ABSTRACT:
In cascaded-type microgrid, the synchronization and
power balance of distributed generators become two new issues that needs to be addressed
urgently. To that end, an f-P/Q droop control is proposed in this letter,
and its stability is analyzed as well. This proposed droop control is capable
to achieve power balance under both resistive-inductive an resistive-capacitive
loads autonomously. Compared with the inverse power factor droop control, an
obvious advantage consists in extending the scope of application. Finally, the
feasibility of the proposed method is verified by simulation results.
KEYWORDS:
1. Cascaded-type
microgrid
2. Droop control
3. Power balance
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Structure of islanded cascaded-type microgrid.
CONTROL SYSTEM:
Fig.
2. The local control diagram of the i-th DG.
EXPECTED SIMULATION RESULTS
Fig.3.
Simulation results of case I. (a) Active power. (b) Reactive power
Fig.
4. Simulation results of case II. (a) Active power. (b) Reactive power.
A
bridge modular switched-capacitor-based multilevel inverter with optimized
UFD-SPWM control method is proposed in the paper. The switched-capacitor-based
stage can obtain high conversion efficiency and multiple voltage levels. Meanwhile,
it functions as an active energy buffer, enhancing the power decoupling ability
and conducing to cut the total size of the twice-line energy buffering
capacitance. Furthermore, voltage multi-level in DC-link reduces the switching
loss of inversion stage because turn-off voltage stress of switches changes
with phase of output voltage rather than always suffers from one relatively
high DC voltage. Most importantly, the control method of UFD-SPWM, doubling equivalent
witching frequency, is employed in the inversion stage for a high quality
output waveform with reduced harmonic. In addition, the optimized voltage level
phase maximizes the fundamental component in output voltage pulses to reduce
harmonic backflow as possible. Hence, the comprehensive system efficiency has
been promoted and up to peak value of 97.6%. Finally, two conversion stages are
controlled independently for promoting reliability and decreasing complexity.
In future work, detailed loss discussion, including theoretic calculation and
validation of loss breakdown, will be presented.
REFERENCES:
[1]
M. Jun, "A new selective loop bias mapping phase disposition PWM with
dynamic voltage balance capability for modular multilevel converter," IEEE
Trans. Ind. Electron., vol. 61, no. 2, pp. 798-807, Feb. 2014.
[2]
N. Mehdi, and G. Moschopoulos, "A novel single-stage multilevel type full-bridge
converter," IEEE Trans. Ind. Electron., vol. 60, no. 1, pp. 31-42,
Jan. 2013.
[3]
E. Ehsan and N. B. Mariun, "Experimental results of 47-level switchladder multilevel
inverter," IEEE Trans. Ind. Electron., vol. 60, no. 11, pp.
4960-4967, Nov. 2013.
[4]
J. Lai, “Power conditioning circuit topologies,” IEEE Trans. Ind. Electron.,
vol. 3, no. 2, pp. 24-34, Jun. 2009.
[5]
L. He, C. Cheng, “Flying-Capacitor-Clamped Five-Level Inverter Based on
Switched-Capacitor Topology,” IEEE Trans. Ind. Electron., vol. 63,
no.12, pp. 7814-7822, Sep. 2016.
