光伏项目中经常采用高采低补的方案，即：采样点在高压侧，通过高压侧的CT、PT，测量计量点的电流电压、PF等参数，补偿设备仍然安装在低压侧400V。PF控制器采集高压侧的数据，分析后判定低压侧无功设备发出或吸收多少无功功率。

升压式SVG无功补偿方案由低压SVG（400V或者690V）补偿柜、升压变压器、高压侧电流采样信号及其它辅助电气元件组成。低压SVG实时检测系统电压电流，快速输出补偿无功电流，通过升压变压器变换到高压侧去补偿高压无功功率，从而提升高压母线的PF。

需要注意的是：升压变压器一次侧电压必须与高压系统一致，二次侧电压必须与选择的SVG额定电压一致。升压变压器可以为了SVG单独增加，也可利用现场原有的变压器。系统总电流采样的位置可以选择从总进线柜取，也可选择从计量柜取，具体位置需要根据现场实际取样可行性判断。

高压电流采样，有的系统是A、B、C三相各相一只互感器，有的只有A、C两相有互感器；有三只互感器的系统，可直接将电流采样信号线引入SVG采样电流互感器接线端子即可。如果现场只有A、C两相有互感器，可以构造出B相电流，然后将三相电流采样引入SVG。 

How to monitor the PF after high mining and low replenishment in the cloud?

The high sampling and low compensation scheme is often adopted in photovoltaic projects, that is, the sampling point is on the high voltage side, and the current, voltage, PF and other parameters of the measuring point are measured through CT and PT on the high voltage side. The compensation equipment is still installed on the low voltage side 400V. The PF controller collects data on the high voltage side, analyzes it, and determines how much reactive power the low voltage side reactive equipment emits or absorbs.

The step-up SVG reactive power compensation scheme consists of a low-voltage SVG (400V or 690V) compensation cabinet, a step-up transformer, a high-voltage side current sampling signal, and other auxiliary electrical components. The low-voltage SVG real-time detection system detects voltage and current, quickly outputs compensating reactive current, and compensates for high-voltage reactive power by converting it to the high-voltage side through a step-up transformer, thereby improving the PF of the high-voltage bus.

It should be noted that the primary voltage of the step-up transformer must be consistent with the high voltage system, and the secondary voltage must be consistent with the selected SVG rated voltage. The step-up transformer can be added separately for SVG, or the existing transformer on site can be used. The location for sampling the total current of the system can be selected from the main incoming cabinet or the metering cabinet, and the specific location needs to be determined based on the feasibility of sampling on site.

High voltage current sampling, some systems have one transformer for each phase of A, B, and C phases, while others only have transformers for phases A and C; A system with three transformers can directly introduce the current sampling signal line into the SVG sampling current transformer terminal. If only phases A and C have transformers on site, phase B current can be constructed, and then the three-phase current can be sampled and introduced into SVG.