Energy storage type flexible direct current interconnection device control system and method for factory

Abstract

The invention relates to an energy storage type flexible direct current interconnection device control system and method for a factory area, and belongs to the technical field of power electronic device control. The control system comprises an energy management system, and a load side A, a load side B, a network connection alternating current power supply A and a network connection alternating current power supply B which are respectively connected with the energy management system; the energy storage type flexible DC interconnection device comprises a grid-connected inverter A, a grid-connected inverter B, a bidirectional DC-DC converter and an energy storage device. Wherein the energy management system is connected with the interconnection device and controls the interconnection device in real time. The grid-connected alternating current power supply A is respectively connected with the load side A and the grid-connected inverter A; the grid-connected alternating current power supply B is connected with the load side B and the grid-connected inverter B respectively; one end of the bidirectional DC-DC converter is connected with the two grid-connected inverters, and the other end of the bidirectional DC-DC converter is connected with the energy storage device. According to the invention, peak load shifting of a power utilization curve can be realized, the energy utilization efficiency is improved, and a function of preventing power generation from surfing the Internet is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic device control, and relates to a control system and method for an energy storage type flexible direct current interconnection device used in a factory. Background Art

[0002] With the accelerated development of clean new energy, the continuous access of new energy such as wind and light to the power grid is an important feature of the new distribution system, and these distributed energy sources are characterized by volatility and intermittency. At the same time, the load on the power consumption side also shows a trend of diversified types and unbalanced demand, which puts forward higher requirements on the power supply stability and power quality of the distribution network.

[0003] Currently, many factory power grids and enterprise power grids are connected to new energy sources, and the proportion of nonlinear and impact loads is gradually increasing. The load fluctuations between different feeders are large, and the supply and demand and distribution of electricity on the source side and the load side are becoming more and more prominent. This has also caused the actual demand for electricity to be too high, there is overload or it is not in the economically reasonable operating range. In addition, the large-scale high-efficiency transformation of self-provided generators and the access to low-carbon new energy have caused problems with power generation and access to the grid under many working conditions, seriously affecting the reliable operation of the distribution network. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a control system and method for a flexible energy storage DC interconnection device for a factory area, which adopts a flexible DC interconnection device integrated with energy storage, and through the scheduling control of an energy management system, performs active bidirectional transmission of different grid-connected AC power sources to achieve peak shaving and valley filling, improve energy utilization efficiency, and utilize the characteristics of the flexible DC device, which is equivalent to "controllable power generation" or "controllable load", to control and avoid power generation to the grid.

[0005] To achieve the above-mentioned purpose, the present invention provides, on the one hand, a control system for an energy storage type flexible DC interconnection device for a factory area, wherein the energy storage type flexible DC interconnection device includes a grid-connected inverter A, a grid-connected inverter B, a bidirectional DC-DC converter and an energy storage device, and the control system includes an energy management system, a load side A, a load side B, a grid-connected AC power source A and a grid-connected AC power source B.

[0006] Among them, the energy management system is respectively connected to the load side A, the load side B, the grid-connected AC power source A, the grid-connected AC power source B, the grid-connected inverter A, the grid-connected inverter B, the bidirectional DC-DC converter and the energy storage device; the grid-connected AC power source A is respectively connected to the load side A and the grid-connected inverter A; the grid-connected AC power source B is respectively connected to the load side B and the grid-connected inverter B; one end of the bidirectional DC-DC converter is connected to the grid-connected inverter A and the grid-connected inverter B, and the other end is connected to the energy storage device.

[0007] Furthermore, the energy storage device includes two energy storage methods: battery and supercapacitor.

[0008] Furthermore, both the grid-connected inverter A and the grid-connected inverter B adopt double closed-loop vector control, and the outer loop adopts a power loop.

[0009] On the other hand, the present invention provides a method for controlling an energy storage type flexible DC interconnection device based on the control system, which comprises:

[0010] S1. Use the energy management system to monitor the power utilization and power changes on the load side in real time to determine whether the power supply on both sides is insufficient or the load is overloaded;

[0011] S2. If the power supply on one side is insufficient or the load is overloaded, the control system enters the interconnection mode to allocate power;

[0012] S3. When the power supply on both sides is sufficient and there is no overload, the energy management system collects the current power grid price and makes a comprehensive judgment based on the power consumption on both sides;

[0013] S4. If the electricity price is at its peak or both sides are at their peak electricity consumption, the control system enters the discharge mode, draws energy from the energy storage device and supplies power to the load side; if the electricity price is at its low point or both sides are at their low electricity consumption point, the control system enters the charging mode, charges the energy storage device to store electricity.

[0014] Furthermore, in step S2, if the power supply on one side is insufficient or the load is overloaded, the control system enters the interconnection mode, and the grid-connected AC power supply on the normal side supplies power to the grid-connected AC power supply on the side with insufficient power supply or overload through the grid-connected inverter A and the grid-connected inverter B. In addition, when reverse power occurs on one side, the energy management system transmits the reverse power on this side to the other side through the grid-connected inverter A and the grid-connected inverter B to prevent power backflow.

[0015] Furthermore, in step S4, if the electricity price is at a peak or both sides are at a peak in electricity consumption, the control system enters a discharge mode, transmits the electric energy of the energy storage device to the DC bus through a bidirectional DC-DC converter, and then supplies power to the grid-connected AC power source A and the grid-connected AC power source B through the grid-connected inverter A and the grid-connected inverter B. In addition, in the discharge mode, if reverse power occurs on one side, the energy management system transmits the reverse power on this side to the other side through the grid-connected inverter A and the grid-connected inverter B to prevent power backflow.

[0016] Furthermore, in the control process of the control system, the following constraints need to be met:

[0017]

[0018]

[0019]

[0020] In the formula, and Respectively represent the power of grid-connected inverter A and grid-connected inverter B, represents the power of the bidirectional DC-DC converter, and They represent the maximum reverse power on the side where the grid-connected inverter A is located and the maximum reverse power on the side where the grid-connected inverter B is located. Indicates the charge amount of the energy storage device during the charging phase, E max Indicates the maximum storage capacity of the energy storage device, P A逆平均 and P B逆平均 They represent the average reverse power on the side of grid-connected inverter A and the average reverse power on the side of grid-connected inverter B in one working cycle, respectively. A逆 and t B逆 They respectively represent the duration of the reverse power on the side where the grid-connected inverter A is located and the duration of the reverse power on the side where the grid-connected inverter B is located.

[0021] The beneficial effects of the present invention are:

[0022] 1) The present invention adopts a flexible DC interconnection device to integrate energy storage, and through the dispatching control of the energy management system, performs active bidirectional transmission of different grid-connected AC power sources, and utilizes the characteristics of the flexible DC device, which is equivalent to "controllable power generation" or "controllable load", to control and avoid power generation to the grid.

[0023] 2) The present invention can not only achieve "peak shaving and valley filling" of the electricity consumption curve by configuring energy storage, improve energy utilization efficiency, and better cope with the intermittent and variable output of distributed power sources and short-term load fluctuations, but also has a certain capacity of reactive power compensation and power quality management functions, which can enhance the power supply reliability and stability of the factory area and ensure the safety of the enterprise power grid.

[0024] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 A schematic diagram of the control system structure of an energy storage type flexible DC interconnection device provided in one embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of reverse power when energy storage is not configured;

[0028] Figure 3 This is a control flow diagram of the control system of the energy storage type flexible DC interconnection device. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0030] like Figure 1 The figure shows a control system of an energy storage type flexible DC interconnection device provided by an embodiment of the present invention, wherein the energy storage type flexible DC interconnection device includes a grid-connected inverter A, a grid-connected inverter B, a bidirectional DC-DC converter and an energy storage device, and the control system includes a grid-connected AC power supply A, a load side A, a grid-connected AC power supply B, a load side B and an energy management system.

[0031] Among them, the grid-connected inverter A is connected between the grid-connected AC power source A and the grid-connected inverter B; the grid-connected inverter B is connected between the grid-connected AC power source B and the grid-connected inverter A; the bidirectional DC-DC converter is the interface connecting the grid-connected inverter A and the grid-connected inverter B; the energy storage device is connected to the bidirectional DC-DC converter.

[0032] The energy management system is the monitoring and control center of the control system, which has the functions of data collection, monitoring and power control, and is used to optimize the dispatch of power resources in the plant area, automatically track load changes and power generation output, and monitor the utilization of power in real time. It can also optimize the allocation and management of electric energy through the dispatch of active and reactive power, and realize peak shaving and valley filling and avoid power generation on the grid. The energy management system is respectively connected to the grid-connected AC power source A, the grid-connected inverter A, the load side A, the grid-connected AC power source B, the grid-connected inverter B, the load side B, the bidirectional DC-DC converter, and the energy storage device.

[0033] In this embodiment, the proposed control system includes three working modes: charging, discharging and interconnection.

[0034] Among them, the charging mode refers to when the electricity price is low or the two load sides are in the low electricity consumption stage, the grid-connected AC power source A is rectified into DC power by the grid-connected inverter A to charge the energy storage device; the grid-connected AC power source B is rectified into DC power by the grid-connected inverter B to charge the energy storage device.

[0035] The discharge mode means that when the electricity price is at its peak or the two load sides are at their peak electricity consumption stage, the electric energy of the energy storage device is first transmitted to the DC bus through the bidirectional DC-DC converter, and the DC bus is then inverted into AC power by the grid-connected inverter A to supply power to the load side A. At the same time, it is also inverted into AC power by the grid-connected inverter B to supply power to the load side B.

[0036] The interconnection mode means that when the power supply on one side of the load side A or B is insufficient or the load is overloaded, the power supply on one side supplies power to the power supply on the other side through two grid-connected inverters, playing a flexible interconnection role and realizing mutual assistance and supply transfer. For example, when the power supply on the load side A is insufficient or the load is overloaded, the grid-connected AC power source B supplies power to the grid-connected AC power source A through grid-connected inverters B and A to meet the power demand of the load side A.

[0037] Another embodiment of the present invention shows a method for realizing peak shaving and valley filling and avoiding power generation to the grid by a control system of an energy storage type flexible DC interconnection device used in a steel plant, wherein the energy storage device configured by the control system is a 40MW energy storage battery. The control target of the system is to realize peak shaving and valley filling and avoid power generation to the grid, and the control variables in the control process include:

[0038] The grid-connected inverter (PCS) A power is positive when charging and negative when discharging;

[0039] The power of the grid-connected inverter (PCS) B is positive when charging and negative when discharging;

[0040] Energy storage power, positive when charging and negative when discharging;

[0041] E * : Energy storage capacity.

[0042] The constraints in the control process include:

[0043] (1)

[0044] (2) That is, the PCS power is greater than the maximum actual reverse power

[0045] (3) E max This is equal to 40MWh. After charging, there must be enough power left to ensure reverse power absorption in other stages.

[0046] in, and Respectively represent the power of grid-connected inverter A and grid-connected inverter B; Indicates the power of the bidirectional DC-DC converter; and They represent the maximum reverse power on the side where the grid-connected inverter A is located and the maximum reverse power on the side where the grid-connected inverter B is located respectively; Indicates the charge amount of the energy storage device during the charging stage; E max Indicates the maximum storage capacity of the energy storage device; P A逆平均 and P B逆平均 They represent the average reverse power on the side where the grid-connected inverter A is located and the average reverse power on the side where the grid-connected inverter B is located within a working cycle (a fixed period of time is a working cycle, generally 24 hours); t A逆 and t B逆 They respectively represent the duration of the reverse power on the side where the grid-connected inverter A is located and the duration of the reverse power on the side where the grid-connected inverter B is located. 2逆A ~E 4逆A It indicates the reverse power quantity of side A in each period when no energy storage device is configured, E 2逆B ~E 4逆B It indicates the reverse power quantity of side B in each period when no energy storage device is configured. Figure 2 shown.

[0047] The control strategy of the bidirectional DC-DC converter during the control process is: responsible for keeping the DC bus voltage constant, its power is passively regulated, and meets: Control strategy for grid-connected inverters on both sides: dual closed-loop vector control is adopted, in which the outer loop is the power loop.

[0048] like Figure 3 As shown, in this embodiment, the method of implementing peak load shifting and avoiding power generation to the grid through the control system is specifically as follows:

[0049] S1. The energy management system monitors the power utilization and power changes on the load side in real time.

[0050] S2. Determine whether there is insufficient power supply or overload on the two load sides.

[0051] S3. If there is insufficient power supply or overload on a certain load side, the system enters the interconnection mode, so that the grid-connected AC power supply on the normal side supplies power to the power supply on the other side through two grid-connected inverters, and returns to step S2.

[0052] In interconnection mode, the power of grid-connected inverter A is:

[0053]

[0054] The power of grid-connected inverter B is:

[0055]

[0056] According to the above formula, when reverse power appears on one side, the power setting value of the grid-connected inverter on that side is the reverse power. At this time, the reverse power on that side needs to be transmitted to the other side through the grid-connected inverter to prevent power backflow. At the same time, on the side where reverse power does not appear, the power setting value of its grid-connected inverter is the opposite value of the reverse power on the reverse power side to play a flexible interconnection role. In addition, this side also needs to receive the reverse power transmitted from the reverse power side to prevent power backflow.

[0057] It should be noted that the above power value expression of the grid-connected inverter is not only applicable to the interconnection mode, but also applicable to situations other than the discharge mode and the charging mode.

[0058] S4. If there is no power shortage or overload on both load sides, the energy management system collects the current electricity price of the power grid and makes a judgment based on the power consumption on both sides.

[0059] 1) If the electricity price is at its peak or the electricity consumption on both sides is at its peak, the system executes the discharge mode, transmits the electric energy in the energy storage device to the DC bus through the bidirectional DC-DC converter, and then provides electric energy to the power supply through the grid-connected inverters on both sides.

[0060] In the discharge mode, the power of the grid-connected inverter A is;

[0061]

[0062] The power of grid-connected inverter B is:

[0063]

[0064] According to the above formula, when the reverse power on one side is 0, the power of the grid-connected inverter on that side is executed according to the peak shaving and valley filling setting value; when the reverse power on one side is greater than 0, the power value of the grid-connected inverter on that side is reverse power. At this time, the reverse power on that side needs to be transmitted to the other side through the grid-connected inverter to prevent power backflow.

[0065] 2) If the electricity price is at a low point or the electricity consumption on both sides is at a low point, the system executes the charging mode, and the grid-connected AC power sources on both sides charge the energy storage device through a bidirectional DC-DC converter.

[0066] In charging mode, the power of grid-connected inverters A and B is:

[0067]

[0068] According to the above formula, the power values ​​of the grid-connected inverters A and B are given according to the peak shaving and valley filling setting values, and there is no reverse power problem in the charging mode.

[0069] In summary, the energy storage type flexible DC interconnection device control system proposed in the present invention works in three working modes: discharge, charge, and interconnection. The energy management system monitors the utilization of electric energy in real time by automatically tracking load changes and power generation output, realizes active and reactive scheduling, and realizes optimal configuration and management of electric energy. The control system described in the present invention uses a flexible DC interconnection device with integrated energy storage to achieve "peak shaving and valley filling" of the power consumption curve, which can improve energy utilization efficiency, and uses the characteristics of the flexible DC device that is equivalent to "controllable power generation" or "controllable load", which can control and avoid power generation and access to the grid. In addition, the present invention also has a certain capacity of reactive power compensation and power quality management functions, which can enhance the power supply reliability and stability of the factory area and ensure the safety of the enterprise power grid.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A control system for an energy storage type flexible DC interconnection device for a factory, wherein the energy storage type flexible DC interconnection device comprises a grid-connected inverter A, a grid-connected inverter B, a bidirectional DC-DC converter and an energy storage device, characterized in that: The control system includes an energy management system, a load side A, a load side B, a grid-connected AC power source A, and a grid-connected AC power source B; The energy management system is respectively connected to the load side A, the load side B, the grid-connected AC power source A, the grid-connected AC power source B, the grid-connected inverter A, the grid-connected inverter B, the bidirectional DC-DC converter and the energy storage device; the grid-connected AC power source A is respectively connected to the load side A and the grid-connected inverter A; the grid-connected AC power source B is respectively connected to the load side B and the grid-connected inverter B; one end of the bidirectional DC-DC converter is connected to the grid-connected inverter A and the grid-connected inverter B, and the other end is connected to the energy storage device.

2. The control system according to claim 1, characterized in that: The energy storage device is a battery.

3. The control system according to claim 1, characterized in that: The energy storage device is a super capacitor.

4. The control system according to claim 1, characterized in that: The grid-connected inverter A and the grid-connected inverter B both adopt double closed-loop vector control, and the outer loop adopts a power loop.

5. The control system according to any one of claims 1 to 4, characterized in that: The method for controlling the energy storage type flexible DC interconnection device based on the control system includes: The energy management system monitors the power utilization and power changes on the load side in real time to determine whether there is insufficient power supply or overload on both sides; If the power supply on one side is insufficient or the load is overloaded, the control system enters the interconnection mode to allocate power; When the power supply on both sides is sufficient and there is no overload, the energy management system collects the current grid electricity price and makes a comprehensive judgment based on the power consumption on both sides; If the electricity price is at its peak or the electricity consumption on both sides is at its peak, the control system enters the discharge mode, draws energy from the energy storage device and supplies power to the load side; If the electricity price is at a low point or the electricity consumption on both sides is at a low point, the control system enters the charging mode to charge the energy storage device to store electrical energy.

6. The control system according to claim 5, characterized in that: If the power supply on one side is insufficient or the load is overloaded, the control system enters the interconnection mode to allocate electric energy; the grid-connected AC power supply on the normal side supplies power to the grid-connected AC power supply on the side with insufficient power supply or overload through grid-connected inverter A and grid-connected inverter B; in addition, when reverse power occurs on one side, the energy management system transmits the reverse power on this side to the other side through grid-connected inverter A and grid-connected inverter B to prevent power backflow.

7. The control system according to claim 5, characterized in that: If the electricity price is at its peak or both sides are at their peak electricity consumption, the control system enters the discharge mode, transmits the electric energy of the energy storage device to the DC bus through the bidirectional DC-DC converter, and then supplies power to the grid-connected AC power source A and the grid-connected AC power source B through the grid-connected inverter A and the grid-connected inverter B respectively; in the discharge mode, if reverse power occurs on one side, the energy management system transmits the reverse power on this side to the other side through the grid-connected inverter A and the grid-connected inverter B to prevent power backflow.

8. The control system according to claim 5, characterized in that: In the control process of this control system, the following constraints need to be met: In the formula, and Respectively represent the power of grid-connected inverter A and grid-connected inverter B, represents the power of the bidirectional DC-DC converter, and They represent the maximum reverse power on the side where the grid-connected inverter A is located and the maximum reverse power on the side where the grid-connected inverter B is located. Indicates the charge amount of the energy storage device during the charging phase, E max Indicates the maximum storage capacity of the energy storage device, P A逆平均 and P B逆平均 They represent the average reverse power on the side of grid-connected inverter A and the average reverse power on the side of grid-connected inverter B in one working cycle, respectively. A逆 and t B逆 They respectively represent the duration of the reverse power on the side where the grid-connected inverter A is located and the duration of the reverse power on the side where the grid-connected inverter B is located.

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