Composite direct current power modulation method for out-of-limit control of alternating current section power

Abstract

The invention provides a composite direct current power modulation method for out-of-limit control of alternating current section power, including the following steps of: calculating direct current power modulation quantity Pmod by alternating current tie line power Pac, to achieve control on fluctuation of the alternating current section power; judging whether the alternating current section power is out of limit by the alternating current tie line power Pac, and if yes , executing the step 3; calculating direct current power emergency control quantity Pemg, and thereby completing the out-of-limit control of alternating current section power. According to composite direct current power modulation method for the out-of-limit control of the alternating current section power, through compounding the direct current power emergency control function on the general direct current power modulation function, an additional monitoring device is not required, namely, the power vacancy of the regional power grid is compensated by emergency power control while achieving the cross-distinct power grid alternating current tie line power fluctuation, the steady state stability limit of the alternating current tie line is kept undamaged, and thereby the transient state and dynamic stability characteristics of the large area interconnected power grid with the complex operation mode and under the complex operating condition can be improved at the same time.

Description

technical field [0001] The invention relates to a modulation method, in particular to a direct current power modulation method for compound alternating current section power over-limit control. Background technique [0002] For the AC-DC hybrid grid, the application of DC power modulation technology can suppress the power / voltage / frequency fluctuations of the AC grid. The DC power modulation technology calculates the modulation quantity by collecting the electrical quantity of the AC system and designing a letter, and sends the calculation result to the controlled DC to modulate the DC transmission power, so as to suppress the system oscillation. [0003] The commonly used DC power modulation technology damps the system oscillation by continuously changing the DC transmission power. When the system oscillation is suppressed, the DC transmission system will gradually recover to the transmission power before the fault. However, if the system oscillation is caused by some unce...

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Problems solved by technology

However, if the system oscillation is caused by some uncertain fault that leads to a power shortage in the regional power grid (such as shutdown, DC blocking, etc.), when the system oscillation gradually subsides, the AC grid may still be in an unsafe state, such as The frequency of the regional power grid is suspended, and the transmission power of the cross-region tie line is close to or exceeds the limit of temporary stability / static stability. At this time, the DC modulation function no longer operates, which may cause the system to lose stability.

[0004] For the power shortage of the regional power grid caused by the above-mentioned uncertain faults, the power grid is usually regulated through low-cycle load shedding, AGC (automatic generation control) or frequency modulation of the direct current transmission system, but these methods usually have a shorter action period. Long time and slow response, it is difficult to meet the requirements for stability control of cross-regional power grids

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