Stability of voltage and frequency control in distributed generation based on parallel-connected converters feeding constant power loads

Karlsson, Per Erik; Björnstedt, Johan; Strom, M.

doi:10.1109/epe.2005.219405

Cited by 11 publications

(4 citation statements)

References 4 publications

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“…In [56,63] the method selected here for inverters used in distributed generation systems is to modify the droop functions of the source converters so that the regular droop functions are used in the steady-state case and opposite droops are used in transients, …”

Section: Opposite Frequency/voltage Droop Controlmentioning

confidence: 99%

“…In [55] it is found that for high voltage (mainly inductive lines) grids the regular droop functions can be used. For low voltage (mainly resistive) grids, so-called opposite droop functions could be used instead but the regular droop functions are advantageous since it allows connectivity to higher voltage levels and power sharing also with rotating generators [55][56][57][58].…”

Section: Adopting Conventional Frequency/voltage Droop Controlmentioning

confidence: 99%

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Review of control techniques for inverters parallel operation

Mohd

Ortjohann

Morton

et al. 2010

Electric Power Systems Research

153

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Section: Opposite Frequency/voltage Droop Controlmentioning

confidence: 99%

Section: Adopting Conventional Frequency/voltage Droop Controlmentioning

confidence: 99%

Review of control techniques for inverters parallel operation

Mohd

Ortjohann

Morton

et al. 2010

Electric Power Systems Research

153

View full text Add to dashboard Cite

“…The power sharing among different sources that feed a group of loads through a grid or microgrid can be better managed using the so-called 'droop control' and all its derivatives [17][18][19][20]. The basic idea is to reproduce the characteristic of the synchronous generators connected to a steam/water turbine regulated through a speed governor, which are controlled such that the + - Figure 9.28 A multiloop, again with the AC voltage external and AC current internal.…”

Section: Droop Controlmentioning

confidence: 99%

Grid Converter Control for WTS

Teodorescu

Liserre

Rodríguez

2010

Grid Converters for Photovoltaic and Wind Power Systems

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This chapter discusses the control issues related to the use of a voltage source converter in wind turbine (WT) systems. Before going into detail on the control of the converter, its model is presented. Then different control structures are discussed. In all of them directly or indirectly the two main issues are the control of the DC link voltage (if there is not a DC/DC converter in charge of it) and the control of the AC power. The AC power can be controlled with the aim either of feeding the main grid or of feeding stand-alone loads or a micro-grid. In the first case the WT system may also offer support to the grid. Once the operation of the grid converter is decided and the strategy to select the reference power is also selected, the power control results, using instantaneous power theory (outlined in Appendix B) in a current and/or voltage control (as shown in Figure 9.1). In fact, the converter can be operated as a controlled current source (typically adopted if the converter is grid connected and does not offer any support to the grid) or as a controlled voltage source (typically adopted if the converter is in stand-alone, micro-grid or grid-supporting mode). In the second case, if an LC filter is also employed the current is controlled (see Figure 9.2). The control of currents and voltages can be done in state variables or in a cascade structure. In the case of operation in a micro-grid and in a grid-supporting mode the droop control (or an equivalent one) is needed.Hence AC voltage and DC link voltage controls are briefly outlined. However, the chapter gives details only on the DC link voltage control because the presence of the converter between the DC voltage state variable and the AC current state variable makes the analysis more complex and a deep analysis is needed. The AC voltage control design is a straightforward consequence of the AC current control described in Chapter 12.Then the structures are adopted for implementation of the control (αβ, abc, dq) [1]. Direct power control is also discussed in a separate section. In fact, in this case the current control loop is not present and the control is linear with respect to the decoupling between AC and DC dynamics but it is nonlinear with respect to the AC dynamics that are expressed directly in terms of power. The direct power control can be implemented with or without a separate PWM modulator. If this is present the scheme is quite similar to those

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“…INTRODUCTION Direct-driven WECS can take measures at grid-side converter and DC-side without affecting the normal operation of generator-side converter and wind turbine during grid voltage sags, which shows that direct-driven WECS may have better LVRT capability than DFIG WECS [13]. During grid voltage sags, the generator-side converter is still able to maintain control of the PMSG, however due to the reduced grid voltage, the current of the grid-side converter has to increase when the same power as before the fault should be supplied to the grid, because of the limited thermal capacity of power electronics devices, the current should not become too high for long time, thus the output power will be limited which can cause the power unbalance in DC-side [14]; From equation (4), it can be seen that when the input power is larger than output power on DC-side capacitance, the DC voltage will rise because there is no channel to dissipate the redundant power, which may have serious impact on normal operation of the whole system [15]. Therefore in this paper the damp load in DC-side in DC-side to limit the rise of DC voltage, maintain the power balance in DC-side and make the WECS keep grid-connected during grid faults [2].…”

Section: Control Of Damp Load In Dc-sidementioning

confidence: 99%

Modeling on converter of direct-driven WECS and its characteristic during voltage sags

2008

2008 IEEE International Conference on Industrial Technology

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The output power of direct-driven wind energy conversion system (WECS) will be limited during grid voltage sag, but the operation of wind turbine will not be influenced by adding damp load in DC-side, then the capability of low voltage ride through (LVRT) may be enhanced. Full power back-to-back PWM converter is adopted in direct-driven variable-speed constant frequency WECS using permanent magnet synchronous generator (PMSG), which can effectively improve system efficiency; the principles of generator-side, grid-side converters and damp load are analyzed in detail, and the whole system modeling of converters is realized. Then the simulation model of converters is built based on Matlab7.3/simulink6.5, and the characteristic during grid voltage sag is simulated; the validity of the model and analysis is verified by simulation, and the results show that direct-driven WECS have good fault ride through capability. Index Terms-direct-driven, wind energy conversion system (WECS), permanent magnet synchronous generator (PMSG), voltage sags, low voltage ride through (LVRT), damp load

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Stability of voltage and frequency control in distributed generation based on parallel-connected converters feeding constant power loads

Cited by 11 publications

References 4 publications

Review of control techniques for inverters parallel operation

Review of control techniques for inverters parallel operation

Grid Converter Control for WTS

Modeling on converter of direct-driven WECS and its characteristic during voltage sags

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