Do you need Three Phase Hybrid Inverter solution? Choose us as your partner and we will provide you with a solution that will satisfy you.
Some review papers have been published in the literature [ 11 14 ]. However, this paper focuses on the existing solutions on the market in terms of structure (simplicity), rating powers, and insulation, as well as high efficiency. The main goal of this paper is to propose a general classification of hybrid converters, as well as a brief overview of their state in the marketplace. In this regard, Section 2 presents the ancillary services of converters. Section 3 describes the various functions of the Hybrid converter. The existing solutions for hybrid converters are analyzed in Section 4 . A research overview of isolated and non-isolated hybrid converters is presented in Section 5 and Section 6 respectively. Finally, the conclusion is presented in Section 7
As a result of the limited amount of power that can be injected into the grid by renewable energy produced by local households, the feed-in energy costs of solar systems are decreasing and are expected to be zero in the current decade [ 10 ]. With this in mind, the use of battery storage systems along with renewable energy sources has great importance.
Power electronic converters play a crucial role in the usage of RES [ 2 ]. Power electronic converters are increasingly used in various applications including electric cars, ships, and photovoltaic (PV) panels. An independent power system can be formed by combining renewable energy with local loads. This approach is widely incorporated into modern power systems [ 3 4 ]. In this system, dc and ac loads are provided by different types of energy sources using efficient power electronic converters.
Electrical energy consumption over the whole world is rapidly growing. There is a consistent increase in the demands on power capacity and the efficient production, distribution, and utilization of energy. The general power generation capacity must be increased to meet dynamic load variations [ 1 ]. A decrease in the accessibility of conventional energy resources has prompted power engineers and researchers around the globe to look for better and more productive means of the utilization of renewable energy sources (RES).
Reference [ 20 ] proposed a method based on conservative power theory to detect the harmonic current of the load. In [ 21 ], the Point of Common Coupling (PCC) voltage information for harmonic compensation is used through a voltage control loop. In addition, reactive power compensation methods are discussed in [ 22 ].
When PV systems are used to perform ancillary services to improve grid power quality, they pose several control challenges. For example, in harmonic compensation, it is important to detect the current or voltage harmonic information.
When the electrical energy conversion is made with photovoltaic (PV) arrays, an intermediate converter is needed for the connection to the grid. This converter can be either single-stage or dual-stage [ 19 ]: the first stage is a dc-dc converter, whereas the second is an inverter synchronized with the utility grid. The dc-dc converter boosts the voltage of the PV arrays up to values suitable for the PWM modulation of the inverter. Maximum Power Point Tracking control (MPPT) is usually implemented on the boost converter to extract the maximum power available from the solar source. Finally, the inverter supplies the power generated by the PV array with the desired power factor to the grid.
The Federal Energy Regulatory Commission (FERC) defines ancillary services as “those services necessary to support the transmission of electric power from seller to purchaser given the obligations of control areas and transmitting utilities within those control areas to maintain reliable operations of the interconnected transmission system”. They are needed for grid reliability [ 15 ]. FERC identified six ancillary services including reactive power and voltage control, loss compensation, scheduling and dispatch, load following, system protection, and energy imbalance [ 16 ]. Among these services, the power electronics converters seem to be best suited for providing reactive power and voltage control. Voltage regulation has traditionally been done on transmission lines because distribution networks are passive networks. The diffusion of RES directly connected to the distribution networks gave rise to the problem of voltage regulation on these networks. Voltage regulation can be achieved by compensating the reactive power required by the users and aims primarily to maintain voltages within certain ranges, but it is also concerned with minimizing temporal variations in voltage and harmonic distortion. The voltage that is traditionally controlled is that acting on the ratio-changing devices (e.g., transformer taps and voltage regulators), reactive-power-control devices (e.g., capacitors, static-var compensators, and occasionally synchronous condensers), and harmonic-control devices (active power filters). The system operator must monitor and control these voltages and compensate for the reactive power of the grid. Sometimes the network management may find it more economical to purchase reactive power from a customer than to directly compensate the customer for the same reactive power. In this case, some customers can provide this ancillary service to the network [ 17 18 ].
PV and battery constitute an off-grid system. If PV can supply the required power of the load, the priority is to supply the required power to the load. Any surplus power is used to charge the battery, as shown in Figure 4 a. When PV has insufficient power, the battery is used to supply power to the load ( Figure 4 b).
PV and the grid both supply the load and charge the batteries ( Figure 3 a). When the grid is working smoothly, the battery’s State of Charge (SOC) is always in full state as depicted in Figure 3 b. Batteries discharge only when a grid faults occur ( Figure 3 c).
As illustrated in Figure 2 a,b respectively, if PV has sufficient power to inject the required power of the load, the surplus power of PV is used to charge the battery and feed into the grid. Conversely, when PV has insufficient power, batteries and the grid have the responsibility to supply the load.
Hybrid converters enable the selection and orientation of renewable energy, grid energy, and energy storage based on consumption. Unlike conventional converters, which systematically store energy in batteries, hybrid converters only store energy when it is needed. This system also allows a choice between whether electricity from photovoltaic panels should be stored or consumed through an internal intelligent apparatus control unit. Hybrid converters can operate in different modes: on-grid, off-grid, hybrid (both on-grid and off-grid at the same time), and backup (in case of a black-out) as described in the following subsections.
An intelligent hybrid converter is a trending type of converter for solar applications using renewable energy for home consumption, especially for solar photovoltaic installations. Some see this as a new technology, however, in some parts of the world such products have been around since the 1990s. In solar systems, power generation fluctuates and may not be synchronized with a load’s electricity consumption since solar panels generate electricity only during the day. To fill the gap between what is produced and what is consumed during the evening when solar electricity is not produced, it is necessary to store energy for later use and to manage energy storage as well as consumption with a hybrid converter.
The purpose of this section is to provide a comparative analysis of hybrid solar inverters on the market. Several of the most popular commercial hybrid inverters have been chosen for comparison [ 23 ]. The selected power range is from 3 kW to 5 kW, which is the typical PV power range for residential applications. All characteristics of the commercial hybrid inverters have been obtained from open sources and are shown in Table 1 35 ]. These inverters illustrate a variety of solutions that are available on the market currently. The most popular manufacturers were selected for analysis. Most of the inverters are single-phase with an average maximum efficiency of about 97%.
4-type battery technology, which guarantees a long service life, short charging times, and high depth of discharge. Furthermore, the storage capacity of the Fronius Solar Battery can be adapted to meet individual customer needs. All the selected inverters use the same standard communications—an RS485 connection or a CAN Bus.As Table 1 shows, there are two types of inverters. The first type is those with a low battery voltage range such as the Sungrow SH5K-30, Redback SH5000, and Imeon 3.6. A low voltage range (42–58.8 V) leads to high charging/discharging currents. In the case of the Redback SH5000 inverter, these are 85 A/100 A, respectively. The second type is inverter is those with a high battery voltage. For example, the Solis RHI-1P5K-HVES-5G. The battery voltage of the latter varies from 120 V to 500 V. However, the charging and discharging current in this system is only 20 A. Compatible batteries for inverters are mostly Li-ion. However, according to its datasheet, the 3-phase Fronius SYMO Hybrid uses the LiFePO-type battery technology, which guarantees a long service life, short charging times, and high depth of discharge. Furthermore, the storage capacity of the Fronius Solar Battery can be adapted to meet individual customer needs. All the selected inverters use the same standard communications—an RS485 connection or a CAN Bus.
The possible structure of the hybrid inverters is illustrated in Figure 5 . They consist of solar terminals, a grid-connected Voltage Source Inverter (VSI), a buck-boost cell, which realizes the Maximum Power Point Tracking (MPPT) function, and a common dc-link. In addition, most commercially available inverters have terminals for backup operation.
In the case of string solar hybrid inverters, the battery can be connected directly to the dc-link, or with an additional interface converter, which is integrated into the Energy Storage Systems (ESS), as shown in Figure 5 a,b, respectively.
An example of an inverter with a structure without an additional interface converter is the Huawei SUN2000-5KTL-L1. It is evident that simplicity and low cost are the main advantages, while limited battery types and voltage are the main drawbacks. An example of an inverter with an external ESS with an additional interface converter, as in Figure 5 a, is the Fronius SYMO Hybrid 5.0-3-S. In this case, the company provides the ESS system as an additional feature, while the inverter has dc-link terminals for connection. Other hybrid solar inverters, such as the Sungrow SH5K-30, have an isolated integrated battery interface converter. This corresponds to the structure illustrated in Figure 5 b. A high step-up of the battery voltage can be realized through this topology. In addition, Figure 5 c shows the internal structure of a hybrid inverter where the internal interface battery converter can be connected to the solar panel terminals.
There are several examples of hybrid microconverters. The concept of hybrid microconverters is the same as that of hybrid converters. The difference consists of the power and voltage levels. Usually, microconverters are intended for connecting to a single solar panel in a range from 10 V to 60 V and a low-voltage battery. Due to the significant voltage difference between the input side and the grid, a step-up transformer is utilized [ 36 ]. This concept is illustrated in Figure 5 d. Despite being an interesting idea, which seems to be suitable for residential use, some difficulties are reported in [ 37 38 ]. The main constraints are related to the battery overheating in the case of tied coupling with a solar panel.
The structure of the hybrid inverter can be much more complex. There are many studies dedicated to alternative solutions. The next part of this work is devoted to the detailed analysis of possible solutions.
If you have any questions on Three Phase Hybrid Inverter. We will give the professional answers to your questions.