組串型逆變器的并網(wǎng)控制策略研究及實現(xiàn)
發(fā)布時間：2019-03-27 18:28
【摘要】：并網(wǎng)逆變器廣泛應用于光伏、風力等可再生能源發(fā)電領域,作為分布式電源和電網(wǎng)的接口,其諧波抑制能力和進網(wǎng)電流波形質量是重要的性能指標。本文主要研究了單相LCL型并網(wǎng)逆變器的并網(wǎng)電流控制策略,基于DSP和PV-IPM設計了3kW組串型并網(wǎng)逆變器,并完成了相關仿真和實驗驗證。 本文選用兩級式并網(wǎng)逆變器系統(tǒng)結構,前級DC/DC主要用于滿足最大功率點跟蹤和直流電壓輸入范圍的要求,DC/AC級則進行逆變和并網(wǎng)的控制。首先研究了常見的DC/DC變換器、DC/AC變換器的拓撲電路,分析每種拓撲的優(yōu)缺點及應用場合。進一步研究了Boost電路實現(xiàn)MPPT的調制原理,雙極性、單極性、單極性倍頻式SPWM的調制特點和諧波特性。 LCL型濾波器在高頻段以-60dB/十倍頻衰減,比純電感濾波器具有更好的高次諧波衰減特性,但其控制模型為三階系統(tǒng),在諧振頻率處存在很高的諧振峰,這往往會引起電流波形畸變,因此需要采用適當?shù)目刂撇呗蕴岣呦到y(tǒng)阻尼,增強控制系統(tǒng)穩(wěn)定性。傳統(tǒng)的無源阻尼方案是在濾波器中串聯(lián)或并聯(lián)電阻,但相應的阻尼損耗以及高頻諧波抑制能力的削弱并不令人滿意,典型的有源阻尼技術有分裂電容法,電容電流內環(huán)反饋,無差拍控制等。本文圍繞LCL型并網(wǎng)濾波器,對其參數(shù)設計的約束條件和計算方法,從系統(tǒng)的控制特性、濾波特性、阻尼特性等方面對無源阻尼和有源阻尼控制策略進行了研究和分析。 理想狀態(tài)下調制只產生了高頻諧波,且易被濾波器消除,但實際的非理想狀態(tài)和外部擾動會注入低次諧波,因此需要對電流控制器進一步優(yōu)化,來補償或消除低次諧波污染。本文建立了單相LCL型并網(wǎng)逆變器的系統(tǒng)模型,量化分析了開關管固有特性和死區(qū)效應,直流電壓二次脈動及電網(wǎng)諧波擾動的低次諧波注入。故而針對性提出了諧波補償和抑制策略,最后采用一種重復控制與狀態(tài)反饋相結合,并加入直流電壓前饋解耦和電網(wǎng)電壓前饋補償?shù)姆桨浮?本文開發(fā)了基于DSP和PV-IPM的3kW單相組串型并網(wǎng)逆變器,完成主功率電路、控制電路及控制部分軟件程序的設計,并通過Matlab/Simulink仿真和逆變器樣機實驗,驗證了諧波分析的合理性和復合控制策略的有效性。
[Abstract]:Grid-connected inverters are widely used in the field of photovoltaic, wind and other renewable energy generation. As the interface between distributed power supply and power grid, the harmonic suppression ability and the quality of input current waveform are important performance indexes of grid-connected inverters. In this paper, the current control strategy of single-phase LCL grid-connected inverter is studied. Based on DSP and PV-IPM, the 3kW cascade inverter is designed, and the simulation and experimental verification are completed. In this paper, the two-stage grid-connected inverter system structure is selected. The former DC/DC is mainly used to meet the requirements of maximum power point tracking and DC voltage input range, while the DC/AC stage is used for inverter and grid-connected control. Firstly, the topology circuits of common DC/DC converter and DC/AC converter are studied, and the advantages and disadvantages of each topology are analyzed. The modulation principle, the modulation characteristics and harmonic characteristics of the bipolar and unipolar double frequency SPWM are further studied in this paper. The modulation principle of the Boost circuit to realize the SPWM is also studied. The LCL filter attenuates at the high frequency by-60dB/ ten-fold frequency, which is better than the pure inductor filter. However, its control model is a third-order system, and there is a very high resonance peak at the resonant frequency. This often causes the distortion of current waveform, so it is necessary to adopt appropriate control strategy to improve the damping of the system and enhance the stability of the control system. The traditional passive damping scheme is the series or parallel resistance in the filter, but the corresponding damping loss and the weakening of the high frequency harmonic suppression ability are not satisfactory. The typical active damping techniques include split capacitance method, capacitance current internal loop feedback, and so on. No beat control, etc. In this paper, the control strategies of passive damping and active damping are studied and analyzed from the aspects of system control characteristics, filtering characteristics, damping characteristics and so on. The constraint conditions and calculation methods for the design of LCL type grid-connected filters are discussed in this paper. The modulation only produces high-frequency harmonics in ideal state and is easy to be eliminated by filter, but the actual non-ideal state and external disturbance will inject low-order harmonics, so it is necessary to further optimize the current controller to compensate or eliminate the low-order harmonic pollution. In this paper, the system model of single-phase LCL grid-connected inverter is established, and the inherent characteristics and dead-time effect of switch tube, the second pulsation of DC voltage and the low-order harmonic injection of harmonic disturbance in power network are quantitatively analyzed. Therefore, the strategy of harmonic compensation and suppression is put forward. At last, a scheme of DC voltage feedforward decoupling and grid voltage feedforward compensation is adopted, which combines repetitive control with state feedback. In this paper, a 3kW single-phase series grid-connected inverter based on DSP and PV-IPM is developed. The main power circuit, control circuit and some software programs of the inverter are designed. The simulation of Matlab/Simulink and the prototype experiment of the inverter are carried out. The rationality of harmonic analysis and the effectiveness of compound control strategy are verified.
【學位授予單位】：東華大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM464
本文編號：2448440
[Abstract]:Grid-connected inverters are widely used in the field of photovoltaic, wind and other renewable energy generation. As the interface between distributed power supply and power grid, the harmonic suppression ability and the quality of input current waveform are important performance indexes of grid-connected inverters. In this paper, the current control strategy of single-phase LCL grid-connected inverter is studied. Based on DSP and PV-IPM, the 3kW cascade inverter is designed, and the simulation and experimental verification are completed. In this paper, the two-stage grid-connected inverter system structure is selected. The former DC/DC is mainly used to meet the requirements of maximum power point tracking and DC voltage input range, while the DC/AC stage is used for inverter and grid-connected control. Firstly, the topology circuits of common DC/DC converter and DC/AC converter are studied, and the advantages and disadvantages of each topology are analyzed. The modulation principle, the modulation characteristics and harmonic characteristics of the bipolar and unipolar double frequency SPWM are further studied in this paper. The modulation principle of the Boost circuit to realize the SPWM is also studied. The LCL filter attenuates at the high frequency by-60dB/ ten-fold frequency, which is better than the pure inductor filter. However, its control model is a third-order system, and there is a very high resonance peak at the resonant frequency. This often causes the distortion of current waveform, so it is necessary to adopt appropriate control strategy to improve the damping of the system and enhance the stability of the control system. The traditional passive damping scheme is the series or parallel resistance in the filter, but the corresponding damping loss and the weakening of the high frequency harmonic suppression ability are not satisfactory. The typical active damping techniques include split capacitance method, capacitance current internal loop feedback, and so on. No beat control, etc. In this paper, the control strategies of passive damping and active damping are studied and analyzed from the aspects of system control characteristics, filtering characteristics, damping characteristics and so on. The constraint conditions and calculation methods for the design of LCL type grid-connected filters are discussed in this paper. The modulation only produces high-frequency harmonics in ideal state and is easy to be eliminated by filter, but the actual non-ideal state and external disturbance will inject low-order harmonics, so it is necessary to further optimize the current controller to compensate or eliminate the low-order harmonic pollution. In this paper, the system model of single-phase LCL grid-connected inverter is established, and the inherent characteristics and dead-time effect of switch tube, the second pulsation of DC voltage and the low-order harmonic injection of harmonic disturbance in power network are quantitatively analyzed. Therefore, the strategy of harmonic compensation and suppression is put forward. At last, a scheme of DC voltage feedforward decoupling and grid voltage feedforward compensation is adopted, which combines repetitive control with state feedback. In this paper, a 3kW single-phase series grid-connected inverter based on DSP and PV-IPM is developed. The main power circuit, control circuit and some software programs of the inverter are designed. The simulation of Matlab/Simulink and the prototype experiment of the inverter are carried out. The rationality of harmonic analysis and the effectiveness of compound control strategy are verified.
【學位授予單位】：東華大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM464
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