CN106602689B - System for preventing direct-current power supply bus from losing voltage and operation method thereof - Google Patents

Abstract

The invention relates to a system for preventing the voltage loss of a direct current power supply bus and an operation method thereof, wherein the system is operated in a direct current power supply system which comprises a storage battery pack and the storage battery pack comprises m sections of single storage batteries connected in series, and the system comprises at least one intelligent detection module and one or more DC/DC modules, wherein the intelligent detection module comprises a bus voltage acquisition circuit unit, a control output circuit unit and an intelligent judgment circuit unit; the DC/DC module is provided with an input interface and an output interface, and the invention monitors and compensates the voltage loss of the direct current bus possibly caused, thereby ensuring the safe and stable operation of the direct current system.

Description

A system for preventing DC power bus from losing voltage and its operation method

Technical field

The invention relates to a system for preventing voltage loss of a DC power supply bus and an operation method thereof, and belongs to the field of DC power supply of electric power systems.

Background technique

The DC system of a power plant or substation provides DC power for signaling equipment, protection, automatic devices, emergency lighting, emergency power supply and circuit breaker opening and closing operations. It is an independent power supply that is not affected by generators, station AC and system Influence of the operating mode, during normal operation, the charging device bears the regular load and at the same time recharges the battery pack to supplement the self-discharge of the battery, so that the battery is in standby at full capacity. In the event of external AC power interruption, the backup The power source, the battery pack, continues to provide DC power to the load.

As the core component of the DC power supply system, the battery pack mostly adopts the form of multiple single cells connected in series. As the battery operating time continues to lengthen, and the influence of temperature, humidity and other environments, the performance of each single battery in the battery pack also changes. Constantly changing, which will lead to an increase in the internal resistance of some batteries, a decrease in capacity or other faults. When the DC system is required to provide power to the load, the failure of one or several single batteries will cause the entire battery pack to be unable to output, resulting in The DC bus loses voltage, causing the protective equipment or control equipment to fail to work properly.

Here are some typical accidents:

1) In 2013, two 110kV bus sections of a 220kV substation in the south experienced three-phase faults one after another. The 110kV bus differential outlet tripped five 110kV switches. Due to an abnormality in the DC system of the substation, other circuit breakers in the station failed to trip normally and jumped to the superior power supply. The line tripped, causing the entire substation to lose voltage. The reason is: after a three-phase fault occurs in the 110kV busbar of the 220kV substation, the 10kV voltage drops, the DC charger stops operating, and the 110kV busbar protection operates. However, due to a virtual break in a certain section of the battery pack, the DC power supply is unstable. When an accident occurs, the When the battery discharges outward, the battery pack cannot output voltage, causing multiple 110kV circuit breakers throughout the station to fail to trip.

2) In 2013, a power company in the northwest region experienced a voltage loss in the AC power supply of the station due to an AC side fault. The battery pack had been disconnected before and was not discovered and dealt with. This caused the DC bus to lose voltage and the protective appliance did not operate, causing the main transformer to burn down. 2 units.

3) In 2015, a power company in North China lost power due to the 35kV second section busbar, the 2# station transformer lost power, the 3# station transformer could not be put into operation, and the AC power supply of the entire station lost power. Afterwards, the reason was found to be the 73# battery of the 1# battery pack. An internal open circuit caused a section of the DC bus to lose power. After the 2# battery pack was used to carry the DC load of the entire station, an open circuit occurred inside the 44# battery of the 2# battery pack, and the DC bus of the entire station lost voltage.

Due to the large impact of the accident, relevant units and manufacturers have done some work to avoid such accidents. Patent 201310668765.8 provides a "charge and discharge compensation system for series battery packs", which compensates for single battery failures by setting a charger for each single battery; patent 201010598584.9 provides a "DC power supply based on parallel connection of batteries" System", multiple groups of batteries are connected in parallel through set-up converters. When one or more batteries fail, the non-faulty batteries can still provide power for the DC bus; Patent 201410316418.3 provides a "battery group automatic gapless bypass" "Connection system", a monitoring management unit and a jumper unit are set up on each single battery. When a single battery failure is detected, the battery is automatically jumpered, so that a battery pack composed of fault-free single batteries can be Requirements for continuous power supply.

Although the above technologies solve the bus voltage loss caused by a single battery failure to a certain extent, they all have shortcomings such as cumbersome implementation mechanism and high cost.

Contents of the invention

The object of the present invention is to provide a system and an operating method for preventing DC power bus voltage loss, which operates in a DC power system containing a battery pack (X) and the battery pack (X) contains m single batteries connected in series. Based on the judgment of the bus voltage and voltage change rate, it can automatically compensate the power supply to the DC bus to avoid bus voltage loss.

The technical solution of the present invention is:

A system for preventing DC power bus voltage loss, running in a DC power system containing a battery pack (BT) and the battery pack (BT) containing m single batteries connected in series, including at least one intelligent detection module (J) and an or multiple DC/DC modules (M), characterized in that: the intelligent detection module (J) includes a bus voltage acquisition circuit unit (JY), a control output circuit unit (JS) and an intelligent judgment circuit unit (JP), in which the bus The voltage acquisition circuit unit (JY) is connected to the DC power bus and can detect the voltage of the DC power bus; the DC/DC module (M) has input and output interfaces. If you set up a DC/DC module (M), you need to set at least For an independent battery pack (BT1), the input interfaces of the DC/DC module (M) are connected to both ends of the battery pack (BT1), and its output interface is connected to the DC bus; if multiple DC/DC modules (M) are set up, the DC The input interface of the /DC module (M) can be connected to both ends of a number of consecutive single batteries in the DC power supply system battery bank (BT), or it can be connected to both ends of multiple independent battery banks (BTn). Or a mixture of the above two modes, with its output interface connected to the DC bus.

Further, the intelligent judgment circuit unit (JP) includes at least one microprocessor, and the microprocessor judges whether the DC bus has a tendency to lose voltage through the bus voltage acquisition circuit unit (JY); the DC/DC module ( The input and output of M) are electrically isolated; the output of the DC/DC module (M) is controllable; when the DC bus voltage is normal, the DC/DC module (M) does not output, and when the DC bus has When there is a tendency of voltage loss, instructions are issued through the control output circuit unit (JS) to control the output of the DC/DC module (M).

Further, when the input interface (MI) of the DC/DC module (M) is connected to both ends of several consecutive single cells of the battery pack (BT), the m cells of the battery pack (BT) can be The single batteries connected in series are divided into n groups, and n DC/DC modules (M) are provided corresponding to them.

A method to prevent DC power bus from losing voltage, running on the above-mentioned system for preventing DC power bus from losing voltage, includes the following steps:

1) Collect the DC bus voltage Um;

2) Based on the bus voltage Um collected in step 1) and the set DC system nominal voltage Un, make the following judgment:

a) If Um≥i×Un, it is judged that the DC system battery pack is in a balanced charging state;

b) If i×Un>Um≥j×Un, it is judged that the DC system battery pack is in a float charge state;

c) If j×Un>Um≥Un, it is judged that the output of the DC system charging device is abnormal;

d) If Un>Um, it is judged that the battery pack is in a discharge state.

Among them, i and j are the rate constants.

3) According to the judgment conclusion in step 2), if the system operating status is a) or b) in step 2), return to step 1); if the system operating status is c) or d), make the following judgment:

Collect the bus voltage U(t1) at time t ₁ , collect the bus voltage U(t1+Δt) through the time interval Δt, and calculate the change rate P of the bus voltage within this time interval:

4) Make the following judgment based on the voltage value U(t1+Δt) collected in step 3) and the calculated change rate P:

If P is higher than the set value Ps, or U(t1+Δt) is lower than the set value Us, the control signal (JS) is output and the DC/DC module (M) is put into operation.

Among them, the rate constants i and j in step 3) satisfy the condition: i>j>1.

The present invention adopts the above-mentioned system and method to monitor and compensate for possible DC bus voltage loss to ensure safe and stable operation of the DC system.

Description of drawings

Figure 1 is the basic schematic diagram of the DC power supply system.

Figure 2 is a technical schematic diagram of the system of the present invention.

Figure 3 is a technical principle diagram of Embodiment 1 of the system of the present invention.

Figure 4 is a technical principle diagram of Embodiment 2 of the system of the present invention.

Figure 5 is a technical principle diagram of Embodiment 3 of the system of the present invention.

Figure 6 is a flow chart of the method of the present invention.

Detailed ways

The invention relates to a system for preventing DC power bus voltage loss and an operating method thereof.

Figure 1 is the basic schematic diagram of the DC power supply system. The composition and operation mode of the DC power system are: the power DC system is composed of DC bus, battery pack BT, and charging module AC/DC; the battery pack BT is composed of m single batteries connected in series. For example, for a 220kV substation, 104 cells are generally used A battery with a single voltage of 2V; the charging module AC/DC is one or more devices that can convert AC voltage into DC voltage. Its input terminal is connected to the station AC power supply, and the output terminal is connected to the DC bus. The charger module AC/DC Convert alternating current into direct current for use by DC loads, and at the same time supplement the self-discharge of the battery pack BT; L1-Ln are several load circuits of the DC bus.

Figure 2 is a technical schematic diagram of the system of the present invention. The system of the present invention includes at least one intelligent detection module (J) and at least one DC/DC module (M). The intelligent detection module (J) and the DC/DC module (M) are both connected to the DC bus; the intelligent detection module (J) It is mainly used to measure the voltage of the DC bus and determine the operating status of the DC system. The DC/DC module (M) is mainly used to provide power for the DC bus; the input of the DC/DC module (M) is connected to several sections of the battery pack BT. Or another independent battery pack.

There can be one DC/DC module (M) or multiple DC/DC modules (M). According to the number of DC/DC modules (M) and their inputs, the present invention provides the following four embodiments.

Embodiment 1: Set the inputs of multiple DC/DC modules (M) to come from the battery pack BT.

Figure 3 is a technical principle diagram of Embodiment 1. As shown in the figure, this solution sets up n DC/DC modules (M), n is greater than 1; divide the m single battery packs in the battery pack BT into n groups, and connect the first and last ends of each group to a single DC/DC Module (M); the output of the DC/DC module (M) is connected to the DC bus.

For example, in a 220kV substation in the power grid, the bus voltage of the DC power system is often set to 220V, and a battery pack composed of 104 cells with a single voltage of 2V is used. To apply this solution, you can choose 4 DC/DC modules (M) with input DC48V and output DC220V. Use the 104 cells of the battery pack BT, cells 1-24 as the first DC/DC module (M). Inputs of Sections 25-48 as inputs of the 2nd DC/DC module (M), Sections 49-72 as inputs of the 3rd DC/DC module (M), Sections 73-96 as inputs The input of the fourth DC/DC module (M) and the output of the above four DC/DC modules (M) are connected to the DC220V DC bus.

The beneficial effect of adopting this solution is that when the power system fails, the AC power supply loses power, and the DC bus needs to rely on the battery pack to provide power, if a certain section of the battery pack is disconnected or fails, multiple DC/ The DC module (M) continuously supplies power to the DC bus.

Embodiment 2: Set the input of one or more DC/DC modules (M) to come from another independent battery pack BT2.

Figure 4 is a technical principle diagram of Embodiment 2. This solution also sets n DC/DC modules (M), n is greater than or equal to 1; different from Embodiment 1, in this solution, n independent battery banks (BT1-BTn) are set up correspondingly to n DC /DC module (M) input terminal; the output of DC/DC module (M) is connected to the DC bus

Adopting this solution can also achieve the beneficial effects of Embodiment 1. Since this solution uses an independent battery pack, it is more reliable than Embodiment 1, but it increases the cost of the system.

Embodiment 3: Set the inputs of multiple DC/DC modules (M) respectively from the battery pack BT and another independent battery pack BT1-BTn.

Figure 5 is a technical principle diagram of Embodiment 3. As shown in the figure, this scheme sets j DC/DC modules (M), j is greater than 1; different from Embodiment 1 and Embodiment 2, the input of the DC/DC module (M) in this scheme does not only come from the original A battery pack or a stand-alone battery pack, but a mixture of the two.

Using this solution can also achieve the beneficial effects of Embodiment 1, and its reliability and cost are between Embodiment 1 and Embodiment 2.

The above three embodiments are only based on the three technical solutions of the number of DC/DC modules (M) and their inputs, and also include the following technical solutions:

Set up an intelligent detection module (J), and the intelligent detection module (J) includes a bus voltage acquisition circuit unit (JY), a control output circuit unit (JS) and an intelligent judgment circuit unit (JP), among which the bus voltage circuit unit (JY ) is connected to the DC power bus to detect the voltage of the DC power bus.

The intelligent judgment circuit unit (JP) includes at least one microprocessor, and the microprocessor judges whether the DC bus has a tendency to lose voltage through the bus voltage acquisition circuit unit (JY); the input and output of the DC/DC module (M) It is electrically isolated and the output is controllable; when the DC bus voltage is normal, the DC/DC module (M) does not output. When the DC bus has a tendency to lose voltage, instructions are issued through the control output circuit unit (JS) , controls the output of the DC/DC module (M).

When the input interface (MI) of the DC/DC module (M) is connected to both ends of several consecutive single cells of the battery pack (BT), the m series-connected single cells of the battery pack (BT) can be divided into There are n groups, and n DC/DC modules (M) are set to correspond to them.

The flow chart of the method of the present invention is shown in Figure 6.

The specific implementation steps are:

1) Collect the DC bus voltage Um;

2) Based on the bus voltage Um collected in step 1) and the set DC system nominal voltage Un, make the following judgment:

a) If Um≥i×Un, it is judged that the DC system battery pack is in a balanced charging state;

b) If i×Un>Um≥j×Un, it is judged that the DC system battery pack is in a float charge state;

c) If j×Un>Um≥Un, it is judged that the output of the DC system charging device is abnormal;

d) If Un>Um, it is judged that the battery pack is in a discharge state or an abnormal float charge state.

Among them, i and j are the rate constants.

3) According to the judgment conclusion in step 2), if the system operating status is a) or b) in step 2), return to step 1); if the system operating status is c) or d), make the following judgment:

Collect the bus voltage U(t1) at time t ₁ , collect the bus voltage U(t1+Δt) through the time interval Δt, and calculate the change rate P of the bus voltage within this time interval:

4) Make the following judgment based on the voltage value U(t1+Δt) collected in step 3) and the calculated change rate P:

If P is higher than the set value Ps, or U(t1+Δt) is lower than the set value Us, the control signal (JS) is output to cause the DC/DC module (M) to output voltage to the DC bus.

Among them, the rate constants i and j in step 3) satisfy the condition: i>j>1. For example, for power systems, generally i is 1.1 and j is 1.05.

Claims (2)

1. A method of operating a system to prevent DC power bus voltage loss, running in a DC power system containing a battery pack (BT) and the battery pack (BT) containing m single batteries connected in series, including at least one intelligent detection module ( J) and one or more DC/DC modules (M), characterized by: The intelligent detection module (J) includes a bus voltage acquisition circuit unit (JY), a control output circuit unit (JS) and an intelligent judgment circuit unit (JP). The bus voltage acquisition circuit unit (JY) is connected to the DC power bus for Detect the voltage of the DC power bus; DC/DC module (M) has input and output interfaces; To set up a DC/DC module (M), set up at least one independent battery pack (BT1). The input interface of the DC/DC module (M) is connected to both ends of the battery pack (BT1), and its output interface is connected to the DC bus. or Set up multiple DC/DC modules (M), and the input interface of the DC/DC module (M) is connected to both ends of a number of consecutive single batteries in the DC power supply system battery pack (BT), or to multiple At both ends of the independent battery pack (BTn), its output interface is connected to the DC bus; The intelligent judgment circuit unit (JP) includes at least one microprocessor, and the microprocessor judges whether the DC bus has a tendency to lose voltage through the bus voltage acquisition circuit unit (JY); The input and output of the DC/DC module (M) are electrically isolated; The output of the DC/DC module (M) is controllable; When the DC bus voltage is normal, the DC/DC module (M) does not output. When the DC bus has a tendency to lose voltage, an instruction is issued through the control output circuit unit (JS) to control the DC/DC module (M). output; When the input interface (MI) of the DC/DC module (M) is connected to both ends of several consecutive single cells of the battery pack (BT), m cells of the battery pack (BT) are connected in series. The batteries are divided into n groups, and n DC/DC modules (M) are provided correspondingly; The operation method of the system for preventing DC power bus voltage loss includes the following steps: 1) Collect the DC bus voltage Um; 2) Based on the bus voltage Um collected in step 1) and the set DC system nominal voltage Un, make the following judgment: a) If Um≥i×Un, it is judged that the DC system battery pack is in a balanced charging state; b) If i×Un>Um≥j×Un, it is judged that the DC system battery pack is in a float charge state; c) If j×Un>Um≥Un, it is judged that the output of the DC system charging device is abnormal; d) If Un>Um, it is judged that the battery pack is in a discharge state; where i and j are rate constants; 3) According to the judgment conclusion in step 2), if the system operating status is a) or b) in step 2), return to step 1); if the system operating status is c) or d), make the following judgment: Collect the bus voltage U(t1) at time t 1, collect the bus voltage U(t1+Δt) through the time interval Δt, and calculate the change rate P of the bus voltage within this time interval: 4) Make the following judgment based on the voltage value U(t1+Δt) collected in step 3) and the calculated change rate P: If P is higher than the set value Ps, or U(t1+Δt) is lower than the set value Us , then the control signal (JS) is output and the DC/DC module is put into operation (M). 2. A method of operating a system for preventing DC power bus voltage loss as claimed in claim 1, characterized in that: the rate constants i and j in step 3) satisfy the condition: i>j>1.