A hierarchical control method for parallel operation of energy storage systems

Abstract

The present invention relates to a hierarchical control method for parallel operation of an energy storage system, comprising the following steps: constructing a horizontal distributed self-organizing communication network for an existing energy storage system and an energy storage system to be incorporated; constructing a vertical distributed self-organizing communication network for the existing energy storage system and the energy storage system to be connected; constructing a highest-level coordination controller, the method is as follows: configuring a node agent for the highest-level coordination controller, that is, the N-th-level coordination controller; receiving capacity, active power, and reactive power data uploaded by the N-1-th-level coordination controller, and summing up to obtain the real-time total active power and total reactive power in the system; collecting bus voltage and frequency at the same time; calculating an active power reference value, a reactive power reference value, a voltage compensation value, and a frequency compensation value; if a voltage deviation or a frequency deviation occurs in a bus line, restoring the system voltage and frequency.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a hierarchical control method for an energy storage system. Background Art

[0002] Microgrids are a key component of smart grids. They are a cluster that combines local loads, distributed generation such as wind turbines, solar photovoltaics and energy storage systems, and are attracting more and more attention.

[0003] At the same time, with the increasing severity of the world energy crisis and the continuous development of my country's power grid, the power grid has shown a "high proportion of renewable energy" and "high proportion of power electronic equipment", that is, a "double high" development trend, and has continuously emphasized the use of renewable energy and power electronic equipment. Renewable energy itself has a large volatility. For example, photovoltaic power generation will have different output power over time, and wind power will have different output power with the size of the local wind. In addition, the power electronic equipment itself has the characteristics of low damping and low inertia, which will have an adverse effect on the stability of the microgrid system. Therefore, when renewable energy is incorporated, a corresponding energy storage unit is generally equipped to form a complete energy storage system. At the specific control level, the virtual synchronous generator (Virtual Synchronous Generator) control technology is generally used to simulate the static power electronic device as a rotating motor, and by simulating the primary frequency modulation of the synchronous generator, the inertia of the system is increased, thereby solving the problem of insufficient inertia in the system itself and improving the stability of the AC microgrid. Due to the distribution and capacity limitations of distributed power sources and energy storage in microgrids, their energy storage systems generally use multiple machines in parallel. When the number of energy storage systems in the microgrid system is small, a single coordination controller can directly control all energy storage systems. However, the control capability of a single coordination controller is limited. Due to the capacity limitations of distributed power sources, when there are a large number of energy storage systems in the system, there will be the problem of how to perform hierarchical control of multiple coordination controllers and achieve control expansion. Therefore, it is very important to propose a simple and easy-to-implement hierarchical control method for large-scale energy storage systems.

[0004] The existing parallel operation control methods are mainly divided into the following two categories: the first category is the control architecture using a centralized coordination controller, that is, a single coordination controller is used for control. This method is simple and convenient to implement and easy to expand within the control limit, but it will face the problem of control limit. And any failure of the coordination controller will affect the overall stability of the system, and the stability is poor; the second category is to use the traditional distributed coordination controller control architecture, which can enhance the stability and scalability of the system. However, when virtual synchronous control is required in the system, its own coordination controller will be required to perform a large number of calculations, which will cause its processing rate to decrease, affecting the real-time and scalability of the system. Therefore, the existing parallel operation control structures cannot meet the required reliability and scalability of large-scale energy storage systems with virtual synchronous control.

[0005] In summary, in order to give full play to the improvement effect of VSG on system inertia and improve the reliability and scalability of large-scale energy storage systems with virtual synchronous control, it is of great significance and practical value to study a hierarchical control structure for parallel operation of large-scale energy storage systems. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to overcome the shortcomings of the existing large-scale energy storage system parallel operation control structure, such as large amount of calculation and information transmission, low scalability and reliability, and propose a hierarchical control method for parallel operation of energy storage systems. This control method contains virtual synchronous calculation, comprehensively considers system frequency recovery, and has the characteristics of high reliability and scalability. The technical solution is as follows:

[0007] A hierarchical control method for parallel operation of energy storage systems, comprising the following steps:

[0008] Step 1: Build a horizontal distributed self-organizing communication network for the existing energy storage system and the energy storage system to be incorporated. The method is as follows:

[0009] 1) For all the lowest-level coordination controllers, that is, the coordination controllers located in the energy storage system that directly issue instructions to each energy storage converter in a single energy storage system, it is named the first-layer coordination controller and configured with a node agent, which pre-stores the power capacity of the energy storage system it controls; at the same time, the active power and reactive power of the total output port of the energy storage system it controls are collected;

[0010] 2) Each lowest-level coordination controller sends the collected total active power and reactive power to a higher-level coordination controller; and receives the reference active power, reactive power, voltage compensation value and frequency compensation value sent by a higher-level coordination controller, and sends them to each energy storage converter;

[0011] Step 2: Construct a vertical distributed self-organizing communication network for the existing energy storage system and the energy storage system to be connected. The method is as follows:

[0012] 1) For the existing first-layer coordination controller, a higher-level coordination controller, i.e., the second-layer coordination controller, is constructed to coordinate control; a higher-level coordination controller sends data to q lower-level coordination controllers, and the actual control number q is determined by the actual demand and the control limit of a single coordination controller;

[0013] 2) If the number of coordinated controllers at the first level to be controlled exceeds the control limit of one coordinated controller, the number of coordinated controllers at the second level is increased, and horizontal expansion is performed at the same level to control the remaining coordinated controllers at the lower level;

[0014] 3) Configure a node agent for each coordination controller of the second layer, receive the capacity, active power and reactive power data uploaded by the coordination controller of the first layer, so as to obtain the total capacity and real-time total active power and reactive power of each node, and upload them to the coordination controller of the third layer; at the same time, receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by the coordination controller of the third layer, and send them to the coordination controller of the first layer;

[0015] 4) Similarly, using the same vertical expansion method, for each coordination controller at the i-th level, receive the node active power and capacity data uploaded by each coordination controller at the i-1th level and upload it to the coordination controller at the i+1th level; at the same time, receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by the coordination controller at the i+1th level, and send it to each coordination controller at the i-1th level controlled by it;

[0016] Step 3: Build the top-level coordination controller as follows:

[0017] 1) For the highest level coordination controller, that is, the Nth level coordination controller, configure the node agent and pre-store the active power setting value P set , reactive power setting value Q set , bus voltage reference value V set and frequency reference value f set ;

[0018] 2) Receive the capacity, active power, and reactive power data uploaded by the coordination controller at the N-1th level, and sum them up to obtain the real-time total active power and total reactive power in the system; at the same time, collect the bus voltage and frequency;

[0019] 3) Calculate the active power reference value P ref , reactive power reference value Q refAnd voltage compensation value ΔV, frequency compensation value Δf:

[0020]

[0021] Where S B is the total capacity uploaded by the coordination controller at level N-1, k fp , k fi , k Vp , k Vi To coordinate the control parameters preset in the controller.

[0022] Step 4: If the bus line has voltage deviation or frequency deviation, the system voltage and frequency recovery steps are as follows:

[0023] 1) The highest level, i.e., the Nth level coordination controller, collects and calculates the voltage compensation value ΔV and the frequency compensation value Δf, and sends them to the N-1th level coordination controller under its control;

[0024] 2) The coordination controller at the N-1th layer receives the parameters sent by the coordination controller at the Nth layer, and forwards them to the coordination controller at the N-2th layer controlled by each coordination controller;

[0025] 3) Similarly, each coordination controller receives the compensation value sent by the coordination controller of the previous layer and forwards it to the coordination controller of the next layer;

[0026] 4) After receiving the compensation value, the first-level coordination controller sends it to each energy storage converter, and finally corrects the bus voltage and frequency by modulating the output of the energy storage converter.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The proposed hierarchical control structure for parallel operation of large-scale energy storage systems takes into account the presence of a large number of energy storage systems in the system and realizes the combination of local control and upper-level control in a single energy storage system. Compared with the traditional control structure, it has greater scalability and can achieve horizontal and vertical expansion of the coordinated controller. It is also simpler and easier to implement, and can achieve plug-and-play for individual energy storage systems.

[0029] (2) Compared with the traditional hierarchical control structure, the functions of the coordination controller of the present invention basically do not change with the expansion of scale. And compared with the rapid expansion of the calculation scale of the traditional hierarchical control with the expansion of the system scale, the calculation scale of the hierarchical control structure in the present invention does not increase significantly with the expansion of the system scale, which can greatly reduce the calculation scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1It is a master-slave control architecture within a single energy storage system.

[0031] Figure 2 It is an extension method of the coordination controller in the present invention.

[0032] Figure 3 It is the specific control architecture in the simulation example of the present invention.

[0033] Figure 4 It is a comparison of bus voltage and frequency before and after adding the coordination controller in the simulation example Case 1 of the present invention.

[0034] Figure 5 This is the system expanded using the present invention in the simulation example Case 1 of the present invention.

[0035] Figure 6 It is a comparison of bus voltage and frequency before and after adding the coordination controller in the simulation example Case 2 of the present invention.

[0036] Table 1 shows the system operating parameters in the simulation example of the present invention. DETAILED DESCRIPTION

[0037] The following will describe in detail the hierarchical control structure for parallel operation of a large-scale energy storage system proposed by the present invention in conjunction with the accompanying drawings and specific implementations.

[0038] The present invention will be described in detail with reference to the accompanying drawings and embodiments.

[0039] 1. Grassroots distributed power control

[0040] The control of a single energy storage system involved in the present invention is as follows: Figure 1 As shown, #1 is the host in its single energy storage system, and #2 to #k are its slaves. The reference power P of the host ref and Q ref The host generates the reference current i after calculation. ref Send it to other slaves for master-slave control.

[0041] 2. Large-scale expansion of hierarchical control and voltage recovery and frequency recovery methods

[0042] When the distributed power sources to be controlled in the system reach the control limit of a single coordinated controller, the expansion result of the single coordinated controller in the present invention is as follows: Figure 2 .exist Figure 2 In the figure, system #1 is the initial system, system #2 to system #m are horizontal expansion systems within the same layer, and system #1 to system #u are expansions at the vertical level.

[0043] The specific expansion method is as follows:

[0044] Step 1: Build a vertical distributed self-organizing communication network for the existing energy storage system and the energy storage system to be incorporated. The steps are as follows:

[0045] 1) For all the lowest-level coordination controllers in the system, that is, the coordination controller located in the energy storage system that directly issues instructions to the n energy storage converters in a single energy storage system, it is named the first-layer coordination controller and configured with a node agent, which pre-stores the power capacity of the energy storage system it controls; at the same time, the active power and reactive power of the total output port of the energy storage system it controls are collected;

[0046] 2) Each lowest-level coordination controller sends the total active power and reactive power collected to a higher-level coordination controller; and receives the reference active power, reactive power, voltage compensation value and frequency compensation value sent by a higher-level coordination controller, and sends them to each energy storage converter; Figure 2 The coordination controller in system #1;

[0047] Step 2: Construct a vertical distributed self-organizing communication network for the existing energy storage system and the energy storage system to be incorporated. The steps are as follows:

[0048] 1) For the existing first-layer coordination controller in the system, a higher-level coordination controller, i.e., the second-layer coordination controller, is constructed to coordinate control; a higher-level coordination controller sends data to m lower-level coordination controllers, and the actual control number m is determined by the actual demand and the control limit of a single coordination controller; Figure 2 The coordination controller in the #z system controls the coordination controllers in the #1 to #m systems;

[0049] 2) If the number of coordinated controllers at the first level to be controlled exceeds the control limit of one coordinated controller, the number of coordinated controllers at the second level is increased, and horizontal expansion is performed at the same level to control the remaining coordinated controllers at the lower level; Figure 2 The #z system is expanded horizontally to the #z+1 system at the same level;

[0050] 3) Configure a node agent for each coordination controller of the second layer, receive the capacity, active power and reactive power data uploaded by the coordination controller of the first layer, so as to obtain the total capacity and real-time total active power and reactive power of each node, and upload them to the coordination controller of the third layer; at the same time, receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by the coordination controller of the third layer, and send them to the coordination controller of the first layer; Figure 2 The coordination controller in the #u system controls the #z system and the #z+1 system;

[0051] 4) Similarly, using the same vertical expansion method, for each coordination controller at the i-th level, receive the node active power and capacity data uploaded by m coordination controllers at the i-1th level and upload them to the coordination controller at the i+1th level; at the same time, receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by the coordination controller at the i+1th level, and send them to each coordination controller at the i-1th level controlled by it;

[0052] Step 3: Build the highest level coordination controller. The steps are as follows:

[0053] 1) For the highest level coordination controller, that is, the Nth level coordination controller, configure the node agent and pre-store the active power setting value P set , reactive power setting value Q set , bus voltage reference value V set and frequency reference value f set ;

[0054] 2) Receive the capacity, active power, and reactive power data uploaded by the coordination controller at the N-1th level, and sum them up to obtain the real-time total active power and total reactive power in the system; at the same time, collect the bus voltage and frequency;

[0055] 3) Calculate the active power reference value P ref , reactive power reference value Q ref And voltage compensation value ΔV, frequency compensation value Δf:

[0056]

[0057] Where S B is the total system capacity uploaded by the coordination controller at the N-1th level, k fp , k fi , k Vp , k Vi To coordinate the control parameters preset in the controller.

[0058] Step 4: If the bus line has voltage deviation or frequency deviation, the system voltage and frequency recovery steps are as follows:

[0059] 1) The highest level, i.e., the Nth level coordination controller, collects and calculates the voltage compensation value ΔV and the frequency compensation value Δf, and sends them to the N-1th level coordination controller under its control;

[0060] 2) The coordination controller at the N-1th layer receives the parameters sent by the coordination controller at the Nth layer, and forwards them to the coordination controller at the N-2th layer controlled by each coordination controller;

[0061] 3) Similarly, each coordination controller receives the compensation value sent by the coordination controller of the previous layer and forwards it to the coordination controller of the next layer;

[0062] 4) After receiving the compensation value, the first-level coordination controller sends it to each energy storage converter, and finally corrects the bus voltage and frequency by modulating the output of the energy storage converter.

[0063] 3. Simulation example

[0064] The system used in this simulation example consists of two energy storage systems. The single energy storage system is controlled by a host for virtual synchronization and four slaves for slave control. Four groups of simulation cases are specifically designed to perform power step and frequency voltage recovery functions respectively to verify the effectiveness of the proposed control structure. The simulation model of the master-slave control system in the present invention is built in Pscad software. The specific simulation structure is as follows: Figure 3 The system parameters are shown in Table 1. The system simulation step size is set to 2×10 -6 s, the switching frequency is 3.2kHz.

[0065] Table 1

[0066]

[0067] Case 1: Press Figure 3 The structure, under the overall load P ref =6MW, the traditional hierarchical control is compared with the hierarchical control with voltage recovery and frequency recovery involved in the present invention, and the functions of voltage recovery and frequency recovery are realized. Figure 4 (a)(b) The results of the traditional control structure and Figure 4 (c)(d) It can be seen from the control structure designed by the present invention that the hierarchical control of the present invention can realize the function of restoring the bus voltage and frequency.

[0068] Case 2: Press Figure 3 The structure, under the overall load P ref =6MW, according to the parallel control expansion method involved in the present invention, the system is expanded as follows Figure 5 Structure. Combined Figure 6 (a)(b) The results of the traditional control structure and Figure 6 (c)(d) It can be seen that the present invention can still maintain a good control effect when the system is expanded.

[0069] 4. Conclusion

[0070] The case results show that:

[0071] 1) Compared with the traditional hierarchical control system, which may cause the expansion of computing scale when the system structure expands, the proposed parallel operation hierarchical control structure can greatly simplify the required computing scale and data transmission scale.

[0072] 2) Using the parallel hierarchical control coordination controller mentioned in the present invention, except for the top-level coordination controller, the functions of other coordination controllers are relatively unified, which is conducive to unification and scale, and its computing function is relatively concentrated in the top-level coordination controller, and the lower-level coordination controller undertakes a receiving and forwarding task.

[0073] 3) The method proposed in the present invention can be used for energy management of large-scale energy storage systems, and is particularly suitable for independent microgrids in remote areas with inconvenient transportation and frequent disasters.

Claims

1. A hierarchical control method for parallel operation of energy storage systems, comprising the following steps: Step 1: Build a horizontal distributed self-organizing communication network for the existing energy storage system and the energy storage system to be incorporated. The method is as follows: 1) For all the lowest-level coordination controllers, that is, the coordination controllers located in the energy storage system that directly issue instructions to each energy storage converter in a single energy storage system, it is named the first-layer coordination controller and configured with a node agent, which pre-stores the power capacity of the energy storage system it controls; at the same time, the active power and reactive power of the total output port of the energy storage system it controls are collected; 2) Each lowest-level coordination controller sends the collected total active power and reactive power to another coordination controller at a higher level; And receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by a higher-level coordination controller, and send them to each energy storage converter; Step 2: Construct a vertical distributed self-organizing communication network for the existing energy storage system and the energy storage system to be connected. The method is as follows: 1) For the existing first-layer coordination controller, a higher-level coordination controller, i.e., the second-layer coordination controller, is constructed to coordinate control; a higher-level coordination controller sends data to q lower-level coordination controllers, and the actual control number q is determined by the actual demand and the control limit of a single coordination controller; 2) If the number of coordinated controllers at the first level to be controlled exceeds the control limit of one coordinated controller, the number of coordinated controllers at the second level is increased, and horizontal expansion is performed at the same level to control the remaining coordinated controllers at the lower level; 3) Configure a node agent for each coordination controller of the second layer, receive the capacity, active power and reactive power data uploaded by the coordination controller of the first layer, so as to obtain the total capacity and real-time total active power and reactive power of each node, and upload them to the coordination controller of the third layer; at the same time, receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by the coordination controller of the third layer, and send them to the coordination controller of the first layer; 4) Similarly, using the same vertical expansion method, for each coordination controller at the i-th level, receive the node active power and capacity data uploaded by each coordination controller at the i-1th level and upload it to the coordination controller at the i+1th level; at the same time, receive the reference active power, reactive power, voltage compensation value and frequency compensation value sent by the coordination controller at the i+1th level, and send it to each coordination controller at the i-1th level controlled by it; Step 3: Build the top-level coordination controller as follows: 1) For the highest level coordination controller, that is, the Nth level coordination controller, configure the node agent and pre-store the active power setting value P set , reactive power setting value Q set , bus voltage reference value V set and frequency reference value f set ; 2) Receive the capacity, active power, and reactive power data uploaded by the coordination controller at the N-1th level, and sum them up to obtain the real-time total active power and total reactive power in the system; at the same time, collect the bus voltage and frequency; 3) Calculate the active power reference value P ref , reactive power reference value Q ref And voltage compensation value ΔV, frequency compensation value Δf: Where S B is the total capacity uploaded by the coordination controller at level N-1, k fp , k fi , k Vp , k Vi To coordinate the control parameters preset in the controller; Step 4: If the bus line has voltage deviation or frequency deviation, the system voltage and frequency recovery steps are as follows: 1) The highest level, i.e., the Nth level coordination controller, collects and calculates the voltage compensation value ΔV and the frequency compensation value Δf, and sends them to the N-1th level coordination controller under its control; 2) The coordination controller at the N-1th layer receives the parameters sent by the coordination controller at the Nth layer, and forwards them to the coordination controller at the N-2th layer controlled by each coordination controller; 3) Similarly, each coordination controller receives the compensation value sent by the coordination controller of the previous layer and forwards it to the coordination controller of the next layer; 4) After receiving the compensation value, the first-level coordination controller sends it to each energy storage converter, and finally corrects the bus voltage and frequency by modulating the output of the energy storage converter.

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