• Project Description

Before the distributed photovoltaic installation was connected to the grid, the power factor at the end of the month was basically up to standard. However, after the distributed photovoltaic installation was connected to the grid, the power factor at the end of the month was lower and the power regulation fee was higher.

• Project Analysis

With the upgrading and development of photovoltaic power generation technology, more and more factory users choose distributed photovoltaic power generation, using the roof space of the factory to install photovoltaic power generation components, generating electricity on-site for production use, and adopting the strategy of self-generation and self-use and surplus power connected to the grid. When local electricity consumption is met, the surplus power of the photovoltaic power generation system is sent to the grid to make a profit.

Under the strategy of self-generation and self-use of surplus electricity and grid connection:
1. When the distributed photovoltaic power station generates electricity, the initial power factor of the photovoltaic system is 1, and it does not contain reactive power.
2. When the power load is in production operation, it must be supported by reactive power.

It can be seen that as the power generation of distributed photovoltaic power generation systems gradually increases, in the case of self-generation and self-use, and the surplus power is connected to the grid, the active power taken from the mains by the system decreases, but the reactive power taken is still all taken from the mains, which will make the active power on the mains side of the system approach 0. Assuming that the reactive power remains unchanged:
1. Assume that before the photovoltaic power is connected to the grid, the active power obtained from the grid is 10,000 and the reactive power is 4,000；

After calculation, the power factor at the end of the month can meet the assessment requirements and there will be appropriate rewards.

2. After the photovoltaic grid is connected, the active power obtained from the grid is reduced to 4000, and the total reactive power is 4000.

After calculation, if the power factor does not meet the standard at the end of the month, a power adjustment fee will be incurred. The system power factor PF will decrease as the power of the photovoltaic power generation system changes, which will cause the power factor assessment of the power supply company to fail to meet the standard, resulting in a power adjustment fee fine.(Generally, 10kV branches require the power factor cosφ greater than 0.9, no fine and corresponding rewards.)

At the same time, it should be noted that: the power consumption in the system is not constant, but will fluctuate; the power generation power of the distributed photovoltaic power generation system is also not constant; the superposition of the two fluctuations will cause the active power provided by the power grid to show drastic changes and frequent fluctuations, which will be a more severe test for the response speed and compensation capacity of the reactive power compensation cabinet in the system.

• Solution

This solution aims to meet the power factor of the power assessment on the user’s grid side.
After the distributed photovoltaic power generation system is connected, the active power of the incoming cabinet on the grid side of the system fluctuates frequently and complexly, and the reactive power of the load equipment is compensated by the original reactive compensation cabinet, but there is still a certain compensation gap, and the grid needs to provide compensation.

After the photovoltaic power is connected, the active current used by the grid on site is reduced:

System power factor

It can be seen that the smaller the reactive power Q, the larger the system PF. When Q=0, then

Therefore, in this case, the user’s system reactive power compensation is carried out, and our static VAR generator (SVG) is used to compensate the reactive power in the system.

• Installation location

We recommend using high-voltage meter sampling through MODBUS-RTU/MODBUS-TCP to transmit data for compensation. This solution is more accurate than transformer sampling and has better compensation effect.

After using the static VAR generator (SVG) device for compensation, the reactive power provided by the power grid to the user is controlled within the minimum resolution of the meter.At this time, regardless of the change in the active power provided by the power grid to the user, the user’s power factor (PF) will remain at a high level.

The overall compensation system has four-quadrant compensation, a compensation range of 1~(-1), capacitive, inductive and reactive bidirectional compensation, and real-time conversion to ensure the best compensation effect.