HELICS-based main and distribution network dynamic joint simulation method

Abstract

The invention discloses an HELICS-based main and distribution network dynamic joint simulation method, which comprises the following steps of: establishing a federation for a control center, a main network and a distribution network by utilizing an HELICS platform, establishing a log for recording simulation information, and acquiring specific information including time, voltage, power, phase angle and frequency; initial time and time intervals are set in the control center, the main network and the distribution network respectively, a coordination result of the HELICS platform is waited, so that the control center and the main network and the distribution network keep time synchronization, and joint simulation is carried out; the joint simulation comprises primary frequency modulation and secondary frequency modulation; and issuing and subscribing data between the main and distribution networks and the control center to realize joint simulation between the main and distribution networks. According to the invention, powerful support can be provided for optimal scheduling of a future power distribution system.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a main distribution network dynamic joint simulation method based on HELICS. Background Art

[0002] With the development of society, distributed resources (DER) have penetrated more and more widely into the distribution network, which has aroused great interest in the operators of distribution and transmission systems in monitoring and controlling millions of distributed energy sources. Most distributed resources have high dispatchability and flexibility, and play an important role in maintaining power balance and ensuring the safe and stable operation of the power system. However, distributed resources have the characteristics of strong randomness and low inertia. Therefore, in order to solve the problem that a large number of distributed resources may have an adverse effect on the regional voltage or system frequency after being connected to the power grid, it is necessary to study the main distribution network system after the distributed resources are connected, starting from the stability and reliability of the power system.

[0003] Traditional methods often ignore the distribution network layer, directly equate distributed resources to main network nodes, and do not consider the complex architecture and dynamic characteristics of the distribution network, and cannot accurately simulate the real power flow distribution between the main and distribution networks. The present invention aims to build a dynamic joint simulation platform for the main and distribution networks, and study the dynamic joint simulation method for the main and distribution networks to verify the necessity of considering the impact of the distribution network, and more comprehensively and realistically simulate the impact of a large number of decentralized heterogeneous distributed resources on the main and distribution network systems. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a main distribution network dynamic joint simulation method based on HELICS, which solves the problem that the traditional method directly equates distributed resources to main network nodes and cannot accurately simulate the real power flow distribution between the main distribution network.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0006] The present invention is a main distribution network dynamic joint simulation method based on HELICS, including the following operations:

[0007] Use the HELICS platform to establish a federation for the control center, main network and distribution network, establish a log for recording simulation information, and obtain specific information including time, voltage, power, phase angle and frequency;

[0008] Set the initial time and time interval in the control center, main network, and distribution network respectively, and wait for the HELICS platform to coordinate the control center, main network, and distribution network according to the set initial time and time interval, so that the control center keeps time synchronization with the main network and distribution network, and conduct joint simulation, where the joint simulation includes:

[0009] Perform primary and secondary frequency regulation; publish and subscribe data between the main distribution network and the control center. The distribution network publishes the available load margin to the control center and sends power to the main network. The main network publishes the voltage and phase angle of each distribution network to achieve joint simulation between the main and distribution networks.

[0010] A further improvement of the present invention is to use the HELICS platform to establish a federation for the control center, the main network and the distribution network, establish a log to record simulation information, and obtain specific information including time, voltage, power, phase angle and frequency, specifically including:

[0011] Clean up the federation members of the HELICS platform, register and initialize the federation, including establishing a federation for the control center, main network, and distribution network by reading json files in the control center script, main network script, and distribution network script, and establishing a log to record simulation information and obtain specific information including time, voltage, power, phase angle, and frequency.

[0012] A further improvement of the present invention is that the main network and the distribution network run a simulation instance of a single subsystem.

[0013] A further improvement of the present invention is that the primary frequency modulation adopts droop control. When the frequency deviation is greater than the primary frequency modulation dead band, the distributed resources change the active power output. The additional power output of the distributed resources is:

[0014]

[0015] Where f0 is the reference frequency, db UF For low frequency, db OF For over-frequency dead band, D dn is the frequency reduction gain, P drp is the additional power output of distributed resources, and f is the measured system frequency;

[0016] When the frequency deviation exceeds the set value, it is marked as the location where the frequency deviation occurs, and the secondary frequency modulation is started. When the frequency deviation is less than the threshold, it is marked as the end point of the primary frequency modulation.

[0017] A further improvement of the present invention is that the secondary frequency regulation is realized by the control center through automatic power generation control calculation of the regional control error, and the calculation expression of the regional control error is:

[0018] ACE=10B×(f-f0)

[0019] Among them, B is the frequency offset, ACE is the area control error;

[0020] Proportional integral control is used to calculate the regional control error, and the expression is:

[0021] u(t)=-K P ACE-KI

[0022] Among them, u(t) is the secondary frequency modulation instruction, K P , K I is the AGC PI controller coefficient.

[0023] A further improvement of the present invention is to publish and subscribe data between the main distribution network and the control center, specifically including:

[0024] The control center issues secondary frequency regulation instructions and subscribes to the available load margin from the distribution network and the frequency from the main network; the main network issues the voltage, phase angle and frequency of each distribution network and subscribes to the secondary frequency regulation instructions from the control center and the active power from the distribution network; the distribution network issues active power and available load margin and subscribes to the secondary frequency regulation instructions from the control center and the voltage and phase angle from the main network;

[0025] Set the reference voltage and phase angle in the distribution network for initialization and read the distribution network load value; set a log to view the data and information during the simulation; calculate the active and reactive power of the three phases, convert them into complex numbers, and send them to the main network using the HELICS function;

[0026] Initialize the ratio of active power to reactive power and resistive load parameters in the main grid and run the power flow calculation;

[0027] Call the load_read() function in the distribution network to read the current load data, that is, the distribution network load value, which is stored in the now dictionary in the HELICS platform. The available load margin is summed up and published to the control center using the HELICS function.

[0028] After the control center subscribes to the available load margin from the distribution network, it re-issues the secondary frequency regulation instruction to the HELICS platform. After the main network subscribes to the secondary frequency regulation instruction from the control center and the active power from the distribution network, it updates the voltage, phase angle and frequency of each distribution network and publishes them to the HELICS platform again. After the distribution network subscribes to the secondary frequency regulation instruction from the control center and the voltage and phase angle from the main network, it updates the active power and available load margin and publishes them to the HELICS platform again.

[0029] The beneficial effects of the present invention are as follows: the present invention builds an efficient dynamic joint simulation framework for main and distribution networks based on the open source power transmission and distribution simulation tools ANDES (main network ANDES) and OpenDSS (main network ANDES) and the open source information-physical collaborative simulation framework HELICS platform; designs a development process for a large-scale main and distribution network joint simulation framework, which can operate more efficiently and at a lower cost; comprehensively and realistically simulates the power flow distribution between the main and distribution networks, is scalable, and can simulate the impact of distributed resource grid connection on the main and distribution network systems in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of the method of the present invention;

[0031] Figure 2 is a graph showing the change of the main network frequency over time in an embodiment of the present invention;

[0032] Figure 3 1 is a graph showing the change of the automatic power generation control instruction over time in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] The present invention uses the open source power transmission and distribution simulation tool ANDES and OpenDSS, HELICS platform to build an efficient joint simulation framework for the main grid and multiple distribution grids, and performs joint simulation of the main grid and multiple distribution grids based on the joint simulation framework. The present invention takes into account the complex architecture and dynamic characteristics of the distribution network to accurately simulate the real power flow distribution between the main and distribution networks; proposes a method for realizing secondary frequency modulation through automatic power generation control and regional control errors; and studies the impact of a large number of decentralized heterogeneous distributed resources on the main grid and distribution network systems by using distributed resources as distribution network nodes.

[0035] like Figure 1 As shown, the main distribution network dynamic joint simulation method based on HELICS in this embodiment includes the following steps:

[0036] Step 1: Use the HELICS platform to establish a federation for a control center, a main network, and five distribution networks, establish a log to record simulation information, and obtain data such as time, voltage, power, phase angle, and frequency. In the HELICS platform, federates, namely the main network ANDES and distribution network OpenDSS used in this embodiment, run simulation instances of a single subsystem and send and receive signals to other federations.

[0037] The specific operations of this step include:

[0038] Create the following scripts: control center script: control_center.py; main network script: transmission.py; five distribution network scripts: distribution1.py, distribution2.py, distribution3.py, distribution4.py, distribution5.py, and create a log to record information.

[0039] Clean up the federation members in the HELICS platform to ensure that the federation members are correctly removed from the federation and the related resources are released.

[0040] In the control center script, main network script and five distribution network scripts, the federation is established and initialized for the control center, main network and distribution network by reading the json file for subsequent simulation, and specific information such as time, voltage, power, phase angle, frequency, etc. is obtained and recorded in the log.

[0041] Step 2: Set the initial time and time interval in the control center, main network, and distribution network respectively, and wait for the coordination result of the HELICS platform to achieve time synchronization and joint simulation between the control center and the main distribution network, including:

[0042] The HELICS platform coordinates the control center, main network, and distribution network according to the set initial time and interval time, so that the control center and the main distribution network keep time synchronization, and conduct joint simulation to ensure the consistency and synchronization of each federation member in the simulation, allowing each federation member to exchange data and events in the expected order. Once the HELICS platform determines that all relevant federation members can advance to the requested time, the time can be granted as the simulation time.

[0043] Step 3: Primary Frequency Response (PFR) regulates the generator set through Automatic Generation Control (AGC). Specifically, it includes:

[0044] Initialize the parameters. Since there are five distribution networks, create an array agc_dis_mw with a capacity of 5 to store the automatic power generation control instructions for each distribution network; aggacg is used to find the automatic power generation control value of each distribution network. Set the value of the automatic power generation control to 0, and set the value of each automatic power generation control instruction in the array agc_dis_mw to 0.

[0045] The HELICS platform is used to realize the main grid publishing the distribution network frequency and the control center subscribing to the distribution network frequency published by the main grid. After the control center receives the real-time distribution network frequency published by the main grid, it determines whether the power system has entered a steady state based on whether the frequency deviation exceeds 0.04Hz.

[0046] If the steady state is not reached, the primary frequency regulation is performed. The primary frequency regulation adopts droop control, that is, when the frequency deviation is greater than the PFR dead band, the distributed resource (DER) changes its active power output accordingly. An additional power output P is added to the power generation output. drp :

[0047]

[0048] Where f0 is the reference frequency, db UF For low frequency, db OF For over-frequency dead band, D dn is the gain from unit power output change to 1 unit frequency change (frequency reduction gain), P drp is the additional power output of distributed resources, and f is the measured system frequency.

[0049] After the spontaneous process of primary frequency modulation is completed, determine whether the frequency deviation exceeds 0.04Hz. If so, start secondary frequency modulation.

[0050] Secondary Frequency Response (SFR) is implemented by the automatic generation control to calculate the Area Control Error (ACE). The proportional and integral parts of ACE are calculated every four seconds to obtain the total ACE value. A positive ACE indicates that the system is generating excess power, while a negative ACE indicates that the load is greater than the power generation. The calculation expression of the area control error is:

[0051] ACE=10B×(f-f0)

[0052] Where, B is the frequency offset, in MW / 0.1 Hz, and ACE is the area control error;

[0053] After the frequency error tolerance dead band, ACE is used as the regulation signal to calculate the proportional integral (PI) control applied to the AGC, and the control variable u(t) (i.e., the value of the automatic generation control, as the secondary frequency regulation instruction) is controlled.

[0054] u(t)=-K P ACE-K I

[0055] Among them, u(t) is the secondary frequency modulation instruction, K P , K I is the PI controller coefficient.

[0056] If the frequency is within the normal error range for 20 consecutive time intervals, the frequency modulation is successful, indicating that the secondary frequency modulation is successful and the secondary frequency modulation instruction is closed.

[0057] Step 4: Implement data publishing and subscription between the main distribution network and the control center to achieve joint simulation between the main distribution network. Specifically include:

[0058] The control center issues secondary frequency regulation instructions and subscribes to the available load margin from the distribution network and the frequency from the main network; the main network issues the voltage, phase angle and frequency of each distribution network and subscribes to the secondary frequency regulation instructions from the control center and the active power from the distribution network; the distribution network issues active power and available load margin and subscribes to the secondary frequency regulation instructions from the control center and the voltage and phase angle from the main network;

[0059] Set the reference voltage and phase angle in the distribution network for initialization and read the distribution network load value; set a log to view the data and information during the simulation; calculate the active and reactive power of the three phases, convert them into complex numbers, and send them to the main network using the HELICS function; initialize the ratio of active power to reactive power and resistive load parameters in the main network and run the power flow calculation;

[0060] Call the load_read() function in the distribution network to read the current load data, that is, the distribution network load value, which is stored in the now dictionary in the HELICS platform. The available load margin is summed up and published to the control center using the HELICS function.

[0061] After the control center subscribes to the available load margin from the distribution network, it re-issues the secondary frequency regulation instruction to the HELICS platform. After the main network subscribes to the secondary frequency regulation instruction from the control center and the active power from the distribution network, it updates the voltage, phase angle and frequency of each distribution network and publishes them to the HELICS platform again. After the distribution network subscribes to the secondary frequency regulation instruction from the control center and the voltage and phase angle from the main network, it updates the active power and available load margin and publishes them to the HELICS platform again.

[0062] After the simulation is completed, the federation is cleared and a graph of the main grid frequency changing over time and a graph of the automatic generation control value (automatic generation control instruction) received by each distribution network changing over time are plotted.

[0063] In order to verify the accuracy of the dynamic joint simulation method of the main distribution network of the present invention, this embodiment uses the proposed joint simulation framework to conduct a series of simulation experiments under the benchmark scenarios of the IEEE 14 bus system and the IEEE 13 bus feeder positive sequence model. In these distribution systems, 4 distributed photovoltaic (DPV) units with an output power of 0.5MW are added. Assume that these 4 DPV units jointly provide 10% of the total automatic power generation control response, and each DER provides 2.5% of the automatic power generation control response. At the same time, other conventional generator sets will provide 90% of the automatic power generation control response, which is evenly distributed among the 5 conventional generator sets.

[0064] During the experiment, the main network frequency changes over time as shown below: Figure 2 As shown. By setting a 0.676kV generator trip disturbance, it can be observed that the frequency of generator 5 drops rapidly at 20 seconds, then gradually recovers, stabilizes at 25 seconds, and finally recovers to nearly 60Hz. This result shows that the proposed joint simulation framework can accurately capture the dynamic characteristics of the main distribution network frequency changes during the system transient process and effectively realize the frequency regulation function.

[0065] This example connects the IEEE 8500 node feeder system to further study the proposed joint simulation framework. In the IEEE 8500 node feeder system, the secondary frequency regulation command is sent to each individual DER at an interval of 4 seconds. The value of the automatic generation control changes over time as shown in Figure 3 As shown in the figure, when DERs do not provide SFR, the value of their automatic generation control is zero; once DERs start to provide SFR, their AGC signal will change according to the demand for the value of the overall automatic generation control. This phenomenon further verifies the effectiveness of the proposed framework in dynamic response and provides strong support for the optimal scheduling of future distribution systems.

[0066] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have the same meaning as in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined similarly here.

[0067] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dynamic joint simulation method for main and distribution networks based on HELICS, characterized by: The following operations are included: Use the HELICS platform to establish a federation for the control center, main network and distribution network, establish a log for recording simulation information, and obtain specific information including time, voltage, power, phase angle and frequency; Set the initial time and time interval in the control center, main network, and distribution network respectively, and wait for the HELICS platform to coordinate the control center, main network, and distribution network according to the set initial time and time interval, so that the control center keeps time synchronization with the main network and distribution network, and conduct joint simulation, where the joint simulation includes: Perform primary frequency modulation and secondary frequency modulation; Publish and subscribe data between the main distribution network and the control center. The distribution network publishes the available load margin to the control center and sends power to the main network. The main network publishes the voltage and phase angle of each distribution network to achieve joint simulation between the main and distribution networks.

2. The main distribution network dynamic joint simulation method based on HELICS according to claim 1 is characterized in that: The HELICS platform is used to establish a federation for the control center, the main network and the distribution network, and a log is established to record simulation information, and obtain specific information including time, voltage, power, phase angle and frequency, specifically including: Clean up the federation members of the HELICS platform, register and initialize the federation, including establishing a federation for the control center, main network, and distribution network by reading json files in the control center script, main network script, and distribution network script, and establishing a log to record simulation information and obtain specific information including time, voltage, power, phase angle, and frequency.

3. The main distribution network dynamic joint simulation method based on HELICS according to claim 2 is characterized in that: The main network and the distribution network run a simulation instance of a single subsystem.

4. The main distribution network dynamic joint simulation method based on HELICS according to claim 1 is characterized in that: The primary frequency modulation adopts droop control. When the frequency deviation is greater than the primary frequency modulation dead band, the distributed resources change the active power output. The additional power output of the distributed resources is: Where f0 is the reference frequency, db UF For low frequency, db OF For over-frequency dead band, D dn is the frequency reduction gain, P drp is the additional power output of distributed resources, and f is the measured system frequency; When the frequency deviation exceeds the set value, it is marked as the location where the frequency deviation occurs, and the secondary frequency modulation is started. When the frequency deviation is less than the threshold, it is marked as the end point of the primary frequency modulation.

5. The main distribution network dynamic joint simulation method based on HELICS according to claim 4 is characterized in that: The secondary frequency regulation is realized by the control center through automatic power generation control calculation of the regional control error. The calculation expression of the regional control error is: ACE=10B×(f-f0) Among them, B is the frequency offset, ACE is the area control error; Proportional integral control is used to calculate the regional control error, and the expression is: u(t=-K P ACE-K I Among them, u(t) is the secondary frequency modulation instruction, K P , K I is the AGCPI controller coefficient.

6. The main distribution network dynamic joint simulation method based on HELICS according to claim 1 is characterized in that: The publishing and subscription of data between the main distribution network and the control center specifically includes: The control center issues secondary frequency regulation instructions and subscribes to the available load margin from the distribution network and the frequency from the main network; the main network issues the voltage, phase angle and frequency of each distribution network and subscribes to the secondary frequency regulation instructions from the control center and the active power from the distribution network; the distribution network issues active power and available load margin and subscribes to the secondary frequency regulation instructions from the control center and the voltage and phase angle from the main network; Set the reference voltage and phase angle in the distribution network for initialization and read the distribution network load value; set a log to view the data and information during the simulation; calculate the active and reactive power of the three phases, convert them into complex numbers, and send them to the main network using the HELICS function; initialize the ratio of active power to reactive power and resistive load parameters in the main network and run the power flow calculation; Call the load_read() function in the distribution network to read the current load data, that is, the distribution network load value, which is stored in the now dictionary in the HELICS platform. The available load margin is summed up and published to the control center using the HELICS function. After the control center subscribes to the available load margin from the distribution network, it re-issues the secondary frequency regulation instruction to the HELICS platform. After the main network subscribes to the secondary frequency regulation instruction from the control center and the active power from the distribution network, it updates the voltage, phase angle and frequency of each distribution network and publishes them to the HELICS platform again. After the distribution network subscribes to the secondary frequency regulation instruction from the control center and the voltage and phase angle from the main network, it updates the active power and available load margin and publishes them to the HELICS platform again.

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