Harmonic Issues Assessment on PWM VSC-Based Controlled Microgrids Using Newton Methods

Abstract

Abstract-This paper presents the application of Newton-based methods in the time-domain for the computation of the periodic steady state solutions of microgrids with multiple distributed generation units, harmonic stability and power quality analysis. Explicit representation of the commutation process of the power electronic converters and closed-loop power management strategies are fully considered. Case studies under different operating scenarios are presented: grid-connected mode, islanded mode, variations in the Thevenin equivalent of the grid and the loads. Besides, the close relation between the harmonic distortion, steady state performance of the control systems, asymptotic stability and power quality is analyzed in order to evaluate the importance and necessity of using full models in stressed and harmonic distorted scenarios.

Dynamic Average Converter Model for MVDC Link Harmonic Analysis

“…Traditional converter models used for harmonic studies employ detailed representation of switches which demands extensive computational resources and requires significant simulation time [12]. This problem is aggravated when multilevel topologies or cascaded converter configuration is used.…”

“…Distribution level harmonic studies were usually performed using simplified converter models due to the lack of data from the manufacturers [12]. However, a detailed electromagnetic transient (EMT) converter model, where the topology and control systems of the device under test is masked, is typically provided by the developer for transient studies [9]- [13].…”

“…However, a detailed electromagnetic transient (EMT) converter model, where the topology and control systems of the device under test is masked, is typically provided by the developer for transient studies [9]- [13]. The so called 'black-box model', can be used to analyze harmonic interactions, however, requires long simulation time to cope with the power electronic device switching transition which demands very small-time steps [12]. To this end, the two main approaches used for harmonic interaction studies with VSC technology are frequencydomain and time-domain modelling [11]- [14].…”

“…On the other hand, time-domain models provide an instinctive way of representing each component in the network using a user-friendly interface [9]- [12]. Moreover, they allow a detailed representation of VSC's, cables and overhead lines (OHL's), which significantly impacts the harmonic studies compared to the frequency-domain models [12], [19]. However, the detailed representation deteriorates the computational speed especially when multiple VSC's are connected.…”

Periodic Steady State Assessment of Microgrids with Photovoltaic Generation Using Limit Cycle Extrapolation and Cubic Splines

“…This process incorporates fast and precise mathematical and numerical tools such as Newton Raphson (NR), trapezoidal rule (TR), DN, and CSI, respectively. The proposed TD methodology can be used to assess stability [16,17], power quality [18][19][20], dynamic and periodic steady state operation, fault and transient conditions, among other issues, of microgrids with PV sources [21].…”