Improvement fundamental frequency modulation method for cascade static synchronous compensator
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A technology of static synchronous compensation and fundamental frequency modulation, applied in reactive power adjustment/elimination/compensation, flexible AC transmission system, etc.
Inactive Publication Date: 2013-10-02
STATE GRID CORP OF CHINA +1
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[0005] The purpose of the present invention is to solve the problem that the difference between the output fundamental amplitude and the expected value of the traditional cascaded static synchronous com
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specific Embodiment approach 1
[0027] Specific embodiment one: the improved fundamental frequency modulation method of the cascaded static synchronous compensator (STATCOM) described in this embodiment is realized through the following steps:
[0028] Step 1. Determine system voltage, reactive current that needs to be compensated by connecting reactance and load;
[0029] Step 2. Calculate the initial DC voltage V according to the system voltage determined in step 1, the connected reactance and the reactive current that needs to be compensated by the load. DC0 , DC side capacitance C dc , output voltage V C and capacitive reactive current I 1 ;
[0030] Step 3. Use the following transcendental equation to solve the angle α i ,
[0031] f ( 1 ) = Σ i = 1 ...
specific Embodiment approach 2
[0042] Embodiment 2: The difference between this embodiment and the improved fundamental frequency modulation method of the cascaded static synchronous compensator (STATCOM) described in Embodiment 1 is that the reactive power required to be compensated by the load described in Step 1 is The method of obtaining the current is: detecting the load current, and decomposing the load current into two parts which are the same as the voltage phase and 90 degrees different from the voltage phase, and the part which is 90 degrees different from the voltage phase is the uncompensated part that the load needs to compensate. work current.
specific Embodiment approach 3
[0043] Specific implementation mode three: combination Figure 1 to Figure 7 Describe this embodiment, the difference between this embodiment and the improved base frequency modulation method of the cascaded static synchronous compensator (STATCOM) described in the first embodiment is that the establishment method of the transcendental equation described in the third step includes the following content:
[0044] 1. Establish a mathematical model of a single H-bridge converter
[0045] For the voltage-type static synchronous compensator, according to the static synchronous compensator, the circuit expression is expressed as:
[0046] V C = 4 MV dc 0 π ...
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Abstract
The invention provides an improvement fundamental frequency modulation method for a cascade static synchronous compensator, and relates to the technical field of fundamental frequency modulation for the cascade static synchronous compensator. The method aims to solve the problem that the switching angle acquired by the fundamental frequency modulation of the conventional cascade static synchronous compensator is inaccurate. The method provided by the invention creates transcendental equation according to cascade direct-current-side voltage fluctuation characteristic, so as to acquire a more accurate switching angle; the creating method of the transcendental equation comprises a mathematic model analysis of a single H bridge converter and mathematic model analyses of multi-level cascade converter composed by m H bridge units, introduction of an actual compensating parameter to an alternating current output voltage equation during mathematic model analysis of the single H bridge converter, and the solving of transcendental equation using Newton iteration method. The method provided by the invention has the advantages of good harmonic cancellation effect, large modulation ratio M, and high static synchronous compensator dynamic property; the method can be applied to the cascade static synchronous compensator with stable system voltage.
Description
technical field [0001] The invention relates to the technical field of fundamental frequency modulation of cascaded static synchronous compensators. Background technique [0002] Static synchronous compensator (STATCOM), as a new type of static var compensator, has the incomparable advantages of traditional thyristor-based SVC, and has received extensive attention. Its application and research have also developed to high-voltage and large-capacity. Due to the advantages of low electromagnetic interference and low switching frequency, multilevel converters have become the first choice for high voltage and large capacity, and are widely used in various power electronic devices. Cascaded multilevel converter, in addition to the advantages of small harmonics, low loss, and low cost, also has a simple structure, requires few devices, and is easy to expand and package. It is the best structure for large-capacity multi-level. The focus and focus of research in recent years. [00...
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