An Improved Modulated Carrier Control with On-Time Doubler for Single-Phase Shunt Activ

 ABSTRACT:

This paper proposes an improved modulated carrier control with on-time doubler for the single-phase shunt active power filter, which eliminates harmonic and reactive currents drawn by nonlinear loads. This control method directly shapes the line current to be sinusoidal and in phase with the grid voltage by generating a modulated carrier signal with a resettable integrator, comparing the carrier signal to the average line current and making duty ratio doubled. Since the line current compared to the carrier signal is not the peak, but the average value, dc-offset appeared at the conventional control methods based on one-cycle control is effectively addressed. The proposed control technique extirpates the harmonic and reactive currents and solves the dc-offset problem. The operation principle and stability characteristic of the single-phase shunt active power filter with the proposed control method are discussed, and experimental results with laboratory prototype under various load conditions verify its performance.

KEYWORDS:

1.      Single-phase shunt active power filter

2.       Modulated carrier control

3.       Indirect control

4.      One-cycle control

5.      Harmonic and reactive currents elimination

6.      Nonlinear load

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Single-phase shunt active power filter with nonlinear load.

.

EXPECTED SIMULATION RESULTS

Fig. 2. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system based on the proposed control method at full load condition (vin : 200 V/div, iin : 20 A/div, if : 20 A/div, i- L : 20 A/div).

Fig. 3. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system based on the proposed control method at half load condition (vin : 200 V/div, iin : 20 A/div, if : 20 A/div, iL : 20 A/div).

Fig. 4. Current controller swithcing mechanism.

 Fig. 5. Measured dc-link voltage, line current, APF current and load current waveforms of the shunt APF system in load transient from 800 W to 1600 W (vo : 100 V/div, iin : 20 A/div, if : 20 A/div, iL : 20 A/div).

Fig. 6. Measured grid voltage, line current, APF current and load current waveforms of the shunt APF system at 110 Vrms grid voltage. (vin : 100 V/div, iin : 10 A/div, if : 10 A/div, iL : 10 A/div) Under (a) 200 W, (b) 270 W, (c) 340 W, (d) 400 W load condition.

CONCLUSION:

An improved modulated carrier control for single-phase active power filter has been proposed. The shunt APF with the proposed control method fulfills harmonic and reactive current elimination at the line current by comparing the carrier signal to the average line current and having the duty ratio doubled. On top of that, the control method totally gets rid of the dc-offset problem arisen at the conventional one based on one-cycle control and ameliorates the current control loop stability without additional ramp signal. The operation principle of power stage, the main control mechanism, and the stability characteristic of the current control loop are analyzed in detail. Experimental results with the shunt APF system under assorted conditions verify the performance of the proposed control method in steady and transient states.

REFERENCES:

[1] Elham B. Makram, E.V. Subramaniam, Adly A. Girgis, and Ray Catoe, “Hamonic filter design using actual recorded data,” IEEE Transaction on Industrial Application, vol. 29, no. 6, pp. 1176-1183, Nov. 1993.

[2] F. Z. Peng, “Harmonic sources and filtering approaches,” IEEE Transaction on Industrial Application Magazine, vol. 7, no. 4, pp. 18-25, Jul. /Aug. 2001.

[3] Czarnecki, L. S., Ginn, H. L., “The effect of the design method on efficiency of resonant harmonic filters,” IEEE Transactions on Power Delivery, vol. 20, no. 1, pp. 286-291, Jan. 2005.

[4] Fakhralden A. Huliehel, Fred C. Lee, and Bo H. Cho, “Small-signal modeling of the single-phase boost high power factor converter with constant frequency control,” PESC’92 Record. 23rd annual IEEE Power electronics Specialists Conference, 1992, vol.1, pp. 475 – 482.

[5] R. Martinez, P. N. Enjeti, “A higj-performance single-phase rectifier with input power factor correction,” IEEE Transactions on Power Electronics, vol. 11, no. 2, pp. 311–317, Mar. 1996.

A Bridge Modular Switched-Capacitor-Based Multilevel Inverter With Optimized SPWM Control Method And Enhanced Power-Decoupling Ability

ABSTRACT:

Micro-inverters operating into the single-phase grid from new energy source with low-voltage output face the challenges of efficiency bottleneck and twice-line-frequency variation. This paper proposed a multilevel inverter based on bridge modular switched-capacitor (BMSC) circuits with its superiority in conversion efficiency and power density. The topology is composed of DC-DC and DC-AC stages with independent control for each stage, aiming to improve system stability and simplify the control method. The BMSC DC-DC stage, which can be expanded to synthesize more levels, not only features multilevel voltage gain but also partially replaces the original bulk input capacitor and functions as an active energy buffer to enhance power decoupling ability between DC and AC sides. In DC-AC stage, the control strategy of optimized unipolar frequency doubling sine-wave pulse-width modulation (UFD-SPWM) is proposed to  improve the quality of output waveform. Meanwhile, the multilevel voltage phase has been optimized to reduce the power loss further. Finally, a prototype has been built and tested. Associated with the simulation, the experimental results validate the practicability of these analyses.

KEYWORDS:

1.      Switched-capacitor circuit

2.      Multilevel inverter

3.      Power decoupling

4.      Optimized unipolar frequency doubling SPWM.

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

(a)

(b)

Fig.1 Topology of the proposed converter.(a) General topology of bridge  modular switched-capacitor-based multilevel inverter (b) Seven-level inverter.

EXPECTED SIMULATION RESULTS

(a)

(b)

 (c)

Fig.2 Simulation waveforms of seven-level inverter.(a) Us1_DS, Us3_DS, Us1a_DS

and Us2a_DS. (b) UC2a, Ud, UX, Uo and io. (c) Spectrum of Uo.

(a)

 (b)

(c)

(d)

Fig.3 Simulation comparison of power decoupling ability at different Cin. Under proposed control strategy:(a)Ui and Po. (b)Ud and Po. Under conventional control strategy:(c) Ui and Po. (d) Ud and Po.

CONCLUSION:

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.

aThree-Phase Transformerless Shunt Active Power Filter with Reduced Switch Count for Harmonic Compensation in Grid-Connected Applications

 ABSTRACT:

Shunt active power filter is the preeminent solution against nonlinear loads, current harmonics and power quality problems. APF topologies for harmonic compensation use numerous high-power rating components and are therefore disadvantageous. Hybrid topologies combining low-power rating APF with passive filters are used to reduce the power rating of voltage source inverter. Hybrid APF topologies for high-power rating systems use a transformer with large numbers of passive components. In this paper, a novel four-switch two-leg VSI topology for a three-phase SAPF is proposed for reducing the system cost and size. The proposed topology comprises a two-arm bridge structure, four switches, coupling inductors, and sets of LC PFs. The third leg of the three-phase VSI is removed by eliminating the set of power switching devices, thereby directly connecting the phase with the negative terminals of the dc-link capacitor. The proposed topology enhances the harmonic compensation capability and provides complete reactive power compensation compared with conventional APF topologies. The new experimental prototype is tested in the laboratory to verify the results in terms of total harmonic distortion, balanced supply current, and harmonic compensation, following the IEEE-519 standard.

KEYWORDS:

1.      Harmonics

2.      hybrid topology

3.      nonlinear load

4.      power quality (PQ)

5.      Transformerless inverter

6.      Grid-connected system

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Proposed transformerless APF system

EXPECTED SIMULATION RESULTS:

  

                  

Fig. 2. Steady state operation of the proposed SAPF a) Utility voltage (THDv=4%) b) Utility current (THDi=4.1%) c) Load current (THDi=30.1%) d) Compensating filter current.

Fig. 3. a) DC voltage (50V/div). b) Filter current (100A/div) at filter switched ON (t=0.15).

Fig. 4. Starting performance of the proposed SAPF. a) Utility voltage (THDv=4%) b) Utility current (THDi=4.1%) c) Load current (THDi=30.1%) d) Compensating current at switched ON

Fig. 5. a) On-state and Off-state APF operations. b) Zoom image of utility line current (𝒊𝑺𝒂𝒃𝒄) at 5th and 7th order harmonics.

Fig. 6. Dynamic performance with the R-L load step-change waveforms of the proposed SAPF.

CONCLUSION:

In this paper, a novel three-phase reduced switch count and transformer-less APF circuit, operating with the function of active filtering and enhanced reactive power compensation. The main point of the proposed APF circuit topology, which uses a two-leg bridge structure and only four IGBT power devices in the three-phase power converter. Compared with the other existing topologies, the elimination of the transformer and minimum active and passive component contributes to a significant reduction in the manufacturing cost, volumetric size and weight. The proposed APF system is more robust, efficient and stable to improve the feasibility and harmonic propagation of the power distribution system. A detail analysis of the both the active filter inverter and passive filter, including the reactive power capability and filtering characteristics has been presented. The series LC tuned PF at the 5th and 7th order harmonic frequencies improves the harmonic mitigation performance. However, the series ac coupling inductors can overcome the fixed reactive power compensation caused by the defined value of the LC filter. The control algorithm can ensure the regulated sinusoidal voltage, phase amplitude, and low THD in the power distribution system, along with dc-link voltage control. The experimental and simulation results have verified the feasibility of the proposed APF topology and its excellent performance in terms of both transient and steady states responses to compensate selectively either the reactive power compensation, as well as in damping out the current harmonic distortion. Furthermore, the proposed APF system based on transformerless and power switching device reduced count configuration could be used in extensive applications, such as the grid-connected power converters, grid interfaced distributed energy sources, and so on.

 REFERENCES:

[1] S. D. Swain, P. K. Ray, and K. B. Mohanty, "Improvement of Power Quality Using a Robust Hybrid Series Active Power Filter," IEEE Transactions on Power Electronics, vol. 32, pp. 3490-3498, 2017.

[2] A. Javadi, A. Hamadi, L. Woodward, and K. Al-Haddad, "Experimental Investigation on a Hybrid Series Active Power Compensator to Improve Power Quality of Typical Households," IEEE Transactions on Industrial Electronics, vol. 63, pp. 4849-4859, 2016.

[3] W. U. Tareen, S. Mekhilef, M. Seyedmahmoudian, and B. Horan, "Active power filter (APF) for mitigation of power quality issues in grid integration of wind and photovoltaic energy conversion system," Renewable and Sustainable Energy Reviews, vol. 70, pp. 635-655, 4// 2017.

[4] J. Solanki, N. Fröhleke, and J. Böcker, "Implementation of Hybrid Filter for 12-Pulse Thyristor Rectifier Supplying High-Current Variable-Voltage DC Load," IEEE Transactions on Industrial Electronics, vol. 62, pp. 4691-4701, 2015.

[5] L. Asiminoaei, C. Lascu, F. Blaabjerg, and I. Boldea, "Performance Improvement of Shunt Active Power Filter With Dual Parallel Topology," IEEE Transactions on Power Electronics, vol. 22, pp. 247-259, 2007.

Development of 10kW Three-Phase Grid Connected Inverter

ABSTRACT:

In this paper, modeling, simulation and experimental study of a 10kW three-phase grid connected inverter are presented. The mathematical model of the system is derived, and characteristic curves of the system are obtained in MATLAB with m-file for various switching frequencies, dc-link voltages and filter inductance values. The curves are used for parameter selection of three-phase grid connected inverter design. The parameters of the system are selected from these curves, and the system is simulated in Simulink. Modeling and simulation results are verified with experimental results at 10kW for steady state response, at 5kW for dynamic response and at −3.6 kVAr for reactive power. The inverter is controlled with Space Vector Pulse Width Modulation technique in d-q reference frame, and dSPACE DS1103 controller board is used in the experimental study. Grid current total harmonic distortion value  and efficiency are measured 3.59% and 97.6%, respectively.

KEYWORDS:

1.      Grid Connected Inverter

2.      Inverter Modeling

3.      Space Vector Pulse Width Modulation

4.      Total Harmonic Distortion

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Block diagram of the grid connected inverter.

EXPECTED SIMULATION RESULTS:

              

Fig. 2. THD variation of the grid current for V_dc = 650 V.

Fig. 3. THD variation of the grid current for f_sw = 3 kHz.

Fig. 4. THD variation of the grid current for fsw = 9 kHz.

Fig. 5. Three-phase grid currents and voltage for fsw = 3 kHz.

Fig. 6 d-q components of the grid current for fsw = 3 kHz

Fig. 7. Three-phase grid currents and voltage for fsw = 9 kHz

Fig. 8. d-q components of the grid current for fsw = 9 kHz.

Fig. 9. d-q components of grid current.

CONCLUSION:

In this study, performance of a 10kW three-phase grid connected inverter is investigated for various filter inductance values, DC-link voltages and switching frequencies. The system is modeled in m-file, thus characteristic curves of the inverter are obtained for different parameters. The THD values of grid current for 3 kHz and 9 kHz with 650V DC-link voltage are 10.22%and 3.41%. For verification of the modeling results, the system is simulated in Simulink. The control algorithm is implemented in Embedded Matlab Function in the simulation. The results are compared at 3 kHz and 9 kHz switching frequency, and modeling results are verified with simulation results that are 10.22% are 3.44%. In order to verify the modeling and simulation results, a laboratory prototype that is controlled by dSPACE DS1103 control board is realized. In the experimental study, THD values are measured as 10.68 and 3.59%. Furthermore, dynamic response and reactive power generation capability of the inverter are presented. The experimental results verify the modeling and simulation results. This verification shows that the system can be designed for various system and control parameters using the design curves. The study is realized for 10kW power but it is possible to obtain the characteristic curves for differen power values. According to results, the switching frequency or filter inductance value should be high to meet THD limit. Furthermore, efficiency is another important performance indicator. The efficiency at rated power and the european efficiency of the inverter is 97.6% and 97.2%  at 9 kHz.

REFERENCES:

[1] F. Blaabjerg, M. Liserre and K. Ma: “Power Electronics Converters for Wind Turbine Systems”, IEEE Transactio on Industry Applications, vol.48, pp. 708-719, 2012.

[2] F. Blaabjerg, Z. Chen, S.B. and Kjaer: “Power Electronics as Efficient Interface in Dispersed Power Generation Systems”, IEEE Transactions on Power Electronics, vol. 19,  pp. 1184-1194, 2004.

[3] J.M. Carrasco, L.G. Franquelo, J.T. Bialasiewicz, E. Galvan, R.C.P. Guisado, M.A.M. Prats, J.I. Leon and N.M. Alfonso:  “Power-Electronic Systems for the Grid Integration   of Renewable Energy Sources: A Survey”, IEEE Transactions  on Industrial Electronics, vol. 53, pp. 1002-1016, 2006. 

[4] C. Ramonas and V. Adomavicius: “Research of the Converte  Possibilities in the Grid-tied Renewable Energ  Power Plant”, Elektronika IR Elektrotechnika, vol. 19, pp  37-40, 2013.

[5] D. Meneses, F. Blaabjerg, O. Garcia and J.A. Cobos: “Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application”, IEEE  Transactions on Power Electronics, vol. 28, pp. 2649-2663,  2013.