High-Performance Grid Simulator Using Parallel Structure Fractional Repetitive Control

Liu, Tianqi; Wang, Danwei; Zhou, Keliang

doi:10.1109/tpel.2015.2441732

Cited by 57 publications

(26 citation statements)

References 41 publications

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“…In most existing RC works, N is required to be an integer. However, there is no guarantee that the ratio is an integer in some situations such as: (1) The sampling frequency is not an integral multiple of the reference fundamental frequency [17]. For example, 60 Hz reference AC voltage signal requires an 166.67 delay units when the sampling frequency of the system, which should be an integral division of micro-control unit's clock frequency, is chosen as 10 kHz; (2) For distributed power generation system, it is difficult or even impossible to maintain a constant gird frequency, in which the grid frequency is also the reference voltage or current frequency of gridconnected active power filter or converter [1], [18], [19].…”

Section: Introductionmentioning

confidence: 99%

Virtual delay unit based digital nk ± m-order harmonic repetitive controller for PWM converter

Liu

Zhang

Zhou

2017

2017 IEEE International Conference on Industrial Technology (ICIT)

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Abstract-Repetitive control (RC) scheme presents an attractive solution to achieve excellent steady-state tracking error and low total harmonic distortion (THD) for periodic signals. RC can produce extremely large gains at fundamental and each harmonic frequency of reference signal to achieve all harmonics suppression. However, a DC-AC inverter always has uneven THD distribution, e.g. THD concentrates at 4k ± 1 orders for signal-phase inverter, and 6k ± 1 orders for three-phase inverter. Furthermore, a digital RC requires a integral ratio of the sampling frequency and the reference frequency, whereas the digital control system cannot always meet this requirement. For example, (e.g. 60 Hz reference signal with a 5 kHz sampling frequency, or grid-connected converter under grid frequency fluctuation, etc.). In this paper, virtual delay unit (VDU) based digital nk ± m-order harmonic RC is presented to solve the problems above. The VDU produces a different virtual RC sampling frequency from the system sampling frequency. The virtual sampling frequency for digital RC can be flexibly adjusted based on the integral ratio requirement. The advantage of VDU is that it does not vary the system sampling frequency and it is easy to be realized. Furthermore, nk ± m-order harmonic repetitive controller is selected to provide a selective harmonic compensation (SHC). Experimental results of VDU based nk±m-order harmonic RC for 60 Hz single-phase DC/AC inverter with 5 kHz system sampling frequency are provided to show the effectiveness of the proposed VDU-based SHC.

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Section: Introductionmentioning

confidence: 99%

Virtual delay unit based digital nk ± m-order harmonic repetitive controller for PWM converter

Liu

Zhang

Zhou

2017

2017 IEEE International Conference on Industrial Technology (ICIT)

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“…Controllable AC voltage sources (CVSs) are in recent years emerging in the area of power-hardware-in-the-loop (PHIL) simulations to emulate mains connected loads / generators to analyze power grid dynamics and control strategies [1], [2], to emulate grid faults to test power electronic equipment [3]- [5], to emulate motor / generator characteristics to verify the correct operation of novel drive systems [6], [7], and to develop and conduct type tests on power electronic converters [8]- [11]. Fig.…”

Section: Introductionmentioning

confidence: 99%

“…constant-power loads [16], [17], diode rectifiers [3], [6], [14], and single-phase triac loads [8]. Furthermore, to test power electronic equipment in laboratory or according to international standards, the CVS may need to generate individual harmonics and / or transients in the output voltage of each phase [3]- [5], [18]. To achieve the required flexibility, the output voltages between the phases A, B, and C and the midpoint N ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Optimization and Comparative Evaluation of Multiloop Control Schemes for Controllable AC Sources With Two-Stage <inline-formula> <tex-math notation="LaTeX">$LC$</tex-math> </inline-formula> Output Filters

Boillat

Krismer

Kolar

2016

IEEE Trans. Power Electron.

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This work investigates the control system design and its small-signal properties for the output stage of a high bandwidth, four-quadrant three-phase switch-mode controllable AC voltage source (CVS) with an output power of 10 kW, a switching frequency of 48 kHz, and a two-stage LC output filter. Each output phase of the CVS is operated individually, i.e. the phase voltages are generated with reference to the DC inputvoltage midpoint, to allow maximum flexibility in the generation of the output-voltage waveforms to supply a wide range of different load types, such as DC, single-phase, and general threephase loads including constant-power loads leading to negative small-signal load-resistance values.Three suitable multi-loop control structures with inner currentand outer voltage-control loops are motivated, modeled, and are optimized with respect to different control performance indicators, e.g. small-signal control bandwidth, and for common boundary conditions, e.g. maximum overshoot of the output voltage in case of a reference voltage step. All structures employ conventional P and PI controllers, due to their simplicity and widespread use. Among the three structures, the capacitorcurrent feedback-control structure, which controls the two filter capacitor currents and the output voltage, is identified to be most competitive. The small-signal bandwidth determined for this structure is between 7.1 kHz and 15.5 kHz, depending on the value of the load resistance. This result, in combination with an excellent matching of calculated and measured step responses of the output voltage of a 10 kW hardware prototype, point out the effectiveness of the selected control structure and the usability of control structures that are composed of conventional P and PI controllers. NOMENCLATURE f s Switching frequencyContinuous-time functions of voltages, currents, etc.Discrete-time functions with sampling period T 0 and k ∈ Z X = X(s) = L{x(t)} Laplace transform of the corresponding continuous-time function X(z) = Z{x k } z-transform of the corresponding discrete-time functioñ R load Equivalent small-signal load resistance

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“…However, an integer delay length N cannot be guaranteed in most existing RC works especially when the reference signal is under the influence of frequency fluctuation. Some examples are listed as follows: (1) The reference period is not an integral multiple of sampling period [19]. When a 60 Hz reference AC voltage signal is sampled with a sampling frequency of 10 kHz, the ratio equals to 166.67; (2) For renewable energy based microgrid system, the unstable energy output from wind or photovoltaic generator can easily lead to a sudden power imbalance or a large frequency fluctuation [20].…”

mentioning

confidence: 99%

Virtual Variable Sampling Repetitive Control of Single-Phase DC/AC PWM Converters

Liu¹,

Zhang²,

Zhou³

et al. 2019

IEEE J. Emerg. Sel. Topics Power Electron.

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Abstract-Repetitive control (RC) presents an attractive solution to achieve low steady-state tracking error and total harmonic distortion (THD) for periodic signals. For conventional RC (CRC), it requires that the ratio of reference signal period to the fixed sampling period to be an integer. Therefore, the reference signal with variable frequency or a fractional period ratio will lead to severe performance degradation. Although existing hardware variable sampling rate methods enable CRC to be frequency adaptive, the variable sampling frequency will also influence the overall system stability, and they need that the CPU has variable sampling frequency ability. In this paper, a flexible and easy-to-implement method, virtual variable sampling (VVS), is proposed to enable RC to be frequency adaptive. The proposed VVS method, which creates a virtual delay unit to approximate each variable sampling delay, achieves a flexible variable sampling as similar as hardware-based variable sampling, but it does not influence overall system sampling frequency and stability. Experimental results of a single phase DC/AC converter system are presented to show the effectiveness of the proposed VVS-RC.

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High-Performance Grid Simulator Using Parallel Structure Fractional Repetitive Control

Cited by 57 publications

References 41 publications

Virtual delay unit based digital nk ± m-order harmonic repetitive controller for PWM converter

Virtual delay unit based digital nk ± m-order harmonic repetitive controller for PWM converter

Optimization and Comparative Evaluation of Multiloop Control Schemes for Controllable AC Sources With Two-Stage <inline-formula> <tex-math notation="LaTeX">$LC$</tex-math> </inline-formula> Output Filters

Virtual Variable Sampling Repetitive Control of Single-Phase DC/AC PWM Converters

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