Repetitive-control-based method for controlling compensation current of DSTATCOM (Distribution Static Synchronous Compensator)

Abstract

The invention discloses a repetitive-control-based method for controlling a compensation current of a DSTATCOM (Distribution Static Synchronous Compensator). The method comprises the following steps of: (1) acquiring a grid voltage, a load current and the compensation current; (2) extracting current commands from the load current; and (3) carrying out repetitive control and PI (Proportional-Integral) control according to the current commands, and then, outputting voltage commands to the DSTATCOM. According to the repetitive-control-based method for controlling the compensation current of the DSTATCOM, the no-static-error tracking of the low-order harmonics, comprising fundamental harmonics, of the DSTATCOM can be achieved, the compensation accuracy of the DSTATCOM is improved, the compensation bandwidth of the DSTATCOM is increased, and the compensation capability and accuracy of the DSTATCOM with unbalanced loads are improved, so that the DSTATCOM can have harmonic compensation and suppression capabilities, the use of passive filters at the outlet side of the DSTATCOM is reduced, the harmonic performance of the compensation current of the DSTATCOM is improved, the harmonic output is reduced, and the pollution to a power grid is reduced.

Description

technical field [0001] The invention belongs to the technical field of reactive power compensation, and in particular relates to a compensation current control method based on repetitive control DSTATCOM. Background technique [0002] In recent years, with the rapid development of industrial technology, the degree of social electrification has been continuously improved. In the power grid, especially in the distribution network, various large-capacity induction motors, special motors and other reactive loads, electric arc furnaces, large rolling mills, electric locomotives and other various Impulsive, fluctuating unbalanced loads, increasing capacity, power electronic devices and complete sets of devices and other nonlinear loads are widely used. The operation and use of these devices not only consume a lot of reactive power, but also generate a lot of harmonics, which seriously pollute the power grid and reduce the power grid The use efficiency affects the quality and relia...

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Problems solved by technology

[0004] Tang Jie and Luo An et al. proposed a fuzzy adaptive The PI control strategy improves the flexibility and robustness of device control, and has fast dynamic response and small overshoot when the load fluctuates; however, this method belongs to open-loop control for the output current of the device, and cannot guarantee that the output current of DSTATCOM is stable and without difference Tracking instructions, for unbalanced loads, harmonic loads, grid voltage waveform distortion has no ability to control

[0005] Tu Chunming, Li Hui and others analyzed the impact of grid voltage asymmetry on D-STATCOM and its suppression (Journal of Electrotechnical Society, 2009, (10): 114-121) which analyzed the influence of grid voltage asymmetry on D-STATCOM. Due to the influence of voltage output characteristics, a method to suppress the third harmonic output of the device by changing the switching function is proposed to improve the output characteristics of the device; however, the structure of the controller is complex, and the control performance is affected by the negative sequence detection of the grid voltage. This method does not solve the problem of grid voltage. Issues in ensuring device output performance and harmonic load tracking accuracy during distortion

[0006] Tan Tianyuan, Jiang Qirong and others proposed a set of triangular wave comparison based on the article titled "Control method of three-level DSTATCOM device based on current tracking control" (Power System Automation, 2007, (4): 61-65). The current direct tracking strategy of the three-level converter can reduce the command tracking error and the fluctuation of the switching frequency of the switching device to a certain extent, but this strategy makes the switching frequency of the device low, the output filter design is large, and the steady-state error cannot be eliminated

[0007] Wu Chunhui, Jiang Qirong and others proposed a switch based on selective harmonic elimination in the article titled "An Optimization Method for Three-level Specific Harmonic Elimination Pulse Width Modulation" (Power Electronics Technology, 2005, (5)) The angle optimization calculation method enables the inverter output to obtain better harmonic characteristics at a lower switching frequency. However, under the influence of large-capacity impact loads in the distribution network, the voltage of the access node has large fluctuations. Due to the influence of detection error and delay, the response speed is slow, and the specific harmonic elimination bandwidth is limited, it is impossible to track the harmonic load without static error, and the work performance is poor under the grid imbalance and distortion

[0008] In addition, some DSTATCOM nonlinear control based on advanced control theory, adaptive deadbeat control, etc. do not have high requirements on the accuracy of the system model, and can adaptively change the system parameters to obtain higher compensation accuracy, but due to the controller design Complexity, poor real-time performance, lagging response, and limited switching frequency, it is difficult to be widely used in engineering

Therefore, none of the existing DSTATCOM current control strategies can take into account good harmonic output performance, precise steady-state control accuracy, superior dynamics, and strong adaptability to load and grid voltage disturbances.

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