ABSTRACT:
This paper presents a new control technique for grid-connected full-bridge AC–DC converters. The proposed control scheme is based on one-cycle control approach and enables the converter to process power in all four quadrants. In the proposed method, switching pulses are generated using a discrete control law with a superimposed fictitious reactive current term. This term enables seamless four-quadrant operation of the converter. Implementation of the discrete controller includes estimation of the current ripple based on measured values of the input current and voltages, sampled at the beginning of each switching cycle. The estimated current ripple is then used for a carrier-less implementation of the proposed control technique. A detailed controller stability analysis using Lyapunov theory is also presented. Theoretical analysis, simulation results, and experimental results show fast dynamic response for the grid current.
KEYWORDS:
1. AC–DC
Converters
2. One-Cycle
Control (OCC)
3. Predictive-Digital
Control
4. Reactive
Power Control
5. Power
Factor (PF)
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. The circuit diagram of the full-bridge AC–DC converter with the proposed four-quadrant
OCC technique.
EXPECTED SIMULATION RESULTS:
Fig.
2. Simulation Results for operation of converter using conventional OCC
technique at (a) Heavy load operation - showing stable operation, (b) Light load
- showing saturated variables.
Fig.3.
Simulation results for stable operation of converter with proposed scheme of
reactive power control using one-cycle control.
Fig.
4. Simulation results for stable operation of converter using fictitious
resistance at (a) Rectifier Mode - Heavy load operation, (b) Rectifier Mode - Medium
load operation(same operating point as the one in Fig. 8(b)), (c) Rectifier
Mode - No Load operation, (d) Inverter Mode - stable heavy load operation, and
(e) Inverter Mode - unstable heavy load operation
Fig.
5. Simulation results for transient performance of converter with active power
control using conventional fictitious current based OCC ((a) & (b)), and reactive
power control using proposed fictitious reactive current based OCC ( (c), (d),
(e) & (f)).
Fig.
6. Simulation results for comparing the transient performance of the proposed
digital OCC with the conventional digital OCC. The conventional controller (b)
takes longer time as compared to the proposed controller (a) to reach steady
state after a reactive current transient is applied to the converter.
Fig.
7. Simulation results for grid voltage transient applied to converter with four
quadrant power control.
CONCLUSION:
A
novel discrete current control technique based on one cycle control scheme has
been proposed in this paper. Four quadrant power flow has been achieved using
the proposed control technique. By using this strategy, a fast transient response
is achieved for EV battery charger applications. The proposed OCC includes a
novel carrier-less implementation method using current ripple estimation, which
simplifies its digital implementation. In addition, a generalized stability analysis
of OCC scheme has been performed using discrete Lyapunov stability theory to
ascertain the limits of stable converter operation. The simulation and
experimental results presented in this paper verified that the proposed control
technique is suitable for the operation of a single-phase ACDC converter in all
four quadrants.
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