阅读说明：本技术 带有动态无功补偿装置的直流系统及其控制方法 (Direct current system with dynamic reactive power compensation device and control method thereof ) 是由 韩连山 王新宝 葛景 周启文 高玉喜 汪莹 王蒙 孙骁强 于 2019-11-14 设计创作，主要内容包括：本发明公开一种带有动态无功补偿装置的直流系统及控制方法,所述直流系统中采用动态无功补偿装置部分或者全部替换常规直流系统的固定电容补偿、或者5次及以下交流滤波器。当常规直流有功功率需要调节时,通过采集换流站电压、与系统交换电流等电气量,实现无功交换和电压联合动态无功控制,部分取代常规直流功率调制时投切滤波器操作；同时结合控制保护系统控制命令进行动态无功功率控制,进行单组滤波器投切时无功平滑控制。本发明可以减少常规直流在有功调制时交流滤波器频繁投切问题,同时单组滤波器投切与动态无功补偿协调控制,实现无功平滑控制,使常规直流适应频繁有功功率调制场合,为常规直流换流站提供动态无功支撑。(The invention discloses a direct current system with a dynamic reactive power compensation device and a control method, wherein the direct current system adopts the dynamic reactive power compensation device to partially or completely replace a fixed capacitor compensation of a conventional direct current system or an alternating current filter for 5 times or less. When the conventional direct current active power needs to be adjusted, the reactive power exchange and voltage combined dynamic reactive power control is realized by collecting the electric quantities such as converter station voltage, system exchange current and the like, and the operation of a switching filter is partially replaced when the conventional direct current power is adjusted; and meanwhile, dynamic reactive power control is carried out by combining a control command of a control protection system, and reactive smooth control is carried out when a single group of filters are switched. The invention can reduce the problem of frequent switching of the alternating current filter when the conventional direct current is subjected to active power modulation, and simultaneously, the switching of the single-group filter and the dynamic reactive power compensation are coordinated and controlled to realize reactive power smooth control, so that the conventional direct current is suitable for the occasion of frequent active power modulation, and dynamic reactive power support is provided for the conventional direct current converter station.)

1. A direct current system with a dynamic reactive power compensation device is a conventional direct current transmission system based on a power grid commutation converter (LCC); the method is characterized in that a dynamic reactive power compensation device is adopted to partially or completely replace a fixed capacitor compensation of a conventional direct current system or an alternating current filter for 5 times or less.

2. The dc system with dynamic var compensation apparatus of claim 1, wherein the dynamic var compensation apparatus comprises a static var generator, a static var compensation apparatus, a phase modulator.

3. The dc system with a dynamic reactive power compensation device according to claim 1, wherein the dc system further comprises a dc protection device, a dynamic reactive power coordination controller, a dynamic reactive power device controller;

the direct current control protection device controls the alternating current filter, the fixed capacitance compensator and the dynamic reactive power compensator according to the operation requirement of the direct current system; receiving dynamic reactive power running information sent by a dynamic reactive power coordination controller, and sending a control command to the reactive power coordination controller;

the dynamic reactive power coordination controller is communicated with the direct current control protection device and the dynamic reactive power controller to comprehensively control dynamic reactive power resources of the converter station;

and the dynamic reactive power controller is used for controlling the dynamic reactive power compensation device body, collecting the running state information of the dynamic reactive power compensation device, sending the running state information to the reactive power coordination controller, and receiving and executing a dynamic reactive power control command of the reactive power coordination controller.

4. The DC system with the dynamic reactive power compensation device according to claim 3, wherein the dynamic reactive power coordination controller communicates with each dynamic reactive power controller in a downward direction, obtains the running state information of all the dynamic reactive power compensation devices, dynamically evaluates all the dynamic reactive power compensation capabilities of the converter station, and sends a dynamic reactive power control command to the dynamic reactive power controller; and the pair is communicated with the direct current control protection device, receives the control command and the related control information sent by the direct current control protection device, and sends the dynamic reactive power evaluation result to the direct current control protection device.

5. The dc system with dynamic reactive power compensation device of claim 3, wherein the dc protection device controls the minimum branch of the ac filter and the fixed capacitance compensator or controls the whole group of branches consisting of several branches; the dynamic reactive power compensation device is controlled through communication interaction control commands and control information of the reactive power coordination controller, and a connecting switch between the dynamic reactive power compensation device and the converter station can be cut off.

6. The direct current system with the dynamic reactive power compensation device according to claim 3, wherein the dynamic reactive power coordination controller collects the voltage of a bus at the high-voltage side of the converter station, the three-phase current of all connecting lines of the converter station and the alternating current system, calculates the reactive power exchanged between the converter station and the direct current system, the collected voltage of the bus at the high-voltage side of the converter station is used for voltage control of the dynamic reactive power coordination controller, and the calculated reactive power is used for additional control of reactive power exchange.

7. The DC system with the dynamic reactive power compensation device of claim 3, wherein the dynamic reactive power coordination controller and the dynamic reactive power controller adopt high speed communication.

8. A dynamic reactive power control method of a direct current system with a dynamic reactive power compensation device is characterized in that when the reactive voltage of the system changes due to the adjustment of direct current power, steady-state reactive voltage control is carried out, and the method specifically comprises the following steps:

step 11: the dynamic reactive power coordination controller evaluates the capacitive and inductive compensation capabilities of the dynamic reactive power compensation device in real time and sends the capacitive and inductive compensation capabilities to the direct current protection device in real time;

step 12: the dynamic reactive power coordination controller calculates the target power of the dynamic reactive power compensation device according to the reactive power of the tie line/tie transformer exchange and the requirements of the upper limit and the lower limit of the reactive power exchange and sends the target power to the dynamic reactive power controller;

step 13: when the needed reactive power exceeds the compensation capability of the dynamic reactive power compensation device, the direct current control protection device switches the alternating current filter or the fixed capacitance compensator.

9. The dynamic reactive power control method of the direct current system with the dynamic reactive power compensation device is characterized in that when the voltage of the alternating current system changes greatly, transient reactive voltage combined control is carried out, and the method specifically comprises the following steps:

step 21: when the voltage change of the alternating current system is within a set value range, the dynamic reactive power control adopts the fixed reactive power control;

step 22: when the voltage change of the alternating current system exceeds a set fixed value, the dynamic reactive power control is automatically switched to the voltage control, and the reactive power of the dynamic reactive power compensation device is adjusted according to the voltage closed loop of the alternating current system;

step 23: when the voltage of the alternating current system is recovered to a set value within a first preset time, the dynamic reactive power control is automatically switched to the fixed reactive power control, and the reactive power control aims at the reactive power before the switching to the reactive power control.

10. A dynamic reactive power control method of a direct current system with a dynamic reactive power compensation device is characterized in that when a direct current protection device switches a filter, the switching of the filter is smoothly controlled, and the method specifically comprises the following steps:

step 31: the dynamic reactive power coordination control device evaluates the reactive power before and after switching of the required switching alternating current filter or the fixed capacitor compensator in real time according to the current voltage;

step 32: the dynamic reactive power coordination control device acquires a switching filter trip signal from the direct current protection device and executes the following operations by combining the reactive power:

(1) the reactive power before switching is maintained to be unchanged through dynamic reactive power control;

(2) and smoothing transition control within a second preset time by taking the evaluated magnitude of the switched reactive power as a target.

Technical Field

The invention relates to a conventional direct current system with a dynamic reactive power compensation device and a dynamic reactive power control method thereof, in particular to a dynamic reactive power configuration and control method of a conventional direct current converter station.

Background

Energy development in China has certain regionality, and new energy represented by photovoltaic and wind power is usually concentrated in areas with rich illumination and wind energy, such as northwest areas of China. In order to improve the power transmission capacity of the western and east electricity, a plurality of loops of high-capacity direct current are constructed in a matching way.

At present, the conventional direct-current transmission technology based on a power grid commutation converter (LCC) is mostly adopted for large-scale direct-current transmission, and when the direct-current transmission is operated, the converter generates a large amount of harmonic waves and needs to be provided with a large amount of filters for filtering; the larger the direct current power is, the higher the harmonic content is, the more the number of filter groups is required, and the filter needs to be dynamically switched according to the direct current power. In addition, the conventional direct current is closely coupled with active power and reactive power, when the operating power of a direct current system changes, the reactive power consumed by a converter changes, and in order to maintain the reactive power exchanged with an alternating current power grid or the voltage of a converter station basically unchanged, compensation is carried out by switching an alternating current filter or a fixed capacitor compensator.

Due to national environmental protection requirements, a low-power thermal power generating unit with high energy consumption is gradually shut down, the permeability of new energy is continuously increased along with the large-scale development of new energy in the future, the peak regulation problem of a power grid is more and more prominent, the peak regulation requirement of the power grid cannot be met only by relying on the peak regulation of conventional units such as thermal power and the like, conventional direct current is required to participate in the peak regulation of the power grid, however, after the conventional direct current is actively regulated, the reactive power consumption is changed, the switching is required to be matched with an alternating current filter or a fixed capacitor compensator, and the frequent switching of a mechanical.

In addition, large-scale new energy development deteriorates the frequency characteristic of a power grid, the frequency of the power grid changes obviously after a high-power direct current fault occurs, if direct current participates in power grid frequency modulation, the problem of the power grid frequency can be obviously relieved, however, the problem is limited by the problem of filter switching, and conventional direct current cannot deeply participate in the power grid frequency modulation.

Disclosure of Invention

In order to solve the problem of frequent action of an alternating current filter or a fixed capacitance compensator switch caused by frequent regulation of conventional direct current power, the invention provides a direct current system with a dynamic reactive compensation device and a dynamic reactive control scheme thereof, which can increase the frequent regulation range and depth of conventional direct current and are beneficial to frequent participation of conventional direct current in system frequency modulation and peak regulation.

In order to achieve the purpose, the invention adopts the technical scheme that:

a direct current system with a dynamic reactive power compensation device is a conventional direct current transmission system based on a power grid commutation converter (LCC); the dynamic reactive power compensation device is adopted to partially or completely replace the fixed capacitance compensation of a conventional direct current system or an alternating current filter for 5 times or less.

Further, the dynamic reactive power compensation device comprises a static var generator, a static var compensation device and a phase modulator.

Further, the direct current system further comprises a direct current protection device, a dynamic reactive power coordination controller and a dynamic reactive power device controller.

The direct current control protection device controls the alternating current filter, the fixed capacitance compensator and the dynamic reactive power compensator according to the operation requirement of the direct current system; and receiving the dynamic reactive power running information sent by the dynamic reactive power coordination controller, and sending a control command to the reactive power coordination controller.

The dynamic reactive power coordination controller is communicated with the direct current control protection device and the dynamic reactive power controller to comprehensively control dynamic reactive power resources of the converter station.

And the dynamic reactive power controller is used for controlling the dynamic reactive power compensation device body, collecting the running state information of the dynamic reactive power compensation device, sending the running state information to the reactive power coordination controller, and receiving and executing a dynamic reactive power control command of the reactive power coordination controller.

Further, in the above dc system, the dynamic reactive power coordination controller communicates with each dynamic reactive power controller downward, obtains running state information of all dynamic reactive power compensation devices, dynamically evaluates all dynamic reactive power compensation capabilities of the converter station, and sends a dynamic reactive power control command to the dynamic reactive power controller; and the pair is communicated with the direct current control protection device, receives the control command and the related control information sent by the direct current control protection device, and sends the dynamic reactive power evaluation result to the direct current control protection device.

Further, in the above dc system, the dc protection device controls a minimum branch of the ac filter and the fixed capacitance compensator or controls a large group of branches composed of a plurality of branches; the dynamic reactive power compensation device is controlled through communication interaction control commands and control information of the reactive power coordination controller, and a connecting switch between the dynamic reactive power compensation device and the converter station can be cut off.

Further, in the above dc system, the dynamic reactive power coordination controller collects a voltage of a bus at a high voltage side of the converter station, and three-phase currents of all connection lines of the converter station and the ac system, and calculates a reactive power exchanged between the converter station and the dc system, where the collected voltage of the bus at the high voltage side of the converter station is used for voltage control of the dynamic reactive power coordination controller, and the calculated reactive power is used for additional control of reactive power exchange.

Further, in the above dc system, the dynamic reactive power coordination controller and the dynamic reactive power controller adopt high-speed communication.

The invention also provides a dynamic reactive power control method of the direct current system with the dynamic reactive power compensation device, when the reactive voltage of the system changes due to the adjustment of the direct current power, the steady-state reactive voltage control is carried out, and the method specifically comprises the following steps:

step 11: the dynamic reactive power coordination controller evaluates the capacitive and inductive compensation capabilities of the dynamic reactive power compensation device in real time and sends the capacitive and inductive compensation capabilities to the direct current protection device in real time;

step 12: the dynamic reactive power coordination controller calculates the target power of the dynamic reactive power compensation device according to the reactive power of the tie line/tie transformer exchange and the requirements of the upper limit and the lower limit of the reactive power exchange and sends the target power to the dynamic reactive power controller;

step 13: when the needed reactive power exceeds the compensation capability of the dynamic reactive power compensation device, the direct current control protection device switches the alternating current filter or the fixed capacitance compensator.

The invention also provides another dynamic reactive power control method of the direct current system with the dynamic reactive power compensation device, when the voltage of the alternating current system is greatly changed, the transient reactive voltage combined control is carried out, and the method specifically comprises the following steps:

step 21: when the voltage change of the alternating current system is within a set value range, the dynamic reactive power control adopts the fixed reactive power control;

step 22: when the voltage change of the alternating current system exceeds a set fixed value, the dynamic reactive power control is automatically switched to the voltage control, and the reactive power of the dynamic reactive power compensation device is adjusted according to the voltage closed loop of the alternating current system;

step 23: when the voltage of the alternating current system is recovered to a set value within a first preset time, the dynamic reactive power control is automatically switched to the fixed reactive power control, and the reactive power control aims at the reactive power before the switching to the reactive power control.

The invention provides a dynamic reactive power control method of a direct current system with a dynamic reactive power compensation device, which is used for carrying out filter switching smooth control when a direct current protection device switches a filter, and specifically comprises the following steps:

step 31: the dynamic reactive power coordination control device evaluates the reactive power before and after switching of the required switching alternating current filter or the fixed capacitor compensator in real time according to the current voltage;

step 32: the dynamic reactive power coordination control device acquires a switching filter trip signal from the direct current protection device and executes the following operations by combining the reactive power:

(1) the reactive power before switching is maintained to be unchanged through dynamic reactive power control;

(2) and smoothing transition control within a second preset time by taking the evaluated magnitude of the switched reactive power as a target.

The invention has the beneficial effects that:

(1) the dynamic reactive power compensation device is used for replacing a conventional low-order alternating current filter or a fixed capacitor compensator of the direct current converter station, when the direct current running power changes, the dynamic reactive power compensation device is mainly used for reactive power control, and the times of switching the alternating current filter or the fixed capacitor compensator are reduced by changing the reactive power of the dynamic reactive power compensation device, so that the conventional direct current can better participate in system peak regulation, and the new energy accepting capability of a power grid is improved. When the low-order filter is replaced by the dynamic reactive power compensation device, the dynamic reactive power compensation device has the double functions of active filtering and dynamic reactive power compensation.

(2) The conventional direct current converter station does not have dynamic reactive power compensation capability, and a certain dynamic reactive power compensation capability is provided for the conventional direct current by substitution, so that the voltage stability level of a system is enhanced, and the voltage fluctuation level of the system after faults such as phase change failure and the like is reduced.

(3) The invention also implements smooth control on the switching of the single group of filters, and reduces the reactive impact of the switching of the filters and the like on the power grid.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic configuration diagram of a dc converter station with a dynamic reactive power compensation device according to the present invention;

FIG. 2 illustrates the connection and communication flow between controllers in a DC system;

FIG. 3 is a schematic diagram of a tie line (change) swap reactive power control flow;

FIG. 4 is a reactive voltage combination control flow chart;

fig. 5 is a schematic diagram of cutting off reactive power variation of a single set of ac filter systems.

Detailed Description

The invention will be further explained with reference to the drawings.

The direct current system with the dynamic reactive power compensation device is a conventional direct current transmission system based on a power grid commutation converter (LCC); the dynamic reactive power compensation device is adopted to partially or completely replace the fixed capacitance compensation of a conventional direct current system or an alternating current filter for 5 times or less. The dynamic reactive power compensation device comprises a static reactive power generator, a static reactive power compensation device and a phase modulator. When the filter bank is replaced by 5 times or less, the dynamic reactive power compensation device has double functions of active filtering and dynamic reactive power compensation.

In the embodiment shown in fig. 1, the dc rectifying side converter station and the inverter side converter station are both conventional, and the rectifying side filtering system is divided into four groups according to the filter and fixed capacitance compensator types, each group includes a group of 11 and 13 (HP11/13) filters, a group of 24 and 26 (HP24/26) filters, a group of 3 (HP3) filters and two groups of fixed capacitance compensators (SC), and each group of filters or fixed capacitance compensators has a capacity of 200 MVar. The inverter side filtering system is also divided into four large groups according to the types of the filters and the fixed capacitance compensators, each large group comprises a group of 12-order (HP12/14) filters and 14-order (HP12/14) filters and two groups of fixed capacitance compensators (SC), and the capacity of each group of filters or fixed capacitance compensators is 200 MVar.

The embodiment adopts a dynamic reactive power compensation device, namely a static var generator (SVG/STATCOM), to replace a fixed capacitance compensator, as a conventional device with dynamic reactive power compensation, as shown in FIG. 1.

In this embodiment, the voltage class of the dc-side ac system is 500kV, and the dc voltage class is 800 kV.

After the conventional direct current converter station is provided with a part of dynamic reactive power compensation devices, the control part acquires the electric quantities such as converter station voltage, system exchange current and the like to realize reactive power exchange and voltage combined dynamic reactive power control, and the switching filter is operated when the conventional direct current power modulation is partially replaced; and meanwhile, dynamic reactive power control is performed by combining a control command of a control protection device, and reactive smooth control is performed when a single group of filters are switched. The invention can reduce the problem of frequent switching of the alternating current filter and the fixed capacitance compensator when the conventional direct current is subjected to active power modulation, and simultaneously, the switching of the single-group alternating current filter and the dynamic reactive power compensation are coordinated and controlled to realize the reactive power smooth control, so that the conventional direct current is suitable for the occasion of frequent active power modulation.

As shown in fig. 2, the dc system further includes a dc protection device, a dynamic reactive power coordination controller, and a dynamic reactive power device controller, for controlling the reactive power of the system.

The direct current control protection device controls the alternating current filter, the fixed capacitance compensator and the dynamic reactive compensator according to the operation requirement of a direct current system; and receiving the dynamic reactive power running information sent by the dynamic reactive power coordination controller, and sending a control command to the reactive power coordination controller.

The dynamic reactive power coordination controller is communicated with the direct current control protection device and the dynamic reactive power controller to comprehensively control dynamic reactive power resources of the converter station.

The dynamic reactive power controller is used for controlling the dynamic reactive power compensation device body, collecting running state information of the dynamic reactive power compensation device, sending the running state information to the reactive power coordination controller, and receiving and executing a dynamic reactive power control command of the reactive power coordination controller. And the dynamic reactive power coordination controller and the dynamic reactive power controller adopt high-speed communication.

In a preferred embodiment, the dynamic reactive power coordination controller communicates with each dynamic reactive power controller to obtain the running state information of all dynamic reactive power compensation devices, dynamically evaluates all dynamic reactive power compensation capabilities of the converter station, and sends a dynamic reactive power control command to the dynamic reactive power controllers; and the pair is communicated with the direct current control protection device, receives the control command and the related control information sent by the direct current control protection device, and sends the dynamic reactive power evaluation result to the direct current control protection device.

In a preferred embodiment, the dc protection device controls a minimum branch of the ac filter and the fixed capacitance compensator or controls a large group of branches composed of a plurality of branches; the dynamic reactive power compensation device is controlled through communication interaction control commands and control information of the reactive power coordination controller, and a connecting switch between the dynamic reactive power compensation device and the converter station can be cut off.

In a preferred embodiment, the dynamic reactive power coordination controller collects the voltage of a bus at the high-voltage side of the converter station and the three-phase current of all connecting lines of the converter station and the alternating current system, calculates the reactive power exchanged between the converter station and the direct current system, uses the collected voltage of the bus at the high-voltage side of the converter station for voltage control of the dynamic reactive power coordination controller, and uses the calculated reactive power for additional control of reactive power exchange.

The dynamic reactive power control method of the direct current system mainly comprises three methods, namely a method 1: controlling steady-state reactive voltage; the second method comprises the following steps: performing transient reactive voltage joint control; the third method comprises the following steps: and (5) smoothly controlling the switching of the filter.

An embodiment of a dynamic reactive power control method of a dc system with a dynamic reactive power compensation device according to the present invention is shown in fig. 3, and when a reactive voltage of the system changes due to adjustment of dc power, steady-state reactive voltage control is performed, and the specific control method is as follows:

step 1: the dynamic reactive power coordination controller evaluates the capacitive and inductive compensation capabilities of the dynamic reactive power compensation device in real time and sends the capacitive and inductive compensation capabilities to the direct current protection device in real time;

step 2: the dynamic reactive power coordination controller calculates the target power of the dynamic reactive power compensation device according to the reactive power exchanged by the connecting line (transformer) and the requirements of the upper limit and the lower limit of the reactive power exchange and sends the target power to the dynamic reactive power controller;

and step 3: when the needed reactive power exceeds the compensation capability of the dynamic reactive power compensation device, the direct current control protection device switches the alternating current filter or the fixed capacitance compensator.

Fig. 4 shows an embodiment of a dynamic reactive power control method for a dc system with a dynamic reactive power compensation device, which performs transient reactive voltage joint control when the ac system voltage changes greatly due to a fault in the ac system or the dc system, and the like, and specifically includes the following steps:

step 1: when the voltage change of the alternating current system is within a set value range, the dynamic reactive power control adopts the fixed reactive power control;

step 2: when the voltage change of the alternating current system exceeds a set fixed value, the dynamic reactive power control is automatically switched to the voltage control, and the power of the dynamic reactive power compensation device is adjusted in a closed loop mode according to the voltage of the alternating current system;

and step 3: when the voltage of the alternating current system is recovered to a set fixed value within the time Tdelay, the dynamic reactive power control is automatically switched to the fixed reactive power control, and the reactive power control aims at the reactive power before the reactive power control is switched.

In the third embodiment of the dynamic reactive power control method for the direct current system with the dynamic reactive power compensation device, when the direct current protection device switches the filter, the switching of the filter is smoothly controlled, and the specific control method comprises the following steps:

step 1: the dynamic reactive power coordination control device evaluates the reactive power before and after switching of the required switching alternating current filter or the fixed capacitor compensator in real time according to the current voltage;

step 2: the dynamic reactive power coordination control device acquires a switching filter trip signal from the direct current protection device and executes the following operations by combining the reactive power:

(1) the reactive power before switching is maintained to be unchanged through dynamic reactive power control;

(2) and (5) smoothly transiting control within the time Tset1 by taking the evaluated reactive power after switching as a target. The schematic diagram of the reactive power change of the cut-off single-group alternating current filter system is shown in figure 5.

The above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and various modifications or changes made with reference to the above embodiments are within the scope of the present invention.