A New Discrete Four Quadrant Control Technique for Grid-Connected Full-Bridge AC-DC Converters Wind Energy Projects

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.

REFERENCES:

[1] B. K. Bose, “Global energy scenario and impact of power electronics in 21st century,” IEEE Transactions on Industrial Electronics, vol. 60, no. 7, pp. 2638–2651, Jul. 2013.

[2] R. Doolan and G. Muntean, “Reducing carbon emissions by introducing electric vehicle enhanced dedicated bus lanes,” in IEEE Intelligent Vehicles Symposium Proceedings, Dearborn, MI, USA,, 2014, pp. 1011– 1016.

[3] M. Yilmaz and P. T. Krein, “Review of the impact of vehicle-to grid technologies on distribution systems and utility interfaces,” IEEE Transactions on Power Electronics, vol. 28, no. 12, p. 5673–5689, Dec. 2013.

[4] C. A. Hill, M. C. Such, D. Chen, J. Gonzalez, and W. M. Grady, “Battery energy storage for enabling integration of distributed solar power generation,” IEEE Transactions on Smart Grid, vol. 3, no. 2, pp. 850–857, Jun. 2012.

[5] B. Koushki, A. Safaee, P. Jain, and A. Bakhshai, “Review and comparison of bi-directional AC-DC converters with V2G capability for onboard EV and HEV,” in IEEE Transportation Electrification Conference and Expo (ITEC), Dearborn, MI, USA, 2014, pp. 1–6.

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