A New Variable-Speed Wind Energy Conversion System Using Permanent-Magnet Synchronous Generator and Z-Source Inverter


With the growth of wind energy conversion systems (WECSs), various technologies are developed for them. Permanent-magnet synchronous generators (PMSGs) are used by these technologies due to special characteristics of PMSGs such as low weight and volume, high performance, and the elimination of the gearbox. In this paper, a new variable-speed WECS with a PMSG and Z-source inverter is proposed. Characteristics of Z-source inverter are used for maximum power tracking control and delivering power to the grid, simultaneously.  Two control methods are proposed for delivering power to the grid: Capacitor voltage control and dc-link voltage control. Operation of system with these methods is compared from the viewpoint of power quality and total switching device power (TSDP). In addition, TSDP, current ripple of inductor, performance, and total harmonic distortion of grid current of proposed system is compared with traditional wind energy system with a boost converter.



Fig. 1. Proposed PMSG-based WECS with Z-source inverter.


Fig. 2. DC voltage and optimum rotor speed relation: simulated and approximated and calculated (actual).

Fig. 3. Wind speed variation.

Fig. 4. PMSG rotor speed (capacitor voltage control).

Fig. 5. Maximum mechanical power of turbine and the extracted mechanical power from turbine (capacitor voltage control).

Fig. 6. Capacitor voltage (capacitor voltage control).

Fig. 7. Active and reactive powers (capacitor voltage control).

Fig. 8. Active power delivered to the grid and extracted mechanical power

(capacitor voltage control).

Fig. 9. Inductor current of Z-source inverter (capacitor voltage control).

Fig. 10. Input voltage of Inverter (Vi ) (capacitor voltage control).

Fig. 11. PMSG rotor speed (dc-link voltage control).

Fig. 12. The maximum mechanical power of turbine and the extracted mechanical  power from turbine (dc-link voltage control).

Fig. 13. Active power delivered to the grid and extracted mechanical power (dc-link voltage control).

Fig. 14. Capacitor voltage (dc-link voltage control).

Fig. 15. Input voltage of Inverter (Vi ) (dc-link voltage control).

Fig. 16. DC-link voltage across the rectifier.


Fig. 17. DC-link voltage across the Z-source inverter.

Fig. 18. Inductor current of Z-source inverter.

Fig. 19. Inductor current of Z-source inverter (zoomed).

Fig. 20. Grid current in proposed WECS.

Fig. 21. Spectra of grid current in proposed WECS.


Fig. 22. Inductor current of boost converter (zoomed).

Fig. 23. Inductor current of boost converter.

Fig. 24. Grid current in traditional WECS without dead time.

Fig. 25. Spectra of grid current in traditional WECS without dead time.

Fig. 26 Grid current in traditional WECS with dead time.

Fig. 27. Spectra of grid current in traditional WECS with dead time.

Fig. 28. Active power delivered to the grid in conventional and proposed WECSs.

Fig. 29. Efficiency of conventional and proposed WECSs.


In this paper, a PMSG-based WECS with Z-source inverter is proposed. Z-source inverter is used for maximum power tracking control and delivering power to the grid, simultaneously. Compared to conventional WECS with boost converter, the number of switching semiconductors is reduced by one and reliability of system is improved, because there is no requirement for dead time in a Z-source inverter. For active power control, two control methods: capacitor voltage control and dc-link voltage control is proposed and compared. It is shown that with dc-link voltage control method, TSDP is increased only 6% compared to conventional system, but there is more power fluctuations compared to capacitor voltage control. With capacitor voltage control TSDP in increased 19% compared to conventional system. It was also shown that due to elimination of dead time, the THD of proposed system is reduced by 40% compared to conventional system by 5mS dead time. Finally, with same value of passive components, inductor current ripple is the same for both systems.

A Novel Design of PI Current Controller for PMSG-based Wind Turbine Considering Transient Performance Specifications and Control Saturation


This paper introduces a novel plan procedure of decoupled PI current controller for changeless magnet synchronous generator (PMSG)- based breeze turbines sustaining a lattice fixing inverter through consecutive converter. In particular, the plan procedure comprises of consolidating aggravation eyewitness based control (DOBC) with criticism linearization (FBL) system to guarantee ostensible transient execution recuperation under model vulnerability. By rearranging the DOBC under the input linearizing control, it is demonstrated that the composite controller decreases to a decoupled PI current controller in addition to an extra term that has the primary job of recuperating the ostensible transient execution of the criticism linearization, particularly under advance changes in the reference. Also, an enemy of windup compensator emerges normally into the controller while considering the control input immersion to plan the  DOBC. This licenses to expel the impact of the immersion squares required to constrain the control input. The proposed control plot is executed and approved through experimentation directed on 22-post, 5 kW PMSG. The outcomes uncovered that the proposed system can effectively accomplish ostensible execution recuperation under model vulnerability just as enhanced transient exhibitions under control immersion.



 Fig. 1. Configuration of a direct-drive PMSG-based WECS connected

to the host grid.



Fig. 2. System’s response under the composite controller consisting of the feedback controller (13) and the PI-DO (34)–(37). The controller was tested experimentally using the block diagram of Fig. 3. Specifically, the PI-DO (34)–(37) was evaluated with and without the consideration of the reference jump .

Fig. 3. System’s response under the composite controller consisting of the feedback controller (13) and the DOBC (25). The controller was tested experimentally using the block diagram depicted in Fig. 2.

Fig. 4. System’s response under a conventional PI current controller [17].

Fig. 5. Performance evaluation of the proposed PI-DO under model uncertainty.

Fig. 6. Experimental results: Performance testing of the proposed PI current controller under MPPT algorithm, with id (2 A/div), iq (4 A/div), ia (10 A/div), ws (5 [m/s]/div), iga (6 A/div), r (50 [rpm/min]/div), and time (400 ms/div)


This paper has introduced a novel structure of decoupled PI controller to upgrade the transient execution for the present control of PMSG-based breeze turbine. The proposed controller strategy was built up by consolidating a DOBC with criticism linearizing control law. For reasons unknown, the composite controller has a decoupled PI-like structure in addition to two extra parts. The initial segment is fundamentally an enemy of windup compensator, while the second part utilizes the reference bounce data to counteracts the impact of the sudden advance changes in the power request on the transient reaction. This change of the decoupled PI controller grants to ensure zero enduring state blunder without giving up the ostensible transient execution indicated by the state input controller. This remarkable element can’t be accomplished under the current decoupled PI controller, especially when the model parameters are not precise. Trial tests have been performed, and the outcomes bolster the utilization of the reference bounce data to enhance the transient execution under the decoupled PI controller. Along these lines, the proposed methodology furnishes professionals with a substitute strategy in structuring a vigorous decoupled PI current controller for PMSG-based breeze vitality change framework.

Permanent Magnet Synchronous Generator-Based Standalone Wind Energy Supply System


In this paper, a novel calculation, in view of dc interface voltage, is proposed for successful vitality the executives of an independent permanent magnet synchronous generator (PMSG)- based variable speed wind vitality transformation framework comprising of battery, energy unit, and dump stack (i.e., electrolyzer). Additionally, by keeping up the dc connect voltage at its reference esteem, the yield air conditioning voltage of the inverter can be kept consistent regardless of varieties in the breeze speed and load. A compelling control system for the inverter, in view of the beat width adjustment (PWM) conspire, has been created to make the line voltages at the purpose of basic coupling (PCC) adjusted when the heap is uneven. Thus, an appropriate control of battery flow through dc– dc converter has been completed to diminish the electrical torque throb of the PMSG under an uneven load situation. In light of broad reproduction results utilizing MATLAB/SIMULINK, it has been set up that the execution of the controllers both in transient just as in relentless state is very palatable and I can likewise keep up most extreme power point following.




Fig. 1. PMSG-based standalone wind turbine with energy storage and dump load.



Fig. 2. Response of mechanical torque for change in wind velocity.

 Fig. 3. (a) Load current; (b) wind speed.

Fig. 4. DC link voltage.

Fig. 5. RMS output voltage (PCC voltage).

Fig. 6. Instantaneous output voltage at s.

Fig. 7. Instantaneous output line current.

Fig. 8. Powers.

Fig.9. Powers.

Fig. 10. DC link voltage.

Fig. 11. Powers.

Fig. 12. DC link voltage.


Fig. 13. Response of controllers.

Fig. 14. Three phase currents for unbalanced load.

Fig. 15. Electrical torque of PMSG with and without dc–dc converter controller.

Fig. 16. Instantaneous line voltages at PCC for unbalanced load.


Fig. 17. (a) RMS value of line voltages at PCC after compensation; (b) modulation indexes.

Fig. 18. Instantaneous line voltages at PCC after compensation.


Control techniques to direct voltage of an independent variable speed wind turbine with a PMSG, battery, power device, and electrolyzer (goes about as dump stack) are displayed in this paper. By keeping up dc interface voltage at its reference esteem and controlling adjustment records of the PWM inverter, the voltage of inverter yield is kept up consistent at their evaluated qualities. From the reproduction results, it is seen that the controller can keep up the heap voltage great regardless of varieties in wind speed and load.An calculation is created to accomplish clever vitality the executives among the breeze generator, battery, power device, and electrolyzer. The impact of uneven load on the generator is examined and the dc– dc converter control plot is proposed to diminish its impact on the electrical torque of the generator. The dc– dc converter controller not just aides in keeping up the dc voltage steady yet additionally goes about as a dc-side dynamic channel and diminishes the motions in the generator torque which happen because of unequal load. PWM inverter control is consolidated to make the line voltage at PCC adjusted under an uneven load situation. Inverter control additionally helps in decreasing PCC voltage journey emerging because of moderate elements of water elctrolyzer when control goes to it. The complete consonant mutilation (THD) in voltages at PCC is about 5% which portrays the great nature of voltage produced at the client end. The recreation results exhibit that the execution of the controllers is agreeable under unfaltering state just as unique conditions and under adjusted just as lopsided load conditions.

Offshore Wind Farm Power Control Using HVdc Link Control de puissance d’un parc éolien en mer utilisant la liaison CCHT


In this paper, a method is presented to control offshore wind farm output power. This method is able to fix the wind farm output power even during wind speed variations. In the proposed method, the offshore wind farm is connected to the onshore grid through the high-voltage dc (HVdc) cable. Moreover, the power control of the wind turbines is achieved by controlling the HVdc convertors. In the proposed system, the generator side convertors have to control the active power absorbed from the wind, and the grid side ones are obtained to control the HVdc link voltage. The control system is based on applying the appropriate modulation index to the voltage source converters. Two control strategies are proposed and analyzed to control wind farm output power. The simulation results illustrate that the proposed method is able to smooth the output power of the offshore wind farms appropriately. The proposed wind farm configuration and the control system are validated by simulations in the MATLAB/Simulink environment.


  1. Current source inverter (CSI)
  2. Offshore wind farm
  3. Permanent magnet synchronous generator (PMSG)
  4. PQ-bus
  5. Voltage source converter (VSC)



Fig. 1. Proposed configuration of wind turbines connection.



 Fig. 2. (a) Wind speed variations (m/s). (b) Turbine rotational speed (rad/s).

(c) Turbine efficiency.

Fig. 3. HVdc link voltage.

Fig. 4. Wind farm output power.


In this paper, the configuration and control methods have been proposed for the offshore wind turbines, connected to the onshore grid. This method is capable to control and smooth the wind farm output power, injected to the onshore grid. The proposed system can mitigate the fluctuations of wind farm output power, even during wind speed variations. In other words, the wind farm can operate such as a PQ-bus. Moreover, two strategies (fixed power and MPPT) have been analyzed and compared with each other. Finally, the proposed method is compared with other similar works to smooth the output power of the wind farm. The main result is that the proposed method can smooth the output power better than the TSR, PAC, and OTC methods. But it is a bit weaker than the KEC method in power smoothing issue. Moreover, using this method, the wind farm is able to cooperate in frequency control of the onshore grid by controlling the desired active power, to improve the power system operation, which is the future work of the authors.


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Reactive Power Control of Permanent-Magnet Synchronous Wind Generator With Matrix Converter


In this paper, the reactive power control of a variable speed permanent-magnet synchronous wind generator with a matrix converter at the grid side is improved. A generalized modulation technique based on singular value decomposition of the modulation matrix is used to model different modulation techniques and investigate their corresponding input reactive power capability. Based on this modulation technique, a new control method is proposed for the matrix converter which uses active and reactive parts of the generator current to increase the control capability of the grid-side reactive current compared to conventional modulation methods. A new control structure is also proposed which can control the matrix converter and generator reactive current to improve the grid-side maximum achievable reactive power for all wind speeds and power conditions. Simulation results prove the performance of the proposed system for different generator output powers.


  1. Matrix converter
  2. Permanent-magnet synchronous generator (PMSG)
  3. Reactive power control
  4. Singular value decomposition (SVD) modulation
  5. Variable-speed wind generator



Fig. 1. Simplified control block diagram of a PMSG.


Fig. 2. Generator-side active and reactive power and the maximum grid side

reactive power versus generator shaft speed  ɷm for different strategies.

Fig. 3. Matrix converter grid-side reactive power and the generator direct axis current (Igd) , terminal voltage and losses for ɷm = 1 rad/s.

Fig. 4. Matrix converter grid-side reactive power and the generator direct axis

Current (Igd) , terminal voltage, and losses for ɷm = 4.5 rad/s.


In this paper, a new control strategy is proposed to increase the maximum achievable grid-side reactive power of a matrix converter-fed PMS wind generator. Different methods for controlling a matrix converter input reactive power are investigated. It is shown that in some modulation methods, the grid-side reactive current is made from the reactive part of the generator-side current. In other modulation techniques, the grid-side reactive current is made from the active part of the generator-side current. In the proposed method, which is based on a generalized SVD modulation method, the grid-side reactive current is made from both active and reactive parts of the generator-side current. In existing strategies, a decrease in the generator speed and output active and reactive power, will decrease the grid-side reactive power capability. A new control structure is proposed which uses the free capacity of the generator reactive power to increase the maximum achievable grid-side reactive power. Simulation results for a case study show an increase in the grid side reactive power at all wind speeds if the proposed method is employed.


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Stability Enhancement of Wind Power System by using Energy Capacitor System



This paper presents Permanent Magnet Synchronous generator (PMSG) based a variable speed wind turbine systems including energy capacitor system (ECS). The ECS is the combination of electric double layer capacitor (EDLC) known as super capacitor and power electronic devices for wind power application with its detailed modeling and control strategy which can supply smooth electrical power to the power grid and makes the system better stable and reliable. As generated power from wind fluctuates randomly, the objective of this control system is to select a line power reference level and to follow the reference level by absorbing or providing active power to or from ECS to smooth output power fluctuation penetrated to the grid and to keep the wind farm terminal voltage at a desired level by supplying necessary reactive power. The performance of the proposed system is investigated by simulation analysis using PSCAD/EMTDC software.


  1. Variable speed wind generator
  2. Permanent Magnet Synchronous generator (PMSG)
  3. Energy Capacitor System (ECS)




Fig. 1. Model System



Fig. 2. Response of real wind speed data [case-I]


Fig. 3. Response of PMSG generated Active Power [case-I]


Fig. 4. Grid terminal voltage without & with ECS [case-I]


Fig. 5. Grid Power with/without EDLC and EDLC power [case-I]


Fig. 6. Grid Active Power without and with EDLC [case-I]


Fig. 7. EDLC active Power [case-I]


Fig. 8. EDLC energy [case-I]


Fig. 9. Comparison with SMA and ECS


Fig. 10. Response of Wind speed [case-II]


Fig. 11. PMSG generated Active Power [MW] [case-II]


Fig. 12. Grid Active Power without and with EDLC [case-II]


Fig. 13. EDLC active power [case-II]


Fig. 14. EDLC energy [case-II]


Fig. 15. Grid terminal voltage without & with ECS [case-II].


Fig. 16. Frequency deviation of SMA, ECS & without ECS [case-I].


The simulation results show that the quality of the terminal voltage and output power penetrated to the grid is not good but continuously varying without ECS system. Besides, when we used ECS system, the terminal voltage and grid power is almost constant and quality of voltage and power is excellent. So, using ECS system smoothed power can be supplied to the grid by charging and discharging of EDLC. By using low pass filter to calculate line power reference instead of SMA, EMA makes the system very simple, compact and cost effective. Therefore, it can be concluded that this proposed system can be applied effectively in power systems to generate high quality electrical power from the natural fluctuating wind.


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