This paper first discusses the operating principle of instantaneous reactive power theory. Then, the theory is introduced into shunt active power filter and its control scheme is studied. Finally, Matlab/Simulink powe...This paper first discusses the operating principle of instantaneous reactive power theory. Then, the theory is introduced into shunt active power filter and its control scheme is studied. Finally, Matlab/Simulink power system toolbox is used to simulate the system. In the simulation model, as the most common harmonic source, 3-phase thyristor bridge rectifier circuit is constructed. The simulation results before and after the shunt active filter was switched to the system corresponding to different firing angles of the thyristors are presented and analyzed, which demonstrate the practicability and reliability of the proposed shunt active filter scheme.展开更多
Considering the detection principle that “when load current is periodic current, the integral in a cycle for absolute value of load current subtracting fundamental active current is the least”, harmonic current real...Considering the detection principle that “when load current is periodic current, the integral in a cycle for absolute value of load current subtracting fundamental active current is the least”, harmonic current real-time detection methods for power active filter are proposed based on direct computation, simple iterative algorithm and optimal iterative algorithm. According to the direct computation method, the amplitude of the fundamental active current can be accurately calculated when load current is placed in stable state. The simple iterative algorithm and the optimal iterative algorithm provide an idea about judging the state of load current. On the basis of the direct computation method, the simple itera- tive algorithm, the optimal iterative algorithm and precise definition of the basic concepts such as the true amplitude of the fundamental active current when load current is placed in varying state, etc., the double linear construction idea is proposed in which the amplitude of the fundamental active current at the moment of the sample is accurately calculated by using the first linear construction and the condition which disposes the next sample is created by using the second linear construction. On the basis of the double linear con- struction idea, a harmonic current real-time detection method for power active filter is proposed based on the double linear construction algorithm. This method has the char- acteristics of small computing quantity, fine real-time performance, being capable of ac- curately calculating the amplitude of the fundamental active current and so on.展开更多
Relative to the power grid, the short-capacity system has smaller inertia and weaker ability to bear disturbance. As a result, the synchronous generator in short-capacity system will be greatly influenced by harmonic....Relative to the power grid, the short-capacity system has smaller inertia and weaker ability to bear disturbance. As a result, the synchronous generator in short-capacity system will be greatly influenced by harmonic. To reveal how harmonic influence the generator, this article analyzed how harmonic current will influence the output voltage. Deduced a formula that can describe the electromagnetic torque pulsation brought by the theory of Instantaneous Power, which can explain why generator’s shaft vibrates. Then this article evaluated the applicability of current filtering methods in view of characteristics of the small capacity of the system. As a result, it was demonstrated that active filtering method is best suited for small capacity system. At last, it conducted the experiment that diesel generator set supply power to non-liner load to demonstrate the conclusion of theoretical analysis.展开更多
文摘This paper first discusses the operating principle of instantaneous reactive power theory. Then, the theory is introduced into shunt active power filter and its control scheme is studied. Finally, Matlab/Simulink power system toolbox is used to simulate the system. In the simulation model, as the most common harmonic source, 3-phase thyristor bridge rectifier circuit is constructed. The simulation results before and after the shunt active filter was switched to the system corresponding to different firing angles of the thyristors are presented and analyzed, which demonstrate the practicability and reliability of the proposed shunt active filter scheme.
文摘Considering the detection principle that “when load current is periodic current, the integral in a cycle for absolute value of load current subtracting fundamental active current is the least”, harmonic current real-time detection methods for power active filter are proposed based on direct computation, simple iterative algorithm and optimal iterative algorithm. According to the direct computation method, the amplitude of the fundamental active current can be accurately calculated when load current is placed in stable state. The simple iterative algorithm and the optimal iterative algorithm provide an idea about judging the state of load current. On the basis of the direct computation method, the simple itera- tive algorithm, the optimal iterative algorithm and precise definition of the basic concepts such as the true amplitude of the fundamental active current when load current is placed in varying state, etc., the double linear construction idea is proposed in which the amplitude of the fundamental active current at the moment of the sample is accurately calculated by using the first linear construction and the condition which disposes the next sample is created by using the second linear construction. On the basis of the double linear con- struction idea, a harmonic current real-time detection method for power active filter is proposed based on the double linear construction algorithm. This method has the char- acteristics of small computing quantity, fine real-time performance, being capable of ac- curately calculating the amplitude of the fundamental active current and so on.
文摘Relative to the power grid, the short-capacity system has smaller inertia and weaker ability to bear disturbance. As a result, the synchronous generator in short-capacity system will be greatly influenced by harmonic. To reveal how harmonic influence the generator, this article analyzed how harmonic current will influence the output voltage. Deduced a formula that can describe the electromagnetic torque pulsation brought by the theory of Instantaneous Power, which can explain why generator’s shaft vibrates. Then this article evaluated the applicability of current filtering methods in view of characteristics of the small capacity of the system. As a result, it was demonstrated that active filtering method is best suited for small capacity system. At last, it conducted the experiment that diesel generator set supply power to non-liner load to demonstrate the conclusion of theoretical analysis.
