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.
- Matrix converter
- Permanent-magnet synchronous generator (PMSG)
- Reactive power control
- Singular value decomposition (SVD) modulation
- Variable-speed wind generator
Fig. 1. Simplified control block diagram of a PMSG.
EXPECTED SIMULATION RESULTS:
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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