A current-limited controllable phase shifter and a control method thereof

Abstract

The application discloses a current-limiting controllable phase shifter and a control method thereof, which is installed at a power distribution network loop closing point to realize AC loop closing of the power distribution network, and comprises a controllable phase shifter, a current-limiting reactor and a fast tie switch K2 connected in series, and fast bypass switches K1 connected in parallel at both ends of the current-limiting reactor; each component is controlled to adapt to different operation states of the power distribution network. The application can realize AC loop closing of the power distribution network, solves the contradiction between poor reliability of open-loop operation and electromagnetic loop network existing in closed-loop operation of the power distribution network, and has low equipment cost and saves land occupation; meanwhile, the application realizes power flow control after being connected, and can greatly promote local consumption of new energy.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flexible alternating current equipment and its control and protection, and particularly relates to a current-limiting controllable phase shifter and a control method thereof. BACKGROUND

[0002] The existing distribution network has a single network structure, and generally adopts an open-loop operation mode, but the power supply reliability is poor. The closed-loop power supply mode can improve the operation economy and reliability of the distribution system to a certain extent, but the negative problems such as circulating power, electromagnetic loop network, expansion of fault range, and increase of short-circuit current may be brought about, which greatly limits the application scenarios of the closed-loop mode.

[0003] Regional interconnection can be realized through power electronic equipment such as flexible direct current systems, but there are problems such as low reliability, high investment, complex operation and maintenance, and strong application scenario limitations. SUMMARY

[0004] The purpose of the present application is to provide a current-limiting controllable phase shifter and a control method thereof, which can realize distribution network alternating current loop closing and solve the contradiction between the poor reliability of open-loop operation of the distribution network and the electromagnetic loop network existing in the closed-loop operation.

[0005] Technical solution: The current-limiting controllable phase shifter of the present application is installed at the loop closing point of the distribution network to realize distribution network alternating current loop closing, and comprises a controllable phase shifter, a current-limiting reactor and a fast tie switch K2 connected in series, and the current-limiting reactor is connected with a fast bypass switch K1 in parallel at both ends; each component is controlled to adapt to different operating states of the distribution network.

[0006] The fast bypass switch K1 and the fast tie switch K2 use current instantaneous value as the basis for judging the opening and closing actions, so as to improve the data processing speed, and the opening and closing actions can usually be completed within tens of milliseconds.

[0007] The present application also includes a control method for the current-limiting controllable phase shifter, and the control method comprises non-power-off switching operation control, steady-state optimal operation control, power flow transfer limit control and loop line short-circuit fault isolation control.

[0008] The steady-state optimal operation control is performed during normal operation, the fast bypass switch K1 and the fast tie switch K2 are both closed, and the controllable phase shifter controls the tie line to realize power flow regulation.

[0009] The controller of the controllable phase shifter controls the controllable phase shifter according to the collected line outgoing current, the controller calculates the controllable phase shifter adjustment amount in combination with the control target, and sends the adjustment amount to the adjustment mechanism of the controllable phase shifter to execute power flow regulation.

[0010] When the distribution network line performs no power switching operation, the no power switching operation control is performed, the fast bypass switch K1 and the fast contact switch K2 are both closed, the controllable phase shifter is used to control the voltage on both sides of the switch to be closed during switching, so as to avoid the excessive impact current or steady current during closing, which causes the distribution network protection to act.

[0011] The controller of the controllable phase shifter calculates the adjustment amount of the controllable phase shifter according to the voltage on both sides of the switch to be closed, combines the control target, and sends the adjustment mechanism of the controllable phase shifter to execute voltage adjustment.

[0012] The controllable phase shifter adopts a mechanical controllable phase shifter or a thyristor controllable phase shifter, wherein the adjustment mechanism of the mechanical controllable phase shifter is a load regulating switch, and the adjustment mechanism of the thyristor controllable phase shifter is a power electronic device.

[0013] When the power flow transfer causes the current of the ring line to exceed the limit, the power flow transfer over-limit control is performed, the controller of the controllable phase shifter controls the fast bypass switch K1 to be opened, the current limiting reactor is connected to the ring network, and the fast contact switch K2 remains closed, so that the controller of the controllable phase shifter controls the power exchange between the two sides of the power grid.

[0014] When the ring line short circuit fault occurs in the distribution network, the ring line short circuit fault isolation control is performed, the controller of the controllable phase shifter controls the fast contact switch K2 to be opened quickly, and the fast bypass switch K1 remains closed.

[0015] The present application has the following advantages compared with the prior art: (1) The phase shifter, fast switch and current limiting reactor are jointly designed and combined to meet the four operating conditions of ring closing operation, steady state optimization operation, power flow transfer and short circuit current limiting, and the main contradiction of AC ring closing operation is solved. The AC ring closing operation improves the reliability and flexibility of the distribution network operation, and can realize the optimal adjustment of power flow. (2) The controllable phase shifter is used, and the manufacturing difficulty and mechanical structure are similar to those of a transformer. Compared with the regional interconnection through flexible DC system and other power electronic equipment, the controllable phase shifter has the advantages of high ring closing reliability, low investment and simple operation and maintenance. (3) Through the power flow optimization control, the local consumption of new energy can be promoted, and the realization of the double carbon target can be supported. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The topology diagram of the current limiting controllable phase shifter of the present application is shown in the figure.

[0017] Figure 2 The flow chart of the current limiting controllable phase shifter of the present application for ring closing operation is shown in the figure. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be described in detail below in combination with the specific embodiments and the drawings of the specification.

[0019] As Figure 1 shown, the current-limiting controllable phase shifter of the present application comprises a controllable phase shifter, a current-limiting reactor, a fast bypass switch K1 and a fast tie switch K2, wherein the controllable phase shifter, the current-limiting reactor and the fast tie switch K2 are connected in series, and the fast bypass switch K1 is connected in parallel across the current-limiting reactor. The current-limiting controllable phase shifter of the present application is installed at a tie-in point of a distribution network, realizes interconnection of an AC system of the distribution network, and improves power supply capacity of the two sides of the distribution network. The controllable phase shifter can be a mechanical controllable phase shifter, a thyristor controllable phase shifter, a transverse adjustment type controllable phase shifter, a longitudinal adjustment type controllable phase shifter or a comprehensive adjustment type controllable phase shifter, wherein the voltage regulating mechanism of the mechanical controllable phase shifter is a load regulating switch, and the voltage regulating mechanism of the thyristor controllable phase shifter is a power electronic device. In the embodiment, the controllable phase shifter is a mechanical controllable phase shifter. The fast bypass switch K1 and the fast tie switch K2 use current instantaneous value as a basis for judging the on-off action, so as to improve data processing speed, and the on-off action can be completed within tens of milliseconds.

[0020] The present application also includes a control method of the current-limiting controllable phase shifter, which jointly designs and combines controls the controllable phase shifter, the fast switch and the current-limiting reactor, and can adaptively regulate power flow and quickly limit current or open according to operating conditions, so as to meet requirements of tie-in operation, steady-state optimal operation, power flow transfer and short-circuit current limiting, solve main contradictions of AC tie-in operation, and the action of the current-limiting controllable phase shifter and control targets under each operating condition are shown in Table 1.

[0021] Table 1 Action of the current-limiting controllable phase shifter under each operating condition

[0022]

[0023] Steady-state optimal operation control: when normally operating, the fast bypass switch K1 and the fast tie switch K2 are both on, and the controllable phase shifter controls power flow of the tie line. The controller of the controllable phase shifter collects line outgoing current through a current transformer, calculates controllable phase shifter adjustment amount according to a control target, and sends the load regulating switch of the controllable phase shifter to execute power flow regulation. The control target can include power flow balancing, prevention of overcurrent limiting, etc.

[0024] Non-power-off switching operation (tie-in operation) control: when a distribution network line connected thereto performs switching operation, it can be used to realize non-power-off switching operation. When performing switching operation, the fast bypass switch K1 is on, the fast tie switch K2 is on, and the controllable phase shifter controls voltages on both sides of the switch to be on during switching operation to be equal, so as to avoid excessive switching current or steady-state current during switching on causing distribution network protection action. The controller collects voltages on both sides of the switch to be on during switching operation through a voltage transformer, calculates controllable phase shifter adjustment amount according to a control target, and sends the load regulating switch of the controllable phase shifter to execute voltage regulation.

[0025] As Figure 2 shown, the current limiting controllable phase shifter auxiliary power grid loop operation includes the following steps:

[0026] (1) Calculate whether the loop current without phase shifter meets the allowable condition, if it meets, directly develop loop hot reverse operation; If it does not meet the condition, auxiliary power grid loop hot reverse is developed by using controllable phase shifter;

[0027] (2) The voltage phase angle of the access point is calculated and executed by the controllable phase shifter;

[0028] (3) Test whether the loop current after the adjustment of the controllable phase shifter meets the allowable condition, if it meets, develop phase shifter auxiliary loop hot reverse operation; If it does not meet the condition, the controllable phase shifter is recalculated and adjusted.

[0029] Tidal transfer control: the line current is collected by the current transformer, when the controller of the controllable phase shifter detects that the line current exceeds the set value 1, it is determined that the loop current tidal transfer, the controller controls the fast bypass switch K1 to quickly open, the current limiting reactor is quickly inserted into the loop network, the fast tie switch K2 remains closed, so that the controller of the controllable phase shifter two sides of the power grid power mutual aid, and avoids the protection action caused by the current surge.

[0030] Loop line short circuit fault isolation control: when the controller of the controllable phase shifter detects that the line current exceeds the set value 2, it is determined that the loop line is short-circuited, the controller controls the fast tie switch K2 to quickly open, the fast bypass switch K1 remains closed, the controllable phase shifter two sides of the distribution network is divided into two columns, avoiding the expansion of the fault range.

Claims

1. A control method for a current-limiting controllable phase shifter, characterized in that, This method is applied to a current-limiting controllable phase shifter, which is installed at the loop closing point of the distribution network to realize AC loop closing of the distribution network. It includes a controllable phase shifter, a current-limiting reactor and a fast tie switch K2 connected in series, and a fast bypass switch K1 connected in parallel across the two ends of the current-limiting reactor. By controlling various components, it can adapt to different operating states of the power distribution network; The control method includes uninterrupted switching operation control, steady-state optimized operation control, power flow transfer over-limit control, and loop short-circuit fault isolation control; wherein, the uninterrupted switching operation control includes the following steps: (1) Calculate whether the loop current without phase shifter meets the allowable conditions. If it does, carry out the loop hot-swap operation directly. If it does not meet the conditions, use a controllable phase shifter to assist in carrying out the distribution network loop hot-swap. (2) The voltage phase angle adjustment at the access point is calculated and executed by a controllable phase shifter; (3) Check whether the closed-loop current after adjustment by the controllable phase shifter meets the allowable conditions. If it does, carry out the phase shifter-assisted closed-loop hot-swap operation; if it does not meet the conditions, the controllable phase shifter will recalculate and adjust.

2. The control method for the current-limiting controllable phase shifter according to claim 1, characterized in that: The fast bypass switch K1 and fast contact switch K2 use the instantaneous current value as the basis for judging the opening and closing actions.

3. The control method for the current-limiting controllable phase shifter according to claim 1, characterized in that: During normal operation, steady-state optimization control is performed. Both the fast bypass switch K1 and the fast tie switch K2 are closed, and power flow regulation is achieved by controlling the tie line through a controllable phase shifter.

4. The control method for the current-limiting controllable phase shifter according to claim 3, characterized in that: The controller of the controllable phase shifter calculates the adjustment amount of the controllable phase shifter based on the collected line outgoing current and the control target, and sends it to the adjustment mechanism of the controllable phase shifter to perform power flow regulation.

5. The control method for the current-limiting controllable phase shifter according to claim 1, characterized in that: When the distribution network line is subjected to uninterrupted switching operation, the uninterrupted switching operation control is implemented. The fast bypass switch K1 and fast tie switch K2 are both closed. The voltage on both sides of the switch that needs to be closed during the switching is equal through the controllable phase shifter.

6. The control method for the current-limiting controllable phase shifter according to claim 5, characterized in that: The controller of the controllable phase shifter calculates the adjustment amount of the controllable phase shifter based on the voltages on both sides of the switch that is about to close the loop, combined with the control target, and sends it to the adjustment mechanism of the controllable phase shifter to perform voltage adjustment.

7. The control method for the current-limiting controllable phase shifter according to claim 4 or 6, characterized in that: The controllable phase shifter is either a mechanical controllable phase shifter or a thyristor controllable phase shifter. The adjustment mechanism of the mechanical controllable phase shifter is an on-load tap changer, while the adjustment mechanism of the thyristor controllable phase shifter is a power electronic device.

8. The control method for the current-limiting controllable phase shifter according to claim 1, characterized in that: When the current transfer causes the current in the loop to exceed the limit, the current transfer over-limit control is performed. The controller of the controllable phase shifter controls the fast bypass switch K1 to open, the current limiting reactor is connected in series with the loop network, and the fast tie switch K2 remains closed.

9. The control method for the current-limiting controllable phase shifter according to claim 1, characterized in that: When a loop short circuit fault occurs in the distribution network, loop short circuit fault isolation control is performed. The controller of the controllable phase shifter controls the fast interconnection switch K2 to open quickly, while the fast bypass switch K1 remains closed.

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