detection And Compensation Technology For Harmonics And Reactive Current Of Novel Ship Electric Power System

Ship integrated electric propulsion system realizes the full mixture of electric power system and motive power system according to the ideology of mixing the ship's energy as a whole, improving the utilization and transformation ratio of the ship's whole energy. However, this also employs lots of nonlinear loads, which aggravate the harmonics and reactive power damage of ship electric power system, affecting the ship's economical run and reliability, and cutting down its safety. To solve this actual problem, by analyzing the ship's practical run and environment condition, this paper presents an effective method, which can compensate the ship's harmonics and reactive current dynamically, and explores the key techniques of the method's engineering practice. The paper's major work, results and conlusions as follows:The structure and running characteristic of the ship's electrical power system are introduced. The origination cause and damage of harmonics and reactive current are analysed. By studying the shortage of the conventional methods of harmonics and reactive power compensation, a novel compensation method, which adopts shunt active power filter (APF) to compensate the ship's harmonics and reactive current, is presented. And the research situation, development tendency and application prospect on ship of APF are summarized;The paper introduces the types of APF, studies the inherent essence mechanism of the harmonic causes and the harmonic compensation deeply, analyzes the structure and principle of shunt APF, discusses the principle of energy exchange among the APF, the ship's source and the loads, and establishes the mathematical models of the three-phase three-wire shunt APF;The common detection method for the harmonics and reactive current are studied. Also, the theories of harmonics and reactive current detection based on unity power factor (UPF) are researched deeply. Then an improved UPF harmonic current detection method——ageneralized reactive current dynamic correction method of k is presented, the aforementioned method has higher precision and better real-time property;The paper studies the control algorithms, uses hysteresis comparison control to track instruction current. In the respect of dc-link voltage control, the paper presents an improved method of the dc-link voltage PI control based onΔk compensation, and makes a definite explain for the cause of the dc-link voltage undulation from another physical sense for the first time;This paper researches main circuit of voltage APF deeply, including the choice of switch parts and switch frequency, besides, the designs of dc-link capacitance, dc-link voltage and ac-link inductance are presented in detail, which take decisive effects of on tracking performance of compensation current.The design principles and related calculating formulas of these parameters in case of definite compensating objects are given, and the responding simulations are also made;A set of experimental device (containing a harmonics and reactive current generator consisted of thyristor rectification devices and an APF compensation device based on digital signal processor (DSP), the respective capability is 12 kVA and 15 kVA) is designed for verifying the related theories and technical methods of the system according the engineering and practical design ideology. The results of test show that the proposed method for the ship's harmonics and reactive currents compensation of the ship's electric power system is right and effective, and the designed compensation device can compensate harmonics and reactive currents accurately.