The cost of solar PV has dropped significantly over the past decade, and the technology can now compete with conventional power generation in many regions. The global average cost of utility-scale PV system hardware fell by a staggering 50% from 2013 to 2018, with the average cost falling below $1/W in 2018 (well below this level in many regions). In terms of capex PV systems following such impressive cuts, the technology is currently considered more mature, with relatively small profit margins and minimal cost improvements. As a result, the focus has shifted more towards systems that improve performance and reliability to reduce LCOE (Levelized Cost of Electricity). At times, some of these innovations can result in a significant increase in the up-front cost of the system — such as trackers, which are now commonplace in utility-scale systems around the world — but the overall improvement in system output is more than offset by the overall higher cost of the system. low LCOE. Another major trend in this regard is the move to higher DC voltages, with a rapid shift to 1500 Volt (V) systems in the global utility-scale PV market. One of the main drivers of this trend is the increasing number of 1500V inverters now available in this market

Why switch to a higher voltage?

The rationale for driving higher voltages in photovoltaic systems is actually rooted in a fairly basic science and classroom relationship between electrical power (P), current (I) and voltage (V) – “P=IV”. This formula relationship shows that to deliver a fixed amount of power, the amount of current required decreases as the voltage increases. As it happens, at lower current levels, the electrical losses are also smaller. For the same reasons that high voltages are used when transmitting power over long distances along transmission lines, photovoltaic system voltages have been increasing as much as possible to reduce power losses in the system, thereby increasing the yield of the system. Additionally, the ability to create longer—and therefore fewer—strings also simplifies the system and can reduce the number of other components required (such as string combiners), aiming to lower the overall cost of the system.

There has been a long-standing trend to increase the voltage. The transition to 1000V inverters was discussed in the industry about a decade ago, and is now common in PV systems in much of the world. Back in 2012, German integrator Belectric announced that it had used 1500V inverters in its ground-mounted factories in Germany. The following year, it announced that they would continue to roll out the technology. Since then, 1500V inverter technology has ceased to be trade shows and conferences, deployed around the world in very real numbers, with the most significant early numbers being installed in countries such as the US, Germany, UK, Chile and Mexico /area.

1500V has quickly become a requirement for large-scale photovoltaic projects. Numerous notable projects using 1500V technology, including the 300 MW project in Sarkaka, Saudi Arabia, which signed a record-breaking deal to sell electricity at around 2.3 cents/kWh (Halala 8.78/kWh) in 2018 . Major utility-scale tenders in India, the second-largest utility-scale market after China in the next three years, are also dominated by 1500V technology, with other markets following the same trend.

In fact, IHS Markit predicts that outside China (where adoption of the technology has been relatively slow compared to international markets), 1500V products will account for 84% of high-power PV inverter shipments in 2020, compared with 4 years forward.

Figure 1: Three-Phase PV Inverter Shipments by Voltage – Worldwide Excluded. China (% of MW)

What are the challenges?

Of course, transitioning to a 1500V PV system also presents some specific challenges. Earlier this trend was hindered by the availability of suitable components such as fuses and switches, in addition to the lack of PV modules with 1500V output. Over the past few years, suppliers have responded, and mature supply chains are now in place, ready to supply the required electrical and PV modules.

While 1500V is becoming the standard for large PV systems, adoption of rooftop systems has lagged. In such systems, the deployment of 1500V is limited by safety standards, building codes and electricity regulations. In some cases, local regulations may allow the use of such systems in commercial buildings, but widespread rollout is not expected. 1500V systems are not expected to be used in the residential sector for the foreseeable future.

String inverters also use 1500V technology

In addition to the increasing adoption of 1500V technology, the utility-scale PV industry has also increasingly turned to “string” inverters in recent years. Led by Chinese telecom giant Huawei, the benefits of a more distributed PV inverter approach have been heavily promoted, and global EPCs have begun to favor the large central inverter approach. IHS Markit estimates that nearly 25 GW of string inverters were shipped to utility-scale PV installations in 2017. Of course, with string inverter suppliers now aggressively targeting the large-scale PV segment, they are now releasing more and more 1500V products to capitalize on this growing trend. The table below shows the 1500V product portfolio of the world’s 12 largest PV inverter suppliers. It clearly shows that every high-power (central) inverter supplier already offers a 1500V product. Six out of ten low-power string inverter suppliers have also released products, and more product releases are expected as 1500V string inverter projects are increasingly adopted by large-scale projects around the world .

Figure 2: 1500V Combination of 12 Large PV Inverter Power Supplies

The future of 1500V inverters

Clearly, 1500V PV inverter technology is gaining significant traction in the industry, and the benefits of this approach are increasingly being embraced by EPCs, developers and project owners.

Figure 3: Global 1500V PV Inverter Shipments (GW)

The transition to 1500V systems is a major global trend and their use is expected to continue to grow – especially in large utility-scale systems (defined by IHS Markit as greater than 5 MW), where they will become mainstream by 2020. With shipments growing from 2 GW in 2016 to a milestone of over 30 GW in 2018, IHS Markit forecasts that 1500V inverters will continue their growth trajectory, with combined shipments exceeding 100 GW in 2019 and 2020.

Reviewing Editor: Peng Jing

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