Energy storage system capable of realizing power quality control and control method thereof

Abstract

The present invention relates to an energy storage system and a control method thereof capable of realizing power quality control. The system includes a sampling module, a controller and an output module. The controller measures the voltage and current signals in the current system through the sampling module. After processing and calculating the sampled data, the controller analyzes and obtains the current operating state of the system, and updates the current output instruction in combination with the current power grid situation, system state and preset control parameters. The controller sends the updated current instruction to the output module for control output, and controls the sampling module for signal sampling at the same time; the output module updates the output current amplitude and mode according to the current output instruction sent by the control end. Compared with the prior art, the present invention has the following advantages: effectively reducing the economic cost of the energy storage system, realizing the rational application of resources of the energy storage device, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy storage, and in particular to an energy storage system capable of realizing electric energy quality control and a control method thereof. Background Art

[0002] In recent years, the use of power storage technology to connect renewable energy to the grid and ensure its stable operation has become a mainstream means of grid regulation. After the introduction of the energy storage system, users can achieve the rational allocation of electric energy in time and space, thereby achieving the goal of improving energy utilization. In the process of introducing the energy storage system into the power grid, the peak load of the power grid needs to be taken into account when calculating the capacity. The peak load time of the power grid is usually short, which means that part of the capacity of the energy storage system will be idle for most of its operating time. In addition, in order to ensure the operational stability of the energy storage system, a certain amount of redundant capacity is usually configured for the system. Based on the above two points, the energy storage system has capacity redundancy to varying degrees in time and space. Although this part of the redundant capacity strengthens the overall stability of the system and weakens the system's requirements for the level of a single module and its internal power electronic devices, it also increases the economic cost of building the entire system.

[0003] After searching, Chinese patent publication number CN205123263U discloses a new multifunctional power distribution device with power quality control function, including a new energy storage system, the new energy storage system includes a storage battery and a new energy storage inverter, the new energy storage inverter includes a BPCS conversion bidirectional unit, a power capacitor, an inverter and a filtering / isolating device, but the device does not rationally apply the resources of the energy storage device to improve the utilization rate of the energy storage system. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an energy storage system and a control method thereof that can realize power quality control.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] According to one aspect of the present invention, there is provided an energy storage system capable of realizing power quality control, the system comprising a sampling module, a controller and an output module, wherein the controller measures voltage and current signals in the current system through the sampling module, and after processing and calculating the sampled data, the controller analyzes and obtains the current operating state of the system, and updates the current output instruction in combination with the current power grid condition, the system state and preset control parameters, and the controller sends the updated current instruction to the output module for controlling the output, and controls the sampling module for signal sampling at the same time; the output module updates the output current amplitude and mode according to the current output instruction sent by the control end.

[0007] As a preferred technical solution, the controller includes an adaptive notch filter, which performs notch processing on the voltage and current signals input by the sampling module.

[0008] As a preferred technical solution, the adaptive notch filter adopts a fast RLS algorithm.

[0009] As a preferred technical solution, the sampling module includes a current sampling circuit and a voltage sampling circuit.

[0010] As a preferred technical solution, the notch processing of the controller includes filtering out the harmonic components and extracting the fundamental components in the system.

[0011] As a preferred technical solution, the filtering of harmonic components and the extraction of fundamental components specifically include the following steps:

[0012] Step 1: The sampling module sends the sampling signal to the adaptive notch filter in the controller;

[0013] Step 2: The adaptive notch filter uses a fast RLS algorithm to jointly estimate the weight coefficients based on the feedback signal and the reference input, so that the amplitude and phase angle of the obtained combined sine wave are consistent with the fundamental component in the input signal, thereby achieving the purpose of notching and filtering out the harmonic components in the input signal;

[0014] Step 3, performing Clark transform on the fundamental signal output by the adaptive notch filter;

[0015] Step 4: construct a 90° phase shift factor to obtain a three-phase fundamental orthogonal signal corresponding to the three-phase fundamental signal;

[0016] Step 5: Send the three-phase fundamental signal and its corresponding orthogonal signal to the positive and negative sequence extraction link to obtain the fundamental positive and negative sequence signal without harmonic components.

[0017] According to another aspect of the present invention, there is provided a control method for an energy storage system that uses the energy storage system capable of realizing power quality control. The method first determines the energy storage capacity and the power quality compensation capacity according to application requirements, then determines the occupancy ratio of the current output capacity to the total capacity by monitoring the charge state of the energy storage device, and finally switches the charge and discharge state of the energy storage device according to the current output state of the energy storage device and the remaining capacity value.

[0018] As a preferred technical solution, the control method specifically includes the following steps:

[0019] Step 1: monitor the current system operation status through sampling detection, and make status judgments on the parts of the capacity divided into energy storage capacity and power quality compensation capacity respectively;

[0020] Step 2: The energy storage capacity and power quality compensation capacity initially set in the energy storage device are equivalent to an equivalent model consisting of two parallel battery groups, and the energy storage device is defined into eight application states according to their respective charge states;

[0021] Step 3: The controller adjusts the control strategy and output command according to the current application state of the energy storage device, and continues to monitor the system operating environment.

[0022] As a preferred technical solution, the eight application states include:

[0023]

[0024] Among them, Bstate and Rstate are used to indicate the current charge state of the energy storage capacity and the power quality compensation capacity respectively, "+" and "-" represent that the energy storage capacity is in the discharge state or the charge state respectively, BQlow and BQhigh represent the minimum and maximum limits of the energy storage capacity respectively, and RQlow and RQhigh represent the minimum and maximum limits of the power quality compensation capacity respectively.

[0025] As a preferred technical solution, corresponding to the current application state of the energy storage device, the control strategy and output command of the controller include:

[0026] Application state 1: In this state, the system enters the energy storage capacity over-discharge protection mode. The power quality compensation capacity can still switch between the charge and discharge states according to system requirements. The system's discharge requirements are all met by the power quality compensation capacity, and the energy storage capacity no longer responds to the discharge command; the system's charging command is preferentially responded to by the energy storage capacity;

[0027] Application state 2: In this state, the system enters the energy storage capacity overcharge protection mode. The power quality compensation capacity can still switch between the charging and discharging states according to system requirements. The system's charging requirements are all met by the power quality compensation capacity, and the energy storage capacity no longer responds to charging commands; the system's discharge commands are responded to by the energy storage capacity first;

[0028] Application state 3: In this state, the system enters the power quality compensation capacity over-discharge protection mode. The energy storage capacity can still switch between the charge and discharge states according to system requirements. The system's discharge requirements are all met by the energy storage capacity, and the power quality compensation capacity no longer responds to the discharge command; the system's charging command is preferentially responded to by the power quality compensation capacity;

[0029] Application state 4: In this state, the system enters the power quality compensation capacity overcharge protection mode. The energy storage capacity can still switch between the charging and discharging states according to system requirements. The system's charging requirements are all met by the energy storage capacity, and the power quality compensation capacity no longer responds to charging commands; the system's discharge commands are preferentially responded to by the power quality compensation capacity;

[0030] Application state 5: In this state, the system enters the energy storage capacity over-discharge protection mode and the power quality compensation capacity over-charge protection mode. The system's discharge commands are all responded to by the power quality compensation capacity, and the system's charging commands are all responded to by the energy storage capacity.

[0031] Application state 6: In this state, the system enters the energy storage capacity overcharge protection and the power quality compensation capacity over-discharge protection mode. The system's charging commands are all responded to by the power quality compensation capacity, and the system's discharge commands are all responded to by the energy storage capacity.

[0032] Application state 7: In this state, the system enters the over-discharge protection mode. The system only responds to the charging command and sends a low charge state alarm to the outside.

[0033] Application state 8: In this state, the system enters the overcharge protection mode. The system only responds to the discharge command and sends an alarm indicating that the system charge state is too high.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. The present invention provides an energy storage system and a control method thereof that can utilize the redundant capacity of an energy storage device to achieve power quality control of a power grid, which can effectively reduce the economic cost of the energy storage system and realize the rational application of resources of the energy storage device.

[0036] 2. The present invention introduces a system capacity interval management method to achieve quantitative on-demand allocation management of system capacity, so that the overall system can achieve a higher capacity utilization rate while retaining redundant capacity.

[0037] 3. The system of the present invention introduces an adaptive notch filter using a fast RLS algorithm to extract the fundamental wave, which can realize a filtering process with strong robustness to phase changes.

[0038] 4. The fast RLS algorithm of the present invention can estimate the gradient of the objective function under the condition of retaining the input at the past moment and the expectation, and at the same time reduce the algorithm calculation amount by adjusting the structure of the information data, so as to achieve a balance between accuracy and resource usage.

[0039] 5. The system of the present invention is easy to implement and easy to realize digital control. The system can be connected to an external human-machine control interface to facilitate users to set and modify the control strategy and control parameters of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0041] Figure 2 It is the controller filtering flow chart of the present invention;

[0042] Figure 3 This is a diagram of the system charge and discharge control state conversion process adopted by the present invention. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0044] The system of the present invention adopts a PCS inverter with a DC / DC cascade DC / AC topology. The DC / AC circuit in the system can be used for power quality compensation while meeting the needs of energy storage and current conversion, realizing multiple uses of one machine. It can not only solve the original power quality problems in the application scenario, but also deal with the power quality problems that arise after the introduction of the energy storage system. In a certain sense, it reduces the construction cost of the overall system, optimizes the user's power environment, and truly realizes the effective use of energy.

[0045] The principle of the present invention is as follows: firstly, the energy storage capacity and the power quality compensation capacity are determined according to the application requirements; then, the occupancy ratio of the current output capacity to the total capacity is judged by monitoring the charge state of the energy storage device; finally, the charge and discharge state of the energy storage device is switched according to the current output state of the energy storage device and the remaining capacity value.

[0046] like Figure 1 As shown, the system controls the sampling module through the controller to measure the voltage and current signals in the current system and transmits the sampling information back to the controller.

[0047] After receiving the sampled data sent back by the sampling end, the controller filters and traps the sampled data. After extracting and calculating the data, the current operating state of the system is analyzed. The output current command is updated according to the current power grid conditions, system status and preset control parameters. The updated current command is sent to the output module for control output, and the sampling end is controlled to perform signal sampling.

[0048] The output module updates the output current amplitude and mode according to the current output instruction sent from the control end.

[0049] like Figure 2As shown, the present invention uses an adaptive notch filter to perform filtering to complete the extraction of positive and negative sequence components of the fundamental wave. The specific process includes the following steps:

[0050] The controller sends the three-phase signals sent by the sampling end to their respective adaptive notch filter links. The adaptive notch filter uses a fast RLS algorithm to perform notch filtering operations on the three-phase signals according to the set filtering order.

[0051] In the notch filter link, the fast RLS algorithm is used, and the notch filter jointly estimates the weight coefficients according to the feedback signal and the reference input, so that the amplitude and phase angle of the obtained combined sine wave are consistent with the fundamental component in the input signal, thereby achieving the purpose of notching and filtering out the harmonic components in the input signal.

[0052] After the controller sends the input signal to the notch filter, a three-phase fundamental wave signal can be obtained at the output end of the notch filter. Subsequently, the three-phase fundamental wave signal is subjected to Clark transformation so that the fundamental wave signal is located in a two-phase stationary coordinate system.

[0053] By constructing a 90° phase shift factor for the fundamental signal in a two-phase stationary coordinate system, an orthogonal signal of the fundamental signal is obtained.

[0054] The orthogonal signal group of the fundamental wave signal is sent to the positive and negative sequence extraction link, and finally the fundamental wave signal containing positive and negative sequence components is obtained.

[0055] like Figure 3 As shown in the figure, the system charge and discharge control state conversion process diagram adopted by the present invention, by executing this process, the system can realize reasonable call of capacity according to the preset operation mode under the condition of mastering the current equipment operation state, and the specific process includes the following steps:

[0056] The current system operating status is monitored through sampling detection. First, the status of the part of the capacity divided into energy storage capacity is judged. According to its current usage, it can be divided into higher than the upper limit of capacity, between the upper and lower limits, and lower than the lower limit of capacity.

[0057] When the current state of the energy storage capacity is determined, the same state detection is performed on the power quality compensation capacity. This part of the capacity also has three operating states like the energy storage capacity.

[0058] Combined with the current operating status of the energy storage capacity and the power quality compensation capacity, the input and output of the overall capacity are controlled according to the system control strategy, while continuing to monitor the system operating environment.

[0059] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An energy storage system capable of realizing power quality control, characterized in that: The system includes a sampling module, a controller and an output module. The controller measures the voltage and current signals in the current system through the sampling module. After processing and calculating the sampled data, the controller analyzes and obtains the current operating state of the system, and updates the current output instruction in combination with the current power grid situation, system state and preset control parameters. The controller sends the updated current instruction to the output module for control output, and controls the sampling module to perform signal sampling at the same time. The output module updates the output current amplitude and mode according to the current output instruction sent by the control terminal; The controller includes an adaptive notch filter, which performs notch processing on the voltage and current signals input by the sampling module; The notch processing of the controller includes filtering out the harmonic components and extracting the fundamental components in the system; The filtering of harmonic components and the extraction of fundamental components specifically include the following steps: Step 1: The sampling module sends the sampling signal to the adaptive notch filter in the controller; Step 2: The adaptive notch filter uses a fast RLS algorithm to jointly estimate the weight coefficients based on the feedback signal and the reference input, so that the amplitude and phase angle of the obtained combined sine wave are consistent with the fundamental component in the input signal, thereby achieving the purpose of notching and filtering out the harmonic components in the input signal; Step 3, performing Clark transform on the fundamental signal output by the adaptive notch filter; Step 4: construct a 90° phase shift factor to obtain a three-phase fundamental orthogonal signal corresponding to the three-phase fundamental signal; Step 5: Send the three-phase fundamental signal and its corresponding orthogonal signal to the positive and negative sequence extraction link to obtain the fundamental positive and negative sequence signal without harmonic components.

2. An energy storage system capable of realizing power quality control according to claim 1, characterized in that: The adaptive notch filter adopts a fast RLS algorithm.

3. The energy storage system capable of realizing power quality control according to claim 1, characterized in that: The sampling module includes a current sampling circuit and a voltage sampling circuit.

4. A control method for an energy storage system capable of realizing power quality control using the energy storage system of claim 1, characterized in that: This method first determines the energy storage capacity and power quality compensation capacity according to application requirements, then determines the occupancy ratio of the current output capacity to the total capacity by monitoring the charge state of the energy storage device, and finally switches the charge and discharge state of the energy storage device according to the current output state of the energy storage device and the remaining capacity value.

5. The control method according to claim 4, characterized in that: The control method specifically comprises the following steps: Step 1: monitor the current system operation status through sampling detection, and make status judgments on the parts of the capacity divided into energy storage capacity and power quality compensation capacity respectively; Step 2: The energy storage capacity and power quality compensation capacity initially set in the energy storage device are equivalent to an equivalent model consisting of two parallel battery groups, and the energy storage device is defined into eight application states according to their respective charge states; Step 3: The controller adjusts the control strategy and output command according to the current application state of the energy storage device, and continues to monitor the system operating environment.

6. The control method according to claim 5, characterized in that: The eight application states include: Among them, Bstate and Rstate are used to indicate the current charge state of the energy storage capacity and the power quality compensation capacity, respectively. "+" and "-" represent that the energy storage capacity is in the discharge state or the charge state, respectively. BQlow and BQhigh represent the minimum and maximum limits of the energy storage capacity, respectively. RQlow and RQhigh represent the minimum and maximum limits of the power quality compensation capacity, respectively.

7. The control method according to claim 6, characterized in that: Corresponding to the current application state of the energy storage device, the control strategy and output commands of the controller include: Application state 1: In this state, the system enters the energy storage capacity over-discharge protection mode. The power quality compensation capacity can still switch between the charge and discharge states according to system requirements. The system's discharge requirements are all met by the power quality compensation capacity, and the energy storage capacity no longer responds to the discharge command; the system's charging command is preferentially responded to by the energy storage capacity; Application state 2: In this state, the system enters the energy storage capacity overcharge protection mode. The power quality compensation capacity can still switch between the charging and discharging states according to system requirements. The system's charging requirements are all met by the power quality compensation capacity, and the energy storage capacity no longer responds to charging commands; the system's discharge commands are responded to by the energy storage capacity first; Application state 3: In this state, the system enters the power quality compensation capacity over-discharge protection mode. The energy storage capacity can still switch between the charge and discharge states according to system requirements. The system's discharge requirements are all met by the energy storage capacity, and the power quality compensation capacity no longer responds to the discharge command; the system's charging command is preferentially responded to by the power quality compensation capacity; Application state 4: In this state, the system enters the power quality compensation capacity overcharge protection mode. The energy storage capacity can still switch between the charging and discharging states according to system requirements. The system's charging requirements are all met by the energy storage capacity, and the power quality compensation capacity no longer responds to charging commands; the system's discharge commands are preferentially responded to by the power quality compensation capacity; Application state 5: In this state, the system enters the energy storage capacity over-discharge protection mode and the power quality compensation capacity over-charge protection mode. The system's discharge commands are all responded to by the power quality compensation capacity, and the system's charging commands are all responded to by the energy storage capacity. Application state 6: In this state, the system enters the energy storage capacity overcharge protection and the power quality compensation capacity over-discharge protection mode. The system's charging commands are all responded to by the power quality compensation capacity, and the system's discharge commands are all responded to by the energy storage capacity. Application state 7: In this state, the system enters the over-discharge protection mode. The system only responds to the charging command and sends a low charge state alarm to the outside. Application state 8: In this state, the system enters the overcharge protection mode. The system only responds to the discharge command and sends an alarm indicating that the system charge state is too high.

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