The grid-connected converter(GCC) is widely used as the interface between various distributed generations and the utility grid. To achieve precise power control for GCC, this paper presents a model predictive direct p...The grid-connected converter(GCC) is widely used as the interface between various distributed generations and the utility grid. To achieve precise power control for GCC, this paper presents a model predictive direct power control(MPDPC)with consideration of the unbalanced filter inductance and grid conditions. First, the characteristics of GCC with unbalanced filter inductance are analyzed and a modified voltage control function is derived. On this basis, to compensate for the power oscillation caused by unbalanced filter inductance, a novel power compensation method is proposed for MPDPC to eliminate the DC-side current ripple while maintaining sinusoidal grid current. Besides, to improve the control robustness against mismatched filter inductance, a filter inductance identification scheme is proposed. Through this scheme, the estimated value of filter inductance is updated in each control period and applied in the proposed MPDPC. Finally, simulation results in PSCAD/EMTDC confirm the validity of the proposed MPDPC and the filter inductance identification scheme.展开更多
Unbalanced operating condition in a power system can cause partial overloading of the generators in the network,a condition where one or two of the three phases of the generator become overloaded even if the total 3-p...Unbalanced operating condition in a power system can cause partial overloading of the generators in the network,a condition where one or two of the three phases of the generator become overloaded even if the total 3-phase power output of the generator is within its specified limit.Partial overloading of generators beyond certain limits is undesirable and must be avoided.Distribution systems are often subjected to highly unbalanced operating conditions.Introduction of distributed generations(DGs),therefore,has rendered today’s distribution systems quite susceptible to this problem.Mitigation of this problem requires the issue to be addressed properly during analysis,operation and planning of such systems.Analysis,operation and planning of power networks under unbalanced operating condition require 3-phase load flow study.The existing methods of 3-phase load flow are not equipped to take into account any limit on the loadings of the individual phases of the generators.In the present work,a methodology based on NewtonRaphson(N-R)3-phase load flow with necessary modifications is proposed.The proposed methodology is able to determine the safe loading limits of the generators,and,can be adopted for operation and planning of power networks under unbalanced operating conditions to overcome the above difficulties.Test results on IEEE-37 bus feeder network are presented to demonstrate the effectiveness of the proposed method.展开更多
基金supported by the Science and Technology Projects of State Grid Corporation of China “Key Technologies and Demonstration Application of Distributed Power Clusters Regulation”(No. 52153220000U)。
文摘The grid-connected converter(GCC) is widely used as the interface between various distributed generations and the utility grid. To achieve precise power control for GCC, this paper presents a model predictive direct power control(MPDPC)with consideration of the unbalanced filter inductance and grid conditions. First, the characteristics of GCC with unbalanced filter inductance are analyzed and a modified voltage control function is derived. On this basis, to compensate for the power oscillation caused by unbalanced filter inductance, a novel power compensation method is proposed for MPDPC to eliminate the DC-side current ripple while maintaining sinusoidal grid current. Besides, to improve the control robustness against mismatched filter inductance, a filter inductance identification scheme is proposed. Through this scheme, the estimated value of filter inductance is updated in each control period and applied in the proposed MPDPC. Finally, simulation results in PSCAD/EMTDC confirm the validity of the proposed MPDPC and the filter inductance identification scheme.
文摘Unbalanced operating condition in a power system can cause partial overloading of the generators in the network,a condition where one or two of the three phases of the generator become overloaded even if the total 3-phase power output of the generator is within its specified limit.Partial overloading of generators beyond certain limits is undesirable and must be avoided.Distribution systems are often subjected to highly unbalanced operating conditions.Introduction of distributed generations(DGs),therefore,has rendered today’s distribution systems quite susceptible to this problem.Mitigation of this problem requires the issue to be addressed properly during analysis,operation and planning of such systems.Analysis,operation and planning of power networks under unbalanced operating condition require 3-phase load flow study.The existing methods of 3-phase load flow are not equipped to take into account any limit on the loadings of the individual phases of the generators.In the present work,a methodology based on NewtonRaphson(N-R)3-phase load flow with necessary modifications is proposed.The proposed methodology is able to determine the safe loading limits of the generators,and,can be adopted for operation and planning of power networks under unbalanced operating conditions to overcome the above difficulties.Test results on IEEE-37 bus feeder network are presented to demonstrate the effectiveness of the proposed method.
