Harmonic Instability Analysis of a Single-Phase Grid-Connected Converter Using a Harmonic State-Space Modeling Method

Abstract

The increasing number of renewable energy sources in the distribution grid is becoming a major issue for utility companies since grid-connected converters are operating at different operating points due to the probabilistic characteristics of the renewable energy. Usually, the harmonics and impedance from other renewable energy sources are not taken carefully into account in the installation and design of the systems. It can bring an unknown harmonic instability into a multiple power sourced system and makes the analysis difficult due to the complexity of the grid network. This paper proposes a new model of a single-phase grid-connected renewable energy source by using the Harmonic State-space Modeling approach, which can identify such problems. The model can be extended to a multiple connected converter analysis. The modeling results show the harmonic impedance matrixes, which represent the harmonic coupling characteristic as well as different dynamic characteristics. The theoretical modeling and analysis are verified by simulations as well as experimental results.

A Numerical Matrix-Based Method for Stability and Power Quality Studies Based on Harmonic Transfer Functions

“…This is the case in AC systems where all steady state quantities are periodic with the system frequency. One way to study these systems is to use Harmonic State Space (HSS) equations that need complete model of the system under study [18]. However, in this paper it is considered that no information about the structure is available and only the input/output characteristics can be obtained from measurements.…”

Stability Assessment of Power-Converter-Based AC systems by LTP Theory: Eigenvalue Analysis and Harmonic Impedance Estimation

“…The average model is given in (20), which is a fourteenth-order Non-Linear Time Periodic system, as in (1), with all the statespace variables being T g -periodic. To maximise the accuracy of the model while retaining low complexity and to generalise the analysis, the elements modelling the digital control, such as the computational delay (T s = 1/f s ), along with the zeroorder hold (ZOH) delay of the pulse-width modulator (PWM), 0.5T s , are included in the analysis through their continuoustime equivalents [25], [26].…”

“…Based on (20), in the following sections the steady-state solution is evaluated, linearisation is applied and stability analysis is performed on the linearised model.…”

“…The formulation of the LTP analysis permits easy inclusion of an arbitrary number of harmonic coefficients in the stability assessment, and this is an advantage compared to Harmonic Linearisation and Dynamic Phasor approaches, where truncations are usually introduced to deal with the more complicated mathematical formulation. In [20] and [21] the HSS model and stability analysis are addressed for a single-phase and a three-phase grid connected converter, but without considering the dynamics due to the PLL and the impact of digital-computational delays. In [22] an impedance-based stability method is derived and a singlephase grid-connected converter with PLL is used as a test case; however, precise stability boundaries are not provided.…”

Feedforward Harmonic Mitigation Strategy for Single-Phase Voltage Source Converter

“…Before the suppression strategy is put forward, it is important to establish an accurate harmonic analysis model which can reflect the harmonic generation mechanism. As an alternative to the traditional modeling approach [19,20], dynamic phasor (DP) method is very useful for the harmonic analysis of SPVSC [21][22][23]. It was based on a linear time varying periodic (LTP) theory and considered the detailed switching dynamic of power electronic devices.…”