Control of grid inverter based on opposite vectors hodographs

Abstract

Purpose

This paper presents control strategy of VSC connected to the unbalanced grid in stationary coordinates system. The algorithm shown in the paper can be applied to typical inverter to reduce or even eliminate oscillation of DC‐link voltage under unbalanced operation. That has a direct influence on constant flow of p component of power which is essential for drives system for reducing torque ripples.

Design/methodology/approach

The presented strategy of control assumes that orientation of grid voltage and line current vectors hodographs have to be opposite. Mathematical analysis and simulation has been done. Laboratory tests on low power has also been carried out.

Findings

This method leads to fixed p component of power flow and fixed DC bus voltage. The presented idea of control may cause reduction of voltages asymmetry in three‐phase network with significant impedance (local grid, microgrid, isolated grid).

Research limitations/implications

For 50 Hz power system, the presented control strategy has at least 5 ms response time because calculations are based on current and 5 ms delayed values of grid voltage. The paper presents only a simple steady state laboratory test that has been done in low scale of voltage and current.

Practical implications

The paper shows an example of implementation of the method with simple dead‐beat current controller based on DSP microprocessor. The algorithm can be easy applied in a DC/AC converter for elimination DC‐link oscillations under unbalanced working conditions.

Originality/value

Control methods presented in many other papers always provide sinusoidal, symmetrical three‐phase currents irrespective of grid voltage symmetry. The presented idea of control causes reduction of DC‐Link voltage and p, q components of power oscillations due to grid voltage asymmetry.

Citation

Drązikowski, Ł. and Iwański, G. (2012), "Control of grid inverter based on opposite vectors hodographs", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 31 No. 1, pp. 313-323. https://doi.org/10.1108/03321641211184995