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Method and system for controlling transient electric quantity of fan

A control method and transient current technology, applied in the direction of electrical components, DC power supply parallel operation, load balance in DC network, etc., can solve problems such as insufficient voltage inertia, poor DC voltage mutation ability, small value of voltage stabilizing capacitor, etc. To achieve the effect of expanding the voltage margin, increasing the electromagnetic power, and reducing the rotor speed

Pending Publication Date: 2021-11-30
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, DC power grids pay more attention to steady-state operation when selecting electrical equipment. The value of the voltage stabilizing capacitor on the DC side is generally small, and the voltage inertia is insufficient after encountering disturbances, and the ability to suppress DC voltage mutations is poor.
With the continuous increase of distributed power sources and constant power loads, the negative damping characteristics of DC voltage in the dynamic process aggravate the risk of induced voltage oscillation

Method used

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  • Method and system for controlling transient electric quantity of fan
  • Method and system for controlling transient electric quantity of fan
  • Method and system for controlling transient electric quantity of fan

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0092] In order to verify the effectiveness of the proposed control strategy, this embodiment builds a DC power grid hardware-in-the-loop simulation test system, such as Figure 4 shown. In the test system, the energy storage side converter B-DC adopts the U-I droop control method; the load side converter L-VSC (AC load) and L-DC (DC load) both adopt constant power control; the fan adopts MPPT ( Maximum Power Point Tracking (Maximum Power Point Tracking) control, the power collected by the wind turbine side converter W-VSC is connected to the DC grid. The basic parameters of the model are shown in Table 1. In order to test whether the DC voltage limit value is consistent with the theoretical analysis, the droop characteristic coefficient is set to k in the test system Bi = 3, the value of this coefficient is slightly larger than the droop coefficient in traditional control, and it is used to simulate the low-pressure operating state of the system.

[0093] Table 1 Model par...

example 2

[0099] In order to verify the voltage limit value in the second layer control mode of the DC grid, the system is in different degrees of step-down operation state by changing the voltage droop reference value of the energy storage side converter. The following three schemes are selected: at 1.0s, the DC voltage droop control reference value is reduced from the initial value of 500V to 485V, 470V, and 450V, respectively, and they are all restored after 1.5s. DC current I of equivalent load dc , DC voltage U dc and active power P LΣ The dynamic response of Figure 5 , 6 , 7 shown.

[0100] combine Figure 8 , in the first two calculation examples, the calculated values ​​of the stable DC voltage are 312V and 270V respectively, which are higher than the limit value of 233V, and the unbalanced current accumulated power ΔQ LΣ -ΔQ sΣ They are 0.075C and 0.195C respectively, both of which are less than the maximum charge ΔQ allowed by the system 2max . However, in Calculatio...

example 3

[0103] In order to verify the support effect of wind turbine transient power control on DC voltage transient stability, the following three calculation examples are set up:

[0104] 1) With traditional control, the voltage drops to U dc C2 , remove the fault;

[0105] 2) The fan side adopts transient power control, and the voltage drops to U dc C2 , remove the fault;

[0106] 3) Transient power control is adopted on the fan side, and the failure time is further extended. The dynamic response of the system is as Figure 9 shown.

[0107] Known U dc * =500V, C dc = 3mF, combined with the test data in Example 1, when the traditional control is adopted, the actual initial voltage U of the stable operation of the system B0 = 330V. Such as Figure 9 As shown, in Calculation Example 1, after a fault occurs on the DC side, the bus voltage drops rapidly to 230V, which is close to the theoretically calculated voltage limit. After the fault is cleared, since the converters at ...

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Abstract

The invention discloses a method and system for controlling the transient electric quantity of a fan. The method comprises the steps of detecting a bus voltage instantaneous value of a direct-current power grid, and judging whether the bus voltage instantaneous value is less than a two-layer voltage limit value in a second-layer control mode or not; and when the bus voltage instantaneous value is lower than the two-layer voltage limit value, enabling the fan side to adopt a transient electric quantity control method for control, wherein the step specifically comprises the sub-steps of calculating transient electric quantity required to be provided by the fan in a third-layer control mode according to the maximum discharge electric quantity of two-layer control of the direct-current power grid determined by a second-layer control mode; calculating additional transient current according to the transient electric quantity; and introducing the additional transient current into the fan side converter. According to the invention, it is ensured that the system still has the capability of establishing stable operation after disturbance or fault recovery, and the transient stability of the direct current system is enhanced.

Description

technical field [0001] The invention relates to the technical field of direct current power grid power control, in particular to a method and system for controlling transient power of a wind turbine. Background technique [0002] The DC power grid not only simplifies the commutation links of wind power, photovoltaic and DC loads, but also reduces the cost of networking and operation, and there are no problems such as frequency, power angle and reactive power compensation. power supply. However, DC power grids pay more attention to steady-state operation when selecting electrical equipment. The value of the voltage stabilizing capacitor on the DC side is generally small, and the voltage inertia is insufficient after encountering disturbances, and the ability to suppress DC voltage mutations is poor. With the continuous increase of distributed power sources and constant power loads, the negative damping characteristics of DC voltage in the dynamic process aggravate the risk o...

Claims

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Application Information

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IPC IPC(8): H02J1/10H02J1/14
CPCH02J1/10H02J1/14H02J2300/28
Inventor 张祥宇赵欣艳付媛
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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