CN104300571B

CN104300571B - Distributed Generation in Distribution System maximum injection power determines method

Info

Publication number: CN104300571B
Application number: CN201310303673.XA
Authority: CN
Inventors: 徐晶; 迟福建; 刘洪�; 谢秦; 刘聪; 崔荣靖; 吴黎明; 李娟�; 吴树茂; 王海滨; 王翠香; 王庆彪; 张金华
Original assignee: Tianjin University; State Grid Corp of China SGCC; State Grid Tianjin Electric Power Co Ltd
Current assignee: Tianjin University; State Grid Corp of China SGCC; State Grid Tianjin Electric Power Co Ltd
Priority date: 2013-07-18
Filing date: 2013-07-18
Publication date: 2016-08-17
Anticipated expiration: 2033-07-18
Also published as: CN104300571A

Abstract

The invention discloses a method for determining the maximum injected power of a distributed power supply in a distribution network. The steps are to determine the power constraint limit S _inv of the reverse flow, determine the voltage fluctuation limit U _lim , and obtain the maximum short circuit allowed by the distributed power supply Current increment ΔI _lim , input the injected power S ₀ of distributed power into the distribution line or busbar, verify whether the injected power S ₀ satisfies the reverse flow constraint condition, verify whether the injected power S ₀ meets the voltage fluctuation constraint condition, and verify the injected power S 0 Whether S ₀ satisfies the short-circuit current constraint condition, if the injected power S ₀ satisfies the above three constraints, then increase the injected power until any constraint is no longer satisfied, and output the injected power of the previous round. The method of the invention is simple, feasible, scientific and reasonable.

Description

Determination method of maximum injected power of distributed generation in distribution network

技术领域technical field

本发明属于电力系统分布式电源与配电网领域，尤其涉及一种配电网中分布式电源最大注入功率确定方法。The invention belongs to the field of distributed power sources and distribution networks in power systems, and in particular relates to a method for determining the maximum injected power of distributed power sources in a distribution network.

背景技术Background technique

分布式电源一般是指发电功率在数千瓦至50兆瓦的小型化、模块化、分散式、布置在用户附近为用户供电的连接到配电系统的小型发电系统。随着电力政策的放开，分布式电源作为一种新兴的发电模式显现出来，这种小容量的发电机组在配电网用户附近提供电力，可以成为集中式发电的有益补充。它可以减少电力传输时功率的损耗以及由配网升级带来的费用。而对于用户来说，较低的费用、较高的可靠性、较好的电能质量、较高的能源利用率和一定独立性的能源供应是他们引入分布式电源的兴趣所在。同时，运用可再生能源技术的分布式发电，如风力发电、太阳能光伏发电、水力发电，还提供了相当好的环境效应。集中式发电仍将主导电力供应是公认的，然而，世界范围内能源的紧张、环境保护问题的突出、电力市场改革的深入，迫切需要分布式电源这种新的有价值的发电模式出现和发展。Distributed power generation generally refers to a small power generation system connected to the power distribution system that is miniaturized, modularized, decentralized, and arranged near the user to provide power to the user with a power generation of several thousand watts to 50 megawatts. With the liberalization of power policies, distributed power generation has emerged as an emerging power generation model. This small-capacity generator set provides power near users of the distribution network, which can be a useful supplement to centralized power generation. It can reduce the loss of power during power transmission and the cost of upgrading the distribution network. For users, lower costs, higher reliability, better power quality, higher energy utilization and a certain degree of independent energy supply are their interests in introducing distributed power. At the same time, distributed power generation using renewable energy technologies, such as wind power, solar photovoltaic power generation, and hydropower generation, also provides quite good environmental effects. It is recognized that centralized power generation will still dominate power supply. However, the shortage of energy sources worldwide, the prominent environmental protection issues, and the deepening of power market reforms urgently require the emergence and development of distributed power, a new and valuable power generation model. .

分布式电源接入配电网将会对电压波动，短路电流，潮流流向等方面带来不利影响。为了使配电网在接入分布式电源后仍然能够安全稳定的运行，需要考虑分布式电源的最大注入功率问题。The access of distributed power to the distribution network will have adverse effects on voltage fluctuations, short-circuit currents, and power flow. In order to ensure that the distribution network can still operate safely and stably after accessing distributed power, it is necessary to consider the issue of the maximum injected power of distributed power.

发明内容Contents of the invention

本发明要解决的技术问题是提供一种方法简单易行、科学合理的配电网中分布式电源最大注入功率确定方法。The technical problem to be solved by the present invention is to provide a simple, feasible, scientific and reasonable method for determining the maximum injected power of a distributed power supply in a distribution network.

为了解决上述技术问题，本发明包括如下步骤：In order to solve the problems of the technologies described above, the present invention comprises the following steps:

1）确定分布式电源所接入配电线路或者母线的最大负荷，进而确定出逆流的功率约束限值S_inv；1) Determine the maximum load of the distribution line or busbar connected to the distributed power generation, and then determine the power constraint limit S _inv of the reverse flow;

2）获取分布式电源所接入配电线路或者母线的电压和等值阻抗参数，用以进行电压波动约束条件的计算，进而确定出电压波动限值ΔU_lim；2) Obtain the voltage and equivalent impedance parameters of the distributed power generation connected to the distribution line or busbar to calculate the voltage fluctuation constraint conditions, and then determine the voltage fluctuation limit value ΔU _lim ;

3）确定分布式电源接入电压等级下的短路电流限值，以及分布式电源接入前的短路电流水平，从而得出分布式电源允许引起的最大短路电流增量ΔI_lim；3) Determine the short-circuit current limit at the access voltage level of the distributed power supply, and the short-circuit current level before the distributed power supply is connected, so as to obtain the maximum short-circuit current increment ΔI _lim that the distributed power supply is allowed to cause;

4）向配电线路或者母线中输入一个分布式电源的注入功率S₀；4) Input the injected power S ₀ of a distributed power supply into the distribution line or busbar;

5）验证注入功率S₀是否满足逆流约束条件，逆流约束的条件为：5) Verify whether the injected power S ₀ satisfies the reverse flow constraint condition, the condition of the reverse flow constraint is:

S_inv=k×L_max S _inv =k×L _max

S₀<S_inv S ₀ <S _inv

其中，S_inv为逆流的功率约束限值，L_max为最大负荷，k可以依情况取值，S₀为分布式电源的注入功率，Among them, S _inv is the power constraint limit of reverse flow, L _max is the maximum load, k can be selected according to the situation, S ₀ is the injected power of distributed power,

若满足逆流约束条件，则进行下一步验证，若不满足逆流约束条件，则输出注入功率S₀-ΔS，其中，ΔS为注入功率变化量且S₀-ΔS为满足条件的分布式电源的最大注入功率；If the reverse flow constraints are met, proceed to the next step of verification. If the reverse flow constraints are not met, then output the injected power S ₀ -ΔS, where ΔS is the variation of injected power and S ₀ -ΔS is the maximum value of the distributed power generation that meets the conditions Inject power;

6）验证注入功率S₀是否满足电压波动约束条件，电压波动约束的条件为：6) Verify whether the injected power S ₀ satisfies the voltage fluctuation constraint condition, the condition of the voltage fluctuation constraint is:

$ΔU Δ U = = (({R R}_{s the s} + + {jX wxya}_{s the s})) \cdot &Center Dot; (({ΔI ΔI}_{p p} + + jΔ jΔ {I I}_{q q}))$

$= = | | {Z Z}_{s the s} | | ((cos cos φ φ + + j j sin sin φ φ)) \cdot &Center Dot; | | ΔI ΔI | | ((cos cos θ θ + + j j sin sin θ θ))$

$= = \frac{{u u}^{22}}{{S S}_{k k}} \frac{{ΔS ΔS}_{n no}}{U u} \cdot \cdot [[((cos cos φ φ cos cos θ θ - - sin sin φ φ sin sin θ θ)) + + j j ((sin sin φ φ cos cos θ θ + + cos cos φ φ sin sin θ θ))]]$

ΔU<ΔU_lim ΔU< _ΔUlim

其中，ΔU为发电量波动时接入点的电压变化值，S_k为并网接入点短路容量，ΔS_n为分布式电源注入的功率变化，θ为分布式电源功率因数角，(R_s+jX_s)为电网等效阻抗，U为接入点电压，φ为从接入点看入的电网阻抗角，ΔU_lim为电压波动限值，Among them, ΔU is the voltage change value of the access point when the power generation fluctuates, S _k is the short-circuit capacity of the grid-connected access point, ΔS _n is the power change injected by the distributed power supply, θ is the power factor angle of the distributed power supply, (R _s +jX _s ) is the grid equivalent impedance, U is the access point voltage, φ is the grid impedance angle seen from the access point, ΔU _lim is the voltage fluctuation limit,

若满足电压波动约束条件，则进行下一步验证，若不满足电压波动约束条件，则输出注入功率S₀-ΔS，其中，ΔS为注入功率变化量且S₀-ΔS为满足条件的分布式电源的最大注入功率；If the voltage fluctuation constraints are met, proceed to the next step of verification. If the voltage fluctuation constraints are not satisfied, the injected power S ₀ -ΔS is output, where ΔS is the variation of injected power and S ₀ -ΔS is the distributed power supply that satisfies the conditions The maximum injection power of

7）验证注入功率S₀是否满足短路电流约束条件，短路电流约束的条件为：7) Verify whether the injected power S ₀ satisfies the short-circuit current constraint condition, and the short-circuit current constraint condition is:

ΔI_lim=I_thr-I₀ ΔI _lim =I _thr -I ₀

ΔI<ΔI_lim ΔI<ΔI _lim

其中，I₀为配电网中未接入分布式电源时短路电流水平，I_thr在同一电压等级下的短路电流极限值，ΔI_lim为分布式电源允许引起的最大短路电流增量，Among them, I ₀ is the short-circuit current level when the distributed power supply is not connected to the distribution network, I _thr is the short-circuit current limit value at the same voltage level, ΔI _lim is the maximum short-circuit current increment allowed by the distributed power supply,

若满足短路电流约束条件，则增大注入功率，即在原注入功率的基础上增加注入功率变化量ΔS并重新返回到上述第5）步骤，再次逐步验证直到出现任何一个约束条件不再满足，输出前一轮的注入功率，则此时输出的注入功率即为分布式电源的最大注入功率；若不满足短路电流约束条件，则输出注入功率S₀-ΔS，其中，ΔS为注入功率变化量且S₀-ΔS为满足条件的分布式电源的最大注入功率。If the short-circuit current constraints are met, increase the injection power, that is, increase the injection power variation ΔS on the basis of the original injection power and return to step 5) above, and verify step by step again until any constraint condition is no longer satisfied, output The injected power of the previous round, the injected power output at this time is the maximum injected power of the distributed power supply; if the short-circuit current constraint condition is not satisfied, the injected power S ₀ -ΔS is output, where ΔS is the change in injected power and S ₀ -ΔS is the maximum injected power of distributed power generation that meets the conditions.

初始化时，向配电线路或者母线中输入一个分布式电源的初始注入功率S′，所述初始注入功率S′满足所述逆流约束条件、电压波动约束条件及短路电流约束条件，且初始化时，S₀=S′。During initialization, an initial injection power S' of a distributed power supply is input into the distribution line or bus bar, and the initial injection power S' satisfies the reverse current constraint condition, voltage fluctuation constraint condition and short-circuit current constraint condition, and during initialization, S ₀ =S'.

采用上述技术方案，本发明的有益效果是：Adopt above-mentioned technical scheme, the beneficial effect of the present invention is:

1、方法简单易行，科学合理；1. The method is simple, easy, scientific and reasonable;

2、能够在满足技术要求的前提下，确定出分布式电源的最大注入功率；2. Be able to determine the maximum injected power of the distributed power supply under the premise of meeting the technical requirements;

3、指导和促进分布式电源并网，获得可观的经济和社会效益。3. Guide and promote the grid connection of distributed power sources, and obtain considerable economic and social benefits.

附图说明Description of drawings

图1为本发明配电网中分布式电源最大注入功率确定方法的计算流程图；Fig. 1 is the calculation flowchart of the method for determining the maximum injected power of distributed power supply in distribution network of the present invention;

图2为含分布式电源的系统在其接入点上的戴维南等效电路。Fig. 2 is the Thevenin equivalent circuit on the access point of the system containing distributed power supply.

具体实施方式detailed description

下面结合附图和具体实施方式对本发明作进一步详细的说明：Below in conjunction with accompanying drawing and specific embodiment the present invention will be described in further detail:

参见图1和图2，本发明的配电网中分布式电源最大注入功率确定方法包括如下步骤：Referring to Fig. 1 and Fig. 2, the method for determining the maximum injected power of a distributed power supply in a distribution network of the present invention includes the following steps:

S_inv=k×L_max S _inv =k×L _max

S₀<S_inv S ₀ <S _inv

$= = | | {Z Z}_{s the s} | | ((cos cos φ φ + + j j sin sin φ φ)) \cdot \cdot | | ΔI ΔI | | ((cos cos θ θ + + j j sin sin θ θ))$

ΔU<ΔU_lim ΔU< _ΔUlim

ΔI_lim=I_thr-I₀ ΔI _lim =I _thr -I ₀

ΔI<ΔI_lim ΔI<ΔI _lim

下面对三个约束条件作进一步说明：The following three constraints are further explained:

1.逆流约束1. Countercurrent Constraint

在配电网中，分布式电源发出功率不允许穿越其接入设备注入上一电压等级。为防止逆流对上一级电网产生较大的影响，导致上一级电网需要在继电保护设置等方面做出大范围的调整，分布式电源所产生的电力电量应该尽量在本级配电区域内平衡，因此分布式电源的最大出力应该小于该电压等级下变压器供电范围内的最大负荷。In the distribution network, the distributed power output power is not allowed to pass through its access equipment and inject the previous voltage level. In order to prevent the reverse current from having a greater impact on the upper-level power grid, resulting in the need for a large-scale adjustment of the upper-level power grid in terms of relay protection settings, the power generated by the distributed power supply should be as far as possible in the power distribution area of the same level. Internal balance, so the maximum output of the distributed power supply should be less than the maximum load within the power supply range of the transformer at this voltage level.

对于10kV就地接入模式，考虑负荷峰谷差这一因素，为了使分布式电源所产生的电力能在本供电区域内全部平衡掉，需要满足在分布式电源出力为额定功率且负荷为其谷值时依然能够满足不出现逆流的限制，就必须使得接入分布式电源的最大出力小于负荷的谷值。据统计，典型地区“负荷谷值/负荷峰值”这一比值约为0.4-0.6。因此，分布式电源总容量必须不超过中压馈线最大负荷的40%-60%，即可保证分布式电源所产生电力在本级配电区域内平衡。若考虑负荷发展的不确定性，则应考虑分布式电源总容量不超过中压馈线最大负荷的30%。For the 10kV local access mode, considering the factor of load peak-valley difference, in order to make the power generated by the distributed power supply fully balanced in the power supply area, it is necessary to meet the requirements that the output of the distributed power supply be the rated power and the load be If the valley value can still meet the restriction of no reverse flow, it is necessary to make the maximum output of the distributed power supply less than the valley value of the load. According to statistics, the ratio of "valley load/peak load" in typical areas is about 0.4-0.6. Therefore, the total capacity of the distributed power generation must not exceed 40%-60% of the maximum load of the medium-voltage feeder, which can ensure that the power generated by the distributed power generation is balanced in the power distribution area of the same level. If the uncertainty of load development is considered, it should be considered that the total capacity of distributed generation should not exceed 30% of the maximum load of the medium-voltage feeder.

对于专线接入模式，国家电网在《分布式电源接入电网技术规定》中指出：分布式电源总容量原则上不宜超过上一级变压器供电区域内最大负荷的25%。因此，在分析专线接入问题时，分布式电源容量最大不超过变压器所带负荷的25%。For the dedicated line access mode, the State Grid pointed out in the "Technical Regulations on Distributed Power Supply Access to the Grid" that the total capacity of distributed power supply should not exceed 25% of the maximum load in the upper-level transformer power supply area in principle. Therefore, when analyzing the problem of dedicated line access, the maximum capacity of the distributed power supply should not exceed 25% of the load carried by the transformer.

综合以上情况逆流约束的现值可以取为：Based on the above conditions, the present value of the countercurrent constraint can be taken as:

S_inv=k×L_max (1)S _inv =k×L _max (1)

其中，S_inv表示逆流的功率约束限值，L_max表示最大负荷，k可以依情况取值。Among them, S _inv represents the power constraint limit of reverse flow, L _max represents the maximum load, and k can be selected according to the situation.

逆流约束要求：Countercurrent Constraint Requirements:

S₀<S_inv (2)S ₀ <S _inv (2)

其中，S_inv表示逆流的功率约束限值，S₀表示分布式电源的注入功率。Among them, S _inv represents the power constraint limit of the reverse flow, and S ₀ represents the injected power of the distributed generation.

2.电压波动约束2. Voltage fluctuation constraints

分布式电源接入电网后，公共连接点的电压偏差应满足GB/T12325-2008《电能质量供电电压偏差》的规定，即：35kV及以上供电电压正、负偏差的绝对值之和不超过标称电压的10%。20kV及以下三相供电电压偏差为标称电压的±7%。After the distributed power supply is connected to the grid, the voltage deviation of the public connection point should meet the requirements of GB/T12325-2008 "Power Quality Supply Voltage Deviation", that is, the sum of the absolute values of the positive and negative deviations of the power supply voltage of 35kV and above does not exceed the standard 10% of the voltage. The three-phase power supply voltage deviation of 20kV and below is ±7% of the nominal voltage.

分布式电源引起的电压波动并网接入点的影响是最大的，因此，以此点来评估电压变化，图2为并网接入点的戴维南等效电路。The impact of the voltage fluctuation caused by the distributed power supply on the grid-connected access point is the greatest. Therefore, to evaluate the voltage change at this point, Figure 2 is the Thevenin equivalent circuit of the grid-connected access point.

当分布式电源注入系统的功率发生改变时，线路上的电流变化值ΔI。当发电量波动时，接入点的电压变化值为ΔU。由图2估算如下：When the power injected into the system by distributed power generation changes, the current on the line changes by ΔI. When the power generation fluctuates, the voltage change value of the access point is ΔU. It is estimated from Figure 2 as follows:

$ΔU Δ U = = (({R R}_{s the s} + + {jX wxya}_{s the s})) \cdot \cdot (({ΔI ΔI}_{p p} + + jΔ jΔ {I I}_{q q})) - - - - - - ((33))$

在上式中，并网接入点短路容量为S_k，分布式电源注入的功率变化为ΔS_n，分布式电源功率因数角θ，电网等效阻抗为(R_s+jX_s)，接入点电压U，从接入点看入的电网阻抗角为φ。In the above formula, the short-circuit capacity of the grid-connected access point is S _k , the power change injected by the distributed power supply is ΔS _n , the power factor angle of the distributed power supply is θ, the equivalent impedance of the grid is (R _s +jX _s ), and the access The point voltage U, the grid impedance angle seen from the access point is φ.

分布式电源并网点接至无限大系统引起的电压降落为：The voltage drop caused by the distributed power grid connection point connected to the infinite system is:

$ΔU Δ U = = \frac{PR PR + + QX QX}{{U u}_{N N}} + + j j \frac{PX PX - - QR QR}{{U u}_{N N}} - - - - - - ((44))$

式中，P为注入系统的有功；Q为注入系统的无功；U_N为系统额定电压；R+jX为线路阻抗。In the formula, P is the active power injected into the system; Q is the reactive power injected into the system; U _N is the rated voltage of the system; R+jX is the line impedance.

当分布式电源采用电力电子装置并网时，电网线路较短，两端电压相角相差不大，可忽略(4)式的虚部分量，当注入功率发生变动时，对功率分量求微分得电压波动的表达式为：When the distributed power supply is connected to the grid using power electronic devices, the grid line is short, and the phase angle difference between the voltages at both ends is not large, so the imaginary component of (4) can be ignored. When the injected power changes, the power component can be differentiated to obtain The expression of voltage fluctuation is:

$d d ((ΔU Δ U)) = = \frac{d d ((P P)) R R + + d d ((Q Q)) X x}{{U u}_{N N}} - - - - - - ((55))$

含分布式电源的配电网电压等级一般较低（≤35kV）。中低压传输线和高压输电线路参数特点不同，高压输电线呈现电抗特性，而分布式电源并网的中低压配电网，系统呈现电阻性质，R>>X，故分析时电抗可以忽略不计，式(5)可以简化为：The voltage level of the distribution network with distributed power is generally low (≤35kV). The characteristics of medium and low-voltage transmission lines and high-voltage transmission lines are different. High-voltage transmission lines exhibit reactance characteristics, while distributed power grid-connected medium and low-voltage distribution networks, the system presents resistance properties, R>>X, so the reactance can be ignored during analysis. (5) can be simplified as:

$d d ((ΔU Δ U)) \approx \approx \frac{d d ((P P)) R R}{{U u}_{N N}} - - - - - - ((66))$

由此可见，线路电阻R和电网额定电压U_N恒定的情况下，分布式电源采用电力电子装置并网引起的电压波动主要取决于有功功率的波动。It can be seen that when the line resistance R and the grid rated voltage _U are constant, the voltage fluctuation caused by the distributed power supply using power electronic devices connected to the grid mainly depends on the fluctuation of active power.

通过以上的公式计算可以获得分布式电源接入点的电压波动ΔU值，与相应电压等级的电压波动限值ΔU_lim相比较，能够验证当时分布式电源注入功率是否满足电压波动约束。Through the calculation of the above formula, the voltage fluctuation ΔU value of the distributed power access point can be obtained. Compared with the voltage fluctuation limit value ΔU _lim of the corresponding voltage level, it can be verified whether the distributed power injection power meets the voltage fluctuation constraint at that time.

3.短路电流约束3. Short-circuit current constraints

中小容量的分布式电源接入配电网中，在故障发生时将对故障点提供故障电流。分布式电源可以用一个电源串联电抗的模型来表示。因此所需要考虑的是，在故障发生时分布式电源能够提供多大的故障电流。对于不同类型的分布式电源，其电抗值是不同的，它代表着该电源的故障电流注入能力。各种类型分布式电源的故障电流注入能力如表1所示。Distributed power generation with small and medium capacity is connected to the distribution network, and will provide fault current to the fault point when a fault occurs. Distributed power can be represented by a power supply series reactance model. Therefore, what needs to be considered is how much fault current the distributed power supply can provide when a fault occurs. For different types of distributed power sources, the reactance value is different, which represents the fault current injection capability of the power source. The fault current injection capabilities of various types of distributed power sources are shown in Table 1.

表1不同类型分布式电源的短路电流注入能力Table 1 Short-circuit current injection capability of different types of distributed power

从表中可以发现，以同步发电机作为接口的分布式电源最大的故障电流注入能力可以达到1000%，该值可用于短路计算以确定最坏的故障情况。It can be found from the table that the maximum fault current injection capability of the DG with the synchronous generator as the interface can reach 1000%, and this value can be used for short-circuit calculation to determine the worst fault condition.

分布式电源接入配电网引起的最大短路电流增量可以按照电路理论中的叠加法进行计算。分布式电源可以依据其并网接口处理成电流源或者电压源。The maximum short-circuit current increment caused by distributed power generation access to the distribution network can be calculated according to the superposition method in circuit theory. Distributed power can be treated as a current source or a voltage source according to its grid-connected interface.

配电网中未接入分布式电源时短路电流水平是I₀，在该电压等级下的短路电流极限值是I_thr，则接入的分布式电源允许引起的最大短路电流增量为：When the distributed power supply is not connected to the distribution network, the short-circuit current level is I ₀ , and the short-circuit current limit value at this voltage level is I _thr , then the maximum short-circuit current increment allowed by the connected distributed power supply is:

ΔI_lim=I_thr-I₀ (7)ΔI _lim =I _thr -I ₀ (7)

当一定功率的分布式电源接入配电网引起的短路电流增量ΔI满足ΔI<ΔI_lim时，即认为此时的注入功率是满足短路电流约束的。When the short-circuit current increment ΔI caused by the distributed generation of a certain power connected to the distribution network satisfies ΔI<ΔI _lim , it is considered that the injected power at this time meets the short-circuit current constraint.

综上所述，本发明的内容并不局限在上述的实施例中，本领域的技术人员可以在本发明的技术指导思想之内提出其他的实施例，但这些实施例都包括在本发明的范围之内。In summary, the content of the present invention is not limited to the above-mentioned embodiments, and those skilled in the art can propose other embodiments within the technical guidance of the present invention, but these embodiments are all included in the scope of the present invention. within range.

Claims

1. a method for determining the maximum injected power of a distributed power supply in a distribution network, comprising the steps of:

1) Determine the maximum load of the distribution line or busbar connected to the distributed power supply, and then determine the power constraint limit S _inv of the reverse flow;

2) Obtain the voltage and equivalent impedance parameters of the distributed power supply connected to the distribution line or the busbar to calculate the voltage fluctuation constraint conditions, and then determine the voltage fluctuation limit value ΔU _lim ;

3) Determine the short-circuit current limit value under the access voltage level of the distributed power supply, and the short-circuit current level before the distributed power supply is connected, so as to obtain the maximum short-circuit current increment ΔI _lim that the distributed power supply is allowed to cause;

4) Input the injected power S ₀ of a distributed power supply into the distribution line or the bus bar;

5) Verify whether the injected power S ₀ satisfies the reverse flow constraint condition, the condition of the reverse flow constraint is:

S _inv ＝k×L _max

S ₀ <S _inv

Among them, S _inv is the power constraint limit of reverse flow, L _max is the maximum load, k can be selected according to the situation, S ₀ is the injected power of distributed power,

If the reverse flow constraints are met, proceed to the next step of verification. If the reverse flow constraints are not met, then output the injected power S ₀ -ΔS, where ΔS is the variation of injected power and S ₀ -ΔS is the maximum value of the distributed power generation that meets the conditions Inject power;

6) Verify whether the injected power _S0 satisfies the voltage fluctuation constraint condition, the condition of the voltage fluctuation constraint is:

\begin{matrix} Δ Δ U u = = (({R R}_{s the s} + + {jX wxya}_{s the s})) \cdot \cdot (({ΔI ΔI}_{p p} + + {jΔI jΔI}_{q q})) \\ = = | | {Z Z}_{s the s} | | ((cos cos φ φ + + j j sin sin φ φ)) \cdot &Center Dot; | | Δ Δ I I | | ((cos cos θ θ + + j j sin sin θ θ)) \\ = = \frac{{U u}^{22}}{{S S}_{k k}} \frac{{ΔS ΔS}_{n no}}{U u} \cdot &Center Dot; [[((cos cos φ φ cos cos θ θ - - sin sin φ φ sin sin θ θ)) + + j j ((sin sin φ φ cos cos θ θ + + cos cos φ φ sin sin θ θ))]] \end{matrix}

= = \frac{U u \cdot &Center Dot; {ΔS ΔS}_{n no}}{{S S}_{k k}} \cdot &Center Dot; [[((cos cos φ φ cos cos θ θ - - sin sin φ φ sin sin θ θ)) + + j j ((sin sin φ φ cos cos θ θ + + cos cos φ φ sin sin θ θ))]]

ΔU< _ΔUlim

Among them, ΔU is the voltage change value of the access point when the power generation fluctuates, S _k is the short-circuit capacity of the grid-connected access point, ΔS _n is the power change injected by the distributed power supply, θ is the power factor angle of the distributed power supply, R _s + jX _s is the grid equivalent impedance, U is the access point voltage, φ is the grid impedance angle seen from the access point, ΔU _lim is the voltage fluctuation limit, and ΔI is the short-circuit current caused by the distributed power supply accessing the distribution network increment,

If the voltage fluctuation constraints are met, proceed to the next step of verification. If the voltage fluctuation constraints are not satisfied, the injected power S ₀ -ΔS is output, where ΔS is the variation of injected power and S ₀ -ΔS is the distributed power supply that satisfies the conditions The maximum injection power of

7) Verify whether the injected power _S0 satisfies the short-circuit current constraint condition, the condition of the short-circuit current constraint is:

ΔI _lim =I _thr -I ₀

ΔI<ΔI _lim

Among them, I ₀ is the short-circuit current level when the distributed power supply is not connected to the distribution network, I _thr is the short-circuit current limit value at the same voltage level, ΔI _lim is the maximum short-circuit current increment allowed by the distributed power supply,

If the short-circuit current constraints are met, increase the injection power, that is, increase the injection power variation ΔS on the basis of the original injection power and return to step 5) above, and verify step by step again until any constraint condition is no longer satisfied, output The injected power of the previous round, the injected power output at this time is the maximum injected power of the distributed power supply; if the short-circuit current constraint condition is not satisfied, the injected power S ₀ -ΔS is output, where ΔS is the change in injected power and S ₀ -ΔS is the maximum injected power of distributed power generation that meets the conditions.

2. According to the method for determining the maximum injected power of distributed power sources in the distribution network according to claim 1, it is characterized in that: during initialization, an initial injected power S' of a distributed power source is input into the distribution line or busbar, and the The initial injection power S' satisfies the reverse current constraint condition, the voltage fluctuation constraint condition and the short-circuit current constraint condition, and S ₀ =S' during initialization.