Composite control method for grid-connected inverter based on repetitive control and disturbance observer

Abstract

The invention discloses a composite control method for a grid-connected inverter based on repetitive control and a disturbance observer. The method comprises the following steps: (1) acquiring network voltage, grid-connected current and capacitance current; (2) acquiring network voltage phase angle through PLL phase locking of the network voltage, converting the grid-connected current and the capacitance current to alpha belta coordinates through transformation of coordinates; (3) adjusting the network voltage phase angle, as well as the grid-connected current and the direct current reference signal thereof both under the alpha belta coordinates through repetitive control; (4) subtracting the output value of the disturbance observer and the capacitance current under the alpha belta coordinates from the output value of the repetitive control; (5) converting the output value after final subtraction to abc coordinates through transformation of coordinates, and generating PWM (Pulse Width Modulation) impulses to control the output of a three-phase full-bridge inverter, so that the grid-connected power generation of the distributed power generation system is achieved. According to the composite control method, the dynamic property of the overall grid-connected control system is good, the steady accuracy is high and the robustness is strong; the composite control method is an accurate and efficient inverter control method, and has a bright development future.

Description

technical field [0001] The invention relates to a combined control method of a grid-connected inverter based on repetitive control and a disturbance observer, and belongs to the technical field of electric power industry. Background technique [0002] With the increasingly widespread application of photovoltaic grid-connected power generation systems, IEC61727-2004 proposed by the International Electrotechnical Commission and the national technical requirements for grid-connected photovoltaic systems have strict requirements on grid-connected current harmonics. At present, current control schemes are mostly used for inverter control. The control strategies include: PID control, current hysteresis control, state feedback control, deadbeat control, proportional resonance control, sliding mode control, repetitive control, and other intelligent control etc. Among them, there are proportional resonance control and repetitive control that have better processing capabilities for h...

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Problems solved by technology

[0003] Proportional resonance control uses the high gain provided by the resonance link at the resonance frequency point to achieve no static error control of the frequency signal, so it can handle various harmonics; however, its disadvantage is that if it is necessary to track several harmonic signals A corresponding number of controllers are required, resulting in complex system structure and difficult implementation, increasing the computational burden of DSP, and when the harmonics to be compensated are close to the shear frequency, the high gain peak of proportional resonance control will affect the stability of the system

[0005] Zhang Fan proposed 1 / 4 cycle repetitive control in his article titled "Research on Repetitive Control Method of SPWM Inverter" ([Master's Dissertation], Zhejiang University of Technology, 2011), which improves the dynamic response of the system, but the repetitive control device design complex

[0006] Shuai Jiang, Dong Cao and Yuan Li et al. in a paper titled "Low-THD, Fast-Transient, and Cost-Effective Synchronous-Frame Repetitive Controller for Three-Phase UPS Inverters," (IEEE Trans.Power Electron.,vol.27 , no.6, pp.2994–3005, June.2012) proposed a 1 / 6 cycle repetitive control, which further improves the dynamic response of the system, but requires 6 coordinate transformations and 6 repetitive controls device, the control structure is complex

[0007] Zhang Peng, Jin Hai, Liang Xingxing, Yu Feng et al. proposed a repetitive The combined control strategy of the control and PI in parallel, but the mutual interference between the two regulators will cause the decline of the steady-state performance index

[0008] In addition, there is a combined control method based on state feedback and repetitive control, but the effect of state feedback depends on the accurate establishment of the control object model, which has poor robustness and is difficult to be widely used in engineering

Therefore, the existing repetitive control strategies and their combined control methods cannot take into account good dynamic characteristics, precise steady-state control accuracy and strong robustness

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