Reactive Power Synchronization Method for Voltage-Sourced Converters

Abstract

There is a growing interest in the parallel operation of Voltage Source Converters (VSCs) both in an isolated microgrid or connected to the utility grid. The most common solution in the literature for the paralellization of VSCs is the socalled droop control, which brings about a relationship between active power and frequency. In this paper, a different approach is proposed where reactive power is used instead of active power to ensure synchronous operation. Active and reactive power are independently controlled using a dq-frame representation based on the vector oriented control, which inherently provides current limitation capability. A detailed dynamic model of the system is used to demonstrate the relation between reactive power and frequency. Due to the intrinsic synchronizing mechanism, the proposed scheme can operate in both isolated and gridconnected modes. As opposed to droop control schemes, active power is not used for synchronization and thus synchronization is possible even if active power is not controllable. Simulation and experimental results, for a case study where a VSC is connected to a host grid, are presented to validate the proposal.

VSC Control Strategy for Systems with high penetration of Power Electronic Converters

“…With the frequency deviation obtained, the reference angle is given by: Fig. 2 shows the reference angle calculation from ∆ω using reactive power deviation with a droop constant , according to equations (5) and (6), which has been proven to be more stable than the active power synchronization [12], and it has better behaviour than the widely used PLL synchronization methods.…”

“…Trying to emulate the synchronous generator's synchronizing torque, the idea of a Virtual Synchronous Machine has been proposed by many authors [7]- [9]. VSMs have been proven as an effective method for both grid supporting and grid forming operations, facing many stability issues and providing virtual inertia to the power system [10]- [12]. Nowadays, this transition between grid forming and grid supporting control strategies is being addressed very often in the literature [13]- [15].…”

Damping Low-Frequency Oscillations in Power Systems Using Grid-Forming Converters

“…) 𝜔 (27) but with the difference that the output signal is a voltage instead of a frequency. As the voltage variation gives rise to a reactive power exchange, the compensator is denoted as POD-Q.…”

“…In [26], a grid-forming converter tuning method for damping subsynchronous interaction in electrical grids using artificial intelligence is presented. All the aforementioned techniques use an active power synchronization (APS) loop; however, a similar technique based on reactive power synchronization (RPS) has been reported in [27] and [28]. In [29], the POD-P control proposed acts on the internal frequency deviation of the synchronization loop using the active power increment as input.…”

Effective and Simple Control of Grid-Connected Three-Phase Converter Operating at a Strongly Distorted Voltage

“…Power electronics converters (PECs) make the electrical distribution grid more flexible by the integration of different types of sources, loads, digital control modules. Electrical energy can be more accurately monitored and managed at every processing step, from generation through distribution, conversion, and storage to consumption [1], [2]. Adaptation of PECs to the existing state of distribution system demand many challenges in order to maintain high power quality and efficiency as well as high reliability and low cost in comparison to currently used technology.…”