Stability analysis of DC microgrids with constant power load under distributed control methods

Abstract

Constant power loads (CPLs) often cause instability due to its negative impedance characteristics. In this study, the stability of a DC microgrid with CPLs under a distributed control that aims at current sharing and voltage recovery is analyzed. The effect of the negative impedance on the behavior of distributed controller are investigated. The small-signal model is established to predict the system qualitative behavior around equilibrium. The stability conditions of the system with time delay are derived based on the equivalent linearized model. Additionally, eigenvalue analysis based on inertia theorem provides analytical sufficient conditions as a function of the system parameters, and thus it leads to a design guideline to build reliable microgrids. Simulations are performed to confirm the effectiveness and validity of the proposed method.

Wind Power Short-Term Prediction Based on LSTM and Discrete Wavelet Transform

“…Wind power generation is one of the fastest-increasing types of renewable energy generation [12][13][14][15]. Due to the intermittent and variable nature of wind power, wind power prediction [16] is of great importance for the safety [17,18], stability [19,20], and economic efficiency [21,22] of power grids. Wind power prediction (WPP) models can provide useful information about the upcoming wind power generation profile [12].…”

Impedance-Based Interactions in Grid-Tied Three-Phase Inverters in Renewable Energy Applications

“…In grid-feeding mode, when the feedback control is taken from the input-terminal variable [73], the input impedance of the converter usually stays passive, and therefore, the well-designed cascaded system composing of the energy source and the converter is stable. In grid-forming mode, when the outmost feedback is taken from the output-terminal variable [27,[41][42][43]65,73], the input impedance of the converter will exhibit negative incremental-resistor-like characteristics [12]. In this case, the instability will take place, when the operating point of the converter enters into the MPP of the input energy source [69][70][71][72][73][74][75][76][77].…”

“…The origin of the stability problems in grid-connected systems is usually the negativeincremental-resistor-like behavior at the input or output impedance of the three-phase converter [29][30][31] similarly as in DC-DC converters discussed in References [1,2]. In three-phase converters, the negative-incremental-resistor-like behavior is either the consequence of the grid synchronization [29][30][31][32][33][34][35] or the feedback control from the output-terminal variables [36][37][38][39][40][41][42][43]. In case of grid synchronization, the instability can be mitigated in some extends by lowering the control bandwidth of the phase locked loop (PLL) adaptively when the grid impedance is increasing as discussed in Reference [44].…”

Model-Based Current Sharing Approach for DCM Interleaved Flyback Micro-Inverter

“…The first type requires additional hardware, such as equivalent resonant capacitor and series bus capacitors, which would increase the system cost directly. The second type uses a current sharing control method, which includes the droop control method [32][33][34], distributed control method [35] and PI control [17,18]. The droop control and distributed control have been applied to power supply modules.…”

“…The droop control method noted for being simple, inexpensive and efficient, since there is no communication connection among power supply modules [33]. The distributed control method uses the consensus algorithm, in which information such as current and voltage of the distributed modules is required [35]. The current sharing is achieved through feedback of output signals to the control duty cycle, which could cause a control delay compared to the method of controlling the primary side current directly [19].…”