Smoothing method for network side output power of charging station

Abstract

The invention belongs to the technical field of charging station power regulation, and particularly relates to a smoothing method of charging station network side output power, which comprises the following steps of: 1) calculating a set time period before the current moment and an average value of charging total demand power of a charging station at the current moment; 2) obtaining the network side target power of the charging station at the current moment according to the average value of the charging total demand power; and (3) calculating a difference value between the total required power of the charging station at the current moment and the grid-side target power, and adjusting the power of the energy storage system according to the difference value so as to enable the grid-side output power of the charging station to reach the grid-side target power. Through the method, the network side target power of the charging station cannot be suddenly and greatly increased or smaller, the network side power can be adjusted according to the network side target power of the charging station, so that the change of the network side power is smoother, larger impact on the power distribution network cannot be generated, and the stable operation of the charging station and the power distribution network can be ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of charging station power regulation, and in particular relates to a method for smoothing the output power of a charging station network side. Background Art

[0002] With the development of the electric vehicle industry, the demand for charging power is increasing, and corresponding high-power charging piles have also emerged. The current single-gun charging power can reach about 500kW. Although high-power charging can solve the problem of charging anxiety, it is accompanied by a sharp fluctuation in the power distribution power of the power grid, which is very unfavorable for the stable operation of the power grid, especially irregular charging behavior (such as stopping the current charging by emergency stop, etc.) The impact on the power grid is more serious. With the construction of large-scale charging stations, this unfavorable factor will become more and more obvious, which will have a huge impact on the normal operation of the power grid. For example, when a user suddenly stops or starts charging, the total charging power demand of the charging station will drop or rise sharply. At this time, if the target power on the grid side is directly equal to the total charging power demand of the charging station, the power on the grid side will also change rapidly, which will have an impact on the distribution network and affect the normal operation of the distribution network. Summary of the invention

[0003] The object of the present invention is to provide a method for smoothing the output power of a charging station network, so as to solve the technical problem of sharp fluctuations in power distribution network caused by sudden stopping or starting of charging of a high-power charging pile.

[0004] In order to solve the above technical problems, the present invention provides a method for smoothing the output power of the charging station network side, comprising the following steps:

[0005] 1) Calculate the average value of the total charging power demand of the charging station in the set time period before the current time and at the current time;

[0006] 2) Obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power;

[0007] 3) Calculate the difference between the total power demand of the charging station at the current moment and the target power on the grid side, and adjust the power of the energy storage system according to the difference so that the grid-side output power of the charging station reaches the target power on the grid side.

[0008] Furthermore, the method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is: using the average value of the total charging demand power minus the average power generation power of the photovoltaic power generation unit in the set time period and the current moment to obtain the grid-side target power of the charging station at the current moment; the calculation formula for the average power generation power of the photovoltaic power generation unit in the set time period and the current moment is:

[0009]

[0010] Where P 光平均t1 is the average power generation of the photovoltaic power generation unit in the set time period and at the current moment, P 光t is the photovoltaic power generation at time t, t1 is the current time, t1-m is the starting time of the set time period, and m is the duration of the set time period;

[0011] The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference minus the power generation power of the photovoltaic power generation unit at the current moment.

[0012] Furthermore, the method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is: using the average value of the total charging demand power minus the power adjusted by the electricity price at the current moment to obtain the grid-side target power of the charging station at the current moment; the calculation formula of the power adjusted by the electricity price at the current moment is:

[0013] P 电价调 =k1*P*f(sr)

[0014]

[0015] Where P 电价调 is the power adjusted by the electricity price, k1 is the power coefficient adjusted by the electricity price, 0<k1≤1, P is the rated power of the energy storage system, s is the real-time SOC value of the energy storage system, r is the target SOC value of the energy storage system, k2 is the set multiple, a is the lower limit of the SOC difference, and b is the upper limit of the SOC difference;

[0016] The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference.

[0017] Further, the method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is: using the average value of the total charging demand power minus the electricity price adjustment power at the current moment, and then minus the electricity price adjustment power at the current moment to obtain the grid-side target power of the charging station at the current moment;

[0018] The calculation formula for the average power generation of the photovoltaic power generation unit in the set time period and the current moment is:

[0019]

[0020] Where P 光平均t1 is the average power generation of the photovoltaic power generation unit in the set time period and at the current moment, P 光t is the photovoltaic power generation at time t, t1 is the current time, t1-m is the starting time of the set time period, and m is the duration of the set time period;

[0021] The calculation formula of the power adjustment by the electricity price at the current moment is:

[0022] P 电价调 =k1*P*f(sr)

[0023]

[0024] Where P 电价调 is the power adjusted by the electricity price, k1 is the power coefficient adjusted by the electricity price, 0<k1≤1, P is the rated power of the energy storage system, s is the real-time SOC value of the energy storage system, r is the target SOC value of the energy storage system, k2 is the set multiple, a is the lower limit of the SOC difference, and b is the upper limit of the SOC difference;

[0025] The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference minus the power generation power of the photovoltaic power generation unit at the current moment.

[0026] Furthermore, the method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is: making the grid-side target power of the charging station at the current moment equal to the average value of the total charging demand power;

[0027] The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference.

[0028] Furthermore, the target value of the SOC of the energy storage system is set according to the real-time electricity price. The higher the real-time electricity price, the lower the target value of the SOC of the energy storage system.

[0029] The present invention is an improved invention creation, and its beneficial effects are as follows: the method for smoothing the grid-side output power of the charging station of the present invention uses the average value of the total demand power of the charging station in the set time period before the current moment to obtain the grid-side target power of the charging station. When the total demand power of the charging station at this moment fluctuates greatly, since the average value of the total demand power of the charging station in the set time period is smoothed by data at other moments, the grid-side target power of the present invention will not have a large mutation. Compared with the adjustment method of directly making the grid-side target power equal to the total demand power of the charging station at this moment, the method for smoothing the grid-side output power of the charging station of the present invention, the grid-side target power of the charging station will not suddenly increase or decrease significantly. Adjusting the grid-side power according to the grid-side target power of the charging station can make the change of the grid-side power smoother, will not have a large impact on the distribution network, and can ensure the smooth operation of the charging station and the distribution network. According to the difference between the total demand power of the charging station at the current moment and the grid-side target power, the power of the energy storage system is adjusted, ensuring that the grid-side output power of the charging station can reach the grid-side target power when the total demand power of the charging station at the current moment can be met. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic structural diagram of a photovoltaic charging station according to Embodiment 1 of the present invention;

[0031] Figure 2 It is a flow chart of a method for smoothing the output power of a charging station network side according to Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0032] The method for smoothing the grid-side output power of the charging station of the present invention uses the average value of the total power demand of the charging station in the set time period before the current moment to obtain the grid-side target power of the charging station. When the total power demand of the charging station at this moment fluctuates greatly, since the average value of the total power demand of the charging station in the set time period is smoothed by data at other moments, the grid-side target power of the present invention will not have a large mutation. Compared with the adjustment method of directly making the grid-side target power equal to the total power demand of the charging station at this moment, the method for smoothing the grid-side output power of the charging station of the present invention will not suddenly increase or decrease the grid-side target power of the charging station. Adjusting the grid-side power according to the grid-side target power of the charging station can make the change of the grid-side power smoother, will not have a large impact on the distribution network, and can ensure the smooth operation of the charging station and the distribution network. According to the difference between the total power demand of the charging station at the current moment and the grid-side target power, the power of the energy storage system is adjusted to ensure that the grid-side output power of the charging station can reach the grid-side target power when the total power demand of the charging station at the current moment can be met.

[0033] Embodiment 1:

[0034] For ease of understanding and explanation, this embodiment uses a photovoltaic charging station with a charging pile, an energy storage system, and a photovoltaic power generation system for explanation. The structure of the photovoltaic charging station is as follows: Figure 1 As shown; the present invention solves the problem that the total power demand of the charging station cannot be met after the grid-side power is smoothed by adjusting the power of the energy storage system. The energy storage system can both charge and discharge, and no matter whether the total power demand suddenly increases or decreases, it can be met by the energy storage system.

[0035] like Figure 1 As shown, the DC bus photovoltaic storage and charging system of this embodiment includes: a bidirectional AC / DC converter connecting the 0.4kV distribution network and the DC bus; an isolated DC / DC module connecting the DC bus and the charging gun; a bidirectional DC / DC module connecting the DC bus and the battery pack; and a DC / DC module connecting the DC bus and the photovoltaic panel.

[0036] The method for controlling the grid-side power of a charging station of the present invention obtains the grid-side target power of the charging station based on the average value of the total charging demand power of the charging station over a period of time in the past, the average value of the photovoltaic power generation power and the real-time electricity price adjustment power, and adjusts the charging and discharging power of the energy storage unit of the charging station according to the grid-side target power of the charging station, so that the actual grid-side power reaches the target power.

[0037] like Figure 2 As shown, the method for smoothing the output power of the charging station network side of the present invention includes the following steps:

[0038] Step 1: Calculate the average value P of the total charging power demand of the charging station within the set time period before time t1 (including time t1) 充平均t1 And the average value of photovoltaic power generation P 光平均t1 .

[0039] The specific calculation method is as follows:

[0040]

[0041] Where P 充平均t1 is the average value of the total charging demand power during the set time period before time t1 and at time t1, P 光平均t1 is the average value of the photovoltaic power generation power in the set time period before time t1 and at time t1, P 充i The real-time power required for charging a single charging gun, P 充总t is the real-time power demand of all charging guns in the charging station at time t, P 光t is the real-time power of photovoltaic power generation at time t, t1 is the current time, t1-m is the starting time of the set time period, and m is the duration of the set time period.

[0042] Step 2: Get the target power P of the charging station network at time t1 网目标t1 .

[0043] The specific calculation method of the grid-side target power is as follows:

[0044] P 网目标t1 =P 充平均t1 –P 光平均t1 –P 电价调t1

[0045] Where P 网目标t1 is the grid-side target power of the charging station at time t1, P 电价调t1 The real-time electricity price at time t1 adjusts the power, P 充平均t1 is the average value of the total charging demand power during the set time period before time t1 and at time t1, P 光平均t1 It is the average value of the photovoltaic power generation in the set time period before time t1 and at time t1.

[0046] P 电价调t1 The calculation method is as follows:

[0047] P 电价调t1 =k1*P*f(s t1 -r t1 )

[0048]

[0049] Where P 电价调t1 is the real-time electricity price adjustment power at time t1, k1 is the adjustment coefficient, 0<k1≤1, and the value is 0.1 in this embodiment, P is the rated power of the energy storage system, s t1 is the real-time SOC value of the energy storage system at time t1, r t1 is the SOC target value of the energy storage system at time t1, k2 is the setting multiple ranging from 50 to 100, and in this embodiment the value is 50, a is the lower limit of the SOC difference ranging from -0.01 to -0.02, and b is the upper limit of the SOC difference ranging from 0.01 to 0.03.

[0050] First, since it is uncertain whether the energy storage system needs to discharge or charge at the next moment, the SOC value of the energy storage system should be maintained within a moderate range to ensure that the energy storage system can both discharge and charge at any time to cope with different power regulation requirements of the distribution network. On this basis, this embodiment proposes a means of regulating the target SOC of the energy storage system as the electricity price changes. The lower the electricity price, the higher the target SOC of the energy storage system, and the higher the electricity price, the lower the target SOC of the energy storage system; when the electricity price is high, the energy storage system SOC target value is set to 40%, which can discharge more electricity and obtain more benefits; when the electricity price is low, the energy storage system SOC target value is set to 70%, charging more low-priced electricity and reducing costs; thereby improving the economic benefits of charging station operations.

[0051] Step 3: Calculate the difference between the total power demand of the charging station at the current moment and the target power of the charging station grid side, and adjust the charging and discharging power of the energy storage unit of the charging station according to the difference so that the actual power of the grid side reaches the target power.

[0052] The calculation method of the charging and discharging power of the energy storage unit of the charging station at the current moment is (assuming that the discharging power of the energy storage unit is positive): the charging and discharging power of the energy storage unit of the charging station at the current moment is equal to the grid-side target power of the charging station at the current moment plus the real-time power of photovoltaic power generation at the current moment, and then subtracting the real-time power of the total charging demand of the charging pile at the current moment to obtain the power value. It can be expressed as the following formula:

[0053] P 储t1 =P 充总t1 -P 网目标t1 -P 光t1

[0054] Where P 储t1 is the energy storage unit discharge power at time t1, P 网目标t1 is the grid-side target power at time t1, P 光t1 is the photovoltaic power generation at time t1, P 充总t1is the total charging power required by the charging station at time t1.

[0055] Through the above method, the grid-side target power of the charging station finally calculated is equal to the average value of the total charging demand power of the charging station in the set time period before the current moment and at this moment, minus the average value of photovoltaic power generation and then minus the real-time electricity price adjustment power, which is equivalent to smoothing the grid-side target power of the charging station by using the average power in the sliding time window to prevent impact on the distribution network and ensure the safe operation of the distribution network. At the same time, since the smoothed grid-side power cannot meet the total demand power of the charging station at the current moment, in order to solve this problem, the present invention meets the total demand power of the charging station by adjusting the power of the energy storage system. For example, when a new vehicle to be charged is connected to the charging station, the total charging power demand of the entire station suddenly increases. At this time, the traditional adjustment method is used, and the grid-side target power is directly equal to the target power, which will cause a large fluctuation in the power of the distribution network, impact the grid, and affect the normal operation of the distribution network; but when the charging station grid-side power control method of the present invention is used, when the total charging power demand of the charging station suddenly increases at time t1 (assuming that the total charging power demand of the charging station does not change after the sudden increase), the calculation result of the grid-side target power at time t1 will not be greatly affected. The grid-side target power will increase to a certain extent but the amplitude is not large, which has the effect of smoothing the grid-side power. At the same time, the output power of the energy storage system should be increased to meet the total power demand of the charging station. As time goes by and the sliding window slides, P 网 will gradually increase, and the output power of the energy storage system will gradually decrease until t1+m, P 网 The total charging demand power rises to time t1 (without considering the photovoltaic power generation system). That is, the fluctuation of the network-measured target power is smoothed through the sliding time window, and then the grid-side output power is adjusted according to the smoothed grid-side target power, and the original grid-side output power changes rapidly with the demand power to change slowly with the average value of the demand power (target power) in the sliding time window, and reaches the value after the grid-side power fluctuation after the delay time window width m.

[0056] Embodiment 2:

[0057] The difference between this embodiment and embodiment 1 is that step 2 obtains the target power P of the charging station network at time t1. 网目标t1 The method is different, and the remaining steps are the same as those in Example 1.

[0058] In the second step of this implementation, the target power P of the charging station grid side at time t1 is obtained. 网目标t1 The method is: use the average value of the total charging demand power obtained in step 1 to subtract the average power generation of the photovoltaic power generation unit in the set time period and the current moment to obtain the grid-side target power of the charging station at the current moment. The specific calculation formula is:

[0059] P 网目标t1 =P 充平均t1 –P 光平均t1

[0060] Where P 网目标t1 is the grid-side target power of the charging station at time t1, P 充平均t1 is the average value of the total charging demand power during the set time period before time t1 and at time t1, P 光平均t1 It is the average value of the photovoltaic power generation in the set time period before time t1 and at time t1. It can also smooth the sudden change of photovoltaic power generation.

[0061] Embodiment 3:

[0062] The difference between this embodiment and embodiment 1 is that step 2 obtains the target power P of the charging station network at time t1. 网目标t1 The method of adjusting the charging and discharging power of the energy storage unit of the charging station according to the difference in step 3 is different, and the remaining steps are the same as those in embodiment 1.

[0063] In this embodiment, the photovoltaic power generation unit does not need to be used. In step 2, the target power P of the charging station grid side at time t1 is obtained. 网目标t1 The method is: use the average value of the total charging demand power obtained in step 1 minus the current electricity price adjustment power to obtain the grid-side target power of the charging station at the current moment. The specific calculation formula is:

[0064] P 网目标t1 =P 充平均t1 -P 电价调t1

[0065] Where P 网目标t1 is the grid-side target power of the charging station at time t1, P 电价调t1 The real-time electricity price at time t1 adjusts the power, P 充平均t1 It is the average value of the total charging demand power during the set time period before time t1 and at time t1.

[0066] In step 3 of this embodiment, the method for adjusting the charging and discharging power of the energy storage unit of the charging station according to the difference is: adjusting the power of the energy storage system to be equal to the difference. The specific calculation formula is:

[0067] P 储t1 =P 充总t1 -P 网目标t1

[0068] Where P 储t1 is the energy storage unit discharge power at time t1, P 网目标t1 is the grid-side target power at time t1, P 充总t1 is the total charging power required by the charging station at time t1.

[0069] Embodiment 4:

[0070] The difference between this embodiment and embodiment 1 is that step 2 obtains the target power P of the charging station network at time t1. 网目标t1 The method of adjusting the charging and discharging power of the energy storage unit of the charging station according to the difference in step 3 is different, and the remaining steps are the same as those in embodiment 1.

[0071] In this embodiment, the photovoltaic power generation unit does not need to be used, and the calculation of the grid-side target power does not need to consider the power adjustment of the electricity price. In step 2, the grid-side target power P of the charging station at time t1 is obtained. 网目标t1 The method is: make the grid-side target power of the charging station at the current moment equal to the average value of the total charging demand power. The specific calculation formula is:

[0072] P 网目标t1 =P 充平均t1

[0073] Where P 网目标t1 is the grid-side target power of the charging station at time t1, P 充平均t1 It is the average value of the total charging demand power during the set time period before time t1 and at time t1.

[0074] In step 3 of this embodiment, the method for adjusting the charging and discharging power of the energy storage unit of the charging station according to the difference is: the energy storage system power is equal to the difference. The specific calculation formula is:

[0075] P 储t1 =P 充总t1 -P 网目标t1

[0076] Where P 储t1 is the energy storage unit discharge power at time t1, P 网目标t1 is the grid-side target power at time t1, P 充总t1 is the total charging power required by the charging station at time t1.

Claims

1. A method for smoothing the output power of a charging station network side, characterized in that: The following steps are involved: 1) Calculate the average value of the total charging power demand of the charging station in the set time period before the current time and at the current time; 2) Obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power; 3) Calculate the difference between the total power demand of the charging station at the current moment and the target power on the grid side, and adjust the power of the energy storage system according to the difference so that the grid-side output power of the charging station reaches the target power on the grid side.

2. The method for smoothing the output power of the charging station network side according to claim 1, characterized in that: The method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is as follows: the grid-side target power of the charging station at the current moment is obtained by subtracting the average power generation power of the photovoltaic power generation unit in the set time period and the current moment from the average value of the total charging demand power; the calculation formula for the average power generation power of the photovoltaic power generation unit in the set time period and the current moment is: Where P 光平均t1 is the average power generation of the photovoltaic power generation unit in the set time period and at the current moment, P 光t is the photovoltaic power generation at time t, t1 is the current time, t1-m is the starting time of the set time period, and m is the duration of the set time period; The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference minus the power generation power of the photovoltaic power generation unit at the current moment.

3. The method for smoothing the output power of the charging station network side according to claim 1, characterized in that: The method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is: using the average value of the total charging demand power minus the current electricity price adjustment power to obtain the grid-side target power of the charging station at the current moment; the calculation formula of the current electricity price adjustment power is: P 电价调 =k1*P*f(s-r) Where P 电价调 is the power adjusted by the electricity price, k1 is the power coefficient adjusted by the electricity price, 0<k1≤1, P is the rated power of the energy storage system, s is the real-time SOC value of the energy storage system, r is the target SOC value of the energy storage system, k2 is the set multiple, a is the lower limit of the SOC difference, and b is the upper limit of the SOC difference; The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference.

4. The method for smoothing the output power of the charging station network side according to claim 1, characterized in that: The method for obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is: using the average value of the total charging demand power minus the electricity price adjustment power at the current moment, and then minus the electricity price adjustment power at the current moment to obtain the grid-side target power of the charging station at the current moment; The calculation formula for the average power generation of the photovoltaic power generation unit in the set time period and the current moment is: Where P 光平均t1 is the average power generation of the photovoltaic power generation unit in the set time period and at the current moment, P 光t is the photovoltaic power generation at time t, t1 is the current time, t1-m is the starting time of the set time period, and m is the duration of the set time period; The calculation formula for the power adjustment of the electricity price at the current moment is: P 电价调 =k1*P*f(s-r) Where P 电价调 is the power adjusted by the electricity price, k1 is the power coefficient adjusted by the electricity price, 0<k1≤1, P is the rated power of the energy storage system, s is the real-time SOC value of the energy storage system, r is the target SOC value of the energy storage system, k2 is the set multiple, a is the lower limit of the SOC difference, and b is the upper limit of the SOC difference; The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference minus the power generation power of the photovoltaic power generation unit at the current moment.

5. The method for smoothing the output power of the charging station network side according to claim 1, characterized in that: The method of obtaining the grid-side target power of the charging station at the current moment according to the average value of the total charging demand power is as follows: making the grid-side target power of the charging station at the current moment equal to the average value of the total charging demand power; The method for adjusting the power of the energy storage system according to the difference is: adjusting the power of the energy storage system to be equal to the difference.

6. The method for smoothing the output power of the charging station network side according to claim 4 or 5, characterized in that: The target value of the energy storage system SOC is set according to the real-time electricity price. The higher the real-time electricity price, the lower the target value of the energy storage system SOC.

Images