A control method for avoiding voltage swing in variable frequency drive of important industrial plants

Abstract

The present invention discloses a control method for avoiding voltage swings in variable frequency transmission of important industrial plants and stations. First, for an important industrial plant and station including N variable frequency transmission devices, a voltage swing avoidance energy storage configuration structure is constructed that is embedded in the DC side. Then, the DC side bus voltage V is monitored. dc , when the absolute value of the voltage change |ΔV dc When the voltage change is greater than the set threshold δ, the voltage change ΔV dc Calculate the compensation current value I dc , and further according to the voltage change ΔV dc The energy storage unit is controlled by the state of charge SOC of the energy storage unit to maintain the DC bus voltage V dc Constant or limited DC bus voltage V dc The present invention can timely adjust the output of the energy storage unit. When a voltage fluctuation occurs, the DC link voltage briefly fluctuates before returning to the rated value within 0.5 seconds. This means that the present invention can achieve the goal of avoiding voltage fluctuations and maintaining DC link voltage stability in variable frequency drives for important industrial plants.

Description

Technical Field

[0001] The present invention belongs to the technical field of voltage fluctuation in industrial plants and stations, and more specifically, relates to a control method for avoiding voltage fluctuation in a variable frequency drive of an important industrial plant and station. Background Art

[0002] The industrial power grid is the most important infrastructure for industrial production and life, and the power supply system that directly provides energy to important factories and stations on the front line of industrial production has become the lifeblood of industrial production. The quality of power supply is directly related to whether the production of industrial factories and stations can operate safely, normally and stably, and is also related to the competitive survival ability of industrial enterprises and whether they can develop long-term, sustainable and healthy.

[0003] Currently, industrial power supply systems are plagued by voltage fluctuations, voltage swells, voltage sags, short interruptions, and long interruptions. Serious power grid quality issues can directly lead to major industrial accidents and substantial property losses. For example, a typical pilot thermal recovery industrial boiler softening water station is responsible for the critical task of supplying softened water to hundreds of industrial steam injection boilers. A failure of a variable frequency feedwater pump can trigger a low feedwater pressure alarm, leading to widespread boiler shutdowns and potentially a series of major incidents. This demonstrates the significant impact of power supply quality on industrial power supply systems. These issues can be caused by grid line faults (such as grounding), unstable power grids in upstream substations, and faults in nearby power equipment. These can cause transient power fluctuations and voltage sags within the station's power supply system, ultimately causing the inverter to shut down due to low voltage alarms.

[0004] Currently, the main method to solve the voltage fluctuation problem is to use the online AVC (Active Voltage Conditioner) method, but it still has the following problems:

[0005] First, online AVC can only control 40% of shallow voltage fluctuations, and electrical equipment can only avoid being affected by shallow voltage sags and voltage swells.

[0006] Second, the online AVC method cannot compensate for deep sags. Shallow sags can only be compensated for more than 10 seconds, but voltage sag events are all within 2 seconds. Therefore, it is more important to control sags over the entire sag depth range.

[0007] Third, the online AVC method uses compensation energy from the grid, which inevitably leads to a significant increase in the current of the front-end grid. If the upstream circuit breakers, protection relays, transformers, and other equipment do not have sufficient margin, this can lead to equipment damage and power outages. In other words, online AVC has a significant impact on the reliability of peripheral equipment.

[0008] Fourth, the online AVC method has an efficiency of 98-99% at full load, resulting in large losses. Summary of the Invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a control method for avoiding voltage fluctuations in variable frequency drives of important industrial plants and stations to control deep voltage fluctuations.

[0010] To achieve the above-mentioned object, the present invention provides a method for controlling voltage fluctuations in a variable frequency drive of an important industrial plant, characterized by comprising the following steps:

[0011] (1) For an important industrial plant station including N variable frequency transmission devices, a voltage-swing-avoiding energy storage configuration structure embedded in the DC side is constructed, wherein the voltage-swing-avoiding energy storage configuration structure includes an energy storage unit, a bidirectional DC-DC converter, and a controller, wherein the positive and negative terminals on one side of the bidirectional DC-DC converter are respectively connected to the positive and negative terminals of the energy storage unit, and the positive and negative terminals on the other side are respectively connected to the positive and negative terminals of the DC side busbars of the N variable frequency transmission devices;

[0012] (2) Monitor the DC bus voltage V of N variable frequency drive devices dc , calculate its voltage change ΔV dc :

[0013]

[0014] in, is the rated value of the DC bus voltage;

[0015] (3) The absolute value of the voltage change |ΔV dc | is compared with the set threshold δ, if the absolute value |ΔV dc | is less than or equal to the threshold δ, then return to step (2) and continue to adjust the DC bus voltage V dc Monitor, if the absolute value |ΔV dc | is greater than the threshold δ, then go to step (4);

[0016] (4) According to the voltage change ΔV dc Calculate the compensation current value I dc , and further according to the voltage change ΔV dc And the state of charge SOC of the energy storage unit to control the energy storage unit:

[0017] 4.1) If the voltage change ΔV dc <0, and the state of charge SOC is less than the high state of charge SOC high , the controller controls the bidirectional DC-DC converter to obtain power from the DC bus of N variable frequency drive devices at a higher rate to charge the energy storage unit to maintain the DC bus voltage V dc constant;

[0018] 4.2) If the voltage change ΔV dc <0, and the state of charge SOC is greater than or equal to the high state of charge SOC high But less than the upper limit of state of charge SOC max , the controller controls the bidirectional DC-DC converter to obtain electric energy from the DC bus of N variable frequency drive devices at a lower rate to charge the storage unit, limiting the DC bus voltage V dc Ascent rate;

[0019] 4.3) If the voltage change ΔV dc >0, and the state of charge SOC is greater than the low state of charge SOC low , the controller controls the bidirectional DC-DC converter to discharge the energy storage unit at a higher rate, obtains electrical energy and outputs it to the DC bus to maintain the DC bus voltage V dc constant;

[0020] 4.4) If the voltage change ΔV dc >0, and the state of charge SOC is less than or equal to the low state of charge SOC low But it is greater than the lower limit of state of charge SOC min , the controller controls the bidirectional DC-DC converter to discharge the energy storage at a lower rate, discharge the energy storage unit, obtain electrical energy and output it to the DC bus to limit the DC bus voltage V dc descent rate;

[0021] The controller controls the bidirectional DC-DC converter by obtaining a duty cycle signal through current loop control, and controls the bidirectional DC-DC converter with the duty cycle signal to control the charging and discharging behavior of the energy storage unit until the DC side bus voltage V dc The monitoring result is lower than the threshold value, i.e. the absolute value |ΔV dc | is less than or equal to the threshold δ.

[0022] The object of the invention of the present invention is achieved like this:

[0023] The present invention provides a control method for avoiding voltage swings in variable frequency transmission of important industrial plants and stations. First, for an important industrial plant and station including N variable frequency transmission devices, a voltage swing avoidance energy storage configuration structure is built on the DC side. Then, the DC side bus voltage V is monitored. dc , when the absolute value of the voltage change |ΔV dc When the voltage change is greater than the set threshold δ, the voltage change ΔV dc Calculate the compensation current value I dc , and further according to the voltage change ΔV dc The energy storage unit is controlled by the state of charge SOC of the energy storage unit to maintain the DC bus voltage V dc Constant or limited DC bus voltage Vdc The present invention can timely adjust the output of the energy storage unit. When a voltage fluctuation occurs, the DC link voltage briefly fluctuates before returning to the rated value within 0.5 seconds. This means that the present invention can achieve the goal of avoiding voltage fluctuations and maintaining DC link voltage stability in variable frequency drives for important industrial plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a flow chart of a specific implementation method of the control method for avoiding voltage swings in variable frequency transmission of important industrial plants and stations of the present invention;

[0025] Figure 2 This is a schematic diagram of the control principle of the variable frequency drive to avoid voltage fluctuations in important industrial plants and stations;

[0026] Figure 3 yes Figure 2 The schematic diagram of the principle of the voltage-swing-avoiding energy storage configuration structure is shown;

[0027] Figure 4 It is based on the voltage change ΔV dc A flow chart for controlling the energy storage unit based on the state of charge (SOC) of the energy storage unit;

[0028] Figure 5 This is a principle block diagram of a specific implementation method of controlling the energy storage unit during voltage fluctuations of the present invention;

[0029] Figure 6 This is a specific example result diagram of the energy storage unit voltage simulation when voltage fluctuation occurs;

[0030] Figure 7 This is a specific example result diagram of the DC bus voltage simulation when a voltage swing occurs. DETAILED DESCRIPTION

[0031] The following describes the specific embodiments of the present invention in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when detailed descriptions of known functions and designs may dilute the main content of the present invention, such descriptions will be omitted here.

[0032] Figure 1 This is a flow chart of a specific implementation method of the control method for avoiding voltage swings in variable frequency transmission of important industrial plants and stations of the present invention.

[0033] In this embodiment, if Figure 1 As shown, the control method for avoiding voltage fluctuations in the variable frequency drive of an important industrial plant of the present invention includes the following steps:

[0034] Step S1: Construct a voltage-swing-avoiding energy storage configuration structure embedded in the DC side

[0035] like Figure 2 As shown, for an important industrial plant containing N variable frequency transmission devices, based on the characteristics of the variable frequency transmission devices using AC-DC-AC converters, a voltage-swing-avoiding energy storage configuration structure embedded on the DC side is constructed. The voltage-swing-avoiding energy storage configuration structure includes an energy storage unit, a bidirectional DC-DC converter, and a controller. The positive and negative ends of one side of the bidirectional DC-DC converter are respectively connected to the positive and negative ends of the energy storage unit, and the positive and negative ends of the other side are respectively connected to the positive and negative ends of the DC side bus of the N variable frequency transmission devices, that is, the positive and negative ends of the DC side bus of the N variable frequency transmission devices are respectively connected in parallel to the positive and negative ends on the other side of the bidirectional DC-DC converter.

[0036] The energy storage unit can be a supercapacitor or a high-rate battery. The amount of stored charge changes with the charge and discharge process. This change can be described by the state of charge (SOC). SOC represents the parameter of the charge storage degree of the energy storage unit. It is usually expressed in percentage form, from 0% (fully discharged) to 100% (fully charged). In addition, in order to ensure the performance and life of the energy storage unit, the SOC sets an upper limit SOC. max and lower limit SOC min , which means that the energy storage unit will not be charged beyond its upper limit nor discharged below its lower limit during use, thereby optimizing its operating efficiency and maintenance safety.

[0037] A bidirectional DC-DC converter implements a bidirectional connection across a DC bus, allowing current and voltage to flow in both directions between the high-voltage and low-voltage sides. The topology primarily consists of the following key components: IGBT switching devices, inductors, and stabilizing capacitors. When the switch is on, the inductor stores energy; when the switch is off, the inductor releases the stored energy, delivering current to the load through the diode and output filter capacitor. Figure 3 The basic topology of a bidirectional converter used to sink or deliver power to the DC bus is shown.

[0038] The inductor stores and transfers energy based on the IGBT's operating state. When the grid voltage experiences an anomaly, such as a power surge, the inverter's DC bus voltage fluctuates accordingly. When the voltage drops below a preset value, the IGBT conducts forward, and the DC-DC converter quickly responds with power output and controls the discharge of the energy storage unit based on the load current, maintaining the device's DC output voltage stable at the preset value and ensuring normal system operation. When the grid voltage returns to normal, the inverter bus's internal rectification restores it to its normal value, at which point the IGBT switches to reverse direction, and the energy storage unit enters standby mode.

[0039] The control goal of the controller is to keep the DC link voltage constant, and the PI control method is used to achieve voltage and current dual closed-loop control.

[0040] Step S2: Monitor the DC bus voltage V dc And calculate the voltage change ΔV dc

[0041] Monitor the DC bus voltage V of N variable frequency drive devices dc , calculate its voltage change ΔV dc :

[0042]

[0043] in, is the rated value of the DC bus voltage.

[0044] Step S3: Determine the absolute value of the voltage change |ΔV dc |Is it greater than the set threshold δ

[0045] The absolute value of the voltage change |ΔV dc | is compared with the set threshold δ, if the absolute value |ΔV dc | is less than or equal to the threshold δ, then return to step S2: continue to measure the DC side bus voltage V of N variable frequency drive devices dc Monitor, if the absolute value |ΔV dc | is greater than the threshold δ, then proceed to step S4.

[0046] Step S4: According to the voltage change ΔV dc Calculate the compensation current value I dc , and further according to the voltage change ΔV dc The energy storage unit is controlled by the state of charge SOC of the energy storage unit, as shown in the following example: Figure 4 As shown, the following steps are included:

[0047] Step S4.1: If the voltage change ΔV dc <0, and the state of charge SOC is less than the high state of charge SOC high , the controller controls the bidirectional DC-DC converter to obtain power from the DC bus of N variable frequency drive devices at a higher rate to charge the energy storage unit to maintain the DC bus voltage V dc constant;

[0048] Step S4.2: If the voltage change ΔV dc <0, and the state of charge SOC is greater than or equal to the high state of charge SOC high But less than the upper limit of state of charge SOC max , the controller controls the bidirectional DC-DC converter to obtain electric energy from the DC bus of N variable frequency drive devices at a lower rate to charge the storage unit, limiting the DC bus voltage V dc Ascent rate;

[0049] Step S4.3: If the voltage change ΔV dc >0, and the state of charge SOC is greater than the low state of charge SOC low , the controller controls the bidirectional DC-DC converter to discharge the energy storage unit at a higher rate, obtains electrical energy and outputs it to the DC bus to maintain the DC bus voltage V dc constant;

[0050] Step S4.4: If the voltage change ΔV dc >0, and the state of charge SOC is less than or equal to the low state of charge SOC low But it is greater than the lower limit of state of charge SOC min , the controller controls the bidirectional DC-DC converter to discharge the energy storage at a lower rate, discharge the energy storage unit, obtain electrical energy and output it to the DC bus to limit the DC bus voltage V dc descent rate;

[0051] The controller controls the bidirectional DC-DC converter by obtaining a duty cycle signal through current loop control, and controls the bidirectional DC-DC converter with the duty cycle signal to control the charging and discharging behavior of the energy storage unit until the DC side bus voltage V dc The monitoring result is lower than the threshold value, i.e. the absolute value |ΔV dc | is less than or equal to the threshold δ.

[0052] In this embodiment, if Figure 5 As shown, the voltage change ΔV dc Calculate the compensation current value I dc for:

[0053] The DC bus voltage V dc The voltage change ΔV dc (i.e. error signal) is sent to the voltage controller (PI controller). The voltage controller is designed to quickly and accurately calculate the required compensation current value I according to the size and change trend of the error signal. dc :

[0054]

[0055] in, and are the proportional and integral term coefficients respectively.

[0056] In this embodiment, the step S4.1: if the voltage change ΔV dc <0, and the state of charge SOC is less than the high state of charge SOC high, the controller controls the bidirectional DC-DC converter to obtain power from the DC bus of N variable frequency drive devices at a higher rate to charge the energy storage unit to maintain the DC bus voltage V dc Constant is:

[0057] In this case, the DC bus voltage V dc Increases, and the energy storage unit has a large charging capacity, charging the energy storage at a higher rate to maintain a constant DC side voltage. At this time, the reference current of the energy storage unit for:

[0058]

[0059] Where, τ f is the time constant of the energy storage system.

[0060] In this embodiment, if the voltage change ΔV in step S4.2 is dc <0, and the state of charge SOC is greater than or equal to the high state of charge SOC high But less than the upper limit of state of charge SOC max , the controller controls the bidirectional DC-DC converter to obtain electric energy from the DC bus of N variable frequency drive devices at a lower rate to charge the storage unit, limiting the DC bus voltage V dc The rate of ascent is:

[0061] In this case, the DC bus voltage V dc Increase, and the energy storage unit has a small charging capacity, charging the energy storage at a lower rate, limiting the DC side voltage rising rate, at this time the reference current of the energy storage unit for:

[0062]

[0063] Among them, 0 <k ESS <1 is a constant.

[0064] In this embodiment, the step S4.3: if the voltage change ΔV dc >0, and the state of charge SOC is greater than the low state of charge SOC low , the controller controls the bidirectional DC-DC converter to discharge the energy storage unit at a higher rate, obtains electrical energy and outputs it to the DC bus to maintain the DC bus voltage V dc Constant is:

[0065] In this case, the DC bus voltage V dc Decreases, and the energy storage unit has a large discharge capacity, and discharges the energy storage at a higher rate to maintain a constant DC side voltage. At this time, the energy storage unit reference current for:

[0066]

[0067] In this embodiment, the step S4.4: if the voltage change ΔV dc >0, and the state of charge SOC is less than or equal to the low state of charge SOC low But it is greater than the lower limit of state of charge SOC min , the controller controls the bidirectional DC-DC converter to discharge the energy storage at a lower rate, discharge the energy storage unit, obtain electrical energy and output it to the DC bus to limit the DC bus voltage V dc The descent rate is:

[0068] In this case, the DC bus voltage V dc The energy storage unit has a smaller discharge capacity and discharges the energy at a lower rate to limit the DC side voltage drop rate. At this time, the energy storage unit reference current for

[0069]

[0070] In this embodiment, the controller in the voltage swing avoidance energy storage configuration structure aims to stabilize the DC side voltage of the variable frequency drive device, obtains a duty cycle signal through current loop control, and controls the bidirectional DC-DC converter with the duty cycle signal to control the charging and discharging behavior of the energy storage unit until the DC side bus voltage V dc The monitoring result is lower than the threshold value, i.e. the absolute value |ΔV dc | is less than or equal to the threshold δ, such as Figure 5 Specifically:

[0071] The energy storage unit reference current and the energy storage unit measuring current I ESS The difference is fed into the current controller, and the PI control strategy is also adopted to obtain the duty cycle signal D ESS , as shown in the formula:

[0072]

[0073] in, and are the proportional and integral term coefficients respectively.

[0074] The duty cycle signal D ESS The current to duty cycle transfer function G ESS,ID , get the actual current of the energy storage unit at this time

[0075]

[0076] Among them, Cdc is the DC link capacitance, R L is the load resistance, L ESS is the converter inductor.

[0077] Actual current of energy storage unit Through the transfer function G f (s) Get the energy storage unit measurement current I ESS :

[0078]

[0079] The actual current of the energy storage unit is obtained The actual DC bus voltage is obtained through the current-to-voltage transfer function.

[0080]

[0081] Actual DC bus voltage Through the transfer function G f (s) Get the DC bus voltage V dc :

[0082] According to the above steps, the charging and discharging behavior of the energy storage unit is controlled until the DC bus voltage V dc The monitoring result is lower than the threshold δ.

[0083] To verify the correctness of the control method for avoiding voltage swing in the variable frequency drive of industrial power plants, a simulation model was established in MATLAB software and simulation verification was performed. The simulation duration was set to 9s. At 2.5s, 4s, 5.5s, and 7s, the AC bus voltage fluctuated, causing the absolute value of the DC bus voltage change to be |ΔV dc | is greater than the set threshold δ. At this time, in order to maintain the stability of the DC link voltage, according to step S4: control the charging and discharging of the energy storage unit, monitor the voltage of the energy storage unit when the voltage fluctuation occurs, and the result is as follows: Figure 6 As shown; while monitoring the DC bus voltage V dc , the results are as follows Figure 7 shown.

[0084] from Figure 6 、 7 It can be seen from the figure that the present invention can timely adjust the output of the energy storage unit. When voltage fluctuation occurs, the DC bus voltage V dc After a short fluctuation, it can recover to the rated value within 0.5s, that is, the present invention can realize the variable frequency drive of important industrial plants to avoid voltage swings and maintain the DC side bus voltage V dc Stable target.

[0085] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concepts of the present invention are protected.

Claims

1. A control method for avoiding voltage fluctuations in variable frequency drives of important industrial plants, characterized in that: The following steps are involved: (1) For an important industrial plant station including N variable frequency transmission devices, a voltage-swing-avoiding energy storage configuration structure embedded in the DC side is constructed, wherein the voltage-swing-avoiding energy storage configuration structure includes an energy storage unit, a bidirectional DC-DC converter, and a controller, wherein the positive and negative terminals on one side of the bidirectional DC-DC converter are respectively connected to the positive and negative terminals of the energy storage unit, and the positive and negative terminals on the other side are respectively connected to the positive and negative terminals of the DC side busbars of the N variable frequency transmission devices; (2) Monitor the DC bus voltage V of N variable frequency drive devices dc , calculate its voltage change ΔV dc : in, is the rated value of the DC bus voltage; (3) The absolute value of the voltage change |ΔV dc | is compared with the set threshold δ, if the absolute value |ΔV dc | is less than or equal to the threshold δ, then return to step (2) and continue to adjust the DC bus voltage V dc Monitor, if the absolute value |ΔV dc | is greater than the threshold δ, then go to step (4); (4) According to the voltage change ΔV dc Calculate the compensation current value I dc , and further according to the voltage change ΔV dc And the state of charge SOC of the energy storage unit to control the energy storage unit: 4.1) If the voltage change ΔV dc <0, and the state of charge SOC is less than the high state of charge SOC high , the controller controls the bidirectional DC-DC converter to obtain power from the DC bus of N variable frequency drive devices at a higher rate to charge the energy storage unit to maintain the DC bus voltage V dc constant; 4.2) If the voltage change ΔV dc <0, and the state of charge SOC is greater than or equal to the high state of charge SOC high But less than the upper limit of state of charge SOC max , the controller controls the bidirectional DC-DC converter to obtain electric energy from the DC bus of N variable frequency drive devices at a lower rate to charge the storage unit, limiting the DC bus voltage V dc Ascent rate; 4.3) If the voltage change ΔV dc >0, and the state of charge SOC is greater than the low state of charge SOC low , the controller controls the bidirectional DC-DC converter to discharge the energy storage unit at a higher rate, obtains electrical energy and outputs it to the DC bus to maintain the DC bus voltage V dc constant; 4.4) If the voltage change ΔV dc >0, and the state of charge SOC is less than or equal to the low state of charge SOC low But it is greater than the lower limit of state of charge SOC min , the controller controls the bidirectional DC-DC converter to discharge the energy storage at a lower rate, discharge the energy storage unit, obtain electrical energy and output it to the DC bus to limit the DC bus voltage V dc descent rate; The controller controls the bidirectional DC-DC converter by obtaining a duty cycle signal through current loop control, and controls the bidirectional DC-DC converter with the duty cycle signal to control the charging and discharging behavior of the energy storage unit until the DC side bus voltage V dc The monitoring result is lower than the threshold value, i.e. the absolute value |ΔV dc | is less than or equal to the threshold δ.

2. The control method for avoiding voltage fluctuations in variable frequency drives of important industrial plants according to claim 1 is characterized in that: According to the voltage change ΔV dc Calculate the compensation current value I dc for: The DC bus voltage V dc The voltage change ΔV dc The voltage controller is designed to quickly and accurately calculate the required compensation current value I according to the size and change trend of the error signal. dc : in, and are the proportional and integral term coefficients respectively.

3. The control method for avoiding voltage fluctuations in variable frequency drives of important industrial plants according to claim 2 is characterized in that: In step 4.1), the reference current of the energy storage unit for: Among them, τ f is the time constant of the energy storage system; In step 4.2), the reference current of the energy storage unit for: Among them, 0 <k ESS <1 is a constant; In step 4.3), the energy storage unit reference current for: In step 4.4), the energy storage unit reference current for:

4. The control method for avoiding voltage fluctuations in variable frequency drives of important industrial plants according to claim 1 is characterized in that: The duty cycle signal is obtained by current loop control, and the duty cycle signal is used to control the bidirectional DC-DC converter to control the charging and discharging behavior of the energy storage unit until the DC side bus voltage V dc The monitoring result is lower than the threshold value, i.e. the absolute value |ΔV dc | is less than or equal to the threshold δ: The energy storage unit reference current and the energy storage unit measuring current I ESS The difference is fed into the current controller, and the PI control strategy is also adopted to obtain the duty cycle signal D ESS , as shown in the formula: in, and are the proportional and integral term coefficients respectively; The duty cycle signal D ESS The current to duty cycle transfer function G ESS,ID , get the actual current of the energy storage unit at this time Among them, C dc is the DC link capacitance, R L is the load resistance, L ESS is the converter inductance; Actual current of energy storage unit Through the transfer function G f (s) Get the energy storage unit measurement current I ESS : The actual current of the energy storage unit is obtained The actual DC bus voltage is obtained through the current-to-voltage transfer function. Actual DC bus voltage Through the transfer function G f (s) Get the DC bus voltage V dc : According to the above steps, the charging and discharging behavior of the energy storage unit is controlled until the DC bus voltage V dc The monitoring result is lower than the threshold δ.

Images